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Concrete-encased concrete-filled steel tube (CECFST) columns have recently been regarded as the optimum option for high-rise or heavy-loaded buildings due to superior structural resistance over traditional concrete-filled steel tube (CFST) and reinforced concrete (RC). Thus, in developed countries with severe manpower shortages such as Singapore, advanced precast dry connections were proposed for the CECFST columns to facilitate construction and tackle manpower crunch. Moreover, current research shows that the proposed connection has comparable structural resistance with conventional cast-in-place (CIP) connections, demonstrating huge application potential. However, the existing research is only limited to the performance of precast connections without any experimental studies on jointed columns, which hinders the implementation of the precast connections in engineering of practices. In this paper, to address this research gap, a comprehensive experimental programme was initiated, followed by extensive numerical studies. A total of six intermediate and slender jointed precast columns were tested to investigate the effect of precast connections on load-carrying behaviour of the jointed CECFST columns by considering column slenderness, connection detailing, connection position and load eccentricity. Besides experimental studies, extensive 3D finite element (FE) simulations were performed to investigate the relationship between connection integrity, constructability, and load-carrying performance of the jointed CECFST columns. The numerical studies showed that implementing the conventional "Equivalent to CIP" concept into the design of jointed precast CECFST columns would significantly compromise the constructability of such columns. To address this concern, a performance-based design method was proposed for jointed CECFST columns. Parametric studies showed that adopting the performance-based design method could not only improve constructability but also achieve sufficient column resistance. • Six jointed precast CECFST columns were tested under eccentric compression. • Column slenderness ratio, load eccentricity, connection detailing and connection position were considered in the testing. • Elaborate 3D finite element modelling was established to simulate precast CECFST columns. • Extensive parametric studies were carried out to discuss compression performance of the precast CECFST columns. • Performance-based design approach is recommended for the design of precast CECFST columns. [ABSTRACT FROM AUTHOR]

A new fire design method by Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA) and using strain limits is proposed for stainless steel columns in this paper. In the proposed design method, owing to their computational efficiency, beam finite elements are employed to carry out the GMNIA of stainless steel columns in fire whereby the material strength and stiffness deterioration at elevated temperatures, the spread of plasticity, global instability effects, indirect fire actions and thermal expansion are directly taken into account. Due to the inability of beam finite elements to consider local buckling effects, the use of strain limits determined based on a modified continuous strength method (CSM) is proposed to capture the deleterious influence of the local instability effects on the structural resistances of stainless steel columns in fire. The ultimate capacity of a stainless steel column in fire is determined by (i) the temperature level at which the CSM strain limit is attained or (ii) the critical temperature at which the column is no longer able to carry the applied initial room temperature loading, whichever occurs first. In this study, stainless steel square hollow section (SHS) and rectangular hollow section (RHS) columns with and without axial and/or rotational end-restraints are taken into consideration. The capacity predictions obtained using the proposed design method are extensively verified against the benchmark results from shell finite element modelling and also compared against the predictions from the European structural steel fire design standard EN 1993–1-2. • A new advanced fire design method for stainless steel SHS and RHS columns based on GMNIA with strain limits is proposed. • Extensive numerical parametric studies are carried out, considering 2268 stainless steel SHS and RHS columns in fire. • Accuracy, safety and reliability of the proposed fire design method for stainless steel SHS and RHS columns are verified. • The proposed fire design method leads to more accurate and reliable ultimate resistance predictions relative to EN 1993-1-2 provisions. • The proposed method leads to an advanced and streamlined fire design, directly providing the failure temperatures and failure modes. [ABSTRACT FROM AUTHOR]

Debonding is one of the most critical failure modes for bonded joints under fatigue loads. Numerical prediction on the fatigue debonding behaviour of bonded interfaces with complex geometry still remains a problem. This paper proposes a numerical methodology based on fracture mechanics to predict crack growth in a complex bi-material interface and illustrates the prediction procedure by a case study on wrapped composite joints. Interface coupon tests provide the fatigue crack growth properties at the composite-to-steel interface used as inputs for finite element (FE) modelling. The FE model is calibrated against fatigue tests of small scale wrapped composite joints with different steel surface roughness subject to different load levels. A sensitivity analysis is conducted to investigate the influence of key modelling parameters. The calibrated model is validated against fatigue tests on upscaled joints. Good agreements are shown between the test and modelling results in terms of crack growth and stiffness degradation, demonstrating the potential of the proposed numerical methodology for predicting fatigue debonding behaviour of complex bi-material interfaces. • Fatigue debonding at complex bi-material interfaces is predicted numerically. • Interaction of debonding at different crack paths is predicted. • Modelling parameters are calibrated by small scale wrapped composite joint tests. • The numerical model is validated through upscale joint tests. [ABSTRACT FROM AUTHOR]

Full-scale experimental crash tests are important to determine the occupant risk factors and understand barrier system behaviour in vehicle-barrier impacts. Due to the expensive and time-consuming nature of such crash tests, finite element simulations of full-scale crash tests to analyse and design road safety structures have gained popularity as a more practical method of assessment. In this research, a simplified simulation technique was employed by dividing the barrier system into two sections called the Impact Zone and the Rigid Zone, which was adopted for concrete crash barriers for the first time. A previously performed experimental crash test was used to successfully validate the numerical model. The numerical crash model accurately predicted the critical parameters of the barrier performance. The numerical simulation was further used to extract otherwise difficult or impossible results from the experimental crash test, such as internal energies and exit angles. The importance of the use of optimised Karagozian and Case concrete material parameters was demonstrated through a parametric study carried out with autogenerated parameters. A parametric study performed with impact speed and angle proved that increased speed is more harmful for occupants than a more oblique impact angle. The potential benefits of replacing traditional concrete with improved energy absorbing concrete to reduce occupant risks were also investigated. The comparison of results between the numerical models and experimental crash test confirms the trustworthiness of the developed models to simulate the vehicle-barrier crashes for analysing existing barrier designs and further developing new barrier designs to increase road safety. • K&C material model calibration to represent the concrete performance. • Efficiency of modelling crash tests with calibrated material model parameters. • The effect of friction on the crash-barrier performance. • The benefits of using an energy absorbing concrete for road barriers. [ABSTRACT FROM AUTHOR]

Given that the stiffness of joints has an important influence on the global behavior of steel structures, considerable efforts have been made to develop methods to characterize their behavior. In the component method, that is adopted by Eurocode 3, one of the most relevant components is the column web panel in shear; however, this component has never been the subject of research when additional plates are welded between the column flanges to attach the secondary beams to the minor axis of the column. This paper proposes a stiffness formulation for the component column web panel in shear with additional plates, taking into account the stiffening contribution of these additional plates. To archive this, four experimental tests of beam-to-column joints were carried out, a finite element model was calibrated with the experimental data by comparing moment-rotation and moment-deformation curves, a parametric study of sixty different configurations was performed with the calibrated finite element models to obtain the stiffness of the component column web panel in shear and the initial stiffness of the joint. Then, the proposed stiffness formulation for the component was validated with the results of the parametric study, obtaining a very good agreement. Finally, a compilation of the stiffness formulation of all the components of the joint type extended end plate with additional plates was made and validated, when comparing this analytical stiffness with the initial stiffness of the joints of the parametric study, satisfactory concordance was found. [Display omitted] • Study of end plate bolted steel joint with additional plates welded between column flanges to attach secondary beams. • Experimental work to validate finite element models. • Development of a parametric study with finite element models. • Proposal of a formulation for the component column web panel in shear with additional plates welded between column flanges. • Compilation and validation of the stiffness formulation for all the components of the studied joint. [ABSTRACT FROM AUTHOR]

Stress-strain constitutive model for confined ultra-high-performance concrete (UHPC) plays a pivotal role in the design and modelling of UHPC structures. However, while extensive research exists on the stress-strain responses of unconfined UHPC, a notable dearth of studies focuses on the stress-strain constitutive model for confined UHPC. Accordingly, this study introduces a novel hybrid machine learning (ML)-based stress-strain constitutive model for UHPC confined with normal-strength steel (NSS) or high-strength steel (HSS) spirals. Given the limited experimental data available, a numerical model was developed and validated against experimental results of confined UHPC. Subsequently, it was employed to generate a comprehensive dataset of confined UHPC stress-strain responses, which were then used to train the hybrid ML model. Hyperparameters of the model are subsequently optimized using Optuna along with a cross-validation technique. The optimized hybrid ML model exhibited exceptional accuracy in predicting the stress-strain response of confined UHPC with NSS or HSS spirals, as demonstrated by high coefficients of determination (R2) values ranging from 0.905 to 0.999 and low error metrics across varying stress levels and datasets. Moreover, the capability of the model to simultaneously predict both stress and strain responses was further validated through canonical correlation analysis (CCA). The results of the analysis demonstrated robust predictive performance of the model, with high CCA scores that ranged between 93.3% and 99.4%. To facilitate the practical implementation of the model, an end-to-end interactive software tool is developed. In addition, this study proposes predictive equations for the peak and ultimate stress-strain responses of confined UHPC. The evaluation of the developed predictive equations demonstrates their efficacy in accurately predicting the stress-strain responses of confined UHPC, as evidenced by the high R2 values, which ranged from 83–91%. • Developed a numerical model for predicting the stress-strain response of confined UHPC. • Introduced a hybrid machine learning-based constitutive model for UHPC confined with NSS or HSS spirals. • The proposed model achieved accurate predictions substantiated by various statistical evaluation metrics. • Established HAI-CONCise-UHPC: Hybrid Artificial Intelligence-based CONstitutive model for Confined UHPC. • Proposed predictive equations for the peak and ultimate stress and strain responses of confined UHPC. [ABSTRACT FROM AUTHOR]

The structural behaviour of S960 ultra-high strength steel (UHSS) welded I-section beam–columns is studied in the present paper. Nonlinear finite element (FE) models were first created and validated against relevant test results collected from the literature; the models were then used to carry out parametric studies to obtain additional FE data over an extensive spectrum of cross-section dimensions, member lengths and loading combinations. Given the lack of existing design rules for S960 UHSS structures, the codified beam–column interaction curves prescribed in the current European (EC3) and American (AISC 360) design specifications for lower strength steel members, were assessed for their applicability to the studied S960 UHSS non-slender welded I-section members, utilizing the generated numerical data. It was found that EC3 yielded conservative failure load predictions for Class 1 and 2 S960 UHSS welded I-section beam–columns buckling about either principal axis; similar results were found for Class 3 members under combined compression and strong-axis bending, with the mean FE to predicted failure load ratio being 1.29, the corresponding COV being 0.12, but rather conservative strength predictions arose for Class 3 members under combined compression and weak-axis bending, with the mean FE to predicted failure load ratio being 1.50. AISC 360 led to overall accurate and consistent failure load predictions for S960 UHSS non-slender welded I-section beam–columns, but resulted in some unconservative strength predictions for members under combined compression and weak-axis bending. New design proposals, adopting the format of EC3 design interaction curve, but with more accurate compression and bending end points, interaction factors and buckling reduction factors determined from the continuous strength method (CSM), were proposed and shown to lead to improved design accuracy. • The structural behaviour of S960 UHSS non-slender welded I-section beam–columns is studied. • FE models are developed and validated against test results and then used to perform parametric studies. • The current design rules are assessed for their applicability to S960 UHSS non-slender welded I-section beam–columns. • A CSM-based design approach is proposed and shown to lead to improved design accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a detailed numerical investigation into the inelastic cyclic performance of circular steel tubes filled with rubberised concrete materials. The study considers rubberised concrete infills with relatively high values of up to 60% volumetric rubber replacement of conventional mineral aggregates, which is lacking in existing investigations. Co-existing axial loads of up to 30% of the nominal composite cross-section capacity are also considered. Modified continuum finite element modelling procedures are proposed and employed to account for the high cumulative deformations and damage development of rubberised concrete under cyclic loading. In particular, the influence of crack opening and closure in concrete under cyclic loading is examined and discussed. In addition to full numerical cyclic analyses, idealised monotonic simulations are also proposed and verified to enable computationally efficient representation of the envelope response. Validations of the full-cyclic and envelope-monotonic models are carried out against available experimental cyclic results, indicating the suitability of the models for representing the inelastic response and degradation of confined concrete with high rubber content. Parametric assessments are then undertaken to examine the influence of key material and geometric parameters, including the rubber content, material strength and cross-section properties, on the inelastic large deformation behaviour. The results of the parametric studies are used to quantify the main response parameters, with focus on the member stiffness, moment-axial strength interaction, local buckling criteria and other ductility measures. Based on the findings, modifications are proposed to current design procedures in order to provide a reliable prediction of the inelastic cyclic response characteristics of rubberised concrete filled circular steel tubes. Apart from providing experimentally validated numerical approaches that can be used in future studies, the proposed analytical and design procedures are suitable for implementation in practical assessment and design applications. • Numerical models are proposed for cyclic response of rubberised concrete filled steel tubes. • Rubber ratios up to 60% and axial load ratios up to 30% are validated against testing data. • Parametric assessments are conducted and key material and geometric factors are investigated. • Existing design procedures are evaluated and modifications are proposed. [ABSTRACT FROM AUTHOR]

In-service masonry arch road bridges, mainly realised before the first half of the last century, represent a wide portion of the entire worldwide infrastructural asset. Given their age, during their service life these structures could have experienced damage due to anthropic (i.e. traffic) and natural (i.e. earthquakes, soil settlements, degradation, etc.) actions which may have inevitably affected their load-bearing capacity. The present study addresses the problem of the residual capacity estimation of damaged bridges by investigating the impact of previous loading on the actual strength of the structure. In particular, reference to a past experimental activity retrieved from the literature on reduced-scale bridges subjected to concentrated vertical loads has been made to calibrate a reliable detailed finite element model in Abaqus software. Then, damage of different extent has been introduced by simulating the transit of vehicles of various weights on the structure and the residual capacities of the bridge have been assessed and compared against the undamaged configuration. The results confirm that pre-existing damage due to traffic loading may significantly influence the capacity of such structures, with peak load reductions up to 60% estimated through the proposed methodology. • Pre-existing damage affects the actual capacity of existing masonry arch bridges. • Numerical models can be profitably adopted to simulate the presence of pre-existing damage. • Damage can be introduced in numerical models by simulating their causes. • Rigid-block analyses can provide conservative estimation of the actual capacity of masonry arch bridges. [ABSTRACT FROM AUTHOR]

• Full-range true stress-strain curves of S275 and S690 steels up to fracture are measured. • Digital image correlation technique is adopted to measure instantaneous dimensions and strain fields in tensile tests. • Non-uniform stress and strain distributions across critical cross-sections are found in FE modelling. • Iterations are formulated for corrections of full-range true stress-strain curves. • Constitutive models for both S275 and S690 steel materials under monotonic actions are proposed. Standard tensile tests are commonly used to determine mechanical properties of metallic materials, such as yield strength and tensile strength as well as ductility. In general, these standard tensile tests are able to provide basic mechanical properties of steel materials, commonly referred as engineering stress-strain curves. These curves are considered to be effective for linear elastic and post yielding deformations up to mobilization of tensile strengths, and they are widely adopted in structural design and analysis of steel structures. However, for detailed investigations into structural behaviour of steel structures in large deformations beyond onset of necking, cross-sectional changes in the steel materials often become very large. Hence, an improved stress-strain curve, commonly known as a true stress-strain curve, with proper adjustment according to large longitudinal deformations should be adopted in advanced finite element models. In order to develop full range true stress-strain curves of various steel materials for large deformations, a research project is conducted to perform an integrated experimental and numerical study. Standard tensile tests on two S275 steel coupons and two S690 steel coupons are carried out, and advanced optical measurements using a digital imaging correlation technique are adopted to measure deformation fields of these coupons with a high precision during the entire deformation ranges. After data analyses using three different transformation rules, namely, i) Power Law Method, ii) Linear Law Method, and iii) Instantaneous Area Method, three different true stress-strain curves for each of S275 and S690 steel materials are derived. These curves are then incorporated into advanced finite element models to simulate large deformations of these steel coupons observed in the tensile tests. Improvements to the true stress-strain curves derived from Instantaneous Area Method are made through successive corrections according to measured and predicted deformation characteristics of the steel coupons. Consequently, the proposed true stress-strain curves determined with Instantaneous Area Method are shown to be highly acceptable for numerical analyses of steel structures undergoing large plastic deformations up to fracture. Expressions of the proposed full range true stress-strain curves for S275 and S690 steel materials are also provided. [ABSTRACT FROM AUTHOR]

• Review of past finite element modeling work related to light-frame wood structures. • Development of a practical method to identify weak links in the vertical load path. • Calculation of demand-to-capacity ratios using linear finite element models. • Identification of points of vulnerability in light-frame wood roofs under wind uplift. Wood-frame residential roof failures due to extreme wind events are among the most common and expensive types of damage. Following extreme wind events, forensic damage investigations observe the final state of failed structures, and research must work backwards to identify the likely points of failure initiation under the expected wind loads. Based on previous studies, hip roofs are commonly understood to be more resilient during extreme wind in relation to gable roofs. Two predominant modes of residential roof failure have been studied in the literature; sheathing loss and failure of the roof-to-wall connection (RTWC). Hip roofs have specifically been proven more resilient to damage through these two modes. However, inspection of damage survey data from several recent tornadoes has identified that failures may have occurred in hip roofs at the roof framing members and their connections, rather than in the RTWC. Under wind uplift, the vertical load path through typical light-frame wood structures is still not well-defined, especially considering the possibility of failure of the framing members and connections. To prove the concept of partial failures within the frame of a hip roof, while conserving experimental resources, a finite element modelling technique is required. In the present work, a modelling method is developed to analyze the internal load effects and strength behaviour of the components of a wood-frame roof under wind uplift. Due to the uncertainties in construction of connections, lack of experimental data required for validation, and variability of the parameters affecting joint stiffness, the current study proposes a method which takes an envelope of the extreme member and joint forces under uplift, and compares them with unfactored strength values to produce conservative demand-to-capacity (D/C) ratios. Two-dimensional truss models are developed and validated against data from the literature to prove the modelling method before the D/C analysis is done for a truss under uplift. This method allows for performance, in terms of relative D/C ratios, of the structural components to be compared and the "weak-links" to be identified. Then, comparing the results for the framing members and connections to the known wind resistance of RTWCs provides a point of comparison for the observed framing failures. The results show that toe-nailed RTWCs are likely to be the weak-link, however the D/C ratios of certain truss connections confirm that their failure may be possible in certain configurations, or when the RTWCs are strengthened using hurricane ties. [ABSTRACT FROM AUTHOR]

Highlights • Effects of axial force and bending moment on the burst pressure of corroded pipelines are studied. • Burst pressure is significantly reduced under compressive axial force and closing bending moment. • Developed failure loci considering axial forces, bending moments and internal pressures. • The failure loci are found to depends on corrosion depths and load combinations. • The failure loci can be used for burst pressures assessment with known axial force and bending moment. Abstract The remaining strength of corroded pipeline is generally assessed considering the internal pressure only. However, pipelines are often subjected to axial forces and bending moments due to external loadings, which may significantly reduce the burst pressure of the pipeline. This paper presents a study using finite element analysis on the effects of axial forces and bending moments to the burst pressures of corroded pipelines. It is revealed that the compressive axial force and the closing bending moment, causing compression in the corroded area, affect the burst pressure most significantly. Considering the axial compression and closing bending moment, failure loci of combined bending moments and internal pressures are developed for different axial forces. The developed failure loci can be used for assessing the burst pressure of corroded pipelines subjected to axial forces and bending moments. [ABSTRACT FROM AUTHOR]

Highlights • A novel, theoretical 3D model of a drilling rig – subsoil system is proposed. • Subsoil-drilling rig interaction characteristics are obtained with aid of 3D FEM. • Practical examples concerning stability of a drilling rig are given. • A brief state-of-the-art report is included. Abstract The main goal of the article is the theoretical formulation and elaboration of a numerical solution to the stability problem with heavy drilling rigs moving on weak subsoil. All static loadings and inertia effects caused by the machines' movement, as well as geometrical imperfections, are taken into account. The machine-subsoil interaction problem is solved using the ZSoil software [13]. In the programme, the subsoil and working platform are modelled as an elastic-plastic continuum, using fully drained conditions for the working platform and undrained conditions for the weak subsoil, while the machine base is treated as a quasi-rigid body. A theoretical mechanical model and algorithms to design working platform, for a given machine with its movement parameters (velocities and accelerations), or to assess limit conditions on machine movement, for a given subsoil properties, are elaborated. Two selected case studies are analysed, to prove the robustness of the proposed approach. [ABSTRACT FROM AUTHOR]

Highlights • Investigation of the structural behaviour of prestressed high strength steel arched trusses. • Testing of four prestressed arched trusses fabricated from S460 hot finished square hollow section members. • Finite element modelling of prestressed arched truss systems and validation of models against the conducted tests. • Parametric studies examining the effect of prestress level, material grade and the top chord cross-section. • Development of design recommendations for prestressed arched truss systems. Abstract The structural behaviour of prestressed high strength steel arched trusses is studied in this paper through experimentation and numerical modelling. Four 11 m span prestressed arched trusses fabricated from S460 hot finished square hollow section members were loaded vertically to failure. Three of the tested trusses were prestressed to different levels by means of a 7-wire strand cable housed within the bottom chord, while the fourth truss contained no cable and served as a control specimen. Each truss was loaded at five points coinciding with joint locations along its span, and the recorded load-deformation responses at each loading point are presented. Inclusion and prestressing of the cable was shown to delay yielding of the bottom chord and enhance the load carrying capacity of the trusses, which ultimately failed by either in-plane or out-of-plane buckling of the top chord. For the tested trusses, around 40% increases in structural resistance were achieved through the addition of the cable, though the self-weight was increased by only approximately 3%. In parallel with the experimental programme, a finite element model was developed and validated against the test results. Upon successful replication of the experimentally observed structural response of the trusses, parametric studies were conducted to investigate the effect of key parameters such as prestress level, material grade and the top chord cross-section on the overall structural response. Based on both the experimental and numerical results, design recommendations in the form of simple design checks to be performed for such systems are provided. [ABSTRACT FROM AUTHOR]

Highlights • A framework for multi-platform simulation of complex RC structures is presented. • It enables to accurately consider both the global and local behaviour of the structure. • It eliminates analysis calibrations commonly used for modelling complex structures. • The application of the method was investigated using various types of case studies. Abstract This study presents a framework for multi-platform analysis and hybrid simulation of reinforced concrete (RC) structures. In this approach, each subpart of the structure, based on its mechanical characteristics, is modelled using the most suitable finite element analysis tool or represented with a test specimen. The proposed framework combines all the substructure modules and takes into account the interactions between them by satisfying compatibility and equilibrium requirements. The main contribution of the study lies in demonstrating the effectiveness of multi-platform modelling in accurate and practical analysis of complex RC structures or multi-disciplinary RC systems with a particular focus on shear behaviour. Three application examples including a wide-flange shear wall, a three-storey frame with critical joints, and a soil-structure interaction simulation are discussed in detail. It is concluded that the multi-platform analysis can compute the behaviour of such structures with a level of accuracy that was previously difficult to achieve with most single-platform analysis software. [ABSTRACT FROM AUTHOR]

Highlights • Numerical study on the seismic behaviour of masonry towers. • Critical insight into the results obtained. • Comparison between seismic risk of confined and unconfined structure. Abstract This study analyses the seismic risk of a confined historic masonry tower located in Italy (San Gimignano) critically discussing the multilevel assessment path proposed by the Italian "Guidelines for the assessment and mitigation of the seismic risk of the cultural heritage". Specifically, these guidelines identify a methodological path which aims to coordinate the phases of investigation and drive the grade of resolution of the structural assessment, depending on different possible objectives. The paper compares the results obtained with the three different levels of evaluation employed to estimate the seismic risk of the tower: level LV1 (analysis at territorial scale), level LV2 (local analysis) and level LV3 (global analysis). The main variables considered are the mechanical properties of the masonry walls and the degree of constraint generated by the buildings surrounding the tower with specific attention to the latter variable. Numerical insights on the seismic behaviour of the tower are presented and discussed through a comparative approach. The obtained results show significant differences between the numerical models of the confined and the isolated tower in terms of both capacity curves and damage pattern and point out the needs of additional studies regarding the numerical assessment of the effects of the interaction between a tower and its adjacent lower buildings. [ABSTRACT FROM AUTHOR]

Highlights • Results of experimental study on stainless steel I-section beam-columns presented. • FE models validated against new and existing test results. • Numerical parametric studies carried out to generate further data. • Existing structural design provisions for stainless steel beam-columns assessed. • New design provisions developed, and reliability assessed against EN 1990 requirements. Abstract The stability and design of laser-welded stainless steel I-section beam-columns are explored in this study. Owing to the high precision and low heat input of laser-welding, structural cross-sections produced using this fabrication method have smaller heat affected zones, lower thermal distortions and lower residual stresses than would typically arise from traditional welding processes. Eighteen laser-welded stainless steel beam-columns were tested to investigate the member buckling behaviour under combined compression and bending. Two I-section sizes were considered in the tests: I-50 × 50 × 4 × 4 in grade EN 1.4301 and I-102 × 68 × 5 × 5 in grade EN 1.4571 austenitic stainless steel. The two cases of minor axis bending plus compression and major axis bending plus compression with lateral restraints were investigated. The initial loading eccentricities in the beam-column tests were varied to provide a wide range of bending moment-to-axial load ratios. The test results obtained herein and from a previous experimental study were used to validate finite element (FE) models, which were subsequently employed for parametric investigations to generate further structural performance data over a wider range of cross-section sizes, member lengths and loading combinations. The obtained test and FE results were utilized to evaluate the accuracy of the beam-column capacity predictions according to the current European and North American design provisions and a recent proposal by Greiner and Kettler. Finally, an improved approach for the design of stainless steel I-section beam-columns is proposed. [ABSTRACT FROM AUTHOR]

• Stability and design of stainless steel hollow section columns in fire are investigated. • Comprehensive numerical parametric studies are performed, considering 26,760 stainless steel hollow section columns. • New column fire design rules for stainless steel hollow section columns are established. • Accuracy, safety and reliability of the proposed fire design rules are extensively verified. • The proposed fire design rules lead to significantly more consistent ultimate resistance predictions relative to EN 1993-1-2. This paper investigates the stability and design of stainless steel circular, elliptical, square and rectangular hollow section (CHS, EHS, SHS and RHS) columns at elevated temperatures. Nonlinear shell finite element models are employed to conduct comprehensive parametric studies whereby extensive benchmark structural performance data on the behaviour and resistance of stainless steel hollow section columns at elevated temperatures is generated. In total, 26,760 cold-formed and hot-rolled austenitic, duplex and ferritic stainless steel CHS, EHS, SHS and RHS columns at elevated temperatures are taken into account, considering various member slendernesses, cross-section geometries, cross-section slendernesses and elevated temperature levels. New flexural buckling design rules are put forward for stainless steel hollow section columns in fire, which consistently considers the elevated temperature strength at 2% total strain f 2,θ as the reference material strength for all cross-sections classes. The accuracy, safety and reliability of the proposed new design rules are assessed for a wide range of cases. Comparisons are also made against the results obtained through the column fire design rules of the European structural steel fire design standard EN 1993-1-2 [1]. It is demonstrated that the proposed new design rules furnish more accurate, safe-sided and reliable flexural buckling resistance predictions for stainless steel hollow section columns at elevated temperatures relative to the column fire design provisions of EN 1993-1-2 [1]. [ABSTRACT FROM AUTHOR]

• An innovative precast concrete-encased concrete-filled steel tube column-to-column connection is proposed. • Five connection tests were conducted to investigate compression behaviour of the precast connection. • The proposed precast connection exhibited comparable compression resistance to continuous CECFST columns. • Comprehensive finite element modelling was performed to identify key variables that affect compression resistance of the connection. • A simplified analytical model was proposed to evaluate compression resistance of the precast connection. Concrete-encased concrete-filled steel tube (CECFST) is a new type of composite member featuring superior structural performance and high construction productivity. This form of structural members has been increasingly used as columns in high-rise buildings and as piers in long-span bridges. Recently, to promote the application of CECFST columns in countries short of labour, e.g., Singapore, North America and Europe, an advanced precast CECFST column-to-column connection with rapid construction and excellent tensile performance was developed by the authors. However, behaviour of the developed precast connection subjected to axial and eccentric compression has not been studied so far. In this paper, an experimental programme including five connection tests was conducted to investigate compression performance of the developed precast connection. The test results showed that compression resistance of the precast connection could achieve that of CECFST columns, indicating that it is feasible to connect CECFST columns by the newly proposed precast connection to enhance construction productivity. Furthermore, an extensive finite element (FE) modelling programme was carried out to generate more numerical data by conducting parametric studies. The experimental and numerical results showed that connection configuration plays a pivotal role in load-carrying capacity of the precast connection. Based on EN 1994-1-1, one simplified strength prediction model was proposed for the proposed precast CECFST column-to-column connection. Compared with experimental and numerical results, the predicted strength was conservative and consistent, indicating that the proposed approach can be used in the design of the precast connection. [ABSTRACT FROM AUTHOR]

Highlights • Performance of cold-formed high strength steel tubular columns was investigated. • A FE model for the columns was validated and used to conduct parametric studies. • Results of parametric studies and experiments were used to assess design rules. • Strength predictions using existing design rules for the columns were conservative. • Design recommendations and a more accurate column buckling curve were proposed. Abstract This paper presents a numerical investigation into the structural performance of cold-formed high strength steel tubular columns with square, rectangular and circular cross-sections. A finite element model was developed and validated against experimental results on the cold-formed high strength steel tubular columns. Parametric studies using the validated finite element model were carried out to determine the strengths of cold-formed tubular columns with various cross-sectional dimensions, member slenderness values, geometric imperfections and steel grades of S700, S900 and S1100. It was found that increasing the steel grade of the columns led to higher normalised column strengths which were less severely affected by geometric imperfections. The effect of material tensile strength to yield strength ratio on the column strengths was found to be insignificant. Based on the experimental results in literature and the results obtained from parametric studies, the applicability of the design rules in European, Australian and American Standards to cold-formed high strength steel tubular columns was evaluated. The reliability of the design rules was also assessed by performing reliability analysis. The design rules in these standards provide conservative predictions for the strengths of cold-formed high strength steel tubular columns. Recommendations on the column buckling curve selection are discussed. An improved column buckling curve expression considering the increment in normalised column strength with increasing steel grade is also proposed. [ABSTRACT FROM AUTHOR]

Highlights • Pull-pull tests on the glulam joints with glued-in single rod were conducted. • A finite element model considering bond-slip location function was established to investigate the bond behaviour of the glulam and the glued-in rod. • The numerical results considering bond-slip location function show better agreement with the experimental results compared to that without considering bond-slip location function. • The proposed calculation model can be able to predict the joint withdrawal stiffness effectively. Abstract It was frequently reported that the bond-slip relationships at different locations along the bonded length are different, which can be illustrated as bond-slip location effect. In order to reveal the influence of this effect on the bond behaviour between glue laminated timber (glulam) and glued-in rod, a 3D finite element model considering bond-slip location function is developed for the glulam joints with glued-in rod in this paper. Moreover, an experimental program conducted on the glulam joints with glued-in rod is also presented. The numerical and experimental results are compared and discussed in terms of withdrawal capacity, typical failure modes, load-slip behaviour, strain development of glued-in rod and the interface shear stress distribution. It is indicated that the non-linear spring elements can be used to simulate the bond behaviour between the glulam and the glued-in rod effectively. The numerical results obtained considering the bond-slip location function are generally in better agreement with the experimental results compared to that obtained neglecting the bond-slip location function. Finally, the withdrawal stiffness of the glued-in rod glulam joints is evaluated by a theoretical approach based on the Volkersen theory. The withdrawal stiffness calculated by the proposed model shows good agreement with the experimental results, which confirms that the calculation model is effective for predicting the withdrawal stiffness of the glulam joints with glued-in rod. [ABSTRACT FROM AUTHOR]

Highlights • Experiments performed on stainless steel I beams under IOF and ITF loading. • Out-of-plane deformation fields measured using digital image correlation. • Nonlinear finite element simulations and parametric studies conducted. • Assessment of American and European design provisions carried out. Abstract The behaviour and design of stainless steel I-section beams under concentrated transverse loading are investigated in this study. Twenty-four experiments on stainless steel I-sections, formed by the welding of hot-rolled plates, were performed. The tests were conducted under two types of concentrated transverse loading – internal one-flange (IOF) and internal two-flange (ITF) loading. The experimental set-up, procedure and results, including the full load-displacement histories, ultimate loads and failure modes, are reported. A complementary nonlinear finite element modelling study was also carried out. The models were first validated against the results of the experiments. A parametric investigation into the influence of key parameters such as the bearing length, web slenderness and level of coexistent bending moment, on the structural response was then performed. Finally, an assessment of current design provisions for the resistance of stainless steel welded I-sections to concentrated loading is presented. The results show that the current design formulae yield safe-sided, but generally rather scattered and conservative capacity predictions, with considerable scope for further development. [ABSTRACT FROM AUTHOR]

Highlights • Conducted an experimental investigation on short SHS columns strengthened with different CFRP wrapping systems. • Developed and validated FE models to simulate CFRP strengthened short SHS columns. • Conducted a parametric study on the effect of steel section, CFRP orientation and steel grade on the capacity. • Developed new design equations for the compression capacity of CFRP strengthened short SHS columns. Abstract This paper presents the details of experimental and numerical investigations on the behaviour and axial compression capacity of Carbon Fibre Reinforced Polymer (CFRP) strengthened cold-formed, short Square Hollow Section (SHS) steel columns. Initially, an experimental investigation consisting of seven test columns was conducted to investigate the influence of CFRP strengthening layout on the axial compression capacity of short SHS steel columns. In addition, the effect of CFRP wrapping end condition was also investigated. Experimental results showed that CFRPs are very effective in strengthening short SHS columns, where axial compression capacity enhancements up to 2.6 times were observed. Then a numerical simulation was implemented using ABAQUS by which CFRP and adhesive were modelled using continuum and cohesive elements deploying Hashin and cohesive law criteria. The finite element models were validated using experimental results and then used in a detailed parametric study. Using the finite element analysis results suitable improvements were proposed to the existing design equations available in the literature. Finally, a new set of design equations based on Direct Strength Method (DSM) is proposed in this paper to determine the axial compression capacity of CFRP strengthened SHS columns subjected to local buckling. [ABSTRACT FROM AUTHOR]

Highlights • FE models validated against test results on cold-formed steel SHS/RHS. • Validated FE models used to perform parametric studies considering key parameters. • EN 1993-1-1 and AISC-360-16 provisions assessed using test and FE data. • CSM extended and modified to cover the design of cold-formed steel SHS/RHS. • Reliability of different methods evaluated by means of statistical analyses. Abstract Cold-formed steels typically exhibit a rounded stress-strain response with gradual yielding merging into strain hardening. This form of stress-strain curve is at odds with the elastic, perfectly plastic material model that underpins many of the provisions set out in current structural steel design standards. In particular, the beneficial influence of strain hardening on cross-section capacity is neglected. The continuous strength method (CSM) is a deformation-based design method that enables material strain hardening properties to be exploited, thus resulting in more accurate and consistent capacity predictions. The aim of this study is to extend the CSM to the design of cold-formed steel non-slender tubular cross-sections subjected to compression, bending and combined loading, and to verify the proposals through comparisons with existing test data from the literature and finite element results generated herein. The finite element models were first developed and validated against test results on cold-formed steel cross-sections collected from the literature. An extensive parametric study was then conducted to generate additional data over a wider range of cross-section geometries, slendernesses and loading conditions. The numerical results together with the experimental results were then compared with capacity predictions, calculated according to the current design rules in European Standard EN 1993-1-1 (2005) and American Specification AISC-360-16 (2016) as well as the CSM. The CSM is shown to provide more accurate and consistent design predictions for cold-formed steel cross-sections under different loading conditions than those obtained from existing design methods. The improvements arise from the use of the continuous deformation based design approach, as well the rational exploitation of strain hardening. Finally, the reliability levels of the different design methods were assessed by conducting reliability analyses in accordance with EN 1990 (2002). [ABSTRACT FROM AUTHOR]

Highlights • It is a corrosion-resistant and high-strength anchorage system for CFRP plates. • A mathematical model was developed to investigate the effect of contact pressure. • The mathematical model was used to predict the thickness of the anchor. • Additive manufacturing method was used to make a 3D printed prototype of the anchor. • Advanced finite element simulation was carried out to optimize the anchor design. • The anchor can carry 100% capacity of the CFRP plate proved by experimental study. Abstract Efficient use of pultruded thin composite plates in the mechanical and the structural applications largely depends on the performance of the anchor used at the two ends of the plates. This research studies the feasibility and effectiveness of an optimized, corrosion-resistant, thin, and light-weight anchor for the carbon fibre-based composite plates. The main objective is to investigate the effect of the material and the thickness of the barrel and the wedges on the performance of the anchor. Several materials were investigated; and finally, the corrosion-resistant heat-treated 440C stainless steel was chosen. This article also presents the development of an analytical model towards the design and optimization of an innovative prestressing anchor. The analytical model was developed and used to predict the contact pressure distribution on the composite plate inside the anchor under loading to avoid any premature failure of the plate. This analytical model was also used to predict a preliminary thickness of the new anchor. A three-dimensional finite element model was developed to analyze and optimize the anchor design. A detailed experimental study was also conducted to validate the analytical and the finite element simulation results. [ABSTRACT FROM AUTHOR]

Highlights • A softened damage-plasticity model with compression-softening is used for concrete. • A stress-slip model is developed for precast concrete to reflect bond-slip effect. • A pre-post concrete interface layer is developed in the finite element model. • 3D numerical examples of cyclic tests of connections were performed and validated. Abstract In this paper, a finite element modelling approach is developed for the analysis of the cyclic behavior of precast beam-to-column connections. In particular, the modelling takes into account the compression-softening of concrete, the bond-slip effect in the critical regions and the representation of the post-cast concrete interface. A newly developed softened damage-plasticity model, which can reproduce the typical cyclic behavior of reinforced concrete, is adopted for concrete. Meanwhile, to reflect the significant bond-slip effect between concrete and reinforcement bars, the M-P stress-strain model is modified to account for the slippage by assuming the bar strain is the sum of the bar deformation and the slip, while the anchorage slip is theoretically derived and validated through benchmarking the pull-out tests. Additionally, a concrete layer between the precast concrete and the cast-in-situ concrete is incorporated to reflect the features of the interface. The proposed numerical modelling approach is validated through simulation of both interior and exterior precast beam-to-column connection tests. The validated models are subsequently employed to investigate the influences of key factors such as the compression-softening and the bond-slip effect on the analysis of the cyclic behavior of the precast beam-to-column connections. Results demonstrate that the proposed model is capable of reproducing the typical behavior of precast beam-to-column connections and can serve as an effective tool for the seismic performance analysis and investigation of design parameters of precast connections. [ABSTRACT FROM AUTHOR]

Highlights • Extent of temperature-induced transient creep in concrete columns is investigated. • A numerical model for transient creep effect in fire resistance analysis is proposed. • Effect of critical parameters governing transient creep is quantified. Abstract This paper quantifies effect of transient creep on response of reinforced concrete (RC) columns under severe fire exposure scenarios. A three-dimensional finite element model is built in ABAQUS to trace the influence of transient creep on RC columns under simultaneous loading and fire exposure. Temperature induced transient creep strains in concrete and reinforcing steel are explicitly accounted for in fire resistance analysis, together with property degradation in constituent materials, and associated material and geometrical nonlinearities. The model is applied to assess influence of transient creep on fire response of RC columns under different conditions, including different fire exposures, load levels, and number of exposed sides. Results from the numerical studies clearly indicate that severe fire exposure induces higher capacity degradation in RC columns in much shorter duration than exposure to a standard building fire. Moreover, asymmetric thermal gradients resulting from two or three side fire exposure on a column can increase transient creep effects and, thus, affect fire resistance. Overall, results from the analysis infer that neglecting transient creep can lead to lower estimation of axial displacements and, thus, overestimation of fire resistance in RC columns, particularly when subjected to severe fire scenarios and with higher thermal gradients. [ABSTRACT FROM AUTHOR]

When constructing reinforced concrete building structures, shores are normally used to transmit the loads from freshly poured slabs to lower floors. However, certain problems are involved in this process, including: (a) the loads on the shores may be higher than expected, which can lead to the collapse of the shoring system or even of the whole structure, and (b) the limited range of shore types in commercial catalogues, which often means that the shores used are oversized. This paper describes the study carried out on the development of a new load-limiter (LL) that can be fitted to shores to improve safety and reduce the cost of constructing building structures. The study shows that combining mechanical and civil engineering fields made it possible to produce a novel device that could revolutionise the shoring techniques at present in use. The method of designing and implementing the LLs involved: (a) the design of prototypes by using numerical simulations, (b) the use of the design of experiments technique, (c) an ambitious experimental campaign in which LL were tested, (d) the detailed simulation of the final design, and (e) the formulation of a simplified model that considers the behaviour of the shore-LL as a unit. [ABSTRACT FROM AUTHOR]

An innovative concept, whereby the load-carrying capacity and serviceability performance of cold-formed steel beams are enhanced by utilising prestressing techniques, is presented. The prestressing force is applied by means of a high-strength steel cable, which is housed at a location eccentric to the strong geometric axis within the bottom hollow flange of the cold-formed steel beam, inducing initial stresses in the beam that are opposite in sign to those introduced during the subsequent loading stage. As a consequence, the development of local instabilities during loading is delayed and thus the capacity of the beam is enhanced. Furthermore, the pre-camber induced during prestressing, as well as the contribution of the cable to the bending stiffness of the system, decrease the overall vertical deflections of the beam. The conceptual development of prestressed cold-formed steel beams and a study investigating the potential benefits are presented. The mechanical behaviour of the proposed beams in both the prestressing and imposed loading stages is described in terms of analytical expressions, while failure criteria for the design of the cold-formed steel beam and the cable are also developed by employing interaction equations in conjunction with the Direct Strength Method. Geometrically and materially nonlinear finite element analysis with imperfections is employed to simulate the behaviour of the proposed beams. Sample numerical results are presented and compared with the developed analytical expressions and failure criteria, demonstrating the substantial enhancement in moment capacity and serviceability performance offered by these beams. [ABSTRACT FROM AUTHOR]

The findings from a numerical investigation into the degree of composite action that may be mobilised within floor systems comprising cold-formed steel joists and wood-based particle boards are presented herein. Finite element models have been developed, simulating all the components of the examined systems, as well as the interaction between them. The models include initial geometric imperfections, the load-slip response of the fasteners employed to achieve the shear connection as well as both geometric and material nonlinearities. The developed models were first validated against 12 physical tests reported in the literature, which showed them to be capable of accurately capturing the load-deformation curves and failure modes exhibited by the tested specimens. Parametric studies were then performed to examine the influence of key parameters on the structural behaviour of these systems, including the depth and thickness of the cold-formed steel section, as well as the spacing of the employed fasteners; in total, about 100 systems have been examined. Significant benefits in terms of structural response have been identified from the presented numerical study as a result of the mobilisation of composite action; for the systems investigated, which were of typical, practical proportions, up to 140% increases in moment capacity and 40% increases in stiffness were found. The presented research reveals the substantial gains in structural performance and the influence of the key governing parameters for this novel form of composite construction. [ABSTRACT FROM AUTHOR]

The instability behaviour of eccentrically loaded circular masonry columns is investigated. Two approaches are considered for the analysis. One is based on a semi-analytical formulation of the relevant boundary-value problem for a no-tension material response; the other employs a plastic-damage-contact constitutive model, the CraftS model, to capture the complex microstructural behaviour of the material. The latter has been implemented in the finite element program LUSAS and has been already successfully employed to describe progressive instability in eccentrically loaded brickwork wallettes of rectangular cross section. Equilibrium paths and limit load estimates are computed for both analysis approaches for a range of column aspect ratios and load eccentricities. It is shown that the type of material response becomes less important for specimens with height-to-diameter aspect ratios greater than 7.5 and for loads applied to points in the kernel of the cross section, while for higher eccentricities the presence of a tensile strength increases considerably the limit load. The damage evolution predicted by the models is also investigated for selected cases, showing that the formulation based on the no-tension material is able to capture with good agreement the damaged zone of the column for loads with low eccentricities. For the same type of loading, a useful design formula is provided. [ABSTRACT FROM AUTHOR]

The continuous strength method (CSM) is a deformation-based structural design approach that enables material strain hardening properties to be exploited, thus resulting in more accurate and consistent capacity predictions. To date, the CSM has featured an elastic, linear hardening material model and has been applied to cold-formed steel, stainless steel and aluminium. However, owing to the existence of a yield plateau in its stress-strain response, this model is not well suited to hot-rolled carbon steel. Thus, a tri-linear material model, which can closely represent the stress-strain response of hot-rolled carbon steel, is introduced and incorporated into the CSM design framework. Maintaining the basic design philosophy of the existing CSM, new cross-section resistance expressions are derived for a range of hot-rolled steel structural section types subjected to compression and bending. The design provisions of EN 1993-1-1 and the proposed CSM are compared with experimental results collected from the literature and numerical simulations performed in this paper. Overall, the CSM is found to offer more accurate and consistent predictions than the current design provisions of EN 1993-1-1. Finally, statistical analyses are carried out to assess the reliability level of the two different design methods according to EN 1990 (2002). [ABSTRACT FROM AUTHOR]

Timber-concrete hybrid buildings are an innovative solution to increase the amount of timber materials used in modern buildings. This study presents a dynamic evaluation of a nine-storey timber-concrete hybrid residential building during construction. The building has an irregular shape and consists of three to seven storeys of cross-laminated timber (CLT) on top of two storeys of concrete. In order to study the influence of non-structural elements and a heavily increased slab load in construction, ambient vibration tests were conducted seven times during the 13-month construction period. The results show a clear decrease in the natural frequencies of the building as the building gets higher and more elements are installed. However, a slight increase in the natural frequency was observed following the installation of the non-structural walls in the final construction stage. A corresponding finite element analysis is presented for each test, providing additional insights into the parameters typically used in the structural design process. The study demonstrates the importance of properly selecting reduction factors for CLT elements in a dynamic finite element analysis. It also shows the importance of considering non-structural walls, both regarding weight and stiffness, even in buildings where the number of non-structural walls is relatively small compared to structural walls. • Modal properties of an irregularly shaped nine-storey timber-concrete hybrid building are presented. • AVTs were performed during construction, quantifying the influence of non-structural elements on the natural frequencies. • The in-plane shear stiffness of CLT walls significantly influences the dynamic response. [ABSTRACT FROM AUTHOR]

In the past decade, with a growing interest in long span bridge girders, designers are using an increasing number of prestressing strands. This scaling up has led to cracking issues in the end zone of narrow stemmed bulb-tees and I-girders, impacting the service life and possibly design capacities in case of excessive cracking. In a project funded by the Alabama department of transportation (DOT), a 180 ft long girder design was developed by modifying a standard Bulb-Tee girder and using a 10 ksi self-consolidating concrete mix. The new girder is 78 in. deep and has 66–0.6 in. strands. The impact of the draping angle and debonding on the end zone cracking was first evaluated using a 3 D finite element model (FEM) developed in ABAQUS. Subsequently, the critical stresses were monitored during the detensioning process of four 54 ft long full-scale girders with different end zone details. It was found that the combination of limiting the draping angle and debonding the strands resulted in minimizing the end zone cracking. The detailed FEA model which was developed is also verified using experimental field data. The results of this experimental and analytical investigation will be presented in this paper. [ABSTRACT FROM AUTHOR]

Since timber is a combustible material, its safe use in construction will depend on a proper knowledge and modelling of the physical and chemical reactions involved in the pyrolysis, that affect the temperature growth and thus the performance of timber in fire. Based on the comprehensive one-dimensional analytical models of the pyrolysis available in the literature, it is required to implement a predictive FE model via a user-defined subroutine in the dedicated commercial software in order to describe more closely the real physical phenomena that undergo timber exposed to fire. This paper presents the implementation of the UMATHT subroutine in the Abaqus software. The obtained results showed a fairly good agreement with experimental ones from the literature. However, at this stage of the study the pyrolysis is taken into account implicitly in the developed UMATHT through gradually modified thermo-physical properties of the timber, as commonly adopted in the published literature. Work is now in progress to implement explicitly the different reactions of the pyrolysis in the developed UMATHT. [ABSTRACT FROM AUTHOR]

• Cross-section response and design of stainless steel CHS and EHS at elevated temperatures are investigated. • Nonlinear shell finite element modelling was used to replicate the structural response of stainless steel CHS and EHS in fire. • Very large number of stainless steel CHS and EHS with various cross-section slendernesses were considered. • New cross-section design rules for stainless steel CHS and EHS under different loading conditions at elevated temperatures are established. • Accuracy, safety and reliability of proposed design rules are verified against very extensive numerical data. • Cross-section design rules proposed in this study furnish considerably more accurate and reliable ultimate cross-section resistance predictions for CHS and EHS at elevated temperatures relative to EN 1993-1-2. The structural behaviour and design of stainless steel circular hollow sections (CHS) and elliptical hollow sections (EHS) at elevated temperatures are investigated in this paper. Shell finite element models of stainless steel CHS and EHS are created and validated against experimental results from the literature, which are subsequently used to generate benchmark structural performance data. Parametric studies are performed on a large number of cold-formed and hot-rolled austenitic, duplex and ferritic stainless steel CHS and EHS subjected to (i) pure axial compression, (ii) pure bending, (iii) combined axial compression and bending and (iv) combined bending and shear at elevated temperatures; the studied cases comprise 24,495 stainless steel CHS and EHS in fire and cover a wide range of cross-section slendernesses and elevated temperature levels. Calibrated against the benchmark structural performance data obtained from the numerical parametric studies, new design proposals for predicting the cross-section resistances of stainless steel CHS and EHS in fire are put forward. The accuracy, safety and reliability of the new design proposals are assessed. It is shown that in comparison to the design provisions of the European structural steel fire design standard EN 1993-1-2, the proposed design methods provide more accurate and safe-sided cross-section resistance predictions for stainless steel CHS and EHS at elevated temperatures. [ABSTRACT FROM AUTHOR]

• A new residual stress model for S235 to S960 steel welded I-sections has been proposed. • Tests on HSS homogeneous and hybrid welded I-section columns buckling about the major axis have been carried out. • Numerical models have been established and validated against test results. • Numerical parametric studies have been performed considering different key parameters. • Current codified design rules on flexural buckling of welded I-section columns have been assessed. • A new design method has been devised providing more accurate and consistent flexural buckling resistances. The flexural buckling behaviour and design of homogeneous and hybrid welded I-section columns, considering a wide range of steel grades, are investigated in the present study. Residual stresses are first examined through the statistical analysis of 71 existing experimental results collected from the literature; on the basis of the findings, a new residual stress model for S235 to S960 steel welded I-sections is proposed. Experiments on a total of five pin-ended homogeneous (S690) and hybrid (S355 web and S690 flanges) welded I-section columns buckling about the major axis are then presented. In parallel with the experimental programme, finite element (FE) models were created and validated against the experimental results obtained from the present study, as well as those collected from the literature. The developed FE models were shown to be capable of accurately replicating the key experimental responses, and were then utilised to carry out extensive parametric studies, through which additional 6000 numerical column buckling data covering a wide range of steel grades, cross-section geometries and member slendernesses were generated. The combined experimental and numerical data were used to evaluate the accuracy of the flexural buckling design rules for welded I-section columns set out in the current European and North American design standards, where shortcomings relating to the consideration of steel grade were identified. A modified Eurocode 3 (EC3) method was devised to reflect the influence of yield strength on the buckling resistances of welded I-section columns more systematically and shown to provide substantially improved resistance predictions in terms of accuracy and consistency; the reliability of the modified approach was statistically verified following the procedure set out in Annex D of EN 1990 and is considered to be suitable for incorporation into future revisions of Eurocode 3. [ABSTRACT FROM AUTHOR]

This article studies the dynamic properties of a single span pedestrian timber bridge by in-situ testing and numerical modelling. The in-situ dynamic tests are performed at four different construction stages: (1) on only the timber structure, (2) on the timber structure with the railings, (3) on the timber structure with railings and an asphalt layer during warm conditions and (4) same as stage 3 but during cold conditions. Finite element models for the four construction stages are thereafter implemented and calibrated against the experimental results. The purpose of the study is to better understand how the different parts of the bridge contribute to the overall dynamic properties. The finite element analysis at stage 1 shows that longitudinal springs must be introduced at the supports of the bridge to get accurate results. The experimental results at stage 2 show that the railings contributes to 10% of both the stiffness and mass of the bridge. A shell model of the railings is implemented and calibrated in order to fit with the experimental results. The resonance frequencies decrease with 10–20% at stage 3 compared to stage 2. At stage 3 it is sufficient to introduce the asphalt as an additional mass in the finite element model. For that, a shell layer with surface elements is the best approach. The resonance frequencies increase with 15–30% between warm (stage 3) and cold conditions (stage 4). The stiffness of the asphalt therefore needs to be considered at stage 4. The continuity of the asphalt layer could also increase the overall stiffness of the bridge. The damping ratios increase at all construction stages. They are around 2% at warm conditions and around 2.5% at cold conditions for the finished bridge. • Longitudinal springs are required at the bridge supports to match the experiments. • The railings increase the stiffness and mass of the bridge equally much. • The asphalt is mainly an added mass at warm conditions (40 °C). • The stiffness of the asphalt must be considered at cold conditions (0 °C). [ABSTRACT FROM AUTHOR]

• The proposed inter-module joint connection method significantly reduces the joint size in modular construction. • Good prediction of bond strength by finite element analysis. • Effects of geometrical parameters on bond strength investigated through numerical analysis. • Simple charts and equations developed for the design calculations of the proposed joint connection method. In modular construction, the optimization of joint design has always been a major challenge. The joint size is primarily governed by rebar-concrete bond strength, as tensile stress is transferred from one lapped bar to the other through the concrete substrate. The complex mechanism of rebar-concrete bond degradation is dependent on both the property of the bonded interface and the damage of surrounding concrete. By virtue of its exceptional mechanical performance that contributes to the enhancement in rebar bond property, high-strength fiber-reinforced cementitious composites (HSFRCC) are often adopted in precast construction to locally replace conventional concrete in the joint area. In a previous study, the authors explored the application of HSFRCC in modular construction and developed a novel inter-module joint design. Based on the mechanical properties of the materials and the explicit geometry of the bonded interface, a 3D finite element model was introduced and showed good agreement with pull-out test results. Building on the preceding works, this paper aims to further validate the numerical model and demonstrate its general applicability using HSFRCCs with different steel fiber content. With the validated model, the effects of rebar bond length, HSFRCC cover thickness, and thickness of steel plate confinement on the bond performance are investigated in parametric studies, which establishes the basis for formulating a rational design approach for the proposed joint method. [ABSTRACT FROM AUTHOR]

• Reliable 3D finite element models are developed for FRP-confined concrete-encased cross-shaped steel columns (FCCSCs). • An in-depth understanding on the complex confinement mechanism of FCCSCs is achieved. • The effects of key parameters on the mechanism and behaviour of FCCSCs are thoroughly examined. Fibre-reinforced polymer (FRP)-confined concrete-encased cross-shaped steel columns (FCCSCs) are an emerging type of hybrid columns. In an FCCSC, the concrete is subjected to combined confinement from the steel section and the FRP tube, leading to an enhanced load capacity and excellent ductility of the column. While several recent experimental studies have demonstrated the excellent structural performance of FCCSCs, the complex confinement mechanism behind their structural behaviour has not been clarified or thoroughly examined. This paper presents a comprehensive study aiming to investigate the confinement mechanism of FCCSCs. In this paper, the experimental observations of FCCSCs are first summarized, followed by three-dimensional FE modelling of the columns. The FE models, after being verified against the test results in various aspects, are used for a systematic parametric study. In this study, the complex interaction between the three components of FCCSCs (i.e., FRP tube, steel section and concrete) is illustrated explicitly and the effects of key parameters (i.e., flange width, flange thickness, web thickness and FRP tube thickness) are examined separately and thoroughly, leading to an in-depth understanding of the confinement mechanism of FCCSCs. In particular, through the examination on the distribution of steel flange-to-concrete normal pressure, it is shown quantitatively that the variations of the dimensions of the steel section in a practically wide range have only marginal effects on its confinement to the concrete, while the increase of FRP tube thickness tends to reduce the confinement effect from the steel section. [ABSTRACT FROM AUTHOR]

In this paper, the shear resistance and design of stainless steel plate girders at elevated temperatures are investigated. A broad range of parameters influencing the structural response of stainless steel plate girders in fire are taken into account, considering (i) austenitic and duplex stainless steel grades, (ii) rigid and non-rigid end posts, (iii) different aspect ratios for the unstiffened portions of the plate girders, (iv) various web slendernesses and (v) different elevated temperature levels. The influence of these parameters on the behaviour of stainless steel plate girders at elevated temperatures is considered. Currently, there is an absence of specific design rules on the fire design of stainless steel plate girders in the European structural steel fire design standard EN 1993-1-2. Considering this, an accuracy assessment of the room temperature stainless steel plate girder design recommendations of the European structural stainless steel design standard EN 1993-1-4 applied with the elevated temperature material properties of stainless steel is performed. The results indicate that this approach leads to unsafe and scattered ultimate strength estimations for stainless steel plate girders in fire. New fire design recommendations for stainless steel plate girders that are in accordance with the existing design provisions of EN 1993-1-2 and EN 1993-1-4 are proposed. The accuracy and safety of the proposed new design recommendations are comprehensively verified against the results from nonlinear finite element modelling. • Structural response of stainless steel plate girders in fire is explored. • Ultimate resistances are determined through advanced nonlinear FE modelling. • New fire design rules for stainless steel plate girders are put forward. • In comparison to existing methods, proposed design rules lead to improved accuracy. • Verification of accuracy and reliability of proposed design rules is provided. [ABSTRACT FROM AUTHOR]

The behaviour and design of high strength steel (HSS) beams are addressed in the present study. Six in-plane three-point bending tests on three different welded I-sections − two homogeneous S690 steel welded I-sections and one hybrid welded I-section with S690 steel flanges and an S355 steel web, were first conducted. The beam tests were carried out in major axis bending and a bespoke restraint system was designed and employed in the test programme to prevent lateral-torsional buckling. Following the experimental investigation, a thorough finite element (FE) modelling programme was performed, which included a validation study confirming the accuracy of the developed FE models in replicating the flexural behaviour of HSS welded I-section beams, and a parametric study generating additional FE data on HSS welded I-section beams over a broader range of cross-sectional slendernesses, steel grades and loading configurations. The test results obtained in the present study and collected from the literature, together with the generated FE data from the parametric study, were used to evaluate the suitability of the current Eurocode 3 cross-section slenderness limits for HSS homogeneous and hybrid welded I-sections in bending. It is shown that the current Eurocode Class 2 and Class 3 slenderness limits are suitable for the classification of the outstand flange (in compression) and internal web (in bending) elements of both HSS homogeneous and hybrid welded I-sections subjected to major axis bending, while stricter Class 1 slenderness limits are considered necessary to achieve sufficient rotation capacity for plastic design. The findings from the present study indicate that plastic design can be used for HSS structures, provided the proposed stricter Class 1 slenderness limits are employed. [ABSTRACT FROM AUTHOR]

• Interaction between vibratory roller and ground is simulated via 3D finite element method considering soil-structure interaction. • The comprehensive dataset is utilised to correlate the predicted ground modulus via machine learning algorithm extended Support Vector Regression. • The proposed extended Support Vector algorithm with Gaussian kernel and Generalised Gegenbauer Kernel functions could predict the double-layered soil stiffness. • It was observed that selection of 40% of data for training was the optimum in terms of satisfying both accuracy and minimized computational time. Intelligent Compaction (IC) has been acquiring a growing interest in real-time quality control of compacted soil layers because of its high efficiency and full-area coverage. The current intelligent compaction technology allows the determination of the uniformity level of compaction over large areas according to the dynamic response of the roller. However, accurate real-time determination of the soil modulus during compaction based on roller acceleration has been challenging due to the multi-layered composite nature of the soil and the nonlinearities of the governing dynamic equations of motion and soil response. This study adopts a double-layered soil profile, and a three-dimensional finite element model, accounting for soil-drum interaction, is utilised for the analysis. The isotropic hardening elastoplastic hysteretic model was implemented to simulate the soil behaviour subjected to cyclic loading ranging from small to large strain amplitudes and account for stiffness degradation. The comprehensive dataset composed of the roller acceleration response and ground characteristics is then used to correlate the predicted soil modulus via an advanced machine learning approach. The adopted machine learning method incorporating Gaussian Kernel and Generalised Gegenbauer Kernel functions can reasonably predict the double-layered soil modulus during roller compaction. Additional analyses were conducted to observe the proper training size and number of iterations to achieve real-time quality control to be used by site engineers. Furthermore, the influences of the relative modulus ratio, drum length and top layer modulus on the soil surface dynamic displacement are discussed. [ABSTRACT FROM AUTHOR]

• 15 hybrid welded T-section stub columns were tested under axial compression. • Material properties and residual stresses were measured. • Numerical models were developed. • Extensive parametric studies were carried out. • Design codes and design approaches of DSM and CSM were evaluated and compared. Comprehensive experimental and numerical investigations on hybrid T-section stub columns under compressive load were performed and are presented in this paper. The hybrid welded T-section stub columns comprise high strength steel Q690 flange and normal strength steel Q355 web. Material property studies were implemented through tensile coupon tests. Residual stress in membrane type was measured and recorded and its impact on structural performance was also assessed. Initial local geometric imperfection measurements were conducted for all the specimens. In conjunction with experimental studies, numerical investigation was performed to generate more test specimens extending the range of cross-section dimensions by which test data pool can be supplemented. The Eurocode of EN 1993-1-1, EN 1993-1-5 and EN 1993-1-12, the North American code of ANSI/AISC 360-16 and the Australian code of AS 4100 together with design approaches of Direct Strength Method and Continuous Strength Method were examined for its applicability for cross-section classification and compression resistance predictions of hybrid T-sections. Overall, the current specified limits were applicable for hybrid welded T-section and strength predictions from design codes were comparatively consistent and reliable. Strength predictions from Direct Strength Method and Continuous Strength Method were relatively appropriate though overly conservative predictions were provided for cross-section with large slenderness. In this study, modifications on the Direct Strength Method and Continuous Strength Method are proposed, which is shown to provide accurate predictions at cross-sectional level in a reliable manner. [ABSTRACT FROM AUTHOR]

• A refined finite element model for screw connections is proposed. • The pull-out strength and the thread pitch are negatively correlated. • The failure modes are divided into screw hole extrusion and thread shear failure. • The evaluation results reveal that current design formulas are conservative. • The trend of values predicted by a reference is consistent with theoretical line. Screw connections have been extensively used in cold-formed steel constructions due to convenient construction and high capacity. However, little attention has been paid to the pull-out performance and parametric effects of screw connections. In this paper, the pull-out performance of screw connections is experimentally and numerically investigated. The objective of this study is to develop a refined finite element (FE) model that can be used to parametrically analyze the pull-out performance of screw connections. Eight sets of experimental results are selected for comparison with the FE results to validate the accuracy of the FE model. Based on the validated FE model, parametric analyses of the main variables in screw connections are conducted to discuss the effects of the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness on the pull-out performance of screw connections. The results indicate that the failure modes of specimens are mainly classified into screw hole extrusion and thread shear failure. It is also found that the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness have significant effects on the pull-out resistance of screw connections. Particularly, the numerically obtained pull-out resistance are used to assess the accuracy of the codified design rules for screw connections, as given in the Chinese Code, North American Specification, British Standard and European Norm. The evaluation results reveal that the current design formulas are relatively conservative. The formula proposed by one referenced paper is insecure, while the distribution trend is basically consistent with the straight line of P S / P FEM = 1.0 (the ratio of the calculated values to the FE values is equal to1.0), therefore, it can be used as a good reference for calculating the pull-out resistance of screw connections. Besides, the modified design formula in this study has good applicability. [ABSTRACT FROM AUTHOR]

The assessment of the structural resistance of historical metal structures involves a depth understanding of many factors, such as the properties of the constructions materials and the structural behaviour of the connection mode. Available information regarding the behaviour of historical riveted connections is quite limited and more information about the residual strain and stress state is still needed in order to allow the preservation of these existing structures. This paper deals with the assessment of stress and strain field which exist around the rivet hole due to the hot riveting process. Experimental specimens were manufactured with riveting technique used in aged metal bridges and different metallic materials for the joined plates were considered. Strain and thermal measurements were done during and after the overall riveting process. The results of the experimental investigation allowed the assessment of the residual strain state and the thermal response of the riveted joint. The experimental results were then used for validation of a 2D axisymmetric model. On the basis of the results obtained, the pre-stress state can be evaluated as well as the stress concentration areas where fatigue cracks may initiate. Thus, the provide findings constitute a supportive tool for further studies regarding the assessment and rehabilitation of historical riveted structures. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective load-displacement relationships as well as the failure modes. The calibration of the numerical model (finite element method) was carried out based on the experimental results. Within this framework, a micro-modelling approach was considered. The behaviour of the rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between the layers. Although the numerical results achieved a satisfactory agreement with the experimental results a sensitivity analysis of the parameters involved was performed. The sensitivity analysis aimed at determining which parameters of the model have a significant impact in the model’s results. As expected the sensitivity analysis pointed out that the sliding failure occurrence is mainly influenced by two parameters of the interface elements: the interface tensile strength f i t and the friction angle φ. Moreover the cohesion c and the layers thickness showed a limited effect on the shear behaviour. It should be noted that the results mentioned above are related to the cases where a significant level of vertical compressive stress σ is employed. [ABSTRACT FROM AUTHOR]

Timber has been widely used all over the world as a structural material. The defects such as knots could significantly reduce the mechanical properties of timber, thus significantly affecting the performance of timber structures. Existing studies have demonstrated the ability to use fibre reinforced polymer (FRP) composites to increase the strength, stiffness and the ductility of glulam beams. Such strengthening however, often becomes uneconomical due to higher FRP material volume and the use of expensive FRPs such as carbon FRP and glass FRP. Oppose to current approaches of strengthening glulam beams using FRPs, use of minimal amount of FRPs to reinforce weaker sections, thus reducing the variability and resulting in a higher load carrying capacity, may provide better economical solutions. In addition, the use of cost effective FRPs such as basalt FRP could further reduce the costs. This paper presents an experimental and theoretical investigation aimed at understanding the behaviour of BFRP-strengthened timber sections. The experimental component of the study presented consists of 54 tensile specimens with and without BFRP. In some of the specimens, holes were cut in the mid span to simulate a defect. The experimental study showed that BFRP increases both the strength and stiffness of the timber specimens. Findings of an FE study of BFRP-strengthened timber specimens are also presented. Stress and strain distributions of the specimens, obtained from the FE study are presented and discussed. Based on the findings of the FE study, and idealized strain distribution is presented. This idealized strain distribution was then used to develop analytical models for an equivalent elastic modulus of the regions with defects. In addition, analytical models are also presented to predict the ultimate load carrying capacity of the pure timber and BFRP-strengthened timber specimens. The predictions agreed well with the experimental results. The analytical models were then used in Monte Carlo simulations to demonstrate the effectiveness of the BFRP strengthening. It was found that BFRP could yield significant benefits in terms of increasing the strength and stiffness for the timber sections with defects. [ABSTRACT FROM AUTHOR]

In the presented paper, the creep of steel spiral strands with a construction of 1 × 7 and 1 × 19 round wires subjected to constant axial loads is studied numerically. The principal aim of this contribution is to define and describe a novel design computational tool for the numerical simulation and prediction of creep strains in spiral strands. For this purpose, finite element models are developed using ANSYS software. Wires of the strands are modelled using 3D geometrically nonlinear beam elements. An approach is based on the Timoshenko beam theory and Saint Venant torsion theory. The wire material is both linearly elastic and isotropic. Creep strain of strands is caused by the creep strain of wires due to the tensile load acting on them and by extension due to the construction of the strand when the strand is tightened. The constitutive creep equations of wires and selected initial clearances between wire layers are incorporated into the finite element models. The models are set up and calibrated on the basis of data obtained by the creep tests. In principle, the required functionality and performance have been implemented in the software and a good agreement with test results has been obtained. [ABSTRACT FROM AUTHOR]

A self-centering concrete wall system has been developed that consists of a Precast Wall with End Columns (PreWEC). A finite element model was developed to investigate the cyclic lateral-load response of the PreWEC system that included allowance for uplift at the wall-to-foundation interface, inclusion of the energy dissipating O-connectors, and inelastic behaviour of the confined concrete in the toe of the wall. The model showed good correlation with the results of a large-scale experimental test of the PreWEC system for both the global and local responses, closely matched the experimental lateral force–displacement response, unbonded tendon stress, neutral axis depth, concrete compressive strains, and connector deformation. Additional analyses were conducted to investigate modifications to the PreWEC design. These modified designs highlighted the influence of the inelastic behaviour of the wall toe and showed that in the PreWEC system the axial load on the wall panel is independent of the number of energy dissipating connectors. Lastly, analyses were conducted to investigate wall-to-floor interaction with the PreWEC system. It was shown that a rigid wall-to-floor connection would result in some damage to the floor diaphragms and an overstrength that should be considered when designing the wall for shear. Alternatively, connectors could be used with the PreWEC system to isolate the floor from the uplift of the wall and eliminate damage to the floor diaphragm. [ABSTRACT FROM AUTHOR]