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In this paper, a novel equilibrium-based form-finding approach for a mega-latticed structure is presented based on vector-based 3D graphic statics and the Combinatorial Equilibrium Modelling (CEM). This approach can be effectively applied to the conceptual design phase of the structures with various design objectives under conservative loads. It allows us to adjust the design parameters in real time during the design phase and to obtain the resultant forms immediately. Based on a certain selection strategy, the forms have a better state of internal membrane forces compared to the original spherical structure. An ANSYS Parameter Design Language (APDL)-based automatic geometric modelling method for mega-latticed structures with various surface forms is developed. The proposed method solves the problem that the existing modelling methods are only available for spherical structures. It is highly applicable for modelling mega-latticed structures with spherical, cylindrical, and other heterogeneous surfaces. Furthermore, a complete design workflow that combines the proposed form-finding approach (for conceptual design), the automatic geometric modelling method (for transformation), and the finite element method (for deepening design and analysis), is discussed. This paper provides a reference for the design of mega-latticed structures and similar truss-based spatial structures. • A new equilibrium-based form-finding approach for a mega-latticed structure is proposed. • An automatic geometric modelling method for mega-latticed structures is improved. • A design workflow combining the form-finding approach and finite element method is discussed. • A case study is performed to verify the validity of the whole structural design process. [ABSTRACT FROM AUTHOR]

This paper is concerned with the behaviour of square concrete-filled dual-stiffened steel tubular (CFDSST) slender columns with a concentrically-placed inner circular steel tube. Previous studies have illustrated that these columns have greater structural performance in terms of load-carrying capacity compared with conventional concrete-filled stiffened steel tubular (CFSST) columns. However, the behaviour of CFDSST slender columns filled with ultra-high strength concrete (UHSC) has not been investigated and current design codes do not include provisions for UHSC, although it is increasingly popular owing to demands for structures to be lighter and more sustainable. Accordingly, the current paper fills that gap in existing knowledge and explores the behaviour of CFDSST slender columns using finite element (FE) analysis. The available test results from previous studies were collated and are employed to validate the numerical model. The validated FE model is then employed to investigate the axial load versus deflection responses for a wide variety of UHS-CFDSST slender columns. The behaviour of both intermediate-length and long columns is assessed through parametric analyses. The results of these studies show that the strength of the concrete sandwiched between the two steel sections, the yield strength of outer steel tube, and the outer tube slenderness ratio have a significant effect on the axial resistance of UHS-CFDSST intermediate-length columns, while the capacity of long columns is most affected by the sandwiched concrete strength. The ultimate resistances are compared with different available design methods, and AISC 360–16 code is recommended for predicting the ultimate resistance of UHS-CFDSST slender columns with modifications proposed to account for the different components forming this innovative cross-section. • New research is presented on the behaviour of square concrete-filled dual-stiffened steel tubular (CFDSST) slender columns. • Ultra high strength concrete is employed for the infill, for the first time. • An advanced finite element model is developed and validated. • The behaviour of intermediate-length and long columns is assessed by parametric analyses and reliable design is proposed. • The results show the potential of these sections to offer innovative structural solution for heavily loaded scenarios. [ABSTRACT FROM AUTHOR]

To address two main challenges (excessive mid-span deflections and numerous cracks in the main girder) in long-span prestressed concrete (PC) box-girder bridges, this paper proposes a long-span simply-supported UHPC box-girder bridge. In comparison to conventional PC box-girder bridges with three-dimensional prestress, the proposed UHPC box-girder consists only one-dimensional (longitudinal) prestress, and the thickness of the bottom/top plate and web of the UHPC box-girder are relatively thin and are strengthened with dense diaphragms and stiffening ribs. The 4th Beijiang River Bridge adopts this type of bridge with a span of 102 m, which is the longest span simply supported prestressed UHPC box-girder highway bridge in the world. Considering the fact that the thickness of the top plate of the UHPC box-girder is relatively thin (only 20 cm) and the transverse prestress is removed from the top plate, thus, under the direct action of wheel loads, the risk of bridge deck cracking may correspondingly increase. To investigate the mechanical behavior of the deck system of UHPC box-girder bridges, a 1:2 scaled experimental specimen associated with the field bridge is tested. The mechanical behavior of the new deck system is investigated and discussed. It is found that because the support strength of the stiffening rib is significantly weaker than that of the web, the UHPC deck slab should still be regarded as a two-way slab rather than a one-way slab in the elastic stage. In addition, although the test load location is unfavorable to the UHPC deck slab and the first crack appears on the UHPC deck slab, this deck system finally suffers from bending failure of the transverse rib. Furthermore, finite element analysis is carried out to study the mechanical behavior of this new deck system. Parametric analysis considers some factors including the reinforcement ratio in the transverse rib, the height of the transverse rib, and the space between transverse ribs. The results provide a good reference for design and optimization in the new deck system of UHPC box-girder bridges. • Proposing a long-span simply-supported prestressed UHPC box-girder bridge. • Stress mode of proposed bridge's deck system is analyzed under line-elastic condition. • The mechanical behavior of the new deck system of UHPC box-girder bridges have been experimentally conducted. • The corresponding structural responses are numerically investigated based on finite element analysis. [ABSTRACT FROM AUTHOR]

The triangular strand wire rope exhibits superior performance and holds substantial potential over its round strand counterpart, which is brought by its unique and excellent structural design. However, the investigation of specialized strand components with such distinctive shapes remains limited, and the predominant challenge resides in modeling. This paper introduces a precise vector expression for the spatial trajectory of distinct steel wire types within the triangular strand wire rope structure. Moreover, a comprehensive suite of parametric modeling methodologies tailored for finite element analysis have been established, based on ABAQUS/CAE. The finite element model has been validated by experiments. Furthermore, a series of examples with various boundary conditions and parameters are intended to evaluate the factors affecting the accuracy of the FE model. Employing the established parametric modeling method, triangular strand wire ropes with a range of lay length were established, the differences in their mechanical properties under tensile load were compared, yielding insights that form the basis for proposed design considerations regarding lay length ratios. This model is apt for investigating the macroscopic mechanical response and local force characteristics of triangular strand wire ropes during typical service processes. Moreover, its versatility extends to the realm of other complex rope structures, promising to address the behavioral analysis of intricate strands and rope configurations. [Display omitted] • A new spatial structure expression for triangular strand wire rope was developed. • The mechanical characteristics of triangular strand wire rope were obtained. • The influence of lay length on the performance of the wire ropes was compared. • Optimum structural parameters for various wire rope can be designed by the FE model. [ABSTRACT FROM AUTHOR]

Concrete-filled corrugated steel tubular (CFCST) column is a novel type of steel-concrete composite column, comprising four corrugated steel plates, four square-section steel bars at the corners, and infilled concrete. The transversely placed corrugated steel plates can effectively prevent their premature local buckling, release the axial load, and provide lateral confinement effects on the infilled concrete. This paper investigated the axial compressive behavior of CFCST columns through experimental, numerical, and theoretical approaches. Experiments were conducted on 20 specimens, focusing on their axial load-resistant behavior. The specimens demonstrated excellent axial bearing capacity, ductility, and residual bearing capacity. Besides, the mechanical behavior of corrugated steel plates throughout the loading process was analyzed through the development of the horizontal and vertical strains. Furthermore, a finite element (FE) model was developed to simulate the axial compressive behavior of CFCST columns, which was validated against the experimental data. The FE model was used to analyze the compressive behavior of each part in CFCST columns, revealing that the infilled concrete and steel bars primarily bear the axial load, while the corrugated steel plates mainly provide lateral supports to the infilled concrete. Finally, a simplified method for calculating the critical width of corrugated steel plates and a formula for the axial bearing capacity of CFCST columns were proposed. It was indicated that the limiting width-to-thickness ratio of the corrugated steel plates was larger than that of the steel elements in conventional CFST columns. These formulas were demonstrated to be accurate enough and suitable for the engineering designs. • Axial compression tests involving 20 CFCST columns were performed. • Finite element models were developed and validated against test results. • The mechanical behavior of each part of the CFCST column was analyzed in detail. • A theoretical analysis was conducted to determine the critical width of the corrugated steel plate. • Theoretical formula of the axial bearing capacity of the CFCST columns was proposed. [ABSTRACT FROM AUTHOR]

Being critical components in composite structures, the short-term structural behaviour of stud shear connectors has been extensively investigated. Despite this, there has been somewhat limited attention devoted to their time-dependent behaviour. In this paper, the results of four long-term push-out tests are reported: the test parameters including the loading age and stud diameter. The test results are shown to be simulated accurately by a finite element model established using ABAQUS, in which the long-term behaviour of the concrete is considered by implementing a stepwise approach. The numerical procedure is applied to conduct a parametric analysis, with the effects of different parameters, viz., the loading age, concrete material, external environment, stud size and reinforcement ratio being considered. Based on the numerical results, an analytical formulation is derived for the creep coefficients of composite members with different loading ages. Comparisons with FE model data shows that the derived equation has sufficient accuracy and can be applied for designing composite structures considering their long-term response. • Tests of stud connections under sustained loading; • Significant creep slip of the connection found during the tests; • Creep model of stud connection proposed for analysis of composite structures. [ABSTRACT FROM AUTHOR]

Although extensive experimental and numerical studies have been conducted on the axial performance of steel tube and sandwiched concrete jacketed CFST columns, contableurations with outer square tubes and inner circular CFST components are rarely found. This paper investigates the axial performance of square steel tube and sandwiched concrete jacketed circular CFST columns, examining the effects of outer steel ratio and sandwiched concrete strength on failure patterns, relative load-strain curves, and load-bearing capacity. The analysis of ultimate compressive capacity confirmed the effective confinement provided by the outer square steel tube. Based on the experimental results, a finite element model was established to further study the working mechanism of retrofitted columns. The load on components, distribution of longitudinal stress and transverse constraint stress on concrete revealed that the inner concrete experiences dual confinement effects from both inner and outer steel tubes, with the constraint of the outer square steel tube becoming significant only during the load dropping phase. Furthermore, a simple equation was proposed for predicting the axial compressive load-bearing capacity of retrofitted columns using superposition methods and design codes. Comparison results demonstrated good agreement between experimental and calculated values. • The axial performance of circular CFST columns strengthened with square steel tube and sandwiched concrete jackets was investigated. • The outer tube thickness had a greater impact on the compressive strength of retrofitted columns compared to the sandwiched concrete strength. • A finite element model was established to study the force mechanism of axially-loaded circular CFST columns strengthened with square STSCJ. • An equation was proposed to calculate the axial compressive capacity of retrofitted columns based on the superposition methods and design codes. [ABSTRACT FROM AUTHOR]

This paper studied the seismic behavior of a novel self-centering concrete-filled steel tubular column-steel beam (SCSTCSB) joint. The restoring force was provided by the post-tensioned tendons arranged in the CFST columns. Cyclic loading tests were performed on five 1/3 scaled specimens by varying the parameters of steel tendon type, concrete strength (f c), and axial compression ratio (n). The failure modes, hysteresis behavior, stiffness and strength degradation, energy dissipation, post-tensioned tendons response, residual deformation, and strain distribution were studied in detail. The finite element models were established to capture the stress distribution of the joints. In addition, parameter analysis was performed by expanding 17 finite element models. The results show that the ratio of residual deformation to beam rotation angle of the specimens ranged from 0.068 to 0.172. And the proposed joints demonstrated excellent self-centering ability. The self-centering (SC) performance of joints with ordinary steel tendons was better than that of joints with high-strength steel tendons. With the increase of n , the SC performance of the joints intensified at the lower ratio (n from 0.1 to 0.3) and weakened after n = 0.3. The flexural capacity of the joints improved with the increase of axial compression ratio (n), width-thickness ratio (D / t), diameter of steel tendons (d), and assembly part strength (f y,a). • The seismic behavior of self-centering CFST column-beam joints with PT tendons arranged in column was investigated under cyclic loading. • Ordinary steel tendons exhibited better results than high-strength steel tendons in self-centering (SC) performance. • With increase of axial compression ratio, the SC performance of joints intensified at the lower ratio (0.1-0.3) and weakened after n = 0.3. • The flexural capacity of the joints increased with increasing axial compression ratio, concrete strength, diameter of steel tendons and assembly part strength. [ABSTRACT FROM AUTHOR]

Highlights • First, a new type of buckling restrained brace (BRB), namely, an all steel assembled Q195 low yield point buckling restrained brace (LYBRB), is proposed in this paper. • Second, to prevent residual stress, water cutting is used when cutting the core plate. • Third, more comprehensive seismic performance indices of the LYBRB is analyzed. Abstract A new type of buckling-restrained brace (BRB), namely, an all-steel assembled Q195 low-yield-point buckling-restrained brace (LYBRB), is proposed in this paper. The difference between the LYBRB and a traditional BRB is that Q195 low-yield point steel with an in-line cross-section (which can better absorb seismic energy) of the core material is adopted. A Q235 steel core is used for the comparative analysis. Additionally, to prevent residual stress, water cutting is performed to cut the core plate. A quasi-static low-cycle reciprocating load test is conducted to determine its failure mode, hysteretic response and restoring force model. The seismic behavior of the LYBRB is evaluated according to the following performance indices: the hysteresis curve, skeleton curve, tension and compression nonuniform coefficient, energy dissipation coefficient, equivalent viscous damping ratio, plastic deformation performance, and in-plane and out-of-plane lateral displacements of the external restraining plate of the LYBRB. The failure mode of the LYBRB is tension-controlled; its hysteresis curve shows good symmetry, stability and fullness; and its energy dissipation capacity support is better. Combined with the restoring force model obtained via an experiment, the bilinear kinematic hardening model is adopted to conduct finite element (FE) numerical simulation analysis of the core plate. Comparison with the test results shows that both the failure mode and the hysteretic response are in good agreement. The influence factors (such as the gap-thickness ratio between the core plate and external restraining plate, width-thickness ratio, core material properties and slenderness ratio of the core plate in the weak-axis direction for the LYBRB) are then used to carry out a parametric analysis to provide better insight into the LYBRB. [ABSTRACT FROM AUTHOR]

• This paper applied the lightweight aggregate concrete (LWAC) into partially encased steel-concrete composite (PEC) stub columns. • The axial compression test was conducted to explore the work properties of partially encased steel-concrete composite stub columns with LWAC. • The finite element models of the PEC-LC column were established to conduct a systemic parametric investigation. • The axial strength calculation method of PEC-LC columns was proposed considering the flange strength reduction and core concrete enhancement. This paper applied lightweight aggregate concrete (LWAC) in the partially encased steel-concrete composite (PEC) stub columns to achieve the advantages of lightweight and easy assembly. A total of 8 axial-loaded specimens were tested to explore the effect of concrete type, concrete strength, link spacing, longitudinal rebars, and height-to-width ratio on the compressive behavior of the partially encased steel-concrete composite stub columns with lightweight aggregate concrete (PEC-LC). Then, the finite element models of PEC-LC columns were established to conduct a systemic parametric investigation. The results demonstrated that the PEC-LC column experienced failure due to concrete crushing and local buckling of flanges, similar to the PEC column. Compared to the PEC column, the PEC-LC column exhibited a similar load-bearing capacity but poorer post-peak compressive performance, which could be improved by closer link spacing. Consequently, applying LWAC to reduce the self-weight of prefabricated members is a feasible option. Besides, the contact stress and the stress distribution at typical cross-sections were analyzed to reveal the confinement effect of H-shaped steel and links on the filled LWAC. Finally, A calculation method for estimating the axial compression capacity of the PEC-LC column was proposed, taking into account the reduction in flange strength and enhancement of core concrete. The accuracy of the calculation method was verified by comparison with experimental and numerical data. Overall, this research serves as a valuable reference for promoting the adoption of the PEC-LC column in assembled structures. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study and nonlinear finite element analysis (NLFEA) using the FE ANSYS© code modelling the composite effect of stirrups and steel fibres on the shear behaviour of reinforcedconcrete beams. To achieve this objective, fifty-eight (58) steel-fibre-reinforced concrete (SFRC) beams made of normal-strength concrete (NSC) and high-strength concrete (HSC) with and without stirrups were tested under bending and subjected to two concentrated and symmetrical loads using digital image correlation (DIC). The main test variables were concrete compressive strength (C30 and C60 MPa), stirrup aspect ratio (0 % and 0.56 %), steel fibre volume fraction (0 %, 0.5 %, 1 %, 2 % and 3 %) and steel fibre aspect ratio (l f /d f of 65 and 80). The experimental results show that the shear capacity of SFRC beams increases significantly as the percentage of steel fibres increases. The combination of stirrups and steel fibres can change the failure mode of the beams from brittle by shear to ductile by bending. The shear behaviour of SFRC beams without stirrups is similar to, and sometimes better than, that of SFRC beams with stirrups, suggesting the possibility of replacing stirrups with steel fibres in sufficient quantities. The measured shear strength is compared with the theoretical values obtained from the models available in the literature, and the correlation is satisfactory. Acceptable agreement was also found between the experimental and NLFEA results for the first diagonal crack load and ultimate load. The predicted FE values for the steel-fibre orientation factor of 0.45 are in agreement with the experimental values. • The addition of steel fibres does not improve the compressive strength of high strength concrete (HSC), but it does improve the ductility of this material. • The failure mode of HSC changes from sudden and explosive to ductile behaviour. • The addition of steel fibres improves the tensile strength of normal strength concrete (NSC) and HSC, especially when the steel fibres have a higher aspect ratio. The improvement in this mechanical property is not proportional to the volume fraction of steel fibres added. • The failure mode of the tested beams changes from shear to flexion in the series of beams with stirrups and with steel fibres, and in the series of beams without stirrups and with sufficient amounts of steel fibres (ρ f > 1 %), and the ultimate load is improved. • The shear behaviour of the steel fibres reinforced concrete (SFRC) beams without stirrups is similar to that of SFRC with stirrups, and sometimes better, when the steel fibres are used in higher quantities (ρ f > 1 %), which shows that the replacement of stirrups by steel fibres in the RC beams does not have a negative effect on the shear behaviour. • The experimental results for the ultimate shear strength of the fibres reinforced HSC beams without stirrups (FHB-S0) are similar to the theoretical values predicted by the different models used to estimate the contribution of the concrete and the steel fibres to the shear capacity of the beams. • The contribution of the stirrups is overestimated by the model proposed in Eq. (6) because it is based on the yielding of the stirrups, which is not observed in the failure of the tested beams. • The numerical FEA presented in this study is able to reproduce the flexural response of the RC beams (with or without stirrups) observed experimentally, with all types of concrete, with an acceptable degree of accuracy. It is also found that the numerical models based on the FEA approach produce higher values than the experimental models. Furthermore, when the value of the steel fibre orientation factor is 0.45, close agreement is obtained between the measured experimental data and the FEA prediction of the first diagonal crack load and ultimate load results. [ABSTRACT FROM AUTHOR]

This paper presents a new and accurate finite element contact-modeling approach, to predict the axial compressive behaviour of bare cold-formed steel (CFS) lipped-channel sections (studs) set in tracks under concentric, static axial compressive loading. Detailed finite element analysis (FEA) models of the stud-track assemblies are developed using the ABAQUS software. The new modeling approach is validated against test results and captures stud-to-track gap and contact normal behaviour, which significantly influences studs' axial compressive performance. Hard contact (HC) has been used widely in literature for its simplicity, although it overestimates axial structural stiffness. Two softened pressure-overclosure relationships, with linear (LSC) and piecewise linear (PLSC) functions, were investigated for the first time in axially loaded bare CFS studs. PLSC best-replicated studs' axial-compressive behaviour, post-peak response, and failure mechanism under track boundary conditions. PLSC slightly overestimated the axial stiffness by 1 %, underestimating axial shortening and ultimate capacity by 3 % and 6 %, respectively. HC significantly overestimated the axial stiffness by a factor of 3, with a 5 % overestimation of ultimate capacity. LSC failed to predict the accurate failure mechanism for studs having gauge thicknesses less than 3 mm. PLSC scale factors were established and were found to be closely correlated with studs' non-dimensional slenderness (λ), following bilinear relationships. New predictive equations were developed to determine the PLSC scale factors for λ ranging between 0.49 and 1.2 to enable designers to use accurately calibrated models to capture bare studs' complex axial compressive behaviour in the elastic and inelastic range. • Axial compressive contact modeling of bare cold-formed steel studs set in track. • Studied two softened pressure overclosure relations: Linear (LSC) and Piecewise linear (PLSC). • Compared softened contact results with hard contact (HC) and forty-two test data. • PLSC captured the most accurate peak load, axial stiffness, and failure mechanism. • Proposed novel bilinear equations to determine accurate PLSC scale factors. [ABSTRACT FROM AUTHOR]

The steel bridge system referred to as Simple for Dead Load and Continuous for Live Load (SDCL) has gained popularity in non-seismic regions of the United States of America. The system provides enhanced service life and lower inspection and maintenance costs as compared to conventional steel systems. To-date, no research studies have been carried out to evaluate the behavior of the SDCL steel bridge system in high seismic regions. The SDCL concept for seismic regions requires a suitable connection between the girder and pier. The research presented in this paper investigates an integral pier SDCL steel bridge system. The structural behavior and force resistance mechanism of a proposed seismic detail was evaluated through an analytical study. An equation was developed to predict the ultimate connection capacity under seismic loading. This paper presents the results of Phase I of an ongoing, three-phase effort, that will culminate in the development of a set of details and associated design provisions to develop a version of the SDCL steel bridge system suitable for use in high seismic regions. [ABSTRACT FROM AUTHOR]

Concrete production and construction are responsible for a considerable share of the total carbon emissions annually. With the emerging need to cut carbon emissions from the construction sector, there has been a big interest in optimising the embodied carbon of superstructures. However, limited attention is given to optimising the embodied carbon of foundations as most designers are more interested in addressing the optimal foundations cost instead. For the first time in the open literature, this paper presents a generic genetic-algorithm-based tool to optimise the design of reinforced concrete piles. The algorithm is capable of allocating the optimal design parameters and geometry for reinforced concrete piles at any given soil conditions and required pile capacities. The algorithm is used to compare the environmental impact of different concrete pile types; solid cylindrical piles, hollow cylindrical piles, solid tapered piles and hollow tapered piles at different load capacities, the optimisation results are then compared to common industrial pile designs to quantify the possible carbon and material savings. Results show that a significant cut of more than 70% of the embodied carbon values can be achieved if the optimal pile type is used compared to common industrial design. Moreover, a finite element model built and validated over ABAQUS is used to compare the geotechnical performance of the different pile geometries. Finite element analysis results show a negligible difference between the stiffness of the different pile types when tested in the same soil conditions highlighting an outstanding optimisation efficiency of the proposed optimisation tool. [Display omitted] • A novel pile optimisation algorithm is proposed. • The embodied carbon of different pile geometries is compared. • A finite element model is presented to compare the different piles' stiffnesses. • Optimal pile geometries can save up to 70% of the carbon emissions compared to common pile designs. [ABSTRACT FROM AUTHOR]

To explore a cost-efficient bridge structure system and expand the options for long-span bridges in mountainous regions, we propose an innovative cable-stayed deck arch (CSDA) bridge with significant potential benefits. This paper discusses the conceptualization, structural design considerations, and implementable construction methods of this bridge-type. We trial designed two CSDA bridges with span arrangements of 268 + 350 + 268 m and 280 + 3 × 380 + 280 m to demonstrate the versatility of our proposal in different topographic situations and its ability to accommodate both single and multiple main spans. The finite element analysis confirms the mechanical properties and structural feasibility of the conceptual designs. A comprehensive comparison with other types of bridges under identical conditions reveals that this new hybrid bridge is not only lightweight in structure, excellent in performance, and elegant in form, but also cost savings and with minor environmental impact. The preliminary study indicates that the CSDA bridges are suitable for the construction demand of high-rise pier and long-span bridges in mountainous terrain, and also an economical option for the main span between 350 to 400 m. • An innovative cable-stayed deck arch bridge is proposed, taking into account the design considerations and construction methods. • The bridge type accommodates different hilly terrain conditions and can be arranged with either single or multiple main spans. • The cable-arch load ratio is derived analytically and has proved the rationality of the structure system. • The proposed bridge exhibits excellent structural performance and other advantages. [ABSTRACT FROM AUTHOR]

• Interaction stresses and load deformation histories of each component were studied. • Parameters effect on confining stress and infill concrete strength were discussed. • The constitutive models of infill concrete and stainless steel tube were proposed. • The fiber element models using proposed models were verified. • The international design codes were assessed and new design equation was proposed. Concrete filled double-skin tubular (CFDST) stub column with outer stainless steel circular hollow section (CHS) and inner carbon steel CHS is presented in this paper. It combines the strength of stainless steel, concrete and carbon steel, and also provides the stainless steel's durability, ductility and corrosion resistance properties along with the lighter weight due to the sectional feature. Finite element analysis (FEA) is done in this paper and the developed FE models are verified with the available test results on the basis of failure modes, full load-deformation curves and ultimate strengths of the specimens. Afterward, a series of parametric analysis are conducted to investigate the structural performance of each component and the overall column as well as the confining stresses between the tubes and concrete. In addition, the effect of stainless-steel grade, concrete strength, carbon-steel strength, diameter-to-thickness ratio of outer tube, diameter-to-thickness ratio of inner tube and hollow ratio on confining stress and mechanical property of sandwiched concrete is studied. The constitutive models of sandwiched concrete and outer stainless steel tube under plane stress are proposed. Based on these proposed models, the fiber element model is used to predict the mechanical properties of this composite column and then checked with the finite element modelling (FEM) outputs. Different design methods such as ACI code, European code, continuous strength method (CSM), Han et al. method and Nie et al. method are assessed to evaluate the applicability and accuracy. Finally, a new design method for calculating the ultimate bearing capacity of the CFDST stub column is proposed, which exhibits good agreement with the results of the FEA. [ABSTRACT FROM AUTHOR]

Prestressing is a viable and effective technique used in concrete structures that allows the improvement of their performance. Its efficiency depends on the layout of the tendons, understood as the number of strands, their profile, curvature, and eccentricities. Layout design is a laborious and usually iterative trial-and-error process that aims to ensure that stress limits are not exceeded while, on the other hand, to minimize the total weight of prestressing steel. To automate the process, this research presents a novel genetic algorithm and a machine learning-based approach with a parametrically defined geometry of a tendon consisting of straight lines and circular arcs. The paper describes assumptions, implementation, and validation of the methods using a two-span two-girder bridge structure as an example. The genetic algorithm was incorporated to minimize the total weight of prestressing steel and ensure a correct design with no limit state exceedances. Since prestress evaluation in statically indeterminate structures requires repetitive and time-consuming numerical simulations, usually finite element analysis (FEA), a neural network was used to predict numerical output based on the layout parameters. The introduction of the neural network significantly reduced the total computation time. The results show the usability of the proposed approach in further studies and in engineering practice. • Genetic algorithm and neural network combined establish an effective optimization framework for prestressed concrete design. • Genetic algorithm is able to find optimal solutions even when all candidates in initial generations exceed the constraints. • Neural network can successfully replace time-consuming Finite Element Analysis (FEA) in design process. • The profile geometry of a tendon can be easily parametrized using linear segments and circular arcs. [ABSTRACT FROM AUTHOR]

Shear walls are widely used as lateral load-resisting systems in high-rise building structures. The design and nonlinear analysis of shear walls under seismic loads for recoverability are complicated and challenging, which demands nonlinear computer modeling procedures. This paper presents a novel finite element named Double Vertical Beam-column with Shell Element (DVBSE) for the nonlinear analysis of complex reinforced concrete shear walls with columns. The DVBSE is implemented in the open-source finite element program OpenSees. The theoretical formulations of DVBSE are described in detail. The accuracy of the developed DVBSE is established by comparing the finite element analysis results with existing experimental data on recoverable steel-GFRP composite bar reinforced concrete shear walls. The comparative study demonstrates that the proposed DVBSE is superior to the commonly used finite element model in simulating the responses of recoverable complex shear walls under seismic loads. These research findings contribute to further advancements in the development of new shear wall elements and lay a solid foundation for the nonlinear numerical simulation of innovative shear walls. • A new finite element DVBSE is developed for modeling shear walls under seismic loads. • The DVBSE incorporates vertical fiber-based beam-column elements and shell elements. • The DVBSE is implemented in the open-source finite element program OpenSees. • The accuracy of the DVBSE is verified by test results of recoverable complex shear walls. • The DVBSE offers an efficient approach to simulate the seismic behavior of shear walls. [ABSTRACT FROM AUTHOR]

Headed stud shear connectors are commonly implemented in steel-concrete composite floors for connecting the concrete slab to the steel beam and providing composite action between those two elements. The orientation of profiled sheeting is usually transverse or parallel to the supporting beam, and for those cases, design codes provide specific detailing requests and relations for obtaining headed stud resistance. Nevertheless, design codes do not recognise specific configurations when the angle between profiled sheeting ribs and the beam is in the range between 0° and 90°, which is characteristic of irregular-shaped floor structures. Due to the lack of design recommendations for headed stud resistance in these cases, investigations of the effect of the rib-to-beam angle on headed stud shear performance were conducted and presented in this paper. Experimental work included push-out tests conducted on specimens with rib-to-beam angles of 45° and 60°, as well as control specimens with ribs transverse to the beam. The influence of varied rib-to-beam angles on shear connector properties such as shear resistance, stiffness, ductility, and failure mode was discussed. According to experimental research, finite element models of push-out tests were created and verified. The parametric numerical analysis covered key parameters such as concrete class, headed stud height and diameter, and rib-to-beam angle. According to the results, an analytical relation for obtaining headed stud resistance in profiled steel sheeting with a rib-to-beam angle between 30° and 90° was proposed. • Rib-to-beam angles between 0° and 90° in steel-concrete composite beams. • Experimental push-out tests on headed studs with rib-to-beam angles of 45° and 60°. • Development of finite element numerical models. • Parametric study for different rib-to-beam angles, concrete classes and stud geometry. • Analytical relation for stud resistance for varied rib-to-beam angles. [ABSTRACT FROM AUTHOR]

In this paper, a composite column using carbon fibre reinforced plastics and polyvinyl chloride composite tube (CFRP-PVC) to constrain coral aggregate seawater sea-sand concrete (CSSC) was proposed, and CFRP was pasted on the inner and outer walls of the PVC tube. To investigate the effects of the number of CFRP layers and void defects on the axial compression performance of PVC tubes, six specimens were made for axial compression loading tests and finite element parameter analysis. The results indicate that due to PVC improving the integrity of CFRP, PVC tube provide a stress transfer path for CFRP, placing CSSC in a triaxial compression state. When both the inner and outer walls of the tube are pasted with CFRP, brittle failure of CFRP-PVC tube can be effectively avoided and have relatively superior mechanical properties. In the same situation, when one layer of CFRP is pasted on the inner wall of the tube, it has better ductility and bearing capacity. When two layers of CFRP are pasted on the outer wall of the tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defect only has a significant impact on ductility. A finite element model of CFRP-PVC confined CSSC columns considering Hashin damage criterion was established based on ABAQUS, accurately predicting the failure process and CFRP damage morphology of test columns under axial load. Parameter analysis shows that when the confinement coefficient of CFRP-PVC confined CSSC columns is less than 0.3 and the height-diameter ratio is greater than 15, the load-displacement curve will lose the strengthening stage, and increasing the number of outer CFRP layers will slightly increase the stiffness of the strengthening stage. A bearing capacity calculation method suitable for CFRP-PVC confined CSSC was proposed based on the model of steel tube confined concrete, with an error of 1.2%. ● CFRP-PVC tube confined coral aggregate seawater sea-sand concrete (CSSC) column was proposed. ● The axial compression test was conducted to explore the mechanical properties of CFRP-PVC confined CSSC columns. ● The finite element models of the CFRP-PVC confined CSSC column were established to conduct parametric investigation. ● The axial strength calculation method of CFRP-PVC confined CSSC columns was proposed considering the CFRP-PVC tube restraint efficiency. [ABSTRACT FROM AUTHOR]

The use of cold-formed steel (CFS) built-up sections in engineering practice is widely gaining popularity due to their ability to provide sustainable solutions and optimised section design opportunities. This paper presents an experimental and numerical investigation conducted on CFS built-up stiffened box section columns under axial compression. A total of 13 new experimental tests were conducted with specimens having an overall web depth up to 550 mm. Detailed nonlinear elasto-plastic finite element (FE) models were then developed and verified against the test results. Upon verification, a parametric study involving 144 FE models was carried out to investigate the effects of section thickness, column length, and screw spacing on the buckling resistance of CFS built-up stiffened box sections. The test and finite element analysis (FEA) results were compared with the buckling resistances determined by the American Iron and Steel Institute (AISI S100) and Australian and New Zealand Standards (AS/NZS 4600). It was found that the buckling resistances determined by the AISI S100 and AS/NZS 4600 for CFS built-up stiffened box sections were conservative by 9.3% on average, compared to experimental and FEA results. Modified Direct Strength Method (DSM) design equations for predicting the buckling resistances of CFS built-up stiffened box sections were then proposed, and a reliability analysis was conducted to assess the feasibility of the proposed equations. • Buckling resistance of axially loaded CFS built-up stiffened box sections was studied experimentally and numerically. • A nonlinear finite element model was developed and validated against the test results. • A parametric study was conducted to investigate the effects of different parameters. • Assessment of the current design guidelines was conducted. • New design equations for predicting the buckling resistance were proposed. [ABSTRACT FROM AUTHOR]

To promote the reuse of precast concrete pavement units, an innovative demountable stainless steel bar connection system is proposed in this paper. Monotonic load tests were conducted to investigate the effects of the width of the stainless steel bar connection, the width and the end distance of the stainless steel plate on the mechanical behaviour of the proposed connection system. As localised concrete crushing was observed after tests, the stainless steel bar connection system was updated with an expanded contact area between concrete and steel. Test results revealed that specimens with the updated connection system exhibited high initial stiffness with low concrete compressive stress concentration. Finite element analysis (FEA) was then carried out to further investigate the parameters that affected the structural performance of the updated connection system. According to the deformations of the stainless steel bar connection and high-strength bolts, an analytical approach was developed to predict the design load of the proposed connection system. Design recommendations were finally summarised based on the obtained test and parametric analysis results to guide the demountable connection design. • The demountable connection system can achieve reusability of precast pavements. • Stainless steel bar connection can be reused in precast concrete pavements. • Demountable connection system performs high initial stiffness and ultimate load with low compressive stress concentration. • Analytical solution to predict the design load of the demountable connection system is derived. • Design recommendations on the demountable connection system are proposed. [ABSTRACT FROM AUTHOR]

In predicting the capacity of screw anchors under static tensile loading, the Concrete Capacity (CC) method is the state-of-the-art prediction model which covers concrete cone capacities in uncracked and cracked concrete up to 0.3 mm crack width. However, in seismic applications, anchors may be subjected to large crack widths of up to 0.8 mm. With large crack width, the behaviour of small-sized (typically 6 mm) screw anchors has not been studied. In this study, experimental investigations were conducted for a total of 29 anchors in uncracked and cracked concrete with large crack widths up to 0.8 mm. The experimental results showed that the load-carrying capacity of screw anchors significantly dropped resulting in a reduction factor of 0.13–0.47 for cracked concrete with 0.8 mm crack width (significantly lower than 0.7 assumed by the CC method for a crack width of up to 0.3 mm). This paper focused on developing modelling technique for predicting the performance of screw anchors in cracked concrete with a crack width of up to 0.8 mm since screw anchor in cracked concrete has not been studied using finite element analysis. Three-dimensional finite element models were developed for screw anchors in uncracked and cracked concrete and validated by the experimental results. Further, parametric analysis showed that dilation angle and shape factor are the two most influencing parameters among other of the concrete damage plasticity model. • Behaviour of 6 mm screw anchors in cracked concrete of large crack width up to 0.8 mm. • Finite element analysis of screw anchors in cracked concrete with large crack width. • Parametric analysis of concrete parameters of concrete damaged plasticity (CDP) model. [ABSTRACT FROM AUTHOR]

This paper develops a three-dimensional damage plasticity based finite element model (FEM) to study the ultimate strength of the steel–concrete–steel (SCS) sandwich shell structure under patch loading. The FEM considers complex geometric nonlinearities of hundreds of stud connectors in the structure, complex interaction between the connectors and concrete, and material nonlinearities of steel and concrete used in the structure. In the developed FEM, the concrete core material adopts the concrete damage plasticity model to predict the post-peak softening and residual strength; the stud connectors and steel shells adopt a continuum damage model to phenomenologically describe the damage evolution in the steel material. The reasonable agreement between FE analysis and the quasi-static tests on the SCS sandwich shell structure confirms the accuracy of the FEM in predicting the ultimate shear resistance, load–deflection relationship, cracks in the concrete core, and punching shear failure of the top steel shell. A subsequence parametric study based on the validated FEM investigates the influence of the curvature on the first peak resistance of the SCS sandwich structure. Finally, the paper validates accuracy of an analytical model on the punching shear resistance of the concrete core of the SCS sandwich shell. [ABSTRACT FROM AUTHOR]

This paper explores the use of three-dimensional (3D) laser scanning to evaluate deteriorated steel bridge girders due to corrosion. Initially, a naturally corroded beam from a decommissioned bridge in MA was scanned in the laboratory, and thickness contour maps were developed for mapping the remaining material of corroded parts. The contours are compared to thickness measurements obtained by ultrasonic thickness gauge, and the results validate the efficiency of 3D scanning as a potential technology for bridge inspections. Then, in a second phase, experimental testing of a corroded girder is performed to obtain the capacity and the mode of failure. Finally, in the last part of the paper, the 3D scanning data are combined through an automated procedure with finite element analysis and analytical provisions to examine whether 3D scanning can inform these two tools reasonably for accurate capacity predictions. The results provide good agreement between experimental and predicted failure loads, paving the way for a more efficient, safe, and time-saving inspection protocol. • 3D laser scanning of two naturally corroded girders is conducted. • 2D thickness representations are proposed for corrosion mapping. • Full scale experimental testing of a naturally corroded girder is performed. • An automated procedure is developed to combine 3D scanning data and FEM. • Post-processed 3D scanning data are combined with analytical procedures. [ABSTRACT FROM AUTHOR]

In parallel with the experimental study described in the companion paper (Zhao et al., submitted for publication), a numerical modelling programme has been carried out to investigate further the structural behaviour of stainless steel cross-sections under combined loading. The numerical models, which were developed using the finite element (FE) package ABAQUS, were initially validated against the experiments, showing the capability of the FE models to replicate the key test results, the full experimental load–deformation histories and the observed local buckling failure modes. Upon validation of the FE models, parametric studies were conducted to generate additional structural performance data over a wide range of cross-section slenderness and combinations of loading. The experimental and numerical results were then compared with the design capacity predictions from the current European Standard EN 1993-1-4 (2006) and American Specification SEI/ASCE-8 (2002) for stainless steel structures. The comparisons revealed that the current design standards can significantly under-estimate the resistance of stainless steel cross-sections subjected to combined loading; this under-prediction of capacity can be primarily attributed to the lack of consideration of strain hardening of the material under load. The Continuous Strength Method (CSM) is a deformation-based design approach that accounts for strain hardening and has been shown to provide accurate predictions of cross-sectional resistance under compression and bending, acting in isolation. In the present paper, proposals are made to extend the scope of the CSM to the case of combined loading. Comparisons between the CSM design proposals and the test and FE results indicated a high level of accuracy and consistency in the predictions. The reliability of the proposals was confirmed by means of statistical analyses according to EN 1990 (2002). [ABSTRACT FROM AUTHOR]

In the component-based method, the ductility characterisation of the tension component plays a primary role in accurately predicting the rotation capacity of the whole connection. In this paper, a refined finite element (FE) model is presented to assess the complete force–displacement response of the T-stub component, from the initial stiffness up to the fracture point. The refined FE model includes a non-linear continuum damage mechanics model that considers the onset of the damage, the damage evolution law, and the component failure. A parametric study was conducted to evaluate the influence of the damage parameters in the overall response of the T-stub component. The numerical results obtained from the refined FE model strongly agree with the experimental results of 18 test specimens. The comparison reveals the proposed FE model’s satisfactory accuracy, with an average fitting error below 9%. This paper constitutes the first part of a comprehensive methodology based on combining FE analysis and soft computing techniques. The ultimate goal of this methodology is to predict the key parameters that define the force–displacement response of the T-stub component. [ABSTRACT FROM AUTHOR]

In this paper, the structural response of steel tubular wind turbine towers with various design configurations is analysed using FEM modelling. Towers of various heights between 50 and 250 m are considered and investigated with three different design options as follows: (i) thick walled tower with internal horizontal stiffening rings, (ii) thick walled tower without stiffening rings and (iii) thin walled tower with stiffening rings. Based on this analysis, weight reduction ratios are examined in relation to the horizontal sway and von Mises stress increase ratios in order to identify a more efficient design approach between reducing the wall thickness and adopting internal stiffeners. All studied design solutions satisfy the strength and serviceability requirements as specified by the design codes of practice. In the final part of paper, the dynamic characteristics of these three types of towers have been examined to obtain the natural frequencies and mode shapes. The studied model ignored the mass of nacelle-rotor system and the wind turbines, namely, only the isolated tower was included. Furthermore, the recommendations to avoid resonance for each height case are proposed. [ABSTRACT FROM AUTHOR]

• LC sheet is characterised by a rounded stress–strain response with two "knee" regions. • A simplified full-range engineering stress–strain model for LC sheets is proposed. • An average weight method is used to determine post-necking true stress–strain curves. • Recommended values of weight factor and toughness coefficient for LC sheets are obtained. Laser cladding (LC) is being used increasingly in civil engineering owing to its high efficiency and minimal distortion since requiring little heat input; especially for repairing or strengthening damaged metal structures. LC stainless steel sheets are characterised by a rounded stress–strain response, with two "knee" regions and no sharply defined yield point. Such behaviour cannot be accurately represented by using previous stress–strain models. Moreover, determining the true stress–strain curve and toughness coefficient for the fracture model is essential to carry out a non-linear finite element analysis for solving elastoplastic problems. In the present study, one simplified full-range engineering stress–strain model for LC 316L stainless steel sheets is proposed based on the three-stage Hradil model and is validated against the experimental results of thirty tensile coupon tests. The proposed model redefines the second and third stages of the stress–strain curve following the experimental observations. All parameters in this simplified model can be derived directly from only four basic material property parameters: the initial elastic modulus, 0.2 % proof stress, ultimate stress and the strain corresponding to the ultimate stress. For defining the fracture model of LC stainless steel sheets, an average weight method is employed to determine the post-necking true stress–strain curves. The recommended values of the weight factor and toughness coefficient for the LC sheets are also obtained based on the available tensile coupon test results. The comparisons between the experimental force–displacement curves of the tensile coupons and the finite element analysis results using the proposed stress–strain relationship and fracture model for the LC sheets shows both results to be in good agreement. Therefore, the stress–strain relationship and fracture model proposed in this paper is suitable for use in the analytical and numerical modelling of structures having LC 316L stainless steel sheets. [ABSTRACT FROM AUTHOR]

• The linear stiffness ratio of beam to column plays a key role in determine the failure mode of beam-column connection. • The increase of beam stiffness will improve the load capacity of the connection. The increase of column length will decrease the load capacity of the connection. • The perpendicular short RC walls restrained cracking development in the core area effectively. Adding an in-plane RC wall to the connection can effectively enhance the seismic performance, and transfer the column failure to beam failure mode. • Increasing the axial compression ratio improved the stiffness of the connection, the load capacity was improved but less than 5%, the ductility reduced a lot and the strength degradation in the later stage was accelerated. This paper reports test results and numerical analysis of special-shaped beam-column connections based on a frame-shear wall structure. Four connections of 1/5 scale ratio were tested under constant axial force and reversed lateral load on the top of column. The experiment investigated the effect of steel reinforced concrete (SRC) beam, in-plane and out of-plane reinforced concrete (RC) wall on the connections' seismic behavior. The failure modes, hysteresis curves, ductility, strength degradation and energy-dissipating capacity of test specimens are reported. The results indicated that test joints were susceptible to suffer more brittle failure caused by formation of plastic hinge on column, which is considered unfavorable compared to conventional joint with regular shape in earthquake resisting. Adding in-plane shear walls to the connection switched column failure to beam failure mode, and significantly improved the connection's strength, stiffness and ductility. Finite element models were detailed established and validated through experiment data. Influence of parameters including axial load ratio, concrete strength grade, section area and steel ratio of upper column, transverse hoops volumetric, RC wall of two orthogonal directions on connection's seismic behavior were studied through modeling results. [ABSTRACT FROM AUTHOR]

• This paper presents a finite element analysis of cold-formed stainless steel channels with circular web holes, subjected to interior-one-flange loading condition. • To investigate the effect of web hole size, web hole location and bearing length on the web crippling strength of such sections, a parametric study involving 1,728 FE models was performed. • The parametric study results were used to propose new web crippling strength equations and strength reduction factor equations. • A reliability analysis was performed to check the reliability of proposed equations. This paper presents a numerical study on structural behaviour of cold-formed stainless steel channels with circular web holes, under interior-one-flange loading case. The material properties of stainless steel types EN 1.4509 (Ferritic), EN 1.4462 (Duplex) and EN 1.4301 (Austenitic) were taken from the literature. In order to study the influence of web hole size, web hole location and load-bearing length on the web crippling strength of such sections, a parametric study involving 1,728 finite element models was conducted. The parametric study results were used to propose new web crippling strength equations and strength reduction factor equations which performed better than those of American Society of Civil Engineers Specification (ASCE 8–02), American Iron and Steel Institute Specification and Australia/New Zealand Standard (AISI&AS/NZS) and Lian et al (2016). A reliability analysis was then carried out, and the results showed that the proposed design equations can accurately predict the web crippling strength of of cold-formed stainless steel channels with and without web holes when loaded under interior-one-flange condition. [ABSTRACT FROM AUTHOR]

• High-strength concrete filled box columns (CFBCs) are investigated. • Five column specimens are laterally and cyclically tested after axial compression (0.2–0.4 P n). • The addition of concrete infill inside a hollow column does not improve the ductility of CFBCs. • The b/t limit of the code cannot assure good seismic behavior of CFBCs under high axial load. This paper presents an experimental study of the seismic performance of high-strength concrete-filled box columns (CFBCs) under combined axial and cyclic lateral loads. Specimens were made of high-strength SM 570 M steel (with yield strengths between 520 and 580 MPa), and concrete with compressive strength (f c ') greater than 80 MPa. Three parameters that affect the seismic performance of CFBCs were investigated: the width-to-thickness (b/t) ratio of the steel column, magnitude of the axial load, and the addition of concrete infill. The specimens, which were 280–420 mm in width and 2000 mm in height, were tested under combined axial (4058–10,090 kN) and cyclic lateral loads. Experimental results indicated that the lateral displacement ductility decreases significantly with an increase in either the axial load or b/t ratio. The addition of concrete infill inside a hollow steel box column does not improve the lateral displacement ductility of CFBCs under high axial load. Although the CFBC specimens satisfied the b/t requirement of a highly ductile member, as per AISC Seismic Provisions (2016), specimens under high axial load (40% P n) failed at 4% drift, indicating that the requirement does not guarantee that CFBCs will sustain high axial load under significant drift (i.e., >3%). The Eurocode 4 (2009), AISC Specification (2010), and Architectural Institute of Japan (2014) reasonably estimate the flexural strength of high-strength CFBCs under axial load; however, ACI 318 (2011) does not. The finite element analysis program ABAQUS can be used to estimate the hysteretic behavior of specimens before significant strength degradation. [ABSTRACT FROM AUTHOR]

Highlights • Based on four static loading experiments, a finite element simulation method of reticulated shell with roofing system is established; roofing system improve buckling load and plastic development, purlin is the main component in roofing system bearing static load together with the reticulated shell, the roofing panels play a relatively minor role. • The effect of roofing system tends to decrease when the span of reticulated shell increases. • The roofing system has a more significantly effect on the shell with larger initial geometric imperfections. Abstract The static stability of a single-layer reticulated shell has been systematically studied, but nearly all scholars have neglected the effect of the roofing system, and the simplified analytical method may lead to deviations between finite element analysis and the actual situation. In this paper, four full-scale reticulated shell substructure models with a roofing system were experimentally investigated to verify the effect of the roofing system. The finite element analysis (FEA) were established based on the experimental models, the connections between the purlin and purlin hanger were modelled as semi-rigid joints, the profiled sheets were modelled as equivalent orthotropic flat panels, and a weakened area was established to model the connection between the purlin and the roof panel. A series of finite element analysis models (FEM) of full-scale reticulated shells with roofing systems were established, and the effect of the roofing system on the full-scale reticulated shells' static stability was analysed. [ABSTRACT FROM AUTHOR]

Highlights • A newly developed polymeric material was applied to a steel-polymer hybrid floor panel. • The hybrid panel exhibited very ductile and stable behavior maintaining its structural integrity. • The bond strength of polymer was sufficient to resist the forces generated between steel and polymer. • Design equations for predicting flexural strength and stiffness of the proposed panel were established. • The experimentally-validated cutting and joining methods for field applications were also presented. Abstract A new floor system for steel buildings was developed that can replace conventional concrete deck slab systems. The floor system is designed with a new type of composite panel with a polymeric material filling between the top and bottom steel plates. Its salient features are its light weight and simple installation that reduce structural materials and shorten the construction period. Experiments with various independent variables were performed to evaluate the flexural capacity of the proposed composite panel, and a finite element analysis was also conducted to examine the state of the stresses generated between the steel plate and the polymeric core. The test results showed that the proposed panel exhibited very ductile behavior and maintained its structural integrity even after a maximum load. No other failure mode than the face yielding of the top and bottom steel plates was observed. The bond strength between the polymeric material and the steel plates was confirmed to be sufficient, even without any special surface treatment or any additional shear connectors, to maintain the stability of the proposed panel and to resist the forces generated at the interface between the two materials. Design equations for predicting the flexural strength and stiffness of the proposed panel were proposed, and its suitability was verified. Additionally, the experimentally tested efficient methods for field applications of the proposed panel regarding cutting and joining were presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the cracking pattern in a historical Italian palace proposing a diagnosis for the origin of the actual damage state. The analyzed building, which dates back to the seventeenth century, is a masonry building with a rectangular plan section located in Piancastagnaio (South Tuscany, Italy). The building exhibits a severe and variegated vertical and horizontal cracking pattern mainly affecting the southern and eastern façades. Due to the damage, the palace was evacuated by the Public Authorities during the 1980s and a series of provisional remedies (mainly steel chains) was added. Through the use of the finite element technique, the paper provides an interpretation of the manifested damage. The aim of the diagnosis, supported by the numerical results, is to design an extensive in-situ investigation on the palace. Moreover, the paper aims at evaluating the effectiveness of the actual temporary retrofitting (mainly steel chains) used to freeze the present damage. At the end of the paper the in-situ investigation is presented and discussed. [Copyright &y& Elsevier]

Abstract: The strength or stiffness of a reinforced concrete (RC), metallic or timber member can be increased by bonding a thin FRP or steel plate to its external surface. In such plated members, debonding of the thin plate from the original member is often the controlling failure mode, and such debonding depends strongly on the interfacial stresses in the adhesive layer between the member and the plate. This paper is concerned with the prediction of these interfacial stresses using the finite element method. The paper is primarily focused on simply-supported straight plated beams subjected to a uniformly-distributed load as a widely studied benchmark case. Five different finite element modeling approaches based on different assumptions for the deformations of the three components of such a plated beam (beam, adhesive layer and plate) are described. The predictions of the five models are then compared with each other and with analytical solutions of different levels of sophistication. These comparisons illustrate clearly how each assumption affects the predicted interfacial stresses and identify the beam–spring–beam (B–S–B) model as a relatively simple yet sufficiently accurate model for practical use in predicting interfacial stresses and debonding failure in more complex structural members bonded with a thin plate. To illustrate the versatility and power of the B–S–B type model, interfacial stresses in two more complicated structures (a plated flat panel and a plated curved panel) obtained from the same type of model are presented and discussed. These results provide useful insight into the risk of debonding in such plated panels. [Copyright &y& Elsevier]

[Display omitted] • - A type of new shell-the complicated shells are investigated in the paper. • - The dynamical characteristics of the shells are analyzed using the analytical approach for six types. • - The numerical results are validated to the FEA. The paper builds the novel models of the shells with the profile changes according to the sinusoidal and cosine functions that are temporarily named the sinusoidal and cosine shells. Two types I and II are corresponding to the sine and cosine shells that are investigated three cycles for each type. The used materials for the types of the shells are the graphene nanoplatelet reinforced polymer that is estimated through the Halpin-Tsai micromechanical model. Based on the classical shell theory and the Von Karman geometrical nonlinearity assumption, the governing equations for the materials and structural models are built and then, the fundamental frequencies and nonlinear dynamical behaviors of the shells are found out. In addition, the obtained results include the numerical and graphical presents and are validated with the Finite Element Analysis (FEA) to confirm the reliability of the analytical approach. The effects of the environment, geometrics and materials are scrutinized through the charts, 2D and 3D graphical results. The attained results are considered to contribute to the important applications in science and industry. [ABSTRACT FROM AUTHOR]

This paper investigates the response of multi-storey structures under simulated earthquake loads with friction dampers, viscoelastic dampers and combined friction-viscoelastic damping devices strategically located within shear walls. Consequently, evaluations are made as to how the damping systems affect the seismic response of these structures with respect to deflections and accelerations. In particular, this paper concentrates on the effects of damper types, configurations and their locations within the cut-outs of shear walls. The initial stiffness of the cut out section of the shear wall is removed and replaced by the stiffness and damping of the device. Influence of parameters of damper properties such as stiffness, damping coefficient, location, configuration and size are studied and evaluated using results obtained under several different earthquake scenarios. Structural models with cut outs at different heights are treated in order to establish the effectiveness of the dampers and their optimal placement. This conceptual study has demonstrated the feasibility of mitigating the seismic response of building structures by using embedded dampers. [Copyright &y& Elsevier]

• Numerical analysis of RC columns, beams, walls under fires with cooling phases. • Effect of thermal wave on structural stability is quantified. • Slower cooling rates increase propensity to fail after the peak fire temperature. • RC beams' stability can be linked to reinforcement maximum reached temperature. • RC columns and walls' behavior is more complex and requires thermal-structural analysis. Fire exposed structures may collapse during or after the fire decay phase, with risks for building occupants and firefighters; yet, understanding of the effects of the fire decay phase on structural loadbearing capacity remains limited. This paper describes a numerical investigation on the behavior of reinforced concrete columns, beams, and walls under natural fires including cooling down phases. Finite element models are benchmarked against experiments capturing the behavior during heating. The models are then used to simulate the structural response of the concrete members under fires with various cooling rates and load ratios. The analyses capture the irreversibility of material properties through tracing of the temperature history in the structure. The results show that temperatures and deformations continue increasing after the end of the fire heating phase. As a result, concrete columns, beams, and walls may fail during the cooling phase. Faster cooling rates reduce the likelihood of failure in cooling. For beams, failure can be inferred from the maximum reinforcement temperature reached throughout the fire, but for columns and walls a thermal–mechanical analysis of the member throughout the fire history is needed. A relationship is proposed to evaluate the burnout resistance from the fire resistance rating and cooling rate. The presented numerical method allows assessing the structural stability throughout a fire event, an important requirement for designing a fire resilient built environment. [ABSTRACT FROM AUTHOR]

• A numerical method is proposed for the fatigue analysis of steel-UHPC composite decks. • Fatigue degradation of stud connectors is considered in the numerical method. • Effects of stud degradation and stud arrangement on the fatigue performance of steel-UHPC composite decks are evaluated. The fatigue degradation of stud connectors is generally neglected in the fatigue analysis of steel-UHPC composite decks, which may lead to inaccurate results. This paper studies the effects of stud degradation and stud arrangement on the fatigue behavior of steel-UHPC composite decks via finite element analysis. A numerical method for the fatigue analysis of composite decks is proposed considering the fatigue degradation of studs. The numerical method is experimentally validated and applied to evaluate the fatigue performance of composite decks. The effect of stud arrangement on the fatigue response of composite decks is studied by parametric analysis. The results indicated the fatigue degradation of studs and the decrease in stud spacing caused more uniform distribution of shear forces at steel-UHPC interfaces. The fatigue degradation of stud connectors reduced the structural stiffness, while reducing the stud spacing enhanced the local stiffness but increased the stress ranges of some fatigue-critical details. Neglecting the stud degradation could lead to an underestimation of the fatigue life of stud connectors. This study advances the understanding of the fatigue behavior and the ability to analyze the fatigue behavior of steel-UHPC composite decks. [ABSTRACT FROM AUTHOR]

• Cellular filled composite crash boxes can be successfully fabricated by using carbon fibre reinforced polymer (CFRP) prepreg fabrics. • Empty cylinder (EC) type composite crash box provides better specific energy absorption ability than empty square (ES) and hexagon (EH) counterparts. • Hexagonal and square cellular fillers increase significantly crush strength and energy absorption performance of the composite crash boxes. • Finite elements method (FEM) presents an effective solution in modelling crushing response of the composite crash boxes. • The cellular filled composite crash boxes exhibit deformation behaviour in the form of opening outward during crushing. Composite structures have been used in the automotive and aircraft industries because of their superior properties such as specific energy absorption ability, lightweight and crashworthiness. This paper aims to determine energy absorbing and deformation behaviours of composite crash boxes designed in different geometries by an innovative approach. The hand-layup vacuum bagging method was utilized to produce the composite crash boxes, which were developed with three different outer wall geometries (square, hexagon, and cylinder), and cellular filled square and hexagonal interiors. Carbon fibre reinforced polymer (CFRP) material was used in fabrication of the crash boxes. Experimental and numerical studies were conducted to investigate the energy absorbing and deformation behaviours under static compression load of the composite crash boxes. A commercial finite elements (FE) software (Ls-Dyna) was used for the numerical model. The study's findings revealed that cellular-filled composite crash boxes perform significantly better in terms of energy absorption performance. It was observed that filling an empty square type composite crash box with hexagonal cells increased the box's specific energy absorption capacity by around 140%. [ABSTRACT FROM AUTHOR]

• A splitting resistance equation was proposed for highly prestressed UHPC girders. Ultra-high performance concrete (UHPC) has gained popularity gradually because of its superior mechanical properties, including high compressive and tensile strengths, and exceptional durability. Many researchers have explored the possibility of using long, precast prestressed UHPC girders in buildings and bridges. To do so, the girders generally require a large number of prestressing strands, which causes concern about potential cracking in the end zones at prestress release. Currently, there are no specifications or codes on end zone designs for precast prestressed UHPC girders in the United States. Thus, this paper presents an analytical study that explores highly prestressed UHPC girders' end zone behavior. Finite element analyses were conducted to analyze the end zones of a series of UHPC girders, including one 889-mm-deep and two 813-mm-deep I-girders, and the analysis results were validated with test data. Additional finite element models were developed for other girders with heights of 1,829 mm and 2,743 mm using various reinforcement details. Bursting stress variations in the reinforcement and UHPC were reported based upon the analytical and test results. An equation for splitting resistance attributable to the reinforcement and UHPC was proposed for highly prestressed girders. [ABSTRACT FROM AUTHOR]

• A new kind of composite columns with a concrete column and an encased angle steel frame was studied in this paper. • Seismic performance of ASFCs was investigated via experiment and simulation research. • Based on experiment and simulation results, stress and strain state, plastic hinge length were studied. • Assembly of steel battens, size of steel batten and angle steel bar can characterize the seismic performance of ASFCs. • Finite element model of ASFCs was proposed and verified in this paper. • Expanding study for influence factors of ASFCs was finished via finite element analysis. Angle steel frame confined concrete columns (ASFCs) are an improved form of steel-jacketed concrete composite columns. An ASFC consists of an concrete column and an inner angle steel frame (ASF). The ASF offers two advantages: confining core concrete and improving seismic performance. The existing studies have been limited on seismic performance of ASFCs. This paper presents experimental and numerical studies on seismic performance of ASFCs. The experimental program included the lateral quasi-static cyclic tests of eight specimens, with the main variables being the axial compression ratio, the section form and the assembly of steel batten. The numerical program included establishment process of numerical models in finite element analysis software (OpenSees), and the expanding analysis on influence factors of ASFCs. The experimental results showed that all ASFCs have high bearing capacity, high ductility and full hysteretic curve. The numerical model could provide reasonably accurate prediction of experimental results. The factor analysis showed that axial compression ratio and steel content of angle steel are two main factors for seismic factors, and the confining effect exerts great influence on dividing axial compression ratio. [ABSTRACT FROM AUTHOR]

Axially functionally graded (AFG) beams, with variable coefficients in the governing equation, are a novel class of composites structures that have continuous variations in material properties from one component to another. In this paper, the asymptotic development method (ADM) is utilized to investigate the free vibration of uniform AFG beams with different boundary conditions. By decomposing the variable flexural stiffness and mass per unit length into reference invariant parts and variant parts, perturbation theory is introduced to obtain an approximate formula of the natural frequencies of the uniform AFG beams. The numerical results of the proposed method are confirmed by comparing the obtained results with those obtained via finite element analysis and the published literature results, the comparison reveals the proposed method yields an accurate estimate of the first three order natural frequencies of the AFG beam. Moreover, the influences of the gradient parameter and support conditions on the first three natural frequencies are discussed. The proposed analytical method is simple and efficient and can be used to conveniently analyze uniform AFG beams with arbitrary changes in the material properties along the axial direction. [ABSTRACT FROM AUTHOR]

This paper presents the results of 3D finite element (FE) modelling of corrosion-damaged reinforced concrete (RC) beams strengthened in flexure with externally-bonded composites. The models were validated against the results of experimental tests conducted on ten unstrengthened and strengthened beams. The investigated parameters included the corrosion levels (10 and 20% mass loss of steel reinforcement), the type of composite (fabric-reinforced cementitious matrix (FRCM) and fiber-reinforced polymers (FRP)), and the number of composite layers (one, two, and four). The predicted results showed good agreement with those of the experimental tests. The FE models were able to capture the non-linear behavior of the strengthened beams. The interfacial bond stress-slip models at the fabric/matrix and composite/concrete interfaces and the number of composite layers had the most significant impact on the predicted response of the strengthened beams whereas the corrosion level, modeled as a reduction in the steel reinforcement cross-section, showed a slight effect on their performance. The validated models were used in a parametric study to investigate the effect of varying the compressive strength of the concrete substrate and the thickness of concrete cover on the flexural performance of the strengthened beams. It was observed that lowering the concrete compressive strength or increasing the concrete cover decreased the load-carrying capacities of the strengthened beams regardless of the strengthening system used (FRCM or FRP). Unlike the FRP-strengthened beams, the failure of FRCM-strengthened beams was independent of both parameters and was solely governed by the fabric slippage within the matrix. [ABSTRACT FROM AUTHOR]

This paper describes the large-scale testing and the finite element simulations of the collapse of a steel-composite joint, both bolted and bonded. The joined structures are typical ones of shipbuilding and namely of naval ships. Composite superstructures, beside a valuable weight reduction, may improve the signature features of the ship by embedding installed electronic devices into a composite mast. In the frame of a broader research project, including the electromagnetic characterization of the composite structures, also the structural design and its optimization were exploited, embracing, among other issues, the joining solutions between the steel deck structures to the composite ones of the superstructure side shell. A large-scale specimen of the joint was conceived and collapse tested while, in parallel, design simulations were carried out at different levels of detail. Eventually, a complete description of the collapse of the joint, including the nonlinear simulation by finite element analysis of the progressive failure of the composite laminates of the side shell was obtained and test results were used to validate the numerical models. Depending on the design stage, various scantling procedures, from a very simplified one to a rather complex and time-consuming numerical analysis, can now be applied to verify the structural behavior of these steel to composite joints as well as to select the most cost-effective solution among several options. [ABSTRACT FROM AUTHOR]

Local buckling remarkably reduces the strength of steel plates in rectangular thin-walled concrete-filled steel tubular (CFST) columns at ambient temperature. This effect is more remarkable at elevated temperature. However, there have been very limited experimental and numerical investigations on the local and post-local buckling behavior of steel plates in CFST columns at elevated temperatures. This paper presents numerical studies on the local and post-local buckling behavior of thin steel plates under stress gradients in rectangular CFST columns at elevated temperatures. For this purpose, finite element models are developed, accounting for geometric and material nonlinearities at elevated temperatures. The initial geometric imperfections and residual stresses presented in steel plates are considered. Based on the finite element results, new formulas are proposed for determining the initial local buckling stress and post-local buckling strength of clamped steel plates under in-plane stress gradients at elevated temperatures. Moreover, new effective width formulas are developed for clamped steel plates at elevated temperatures. The proposed formulas are compared with existing ones with a good agreement. The effective width formulas developed are used in the calculations of the ultimate axial loads of rectangular CFST short columns exposed to fire and the results obtained are compared well with the finite element solutions provided by other researchers. The initial local buckling and effective width formulas can be implemented in numerical techniques to account for local buckling effects on the responses of rectangular thin-walled CFST columns at elevated temperatures. [ABSTRACT FROM AUTHOR]

A corrugated web beam (CWB) is a variation to the universal hot rolled or welded I section. CWBs usually comprise of wide thick plate flanges and a thin corrugated web. Due to the accordion effect shear is carried primarily by the corrugated web while bending moments are resisted by the flanges. Under shear action three different modes of shear buckling may be realised in the web – local, global or interactive. This paper describes analyses performed to investigate the local shear buckling behaviour of beams with trapezoidal corrugated webs. Finite element models of cantilever beams with different web geometries were prepared and an elastic eigenvalue buckling analysis was performed using the program ABAQUS. The influence of web thickness, panel width and web height on the local shear buckling coefficient k L was investigated. Values of k L were compared against existing equations from theory and other research. The effect of these dimensions on the local shear buckling stress was also considered. In total, 90 models were analysed. Overall, it was found that the value of k L lies between 5.34 and 8.98. This corresponds to panel boundary conditions that are between simply supported and clamped. The analysis results revealed that k L increases with stockier panels (large panel width to height ratio) but decreases with thicker webs. When the panel width was decreased, local shear buckling occurred at larger stress values. Similar results were observed when the web height was decreased and the panel thickness was increased. These results are consistent with plate buckling theory. Finally, based on these findings an equation to approximate the local shear buckling coefficient in corrugated web beams is recommended. [ABSTRACT FROM AUTHOR]

Insulated sandwich panels consist of two wythes separated by a non-structural insulation layer. These two wythes are connected using shear connectors. In recent years, Fiber-Reinforced Polymer (FRP) shear connectors have been increasingly used due to their low thermal conductivity. However, they have lower stiffness compared to other rigid shear connectors, resulting in partial degree of composite action (DCA) for the sandwich panels. Until now, insulated sandwich panels are designed based on the assumption that the longitudinal stress is uniform across the wythe, which is not reasonable since the in-plane shear flexibility of the wythe causes non-uniform distributions of the stress, which is called shear lag effect. This paper presents an analytical solution to study the behavior of insulated sandwich panels with flexible shear connecotors. To this end, a solution based on the shear lag model is firstly developed, where the partial DCA and boundary conditions from various configuations of the flexible shear connectors are considered. The effective width, an important parameter to describe the shear lag effect, is defined. The analytical model is then verified through close correlations among experimental, Finite Element (FE) and analytical resutls for multi-cell box girders; and FE and analytical results for an insulated concrete sandwich panel with FRP shear connectors. A parametric study is finally conducted using the analytical model to study the effects of deck stiffness and aspect ratio on the effective width. The results from this study can be used for the design of insulated sandwich panels. [ABSTRACT FROM AUTHOR]

In this paper, two new design approaches are proposed to design structural nodes of complex shapes for gridshell structures, seeking improved structural performance and design efficiency by using the transitional section method and the bi-directional evolutionary structural optimization (BESO) method, respectively. Detailed design methodologies are introduced and compared with two types of conventionally designed structural nodes in real use, i.e., Seele node and Sun Valley node. Finite element analyses are conducted to evaluate the stress distribution, maximum stress and mean compliance of different structural nodes. The results show that, although the BESO node has the highest stiffness and the lowest structural volume, it seems to have a higher maximum stress level. Multiple load cases are considered in the analysis and design optimization processes. Moreover, the application of Laplacian smoothing in structural node design effectively reduces the stress concentration. Prototypes of the newly designed structural nodes are fabricated by additive manufacturing, which enables the rapid and precise manufacturing of customized structural nodes optimized for specific loading and boundary conditions. [ABSTRACT FROM AUTHOR]