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Friction Pendulum Bearing (FPB) with shearing keys will exhibit friction-coupling effect and collision phenomenon subjected to horizontal orthogonal ground motions. This paper establishes a numerical analysis model of FPB with four shear keys and viscous damping, considering the impact of the friction coupling effect and collision between the FPB and the shear keys on its displacement response. The influence of parameters of FPB on seismic displacement response with considering collision effect under horizontal orthogonal ground motions was studied. The results suggest that adjustments in damping and equivalent stiffness exclusively impact the amplitude of the displacement response, maintaining the response waveform. Conversely, variations in friction significantly alter the response waveform, as friction induces changes in the natural frequency of FPB. A heightened collision impact is noted with reduced spring stiffness. The displacement response is particularly amplified when the collision occurs at the vicinity of peak displacement in the time-history response of FPB. When the restoring stiffness and Peak Ground Acceleration (PGA) are low, the friction coupling effect significantly reduces the amplification of displacement response caused by collision effects. Viscous damping can considerably reduce the impact of collisions on the peak displacement of FPB and prevent the collision effects from noticeably amplifying or diminishing the peak displacement of FPB. • This paper proposes a numerical model of FPB considering shear key collisions. • Theoretical derivations and categorizations of collision and shearing scenarios involving shear keys are presented. • This model enables a decoupled analysis of the displacement response of FPB with shear keys under orthogonal horizontal seismic motions. [ABSTRACT FROM AUTHOR]

Abstract: In the aforementioned paper, optimum design of tuned mass dampers (TMD) installed on multiple degree of freedom (MDOF) structures under seismic excitations is proposed. Equations of motion for structures with and without TMD were solved by the modal analysis procedure. Results of numerical studies in this discussion show that using modal method for solving the differential equations governing the motion of controlled structures by TMD dampers usually is not corrected because such systems essentially have not classical damping. [Copyright &y& Elsevier]

Numerical analysis is conducted to investigate the behavior of double shear combination connections made with pretensioned high-strength bolts and longitudinal fillet welds. The finite element (FE) models were validated using the results of an experimental investigation and utilized to develop a better understanding of the influence of critical input parameters on the connection behavior. Slip-dependent surface frictional and weld ductile fracture models were incorporated into the numerical models to simulate the nonlinear behavior of the connections. The numerical simulations confirm that at low slip displacements, the force carried by the combination connection can be estimated as the summation of the friction resistance introduced by the pretensioned bolts and the shear force carried by the fillet welds. The results also indicate that the behavior and capacity of the combination connection are not sensitive with respect to the weld location compared to the center of gravity of the bolts as long as no eccentricity is introduced within the force transfer mechanism. The paper also investigates the stress distribution within the connection plates and studies the effect of fillet weld size on the behavior of combination connections. • Comprehensive approach for modeling the nonlinear behavior of combination connection. • New surface frictional models are developed to capture the slip behavior of the connections. • Ductile fracture models are utilized to properly simulate the behavior of weld lines. • Large set of experimental investigations is used to validate the finite element models. • The effect of dimensions and location of weld lines on the behavior is quantified. [ABSTRACT FROM AUTHOR]

The connection system controls the behavior of the Cross-laminated timber (CLT) structures under horizontal loads. This paper introduced an innovative energy-dissipation angle bracket for CLT structures, which takes advantage of the soft-steel bracket and high-damping rubber to provide superior ductility and energy-dissipating capacity. Experimental tests under monotonic and reversed cyclic loading were performed to investigate the failure mechanism and mechanical properties of this energy-dissipation connector. After validating the detailed finite element models based on the test results, numerical parametric analysis was conducted to evaluate the influence of several parameters. The results show that the energy-dissipation angle bracket connector mainly exhibits three failure modes, including the rupture of dissipative ribs, local bearing failure of the base, and the debonding of the internal rubber. The ribs' rupture is the dominant failure mode, especially under cyclic loading, after which the connector can still work integrally because of the rubber that is tightly bonded to the steel skeleton. All the tested connectors show high ductility and great energy-dissipating capacity, as indicated by the ductility larger than 9.5 and the equivalent viscous damping ratio within 9 %− 26 %. According to the numerical parametric analysis, the load-carrying capacity of the energy-dissipation angle bracket is positively correlated with the steel skeleton's thickness and ultimate strength, and the adoption of the washer, while the rubber's height has little impact on the load-carrying capacity. The outcomes of this study provide valuable references for subsequent improvement and potential applications of the innovative angle bracket for CLT structures. • An innovative energy-dissipation angle bracket for CLT structures was proposed. • Failure mechanisms and mechanical properties were investigated by experimental tests. • 3D detailed finite element models were developed with validation of test results. • The influence of several parameters was evaluated by numerical parametric study. [ABSTRACT FROM AUTHOR]

Prefabrication assembly technology has been widely recognized due to its rapid construction, minimal environmental impact, and superior quality of precast components. The reliability and construction convenience of the connection joints of precast components are particularly important. In this paper, a novel Ultra High-Performance Concrete (UHPC)-filled concrete-filled steel tube (CFST) socket connection (UCSC) was proposed for the column-beam connection. To explore the shear behavior and shear load transfer mechanism of UCSC joints, four direct shear experiments were conducted in terms of different parameters (socket depth, presence of studs). Meanwhile, ABAQUS was used to perform a systematic parametric analysis (socket length, embedded length, outer diameter of CFST, thickness of steel tube). The results indicated that the shear performance of UCSC joints was significantly influenced by both the socket depth and the outer diameter of CFST. The proposed finite element model (FEM) can predict the load-displacement relationships of UCSC joints with a maximum peak load error of 2.3 %. Combining the experimental results and numerical results, a simplified calculation model was formulated to accurately estimate the shear bearing capacity of UCSC joints, and was verified by numerical and experimental results with a maximum error of 8.6 %. The research results have practical implications for the preliminary design of UCSC joints to avoid non-ideal failure mode. • Experimental studies were conducted to evaluate the shear performance of UCSC. • A FEM was established to predict the force-displacement curve and shear failure mode of UCSC. • A simplified calculation model was developed to predict the ultimate shear bear capacity of UCSC. [ABSTRACT FROM AUTHOR]

Infill walls are a primary source of structural loss under service level and design basis earthquakes, so developing high-performance infill wall is an effective strategy to reduce seismic loss. While several high-performance infill walls have been proposed, most studies only reveal the damage characteristics of infill walls at the component level. However, the interaction between infill walls and structures can alter the seismic response of structures and consequently affect the loss of infill walls under earthquakes. Therefore, it is necessary to investigate the seismic responses and loss of high-performance infill wall at the structural level. In this paper, the working mechanism and damage characteristics of the slotted infill wall (SIW) are firstly introduced and verified through cyclic loading test. Then, an in-plane hysteresis model of SIW is developed, and the calculation method of key parameters is proposed. Finally, a numerical analysis model of a 10-story frame with slotted infill wall (SIW-F) is developed to study the seismic response and seismic losses. The results indicate that SIW-F's displacement response is larger than that of the frame with ordinary infill wall (OIW-F) on most floors. However, the floor acceleration response is less. The seismic loss of SIW-F is less than that of OIW-F, particularly under design basis earthquakes. The repair cost ratio of infill wall decreases from 19% to 8%, the total repair cost of the SIW-F decreases by 41%, and the total repair time also reduces by 25%. • The working mechanism and damage characteristics of the SIW is Introduced and verified. • A general in-plane hysteresis model of SIW is proposed, and calculation methods of key parameters are suggested. • The seismic responses of 10-story frames with SIW and OIW are comparatively evaluated. • The seismic loss including repair cost and time of 10-story frames with SIW and OIW are discussed. [ABSTRACT FROM AUTHOR]

Welding-induced residual stresses evolve under external loading and fatigue actions. This paper examines the effects of a variety of influencing factors on the residual stress evolution, such as the pre-tension, load ratio, variable amplitude loading, overloading, plate thickness, and crack depth, for which a comprehensive understanding is yet to be nurtured. The experimental and numerical findings demonstrate that the variable amplitude loading and overloading impose significant effects on the evolution of residual stresses during the cyclic loading test. Based on the experimental observations and numerical analysis, this paper presents four evolution forms of residual stresses and reveals their mechanical principles by the effective stress-strain curves in both the undamaged specimens and the fatigue-cracked specimens. The interaction between the positions with different incremental plastic strains changes the magnitude of residual stress and thus dominates the residual stress evolutions. • We investigate the effects of fatigue actions on the residual stress evolution. • We propose four residual stress evolution forms and reveal their mechanical principles. • Variable amplitude loading and overloading impose significant effects on residual stresses. • Interactions between materials with different Δε p dominates the residual stress evolutions. [ABSTRACT FROM AUTHOR]

In this paper, full-scale field tests and numerical simulations are used to study the dynamic behaviour and destruction process of the laminated glass windows under combustible gas explosions. The blast overpressure caused by the explosions of combustible gas, the mid-span displacement and damage process of the windows were all documented during the field tests. The results are analyzed and presented in this paper. It is found that the laminated glass windows under blast loads of combustible gas explosions exhibit a characteristic bending failure, which differs from those under high explosives explosions. Numerical model of dynamic behaviour and destruction of laminated glass windows is developed in LS-DYNA and validated by the test results. The factors affecting the resistance of laminated glass windows to explosions of combustible gas are analyzed through numerical simulations. The results show that increasing the thickness of the glass panel and the interlayer, using soft supports and providing sufficient bite depth for the laminated glass window can significantly enhance its capacity to resist combustible gas explosions. • The failure modes of laminated glass window subjected to combustible gas explosion in full-scale field tests. • Differences of the failure process subjected to the combustible gas explosion comparing with that under TNT explosions. • The factors affecting the resistance of laminated glass windows to combustible gas explosions. [ABSTRACT FROM AUTHOR]

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis. • Quantitatively characterized the impact of corrosion on the geometric characteristics of steel columns. • The effect of corrosion on the buckling behavior of intermediate compression-bending corroded H-shaped steel columns. • Established a morphology-based numerical method to predict the buckling performance of corroded columns. • The failure mechanism of the corroded intermediate steel columns was observed and analyzed by tests and simulations. [ABSTRACT FROM AUTHOR]

Longitudinal cracks at the bottom of the deck are a common form of hidden damage in box girder bridges. Timely detection of deck cracking is critical to ensure the safe operation of box girder bridges. This paper proposes a damage detection method for the deck of box girder bridges using mode shapes constructed from a moving vehicle. One stationary excitation vehicle excites the local bending modes of the deck, and the other vehicle moves along the planned path. The moving vehicle acceleration is collected to construct mode shapes on the driving path. First, generalized beam theory is used to analyze the dynamic behavior of the box girder bridge. The theoretical model of the proposed approach is built to analyze the response of the vehicle-bridge system under shaker excitation, and mapping relationship between the instantaneous amplitude of the vehicle response and the local bending mode of the deck is deduced. The damage indicator based on the mode curvature is used to determine the crack position. Then, a damage detection process for field testing is proposed. Technical details such as excitation parameters, driving path, and narrowband filtering are explained. Finally, factors that affect damage detection, including road roughness, crack length, and crack height are investigated via numerical analysis. Results show that the proposed method can detect medium damage. • Dynamic characteristics of the box girder bridge are analyzed through generalized beam theory (GBT). • Vibration characteristics of the deck are clarified based on the proportion of each GBT deformation mode. • Relation between the vehicle response and the bending mode of the deck is revealed by Hilbert transform. • Damage detection process for field testing of bridges is proposed, and technical details are explained. • Influence of road roughness, crack length and crack height, are investigated via numerical analysis. [ABSTRACT FROM AUTHOR]

Determining frequency of buildings has a crucial impact on proper analysis and design of structures. Conventional methods (i.e., in situ and numerical analysis) are generally costly and time-consuming. This study aims at developing Machine Learning (ML)-based methods for obtaining frequency of structures with the focus on masonry towers (i.e., bell towers). To this end, a database including the results of either in situ or numerical analysis on over 90 masonry towers available in literature is collected. Additionally, frequencies of 18 towers located in Venice, Italy are measured by site survey, and added to the database. Parameters with the highest influence on tower's frequency, namely height, plan dimensions and modulus of elasticity are defined as input variables for predicting natural frequency of a tower by ML-based techniques including Decision Tree (DT), Random Forest (RF), XGBoost and K-Nearest Neighbors (KNN). The models' performance is analyzed by comparing the correlation between the predicted and real values. Moreover, the models' accuracy is assessed through common performance metrics and Taylor diagram, and the most accurate model is introduced accordingly. Results highlighted the high capability of ML-based approaches for predicting towers' frequency, and the XGBoost model exhibited the highest accuracy. In the second part of the paper, the values predicted by the most accurate model are compared to those calculated by the equations proposed by design Codes (i.e., NTC008, NCSE, ASCE) and literature. Lastly, for deeper investigating the performance of masonry towers a sensitivity analysis is performed by the proposed XGBoost model, and an equation is suggested for calculating their natural frequency based on their height and plan width. • A database of the natural frequency of towers is collected from the literature as well as on-site surveys. • ML-based models are proposed for predicting the natural frequency of towers. • Accuracy of the ML-based models is compared to that of equations available in design codes. • An equation is proposed for calculating natural frequency of towers based on their height and plan width. [ABSTRACT FROM AUTHOR]

This paper studies the novel vibration control of an inerter-enhanced mega sub-controlled structure system (MSCSS). The seismic response of MSCSS is investigated using a tuned viscous mass damper inerter (TVMDI) and compared with existing control methods. This novel strategy evaluates two kinds of TVMDIs on MSCSS, including the inter-story TVMDI, where the TVMDIs are installed inter-story, and the outrigger-based TVMDI, where the TVMDIs are vertically connected between the outrigger and the perimeter of the MSCSS's column to achieve significant energy dissipation. First, a finite element model of MSCSS is established and validated with the experimental model of MSCSS. The governing equation of the enhanced MSCSS is derived from the uncontrolled model. Subsequently, the MSCSS equipped with TVMDIs is thoroughly examined and compared to the existing methods. The effectiveness of the proposed strategy subject to ground motion records via the numerical analysis method is also demonstrated. Finally, the reliability analysis of the enhanced MSCSS based on the probability density function is presented. Results from the numerical investigation of the MSCSS enhanced strategies have revealed that the inter-story and outrigger TVMDI system generally improved the response effectiveness of MSCSS better than the viscous damper (VD) and middle story isolation (MSI) systems. However, the outrigger TVMDI enhanced mega frames control effectiveness more effectively than the story-based TVMDI, whereas the latter is more suitable for substructures. ● The novel vibration control of an inerter-based enhanced MSCSS is studied. ● An uncontrolled FEM of MSCS is presented and validated with the experimental model. ● The dynamic equation of MSCS equipped with TVMD is derived from uncontrolled model. ● The proposed strategies is examined and compared to the existing control methods. ● The reliability analysis of the TVMD-enhanced MSCSS based on the PDF is presented. [ABSTRACT FROM AUTHOR]

Recent developments have demonstrated that the behaviour of segmental grey cast iron (GCI) tunnel linings can be simulated accurately with sophisticated 3D numerical models where the geometry of the segments and joints is considered explicitly. Such a 3D model is, however, impractical for geotechnical numerical analyses where the tunnel lining is usually simulated with simpler, structural elements. In this paper, a novel tunnel joint model specifically developed for simulating the behaviour of GCI longitudinal joints with beam elements in geotechnical finite element analysis is introduced. Unlike existing models, the model considers the contribution of the bolts to the joint response and the nonlinear decay of the rotational stiffness after joint opening as well as the dependency on the compression level. After calibration of the model parameters, the model was utilised in a series of parametric analyses replicating the elastic continuum model using 2D beam elements. The response of the segmental GCI lining was essentially equivalent to that predicted by an advanced 3D model which validated the new modelling approach. The development of the joint beam model enables the nonlinear behaviour of segmental GCI tunnel linings to be accounted for in routine geotechnical numerical analyses. • A new model is proposed to represent the bending moment-rotation behaviour of tunnel joints. • The bending moment-rotation relationship is dependent on the axial force and characterised by a hyperbolic expression. • The joint model captures the bending moment-rotation behaviour as predicted with 3D modelling. • The behaviour of segmental grey cast iron tunnel linings can successfully be simulated with beam elements. [ABSTRACT FROM AUTHOR]

• This paper presents a comprehensive numerical study on curved steel plate I-girders subjected to patch loading. • The results obtained from FE analyses were verified against experimental results. • The ultimate load decreases in curved I-girders when the radius of curvature decreases. • Practical recommendations are proposed to the applicability of the design provisions prescribed in EN 1993-1-5 for straight girders to curved I-girders. Curved steel plate girders are often utilized in bridges built in congested urban areas, where intricate plan alignments are required. Their performance and design is, however, more complex than that of equivalent straight girders, especially regarding concentrated forces: while AASHTO adopts a simplified and empirical approach for the design of curved steel girders, the Eurocode for plated structures EN 1993-1-5 does not address the patch loading design of steel plate girders curved in plan, being only applicable to straight girders. Therefore, it is necessary to carry out further research in order to achieve a better understanding of the behavior of curved steel plate girders so that suitable design approaches accounting for the specific response of these structures can be developed. This paper presents a comprehensive numerical study on curved steel plate I-girders subjected to patch loading, considering material and geometric nonlinearities as well as initial imperfections. The numerical models are developed by means of the advanced finite element software ABAQUS and validated against experimental tests available in the literature. The numerical results demonstrate that the elastic critical buckling loads increase with increasing span-to-plan radii, which can be conservatively estimated using the EN 1993-1-5 provisions for straight steel girders, and that the ultimate patch loading resistance decreases with the radius of curvature. Based on this, practical recommendations are proposed to extend the applicability of the design provisions prescribed in the next version of EN 1993-1-5 for straight steel I-girders to the case of curved steel I-girders. [ABSTRACT FROM AUTHOR]

• Two innovative retrofit methods are presented in this paper. • Pre-stressed steel strapping technique is applied to retrofit deficient RC joint. • A numerical model is proposed to simulate the cyclic behaviors of specimens. • Softened strut and tie model is applied to obtain the shear capacity of specimens. This paper presents the results of an experimental and numerical study on strapping method for retrofitting deficient interior RC beam-column joints, which do not meet the requirements of current seismic design codes due to some deficiencies including low strength of concrete, inadequate transverse reinforcements, and low construction quality. In order to explore the seismic behavior of the retrofitted RC joints, six interior joint specimens, including two deficient RC joints with inadequate transverse rebar, three RC joints retrofitted with prestressed high-strength steel strips and one RC joint retrofitted with adhesively-bonded steel and prestressed high-strength steel strips, were designed and tested under cyclic loading. The main variables included the retrofit methods, axial compression ratio and volume of steel strips. The test results indicated that the prestressed steel strips worked together well with the deficient RC joints, and the retrofitted specimens exhibited better seismic behavior than the deficient control specimens, especially in deformability and energy dissipation. On the basis of the experimental study, the corresponding numerical model was established using the Open System for Earthquake Engineering Simulation (OpenSEES) and then verified to be valid. Finally, the modified softened strut and tie model was proposed in this paper to calculate the shear capacities of the specimens, and the calculated results agreed well with the test results. [ABSTRACT FROM AUTHOR]

• Sectional analysis and moment curvature approach provide accurate results. • Type of material models strongly affect the predicted fire resistance and deformation of a column. • Temperature elongation of materials has significant effect on column deformation. In the paper, a numerical procedure for investigation of slender reinforced concrete columns and steel-concrete composite columns at normal and high temperatures is presented. The procedure is based on sectional analysis and moment-curvature approach. Its applicability is illustrated on validation examples in which the results obtained by the simulations are compared with the test data given in literature. It is shown that the procedure provides sufficiently accurate results. The procedure was implemented in an in-house MATLAB code. The code is employed for the calculation of the examples presented in the paper. The code was also included in freely available scientific computer programs. The procedure is applicable for normal and high temperature conditions and for columns of symmetrical cross-sections of any type and shape. It is applicable in connection with any type of temperature-time curve, heat transfer model, and material models. [ABSTRACT FROM AUTHOR]

Highlights • Geometrically nonlinear behavior of corrugated laminated shell is investigated. • Specimens are made by unidirectional glass/epoxy prepreg and autoclave process. • The practical challenges during curing process are discussed. • A new technical material model is also adapted to solve the problem numerically. Abstract This paper presents experimental and numerical studies on the geometrically nonlinear behavior of corrugated laminated composite shells (CLCS) under quasi-static loading along the corrugated direction. A geometrically nonlinear layer-wise shell finite element formulation is adopted to study the behavior of CLCS under large deformation by modeling of incremental different moduli in the tensile and compressive regimes through the thickness, where the spatial location of neutral axis shifts with deformation. A master curve is presented to estimate the value of compressive modulus from given tensile and flexural moduli. Using the prepreg autoclave method, the paper also describes practical challenges in the manufacturing of CLCS and reveals significant influence of thickness on the nonlinear elastic behavior of two thin and moderately thick CLCS. The proprietary layer-wise shell FE formulation is verified with solid-finite-element modeling and employing a developed user material (USERMAT) subroutine in the commercial software ANSYS. Resulting improvements in numerical modelling are assessed in both general and local behaviors. [ABSTRACT FROM AUTHOR]

Highlights • Footbridges require attention to ensure proper functional features and comfort of use. • FRP and GFRP materials became competitive solutions in the construction of bridges. • In the paper numerical analysis of dynamic behaviour of GFRP footbridges is presented. • Vibration serviceability due to pedestrian-induced load and traffic load was studied. Abstract Over the past few decades, fibre-reinforced polymer (FRP) materials in general and glass-fibre-reinforced polymer (GFRP) in particular have become popular and competitive solutions in the construction of bridge objects. Because of their properties – such as high strength to weight ratios, ease of structure assembly, non-conductivity and chemical resistance – significant applications of the composite materials have been realised in the construction of footbridges in particular. In this paper, a numerical evaluation of the serviceability behaviour of two examples of composite material footbridges is presented. For the purpose of the study, it was assumed that the footbridges were made of the same composite material but they differ from each other with regard to structural geometry. The first stage of the study was the numerical estimation of the modal characteristics of the footbridges, i.e. their mode shapes and natural frequencies. The risk of the resonance phenomenon caused by pedestrian loading was then considered for both structures. In the next step of the calculations, the authors assessed the dynamic response of the footbridges to typical traffic loads; these types of load are transmitted to the structure through the ground and foundations. For numerical analysis, finite element (FE) models of the footbridges were prepared in the ABAQUS/Standard software program. The calculations included the representative time histories of the passage of a heavy goods vehicle and trains. Finally, the vibration comfort criteria for both footbridges were checked. The obtained results show that the comfort criteria are fulfilled. [ABSTRACT FROM AUTHOR]

Highlights • A model for the slim-floor beam behaviour at elevated temperatures is presented. • The presented model is validated against experimental data. • A parametric study is carried out to provide extended results. • Detailed design recommendations are provided to assist practitioners. Abstract Slim-floor beams are a novel typology of steel beams where the steel profile is fully embedded within the concrete floor depth. While the use of this system is increasing fast in the construction practice, the available investigations on its fire performance are still scarce. This paper focuses on analysing the fire behaviour of slim-floor beams combined with hollow core slabs as flooring system. Two configurations are studied, namely Integrated Floor Beam (IFB) and Shallow Floor Beam (SFB). A finite element model is developed and validated by comparison with experimental results available in the literature as well as with thermal tests carried out by the authors. Subsequently, parametric studies are conducted with the aim of providing practical design recommendations. The influence of the composite beam configuration, concrete type, longitudinal reinforcement and steel plate thickness is studied. The conclusions drawn in this paper suggest that the SFB configuration may provide a significant enhancement in terms of fire resistance compared to IFB, provided that the appropriate combination of the parameters studied is used. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

Highlights • This paper presents results of shaking table testing for full-scaled CLT building and a design procedure. • This building system is suitable for midrise CLT building with high ductility produced through rocking. • The structure was shown to behave well during severe strong motion as specified in the Japanese building standard law and to have survived the 1995 Kobe earthquake despite the occurrence of a compressive rupture in its shear wall as well as a support element against the vertical load. • Element tests and connection tests for various types of shear wall were conducted to define a numerical model and its parameters, and a shaking table test was conducted to confirm the model and its parameters and to evaluate structural performance. • A target Structure composed of narrow shear walls and high ductile tensile bolts was designed so as to satisfy the minimum requirement of Japanese building standard law. • Story shear capacity calculated from a numerical model and element tests (such as connections) were safely evaluated; but to evaluate the capacity correctly, further research is required in the element and system levels. • Though a variety of undetermined issues and challenges remains, the Building Standard Law and Notification for three different CLT construction systems was enforced in April 2016 to ensure the construction of safe CLT buildings. Abstract A national research project to investigate proper structural design methods for cross-laminated timber (CLT) buildings has been initiated by a subsidiary of the Ministry of Land, Infrastructure, Transport and Tourism of Japan since 2011. In the final stage of the project, shaking table tests were conducted for CLT buildings designed according to a proposed structural design procedure which confirmed damage limit state, safety limit state, allowable stress, and ductile factors, etc. This paper presents results of shaking table testing for full-scaled CLT building and a design procedure. The three different systems examined are buildings composed of narrow panels, wide panels with an edge tensile connection, and wide panels with an edge tensile connection for each no-window shear part. The focus of this paper is the building of narrow panels. This building system is suitable for midrise CLT building with high ductility produced through rocking. The structure was shown to behave well during severe strong motion as specified in the Japanese building standard law and to have survived the 1995 Kobe earthquake despite the occurrence of a compressive rupture in shear walls which are support elements against the vertical load. Story shear capacity calculated from a numerical model and element tests (such as connections) were safely evaluated; but to evaluate the capacity correctly, further research is required in the element and system levels. Though a variety of undetermined issues and challenges remains, the Building Standard Law and Notification for three different CLT construction systems was enforced in April 2016 to ensure the construction of safe CLT buildings. [ABSTRACT FROM AUTHOR]

Shear design and verification of bridge deck slabs subjected to concentrated loads (as those of wheels from traffic) is a topic subjected to scientific and engineering debate, where several questions remain open. Several design procedures have been proposed in the past to determine suitable values of the internal forces for design, such as the so-called load-spreading rule or considering a smoothing length for redistribution of the internal forces calculated based on linear elastic approaches. Despite these previous efforts, several instrumental aspects governing the response of bridge deck slabs still need to be clarified and subjected to scientific discussion. An important one relates to the location of the governing control section. Typically, for the case of cantilever bridge deck slabs, two control sections are checked: one close to the webs (acting as linear support) and another near the concentrated loads. While there is no debate about the shear check performed at the section close to the linear support (similar to a one-way slab response), how the check has to be done at the section close to the load introduction zone remains unclear (which can be interpreted as punching or as a one-way shear phenomenon). Another aspect under discussion is the determination of the internal forces considering the redistributions related to the non-linear behavior of the slab, avoiding too simplistic and overly conservative rules. To better understand the phenomenon and to lead to more comprehensive and consistent design approaches, the behavior of cantilever bridge deck slabs subjected to concentrated loads is thoroughly investigated in this paper. The study starts with several phenomenological observations on shear failures in cantilever bridge deck slabs obtained from previous experimental programs. Then, a refined analysis is presented considering a realistic out-of-plane shear response of reinforced concrete slabs. From these analyses, the internal forces can be evaluated in a sound manner accounting for a gradual reduction of the out-of-plane shear stiffness as a function of bending moments and shear forces. This new feature allows tracking the location of the potential shear-critical regions and examining the forces redistributions related to non-linear behavior. Unlike traditional approaches (like the "load-spreading rule" or smoothing lengths), the presented numerical analyses can consider shear failures at any location. The main findings from the physical observations and refined analysis are eventually used to propose a simple but phenomenologically consistent design methodology aimed at practical applications. • Observation on bridge deck tests collected from the literature indicates significant internal forces redistribution. • The geometry and kinematics of the failure cracks of such bridge decks are more similar to the shear cracking of beams without shear reinforcement. • A novel numerical modeling strategy was developed based on a smeared approach to account for the presence of shear redistribution. • A parametric (numerical) study on full-size bridge decks confirmed the influence of direct strutting and flexural reinforcement curtailment. • A phenomenologically consistent design methodology aimed at practical applications was ultimately proposed. [ABSTRACT FROM AUTHOR]

Cement-based columns in combination with geosynthetic reinforcement is a well-established soft ground improvement technique to enhance embankment stability. This paper aims to present a finite-element (FE) study based on a case history of a geosynthetic-reinforced column-supported (GRCS) embankment over soft soil. In this study, the columns are simulated with an advanced Concrete model to simulate the development of possible cracking and induced strain-softening. Numerical results are compared against published centrifuge tests, giving confidence to the established FE model with the Concrete model. New insights into the progressive failure mechanisms of GRCS embankments over soft soil are then discussed by examining the stress paths, internal forces, and cracks, as well as the plastic failure zones of columns. In addition, the role of columns and geosynthetics on the progressive failure mechanisms (failure loads and sequences) is also examined by an extensive parametric study. The results suggest that provided the optimization of compressive and tensile forces in the columns combined with the tensile stiffness of the geosynthetics is put in place, more columns can be mobilized to resist global sliding failure and to improve the bearing capacity of GRCS embankments. • The crack-induced softening of DCM columns is captured using the Concrete model. • Progressive mechanisms of GRCS embankments over soft clay are interpreted. • The role of geosynthetic and columns on progressive failure mechanisms of GRCS embankments are identified. [ABSTRACT FROM AUTHOR]

The tuned inerter damper (TID) is a viable solution for addressing the vibration issue of the adjacent-building system. However, the conventional optimal calibration of the TID is conducted based on the classic 3-degree-of-freedom (3-DOF) model with one resonant DOF for each structure, which ignored the background flexibility contribution that comes from non-resonant modes of each one, and thus leads to non-optimal control performance. This paper developed a novel analogue 3-DOF model, in which the background flexibility contribution of each flexible building at the damper attachment location is represented by an equivalent stiffness element. An enhanced formula for the TID optimal frequency is developed accordingly (targeting the fundamental mode of the taller building) using the 'root-locus' method, where the background flexibility as well as the resonant mode contributions that come from both buildings are accounted for. For completeness, the optimal frequency formula that ignores the background flexibility contribution is derived based on the classic 3-DOF model. A robust approach is adopted to determine the optimal damping ratio based on the classic model. Numerical analysis is conducted based on a 25-15 floors adjacent-building system. Results demonstrate that when the enhanced frequency-tuning formula is used, a much more balanced frequency response curve of the taller building is achieved. Further, time-domain seismic analysis indicates that the TID performance is consistently improved when background flexibility is accounted for in the design formulas. • A 3DOF TID-adjacent-building model developed involving background flexibility. • Optimal TID frequency formula developed with background flexibility represented. • Theoretically prove the incapability of TID for controlling similar adjacent buildings. • The proposed formula leads to superior control performance than the classic one. • Increase of inertance value cannot always guarantee a better control performance. [ABSTRACT FROM AUTHOR]

High-strength centrifugal precast (HSCP) reinforced concrete (RC) hollow pipe columns using grouted corrugated duct connection (GCDC) is a novel structure form in accelerated bridge construction (ABC). Nevertheless, the confinement effect of the HSCP hollow column core concrete provided by single-layer transverse rebar and its impact on ductility is not clear. Therefore, in this paper, the confinement effect and the ductility of hollow columns is studied using finite element analysis (FEA) method. A modified model is established to evaluate the constitutive relation of the core concrete confined by single layer transverse rebar. Based on the modified model, a simplified fiber model for predicting the hysteric response of HSCP hollow pipe column using GCDC, which considers bond-slip effect in GCDC joint was developed. The results indicate that the confinement effect of HSCP hollow pipe column is sensitive to the wall thickness ratio. When the wall thickness ratio decreases, the ultimate strain of the core concrete significantly decreases, while the effect on strength is not significant. The simplified model which considers confinement effect is more accurate in predicting the ductility of HSCP hollow columns. It proves that the weak confinement effects can lead to early cracking of the inner wall of hollow columns, which leads a significant impact on the ductility of HSCP hollow columns. Based on the parametric analysis, the peak load of the hollow column increases by 16.7% when the wall thickness ratio rises from 0.1 to 0.2, but only slightly changes when the wall thickness ratio is increased beyond 0.2. The wall thickness ratio of HSCP hollow pipe columns should be set above 0.2 to ensure the strength and ductility. In addition, a ductility evaluation method and a design example were developed to guide preliminary ductile design of HSCP hollow columns. • A modified model is proposed to predict the constitutive relation of HSCP hollow column core concrete. • A simplified fiber model is developed to predict the hysteretic response of HSCP hollow pipe columns using GCDC. • A ductility evaluation method is developed to guide seismic design of HSCP hollow pipe columns using GCDC. [ABSTRACT FROM AUTHOR]

Numerical investigation of the mechanical behaviour of concrete-filled wire arc additively manufactured (WAAM) steel tube under axial compression is presented in this paper. Typical structural performances of concrete-filled WAAM steel tube are extensively analyzed based on the experimental results firstly. FE models are established based on 3D models obtained by 3D laser scan technology, whilst the material anisotropy of WAAM steel tube is taken into account. The sensitivity study on the finite element (FE) model parameters is developed to assess their influence on the simulation results. The established FE models are verified against the test results demonstrating their effectiveness in predicting the structural behaviour of the concrete-filled WAAM steel tube. The composite action between the WAAM steel tube and inner concrete is analyzed through the validated FE models, indicating that it should be emphasized within the strain range from 0.003 to 0.01. The influences of the concrete and steel strengths are evaluated to investigate the confinement effect, showing that the concrete and steel strength exhibit a negative and positive impact on the confinement effect, respectively, and a positive correlation between the steel strength and biaxial stresses of the WAAM steel tube can be obtained. Finally, the design method of concrete-filled WAAM steel tube under axial compression, which considers the effect of the geometric undulations and material anisotropy of the WAAM steel tube, is proposed based on the theory of confining effect. The comparison results indicate that the proposed method can predict the axial compressive strengths of the concrete-filled WAAM steel tubes with reasonable accuracy. • Axial compressive behaviour of concrete-filled WAAM steel tube numerically assessed. • Structural performances of concrete-filled WAAM steel tube experimentally analyzed. • Sensitivity study of FE model parameters developed. • Composite action between the WAAM steel tube and inner concrete analyzed. • Design method of concrete-filled WAAM steel tube under axial compression proposed. [ABSTRACT FROM AUTHOR]

This paper presents a novel damping plate-restrained isolation bearing (DP-bearing) that exhibits a range of advantages such as multi-stage energy dissipation, multi-directional restraining effect, and easily assembled/dismountable. The study commences with introducing the fundamental working principle of the proposed DP-bearing, followed by an investigation into the material properties of the damping plates using monotonic tensile and quasi-static cyclic tests. Subsequently, full-scale DP-bearing specimens, considering different numbers and orientations of the inserting damping plates as well as various free traveling distances ("predetermined gaps"), are tested. The test results confirm the multi-function of the damping plates which serve as energy dissipation sources and restrainers simultaneously. Prior to the predetermined gap, the load-displacement curves exhibit a rectangular shape that results from Coulomb friction. Once the gap is reached, the damping plates are activated and provide damping and restraint through shear or tension. The shear and tensile damping plates contribute to over 90% of the total horizontal peak resistance, with the former contributing to more than 70% of the energy dissipation. The study then presents a simplified numerical modeling approach, followed by design recommendations based on the simulation results. Furthermore, the numerical investigations provide supplementary evidence illustrating the effectiveness of the DP-bearing in different loading directions. The variations in the loading angle may induce a combined shear-tensile damage mode that differs from the modes observed in the tests. • A novel damping plate-restrained bearing is proposed. • Both the monotonic and cyclic loading material tests are conducted. • Experimental study on a full-scale bearing specimen is conducted. • The analytical model provides a straightforward method for designing the bearing. • Numerical studies validate and further interpret the experimental results. [ABSTRACT FROM AUTHOR]

• New computer-aided optimization design and additive manufacturing paradigm for steel joints in spatial grid structures is proposed. • Parametric topology optimization design method and numerical model for optimized joints are developed. • The structural performance of the optimized joints is investigated and compared with traditional joints. • A case study on double-layer spatial grid structure with hundreds of joints is presented to illustrate the applicability of the proposed paradigm. • Representative optimized joint is additively manufactured by selective laser melting using 316L stainless steel. This paper presents a complete computer-aided workflow for the parametric topology optimization (TO) design, numerical analysis and additive manufacturing (AM) of steel joints in spatial grid structures. A fully parametric TO design framework for steel joints in spatial grid structure was developed based on the Grasshopper platform. The joint models were parametrically established based on subdivision surface technology and further topology optimized through the bi-directional evolutionary structural optimization (BESO) algorithm with the support of cloud computing server. The structural performance of the optimized joints was thoroughly investigated via the parametric finite element analysis. Variables of loading conditions and TO parameters (target volume and filter radius) that affect the compliance, maximum displacement, maximum stress and stress distribution were taken into account. Analysis showed that the target volume governed the joint structural behaviour while the filter radius affected the geometric details of optimized joint. The practicability of proposed workflow was demonstrated through a parametric optimization design framework of a double-layer spatial grid structure with hundreds of steel joints. A typical optimized joint made of 316L stainless steel was additively manufactured using selective laser melting. This workflow is highly automatic and featured by high design flexibility and integration degree as well as good transplanted ability. [ABSTRACT FROM AUTHOR]

• Water storage tanks for fire suppression can be utilized to fulfill the function of structure control as Tuned Liquid Damper (TLD) if properly designed. • A TLD is outfitted with a perforated floor to allow for water passage between compartments to meet both volume and flow rate fire code requirements. • A 2D macroscopic SPH model is employed to model the dual function rectangular tank with a perforated floor. • The model showed excellent agreement when compared with an explicit microscopic model (MM), with significant decrease in computational time. • For a structure-TLD system subjected to random excitation, the tank with a perforated floor was tested against tanks with a solid floor and a fire reserve. • The tank with a perforated floor enhanced the performance of the TLD compared to other tanks, while obtaining the required water volume for fire suppression. Exceeding serviceability limits due to wind-induced motions in tall buildings can cause discomfort for residents and adversely affect auxiliary building services, such as elevator operations. A tuned liquid damper (TLD) is an attractive type of dynamic absorber because of its simplicity and affordability. However, its dimensions and geometry can be limited by available floor space. Utilizing dual-purpose water tanks for both damping and fire suppression purposes can be a feasible resolution to fire code requirements and building motion control. Several design criteria need to be considered to accommodate the fire code requirements and the proper tuning of the TLD. Consequently, in this study, a TLD tank is fitted with a perforated floor to divide it into two compartments that allow water transmission to meet fire code requirements. However, the sloshing motion within the tank is complex and computationally expensive to capture when using traditional simulation models. This paper presents a 2D ISPH code equipped with a macro-level model to capture the effect of the perforated floor on the overall sloshing response of the tank. The model is first evaluated using existing results from previous studies on tanks with horizontal baffles. Next, the ISPH model is used to numerically model the perforated floor using the Ergun resistance (ER) macro-level model. In addition, the perforated floor is also explicitly micro-level modelled using rigid boundary particles to validate the proposed ER model. A numerical analysis is then conducted under different excitation amplitudes and frequencies, with both time history and frequency response results being presented. A structure-TLD model is subsequently used to capture the structure-TLD system response under random excitation. Results show that the ER model can efficiently model tanks with dual functions under both harmonic and random excitation and across a wide range of amplitudes and frequencies, with appreciable computational time savings. The proposed tank with a perforated floor is found to be effective in serving as a dual-purpose TLD and storage tank for fire suppression in buildings. [ABSTRACT FROM AUTHOR]

In this paper, a simplified calculus model for the prediction of the compressive response of RC column footing with a square cross-section is presented. As it is well-known RC concrete footing are designed adopting uniform contact pressures on the substrate and assuming a strut and tie model in deep members and a cantilever beam or slab model in flexible members. Deep and flexible members are distinguished in literature only based on the tangent of the angle expressed as the ratio between the depth and the shear span of the footing. In this paper, several subgrade contact pressures distribution for column footings (rigid or soft soils) were considered in developing a mechanical model able to derive the complete load displacement curves of RC deep and flexible footing in compression. The objective of the research was the more appropriate choice of the calculus model to predict the compressive response of single column footing. In particular, if the angle, expressed as the ratio between the depth and the shear span of the footing, is higher than 45° the strut and tie model was suggested for best prediction, while, if the angle is lower than 45°, the beam or the slab models with punching shear were adopted. For both cases simplified loading soil profiles corresponding to rigid, flexible or winker model were adopted. Effects of main parameters such as geometry (depth, width) and shape of footing (single or shaped), the mechanical ratio of longitudinal reinforcement and type of soil are investigated both numerically and analytically. Numerical results and available experimental results were utilized to verify the model. The comparison between analytical and numerical results allows one to validate the proposed model and to define the range of application of the strut and tie or beam model depending on the footing geometry, the mechanical ratio of longitudinal reinforcement and type of soil. Finally, the comparison between analytical and experimental results available in the literature gives a further confirmation on the reliability of the proposed model. [ABSTRACT FROM AUTHOR]

This paper numerically studies the wind effect on grooved and scallop domes. The introduction of a groove on a spherical dome causes abrupt change on its wind pressure coefficient (Cp) in the vicinity of the groove. The sharpness of indentation varies with the position angle of the axis of the groove to wind direction and obtains its highest effect at 90°. This paper develops equations for the distribution of Cp on the surface of spherical, grooved and scallop domes with rise to span ratios [0, 0.7]. The results of the equations agree reasonably well with that of CFD. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of much-needed numerical and experimental models for understanding the mechanical behaviour, section capacity and energy absorption of the innovative fabricated columns consisting of corrugated mild-steel plates. The corrugated square columns proposed in this paper are fabricated by welding four corrugated plates which are originally produced from 3 mm thick flat mild steel plates. The experiments consist of applying a compressive axial force to the columns to determine load–displacement curves of the fabricated sections. The effects of geometric parameters such as inclination angle and corrugation height are also investigated experimentally by considering three different types of corrugated columns. Moreover, a finite element model in which the effects of material and geometric nonlinearities as well as residual stresses are taken into account is developed using ABAQUS. The experimental results are also compared with those given by the finite element (FE) model whilst a good agreement is achieved. A cost analysis is also conducted in which the cost of the innovative columns proposed in this research is compared to those of conventional welded columns currently available in the civil engineering market. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new retrofitting method for structural steel members is investigated. • A parametric study was conducted using numerical approach. • The effectiveness of the retrofitting is interpreted with design parameters. • A design concept is suggested using machine learning algorithm. • A design example is illustrated for the practical implementation. The paper presents a numerical investigation on the retrofitting of Hot-Rolled Steel (HRS) beams using Cold-Formed Steel (CFS) encasing channels. The open cross-section HRS channel is transformed into a closed cross-section by encasing the CFS channel. This transformation increases the torsional rigidity of the structural member and helps in reducing the vulnerability of Lateral-Torsional Buckling (LTB). Parametric studies were carried out using numerical analysis. The existing experimental results were used for validation of the numerical model. A total of 600 numerical simulations including design parameters such as thickness of the CFS channel, intermediate spacing between the spot welds (connecting HRS and CFS channels), slenderness ratio, and the cross-sectional dimensions of the HRS beam were considered. The analyses indicated that the effectiveness of the retrofitting increases with an increase in the slenderness ratio of the HRS channel. Machine Learning (ML) method called Symbolic Regression (SR) was used to formulate an equation predicting the increment in the moment capacity as a function of parameters investigated. Finally, a simple design concept is suggested to determine the required CFS channel thickness and intermediate spot weld spacing to achieve the required increment in the moment capacity after retrofitting. [ABSTRACT FROM AUTHOR]

• The impact of scour on masonry arch bridges is numerically investigated. • The sensitivity to different scour scenarios of a wide set of response parameters is analysed. • Both kinematic and modal parameters are analysed to find proper damage metrics. • Refined 3D Abaqus model developed to simulate typical failure mechanisms of masonry arch bridges. • The scour levels activating the various failure mechanisms are identified. • Results provide insights into the optimal sensor choice and placement in a monitoring system. Scour constitutes a significant treat to bridges. When it is not directly measured, it can be very difficult to detect and may go unnoticed until it produces catastrophic effects. Thus, understanding the effects of scour on bridge structures is of paramount importance for the development of effective scour monitoring strategies and early warning scour systems. This paper investigates the impact of scour on masonry arch bridges, which are the bridge typology most vulnerable to such a hazard. It aims at identifying synthetic damage parameters that can be used for bridge vulnerability and risk assessment, as well as at providing information about the optimal sensor placement in a monitoring system. For this purpose, extensive numerical analyses are performed on a representative bridge prototype to quantify how different response parameters, including kinematic parameters and modal parameters (i.e., the natural frequencies, and qualitatively the transverse mode-shapes), evolve under scour scenarios of increasing severity. The most recurrent damage scenarios involving piers, spandrel walls and arches are analysed to quantify the scour levels activating the various failure mechanisms, which can be finely detected and assessed through the numerical simulations. The study results allow identifying the parameters that are most sensitive to scour and the relevant limit values of interest for risk analysis. They are also useful to inform the development of optimal monitoring strategies for masonry arch bridges exposed to scour. [ABSTRACT FROM AUTHOR]

• An adaptive beam string structure based on internal force minimization is presented. • A downscaled model with monitoring and controlling systems is devised and fabricated. • Strategy search algorithm is created combining gradient descent & genetic algorithm. • Strategy prediction network is trained applying backpropagation learning algorithm. • Adaptation of the structure to loading is verified by simulations and experiments. In this study, a novel adaptive beam string structure (ABSS) designed to cope with external loading through sensing and mechanical actuation was developed. Unlike traditional beam string structures, ABSS further contains the monitoring and controlling systems, which allows it to sense and react to loading in real-time. The active control method for ABSS based on internal force minimization was established by using the strategy search algorithm (SSA) and strategy prediction network (SPN). SSA is a global search algorithm proposed through combining the strengths of genetic algorithm and gradient descent, and SPN is an artificial neural network established by applying the backpropagation learning algorithm. The downscaled model and test scheme of ABSS were designed and deployed to clarify its effectiveness. The numerical simulation and field experiments were conducted, and simulation results agree well with measurements. Through comparative analysis of simulation and test results, the adaption of ABSS to loading and validity of control method were verified, and ABSS possesses good control capability on internal forces, which is reflected in two ways: 1) reducing the beam stress responses; and 2) improving the beam stress distribution. The research methods and conclusions of this paper can provide valuable references for the design, fabrication, and control of adaptive structures. [ABSTRACT FROM AUTHOR]

• 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]

• The UHPC rubber-sleeved stud connector was proposed. • Push-out test and numerical study were carried out to study the behavior. • Parametric analysis was performed through the validated finite element model. • An empirical formula was developed to predict the stiffness of UHPC rubber-sleeved stud connector accurately. Ultrahigh-performance concrete (UHPC) has been widely used for field-cast connections of steel–concrete composite structures to accelerate bridge construction. This paper proposed a UHPC rubber-sleeved stud connector, composed of the ordinary stud (OS) connector, rubber sleeve, and infilling UHPC, which could enhance the deformation ability of composite structures. Push-out tests and numerical simulations were carried out to study the behavior. The UHPC rubber-sleeved stud connector had a greater peak and ultimate slip than the OS connector, while the ultimate capacity was similar. The validated FE models were used for parametric analysis to determine the impact of several variables on the performance of UHPC rubber-sleeved stud connectors. Increasing the rubber sleeve's height and thickness could remarkably reduce the stiffness while little influence on the shear strength. The stud diameter had a beneficial impact on the stiffness and strength, but the UHPC compressive strength did not affect the ultimate capacity. Finally, a new formula was proposed to evaluate the shear stiffness and the average value of the calculated s to FE results was 1.003, which indicated the proposed formula could accurately predict the stiffness of UHPC rubber-sleeved stud connectors. [ABSTRACT FROM AUTHOR]

• Tests and numerical analysis of the steel–concrete composite beams strengthened with NSM CFRP systems. • Effects of the end anchorage and the number of CFRP bars on the flexural performance of strengthened composite beams. • Parametric studies based on the FE model of the composite beams strengthened with NSM CFRP systems. Compared with conventional strengthening methods, the near-surface mounted (NSM) technique is more suitable for strengthening steel–concrete composite beams, especially at the hogging-moment regions. This paper investigates the flexural performance of steel–concrete composite beams strengthened with NSM CFRP systems. Four-point bending tests are carried out on four composite beam specimens, including one control beam without strengthening and three strengthened beams with NSM CFRP systems. The failure mode, ultimate load-carrying capacity, deflection distribution, and material strain distribution of the composite beams are presented, based on which the effects of the anchorage method and the number of CFRP bars are studied. The test results demonstrate that the main failure mode of the strengthened beams is the buckling of the steel beam. Compared with the control beam, the load-carrying capacity of the strengthened composite beams with two and four CFRP bars is increased by 10% and 20%, respectively. The use of end anchorage has a slight effect on the flexural capacity of the strengthened beams, while significantly improves the ductility during the later stage of loading. In addition, a nonlinear finite element (FE) model is proposed and calibrated, based on which a parametric study is performed to investigate the effects of the length and section area of CFRP bars, the spacing of grooves, and the thickness of bottom steel flange on the ultimate load-carrying capacity of the strengthened beams. [ABSTRACT FROM AUTHOR]

• Direct shear box tests on backfill materials and large interface shear box tests on masonry-to-backfill interfaces are performed. • The interface shear behaviour between masonry and backfill materials is characterised. • The effects of masonry bond patterns and backfill properties on the shear parameters of masonry-to-backfill interfaces are assessed. • Ratios of friction angle between backfill materials and masonry-to-backfill interfaces are summarized. This paper presents the results from an experimental campaign to characterise the shear behaviour of the brickwork-backfill interaction in masonry arch bridges. Two representative backfill materials found in real masonry arch bridges (compacted crushed limestone and clay) were sheared against brickwork masonry specimens with two different bond patterns (a soldier course bond and an English bond). The results demonstrated that the interface shear behaviour between masonry and backfill was different from the internal shear behaviour of backfill materials. When compacted crushed limestone was adopted as the backfill material, the ratio between the masonry-limestone interface friction angle (φ i) and the internal friction angle (φ) of limestone was determined to lie within the range from 0.70 to 0.75. However, when clay was used as backfill material, the φ i / φ ratio was much lower, and of the order of 0.51 to 0.52 under the assumption of zero-cohesion at the interface, or 0.35 to 0.39 if interface cohesion was considered. Moreover, the properties of the backfill material had a significant influence on the interface shear behaviour, whereas the effects of brickwork bonding pattern were marginal. This study provides valuable insight into the identification of brickwork-backfill interface parameters for the numerical analysis of masonry arch bridges. [ABSTRACT FROM AUTHOR]

• Novel technique using tile vaults as formwork for doubly-curved reinforced concrete shells. • The technique reduces costs and waste, while providing a unique finishing at the intrados. • Material characterization of masonry, concrete and steel reinforcement. • Experimental validation by load testing and monitoring full-scale, composite sail domes. • Definition of calibrated FE structural model of proposed hybrid structure. Conventional formworks for concrete curved shells either are expensive, complex and wasteful or have formal restrictions. Using tile vaults (also known as timbrel, Guastavino, thin-tile or Catalan vaults) as stay-in-place formwork for concrete shells could significantly reduce construction costs and material waste. Tile vaults only require formwork at the boundaries and provide a high formal flexibility. The combination of masonry and reinforced concrete creates a new type of composite structure that needs experimental validation and new structural analysis models to deal with the specific features of the system. This paper presents experimental research on the component materials, load tests on doubly-curved, full-scale prototypes and the definition of a reliable Finite Element structural model for the analysis of the proposed hybrid structure. The experimental research has involved the characterisation of the bricks, mortar, concrete and reinforcement composing the proposed system in order to provide the material properties to be considered in the structural analysis. The construction and testing of two composite sail domes in the laboratory have allowed the validation of the proposed FE model by comparing its predictions with the collapse mechanisms, damage, ultimate loads and load–displacement curves obtained experimentally. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear finite element analysis of slab-beam-column connection in precast concrete structures is presented. The detailed experimental results of the full-scale connection have been discussed in a different paper. However, due to the complexity of slab-beam-column connection and the unique features of the tested specimen, the numerical study was carried out to better understand the structural behavior. The internal connection was comprised by corbels, dowels and a continuity bars passing though the column. The FE model was validated using the experimental results of the precast concrete connection and it showed good capacity to represent the behavior observed in laboratory. A parametric analysis was conducted with the variation of the diameter of the continuity bars and the properties of the cast in place concrete. As a result of this study, some information about stresses, strains and displacements not obtained experimentally was determined in the numerical simulation and, with the parametric analysis it was concluded that the diameter of the continuity bars had more influence in the precast concrete connection capacity than the concrete compressive strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • A design method of curved origami metamaterial (CMM) with various origami creases is proposed. • The CMM with glass fiber-reinforced polyamides are beneficial to strengthen its load-bearing level. • The crushing behavior of the CMM with graded origami creases is more stable than that of uniform origami creases. • The deformation mode and energy absorption efficiency of the CMM are sensitive to the configuration of origami creases. This paper investigates the crushing characteristic of a novel curved Miura-ori metamaterial (CMM) with glass fiber-reinforced polyamides under multi-directional crushing loads. Based on the experimental test and numerical analysis, the deformation mechanism, crushing stress and energy absorption capability of the CMM are explored under multi-directional (0°, 10°, 20°, 30°) crushing loads. The progressive deformation mechanism of CMM with graded origami crease (CMM-G) is demonstrated, which follows its origami creases and exhibits high energy dissipation efficiency and load-bearing capability. There are worthy crushing merits in the CMM-G compared with CMM with uniform origami crease under multi-directional crushing loads, where the specific energy absorption of CMM-G improves by 24.93% under 0° crushing load. Moreover, the influence of geometric configurations of CMM-G is positive on crushing behavior. The deformation mode, load-bearing level and energy dissipation efficiency are sensitive to the origami amplitude A , the number of origami crease N z and gradient coefficient e of the CMM-G under multi-directional crushing loads. This paper illustrates the valuable mechanical performance of curved origami metamaterial with gradient and composite reinforcement, which opens wide potential applications as energy absorbers or load-bearing devices. [ABSTRACT FROM AUTHOR]

Crowd induced dynamic loading in large structures, such as gymnasiums or stadiums, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these Fourier coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lags among individuals inside the crowd. This paper presents the results of some studies carried out in order to compare the existing load models used to simulate periodic jumpings and develop a new load model. Generally the testing is performed on platforms or structures that can be considered rigid because their natural frequencies are higher than the excitation frequencies associated with crowd loading. But in this paper, to validate these load models test have been performed on a structure designed to be a gymnasium, which has natural frequencies within that range. Test results have been compared with predictions based on the load modelling alternatives with quite good agreement. A calibrated finite element model of the structure has been used for this purpose. The new model provides a clear improvement in the energy contained within higher frequencies. [ABSTRACT FROM AUTHOR]

• Flexural behavior of a large-scale prestressed UHPC T -shaped girder is investigated through bending test. • A nonlinear analysis program for UHPC girders is developed and validated. • γ m is suggested as 1.0 to determine the cracking moments of UHPC girders. • Increasing prestress of the prestressing tendons and height-to-span ratio can effectively improve the cracking-resistance and flexural capacity of UHPC girders. A large scale (10 m long) prestressed ultra-high-performance-concrete (UHPC) T -shaped girder was experimentally investigated in this paper to study its flexural behavior, cracking moment, and ultimate flexural capacity through the bending test. By considering contribution of the tensile strength of UHPC, this paper suggested a modified tensile constitutive model of UHPC to achieve a reliable cracking moment and ultimate flexural design scheme for the prestressed UHPC girders. Effectiveness of this design scheme was demonstrated through the comparative studies on the developed load–deflection curves and ultimate flexural capacity of the girder obtained from the experimental results and that from the suggested design scheme. In addition, this study developed a nonlinear numerical analysis program to investigate the nonlinear flexural performance of the girder, and its flexural capacity calculated by using this program agreed well with the experimental results. Moreover, parametric studies regarding the influences of reinforcement ratios, prestresses of the prestressing tendons, and girder depths on the girder's flexural resistance were also conducted. Finally, it is concluded that (1) UHPC girder exhibited good ductility and excellent flexural deformation capacity and cracking performance; (2) the tensile strength of UHPC has limited contribution to the ultimate flexural capacity of UHPC girders; and (3) appropriately increasing reinforcement ratio of the prestressing tendons, ultrahigh compressive strength of UHPC could be fully utilized, and thus the cracking moment and ultimate flexural capacity of UHPC girders could be effectively improved. [ABSTRACT FROM AUTHOR]

• In the paper the in-plane response of decoupled masonry infills in reinforced concrete frames is investigated by means of numerical modelling. • Detailed numerical model is developed and validated against experimental results. • Due to the decoupling with elastomers, infill activation is rather low and it is postponed to high drift levels. • Parametric study performed in order to deeply understand the behaviour of decoupling system, showed significant benefits in the performance of masonry infilled frames under seismic loading. Damage of reinforced concrete (RC) frames with masonry infill walls has been observed after many earthquakes. Brittle behaviour of the masonry infills in combination with the ductile behaviour of the RC frames makes infill walls prone to damage during earthquakes. Interstory deformations lead to an interaction between the infill and the RC frame, which affects the structural response. The result of this interaction is significant damage to the infill wall and sometimes to the surrounding structural system too. In most design codes, infill walls are considered as non-structural elements and neglected in the design process, because taking into account the infills and considering the interaction between frame and infill in software packages can be complicated and impractical. A good way to avoid negative aspects arising from this behavior is to ensure no or low-interaction of the frame and infill wall, for instance by decoupling the infill from the frame. This paper presents the numerical study performed to investigate new connection system called INODIS (Innovative Decoupled Infill System) for decoupling infill walls from surrounding frame with the aim to postpone infill activation to high interstory drifts thus reducing infill/frame interaction and minimizing damage to both infills and frames. The experimental results are first used for calibration and validation of the numerical model, which is then employed for investigating the influence of the material parameters as well as infill's and frame's geometry on the in-plane behaviour of the infilled frames with the INODIS system. For all the investigated situations, simulation results show significant improvements in behaviour for decoupled infilled RC frames in comparison to the traditionally infilled frames. [ABSTRACT FROM AUTHOR]

• The difficulty of computing the lateral thrusts in buckling-restrained braces is discussed. • The main cause for this is identified in their sensitivity to imperfections. • A comparison is done among several FEM models for the choice of an "optimal" one. • An analysis of damage and of asymmetric tension/compression behavior for the BRB core steel is performed. • The difficulty in the accurate computation of the lateral thrust in BRB is proved numerically. The paper discusses the numerical analysis of all-steel buckling-restrained braces. These devices are designed to work in an inherently unstable regime, and their behavior is acutely sensitive both to any configuration detail in reality, and to any adopted parameter in their analysis. Their dissipative axial behavior can be reasonably well predicted by any suitable FEM model, if a good constitutive law is available. Nevertheless, it is shown here that an apparently accurate FEM calculation of the lateral contact forces, generated by the buckled core when it contacts the external containment profiles, produces results so sensitive to modelling details that they are practically devoid of an acceptable degree of accuracy. These observations might raise some doubts about the advisability of employing this type of bracing in normal engineering practice. In our viewpoint, a similar conclusion could be reached for any structural element designed to work in an unstable regime, unless the imperfections – of any type, including possible modelling details – could be explicitly taken into account, either parametrically or in a statistical way. [ABSTRACT FROM AUTHOR]

• Yielding in steel beams varies with moment distribution and residual stresses. • Yielding reduces effective in-plane and out-of-plane section rigidities. • In-plane moment distribution in continuous beams is affected by reduced rigidities. • Lateral buckling resistance is affected by moment distribution and reduced rigidities. • Buckling prediction requires iterative numerical analysis. The inelastic behaviour of a steel beam is complicated by reductions in the section rigidities which depend on the moment distribution and residual stress pattern. The inelastic beam is effectively tapered and mono-symmetric, and iterative numerical methods need generally to be used for the analysis. The in-plane moment distribution in an inelastic continuous beam lies between the commonly assumed rigid-plastic "plastic" path and a "yield" moment path. The yield path is the more critical for lateral buckling of the continuous beams considered in this paper. Approximations of the inelastic out-of-plane moduli of continuous beams developed from closed form lateral buckling solutions for simply supported beams in uniform bending can be used in a computer program for the buckling analysis of tapered mono-symmetric beams. Residual stresses cause significant reductions in the inelastic buckling resistance. The AISC design code predicts strengths which are similar in shape but significantly higher in magnitude than the inelastic buckling resistances of simply supported beams in uniform bending. The predictions for beams with central concentrated loads are much higher than the corresponding inelastic buckling resistances. Closer but still conservative approximations are obtained by using the method of design by inelastic buckling, which can also be used for continuous beams. This method is much simpler than those used to obtain accurate predictions. [ABSTRACT FROM AUTHOR]

• A quasi-static pushover test on RC pylon of cable-stayed bridges is first reported; • A simplified and efficient two-node lateral load-pattern for loading scheme is proposed; • A refined numerical model of the RC pylon is built and validated by the test; • Transverse failure mechanism and ductility of the RC pylon are summarized. Although often designed to behave elastically, seismic damage to reinforced concrete (RC) pylons of cable-stayed bridges have been witnessed in history such as the 1999 Chi-chi earthquake. This paper aims to assess the transverse seismic failure mechanism and ductile properties of typical inverted Y-shape RC pylons for long span cable-stayed bridges using quasi-static model tests and numerical analyses. To facilitate the limited laboratorial loading system, a simplified displacement-controlled two-node load-pattern, one at the bifurcation-node and the other at the crossbeam, is first proposed using numerical analyses. It is found the ratio of displacements at the two loading nodes is correlated generally well with the ground motion parameter, bracketed duration. A displacement ratio of 5.0 is then adopted in the test. Test results indicate a flexural damage mode with considerable ductility: plastic hinges were detected first at bottom of the upper column (i.e., above the crossbeam), then at bottom and top of the lower column, successively; multi-level displacement ductility factors are proposed to associate with numbers of plastic hinges formed in the pylon. Moreover, an experimentally validated numerical model is adopted to study the impact of loading displacement ratios on the failure mechanism and ductility. It is found that the loading displacement ratios may significantly affect them. Smaller displacement ratios tend to transfer the location of first plastic hinge from the bottom of the upper column to that of the lower column. [ABSTRACT FROM AUTHOR]

Highlights • A by-hand procedure for the non-linear capacity curve of RC wall/frame systems is proposed. • The mechanical interaction among frame(s) and wall(s) is explicitly considered. • 28 case studies: different geometry, wall-to-frame strength ratio and plastic mechanism. • Comparison with pushover analyses shows a maximum 5% error (base shear and displacement). Abstract A paramount step in seismic assessment of existing structures is the determination of the structural capacity. It is widely recognised that non-linear numerical approaches are arguably the most reliable tool to achieve this goal. However, reliable yet simple analytical procedures are needed to identify potential structural weaknesses and their influence on the overall capacity, to cross-check and/or interpret numerical analyses. This paper presents a novel analytical -or "by-hand"- procedure to calculate the non-linear capacity curve of RC dual wall/frame systems within the framework of the Simple Lateral Mechanism Analysis (SLaMA). The mechanical interaction among frame(s) and wall(s) is explicitly considered to calculate their base shear and overturning moment contributions. The procedure is outlined and applied to 28 case studies with different geometry, wall(s) position, wall-to-frame strength ratio and plastic mechanism. The results are compared to refined numerical pushover analyses, showing a maximum 5% error both in terms of ultimate base shear and displacement for the majority of the case studies. [ABSTRACT FROM AUTHOR]

Highlights • Various parametric effects on load-resisting mechanisms of 3D composite floor systems under an internal column removal scenario are investigated by FE simulations. • Effects of slab aspect ratio and joint type on robustness of 3D composite floor systems are assessed by an analytical model. • A few joint combinations are recommended for building robust composite floor systems against column removal scenario. • Consistency between the FE simulations and the analytical predictions is confirmed through a comparison of energy stored in different structural members. Abstract This paper presents parametric studies on three-dimensional steel-frame-composite-floor systems (3D composite floor systems) subjected to column loss using macro-based finite element (FE) models and a verified analytical method. The FE modelling method is verified by four actual experimental tests with three important variables, viz. slab aspect ratio, boundary condition and degree of composite action between composite slabs and steel beams. To overcome the shortage of data acquisition in the actual composite floor system tests, the FE models can be used to investigate the effects of these variables on load-resisting mechanisms, such as flexure and catenary action in the double-span girder and the double-span beam over the missing column, and flexure and tensile membrane action in composite slabs. In addition, the parametric studies are extended to include slab thickness. In a similar manner, the analytical model is used to study the effects of slab aspect ratio and joint type on robustness of 3D composite floor systems. After evaluating the robustness of eight sub-structures with different combinations of extended-end-plate, flush-end-plate, web-cleat and fin-plate joints, a few combinations are recommended. Lastly, consistency between FE simulations and the analytical predictions is confirmed through a comparison of energy stored in different structural members. [ABSTRACT FROM AUTHOR]