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This paper presents laboratory tests, numerical simulations and web crippling design of high strength steel unlipped channel sections under interior-two-flange loading. An experimental programme comprising 10 test specimens (with six for grade S690 high strength steel and four for grade S960 high strength steel) was firstly implemented, and test results including failure modes, full load-deformation curves and ultimate loads were reported. Subsequently, finite element models were constructed and validated against the obtained test results, and then used to conduct supplementary parametric studies to widen the examined parameter ranges of high strength steel unlipped channel sections. Considering that relevant codified design rules are absent, the applicability of the design rules of EN 1993–1-3, EN 1993–1-5 and AISI S100 for normal strength steel unlipped channel sections to their high strength steel counterparts was evaluated against the obtained test and numerical results. It is shown that the resistance predictions from the codified design provisions were generally inaccurate and scattered. Hence, a modified AISI S100 design method and a slenderness-based design method were proposed and demonstrated to be accurate, consistent and reliable for the web crippling design of high strength steel unlipped channel sections under interior-two-flange loading. • Web crippling of high strength steel unlipped channel sections under ITF loading is studied. • A total of 10 web crippling tests and 150 finite element simulations are carried out. • The codified European and American design methods are found to be inaccurate. • An improved AISI S100 design method and a slenderness-based design method are proposed. [ABSTRACT FROM AUTHOR]

Highlights • A method is developed to assess the non-stationary instantaneous frequencies. • A sampling algorithm is proposed to reconstruct the mode shapes of beams. • The proposed approach is more practical because external exciter is not required. • Numerical simulations and experiments are conducted to verify the approach. Abstract This paper presents a method to estimate mode shapes of beam like structures by using the acceleration of a moving lumped mass. In fact, the coupled frequencies of the vehicle-beam interaction system are time varying and the non-stationary instantaneous frequencies (IFs) contain information of mode shapes. The theoretical analysis in this paper shows that the mode shapes can be re-constructed by using the IFs; therefore, extracting mode shapes becomes a problem of IF estimation. A modified time-frequency analysis method based on weighted polynomial chirplet transform is developed to estimate the non-stationary IFs. Moreover, a new sampling algorithm based on accumulative measured energy is proposed to reconstruct the mode shapes, in which more data are sampled at the area with higher measured energy, making it more robust to noise. The proposed method is more convenient since only a lumped mass with a single accelerometer is required, and it is more practical because external exciter is not required, and the surface roughness can be the source of excitation. Numerical simulations and laboratory scale experiments have been carried out, which show that the proposed method performs well in extracting mode shapes, even if the travelling speed is high. [ABSTRACT FROM AUTHOR]

Highlights • There has been growing interest in the study of masonry cross vaults. • Cross vaults structural pathologies and repairing interventions are discussed. • The paper analyses the leading numerical strategies adopted for masonries. • This paper describes the main advances in the field of masonry cross vaults. Abstract Masonry cross vaults, which began to be built in Europe in the times of the Roman Empire and reached heights of extraordinary splendor during the Gothic Period, are part of an impressive architectural heritage, which stand in need of evaluation, maintenance and repairs or renovation. Nowadays, the requirements of preservation and conservation of the historical heritage call for a strategy oriented on the description of the structural behaviour from different characteristic perspectives without neglecting the functional, architectonic and structural features. The present paper is intended to discuss the different research approaches adopted by several authors during the past and to show how numerical simulations in conjunction with experimental studies can provide the tools for the quantification of the damages produced by a variety of different critical events. To this scope, this paper includes an extensive and somewhat ambitious review, dealing with a wide variety of aspects, such as: (a) a bibliometric study, (b) classification of the types of cross vaults, (c) structural behavior, (d) types of failures and damage, (e) numerical simulation, (f) experimental testing, (g) monitoring, and (h) retrofitting. The review is expected to be of great interest for architects and engineers working in the field of evaluating and retrofitting the architectural heritage, as well as to those researchers who would find it useful to have at hand in a single document the most important advances made in the field of masonry cross vaults in recent years. [ABSTRACT FROM AUTHOR]

The resilient fastener slab track (RFS track) has found extensive application in urban railways, effectively mitigating vibration and noise resulting from train operations. However, the structure elasticity of the RFS track is higher than the normal slab track (NS track), which can affect train running stability and cause abnormal vibration phenomenon. This paper explores the track structure elasticity on vehicle-track interaction and train running stability through experimental tests and numerical simulations. The vibrational properties of the RFS track and the NS track are obtained through field tests. A 3D metro vehicle-track coupled dynamics model is developed and utilized to simulate the dynamic performance of metro vehicles moving on different track structures. The impact of track structure parameters upon the vehicle-track interaction and train running stability are discussed. The findings indicate that the track structure elasticity can reduce train hunting stability and cause abnormal vibration phenomena in metro vehicles under certain conditions. The reasonable matching of the fastener lateral and vertical stiffness can not only accomplish vibration attenuation but also minimize the impact on train running stability. In addition, the rail surface wear and track gauge variation also exert influence on the running stability and dynamic performances of metro vehicles. • Track structure elasticity on vehicle-track interaction and train running stability was investigated. • Train hunting mechanism running on resilient fastener slab (RFS) track was revealed. • Vibrational properties of RFS track and normal slab track were tested on site. • The impact of track structure parameters upon vehicle dynamic performances was evaluated. • The track structure elasticity reduces hunting stability of metro vehicles. [ABSTRACT FROM AUTHOR]

Vibration control systems are usually classified into: passive, active and semi-active. Semi-active control systems are based on formerly passive mechanical devices, such as springs and dampers, whose characteristics are adjusted in real-time by active means. The attractiveness of semi-active control systems mainly relies on their assumed “inherent stability”, which makes them almost as reliable and fault-tolerant as passive control systems. The present paper shows that these assumptions are only partially true, by applying passivity formalism and bounded-input bounded-output stability definitions. Based on this study, semi-active control devices are rationally classified into three classes with two subclasses each: (1.1) non-negative variable-damping dampers, (1.2) possibly-negative variable-damping dampers, (2.1) independently-variable-stiffness springs, (2.2) resettable-stiffness springs, (3.1) independently-variable-inertance inerters, and (3.2) resettable-inertance inerters. It is found that a control system using any of the semi-active control devices of type (1.2), (2.1) or (3.1) is not inherently stable, as it is assumed in some previous papers; because those devices are “active” from the perspective of the passivity formalism. Interestingly, hybrid combinations of independently-variable-inertance inerters with non-negative variable-damping dampers can be designed to produce inherently-stable control systems. Following this framework, several published works on semi-active control systems are reviewed and classified. The presented methodology is useful when developing new devices. This is demonstrated by proposing a novel control device, which is classified and assessed in terms of inherent passivity. Moreover, this passivity assessment is conveniently used to propose a control law for the device. Finally, a frame structure controlled by the device is numerically simulated through a number of scenarios including instability and a countermeasure for its mitigation. [ABSTRACT FROM AUTHOR]

This paper presents a novel self-centering energy dissipating RC rocking column (SCERC) in which a steel tube protects the concrete from spalling and crushing at the column base. It incorporates an easily repairable pre-pressed disc spring self-centering device (SC) to restore the rocking column to its original position and a straightforward slip friction energy dissipation device (ED) to ensure adequate energy dissipation capacity. The working principle of the SC was investigated, and an analytical method was proposed. Subsequently, a theoretical hysteresis model for the SCERC considering different limit states is developed through reliable analyses. Lastly, the preliminary design parameters of the SCERC were determined, with numerical simulations conducted to validate the theoretical model. These simulations aim to explore the hysteresis characteristics, energy dissipation capabilities, and self-centering performance of the SCERC under different axial pressures and self-centering ratios. The results indicate that the theoretical hysteresis model was consistent with the numerical simulations, revealing that the SCERC exhibits a "flag-shaped" hysteresis response. The proposed SCERC displays satisfactory energy dissipation and self-centering characteristics. The SC provide sufficient restoring forces, with the EDs accounting for much of the energy dissipation. Plastic deformation was not observed in the concrete column, except for the unavoidable deformation occurring in the steel tube at the point of rotation. While a rocking column naturally possesses self-centering capabilities under axial forces, it requires SCs to counteract the negative stiffness caused by the P -∆ effect. As the self-centering ratio decreases, both the load capacity and energy dissipation capacity of the SCERC increase, leading to an increase in the residual deformation of the column; hence, the design should balance these two aspects for a suitable self-centering rate. • A rocking column with pre-pressed disc springs and enhanced column base is proposed. • A theoretical hysteresis model for different limit states is established. • Design parameters of the rocking column is investigated. • A numerical simulation is conducted to explore the resilient property. [ABSTRACT FROM AUTHOR]

The unreinforced masonry (URM) is a complex and variegate construction material characterized by a prominent nonlinear response. For this reason, advanced numerical simulations are required to assess URM buildings, especially in case of severe loading conditions as earthquakes. However, given the theoretical and computational difficulties of detailed non-linear analyses, linear elastic methods are still adopted in current practice. This results in conservative seismic assessments and, consequently, invasive and expensive strengthening interventions to guarantee seismic safety. Starting from these statements, the aim of the paper is to provide closed-form equations useful for a preliminary strength and ductility assessment of unreinforced masonry rectangular cross-sections. Expressions for direct calculation of M-N (bending moment – axial load) strength domains and M-χ (moment – curvature) ductility diagrams for different constitutive laws are provided. The expressions are firstly applied to a representative URM cross-section and secondarily used for the numerical simulation of a recent out-of-plane loading experimental test available in the literature. For a better comprehension of URM members behavior under axial-bending loading condition, 3D M-N-χ diagrams are presented in the paper. [ABSTRACT FROM AUTHOR]

Angles exhibit a complex structural behaviour, responsible for the fact that, in the current North American Specification for Cold-Formed Steel Structures, short-to-intermediate equal-leg angle columns are (i) not yet pre-qualified for the Direct Strength Method (DSM) design and (ii) excluded from the application of the LFRD resistance factor ϕ = 0 . 85, valid for all other cold-formed steel compression members. Recently, the specific behavioural features exhibited by the above angle columns were incorporated into the proposal of a novel DSM-based design approach, for both fixed-ended and pin-ended columns, and it was shown that this added rationality goes along with quite accurate and reliable failure load predictions. However, the investigation leading to this design proposal also unveiled that there are no available experimental failure loads of slender pin-ended columns with intermediate-to-high slenderness values, which implied that the design procedure was validated for such columns exclusively on the basis of numerical failure loads. The research work reported in this paper provides a contribution towards filling this gap, since it mainly consists of an experimental study, carried out at the Federal University of Rio de Janeiro, on the behaviour and collapse of short-to-intermediate slender pin-ended cold-formed steel equal-leg angle columns. After addressing the selection of the columns to be tested, the experimental set-up and test procedure are described in detail and the results obtained are presented and discussed. Such results involve (i) initial imperfection measurements, (ii) equilibrium paths relating the applied load to key column displacements, (iii) deformed configurations (including the collapse mode) and (iv) failure loads. Next, those same experimental results are used to validate a shell finite model previously developed by the authors, which is subsequently employed to obtain additional numerical failure load data concerning the pin-ended angle columns under scrutiny. Then, attention is turned to assessing the merits of the novel design approach. The comparison between the experimental and numerical values obtained in this work and their estimates provided by the design equations shows a very good correlation, perfectly in line with that observed in the recent studies available in the literature − this means that the validation and calibration of the above design approach may be deemed (successfully) completed. Finally, the paper closes with the presentation and assessment of small alterations to the existing design expressions, aimed at improving their accuracy and rationality, thus paving the way towards codification in the near future. [ABSTRACT FROM AUTHOR]

This paper proposes a new pretension simulation algorithm and examines the pretension feasibility for a new type of cable dome: a negative Gaussian curvature cable dome. First, the paper gives a pretension simulation algorithm based on the fuzzy relationship between the prestress and internal force. Second, a negative Gaussian curvature cable dome is proposed and the corresponding experimental model is designed and pretensioned according to the simulation results from the proposed simulation algorithm. The results indicate that the pretension simulation algorithm is efficient and accurate for simulating the pretension process and guiding the practical pretension. And the results also confirm that the negative Gaussian curvature cable dome can be pretensioned successfully, thus it can be constructed as a new type of cable dome. [ABSTRACT FROM AUTHOR]

This paper derives the theoretical equations to calculate the stiffness, strength, and yield displacement of the tall RC two-column piers with and without BRBs. A structural fuses-based design method was proposed to design the tall RC two-column piers with and without BRBs, and the corresponding scale models were designed and constructed. The numerical simulations and shaking table tests were separately conducted to verify the reasonable of the derivation theoretical equations and proposed design method and validate the effects of BRBs on controlling the seismic response and damage of the tall RC two-column pier. The seismic responses, including displacement and curvature, were discussed when the tall RC two-column piers with and without BRBs were subjected to different seismic waves. These results indicate that the BRB remarkably decreases the displacement and curvature of the column due to the BRBs yielding and dissipating the seismic energy. The seismic damage based on the yield curvature occurs in the tall RC two-column pier without BRBs, while the tall RC two-column pier with BRBs does not experience seismic damage under the design seismic waves with 0.4 g. Therefore, the BRBs can effectively control seismic damage and make the tall RC two-column pier satisfy the performance target according to the structural fuses concept. Also, the tall RC two-column piers with and without BRBs undergo seismic damage under the E2 earthquakes with 0.68 g. However, the curvature responses of the tall RC two-column pier with BRBs are far less than the tall RC two-column pier without BRBs under the E2 earthquakes. Consequently, BRBs can improve the seismic resilience of tall RC two-column piers. • Theoretical equations were derived for the strength and stiffness of a tall RC two-column pier with BRBs. • Dynamic simulations and tests were conducted for tall RC two-column piers with and without BRBs. • Seismic responses were compared for tall RC two-column piers with and without BRBs. • Theoretical equations were validated using dynamic simulations and tests. • BRBs effects on controlling seismic damage to tall RC two-column piers were verified. [ABSTRACT FROM AUTHOR]

The characterization of the constitutive mechanical behaviour of Fabric Reinforced Cementitious Composites (FRCM) is a widely discussed topic in the scientific community. Several research studies pointed out the difficulties in assessing reliable constitutive laws able to reproduce the local phenomena inner in the mechanics of FRCM materials. This paper presents the proposal of a model updating procedure based on a Genetic Algorithm (GA), able to obtain the parameters to be used for a simplified numerical modelling of the fabric-to-matrix interface. The procedure is applied to a truss-based Finite Element (FE) model, and it aims to minimize the difference between the simulations and the experimental results. The calibration procedure is performed against a large experimental database of bond tests in FRCM-to-masonry assemblies, allowing to express the model parameters as a function of geometrical and mechanical characteristics of the FRCM. • FRCM-to-masonry bond is studied. • A simplified FE model is proposed. • A GA-based model updating procedure is implemented. • Comparisons with experimental results prove the efficacy of the procedure. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical solution for bond-slip behavior of SRC interface based on experiment, numerical simulation, and theoretical derivation. Push-out tests of five specimens were firstly carried out, based on which, the simplified bond-slip model was proposed. The specimen was fabricated using the Q345H-shape steel (400 mm × 200 mm×13 mm × 8 mm) and C50 concrete (350 mm × 600 mm) with a bonding length of 500 mm. A FE model was established based on the bond-slip model to analyze the nonlinear bonding stress that are difficult to obtain from the experiment. The research shows that although the bonding stress in the elastic stage is not uniformly distributed, it is basically uniformly distributed when the ultimate bearing capacity is reached. It proves that assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable, which is crucial for designer to estimate interface bearing capacity and maximum bonding stress. Moreover, five different stages were obtained by the FE model analysis and the theoretical equations of bonding stress nonlinear distribution were obtained based on the boundary condition of each stage. The theoretical solution clearly showed the relationship between interface nonlinear stress distribution and influencing parameters including the bond area, elasticity modulus of material, section area of specimen, bond-slip constitutive model, and the external load. Based on the theoretical model, the influences of different parameters can be directly obtained without conducting further experiments and establishing different FE models. • The simplified bond-slip model was proposed and nonlinear distributiion of interfacial bonding stress was analyzed. • Assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable. • Corresponding analytical formulas for the interfacial stress in five different stages were established, respectively. • The theoretical solution showed the quantitative relationship between interface nonlinear stress and influencing parameters. [ABSTRACT FROM AUTHOR]

Surface ruptures resulting from seismic faulting have the potential to inflict substantial damage to bridges straddling fault lines; hence, it is imperative to investigate the impact of ground motions documented on either side of fault rupture planes—termed as across-fault ground motion—on the seismic resilience of bridges. In this paper, the object of study is a three-span, simply supported beam bridge traversing a strike-slip fault. Utilizing the LS-DYNA finite element software platform, a sophisticated three-dimensional finite element model of the selected bridge is constructed, meticulously accounting for material damage nonlinearity and structural collision contact nonlinearity. A synthetic across-fault ground motion serves as the excitation for the seismic analysis of the bridge, systematically examining the influence of the fault-crossing angle (FCA), fault sliding rise time, and ground surface permanent rupture displacement on the dynamic response and seismic damage incurred by the simply supported beam bridge. The findings demonstrate that a diminutive fault-crossing angle (FCA) corresponds to an elevated risk of longitudinal beam collapse when a simply supported beam bridge does not intersect a fault vertically. The impact of the fault sliding rise time on the magnitude of seismic response and damage sustained by the simply supported beam bridge is relatively minuscule and can be neglected. Conversely, the ground surface permanent rupture displacement profoundly influences the dynamic response and seismic damage of the bridge. The emergence of fling-step pulses from the development of ground surface permanent rupture displacement amidst seismic activity induces a shift in failure mode-from the designer-intended bending failure to an unforeseen shear failure. • A FE model of a simply-supported beam bridge is established with consideration of material and contact nonlinearity. • The systematic parameter analysis of the simply-supported beam bridge is conducted. • The failure mode and damage process of the simply-supported beam bridge are revealed. • Recommendations for the seismic design of simply-supported beam bridges subjected to strike-slip faulting are drawn. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic explicit finite element (FE) simulation method to predict the highly nonlinear response of axially and rotationally restrained reinforced concrete (RC) beams at ambient temperature and in fire condition. Catenary action, developed during the large deflection behaviour of RC beams, is an important mechanism of resisting progressive collapse. This paper explains the numerical simulation challenges, including temporary instabilities, local failure of materials, non-convergence and long simulation time, and proposes methods to resolve these challenges. The effectiveness of the proposed simulation model is checked by comparison of the simulation results against relevant test results of restrained RC beams at ambient temperature and in fire. It has been found that using the explicit simulation method can follow the whole range behaviour of restrained RC beams until complete structural failure. Either load factoring or mass scaling may be used to speed up the simulation process. Damping can be applied to minimise significant dynamic effects following beam bending failure. This paper will give guidance on how to select the appropriate load factoring, mass scaling and damping values. [ABSTRACT FROM AUTHOR]

• A comprehensive database of fitted moment-rotation curves and deduced response parameters for flush end-plate connections. • Classification assessment of flush end-plate connections with different topologies, as per European and American standards. • Quantification of response parameters' probabilistic distributions (median and dispersion). • Holistic assessment of connections' flexibility, strength and ductility characteristics. Flush end-plate (FEP) connections are one of the most popular bolted steel connections in construction practice. These connections possess a semi-rigid moment-rotation behavior that betwixt that of rigid and pinned connections. Nonetheless, they are commonly idealized as pinned connections in design and numerical simulations. This paper investigates the flexibility, strength and ductility of such connections in a holistic manner, based on a recently compiled comprehensive database of more than 420 specimens that were tested within the past 50 years. The paper describes the systematic methodology used to deduce response parameters from the moment-rotation curves. This includes deduction of the elastic, post-yield stiffnesses, the effective yield and maximum moments as well as the ultimate rotation at failure. The deduced parameters are made publically available to support further analysis by other researchers. The median value of each parameter and associated variability are quantified with respect to different connection topologies and loading histories. The data are then used to assess the connection classification and performance in terms of flexibility, strength and ductility based on existing standards. [ABSTRACT FROM AUTHOR]

• A new empirical formulation for the evaluation of the out-of-plane resistance of masonry infills is presented. • The formula is based on a hybrid dataset made of real experimental tests and refined numerical simulations. • An in-depth finite element investigation is carried out with a refined micromodel properly validated. • The new formula takes into account the effect of vertical loads on the out-of-plane resistance of infills. • A conversion factor is introduced to compare point-load and distributed load out-of-plane tests. • A comparison with literature models confirms large improvement of predictive capacity by the proposed model. The paper presents a new empirical expression estimating the out-of-plane (OOP) resistance of infilled reinforced concrete frames subject to horizontal forces. The new model is calibrated through an optimization process based on a hybrid dataset, including experimental data from real tests and from numerical simulations obtained from a refined FE micro-model realized in Abaqus®. The new expression considers the effect of vertical loads and also introduces a conversion factor to uniformize point-load and uniform load out-of-plane tests. The final expression is also flexible with respect to available data on the infill material properties, as it is specialized in two versions, one providing the conventional compressive strength of the units, the other providing the conventional compressive strength of masonry as possible inputs. Results presented in the paper will show a noticeable accuracy of the proposed model in estimating the ultimate out-of-plane load of a masonry infill wall, with respect to available models. The formula provides the reference undamaged OOP resistance and can be easily combined with available strength-reduction functions to consider the effect of prior in-plane loading. [ABSTRACT FROM AUTHOR]

This paper presents the derivations of an analytical method to evaluate the tying resistance of reverse channel connection to rectangular/square concrete filled tube (CFT). The analytical derivations are based on results of an extensive series of numerical parametric study of this type of connection, covering a range of design parameters, including tubular section size, tubular section width to thickness ratio, reverse channel flange size and gap between the reverse channel flanges. Under a tying force, the tubular section may fail in two modes: formation of yield line mechanism or fracture under tensile membrane action in the tubular wall. In most cases, the membrane resistance governs. However, if the tubular section is thick, the yield line resistance is higher than the membrane resistance and membrane action does not develop. The tying resistance of the connection is the higher of the two values. This paper derives analytical equations for calculating these two typing resistance values. The membrane resistance depends on the ultimate lateral deformation of the tubular wall and this paper also presents a method for its calculation. Comparisons between the analytical calculation results and the numerical simulation results indicate that the proposed analytical equations give reasonably accurate calculations and the analytical method may be used in practical design. [ABSTRACT FROM AUTHOR]

Vibration based structural health monitoring methods often use the changes in the modal parameters to identify damage. However, the modal parameters are not only influenced by damage but also by environmental factors including thermal and humidity conditions. The environmental effects can be large enough to mask the changes caused by damage, especially in the bridge structures that are always exposed to environmental elements. In this paper, a simulation study is conducted to examine the variations in the modal frequencies of concrete box girder and T-beam bridge structures caused by the ambient temperature, solar irradiance and wind speed, utilizing the environmental data recorded at a site in North Carolina, USA. The study includes the effects of temperature dependent material modulus, thermal gradients and prestressing effects on the modal frequencies. Like the environmental temperature variations, the bridge temperatures and model frequencies variations have strong yearly (seasonal) and diurnal trends. The study provides temperature–frequency data at hourly intervals for each bridge structure for future studies and the companion paper where, recognizing the observed seasonal and diurnal trends, the models are proposed to estimate frequencies across seasons from the measured temperature values of a bridge structure. [ABSTRACT FROM AUTHOR]

• An improved generalized S-transform (IGST) is put forwarded by optimizing the window function of GST. The parameters of window function in IGST are obtained by the energy concentration measure (CM) and the optimization methodology. • Applying IGST in association with SET, the improved synchroextracting generalized S-transform (ISEGST) method has been proposed in this paper. • A nonlinear Duffing system, a two-layer shear frame model, and a time-varying cable test are used respectively to verify the effectiveness of the proposed method. In this paper, an improved time-frequency analysis (TFA) method based on generalized S-transform (GST) and synchroextracting transform (SET), named improved synchroextracting generalized S-transform (ISEGST) is proposed to improve the accuracy of structural instantaneous frequency (IF) identification. Namely improved generalized S-transform (IGST), a new transform is first put forwarded by optimizing the window function of GST. The parameters of window function in IGST are obtained by the energy concentration measure (CM) and the optimization methodology. Applying IGST in association with SET, the ISEGST is then derived. Compared with the TFA methods in the literature, the performance of ISEGST in numerical signals has been significantly improved, especially in the presence of noise. In simulation, a nonlinear Duffing system and a two-layer shear frame model are used respectively to verify the effectiveness of the proposed method. Moreover, a time-varying cable test is conducted. Acceleration responses of the structure under linear and sinusoidal varying tension force are collected respectively. Then, the ISEGST is used for IF identification. Numerical simulation and experimental results show that the ISEGST can effectively identify IF of structures with non-stationary response signals, and it has high accuracy and good stability. [ABSTRACT FROM AUTHOR]

• The beam-upright connections of racks play a relevant role in their seismic capacity. • This work supplements a previously-conducted testing campaign on such connections. • In those tests, different weld paths were compared, looking for ductile break modes. • In this paper, numerical simulations are performed in order to deepen the tests observations. • The influence of the weld paths on the connection stiffness, stress elastic distribution, and yielding onset is studied. This paper presents numerical simulations of a suite of cantilever seismic tests of speed-lock connections between beam and upright members of adjustable pallet rack systems. The tested specimens differ in the endplate-to-beam weld beads geometric configuration; the experimental results show that each weld configuration leads to different behavior, significantly affecting the connection capacity and ductility. As a result, the performed numerical simulations aim to better understand and deepen these observations. Special attention is paid to the initial (elastic) behavior of the tested assembly, albeit the stress redistribution after the first yielding has also been studied and found to be relevant. The numerical results are satisfactory compared with the experimental ones, and specific remarks are derived. This work is a part of a broader research effort aimed to improve the dissipative seismic behavior of racks; such research activity involves also upright-base plate connections testing, advanced numerical simulation, and proposal of rack ductility behavior factors. [ABSTRACT FROM AUTHOR]

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

Abstract: On March 11, 2011, Japan was shaken by the 2011 off the Pacific coast of Tohoku earthquake (the Great East Japan Earthquake). This paper reports some aspects of this earthquake related to long-period ground motions and its impact on building structural design. It was reported that long-period ground motions were induced extensively in Tokyo, Nagoya and Osaka. The response of high-rise buildings to the recorded ground motions during this earthquake and the simulated ground motions provided by the Japanese Government is discussed from the viewpoint of resonance and critical excitation. The main topics of this paper are (i) the investigations on uncertainties in long-period ground motions (uncertainty in predominant frequency, duration and amplitude) and (ii) its impact on structural design of super high-rise buildings. It is shown finally that the earthquake input energy and its bound analysis lead to clearer understanding of the effect of long-period ground motion on building structural design. [Copyright &y& Elsevier]

Abstract: Bridge structures across navigable waterways are vulnerable to barge collisions. To protect the bridge structure, bridge piers should be specially designed to resist barge impact load. In order to quantify the impact load, barge–pier impact tests and/or reliable theoretical or numerical predictions should be conducted. However, very limited impact tests were carried out to evaluate barge impact force and pier response due to the cost and site limitations. This paper presents laboratory tests and numerical simulation results of barge impacting on bridge piers. A scaled circular reinforced concrete pier is built and tested first with a pendulum impact test system. Impact load profile and pier top displacement were recorded and analyzed. A numerical model is then developed to simulate the laboratory tests. Nonlinear materials are used to model the concrete and steel reinforcements with strain rate effects. The accuracy of the pier model is calibrated by comparing the experimental and numerical results. Using the validated numerical model, a full scale bridge pier model is developed to simulate the barge impact on bridge piers. Pile groups and soil springs are considered to model the soil–pier interaction. Parametric studies are carried out to investigate the effects of barge impact velocity, barge mass, pier diameter and height, superstructure mass and impact location, and soil–pier interaction. Impact load time history and pier displacement response are calculated. Based on the numerical results, empirical formulae are proposed to predict the peak impact force and impulse. The adequacy of the current design code is also discussed in the paper. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to develop a robust numerical model for cold-formed steel square and rectangular structural hollow sections for use as axial loaded members in earthquake engineering applications. Pseudo-static cyclic physical tests of cold-formed steel brace specimens using axially loading are used to develop and calibrate a robust numerical model that mimics the results from the tests. A nonlinear fibre based beam-column element model which considers the spread of plasticity along the element is used. This numerical model includes a low cyclic fatigue model, which wraps the nonlinear fibre based beam-column element material in order to capture fracture in the braces. New parameters to be used for the fatigue model are introduced in this paper. Comparisons of the maximum tensile force (F max), initial buckling load (F c), number of cycles to fracture, the total energy dissipated (W tot) and the energy dissipated at the first cycle of ductility of 4 (Wμ =4) between the numerical models and the physical tests are carried out. In general, the models captured the salient response parameters observed in the physical tests. It is found that the numerical model gives a good prediction of the maximum measured tensile force (F max) and initial buckling load (F c) with the mean values being 0.93 and 0.95 of those measured in the physical tests, respectively. The corresponding coefficients of variation (C V) are 0.11 and 0.08, respectively. Moreover, the mean values of the total energy dissipated (W tot) and the energy dissipated at the first cycle of ductility of 4 (Wμ =4) for the numerical model are found to be 1.12 and 0.98, of those measured in the physical tests, respectively. The corresponding coefficients of variation (C V) are 0.13 and 0.20, respectively. Furthermore, the numerical model was validated using another set of independent physical tests. This validated brace element model can be used in future numerical models of concentrically brace frames buildings to predict the performance of the complete structures under earthquake loading. [Copyright &y& Elsevier]

Abstract: Previous studies of pounding responses of bridge structures to seismic loadings are usually based on the point to point pounding assumption by using the simplified lumped mass model or beam–column element model. It has been found these simplified models can be used to calculate bridge pounding response with consideration of only the longitudinal excitation. In a real bridge structure under seismic loading, pounding could take place along the entire or part of surfaces of the adjacent segments. Moreover, torsional response of the adjacent decks owing to the asymmetric deck or induced by spatially varying transverse ground motions at multiple bridge supports may result in eccentric poundings between adjacent bridge decks. A detailed 3D finite element model is necessary to consider the surface to surface and torsional response induced eccentric poundings and the corresponding damage. This paper performs numerical simulations of pounding damage between bridge girders and between bridge girder and the corresponding abutment of a two-span simply-supported bridge to spatially varying ground motions based on a detailed 3D finite element model by using the explicit finite element code LS-DYNA. The dislocation and unseating potentials of the bridge are also modelled. The bridge components including the bridge girders, abutments, pier, bearings, longitudinal reinforcement bars and stirrups are included in the model. The non-linear material behaviour including the strain rate effects of concrete and steel rebar are considered. The spatially varying ground motions are stochastically simulated. The damage mechanism of the bridge under spatially varying seismic loadings is examined. Numerical results show that the method adopted in the present paper can realistically capture the seismic induced damage of bridge structures. [Copyright &y& Elsevier]

Abstract: Part of the uncertainty in the response of transmission line (TL) towers subjected to extended pressure system (EPS), determined as prescribed by IEC 60826, is assessed in the paper by comparing the code predictions with the dynamic response of the system subjected to numerically simulated 3D-wind fields. In the evaluation process, model uncertainty was accounted for by considering various models for the power spectra of the fluctuating wind velocity components as well as for the correlation functions. The values obtained through the full dynamic analysis are quite similar to those determined by the code, resulting in estimation errors in the range between 5% and 10%. The influence on model uncertainty of the structural model of towers and conductors was studied by the authors in previous contributions, and completes the assessment advanced in the paper. [Copyright &y& Elsevier]

Abstract: Vessel collisions with bridge piers are one of the most frequent accidents that may lead to bridge failure. To reliably assess bridge response and damage due to barge impact, and design the bridge piers to resist such impact, the impact force should be accurately defined. In most of the previous works of numerical simulation of barge collision with bridge piers for defining the barge impact force, the pier was assumed to be rigid or elastic and the interaction between the barge and the pier was neglected. As pier plastic deformation and damage will absorb impact energy and also prolong the interaction time, the impact force acting on the bridge pier might not be accurately predicted with rigid and elastic pier assumption. In this paper, a detailed numerical model of barge–pier impact is developed in LS-DYNA. The bridge pier is modelled with nonlinear materials to more realistically generate the bridge pier characteristics. Barge–pier impact force time history, barge crush depth and pier displacements are calculated in this paper. The reliability of the numerical model is calibrated with some results available in the literature. Based on numerical results simplified formulae are derived to predict the impact force time history with respect to the collision conditions. Numerical results are compared with the previous works. The adequacy of current code specifications is also discussed. [Copyright &y& Elsevier]

• We have proposed a spatial prefabricated self-centering steel frame (PSCF). • The spatial PSCF has avoided on-site aerial tension of steel strands. • A new floor slab is developed to accommodate the frame expansion. • Web friction devices are installed to dissipate energy and protect main structure. • Design targets of the PSCF have been proposed to conduct performance-based design. The structural system of prefabricated self-centering steel frame (PSCF) was proposed previously by the author. Experimental studies focusing on PSCF connections, plane frame, overall structures as well as the numerical simulations were conducted. Compared with the self-centering steel frame (SCF), the PSCF has avoided the on-site aerial tension of steel strands and simultaneously achieves similar seismic performance as well as self-centering capacity. While the self-centering function of both PSCF and SCF may be restrained by conventional floor systems. Based on this thesis, a spatial PSCF with a new type of floor system containing sliding secondary beams was proposed in this paper to enable the frame expansion, and pseudo-dynamic and quasi-static tests toward it were conducted. The test results indicated that the proposed new floor system was reliable and feasible in accommodating the frame expansion. Meanwhile, the spatial PSCF with the new floor system has a favorable self-centering capacity, reliable gap-opening mechanism, superior seismic performance and enough redundancy to withstand multiple aftershocks. [ABSTRACT FROM AUTHOR]

Highlights • The nonlinear dynamics of Z-shaped folded plates with inner resonance are investigated. • The nonlinear dynamical behaviors of the Z-shaped folded plate are conducted by numerical simulation and compared with the results obtained by experiment. • The middle plate yielded more complex vibration forms than the other two plates with increasing transverse excitations. Abstract As one of the classical complex multibody structures, Z-shaped folded plates are widely applied in several engineering structures. In the present paper, the nonlinear vibration characteristics of a Z-shaped folded plate composed of three carbon-fiber composite plates were analyzed through theoretical and experimental investigation. The nonlinear dynamic model of the Z-shaped plate was developed based on the Hamilton principle, von Kármán equations, and the classical laminate plate theory, and the vibration mode shape functions of the system were calculated in ANSYS. Further, the Galerkin approach was employed to discretize the partial differential equations into a two-degrees-of-freedom nonlinear system, and the effects of transverse excitations on the nonlinear dynamic behavior of the Z-shaped folded plate were investigated through a comprehensive numerical simulation. Moreover, the obtained theoretical results were verified by experimental analysis. In addition, the vibration mode shapes of the Z-shaped folded plate were obtained by operational modal analysis (OMA). The modal parameters were first identified successfully using the PolyMAX method and then validated by modal assurance criterion (MAC). Finally, an excitation-measurement test was designed to measure the nonlinear vibration characteristics of the Z-shaped folded plate. [ABSTRACT FROM AUTHOR]

Abstract: The direct design method recommended by ACI is commonly used for the design of flat slabs. Since the flexural stiffness of the waffle slab varies along the span, it is expected that the distribution of moments is different from that of flat slabs. Current design procedures do not provide recommendations specific of waffle slabs. Designers smear the contribution of the ribs and use the design guidelines for flat slabs to design ribbed slabs. In addition, the effect of openings on the response of waffle slabs is not fully explored. Therefore, modified moment coefficients are needed for waffle slabs. In this paper, numerical simulations using ANSYS are used to study the response of waffle slabs with and without openings. The main objectives of this paper are: (1) to obtain the design coefficients for the column and the field strips of the internal panel of a waffle slab and (2) to study the effect of openings and stiffening ribs on the design coefficients. Ninety Linear and non-linear analysis models using ANSYS were performed in the study to evaluate the response of various waffle slabs under uniform loading. The main parameters evaluated are the column size, the solid portion size, the opening size and its location, and the effect of stiffener ribs around the opening. The non-linear finite element model was verified using existing experimental results for two waffle slabs. The moment coefficients developed in this paper were used to modify the existing ACI flat-slab coefficients to be used for waffle slabs. [Copyright &y& Elsevier]

Abstract: Most design codes (Model Code 90, ACI-318-2008 and Eurocode–2-2004) suggest that the effect of a geometrical imperfection ought to be taken into account in the most unfavorable direction when designing slender reinforced concrete columns. If the bending plane of the beam–column is related to the strong axis, this imperfection acting in the opposite direction results in the column being subjected to axial load and biaxial bending, complicating the design procedure and increasing computational costs considerably. Such standards do not indicate when this geometrical imperfection generates a notable loss of resistance in the column. This paper proposes the geometrical slenderness of the weak axis as the variable that determines whether or not to consider the influence of such imperfection. This paper denominates this boundary value the “slenderness limit of the weak axis” (), and this is associated with a loss of resistance of 10% of the bending moment of the unbraced columns with respect to non-sway columns. An approximated equation of this limit is proposed using the results of a numerical simulation. The equation is valid for rectangular columns with doubly symmetric reinforcement and both normal and high strength concrete, and also for short-term and sustained loads. [Copyright &y& Elsevier]

Abstract: Many researchers have conducted comprehensive experimental and numerical investigations to examine civilian structures’ response to explosive loads. Most of the studies reported in the literature deal with building structures and structure components. Studies of bridge structures subjected to blast loads are limited. This study performs numerical simulations of dynamic responses of a large cable-stayed bridge under explosive loadings. All numerical simulations are carried out using the LS-DYNA explicit finite element code. This paper describes the bridge under consideration, blast load estimation, finite element model, material model, and detailed numerical simulation results of the bridge to blast loads from a 1000 kg TNT equivalent explosion at 0.5 m from the bridge tower and pier, and 1.0 m above the deck. Damage mechanism and severity of the bridge tower, pier and deck are examined. The companion paper Hao and Tang (2010)  presents intensive numerical simulation results of the bridge components under blast loads of different scaled distances, progressive collapse analyses of the bridge after either one of the four main bridge components is damaged, and the safe scaled distance for bridge protection before initiating catastrophic collapse. The effectiveness of FRP strengthening of bridge concrete back span for blast load resistance is also investigated. [Copyright &y& Elsevier]

Abstract: This study investigates the blast loading effects on a large cable-stayed bridge. The results are presented in two parts. A companion paper by Tang and Hao (2010) presents the numerical model of the bridge structure and simulation results of the four main bridge components (pier, tower, back span deck and main span deck) to blast load from a 1000 kg TNT explosion at a standoff distance of 0.5 m and 1.0 m, respectively. This paper presents numerical simulation results of the four bridge components to blast loads of different scaled distances, and performs progressive collapse analyses of the bridge structure after damage in either one of the four main bridge components has occurred. The most vulnerable bridge component is identified. The safe scaled distance for bridge protection is determined. The effectiveness of FRP strengthening of concrete back span for blast load resistance is also investigated. It is found that the failure of vertical load-carrying components will lead to catastrophic bridge collapse while above deck explosion may cause severe instability of the bridge. It is also found that the minimum scaled distances for tower and pier for preventing catastrophic bridge collapse are approximately and , respectively. Numerical results presented in this study will help owners and engineers of similar bridges to determine appropriate measures for bridge protection against possible explosion loads. [Copyright &y& Elsevier]

Abstract: The paper presents a case study of progressive collapse analysis of a selected multistory building. The subject of the numerical study is an existing 8-story steel framed structure built for fire tests in the Cardington Large Building Test Facility, UK. The problem is investigated using nonlinear dynamic finite element simulations carried out following the GSA guidelines. The paper focuses on model development for global models subject to increasing vertical loading and notional column removal. Taking advantage of parallel processing on multiprocessor computers, a detailed 3D model with large number of finite elements has been developed for the entire structure. The objective of the presented feasibility study is to identify modeling parameters affecting the final result (potential of progressive collapse) and propose a hierarchical verification and validation program for reducing outcome uncertainties. [Copyright &y& Elsevier]

• A TYRSFB was proposed to esnhance the post-yielding stiffness of the RSFB. • The theoretical top force–displacement curves of RSFB and TYRSFB were derived. • Quasi-static tests and numerical simulations were conducted on the TYRSFB. • Influences of steel rod configuration on the performance of the TYRSFB were studied. The lower post-yielding stiffness of a buckling-restrained brace (BRB) was improved by constructing a two-level yielding BRB by setting an additional unit with a certain stiffness after the yielding of a traditional BRB. In this paper, a pinned steel rod with an initial gap is added at the outside of each buckling-restrained column (BRC) in a rocking steel frame with BRCs (RSFB) to improve the stiffness, lateral carrying capacity and ductility of the RSFB after BRCs yielding, which is named as a two-level yielding RSFB (TYRSFB). This paper studies the seismic performance of the TYRSFB and determines the influence of key constructional parameters of steel rods on structural performance. First, the top force–displacement curves of the TYRSFB are derived. Then, quasi-static tests and numerical simulations are conducted on the TYRSFB and RSFB, and the results show that the proposed TYRSFB can achieve the anticipated seismic performance. Moreover, the numerical simulation results are basically consistent with the calculation results of the proposed theoretical formulas. Finally, parametric studies based on the theoretical formulas and numerical models show that changing the value of the distance between steel rods and the central column, the initial gap, the ratio of the cross-sectional area and the length between the steel rod elastic and energy dissipating portions will influence the structural lateral carrying capacity, ductility and failure mode. [ABSTRACT FROM AUTHOR]

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

The integration of topology optimization procedures into modern structural design frameworks is gaining interest as an innovative approach for achieving more efficient designs. To this end, probabilistic performance-based topology optimization frameworks have recently been proposed for the identification of optimal structural systems subject to extreme wind or seismic events considered in isolation. However, there are large geographic regions that are subject to both wind and seismic hazards. Therefore, the development of methods that can ensure that target performance metrics are met within a multi-hazard setting is a crucial step towards improving the reliability of structural systems. This paper is focused on proposing a simulation-centered performance-based topology optimization framework for the identification of optimal structural systems for multi-hazard wind and seismic environments. A probabilistic performance assessment framework is firstly proposed based on synergistically describing the performance of wind or seismically excited systems. Based on this framework, a multi-hazard topology optimization strategy is proposed. In particular, the methodology is centered on the definition of an approximate optimization sub-problem that not only decouples the simulation-based performance assessment from the optimization loop, but also transforms the dynamic and uncertain optimization problem into an explicit static and deterministic problem therefore enabling its efficient resolution using any gradient-based optimizer. Optimal lateral load resisting systems that rigorously meet the probabilistic performance constraints set within the multi-hazard environment are therefore identified. A case study is presented demonstrating the potential of the proposed framework. [ABSTRACT FROM AUTHOR]

Obtaining an accurate simulation of the boundary conditions is very challenging but it is essential in order to represent the true behaviour of the whole structure in fire. In recent years, hybrid simulation has been emerging as an efficient and economical method for simulating realistic boundary conditions in the field of earthquake engineering. This technique can be used to study the load redistribution that may occur in a structural system as a result of locally elevated temperatures. In this paper, the fire-exposed element will be modelled in one analysis (a 3D model) and the rest of the structure in another analysis (a 2D model). This kind of sub-structuring enables the behaviour of the structural system as a whole to be studied. A hybrid simulation (HS) approach is presented and successfully implemented using the OpenFresco and OpenSees software. This approach enables the simulation of the correct restraint provided by the cold structure to the fire affected structural element. The HS analysis of a composite beam is compared with an unrestrained or simply supported version to highlight the difference in behaviour. Finally, the Cardington restrained beam test is modelled to demonstrate the potential of HS technique. Good agreement with the test results highlights that HS approach can be an effective method for studying the behaviour of the whole structural system. [ABSTRACT FROM AUTHOR]

In progressive collapse analysis, event-independent column loss is commonly used as a design scenario. Yet this scenario does not account for the fire-induced thermal forces that develop in case of a fire. The thermal forces may cause detrimental load redistributions in the structure, notably during the cooling phase. However, as the response of entire structures during the full course of fires until burnout has received little attention, these effects are not well established. The objective of this paper is to analyze the mechanisms of load redistribution in a structural system comprising a column subjected to localized fire, with a focus on the effects of the cooling phase. Numerical simulations by nonlinear finite element method are used, after validation against experimental data. The observed mechanisms result in tension building up in the fire-exposed column and overloading the adjacent columns in compression. Consequently, the damaged vertical member redistributes a force that is larger than the force initially carried. This can lead to failure of vertical members not directly affected by the fire and trigger a progressive collapse. These mechanisms are parametrically studied on a simple system composed of a column and a linear spring. Major parameters influencing the residual tensile force in the fire-exposed column are the maximum reached temperature and the relative stiffness of the remainder of the structure. The analysis of a twenty-story steel frame building under localized fire attacking one ground level perimeter column confirms the development of these mechanisms in a real design. The results have important implications as they question the validity of an event-independent design scenario for capturing the influence of column failure due to fire loading. [ABSTRACT FROM AUTHOR]

Over the last years, the seismic behaviour of infilled reinforced concrete (RC) structures has been the focus of innumerable experimental and numerical studies. A big effort is being made by the scientific community to increase the knowledge regarding the seismic performance of these types of structures and to improve the numerical modelling capabilities to predict their expected behaviour accurately. In 2015, a blind prediction contest was organized by the Faculty of Civil Engineering, University of Osijek, with the main goal of inviting the technical and scientific community to predict the nonlinear seismic behaviour of a 1:2.5 scaled 3D building structure. A three-storey infilled RC structure was subjected to a sequence of ten incremental earthquakes in a shake table test. The blind numerical simulations were carried out by different international teams invited by the organizational committee. The teams knew only the specimen geometry, reinforcement detailing, material properties, and ground motions recorded during the testing. In this context and, in the light of the authors’ success in the contest, the present paper mainly aims at presenting several issues regarding the numerical modelling strategies adopted (and related difficulties) which proved to yield good results while also providing some insight regarding key problems in numerical simulations of infilled RC structures under seismic actions. The main numerical results obtained by all of the participating teams will be presented and compared with the experimental ones. Discussion concerning the reasons behind the mismatching of some results will be presented. Finally, a parametric study was carried out with the aim of assessing the influence of some modelling issues and parameters on the structural global response, in particular when affected by some variations. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of construction method (e.g. false skew, helicoidal and logarithmic method) on the mechanical behaviour and load carrying capacity of single span skew masonry arches. Simulations were performed with the three dimensional computational software, based on the Discrete Element Method of analysis. Each stone/brick of the masonry skew arch was represented by a distinct block. Mortar joints were modelled as zero thickness interfaces which can open and close depending on the magnitude and direction of the stresses applied to them. The variables investigated were the construction method, the angle of skew, the size of masonry blocks and the critical location of the live load along the span of the arch. At each skew arch, a full width vertical line load was applied incrementally until collapse. From the results analysis, it was found that for a skew masonry arch constructed using the false skew method, as the angle of skew increase, sliding between voussoirs in the arch increases and failure load decreases. However, for skew masonry arches constructed using the helicoidal and logarithmic method, as the angle of skew increases, the failure load increases. Three different characteristic failure modes were identified depending on the contact friction angle and the method of construction. These observations provide new insight into the behaviour and lead to suggestions for understanding the load carrying capacity and failure mode of skew arches. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive test database of concentric compression experiments on pultruded fiber-reinforced polymer (PFRP) specimens that failed in a global flexural buckling mode published in literature between 1969 and 2016. A new closed-form equation to determine the reduction factor for global flexural buckling of PFRP structural struts under axial compression is developed on the basis of the Ayrton-Perry formula and observed initial out-of-straightness of PFRP members measured by other researchers. Recognizing that data on initial imperfections may be unavailable, a second new empirical closed-form equation is derived based upon the experimental database. Validation of the two explicit expressions is performed by both comparison to experimental data and comparison with validated numerical simulations. In addition, the accuracies of the two proposed equations are compared with those of five closed-form solutions available in the literature; both results in more accurate predictions than the extant equations. Both new proposed equations can be conveniently used by structural engineers at the preliminary engineering design stage for accurately assessing the reliability and safety of composite structures under concentric compressive loading. [ABSTRACT FROM AUTHOR]

The main challenge in predicting structure-borne sound in wood buildings is to accurately model the vibration transmission between the source and the receiving room. Large variations in model parameters make it difficult to predict absolute vibration levels and to make conclusions regarding the relative effects of different designs. A step towards establishing reliable models is to investigate the possibilities and limitations of using deterministic methods, which requires correlations between simulations and measurements. In this paper, we present a multi-level model correlation approach for low-frequency vibration transmission in wood buildings. We apply the proposed approach to a scaled-size experimental structure representing a part of a two-storey wood building, and we evaluate the results for frequencies up to 100 Hz. We perform correlations between simulations and measurements four different levels: structural components (viz. beams and boards), planar structures (viz. floor, ceiling and walls), room structures and the complete structure. The results indicate that the dynamic behaviour of the experimental structure was to a great extent captured by the developed model. Based on the observations made in the multi-level correlations, we discuss important model parameters and propose modelling guidelines. We conclude that it is possible to employ deterministic methods in order to simulate the low-frequency vibration transmission in wood buildings provided that measurement data for calibration purposes are available. The developed numerical model can be used as a reference model for investigations on the effects of variations and uncertainties in the modelling. [ABSTRACT FROM AUTHOR]

Steel-Equal Angle (SEA) has recently been utilized as longitudinal reinforcement in high-strength concrete columns to improve their strength and ductility. However, investigations have been very limited on the responses of eccentrically loaded SEA Reinforced Concrete (SEARC) columns. This paper presents the development of a computer simulation model based on fiber element discretization for determining the structural behavior of eccentrically loaded SEARC short columns. The inelastic buckling of SEA sections and the concrete confinement induced by SEA sections are explicitly taken into account. The modeling procedures are given for axial load moment-interaction curves and moment-curvature curves of SEARC columns. The accuracy of the developed fiber model is verified against the available test data. The performance of eccentrically loaded SEARC columns incorporating various design parameters is extensively investigated. It is shown that the developed computer simulation model captures well the experimentally measured responses of short SEARC columns and can be utilized in the analysis and design of such columns in practice. It has been found that the behavior of SERAC columns under eccentric loads is significantly influenced by the longitudinal steel ratio, the compressive strength of concrete, and the axial load level. The width of SEA sections and tie spacing considerably influence the ductility of the columns. • A fiber model is developed for the analysis of eccentrically-loaded SEARC columns. • Validation of the developed fiber model of SEARC columns is presented. • Effects of various column parameters on load-moment interaction curves are studied. • Effects of various column parameters on moment-curvature responses are studied. [ABSTRACT FROM AUTHOR]

Recent studies at the Center for Infrastructure Protection and Physical Security (CIPPS) have focused on both active and passive protection, the definition and characterization of combined blast and fragment loads on structural elements, the influence of Ultra High Performance Concrete (UHPC) on the behavior of structural elements, and evaluating analysis approaches for progressive collapse assessment. Those studies have highlighted important issues that have not been sufficiently addressed previously, and this paper is aimed at describing the observations from the CIPPS studies that could be used to treat such difficult issues. [ABSTRACT FROM AUTHOR]

A new type of cellular beams fabricated from hot rolled profiles appeared recently, whose openings have a sinusoidal shape. These beams are used either for steel or composite structures and they allow rectangular ducts, even with large sizes, to pass through their openings. They can thus lead to a substantial reduction of the floor thickness and they contribute to increase the competitiveness of steel buildings. The aesthetic shape of the openings is also an advantage to improve the architectural attractiveness of steel frames. To take benefit from these possibilities, accurate design methods are required and this research project has been undertaken to establish the static behaviour of these beams with sinusoidal openings. This paper presents the results of 4 tests (on 3 steel beams and on a composite beam) and of 287 numerical simulations carried out to determine ultimate loads and failure modes under the simultaneous effects of bending and shear. A new analytical design method is then proposed for the resistance of cellular beams with sinusoidal openings taking into account the Vierendel effect. This new model can be used within the range of the geometrical and mechanical scope. Finally the comparison of the ultimate loads according to this new model and according to the reference database (experimental or numerical data) is provided to assess the safety and accuracy of the proposed expressions. [ABSTRACT FROM AUTHOR]

Global behavior of RC structures during fire events can be predicted using complex nonlinear thermal-structural numerical simulations. However, such simulations are computationally expensive, which limit their use by design engineers. A practical approach to track the performance of RC frames during fire exposure is proposed and validated in this paper. A previously developed simple heat transfer technique is used to calculate an average 1D temperature distribution for heated RC sections. Consequently, the flexural and axial stiffnesses as well as the unrestrained thermal deformations are evaluated using sectional analysis. Based on rational assumptions, simplified expressions are also driven to evaluate those values. The proposed method can be easily applied using available commercial linear structural analysis software to predict the fire performance of RC framed structures. Additional experimental and analytical work is required to validate the proposed method in non-standard fire scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we study the dynamic flexural behaviour of a long bridge, modelled as an infinite periodic structure. The analysis is applied to the ‘Brabau’ bridge across the river Tirso in Italy. The approach reduces to a spectral problem leading to the analytical expression of the dispersion relation, which provides the ranges of frequencies for which waves do and do not propagate. The contributions of the bridge structural elements on the dispersive properties of the structure are investigated in detail. The direct link between frequency intervals determined by the proposed approach and distribution of eigenfrequencies of the full three-dimensional structure is demonstrated. The analysis of the unit cell allows to avoid the tedious computations required when using a finite element code, at least at a preliminary stage of the design. Finally, we demonstrate that a more precise prediction of the eigenfrequency ranges of the bridge can be obtained by studying a single repetitive cell numerically and imposing Floquet-Bloch conditions at its ends. The proposed approach can be implemented as a simple procedure to design structures with repetitive units, with the advantage of simplifying numerical simulations and reducing the computational cost. [ABSTRACT FROM AUTHOR]

In this paper, a new methodology for taking into account uncertainties based on the projection on polynomial chaos is proposed. The new approach is introduced to determine the dynamic behavior of a bevel gear system with uncertainty associated to the performance coefficient of the input aerodynamic torque. The influence of the uncertain parameters must be considered in the analysis of the dynamic response of this system. The simulation results are obtained by using the polynomial chaos approach combined with the ODE45 solver of Matlab. The proposed method is an efficient probabilistic tool for uncertainty propagation. [ABSTRACT FROM AUTHOR]

The present paper quantifies the adverse effects that can generate rebar section loss, induced by corrosion, especially on the bearing capacity of nuclear power plant cooling towers under extreme wind conditions. Numerical simulations, taking into account, appearance of concrete cracks and their evolution via an appropriate material concrete law and rebar’s yielding, are conducted. Different levels of corrosion are considered which are approximated by rebar section loss. Finally, to restore the integrity of these structures, composite material such as a carbon fiber reinforced plastic (CFRP) layer is modelled. The enhancement of the bearing capacity of the damaged structure compared to the undamaged structure is evaluated in the pre- and post-cracking regime. The main conclusion drawn from the numerical results is that the CFRP reinforcement is very effective for improving the integrity of RC cooling tower shells even when the latter present an advanced corrosion rate. [ABSTRACT FROM AUTHOR]