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Velocity pulse with strong energy input is the significant feature of near-fault ground motions. Bridges close to or passing across seismic faults may suffer from higher failure risk, which is inseparable from the influence of velocity pulse. This study aims to evaluate the nonlinear response characteristics of bridge structures under various near-fault ground motion conditions. A typical isolated continuous girder bridge is adopted, and two corresponding finite element models, i.e., considering and ignoring the heating effect of lead core bearings (LRBs), are established based on the OpenSees platform. Then, a total of 40 near-fault ground motion records are selected, and the pulses are extracted. Both the energy-based and deformation-based seismic responses are captured and compared to reveal the differences for the isolated bridge subjected to the original waves and the extracted pulses. The results highlight that the accuracy of the seismic evaluation based on the extracted pulses strongly depends on the precondition that the pulse period is close to the fundamental period of the isolated bridge. Hence, inputting the extracted pulses for predicting the in-elastic seismic response of isolated bridges locating at near-fault region is not an adequate replacement for those original waves of near-fault ground motions. In addition, the heating effect of LRBs will be magnified for the seismic response of isolated bridges subjected to the extracted pulses, and it will mainly affect the seismic responses of bearings and piers, i.e., the former increases and the latter decreases. [ABSTRACT FROM AUTHOR]

This study develops a 2D computational parametric analysis of ordinary reinforced concrete (RC) frames, located in seismic zone, with the aim to evaluate some design suggestions with respect to their effectiveness in increasing the structural robustness. Specifically, a five‐storey and four‐span 2D RC moment resisting frame is considered, designed in a highly seismic area according to both Italian and European codes. Subsequently, respecting the seismic design code provisions through a cyclic design procedure, some modifications are suggested regarding the layout of the longitudinal reinforcement bars of the beams to exploit the continuity, Vierendeel behavior and influence of the side face reinforcement bars in the beams. For the different modifications, nonlinear finite element pushdown analyses of the whole frames are performed by imposing a monotonically increasing vertical displacement at the point of the column removal in Atena‐2D and considering the presence of the orthogonal framed systems. Furthermore, two different failure scenarios are examined. The numerical force‐displacement capacity curves corresponding to the different proposed design suggestions are investigated and compared. The results have demonstrated the effectiveness in improving the structural robustness of the proposed solutions, especially, of the side face reinforcement bars with respect to both flexural and catenary behavior. The outcomes have also highlighted the compatibility between design criteria of both robustness and earthquake engineering. [ABSTRACT FROM AUTHOR]

• Safety formats for NLFEAs of reinforced concrete structures are analyzed. • NLFEAs to assess global resistance of reinforced concrete members are performed. • Different reinforced concrete members with different failure modes are considered. • A proposal of two preliminary NLFEAs to use safety formats is presented. • Failure mode-based safety factor for aleatory uncertainties is proposed. The study describes some proposals regarding the safety formats (i.e., global resistance methods (GRMs) and probabilistic method (PM)) for non-linear finite element analysis within the approach of the global resistance format to estimate the design strength of reinforced concrete structures. Specifically, non-linear finite element models are properly defined to reproduce various experimental tests. Successively, several non-linear finite element analyses are carried out in compliance with the different safety formats for each reinforced concrete structure experimentally tested in order to compare and critically discuss the results in terms of resistance and failure mode. In fact, the different safety formats are investigated to demonstrate if they are able to estimate the corresponding design global resistance capacities and to capture any possible modification in the failure mode for each structure considering the aleatory uncertainties. Then, a methodology based on a specific preliminary evaluation, composed of two non-linear finite element analyses, is proposed to verify the applicability of the simplified GRMs depending on the possible modifications that can occur in the failure mode in comparison with the PM taking into account the aleatory uncertainty on the materials properties. Moreover, in the cases when any GRM cannot be used, the PM is suggested as the unique safety format able to estimate an appropriate value of the global design structural resistance due to the possible modifications in the structural response by the effect of combination of the actual materials strengths. Finally, in order to apply GRMs for their reduced computational effort also in the abovementioned cases, an additional failure mode-based safety factor is proposed for the assessment of the design global resistance. [ABSTRACT FROM AUTHOR]

Highlights • Partial safety factor of the resisting model uncertainties for NLFEAs is proposed. • Several NLFE analyses of reinforced concrete members are performed. • Different r.c. members with different behaviours and failure modes are considered. • Different software codes and constitutive laws for concrete in tension are adopted. • Probabilistic treatment of the model uncertainties through a Bayesian approach. Abstract This work evaluates the partial safety factor related to the resistance model uncertainties in non-linear finite element analyses (NLFEAs) for reinforced concrete structures. Various experimental tests concerning different typologies of structures with different behaviours and failure modes, i.e., walls, deep beams, panels, are simulated by means of appropriate two-dimensional finite elements (FE) structural models (i.e., plane stress configuration). Several FE structural models are defined for each experimental test to investigate the model uncertainty influence on the 2D NLFEAs of reinforced concrete structures in terms of global resistance, considering different modelling hypotheses to describe the mechanical behaviour of reinforced concrete members (i.e., epistemic uncertainties). Subsequently, the numerical results are compared to the experimental outcomes. Then, a consistent treatment of the resistance model uncertainties is proposed following a Bayesian approach. Specifically, the prior distributions of the resistance model uncertainties for the different modelling hypotheses are evaluated and then each one is updated on the basis of the data obtained from the other models to evaluate the posterior distributions. After that, the mean value and the coefficient of variation characterizing the resistance model uncertainties are identified. Finally, in agreement with the safety formats for NLFEAs of reinforced concrete structures, the partial safety factor related to the resistance model uncertainties is evaluated. [ABSTRACT FROM AUTHOR]

The aim of this work is the development of an empirical relationship for evaluating the rotation capacity of RHS temper T4 aluminium alloy beams subjected to non-uniform bending. The proposed relationships are based on the numerical results coming from an extensive parametric analysis performed by means of FE code ABAQUS, which gains insight into the influence of all the geometrical and mechanical parameters affecting the ultimate behaviour of aluminium alloy beams. In particular, the influence of the flange slenderness, the influence of the web restraining effect related to the flange-to-web slenderness ratio and the influence of the moment gradient are investigated. The modelling of the material is carried out by adopting the constitutive law proposed by Eurocode 9, based on the Ramberg-Osgood model whose shape factor characterises the hardening behaviour of the material. The investigations concern these factors considered separately as well as their interaction. The results are herein reported with reference to temper T4, i.e. an alloy characterised by a significant hardening behaviour, and show the importance of some of the investigated parameters on the maximum flexural resistance, corresponding to the complete development of local buckling of compressed flange, and on the rotation capacity of aluminium alloy beams. Successively, by means of monovariate and multivariate non linear regression analyses, empirical relationships are provided in order to predict both the ultimate bending resistance and the rotation capacity of RHS temper T4 aluminium alloy beams starting from their geometrical and mechanical properties. [ABSTRACT FROM AUTHOR]

• Resisting model uncertainty safety factor for seismic NLFE analyses is proposed. • Several NLFE analyses of r.c. members subjected to cyclic loads are performed. • Different reinforced concrete shear walls are considered. • Different software codes and constitutive laws for concrete are adopted. • Probabilistic analysis of the model uncertainties through a Bayesian approach. This study assesses the partial safety factor corresponding to the resistance model uncertainties in the use of non-linear finite element analyses (NLFEAs) for reinforced concrete systems subjected to cyclic loads. Specifically, various walls experimentally tested are considered for this investigation and are simulated through two-dimensional (i.e., plane stress) finite element (NLFE) models. The comparison between the global resistances from the plane stress NLFE structural models and the experimental tests is carried out considering the possible modelling hypotheses available in relation to the mechanical response of reinforced concrete structural systems subjected to cyclic loads. After that, a probabilistic processing of the abovementioned epistemic uncertainties is carried out in line with a Bayesian updating. In detail, each prior distribution of the resistance model uncertainty related to a specific combination of the modelling hypotheses is computed and successively updated with the data achieved from the other models to estimate the posterior distribution. Hence, the coefficient of variation and the mean value of the resistance model uncertainties are evaluated and the corresponding partial safety factor is assessed in line with the NLFEA safety formats of reinforced concrete systems for seismic analyses. [ABSTRACT FROM AUTHOR]

The assessment of existing reinforced concrete structures, especially bridges and viaducts, nowadays is one of the most relevant aspects for engineers. In fact, due to the old age of a large part of the infrastructure assets and the deteriorating conditions affecting the structural elements, their safety with respect to the ultimate limit states may be compromised. In this perspective, the assessment by means of global safety formats employing non-linear finite element analyses can be an extremely useful tool. In this context, the study proposes to relate the safety level to the damage through 3D global non-linear numerical analyses. Specifically, the assessment of an existing prestressed reinforced concrete bridge deck is carried out by means of the global safety format denoted as "Estimation of Coefficient of Variation" (ECOV) assuming different damage scenarios. In fact, the safety of the structure is initially assessed with respect to the ultimate limit state in its undamaged condition. Subsequently, different damage scenarios, derived from the inspections, are numerically studied. For each damage scenario, the safety of the deck is evaluated with respect to the ultimate limit state relating the safety loss to the damage level. Finally, damage thresholds for this type of structure are defined on specific static parameters. • Safety of an existing prestressed reinforced concrete bridge deck is assessed. • 3D NLFE models are defined within the global safety format ECOV. • A visco-elastic analysis is performed to reproduce the time-dependent effects. • Different damage scenarios are simulated by varying degradation characteristics. • Specific damage thresholds are numerically proposed and related to damage level. [ABSTRACT FROM AUTHOR]