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For many mid- and high-rise concrete buildings in seismic regions, earthquake loads are resisted by reinforced concrete walls that respond primarily in flexure (i.e. yielding in flexure without exhibiting significant shear damage or shear failure). Under lateral loading, flexural walls may sustain compressive damage to concrete and reinforcing bars as well as tensile rupture of reinforcement, with the onset of lateral strength loss resulting from one or more of these damage mechanisms. Given the prevalence of concrete walls, there is interest in advancing numerical modeling to enable improved prediction of wall response as well as in advancing wall design and detailing to achieve enhanced performance. The research presented here does both. First, modeling recommendation for nonlinear finite element analyses were developed and validated using data from prior laboratory tests of large-scale structural walls. Second, the validated modeling approach was used to conduct a parametric study to investigate the impact of two critical design parameters, normalized shear stress demand and cross-sectional aspect ratio, on the deformation capacity corresponding to onset of lateral strength loss. Few tests have considered the larger cross-sectional aspect ratios and shear stress demands that are common in design of modern walls. Results of this study show that walls with large cross-sectional aspect ratios and moderate to high shear demands develop high minimum principal stresses within the web region of the wall at the web-boundary element interface; these high stresses can lead to lateral strength loss at relatively low drift levels due to concrete crushing and bar buckling within the web. This failure mode is termed a compression-shear failure. The third phase of the study used the validated modeling approach to conduct a parametric study to develop a mitigation strategy for walls susceptible to compression-shear failure, namely extension of the boundary element confinement into the web of the wall. The results of this study were combined with test data to determine the confined length required to suppress the compression-shear mode. This required confined length is a function of the shear stress demand and is conservatively estimated as c, where c is the depth of the compression region when the wall achieves nominal flexural strength.

Reinforced concrete (RC) structural walls can provide superior stiffness in tall buildings while maintaining notable ductility when subjected to seismic demands. In flexure-dominated walls, this ductility is based on the ability of the end regions (also known as boundary elements) to maintain load carrying capacity through increasing tension and compression cycles. In order to achieve this behavior, modern design practice aims to force substantial yielding in tension prior to loss of compressive strength. As such, a sound understanding of the compressive behavior of wall end regions is paramount to understanding RC wall ductility. A database of both rectangular RC prism (axial) and RC wall tests was assembled, and the results were compared with a popular analytical constitutive model for confined concrete. The existing model assumes that compressive behavior is based on fracture of the transverse reinforcement, however the data indicates that bar buckling and/or crushing of the core can occur well before transverse bar fracture. Therefore, the existing model significantly overestimates both compressive strength and strain capacity in many conditions consistent with modern design. Formulations for compressive strength and strain capacity, as well as a monotonic constitutive model, are proposed to capture the compressive behavior observed in the data. Both the number of longitudinal bars and the use of crossties in place of closed hoops were found to have a significant impact on the compressive behavior of confined concrete, and are therefore integral to the proposed model. The model was developed based on tests performed by the authors, and then validated using the aforementioned database.

The DesignSafe cyberinfrastructure (www.designsafe-ci.org) is part of the NSF-funded Natural Hazard Engineering Research Infrastructure (NHERI) and provides cloud-based tools to manage, analyze, understand, and publish critical data for research to understand the impacts of natural hazards. The DesignSafe Data Depot provides private and public disk space to support research collaboration and data publishing through a web interface. The DesignSafe Reconnaissance Portal uses a map interface to provide easy access to data collected to investigate the effects of natural hazards, and the DesignSafe Workspace provides cloud-based tools for simulation, data analytics, and visualization; as well as access to high performance computing (HPC). This paper provides an overview of the DesignSafe cyberinfrastructure and describes specific examples of the use of DesignSafe in research for natural hazards. These examples include electronic data reports that use Jupyter notebooks to allow researchers to interrogate data interactively within the web portal, computational workflows that integrate ensembles of HPC-based simulations and surrogate modeling, and the publication of field research data after natural hazard events that utilize a variety of DesignSafe tools. The paper also provides an overall assessment of current DesignSafe impact and usage, demonstrating how DesignSafe is enhancing research in natural hazards.

With the goal to facilitate research to evaluate the risks from natural hazards and alternate risk mitigation strategies, the Natural Hazards Engineering Research Infrastructure’s Computational Modeling and Simulation Center (NHERI SimCenter) is developing computational workflows for regional hazard simulations. These simulations enable research to integrate detailed assessments of individual facilities with comprehensive regional-scale simulations of natural hazard effects. This approach enables fine (parcel level) granularity on assessing natural hazard impacts on buildings, infrastructures systems and other constructed facilities, which can enable engineering informed assessment of policy considerations and socio-economic impacts. Effective development of research platforms for high-resolution regional simulations requires modular workflows that can integrate state-of-the-art models with information technologies and high-performance computing resources. In this paper, the modular architecture of the computational workflow models is described and illustrated through testbed applications to evaluate regional building damage under an earthquake and a hurricane scenario. Developed and disseminated as open-source software on the NHERI Design Safe Cyberinfrastructure, the computational models and workflows are enabling multi-disciplinary collaboration on research to mitigate the effects of natural hazard disasters.

Natural hazards and disaster reconnaissance investigations have provided many lessons for the research and practice communities and have greatly improved our scientific understanding of extreme events. Yet, many challenges remain for these communities, including improving our ability to model hazards, make decisions in the face of uncertainty, enhance community resilience, and mitigate risk. State-of-the-art instrumentation and mobile data collection applications have significantly advanced the ability of field investigation teams to capture quickly perishable data in post-disaster settings. The NHERI RAPID Facility convened a community workshop of experts in the professional, government, and academic sectors to determine reconnaissance data needs and opportunities, and to identify the broader challenges facing the reconnaissance community that hinder data collection and use. Participants highlighted that field teams face many practical and operational challenges before and during reconnaissance investigations, including logistics concerns, safety issues, emotional trauma, and after-returning, issues with data processing and analysis. Field teams have executed many effective missions. Among the factors contributing to successful reconnaissance are having local contacts, effective teamwork, and pre-event training. Continued progress in natural hazard reconnaissance requires adaptation of new, strategic approaches that acquire and integrate data over a range of temporal, spatial, and social scales across disciplines. U.S. National Science FoundationNational Science Foundation (NSF) [1611820] The U.S. National Science Foundation supported this work under grant number 1611820. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

In 2016, the National Science Foundation (NSF) funded a multi-institution interdisciplinary team to develop and operate the Natural Hazards Reconnaissance Facility (known as the "RAPID") as part of the Natural Hazards Engineering Research Infrastructure (NHERI) program. During the following 2 years, the RAPID facility developed its instrumentation portfolio and operational plan with input from the natural hazards community, the facility's leadership team, and an external steering committee. In September 2018, the RAPID began field operations, which continue today and include instrumentation, software, training, and support services to conduct reconnaissance research before, during, and after natural hazard and disaster events. Over the past 2 years, the RAPID has supported the data collection efforts for over 60 projects worldwide. Projects have spanned a wide range of disciplines and hazards and have also included data collection at large-scale experimental facilities in the United States and abroad. These projects have produced an unprecedented amount of high-quality field data archived on the DesignSafe cyberinfrastructure platform. This paper describes the RAPID facility's development, instrumentation portfolio (including the mobile application RApp), services and capabilities, and training activities. Additionally, overviews of three recent RAPID-supported projects are presented, including descriptions of field data collection workflows, details of the resulting data sets, and the impact of these project deployments on the natural hazard fields. NSFNational Science Foundation (NSF) [1904653, 1904327, CMMI: 1611820]; NSF through GEER [1826118]; Oregon DOT; FHWA [SPR807] The RAPID Facility operates under a cooperative agreement with the NSF under Award No. CMMI: 1611820. Research on the performance of LRLVBs in Hurricane Michael was supported by the NSF under award nos. 1904653 and 1904327. Research on the flow slide during the Palu, Indonesia earthquake was supported by the NSF through GEER under award number 1826118. Any opinions, findings, conclusions, and recommendations presented in this paper are those of the authors and do not necessarily reflect the views of the National Science Foundation. Funding for the Hooskadaden Landslide case study were provided by Oregon DOT and FHWA (SPR807).

This study presents a physics-based rib-scale finite element (FE) model to study bond-zone behavior for spliced longitudinal bars in reinforced concrete beams subjected to monotonically increasing loading. In this model, a high-resolution mesh is used in the vicinity of the bar-concrete interface to capture the geometry of the ribs on the reinforcing steel. At the concrete-bar interface, a contact formulation that properly represents normal and frictional force transfer is used; adhesion between concrete and steel is ignored. The FE model is calibrated using data from beam splice tests performed by Ramirez and Russell [1] . It is observed that concrete tensile strength and tangential friction at the concrete-steel interface determine simulated response; these quantities are calibrated to provide accurate simulation of experimental results. The calibrated model provides results in good agreement with test data. Load-displacement response as well as concrete crack patterns are accurately simulated, and the proposed model can distinguish between the behavior of uncoated and epoxy-coated deformed bars as well as simulate the impact on bond strength of confinement provided by transverse steel.

A multimechanism, shear-assessment procedure has been developed by combining and modifying a shear-strength model for truss-tension failures with a softened strut-and-tie model for strut-co...

Reinforced concrete walls are a common lateral load–resisting system for buildings. Common wall configurations are solid planar or solid flanged (H, I, T, L, or C-shaped cross sections) and...

As part of a Network for Earthquake Engineering Simulation research project led by researchers at the University of Washington with collaborators at University at Buffalo, and Taiwan National Center for Research on Earthquake Engineering, a self-centering steel plate shear wall (SC-SPSW) system has been developed to achieve enhanced seismic performance objectives, including recentering. The SC-SPSW consists of thin steel infill panels, referred to as web plates that serve as the primary lateral load-resisting and energy dissipating element of the system. Posttensioned (PT) beam-to-column connections provide system recentering capabilities. A performance-based design procedure has been developed for the SC-SPSW, and a series of nonlinear response history analyses have been conducted to verify intended seismic performance at multiple hazard levels. Quasi-static subassembly tests, quasi-static and shake table tests of scaled three-story specimens, and pseudo-dynamic tests of two full-scale two-story SC-SPSWs have been conducted. As a culmination of this multi-year, multi-institutional project, this paper will present an overview of the SCSPSW numerical and experimental research programs. This paper will also discuss innovative PT connection and web plate designs that were investigated to improve constructability, resilience, and seismic performance and that can be applied to other self-centering and steel plate shear wall systems.

An advanced modelling technique is developed to model the nonlinear cyclic response of circular RC columns using fibre-based section discretisation method. A comparison between different reinforcing steel models is made. Through a comprehensive parametric study the influence of inelastic buckling of vertical reinforcement on the cyclic response of circular RC columns is investigated. The results have been compared and validated against a set of experimental datasets. The proposed calibrated model accounts for the influence of inelastic buckling of vertical reinforcement and interaction of stiffness of horizontal ties reinforcement with vertical reinforcement. The model also accounts for the fracture of vertical bars due to low-cycle high-amplitude fatigue degradation. Therefore, this model is able to predict the nonlinear cyclic response of circular RC columns up to complete collapse. The results show that the existing uniaxial material models of reinforcing bars that are calibrated using stress–strain behaviour of isolated bars cannot represent the behaviour of reinforcing bars inside RC columns. Moreover, it is found that the buckling length of vertical reinforcement has a significant influence on the pinching response of RC columns and also reduces the low-cycle fatigue life of buckled reinforcement.

The research presented here developed a model for simulating the nonlinear cyclic response of flexure-controlled concrete walls, which meets the dual objectives of accuracy and computational efficiency. The proposed model represents a significant advancement in that it provides accurate simulation of the dominate failure mechanism exhibited by flexural walls in the laboratory and field: compression-controlled failure characterized by simultaneous crushing of concrete and buckling of longitudinal reinforcement. The first steps in the model development effort comprised assembly of an experimental database and review of current modeling approaches for walls (e.g., lumped plasticity, distributed plasticity, and continuum elements). Model evaluation indicated that the most viable option to achieve accuracy and efficiency was the use of beam–column line elements with fiber-type cross-section models at the integration points. Initially, both displacement-based and force-based element formulations were evaluated; however, the displacement-based formulation resulted in an inaccurate representation of the axial force distribution along the length of the element. Therefore, only the force-based formulation was chosen for further study. The basic model included standard 1D constitutive models for confined concrete, plain concrete and reinforcing steel. Comparing simulated and measured response data showed that the concrete and steel material models must be regularized using a mesh-dependent characteristic length and a material-dependent post-yield energy to enable accurate, mesh-objective simulation of strength loss due to compression failure. The post-yield energy values were determined using relevant experimental data, an important but missing component of prior research on material regularization. The results of this study show that use of the regularized constitutive models significantly improved the accuracy of response predictions.

A finite element (FE) model is used to simulate bond-zone behavior in a pullout test of a single bar embedded in concrete. The proposed FE model treats both the concrete and reinforcing bar in the bond-zone with refined solid elements to explicitly represent the deformations of rebar and the surrounding concrete and employs the surface-to-surface contact model on the concrete-rebar interface to simulate proper load transfer. In modeling of pullout tests, the significance of using a concrete model that can accurately simulate nonlinear response under high confining pressures is emphasized. Two concrete models are discussed and compared from a constitutive modeling perspective: (1) concrete damaged-plasticity (CDP) model and (2) concrete damage plasticity model 2 (CDPM2). Three pullout tests are simulated via the proposed modeling approach each with two concrete models. It is shown that the FE model with CDPM2 produced bond stress and slip responses comparable to test data, while the FE model with CDP model overpredicted bond stress due to concrete response overestimated under high confining stress states. The FE models with CDPM2 can capture different failure modes for different types of specimens: splitting failure for the specimen without confinement and pullout failure for the specimen with confinement.

Experimental testing was conducted on four large-scale, flexure-yielding walls with rectangular cross sections to investigate the impact of imposed axial load ratio (10, 14, and 20% of axia...

Hysteretic behaviour of corroded bars.Analytical modelling of post-yield buckling of corroded bars.Influence of corrosion on low-cyclic fatigue behaviour of reinforcing bars.Modelling the impact of corrosion on cyclic degradation of corroded bars. A new phenomenological hysteretic model for reinforcing bars with and without corrosion damage is presented. The model simulates buckling of reinforcement, deterioration in post-buckling compressive strength due to strain history and the impact of low-cycle fatigue on tension response. The model, for uncorroded reinforcing bars, is calibrated using data from numerical simulations and corrosion damage parameters are calibrated using experimental data. The model is evaluated using a comprehensive experimental data set, and the results show that the model is in a good agreement with the data.

Summary Current seismic design codes and damage estimation tools neglect the influence of successive events on structures. However, recent earthquakes have demonstrated that structures damaged during an initial event (mainshock) are more vulnerable to severe damage and collapse during a subsequent event (aftershock). This increased vulnerability to damage translates to increased likelihood of loss of use, property, and life. Thus, a reliable risk assessment tool is required that characterizes the risk of the undamaged structure subjected to an initial event and the risk of the damaged structure under subsequent events. In this paper, a framework for development of aftershock fragilities is presented; these aftershock fragilities define the likelihood that a building damaged during a mainshock will exhibit a given damage state following one or more aftershocks. Thus, the framework provides a method for characterizing the risk associated with damage accumulation in the structure. The framework includes the following: (i) creation of a numerical model of the structure; (ii) characterization of building damage states; (iii) generation of a suite of mainshock–aftershocks; (iv) mainshock–aftershock analyses; and (v) development of aftershock fragility curves using probabilistic aftershock demand models, defined as a linear regression of aftershock demand–intensity pairs in a logarithmic space, and damage-state prediction models. The framework is not limited to a specific structure type but requires numerical models defining structural response and linking structural response with damage. In the current study, non-ductile RC frames (low-rise, mid-rise, and high-rise) are selected as case studies for the application of the framework. Copyright © 2015 John Wiley & Sons, Ltd.

Summary Previous research has shown that self-centering steel plate shear walls (SC-SPSWs) are capable of achieving enhanced seismic performance at multiple hazard levels, including recentering following design-level earthquakes. When modeling SC-SPSWs numerically, these studies considered an idealized tension-only steel plate shear wall (SPSW) web plate behavior. Research has shown that web plate behavior is more complex than predicted by the idealized model, and web plates can provide more strength, stiffness, and energy dissipation than predicted by the idealized model. The idealized model of web plate behavior is used widely in SPSW numerical models where the moment-resisting boundary frame provides supplemental hysteretic damping and stiffness; however, in SC-SPSWs, where the post-tensioned boundary frame is designed to remain elastic during an earthquake, accounting for the more complex web plate behavior can have a significant impact on seismic performance estimates from numerical simulation. This paper presents different methods for modeling SC-SPSWs. Responses from these models are compared with experimental results. A simple modification of the tension-only model, referred to as the tension-compression strip model, is shown to provide a reasonable approximation of SC-SPSW behavior. Results from nonlinear response history analyses of SC-SPSWs with the tension-only and tension-compression web plate models are compared to assess how the approximation of web plate behavior affects SC-SPSW seismic performance. Copyright © 2015 John Wiley & Sons, Ltd.

In the self-centering steel plate shear wall (SC-SPSW) system, thin steel web plates provide the primary lateral strength and energy dissipation, while post-tensioned connections in the boundary frame provide recentering and mitigate frame damage. In most steel plate shear walls (SPSWs), web plates are connected to the beams and columns; however, connecting the web plates to the beams only has been proposed as a means of reducing boundary frame demands and mitigating web plate damage. This paper investigates the impact of using beam-only-connected web plates on SC-SPSW design and seismic performance. Expressions for determining beam demands for purposes of design are developed. Three- and nine-story prototype SC-SPSWs are designed using beam-only-connected web plates and are compared with equivalent SC-SPSWs designs with fully-connected web plates. To evaluate the potential for material savings, the weight of steel required for each system is compared. The seismic performance of the SC-SPSWs with beam-only-connected and fully-connected web plates is compared using results of nonlinear response history analyses in which relatively simple, yet conservative, modeling techniques are employed.

Natural hazards engineering plays an important role in minimizing the effects of natural hazards on society through the design of resilient and sustainable infrastructure. The DesignSafe cy...

Concrete walls are used commonly as part of the lateral-load resisting system for buildings in regions of high seismicity. Damage to walled buildings in recent earthquakes has highlighted t...

An optical surface measurement technique was used to characterise three-dimensional corrosion pattern of reinforcing bars subjected to accelerated corrosion. After the optical measurement process was performed, the corroded bar specimens were tested under monotonic and cyclic axial loading. The optical measurement data were used to develop a 3D micro-fibre finite element model developed for simulation of the physical testing and parametric study of the influence of corrosion pattern on stress–strain response of corroded bars. It was observed that the irregular cross sectional shape of pitted sections has a significant influence on the inelastic buckling and nonlinear cyclic response.

Current postearthquake inspection of structures relies on certified inspectors to make an assessment of the existing safety of the structure based primarily on qualitative measures. Complet...

Experimental and numerical studies have shown self-centering steel plate shear walls (SC-SPSWs) to exhibit enhanced performance including recentering during extreme loading, making them a viable lateral load resisting system for high seismic regions capable of reducing structural repair costs and loss of building functionality after an earthquake. SC-SPSWs utilize thin steel web plates to provide lateral load resistance and energy dissipation, while rocking post-tensioned (PT) beam-to-column connections recenter the building and, if properly designed, eliminate costly damage to the boundary frame. A series of quasi-static cyclic tests have been conducted on SC-SPSW subassemblages. The purpose of these tests is to better understand SC-SPSW and component behavior and the impact of certain web plate and PT connection parameters on performance. This paper presents the results from the test program and also compares the experimental results to those of simple numerical models.

RC core walls are used commonly in modern building construction as the primary lateral load–resisting system. To meet architectural constraints, including elevator, stair, and doorway openings, common configurations include walls coupled together with heavily reinforced, low-aspect-ratio coupling beams. Numerous studies have focused on coupling beams and improved seismic performance and design of coupling beams. However, far fewer research programs have studied the seismic behavior of the coupled wall system. Coupled walls are typically used in mid- to high-rise construction, and understanding their seismic response requires simulation beyond the coupling beam and must include all important yielding components of the system. A research project was undertaken to investigate the response of a midrise coupled wall designed to meet current codes. The advanced testing capabilities of the University of Illinois at Urbana-Champaign George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES)...

The use of concretes with supplementary cementitious materials (SCM concretes) is a mechanism to improve the sustainability of structural systems. However, most reinforced concrete (including cast-in-place and precast) structural components rely on early stiffness and strength of the concrete to resist self-weight and construction loadings after release of the formwork. In contrast to cement-only concretes, SCM concretes require more time to reach the target strength and stiffness values and therefore a structural component that does not depend on these engineering properties during construction is required. Use of concrete-filled tubes (CFTs) is a solution. With a CFT, the steel tube is able to support construction loads while the high SCM concrete fill develops its strength and stiffness. However, there are concerns about load transfer (from the concrete to the steel tube) during the development of these properties and the long-term deformations (creep) of high SCM concrete and its impact on CFT performance. This research develops models to predict the long-term (creep) response of SCM concretes and uses those predictive models to assess the long-term response of CFTs with SCM concrete fill. Three time-dependent models were developed: compressive strength, elastic modulus, and creep. The models were validated using a large SCM database and two full-scale CFTs with SCM concrete fill that were tested under sustained loading. Once verified, a parametric study was conducted. The results indicate that SCM concretes with binder ratios (total ratio of CaO/(SiO2 + Al2O3) in all binders—cement and SCMs) greater than 0.5 behaved similarly to CFTs with cement-only concrete fill.

A numerical model is presented that enables simulation of the nonlinear flexural response of corroded reinforced concrete (RC) components. The model employs a force-based nonlinear fibre beam-column element. A new phenomenological uniaxial material model for corroded reinforcing steel is used. This model accounts for the impact of corrosion on buckling strength, postbuckling behaviour, and low-cycle fatigue degradation of vertical reinforcement under cyclic loading. The basic material model is validated through comparison of simulated and observed responses for uncorroded RC columns. The model is used to explore the impact of corrosion on the inelastic response of corroded RC columns.

Purpose In this paper the impact of corrosion of reinforcing steel in RC columns on the seismic performance of a multi-span concrete integral bridge is explored. A new constitutive model for corroded reinforcing steel is used. This model simulates the buckling of longitudinal reinforcement under cyclic loading and the impact of corrosion on buckling strength. Cover concrete strength is adjusted to account for corrosion induced damage and core concrete strength and ductility is adjusted to account for corrosion induced damage to transverse reinforcement. This study evaluates the impact which chloride induced corrosion of the reinforced concrete columns on the seismic fragility of the bridge. Fragility curves are developed at a various time intervals over the lifetime. The results of this study show that the bridge fragility increases significantly with corrosion. Design/methodology/approach This paper firstly evaluates the impact which chloride induced corrosion of the columns has on bridge fragility. Finally, fragility curves are developed at various time intervals over the lifetime of the bridge. The results of this study show that the bridge fragility increases significantly with corrosion. Findings 1) It was found that columns dominate the system fragility at all levels of deterioration. Therefore, it highlights the importance of good column design in terms of both seismic detailing and durability for this integral bridge type. 2) In terms of foundation settlement coupled with corrosion, it was found that settlements on the order of the discrete levels adopted for this study increased the system fragility at the slight, moderate and extensive damage states but their impact at the complete damage states is negligible. 3) Ageing considerations are currently neglected in widespread regional risk assessment and loss estimation packages for transport infrastructure. The result of this study provides a methodology that enables bridge managers and owners to employ in seismic risk assessment of existing aging bridges. Originality/value The modelling technician developed in this paper considers the impact of detailed corrosion damaged of RC column on nonlinear dynamic response and fragility of a corroded integral bridge under earthquake loading. The current modelling technique is the most comprehensive 3D fibre element model for seismic analysis and risk assessment of corroded bridges.

Purpose A new modelling technique is developed to model the nonlinear behaviour of corrosion damaged reinforced concrete (RC) bridge piers subject to cyclic loading. The model employs a nonlinear beam-column element with multi-mechanical fibre sections using OpenSees. The nonlinear uniaxial material models used in the fibre sections account for the effect of corrosion damage on vertical reinforcing, cracked cover concrete due to corrosion of vertical bars and damaged confined concrete due to corrosion of horizontal tie reinforcement. An advance material model is used to simulate the nonlinear behaviour of the vertical reinforcing bars that accounts for combined impact of inelastic buckling and low-cycle fatigue degradation. The basic uncorroded model is verified by comparison of the computation and observed response of RC columns with uncorroded reinforcement. This model is used in an exploration study of recently tested reinforced concrete components to investigate the impact of different corrosion models on the inelastic response of corrosion damaged RC columns. Design/methodology/approach A series of pushover and cyclic analyses on a hypothetical corroded RC columns are conducted. The impact of corrosion on reinforcing steel and concrete is modelled. The influence of cyclic degradation due to low-cycle fatigue is also modelled. Findings (1) Corrosion has a more significant impact on ductility loss of RC columns than the strength loss (plastic moment capacity). (2) It was found that the flexural failure is initiated by buckling of vertical bars and crushing of core concrete which then followed by fracture of bars in tension. (3) The analyses results showed that for seismic performance and evaluation of existing corroded bridges monotonic pushover analysis is insufficient. The cyclic degradation due to low-cycle fatigue has a significant influence on the response of corroded RC columns. Originality/value The finite element developed in this paper is the most comprehensive model to date that is able to capture the onlinear behaviour of corroded RC columns under cyclic loading up to complete collapse.

Reinforced concrete structural walls are used commonly as the primary lateral-load resisting system in buildings. The research presented here represents the results of the first phase of a multi-year research effort aimed at developing tools to enable performance-based earthquake engineering (PBEE) of structural walls. The first phase of the research effort focused on the seismic behavior and analysis of slender planar walls and included laboratory testing of four planar wall sub-assemblages. The walls simulated the bottom three stories of a 10-story prototype building; loading apparatus available at the University of Illinois, Network for Earthquake Engineering Simulation laboratory were used to simulate the load demands, permitting maximum test-specimen scale and realistic demand patterns. The walls were detailed to modern code requirements and standard practice and included heavily reinforced boundary elements. The test matrix studied the effects of reinforcement layout, shear demand, and lap splices at the base of the wall. All of the walls exhibited damage in the compression region, even at relatively low drifts. The splice affected the location of the damage. Walls without splices sustained damage at the base of the wall; walls with splices sustained damage at both the top of the splice and the base of the wall, with the critical region depending on the shear demand. Shear demand also affected response; a moderate increase in shear demand resulted in the failure mechanism changing from bar fracture to flexure–compression failure of the boundary elements.

A series of subassembly tests were conducted to investigate the behavior of the self-centering steel plate shear wall (SC-SPSW) system under cyclic loading. The SC-SPSW system utilizes thin steel web plates to provide energy dissipation and the primary strength and stiffness of the system, whereas posttensioned (PT) beam-to-column connections provide recentering capabilities. In this new system, the web plate is intended to yield under cyclic loading, whereas the boundary elements and PT connection elements remain undamaged. The web plate can then be replaced relatively easily following significant inelastic cycles. This experimental program studies the effects of various design parameters on the system and connection response and compares the response with approximate analytical formulas. The experimental results show that the SC-SPSW system has high ductility, high initial stiffness, recentering capabilities, an overall system response as anticipated, and more energy dissipation than expected.

Fragility functions are developed to predict the method of repair required for steel plate shear walls damaged due to earthquake loading. The results of previous experimental studies are used to develop empirical relationships between damage states and story drift. Damage states are proposed and linked deterministically with commonly employed methods of repair; these damage states are characterized by parameters such as yielding and tearing of the steel plate and yielding, buckling and fracture of frame members. Lognormal probability distributions are fit to the empirical data and evaluated using standard statistical methods. The results of this effort are families of fragility functions that predict the required method of repair for a damaged wall.

The self-centering steel plate shear wall (SC-SPSW) is a new seismic load-resisting system that combines the strength and stiffness properties of the SPSW with the recentering capabilities of postt...

A model is developed to simulate the nonlinear response of planar reinforced-concrete frames including all sources of flexibility. Conventional modeling approaches consider only beam and column flexibility using concentrated plasticity or springs to model this response. Although the joint may contribute the majority of the deformation, its deformability is typically not included in practice. In part, this is because few reliable, practical approaches for modeling all sources of frame nonlinearity are available. The research presented herein was undertaken to develop a practical, accurate nonlinear model for reinforced concrete frames. The model is appropriate for predicting the earthquake response of planar frames for which the nonlinearity is controlled by yielding of beams and/or non-ductile response of joints and is compatible with the ASCE/SEI Standard 41-06 nonlinear static procedure. The model was developed to facilitate implementation in commercial software packages commonly used for this type of nonlinear analysis. The nonlinearity is simulated by introducing a dual-hinge lumped-plasticity beam element to model the beams framing into the joint. The dual-hinge comprises two rotational springs in series; one spring simulates beam flexural response and one spring simulates joint response. Hinge parameters were determined using data from 45 planar frame sub-assemblage tests. Application of the model to simulate the response of these sub-assemblages shows that the model provides accurate simulation of stiffness, strength, drift capacity and response mechanism for frames with a wide range of design parameters.

The results of previous experimental tests indicate that reinforced concrete interior beam column joints may exhibit significant strength and stiffness loss under earthquake loading, and the results of post-earthquake reconnaissance indicate that joint failure may result in structural collapse. Thus seismic evaluation and design of reinforced concrete frames requires accurate prediction of the potential for joint failure. This paper presents a binomial logit model, developed using data from 110 experimental tests, which define the probability that a reinforced concrete interior beam–column building connection, with a specific set of design parameters, will exhibit either a non-ductile joint shear failure prior to beam yielding or a ductile failure that initiates with beam yielding. The calibrated model identifies the relative importance of various design parameters in determining the connection’s response mechanism. The model can be used by an engineer designing a new connection, constructed of normal or high-strength materials, to estimate the likelihood of joint failure initiation. The model can also be used by an engineer evaluating an existing structure to estimate the likelihood of joint failure, determine the factors that most significantly affect this likelihood, and, thereby, develop a suitable and efficient retrofit strategy.

Typical steel moment-frame structures in the United States comprise a few seismic frames and many gravity frames, which include “continuous columns” that are pin-connected to beams. These continuous columns, which are often ignored in seismic design, can improve the seismic performance of the structure. This study investigates the effects of continuous columns on the structural stability and seismic response of building frames. Stability coefficients representing the separate and combined effects of geometric and material nonlinearities are used with a simplified modeling technique, which separates the shear-type and flexural-type lateral-force-resisting systems in moment frames. Relationships between continuous column stiffness ratio and the stability coefficients, inter-story drift, and the drift concentration factor are presented. It is shown that for realistic structures, the columns in the seismic frames are generally sufficient to prevent unstable response and large drift concentrations, and the inclusion of gravity continuous column stiffness tends to decrease both the drift concentration and inter-story drift.

This paper presents the results of a probabilistic evaluation of the seismic performance of 3D steel moment-frame structures. Two types of framing system are considered: one-way frames typical of construction in the United States and two-way frames typical of construction in Japan. For each framing system, four types of beam–column connections are considered: pre-Northridge welded-flange bolted-web, post-Northridge welded-flange welded-web, reduced-beam-section, and bolted-flange-plate connections. A suite of earthquake ground motions is used to compute the annual probability of exceedence (APE) for a series of drift demand levels and for member plastic-rotation capacity. Results are compared for the different framing systems and connection details. It is found that the two-way frames, which have a larger initial stiffness and strength than the one-way frames for the same beam and column volumes, have a smaller APE for small drift demands for which members exhibit no or minimal yielding, but have a larger APE for large drift demands for which members exhibit large plastic rotations. However, the one-way frames, which typically comprise a few seismic frames with large-sized members that have relatively small rotation capacities, may have a larger APE for member failure. The probabilistic approach presented in this study may be used to determine the most appropriate frame configuration to meet an owner's performance objectives. Copyright © 2008 John Wiley & Sons, Ltd.

A proposed supplement to ASCE/SEI 41 Seismic Rehabilitation of Existing Buildings has been developed for the purpose of updating provisions related to existing reinforced concrete buildings. Based on experimental evidence and empirical models, the proposed supplement includes revisions to modeling parameters and acceptance criteria for reinforced concrete beams, columns, structural walls, beam-column joints, and slab-column frames. The revisions are expected to result in substantially more accurate and, in most cases, more liberal assessments of the structural capacity of concrete components in seismic retrofit projects. DOI: 10.1193/1.2757714

Fragility functions are developed to predict the method of repair required for modern reinforced-concrete beam-column building joints subjected to earthquake loading. These fragility functions, in combination with similar fragility functions developed previously for older joints, are used to compare damage progression in older versus modern joints. To develop fragility functions for modern joints, the results of previous experimental investigations are used to generate empirical relationships between damage and earthquake demand, damage states are linked deterministically with commonly employed methods of repair, and the empirical data are modeled using a standard probability distribution. The demand parameters, damage states, methods of repair, and probability distribution used in the current study are chosen to facilitate comparison with results from the previous study. The results of this study are a family of fragility functions that can be used to predict the method of repair required for a modern joint damaged due to earthquake loading and an improved understanding of the relative vulnerability of older versus modern components.