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Recent earthquakes have demonstrated that code-conforming modern (i.e. post-1970s) reinforced concrete (RC) buildings can satisfy life safety performance objectives. However, the accumulated earthquake damage in these modern buildings raised concerns about their performance in future events, contributing to widespread demolition and long-term closure of damaged buildings. The economic and environmental impacts associated with the demolition and long-term closure of modern buildings led to societal demands for improved design procedures to limit damage and shorten recovery time after earthquakes. To address societal demands, this study proposes a damage-control-oriented seismic design approach that targets functional recovery by ensuring structural component demands do not exceed the damage-control limit state (DLS) under design-level events. Herein, DLS is defined as the post-earthquake state beyond which the strength and deformation capacity of a structural component is compromised, and its performance in a future event cannot be relied upon without safety-critical repair. This study proposes a methodology to determine component deformation limits for the design of structures for damage control. Using the developed methodology, we propose component rotation limits for RC beams, columns, and walls. The seismic performance and capability of buildings designed using the proposed design approach to satisfy recovery-based performance objectives is demonstrated through nonlinear response history and recovery analyses (using the ATC-138 methodology) of four archetype frame buildings, designed per New Zealand standards to different beam deformation limits. The analyses show that building codes can achieve functional recovery using the proposed component deformation limits without the need for sophisticated recovery analyses.

Summarized in this article are the major findings from a detailed damage investigation of an instrumented ductile reinforced concrete moment frame building subjected to a design-level earthquake. The building sustained widespread damage during the 2016 M-7.8 Kaikoura earthquake and was subsequently demolished. Prior to demolition, the structural system was extensively surveyed to document the severity and distribution of the damage sustained in the reinforced concrete frames and the flooring system. Furthermore, the building response during the earthquake was reconstructed from the acceleration records obtained from instruments installed throughout the building. The site seismic demands were also obtained from a local free-field instrument. The data collected from this damage investigation provide a high-quality dataset that is valuable to researchers investigating different parameters related to the seismic performance of reinforced concrete moment frame buildings. The dataset is published and publicly available on DesignSafe-CI (project PRJ-3444); https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-3444v2. The data collection methodology is described, and a roadmap for navigating the dataset is presented to support future use of the archived dataset.

Post-earthquake assessment procedures require component deformation limits to identify locations for visual inspection and locations needing structural repair. This study proposes a framework for defining component deformation limits for detailed visual inspection and repair for earthquake-damaged concrete buildings. First, observations from cyclic tests of ductile concrete components (beams, columns, and walls) suggested that the residual capacity (in terms of strength and deformation capacity) of such components is likely uncompromised if the deformation at the initiation of lateral strength loss (LSL) is not exceeded in prior loading histories. The results also revealed that the deformation at the initiation of LSL typically corresponds to the onset of longitudinal bar buckling in ductile components. Furthermore, using experimental data, multipliers are developed as fractions of ASCE/SEI 41 modeling parameters at lateral failure (i.e. aor d) to predict deformation at initiation of LSL. Subsequently, a probabilistic approach is proposed for defining the component deformation limits, considering uncertainty in both capacity and demand. Component deformation limits for detailed visual inspection are defined such that there is a low probability (adopted as <10%) of exceeding the deformation at the initiation of LSL. The component deformation limit for repair is defined as the median deformation at the initiation of LSL (i.e. 50% probability of exceedance).

Post-earthquake cordons have been used after seismic events around the world. However, there is limited understanding of cordons and how contextual information such as geography, sociocultural characteristics, economy, and institutional and governance structures affects decisions and operational procedures, including aspects related to spatial and temporal attributes of cordon establishment. This research aims to fill the gap in cordon knowledge through a qualitative comparative case study of two cities: Christchurch, New Zealand (Mw6.2 earthquake, February 2011) and L’Aquila, Italy (Mw6.3 earthquake, 2009). Both cities suffered comprehensive damage to their city centers and had cordons established for extended periods of time. Data collection was done through purposive and snowball sampling whereby 23 key informants were interviewed in total. Research participants held expert knowledge in their roles and responsibilities, that is, council members, emergency managers, politicians, business/insurance representatives, academics, and police. Results illustrate that cordons were primarily established to ensure safety of people and to maintain security. The extent and duration of the cordons were affected by the recovery approaches taken in respective cities, that is, in Christchurch demolition was widely undertaken which supported recovery and allowed for faster removal of cordons. In contrast, authorities in L’Aquila placed high value on heritage buildings which led to recovery strategy based on preserving and restoring most of the buildings which extended the duration of cordon. Extended cordons have many similarities but evolve overtime. This evolution of cordons is affected by site-specific needs; thus, cordons should be understood and planned based on contextual realities.

The shake table tests presented in this article aims to explore seismic displacement demands for existing reinforced concrete buildings resulting from inelastic torsion associated with different sources of irregularities. Two half-scale seven-story reinforced concrete structures were subjected to unidirectional earthquake excitations on the shake table at the National Center for Research on Earthquake Engineering (NCREE) Tainan laboratory. The specimens reflected structural weaknesses of buildings which collapsed during the Meinong earthquake in Taiwan. This data paper presents an overview of the project as well as the organization of obtained test datasets. The data are available for public use under the Designsafe-CI project “Shake table tests of seven-story reinforced concrete structures with torsional irregularities.”

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures.

Seismic provisions in building codes arguably constitute the most important and effective means for improving the performance of the built environment during earthquakes. Because they serve as the minimum and mandatory requirements for new construction that accumulates over time, building codes can and have reduced disaster risk in cities around the world; moreover, codes have evolved with improvements in scientific and engineering understanding, technology, and professional standards. Yet many have questioned whether the “life safety” objectives used in codes around the world are adequate or appropriate. In this opinion paper, we argue that seismic code objectives should reflect how society expects the built environment to perform in an earthquake. Social science methods can be employed to overcome the challenges of understanding what standards society holds for seismic performance. This opinion paper suggests four guiding principles on eliciting public perspectives and reviews examples of how elicitation has been applied around the world in the natural hazards field. It concludes with recommendations and further research needs.

Modern reinforced concrete buildings are often designed to dissipate energy during strong earthquakes by permitting the controlled formation of plastic hinges. Plastic hinges require assessment of residual capacity in post-earthquake situations. However, few past studies have investigated this topic, and results from experiments focused on undamaged structures are not always transferable to post-earthquake situations. Data from an experimental program, in which both cyclic and earthquake-type loadings were applied to nominally identical reinforced concrete beams, are used to investigate the relationship between residual crack widths and rotation demands. Assessment of the peak deformation demands incurred during a damaging earthquake is critical for post-earthquake assessments, but residual crack widths are shown to be dependent on several factors in addition to the peak rotation demand. Non-dimensional metrics capturing the distribution of cracking are proposed as a more informative alternative. The reduction in stiffness that occurs as a result of earthquake-induced plastic hinging damage was also investigated. A proposed model is shown to give a lower-bound estimate of the residual stiffness following arbitrary earthquake-type loadings.

The use of deformation capacity limits is becoming increasingly common in seismic design and assessment of reinforced concrete (RC) walls. Deformation capacity limits for RC walls in existing design and assessment documents are reviewed using a comprehensive database. It is found that the existing models are inconsistent and do not account for variation in deformation capacity with changes in the ratio of neutral axis depth to wall length (c/Lw) and ratio of transverse reinforcement spacing to longitudinal bar diameter (s/db) at the wall end region. A new mechanics-based model considering strain limits on the concrete and reinforcement is recommended. Concrete compressive strain limits for different levels of wall end region detailing are selected based on curvature ductilities for the walls in the database. Reinforcement tensile strain is limited based on a model for bar buckling. The proposed model, which accounts for c/Lwand s/db, is shown to have less dispersion and more accuracy than existing models when compared against experimental data and provides consistency between assessment and design provisions.

A set of tests on 17 large-scale, nominally identical, beam specimens with variations in loading protocol, loading rate, and restraint to axial elongation are described. Three specimens were also repaired by epoxy injection following an initial damaging earthquake loading. This paper provides a detailed description of the test program, and the corresponding data are made available at Design-Safe (DOI: 10.17603/DS2SQ2K). While the primary goal of the test program was to improve the state of knowledge regarding the post-earthquake residual capacity of reinforced concrete plastic hinges in beams, the data are useful for modeling approaches that consider loading rate, plastic hinge elongation, cyclic degradation, and flexure–shear–axial interaction, in addition to investigating the effectiveness of post-earthquake repair techniques by epoxy injection of cracks.

Benefit-cost analyses for the seismic retrofit of unreinforced masonry (URM) buildings in downtown Victoria, British Columbia, Canada, were undertaken, considering the seismic hazard, building value, occupant/pedestrian exposure, a variety of strengthening measures, and local construction costs. The analyses are underpinned by building motion-damage relationships developed based on observed damage in past earthquakes in California and New Zealand. The considered upgrading measures ranged from parapet bracing to comprehensive seismic upgrades consistent with local practices. Parapet bracing and other partial retrofits were shown to have favorable benefit-cost ratios and thus be strong candidate measures for risk mitigation programs. Full upgrades were shown to have less favorable benefit-cost ratios. While applied to Victoria, the generality of the methodology and the use of observed damage data from California and New Zealand make the findings of this study particularly relevant for similar locations throughout the Pacific Northwest and abroad.

The high demolition rate (∼60%) of reinforced concrete (RC) buildings that generally performed well in Christchurch, New Zealand, has been one of the most important lessons from the Canterbury Earthquakes. In an effort to understand such an outcome, various factors influencing the post-earthquake decisions on buildings (demolition or repair) are explored, focusing on multi-story RC buildings in Christchurch Central Business District (CBD). Using empirical data, logistic regression analysis was conducted to explain the likelihood of building demolition. Several explanatory factors were found to be statistically significant: assessed damage, occupancy type, heritage status, number of floors, and construction year. From in-person interviews conducted in New Zealand, contextual factors such as insurance policy and changes in legislation were also found to play a significant role in the post-earthquake decisions on buildings.

This paper represents the second part of a series of four publications on response history analysis for new buildings. It specifically focuses on modeling assumptions, consideration of important effects in the analysis, and interpretation of analysis results via global and local acceptance criteria. A statistical basis for development of both force- and deformation-controlled acceptance criteria consistent with the collapse probability goals of ASCE/SEI 7 is illustrated. More explicit sub-classifications of force- and deformation-controlled actions are proposed within the statistical framework. Additional philosophical discussion and simple probabilistic arguments are presented on the topic of consideration of unacceptable response, and guidance on addressing unacceptable response is given. Similarities and differences between the new requirements and those in other performance-based design guidelines are also enumerated.

A detailed inventory of about 350 concrete shear wall buildings in western Canada with 7 or more stories and built prior to 1980 was created. About one hour was spent collecting information from drawings for each building so wall capacities could be estimated and simplified linear dynamic analysis could be used to estimate seismic demands on the building. Non-ductile behavior is expected in many of the buildings because of insufficient and/or poor arrangement of shear walls to adequately control building drifts, thin walls that are poorly detailed, and discontinuities in the shear walls. The analysis indicated that the drift demands on the buildings for the 2% in 50-year hazard level were not particularly large, however the flexural capacities of the walls are low considering their limited ductility. The shear capacities of the walls were typically less critical. The current study demonstrates that a detailed inventory can be used to distinguish between the performance of similar buildings, which can be used to refine a regional risk assessment or inform policy decisions for the group of buildings.

Given sufficient anchorage to the diaphragms, an unreinforced masonry (URM) wall subjected to out-of-plane inertial forces will likely develop a horizontal crack at an intermediate height about which the wall will rock as semirigid bodies. The effect of wall slenderness on out-of-plane stability has been demonstrated in past studies, but treatment of the effects of diaphragm flexibility and ground motion variability has been limited. This paper presents an experimental study examining the out-of-plane stability under seismic loading of URM walls connected to flexible diaphragms. Five full-scale unreinforced solid clay brick wall specimens spanning one story were subjected to earthquake ground motions using a shake table. The top and bottom of the walls were independently connected to the shake table through coil springs, simulating the flexibility of diaphragms. Variables examined experimentally included diaphragm stiffness and wall height. Both the amount of rocking observed as well as the ground motion scale causing collapse varied significantly with changes in the diaphragm properties. The test results provided data used for validation of a rigid-body rocking model, enabling an extensive parametric study on wall stability and the development of new assessment guidelines in a companion paper.

A numerical rigid body model for the out-of-plane response of unreinforced masonry (URM) walls connected to flexible diaphragms is validated against the shake table test results presented in a companion paper. It is demonstrated that the model is able to reproduce the observed rocking behavior with reasonable accuracy, particularly the intensity of shaking resulting in collapse of the walls. The validated model is used to undertake a parametric study investigating the effects of numerous parameters on out-of-plane wall stability. Ground motion variability is accounted for by using a large suite of motions. Based on the results of the modeling, an updated out-of-plane assessment procedure is proposed. The procedure, which could be incorporated into ASCE 41, provides reference curves of h/tversus Sa(1.0), along with correction factors for axial load, wall thickness, ground-level walls, and exposure.

The Canterbury earthquakes, which involved widespread damage in the February 2011 event and ongoing aftershocks near the Christchurch central business district (CBD), presented decision makers with many recovery challenges. This paper identifies major government decisions, challenges, and lessons in the early recovery of Christchurch based on 23 key-informant interviews conducted 15 months after the February 2011 earthquake. It then focuses on one of the most important decisions—maintaining the cordon around the heavily damaged CBD—and investigates its impacts. The cordon displaced 50,000 central city jobs, raised questions about (and provided new opportunities for) the long-term viability of downtown, influenced the number and practice of building demolitions, and affected debris management. Despite being associated with substantial losses, the cordon was commonly viewed as necessary, and provided some benefits in facilitating recovery. Management of the cordon poses important lessons for planning for catastrophic urban earthquakes around the world.

Detailed observations are reported for eight shear wall buildings from the Concepción region that experienced severe damage during the 27 February 2010 Chile earthquake. The repetitive nature of some of the damage suggests that these field observations may be applicable to similar buildings elsewhere, whereas other damage may be unique. Several shear walls experienced failures that apparently started at the boundaries due to the high compression in these unconfined edges, and propagated into the wall web. Other walls, including horizontal and vertical wall segments in perforated walls, experienced shear failure. Damage also was observed in columns, beams, and coupling slabs. In most cases, the percentage of damaged elements was less than 10% of the lateral force-resisting elements of the building, suggesting that these structures were not capable of distributing damage. Several building indices are calculated, including vibration periods and regularity indices, for comparison with observed behavior.

This study introduces a methodology for anticipating the post-earthquake functionality of hospitals in a region. Performance levels for interacting systems (structural, nonstructural, lifeline, and personnel) in a hospital are operationally defined, empirically correlated, and probabilistically modeled using damage data from past earthquakes. Separate models are developed for buildings built before and after the 1973 California Hospital Seismic Safety Act. Performance estimates of the systems are used to anticipate overall hospital functionality. Effects of external power and water outage are also included. As a case study, the methodology is utilized to predict the functionality of hospitals in Los Angeles County for two earthquake scenarios. Findings indicate that in a M6.9 Verdugo fault earthquake scenario, nearly half of county hospitals have at least a 50% chance of experiencing significant loss of functionality. Such findings can support emergency response planning as well as seismic retrofit prioritization.

Unreinforced masonry (URM) walls with sufficient anchorage to the diaphragms will crack above mid-height when subjected to out-of-plane ground motions. This study investigates the sensitivity of the out-of-plane response to varying height-to-thickness (h/t) ratios for URM walls connected to rigid diaphragms. ASCE 41, Seismic Rehabilitation Standard, provides guidelines for permissible h/tratios for out-of-plane URM walls. To assess these limits, a rigid-body numerical model, calibrated to full-scale shake table tests, was used. The focus of the analysis was to identify the minimum h/tratio that would cause collapse of the wall when subjected to seismic shaking. The analysis was performed for 80 input motions and accounted for variability in the crack location. The results of the study suggest that the probability of collapse is dependent on the site class and that walls with limited overburden and satisfying the h/tlimits in ASCE 41 have a very low probability of collapse.

A proposed supplement to ASCE/SEI 41 Seismic Rehabilitation of Existing Buildingshas 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.

An idealized backbone model defining the key damage states of an existing reinforced concrete column (flexural yielding, shear failure, and axial load failure) is developed using drift capacity models. Assumptions and limitations of the drift capacity models are discussed. To demonstrate the application of the idealized backbone model to the evaluation of existing reinforced concrete columns, the model is compared to data from shake table tests and measured drifts from an instrumented building damaged during the Northridge earthquake. The results from the backbone model are also compared with modeling parameters recommended in current seismic rehabilitation guidelines. Copyright © 2006 John Wiley & Sons, Ltd.

The 26 December 2004 earthquake and tsunami resulted in over 100,000 damaged or destroyed homes and over 500,000 internally displaced people in northern Sumatra. Reconstruction and recovery from these massive losses requires the coordination of many stakeholders, including multiple levels of government, nongovernment relief organizations, donors, and the people of northern Sumatra. Although efforts have been taken by the Government of Indonesia to develop standards for the reconstruction of houses and establish a coordinating body, the reconstruction effort in Sumatra still faces many challenges. A broad range of housing types, with varying degrees of construction quality, have been constructed as part of the recovery effort. A field study team visited Banda Aceh, Meulaboh, and Nias seven months after the December event and documented the process of reconstruction, the interaction of the stakeholders, and the types of housing construction.

Existing reinforced concrete columns with light transverse reinforcement are vulnerable to shear failure during seismic response. Shear strength models, modeling the degradation of shear strength with increasing displacement ductility demand, have been widely used to evaluate the interstory drift capacity of such columns. The application of a shear strength model to determine the drift capacities for a database of 50 shear-critical columns demonstrates significant inaccuracies with such a method. An empirical drift capacity model based on the shear-critical column database provides a better estimate of the interstory drift at shear failure. The new drift capacity model identifies the most critical parameters affecting the drift capacity of shear-critical columns, namely, transverse reinforcement ratio, shear stress demand, and axial load ratio.