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The failure mode of concrete columns in subway stations during seismic events can be affected by the dynamic fluctuation of the axial forces. This study conducted quasi-static tests with bidirectional loading on three scaled rectangular columns to investigate the influence of highly variable axial compression ratio (ACR). A detailed analysis was conducted of the impact of the highly variable ACR on the column failure mode, reinforcement strains, and hysteretic behavior, and the repairability assessment was discussed. Numerical analysis of the effect of ACR variations was carried out based on the experimental results. In these experiments, the failure modes of central columns in Dakai Station, Japan, during the Kobe earthquake were reproduced, and three columns exhibited compressive-bending-shear damage and compressive-bending damage. As the ACR varied up to three cycles during one horizontal loading cycle, the hysteresis curve of the columns exhibited notable asymmetry. Furthermore, with a large variation of ACR amplitude, the stirrups of the column were fractured due to excessive shear effects. The bearing capacity, energy dissipation, and stiffness degradation of the columns were significantly adversely affected. A reparability assessment of the columns, based on the distribution of reinforcement strains, residual displacements, and concrete damage, is proposed. The effects of varying frequency and amplitude of different vertical ACRs on the hysteretic behavior of columns were analyzed numerically. [ABSTRACT FROM AUTHOR]

A method to calculate structural functionality for building structures based on structural natural frequency was proposed for seismic loading events. Structural functionality loss and recovery were determined by monitoring the change of structural natural frequency during the earthquake events or repair activities. A shape factor was introduced, structural functionality recovery function (SFRF), to consider the repair strategy and repair speed. As an example, this method was applied to obtain the structural functionality curve and seismic resilience of a half scale two-story reinforced concrete (RC) frame structure. This structure was subjected to a series of ground motions on a shake table and then repaired by carbon fiber cloth a total of four times. The results indicate that the SFRF is able to capture the recovery trend of a structure in the repair process. Meanwhile, a damage index-repair target (DI-RT) curve, representing the 5% difference between the proposed and traditional SFRFs, was used to investigate the impact of structural damage degree and repair target. The areas above the curve indicates that the difference between the proposed and traditional SFRFs cannot be ignored. [ABSTRACT FROM AUTHOR]

In July 2009, a full-scale midrise light-frame wood apartment building was subjected to a series of earthquakes at the word's largest shake table in Miki, Japan. This article focuses on the test results of that full-scale six-story light-frame wood building. The objectives of the testing program were to (1) demonstrate that the performance-based seismic design procedure developed as part of the NEESWood project worked on the full-scale building, i.e., validate the design philosophy to the extent one test can and (2) gain a better understanding of how midrise light-frame wood buildings respond, in general, to a major earthquake while providing a landmark data set to the seismic engineering research community. The building consisted of l,350 [m.sup.2] (14,000 [ft.sup.2]) of living space and had 23 apartment units; approximately one-half one-bedroom units and one-half two-bedroom units. The building was subjected to three earthquakes ranging from seismic intensities corresponding to the 72-year event to the 2,500-year event for Los Angeles. In this paper, the construction of the NEESWood Capstone Building is explained and the resulting seismic response in terms of base shears, selected wall drifts, global interstory drifts, accelerations, hold-down forces, and roof drifts are presented. Detailed damage inspection was performed following each test and those results are summarized also. The building performed excellently with little damage even following the 2,500-year earthquake. The global drift at roof level was approximately 0.25 m and maximum interstory drifts were approximately 2% for the floor average with individual wall drifts reaching just over 3% in one corner of the building at the fifth story. DOI: 10.1061/(ASCE)ST.1943-541X.0000222 CE Database subject headings: Shake table testing; Seismic tests; Earthquake; Frames; Buildings, multistory. Author keywords: Shake table testing; Seismic tests; Earthquake; Woodframe; Light-frame wood; Midrise building.

This paper presents a simplified direct displacement design (DDD) procedure which was used to design the shear walls for a six-story woodframe structure. The building was tested in the final phase of a Network for Earthquake Engineering Simulation (NEES) project. Specifically, NEESWood Capstone Building was designed to meet four performance expectations: damage limitation, life safety, far-field collapse prevention (CP), and near-fault CE The performance expectations are defined in terms of combinations of interstory drift limits and prescribed seismic hazard levels associated with predefined nonexceedance probabilities. To verify that design requirements were met, a series of nonlinear time-history analyses (NLTHAs) was performed using suits of both far-field and near-fault ground motion records. The distributions of interstory drifts obtained from the NLTHA confirm that the Capstone Building designed using DDD meets all four target performance expectations, thereby validating the DDD procedure. Additionally, collapse analysis in accordance with the recently proposed Applied Technology Council project 63 (ATC-63) methodology was performed. The results of incremental dynamic analyses confirmed that the Capstone Building designed using the DDD procedure has adequate capacity margin against collapse, as dictated by the ATC-63 methodology. DOI: 10.1061/(ASCE)ST.1943-541X.0000181 CE Database subject headings: Displacement; Wood structures; Structural design; Shear walls; Earthquake engineering; Seismic effects. Author keywords: Displacement-based design; Wood structures; Shear walls; Earthquake engineering; Seismic hazard; Structural engineering; Performance-based design.

The experimental seismic responses of a full-scale two-story light-frame wood townhouse building, designed to modern U.S. engineered seismic design requirements, were compared against the predictions of a new software package entitled seismic analysis package for woodframe structures (SAPWood) developed recently within the NEESWood Project. The main objective of this paper was to verify the accuracy of the predictions from the SAPWood model, which incorporates shear deformations of shear walls as well as cumulative floor displacements caused by the out-of-plane rotations of the floor and ceiling diaphragms. A comparison was conducted on interstory drifts and shear wall deformations for various structural configurations (construction phases) of the test building and excitation levels. Good agreement was found between the numerical predictions and test results for the four different construction phases. The SAPWood model was shown to be a promising numerical tool for predicting the seismic response of light-frame wood structures. DOI: 10.1061/(ASCE)ST.1943-541X.0000086 CE Database subject headings: Seismic analysis; Numerical models; Earthquakes; Frames; Wood structures; Computer software. Author keywords: Seismic analysis; Numerical model; Time history; Earthquakes; Wood structures.

Performance-based seismic design (PBSD) of wood frame structures has been only preliminarily investigated by a handful of researchers around the world and is currently under development in the United States as well as other countries worldwide. This paper presents the basic concept of applying system identification logic as one alternative for PBSD of wood frame structures. In PBSD of wood frame structures, one prescribes combinations of hazard level and corresponding performance, and 'designs' the system such that these performance metrics ate met. For wood frame buildings this procedure fits the definition of a system identification problem, i.e., the input and output are known and the nonlinear system between them is sought. In most cases the shearwall locations, i.e., geometry, are known, and only the wall design is sought. In this papel the concept is presented and a procedure to apply it within a PBSD framework is proposed. The validity of the procedure is confirmed through two illustrative examples, namely the design for a two-story wood shearwall and a two-story wood frame building. An existing ten-parameter hysteresis model commonly used for seismic analysis of wood frame structures was used in both examples to represent the nonlinear system to be identified. The 'design' is then checked by applying a suite of ordinary ground motion records and compafing the multirecord incremental dynamic analysis of the peak deformation response to the target (performance) curve. The approach was found to work well for the example structures and shows promise for extension to more complicated structures and performance measures. DOI: 10.1061/(ASCE)0733-9445(2008)134:2(240) CE Database subject headings: Seismic design; Wood structures; System analysis; Identification; Frames; Probability.