This study examines the influence of ground motion duration on the collapse capacities of a modern, five-story steel moment frame and a reinforced concrete bridge pier. The effect of duration is isolated from the effects of ground motion amplitude and response spectral shape by assembling sets of "spectrally equivalent", long and short duration records, and employing them in comparative non-linear dynamic analyses. For the modern steel moment frame, the estimated median collapse capacity is 29% lower when using the long duration set, as compared to the short duration set. For the concrete bridge pier, the collapse capacity is 17% lower. A comparison of commonly used duration metrics indicates that significant duration is the most suitable metric to characterize ground motion duration for structural analysis. Sensitivity analyses to structural model parameters indicate that structures with high deformation capacities and rapid rates of cyclic deterioration are the most sensitive to duration.

This study evaluates the effect of considering ground motion duration when selecting hazard-consistent ground motions for structural collapse risk assessment. A procedure to compute source-specific probability distributions of the durations of ground motions anticipated at a site, based on the generalized conditional intensity measure framework, is developed. Targets are computed for three sites in Western USA, located in distinct tectonic settings: Seattle, Eugene, and San Francisco. The effect of considering duration when estimating the collapse risk of a ductile reinforced concrete moment frame building, designed for a site in Seattle, is quantified by conducting multiple stripe analyses using groups of ground motions selected using different procedures. The mean annual frequency of collapse ( collapse ) in Seattle is found to be underestimated by 29% when using typical-duration ground motions from the PEER NGA-West2 database. The effect of duration is even more important in sites like Eugene ( collapse underestimated by 59%), where the seismic hazard is dominated by large magnitude interface earthquakes, and less important in sites like San Francisco ( collapse underestimated by 7%), where the seismic hazard is dominated by crustal earthquakes. Ground motion selection procedures that employ causal parameters like magnitude, distance, and Vs 30 as surrogates for ground motion duration are also evaluated. These procedures are found to produce poor fits to the duration and response spectrum targets because of the limited number of records that satisfy typical constraints imposed on the ranges of the causal parameters. As a consequence, ground motions selected based on causal parameters are found to overestimate collapse by 53%.

Six buildings in the Wellington region and the upper South Island, instrumented as part of the GeoNet Building Instrumentation Programme, recorded strong motion data during the 2016 Kaikoura earthquake. The response of two of these buildings: the Bank of New Zealand (BNZ) Harbour Quays, and Ministry of Business, Innovation, and Employment (MBIE) buildings, are examined in detail. Their acceleration and displacement response was reconstructed from the recorded data, and their vibrational characteristics were examined by computing their frequency response functions. The location of the BNZ building in the CentrePort region on the Wellington waterfront, which experienced significant ground motion amplification in the 1–2 s period range due to site effects, resulted in the imposition of especially large demands on the building. The computed response of the two buildings are compared to the intensity of ground motions they experienced and the structural and nonstructural damage they suffered, in an effort to motivate the use of structural response data in the validation of performance objectives of building codes, structural modelling techniques, and fragility functions. Finally, the nature of challenges typically encountered in the interpretation of structural response data are highlighted.

This study investigates the influence of ground motion duration on the dynamic deformation capacity of a suite of 10 modern reinforced concrete moment frame buildings. A robust numerical algorithm is proposed to estimate the dynamic deformation capacity of a structure by conducting incremental dynamic analysis. The geometric mean dynamic deformation capacity of the considered buildings was, on average, found to be 26% lower under long duration ground motions, compared to spectrally equivalent short duration ground motions. A consistent effect of duration on dynamic deformation capacity was observed over a broad range of structural periods considered in this study. Response spectral shape, however, was found to not significantly influence dynamic deformation capacity. These results indicate that the effect of duration could be explicitly considered in seismic design codes by modifying the deformation capacities of structures.

A practice-oriented modal superposition method for setting elastic floor acceleration response spectra is proposed in this paper. The approach builds on previous contributions in the literature, making specific recommendations to explicitly consider floor displacement response spectra and accounts for uncertainty in modal characteristics. The method aims to provide reliable predictions which improve on existing code methods but maintain simplicity to enable adoption in practical design. This work is motivated by recent seismic events which have illustrated the significant costs that can be incurred following damage to secondary and nonstructural components within buildings, even where the structural system has performed well. This has prompted increased attention to the seismic performance of nonstructural components with questions being raised about the accuracy of design floor acceleration response spectra used in practice. By comparing floor acceleration response spectra predicted by the proposed method with those recorded from instrumented buildings in New Zealand, it is shown that the proposed approach performs well, particularly if a good estimate of the building’s fundamental period of vibration is available.

The widely used incremental dynamic analysis (IDA) offers attractive efficiencies to organize and conduct nonlinear dynamic structural analyses under earthquake ground motions. However, its use of a fixed ground motion set limits its ability to resolve ground motion characteristics that vary based on location and intensity. To overcome this limitation and utilize IDA in site-specific seismic risk analysis, a new method is proposed, called the site-specific adjustment framework for incremental dynamic analysis (SAF-IDA), which involves two modifications to conventional IDA. The first is a process to select input ground motions for the IDA over a distributed grid of ground motion characteristics that influence structural response. The second is a post-processing procedure to develop a surrogate model from the raw IDA data to adjust the structural response results based on site- and intensity-specific ground motion hazard parameters. The proposed SAF-IDA method is illustrated in case study analyses of archetype building structures and validated through comparison with analysis results based on more computationally intensive multiple stripe analysis (MSA), which employs site-specific selection of ground motions for each intensity level.

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