Evaluation of the Floor Acceleration Amplification Demand of Instrumented Buildings

The floor acceleration amplification (FAA) factor is one of the most critical parameters in computing the equivalent seismic force of nonstructural component (NC). To evaluate the heightwise FAA distribution profile, the recorded acceleration response of the instrumented buildings was analyzed using the California Strong Motion Instrumentation Program (CSMIP) database. The FAA demands for three groups of buildings consisting of reinforced concrete, steel, and masonry buildings were analyzed. In each group, the buildings were classified into four subgroups according to their heights. Parabolic distribution profiles were suggested that could envelop most of the FAA data, as demonstrated by the processed results. An earthquake experience-based importance factor was suggested in terms of the percentage of the enveloped records. The obtained FAAs at the roof were generally larger than those in other levels. The percentile distributions of the roof acceleration amplification (RAA) were computed. The results showed that the roof FAA was underestimated in ASCE 7-16. The magnitudes of the FAA and the RAA correlated to the fundamental period of the building, which was considered by classifying the buildings according to the period ranges. The RAA profile against the period was obtained from a regression analysis. The developed FAA profile is expected to be useful in the seismic design of NCs, and it is expected to be adopted in future code provisions.

Forecasts on the seismic behavior of buildings constructed with the Great Soviet Panel

After a visual inspection of a representative sample of 200 buildings, pathological deterioration in structural elements and joints, with severe levels of damage, was detected in the buildings built with the Great Soviet Panel prefabricated system in Santiago de Cuba. Likewise, increases in weight and changes in rigidity were found, due to the contraventions of the inhabitants. In this research, with the aim of forecasting the seismic behavior of some buildings built with the Great Soviet Panel precast system, the values of the fundamental periods are determined through the environmental vibrations of 7 buildings that make up the sample studied. It is concluded that changes are expected in the seismic behavior of these instrumented buildings.

Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

A practice-oriented method for estimating elastic floor response spectra

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.

Highlights of a Cursory Study of Behavior of Three Instrumented Buildings during the Mw 7.1 Anchorage, Alaska, Earthquake of 30 November 2018

This is a cursory study of the recorded responses of three buildings instrumented by the U.S. Geological Survey (USGS) in Anchorage, Alaska, during the Mw 7.1 earthquake of 30 November 2018. The earthquake caused the strongest shaking in Anchorage since the well‐known 1964 Mw 9.2 Great Alaska earthquake. Since the 1964 event, several structures (buildings and bridges) in Anchorage have been instrumented by the USGS, and their responses have been recorded during multiple events. For each of the three buildings (the 14‐story Frontier Building, the 20‐story Atwood Building, and the 22‐story Hilton Hotel) studied herein, essential dynamic characteristics and significant behavioral aspects such as beating and torsional motions are identified. Recorded peak accelerations and displacements are provided, and average drift ratios are computed using the peak displacements at the roof levels with respect to the ground level. These average drift ratios imply that the motions are at levels expected not to cause damage to the buildings. Visualization videos of both the 14‐story Frontier and the 20‐story Atwood Buildings have been developed to display overall shaking of the buildings during the earthquake.