Evaluation of ASCE 7 equations for designing acceleration‐sensitive nonstructural components using data from instrumented buildings

Abstract

Summary This study uses instrumented buildings and models of code‐based designed buildings to validate the results of previous studies that highlighted the need to revise the ASCE 7 Fp equation for designing nonstructural components (NSCs) through utilizing oversimplified linear and nonlinear models. The evaluation of floor response spectra of a large number of instrumented buildings illustrates that, unlike the ASCE 7 approach, the in‐structure and the component amplification factors are a function of the ratio of NSC period to the supporting building modal periods, the ground motion intensity, and the NSC location. It is also shown that the recorded ground motions at the base of instrumented buildings in most cases are significantly lower than design earthquake (DE) ground motions. Because ASCE 7 is meant to provide demands at a DE level, for a more reliable evaluation of the Fp equation, 2 representative archetype buildings are designed based on the ASCE 7‐16 seismic provisions and exposed to various ground motion intensity levels (including those consistent with the ones experienced by instrumented buildings and the DE). Simulation results of the archetype buildings, consistent with previous numerical studies, illustrate the tendency of the ASCE 7 in‐structure amplification factor, [1 + 2(z/h)], to significantly overestimate demands at all floor levels and the ASCE 7 limit of ap=212 to in many cases underestimate the calculated NSC amplification factors. Furthermore, the product of these 2 amplification factors (that represents the normalized peak NSC acceleration) in some cases exceeds the ASCE 7 equation by a factor up to 1.50.

An engineering approach for evaluating the dynamic response of acceleration‐sensitive secondary systems in flexible structures

“…12 In the early 1990s, Soong et al 47 proposed modifications on the 1991 NEHRP design force equations for nonstructural components that incorporated a set of dynamic characteristics of these components. The correlation between the dynamic characteristics of the supporting structure and those of the secondary system in the amplification of the latter's dynamic response was also verified through the recorded response of actual buildings subjected to earthquake excitations by Fathali and Lizundia, 40 by Anajafi and Medina, 48 and by Kazantzi et al 49 In the case of multiply-supported secondary systems (see Figure 1B), most of the reported research on the influence of the vibrating supporting structure is investigated by decoupling the equations of motion of the supporting structure from those of the secondary systems. [50][51][52][53]…”

“…This holds true for many instrumented buildings used for examining the in-structure amplification of absolute ground accelerations. 40,48,49 For this category of supporting structures, the tuning phenomenon for LSS applies to components with a fundamental period of vibration, T C1,i , close to T S1,i . When seismic motions activate q higher modes of vibration of the supporting structure whose periods, T Sq,i , correlate with the dominant period of vibration of the earthquake, and at the same time T S1,i falls within the low range of the acceleration response spectrum of the earthquake, then the tuning phenomenon in LSS is controlled by T Sq,i rather than by T S1,i .…”

Analysis and optimization of a nonlinear dual‐mode floor isolation system subjected to earthquake excitations

“…This reduction of acceleration results in uninterrupted operation of missioncritical equipment and less downtime following an earthquake, which improves the resilience of the community served. [3] To date, several approaches to protecting sensitive yet vulnerable equipment or other valuable objects housed inside buildings have been used: (1) base isolation of the entire building, [4][5][6][7] (2) isolating an individual object, [8][9][10][11] and (3) isolating a group of objects [12] or a floor inside the building. [13][14][15][16][17] There has been a growing interest in the later two approachescollectively termed secondary isolation systems hereinafter-due to the relatively lower cost of implementation, as well as ease of application as a retrofit strategy.…”

Deformation-dependent peak floor acceleration for the performance-based design of nonstructural elements attached to R/C structures

“…To design the ''acceleration-sensitive'' NSCs in the framework of PBSD, it is essential to estimate the peak floor acceleration (PFA) response corresponding to the target deformation (or performance levels) of the supporting structure. However, the current seismic design codes, such as Eurocode 8 (EC8, 2004) and FEMA P-1050 (FEMA, 2015), ignore the deformation demands of the supporting structure in estimating the PFA by merely assuming a linearly increasing profile, which results in highly overestimating the NSCs' acceleration demands (Anajafi and Medina, 2018;Petrone et al, 2016). Lin and Mahin (1985) were the first to observe the influence of increasing building inelasticity in reducing the PFA.…”