Simplified Pushover Analysis for Rapid Assessment of Shear-Type Frames

Raihan Rahmat Rabi,Marco Vailati,Giorgio Monti

doi:10.3390/app112411711

Raihan Rahmat Rabi, Marco Vailati + Show 1 more

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https://doi.org/10.3390/app112411711

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Abstract

A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is presented. The frame global force-displacement capacity is described as a trilinear curve passing through three limit states (LS): Damage LS (DLS), Life safety LS (LLS), and Collapse LS (CLS). The global LSs are obtained consequently to the attainment of story-level, element-level, and section-level LSs. All LS capacities are described through closed-form equations. The validity of the proposed method is verified by applying it on several reinforced concrete (RC) frames with a varying number of stories. The results obtained with such an analytical procedure show a good match with those obtained from pushover based on finite element method (FEM) analysis models, in terms of both global force-displacement capacity curves and story displacements at various LSs. The proposed method has the potential to be conveniently applied in large-scale vulnerability/risk assessment studies, where the quality and quantity of the available data call for the use of simplified yet accurate models. More refined models would in fact require significantly heavier computational efforts, not justified by the quality of the results that are usually obtained. The simplicity of the proposed method in such a context is demonstrated through the development of the fragility curves of a five-story shear-type reinforced concrete frame, starting from a predefined set of mechanical and geometrical features characterizing a building typology.

Highlights

Seismic risk estimation and mitigation has become increasingly important due to the losses sustained by infrastructure, buildings, and humans in the aftermath of earthquakes around the world
The adaptive profile is applied in assessment of taller irregular structures where the deformation and inertial forces are not dominated by first mode [13,14,15,16]
The method is extremely efficient thanks to mechanics-based closed-form equations describing the capacity of the resisting mechanism, from the local to the global level, and can be readily implemented in a spreadsheet

Summary

Introduction

Seismic risk estimation and mitigation has become increasingly important due to the losses sustained by infrastructure, buildings, and humans in the aftermath of earthquakes around the world. Seismic risk is a composition of hazard, exposure, and vulnerability The latter is where the efforts of the structural engineering community are focused, since it can be mitigated by retrofitting interventions applied on seismically deficient buildings. Two nonlinear procedures are available for the seismic assessment of structures: (a) nonlinear dynamic analysis (NDA) [1] and (b) nonlinear static analysis, known as pushover analysis [2,3]. Pushover analysis aims to describe the dynamic nonlinear response of a structure through the application of an equivalent static system of forces or displacements. The fixed profile is effective in estimating the response of low-to-mid-height structures where the contribution of higher modes is negligible, and the plastic deformations are well distributed throughout the height [5,6,7,8,9,10,11,12]. The adaptive profile is applied in assessment of taller irregular structures where the deformation and inertial forces are not dominated by first mode [13,14,15,16]

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