IMPAβ: Incremental Modal Pushover Analysis for Bridges

Alessandro Vittorio Bergami,Davide Lavorato,Camillo Nuti,Bruno Briseghella,Gabriele Fiorentino

doi:10.3390/app10124287

Alessandro Vittorio Bergami, Davide Lavorato + Show 3 more

Open Access

https://doi.org/10.3390/app10124287

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Journal: Applied Sciences	Publication Date: Jun 22, 2020
Citations: 11	License type: CC BY 4.0

Affiliation: Roma Tre University, Fuzhou University

Abstract

In the present study, the incremental modal pushover analysis (IMPA), a pushover-based approach already proposed and applied to buildings by the same authors, was revised and proposed for bridges (IMPAβ). Pushover analysis considers the effects of higher modes on the structural response. Bridges are structurally very different from multi-story buildings, where multimodal pushover (MPA) has been developed and is currently used. In bridges, consideration for higher modes is often necessary: The responses of some structural elements of the bridge (e.g., piers) influence the overall bridge response. Therefore, the failure of these elements can determine the failure of the whole structure, even if they give a small contribution total base shear. Incremental dynamic analysis (IDA) requires input accelerograms for high intensities, which are rare in the databases, while scaling of generated accelerograms with a simple increment of the scaling acceleration is not appropriate. This fact renders IDA, which is by its nature time-consuming, not straightforward. On the contrary, the change of input spectrum required by IMPA is simple. IMPAβ also utilizes a simple complementary method coupled to MPA, to obtain bounds at very high seismic intensities. Finally, the two incremental methods based on static nonlinear and dynamic nonlinear analyses are compared.

Highlights

Bridges are often sensitive to higher modes, so the seismic response depends on local behavior
A third possibility is to derive the response spectra (RS) from a set of ground motions (GMs), The two case studies selected were from straight bridge with four equal spans generated or selected by investigating theboth localderived seismicity foraeach intensity level
The procedure required us to apply to the bridge two load patterns for pushover, multimodal (MPA) and uniform (UPA), to obtain the response according to an envelope of base shear and displacements

Summary

Introduction

Bridges are often sensitive to higher modes, so the seismic response (e.g., the response of the critical piers) depends on local behavior. Similar to what happened for building structures [1,2,3,4,5], many scientific works have been oriented to propose innovative NSA procedures for bridges. In 2006, Isakovic et al [6] discussed, through the application to a case study of a continuous-deck viaduct, the relevance of higher modes, performing a simplified inelastic seismic analysis and indicated that there are major differences between the structural system and the seismic response of buildings and bridges, when the response of a bridge is analyzed in transverse direction.

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