Sensitivity of NLTH Analysis of MDOF Bridges to Choice of Viscous Damping Models

Arjun Jayaprakash

2017/04/27

Introduction

There has been a rising interest among engineers to conduct non-linear time history (NLTH) analysis as part of the seismic design procedure for bridges. A good understanding of member parameters such as strength, stiffness and damping are crucial for accurate results from NLTH analysis. Strength and stiffness in dynamic analyses are well understood but the viscous damping model that is mostly being used in commercial analysis programs, namely initial stiffness proportional Rayleigh damping, is questionable. This model prescribes a constant damping matrix proportional to the initial stiffness matrix of a structure. Theoretically, this is inaccurate because of three main reasons.

Albeit, the above can be stated in theory, if the sensitivity of response prediction to the variation in damping models is minor, the simplest model would serve the purpose. Sensitivity of displacement predictions of SDOF systems to choice of initial stiffness and tangent stiffness proportional damping models in NLTH analysis have been studied in the past. It was found that the results vary considerably, with the tangent stiffness proportional model better representing actual tests. This project makes an effort towards understanding the sensitivity of response predictions of MDOF systems to the choice of four different damping models in NLTH analysis.

Research Report

For more details on this project, please read this report.