Derivation of resistance deflection relationship of RC members using softening model

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2008

Authors

Wu, C.
Oehlers, D.

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Conference paper

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Tenth International Symposium on Structural Engineering for Young Experts (ISSEYE-10), Changsha, China, 19-21 Oct 2008

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International Symposium on Structural Engineering for Young Experts (10th : 2008 : Changsha, China)

Abstract

The resistance-deflection function of RC members plays an important role in the structural dynamic response analysis against blast loads. Previous studies recommend the use of a quasi-static resistance function modified by dynamic increase factors (DIF). However, the DIF value is estimated by using averaged strain rates and a constant plastic hinge length of 0.7 times the depth of the cross section is assumed in the analysis although the loading rate profile is not a constant over a cross-section and hinge length is varying with loading conditions. In this paper, a new strain rate formula over cross-section of a member under blast loading is derived based on structural dynamics theory. A layered analysis model together with the derived strain rate effects over a cross-section is used to calculate blast resistance capacity of the RC member. A softening model with variable hinge length rather than constant hinge length is used to determine the curvature profile along the member. It is then integrated along the length to obtain the rotation at all points of the member. The rotation curve is then integrated along half the length of the member to determine the deflection at the centre of the member. For each of the points on the moment-curvature relationship the resistance is determined from the moment profile and the deflection by double integrating the curvature profile, resulting in a full resistance-deflection relationship for the member.

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