Kaori Shishido
Evaluation of coupled flexure and shear strength of hybrid plate girders
Masatsugu Nagai
A hybrid plate girder is comprised of the high-strength flanges and a lower-strength web. In recent years, hybrid plate girders are focused by the reasons of span increased demand and the development of high-strength steel. However, in current specifications, yield phenomenon is defined as the limit state so that economic benefit isn”Ēt obtained. Therefore, it is essential that the introduction of the Limit State Design, and necessary to obtain much more data for verifying the correlation relationships of coupled flexure and shear strength.
This paper presents evaluation of coupled flexure and shear strength of hybrid plate girders. Finite element analyses (FEAs) were performed for ninety-six I-girder models with various combinations of moment and shear load. Shear capacity obtained from FEAs are analyzed for examining the accuracy of existing strength formulae. Based on the analytical results, a method for evaluating shear, flexure and coupled strength of hybrid plate girders will be proposed.
From the analytical results, conclusions are summarized as follows:
(1) Three shear strength formulae were applied to examine the accuracy and precision for several models which web shear buckling was dominant. Basler”Ēs formula has an unsafe evaluation, whereas Mikami”Ēs formula has a conservative evaluation. On the other hand, precision of Maeda”Ēs formula became lower along with increasing aspect ratio.
(2) Correlation relationship of coupled flexure and shear strength was discussed. There was a significant interaction when applied moment or shear load were large. It is also confirmed that correlation curves is closer to the forth power correlation curve.
(3) For models which post-buckling is dominant, it is confirmed the formation of tension field action on test panels by analyzing contour drawings of deformation and stress on the limit state. For models which flexure is dominant, it is also confirmed that local buckling were occurred on the upper flange of test panels.
(4) A method for evaluating shear, flexure and coupled strength of hybrid plate girders was proposed for non-composite hybrid plate bridges and composite hybrid plate bridges in an erection stage.
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