دانلود رایگان مقاله رفتار بتن پر شده بیضوی لوله های فولادی عمیق تحت خمش-برش

Abstract

A concrete filled elliptical steel tubular, abbreviated as CFEST, member consists of an elliptical hollow steel tube and in-filled concrete. The CFEST member is a family of concrete filled steel tubular (CFT) member having large deformability and toughness due to the confinement effect between the steel tube and the in-filled concrete. When the CFEST member is applied to bridge piers in the river, reduction of the bottom scouring due to the water flow can be expected. The present study aims to investigate, experimentally, the bending shear characteristics of CFEST deep beams through asymmetric four-point loading test method. The selected testing parameters are diameter-to-thickness ratio and two loading directions, namely the major and the minor axes. The results showed that shear capacity of CFEST members is strongly affected by the diameter-to-thickness ratio. The observed failure modes were cracking of the tube and/or shear failure of the in-filled concrete. A method to predict simple shear capacity of the CFEST deep beam is mainly discussed. Additionally, elasto-plastic principal stress behavior of the steel tube is also mentioned.

4. Conclusions

Bending-shear test on the concrete filled elliptical steel tubular deep beam subjected to bending and shear through asymmetric four-point loading test was conducted in order to be applied to the bridge pier. Additionally, shear strength of CFEST was compared with that of circular CFT having larger or smaller diameter of the CFEST. From the results, following conclusions are drawn. 1) Observed failure modes are cracking of the elliptical steel tube near the point of maximum bending tensile stress. With respect to the major test and circular CFT with D = 160 m specimens, shear failure of in-filled concrete between loading point and supports may be assumed. 2) Experimental shear strengths of the CFEST deep beam (Vexp) can be correctly predicted by the shear strength (Vest-R), which is the sum of concrete and steel tube shear strengths. 3) Experimental bending strength of the CFEST (Mexp) without confinement strength of in-filled concrete is, either in good agreement with, or larger than, the estimations. 4) The shear deformability of the two axes tests on the CFEST beams are strongly affected by diameter-to-thickness ratio of the elliptical steel tube. Additionally, the specimens with t = 1.6 mm approximately kept maximum values for the 5% displacement (δ/H).