Shear Strength of Prestressed Steel Fiber Concrete I-Beams

Padmanabha Rao Tadepalli,Hemant B Dhonde,Y L Mo,Thomas T C Hsu

doi:10.1007/s40069-015-0109-4

Abstract

Six full-scale prestressed concrete (PC) I-beams with steel fibers were tested to failure in this work. Beams were cast without any traditional transverse steel reinforcement. The main objective of the study was to determine the effects of two variables—the shear-span-to-depth ratio and steel fiber dosage, on the web-shear and flexural-shear modes of beam failure. The beams were subjected to concentrated vertical loads up to their maximum shear or moment capacity using four hydraulic actuators in load and displacement control mode. During the load tests, vertical deflections and displacements at several critical points on the web in the end zone of the beams were measured. From the load tests, it was observed that the shear capacities of the beams increased significantly due to the addition of steel fibers in concrete. Complete replacement of traditional shear reinforcement with steel fibers also increased the ductility and energy dissipation capacity of the PC I-beams.

Highlights

When a concrete element is subjected to shear stress it causes principal diagonal tensile and compressive stresses in the element
Application of load and support arrangements were symmetric for all the beams; only in the case of Beam R2 web-shear failures occurred simultaneous at both the ends
Even though Beam R3 failed in flexure, the shear load at failure at both the ends was close to the web-shear capacity, as indicated by the spalling of concrete struts in the web region of this beam

Summary

Introduction

When a concrete element is subjected to shear stress it causes principal diagonal tensile and compressive stresses in the element. Concrete starts cracking when the applied principal tensile stress exceeds the tensile strength of concrete. This cracking causes softening in the other principal direction and reduces the compressive strength of concrete. When the applied principal compressive stress exceeds the softened compressive strength, crushing of concrete occurs. This phenomenon is known as shear failure. This failure could be very brittle since tensile strength of concrete is much less than its compressive strength. To enhance the behavior of concrete subjected to shear forces, one of the methods is to improve its tensile strength by adding steel fibers

Objectives

Results

Conclusion