Cfrp Strands for Flexural Strengthening of Steel Bridges

This paper explores the use of Carbon fiber reinforced polymer (CFRP) material for strengthening of steel bridges. The research work includes an experimental program to study the effectiveness of using very small diameter CFRP strands, configured in a sheet format, for strengthening of steel structures. The experimental program includes scaled steel-concrete composite beams strengthened with this material at the bottom flange of the steel beams to increase the flexural capacity. The parameters that were considered in the experimental program were the type of CFRP, reinforcing ratio and type of loading. The two types of CFRP materials that were examined for strengthening are High Tensile CFRP and High Elastic Modulus CFRP material. The three types of loading investigated were Static, Cyclic and Fatigue loadings. Test results were used to determine the most effective strengthening system. The selected system was tested under fatigue and cyclic loading. This paper describes the experimental program, presents test results, including the failure modes, and provides guidelines for the design of flexural strengthening system for steel structures. INTRODUCTION Several researches have been reported recently on strengthening of steel structures using variety of methods (references 1, 2, 3 and 4). The goal of these researches was to explore the most efficient and effective strengthening system that can be used for steel structural members. Corrosion of steel structural members due to environmental conditions and increase in live loads are the main reasons for requirement of strengthening systems. Conventional strengthening systems such as using steel bars and plates as a reinforcement for steel members are common in current practice but these methods have several disadvantages including the heavy weight of steel plates which makes them hard to handle in addition to their low corrosion resistance. Recently, few researches explored the use of FRP materials for strengthening steel structures. FRP strengthening systems are light, easy to handle and have a relatively less tendency to corrode. Some of the researches have focused on key parameters that could affect the behavior of FRP strengthening systems for steel structural members. At North Carolina State University, two research programs were conducted to study the effect of externally bonded CFRP lam paper exp The new MATER The CFR Company Modulus propertie H Inter In order strengthe machine. & Sumik strap join strands is inates on th lores a new material prov IAL PROPE P material u , Japan. The (IM) CFRP. s of CFRP ma CFRP Type igh Tension mediate Mod to evaluate ned with one The epoxy us in Steel Com ts are shown approximatel Figure e stiffness an type of carbo ides solution RTIES sed for flex two types of Several tensil terials. Table Stra 1.03 ulus 0.95 the developm layer of the h ed for strengt pany. The m in Figure 1. y of 280 mm 1: Ultimate L d the ultimate n fiber reinfo to the problem ural strength CFRP used fo e coupons we 1 presents th Table nd Area U 23 mm 48 mm ent length igh tensile C hening was “ easured ultim Test results ”.