Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
The use of composite materials such as Fiber Reinforced Polymer (FRP) to strengthen concrete structures has surged during the past two decades as an alternative for conventional methods of structural strengthening and repair. FRP materials are light and relatively easy to install. They are noncorrosive, durable and less vulnerable to environmental conditions in comparison to other construction and retrofitting materials. The knowledge and applications of composites for strengthening steel structures are relatively smaller when compared to concrete strengthening applications. Strengthening-By-Stiffening (SBS) is a new strengthening alternative that was developed at Louisiana State University. SBS has proven to be a practical technique for inhibiting local buckling in shear-controlled steel beams. This technique relies on the out-of-plane stiffness of pultruded composite sections as opposed to the in-plane strength of thin composites that is often reported in the literature. Preliminary results showed that gains in shear strength of more than 40% are achievable using SBS. The objective of this study is to establish a coefficient for the efficiency of FRP stiffeners as compared to steel stiffeners. This coefficient can be multiplied by the capacity of steel stiffened structures to obtain the capacity of an FRP stiffened member using a SBS design approach, which is lacking in the current codes that do not address FRP stiffening. Four steel beams were first experimentally tested to verify the developed analytical model under a single point loading over the first internal stiffener and the results were compared to those obtained from a nonlinear finite element (FE) analysis. The beams were designed to evaluate the effects of bonding area between pultruded Glass Fiber Reinforced Polymer (GRFP) stiffener and the web of steel plate girders in addition to the effect of web slenderness and the aspect ratio of the shear panel. The results show that there is a good agreement between the FE model and the experimental results. The average estimated strength of the tested beams was about 98% of the experimentally obtained capacities. The parametric studies show that the predicted shear capacity of the SBS beams was almost identical with the shear capacity of steel stiffened beams.
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BabaizadehRoshanfekr, Hamed, "FRP stiffener efficiency coefficient for SBS shear strengthening applications" (2012). LSU Master's Theses. 2060.