Stability and failure characterization of fiber reinforced pultruded beams with different stiffening elements, part 2: Analytical and numerical studies

摘要

Unstiffened I-beams are prone to local and per-mature failure. Stiffened beams having improper stiffening technique or size of stiffening element may have lesser failure load than that of unstiffened beams. In this paper, flexural characteristics of stiffened and unstiffened FRP I-beams is determined analytically and numerically; and verified with experimental investigation. There are no code provisions for designing of FRP beams with stiffening elements. Hence, equation to calculate the deflection of beams with different stiffening elements is derived using Castigliano's theorem. In order to get the better understanding of failure of FRP beams, various formulae for beams without stiffening elements available in design manuals are incorporated in the analytical model for prediction of failure load and mode. Further, a failure criterion is recommended for prediction of failure load of beams with and without stiffening elements. The results obtained from analytical and finite element models give the good comparison of results with experimental investigation. Further, a parametric study is performed on beams having different flange width-to-thickness ratios (5 - 15), depth-to-thickness ratios (21 - 40), and length-to-depth ratios (3 - 11) with different sizes of stiffening elements. It is observed that failure load of beams increases up to certain length of bearing plate, later it becomes constant. Under flexural loading, bearing stiffeners of a beam is found to fail, if the length of bearing plate is less than the flange width of T-shaped bearing stiffener. Similarly, if the length of cover angle or carbon fiber layer provided is less than the length of bearing plate, then the failure load is equivalent to the beam with having bearing plate only. Carbon fiber angles are less effective than beam with cover angle for effective depth-to-thickness ratio more than 21.