Analysis of bending tests on CFRP-stiffened pultruded GRP beams

The equations for the mid-span deflection and end rotations of carbon fibre reinforced plastic (CFRP) stiffened pultruded glass reinforced plastic (GRP) shear deformable beams with semi-rigid end connections are introduced. Two series of three-point flexure tests on simply supported pultruded GRP beams are described. In the first series the beams were tested in the unstiffened state and in the second series the beams were tested with pairs of CFRP strips of varying length bonded to their soffits. A third series of three-point flexure tests on a similar pultruded beam with the CFRP strips bonded over the whole span and with bolted stainless steel and GRP cleat end connections is also described. The shear deformable semi-rigid beam equations are used to predict the loads, deflections, end rotations and surface strains recorded in the three test series. It is shown that the correlation between the measured deflections, rotations and strains is generally good, given the nature of uncertainty surrounding some of the material properties. For example, the largest percentage difference between measured and predicted deflections was about 6% for the first two test series and 12% for the third series. It is concluded that this level of correlation between actual and predicted deformations vindicates the use of refined beam analysis for the more efficient design of CFRP stiffened pultruded GRP beams with practical end connections.