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Bending of unequal span continuous pultruded glass fibre reinforced polymer (GFRP) beams

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Flexural deformation tests on a continuous, pultruded glass fibre reinforced polymer (GFRP) beam are described. The two-span beam was loaded incrementally up to the deflection serviceability limit in both major and minor-axis flexure by a vertical point load applied at the centre of the longer span. The tests were repeated three times with respect to each flexural axis. Mid-span deflections, support rotations and axial strains on the flanges’ outer surfaces at three cross-sections were recorded during both loading and unloading. It is shown that deflections, support rotations and surface strains are both linear and repeatable. A new exact analysis, based on classical shear-rigid beam theory, has been completed for simply supported, two-span continuous beams for any span ratio and with the longer span subjected to a mid-span point load. Formulae are presented for mid-span bending moments, support reactions, mid-span deflections, support rotations and surface strains. The deflection, rotation and strain formulae are used to predict the experimental deflections, rotations and strains corresponding to the serviceability load using the average longitudinal elastic modulus of the pultruded GFRP material (derived from tension coupon tests) and the beam’s cross-section properties. It is shown that the predicted deformations and strains are in good agreement with the corresponding experimental values. The analysis has been developed further to include shear deformation, but, because the beam’s two span-to-depth ratios are large (approximately 30:1 and 20:1), its effect on the predicted deformations is very small.