Research On The Shear Properties And Prestress Losses Of Transversely Prestressed Concrete Beams

Transfer beams in engineering applications often face the problem of excessive cross-section, the reason of that is because the shear force of the transfer beam is often very large and the section dimension is controlled by the shear capacity. If we can find a way to effectively improve the beam's shear capacity, and ease of construction, will likely decrease the section dimension of the transfer beam. As for this question, in order to inspect the application prospect of using the transversely prestressed concrete beams in the transfer beams, systematic investigation was conducted in this dissertation on the transversely prestressed concrete beams using high strength bolts of grade 10.9 as transverse prestressing bars.This dissertation describes the experimental research and nonlinear finite element analysis of the shear properties and prestress losses of transversely prestressed concrete beams when using high strength bolts of grade 10.9 as transverse prestressing bars. The following work and achievements are included.1. Four transversely prestressed concrete beams and one ordinary reinforced concrete beam were tested. The influence of prestressing force level, the diameter and spacing of transversely prestressing bars on shear capacity, inclining crack resistance and distortion ability of transversely prestressed concrete beams were studied.2. Nonlinear finite element analysis of the five tested specimens is carried out and the results are compared with the tested results to verify the accuracy of the FE models. In order to investigate the effect of concrete strength, shear span-depth ratio, stirrup ratios, prestressing force level, the diameter and spacing of transversely prestressing bars, and steel plate, the parametric study is carried out. At last, a formula to compute the ultimate shear strength of transversely prestressed concrete beams was suggested.3. Experimental study on the prestress losses when using high strength bolts of grade 10.9 as transverse prestressing bars of two ladder-type specimens was carried out, long-term observation has continued for 30 days. The influence of length and spacing of transversely prestressing bars on prestress losses were studied. At last, a formula to compute the prestress losses when using high strength bolts of grade 10.9 as transverse prestressing bars was suggested.4. According to the test data of the two ladder-type specimens, the torque coefficients of high-strength bolts were calculated. By pasting strain rosette on the high-strength bolts, the actual stress distribution of high-strength bolts were measured, and the shear stress coefficient in the formula of calculating pretension force of high strength bolts was improved. At last, the measures of enhancing construction quality were proposed.5. Make a preliminary investigation on the feasibility of outer transversely prestress on the enforecement of the older structures. In order to ensure the reinforcement effect of the outer transversely prestressed concrete beams and make sure that the prestresses were applied on the concrete beams efficiently, the combination of topslab (baseplate), side board and the ribbed slab was designed. And the optimization dimension of composite steel plate was determined according to the analysis of the Finite Element Method. At last, the improvement of tention craft of high strength bolt was explored.