Numerical Simulation Of Concrete Beams Strengthened By Externally Prestressed Tendons With Tilted Web Members

Strengthening technology with externally prestressed tendons is widely used for increasing bearing capacity, unloading, reinforcement and transformation of reinforced concrete simply supported beams, continuous beams and slabs. The friction loss of the prestressing tendons at deviators is big, especially in fold line shape prestressed tendons of multi-span structure which prestressing make the axial compression ratio of the columns increased. Based on the nation natural science fund subsidiary item(04-020210), the paper study simply supported beams and frame beams Strengthened with externally prestressed tendons using finite element software ABAQUS. The main contents and results of simulations are as following:(1) The bearing capacity, deformation, cracking pattern and failure mode of reinforced concrete simply supported beams strengthed by externally prestressed tendons with four segments and three tileted web members were studied.Parameter Analysis was designed for strengthed beams which have different initial stress levels, different cable sags and cable diameters. Conclusion was that: Strengthening technology by externally prestressed tendons with tileted web members could improve the flexural stiffness, enhance the ultimate bearing capacity, and improve significantly the anti-cracking ability. The reinforcement effect was obvious through Increased the initial prestress and cable sag, but not obvious through increasing the cable diameter.(2)Four single reinforced concrete frames which stiffness ratio of beam to column was 0.12, 0.41, 0.72 and 1.0 respectively were designed. The reversed arch, horizontal displacement on the top of columns, axial force, shearing force, bending moment of beams and columns of frames strengthed by externally prestressed tendons with four segments and three d tileted web members were studied. It was showed that the reversed arch of beams and horizontal displacement on the top of columns were small and could be ignored, as well as axial force, shearing force, bending moment of beams; adverse effects of shearing force, bending moment of columns could not be ignored if necessary.(3) Externally prestressed tendons with four segments and three tileted web members which the intial prestress was 40 KN and cable sag was 200 mm, were designed. The bearing capacity, deformation, cracking pattern and failure mode of the above four frames, and the stress increments of prestressed tendons were studied. It was showed that strengthening technology by externally prestressed tendons with diagonal webs could improve the flexural stiffness of beams, enhance the ultimate bearing capacity, change the distribution of internal force of frames. It also decreased the bending moments of beam end.