Experimental Research On Bi-prestressed Concrete Beam

The bi-prestressed concrete is a new system beam which has many advantages such as reduction of the beam's height, improvement of beam's span ability and load capacity. So the bi-prestressed concrete can be used in urban bridge or big span bridge. Bi-prestressed concrete beam is developed on the basis of common prestressed concrete beam, which means putting compressed stress tendon in the top side of the common prestressed beam, in order to offer the beam an effective prestress, then the very beam will become a new system which is called bi-prestressed concrete beam. By using this system, the tension capability of concrete was strengthened and the behaviors of the concrete will be improved a lot.In this paper, the different construction technology of bi-prestressed beam which include pre-compressive and post-compressive is studied mainly through 5 bi-prestressed concrete beams'fabrication, presents the differences of the key technology in construction and also compares differences between the two construction techologies. Finally depending on fabrication practice and combining with relational theories, a respective construction technology procedure is summed up. At the same time through the dead load test of the tested beams we got the characteristics of the bi-prestressed concrete beam, such as strains, deflections, cracking load, and ultimate load carrying capacity. It is observed that the bi-prestressed beam is not only able to work effectively in the elastic behavior state before it cracks, but also can work effectively in the elastic behavior state when it is in initial stage of crack. According to the compare of the bi-prestressed concrete beam L-5 and common prestressed concrete beam L-6, testify that when similar bi-prestressed concrete beam and common prestressed concrete beam cracked on the same cracking load, the bi-prestressed concrete beam's height is lower than the common prestressed concrete beam's. Accordingly, when the bi-prestressed concrete beam and the common prestressed concrete beam have the same height, the former's cracking load is bigger than the latter's.