Experimental Study On Deformation And Crack Propagation Of Prestressed Concrete Slabs Reinforced With PCB

Steel Bar for Prestressed Concrete (PCB) is a type of newly developed medi-um-strength(970MPa & 800MPa)prestressing steel for concrete structures. The defor-mation and cracking under serviceability state are difficult to control due to the low re-inforcement ratio when high strength steel strands are used as reinforcing steel to meet the ultimate limit state. On the contrary, the deformation as well as cracking control would be facilitated for prestressed concrete slabs reinforced with PCB, besides, the strength of the PCB would be full used. Experiment study is carried out in this thesis to investigate the influence of the bonding behavior between PCB and the concrete, dif-ferent tension control stress levels as well as the reinforcement ratio on deformation and crack propagation of prestressed concrete slabs reinforced with PCB. The main contents are described as follows.Tests on deformation and crack propagation of 28 prestressed concrete slabs rein-forced with PCB and with the effective span of 3.9m are performed. The specimens are divided into four groups based on the strength grade (970MPa, 800MPa) and the diam-eter (9mm, 7mm) of the PCB, with the tension control stress of the 7 slabs in each group set to four gears, i.e. 0.4fptk, 0.5fptk, 0.6fptk, 0.7fptk, and the relative height of the com-pression zone set to 0.05, 0.10, 0.15, 0.20, 0.25. The cracking moment , load-displacement curves,cracking distribution and propagation on both the bottom and profile of the prestressed concrete slabs reinforced with PCB are obtained.It is indicated by the experiment that fairly immense difference exists as for the bonding behavior of between the PCB and the concrete compared with ordinary rebar and steel strand, hence coefficient of relative bonding behavior between the PCB and the concrete as well the influential coefficient to consider the impact of the extension of the concrete between the average cracking spacing are fitted out based on the tested re-sults and the integrated cracking theory, besides, formula suit for the calculation of av-erage crack spacing and width of prestressed concrete slabs reinforced with PCB are proposed. Formula of the short-term stiffness of prestressed concrete slabs reinforced with PCB is fitted out based on the bilinear form. The ductility coefficient of all the tested slabs is greater than 2.02, which proves that fairly good ductility is achieved for prestressed concrete slabs reinforced with PCB. This thesis provides a reference for de-formation and cracking calculation as well as design of prestressed concrete slabs rein-forced with PCB.