An Experimental Study On Strengthening Reinforced Concrete Hollow-slab Girder Using New Material Polyuethane-Cement(MPC)

For a long time, due to the restriction of many factors, such as the low level of national economic development and large heavy traffic, the vast majority of domestic in-service reinforced and prestressed concrete hollow slab bridges generally exist various serious diseases such as low-grade design load, concrete cracking, steel corrosion, the loss of force transmission function of wet joint, leakage and so on, which greatly reduce the carrying capacity and service life of the bridge and result in serious potential traffic danger. At present, domestic conventional methods for bridge strengthening include increasing cross section, bonding steel plates, bonding FRP and externally prestressed application. However, the survey results show that these methods all exist various key technical problems, which bring about not ideal performance. Given these situation, the author has developed a kind of cast-in-place modified polymer concrete(MPC for short), which possesses not only some outstanding features such as lightweight, high strength, good bonding properties with reinforced concrete and so on, but also frost-resistance, anti-permeability, simple construction technology and construction quality that could be conctrolled easily. The material is especially adapted to the rapid maintenance and strengthening for the highway bridge under the condition of ensuring the smooth traffic.For the purpose of studying the applied technology for the reinforced concrete hollow slab bridge strengthened by MPC material, firstly, the material test is conducted to study the mechanical properties of MPC composites, such as flexural strength and elastic modulus.Secondly, the reinforced concrete hollow slab bridges have been in use for many years are applied a series of load test before and after the reinforcement. It is verified through load test that MPC composites strengthening reinforced concrete hollow slab bridge can not only increase the carrying capacity of the original beams, but control the velocity of crack propagation.Thirdly, the formula about flexural carrying capacity of normal section strengthened by MPC composites, as well as average crack spacing and average crack width, is derived on the basis of reinforced concrete design principle.Fourthly, FEM numerical simulation can analyze well the whole process of load test about MPC composites strengthening reinforced concrete hollow slab.Finally, it is verified through in situ load test that after the White River Bridge is strengthened by MPC material, the technical indicators all meet the technical requirements the national bridge design specification specified, which achieved desired reinforcement effect.