Experimental Investigation And Study On The Bridges Strengthened Using Steel Plate And Concrete Composite Strengthening Technique

Steel Plate and Concrete Composite Strengthening (SPCCS) is a new technique based on Steel Plate and Concrete Composite (SPCC) beams. By reasonable interface treatmeant solution and connection messurement, it will bring the enlarged section and adhesive steel plate into fullplay, which is an effective combination of bonded steel plate method and RC&PC strengthening method. At present, the relevant research about SPCCS is rare in international level. In order to furtherly study the engineering adaptablity of the SPCCS, basing on the research work which was done earlier before,in this paper we do experimental sdudy on this new kind of strengthening method,and also bring the SPCCS in practical engineering that is Yao Zhou overpass, estimate the strengthing effect as well, which will lay the foundation for application in bridge engineering.Four rectangular concrete bending strengthing beams using SPCCS technique were tested with the purpose of studying the influence of damage level, shearing connector and ratio of shear span on the strengthing effect and failure modes. The applied load, deflection, strein and crack initiation and propagation regular were measured. Two beams were tested, and the testing result shows that SPCCS technique can highly improved ultimate bending capacity. Theoretical results calculated using the simplified folula or finite element method agree with test results. Four rectangular concrete shearing strengthing beams using SPCCS technique were designed. The effect of variation parameter, including damage level and strengthening height, on SPCCS technique was studied.After finishing strengthening work and having serviced normally for one year and a half, two loading test on Yao Zhou overpass were organized respectively, meanwhile, a six-day traffic information observation and dynamic strein monitoring were carried out as well. The lording test and dynamic strein monitoring result all shows that the Yao Zhou overpass was at good condition since reinforcement, which would meet the requirement.In order to study the influence of the SPCCS technique to the spans of Yao Zhou overpass which were burned in a fire accident under different states, the behavior of these spans were analyzed under the ultimate limit state (ULS) and the serviceability limit state (SLS). The deflection, stress, and the ultimate bearing capacity (UBC) were evaluated. The behavior of these spans before and after reinforcement under the SLS were analyzed by the finite element software Ansys and Midas. The UBC of the key sections of the bridge before and after reinforcement were calculated by Ansys and using the simplified formula.Evaluation results showed that:(1) The behavior of the spans which were burned in a fire accident of the uplink and downlink of Yao Zhou overpass can be improved obviously under the SLS using SPCCS technique and adhesively bonding steel plate, as well as the stiffness of the total bridge, which was stiffen than the original bridge. (2) The UBC of the key sections of the bridge increased by 75% and 129% using SPCCS technique, which was two times of the most disadvantageous combination of load effect and the safety margin was improved correspondingly.