Study On The Bearing Capacity Calculation And Safety Evaluation Technology Of Cast-in-Site Application Of Bridge Over Bridge(Interchange)

Since the reform and opening up, China’s comprehensive nationalstrength has gradually increased, urban transport industry has been rapidlydeveloped. Bridges act as throat position in construction of traffic, as thecomplex process, high technology, construction difficulty, and with theincreased bridge span, the work environment of bridge constructionbecomes more and more complex, the engineering changes of constructionconditions have been more and more restricted, so it advances high demandfor bridge construction.In bridge construction, new bridge across the old bridge to the existingbridge as a support for the new bridge site pouring concrete operations,how to determine the carrying capacity of the existing bridge becomesdifficult. Therefore, it has be figured out the existing bridge carryingcapacity by through the theoretical calculations, and then choose areasonable construction plan. Based on the bridge construction contractsection13of Qingdao Jiao Zhou Bay Crossing Sea Bridge, the main worksof this dissertation are:(1) According to the “bridge and culvert design specification ofhighway reinforced concrete and prestressed concrete”（JTJ023-85&JTGD62-2004）,the flexural carrying capacity of the normal cross section ofprestressed RC Voided Slab of original bridge and the shear capacity aswell as the crack moment of oblique plane were calculated, at the meattime, they were compared. The similarities and differences of the designstandard of the old and new bridge on bearing capacity, crack moment andthe material strength value were analyzed. The results showed that thebearing capacity in new bridge design standard was higher than that in theold one, also enhanced the crack resistance. (2) According to the design documentation of the original bridge andnew constructed flyover, Load calculations were taken to provide basis ofbearing capacity checking of the original bridge.(3) The theory and calculation method of axial compression memberwere studied, which put forward the calculation formula of bearingcapacity of axial compression member. The results showed that the bearingcapacity of axial compression member of the pier and bearing capacity ofaxial compression member of the pile can meet the requirement of theconstruction of the new bridge.(4) The theory and calculation method of the bearing capacity of rocksocketed pile were studied. Which put forward the calculation formula ofbearing capacity of rock socketed pile, and the bearing capacity of the rocksocketed pile of the original bridge was calculated and checked. The resultsshowed that, the bearing capacity of axial compression member of the pierand bearing capacity of pile foundation of the original bridge can meet therequirement of the construction of the new bridge;(5) According to the bearing capacity calculation and checking of theoriginal bridge above, the construction plan of the new overpass bridge wasanalyzed, finally proposed the construction plan of “cast-in-site concrete ofnew overpass bridge while setting the original beam as the supporting”，and the feasibility and safety of the construction plan were checked, theresults showed that the plan can be implemented safely.