Research On Crack Resistance Design Of Underground Prestressed Concrete Slab Column Structure Considering Temperature Shrinkage And Thick Overburden

The prestressing technique has a good effect on controlling the temperature stress of the super-long concrete structure,but a large amount of overlying soil as a permanent load has not yet existed after the prestressed tensioning construction period and the support dismantling.So it is of great significance to study the optimum selection of slab span-depth ratio and balanced load to meet the crack resistance requirements before and after the heavy cladding load.In this paper,based on the on-site monitoring data of the station square in front of Hefei Railway Station and SAP2000 finite element analysis software,the reasonable structural layout of the prestressed slab-column structure is studied.Firstly,the long-term monitoring of the strain and temperature of super-long underground prestressed concrete structures is performed by vibrating string extensometers.Based on the monitoring results,the long-term distribution rule of temperature and actual strain in the structure and the stress and strain produced by the concrete after prestressing are analyzed.Second,using the finite element analysis software SAP2000 finite element simulation of the structure,considering the effects of temperature shrinkage and creep,the stress and strain after prestressed,load standard combination and other conditions were studied,the share factors of the two factors of stress and non stress are analyzed,and the accuracy of the finite element software is verified by comparing with the on-site monitoring results.Finally,according to the experimental and finite element simulation results,the prestress design of the slab-column structure under the heavy overburden soil loading is optimized through the example.Through the finite element example,the law of the span-depth ratio,the proportion of the balance live load and the crack resistance of the structure is analyzed,and the optimum selection of the slab span-depth ratio and the balance load is obtained to meet the crack resistance requirements before and after the loading of the soil.After the study,the following conclusions can be drawn: The variation trend of temperature of each measuring point with time is basically the same with seasonal temperature.After the prestressing,the maximum tensile stress is generated in the top span of the plate,and the test value is 1.38~1.72MPa;which is coincided with the simulated values.The maximum tensile stress value of the structure during the whole period does not exceed the crack resistance and the ratio of span-depth of the project and the balance of live load is reasonable.And the share of temperature drop accountsfor about 49%~55% of the total share.Reducing the span-depth ratio and increasing the degree of prestress can improve the crack resistance of the structure.It is more reasonable that the ratio of span-depth is between 19 and 24,and the ratio of the balanced live load is between 50% and 70%.