Research On Thermal Stress Of Super-long Prestressed Concrete Floor Structure

In the case of the transport hub of West square of Shenzhen North railway station,thermal stress of super-long concrete floor has been monitored for a year. Base on theresearch of thermal stress of super-long prestressed concrete floor structure and researchfindings of thermal stress at home and abroad in recent years. The distribution law and effectfactors have been researched on the system of research method. The content is mainlyincluded:The temperature stress of the super-long concrete slab has been monitored during theconstruction phase. The vibrating steel stress meter is arranged on the floor reinforcement,testing the age from7to70days of concrete structure internal force changes. These data arebehind the basis for data analysis and FEM simulation by collecting the internal stress data ofthe super-long concrete slab reinforcement.After pouring the concrete, the internal stress of concrete have made a change due toshrinkage and temperature changes of the concrete. Such change could have a big impact onpartial stress. Through the analysis of test data, we can get the variation and influencingfactors of shrinkage and temperature stress. Results show that the stress distribution producedin a cycle with temperature periodic change. Stress is higher at the high temperatures andlower at the low temperature. There is compressive stress commonly expressed through thestress distribution in plate. As the concrete age grew, due to the effects of temperature andshrinkage in making internal tensile stress increases, compressive stress will reduce, withinthe constraints of small stress changes smaller, constrained where large stress changes larger.Generally speaking, in the middle of the slab, the compressive stress is small and the tensilestress is large. While, in the edge of the slab, the compressive stress is large and the tensilestress is small.Thermal stress of the super-long concrete slab has been simulated using finite elementmethod. The thermal stresses of the slabs and the beams have also been simulated. Throughthe comparison between measured data and simulation data, the law is summarized byanalysing of the stress of the measure point. Results show that the distribution law ofmeasured data and simulation data is homogeneous. Due to the large horizontal constraintlocated in the middle of the slab, there is higher stress when temperature and shrinkagedeforms. Prestressing can significantly improve internal stress distribution. In addition, it canreduce tensile stress. At last, it has discussed the best reinforcement in the slab.