The Research Of Caculation Model Of Concrete Beam And Post-performance Prediction Of Concrete Under Freeze-thaw Enviroment

This research is a vital sub-item of"Behavior and calculation model ofconcrete structures under freeze-thaw environment"which is imbursed by NationalNatural Science Foundation of china(item approval number:50278025).With the development of science and technology of concrete,the durability ofconcrete has received increasing attention. Today, the durability of concrete structures has been compared to the safety and security operational life and directly determines the economic and social benefits of concrete structures. The frost resistance of concrete is one of the major problems of concrete durability. So strengthening the research of calculating method and late performance of the concrete structures (components) under freeze-thaw environment has great significance to ensure the safety of concrete projects.In this paper, an intensive research was conducted of flexural capacity calculations and the establishment of BP neur alnetwork model to predict the late performance of the concrete beam under freeze-thaw environment. Followings are the research works:(1)The stress-strain curve of axial compression, the compressive strength, the ultimate compressive strain and the peak compressive strain of concrete under freeze-thaw were determined by researching the existing experimental data. Based on which the relevant parameters were provided for the calculation model of the flexural capacity of concrete beam.(2) The beam flexural capacity calculation formula was founded according to the code for design of concrete structures (GB 50010-2002), the section reduced method and the numerical analysis method. The flexural capacity of concrete beams with different freeze-thaw numbers were calculated by these three methods. Compared with each other, there is little difference between the results calculated. The practical engineering designing method of the flexural capacity of concrete beam under freeze-thaw environment was proposed by the conception of the equivalent live load of board.(3) The post-performance of concrete under freeze-thaw environment was predicted by intelligent features of BP neural network. The models of the 28 days compressive strength of concrete, the compressive strength of concrete and the ultimate moments of concrete beams under freeze-thaw environment were founded by BP neural network. The residual life of concrete was predicted.