Numerical Analysis Of Anchor Concrete Crack Controlling In Suspension Bridge At Construction Stage

In the mass concrete construction process, the cement hydration heat causes the concrete interior temperature to elevate suddenly, but surface temperature becomes to be low because of radiation in to the air, which causes temperature difference between inside and outside to grow, and tensile stress on the surface, then crack appears.This article researches on the basic principle and the lamination computational method of the mass concrete hydration thermal response temperature field and the stress field. It analyzes the pipe cooling and compound layer methods in the mass concrete construction process with examples. And taking the mass concrete of the south anchor of Dongjiang Bridge as the object of study, it works out the rules of variation of temperature and tensile stress inside the mass concrete by simulating the construction process. Some suggestions about the anchor mass concrete construction are put forward.(1) High strength concrete thermal spike appears in 3-5d, and low intensity concrete thermal spike appears in 5-7d;(2) The temperature of old concrete is obviously affected by the newly-laid concrete, and the factors mainly depend on the new construction level thickness as well as on the interval time between casting every two layers;(3) Temperature turns down much more under the condition of cooling pipe than without this condition, and temperature decrease from 1 to 7, which can control temperature difference well. The stadium of compound layers, which simplifies the calculation and hardly influences the final result, is distributed rationally on the base of 7d;(4) Temperature difference between inside and outside reaches the peak from 3d to 7d after casting, where intensity and creep of the concrete both are in grow, and temperature stress intensity becomes so powerful that crack will appear likely. Therefore, the most important thing of preventing crack is controlling temperature difference at that time and enhancing the intension of related materials;(5) According to calculating of the value in the simulated construction of the south anchor of Dongjiang Bridge, some suggestions about the anchor mass concrete construction are put forward on selecting materials, precooling materials, casting interval time, selecting maintenance measures and so on.