Study On The Axial Bearing Capacity Of Prefabricated Composite Walls With Heat Preservation Layer After One-Side Fire

With the rapid development of economy, the shortage of energy resource has become a serious problem in china. To meet the requirements of sustainable development, a number of worldwide researchers have been attracted by energy efficiency, and find building energy saving is an important way to improve social energy using efficiency. As an response to energy-saving work, prefabricated composite walls with heat preservation layer are applied widely because they realized a variety of functions, including of precast, bearing capacity and energy-saving. Followed building hazards, however, are increased. In order to accurately evaluate, repair and strengthen the fire-damaged shear wall, it is extremely urgent to analyze its mechanical properties after fire.Based on this, the axial bearing capacities of these new walls were tested after exposing to high temperature and corresponding theoretical analysis is carried out in this paper. Specific work is as follows:1. The residual compressive strength, residual tensile strength, elastic modules, compressive and tensile stress-strain curve of concrete after high temperature are generalized and collected systematically. So it is with the ultimate strength, yield strength, elastic modules, elongation and stress-strain curve of steel bars after high temperature.2. Based on the tests of axial compression bearing capacity for two walls at ambient temperature and another two walls with the same thermal insulation thickness after one-side fire, damage characteristics of these four walls were described. The axial compressive capacity, load-displacement curve, load-concrete strain curve and load-steel bar's strain curve of two specimens after fire have been compared with the rest two walls without fire. Research shows that:the yield load of specimens after one-side fire whose thermal insulation thicknesses are 40mm and 60mm decrease by 21.8% and 16.8%, respectively, compared with the normal temperature. And when the thermal insulation thicknesses are the same, the displacement, concrete strain and steel bar's strain of the walls after fire are all bigger than the corresponding walls without fire, when they bear the same load. No matter whether the walls are by fire, if the load is the same, these with a thermal insulation thickness of 60mm have a bigger displacement, concrete strain and steel bar's strain than those with a thermal insulation thickness of 40mm because of the relative thickness of concrete decreasing with the increase of the insulation layer thickness.3. Using finite element software, this paper analyzes the mechanics properties of each wall under axial loading, compares with the test results analysis, and provides the theoretical thinking.4. According to the calculating formula of eccentric compression supporting in concrete standard, taking the three step model to consider concrete compressive strength at elevated temperatures, the different time under fire, different axial compression ratios and different concrete cover thicknesses taken into account, the formula calculated the ultimate axial bearing capacity of prefabricated composite walls with heat preservation layer after one-side fire is established.