In the present study,the insulation mechanism of building walls during the summer days and nights is investigated with a realistic approach to enhance their performance.A fiber layer,as a porous medium with air gaps,i...In the present study,the insulation mechanism of building walls during the summer days and nights is investigated with a realistic approach to enhance their performance.A fiber layer,as a porous medium with air gaps,is used along the wall layers to decrease the energy loss.Meanwhile,the radiation heat flux variation during five days in a row has been considered for each side of the building,and it is tried to reach the optimum values for geometrical factors and find suitable insulation for each side of the building.A lattice Boltzmann method(LBM) based code is developed to simulate the actual chain of the heat transfer which consists of radiation,conduction,forced and natural convection combination within wall layers including fiber porous insulation.The results indicate that for the current insulation model,the effect of natural convection on the heat transfer is not negligible and the existence of the porous layer has caused a positive impact on the heat loss reduction by decreasing the circulation speed.Also,by using the optimum location and thickness for the insulation layer,it is showed that each side of the building has different rates of energy loss during a day,and for the appropriate insulation,they need to be evaluated separately.展开更多
The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interfa...The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.展开更多
文摘In the present study,the insulation mechanism of building walls during the summer days and nights is investigated with a realistic approach to enhance their performance.A fiber layer,as a porous medium with air gaps,is used along the wall layers to decrease the energy loss.Meanwhile,the radiation heat flux variation during five days in a row has been considered for each side of the building,and it is tried to reach the optimum values for geometrical factors and find suitable insulation for each side of the building.A lattice Boltzmann method(LBM) based code is developed to simulate the actual chain of the heat transfer which consists of radiation,conduction,forced and natural convection combination within wall layers including fiber porous insulation.The results indicate that for the current insulation model,the effect of natural convection on the heat transfer is not negligible and the existence of the porous layer has caused a positive impact on the heat loss reduction by decreasing the circulation speed.Also,by using the optimum location and thickness for the insulation layer,it is showed that each side of the building has different rates of energy loss during a day,and for the appropriate insulation,they need to be evaluated separately.
基金Project(50578027) supported by the National Natural Science Foundation of China
文摘The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.
