Study On Heat Transfer Of The Vertical Joints With Dry Connection For Precast Wall Structure

There are inevitably typical joints between prefabricated components in prefabricated concrete buildings.The connection and construction of joints are not only related to structural safety,but also to the thermal performance of buildings.If the joints between prefabricated wall-boards are not treated properly,there may be a thermal bridge.Therefore,it is necessary to study the heat transfer at the joints,take measures to reduce energy consumption,protect the main structure,extend the service life and improve the durability.Based on the new building system of the new type of load-bearing composite wall,considering the insulation,waterproofing and tightness of joints,the joint structure of dry connection is designed:the slot structure is used on both sides of the joint,and the water sealing rubber strip,EPS foam strip and building sealant are filled in from the inside and outside side by the notch.Fill the gap with grouting,and finally level the vertical joint with mortar.In order to explore the heat transfer performance of the vertical joints of the fabricated load-bearing composite wall structure,two-dimensional and three-dimensional software was used to simulate and verify the heat transfer performance.Through the observation of infrared thermal imager,the weak position of its thermal insulation performance was found out,and the temperature and heat flow distribution characteristics of its joints were analyzed by ANSYS finite element thermal analysis method.Using the two-dimensional steady-state heat transfer method of PTemp thermal bridge,the linear heat transfer coefficient of three typical joints between wall-boards was calculated and the condensation risk was checked,and the factors such as connectors,materials,joint width and so on were explored for the joints of dryly connected building wall-boards Energy plus is used to simulate the energy consumption and verify the feasibility and energy saving effect of the joint construction method.Compared with other dry connection methods,bolt connection is the most stable in heat transfer and the most simple in construction.It is recommended to be used preferentially.The joint of joint steel plate and steel plate has the smallest thermal resistance and the largest heat flow density,and the steel plate has a great influence on the heat transfer at the joint.Verify the heat flux and temperature distribution of the joint between 5 and 50 mm width by finite element method.The width of vertical joint should be taken in a reasonable range of 10～20 mm,which verifies the requirements of the fabricated code for the treatment of vertical joint width of dry connected non thermal insulation wallboard.Such dry connection wallboard should adopt EPS external insulation structure with thickness of more than 50mm in cold area,and cover wallboard and joint at the same time.When the joint structure proposed in this study is used,the line heat transfer coefficient valueψ=0.01W/(m·K),which is the same as the finite element calculation value,meets the requirement that the limit value of line heat transfer coefficient is less than or equal to 0.01W/(m·K).The feasibility of this joint structure is verified again.The simulation results show that the annual cumulative heat load index of unit area at the vertical joint of multi ribbed composite wall panel without treatment is43.63(Kw·h)/m~2,and the annual cumulative heat load index of unit area at the vertical joint is 39.12(Kw·h)/m~2,which is 4.51(Kw·h)/m~2 lower than the original overall energy saving scheme,and the energy saving efficiency is increased by about 10.3%.