Experimental Study And Numerical Investigation On Connector’s Mechanical Properties And Thermal Performance For The Prefabricated Concrete Sandwich Panel

Prefabricated concrete sandwich panel has a great application prospect for its advantage of meeting the requirements of energy efficiency in building and housing industrialization. However, domestic research is still in the initial stage so further study is needed to conduct to support its application in practical engineering. Connector, the key component, is a guarantee of ensuring the internal layer, the external layer and the insulation layer working together in the prefabricated concrete sandwich panel, whose security and durability are significant contacts with the connector’s mechanical properties. The exterior wall of the building is a large energy consumption and its thermal performance directly decides the level of the building’s energy-consumption. This paper carried out the experimental study and numerical investigation on connector’s mechanical properties and thermal performance based on the prefabricated concrete sandwich panel system.Firstly, the experimental study has conducted for the mechanical properties of the connector, including the unilateral tension performance and the unilateral shear performance, the both side tension performance and the both side shear performance. In addition, the influence of the position relationship of the connector and the steel fabric on the ultimate bearing capacity is analyzed. The experimental results show that the connector’s average tension bearing capacity is 12.1k N~27.3k N and the mean value of the shear bearing capacity is 15.5k N~18.8k N, which are at least 10 times higher than the design values and provide an enough safety reserve. The failure modes of the connector’s tension experiment and shear experiment are both brittle. the connector’s and the steel fabric’s position relationship has no effect on the ultimate bearing capacity, but the steel fabric can delay the connector’s joint spider pull-out process from the external layer. Based on the test results, the tension capacity calculation formula and the shear failure model are put forward for the composite connector.Secondly, the experimental research of the thermal performanc e for the prefabricated concrete sandwich panel is carried out. 4 pieces of sandwich panel were designed and made according to the diffirance of the insulation layer thickness, the insulation materials and the connector’s location. The heat transfer coefficients of the 4 panels were tested by the “hot box- heat flow meter method” and their theoretical value were also calculated. The results indicate that the thermal bridge is formed at position of the composite connector, which leads to the average value o f the panel’s heat transfer coefficient increase by 32.4%. Furthermore, the insulation layer thickness and the insulation materials have significant effect on the panel’s thermal performance. The theoretical values of the heat transfer coefficient which are based on the assumption of the one-dimension heat transfer theory are obvious less than that of the test results, as the panel’s heat transfer process has become the multi-dimension from the one-dimension due to the connector’s existing.Finally, the finite element analysis to the experimental panels has been conducted by the general finite element software ANSYS and the therma l bridge effect was simulated at the connector’s position. As the FEA model is verified by the eperiemntal results, the impact factors of the panel’s heat transfer coefficient have been investigated such as the material’s thermal conductivity, the insulation layer thickness, the connector’s arrangement distance etc. The FEA results demonstrate that relative errors of the heat transfer coefficient between the FEA results and the test results are within 30% and the changing rules are exactly same which are the inner and outer temperature of the panel’s surface, the inner heat flux of the panel’s surface and the heat transfer coefficient between the FEA results and the test results. The parameter analysis results indicate that the panel’s heat transfer coefficient decreases by 15.4% after the connector’s steel covered the nylon. The thermal conductivity of the concrete has a great influence on the heat transfer coefficient of the prefabricated concrete sandwich panels which is nearly linearly increased with the thermal conductivity of insulation increasing. The larger the steel’s thermal conductivity is, the higer the panel’s heat transfer codfficent is and the more influence degree to the panel’s heat transfer coefficient it is. when the steel itself has a low thermal conductivity(λ_steel≤20 W/(m2?K)), the impact of the covered nylon on panel’s heat transfer coefficient is not obvious. On the premise of the safety of the structure, increasing the arrangement distance and decreasing the steel bar diameter of the composite connector can both substantially improve the panel’s thermal performance.. Moreover, there is little impact on the panel’s heat transfer coefficient by means of increasing the thickness of the covered nylon.