| At the same time as China's urban construction is in full swing,construction waste is also produced,which has become an important practical problem facing China's urbanization process.In 2017,China generated more than 2 billion tons of construction waste,but most of it was treated in the landfill,and the resource reutilization rate was very low.On the other hand,China's traditional high-energy-consumption and high-pollution traditional building construction model has prominent drawbacks,and it is urgently needed to transform to a new type of prefabricated building industrialization.The CPC Central Committee and the State Council's "Several Opinions on Further Strengthening Urban Planning and Construction Management"(2016)clearly stated:(1)Strive to basically complete the transformation of existing urban shantytowns,urban villages and dilapidated houses by 2020,and strive to dispose of construction waste Recycling utilization rate increased to more than 35%;(2)It should take about 10 years to make prefabricated buildings account for 30% of newly built buildings.Obviously,the use of construction waste to regenerate concrete aggregates for research and development of Prefabricated building components,and the application of renewable resources to the industrialization of Prefabricated buildings,can both reduce environmental pollution and save raw material consumption,which is of great strategic significance to promote the healthy development of China's construction industry.In the prefabricated building structure,the envelope system accounts for about 70%,and its performance directly affects the promotion and development of the prefabricated structure.The outer wall is the envelope system that has the most contact with the outdoor environment.Its thermal insulation performance has a great influence on the energy consumption of the building.The envelope system accounts for about 30% of the total energy consumption in heating energy consumption.Therefore,how to improve the thermal insulation performance of the wall and ensure its good mechanical properties has become a hot topic of precast wall panels.To this end,this article uses construction waste recycled aggregates,combined with BFRP shear connectors,to develop a new type of precast recycled concrete sandwich wall panels,and uses a combination of theoretical analysis,numerical simulation and experimental research to discuss the type.The flexural performance of sandwich panel is intended to provide theoretical basis and experimental data for its application in prefabricated building structures.The main contents and conclusions of the study are as follows:(1)The experimental research and numerical analysis of the shear resistance of BFRP connectors were carried out.Using recycled aggregate content and BFRP connection angle as variables,a recycled concrete sandwich member was designed and prepared.A series of double shear tests were carried out to discuss the shear resistance of the BFRP connector in the recycled concrete sandwich layer.The finite element model was established and the parameters were analyzed.The results of the study indicate that the addition of recycled aggregates will reduce the load-bearing capacity of the sandwich member compared to the natural concrete members.When the recycled aggregate replacement rate is 100%,the ultimate load will be reduced by 55%;the equivalent shear modulus of the sandwich layer As the connector angle increases,it decreases.Compared with the connector angle of 30 °,the shear modulus at the connector angle of 60 ° decreases by 38%.(2)Designed and prepared 8 full-scale precast recycled concrete sandwich wall panels,divided into 2 groups of partial composite panels and non-composite panels,with 0%,50%,100% recycled aggregate replacement rate and BFRP connectors inserting angles of 30 °,45 °,and 60 ° as test variables,the four-point bending test was carried out to discuss the bending behavior of this new type of precast concrete sandwich wall panels.The research results show that the fabricated recycled concrete sandwich wallboard prepared in this study has good bending resistance;the shear stiffness of the sandwich wallboard increases as the angle of the BFRP connector decreases;the replacement rate of recycled aggregate is 50 % of the components are better than the components with 100% replacement rate in terms of composite degree,deformability,bearing capacity,etc.;in the liner phase,the composite degree of the component decreases with the increase of the angle of the BFRP connector.The components with connector of 30 °-45 ° perform better than the components with connector of 60 ° in all aspects.(3)This article introduces the classic sandwich panel analysis theory,lists the theoretical analysis methods used for symmetric sandwich panels and asymmetric sandwich panels,and uses the one cross section theory to derive the load of the four-point bending test of sandwich wall panels in this paper.The deflection formula takes the equivalent shear mode of the middle layer in the numerical simulation results of the double-shear test as the parameter,and compares the test value and the calculated value,and discusses the applicability of the formula under different variables.The research results show that the deflection in the limit state is partially safe based on the formula proposed in this paper. |
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