Study On Statics And Insulation Performance Of Straw Sandwich Concrete Beetle Elytron Plate Wallboards

With the rapid development of China’s economy and construction industry,the annual consumption of building materials such as cement is huge.In the heat loss of the whole building,the heat loss of maintenance structure heat transfer is as high as 70%～ 80%.As a good thermal insulation material,the annual yield of straw is huge but the utilization rate is not high,and some are still burned in the field,resulting in a waste of resources and air pollution.The development of prefabricated buildings,especially the new prefabricated wall panels filled with crop straw can alleviate the aforementioned problems.On the other hand,it has been proved that the beetle elytron plate proposed for the first time based on the three-dimensional structure of beetle forewing has excellent mechanical properties of light weight and high strength.Therefore,this study proposed two nonbearing prefabricated straw sandwich beetle elytron plate wallboardsstraw sandwich concrete end-trabecular beetle elytron plate（EBEPsc）and straw sandwich concrete I-beam beetle elytron plate（IBEPsc）.The effects of the structure parameters on the mechanical and thermal insulation performance of the two wallboards were respectively investigated with ABAQUS.On the basis of parameter optimization,the optimal structural parameters were respectively given and two types of bionic prefabricated wall panels which can meet the mechanical and self-insulation requirements of nonbearing walls in level 12 typhoon-prone areas were put forward.And the comprehensive comparative analysis and evaluation of the four beetle elytron plate wallboards developed by our group including the above two were made,which will be helpful for the popularization and application of beetle elytron beetles and lightweight functional prefabricated wall panels.The main conclusions are as follows:（1）Research and development of a straw sandwich concrete end-trabecular beetle elytron plate wallboardThe effects of parameters such as concrete panel thickness T,honeycomb side length L and honeycomb wall thickness t on the mechanical and thermal insulation performance of the straw sandwich concrete end-trabecular beetle elytron plate（EBEPsc）were investigated with ABAQUS.The results are as follows: The bearing capacity of the EBEPsc is controlled by the maximum principal tensile stress,and the order of influence is T,L and t.The influence of T and t is large when the material is thin and small after thickening,while L has a small influence at both extremes and a large influence in the middle.Based on this result,considering the engineering application,a refined analytical interval of the structural parameters,a secondary simplified model and its optimal structural parameters are given,and a simplification method for the EBEP is presented for the first time.The thermal conductivity of concrete is more than 20 times that of straw,so the insulation performance of the EBEPsc is closely related to the area ratio of the concrete core.Therefore,the key to reducing the thermal bridge effect is to reduce the area ratio through structural optimization.The optimized EBEPsc can meet the mechanical and self-insulation requirements of a nonbearing wall under a level 12 typhoon.（2）Research on the mechanics and thermal insulation performance of I-beam beetle elytron platesThe effect of certain structural parameters（e.g.,panel thickness T,number of Icores N and core height h）on the mechanical and thermal insulation performance of the straw sandwich concrete I-beam beetle elytron plate（IBEPsc）was investigated by using the finite element method.The results are as follows: Like EBEPsc,the bearing capacity of the IBEPsc is controlled by the maximum principal tensile stress.Aside from T,h has the most significant influence on its mechanical properties,and the composite stress characteristics of the IBEPsc are similar to those of several I-beams.Its thermal performance depends on the thermal bridge effect of t and N.Based on this,the optimal structural parameters of the IBEPsc for a self-insulated wall with a large safety margin are presented.The consideration of strip vs.whole and the selected upper bearing constraint type have little influence on the mechanical properties.In practical applications,the production of strips and whole plates and bearing constraint types can be reasonably selected according to engineering needs.According to a qualitative analysis and comparison with common I-shaped thermal insulation walls,the IBEPsc requires the least material and weight while ensuring a sufficient safety margin in terms of mechanical and thermal insulation performance.Hence,bionic techniques played a key role in breaking through the limitations of the traditional structures.（3）Study on the characteristics and engineering applicability of four types of beetle elytron plate wallboardsUnder the premise of the same thickness of plate and core height,the finite element analysis and comparative analysis of mechanical and thermal insulation performance of four nonbearing straw sandwich concrete beetle elytron plate（the trabecular beetle elytron plate,vertical trabeculae beetle elytron plate,end-trabecular beetle elytron plate and I-beam elytron plate）wallboards under wind load and self-weight were carried out according to the structural parameters of their respective optimal models.The results are as follows: The deflections of the four models are all very small and far below their limits,so the mechanical properties of the four models are controlled by the maximum principal tensile stress.The trabecular beetle elytron plate has the best thermal performance,but its mechanical property is the worst and has exceeded the safety limit.The vertical beetle elytron plate has good performance of both kinds of properties,but the concrete consumption and the equivalent density are the largest.Both the endtrabecular beetle elytron plate and I-beam elytron plate have higher heat flux,which do not exceed the limit.Their mechanical properties are far better than those of the trabecular beetle elytron plate,and the mechanical properties of the I-beam beetle elytron plate are the best in the whole group.And the reasons for the above conclusions are explained from the perspectives of geometrical characteristics of each core structure.This paper provides some reference for the selection of various beetle elytron plate wallboards in engineering.At the same time,based on the existing codes,the EBEPsc and IBEPsc were taken as examples to calculate the thermal insulation performance of beetle elytron plate wallboards（referred to as the "code solutions"）,and compared with the finite element solutions respectively.The results show that the difference between the code solutions and the finite element solutions of the thermal insulation performance of the two beetle board walls are less than 6%,and the finite element solutions have strong reliability.It provides a certain theoretical support for this paper and subsequent studies.