Research On Structural Mechanics And Thermal Performance Of Balcony Slab With BFRP Thermal Break

With the global energy and ecological environment problems outstanding,people pay more and more attention to the problem of building energy consumption.In view of this,Europe and The United States first put forward the concept of "Passive House",put forward specific requirements for building energy conservation,among which reducing building thermal bridge is a key point in the design of passive building.A typical thermal bridge in a building is the balcony thermal bridge,which can easily lead to condensation,bacteria and mildew on the indoor walls,and thus affect the health of the occupants.If the balcony with thermal break is set here,it can reduce local heat transfer,reduce the risk of moldy building,and improve the service life and living comfort of the building.Based on the above background and the actual engineering demand,this thesis proposes a new kind of balcony with thermal break which using the basalt fiber reinforced polymer(BFRP)as the main structural material.This kind of balcony uses the high performance mechanical material and insulation material instead of the concrete at the cantilever end of the balcony to reduce the concentrated transfer of heat in the balcony.It makes full use of the excellent mechanical and thermal properties of BFRP as well as the thermal insulation ability of XPS and reduces the thermal bridge effect while ensuring the integrity of the load transmission path.In this thesis,the mechanical test and thermal simulation verify that the balcony with thermal break can effectively isolate the concentrated transfer of heat between the outdoor balcony and the indoor floor slab,and can safely and reliably transfer the load of the balcony slab to the indoor floor slab and the frame beam.The main research contents of this thesis are as follows:(1)The structure form selection of the balcony with thermal break and the applicable structural material types and thermal insulation material types were discussed in depth,and the mechanical and thermal performance tests were conducted on each component.In this thesis,the tensile properties of BFRP bars and stainless steel bars and the compression properties of large diameter BFRP bars were tested to obtain the ultimate strength,elastic modulus,failure form and other mechanical properties.Thermal conductivity,specific heat capacity,thermal diffusion coefficient and other thermal properties of BFRP are obtained through thermal test.The results show that the BFRP bars with high structural strength and low thermal conductivity are good structural materials of the thermal break.(2)The mechanical properties of the designed BFRP thermal break were tested in this thesis.The length of the compression-shear bar into the concrete,the form of the thermal break,the span of the thermal break and the position of the loading point were variables to study their influence on the structure of the thermal break.Based on the experiment,the optimum length of the compressionshear bar into the concrete was obtained and several reasonable balcony with thermal break were designed,and the influence of the span change on the structure was discussed.At the same time,two kinds of strengthening forms of inclined joint and shear plate were put forward and their strengthening effects were compared.The experimental data shows that the thermal bridge has a certain ductility and can be used in the balcony with the cantilever length less than 1.5m.(3)The temperature field of the designed BFRP balcony node with thermal break was simulated and analyzed.ABAQUS was used to calculate the temperature field of different structural forms,different thermal break spans and ordinary reinforced concrete structures.The linear thermal bridge allowance of the designed thermal break was calculated and the thermal performance of the structure was evaluated systematically.The simulation results show that the thermal insulation performance is greatly influenced by the existence of the thermal break,while the structural form and span of the thermal break have little influence on the thermal insulation performance.Compared with the ordinary concrete balcony,the linear thermal bridge allowance of the thermal break designed in this thesis is lower,which can effectively reduce the local heat transfer of the thermal bridge,reduce the risk of condensation and mildew,reduce the energy consumption of the building and improve the living comfort of the house.