Research On Mechanical Properties And Design Methods Of Rectangular Tube Single-layer Lattice Shells With SLO Node

Single-layer latticed shells have been widely used in practical engineering because of their beautiful shape,simple structure and good mechanical performance.The member forms of singlelayer latticed shell mainly include circular steel tube,rectangular steel tube and H-shaped steel.From the perspective of mechanics and architectural aesthetics,rectangular steel tubes are more suitable for single-layer latticed shells.The joints of single-layer latticed shells mainly include welded joints and bolted joints(assembled joints).Welding joints require a lot of on-site welding,the construction cost and difficulty are high,and the connection quality is not easy to guarantee.Bolted joints have the advantages of fast construction speed,low cost and good quality,which meet the development requirements of China ’s new building industrialization.The SLO joints adopt the connection form with upper bolt and lower bolt,exhibiting excellent comprehensive performance,and making them suitable for the assembly of rectangular steel tube single-layer latticed shells.Currently,there are several shortcomings in the research of the SLO joints single-layer latticed shells: most studies focus on the bending resistance performance of the SLO joints,lacking systematic research on the mechanical properties of the SLO joints single-layer latticed shells;Currently there is a lack of research on the local stability of semi-rigid joints singlelayer lattice shells members.Therefore,determining the out-of-plane calculation length coefficient of SLO joints single-layer latticed shells members is a problem that needs to be addressed in structural design.Based on the above issues,this thesis has conducted the following research on the flexural performance of SLO joints,the static stability behaviors and design methods of the SLO joints single layer latticed shells:(1)The structural form and force transmission mechanism of SLO joints were explained,and pure bending tests of SLO joints were carried out to study the bending resistance and failure mode of the joint system.The results show that SLO joints have simple structure,clear force transmission path,convenient installation and good comprehensive performance,which are suitable assembled joints for single-layer reticulated shells with rectangular tubes.The results of the pure bending tests showed that the SLO joints have good bending resistance performance,and the bending stiffness and bearing capacity of the joints increase with the increase of member section,bolt specification,end plate thickness,and bolt spacing.Under the action of pure bending,the main failure modes of SLO joints include end plate failure,small bolt pulled out of the hub,bolt breakage,and member failure.(2)The SLO joints model based on beam elements was proposed.The beam elements model simplifies the joints into beam elements combination with different cross sections and material properties,and these beam elements combination reflects the mechanical properties of the SLO joints.The beam elements model of SLO joints pure bending tests were established for numerical analysis,and compared with the test results to verify the accuracy of the beam elements model.The comparison results showed that the load-displacement curves and failure modes of the SLO joints beam elements model are in good agreement with the test results,and the stress distribution of the structure is also consistent with the solid elements.Therefore,the SLO joints beam elements model can be used for the analysis of the overall structure of the single-layer latticed shell.(3)Research has been conducted on the out-of-plane computation length coefficient of semirigid joints shells members.The formula for out-of-plane elastic rotational stiffness of the SLO joint was derived based on the beam elements model.and the accuracy of the derived formula was verified by comparing with the pure tests results.The out-of-plane effective length coefficients of single-layer reticulated shell with semi-rigid joints were determined by theoretical calculation and numerical analysis,and the formula for calculating the out-of-plane effective length coefficient of the semi-rigid single-layer latticed shell was fitted.(4)Based on the SLO joints beam elements model,the finite element analysis of K6 singlelayer latticed dome with SLO joints was carried out to investigate the influence of different parameters on the instability mode,stiffness and stability bearing capacity of the whole structure.The results showed that the failure modes of single-layer latticed dome with SLO joints mainly include two types: the in-plane instability of members and the overall instability.The stable bearing capacity of the SLO joints single-layer latticed dome increases with the increase of bolt specifications,member sections,and rise-to-span ratios.When the failure mode of single-layer latticed domes is in-plane instability of the members,the bolt size has little effect on the stiffness and stability capacity of single-layer latticed domes,while the influence of the member section is great,and those with the smaller member aspect ratio have higher stability bearing capacity.When the failure mode of single-layer latticed domes is overall instability,both bolt size and member section have great effects on the stiffness and stability capacity of single-layer latticed domes,and those with the larger member aspect ratio have higher stability bearing capacity.