In-plane Stability Analysis Of Double-limb Cold-formed Thin-walled C-shaped Steel Frame

Compared with traditional structures such as brick-concrete and reinforced concrete,the cold-formed thin-walled steel and portal frame structures are energy-saving and environmentally friendly,have good seismic performance and high space utilization.Combining the two,complementing each other’s advantages,and applying them to grassland areas,a cold-formed thin-walled steel yurt structure was built.The main force-bearing structure in the yurt is a cold-formed thin-walled steel frame,which is different from the ridge node of the ordinary frame.The beams of the yurt frame are connected by ceramic nodes and are restricted by the yurt structure.The rigid frame is mostly a large-slope mountain-shaped portal frame.frame.Therefore,the stability calculation of this kind of special frame has become an urgent problem to be solved.In this paper,referring to the parts library of cold-formed thin-walled C-shaped steel yurt frame with double limbs,a 1/4 scaled frame is designed for in-plane stability test.The instability mode and in-plane stability bearing capacity of rigid frames with different inclined beam slopes and frame height-span ratios under uniformly distributed loads of inclined beams are studied.The research results show that the slope and height-span ratio of the inclined beam have a greater influence on the in-plane stability bearing capacity of the rigid frame.The larger the slope of the inclined beam and the smaller the height-span ratio of the rigid frame,the greater the stability bearing capacity of the rigid frame.The ANSYS finite element software was used to analyze the in-plane stability of the scaled rigid frame model,and compared with the test,it verified the reliability of the in-plane stability of the rigid frame through finite element simulation.A total of 13 full-scale cold-formed thin-walled steel frame finite element models with three sets of different inclined beam slopes,frame height-to-span ratios,and ceramic diameters were established,and the inclined beams were uniformly loaded to perform in-plane stability analysis.And compare with the standard calculation results.In the simulation,all rigid frames are symmetrical instability,and the three sets of variables all have an influence on the in-plane stability of the rigid frame ultimate bearing capacity.Among them,the greater the slope of the inclined beam,the greater the bearing capacity of the rigid frame,and the smaller the calculated length coefficient of the column;the larger the height-span ratio of the rigid frame,the smaller the bearing capacity of the rigid frame and the larger the calculated length coefficient of the column;the larger the diameter of the ceramic brain,the greater the bearing capacity.The greater the force,the smaller the calculated length coefficient of the column.Comparing the calculation results with the specifications,it is found that the calculated length coefficients of the two columns have a certain difference,and the calculated length coefficient of the column changes with the slope of the inclined beam in the opposite way.This is because the standard calculation model ignores the axial force in the inclined beam,and a certain arching effect is produced in the rigid frame with a larger slope of the inclined beam,which leads to a larger in-plane stability limit bearing capacity of the simulated rigid frame,and the column calculation The length factor is small.According to the orthogonal table(3~4),nine full-scale rigid frame finite element models are established and the in-plane stability calculation is performed.The calculation results are sorted and the range analysis is performed to obtain the influence of three sets of parameters on the ultimate bearing capacity of rigid frame in-plane stability.The degree from large to small is the slope of the inclined beam,the height-span ratio of the rigid frame and the diameter of the ceramic brain.Using orthogonal test and the fitting of the calculated column length coefficient obtained from the specification,a column calculation length coefficient correction coefficient formula suitable for cold-formed thin-walled steel chevron frame is obtained.The in-plane stability test data of the predecessor portal frame is used to verify the correction coefficient formula,which proves that the calculated column length coefficient after the correction of this formula is more accurate than the specification.In this paper,the in-plane stability of the rigid frame is studied by a combination of experiment and simulation,and the correction coefficient of the calculated length coefficient of the double-limbed cold-formed thin-walled steel rigid frame column is given,which provides a reference for future engineering design.