Study On Eccentric Compression Bearing Capacity Of Thin-walled Steel Tubular Columns Filled With Sand And Gravel

As vertical bearing member,thin-walled steel square pipe column has the advantages of good ductility and fire resistance.Sand-filled pebbles in steel tubes can improve the stability and ultimate bearing capacity of columns.After the design reference period,the sand and pebble in the steel tube can be reused,which can effectively reduce the generation of construction waste.Secondly,in practical engineering,medium and long columns are the majority of vertical bearing members.Due to the influence of initial defects,material inhomogeneity,manufacturing errors and other factors,most steel tube composite members are in the state of eccentric compression.Therefore,it is necessary to study the static bias performance characteristics of thin-walled square steel tube sand and pebble composite column,as follows:1.Static bias test was carried out on 10 thin-walled square steel tube sand pebble medium and long columns.The experimental control eccentricity was 10 mm,and the main control parameters were the sand pebble compaction coefficient(=0,73.9%,77.7%,82.9%,87.7%,92.9%).The column length is 1200 mm,and the column section size is 100 mm 100mm 3mm.The test results show that the local buckling of the steel tube wall is delayed to a certain extent,the ultimate bearing capacity of the thin-walled square steel tube column is greatly improved,and the overall stability of the column is effectively improved,in order to ensure that the suggested sand pebble compaction coefficient reaches 87.8%,the sand pebble with larger compaction coefficient participates in the force,and ACTS together with the sand pebble and the pipe wall.2.Keep the sand pebble compaction coefficient in the range of more than 88%,the slenderness ratio(12.47,20.78,41.57,51.96,62.35),eccentricity(10mm,20 mm,30mm)as the main variation parameters,for 12 thin-walled square steel sands The pebble column was subjected to a bias test.The failure morphology,ultimate bearing capacity,load-displacement curve and load-strain curve of the test piece were analyzed and compared.The results showed that:(1)Under the same eccentricity,the ultimate load of the test piece decreases as the slenderness ratio increases.For specimens with a wall thickness of 3 mm,when the eccentricity is e=10 mm,the specimens with a length-to-fine ratio of 20.78,41.57,51.96,and 62.35 have a final bearing capacity of 10.86% and 12.7%,respectively.26.8%,31.2%;(2)In the case of the same slenderness ratio,the ultimate load of the specimen decreases as the eccentricity increases.For the specimen with ? = 12.47,when the eccentricity is increased from 10 mm to 20,30 mm,the ultimate bearing capacity of the specimen is gradually decreasing.The eccentricity of the S360 short column bearing capacity increases with the eccentricity,and the specimen is loaded with the ultimate load.The force decreased by 7.8%,17.3%,and 26.3%,respectively.The ultimate bearing capacity of the L1200 long column decreased with the eccentricity,and the ultimate bearing capacity of the specimen decreased by 20.5%,26.2%,and 44%,respectively.It can be seen that with the slenderness ratio and the wall thickness constant,as the eccentricity of the specimen increases,the ultimate bearing capacity changes nonlinearly,and the decreasing amplitude gradually increases.(3)With the increase of slenderness ratio ?,the ductility coefficient of the specimen decreases,the peak load load and yield load decrease;as the eccentricity e increases,the ductility of the specimen increases.3.Based on the research of thin-walled square steel tubular columns and thin-walled square steel tubular columns,based on the calculation method of the flexural bending capacity of concrete-filled steel tubular structures,the calculation method for the biasing capacity of thin-walled square steel-steel sand-cement columns is derived.The test data error is about4%~10%.4.Based on the research of thin-walled square steel tubular columns and thin-walled square steel tubular columns,the characteristics of the static performance of the three types of columns,such as failure mode and stable bearing capacity,are obtained,and the advantages and disadvantages of the combined columns are obtained.The theoretical basis for the design and actual promotion of the column in the future.