Experimental Study and Analysis of Static Load-Bearing Performance of Hybrid Steel Girders

In order to investigate the effect of different height to thickness ratio of web and steel grade combinations on the static load carrying performance of steel beams, one same-grade steel beam and three Hybrid steel girders were designed and fabricated respectively, and four-point bending tests were conducted on the specimens to obtain the damage pattern, load-displacement curve, load-strain curve, corresponding load of web and flange yielding and ultimate load of each specimen, and the theoretical calculated values were compared with the experimental values. Buckling analysis was then performed by ABAQUS, and the calculated results were compared with the experimental results to verify the reasonableness of the finite element model. After that, parametric analysis was carried out to further investigate the effect of height to thickness ratio of web and steel grade combinations on the static load carrying performance of steel beams, and to analyze the economics of changing web height, web thickness and web strength with the variation of steel consumption. Finally, the flange yielding moment, plastic limit bending moment and critical moment of bending and torsional buckling obtained from the parametric analysis are compared with the results of the corresponding theoretical equations to provide some suggestions for the design of hybrid steel girders. The results show:1) The yield load of specimen M-1 flange is 8.7% larger than that of specimen S-1 flange, which indicates that the design capacity of Hybrid steel girders is slightly better than that of the same steel girders under the condition that the ratio of height to thickness ratio of web is the same as that of calculated value of the specification GB 50017—2017 Steel Structure Design Standard. Therefore, in the actual structure, when the web height to thickness ratio of web is large, the flange can use higher strength grade steel, while the web can use lower strength steel, forming Hybrid steel girders instead of the same steel girders, which can appropriately improve the static bearing capacity of steel girders and save the amount of steel at the same time; 2) When the height of the cross-section is increased, the yielding load of web of specimen is improved, and the yielding load of web of specimen M-3 is 12.7% higher than that of M-1, the effect of initial defects on the load carrying capacity of steel beams is mainly reflected in the late loading stage, because the web height to thickness ratio of web increases, the degree of its initial defects will increase, and at the same time, the load carrying capacity will be improved. Therefore, compared with specimen M-1, specimens M-2 and M-3 flank yielding corresponding to the load is not a big difference, and the destructive loads are reduced by 4.7% and 9.4%, respectively;3) By increasing the strength grade of the web, the steel consumption is increased by 7%, and the improvement of flange yielding moment is only 7%, which is ineffective; the improvement efficiency of flange yielding moment can reach 8 times of the improvement efficiency corresponding to the increase of the web thickness when increasing the height of the web; 4) The flange yielding moment, plastic limit moment and torsion critical moment can be determined by referring to the corresponding theoretical calculation formula.