Load Bearing Capacity and Economic Analysis of Cold-Formed Stiffened High-Strength Steel Beams

With the progress of steel-making technology, high-strength steel is gradually applied in the construction field. Compared with ordinary steel, high-strength steel has the advantages of saving steel, reducing section size, reducing structural weight, and improving seismic performance. Local buckling is easy to occur for wide and thick plates under pressure, which reduces the bearing capacity of the members. The setting of stiffening ribs can change the mechanical properties and buckling behavior of the original plate, improve the comprehensive rigidity of the stiffened plate, and the cold-formed stiffening has the advantages of easy production and low processing costs. In order to investigate the load bearing capacity and economy of high-strength steel beams with cold-formed semi-circular stiffeners, the bending analysis model of H-shaped and box-section steel beams with flange and web stiffening was established after verifying the accuracy of the finite element model by comparing the test results of H-shaped steel beams clamped at both ends and loaded at a single point in the mid-span. Four H-section steel beams with different section sizes were selected to investigate the influence of flange stiffening on the strength and stable bearing capacity of steel beams. Three section types, namely, H-section, upper flange stiffening, and both upper and lower flanges stiffening, were simulated by numerical simulation, and the bending strength bearing capacity of steel beams with different section types was compared. By changing the thickness of upper and lower flanges, the thickness of flanges was obtained when the ultimate bearing capacity of steel beams with grade Q355 H-section was the same. The corresponding proportion of steel quantity reduction under different sizes was obtained. The cross-sections of steel beams with stiffened ribs in H-shaped and box-shaped webs were optimized by increasing the thickness of the flanges while keeping the steel consumption of the cross-section unchanged, and comparing the flexural strength load capacity of the stiffened cross-section of Q355 grade webs with that of the unstiffened H-shaped cross-section steel beams for different optimized cross-section sizes.By optimizing the section size, when the same load bearing capacity was obtained, the amount of steel used in the stiffened high-strength Q690 steel beam was less than that of Q355 steel beam. The results show that the upper flange of H-shaped steel beam stiffened outward has higher flexural strength bearing capacity than that stiffened inward, and the flange stiffened will significantly reduce the overall instability bearing capacity; the flexural strength bearing capacity of flange stiffened Q690 steel beam with the same cross-sectional area is more than twice that of Q355 steel beam, and the steel consumption of flange stiffened Q690 steel beam with the same strength bearing capacity is about half that of Q355 steel beam; the thickness of the web is reduced and a stiffener is added to ensure that the flange thickness is increased under the condition of constant steel consumption, and the strength failure bearing capacity of the steel beam is higher; H-shaped Q690 steel beam adopts optimized section, which saves about 40% of steel consumption under the condition of ensuring that the bearing capacity is equal to that of Q355 steel beam; the box Q690 steel beam adopts optimized section, and the steel consumption can be saved by about 30% under the condition of ensuring that the bearing capacity is equal to that of Q355 steel beam.