Structural optimization and engineering application of concrete-filled steel tubular composite supports

Abstract

Concrete-filled steel tubular (CFST) composite supports have a high bearing capacity and are suitable for the support of roadway intersections with complex cross-sections and stress concentrations, especially for cross-point intersections. According to the cross-sectional shape and support frame combination, CFST composite supports are divided into three types: circular arc concrete-filled steel tubular composite support (CCS), rectangular concrete-filled steel tubular composite support (RCS), and circular arc + rectangular concrete-filled steel tubular composite support (CRCS). Through engineering practice and literature review, the top component of portal support frame is the key bearing structure of CFST composite support. Taking the top component of portal support frame as a key component, the bearing performance tests of the circular arch and straight beam were conducted. The bearing performance variation of key component influenced by the diameter of steel pipe, wall thickness of steel pipe, beam to span ratio and bending strengthening parameters were analyzed, providing guidance on the structural optimization of portal support frame. Numerical investigation of these three types of composite supports was carried out. The findings demonstrate that while the maximum deformations of the composite support under the constrained surrounding rock load exhibit the order CCS support frame structure optimization, the ultimate bearing capacities of the composite supports exhibit the order CCS > RCS > CRCS. The simulation found that the portal support frame is the key bearing structure of the composite support. Taking the top arch section of the portal support frame as a typical component, bearing capacity testing of the CFST straight beam and the arch was performed. The difference in the circular arch bearing performance was analyzed based on changes in the steel pipe diameter, steel pipe wall thickness, rise-span ratio, and anti-flexural strengthening, and the results provide a basis for portal support frame structure optimization. Three roadway intersections in practice were used to evaluate the performance of the three types of composite supports. After structural optimization, the composite supports meet practical requirements and generally produce good results, making them a suitable reference for other roadway intersections.