Under the premise that the strength meets the requirements, is it feasible to increase the steel grade to cause the component slenderness ratio or the plate width-thickness ratio to not meet the specification requirements?
In the current code, when calculating the slenderness ratio of components and the width-thickness ratio of plates, it is often necessary to multiply the correction factor of the steel grade, resulting in the higher grade of steel is not easy to meet the requirements. The control of the slenderness ratio of the component and the width-thickness ratio of the plate is mainly considered from the perspectives of structural stiffness requirements, failure mode (buckling or yielding), and yield ductility. When the steel grade is increased, the yield strength increases, but the buckling strength (controlled by stiffness) does not change, which may lead to a change in the buckling and yield failure modes (possibly from yield ductile failure to buckling brittleness) or a decrease in the plastic energy dissipation (rotation) capacity of the structure.
For the space grid steel roof structure (grid, frame, etc.) without seismic requirements (or low anti-resistance), the slenderness ratio control of the components is mainly considered from the stiffness requirements under transportation, installation and normal use, and the correction factor of the steel grade can not be considered in the calculation. Therefore, under the premise that the design requirements have been met, it is feasible to replace the low-grade steel with high-grade steel, but the material strength is excessively remaining.
For axial compression, compression, bending and bending components with seismic requirements, buckling failure before the structural components are generally avoided as much as possible, while the slenderness ratio and width-thickness ratio limits are used to control the overall and local buckling of the structure, so they must meet the "Steel Standard" Article 17Section 3 of the "basic seismic measures" requirements, otherwise the increase of the steel grade will affect the basic seismic performance of the structure and do not meet the design requirements. In satisfying Article 17 of the Steel StandardUnder the premise of the relevant requirements of Section 3, if the slenderness ratio and width-thickness ratio do not meet the relevant requirements of "Anti-Regulation" and "High Steel Specification" due to the increase of steel grade, the design idea of high strength and low ductility can be used to design by using the performance-based design method in Chapter 17 of the "Steel Standard" to judge whether the structural components meet the requirements of strength and ductility.
In special cases, such as very small axial pressures on columns, buckling analysis can be used to further reduce the seismic construction requirements of steel structural components.