Experimental Study on Seismic Performance of Angle Steel-Sleeve Combined Square Steel Tube Column-Honeycomb Beam Joint

Overview of the Research Topic

This study investigates the seismic behavior of an innovative structural joint that combines angle steel reinforcement with a sleeve connection between a square steel tube column and a honeycomb beam. The research is significant because conventional square steel tube column-to-beam connections often suffer from insufficient deformation capacity and brittle failure modes under cyclic loading. The honeycomb beam configuration provides an enlarged connection zone, while the angle steel-sleeve hybrid approach aims to enhance ductility and energy dissipation without excessive welding complexity.

Core Technical Approach

The experimental program involves fabricating full-scale or large-scale specimens of the proposed joint and subjecting them to low-cycle reversed loading to simulate seismic conditions. Key design parameters include the angle steel leg dimensions, sleeve length-to-column-width ratio, beam web thickness, and the interaction between the honeycomb void geometry and the joint stiffness. The angle steel members are typically welded to the outer surface of the square tube column, providing additional moment resistance and strain compatibility at the critical joint region. The sleeve element bridges the gap between the column and the honeycomb beam, distributing stresses more uniformly.

Key Performance Indicators

The test results typically reveal that the joint exhibits a ductile failure pattern characterized by the formation of plastic hinges in the beam flanges near the connection, which is the desired seismic behavior. The angle steel reinforcement effectively prevents local buckling of the column wall at the beam attachment zone, while the sleeve maintains load path continuity.

Interpretation of Technical Points

The combination of angle steel and sleeve elements addresses two fundamental challenges in steel tube-to-beam connections. First, the square tube column has limited access for full-penetration welding, which restricts the available joint configurations. Second, the honeycomb beam introduces geometric discontinuities that can concentrate stresses at the void openings. The angle steel provides external bracing that increases the effective moment of inertia of the column near the joint, reducing the stress gradient in the tube wall. The sleeve, meanwhile, acts as a transition element that accommodates differential deformations between the column and beam.

From a welding perspective, the angle steel attachment welds are fillet welds applied to the exterior of the square tube, which is more accessible than internal welding. This reduces the risk of incomplete fusion and porosity defects associated with restricted welding positions. However, the weld toe at the angle steel base becomes a potential fatigue initiation site, requiring attention to weld quality and surface treatment in seismic applications.

Integration with Engineering Practice

In practical design, the joint's seismic performance must be verified against standards such as GB 50011-2010 for seismic design of building structures and GB/T 19804 for seismic performance requirements of steel structures. The ductility coefficient obtained from cyclic testing should meet or exceed the demands imposed by the building's seismic intensity and structural system classification. Engineers should pay particular attention to the connection between the angle steel and the sleeve, as this interface experiences significant shear and bending during earthquake-induced lateral displacements.

A critical practical consideration is the constructability of the joint in congested structural environments. The angle steel-sleeve combination requires careful coordination with rebar placement in composite systems and with MEP routing in the building interior. The welding sequence should be planned to minimize residual stress accumulation, with preheating applied where necessary for thicker steel sections.

Study Insights and Implications

This research demonstrates that hybrid reinforcement strategies can significantly improve the seismic resilience of steel tube column connections without resorting to overly complex or expensive joint details. The angle steel-sleeve approach represents a practical balance between performance and constructability. However, further parametric studies are warranted to optimize the geometric proportions of the angle steel and sleeve elements for different column sizes and seismic demand levels. The findings should be incorporated into design guidelines for steel tube-concrete composite structures used in earthquake-prone regions, where connection performance governs overall structural safety.