Numerical Simulation of Prefabricated Composite CFST Column and Steel Plate Shear Wall Frame

Literature Overview

The paper by Zhao Junhai, Chen Chen, and Chen Yanxiong, published in Earthquake Engineering and Engineering Dynamics (Vol. 41, No. 3, 2021), investigates the seismic performance of a prefabricated composite concrete-filled steel tubular (CFST) column combined with steel plate shear wall (SPSW) frame system. Based on quasi-static test results, the authors developed finite element models using ABAQUS software, incorporating appropriate material constitutive relationships and damage factors to account for concrete degradation. The simulated hysteresis curves matched experimental results well. The study further analyzed stress distributions and conducted parameter studies on axial compression ratio, steel strength, and SPSW thickness.

Prefabricated CFST Column Fabrication and Assembly

The prefabricated nature of this structural system introduces unique challenges for steel pipe fabrication and on-site assembly. Prefabricated CFST columns are typically manufactured in factory conditions, where the steel tube is filled with concrete under controlled conditions, and then transported to the construction site for erection. The composite CFST column configuration may involve nested tubes or multi-cell configurations to achieve enhanced stiffness and ductility.

From a fabrication standpoint, the following quality aspects are critical:

The column splice connections in prefabricated CFST systems are typically butt-welded or bolted flange connections. For butt-welded splices, the alignment tolerance between column segments must be within 1 mm offset and 1 degree angular misalignment to prevent stress concentration at the weld root. The welding process for these thick-walled tube splices typically involves multi-pass SAW with flux-cored wire, requiring careful control of welding parameters to avoid excessive heat input that could compromise the concrete core integrity.

Steel Plate Shear Wall Integration and Welding Challenges

The steel plate shear wall (SPSW) is a key energy-dissipating component in this structural system. The SPSW is typically a thin steel plate (2 mm to 10 mm thickness) connected to the frame members through boundary elements or perforations. The welding of SPSW boundary connections to the CFST columns involves joining thin steel plates to thick steel tube walls, creating a significant thickness mismatch that poses welding challenges.

Key welding considerations for SPSW connections include:

• The use of gas tungsten arc welding (GTAW) for the root pass to ensure full penetration in thin sections, followed by GMAW or FCAW for fill and cap passes.
• Control of heat input to prevent warping of the thin steel plate, with a recommended heat input of 0.5 kJ/mm to 1.5 kJ/mm for plates thinner than 5 mm.
• The implementation of back-gas shielding (argon or helium) to protect the root of the weld from oxidation when welding thin steel plates.
• Post-weld visual and magnetic particle inspection (MT) of all welds, with UT for full penetration welds where applicable.

The damage factor introduced in the finite element model to account for concrete degradation is particularly relevant for understanding the long-term performance of the CFST columns under cyclic seismic loading. The concrete damage model captures the progressive loss of stiffness and strength in the concrete core, which directly affects the load transfer mechanism between the steel tube and concrete.

Parameter Analysis and Seismic Performance

The parameter study reveals that the axial compression ratio, steel strength, and SPSW thickness significantly influence the seismic performance of the frame. Higher steel strength generally improves the initial stiffness and load capacity but may reduce ductility if not properly detailed. The SPSW thickness directly affects the energy dissipation capacity of the system, with thicker plates providing higher strength but potentially lower ductility.

For engineering practice, the following recommendations are derived:

• The axial compression ratio should be limited to 0.6 for seismic design to ensure adequate ductility of the CFST columns.
• Steel plates for SPSW should be fabricated from high-strength low-alloy steel (HSLA) with a minimum yield strength of 345 MPa and elongation of at least 20%.
• The welding sequence for SPSW boundary connections should be designed to minimize distortion, using symmetric welding patterns and adequate back-up bars.
• Non-destructive testing coverage should include 100% MT of all fillet welds and UT of all butt welds at column splices and SPSW boundary connections.

Study Insights and Summary

This research demonstrates the effectiveness of the prefabricated composite CFST column combined with SPSW system for seismic-resistant construction. The finite element model, validated against quasi-static test data, provides a reliable tool for predicting the inelastic behavior of the system under cyclic loading. From a steel pipe fabrication and welding perspective, the prefabricated nature of the system demands higher factory quality standards, particularly regarding concrete fill quality, weld integrity at column splices, and dimensional accuracy of steel tube segments. The integration of SPSW elements introduces additional welding complexity due to thickness mismatches, requiring careful welding procedure development and qualified welders. The parameter study provides valuable guidance for optimizing the balance between strength and ductility in the design of such systems, with particular attention to the welding details that govern the ultimate seismic performance of the structure.