Progressive Collapse Resistance of Steel Tube Concrete Frames with Steel Bar Truss Deck Plates

Literature Overview

The research by Zheng Long and Wang Wenda from the School of Civil Engineering, Lanzhou University of Technology, investigates the progressive collapse resistance of steel tube concrete (STC) column-steel beam-steel bar truss deck plate systems under edge column removal scenarios. Published in the Journal of Natural Disasters (2023, Vol. 32, No. 3), this study was supported by National Natural Science Foundation grants (Nos. 51268038, 51778274). The work addresses a critical safety concern in building design: the ability of structures to prevent progressive collapse following the sudden loss of a load-bearing element.

Numerical Analysis Methodology

Modeling Approach

The authors employed ABAQUS/Explicit for dynamic explicit analysis of the progressive collapse process. The model incorporated:

Material nonlinearity (plasticity for steel, damage plasticity for concrete)
Geometric nonlinearity (large deformation)
Contact interactions between structural components
Strain rate effects for dynamic loading

Material Properties

Material	Grade	Yield Strength	Ultimate Strength	Damage Model
Steel tube	Q345	345 MPa	470 MPa	Von Mises plasticity
Concrete	C30	N/A	30 MPa	Concrete damage plasticity
Rebar	HRB400	400 MPa	540 MPa	Von Mises plasticity
Deck plate steel	Q235	235 MPa	345 MPa	Von Mises plasticity

Damage Definition and Validation

The accuracy of material property selection, damage definition, and modeling methodology was verified through comparison with experimental results from published literature. The validation process ensured that the numerical model could reliably predict the progressive collapse behavior of the system.

Key Technical Findings

Vertical Bearing Capacity and Failure Mode

The system exhibited good progressive collapse resistance under edge column removal conditions. The failure mode involved:

Initial stage: Elastic response with load redistribution to adjacent members.
Plastic hinge formation: Plastic hinges develop at beam-column connections and mid-span of beams.
Catenary action development: Tensile membrane action develops in beams as displacements increase.
Deck plate contribution: The steel bar truss deck plate contributes through concrete tensile damage and truss bar tension.

Load Transfer Mechanism Quantification

Resistance Mechanism	Contribution at Peak Load
Main beam flexural mechanism	42.7%
Main beam catenary mechanism	23.8%
Deck plate mechanism	33.5%

Damage Distribution Analysis

Concrete tensile damage: Concentrated in the negative bending zone on the upper surface and positive bending zone on the lower surface of the deck plate.
Steel bar truss stress: Tensile stress in truss bars increases progressively with displacement, particularly in regions adjacent to the removed column.
Galvanized steel base plate stress: Tensile stress develops in the base plate, contributing to membrane action.

Beam Behavior Comparison

The study analyzed the behavior of different beams (G1, G2, G6) under edge column removal:

Beam	Early Stage Behavior	Late Stage Behavior
G6	Strong compression arch effect	Limited catenary action due to poor boundary conditions
G1, G2	Moderate compression arch effect	Full catenary action development

The finding that G6 beam exhibits strong compression arch effect in the early stage but cannot fully develop catenary action in the late stage is attributed to the boundary conditions imposed by the edge column removal scenario. The poor tensile restraint at the G6 beam boundary limits its catenary action capacity.

Engineering Practice Implications

Design Considerations for Progressive Collapse Resistance

Deck plate contribution: The steel bar truss deck plate contributes approximately 30% of the total vertical resistance throughout the progressive collapse process. This contribution is significant and should be accounted for in progressive collapse design.
Beam design: Beams adjacent to potential removal locations should be designed with adequate flexural capacity and tensile reinforcement to develop both flexural and catenary mechanisms.
Connection design: Beam-column connections must be designed to accommodate large rotations and displacements without premature failure.

Material and Construction Requirements

From a steel pipe and welding perspective, the STC column-steel beam system requires:

Steel tube manufacturing: The STC columns should use high-quality steel tubes with uniform wall thickness and smooth surfaces. Standards such as GB/T 8162 or GB/T 8163 should be applied.
Welding quality: All welded connections, including beam-column connections and deck plate attachments, must achieve full penetration and be free of critical defects. Standards such as GB 50661 and JGJ 81 should be applied.
Concrete fill quality: The concrete fill within steel tubes must be dense and free of voids, achieved through proper vibration or post-tensioning methods.

Progressive Collapse Design Guidelines

Design Parameter	Recommended Approach
Load path analysis	Identify alternative load paths following element removal
Tensile tie design	Ensure adequate tensile ties for catenary action development
Deck plate design	Consider deck plate contribution in progressive collapse design
Connection design	Design for large deformation capacity
Material ductility	Use ductile materials with adequate strain capacity

Study Insights and Reflections

This research provides valuable quantitative data on the progressive collapse resistance of STC column-steel beam-steel bar truss deck plate systems. The finding that the deck plate mechanism contributes approximately 30% of the total vertical resistance is particularly significant, as it challenges the conventional assumption that deck plates can be neglected in progressive collapse analysis.

The detailed analysis of load transfer mechanisms, including the flexural, catenary, and deck plate mechanisms, provides a comprehensive understanding of how progressive collapse resistance is achieved in these systems. The quantification of each mechanism's contribution at peak load offers a clear basis for design optimization.

The finding that boundary conditions significantly affect catenary action development is practically important. In real structures, the boundary conditions at beam ends depend on the configuration of adjacent elements, which may vary significantly in different locations. This variability should be accounted for in progressive collapse design, potentially through the use of conservative assumptions or detailed analysis.

For engineers involved in the design of buildings requiring progressive collapse resistance, this paper provides a solid foundation for understanding the behavior of STC column-steel beam-deck plate systems. The methodology of combining detailed numerical analysis with quantitative mechanism decomposition can be applied to other structural systems and loading scenarios. The emphasis on deck plate contribution is particularly noteworthy, as it highlights the importance of considering all structural components in progressive collapse design, not just the primary load-bearing elements.