Blast Resistance and Damage Assessment of Double-Walled Hollow Steel Tube Concrete Columns

Literature Overview

This paper by Cui Ying, Zhao Junhai, Zhang Changguang, Sun Shanshan, and Chen Bing, published in Journal of Vibration and Shock in 2015, presents an investigation into the blast resistance and damage characteristics of double-walled hollow steel tube concrete (CFST) columns. The study was supported by the National Natural Science Foundation of China (41202191), the Ministry of Education Doctoral Point Fund (20110205130001), and the China Postdoctoral Science Foundation (2012M520079, 2013T60868). The research combines experimental blast testing with numerical simulation to establish a damage assessment criterion based on the overpressure-impulse (P-I) curve.

Research Context and Motivation

The double-walled hollow steel tube concrete column is an advanced structural system that combines the benefits of steel tube confinement with the added protection of a double-wall configuration. The outer steel tube provides blast resistance and impact protection, while the inner steel tube and concrete core provide structural strength and stability. This configuration is particularly relevant for protective structures in military, nuclear, and critical infrastructure applications where blast loading is a design consideration.

The study addresses a critical need for quantitative damage assessment methods that can be used to evaluate the residual structural capacity of columns after blast loading. The establishment of a P-I based damage criterion provides engineers with a practical tool for post-blast assessment and rehabilitation decisions.

Experimental Program

Test Configuration

The scaled distance of 0.14 m/kg^(1/3) represents a moderate blast loading condition, typical of design scenarios for protective structures. The experimental setup included high-speed cameras, pressure sensors, and displacement transducers to capture the dynamic response of the column.

Key Findings

Blast Response Characteristics

The distribution of peak pressure and damage severity along the column height follows a logical pattern related to the boundary conditions and the dynamic response of the column. The mid-height region, being farthest from the fixed supports, experiences the largest deflection and consequently the highest stresses and most severe damage. The column base, while closer to the support, still experiences significant loading due to the constraint reaction forces. The column top, being closest to the support, experiences the least damage.

Damage Pattern

The blast test revealed that the blast face of the column at mid-height exhibited pronounced plastic bending deformation. This is consistent with the expected behavior of a beam-like element subjected to distributed blast loading. The plastic hinge formation at mid-height indicates that the column has undergone significant inelastic deformation, which is a desirable failure mode from a damage tolerance perspective, as it allows the structure to absorb energy without catastrophic collapse.

Joint Strength Coordination

A critical finding of this study is that the coordination between joint strength and member strength is essential for achieving optimal blast resistance. If the joints are weaker than the members, the joints will fail prematurely, leading to progressive collapse. If the members are weaker than the joints, the members will fail, which may be acceptable if the failure mode is ductile and energy-absorbing. The study emphasizes that the design should ensure that the joints are at least as strong as the members to prevent premature joint failure.