Introduction

In modern structural engineering, improving the blast resistance of buildings is a critical concern, particularly in areas vulnerable to accidental or intentional explosions. Reinforced concrete (RC) columns, as key load-bearing elements, often require additional strengthening to withstand such extreme loads. One promising approach is the incorporation of a steel core, particularly with a unique geometry such as an X-shape, to enhance both energy absorption and structural integrity under blast loading.

This study focuses on the numerical simulation of a coupled Eulerian-Lagrangian (CEL) explosion acting on a composite RC column with an X-shaped steel core using Abaqus/Explicit. The CEL technique enables a detailed analysis of fluid-structure interaction (FSI) by modeling the air and explosive materials in an Eulerian domain and the structural components in a Lagrangian domain.

Explanation of the Simulation

1. Simulation Objective

The main objective is to investigate the response and failure mechanisms of a composite RC column with an X-shaped steel core under blast loading. The simulation aims to:

• Assess the protective role of the steel core.
• Understand stress wave propagation and damage distribution.
• Provide insights for designing blast-resistant structural components.

2. Model Components

• Concrete Column: Modeled using Lagrangian elements with appropriate concrete damage plasticity (CDP) parameters to capture cracking and crushing behavior.
• Steel Reinforcement and X-Shaped Core: Both are embedded in the concrete using an embedded region constraint. The steel is modeled using elastic-plastic behavior with strain hardening.
• Explosive and Air Domain: Modeled using Eulerian elements to simulate the detonation and shock wave propagation.
• coupled Eulerian-Lagrangian (CEL) Coupling: The interaction between the explosion and the structure is handled using the general contact algorithm and FSI constraints, allowing pressure waves to be transferred from the Eulerian (fluid) to Lagrangian (solid) parts.

3. Explosive Modeling

• The explosive is typically represented using a Jones-Wilkins-Lee (JWL) equation of state to simulate detonation products.
• An initial volume fraction defines the explosive material within the Eulerian mesh.
• The explosion is initiated with a detonation point and an initial pressure pulse.

4. Output and Post-Processing

Key outputs include:

• Pressure and stress contours.
• Damage indicators for concrete (cracking/crushing).
• Plastic strain in the steel core and reinforcement.
• Time-history plots of displacement, velocity, and internal energy.

Significance of the X-Shaped Steel Core

The X-shaped steel core plays a dual role:

1. Load Redistribution: Helps share blast-induced stresses and prevents localized failure.
2. Energy Absorption: Deforms plastically under blast loads, dissipating energy before it reaches the concrete.

Its geometry is also beneficial for increasing torsional resistance and providing redundancy, making it superior to traditional reinforcement configurations under impulsive loads.