1. Introduction

Steel-Reinforced-Concrete (SRC) structures are hybrid structural systems that combine the compressive strength of concrete with the tensile and ductile capabilities of embedded steel elements. A key component of SRC systems is the steel-concrete composite beam, which integrates structural steel sections (I-beams or H-sections) and reinforced concrete into a unified structural member.

The bending test analysis of such beams is essential to assess their flexural performance, load-carrying capacity, ductility, and failure mechanisms. These properties are critical for ensuring the safety and serviceability of SRC structures, particularly in buildings and bridges subjected to heavy loads and seismic activity.

2. Overview of Steel-Concrete Composite Beams in SRC Structures

A steel-concrete composite beam in an SRC structure typically consists of:

• A steel section (embedded or partially exposed) acting as the main tension-resisting component.
• Concrete surrounding or encasing the steel section, providing compressive strength and fire resistance.
• Reinforcement bars (rebar) were added to enhance strength and ductility.
• Shear connectors (e.g., studs) are used to ensure composite action between steel and concrete.

This composite action allows for efficient load distribution and greater strength-to-weight ratios compared to traditional reinforced concrete or steel beams alone.

3. Purpose of Bending Test Analysis

The bending test (often conducted as a four-point or three-point loading test) aims to evaluate:

• Moment–curvature relationship
• Elastic and plastic behavior
• Crack initiation and propagation
• Ultimate bending capacity
• Stiffness degradation
• Strain distribution in steel and concrete

This test provides a better understanding of how the composite beam behaves under flexural loading and helps refine design codes and numerical models for SRC structures.

4. Key Parameters Studied in Bending Tests

• Load vs. deflection curve: Indicates stiffness, yield point, and ultimate load.
• Strain distribution: Measured at different points to observe the interaction between steel and concrete.
• Neutral axis position: Helps identify how forces are shared between steel and concrete.
• Crack patterns: Provides insight into failure mechanisms (flexural, shear, bond-slip, etc.).
• Ductility ratio: Shows how much deformation the beam can undergo before failure.
• Failure mode: Such as crushing of concrete, yielding of steel, or interface debonding.

5. Common Failure Modes Observed

• Concrete crushing in the compression zone
• Steel yielding or local buckling
• Shear connector failure or slip
• Delamination or debonding at the interface

Understanding these mechanisms helps in improving design efficiency, structural reliability, and construction detailing of SRC structures.