# Experimental Investigation of Shear Connection in Precast Concrete Sandwich Panels with Reinforcing Ribs

## TL;DR

This study tests how different materials in precast concrete panels affect their strength and thermal efficiency.

## Contribution

The paper introduces a new method for enhancing shear connection in precast concrete panels using polymer-based insulation and CFRP reinforcement.

## Key findings

- Panels with Purenit and Compacfoam CF400 had higher load-bearing capacity than Foamglass F.
- Increasing CFRP reinforcement improved load-bearing capacity but not panel stiffness.
- A composite interaction coefficient of α ≈ 0.03 indicated partial shear interaction between concrete layers.

## Abstract

This paper presents an experimental investigation of the shear connection between outer layers of lightweight precast concrete sandwich panels (PCSP) made of high-performance concrete (HPC). The shear-transfer mechanism is based on reinforcing ribs composed of rigid polymer-based thermal insulation combined with carbon-fibre-reinforced polymer (CFRP) shear reinforcement. A total of seven full-scale sandwich panels were tested in four-point bending. This study compares three types of rigid thermal insulation used in the shear ribs—Purenit, Compacfoam CF400, and Foamglass F—and investigates the influence of the amount of CFRP shear reinforcement on the structural behavior of the panels. Additional specimens were used to evaluate the effect of reinforcing ribs and of polymer-based thermal insulation placed between the ribs. The experimental results show that panels with shear ribs made of Purenit and Compacfoam CF400 achieved significantly higher load-bearing capacities compared to Foamglass F, which proved unsuitable due to its brittle behavior. Increasing the amount of CFRP shear reinforcement increased the load-bearing capacity but had a limited effect on panel stiffness. The experimentally determined composite interaction coefficient ranged around α ≈ 0.03, indicating partial shear interaction between the outer concrete layers. A simplified strut-and-tie model was applied to predict the load-bearing capacity and showed conservative agreement with experimental results. The findings demonstrate that polymer-based materials, particularly CFRP reinforcement combined with rigid polymer insulation, enable efficient shear transfer without thermal bridging, making them suitable for lightweight and thermally efficient precast concrete sandwich panels.