Experimental investigation on the compressive behavior of rat-trap bond wall strengthened with steel plate frame under preload

Rat-trap bond walls are widely used in historical and rural masonry buildings which is often need to be strengthened to ensure their continued use or preservation. However, there is a lack of knowledge on the reinforcement of rat-trap bond walls considering preload. Herein, steel plate frames were used to strengthen rat-trap bond walls and experiments were performed to investigate the compressive behavior of specimens with different preload ratios and steel plate thickness. The steel plate frame effectively enhanced the compressive peak load of the wall, and increasing the steel plate thickness considerably improved compressive strength and confinement effect while facilitating a smoother decline of the load-displacement curve. The preload ratio demonstrated a nonlinear relation with peak load and affected the local buckling of steel plate frame. Peak load at a preload ratio of 0.25 was higher than at ratios of 0 and 0.5. Finite element models were established to consider the live-death elements which can activate and deactivate elements and to verify the experimental results. Based on the observed compressive behavior of rat-trap bond walls and buckling analysis of steel plate frames, the calculation formulas for predicting the compressive peak load were developed. The calculation formulas exhibited acceptable prediction when compared with the experimental results.

Automated summary

This study investigated the reinforcement and compressive behavior of rat-trap bond walls using steel plate frames. The results showed that the steel plate frame effectively enhanced the compressive peak load of the wall, and increasing the steel plate thickness improved compressive strength and confinement effect. Nonlinear relations were observed between the preload ratio and the peak load, and local buckling of the steel plate frame was affected by the preload ratio. Finite element models were used to verify the experimental results, and calculation formulas for predicting the compressive peak load were developed and found to be accurate.