Bolt bearing strength of thin-walled ferrocement

Abstract

This study aims at establishing the bolt bearing strength of ferrocement joints. It describes test results from a total of 90 plate specimens fastened by steel bolts in compression bearing. The main parameters considered were the compressive strength of mortar, volume fraction of reinforcement, plate thickness, diameter and number of bolts, and the size of washer. All tested plates failed in bearing, and the results indicate that an increase in the grade of mortar significantly increases the bearing strength. Similarly, either a decrease in the diameter of bolts or an increase in the size of washers leads to an enhancement in bearing strength, but to a much lesser extent. The effects of plate thickness and volume fraction of reinforcement are practically insignificant. Based on statistical analysis, a simple expression is proposed to predict the bearing strength of ferrocement with a single bolt. In the case of a joint with more than one bolt, loose-fitting bolts may lead to premature failure of the joint. Even for a joint where the bolts are in close fit, the bearing strength is reduced from that of a single bolt. Reduction factors are recommended for joints with two and three bolts placed in a series to account for the group action effect.