Cyclic response of multiple bolted connections

Because of it’s economy, high strength-to-weight ratio and stiffness-to-weight ratio, wood can compete with steel and reinforced concrete as a construction material in a market with an increasing demand for large structures such as community buildings, gymnasiums, schools and bridges. However, continued acceptance or expansion in this market, particularly in high wind or seismic areas, depends upon an expanded scientific knowledge about wood systems. It is well established in the literature that the critical element to system performance under cyclic earthquake or wind loads is the connection. Bolted joints are a principal connector used in wood structures due to the ease of fabrication and economy. Behavior of bolted connections is well known in steel. Yet, the behavior of bolted connections in wood structures is extremely complex and influenced by several variables. Strength, damping ability, and ductility of wood connections are central to a safe and reliable response of wood structures subjected to wind, seismic, and occupancy loads. Recently, researchers have developed analytical tools to predict wood system response under dynamic loads. Mandatory input to these models is the cyclic load-deformation or hysteresis response of connections containing fasteners such as nails and bolts in configurations typically encountered in construction. Previous investigations have focused primarily on single-bolted connections subjected to one-directional loads, and little, if any, research has been reported that explains the effects of load distribution in multiple-bolted connections under reversed cyclic loading. This paper presents part of an ongoing project that was designed to quantify the cyclic performance of multiple–bolted connections with wood members, and to determine the effect of bolt number on load distribution and performance variables, which is accomplished through an analytical model. The experimental program described here is still ongoing and results will be used to validate the model.