Experimental and Numerical Characterization of Monotonic and Cyclic Performance of Cross-Laminated Timber Dowel-Type Connections

Abstract

An immeasurable amount of greenhouse gas emissions during the process of steel purification and concrete production has attracted environmentally friendly engineers’ attention to extend and enhance the use of wood as a structural material. During the last two decades, cross-laminated timber (CLT) has emerged as a high-strength engineered wood product to improve resistance and performance of timber structures, and is being used as a replacement for some mid and low-rise commercial buildings made of concrete and steel in the US. Due to the fact that CLT is a relatively new engineered wood product, there is a lack of knowledge on the mechanical behavior of CLT members and connections. The goal of the present study is to characterize the mechanical properties (specifically shear resistance) of three common types of CLT diaphragm connections including surface spline, half lap, and butt joint, and estimate the behavior of those connections in ultimate limit states, such as earthquake loads, and also serviceability limit states. In doing so, an experimental schedule was developed for a total of 56 tests accounting for different test variables including fastener orientation, type, length, and spacing. More specifically, two types of dowel-type fasteners, namely nail and screw, were considered, while the effect of fastener spacing and inclination was considered by changing the spacing of nails and driven angle of screws. The exerted force and displacement were recorded generating hysteresis curves to assess the failure mechanisms, shear modulus of elasticity, ultimate allowable shear strength and displacement, and energy dissipation of the various connections studied. A finite-element model based on elastoplastic behavior of CLT for a half-lap connection was also developed to estimate the shear behavior of this type of connection numerically and compare it with the experimental findings. Finally, the experimental results were used to compute the optimized hysteretic parameters (and their statistics) for the CUREE-SAWS hysteretic model for further adoption in modeling of diaphragm components by practicing engineers and researchers.