This Chapter provides general information about the manufacturing of CLT that may be of interest to the design community. The information contained in this Chapter may also provide guidance to CLT manufacturers in the development of their plant operating specification document. Typical steps of the CLT manufacturing process are described, and key process variables affecting adhesive bond quality of CLT products are discussed. The manufacturing, qualification, and quality assurance requirements in accordance with the American National Standard for Performance-Rated Cross-Laminated Timber, ANSI/APA PRG 320, are discussed.
Cross-laminated timber (CLT) products are used as load-carrying slab and wall elements in structural systems, thus load duration and creep behavior are critical characteristics that must be addressed in structural design. Given its lay-up construction with orthogonal arrangement of layers bonded with structural adhesive, CLT is more prone to time-dependent deformations under load (creep) than other engineered wood products such as structural glued-laminated timber. Time dependent behavior of structural wood products is addressed in design standards by load duration factors that adjust design properties. Since CLT has been recently introduced into the North American market, the current design standards and building codes do not specify load duration and creep adjustment factors for CLT. Until this can be rectified, an approach is proposed in this Chapter for adopter of CLT systems in the United States. This includes not only load duration and service factors, but also an approach to accounting for creep in CLT structural elements.