Performance of bolted steel laminated bamboo lumber connections under axial cyclic loading

Bolted connections are well known for their simplistic design and installation, and have been used in bare frame structures of various types of materials including steel and timber. Compared with monotonic loading, cyclic loading is more dangerous. Bamboo has excellent toughness and deformation recovery ability but a quantitative description of the mechanical performance of bolted steel laminated bamboo lumber (LBL) connections under cyclic loading has not yet been determined. As a result, tension and compression tests were carried out separately under axial cyclic loading. Obtained experimental results indicated that the tensile specimens suffer brittle failure because of the premature cracking of LBL due to cyclic loading; the bolts remained almost straight after failure. On the other hand, cyclic compressive specimens showed considerable ductile behavior as the bolts underwent plastic deformation since LBL sustained considerable load prior to failure due. Key mechanical connection parameters such as elastic stiffness, yield and ultimate displacement, yield and ultimate load, ductility ratio obtained from the skeleton curves were carefully analyzed to study the influence of bolt number on various properties. The increase in elastic stiffness from two to four bolts is about 60 % for the cyclic tension specimens, whilst that was about 25 % for the cyclic compression specimens. Compared with the cyclic tensile specimens, cyclic compressive specimens have higher ductility ratio, which is mostly greater than 2. In addition, theoretical models for both loading and unloading curves have been proposed, which showed good agreement with test results.