A new joint to assemble light structures of bamboo slats

Abstract

Guadua angustifolia (GA) is an American species of bamboo. It is a sustainable anisotropic material that exhibits high strength along the longitudinal direction of the culm and low strength on the planes of the fibers, which usually leads to premature fissures and failure in the joints of GA structures. Based on the ductile behavior of the material under compression along the thickness of the culm or radial direction, a new joint to connect GA slats was developed. The joint connects two GA slats by using two small curved steel plates, a bolt, and a nut, which are used to apply high compressive deformation in the radial direction. Experiments of the proposed joint showed about a twofold significant increase of strength with respect to a joint without radial compression. To further determine the performance of the joint, two beam prototypes were developed and tested. First, a small beam of 0.93m length and 70N weight that was loaded under three point bending supported a maximum load of 15,500N and failed by buckling and subsequent rupture of a compression element. Next, a prototype of about 3m length and 310N weight that was tested under a 12,000N distributed load showed maximum deflections of about 18mm and complete integrity of the joints and the compression elements. Deflections under constant loading were about 30% of the total for the nine days of testing. Experiments of the beams showed full integrity of the proposed joint, which is a feasible alternative to produce light prefabricated trusses to support house floors and roofs. This joint is a first step for the improvement of structural connections of GA elements, with the intention to extend this idea to join whole culms.