Strengthened of Wooden Trusses Structure and Retrofitting Methods to Increase Load Capacity

ABSTRACT: Assessing damage after strong earthquakes, several wooden truss structures were found to be affected, with failures including dislocation of truss supports, displacement between purlins and truss frames, and damage at the joints themselves. This study examines types and causes of damage and investigates strengthening and retrofitting methods for roof truss elements based on damage level, applicable techniques, and suitable materials. Damage data were obtained from field assessments of wooden trusses after major earthquakes in Indonesia and elsewhere, as well as from segmental testing of truss joints. Failures in tension, compression, shear, and support were primarily attributed to insufficient and improperly configured connectors, as well as aging and inadequate wood preservation. Conventional strengthening using wood, iron, stainless steel, steel wire/cable, and additional connectors (pegs, nails, screws, bolts, steel plates, toothed plates, and anchors) effectively increased strength and stiffness, but did not significantly improve ductility. Alternative materials such as resin-based and polyurethane/polyether adhesives and healed wood showed potential, increasing ductility and strength by 20–40% compared to conventional systems. Retrofitting L-joints with strip plates, C70.35.0.45 stainless steel, and L35.35.3 profiles increased maximum load capacity with ratios of 1.25, 1.64, and 1.87, respectively.