Journal Article

The sudden collapse of a 70 year old parallel chord timber truss led to a number of tests and examinations being carried out on wood from the truss. The object of the work was to obtain an insight into the possible cause (or causes) of failure, and to assess the general viability of the remainder of the trusses in the building. The failure almost certainly occurred at the end of a splice joint near the maximum stress region in the lower chord; the splice utilized rectangular steel keys and cover plates and was typical of a design due to Percy Allan, a prominent Australian Bridge designer in the early 1900's. A number of factors are discussed which have influenced the wood strength in this region. Some previous breakages of a similar type of joint have been reported, and shrinkage stresses created in the joint and low fracture stresses at notches are considered to have been major contributory factors in the failure on this occasion.