Brief Project Description:

Figure 1: Typical layout of timber bridge half-cap scarf splice joints (dimensions in mm, reproduced from Main Roads Department WA Timber Bridge Construction 1979)

22-006 Figure 1 for adverts

Given this context, the proposed project aims to investigate the structural behaviour and strength capacity of scarf splice joints, through finite element modelling (FEM). Linear and non-linear FEM are planned to be carried out using the ANSYS FEM software. The FEM approach will be calibrated and verified using results of a comprehensive experimental programme of scaled-down laboratory-scale half-cap scarf joints. This experimental testing will be carried out as part of an ongoing separate CEED project at UWA, the results of which will be made available early-on during the proposed project.

In addition, it is planned to investigate, using FEM, the viability of possible simplified retrofit repairs for refurbishing half-cap scarf splices which are displaying signs of distress, but yet are maintaining their structural integrity.


The main objectives of the proposed work are to:

  • Investigate, through a finite element modelling based parametric study, the structural behaviour and strength capacity of half-cap scarf splice joints of timber bridges
  • Recommend modifications or updated formulations to existing codified guidelines for assessing the strength capacity of scarf splices
  • Assess, through finite element modelling, the viability of simplified retro-fit repair methods to refurbish half-cap scarf splices displaying signs of distress

Approach and Scope of Works:

Using a FEM approach, calibrated and verified using experimental data, it is planned to conduct a detailed parametric study of the strength capacity of half-cap scarf splice joints, considering several geometric and material strength parameters pertinent to their structural behaviour. Using the results of the afore-mentioned parametric study, modifications or updated formulations are planned to be proposed to existing guidelines for assessing the strength capacity of scarf splices.

It has been observed that many scarf-splice joints currently in service display cracks emanating from the re-entrant corner but of limited length, which have not led to complete loss of structural capacity and integrity. As such, simplified methods such as the use of bolts and coach screws to remedy such defects are aimed to be investigated through FEM. A limited number of experimental tests of such retro-fitted (scaled-down) scarf-splice joints may also form part of the proposed work, in order to verify the FEM findings.

Benefits to Main Roads:

The proposed study would enable MRWA to establish greater confidence regarding the adequacy and safety of existing unstrengthened timber half-cap splice joints in the WA bridge network. The proposed work will complement and further an ongoing, separate CEED project focusing on experimental testing. The development of realistic methods of assessing the strength capacity of scarf splices would also enable half-cap joint strengthening works to be carried out on a more rational basis, thereby potentially resulting in associated cost savings.