Strengthening and rehabilitation of deteriorated timber bridge girders Justin Dewey a,⇑ , Michael Burry a , Rabin Tuladhar a , Nagaratnam Sivakugan a , Govinda Pandey a , Daniel Stephenson b a College of Science and Engineering, JCU, Townsville, Australia b Rockfield Technologies, Townsville, Australia highlights  Deteriorated timber girders can be rehabilitated using fibre reinforced polymers.  Fibre reinforced polymers enhance the strength and ductility of timber girders.  Timber bridge girders can be rehabilitated using ‘‘off the shelf materials”.  FRP’s increase strength and stiffness by bridging local defects and crack openings. article info Article history: Received 15 August 2016 Received in revised form 3 July 2018 Accepted 11 July 2018 Keywords: FRP Timber Wood Bridge Girder abstract Research has shown that strengthening of degraded rectangular timber is possible via the use of Fibre Reinforced Polymers (FRP). Tests were conducted at James Cook University (JCU) using three round tim- ber girders removed from a railway bridge in North Queensland, Australia. These were retrofitted with either a Carbon Fibre Reinforced Polymer (CFRP) or Glass Fibre Reinforced Polymer (GFRP) composite in one of three different strengthening profiles. Due to extensive deterioration, two of those girders failed during preliminary tests and thus were repaired as opposed to strengthened. The repaired members sus- tained enhanced moment capacity and ductility from their initial failure values. The unbroken girder when strengthened, produced a 30% reduction in deflection for the same moment while bending stiffness was increased by 30% from its initial un-strengthened state. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Until modern times, timber has been the material of choice for building bridges in Australia. There are an estimated 40,000 bridges in Australia with many over their intended design life [1]. Due to an inability to adequately rate these structures many asset managers face the prospect of decommissioning or placing load restrictions on these bridges. Most of these aging structures are in rural areas where detours may amount to hundreds of kilo- meters of extra travel distance. Fibre reinforced polymer (FRP) technology is currently the focus of timber strengthening research around the world. Improvements in flexural and shear strength by using FRP strengthening tech- niques in degraded timber specimens as well as new members have been well documented [2–4]. FRP’s have far superior mechan- ical properties over more traditional materials and can increase strength and stiffness by bridging local defects, confining local ruptures and arresting crack openings [5–7]. FRP display excellent strength to weight ratios and outstanding durability in many envi- ronments [8,9]. Much research has also gone into different FRP configurations. Although many different styles have been tried they are generally a variant of three main techniques. Externally bonded reinforcement (EBR) is a technique whereby FRP is attached to the exterior surface of the timber either through application of an epoxy or utilizing pre-pegging technology [10]. Plevris et al. documented increases in stiffness of 60% using CFRP strips in area percentages as low as 1% [11]. The EBR method can be adapted to increase flexural or shear strength in timber mem- bers [9]. An alternative form is the wet layup technique which involves applying an adhesive to the prepared timber surface before layers of uni- or bi-directional sheets are applied [12]. Mul- tiple layers of sheets may be attached in this way [13]. The EBR method is recommended where time restrictions apply or access to the repair site is limited [7]. Near surface mounted (NSM) FRP involves creating a groove along the length of the member parallel to the grain, filling with a thixotropic glue and placing either stiffened FRP strips or https://doi.org/10.1016/j.conbuildmat.2018.07.064 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: justin.dewey@my.jcu.edu.au (J. Dewey). Construction and Building Materials 185 (2018) 302–309 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat