Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

Structures are expected to be designed with the lowest cost and a longer lifetime, without catastrophic service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber exhibits these characteristics and is a more appropriate candidate than most other structural materials, particularly in terms of fire protection, lightness, and seismic resistance. In recent years, timber has been used to design of low-rise commercial and taller residential buildings due to these significant advantages. However, timber degradation can occur as a result of biological decay of the elements and overloading that results in structural damage. Therefore, the load carrying capacity of older timber buildings can be questionable, particularly against lateral boards. This paper investigates damage detection and performance evaluation of older multi-storey timber buildings. In this process a method was implemented in order to provide real-time performance and damage information of a case study building before and after retrofitted improvements. For this purpose, damaged members are identified and then are retrofitted with engineered timber sandwich beams or Sprayed Fibre Reinforced Plastic (SFRP) to extend the life of the structure. Non-linear finite element analysis was carried out to study the behaviour of the structure subject to simulated gravity and lateral loads and to validate the effectiveness of the method of damage detection. This study show that the proposed method is suitable for structural damage detection of aged timber buildings and also the retrofitting methods cited can potentially improve the performance and load carrying capacity of the structure.

Many short span timber beam bridges in regional New South Wales are of unknown reliability, have high traffic loadings and were designed according to codes, many of which have since been superseded. Because asset managers are delaying their maintenance for fiscal reasons, a high proportion of these bridges are structurally degraded and potentially unsafe when excessively loaded. In regional areas, a prioritised maintenance program can be a cost effective alternative to bridge replacement. Such older bridges will require continuous monitoring by low cost methods to assess the temporal probability of their failure. This paper examines the potential for measuring the mid-span deflections of girders caused by high traffic loads to obtain continually updated indicators of the structural health of girders. The mid-span deflection data of a case study bridge were continuously measured using a laser based measuring system, recently developed by the first author. An analysis of the deflection data is used to obtain a reliability index and the probability of bridge failure. Reliability indicators such as these can be used, in conjunction with continuous deflection monitoring, to prioritise cost effective maintenance of older timber bridges in regional New South Wales.

In 2006 the NSW Government announced a Timber Bridge Partnership program to upgrade timber bridges on regional roads. However, limited guidance was available to identify the most cost effective method of upgrading and at the time the most common construction methods available, involved concrete and steel. Hence, despite some timber bridges been replaced by new structures involving timber beams, many engineers and asset managers chose not to use timber. Two reasons for disregarding timber are the lack of adequate data about bridge reliability and lifetime cost. Other reasons relate to lack of knowledge, understanding, skill and confidence in working with timber. Examples are provided, firstly of some NSW bridges that have been part of the NSW Timber Bridge Partnership program and secondly of some overseas structures that have been cited in papers at recent international conferences. The outcomes address some of the research required to improve understanding of how to best upgrade the Australian bridge infrastructure. This paper provides an update and comparison of the state of the art timber bridge design and construction. Novel timber bridges have been recently constructed overseas, but many Australian designs are over 100 years old.

A new method of measuring the mid-span deflections of older timber bridge girders is presented in this paper. There are many timber beam bridges of unknown reliability in regional Australia under high traffic service loadings that were designed according to older codes. In order to identify the current safety index and probability of failure of these girders while in service, it is necessary to measure their deflections under normal and actual loadings. Because of the large numbers of in-service girders that need to be measured, it is important to use a quick, low cost, and easy-to-setup method in the field. A laser-based method is proposed here, which is adjusted to produce an image of the laser on a graduated chart mounted at the mid-span of the bridge girder. The source is mounted on a stable support. Traffic loading deflects the girder and the chart moves up and down in unison. A high speed camera was used to record the movements of the chart relative to the image of the laser. The video recording of the chart movements relative to the laser source was analysed to identify the peak movements. The chart was inscribed so that any movement of the image could be easily read from the graduated scale. It can be inferred from the results that, when the girder is loaded by moving traffic loads, the peak dynamic deflection of a girder can be readily identified.

There are many thousands of timber beam bridges throughout regional Australia, which are monitored primarily by visual inspection. Experience gained from historical failures has led to the clear realisation that visual inspection at intervals of many months or years is insufficient to identify potential failure caused by overloading and biological degradation. A bridge overloaded today can fail tomorrow and there is a need to implement structural health monitoring (SHM) so that the incidence of overloading can be identified soon after it occurs. This need is becoming more vital with the increased expectation to cater for the increased loads during periods of transporting seasonal produce. The measurement mid-span displacement of girders can be used to determine safety indices for the evaluation of structural safety. The detection of real-time damage in timber girder bridges by the use of high-speed camera and laser-based methods offer unique advantages and can lead to low cost measurement techniques. This work reports on the use of continuous monitoring methods for determining the structural reliability of timber-beam bridge girders. Some applications of the use of laser-based displacement sensing systems are discussed in relation to the monitoring of the structural reliability of two older timber beam bridges in regional New South Wales, Australia. Experimental and analytical approaches are presented and used to demonstrate that the probability of failure can be readily determined on a continuous basis using an SHM system.

This paper links past and current research to demonstrate how the structural integrity of timber beam bridge girders can be managed and maintained more effectively. There are a large number of timber beam bridge girders in use on local roads throughout Australia, for which the condition is not well known. For the last decade or so there has been a lack of funding to enable these girders to be maintained in an 'as new' status. The condition of some timber bridges is such that low load limits have been applied because of the difficulty to quantify both the current traffic loads and the girder strengths and not necessarily because the structure is known to be unsafe. Previously measured data, published by others, are evaluated and comparisons made of aged girders comprising a variety of conditions and ages. The wide variation in the values for Modulus of Rupture (MoR) and Modulus of Elasticity (MoE) among the pooled results of previous measurements has not enabled the variation of these parameters to be readily identified for a particular girder. It is inferred from this study that MoE can be used as an indicator of a particular girder's potential MoR and thereby enable useful in-service measurement systems to be created.

This paper reports on the novel use of a high-speed camera to record dynamic movements of a structure under in-service loading without the need for disruptive dedicated proof-loading. For local and state road authorities this represents a significant reduction in resources needed and avoids disruption to existing traffic flow. In regional Australia there are many short span timber beam bridges of unknown reliability. A case study of one multiple span bridge is examined in this paper. Many timber beam bridges were built in the 19th and 20th centuries and were designed to codes that have since been extensively revised. The original design factor of safety for these structures, with new timber, was anticipated to be about five, but full size element testing has historically been used to show that some in-service aged girders have had a factor of safety of about two. Uniform gross vehicle loads have increased and can have significant impact on multiple span bridges. To determine the level of safety for these bridges requires the application of new measurement techniques. The technique used involved a staff, a vernier and a high speed camera. A staff was attached to the mid-span of each girder and its movement monitored with a vernier at ground level. Dynamic movement was recorded with the camera as a vehicle crossed the test-case multi-span bridge at Gostwyck, NSW. The mid-span deflections caused by the test vehicle were compared to data obtained using a simplified SAP2000 model of the bridge and the mid-span influence line inferred.

Any assessment document pertaining to existing bridge infrastructure requires an accurate record of each individual bridge in service, the history of repairs and modification as well as the current state of structural health after each inspection. Bridge inspections need not only be regularly documented, but compared with previous inspections and the probability of ongoing performance assessed. Such knowledge allows the planning of regional sustainability of rural bridges over major and minor transport corridors. This paper examines the variety of timber bridges on rural NSW roads with the data that describe the likely limitations to normal loading. The discussion outlines the level of measurement accuracy required for documenting bridge health and experimental evidence verifying the level of accuracy achievable. Because many timber bridges have had a variety of owners, and society has for many years restricted the funds available for infrastructure maintenance, bridge structural health is poorly understood at any level of quantifiable predictability. Alternative methods of monitoring heavy traffic on rural roads have not been well examined and bridge load limits may often not reflect actual bridge carrying capacity. In the absence of suitable data, some of the structures being replaced may not be the ones at most risk of failure. This is not a new issue and has changed little in the last twenty years. To extend the serviceable life of bridges and to sustain a low probability of structural failure, new low cost measurement systems are required. This paper discusses one such method of measuring mid-span deflection that can be readily used by bridge maintenance crews after short periods of training.