Timber elements, such as timber bridges, are exposed to heavy loads. Therefore, reinforcement might be useful. Due to a lack of wood supplies, poplar, a fast-growing tree, could be used to construct CLT (cross-laminated timber). The low density of fast-growing wood species directly impacts the mechanical properties of CLT. Therefore, in this study, a CLT panel was reinforced with GFRP (glass-fiber-reinforced polymer), and the lateral resistance of double shear lap joints in reinforced CLTs with 0-90-0° arrangements in two strength directions was investigated. Lag screws (Ø = 8 mm) at the end distances of 1 and 3 cm were employed for making the lateral test specimens. First, the effect of the number of GFRP layers on lateral resistance of the joints was investigated. The results revealed that, as the number of GFRP layers changed from one to three, the lateral resistance increased by 45.47%, and then, by four layers, it decreased by 1.3%. Since the joints with three layers of FRP had the highest strength, the effects of the end distance and the CLT panel strength directions on the lateral performance of the reinforced and non-reinforced specimens were investigated. The results indicated that the lateral resistance of reinforced CLTs with GFRP was about 26.5% more than the unreinforced ones. Moreover, CLTs in the major strength direction showed 4.2% more lateral resistance than those in the minor strength direction. Moreover, lag screws at the end distance of 3 cm had 60% more lateral resistance than those at the end distance of 1 cm. In terms of failure modes, bearing, shear, and net-tension modes were observed in the CLTs, while Is, IIIs, and IV modes were observed in the lag screws.
Although a much smaller market than housing, there is a long history of building bridges in wood. For many years, short span bridges particularly for resource roads or roads to access recreational areas were built in timber or glued-laminated timber. While some of these bridges still exist today, many have been replaced with concrete or concrete-on-steel solutions. Along with this decline in new timber bridges is the loss of expertise in timber bridge design and construction, and the adoption of new timber construction technology.
Given the continuing efforts underway to develop the market for the use of mass timber in building construction, restoring the use of timber in bridges can complement this effort and help to provide more opportunities for the developing mass timber supply chain.
Modern timber bridges have shown that timber is a durable option for primary structural members in highway bridges and can perform satisfactorily for 50 years or longer when properly designed, fabricated and maintained. However, various cost assumptions have indicated that timber bridges are more expensive than concrete bridges. This project was undertaken to better understand the benefits and costs of using timber bridges as a viable substitute for other bridge construction materials and designs. Two demonstration construction projects were completed to develop comparative information. A steel girder with a transverse glulam deck bridge with a curbless, crash-tested railing system was built, and a spike-laminated longitudinal deck bridge was constructed. Both projects were completed and allowed for a good comparison to be developed both in terms of project-specific cost and the time required for bridge construction completion. These projects showed that the main advantage of a timber bridge is the speed of superstructure construction with the other costs similar to that of other materials. It is clear from previous case studies, interviews with engineers, contractors, and suppliers, and the projects that timber superstructures can be installed within days to weeks, compared to months for other materials.
Stress-laminated timber (SLT) decks in bridges are popular structural systems in bridge engineering. SLT decks are made from parallel timber beams placed side by side and pre-stressed together by means of steel rods. SLT decks can be in any length by just using displaced butt joints. The paper presents results from friction experiments performed in both grain and transverse direction with different levels of pre-stress. Numerical simulations of these experiments in addition to comparisons to full-scale experiments of SLT decks presented in literature verified the numerical model approach. Furthermore, several alternative SLT deck configurations with different amounts of butt joints and pre-stressing rod locations were modelled to study their influence on the structural properties of SLT decks. Finally, some recommendations on design of SLT bridge decks are given.
Properly designed wooden truss bridges are environmentally compatible construction systems. The sharp decline in the erection of such structures in the past decades can be led back to the great effort needed for design and production. Digital parametric design and automated prefabrication approaches allow for a substantial improvement of the efficiency of design and manufacturing processes. Thus, if combined with a constructive wood protection following traditional building techniques, highly efficient sustainable structures are the result. The present paper describes the conceptual design for a wooden truss bridge drawn up for the overpass of a two-lane street crossing the university campus of one of Vienna’s main universities. The concept includes the greening of the structure as a shading design element. After an introduction, two Austrian traditional wooden bridges representing a good and a bad example for constructive wood protection are presented, and a state of the art of the production of timber trusses and greening building structures is given as well. The third part consists of the explanation of the boundary conditions for the project. Subsequently, in the fourth part, the conceptual design, including the design concept, the digital parametric design, the optimization, and the automated prefabrication concept, as well as the potential greening concept are discussed, followed by a summary and outlook on future research.
Timber bridges have a long history of construction and use throughout North America, including Ontario, for roadways, railways and logging roads. The Canadian Highway Bridge Design Code (CHBDC), together with the Canadian Wood Council publication Wood Highway Bridges from 1992 are typically referenced by designers of timber bridges in Ontario. This new reference is intended to provide updated background information for designers as they embark on proposing and designing timber highway bridges for primary and secondary roads.
This reference is divided into three parts:
Part 1 – Wood Bridges – Design and Use
Part 2 – Opportunities & Current Limitations
Part 3 – Design Examples
Part 1 provides background information on topics including wood materials, bridge systems, prefabrication, durability and species availability. Details of costs, construction cycle and sustainability are also provided. Part 1 concludes with examples of a variety of completed highway bridges from North America and Europe.
Part 2 of this reference is intended to provide designers and authorities with highlights of the current edition of the CHBDC on subjects related to the wood highway bridges, including areas that will require future development in the code. Additional references to other resources for advancing practitioner knowledge of and advancing the state of the art in wood bridge design are provided.
Part 3 has two fully worked design examples of a two-lane 18-m span wood highway bridge designed in accordance with the latest provisions of the CHBDC and the best available information from current literature. Each example is based on a single-span, simply-supported glued-laminated girder bridge. One bridge has a glued-laminated deck and the other has a stress-laminated deck. These examples are intended to help designers understand the key issues as they undertake wood highway bridge design. Durability through detailing and choice of materials is discussed.