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.
The Petawawa Research Forest (PRF) was established in 1918 and is the oldest research forest in Canada. It is located along Highway 17, east of Chalk River, Ontario, and is part of Garrison Petawawa under the jurisdiction of the Department of National Defence. By special agreement, it is managed by the Canadian Wood Fibre Centre, under the Canadian Forest Service, Natural Resources Canada. The research undertaken at the PRF influences forest policy, industry, silvicultural practices, and private forest management practices across the country. Operational commercial harvests also occur at the PRF.
Meridian Road is an access road at the PRF and leads to research, forest management, and recreational sites. A multi-cell culvert system at Young’s Creek recently failed (bottom left), and the crossing needed large-scale maintenance to allow the continued movement of logging trucks, vehicles, and research teams. The culvert failure negatively impacted water flow and habitat. To rectify these issues, a modern, single-lane engineered wood product (EWP) bridge, named Centennial Bridge (bottom right), was installed and built by Corington Engineering Inc., of Renfrew, Ontario. The experience at the PRF is of interest to sustainable forest licence (SFL) holders (and municipalities) looking to gain more knowledge about the construction and design of EWP access road bridges. The goal of this case study was to highlight the main construction and design details of Centennial Bridge and draw some comparisons to conventional steel-logging road bridges.
Nationwide, bridges are deteriorating at a rate faster than they can be rehabilitated and maintained. This has resulted in a search for new methods to rehabilitate, repair, manage, and construct bridges. As a result, structural health monitoring and smart structure concepts have emerged to help improve bridge management. In the case of timber bridges, however, a limited amount of research as been conducted on long-term structural health monitoring solutions, and this is especially true in regards to historic covered timber bridges. To date, evaluation efforts of timber bridges have focused primarily on visual inspection data to determine the structural integrity of timber structures. To fill this research need and help improve timber bridge inspection and management strategies, a 5-year research plan to develop a smart timber bridge structure was undertaken. The overall goal of the 5-year plan was to develop a turnkey system to analyze, monitor, and report on the performance and condition of timber bridges. This report outlines one phase of the 5-year research plan and focuses on developing and attaching moisture sensors onto timber bridge components. The goal was to investigate the potential for sensor technologies to reliably monitor the in situ moisture content of the timber members in historic covered bridges, especially those recently rehabilitated with glulam materials. The timber-specific moisture sensors detailed in this report and the data collected from them will assist in advancing the smart timber bridge.
An innovative concept for a modular timber concrete composite system for short span highway bridges has been designed and key components experimentally validated. The proposed system consists of a Ultra-High Performance Fibre Reinforced Concrete(UHPFRC) deck and glue-laminated timer (glulam) girders linked to act compositely together by reinforcing steel bar shear connectors. This composite system has light, stable modules that can be rapidly constructed on site with less special equipment. Simple design checks indicate that the concept satisfies all serviceability limit state(SLS) and ultimate limit state(ULS) requirements of the Canadian Highway Bridge Design Code. Pull-out tests characterized the embedment lengths of 20M steel bar connectors to be 10 bar-diameters in UHPFRC. Push-off tests determined the embedment lengths of the same bars to be 30 bar-diameters glued into the timber girders. The slip modulus of the connectors is determined to be 67 kN/mm. The stiffness of the crosswise self-tapping screw connectors were tested and found to be structurally insignificant in this application. The excellent tensile and cracking properties of the reinforced UHPFRC deck was experimentally verified. A small amount of reinforcement would further improve the ductility of the UPHFRC deck system.
International Nondestructive Testing and Evaluation of Wood Symposium
In this report, wooden members of sizes typically used in bridge construction are examined using x-ray computerized tomography (CT) to determine the presence of internal decay. This report is part of an overall study in which Douglas-fir (Pseudotsuga menziesii) glue-laminated (glulam) beams and solid sawn timbers were inoculated with brown rot fungus, Fomitopsis pinicola, and exposed to aboveground conditions approximately 25 miles (40 km) north of Gulfport, Mississippi, USA. The goal of the overall study is to develop interior decay within the test specimens and then identify and characterize the decay using a variety of nondestructive testing (NDT) techniques. One NDT technique used is x-ray CT. The pixel brightness (PB) of CT scan images is proportional to the specific gravity (SG) at that location; high SG materials appear brighter whereas low SG materials appear darker. The consumption of wood by fungus decreases the wood SG; however, fungal progression takes place in areas where sufficient moisture is present. The presence of moisture increases wood SG as detected by the CT scan, which masks the effect of the fungal decay, which is a common co-occurrence with many NDT techniques. To identify incipient decay, it is necessary to examine the ring structure both within and outside of the area of moisture. Quantifying the extent of the decay requires correlating the PB to known SG values for both dry wood and wood of varying moisture content. In this report, the relationship between wood SG, moisture content, and PB was quantified.