The most common type of bridges on South Dakota (SD) local roads are prestressed precast double-tee bridges. Currently, there is only one double-tee girder manufacturer in South Dakota (SD). In an attempt to provide more bridge type selection options for local governments, a study was performed at South Dakota State University to investigate the feasibility and performance of new types of single-span bridges suitable for local loads with low traffic. In one part of the study, Mingo (2016) developed a fully precast bridge incorporating full-depth deck-panels and prestressed inverted bulb-tee girders. The study presented in this thesis was performed to investigate the feasibility and performance of glulam timber bridges as additional design alternatives for SD local roads. There are two types of glulam timber bridges: (1) transverse glulam deck on glulam girders and (2) longitudinal glulam deck. The performance of each type was experimentally investigated through full-scale testing. The full-scale glulam girder bridge test model was 50-ft long and 9.25-ft wide. The full-scale glulam slab bridge was 16.5-ft long and 8-ft wide. Both bridges were first tested under the AASHTO Fatigue II limit state loading followed by strength testing. Both bridge types showed minimal damage during the fatigue testing. The only damage of the girder bridge was cracking of male-to-female deck-to-deck connections, which can be eliminated using flat-end panels. Ultimate testing of the two bridge systems confirmed that the AASHTO method of the design for timber bridges is adequate. Girders of glulam girder bridges should be designed as fully non-composite members. Furthermore, design and construction guidelines for both types of bridges were proposed. A cost analysis showed that the superstructure cost of glulam timber bridges and glulam slab bridges can be 70% and 50% respectively of that for double-tee bridges. Based on the construction, testing, and cost analysis, it can be concluded that both types of glulam timber bridges are viable alternatives to the double-tee girder bridges.
Project contacts are James Wacker at the Forest Products Laboratory, Justin Dahlberg and Brent Phares at Iowa State University
The use of cross-laminated timber (CLT) has gained popularity over the past decade, with many advances stemming from completed research and construction projects in Europe. Many inherent advantages of CLT (such as, it is prefabricated, relatively lightweight, dimensionally stable, and environmentally sustainable) have been utilized in vertical construction projects. Despite these advances, the use of CLT in bridge structures has been limited, and the adoption of CLT into governing design codes has been slow. However, CLT shows promise as a complementary or alternative construction material in bridge decks, and additional research would help characterize the structural attributes of CLT decks to guide their use in bridge projects.
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.
This review article presents a state-of-the-art survey on timber-concrete composite (TCC) bridges. It starts with a presentation of a sample of relevant TCC bridges, offering a global perspective on the use of this type of bridge. The number of TCC bridges has clearly increased in the past few years, and some of the reasons for this trend are explored. Next, an extensive literature review is presented regarding the most significant technological innovations and recent developments in the application of TCC structures to bridge construction. Firstly, the engineering specificities and the advantages of TCC bridge structural systems are enumerated. Afterwards, the importance of proper mechanical connection for optimal performance of TCC structures is explained, and a thorough description of the connection systems suitable for bridge construction is provided. Some research into the structural behavior of TCC bridges under service conditions is then presented and discussed. Finally, possible areas of future research regarding the development of TCC bridges are suggested.