Design, Construction, and Quality Control Guidelines for Stress-Laminated Timber Bridge Decks

DTFH61-90-00067This publication is part of a collection of three booklets of the study "Education and Technology Transfer", under the Timber Bridge Research Program. The other two booklets are: FHWA-RD-92-044 - Corrosion Protection of Steel Hardware Used in Modern Timber Bridges; and FHWA-RD-93-024 - Timber Substructures for Bridge Applications.Under the U.S. National Timber Bridge Initiative Program, sponsored by Congress in 1989 and administered by the United States Department of Agriculture, Forest Service, approximately 130 modern timber bridges are currently in service in 41 participating States. Most of these bridges use stress-laminating technology. Considerable research on stress-laminating technology has been completed in the USA and has provided design, construction, and inspection guidelines for timber bridge decks. Guidelines for the design of stress-laminated timber decks have been published by AASHTO, but they do not provide comprehensive information on materials, construction, and inspection. Therefore, this document presents: (1) background information on timber bridge materials and their quality control; (2) a comprehensive step-by-step design procedure based on the 1991 AASHTO Guide Specification; and (3) guidelines for construction, field monitoring, inspection, and maintenance procedures. Potential fabrication problems are discussed, and an inspection checklist is included

The impacts of climate change on expansive soil movements in Australia

The effect of climate change on expansive soil movement has long been the greatest global challenge for built infrastructures. Numerous lightly-loaded residential buildings constructed on expansive soils are subjected to distortions arising from differential ground movements due to seasonal soil moisture (suction) changes. Thornthwaite Moisture Index (TMI) has been widely employed by geo-technical engineers to quantify expansive soil movement resulted from climatic variation. lt is difficult to estimate the patterns of future soil movement due to the inherently highly variable nature of Victorian (Australia) climate, but it is likely that with the collected precipitation and temperature data, the TMI can be derived to infer depth of design soil suction change (Hs) which allows the characteristic ground movement (Ys) to be estimated. This paper outlines an overview of residential footing design in Australia. Three TMI isopleth maps of Victoria are also developed for the convenience of TMI users to infer Hs

Timber Substructures for Bridge Applications

DTFH61-90-C-00067Timber bridges have become a viable alternative for new bridge construction on low-volume roads, where it is imperative that the bridges be economical and long-lasting. Considerable research on superstructural systems has been completed in the U.S. and has provided design, construction, and inspection guidelines for innovative timber bridges. Guidelines for the design of stress-laminated timber decks have been published by AASHTO. However, practical recommendations concerning timber substructural systems are not readily available. Therefore, the objectives of this booklet are: (1) to present background information on timber substructures, (2) to present practical design guidelines for various systems, (3) to recommend guidelines for construction and inspection procedures, and (4) to present sources of additional information on timber substructures for bridge applications. The following five systems were selected: timber piles, steel bent-pile abutments, culverts, crib-wall abutments, and stub abutments. This publication is part of a collection of three booklets for the study "Education and Technology Transfer", under the Timber Bridge Research Program. The other two booklets are: FHWA-RD-92-044 - Corrosion Protection of Steel Hardware Used in Modern Timber Bridges (TRIS 636308); and FHWA-RD-91-120 - Design, Construction, and Quality Control Guidelines for Stress-Laminated Timber Bridge Decks (TRIS 636334)

Strengthening Historic Covered Bridges To Carry Modern Traffic

DTFH61-00-C-00081In this research project, the Constructed Facilities Center (CFC) and the Institute for the History of Technology and Industrial Archaeology (IHTIA) of West Virginia University (WVU) teamed up to develop means and methods to strengthen wooden superstructure components of historic covered bridges, using glass-fiber reinforced polymer (GFRP) composite materials. The strengthening methodologies developed in this project were designed to conform to the Secretary of the Interior\u2019s Standard for Historic Preservation. Specifically, tension and bending tests were conducted to establish the bond strength of GFRP rebars embedded in wood, and to establish the bending strength and stiffness of large-scale floor beams reinforced with GFRP pultruded plates and with GFRP rebars. In addition, methods were developed to enhance the shear capacity of large-scale floor beams reinforced with GFRP pultruded plates bonded on edge in narrow, prerouted vertical slots. The GFRP rebars were developed to be used specifically as axial reinforcement for truss members, while the GFRP were developed to increase the bending and shear capacity of floor beams. The test results showed bonded-in GFRP rebars performed very well in terms of pullout force and bond strength, and the strength and stiffness of GFRP-reinforced floor beams improved significantly. Although the shear strength was also expected to improve considerably with the addition of the GFRP plates placed on edge (resulting in a flitched beam), the shear capacity decreased slightly. The flitched beams tested were severely checked, which degraded their shear strength as compared to the solid control specimen. Further testing will continue in a succeeding study. Additionally, during this research, several methods of concealing the reinforcement were investigated. One successful method took advantage of routing a member on the bottom face and bonding a GFRP plate with an integrated veil to match the wood grain and color of the original aged wood