The use of timber–concrete composite (TCC) bridges in the United States dates back to approximately 1924 when the first bridge was constructed. Since then a large number of bridges have been built, of which more than 1,400 remain in service. The oldest bridges still in service are now more than 84 years old and predominately consist of two different TCC systems. The first system is a slab-type system that includes a longitudinal nail-laminated deck composite with a concrete deck top layer. The second system is a stringer system that includes either sawn timber or glulam stringers supporting a concrete deck top layer. The records indicate that most of the TCC highway bridges were constructed during the period of 1930–1960. The study presented in this paper discusses the experience and per-formance of these bridge systems in the US. The analysis is based on a review of the relevant literature and databases complemented with field inspections conducted within various research projects. Along with this review, a historical overview of the codes and guidelines available for the design of TCC bridges in the US is also included. The analysis undertaken showed that TCC bridges are an effective and durable design alternative for highway bridges once they have shown a high performance level, in some situations after more than 80 years in service with a low maintenance level.
The aim of this document is to report the state of the art in terms of research and practice of Timber-Concrete Composite (TCC) systems, in order to summarize the existing knowledge in the single countries and to develop a common understanding of the design of TCC. This report was made within the framework of WG4-Hybrid Structures within COST Action FP1402. It intends to reflect the information and studies available around the world, but especially in Europe through the active contribution and participation of experts from various countries involved in this Action.
This paper highlights research results from a joint effort between the Forest Products Laboratory (FPL) in the United States of America (USA) and the University of Coimbra (UC) in Portugal (PT). The main objective is the development of a Timber-Concrete Composite system (TCC) that utilizes precast concrete deck panels that accelerate construction times and can easily be removed to facilitate bridge repair/rehabilitation efforts and reuse options. The research is focused on various critical aspects such as the type of interconnection between the concrete deck and the glued laminated timber beams or the interconnection between the precast concrete deck panels. Several practical requirements were addressed that are important to the bridge industry in Portugal and in the USA, such as: accelerated bridge construction time, cost-competitiveness with existing bridge solutions, and eliminating the need for specialized labour skills.
Timber-concrete composite (TCC) solutions are not a novelty. They were scientifically referred to at the beginning of the 20th century and they have proven their value in recent decades. Regarding a TCC floor at the design stage, there are some assumptions, at the standard level, concerning the action of concentrated loads which may be far from reality, specifically those associating the entire load to the beam over which it is applied. This naturally oversizes the beam and affects how the load is distributed transversally, affecting the TCC solution economically and mechanically. Efforts have been made to clarify how concentrated loads are distributed, in the transverse direction, on TCC floors. Real-scale floor specimens were produced and tested subjected to concentrated (point and line) loads. Moreover, a Finite Element (FE)-based model was developed and validated and the results were collected. These results show that the “loaded beam” can receive less than 50% of the concentrated point load (when concerning the inner beams of a medium-span floor, 4.00 m). Aiming at reproducing these findings on the design of these floors, a simplified equation to predict the percentage of load received by each beam as a function of the floor span, the transversal position of the beam, and the thickness of the concrete layer was suggested.
3rd international conference on timber bridges 2017
Research Status
Complete
Summary
The use of timber–concrete composite (TCC) bridges in the United States dates back to circa 1925. Two different TCC systems were constructed during this early period. The first system included a longitudinal nail-laminated deck composite with a concrete deck top layer. The second system included sawn timber stringers supporting a concrete deck top layer. Records indicate that most of the TCC highway bridges were constructed between 1930 and 1960. The current U.S. National Bridge Inventory (NBI) database indicates that there may be well over 1,000 of this bridge type still in service. This paper will review and discuss the current conditions of several TCC bridges that remain in service today. This will be based on the information given in the NBI and other relevant documents, complemented with information provided by 25 field inspections undertaken during June 2016 in the Pacific Northwest states of Oregon and Washington.
Point and line loads are common load cases in slabs, however their effects on timber-concrete composite (TCC) slabs are not fully known. Hence, the importance of investigating the associated structural behaviour and developing technical design rules. For this purpose, an investigation including experimental tests and theoretical analyses was performed. Five composite real scale specimens were built, each one associated with a different parameter whose effect on the load distribution was intended to be analysed. Each specimen was subjected, at a time, to point and line loads over each beam at different locations. Numerical modelling showed good agreement with experimental results and give way to a parameter study. In general, the beam over which the load was applied received the highest share of load and the distribution for the remaining beams is significantly affected by the span.
Cross-laminated timber panels (X-Lam panels) are produced for structural use in Service Classes 1 and 2, in accordance with Eurocode 5 and no producer have been able to certify for use in Service Class 3. The swimming-pools are known to be buildings with high hygrometry and the paper describes the use of X-Lam panels in such use, following a project completed in 2012, in Portugal. X-Lam panels are used within the building, through visible surfaces in walls and ceilings. Constructive solutions are presented in order to discuss the way to deal with the service conditions of the building and two years of continuous monitoring are also presented to analyze the validity of design options.
