Engineered bamboo, produced through the technique of gluing and reconstituting, has better mechanical properties than round bamboo and some wood products. This paper studies the flexural performance of laminated beams produced with timber and engineered bamboo. The six-layer beams were made from Douglas fir, spruce, bamboo scrimber and laminated bamboo, or a combination of these. It is confirmed that glued-laminated wood beams producedwith wood of weak strength, like spruce, can be strengthened by gluing engineered bamboo lumbers on the outer faces, thus achieving better utilization of the fast growing economic wood species. Flexural failure of the laminated beams was primarily triggered by tensile fracture of the bottom fiber in mid-span, followed by horizontal tearing beside the broken surface. No relative slip between layers was observed before failure, therefore the flexural capacity of the laminated beams can be predicted using equilibrium and compatibility conditions according to the plane section assumption
An analysis of glued composite timber-concrete systems is presented. Experimental data obtained from laboratory tests under short-term loading are compared with the analytical calculation and the design procedure for fully composite beams given in the EN 1995-1-1 standard. Numerical linear 2D finite element modelling and an analytical solution assuming linear elastic behaviour of glue and the interlayer slip are also conducted and validated. The effect of composite action in the three mentioned approaches is assessed by comparison of midspan deflections. In this way, a parametric study of the glue-line properties and the interlayer slip stiffness on load-carrying capacity and serviceability of glued composite beams exposed to short-time loading is easily performed.
This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.
The development of wide-span structures occurs high reaction forces at the bearings. The load-bearing capacity is strongly limited, because of the low compression strength and stiffness of wood perpendicular to the grain. One common possibility of strengthening the support is the application of self-tapping screws ,. Subject of the presented research project is the study of a new, practicable and quite easy to manage type of reinforcement for load transfer areas. To increase the load carrying capacity drill holes and block shaped areas filled with polymer concrete are inserted into the timber. Due to the rigid bond between wood and polymer concrete as well as a geometrical adaption to the stress distribution, it is possible to increase the load carrying capacity and the compressive stiffness significantly compared to conventional reinforcement by self-tapping screws.
First inchoate versions of bearing reinforcement have been designed and used very successfully as part of another research project to increase the bending capacity of glulam beams by hybrid material composites ,. Figure 1 shows one example of the tested designs. The diagram in Figure 2 illustrates the increase of the transversal load bearing capacity compared to FE-simulation of the same member without reinforcement.
Timber-Concrete Composite (TCC) systems have been employed as an efficient solution in medium span structural applications; their use remains largely confined to European countries. TCC systems are generally comprised of a timber and concrete element with a shear connection between. A large number of precedents for T-beam configurations exist; however, the growing availability of flat plate engineered wood products (EWPs) in North America has offered designers greater versatility in terms of floor plans and architectural expression in modern timber and hybrid structures. The opportunity exists to enhance the strength, stiffness, fire, and vibration performance of floors using these products by introducing a concrete topping, connected to the timber to form a composite. A research program at the University of British Columbia Vancouver investigates the performance of five different connector types (a post-installed screw system, cast-in screws, glued-in steel mesh, adhesive bonded, and mechanical interlocking) in three different EWPs (Cross-Laminated-Timber, Laminated-Veneer-Lumber, and Laminated-Strand-Lumber). Over 200 mid-scale push-out tests were performed in the first stage of experimental work to evaluate the connector performance and to optimize the design of subsequent vibration and bending testing of full-scale specimens, including specimens subjected to long-term loading.
An extensive body of research is currently available on the behaviour of concrete and steel structures when subjected to blast threats, however, little to no details on how to address the design or retrofitting of wood structures are available. In this paper, preliminary results, both experimental and analytical, are presented on the flexural behaviour of glulam beams under high strain rates. A total of three 80 mm x 228 mm x 2,500 mm glulam beams with a clear span of 2,235 mm were subjected to simulated blast loads using a shock tube. The preliminary experimental results showed that a brash tension failure mode was observed on the tension laminate. It was also shown that a simplified SDOF model, using linear elastic resistance curves, was capable of predicting the failure displacement and level of damage with reasonable accuracy.
April 14-16, 2011, Las Vegas, Nevada, United States
Wood-concrete composite systems are well established, structurally efficient building systems for both new construction and rehabilitation of old timber structures. Composite action is achieved through a mechanical device to integrally connect in shear the two material components, wood and concrete. Depending on the device, different levels of composite action and thus efficiency are achieved. The purpose of this study was to investigate the structural feasibility and effectiveness of using truss plates, typically used in the making of metal-plate-connected wood trusses, as shear connectors for laminated veneer lumber (LVL)-concrete composite systems. The experimental program consisted of two studies. The first study established slip-modulus and ultimate shear capacity of the truss plates when used in an LVL-concrete push out assembly. The second study evaluated overall composite bending stiffness and strength in two full size T-beams when subjected to four-point bending. One beam employed two continuous rows of truss plates and the other employed one row. It was found that the initial stiffness of both T-beams was similar for one and two rows of truss plates but that the ultimate capacity was approximately 20% less with the use of only one row.