Project contact is Luca Sorelli at Université Laval
Summary
Hybrid wood-concrete structures are emerging in the multi-storey wood building market, as they provide effective solutions in terms of lightness, rigidity, vibration and fire resistance (Yeoh et al., 2010, Dagenais et al., 2016). This project aims to reduce the cost of these hybrid floors by reducing the time of construction by prefabrication technology with emphasis on use. In addition, the goal is to explore the use of Ultra High Performance Fiber Composite Concrete (UHPC) to reduce the thickness of the wood slab, and also the use of ductile connections to increase the reliability of the floor (Habel and Gauvreau). 2008, Zhang and Gauvreau 2014, Auclair-Cuerrier et al 2016a). Finally, the concrete slab improves the diaphragm behavior of the floor to seismic actions.
Timber as a primary structural material has been forced to continually evolve to keep abreast with the changing demands of the construction industry. This paper presents further research undertaken by Queen’s University Belfast to evaluate the advantages provided by the post-tensioning of timber members using novel basalt fibre reinforced polymer (BFRP) rods. Using the high strength, low density, highly durable BFRP tendons experimental investigations utilising the four-point bending method were conducted and monitored. From the experimentation it was found that there was an increase in load carrying capacity, a more favourable ductile failure mode and a further benefit of less net deflection due to the precamber induced by the post-tensioning prior to load application.
This paper presents the preliminary design of a rocking Cross-laminated Timber (CLT) wall using a displacement-based design procedure. The CLT wall was designed to meet three performance expectations: immediate occupancy (IO), life safety (LS), and collapse prevention (CP). Each performance expectation is defined in terms of an inter-story drift limit with a predefined non-exceedance probability at a given hazard level. U-shape flexural plates were used to connect the vertical joint between the CLT panels to obtain a ductile behavior and adequate energy dissipation during seismic motion. A design method for ensuring self-centering mechanism is also presented.
This paper presents an experimental study on ductility and overstrength of dowelled connections. Connection ductility and overstrength derived from monotonic testing are often used in timber connection design in the context of seismic loading, based on the assumption that these properties are similar under monotonic and cyclic loading. This assumption could possibly lead to non-conservative connection design. Therefore, it is necessary to quantify ductility and overstrength for cyclic loading and contrast them with their monotonic performance. For this purpose, monotonic and quasi-static cyclic experimental tests were performed on dowelled LVL and CLT connections. The experimental results were also compared with strength predictions from state-of-the-art analytical models in literature that were verified for ductile and brittle failure under monotonic loading. This work also allowed investigation into a generally applicable overstrength factor for push-pull loaded dowelled connections.
In this study, five full-scale bolted glulam beam-to-beam connections with slotted-in steel plates were conducted under a third-point loading, and a three-dimensional finite element method based model was also established to investigate the failure modes and moment resistance of such connections. A material model based on the Continuum Damage Mechanics (CDM) theory was developed to predict damage evolution of wood. Different damage variables were used to consider the ductile and brittle failure modes of wood, respectively. The test results indicated that splitting and shear plug failures were the main failure modes. The numerical analysis model prediction achieved fair agreements with the test results. The research could provide the guide for the design of bolted beam-to-column connections in heavy timber structures.
Timber construction has experienced considerable progress in recent years. In such progress, apart from the implementation of new engineered timber products, the advancement of timber joints has played a significant role. The design procedures for timber connections in most design codes are based mainly on the yielding capacity of the fasteners using the European Yield Model (EYM). While the EYM theory provides accurate predictions for connections that fail in a ductile fashion, it does not take into account the failure of the connections due to the brittle rupture of wood as the consequence of fasteners group effect. Such a significant gap in the design of connections also applies to the New Zealand (NZS 3603) and Australian (AS 1720.1) timber design standards. A new design approach is presented which allows the practitioners to predict the connection capacity associated with different brittle wood failure mechanisms. An extensive testing regime has been conducted on high load-transfer capacity joints using timber rivets under longitudinal and transverse loadings on New Zealand Radiata Pine laminated veneer lumber (LVL) and glulam. The results verify the proposal and prove its reliability. A design guide was also developed which could eventually become a design clause in the next revision of the New Zealand timber design standard NZS 3603.
In the last 15 years timber-concrete composite (TCC) systems have gained market share around the world. To facilitate acceptance of this construction method and to set basis for building TCC bridges in the Province of Quebec, the authors conducted a test program on TCC beams with continuous shear connectors. It included push-out tests on the connection and static bending tests on single-T TCC beams with 4-m and 12-m span and on double-T beams with 4-m span. The goal was to study the elastic and post-elastic performance and failure induced by the connector, analyse the relationship between the interface slip and the flexural behav iour and compare the test results with the predictions using design and analysis methods. The tests on beams with the continuous shear connector showed that it is possible to achieve high degree of the composite action between the concrete slab and timber beam followed by plastic deformation and failure of the connector inducing a ductile performance of the beam required in bridge design. The use of linear and non-linear analysis methods allows predicting the observed structural response of the TCC beams.
This paper presents an experimental and analytical investigation on the application of laminated veneer lumber (LVL) made of European beech wood (fagus sylvatica L.) in timber truss structures. Particular focus is laid on developing improved design approaches for dowel-type connections and on promoting ductile failure behaviour, as the connections in timber trusses are generally governing the performance of the whole structure. Embedment tests were carried out in order to assess the embedment strength values for beech LVL, which are necessary to design dowel-type connections. The results showed higher values for beech LVL, as compared to estimations using existing formulas from design codes. A series of tensile connection tests showed that, using cross-layered beech LVL, ductile dowel-type connections with high load-carrying capacities can be designed, given that premature brittle failures are prevented. Lastly, tests on full truss structures confirmed that the favourable behaviour of dowel-type connections in cross-layered beech LVL can be implemented in truss systems, improving the global behaviour of the whole structural element.
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