The objectives and scope of this study are to conduct long-term experimental test on timber-concrete composite beams, analyse the results to determine the creep coefficient of the composite system and compare the experimental results with the analytical solutions in accordance with Eurocode 5, in which the effective modulus method is used to account the effect of creep. To achieve the aforementioned objectives, a long-term laboratory investigation was started in August 2010 on four 5.8m span TCC beams with four different connector types. The specimens have been under sustained loads of 1.7kPa and subjected to a cyclic humidity conditions whilst the temperature remains quasi constant (22 °C). During the test, the mid-span deflection, moisture content of the timber beams and relative humidity of the air are continuously monitored. The long-term test is still continuing, two TCC beams were unloaded and tested to failure after 550 days, while the other two TCC beams are still being monitored and this report included experimental results up to the first 1400 days only. The long-term investigation on the two timber only composite floor beams commenced on March 2013 and the results are reported for the first 800 days from their commencement.
This thesis focuses on the development of composite floor solutions where Cross Laminated Timber (CLT) panels are used as a base element. Preliminary investigations on shear connections between prefabricated concrete beams and CLT panels were performed. The focus is on investigations on glulam-CLT composite beam elements, and the mechanical shear connectors used to achieve composite action.
The new shear connections system evaluated in this thesis for glulam-CLT floor elements consists of double-sided punched metal plate fasteners. In order to secure the shear connection made with double-sided nail plates and to improve the shear behaviour of the joint, a combination with inclined self-tapping screws was evaluated through a shear test programme. It was found that the double-sided punched metal plate fasteners and inclined screws can effectively be combined.
Project contact is Cristiano Loss at the University of British Columbia
This research is focused on bridging the current knowledge gap on steel-timber composite floors, where CLT panels are connected to steel beams. Most of the current design codes lack provisions and guidelines for the design of steel-timber composite floors.
The wood engineering community has dedicated a significant amount of effort over the last decades to establish a reliable predictive model for the load-carrying capacity of timber connections under wood failure mechanisms. Test results from various sources (Foschi and Longworth 1975; Johnsson 2003; Quenneville and Mohammad 2000; Stahl et al. 2004; Zarnani and Quenneville 2012a) demonstrate that for multi-fastener connections, failure of wood can be the dominant mode.
In existing wood strength prediction models for parallel to grain failure in timber connections using dowel-type fasteners, different methods consider the minimum, maximum or the summation of the tensile and shear capacities of the failed wood block planes. This results in disagreements between the experimental values and the predictions. It is postulated that these methods are not appropriate since the stiffness in the wood blocks adjacent to the tensile and shear planes differs and this leads to uneven load distribution amongst the resisting planes (Johnsson 2004; Zarnani and Quenneville 2012a).
The present study focuses on the nailed connections. A closed-form analytical method to determine the load-carrying capacity of wood under parallel-to-grain loading in small dowel-type connections in timber products is thus proposed. The proposed stiffness-based model has already been verified in brittle and mixed failure modes of timber rivet connections (Zarnani and Quenneville 2013b).
The cross laminated timber (CLT) technology is nowadays a well-known construction system, which that can be applied to several typologies of residential and commercial buildings. However some critical issues exist which limit the full development of the CLT construction technology: problems in handling, difficulty in assembling...
Notched connections are extensively used in timber-concrete (TC) composite beams and floors. Their main advantage is a significantly higher shear strength and stiffness compared to mechanical fasteners. Several mechanical and geometrical aspects, however, should be properly taken into account for design optimization of notched connections, as they strongly affect their structural performance and the corresponding failure mechanisms. In this paper, a preliminary Finite-Element (FE) numerical investigation is carried out by means of full 3D numerical models. The mechanical behaviour of each connection component (e.g. the reinforced concrete topping, the steel coach screw, the timber beam) is properly implemented. Shear or crushing failure mechanisms in the concrete, possible plasticization of the coach screw, as well as longitudinal shear or tension perpendicular to the grain failure mechanisms in the timber beam are taken into account using cohesive elements, damage material constitutive laws and appropriate surface-tosurface interactions. The results of parametric FE studies are compared to experimental data derived from literature, as well as to the results of simplified analytical models, demonstrating that the FE model is capable to capture the experimental behaviour of the connection including the failure mechanisms.
Cross laminated timber (CLT) has become very popular for all types of structures all around the world in last years. CLT consists of uneven number of plank layers oriented in 90° angle to each other and bonded together. Various types of adhesives and technologies are used for bonding and manufacturing of final product. In some cases, gluing is not ideal manufacturing method and there is a demand of other manufacturing processes. Mechanical jointing is logical result of current research at the Czech Technical University. Research is focused on developing and verifying mechanical behaviour of mechanically jointed CLT solid wood panels. Sets of experiments focused on mechanical behaviour of these mechanically jointed CLT panels were performed. This paper summarizes results of wall, floor and timber-concrete composite elements, which have been tested.
The work presented in this thesis deals with the investigation of the dynamic performance of timber only and TCC flooring systems, which is one of the sub-objectives of the research focus at UTS. In particular, the presented research assesses the dynamic performance of long-span timber and TCC flooring systems using different experimental und numerical test structures. For the experimental investigations, experimental modal testing and analysis is executed to determine the modal parameters (natural frequencies, damping ratios and mode shapes) of various flooring systems. For the numerical investigations, finite element models are calibrated against experimental results, and are utilised for parametric studies for flooring systems of different sizes. Span tables are generated for both timber and TCC flooring systems that can be used in the design of long-span flooring systems to satisfy the serviceability fundamental frequency requirement of 8 Hz or above.
To predict the fundamental frequency of various TCC beams and timber floor modules (beams), five different analytical models are utilised and investigated. To predict the cross-sectional characteristics of TCC systems and to identify the effective flexural stiffness of partially composite beams, the “Gamma method” is utilised.
[...] two novel methods are developed in this thesis that determines the degree of composite action of timber composite flooring systems using only measurements from non-destructive dynamic testing. The core of both methods is the use of an existing mode-shape-based damage detection technique, namely, the Damage Index (DI) method to derive the loss of composite action indices (LCAIs) named as LCAI1 and LCAI2. The DI method utilises modal strain energies derived from mode shape measurements of a flooring system before and after failure of shear connectors. The proposed methods are tested and validated on a numerical and experimental timber composite beam structure consisting of two LVL components (flange and web). To create different degrees of composite action, the beam is tested with different numbers of shear connectors to simulate the failure of connection screws. The results acquired from the proposed dynamic-based method are calibrated to make them comparable to traditional static-based composite action results. It is shown that the two proposed methods can successfully be used for timber composite structures to determine the composite action using only mode shapes measurements from dynamic testing.