In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors, and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort, this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house. In this paper, the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal, static uniform load and concentrated load deflection value testing. The evaluation of the deflection value of the floor structure, the mode shape, the coupling of the fundamental frequency mode parameters, and the vibration comfort were also studied. The results show that the fundamental frequency simulation value, one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472 (BS6472-1:2008). That is, the floor structure is not lower than 8 Hz design requirements, and meets the frequency of BS-6472(BS6472-1:2008). The weighted root mean square acceleration is lower than the requirement of 0.45 m/s2; the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413, 31.847 and 48.921 Hz, and the fundamental frequency mode is the bending vibration in the length and width directions. The second order is the bending mode in the length direction, and the third order is the bending mode in the width direction. The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction; and the second-order natural frequency is the second-order bending vibration shape in the X direction. when the uniform load is mainly the weight of floor own, the simulated maximum deflection value is 1.0658 mm; the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design, and the simulation is the largest. The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint, which meets the requirements of National Building Code of Canada-2015 (NBCC). The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm; the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical. The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.
Design methods of cross-laminated timber elements subjected to bending is considered. The methods are based on LVS EN 1995–1–1. The presented methods were checked by the experiment and analytically. Two cross-laminated timber plates with the total thickness of 95 mm were tested under action of static load. The considered cross-laminated timber plates were analysed by FEM method, which is based on the using of computational program ANSYSv14. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that the considered methods can be used for engineering calculations so as the difference between the experimentally and analytically obtained results does not exceed 20%.
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).
Nail-laminated timber-concrete composite (TCC) is a system composed of a nail-laminated timber (NLT) panel connected to a concrete slab through shear connections. When used as flexural elements such as floors, the concrete and NLT are located in the compression and tension zones, respectively...
Study on Seismic Performance of Building Structure with Cross Laminated Timber: Part 12: Objective and Loading Procedure and Accuracy of Static Loading Test
Cross-laminated timber (CLT) is a relatively new heavy timber construction material (also referred to as massive timber) that originated in central Europe and quickly spread to building applications around the world over the past two decades. Using dimension lumber (typically in the range of 1× or 2× sizes) glue laminated with each lamination layer oriented at 90° to the adjacent layer, CLT panels can be manufactured into virtually any size (with one dimension limited by the width of the press), precut and pregrooved into desirable shapes, and then shipped to the construction site for quick installation. Panelized CLT buildings are robust in resisting gravity load (compared to light-frame wood buildings) because CLT walls are effectively like solid wood pieces in load bearing. The design of CLT for gravity is relatively straightforward for residential and light commercial applications where there are plenty of wall lines in the floor plan. However, the behavior of panelized CLT systems under lateral load is not well understood especially when there is high seismic demand. Compared to light-frame wood shear walls, it is relatively difficult for panelized CLT shear walls to achieve similar levels of lateral deflection without paying special attention to design details, i.e., connections. A design lacking ductility or energy dissipating mechanism will result in high acceleration amplifications and excessive global overturning demands for multistory buildings, and even more so for tall wood buildings. Although a number of studies have been conducted on CLT shear walls and building assemblies since the 1990s, the wood design community’s understanding of the seismic behavior of panelized CLT systems is still in the learning phase, hence the impetus for this article and the tall CLT building workshop, which will be introduced herein. For example, there has been a recent trend in engineering to improve resiliency, which seeks to design a building system such that it can be restored to normal functionality sooner after an earthquake than previously possible, i.e., it is a resilient system. While various resilient lateral system concepts have been explored for concrete and steel construction, this concept has not yet been realized for multistory CLT systems. This forum article presents a review of past research developments on CLT as a lateral force-resisting system, the current trend toward design and construction of tall buildings with CLT worldwide, and attempts to summarize the societal needs and challenges in developing resilient CLT construction in regions of high seismicity in the United States.
This paper presents a novel approach for the determination of the loss of composite action for timber composite systems using only measurements from non-destructive vibration testing. Traditionally, the composite action of a system is evaluated from static load testing using deflection measurements. However, static load testing is expensive, time consuming and inappropriate for existing flooring systems. The method proposed in this paper is based on the Damage Index (DI) method, which uses changes in modal strain energies, to detect locations and severities of damage. In the proposed method, a new Loss of Composite Action Index (LCAI), which is derived from direct mode shape measurements obtained from dynamic testing, is introduced to evaluate the loss of composite action. The proposed method is tested and validated on numerical and experimental models of a timber composite beam structure, which consists of two timber components that are connected with different numbers of screws to simulate various degrees of partial composite states. The results obtained from the new method are very encouraging and show a clear trend of the proposed dynamic-based LCAI in indicating the loss of composite action in the investigated timber composite structure.
