The objective of this research is to develop models for predicting lateral strength and stiffness of connections containing inclined self-tapping screws, by considering the contribution of the withdrawal and yield properties of the screws and embedment properties of the connecting members.
In the construction of modern multi-storey mass timber structures, a composite floor system commonly specified by structural engineers is the timber–concrete composite (TCC) system, where a mass timber beam or mass timber panel (MTP) is connected to a concrete slab with mechanical connectors. The design of TCC floor systems has not been addressed in timber design standards due to a lack of suitable analytical models for predicting the serviceability and safety performance of these systems. Moreover, the interlayer connection properties have a large influence on the structural performance of a TCC system. These connection properties are often generated by testing. In this paper, an analytical approach for designing a TCC floor system is proposed that incorporates connection models to predict connection properties from basic connection component properties such as embedment and withdrawal strength/stiffness of the connector, thereby circumventing the need to perform connection tests. The analytical approach leads to the calculation of effective bending stiffness, forces in the connectors, and extreme stresses in concrete and timber of the TCC system, and can be used in design to evaluate allowable floor spans under specific design loads and criteria. An extensive parametric analysis was also conducted following the analytical procedure to investigate the TCC connection and system behaviour. It was observed that the screw spacing and timber thickness remain the most important parameters which significantly influence the TCC system behaviour.
Although engineered wood products such as glued laminated timber (glulam) and cross-laminated timber (CLT) have successfully eliminated the flaws inherently exist in conventional wood products, they are still not comparable with steel and concrete in terms of strength and stiffness. Among all different options for reinforcement, Carbon Fibre is relatively popular due to its high tensile strength, low weight, and easy installation. This study presents an analysis of flexural stiffness and stress distributions of CLT panels reinforced with carbon fibre mats, based on an analytical method and finite element method (FEM).
Cross-laminated timber (CLT) is an innovative construction material that has brought advantages over traditional wood structures, reducing cost and lead time of buildings in recent years; yet CLT benefits primarily from offsite construction methods instead of automation or safety, while keeping the human onsite. The few advancements in automation for CLT panels have been in the implementation of dedicated CNC machines. Nevertheless, using CNC machines for machining CLT panels have disadvantages like clamping batches of massive panels with individual profiles, lacking the flexibility to access all acute machining angles, and struggling with the extraction of dust while the cutting spindle moves through large tight spaces. These disadvantages can be overcome with industrial robots’ help, which the construction industry has not been traditionally favorable on their application, giving then the research gap in this study. This paper explores the introduction of a robotic cell for the machining of cross-laminated timber panels. The robotic cell is designed using 3D modeling and validated through motion simulation in a virtual environment. The proposed cell design is based on a minimum viable product and compared against a minimum throughput benchmarked on the Canadian market. This study aims to research the feasibility of CLT’s automated machining by providing clear production characteristics of the designed robotic cell, such as material and tool utilization rates, lead time, or production efficiency.
The objective of this research is to develop optimum notch profile to achieve maximum connection stiffness and strength properties, characterize notched timber connection MTP-concrete floor systems, including concrete shrinkage and develop floor system details and design procedure.
An increasingly popular composite floor system consists of a Mass Timber Panel (MTP) connected to a concrete slab or topping with mechanical connectors such as Self-Tapping Screws (STS) and a sound insulation layer in between. The concrete topping provides not only structural functions, but also help to enhance acoustic and fire performances. To facilitate the design of these floor systems that meet the criteria of strength, deflection, vibration, acoustics, and fire, pre-determined allowable spans in the format of a table will be beneficial. This report presents the procedure to develop a span table showing allowable spans for specific combinations of timber panel size and grade, concrete thickness, and connection properties.
Project contact is Y.H. Chui at the University of Alberta
The objective of this research is to develop efficient panel-to-panel connection details, and optimum floor configuration, including rigging details, for handling in the factory and at the construction site. Computer modelling will be conducted to develop preliminary recommendations on panel-to-panel connection details and optimum floor panel configuration. These recommendations will then be validated by a testing program in the laboratory.
As an emerging building solution, cross-laminated timber (CLT) floors have been increasingly used in mass timber construction. The current vibration design of CLT floors is conservative due to the assumption of simple support conditions in the floor-to-wall connections. It is noted that end fixity occurs as a result of clamping action at the ends, arising from the gravity load applied by the structure above the floor and by the mechanical fasteners. In this paper, the semi-rigid floor-to-wall connections are treated as elastically restrained edges against rotations to account for the effect of partial constraint. A rotational end-fixity factor was first defined to reflect the relative bending stiffness between CLT floors and elastic restraints at the edges. Then, for the design of vibration serviceability of CLT floors as per the Canadian Standard for Engineering Design in Wood (CSA O86), restraint coefficients were defined and their analytical expressions were derived for natural frequencies and the mid-span deflection under a concentrated load, respectively. In particular, a simplified formula of the restraint coefficient for the fundamental frequency was developed to assist engineers in practical design. At last, by comparing with reported experimental data, the proposed design formula showed excellent agreement with test results. In the end, the proposed end fixity factor with their corresponding restraint coefficients is recommended as an effective mechanics-based approach to account for the effect of end support conditions of CLT floors.
The objective of this research is to characterize concrete-insulation-MTP connection properties, develop structural design procedures for strength and deflection of MTP-concrete composite floors (may account for two-way action) and test MTP-concrete strip beam and full-size floor.
Project contact is Y.H. Chui at the University of Alberta
The overall objective of the proposed project is to develop technical information that supports the use of wood I-joists with sawn lumber flanges in mid-rise building construction in western Canada where the design seismic load is relatively high.