David Yeoh

State of the Art on Timber-Concrete Composite Structures: Literature Review

This paper presents a survey on the state-of-the-art of timber-concrete composite research in the past and recent years. The most important literature references were carefully selected and reviewed to provide an overview and some depth in the development of this construction technique. After highlighting the advantages of the composite system, the standards and design methods currently available are presented. An extensive description of the connection systems developed around the world is also provided. The experimental and numerical investigations performed on connections and beams in both the short- and long-term (at collapse and under sustained load, respectively) are discussed at length in the paper. Other aspects covered are prefabrication, the influence of concrete properties, fatigue tests, fire resistance, vibrations, and acoustics.

Experimental Tests of Notched and Plate Connectors for LVL-Concrete Composite Beams

This paper reports the experimental results of symmetrical push-out tests performed on notched and toothed metal plate connectors for laminated veneer lumber (LVL)-concrete composite floor systems. The characteristic shear strength and slip moduli were evaluated for three types of connectors: (1) a 300-mm-long rectangular notch cut in the LVL joist and reinforced with a 16-mm-diameter lag screw; (2) a triangular notch reinforced with the same lag screw; and (3) two 333-mm-long toothed metal plates pressed in the lateral surface of two adjacent LVL joists. The shear force versus relative slip relationships are presented together with analytical prepeak and postpeak approximations which can be used to carry out nonlinear finite-element analyses of LVL-concrete composite beams. The failure mechanisms of the notched connections are also discussed. Analytical design formulas for shear-strength evaluation of notched connections derived in accordance with New Zealand Standards and Eurocodes are proposed based on four possible failure mechanisms. Good approximation was found if a slight modification of the Eurocodes formulas is introduced.

Preliminary Research Towards a Semi-prefabricated LVL-concrete Composite Floor System for the Australasian Market

Abstract The choice of the best floor solution has always been a key issue in the design and construction of multi-storey timber buildings. Strict performance requirements such as effective acoustic separation of inter-tenancy floors, thermal mass, fi re resistance, limitation of deflection, resistance to vibrations and effective diaphragm action are very hard to comply with if only timber is used. The main purpose of this paper is to present the preliminary and some ongoing research in the short- and long-term carried out ainly at the University of Canterbury, New Zealand, for the realisation of a semi-prefabricated laminated veneer lumber (LVL)-concrete composite floor system in both the local and Australasian market. The paper discusses a novel semi-prefabricated LVL-concrete composite system where panels made from LVL joists and plywood flooring are prefabricated off-site. Once the panels are lifted onto the supports and connected side-by-side, a concrete topping is cast-insitu so as to form a continuous slab connecting all the panels. Composite action between the concrete topping and the panels is achieved using different types of connectors, such as various forms of notches cut from the LVL joists and reinforced with coach screws or toothed metal plates pressed in the LVL joists. After pointing out the advantages of the proposed system over traditional only-timber and only-concrete floor solutions, the paper describes push-out tests in the short-term on connections used in the LVL-concrete composite. Tests to failure of small LVL-concrete composite blocks (push-out tests) with different types and shapes of connection systems were performed at the University of Canterbury, New Zealand, and at the University of Technology Sydney, Australia. The results are parametrically evaluated and discussed in detail. The failure mechanism of the notched connection is highlighted together with the strength and stiffness values for each tested connection system. Subsequently, the four best connection systems were identified and used in beam specimens of 8–10 m in span. The experimental program on the beams is presented briefly in order to provide information of the different phases of the project.

The Design of a Semi-Prefabricated LVL-Concrete Composite Floor

This paper describes the design of a novel semi-prefabricated LVL-concrete composite floor that has been developed in New Zealand. In this solution, the floor units made from LVL joists and plywood are prefabricated in the factory and transported to the building site. The units are then lifted onto the supports and connected to the main frames of the building and to the adjacent units. Finally, a concrete topping is poured on top of the units in order to form a continuous slab connecting all the units. Rectangular notches cut from the LVL joists and reinforced with coach screws provide the composite action between the concrete slab and the LVL joists. This system proved to be an effective modular solution that ensures rapid construction. A design procedure based on the use of the effective flexural stiffness method, also known as the “gamma method” is proposed for the design of the composite floor at ultimate and serviceability limit states, in the short and long term. By comparison with the experimental results, it is shown that the proposed method leads to conservative design. A step-by-step design worked example of this novel semi-prefabricated composite floor concludes the paper.

Connection Performance for LVL-Concrete Composite Floor System

The LVL-concrete composite (LCC) structure is a hybrid in system which the LVL member is well connected to the concrete slab by a connector to produce composite action. Various types of connector with different stiffness and shear capacity are available in the market currently. The stiffness of the connector is identified through the push-out experiment. The notch connections for LVL concrete composite beams have higher stiffness and strength compared to mechanical fasteners. This paper discusses the experimental results of symmetrical push-out tests on 3 different types of connector, 150mm rectangular notch with 10mm diameter screw, 100mm rectangular notch with 8mm diameter screw and 100mm triangular notch with 8mm diameter screw. The experimental test was shear push out to failure and the type of failure was discussed. The 150mm rectangular notch was found to be strongest among all and low cost. The 100mm rectangular notch was found to be slightly stiffer than 100mm triangular notch but 100mm triangular notch is easier to construct with only 2 cut. The maximum strength and stiffness at ultimate limit states and serviceability limit states of each type of connection were discussed in this paper.

Heavy Metal Removal by Crops from Land Application of Sludge

This chapter describes the application of phytoremediation in removing heavy metals from contaminated soils. The types of crops used as well as the characteristics and application of sludge in Malaysia are described. The standards and regulations of sludge application are also discussed. The chapter gives a detailed discussion of principles of phytoremediation and design parameters used in the design of the treatment systems. Moreover, a few case studies and design examples are covered in the chapter.