ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING)
Year:2003 | Volume:4 | Issue:1|Papers Count:6

The bamboo structure can be generally viewed as a Functionally Graded composite material constituted by long and aligned cellulose fibres embedded in a lignin matrix. Analysing the transversal section of a bamboo culm, one can observe that the fibre distribution is variable through its thickness. The non-uniform distribution of fibres prevents the direct application of equations used to model the behaviour of composite materials, as the rule of mixtures equations for strength and modulus of elasticity. These equations assume, besides the perfect bonding between fibre and matrix, uniform distribution of the fibres in the matrix. In bamboo, the fibre distribution follows an organized pattern with a higher concentration of fibres on the outer surface of the culm. Establishing how this variation occurs, the basic equations from the composite materials approach can be modified in order to model the mechanical behaviour of bamboo. This paper presents the meso-structure analyses of bamboo culms through Digital Image Analysis. The variation of the volume fraction of the cellulose fibres across the transversal section of the bamboo is established. The developed methodology is successfully applied to study the volume fraction variation of fibres in two different samples of bamboo species Phyllostachys heterocycla pubenscens, commonly know as "Moso".      

In this paper, the topological optimization of three-dimensional structures based on optimality criteria and artificial material model is briefly reviewed and prevention of undesirable structural elements is discussed. Prevention of formation of checkerboard patterns and the finite element mesh dependency, which are the two well-known instabilities in the process of structural topology optimization, is also considered. The idea of employing the noise cleaning techniques borrowed from image processing techniques, suggested by Sigmund for plane problems [1], is here extended to three-dimensional structures. To demonstrate the efficiency and practicality of the method, especially, when employed together with the continuation method [2] and nonconforming finite elements, some illustrative examples are presented.    

The vibration serviceability requirements for wooden floors in accordance with Eurocode-5 (EC-5) as illustrated by Ohlsson [1] are rated using a combination of Value Analysis (VA) and the Checking Point Method (CPM) of the First-Order Reliability Procedure (FORP). The implied safety indices for the current requirements were first estimated and consequently the associated potential losses were deduced for varying design inputs considered as random variables with practical probability distributions. The preliminary results indicate the direction for enhancing the effective use of timber in flooring systems to withstand human-induced vibrations safely and economically.    

The active control of building vibration is addressed. The aeroelastic lumped mass model of a building is designed to be used as the test bed for the active control system. The five stories lumped parameter model was modeled as a cantilever beam exhibiting planar vibration. A Linear Coupling Control (LCC) strategy was implemented to eliminate the vibrations. An active (moving) mass damper (AMD) was first designed and experimentally implemented to control the first mode vibration of the system. An alternative pendulum control system was then designed and implemented. The proposed pendulum, having three times smaller mass than the AMD, was found to be more effective in reducing the building vibrations.      

The use of high-strength concrete in reinforced concrete slabs is becoming popular in Australia and other countries. Current design provisions of AS3600 and other major codes throughout the world are based on empirical relationships developed from tests on low-strength concrete. In this paper, the experimental results from four research studies are used to review the existing recommendations in design codes for punching shear failure of slabs. Design codes referred in this study are AS3600 and CEB-FIP MC 90. In AS3600 the punching shear strength is expressed as proportional to fc1/2. However in CEB-FIP MC 90 punching shear strength is fc1/3 .It is shown that the present provisions assumed to be proportional to in AS3600 are applicable up to 100 MPa.    

This tentative survey evaluates the influence of fibrous waste (metallic and polypropylene) used on the cracks caused by shrinkage in a mortar prepared from sand of dune (important shrinkage). The achieved tests, to evaluate the free shrinkage or restrained shrinkage, have been reported in this paper. The method described in the article to evaluate the restrained shrinkage consists of using a rigid ring made of steel that is coated by mortar. After hardening, the sample is submitted to conditions required to evaluate the effect of restrained shrinkage. In a given moment, the resistance to the cracking, the number of cracks and the total maximal widths, are measured and compared to what obtained with a plain mortar.