Building Science最新文献

An approximate method is presented for assessing the influence of foundation deformations on the warping stresses of a shear core subject to torsional loading. The core is assumed supported on elastic foundations such that the vertical displacements are proportional to the imposed forces. Solutions have been derived for two general forms of loading, a concentrated torque at any level, and a distributed twisting moment whose intensity is defined as any polynomial in the height coordinate. A numerical example is given to illustrate the reduction in warping stresses which can occur as a result of relative foundation deformations.

An approximate hand method is proposed for lateral force analysis of asymmetric wall-frame structures having constant properties along the height. The coupled torsion-bending differential equations of equilibrium are decoupled using an orthogonal transformation. The deformations and stress resultants in the wall and frame assemblies are obtained by linearly combining the respective coefficients of each of the solved decoupled equations, stresses in members being obtained by simple force distribution formulae. Non-dimensional coefficients for deflection and stress resultants are given for a practical range of system parameters. The method is illustrated by a numerical example.

A method is proposed for the analysis of a central column supporting uniformly loaded cantilevered stairs. Equations for determination of bending moments about two perpendicular axes for hinged and fixed support conditions are given. Tabulated results for these moments and their resultant are presented for the range of spiral turn angles encountered in practice. Maximum resultant span moments obtained by means of the Newton-Raphson method are also given in tabular form. Finally, the method is illustrated by a numerical analysis of three-storey spiral stairs.

A simple graphical solution is presented for the determination of the reinforcement stress in the beam at failure to evaluate the flexural strength of prestressed concrete beams with non-rectangular compressed concrete section consisting of linear segments with or without supplementary non-prestressed reinforcement. This is an extension of the approach presented bu Warwaruk for the case of rectangular beams without non-prestressed reinforcement [1]. It is general in scope; values of reinforcement stress at failure can be obtained for various conditions. This method can be adopted for design purposes.

Comparative measurements are reported of the moisture content, during air drying, of concrete slabs as measured by

• 1.

  (a) a commercial electrical resistance “moisture meter” complying with the requirements of Australian Standard CA37-1966

• 2.

  (b) progressive weight loss to the atmosphere followed by oven drying.

Wide divergence between the results from (a) and (b) were observed for all four concretes tested.

Lesser, but significant, differences were observed in the resistance-moisture relationships of otherwise identical concretes made with different brands of portland cement.

Resistance results from fixed depth electrodes showed a significant thickness effect; this disappeared if the electrode depths were made a fixed proportion of slab thickness. This is explained on the basis of diffusion theory.

No correlation could be found between cement composition and the resistance-moisture relationships of the concrete. This suggests that the physical structure of the cement paste may play a significant part in determining this relationship. It thus appears that the use of electrical resistance meters to determine the moisture content of concrete may produce very misleading results unless the meter is calibrated with concrete having the same characteristics as that to be tested.

It is possible to describe thermal radiation environment at a point in space using the concept of the radiation field. This paper derives the fundamental parameters of the field, and describes how they may be measured. The use of the radiation vector, or its equivalent the vector radiant temperature, is recommended as a measure of the asymmetry of the environment. The relevance of the field concept to thermal comfort studies is discussed.