Kinh H. Ha

Shared conceptual model for the building envelope design process

Abstract The lack of communication and co-ordination among designers during the building envelope design process results in sub-optimal solutions leading to inadequate performance. To reverse this trend and to achieve better performance of the building envelope, professionals must be provided with computer integrated design tools which facilitate communication between participants and improve the transfer of data throughout the design process. This article presents a shared conceptual model that would enable integration in the building envelope design process. The wealth of data is organized into major envelope entities which are then decomposed into cohesive sets of data called primitives to form the conceptual model. Such a conceptual model should facilitate data exchange between design tasks, improve communications among designers and support the growth of data as the design process unfolds. The resulting conceptual model is implemented as a shared central database in an object-oriented database management system to experiment with integration.

Functional analysis of the preliminary building envelope design process

Abstract Integration in the building envelope design process has the potential to reduce the number of envelope deficiencies since it can improve communication among participants and minimize the fragmentation inherent to the building industry. This paper presents the first mandatory steps in creating a computerized approach to support integrated building envelope design : the functional analysis. The envelope design process is described and the principal design requirements are explained and put in context.

Analytical evaluations of local failures in sandwich panels

Abstract This paper discusses the problems of local failures in sandwich panels. Three modes are considered: dimpling, wrinkling, and crimping. Analytical solutions are found for the critical stress in each case. It is found that the known value of 2 for the dimpling coefficient is lower than the analytical one. The wrinkling coefficient is found to be less than the value found in the literature. The effect of initial imperfection on wrinkling phenomena is investigated analytically. By means of the solution found, for any given initial imperfection and core strength, the failing stress can be determined or, conversely, for any given initial imperfection, the core strength required to sustain an axial load can be obtained. Finally, expressions are found for the transition state between symmetric and anti-symmetric wrinkling and also for the crimping load.

Thermal stresses in sandwich plates

An elasticity solution for thermal stresses in sandwich plates under uniform temperature changes is presented. The interlayer shear stresses are considered in this analysis for the first time. For comparison, the finite-element method is used. Analytical and numerical results are found in good agreements. To facilitate the practical applications of the present solution, simple formulas are derived to calculate the maximum normal stress in skins and interlayer shear stresses in sandwich plates under temperature changes.

THERMAL STRESSES IN SANDWICH PANELS WITH INTERLAYER SLIPS

Analytic solutions for sandwich panels subjected to temperature changes are obtained, taking into account the effects of finite bounding stiffnesses. The numerical results show that the bonding stiffness, up to a certain level, has a strong effect on the panel response. The answer to what constitutes “ perfect” bonding is best answered in terms of the ratio of the core stiffness to the bonding stiffness, rather on the individual constituent material. A heat chamber is designed and used to test sandwich specimens under different temperature changes. The experimental values for normal stresses in the skins are in a good agreement with the present theory

Simplified analysis of cold-formed steel shear diaphragms

Research carried out on light-gage metal shear diaphragms clearly indicates that the shear behaviour depends mainly on the behaviour of the fasteners. There is no generally accepted theory to predict the shear stiffness and strength of diaphragms with welded connections, even though there exist some approximate methods for the case of diaphragms with mechanical fasteners. Simplified formulas are presented in this paper for calculating the shear stiffness and strength of metal shear diaphragms. The analysis is based on the observed deformation pattern of the panels and on the failure mode of the fasteners. By using the test data of the fasteners, the shear characteristics of many diaphragms are predicted and compared with the test results. It is of interest to note that the proposed formulas are suitable for diaphragms with any types of fasteners. Because of their generality and simplicity, the theory would be extremely useful for design engineers.