Appupillai Baskaran

Investigation of air flow around buildings using computational fluid dynamics techniques

Abstract The developments of the Computational Fluid Dynamics (CFD) method as a powerful tool for prediction of wind environmental conditions around buildings are presented in this study. CFD techniques have been applied in predicting wind flow conditions: around a single building, between two parallel buildings and around a multiple building configuration. Also presented is a limited model validation for those simulated configurations. Finally, the paper presents the application of CFD techniques for a case study in simulating an existing site together with proposed buildings and the local landscape.

Performance of roof fasteners under simulated loading conditions

Abstract Conventionally, in North America, design loads for roof attachment systems are determined through static testing. While presenting the development of a dynamic setup, this paper compares the fastener pull-out loads under static and dynamic conditions. This has been systematically performed for steel and wooden decks under various fastening parameters. Experimental data have indicated that the fastener failure load and mode differ significantly under dynamic testing in comparison to static testing. With steel decks, the fastener pull-out resistance decreased by 30–50% under dynamic conditions, whereas results with wooden decks, the resistance decreased by 10–30%. Therefore, for the design of mechanically attached roofing systems, one should use for the fasteners the allowable design load derived from dynamic testing. Preliminary investigations have also been carried out and further research efforts are in progress on the fastener service life predictions.

Wind load cycle development for evaluating mechanically attached single-ply roofs

Failure modes resulting from the existing North-American roof certification procedures are often not consistent with failures in the field. To develop test procedures for certifying roofing systems under dynamic wind loads, the National Research Council of Canada (NRC) formed an industry-based consortium. The consortium is known as Special Interest Group for Dynamic Evaluation of Roofing Systems (SIGDERS). Using wind tunnel pressure records as source data, SIGDERS developed a dynamic load cycle. With input from industries, building owners and roofing associations, the developed load cycle has been generalized. Based on this extensive investigation, a simplified laboratory test procedure is proposed for the evaluation of mechanically fastened single-ply roofing system.

A numerical model to evaluate the performance of pressure equalized rainscreen walls

Abstract Advancements in Computational Fluid Dynamics (CFD) and numerical modeling techniques provide new approaches to quantify air flow around buildings and wind induced pressures on the building envelope. This paper describes the progress made on developing a numerical model to predict the performance of Pressure Equalized Rainscreen (PER) wall assemblies. The model is three dimensional and time dependent. The Navier Stokes Equations (NSE) are discretized using a control volume method. External wall boundaries are treated with cyclic pressure differentials, the onlyfluid property available as a boundary condition from the experiment. This paper presents the steps involved in the numerical model development and the effect of static and dynamic parameters on the model predictions. Two types of wall assemblies, one representing an airtight air barrier system and another with a leaky air barrier system, are modeled. Predicted performances of both wall types are analyzed with respect to time and space. Preliminary model validation is performed by comparing computed results with limited experimental data. The paper also includes some of these comparisons for various geometrical configurations of the PER wall assembly.

Numerical computation of wind pressures on buildings

Abstract This paper discusses the computer simulation of wind pressures on buildings. The control volume technique is used to discretize the three-dimensional differential equations of the flow and the standard k - ϵ turbulence model is incorporated in the numerical modelling for closure. A modular-structure, computational tool named TWIST (Turbulent WInd Simulation Technique), has been developed and implemented in various computer systems including, for the first time, microcomputers. Computed mean values of wind-induced pressures on buildings agree well with experimental data obtained from boundary layer wind tunnels. The influence of various computational parameters such as the number of grid nodes on the time of computation and the computed results is also discussed.

Snow Friction Coefficient for Commercial Roofing Materials

AbstractRedistribution of snow loads on two adjacent buildings of different heights is addressed. The term slippery roofs is used but it is not defined. Measurements of friction between snow and co...

Wind engineering studies on tall buildings—transitions in research

Abstract Development of new building materials and advances in architectural concepts have led to light weight and more unconventional buildings. Consequently, unexpected wind forces may act on these structures. Experimental results from wind-tunnel studies are considered as one reliable source for the wind loading information. An extensive literature survey has been conducted; this paper reviews some of the selected studies to show the research transitions in wind engineering studies of tall buildings. Ten different stages and an established pattern have been identified in wind engineering studies of tall buildings.