Computational evaluation of wind loads on low- and highrise buildings

Buildings and other infrastructures located in the coastal regions of the US have a higher level of wind vulnerability. Reducing the increasing property losses and causalities associated with severe windstorms has been the central research focus of the wind engineering community. The present wind engineering toolbox consists of building codes and standards, laboratory experiments, and field measurements. The American Society of Civil Engineers (ASCE) 7 standard provides wind loads only for buildings with common shapes. For complex cases it refers to physical modeling. Although this option can be economically viable for large projects, it is not cost-effective for low-rise residential houses. To circumvent these limitations, a numerical approach based on the techniques of Computational Fluid Dynamics (CFD) has been developed. The recent advance in computing technology and significant developments in turbulence modeling is making numerical evaluation of wind effects a more affordable approach. The present study targeted those cases that are not addressed by the standards. These include wind loads on complex roofs for low-rise buildings, aerodynamics of tall buildings, and effects of complex surrounding buildings. Among all the turbulence models investigated, the large eddy simulation (LES) model performed the best in predicting wind loads. The application of a spatially evolving time-dependent wind velocity field with the relevant turbulence structures at the inlet boundaries was found to be essential. All the results were compared and validated with experimental data. The study also revealed CFD's unique flow visualization and aerodynamic data generation capabilities along with a better understanding of the complex three-dimensional aerodynamics of wind-structure interactions. With the proper modeling that realistically represents the actual turbulent atmospheric boundary layer flow, CFD can offer an economical alternative to the existing wind engineering tools. CFD's easy accessibility is expected to transform the practice of structural design for wind, resulting in more wind-resilient and sustainable systems by encouraging optimal aerodynamic and sustainable structural/building design. Thus, this method will help ensure public safety and reduce economic losses due to wind perils.

Computational Evaluation of Wind Loads on Low- and High- Rise Buildings

Buildings and other infrastructures located in the coastal regions of the US have a higher level of wind vulnerability. Reducing the increasing property losses and causalities associated with severe windstorms has been the central research focus of the wind engineering community. The present wind engineering toolbox consists of building codes and standards, laboratory experiments, and field measurements. The American Society of Civil Engineers (ASCE) 7 standard provides wind loads only for buildings with common shapes. For complex cases it refers to physical modeling. Although this option can be economically viable for large projects, it is not cost-effective for low-rise residential houses. To circumvent these limitations, a numerical approach based on the techniques of Computational Fluid Dynamics (CFD) has been developed. The recent advance in computing technology and significant developments in turbulence modeling is making numerical evaluation of wind effects a more affordable approach. The present study targeted those cases that are not addressed by the standards. These include wind loads on complex roofs for low-rise buildings, aerodynamics of tall buildings, and effects of complex surrounding buildings. Among all the turbulence models investigated, the large eddy simulation (LES) model performed the best in predicting wind loads. The application of a spatially evolving time-dependent wind velocity field with the relevant turbulence structures at the inlet boundaries was found to be essential. All the results were compared and validated with experimental data. The study also revealed CFD’s unique flow visualization and aerodynamic data generation capabilities along with a better understanding of the complex three-dimensional aerodynamics of wind-structure interactions. With the proper modeling that realistically represents the actual turbulent atmospheric boundary layer flow, CFD can offer an economical alternative to the existing wind engineering tools. CFD’s easy accessibility is expected to transform the practice of structural design for wind, resulting in more wind-resilient and sustainable systems by encouraging optimal aerodynamic and sustainable structural/building design. Thus, this method will help ensure public safety and reduce economic losses due to wind perils.

An organizational learning approach to expatriate cross-cultural adjustment, organizational commitment, and job satisfaction

The purpose of this study was to investigate the relationship between organizational learning and expatriation in overseas subsidiaries as well as in organizations as a whole. In doing so, two issues were addressed--(i) the use of expatriation as firms internationalize, and (ii) the significance of various factors to expatriate success as firms gain international experience. The sample of companies for this study was drawn from U.S. Fortune 500 multinational corporations (MNCs) in two sets of related industries--computers/electronics and petroleum/chemicals. Based on the learning that takes place within organizations as they increase their involvement overseas, a positive relationship was expected between international experience and expatriation when internationalization was low, and a negative relationship was expected when internationalization was high. Results indicate a significant positive relationship between country experience and the proportion of expatriates in that subsidiary when subsidiaries were relatively young, and a negative relationship, however not significant, for more mature subsidiaries. The relationship between overall firm degree of internationalization (DOI) and the proportion of expatriates in the firm as a whole was negative regardless of stage of internationalization, but this relationship was significant only for highly internationalized firms. It was further suspected that individual, environmental, and family-related characteristics would have a significant effect on the success of expatriates whose firms were low on internationalization, and that organizational characteristics would play a significant role in highly internationalized firms. Support for these hypotheses was received with respect to certain outcomes and some determinants of success. The preponderance of support was found for those addressing the effects of both environmental and family-related characteristics on the cross-cultural adjustment of expatriates in firms with little international experience. Considerable support was also found for those hypotheses addressing the impact of organizational characteristics on the job satisfaction levels of expatriates assigned to mature subsidiaries. The relevant literatures on organizational learning and expatriation are reviewed, and a model is developed underlying the logic of the hypotheses. Research methods are then described in full detail, results are reported, and implications for theory and for management are discussed. ^