Jon Galsworthy

Ultimate Wind Load Design Gust Wind Speeds in the United States for Use in ASCE-7

This paper presents an overview of the approach employed in the development of the wind speed maps for use in ASCE 7-10. The reason for a reduction in the wind speeds in the new standard as compared to those given in the ASCE 7-98 through 7-05 standards is presented, as well as the reason for the reintroduction of Exposure D along the hurricane coastline. The most significant change in the wind speed maps from the previous version is the shift from a single map for an importance factor for buildings and other structures of 1.0 to three separate maps, one for each category of occupancy, thus eliminating the need for importance factors that vary between hurricane and nonhurricane regions.

Horizontal Wind Loads on Open-Frame, Low-Rise Buildings

Wind tunnel tests of open-frame, low-rise buildings were carried out to determine the drag (base shear) and bracing loads in the direction normal to the frames (parallel to the ridge). In total, 18 configurations were examined in an open country terrain at a scale of 1:100. The worst wind angles for all configurations are between 0°–40° with 20°–30° typically yielding slightly higher loads, 0° being parallel to the ridge. The largest load coefficients are observed for the smallest frame buildings, consistent with observations for enclosed buildings, which is due to three-dimensional (edge) effects. The solidity ratio has a clear effect on the load coefficients with higher coefficients for lower solidity, similar to the behavior observed on lattice frames or trussed towers. However, when these coefficients are multiplied by the solidity ratio, so that they can be directly compared to enclosed building coefficients, it is clear that the total load increases monotonically with solid area. Bracing was observe...

Full-Scale Validation of the Wind-Induced Response of Tall Buildings: Updated Findings from the Chicago Monitoring Project

While high-rise construction serves as one of the most challenging projects undertaken by society each year, tall buildings are one of the few constructed facilities whose design relies solely upon analytical and scaled models, which, though based upon fundamental mechanics and years of research and experience, have yet to be systematically validated in full-scale. In response to this deficiency, a full-scale monitoring project was initiated through the combined efforts of members of academe (University of Notre Dame), practicing design firms (Skidmore, Owings & Merrill LLP, Chicago) and commercial testing laboratories (Boundary Layer Wind Tunnel Laboratory, University of Western Ontario, Canada). The objective of this program is to monitor the full-scale response of some representative tall building structures and compare their actual performance to the predictions from wind tunnel testing and finite element computer models used in their design. As such, this program offers the opportunity to refine the design state-of-the-art based on any discrepancies revealed. As part of this full-scale evaluation, in-situ periods and damping ratios over a range of response amplitudes are being ascertained, which will prove vital for expanding the existing databases of full-scale dynamic properties. This paper presents a brief overview of the program.

VELOCITY MEASUREMENTS IN THE NEAR WAKE OF A FREELY-OSCILLATING CIRCULAR CYLINDER AT LOCK-IN

ABSTRACT Two-component velocity measurements were made with laser Doppler velocimetry in the base region and near wake of a freely vibrating, elastically mounted, light weight circular cylinder at lock-in. Maximum cylinder displacements of 0.75 cylinder diameters were observed for a damping level of about 0.2% of critical. The Scruton number was 1.5, while the Reynolds number at lock-in was about 53,000. The velocity data was phase averaged relative to the periodic loading cycle and are presented at 18° cycle phase intervals. The vortex formation process was observed to be similar to that observed for stationary cylinders. Whereas the spacing ratio of the vortices was 0.16, the same value obtained for fixed cylinders in previous work, differences in the strength of the vortices were observed.