DongHun Yeo

High-Rise Reinforced Concrete Structures: Database-Assisted Design for Wind

Advances in wind pressure measurement and computer technology have made time-domain analyses of wind effects on high-rise structures possible in recent years. Time-domain solutions use aerodynamic and wind climatological databases and provide full phase information on wind-induced response that is lost in the frequency-domain approach; therefore, they can account rigorously for the superposed effects of any number of modes of vibration of any shape; for mode coupling; for wind directionality effects; and for the joint contributions of axial forces, bending moments, and shear forces in interaction equations used for structural design. Unlike the frequency-domain approach, in the time-domain approach, the process of determining wind effects and the structural design process, referred to jointly as database-assisted design (DAD), are integrated, transparent, and fully auditable. The objective of this study is to present the DAD approach as applied to high-rise reinforced concrete (RC) buildings. Given the ti...

Simplified Wind Flow Model for the Estimation of Aerodynamic Effects on Small Structures

The reliable measurement of pressures on low-rise buildings in the atmospheric boundary layer (ABL) flow remains a challenge, as hasbeenshownbythelargediscrepanciesamongresultsobtainedindifferentwindtunnelfacilitiesoreveninthesamewindtunnel.Twomajor causes of the discrepancies are the difficulty of simulating large-scale, low-frequency turbulent fluctuations uniformly across laboratories and the small scale of models in typical civil engineering wind tunnels. To address these issues, it was proposed that a simplified flow be used in laboratory simulations,rather thana conventionalABL flow.In thesimplified flowthe referencemeanwind speedislarger thanthemean wind speed of the ABL flow, and the low-frequency fluctuations present in the ABL flow are suppressed; that is, the peak energy of the missing low- frequency fluctuations is supplied in the simplified flow by the increment in the mean wind speed, which may be regarded as a flow fluctuation with zero frequency. High-frequency turbulent fluctuations, which typically affect flow reattachment, are approximately the same in the ABL and the simplified flow. Because, over small distances, low-frequency fluctuations are highly coherent spatially for small low-rise buildings with dimensions of up to approximately 20 m (e.g., single-family residential homes), the peak aerodynamic effects of the two flows may be hypothesized to be approximately the same. Preliminary experimental results obtained in University of Western Ontarios ABL wind tunnel facility and Florida International Universitys small-scale Wall of Wind facility are shown to support this hypothesis. The use of the proposed simplified flow is currently being tested by the authors for application to computational wind engineering (CWE) applications. Such use eliminatestheneedtosimulatethelowerfrequency fluctuationsoftheboundarylayer flowandthusmakesitpossibletoachievepracticalCWE calculations, and it is advantageous in experiments from the points of view of measurement accuracy, model scaling, repeatability of the simulations, and computational efficiency. DOI: 10.1061/(ASCE)EM.1943-7889.0000508.

Estimation of Hurricane Wind Speed Probabilities: Application to New York City and Other Coastal Locations

AbstractA procedure is presented for estimating parametric probabilistic models of hurricane wind speeds from existing information on state-of-the-art estimates of wind speeds with various mean recurrence intervals (MRIs). Such models may be needed, for example, for the estimation of hurricane wind speeds with long MRIs required for the performance-based design of structures susceptible of experiencing nonlinear behavior. First, the procedure is applied to the case where that information is obtained from ASCE 7-10 wind maps, and examples are provided of its application to a number of coastal mileposts on the Gulf and Atlantic coasts. Next, the procedure is applied by using, in addition to the ASCE 7-10 information, hurricane wind speeds with 1,000,000- and 10,000,000-year MRIs estimated in a 2011 Nuclear Regulatory Commission (NRC) report. It is then argued that ASCE 7-10 Standard basic wind speeds for New York City are not conservative with respect to their counterparts specified in the standard for othe...

Assessment of ASCE 7-10 Standard Methods for Determining Wind Loads

AbstractThe purpose of this paper is to discuss issues associated with ASCE 7-10 standard methods for determining wind loads on buildings and other structures that warrant comment, correction, or improvement. The assessment is intended to serve as a resource in the development of a new version of the ASCE 7 standard and to stimulate a wider participation in that development by the structural engineering community. Issues discussed in the paper include: wind speeds in nonhurricane regions; alternative analytical methods for determining wind loads and wind effects on main wind force resisting systems and components and/or cladding; aerodynamic pressure coefficients; pressures on rooftop equipment; component and cladding pressures on arched roofs; and the wind tunnel procedure. It is noted that the ASCE 49 standard essentially covers wind tunnel testing, rather than the wind tunnel procedure, of which wind tunnel testing is only a part.

Comparisons of Two Wind Tunnel Pressure Databases and Partial Validation against Full-Scale Measurements

AbstractDatabase-assisted design (DAD) is an integrated methodology that calculates wind loadings and wind-induced internal forces. It can also calculate demand-to-capacity indexes for each structural member, and by checking whether they differ significantly from unity, determine the adequacy of the members’ structural design. Its practical usefulness depends on the availability of comprehensive aerodynamic databases. A public domain aerodynamic database produced in 2003 by the University of Western Ontario (UWO) is not sufficiently extensive to satisfy design needs generally encountered in practice. For this reason, the Tokyo Polytechnic University (TPU) recently developed comprehensive sets of aerodynamic databases that are publicly available and would fill large voids present in the UWO database. This paper presents comparisons of aerodynamic pressures and forces based on TPU and UWO data for low-rise buildings to help assess the extent to which the respective aerodynamic pressure measurements are comp...

Testing of Residential Homes under Wind Loads

Aerodynamic testing of low-rise structures is fraught with difficulties that can be the cause of large measurement errors, resulting in the underestimation of aerodynamic pressures by a factor of as much as two. The errors are primarily attributable to the inadequate knowledge and simulation of wind flows affecting low-rise buildings, especially residential homes in suburban environments. A type of aerodynamic testing of sufficiently small low-rise structures is explored that does not entail the simulation of the turbulence intensity and integral turbulence scales. That type of testing would offer several advantages: eliminating a major cause of discrepancies among measurements conducted in different laboratories, allowing the use of larger model scales, and allowing testing in both typical commercial wind tunnels and in open jet facilities of the Wall of Wind (WoW) type. Preliminary tests based on data obtained at the University of Western Ontario wind tunnel and the Florida International University large-scale six-fan WoW facility suggest that the proposed type of testing yields systematically conservative results for the specialized type of measurements considered herein. In most cases, but not all, the degree of conservatism is modest. The results appear to be of sufficient interest to warrant additional research.

Wind Load Factors for Use in the Wind Tunnel Procedure

AbstractPublished standards may be incomplete because they provide no guidance on wind load factors appropriate for use with the wind tunnel procedure. The purpose of this paper is to contribute to...

Planetary Boundary-Layer Modelling and Tall Building Design

Characteristics of flow in the planetary boundary layer (PBL) strongly affect the design of tall structures. PBL modelling in building codes, based as it is on empirical data from the 1960s and 1970s, differs significantly from contemporary PBL models, which account for both “neutral” flows, and “conventionally neutral” flows. PBL heights estimated in these relatively sophisticated models are typically approximately half as large as those obtained using the classical asymptotic similarity approach, and are one order of magnitude larger than those specified in North American and Japanese building codes. A simple method is proposed for estimating the friction velocity and PBL height as functions of specified surface roughness and geostrophic wind speed. Based on published results, it is tentatively determined that, even at elevations as high as 800 m above the surface, the contribution to the resultant mean flow velocity of the component V normal to the surface stress is negligible and the veering angle is of the order of only 5

Calibration of Dynamic Pressure in a Tubing System and Optimized Design of Tube Configuration: A Numerical and Experimental Study | NIST

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