Chris Letchford

Assessing Climate Change Impact on the Joint Wind-Rain Hurricane Hazard for the Northeastern U.S. Coastline

In this chapter, we present results of a study to assess the impact of possible future climate change on the joint hurricane wind and rain hazard along the US eastern coastline. To characterize the hurricane wind hazard, climate change scenarios were coupled with simulation-based hurricane genesis, wind field, and tracking models to examine possible changes in hurricane intensity (maximum wind speed) and hurricane size (radius to maximum winds). A number of different postulated climate change models (IPCC scenarios) were considered. Each scenario suggested changes in sea surface temperature (SST), the driving parameter in most modern hurricane wind field models. The evolution of hurricane genesis frequency and hurricane track behavior were examined, though no temporal trend was apparent in either. A rainfall hazard model was then developed using recorded rainfall data associated with hurricane events and a probabilistic model relating wind and rain was constructed. The pairwise joint distributions of maximum wind speed, spatial extent/storm size, and maximum rainfall rate—under current and future climate scenarios—were developed and compared. Finally, joint multivariate (wind speed intensity, spatial extent/storm size, rainfall rate) distributions were constructed to describe the joint wind-rain hurricane hazard including consideration of projected climate change impacts. Implications for current and future design (code provisions) are discussed.

A Comparison of Wind Loads on Circular Bins, Silos and Tanks

Cylindrical structures -such as grain storage silos, liquid storage tanks and other bulk storage bins - have been widely used for industrial facilities. Wind load design requirements in the current ASCE 7 are lacking for such structures. It has been found that the determinations of wind loads for tanks varies in US industrial standards such as API 650, API 620, AWWA D100, AWWA D103 and NFPA22. The design requirements or approaches are defined in different ways in other standards such as those for Australia and New Zealand (AS/NZS1170.2) and India (IS875 part 3). Detailed wind tunnel tests of such structures in Australia started in the 1980s. Results indicated that the distributions of wind pressures on the walls and roofs of silos and circular tanks are different from those on regular buildings and are functions of aspect ratios (height to diameter), roof slopes and tank spacings. In this study, wind tunnel test results and design provisions from the Australian Standard for wind loading (AS/NZS 1170.2) are reviewed. A proposed codification for ASCE 7 is made. Comparison of wind loads using AS/NZS 1170.2, the proposed ASCE 7 procedure, and those in IS 875 part 3, API 650, API 620, AWWA D100, AWWA D103 and NFPA22 are included.

Observations on ASCE 7-10 Methods for Determining Wind Loads

The purpose of this paper is to discuss 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 as a new version of the American Society of Civil Engineers ASCE-7 Standard is being prepared. Issues discussed in the paper include: wind speeds in non-hurricane regions; alternative analytical methods for determining wind loads and wind effects on Main Wind Force Resisting Systems and Components/Cladding; aerodynamic pressure coefficients; pressures on rooftop equipment; component and cladding pressures on arched roofs; and the wind tunnel procedure.

Transient Wind Loading on a Single and Group of High-Rise Buildings

Thunderstorm downbursts are transient, small-scale events which are, however, the cause of design wind speeds in many parts of the world. The difficulties in predicting when and where such events will occur make capturing full-scale wind loading data for buildings particularly difficult, and so attention has turned to physically simulating downburst flow fields in the laboratory. The University of Birmingham Transient Wind Simulator (UoB-TWS), a 1 m diameter, pulsed impinging jet facility, has been used to physically simulate a downburst and measure the wind-loading on building models which occurs. For the first time, pressure data have been recorded over both single and multiple building model arrangements, allowing interference effects to be quantified. It is demonstrated that the presence of another building nearby can increase drag coefficients by almost 40%, depending on the separation of the building models and the angle of the wind relative to the models.

Implications of hurricane : sea surface temperature relationship

This paper presents a study to assess the impact of possible future climate change on the joint hurricane wind and rain hazard along the northeast US coastline. A postulated climate change model (IPCC scenario) was considered, which suggested changes in sea surface temperature (SST) (i.e., the driving parameter in most modern hurricane models). Relationships between SST and hurricane genesis frequency, genesis location, and track propagation were incorporated into state-ofthe-art hurricane simulation procedures. Results from the SST conditioned hurricane simulations indicate the wind and rain hazards for the northeast US are likely to increase in a warmed climate, while the overall number of landfalling events is likely to decrease. The IPCC Fifth Assessment Report (Pachauri, 2014) states warming of the climate system is unequivocal, and continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. The consideration of extreme environmental event hazards in the presence of such warming would allow for a better understanding of the risk to our existing inventory of civil infrastructure. A more thorough understanding of future risks in turn will ensure that target safety and performance levels are met when designing structures and infrastructure systems in the future. For US coastal regions, specifically along the Atlantic Ocean and Gulf of Mexico, a quantitative assessment of climate change impact on hurricane hazard performance levels is needed. The northeast US coast was selected as the sample study region herein for several reasons. First, the future climate scenario used in this study projects the largest increases over modern day values of sea surface temperature (SST) to occur just off the northeast US coast (see Section 2). The second motivation for choosing the northeast US as the study region comes from the current (already high) vulnerability of many areas in the region, such as New York City and Boston. In addition, increases in both population and development along coastal areas are only expected to increase the vulnerability of this region. 1. FUTURE CLIMATE PROJECTION Representative concentration pathway (RCP) scenarios have been developed recently for climate change projections for the IPCC Fifth Assessment Report and future editions. The RCPs are projections of radiative forcing, based primarily on the forcing of greenhouse gases. This study utilizes RCP 8.5 as the future climate scenario. RCP 8.5 is a high forcing scenario, with 8.5 W/m total radiative forcing in the year 2100, representing a case in which no technology

Windborne Debris in Horizontal Winds and Applications to Impact Testing

This chapter considers the trajectories of compact, rod-type and plate-type windborne debris in horizontal winds, using a combination of experimental and numerical studies. These studies indicate that the ratio of horizontal debris speed to wind gust speed is primarily a function of the horizontal distance traveled by the debris. Empirical expressions to approximate the horizontal speed of these debris as a function of travel distance and time, are developed, and may be used to establish rational debris impact criteria.