James R. McDonald

The application of the Quasi-steady Theory to full scale measurements on the Texas Tech Building

Full scale wind velocity and pressure measurements at the Texas Tech Field Research Laboratory have been used to evaluate the performance of the Quasi-steady Theory. As expected the pressure fluctuations deviate away from the theorys predictions in regions of flow separation, although the incorporation of non-linear terms improves the match. Significantly, the area-averaged loads over substantial parts of the building have high correlation with the approach flow and the probability density functions, as well as the rms and peak pressure coefficients, are well predicted by the Quasi-steady Theory.

Roof corner pressures measured in the field on a low building

Abstract This paper presents roof corner pressure data collected at the Wind Engineering Research Field Laboratory at Texas Tech University. Roof corner pressure data collected at several taps is analyzed for a large ensemble of records roughly covering all angles of attack. Data on area-averaged pressures and plots of instantaneous pressures over the surface area are also given.

Impact resistance of common building materials to tornado missiles

Abstract Objects and debris picked up and transported by tornado winds range in size from roof gravel to railroad cars. The objectives of this project were to identify the most probable missiles transported by tornadoes, to estimate the speeds achieved by these missiles, and to determine the speeds required to perforate walls used in ordinary construction. The two most relevant missiles were identified as a 2 × 4 in. timber plank weighing 15 lbs and a 3 in. diameter steel pipe weighing 75 lbs. The two missiles are typical of a wide variety of objects and debris found in tornado paths passing through residential neighborhoods. The plank and pipe can be accelerated to speeds up to 170 mph and 90 mph, respectively in a tornado rated F5 on the Fujita Scale. Impact tests using an air-actuated missile cannon revealed that residential stud walls consisting of exterior materials other than masonry could not stop the plank at speeds above 50 mph. Most wall configurations defined in Architectural Graphic Standards were tested. Both 8-in. and 12-in. reinforced concrete masonry walls were able to stop the 2 × 4 in. plank, if the cells in the block were reinforced and grouted. At speeds above 100 mph, the planks disintegrated, but the walls remained intact. The 2 × 4 in. plank perforates the face shell of unreinforced concrete masonry at about 65 mph. There-in. diameter pipe impacts have not been tested to date.

Performance of metal buildings in high winds

Abstract Hurricanes Camille (1969), Frederic (1979) and Elena (1985) subjected the Gulf coastal region to wind speed regimes at or near design level events. Additionally, during this time interval, the wind load provisions of ANSI A58.1 and the industrial standard for Metal Building Systems (MBMA) had undergone extensive revisions. Tens of thousands of steel-framed, pre-engineered buildings were affected by these three hurricanes providing valuabel field evidence to assess structural performance. The object of this communication is to review the damage patterns inflicted by these major storms and suggest mitigation strategies for reducing the damage to metal building systems.

The Enhanced Fujita Scale: For Use Beyond Tornadoes?

The Enhanced Fujita (EF) Scale was developed specifically for the estimation of wind speeds based on damage caused by tornado winds. Recently, the question has arisen as to whether or not the EF Scale can be reliably used in reverse to predict the amount of wind damage based on measured or estimated hurricane wind speeds, particularly when wind action is co-mingled with severe storm-surge action and evidence of the exact level of wind damage is obliterated. In considering such use of the EF Scale, we examine separately its two major components: (1) Degrees of Damage and (2) ranges of tornado wind speeds associated with these damage levels. Our experience suggests that, in general, the EF Scale properly describes the overall progression of damage with increasing wind speeds in both tornadoes and hurricanes; however, the wind speeds associated with various degrees of damage are generally expected to be different for structures exposed to hurricanes and tornadoes. Use of the EF Scale to predict hurricane damage based on peak wind speeds is therefore discouraged. DEVELOPMENT AND USE OF THE EF SCALE The original Fujita Scale (Fujita, 1971) was designed as a wind speed scale to provide relative ratings of tornado intensity (McDonald et al., 2009). The scale divided intensity into multiple wind speed ranges and attempted to describe the type of damage one might expect for each wind speed range. This original Fujita Scale did not account for differences in the resistance of various structures. Prior to the 1970s, there was little understanding of the true magnitudes of maximum wind speeds in tornadoes due to a scarcity of tornado wind speed measurements. Engineeringoriented investigations of tornado damage subsequently highlighted the importance of

Wind resistance categorization of buildings for insurance

Abstract The magnitude of insured property losses in windstorms suggests that wind-resistant construction of buildings needs to be improved. Insurance premiums tied to wind resistivity of construction can provide an incentive to improve construction. To be practical, insurance underwriters need a simple categorization of buildings that reflects wind resistivity. Building categorization for structural framing and components and cladding is proposed in this paper.

The Texas Tech project for dissemination of wind engineering research and curriculum via electronic media

Abstract The importance of transferring the wind engineering research into curriculum and practice has been the focus of much attention in the recent past. Also, many Universities are exploring ways to enhance their existing curriculum for both on-campus students and distance education. With the emergence of software and computer hardware specifically designed for multimedia-based presentations and the constantly improving conditions for learning via the Internet, it is now possible to achieve these goals more effectively than ever before. In this paper, three separate efforts at Texas Tech University are described; integrating wind engineering research to the existing curriculum, developing a wind engineering course for distance education, and devising a method for fast dissemination of wind engineering research and curriculum, all involving different forms of electronic media.

The Enhanced Fujita Scale: Development and Implementation

The original Fujita Scale (F Scale) was introduced as a means of estimating the intensity of tornadoes and hurricanes by relating appearance of damage to wind speeds. The relationships were based on the extensive experience of Dr. Fujita but were never independently verified. Furthermore, the importance of construction quality was not recognized, and the number of damage indicators was limited. The Wind Science and Engineering group at Texas Tech University agreed to lead an effort to improve the original scale. The improved scale, known as the Enhanced Fujita Scale (EF Scale), defines 28 damage indicators and a number of degrees of damage for each one. A process of expert elicitation was used to relate estimates of expected, upper and lower bound wind speeds for each degree of damage. The Enhanced Fujita Scale was then correlated with the Fujita Scale by means of a regression equation. The National Weather Service implemented the Enhanced scale in February 2007. In its present form, the EF Scale is applicable only to tornado intensity.

Wind-induced loads on metal edge flashings

This paper reports the results of wind-tunnel and full-scale measurements of wind pressure on metal edge flashings. The wind-tunnel tests provide useful information on failure mechanisms of the flashing-cleat system. The wind pressure data collected at the Texas Tech University Wind Engineering Research Field Laboratory (WERFL) building represent the effects of the natural wind. Finite element analyses using pressure data from the full-scale tests calculate stresses at critical sections of the edge flashing and pull-out forces on the fasteners. The results suggest outward acting fastener pull-out forces, even when the wind is blowing toward the face of the edge flashing (windward wind).

The strange life of Hurricane Gilbert September 11-19, 1988.

Abstract Hurricane Gilbert swept across the Caribbean September 11–19 causing damage in Jamica, the Yucatan Peninsula and Texas. The Committee on National Disasters of the National Research Council dispatched a team to gather perishable data and prepare a quick response report to be published later this year. This paper provides a very brief account of two aspects of the study - the characteristics of the storm and assessment of structural performance of buildings sited in the path of Gilbert or subjected to tornadic winds spawned by the hurricane.