Wind Tunnel Tests on Industrial Shelters and Other Partially Clad Low Rise
Buildings
Kirby Hebert1, Marc Levitan2
1
Professional in Residence, Louisiana State University, Baton Rouge, Louisiana, USA, [email protected]
2
Director, LSU Hurricane Center, Louisiana State University, Baton Rouge, Louisiana, USA,
[email protected]
INTRODUCTION
Many structure types typically used in industrial or agricultural facilities are not adequately covered in
current wind loading codes or in the literature. For example, an application of current ASCE-7[1]
definitions would classify a “tropical shelter”, “industrial shelter” or “compressor shed” as an enclosed
building and direct the user to calculate the wind loads on such a structure as wind loads would be
calculated for an enclosed building. An “industrial shelter” is a structure used to protect industrial
equipment or agricultural products from the effects of sun and rain while allowing maximum ventilation
and open access to housed equipment or product for servicing or storage. This type of building is also
often employed to cover bridge cranes, and for open air recreational spaces. These structures typically
have a fully clad roof with wall cladding extending downward from the eave and ending at an elevation
above the base, with the upper 25% to 75% of the wall area being clad. ASCE-7 defines an open building
as a building having each wall at least 80% open, while the definition of partially enclosed buildings
includes the condition that openings not exceed 20% of the area on the surface areas not receiving
positive external pressure. A building that does not comply with the requirements for open or partially
enclosed buildings is defined as an enclosed building, leaving a structure with more than 20% or less than
80% wall cladding to be considered as aerodynamically similar to a building with no openings.
Free standing roofs or canopies have been shown to have forces due to wind loads that differ from those
of buildings that are open, enclosed or partially enclosed. It is likely that buildings with cladding as
described for industrial shelters may also differ from any of those buildings. It can also be assumed that
the density and placement of internal blockage from the contents of these buildings also will have an
effect on the pressure distribution.
Much study has been done on free standing canopy roofs and guidance for the design of such roofs has
been included in standards such as the Australian Standard, the British Code of Practice, and the Euro
Code, among others, for several years. Cook’s Designer’s Guide to Wind Loading of Building Structures
[2] includes a comprehensive discussion of canopy roofs derived primarily from work sponsored by the
U.K. Building Research Establishment and Oxford University Engineering Laboratory and full scale and
wind tunnel studies by others. ASCE7-05 also includes guidance for free standing canopy roofs based on
works by D.R. Altman [3] and on works by Uematsu and Stathopoulos [4]. Preceding these studies were
numerous relevant works by others. None of these studies of canopies consider the effect of partially clad
walls on roof pressures. Partially clad walls descending from the eave of a building cannot be described
as similar to the type of blockage that has been considered in these studies. Previous studies all
considered full blockage of walls or stepped blockage from the ground up and treated blockage as
contents stacked on the base and not attached to the structure. The partially clad walls of industrial
shelters and similar structures provide blockage from the eave down and also, unlike internal blockage,
transfer horizontal loads to the structure.
EXPERIMENTAL SETUP AND SCOPE
A parametric wind tunnel investigation is underway at the LSU Wind Tunnel Laboratory in order to study
the wind loads on industrial shelters and other partially clad low rise buildings. The wind tunnel
experiments consist of pressure measurements on inside and outside surfaces of the wall and roof
cladding of building models with varying degrees of wall cladding and fully clad roofs of varying slope.
Both solid and porous under roof blockage configurations are also being tested with the various building
models. The goals for this study are: 1) to gain an understanding of the variation in surface pressure due
to cladding arrangements typical to industrial shelters and similar structures; 2) to assess the impact of
various types of blockage and blockage patterns on those pressures; and 3) to identify configurations with
loads that may exceed current design loads. The results of the study are anticipated to be relevant to the
further development of wind loading codes, standards, and guides, such as ASCE-7 and ASCE’s Wind
Loads and Anchor Bolt Design for Petrochemical Facilities [5].
This study is being conducted at the LSU Wind Tunnel Laboratory in a suck-down wind tunnel with a test
section measuring 132 cm wide and 99 cm high. The maximum wind velocity used for the tests is
approximately 11 m/s. Tests are being conducted primarily in exposure C flow with limited test to be
repeated in exposure B for relevance to structures located within dense industrial sites and urban
exposures. Model wall cladding is adjustable to 25%, 50% and 75% wall coverage with roof slope
variable from zero to 45 degrees. The 15cm by 15cm models are geometrically scaled at approximately
1:100 based on typical industrial shelter sizes. Model sections will be connected together to vary the plan
aspect ratio. The vertical aspect ratio will also be varied. Other cladding arrangements are being tested
that are representative of existing structures that may not be well represented by existing code, including a
model with 50% clad side walls and gable-only cladding on end walls as often seen housing bridge
cranes.
The industrial shelter pressure model study is an outgrowth of an already completed work at the LSU
Wind Tunnel Laboratory by Hebert, Amoroso and Levitan [6], where a force model study was undertaken
on other types of partially clad structures. Results of the ongoing experiments should be nearly complete
by April 2009 and will be reported in the full paper.
REFERENCES
[1] ASCE, Minimum Design Loads for Buildings and Other Structures, ASCE Standard SEI/ASCE 7-02,
American Society of Civil Engineers, Reston, VA, 2003.
[2] Cook, N.J., The Designer’s Guide to Wind Loading of Building Structures, Butterworths, London,
1990a, pp. 222-234.
[3] Altman, D.R., 2001. Wind uplift forces on roof canopies. Master’s Thesis, Department of Civil
Engineering, Clemson University, Clemson SC.
[4] Uematsu, Y., Iizumi, E. and Stathopoulos, T., 2005. Wind force coefficients for designing free
standing canopy roofs, in: Proceedings of the 4th European & African Conference on Wind Engineering.
[5] ASCE, Wind Loads and Anchor Bolt Design for Petrochemical Facilities, American Society of Civil
Engineers Task Force Committee on Anchor Bolt Design, American Society of Civil Engineers, New
York, 1997.
[6] Hebert, K., Amoroso, S. and Levitan, M., 2005. Wind Tunnel Tests on Partially Clad Buildings and
Structures, in: Proceedings of the 10th Americas Conference on Wind Engineering.