Lateral loads are horizontal forces acting on a structure; that is, they are applied parallel to the ground. The most common types of lateral load are wind load and seismic load.
A&G design engineers use the relevant codes and standards when designing storage tanks to withstand specific wind and seismic loads for the site location. These lateral loads are discussed below:
Wind Loads
The most common lateral load is a wind load which pounds a structure with a constantly oscillating force. Wind builds up a positive pressure on the windward side and a negative pressure on the leeward side. Depending upon the shape of the structure it may also cause a negative pressure on the side walls or even the roof. The pressure on the walls and roof is not uniform but varies across the surface.
For wind loads, a tank must be designed to withstand the specified wind loads for the site location. In Australia, AS1170.2-2002 provides guidelines for design wind loads for different regions. Meteorological data collected by national weather services are one of the most reliable sources of wind data.
The wind load is an external force, the magnitude of which depends upon the height of the structure, the velocity of the wind and the amount of surface area that the wind “attacks.” A&G engineers design all material thicknesses and supports to accommodate wind load and will also include wind rings welded to the tank shell to further reinforce the structure. Additionally, tanks must be anchored to prevent them from uplifting during high winds.
Seismic Loads
Seismic loads are very complex, uncertain, and potentially more damaging than wind loads. Although the ground under a structure may shift in any direction, only the horizontal components of this movement are usually considered critical in a structural analysis. It is assumed that a load-bearing structure which supports properly calculated design loads for vertical dead and live loads are adequate for the vertical component of the earthquake.
The lateral load resisting systems for seismic loads are similar to those for wind loads. Both are designed as if they are horizontally applied to the structural system. Wind load is more of a constant force while the seismic load is almost instantaneous. The magnitude seismic load depends on the mass of the structure, the type of foundation and supports, the stiffness of the structural system, the type of soil and the acceleration of the surface of the earth.
In Australia, AS1170.4 provides the structural design guidelines for earthquake actions. For seismic loads, tanks must be designed to withstand the specified seismic loads for the site location. The tanks must also be anchored to prevent them from sliding during an earthquake.
Additionally, for tanks containing hazardous materials, additional codes and regulations such as AS3780-2008 – the storage and handling of liquids in containers, must be adhered to ensure the safety of the surrounding area and personnel in case of any failure of the tank.
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A&G Engineering have been manufacturing stainless steel storage tanks and pressure vessels for 60 years. The unmatched combination of experience, flexibility, expertise, and technology for every A&G project serve to minimise production risk and ensure on-time, on-budget, and as-specified delivery.
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