Onshore Structural Design – Computer Aided Design of Above Ground Steel Storage Tank

Storage Tanks

One of the most prevalent structures in industrial facilities are storage tanks. These could be underground or above ground tanks made from concrete, steel and other suitable material. Literature for the design of concrete storage tanks is widely available. For the purpose of these discussions, above ground steel tanks alone shall be the scope. In most cases, storage tanks are classified by materials, roofing system, and mode of anchorage.

See also:

  1. Onshore Structural Design
  2. How to Design Each Facility Feature
  3. Horizontal Vessel Design
  4. Vertical Vessel Design

Storage Tank Roofing System

There are two basic means of classifying roofing systems, they are rigidity of roof and shape. Roofing systems are either fixed or floating roof. For fixed roofs, they could also be self-supporting or supported. While in terms of shape, roofs could be conical, dome or umbrella.

Storage Tank Anchorage

Due to the impact of uplift forces, storage tanks are further classified into self-anchoring and mechanically anchored. This parameter is important during the design of a storage tank with the use of STAAD Foundation.

Sample layout of STAAD Foundation for design

The key parameters for design of above ground steel storage tank

Prior to commencement of design of a storage tank, the civil engineer shall obtain two parameters from the client. Through these information, the complete dimensions, materials and structure can be obtained using standard codes of practice. The two key items a client will need to be satisfied during design are:

  1. The capacity of the tank
  2. The overfill level of the tank
Overfill levels of tank

Tank Height

The height of a tank is usually around 18m in order to limit overturning due to wind and earthquake forces. Modification of tank height will depend largely on the tank capacity, and overfill level. The formula recommended for obtaining the tank dimension parameters:

Design of Above Ground Steel Storage Tank

For a civil engineer, unlike for horizontal and vertical vessels, storage tanks are design in whole by them. From the thickness of the bottom plate to the shell plates, roofing, access platform and steps. And all the loadings are estimated including of the liquids and then transferred to the ring beam foundation and the soil base.

The load from a storage tank is transmitted to the soil at two points. Load is transferred to the soil via the ring beam foundation and then bottom plate and stabilized soil below the tank.

The ring beam supports the tank walls and a limited radial distance offset from the wall. While the stabilized soil supports the tank bottom plate along with the fluid stored above.

Methods for storage tank foundation design:

  1. Manual calculation approach
  2. Computer aided design (CAD) approach

Manual calculation approach

This approach to design is straight forward. The thickness obtained during these calculations are input into the CAD approach. Although the structural engineer designs in whole the storage tank, CAD approach only focuses on the foundation.

Sample shell thickness calculation

CAD Approach

Onshore Structural Design – Step by Step Calculations provides details about how to design storage tanks through manual calculations. Although STAAD Foundation is an easy to use application for storage tank foundation design; however, the version of STAAD Foundation may limit its capability to designing of only self-anchored tanks.

Photo showing disabled design of mechanically anchored tanks

Below is a video showing design of support for Above Ground Steel Storage Tank with the use of STAAD Foundation.

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