How do you design a foundation for a water tower?

1 Type of foundation

The first step is to choose the type of foundation that suits the site conditions and the tower design. There are two main types of foundations for water towers: shallow and deep. Shallow foundations are cheaper and easier to construct, but they require a strong and stable soil layer that can resist settlement and bearing failure. Deep foundations are more expensive and complex, but they can transfer the load to deeper and firmer soil layers or rock formations. Some common examples of shallow foundations are spread footings, mat foundations, and ring beams. Some common examples of deep foundations are piles, drilled shafts, and caissons.

3 Load analysis

The third step is to analyze the loads that act on the foundation from the tower and the water. These loads include the dead load, the live load, the wind load, the seismic load, and the hydrostatic load. The dead load is the weight of the tower structure and the foundation itself. The live load is the weight of the water and any other variable loads, such as maintenance personnel or equipment. The wind load is the horizontal force exerted by the wind on the tower surface. The seismic load is the horizontal and vertical force induced by the ground motion during an earthquake. The hydrostatic load is the pressure exerted by the water on the tank walls and the foundation.

4 Design criteria

The fourth step is to establish the design criteria for the foundation based on the codes and standards that apply to the project. The design criteria define the minimum requirements and specifications for the foundation safety, serviceability, durability, and constructability. Some of the design criteria are the allowable stress, the factor of safety, the allowable settlement, the crack width, the reinforcement ratio, and the concrete strength. The design criteria also depend on the type of foundation chosen, as each type has its own advantages and limitations.

5 Design calculations

The fifth step is to perform the design calculations for the foundation dimensions, reinforcement, and connections. The design calculations involve applying the load analysis results and the design criteria to the foundation type selected. The design calculations aim to ensure that the foundation can resist the applied loads without exceeding the allowable stress or settlement, and that the foundation can transfer the load to the soil without causing bearing failure or excessive deformation. The design calculations also consider the interaction between the foundation and the tower structure, and the effects of temperature, shrinkage, and creep on the foundation.