Tank Design and Construction

Strict Specifications

CROM adheres to the highest standards of professional engineering and construction. Tank structures are design and built in compliance with applicable sections of:

  • ACI 372R Guide to Design and Construction of Circular Wire- and Strand-Wrapped Prestressed Concrete Structures, published by American Concrete Institute.
  • ANSI/AWWA D110 Wire- and Strand-Wound, Circular, Prestressed Concrete Water Tanks, published by the American Water Works Association.

All design drawings and calculations prepared by CROM are signed and sealed by of one of the company’s full-time registered professional engineers.

Structural Design

CROM specializes in the design of thin-shell concrete structures, a unique subset of structural engineering design. This expertise allows us to maximize the natural physical properties of concrete and steel to design durable, efficient and low-maintenance prestressed concrete tanks. The design of our tanks considers various load conditions such as backfill and seismic design.

  • Backfill– Often it is necessary to either partially or fully bury a prestressed concrete tank. Under these conditions, the tank wall and roof are designed to withstand the load from the backfilled soils. The soil load can be uniform or differential, meaning that it can vary in elevation around the tank perimeter.
  • Seismic Design – Every prestressed concrete tank is designed to resist seismic-induced forces to ensure a functioning tank under even the most severe conditions.
FEAThe complex structural behavior of prestressed concrete tanks regularly demands the use of finite element analyses. Combined with classical structural design analysis, the Finite Element Method (FEM) provides a secondary confirmation of stresses, strains, and deflections of the tank under various load conditions.

CFDWhen it is necessary to understand the unique flow or mixing characteristics inside a tank due to piping geometry or baffle configurations, CROM can help clients by performing Computational Fluid Dynamics (CFD) analyses. This analysis simulates the fluid flow, heat transfer, and time-dependent flow of the liquid inside tank to assess water circulation patterns and identify the potential for stagnation in the reservoir.

Complete Tank Construction

CROM provides complete tank construction services to avoid any division of responsibility. Having your tank built by specialized experts provides you the highest quality tank designed and built for long-term performance.

Select the link below to view our tank wall and roof options:

AWWA D-110 Wall Options

Dome and Roof Options

AWWA D-110 Type II Wall

An AWWA D110 Type II wall utilizes shotcrete with full-height, vertically fluted steel diaphragm, prestressed circumferentially by wrapping with high-strength steel wire. The construction process of an AWWA D110 Type II tank wall is described below.

  1. An impermeable galvanized steel shell diaphragm is erected to the specified tank diameter using special formwork. The diaphragm is manufactured with reentrant angles to form a mechanical bond with the cast concrete.
  2. Vertical and horizontal reinforcing steel is installed according to the design requirements.
  3. The exterior of the tank wall is built out by applying successive layers of shotcrete to the design thickness.
  4. The interior of the tank diaphragm is encased with a minimum of 1″ thick shotcrete.
  5. The vertical seams of the erected diaphragm are sealed watertight using an epoxy injection system.
  6. The wall is placed in permanent compression using a high-strength steel wire wrapped around the tank in a continuous helix. The water load acting on the wall, at any given depth, is used to determine the number of wires placed on the tank wall.
  7. The prestressing wires are encased in shotcrete to protect them from corrosion and mechanical damage.

*Shotcrete is high velocity, pneumatically applied grout mix concrete with a high cement content and a low water/cement ratio.

AWWA D-110 Type III Wall

An AWWA D110 Type III wall utilizes cast-in-place concrete with full-height, vertically fluted steel diaphragm, prestressed circumferentially by wrapping with high-strength steel wire. The construction process of an AWWA D110 Type III tank wall is described below.

  1. An impermeable galvanized steel diaphragm is placed on a horizontal casting bed constructed to the specified tank radius. The diaphragm is manufactured with reentrant angles to form a mechanical bond with the cast concrete.
  2. Vertical and horizontal reinforcing steel is installed according to the design to control cracking from differential temperature, shrinkage, and creep effects.
  3. Each panel is cast with ready mix concrete to the specified thickness.
  4. Once cured, the panels are lifted in place and set to the designed tank diameter.
  5. A shotcrete layer is applied to the exterior of the exposed diaphragm.
  6. The vertical joints between panels are sealed watertight.
  7. The wall is placed in permanent compression using a high-strength steel wire wrapped around the tank in a continuous helix. The water load acting on the wall, at any given height, is used to determine the number of wires placed on the tank wall.
  8. The prestressing wires are encased in shotcrete to protect them from corrosion and mechanical damage.

Polylined Modified Type III Wall

A polylined modified Type III wall utilizes cast in place concrete  with full-height HDPE liner, prestressed circumferentially by wrapping with high-strength steel wire.  The construction process of a polylined modified Type III Wall is described below.

  1. An impermeable HDPE sheet is placed on a horizontal casting bed constructed to the specified tank radius. The sheet is manufactured with studs to form a mechanical bond with the cast concrete.
  2. Vertical and horizontal reinforcing steel is installed according to the design to control cracking from differential temperature, shrinkage, and creep effects.
  3. Each panel is cast with ready mix concrete to the specified thickness.
  4. Once cured, the panels are lifted in place and set to the designed tank diameter. The closure joints between the panels are filled with either shotcrete or cast in place concrete.
  5. The wall is placed in permanent compression using a high-strength steel wire wrapped around the tank in a continuous helix. The water load acting on the wall, at any given height, is used to determine the number of wires placed on the tank wall.
  6. The prestressing wires are encased in shotcrete to protect them from corrosion and mechanical damage.

Free-Span Concrete Dome

9481_n_mecklenburg dome

The standard covering for a CROM prestressed concrete tank is a thin shell cast-in-place concrete dome, which is placed in permanent compression with single-wire prestressing. We have successfully designed and built free-span domes exceeding 300 feet in diameter. The benefit of a dome is the lack of interior columns, which eliminates concentrated floor loads and future maintenance of the columns. Standard dome rises are 1/10th and 1/12th. Other rises are available.

Flat Roof

04039 CLERMONT flat roof
When a tank has a height restriction or is to be completely buried, CROM offers a column-supported cast-in-place concrete roof.

Aluminum Dome

alum dome

CROM works closely with several manufacturers of free-span aluminum domes. The top of the tank wall can be designed to accommodate all loads imparted by the dome. The actual dome is installed by the manufacturer.

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