reinforced concrete reservoir assignment

Reinforced concrete reservoir-RC

The choice of tank type and design should always be entrusted to an experienced engineer. Several features, however, should always be present in storage tanks to allow for their fullest and safer utilization in a water supply system.

Their foundations and structure should be sound as water is heavy and even the smallest structural weakness would cause the tank to either leak or completely fail. All tanks should be provided with an outlet hole situated some 20 cm from the bottom; an overflow and vent pipe (with an appropriate screen to avoid the entrance of small animals) and the inlet pipe should always be at the top and at the opposite end to the outlet, to allow for water mixing and aeration; the tank’s bottom should slope towards its lowest point, where a drain should be installed for cleaning and flushing the tank.

The drain’s outlet should be piped away from the tank to avoid the creation of unsanitary conditions around the tank or the destabilization of the tank’s foundations by excess water. A manhole, with an appropriate cover and ladders, should be provided to allow access to the interior for cleaning and inspection purposes; storage tanks should be fenced-off to avoid free access to people, and in many cases, there could be a need to have them guarded to protect the structures and pipe-work from vandalism or to avoid theft of water.

Elevated tanks (water towers) are mainly used to gain the necessary pressure head to allow an efficient gravity flow into the distribution network, to stabilize pressures within the system and to facilitate meeting fluctuations in water demand; if the topography of the camp and its surroundings is adequate (hills of adequate elevation), surface reservoirs should be preferred for this purpose as the economic limit of height and volume of water towers is determined when the supporting structure for an elevated tank becomes more expensive than alternative conduction pipelines.

Details of a Reservoir Tank

NURKUZSANA BINTI MOHD ANAS(05DKA09F2048)

Reinforced concrete reservoirs are used to store clean water for release on demand. They are usually made of concrete reinforced with steel bars or steel mesh, although some low-cost construction techniques use bamboo or other materials to reinforce the concrete. Reservoirs may also be made of masonry, or ferrocement.

Chemical additives are often mixed with the concrete to make it more impermeable to water. Reinforced concrete reservoirs are built at the sit on a solid foundation. If the base is not solid enough, another site should be chosen, or arrangements made to stabilize the construction

To protect the water from contamination, the reservoir is covered with a roof, usually made of reinforced concrete, but other materials can be used. In the top of the tank an aeration pipe with a screen allows fresh air to circulate in the tank, but keeps rodents and insects out.

A manhole in the roof allows access to the tank for cleaning and repairs. Water flows into the reservoir through an inlet pipe above the water level in the reservoir. This prevents back-flow and allows the water to be heard entering the tank. At this point, a chlorine solution is often added for disinfection.

Outlets are built a little above the floor of the reservoir, which has a slope pitched down towards one point with a washout pipe for flushing.


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Construction, Operations and Maintenance

Operation consists of opening and closing the valves, and managing a chlorinator, if provided. If the reservoir does not deliver directly to a tap, water distribution is usually carried out by a caretaker.

A well-designed and well-built reservoir needs very little maintenance. The surroundings must be kept clean on a regular basis; every two months the valves must be closed and opened to prevent them from sticking, and the screens must be checked.

Occasionally, a screen or tap may need to be repaired. Once a year, or sooner if contamination is suspected, the reservoir must be drained, de-silted, cleaned with a brush and disinfected with chlorine.

Any leaks or cracks in the concrete have to be repaired as soon as possible. If needed, a caretaker can be appointed to regulate the inflow and outflow. A concrete reservoir has few other organizational requirements.

Range of depth: Usually between 1.5–3.0 m. Expected useful lifetime: 30 years.

Reinforced concrete reservoir diagram


PRESTRESSED CONCRETE TANKS

These Specifications set the minimum requirements which must be used as a basis for all circular prestressed concrete tank designs which use the strand-wrap system. Alternate designs which do not incorporate machine strand wrapping with continuous electronic recording of prestressing forces shall not be considered.

All circumferential prestressing of tank walls shall be done with hot-dipped galvanized seven-wire strand conforming to these Specifications and placed on the exterior of the cast-in-place corewall. Systems which utilize machine wrapped wire in lieu of strand shall not be accepted.

No system which relies on pulling the wire through a die, to provide a tensioning force, will be allowed. Vertical prestressing shall be provided using galvanized, threaded bar. Wire wrapping shall not be accepted in lieu of strandwrapping.

Only designs incorporating cast-in-place corewalls will be accepted. No corewallsmanufactured by precasting or shotcreting will be allowed

Tank wall systems based on rod type tendons involving the circumferential movement of prestressing steel relative to the wall surface shall not be considered. Tank wall systems which utilize strand cables placed circumferentially inside of ducts cast in the corewall or strands manually placed externally around the corewall shall not be acceptable.

Tank wall designs shall not be based on stress-tolerance and stress-loss deductions less than those indicated in these Specifications.

Clearance between wrapped strands, in any vertical layer, shall not be less than 2.5 strand diameters or 3/8-inch whichever is greater.

Tank wall designs shall not be based on wrapping tolerances less than what the wrapping machinery can factually and continuously meet based on continuous electronically recorded print-outs taken from earlier projects.

Each intermediate strand layer shall be covered with shotcrete of 3/8-inch thicknessover the steel. The minimum cover over the final strand layer shall be 1.5 inches.


Prestressed concrete tanks with flat or dome roof

Pressed steel sectional water tanks


An old “Braithwaite” pressed steel tank (seeCase History), supported by a painted steel

Structure.

The concept of liquid storage in tanks constructed by means of a series of modular steel panels bolted together on site was originally developed and patented in 1901 by Braithwaite in the United Kingdom, an organization which has continued to be active to this day.

There are many beneficial features associated with the pressed steel sectional tank concept. It facilitates construction in an infinite range of sizes and configurations. The profile panel sections provide excellent strength properties while tanks mounted on steel towers above ground level have an aesthetically pleasing appearance.

A major advantage of the sectional tank design is that it facilitates easy handling and transportation over long distances to remote areas, regardless of the final dimensions of the assembled unit. Assembly on site is quickly achieved without the need for sophisticated tooling. In this way premanufactured storage facilities having a capacity even in excess of 15 000 cubic meters, can be provided for a vast variety of applications regardless of the location of the site.


Reservoirs constructed from pressed steel sections are used extensively by the mining industry and municipal authorities. Large storage tanks to this design which are mounted on steel towers can also be seen at many of Eskoms power stations.

Pressed steel sectional water tanks are normally hot dip galvanized for corrosion control in accordance with the requirements of the SANS 121 (ISO 1461) galvanizing standard. The thickness of the hot dip galvanized coating applied is within a range of 80 to 100μm. This is more than five times the thickness of zinc on pregalvanized corrugated steel cylindrical tanks.

Hot dip galvanizing has achieved an impressive record over many years by providing protection from corrosion for tanks constructed from pressed steel sections. Hot dip galvanizing alone provides adequate corrosion control in most applications. Meanwhile, investigations into the feasibility of providing added protection by way of an additional internal lining are presently in progress. \

The purpose is to ensure extended maintenance free life in situations where water with aggressively corrosive properties is required to be stored. Practical test results obtained to date by applying a duplex coating consisting of hot dip galvanizing and an epoxy based organic coating on internal surfaces are extremely promising.


reinforced concrete reservoir assignment

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