DESIGN OF A RCC WATER STORAGE TANK IN SUPPORT FOR THE
PROPOSED DEVELOPMENT OF LUDERITZ
A CONCEPTUAL DESIGN REPORT
Submitted by:
Nghidengwa Grey Harry (202084248)
In partial fulfilment of the requirements of B.Sc. (Hon.) in
Civil & Environmental engineering
[TCVI3881]
Supervisor: Dr. Philemon Arito
UNIVERSITY OF NAMIBIA
FACULTY OF AGRICULTURE, ENGINEERING & NATURAL SCIENCES
SCHOOL OF ENGINEERING AND THE BUILT ENVIROMENT
DEPARTMENT OF CIVIL AND MINING ENGINEERNG
Plagiarism Declaration
I Nghidengwa Grey [Student Number: 202084248] at the University of Namibia, hereby
declare that the conceptual design work presented in this document is fully my own original
work. I have undertaken this design study independently with help from my colleagues and the
supervision of Dr Philemon Arito. All sources used or referenced, whether published or
unpublished, have been duly acknowledged and cited following the appropriate academic
conventions and referencing styles stated by the University of Namibia policy.
Student Name: Nghidengwa Grey Harry
Date……………………………...
[Student]……. 202084248
Dr. Philemon Arito ……………………...
Date……………………………….
[Supervisor]
i
Abstract
This conceptual design report addresses the design of a storage water tank for Lüderitz, a
coastal town in Namibia, to accommodate a new proposed development of the town in order
to grow the fishing and mining sectors in the region. This report presents three conceptual
design solutions for a water storage tank, in order to meet the town’s water supply demand for
the development of Lüderitz. Under the structural department, we explore a primary and two
design alternative solutions. The chosen design focuses more on structural strength and
capacity of the tank. The design concepts align with local development goals, benefiting the
local industries and community livelihoods. It will also focus on the environmental balance,
including a master plan for integration of the proposed tank and other town developments. By
combining sustainability, and collaboration, the design will aim to secure Lüderitz's future
growth.
ii
Table of Contents
1
Introduction ........................................................................................................................ 1
1.1
Background ................................................................................................................. 1
1.2
Design statement ......................................................................................................... 1
1.3
Problem statement ....................................................................................................... 1
1.4
Aims & Objectives ...................................................................................................... 1
1.4.1
2
3
1.5
Scope of the project ..................................................................................................... 2
1.6
Significance of the study ............................................................................................. 2
1.7
Functional Requirements............................................................................................. 2
1.8
Master Plan overview .................................................................................................. 2
1.9
Standards and Guidelines ............................................................................................ 2
Literature Review............................................................................................................... 3
2.1
Allowable Stress on Concrete for Resisting Cracking ................................................ 3
2.2
Allowable Stress in steel ............................................................................................. 4
2.3
Floors of reinforced water tank ................................................................................... 4
2.4
Concrete water tank walls ........................................................................................... 4
2.5
RCC Water Tank roofs ................................................................................................ 4
Design Methodology .......................................................................................................... 5
3.1
Water storage & Demand ............................................................................................ 5
3.1.1
4
Preliminary design of the tank ............................................................................. 5
3.2
Load Assessment ......................................................................................................... 6
3.3
Material selection ........................................................................................................ 6
3.4
Structural Modelling and Analysis .............................................................................. 6
3.5
Design of Sutural members ......................................................................................... 6
Conceptual Designs ........................................................................................................... 7
4.1
Concept 1 Rectangular water tank .............................................................................. 7
4.2
Concept 2 Circular water tank ..................................................................................... 9
4.3
Concept 3 circular water tank.................................................................................... 10
4.4
Comparisons of the conceptual Designs ................................................................... 11
4.4.1
Justification of the selected conceptual.............................................................. 11
4.4.2
Economic, social, environmental, and sustainability, aspects ........................... 12
4.5
5
Specific objectives ............................................................................................... 1
Project timeline ......................................................................................................... 13
References ........................................................................................................................ 14
iii
List of figures
Figure 1 Methodology to be followed during this design project. ............................................. 5
Figure 2 3d view of the proposed rectangular water tank .......................................................... 7
Figure 3 Sectional (1) view of the proposed rectangular water tank ......................................... 8
Figure 4 Sectional view (2) of the proposed rectangular water tank ......................................... 8
Figure 5 3d view of the proposed circular water tank ............................................................... 9
Figure 6 Sectional view of the circular water tank .................................................................... 9
Figure 7 3d view of the domed shaped circular water tank ..................................................... 10
Figure 8 Front view of the dome shaped circular tank. ........................................................... 10
Figure 9 Project timeline for the execution of the works......................................................... 13
List of tables
Table 1 Comparisons of the three conceptual designs solutions.............................................. 11
iv
1
1.1
Introduction
Background
Water tanks play an important role in securing reliable water supply for communities,
industries, and different applications. These tanks are crucial components of water
infrastructure systems, serving to store and distribute water during times of scarcity or high
demand. The design of water storage tanks encompasses a range of engineering considerations.
Structural design is important to withstand internal liquid pressures and external loads like soil,
wind, and snow. The choice of materials, such as concrete, and steel, depends on factors like
durability, corrosion resistance, and cost-effectiveness of tank[1].
1.2
Design statement
In order to grow the local town of Lüderitz the government divided the development into major
parts to focus on including, Transportation, Water & Wastewater management, structural and
geotechnical engineering. Each team was tasked to design and develop detailed concept designs
of different infrastructures in order to accommodate the upgrading of fishing and mining
sectors in the region.
1.3
Problem statement
In line with the goals set forth in Vision 2030 and National Development Plans, the government
of Namibia is dedicated to encouraging economic growth and development. The government's
specific focus is to expand the tourism, fishing and mining sectors within the Lüderitz town.
To achieve this, the town's infrastructure must be designed to accommodate the predicted
growth. In this context, my role as a structural engineer is to design a water tank that can support
Lüderitz's strategic development plan. This water tank should be designed to meet the town's
growing water demands and storage capacity as a result of the new economic activities,
particularly tourism and mining.
1.4
Aims & Objectives
The main objective of this design project is to contribute to the upgrading and development of
Lüderitz in Namibia to in order to grow the fishing and mining sectors in the region.
1.4.1 Specific objectives
•
Design a concrete water storage tank that is strong and stable, capable of withstanding
different pressure loads while keeping its structural form.
1
•
Meet the towns water demand and storage capacity needed to accommodate the
proposed development.
1.5
Scope of the project
The project scope adopts will adopt different methods and aspects to ensure a successful water
tank design. The major components of the scope include. Consulting on the current and
projected water demand to accommodate the growing town of Lüderitz in order to determine
the water storage capacity of the tank. To identify a site plan that outlines the tanks’ location
withing the chosen region and intergrade the towns proposed layout. Develop a detailed
structural design solution for the storage tank to withstand different kinds of loads. Develop
project deliverables project timeline, resources, and bill of quantities for the successful
completion of the project.
1.6
Significance of the study
1.7
Functional Requirements
•
Storage Capacity – Ensuring that enough water is stored for consumption and
emergency.
•
Structural Integrity – Ensuring that the tank is structural stable and durable.
•
Maintenance and Accessibility- The structure should allow maintenance of different
parts to ensure smooth operation during its intended lifetime.
•
Safety considerations- Ensuring that the content inside the tank will not be
contaminated at any time and provide risks to the community health.
1.8
Master Plan overview
To provided, group members still deciding on what to design.
1.9
Standards and Guidelines
The process of designing this RCC water storge tank will follow the recommendations of the
standards listed below.
1.
SANS 10100-3 Design of concrete water retaining structures.
2.
BS 8007 - Design of concrete structures for retaining aqueous liquids
2
2
Literature Review
The structural behaviour of various tank components depends on the shape, and position
relative to the ground which is why it is so significant. Although tanks might be composed of
steel, reinforced concrete (RC), or synthetic materials, only RC tanks have been described in
this design project [2]. The following characteristics are frequently used to categorize the tanks:
•
Form: Round (with flexible or rigid bases), rectangular, Intze, conical, or funnel, among
others.
•
Position with relation to the ground: Below ground, Resting on ground, partially below
ground, and Above ground.
•
Size: Large, Medium, and Small Capacity
According to (Gobena 2016) A sufficient breaking strength should be considered while
designing RCC water tanks to prevent water seepage. These factors form the foundation of the
design[3].
•
The plain section should remain plain following bending.
•
The entire concrete section, including the cover and reinforcement, must be considered
when calculating the stresses for both flexural and direct tension, or combinations
thereof, regarding resistance to cracking.
•
When calculating strength, the tensile strength of the concrete should not be
considered.
2.1
Allowable Stress on Concrete for Resisting Cracking
The water tank shouldn't have any leaks. Concrete of M 20 grade or above should be used for
this purpose, and concrete close to the water face should be constructed such that no cracks
form [4]. It is important to design the water's wall thickness to reduce the stress on the concrete.
These permitted bending stresses apply to the face farthest from the liquid in members with a
thickness less than 225 mm and in contact with liquid on one side.
3
2.2
Allowable Stress in steel
To prevent concrete cracking, the stress in steel should not be allowed to exceed the
following values in a variety of locations [4].
•
When steel is placed next to a member's face that is in contact with liquid, 115 N/mm
for mild steel bars and 150 N/mm for high strength deformed bars are required.
•
The permissible stress in steel should be 125 N/mm for mild steel bars and 190
N/mm for high strength deformed bars when steel is given on the face distant from
the liquid for members 225 mm or greater in thickness.
•
If steel is given on the face of members with a thickness of less than 225 mm to
protect them from liquid, as in the past
2.3
Floors of reinforced water tank
Water tank floors should be designed for bending moments as a result of dead load and water
load. While designing the floor of multi-cell water tank, special attention should be given. If
the walls and floor are attached firmly, then moment at the junction along with other transferred
loads should be taken into consideration in floor design [4].
2.4
Concrete water tank walls
The liquid pressure on plane walls may be resisted by a combination of horizontal and vertical
bending moments. Concrete tank walls are designed to be extended or contracted discretely
from the floor. They can also be designed to resist moments at the base of the wall due to fixity
to the floor [4].
2.5
RCC Water Tank roofs
When the roof and walls are monolithic, ensure sure the movement joints in the roof and the
walls match up to prevent sympathetic cracking. When a tank is used to store water for
domestic use, the roof should be made water-resistant. This can be accomplished by limiting
stresses in the same way that the tank is, by applying a waterproof membrane covering, or by
designing slopes that will retain enough drainage[4].
4
3
Design Methodology
The following procedure shown in the figure below will be used in the project design processes
of the concrete water tank.
Water Demand
& Storage data
collection
Preliminary
design of the
Tank
Load Assesment
and
considerations
Designing of
structural
members
Structural
Modelling &
Analysis [RBT]
Material
Selection
Documentation
& Report
writing
Submission of
Design project
delivables
Figure 1 Methodology to be followed during this design project.
3.1
Water storage & Demand
3.1.1 Preliminary design of the tank
The total water storage of a tank, for a given a given supply system capable of satisfying a
maximum 24 hrs demand can be calculated using the following formula[5].
𝑆 =𝐴+𝐵+𝐶
Where:
A- Fire storage
B- Peak balance demand 25% of maximum demand
C- Emergency storage 25 % A+B
5
3.2
Load Assessment
The proposed tank will be designed resting on the ground therefore for the design of the tank
different loads that will be applied:
3.3
•
Self-weight of the concrete
•
Water pressure in the tank
•
Back fill pressure on the outside of the tank
Material selection
Since Lüderitz is a coastal town, concrete will be used for the construction of the tank, since it
will last longer compared to other alternative construction materials like steel which last for a
shorter period due to corrosion. The tank will be rectangular in shape with a thicker base of
concrete to provide extra load resistance.
3.4
Structural Modelling and Analysis
A software Robot structural analysis will be used to analyse and map the effects of different
load combinations on the tank. LC will be adopted from the appropriate codes of practice. From
the load combination results, bending moments, tensile forces and shear forces will be used to
design the structural members to withstand the forces.
3.5
Design of Sutural members
The design of structural members such as walls, floor and top floor will be design using SANS
10100-3/ BS 8007. Calculations for member design will be provided and drawings with Revit
software.
6
4
Conceptual Designs
For this Design project 3 district conceptual design solutions were drawn up. Although each
design offers unique advantages, after thorough analysis and evaluation, a rectangular tank
with an accessible roof slab was preferred for the construction.
4.1
Concept 1 Rectangular water tank
This design presents a rectangular tank with a flat roof slab that can serve as an accessible
roof for maintenance, and installation of equipment’s during the tank’s operation.
Figure 2 3d view of the proposed rectangular water tank
7
Figure 3 Sectional (1) view of the proposed rectangular water tank
Figure 4 Sectional view (2) of the proposed rectangular water tank
8
4.2
Concept 2 Circular water tank
In this concept the design is in a cylindrical shape with an accessible roof slab for
maintenance and installation of equipment’s
Figure 5 3d view of the proposed circular water tank
Figure 6 Sectional view of the circular water tank
9
4.3
Concept 3 circular water tank
In this concept the design is in a cylindrical shape with an inaccessible dome shaped roof.
Figure 7 3d view of the domed shaped circular water tank
Figure 8 Front view of the dome shaped circular tank.
10
4.4
Comparisons of the conceptual Designs
Table 1 Comparisons of the three conceptual designs solutions
Alternative
Design Solution 1
Design solution 2
Design solution 3
Description
Rectangular tank
Circular tank with
Circular tank with a
with thicker base for
an accessible roof
dome shaped roof.
additional support
for maintenance
No access will be
and an accessible
made for this tank
roof.
Materials Quantities
The materials required for the construction of circular tanks is
more compared to that of a rectangular tank [6].
Form work and
Although form work required for a circular tank is less in m2.
construction
Formwork for constructing circular tanks can be more
challenging, time consuming, and costly compared to that of
rectangular water tanks[7].
Concrete
Cylindrical shaped objects take up more volume in m3 of concrete
compared to rectangular shaped walls.
Reinforcement
For reinforcement the curve in cylindrical tanks makes to require
more reinforcement, and it to prepare it by bending to tank up the
shape of the cylinder. Rectangular tanks have a shape which is
much easier to reinforce and saves time[6].
Structural
When it comes to structural strength circular tanks can be better in
Considerations
terms of resisting pressures that are being exerted on the tank
walls[3].
Cost Considerations
From the comparisons of the two, circular tanks will require
slightly more quantity of materials, time and preparation
compared to rectangular water tank [8].
4.4.1 Justification of the selected conceptual
Based on the information provided in the comparisons table above, a rectangular tank will
appear to be a more favourable option, when it comes to considering overall, cost, time and
construction of the project.
11
4.4.2 Economic, social, environmental, and sustainability, aspects
4.4.2.1 Economical
•
The construction and operation of the water tank project will present opportunities for
the local population.
•
With water demand balance, potential revenue generation can be achieved through the
water tank supplying security to the different sectors being upgraded.
•
The use of a local water supply system will positively boost local economy by
reducing the pumping of water from the current water reservoir.
4.4.2.2 Social
•
Ensuring a reliable water supply will improve the well-being of the community
especially in emergency situations.
•
Support the proposed economic upgrade in the fishing and mining sectors and the
residents.
4.4.2.3 Environmental impacts
•
The tank might occupy too much land and can even affect local landscapes.
4.4.2.4 Sustainability
•
SDG 6 Clean water and sanitation
The water tank project will contribute to this goal through providing a reliable source
of clean water for residents of Lüderitz.
•
SDG 13 Climate action
Although the tank might occupy much land, if planned and designed carefully the
tank can mitigate local dry climate regions and reduce the water scarcity.
•
Decent work & Economic growth.
The tank project can contribute to the decent work through the economic growth of
mining and fishing sectors.
12
1
2
3
4
5
6
7
8
9
10
Beging writing final report
25 days
Continue designing members
7 days
Presentations
1 day
Final Report Writing
31 days
Final Presentation
1 day
Final Report Submission
1 day
08/07/2023
20/9/2023
21/9/2023
25/10/2023
22/9/2023
10/10/2023
27/9/2023
27/9/2023
10/11/2023
22/11/2023
22/11/2023
22/11/2023
27/11/2023
27/11/2023
27/9/2023
23/9/2023
22/9/2023
21/9/2023
20/9/2023
Figure 9 Project timeline for the execution of the works
13
27/11/2023
27/11/2023
26/11/2023
33 days
24/7/2023
22/11/2023
Structural member designs
23/08/2023
25/10/2023
91 days
07/08/2023
24/10/2023
Progress submissions
27/11/2023
10/12/2023
7 days
End Date
24/07/2023
10/11/2023
Conceptual design report
Start Date
10/10/2023
4 days
23/08/2023
Duration
Literature Review
08/07/2023
Task Description
08/04/2023
Task ID
01/07/2023
24/7/2023
Project timeline
28/07/2023
4.5
5
References
[1]
R. KUSHWAHA and D. PATEL, “COMPARATIVE STUDY ON DESIGN OF
CYLINDRICAL WATER TANKS WITH VARYING ASPECT RATIOS,”
International Journal of Recent Development in Civil & Environmental Engineering
[ISSN: 2581-4117 (online)], vol. 2, no. 2, 2017.
[2]
G. Calvi and R. Nascimbene, Seismic Design and Analysis of Tanks. 2023.
[3]
J. A. Gobena, “A Case Study on Water Storage Tank Design and Constrution for
Domestic Purpose in Shashemene Town, Ethiopia,” vol. 8, no. 12, 2016, [Online].
Available: www.iiste.org
[4]
British Standards Institution., British standard code of practice for design of concrete
structures for retaining aqueous liquids. British Standards Institution, 1987.
[5]
SOUTH AFRICAN NATIONAL STANDARD, “Water supply and drainage for
buildings Part 1: Water supply installations for buildings.”
[6]
H. J. Mohammed, “Economical design of water concrete tanks,” European journal of
scientific research, vol. 49, no. 4, pp. 510–520, 2011.
[7]
A. Mas’ud Alfanda, “Comparative Analysis of Circular and Rectangular Reinforced
Concrete Tanks Based on Economical Design Perspective,” American Journal of
Applied Scientific Research, vol. 3, no. 2, p. 14, 2017, doi:
10.11648/j.ajasr.20170302.12.
[8]
M. S. Latha, “Comparison of Analysis between Rectangular and Circular Overhead
Water Tank,” Applied Research on Civil Engineering and Environment, vol. 2, pp. 77–
95, 2021.
14