ISO 18407:2018

Simplified design of prestressed concrete tanks for potable water

This document provides guidelines for the planning, design and construction of a cylindrical tank constructed on the ground with prestressed concrete (PC) for use with potable water tank. This document is applicable to PC tanks for potable water with a capacity of 30 000 m3 or less and the diameter-to-height ratio (D/H) from 1,0 to 3,0. NOTE When designing and constructing a tank not covered by this document (reinforced concrete tanks, underground tanks, elevated tanks, etc.), a designer can refer to this document for common elements where possible.

Conception simplifiée du réservoir pour l'eau potable en béton pré-armé

General Information

• Status: Published
• Publication Date: 23-May-2018
• ICS: 91.080.40 - Concrete structures
• Technical Committee: ISO/TC 71/SC 5 - Simplified design standard for concrete structures
• Drafting Committee: ISO/TC 71/SC 5 - Simplified design standard for concrete structures
• Current Stage: 9092 - International Standard to be revised
• Start Date: 16-Jul-2024
• Completion Date: 13-Dec-2025

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18407
First edition
2018-05
Simplified design of prestressed
concrete tanks for potable water
Conception simplifiée du réservoir pour l'eau potable en béton pré-
armé
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .vi
Introduction .vii
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Symbols .4
5 Design principles .12
6 Load .13
6.1 General .13
6.2 Deadweight .13
6.3 Imposed load .13
6.4 Hydrostatic water pressure .14
6.5 Prestress .14
6.5.1 General.14
6.5.2 Prestressing force immediately after prestressing .14
6.5.3 Effective prestressing force .18
6.5.4 Indeterminate forces due to prestress .19
6.6 Creep and drying shrinkage of concrete .19
6.7 Effect of temperature .19
6.8 Seismic action .20
6.9 Wind load .20
6.10 Snow load .20
6.11 Earth pressure .21
6.12 Uplift pressure force .22
6.13 Other loads .22
7 Structural analysis .22
7.1 Calculation of member force .22
7.2 Concrete .22
7.2.1 Strength .22
7.2.2 Modulus of elasticity.23
7.2.3 Poisson’s ratio .23
7.2.4 Drying shrinkage .23
7.2.5 Creep .23
7.3 Steel .25
7.3.1 Strength .25
7.3.2 Modulus of elasticity.26
7.3.3 Relaxation .26
7.4 Calculation of tensile reinforcement .26
8 Stress limit .27
8.1 General .27
8.2 Stress limit of reinforced concrete members .28
8.2.1 Stress limit of concrete .28
8.2.2 Stress limit of reinforcement .28
8.3 Stress limit of prestressed concrete members .28
8.3.1 Stress limit of concrete .28
8.3.2 Tensile stress limit of prestressing steel .29
8.3.3 Stress limit of reinforcement .29
8.3.4 Augmentation of tensile stress limit of concrete.29
9 Verification of safety against earthquake .29
9.1 Principles of seismic design .29
9.1.1 General.29
9.1.2 Ground motion levels .29
9.1.3 Levels of earthquake resistance .29
9.1.4 Effects of earthquake.30
9.1.5 Seismic design procedure .30
9.2 Input earthquake motion .30
9.2.1 Seismic design method .30
9.2.2 Design seismic coefficients for the seismic coefficient method for Level 1
ground motion .31
9.2.3 Design seismic coefficients for the seismic coefficient method for Level 2
ground motion .32
9.2.4 Seismic input for design by dynamic analysis .33
9.3 Verification of structural safety .33
9.3.1 Effects of earthquake.33
9.3.2 Combination of loads .37
9.3.3 Calculation of member forces .38
9.3.4 Safety verification .47
9.4 Investigation for foundation .54
10 General structural details .54
10.1 Prestressing steel .54
10.1.1 Clear distance .54
10.1.2 Concrete cover .55
10.1.3 Arrangement of curved prestressing steel .56
10.1.4 Arrangement of anchorages and couplers .56
10.1.5 Protection of anchorage zone .56
10.1.6 Reinforcement of concrete near anchorages .56
10.2 Steel reinforcement .56
10.2.1 Clear distance .56
10.2.2 Concrete cover .57
10.2.3 Bend configurations of reinforcement .57
10.2.4 Splices in reinforcement .59
10.2.5 Anchoring of reinforcement .60
10.2.6 Welded wire fabric .61
10.3 Concrete joints .61
10.3.1 Construction joints . .61
10.3.2 Joints between precast concrete members .62
10.4 Reinforcement for opening .62
11 Design of members.63
11.1 Method of calculating member force .63
11.1.1 Analysis method .63
11.1.2 Analysis model .63
11.2 Component division .65
11.3 Roof .65
11.3.1 Structural types.65
11.3.2 Design in general .66
11.4 Tank wall .72
11.4.1 Structural types.72
11.4.2 Design in general .74
11.5 Base slab .91
11.5.1 Structural types.91
11.5.2 Design in general .92
12 Materials .96
12.1 Quality of materials .96
12.1.1 General.96
12.1.2 Concrete materials .96
12.1.3 Concrete . .97
12.1.4 Prestressing steel .97
12.1.5 Steel reinforcement .97
iv © ISO 2018 – All rights reserved

12.1.6 Welded wire fabric .97
12.1.7 Anchorages and couplers .97
12.1.8 Sheath .97
12.1.9 Coating materials for protecting prestressing steel .98
13 Tank appurtenances .98
13.1 Ladders/stairs and handrails .98
13.2 Manhole and water pilot hole .99
13.3 Ventilators .99
13.4 Lightning rods .99
13.5 Piping .99
13.6 Catch basin.100
13.7 Water-level gauge .100
13.8 Rainwater treatment .100
13.9 Protection equipment .100
Annex A (informative) Reference design flow .101
Annex B (informative) Design seismic coefficients for the seismic coefficient method .103
Annex C (informative) Seismic input for design by dynamic analysis .106
Annex D (informative) Example of material specifications .108
Annex E (informative) Example of design calculation .112
Bibliography .174
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and
prestressed concrete, Subcommittee SC 5, Simplified design standard for concrete structures.
vi © ISO 2018 – All rights reserved

Introduction
The aim of this document is to provide rules for the design and construction of prestressed concrete
water tanks to be built in less-developed areas of the world. The design rules are based on simplified
worldwide-accepted strength models. This document is self-contained; therefore actions (loads) and
simplified analysis procedures are included, as well as minimum acceptable construction practice
guidelines.
A great effort was made to include self-explanatory tables, graphics and design aids to simplify the
use of this document and provide procedures. Notwithstanding, the economic implications of the
conservatism inherent in approximate procedures as a substitution to sound and experienced
engineering should be a matter of concern to the designer who employs this document and to the owner
who hires him.
A prestressed concrete tank for potable water generally comprises the roof, wall and base slab. The roof
is made to entirely cover the top of the cylindrical wall so as to protect the water from contamination
with rainwater, etc. In many cases, it is made in the form of a dome shaped like a convex disc cut off
from a sphere. The wall is a vertical cylinder that forms a container for water in combination with
the flat disc base slab. Normally, only the wall of a prestressed concrete water tank is made with
prestressed concrete, while the roof and base slab are made with reinforced concrete. Prestress is
generally applied to the wall using prestressing steel in the vertical and circumferential directions, but
in some cases prestress is applied only to the circumferential direction. For this reason, this document
defines a prestressed concrete cylindrical tank as a structure having prestressing steel at least in the
circumferential direction of the wall to apply prestress, so as to cover both types. Therefore, the roof,
base slab and wall in the vertical direction may not necessarily be of prestressed concrete construction
but may be of reinforced concrete construction.
A prestressed concrete water tank construction is generally adopted to preserve a water storage
facility with the aim of preventing severe secondary disasters and allowing the standing water to be
used as an emergency water supply. For this reason, it is required to be designed as a rule as a high
degree of importance.
The minimum dimensional provisions contained in this document are intended to account for
undesirable side effects that will require more sophisticated analysis and design procedures. Material
and construction provisions are aimed at site-mixed concrete, as well as ready-mixed concrete and
steel of the minimum available strength grades.
The earthquake-resistance provisions are included to account for the fact that numerous underdeveloped
regions of the world occur in earthquake-prone areas. The earthquake resistance is based upon
the employment of structural concrete walls (shear walls) that limit the lateral deformations of the
structure and provide for its lateral strength.
This document contains provisions that can be modified by the National Standards Body due to local
design and construction requirements and practices. The specifications that can be modified are
indicated using [“boxed values”]. The National Standards Body is expected to review the “boxed values”
and may substitute alternative definitive values for these elements for use in the national application of
this document.
INTERNATIONAL STANDARD ISO 18407:2018(E)
Simplified design of prestressed concrete tanks for
potable water
1 Scope
This document provides guidelines for the planning, design and construction of a cylindrical tank
constructed on the ground with prestressed concrete (PC) for use with potable water tank.
This document is applicable to PC tanks for potable water with a capacity of 30 000 m or less and the
diameter-to-height ratio (D/H) from 1,0 to 3,0.
NOTE When designing and constructing a tank not covered by this document (reinforced concrete tanks,
underground tanks, elevated tanks, etc.), a designer can refer to this document for common elements where
possible.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1920-3, Testing of concrete — Part 3: Making and curing test specimens
ISO 1920-4, Testing of concrete — Part 4: Strength of hardened concrete
ISO 6934-1, Steel for the prestressing of concrete — Part 1: General requirements
ISO 6934-2, Steel for the prestressing of concrete — Part 2: Cold-drawn wire
ISO 6934-3, Steel for the prestressing of concrete — Part 3: Quenched and tempered wire
ISO 6934-4, Steel for the prestressing of concrete — Part 4: Strand
ISO 6934-5, Steel for the prestressing of concrete — Part 5: Hot-rolled steel bars with or without subsequent
processing
ISO 6935-1, Steel for the reinforcement of concrete — Part 1: Plain bars
ISO 6935-2, Steel for the reinforcement of concrete — Part 2: Ribbed bars
ISO 6935-3, Steel for the reinforcement of concrete — Part 3: Welded fabric
ISO 12439, Mixing water for concrete
ISO 14654, Epoxy-coated steel for the reinforcement of concrete
ISO 14824-3, Grout for prestressing tendons — Part 3: Test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at https: //www .electropedia .org/
3.1
bending analysis
method for determining the membrane force and bending moment in consideration of the boundary
conditions at the base of the dome
3.2
clearance
distance between the designed high-water level and the upper edge of the tank wall
3.3
convective pressure
water pressure produced by oscillation of the water
3.4
cylindrical prestressed concrete tank
concrete tank comprising the roof, cylindrical wall and base slab, for which prestressing steel is
provided at least in the circumferential direction to apply prestress
3.5
disc part
part other than the ring plate of the base slab that resists bending moments
3.6
dome ring
circular beam provided along the base of the roof of a spherical or other shape of the dome to control
radial displacement at the base of the roof
3.7
dynamic water pressure
water pressure due to the effect of an earthquake
3.8
embedded system
system of applying prestress, whereby circumferential prestressing steel is provided within
concrete members
3.9
fixed support
wall-bottom connection whereby the rotation or horizontal displacement of the wall with respect to
the bottom is not allowed
3.10
foundation slab
reinforced concrete or prestressed concrete slab provided in contact with the bottom surface of the
base slab
3.11
freely sliding support
wall-bottom connection, whereby the rotation and horizontal displacement of the wall with respect to
the bottom are allowed
3.12
hinged support
wall-bottom connection, whereby the rotation of the wall with respect to the bottom is allowed
3.13
hoop tension
circumferential axial tensile force generated by such loads as water pressure
2 © ISO 2018 – All rights reserved

3.14
horizontal thrust
horizontal component of the axial force in the meridian direction of the dome at the base of the dome
3.15
Housner method
conventional approximate analysis method for liquid vibration proposed by G. W. Housner
3.16
imposed load
load of portions not included in the design calculation as structural members and load applied to the
roof for such purposes as inspection
3.17
impulsive pressure
dynamic water pressure (3.7) in response to short-period components of an earthquake and water
pressure associated with inertial force produced by accelerations of the tank wall and directly
proportional to these accelerations
3.18
inertia force
force given by the product of the weight of a body and the design seismic intensity
3.19
in-plane shear force
shear force that acts parallel to the shell surface
3.20
membrane floor
part other than the ring plate of the base slab that does not resist bending moments
3.21
membrane force
in-plane axial force of a shell structure
3.22
out-of-plane shear force
shear force that acts at a right angle to the shell surface
3.23
particular load
special load that acts depending on the natural conditions of the tank construction site
Note 1 to entry: Particular load is judged as a primary load (3.25) or a subsidiary load (3.31) on a case-by-case basis.
3.24
pilaster
rectangular projections from the tank wall along its generatrix lines for anchoring circumferential
prestressing steel
3.25
primary load
load that constantly acts
3.26
ring plate
peripheral part of the base slab for transmitting forces primarily from the tank wall to the ground
3.27
sloshing
vibration of a solid oscillating surface generated in response to relatively long-period components of an
earthquake
3.28
solid mass of water
equivalent weight of water to produce the impulsive force on the tank wall
Note 1 to entry: It is assumed to be fastened rigidly to the tank wall.
3.29
solid oscillating mass
equivalent oscillating weight to produce the convective force on the wall
Note 1 to entry: It is assumed to be fastened to the tank wall by spring.
3.30
spherical dome
curved shell in the form of a part of a sphere cut off by a plane
3.31
subsidiary load
load that rarely acts
3.32
tank empty condition
state in which no water is present in the tank
3.33
tank full condition
state in which the water level in the tank reaches the design high water level
3.34
velocity potential method
method for a theoretical solution to irrotational vibration of a non-compressive and non-viscous fluid
3.35
waterstop
plate inserted in joints between concrete lifts and the wall-bottom joints for waterstopping
4 Symbols
A projection area
A area of concrete subjected to bearing load
b
A total area of concrete surface
c
A surface area of the dome
d
A area subjected to the effect of anchorage set
EP
A cross-sectional area of element i (member between nodes i and i + 1)
i
A cross-sectional area of prestressing steel
p
A cross-sectional area of tensile reinforcement
s
b member width
4 © ISO 2018 – All rights reserved

C wind force coefficient
C earth pressure coefficient
e
C structure characteristic coefficient
s
C correction factor by region
z
D diameter of the tank
D correction factor dependent on damping constant
he
 
Et
 
i
flexural stiffness of node i =
D
i
 
 12 1−ν 
()
 
D pile diameter
p
D response reduction ratio due to plastic deformability
η
E elastic modulus
E elastic modulus of concrete
c
E elastic modulus of prestressing steel
p
E elastic modulus of steel reinforcement
s
f’ design compressive strength of concrete
cd
f’ characteristic compressive strength of concrete
ck
f tensile strength of prestressing steel
pu
f yield strength of prestressing steel
py
f yield strength of steel reinforcement
sy
f design tensile strength of prestressing steel
ud
f design yield strength of steel reinforcement and structural steel
yd
g gravitational acceleration
g uniform pressure
H height or total water depth of the tank
H distance from the bottom of the tank wall to the point of action of the dome inertia force or
G
other partial weight inertia force
H length of thickened wall (haunch height)
h
H thickness of i-th stratum
i
H total height of earth pressure action
s
H horizontal thrust
t
H water depth at an arbitrary point
x
h height from the ground surface
h distance from tank bottom to a solid mass point when dynamic water pressure on base slab is
rE
neglected
h distance from tank bottom to a solid mass point when dynamic water pressure on base slab is
rI
considered
h distance from tank bottom to solid oscillating mass point when dynamic water pressure on
sE
base lab is neglected
h distance from tank bottom to solid oscillating mass point when dynamic water pressure on
sI
base slab is considered
h virtual thickness of member
th
I second moment of area of element i (member between nodes i and i + 1)
i
J vessel function
 
Et
 
K flexural stiffness =
 
 12 1−ν 
()
 
K design horizontal seismic coefficient
h
K standard horizontal seismic coefficient of structure for Level 1 ground motion
ho1
K standard horizontal seismic coefficient of structure for Level 2 ground motion
ho2
K design horizontal seismic coefficient for Level 1 ground motion
h1
K design horizontal seismic coefficient for Level 2 ground motion
h2
K vertical subgrade reaction modulus
v
K vertical spring constants of node i
vi
K rotational spring constants of node i
θi
k spring constant of bearing
k coefficient incorporating the characteristics of foundations
α
k coefficient incorporating the characteristics of base slab
β
L ring plate width
rp
L water depth
w
l length from the tension end of prestressing steel to the design cross-section
l basic development length
d
l maximum spacing of prestressing steel
max
l length of prestressing steel
p
l distance from the top of wall to the beginning point of action of distributed load
6 © ISO 2018 – All rights reserved

l distance from the top of wall to the end point of action of distributed load
Δl set length
M corrected vertical bending moment
a
M vertical bending moment of member
d
M vertical bending moment at the bottom of the tank wall generated by changes in the curvature
e
radius of the tank wall
M design flexural fracture capacity
ud
M vertical bending moment
x
M bending moment at node i determined by planar frame analysis
xi
M torsional moment
xϕ
M restraining moment at the bottom of the tank wall
M vertical bending moment at the bottom of the tank wall with a constant thickness
0c
M vertical bending moment at the bottom of the tank wall generated by curvature changes when
0e
the wall thickness is constant at t
M vertical bending moment at bottom of the tank wall
0f
M vertical bending moment at the bottom of the tank wall incorporating increases in the wall
0h
bottom thickness
M (x) overturning moment at a distance x from the top of the tank wall
0T
M vertical bending moment at the bottom of the tank wall generated by the effect of Poisson’s
0ν
ratio due to vertical prestress, ν, when the wall thickness is constant
vertical bending moment obtained from axisymmetric analysis under equivalent load
M
x
M circumferential bending moment
ϕ
M torsional moment
ϕx
M bending moment per unit length in the circumferential directions
θi
N axial force in the vertical direction
x
N (x) vertical axial force at distance from the bottom of the tank wall
xo
N in-plane shear force
xϕ
N axial force in the circumferential direction
ϕ
N membrane force per unit length of the dome in the meridian direction
ϕd
N in-plane shear force
ϕx
N membrane force per unit length of the dome in the parallel direction
θd
n elastic modulus ratio (=E /E )
p c
P prestressing force in the vertical direction
P (r) maximum impulsive pressure that acts on the base slab
br
P (r) maximum vibration pressure that acts on the base slab
bs
P tensile force of prestressing steel at the jack position
i
P dynamic water pressure at lower edge
l
P horizontal force acting on the solid mass point
r
P concentrated load acting on node i (including moment load)
ri
P horizontal force acting on the s-th soild oscillating mass point
s
P total earth pressure
sh
P concentrated load per unit length acting on node i
si
P tensile force of prestressing steel at jack position after considering the set length
t
P dynamic water pressure at upper edge
u
P wind load
w
P (ξ) maximum impulsive pressure that acts on tank wall
wr
P (ξ) maximum convective pressure that acts on tank wall
ws
P tensile force of prestressing steel at design cross-section
x
P impulsive pressure at the bottom end
0l
P convective pressure at the bottom end
1l
P convective pressure at the top end
1u
p pressure at the bottom of the tank wall
p earth pressure
sh
p hydrostatic water pressure at an arbitrary depth from the water surface
w
p (x) radial component of load
o
Q load at the time of allowable displacement
a
Q cracking load of member
cr
Q elastic response axial tensile force
e
Q circumferential axial tensile force of member by elastic analysis under an earthquake load
he
calculated from design horizontal seismic coefficient
Q load at yielding of prestressing steel
py
Q out-of-plane shear force
x
Q yield load of member
y
Q restrained shear force at the bottom of the tank wall
Q out-of-plane shear force
ϕ
8 © ISO 2018 – All rights reserved

q wind veloci
...