Structural design of buried pipelines under various conditions of loading - Part 4: Parameters for reliability of the design

This Technical Report lists the parameters for the reliability of the structural design of buried water and wastewater pressure pipelines, drains and sewers.
The reliability of the design of buried pipelines is based on the selection of appropriate design parameters for a chosen design method. This document identifies the parameters appropriate to the chosen design method, which should all be clearly stated.
This Technical Report does not aim to specify the requirements for the structural design of water and wastewater pressure pipelines, drains and sewers. EN 1295 1 “Structural design of buried pipelines under various conditions of loading — Part 1: General requirements” defines these requirements.
This Technical Report does not apply for offshore laying, pipes supported on piles, no dig pipelines, or laid above ground. Supplementary considerations need to be taken into account for these specific installations.
Special situations (e.g. landslide, earthquake, fire) are outside the scope of this document.
Design parameters for calculation of longitudinal effects (including bending moments, shear forces and tensile forces resulting for example from non uniform bedding and thermal movements and, in the case of pressure pipelines, from Poisson's contraction and thrust at change of direction or cross-section) are not covered in this document.

Statische Berechnung von erdverlegten Rohrleitungen unter verschiedenen Belastungsbedingungen - Teil 4: Parameter für die Zuverlässigkeit der Auslegung

Calcul de résistance mécanique des canalisations enterrées sous diverses conditions de charge - Partie 4 : Paramètres pour la fiabilité de la conception

Projektiranje vkopanih cevovodov pri različnih pogojih obremenitve - 4. del: Parametri za zanesljivost projektiranja

Cilj tega tehničnega poročila ni določitev zahtev za projektiranje tlačnih cevovodov, vodov in kanalov za odvajanje vode in odpadnih voda. Te zahteve določa standard EN 1295 1»Projektiranje vkopanih cevovodov pri različnih pogojih obremenitve – 1. del: Splošne zahteve«.
To tehnično poročilo se ne uporablja za cevovode, položene na morju, cevovode, podprte s piloti, nevkopane cevovode ali cevovode, položene nad terenom. Za te posebne namestitve je treba upoštevati dodatne dokumente.
Posebne razmere (npr. zemeljski plaz, potres, požar) niso vključene v področje uporabe tega dokumenta.
Parametri zasnove za izračun vzdolžnih učinkov (vključno z upogibnimi momenti, strižnimi in nateznimi silami, ki nastanejo na primer zaradi neenotnega naleganja in toplotnih premikov ter v primeru tlačnih cevovodov na podlagi Poissonovega razmerja med skrčkom in raztezkom ob spremembi smeri ali križišču) niso zajeti v tem dokumentu.

General Information

Status
Published
Publication Date
18-Oct-2015
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
06-Oct-2015
Due Date
11-Dec-2015
Completion Date
19-Oct-2015

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SLOVENSKI STANDARD
SIST-TP CEN/TR 1295-4:2015
01-november-2015
3URMHNWLUDQMHYNRSDQLKFHYRYRGRYSULUD]OLþQLKSRJRMLKREUHPHQLWYHGHO
3DUDPHWUL]D]DQHVOMLYRVWSURMHNWLUDQMD

Structural design of buried pipelines under various conditions of loading - Part 4:

Parameters for reliability of the design
Statische Berechnung von erdverlegten Rohrleitungen unter verschiedenen
Belastungsbedingungen - Teil 4: Parameter für die Zuverlässigkeit der Auslegung

Calcul de résistance mécanique des canalisations enterrées sous diverses conditions de

charge - Partie 4 : Paramètres pour la fiabilité de la conception
Ta slovenski standard je istoveten z: CEN/TR 1295-4:2015
ICS:
23.040.01 Deli cevovodov in cevovodi Pipeline components and
na splošno pipelines in general
SIST-TP CEN/TR 1295-4:2015 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 1295-4:2015
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SIST-TP CEN/TR 1295-4:2015
CEN/TR 1295-4
TECHNICAL REPORT
RAPPORT TECHNIQUE
September 2015
TECHNISCHER BERICHT
ICS 23.040.01
English Version
Structural design of buried pipelines under various
conditions of loading - Part 4: Parameters for reliability of
the design

Calcul de résistance mécanique des canalisations Statische Berechnung von erdverlegten Rohrleitungen

enterrées sous diverses conditions de charge - Partie 4 unter verschiedenen Belastungsbedingungen - Teil 4:

: Paramètres pour la fiabilité de la conception Parameter für die Zuverlässigkeit der Auslegung

This Technical Report was approved by CEN on 13 April 2015. It has been drawn up by the Technical Committee CEN/TC 165.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 1295-4:2015 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

3.1 Installation terms ............................................................................................................................................ 5

3.2 Design terms ..................................................................................................................................................... 7

4 General requirements ................................................................................................................................... 8

5 Declaration of the parameters ................................................................................................................... 9

5.1 General ................................................................................................................................................................ 9

5.2 Input data and characteristics ................................................................................................................. 10

5.2.1 Pipe parameters ........................................................................................................................................... 10

5.2.2 External loads parameters ....................................................................................................................... 11

5.2.3 Internal pressure parameters ................................................................................................................. 14

5.2.4 Pipe own weight parameters ................................................................................................................... 15

5.2.5 Weight of fluid ............................................................................................................................................... 15

5.2.6 Subsidence (differential settlement) parameters ............................................................................ 15

5.2.7 Temperature parameters ......................................................................................................................... 16

5.3 Parameters for limit states analysis ...................................................................................................... 16

5.4 Safety parameters ........................................................................................................................................ 19

Annex A (informative) Checklist for parameters for reliability of the structural design of

buried water and waste water pressure pipelines, drains and sewers ................................... 20

Bibliography ................................................................................................................................................................. 23

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European foreword

This document (CEN/TR 1295-4:2015) has been prepared by Technical Committee CEN/TC 165

“Wastewater engineering”, the secretariat of which is held by DIN.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.

This document, EN 1295: “Structural design of buried pipelines under various conditions of loading”,

consists of the following parts:
— Part 1: General requirements (EN);
— Part 2: Summary of nationally established methods of design (CEN/TR);
— Part 3: Common method (CEN/TR);
— Part 4: Parameters for reliability of the design (CEN/TR).
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Introduction

The structural design of buried pipelines constitutes a wide ranging and complex field of engineering,

which has been the subject of extensive study and research, in many countries over a period of very

many years.

While many common features exist between the design methods, which have been developed and

established in the various member countries of CEN, there are also differences reflecting such matters

as geological and climatic variations, as well as different installation and working practices.

In view of these differences, and of the time required to develop a common design method that would

fully reflect the various considerations identified in particular national methods, a multiple stage

approach has been adopted for the development of a European Standard.

In accordance with this approach, a Joint Working Group, at its initial meeting, resolved “first to

produce an EN giving guidance on the application of nationally established methods of structural design

of buried pipelines under various conditions of loading, whilst working towards a common method of

structural design”.

EN 1295-1, “Structural design of buried pipelines under various conditions of loading — Part 1: General

requirements” represents the implementation of the first part of that resolution, and CEN/TR 1295-2

“Structural design of buried pipelines under various conditions of loading — Part 2: Summary of

nationally established methods of design” represents the full implementation of the first part of that

resolution.

In 2003, CEN/TC 164 and CEN/TC 165 accepted a recommendation from JWG1 that the two structural

design options should be published as CEN/TR 1295-3 “Structural design of buried pipelines under

various conditions of loading — Part 3: Common method”, because there was no prospect of the group

reaching agreement on a “Common Method”, and the human and financial resources needed to continue

were, in any case, no longer available.

In 2011, CEN/TC 165 has decided to complete this approach to list the parameters for the reliability of

the structural design of buried water and wastewater pressure pipelines, drains and sewers in relation

with the installation conditions.
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1 Scope

This Technical Report lists the parameters for the reliability of the structural design of buried water and

wastewater pressure pipelines, drains and sewers.

The reliability of the design of buried pipelines is based on the selection of appropriate design

parameters for a chosen design method. This document identifies the parameters appropriate to the

chosen design method, which should all be clearly stated.

This Technical Report does not aim to specify the requirements for the structural design of water and

wastewater pressure pipelines, drains and sewers. These requirements are defined in EN 1295-1.

This Technical Report does not apply for offshore laying, pipes supported on piles, no dig pipelines, or

laid above ground. Supplementary considerations need to be taken into account for these specific

installations.

Special situations (e.g. landslide, earthquake, fire) are outside the scope of this document.

Design parameters for calculation of longitudinal effects (including bending moments, shear forces and

tensile forces resulting for example from non-uniform bedding and thermal movements and, in the case

of pressure pipelines, from Poisson's contraction and thrust at change of direction or cross-section) are

not covered in this document.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

EN 1295-1, Structural design of buried pipelines under various conditions of loading - Part 1: General

requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Installation terms

Installation terms are given in Figure 1. The same terms apply for embankment installations and for

trenches with sloping sides.
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Key
1 surface 9 trench bottom
2 bottom of road or railway construction, if any 10 depth of cover
3 trench walls 11 depth of bedding
4 main backfill 12 depth of embedment
5 initial backfill 13 trench depth
6 sidefill a thickness of lower bedding
7 upper bedding b thickness of upper bedding
8 lower bedding c thickness of initial backfill
NOTE The terms in Figure 1 are the same as in EN 1610.
Figure 1 — Trench installation
3.1.1
compaction
deliberate densification of soil during the construction process
[SOURCE: EN 1295-1:1997, 3.1.1]
3.1.2
consolidation

time-dependent densification of soil by processes other than those deliberately applied during

construction
[SOURCE: EN 1295-1:1997, 3.1.2]
3.1.3
embedment

arrangement and type(s) of material(s) around a buried pipeline which contribute to its structural

performance
[SOURCE: EN 1295-1:1997, 3.1.3]
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3.2 Design terms
3.2.1
allowable maximum operating pressure (PMA)

maximum pressure occurring from time to time, including surge, that a component is capable of

withstanding in service
[SOURCE: EN 805:2000, 3.1.1]
3.2.2
allowable operating pressure (PFA)

maximum hydrostatic pressure that a component is capable of withstanding continuously in service

[SOURCE: EN 805:2000, 3.1.2]
3.2.3
allowable site test pressure (PEA)

maximum hydrostatic pressure that a newly installed component is capable of withstanding for a

relatively short duration, in order to ensure the integrity and tightness of the pipeline

[SOURCE: EN 805:2000, 3.1.3]
3.2.4
bedding factor

ratio of the maximum design load for the pipe, when installed with a particular embedment, to the test

load which produces the same maximum bending moment
[SOURCE: EN 1295-1:1997, 3.2.1]
3.2.5
design pressure (DP)

maximum operating internal pressure of the system or of the pressure zone fixed by the designer

considering future developments but excluding surge
[SOURCE: EN 805:2000, 3.1.4]
3.2.6
limit states
states beyond which the structure no longer fulfils the relevant design criteria
[SOURCE: EN 1990:2002, 1.5.2.12]
3.2.7
load bearing capacity

load per unit length that a particular combination of pipe and embedment can sustain without

exceeding a limit state
[SOURCE: EN 1295-1:1997, 3.2.3]
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3.2.8
maximum design pressure (MDP)

maximum operating internal pressure of the system or of the pressure zone fixed by the designer

considering future developments and including surge, where:
— MDP is designated MDPa when there is a fixed allowance for surge;
— MDP is designated MDPc when the surge is calculated
[SOURCE: EN 805:2000, 3.1.5]
3.2.9
serviceabilty limit states

states that correspond to conditions beyond which specified service requirements for a structure or

structural member are no longer met
[SOURCE: EN 1990:2002, 1.5.2.14]
3.2.10
silo effect

effect whereby lateral earth pressure in trench backfill causes friction at the trench wall to carry part of

the weight of the backfill
[SOURCE: EN 1295-1:1997, 3.2.5]
3.2.11
system test pressure (STP)

hydrostatic pressure applied to a newly laid pipeline in order to ensure its integrity and tightness

3.2.12
ultimate limit states

states associated with collapse or with other similar forms of structural failure

[SOURCE: EN 1990:2002, 1.5.2.13]
4 General requirements

All pipelines shall withstand the various loadings to which they are expected to be subjected, during

construction and operation, without detriment to their function and to the environment.

The designer of the pipeline shall therefore specify the parameters for the structural design. These

parameters shall be consistent with the requirements of the installation and the earthworks.

The structural designer shall state the chosen method for the design. The structural designer shall

determine whether or not the pipeline comes within the scope of the chosen method of design including

level of safety. The structural designer shall declare the selected parameters to ensure the reliability of

the calculation.

Methods of design, when presented in the form of tables, charts or computer programmes, shall be

deemed equivalent to a full calculation, provided that any simplification does not reduce the level of

safety below that which would be obtained by a full design.

For the chosen design method, the designer shall use the whole method including the associated

allowable limits on the results and shall assess that the chosen method is applicable for the project and

shall express the resulting design safety.
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Probable consequences of pipeline failure shall be identified prior to the structural design. The

structural designer shall consider probable consequences of pipeline failure by establishing an

acceptable level of safety consistent with the chosen design method.

At each stage of the design, the values of the selected parameters, including factors of safety, shall be in

accordance with the chosen method and with site conditions, and shall be stated by the structural

designer.
5 Declaration of the parameters
5.1 General

The designer shall state the chosen method by referring to a published document or by a detailed

description of it.
The designer needs to clearly state the input data used and the analyses done.

The designer shall state the selected parameters, and at least refer to the following:

a) input data and characteristics:
1) pipe parameters;
2) external loads parameters:
i) soil loads parameters,
ii) traffic loads and construction loads parameters,
iii) groundwater parameters;
3) internal pressure parameters;
4) pipes own weight parameters;
5) weight of fluid parameters;
6) subsidence parameters;
7) temperature parameters;
b) parameters for limit state analysis;
c) safety parameters.
As stated in EN 1295-1:

— Field and experimental studies of pipelines show variations in observed earth pressures and pipe

deformations, stresses and strains. The main cause of these variations is the inevitable inconsistency of

soil characteristics and construction practices. The magnitude of the variation can be reduced by good

supervision, control measurement and by the use of fill materials, which are easily placed and treated,

but some degree of variation is inevitable.

— Variations in pipe characteristics, such as strength or elasticity, also occur in practice.

— Appropriate allowance for these variations should be made at the design stage and be in accordance

with one of the following design philosophies:
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1) The design procedure shall aim to predict the mean values of loads, and shall compare these with

the load bearing capacity of the pipeline based on mean values of pipe strength or stiffness

(for example as derived by calculation), and on average earth pressure distribution

assumptions.

2) The design procedure shall aim to predict the maximum possible (high fractile or upper bound)

values of loads, and shall compare these with estimates of the load bearing capacity of the

pipeline based on lower bound (or low fractile) values of pipe strength or stiffness (for

example as established by testing), and on unfavourable earth pressure distribution

assumptions.

— The factors of safety to be employed with designs following philosophy 2) will be lower than those used

in 1), to achieve the same probability of failure.
5.2 Input data and characteristics
5.2.1 Pipe parameters

Many different kinds of pipe materials are used for the production of components to construct buried

pipelines for water and waste water systems. The pipes vary in weight, load bearing capacity and

ductility. Next to that, many different types of jointing methods are used with the different pipe

materials.

European or national standards can include dimensions, as well as material specific information needed

for a structural design purpose.

When considering the pipe parameters to be taken into account, the designer shall at least refer to the

following and shall state the selected parameters:
— pipe material;
— dimensions (diameter, wall thickness, shape);
— unit weight;
— material properties (E , σ );
p ult
— short term;
— long term;
— initial pipe out of roundness;
— pipe ring stiffness;
— Poisson's ratio;
— crushing strength.
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5.2.2 External loads parameters
5.2.2.1 General
The external loads to be considered shall include:
— those due to the backfill;

— those due to the most severe surface surcharge or traffic load likely to occur;

— those due to any other causes, producing a loading of significant magnitude such as self-weight of

the pipe and water weight, as appropriate;
— those due to groundwater;
— those due to trench construction.
As stated in EN 1295-1:

— Of the various factors to be considered in the structural design process, some, such as pipe diameter

and depth of cover, can be regarded as entirely under the control of the designer. Other factors, such

as the methods adopted for trench excavation and for filling around and above the pipeline, are only

under the control of the designer to the extent that they are specified in advance, and supervised

during construction.

— The width of the trench can influence the extent to which the backfill load may be reduced by the silo

effect; this effect is taken into account for certain applications.

— The width of the trench can also influence the quality of the lateral soil support at the sides of the

pipes. This effect is variously covered in the design procedures, via the coefficient of lateral earth

pressure, the bedding factor, the soil modulus, etc.
— The slope of the trench sides can affect the magnitude of
...

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