CEN/TR 16886:2016

SLOVENSKI STANDARD
01-marec-2017
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Guidance on the application of statistical methods for determining the properties of
masonry products
Leitfaden für die Anwendung statistischer Methoden zur Bestimmung der Eigenschaften
von Mauerwerk Produkten
Guide pour l'application de méthodes statistiques pour la détermination des propriétés
des éléments de maçonnerie
Ta slovenski standard je istoveten z: CEN/TR 16886:2016
ICS:
03.120.30 8SRUDEDVWDWLVWLþQLKPHWRG Application of statistical
methods
91.080.30 Zidane konstrukcije Masonry
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 16886
TECHNICAL REPORT
RAPPORT TECHNIQUE
November 2016
TECHNISCHER BERICHT
ICS 03.120.30; 91.100.25
English Version
Guidance on the application of statistical methods for
determining the properties of masonry products
Guide pour l'application de méthodes statistiques pour Leitfaden für die Anwendung statistischer Methoden
la détermination des propriétés des éléments de zur Bestimmung der Eigenschaften von Mauerwerk
maçonnerie Produkten
This Technical Report was approved by CEN on 24 August 2015. It has been drawn up by the Technical Committee CEN/TC 125.

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
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16886:2016 E
worldwide for CEN national Members.

Contents Page
European Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms, definitions and symbols .5
3.1 Terms and definitions .5
3.2 Symbols .8
4 General .9
5 Statistical evaluation . 10
5.1 Factory production control . 10
5.2 Finished product testing . 10
5.2.1 General . 10
5.2.2 Inspection lot. 11
5.2.3 Spot sampling and sample sizes . 11
5.2.4 Production types . 12
5.2.5 Control method A: Batch control . 12
5.2.6 Control method B:'Rolling' inspection . 13
5.2.7 Evaluation of test results . 15
5.2.8 How to come from unknown to known standard deviation? . 18
5.2.9 Conformity . 18
5.2.10 Simple and conservative approach . 19
5.2.11 Non-conforming products . 19
5.2.12 Guidance . 19
6 Product type determination . 22
Annex A (informative)  Normal distribution (Laplace-Gauss distribution) . 23
Annex B (informative) Tables for acceptance coefficient k depending on the used
n
fractile p and confidence level γ (taken from ISO 16269-6:2005) . 24
Annex C (informative)  Examples of statistical evaluation . 40
C.1 Example 1 . 40
C.2 Example 2 . 42
C.3 Example 3 . 44
C.4 Example 4 . 45
C.5 Example 5 . 47
Annex D (informative) Normality test of SHAPIRO – WILK . 50
D.1 General . 50
D.2 Normality test of SHAPIRO-WILK . 50
Bibliography . 54

European Foreword
This document (CEN/TR 16886:2016) has been prepared by Technical Committee CEN/TC 125
“Masonry”, the secretariat of which is held by BSI.
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights. CEN shall not be held responsible for identifying any or all such patent
rights
This document has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association.
Introduction
This document is informative for the guidance of manufacturers and Notified Bodies (NBs), who
want to use statistical methods for the evaluation of conformity and Factory Production Control
of masonry products. Its use is optional. Other statistical methods and non-statistical methods
may be used.
Quality control of building materials and components is an indispensable part of an overall
concept of structural reliability. As quality control is generally a time-consuming and expensive
task, various operational techniques and activities have been developed to fulfil safety
requirements in buildings. Properly employed statistical methods are one way to provide
efficient, economic and effective means of quality control.
Background: “The terms and definitions in EN 1990 (Eurocode: Basis of structural design) are
derived from ISO 2394 (General principles on reliability for structures). For the design of
structures, EN 1996-1-1 (Eurocode 6: Design of masonry structures — Part 1-1: General rules for
reinforced and unreinforced masonry structures) is intended to be used together with EN 1990.
ISO 12491 (Statistical methods for quality control of building materials and components) gives
general principles for the application of statistical methods for the quality control of building
materials and components, in compliance with the safety and serviceability requirements of
ISO 2394. ISO 12491 is applicable to all buildings and other civil engineering works, existing or
under construction, whatever nature or combination of materials used, e.g. concrete, steel, wood,
bricks. The EN 771 series specifies that one method of satisfying the conformity criterion laid
down in these product standards is to use the approach given in ISO 12491.”
This Technical Report gives guidance on how a statistical evaluation can be put into practice
based on the background of ISO 12491.
A simplified method is also given based on information obtained from practice about the
possible distribution in production for specific product characteristics.
The method may also be used for the evaluation of different properties at the different stages of
the factory production control (FPC) with the aim to minimize testing costs for the manufacturer
and to ensure that the requirements are fulfilled.
Detailed examples are given in Annex C. For other more sophisticated techniques and specific
problems, other international standards can be applied.
The initial draft of this document was prepared by the joint working group CEN/TC 125/TG 5
and the Sector Group 10 of Notified Bodies under the Construction Products Directive. The
CEN/TR is a tool available for manufacturers and Notified Bodies.
It is laid down in the hEN’s of masonry products that the manufacturer should demonstrate
compliance for his product with the requirements of the harmonized product standards.
The purpose of this Technical Report is to put statistical evaluation into practice. Detailed
examples are given in the annexes.
1 Scope
In the masonry unit standards and in national legislation, some properties need to be declared
based on a certain fractile and confidence level. To demonstrate compliance with that a
statistical tool can be used.
The purpose of this Technical Report is to exemplify how a statistical tool can be used in
practice. This document should not contradict nor extend the scope of the work and role of a
Notified Body, nor impose additional burdens on the manufacturer, beyond those laid down in
the Construction Products Regulation and the product standards.
Mechanical and other properties of building materials and components are in the report
described by random variables with a certain type of probability distribution. The popular
normal distribution (Laplace-Gauss distribution) is given in Annex A. Normal distribution may
be used to approximate many actual symmetrical distributions. When a remarkable asymmetry
is observed, then another type of distribution reflecting this asymmetry should be considered,
leading to a more complex method to demonstrate compliance with the product standard. More
information on the normality test of Shapiro-Wilk is given in Annex D.
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 1990, Eurocode - Basis of structural design
EN 1996 (all parts), Eurocode 6 — Design of masonry structures
3 Terms, definitions and symbols
For the purposes of this document, the following terms, definitions and symbols apply.
3.1 Terms and definitions
3.1.1
unit
defined quantity of building material, component or element that can be individually considered
and separately tested
3.1.2
population
totality of units under consideration
3.1.3
variable
X
variable which can take any of the values of a specified set of values and with which is associated
a probability distribution
3.1.4
probability distribution
function which gives the probability that a variable X takes any given value (in the case of a
discrete variable) or belongs to a given set of values (in the case of a continuous variable)
3.1.5
distribution function
Π(x)
function giving, for every value of x, the probability that the variable X is less than or equal to x:
P=(x) PX,(≤ x)
3.1.6
(probability) density function
f(x)
derivative (when it exists) of the distribution function
3.1.7
parameter (population)
quantity used in describing the distribution of a random variable in a population
3.1.8
fractile
x
if X is a continuous variable and p is a real number b
...