EN 14358:2016

Timber structures - Calculation and verification of characteristic values

This standard gives statistical methods for the determination of characteristic values from test results on a sample drawn from a clearly defined reference population of e.g. solid wood, fasteners, connectors and wood-based products. The characteristic value is an estimate of the property of the reference population and can be based on a 5-percentile value of strength, resistance or density as well as on a mean value for stiffness.
Parametric methods are given for the determination of lower and upper 5-percentiles. The upper 5-percentile is the 95-percentile.
This standard is suitable for use with any structural product in the frame of type testing as well as factory production control.
Sampling is not covered by this document, but reference is made to the relevant product standards.
This standard also provides the acceptance procedure for verification of a lot.
Depending on the product, characteristic values determined in accordance with this standard may be used directly or may need additional adjustments specified in the relevant product standards.
Note:   For example, in the case of solid timber, specific adjustment factors for calculation of characteristic values are given in EN 384.

Holzbauwerke - Berechnung und Kontrolle charakteristischer Werte

Diese Norm legt statistische Verfahren zur Bestimmung charakteristischer Werte aus Prüfergebnissen für Proben, die einer eindeutig definierten Referenz-Grundgesamtheit von z. B. Vollholz, Befestigungsmitteln, Verbindungsmitteln oder Holzwerkstoffen entnommen wurden, fest. Der charakteristische Wert ist eine Abschätzung der Eigenschaft der Referenz-Grundgesamtheit und kann sowohl auf einem 5 %-Quantilwert der Festigkeit, der Widerstandsfähigkeit oder der Rohdichte als auch auf einem Mittelwert der Steifigkeit basieren.
Zur Bestimmung der unteren und oberen 5 %-Quantile werden parametrische Verfahren angegeben. Das obere 5 %-Quantil ist das 95 %-Quantil.
Diese Norm ist sowohl für die Anwendung mit jedem tragenden Produkt im Rahmen der Typprüfung als auch für die werkseigene Produktionskontrolle geeignet.
Dieses Dokument enthält keine Angaben zur Probenahme, verweist jedoch auf die einschlägigen Produkt¬normen.
Diese Norm legt auch das Abnahmeverfahren zur Überprüfung eines Loses fest.
Abhängig vom Produkt dürfen die nach dieser Norm bestimmten charakteristischen Werte direkt angewendet werden; unter Umständen können zusätzliche Anpassungen, die in den einschlägigen Produktnormen festgelegt sind, erforderlich sein.
ANMERKUNG   Im Fall von Vollholz sind zum Beispiel spezifische Korrekturbeiwerte zur Berechnung charakteristischer Werte in EN 384 angegeben.

Structures en bois - Détermination et vérification des valeurs caractéristiques

Le présent document indique des méthodes statistiques pour la détermination des valeurs caractéristiques à partir de résultats d'essai sur un échantillon provenant d’une population de référence clairement définie par exemple de bois massifs, d’éléments de fixation, d’assembleurs et de produits à base de bois. La valeur caractéristique est une estimation de la propriété de la population de référence et peut être fondée sur une valeur correspondant au fractile à 5 % d'exclusion pour la résistance ou la masse volumique ainsi qu’une valeur moyenne pour la rigidité.
Des méthodes de calcul paramétriques sont indiquées pour la détermination des valeurs correspondant au fractile à 5 % d’exclusion inférieure ou supérieure. La valeur d’exclusion supérieure à 5 % est la valeur à 95% d’exclusion.
Le présent document est applicable à tous les produits de structure dans le cadre d’un essai initial ou dans le cadre du contrôle de la production en usine.
L'échantillonnage n'est pas couvert par le présent document, mais il est fait référence aux normes de produits utiles.
Le présent document indique aussi la procédure d’acceptation pour la vérification d’un lot.
Selon le type de produit, les valeurs caractéristiques déterminées selon la présente norme peuvent être utilisées directement ou peuvent nécessiter des ajustements complémentaires précisés dans les normes produits pertinentes.
NOTE   Par exemple, l'EN 384 donne des facteurs de correction spécifiques pour le calcul des valeurs caractéristiques du bois massif.

Lesene konstrukcije – Izračun in preverjanje karakterističnih vrednosti

Ta dokument določa metode za ugotavljanje karakterističnih 5-percentilnih vrednosti trdnosti in gostote ter povprečnih vrednosti za togost iz rezultatov preskusa za masivni les, vezna sredstva in lesene izdelke v okviru začetnega tipskega preskusa.
Opredeljene so tudi metode za preverjanje lastnosti trdnosti, gostote ali togosti v okviru kontrole proizvodnje v obratu s spremenljivkami. Vzorčenje ni zajeto v tem dokumentu, toda navedeni so sklici na ustrezne standarde za izdelke.
Poleg tega standarda so v ločenih standardih navedene posebne zahteve v zvezi z izdelkom.
OPOMBA: v primeru masivnega lesa so v standardu EN 384 na primer navedeni posebni korekcijski faktorji za izračun karakterističnih vrednosti.

General Information

• Status: Published
• Publication Date: 21-Jun-2016
• ICS: 79.040 - Wood, sawlogs and sawn timber
• ICS: 91.080.20 - Timber structures
• Technical Committee: CEN/TC 124 - Timber structures
• Drafting Committee: CEN/TC 124/WG 2 - Solid timber
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 19-Jul-2022
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 14358:2016 - Timber structures - Calculation and verification of characteristic values

Relations

• Replaces: EN 14358:2006 - Timber structures - Calculation of characteristic 5-percentile values and acceptance criteria for a sample
• Effective Date: 29-Jun-2016

Overview

EN 14358:2016 - Timber structures: Calculation and verification of characteristic values (CEN) specifies statistical methods for deriving characteristic material and resistance values from test results. It covers calculation of 5‑percentile (lower) and 95‑percentile (upper) estimates for strength, resistance and density, and mean values for stiffness (e.g., modulus of elasticity). The standard is intended for both initial type testing and factory production control of structural wood products (solid wood, fasteners, connectors, wood‑based products). It also provides an acceptance procedure for lot verification. Sampling methods are outside its scope; product standards should be consulted for sampling and product‑specific adjustments (e.g., EN 384 for solid timber).

Key topics and technical requirements

• Statistical basis and confidence: Characteristic values are determined with a confidence level of 75% (probability that the characteristic value is greater than the estimator).
• Parametric methods: Parametric calculation assumes either log‑normal (typical for strength) or normal (typical for density, stiffness) distributions. Parametric methods produce lower and upper 5‑percentile estimates and use correction factors (s()kn) derived from t‑ or normal distributions. Parametric methods must only be used if data fit the assumed distribution.
• Non‑parametric methods: Applicable when distributional assumptions are not met. Non‑parametric percentile estimation and lower tolerance limits are defined; non‑parametric methods require sample size ≥ 40.
• Stiffness vs strength: Stiffness properties (mean modulus of elasticity) are handled as characteristic mean values; strength/density/resistance properties are treated by 5‑percentile methods.
• Factory production control: Provides procedures for variable control of production with a significance level of 75%, and specific criteria when standard deviation is known or estimated.
• Acceptance/lot verification: Sampling tests from a lot are compared against declared characteristic values using the standard’s acceptance rules (consumer’s and manufacturer’s risk concepts).

Applications and users

Who uses EN 14358:2016:

• Structural engineers and designers validating characteristic timber values
• Testing laboratories performing type testing or certification
• Manufacturers and quality managers implementing factory production control
• Notified bodies and conformity assessors verifying declared properties
• Standards writers and product committees referencing statistical procedures

Practical uses:

• Deriving characteristic strength or stiffness for design values
• Verifying production lots against declared characteristic properties
• Supporting type testing and CE marking workflows for timber products

Related standards

• EN 384 - Structural timber: determination of characteristic values and conversion factors (product‑specific adjustments)
• EN 1990 (Eurocode) - Basis of structural design (statistical background)
• EN 14358:2006 - previous edition (superseded)

Keywords: EN 14358:2016, timber structures, characteristic values, 5‑percentile, statistical methods, parametric, non‑parametric, factory production control, lot verification, modulus of elasticity, EN 384, CEN.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.GQRVWLHolzbauwerke - Berechnung und Kontrolle charakteristischer WerteStructures en bois - Détermination et vérification des valeurs caractéristiquesTimber structures - Calculation and verification of characteristic values91.080.20Lesene konstrukcijeTimber structuresICS:Ta slovenski standard je istoveten z:EN 14358:2016SIST EN 14358:2016en,fr,de01-september-2016SIST EN 14358:2016SLOVENSKI
STANDARDSIST EN 14358:20071DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14358
June
t r s x ICS
y {ä r v râ
{ sä r z rä t r Supersedes EN
s v u w zã t r r xEnglish Version
Timber structures æ Calculation and verification of characteristic values Structures en bois æ Détermination et vérification des valeurs caractéristiques
Holzbauwerke æ Berechnung und Kontrolle charakteristischer Werte This European Standard was approved by CEN on
t u January
t r s xä
egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä
translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä
CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey and United Kingdomä
EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels
t r s x CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN
s v u w zã t r s x ESIST EN 14358:2016

— y = m for normally distributed variable
— y = ln m for logarithmically normally distributed variable 5.0y Sample 5-percentile from the test data α Confidence level (%) SIST EN 14358:2016

= 75 %, where the confidence level
is defined as the probability of which the characteristic value is greater than the estimator on the characteristic value. NOTE
= 75 % corresponds to the value recommended in EN 1990. 3.2 Calculation of 5 and 95 percentiles values 3.2.1 General a) The characteristic value kmfor a material strength parameter or a resistance m modelled as a stochastic variable is defined as the p-percentile in the distribution function for m, corresponding to an assumed infinitely large test series; b) p = 5 % shall be assumed. 3.2.2 Parametric calculation a) The parametric approach shall not be used on test data not fitting the assumed distribution. In that case, a non-parametric method should be used; b) It is assumed that n test values are available and that these may be assumed to originate from a statistically homogeneous population. The test values, which are assumed to be logarithmically normally distributed or normally distributed and independent, are denoted 12,,,nmmm. The n test values constitute the sample; c) Strength parameters should be assumed as logarithmically normally distributed unless analysis of the data shows that a normal distribution is more appropriate. Density shall be assumed as normally distributed; NOTE Some product standards define the statistical distribution to be used. d) The mean value y and the standard deviation sy shall be determined as:
logarithmically normally distributed normally distributed
==∑11lnniiymn (1) ==∑11niiymn (2)
=−=−∑211(ln)max10,05niyimysn (3) =−=−∑211()max10,05niyimysny (4) The sample coefficient of variation shall not be taken as less than 0,05. For logarithmically normally distributed test values, the standard deviation sy shall not be less than()+≈2ln10,050,05. SIST EN 14358:2016

exp()mykns (5) =−k
...