Materials and Structures

, 50:31 | Cite as

Development of partial safety factors for earth block masonry

  • Philipp Müller
  • Lorenzo Miccoli
  • Patrick Fontana
  • Christof Ziegert
Original Article

Abstract

The main aim of the research was the development of a first valid database for material parameters of earth block masonry (EBM) with particular regard to statistical characteristics. A solid database is needed for the determination of the materials partial safety factor. Therefore, compressive strength tests were carried out with two types of earth blocks and two types of prefabricated earth mortar. The evaluation has shown that the mean variation of the compressive strength was remarkably less than expected, which indicates high quality standards of the components earth block and mortar with regard to industrial production. Using the reliability method, a partial safety factor for EBM subjected to compression was determined on the basis of these test results. The findings have shown that a common calculation method for EBM based on partial safety factors following the valid masonry construction standard is feasible.

Keywords

Partial safety factor Earth block masonry (EBM) Reliability Compressive strength 

List of symbols

a

Parameter showing influence of block strength to masonry strength

b

Parameter showing influence of mortar strength to masonry strength

E

Young’s modulus (N/mm2)

fb

Normalised mean compressive strength of masonry units (N/mm2)

fm

Compressive strength of the mortar (N/mm2)

fk

Characteristic compressive strength of the masonry (N/mm2)

fkc

Characteristic compressive strength from calculation (N/mm2)

fkt

Characteristic compressive strength from tests (N/mm2)

g

Dead load (kN/m)

h

Height (mm)

k

Fractile-factor

K

Block type factor

mX

Mean value of basic variables X

N

Action effects

Pf

Failure probability

q

Quantile (N/mm2)

qDIN

Quantile DIN EN (N/mm2)

qt

Quantile t-distribution (N/mm2)

qn

Quantile normal distribution (N/mm2)

R

Bearing capacity

t

Thickness (mm)

w

Width (mm)

Z

Safety margin

α

Sensitivity factor

αE

Sensitivity factor on action effects side

αR

Sensitivity factor on resistance side

β

Target reliability index

ε

Compressive strain (%)

κ

Smallest singular value (N/mm2)

γ

Partial safety factor

γR

Partial safety factor on the resistance side

ηd

Design value of the possible conversion factor

ρ

Bulk density (kg/m3)

σ

Generic stress (N/mm2)

σ0

Permissible compression stress (N/mm2)

σc

Calculated value of compressive strength (N/mm2)

σDL

Permissible compressive stress according to [1] (N/mm2)

σmax

Maximum compressive stress (N/mm2)

σn

Maximum compressive stress normalised (N/mm2)

σN

Standard deviation of action effects (N/mm2)

σR

Standard deviation of strength (N/mm2)

σσ0

Permissible compression stress determined with conversion factor (N/mm2)

σu

Compressive strength (N/mm2)

Φ

Cumulative distribution function of the normal distribution

Notes

Acknowledgments

The authors wish to acknowledge Mr. André Machura and Mr. Peter Benkendorf for their important support in the test setup and Mr. Michael Schober for his support in statistical analyses.

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Copyright information

© RILEM 2016

Authors and Affiliations

  1. 1.Division Building MaterialsBundesanstalt für Materialforschung und –prüfung (BAM)BerlinGermany
  2. 2.Ziegert | Roswag | Seiler Architekten IngenieureBerlinGermany

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