02-Jun-17

Addis Ababa Institute of Technology

School of Civil and Environmental Engineering

INTRODUCTION TO ES EN 1992:2015

By Dr.-Ing. Girma Zerayohannes

ES EN 1992-1-1:2005 Twelve sections:

 Section 1: General
 Section 2: Basis of design
 Section 3: Materials
 Section 4: Durability and cover to reinforcement
 Section 5: Structural analysis
 Section 6: Ultimate limit states
 Section 7: Serviceability limit states
 Section 8: Detailing of reinforcement and prestressing tendons General
 Section 9: Detailing of members and particular rules
 Section 10: Additional rules for precast concrete elements and structures
 Section 11: Lightweight aggregate concrete structures
 Section 12: Plain and lightly reinforced concrete structures

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Section 1: General Information

 Scope of code
 Principles and application rules
 Symbols

ES EN
1992:2015
EBCS 1995

E Effect of action
MEd Design value of the applied internal bending moment

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Section 2: Basis of Design

 Refers to ES EN 1990/ES EN 1991 for design life, limit state principles,

actions, etc.
 Partial factors for materials for ULS
Design Situations for for for
concre reinforcing prestressing steel
te steel
Persistent & Transient 1.5 1.15 1.15

Accidental 1.2 1.0 1.0

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Section 3: Materials - Concrete

 New in ES EN 1992:2015 is the inclusion of HSC

 C55/67, C60/75, C70/85, C80/95, C90/105 and the associated - relations
and differentiation of - relations for non-linear structural analysis and design
of cross-section

 One project is using HSC

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Section 3: Materials - Concrete

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Section 3: Materials - Concrete

Stress-strain relations for the design of cross-sections

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Section 3: Materials - Concrete

Stress-strain relations for non-linear structural analysis

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Section 3: Materials - Concrete

 Design compressive and tensile strengths

∝
=
∝ , .
=

 Stress – strain relations for the design of cross-sections

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Section 3: Materials - Concrete

• Simplified stress-strain relation- Bi-Linear

• Less accurate – for practical calculation loss of accuracy is very small

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Section 3: Materials - Concrete

 Simplified stress-strain-Rectangular

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Section 3: Materials - Concrete

 Confined concrete higher strength and higher critical strains (NEW)

fck,c = fck(1.0 + 5.02/fck)

c2,c = c2(fck,c/fck)2
cu2,c = cu2 + 0.22/fck (useful in the design of boundary elements
for EQ resistance)

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Section 3: Materials - Reinforcing Steel

Stress-strain diagram of typical reinforcing steel

•Yield strength fyk (or the 0.2% proof stress, f0.2k) and tensile strength ftk

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Section 3: Materials - Reinforcing Steel

 For design either an inclined top branch with a strain limit and maximum
stress or a horizontal top branch without the need to check for the strain
limit (NEW)

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Section 4: Durability and Cover to Reinforcement

 Environmental conditions

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Section 4: Durability and Cover to Reinforcement

 Cover to Reinforcement
= +∆
= ,; ,

 Cover for Bond, , : Depends on the diameter of bar

 Cover for Durability, , : Depends on the exposure class and structure
class
∆ is normally taken as 10 mm

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Section 5: Structural Analysis

 New design methods (strut and tie method) and application rules (global
second order effects in buildings) are included in section 5

 It is a very simple formula that allows the calculation of the lateral stiffness of
vertical bracing elements to limit the 2nd order moments to less than 10%

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Section 5: Structural Analysis

 Why limit the 2nd order moment?

 Instability (critical ULS) is caused because the LFRS is unable to control
(limit) the 2nd order effects leading to instability.
 Therefore limiting the 2nd order moments to less than 10% is a strategy to
preempt stability failure
 Formula is similar to provisions for adequate lateral rigidity according to DIN.
 Economy?
 Good practices in the USA, recommend non-sway structures “which are
more economical than their sway counterparts” (Wight and MacGregor)

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Section 5: Structural Analysis

 Second order effects with axial load

 Methods of analysis
a) Second order analysis based on nominal stiffness
b) Method based on estimation of curvature

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Section 5: Structural Analysis

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Section 5: Structural Analysis

 Effective width of Flanges

 The effective flange width of T and L beams is determined from:

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Section 5: Structural Analysis

 Effective Span of Beams and Slabs

 The effective span l of beam or slab is:
= + + values of a1 and a2 may be determined from the figure

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Section 6: Ultimate Limit States

 Bending with or without axial force

 Plane sections remain plane after bending so that:
a) The strains are linearly proportional to the distance to the
neutral axis and
b) The strain in the concrete is equal to he strain in the
reinforcement at the same depth in the section
 The tensile strength of the concrete is ignored and no contribution is
taken for he concrete below the neutral axis in tension

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Section 6: Ultimate Limit States

Partial view of design aid prepared using the strain distribution at ULS

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Section 6: Ultimate Limit States

Partial view of design aid prepared using the strain distribution at ULS

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Section 6: Ultimate Limit States

 Shear
 The strut inclination method is used for shear capacity checks
 The shear is resisted by concrete struts in compression and shear
reinforcement acting intension
 Shear formulae expressed in terms of force rather that stress
 Designer free to choose a strut angle 22 ≤ ≤ 45
 Notation
o , is the design shear resistance of the member without
shear reinforcement.
o , is the design value of the shear force which can be
sustained by the yielding shear reinforcement.
o , is the design value of the maximum shear force which
can be sustained by the member, limited by crushing of the
compression struts.

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Section 6: Ultimate Limit States

 Shear
 Members not requiring design shear reinforcement

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Section 6: Ultimate Limit States

 Shear
 Members requiring design shear reinforcement
For members with vertical shear reinforcement, the shear resistance is the
smaller value of:

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Section 6: Ultimate Limit States

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Section 6: Ultimate Limit States

 New in the design for shear is also the need to take it further to satisfy
capacity design rules.  Capacity design of members in shear
 It is about complying with the design assumption for DCM and DCH that
frame structures dissipate energy during an EQ through the formation plastic
hinges primarily at the ends of the beams
 So unlike the traditional way, shear designs follow only after flexural designs
with associated detailing is completed because the magnitude of the design
shear force is also a function of the design moment resistances of the beam
end sections.

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Section 6: Ultimate Limit States

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Section 6: Ultimate Limit States

 Instability

In non-sway structures,
individual weak columns
could reach the ULS of
instability individually

Individual weak column

has reached the ULS of
instability

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Section 6: Ultimate Limit States

• In sway buildings on the other hand a weak story, some stories or all stories
will reach the ULS of Instability at the same time. This kind of ULS if allowed,
is catastrophic.
• ES EN Standards have provisions that ensure compliance of buildings with
safety requirements regarding stability.
• The essential requirement to ensure stability is the right choice of the
structural systems. They are also called lateral force resisting systems
(LFRS).
• Failure to comply with the code provisions regarding stability in sway
structures have resulted catastrophic failures (see photos).

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Section 6: Ultimate Limit States

Slender sway structure

with inadequate choice of
structural system

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Section 6: Ultimate Limit States

Catastrophic instability
failure

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Section 7: Serviceability Limit States

 Considered serviceability limit states are

 Stress limitation
 Crack control
 Deflection control
 Crack control
 Without direct calculation : by limiting the maximum bar diameter or
spacing between bars
 With direct calculation and limiting the crack width below the given
allowable values

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Section 7: Serviceability Limit States

 Deflection control
 Without direct calculation : by limiting the span to depth ratio

 With direct calculation and limiting the deflection below ⁄250 or ⁄500

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Section 8: Detailing of Reinforcement

 Spacing of bars

 Anchorage of longitudinal reinforcement

 Laps and mechanical couplers

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Section 9: Detailing of Members and Particular Rules

 Beams
 Solid slabs
 Flat slabs Rules of minimum and maximum area of
 Columns reinforcement, minimum and maximum
spacing between rebars, and additional
 Walls
detailing rules for members are listed in this
 Deep Beams section
 Foundations In addition the much more involved
 Columns additional detailing requirements for EQ
resistance must be observed

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Section 10 -12

 Section 10: Additional rules for precast concrete elements and structures
 Section 11: Lightweight aggregate concrete structures
 Section 12: Plain and lightly reinforced concrete structures

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Thank you!

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