CEng 6506 Earthquake Engineering lecture Notes

Useful Architectural and

Structural Considerations for
Earthquake Resistant
Design

Contents
 Introduction
 Regularity of structures
 Structural wall configuration in structures with dual wall-
frame lateral load resisting systems
 Uniform distribution of mass and stiffness
 Effects of non-structural components
 Multiple defense lines
 Balanced stiffness, strength and ductility
 Desirable features of structural materials for Earthquake
resistant design
 Basic Design Guidelines from Past Earthquakes

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CEng 6506 Earthquake Engineering lecture Notes

Introduction
 Buildings are designed by architects and engineers.
 Architects are responsible for the architectural
configuration of buildings at the start.
 Configuration has to do with the size, shape and
proportion of the 3D form of the building.
 Architectural configuration determines the location,
shape and approximate size of structural and non-
structural elements of the building
 Any architectural design should incorporate effective
seismic design to minimize EQ hazards.

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While the provision of earthquake resistance

is accomplished through structural means, the
architectural design and the decision that
create it, play a major role in determining the
building’s seismic performance

C. Arnold

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CEng 6506 Earthquake Engineering lecture Notes

Importance of Conceptual Design

 In order to reduce uncertainties of the estimation of the

seismic demands, more attention should be paid to the
conceptual design
 Control or decrease ductility demand by:
 the use of base isolation
 the use of energy dissipating device (Structural controls)

 the proper selection of the structural configuration

 Provide large ductility with stable hysteretic behavior

 Achieve integral action of the whole structure by tying
together the main components and detail the plastic
hinge location carefully
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Selection of proper system

configuration for the
superstructure

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CEng 6506 Earthquake Engineering lecture Notes

Appropriate Configurations
 Simple configuration → simple behavior
 Building and its structure Should
 be Simple Symmetric and Regular in Plan and Elevation
 have a uniform and continuous distribution of mass, stiffness,
strength and ductility.
 have the largest possible number of defense lines.
 have well separated non-structural components
 be detailed so that the inelastic deformations can be constrained
(controlled) to develop in desired regions and according to a
desirable hierarchy
 be provided with balanced stiffness and strength between its
members, connections and supports.
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Optimal structural configuration

Attributes Benefits
Low width-to-depth ratio Low torsional effects
Low height-to-base width/depth ratio Low overturning effects
Similar storey heights Elimination of weak/soft storey
Short spans Low unit stress and deformation
Symmetrical plan shape Elimination/reduction of torsion
Identical resistance on both axes Balanced resistance in all directions
Uniform plan/elevation stiffness Elimination of stress concentrations
Uniform plan/elevation resistance Elimination of stress concentrations
Uniform plan/elevation ductility High energy dissipation
Perimeter lateral resisting systems High torsional resistance potential
Redundancy High plastic redistribution
Direct load path, no cantilevers Elimination of stress concentration
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CEng 6506 Earthquake Engineering lecture Notes

Regularity
 An aspect of seismic design of equal if not
greater importance than structural analysis is the
choice of building configuration.
 Lack of symmetry (in mass distribution and/or in stiffness,
strength and ductility)
 leads to torsional effects
 difficult to assess properly
 can be very destructive
 A regular rectangular plan building with
asymmetrical stiffening  irregular (torsion)
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Structural Irregularities
Structural
Irregularity

Elevation
Plan Irregularity
Irregularity

Re-entrant Re-entrant
Non parallel Non parallel
Corners (In-plan Corners (Vert
Offset) LRS Offsets) LRS

LRS LRS
Diaphragm Weak/Soft
Discontinuity Discontinuity
Discontinuity Storeys
(Horz) (Horz)

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CEng 6506 Earthquake Engineering lecture Notes

Irregular structures or framing systems

SEAOC commentary, 1980

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SEAOC commentary, 1980

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CEng 6506 Earthquake Engineering lecture Notes

SEAOC commentary, 1980

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SEAOC commentary, 1980

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CEng 6506 Earthquake Engineering lecture Notes

Regularity in Plan
 Simple & symmetrical building plans give
 more efficient and
 predictable seismic response
 A prerequisite for the desirable interaction between
lateral-force-resisting structural system
 Reentrant corners inviting stress concentrations, hence
should be avoided.
 If necessary separation should be provided
 This may lead to a number of simple, compact, and
independent plans

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Plan Regularity (Cont’d)

 Gaps separating adjacent

structures must large enough to
avoid hammering of adjacent
structures due to out-of-phase
relative motion of the
independent structures
 Openings should not
jeopardize diaphragm action of
the slabs and be symmetrically
placed

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CEng 6506 Earthquake Engineering lecture Notes

Regularity in Elevation
 Tall and slender buildings should be
avoided
 Concentration of masses at the top of a
building should be avoided
 Setbacks should be avoided
 If required, adequate structural separation
should be provided.
 Irregularities within the framing system
should be avoided
 Any connections (bridging) between two
independent buildings should be such as to
prevent horizontal force transfer between
the two structures
 Staggered floor arrangements should be
avoided
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Common Failures caused by Irregularities

Torsional effects created by
irregular shape of building
plan (L configuration) and by
a very stiff off-center core
area in a rectangular (regular)
plan building

Typical example
Hotel Terminal, Guatemala
City. Overall view of this 6-
story hotel, illustrating the
torsional failure of the
second story during the 1976
Guatemala Earthquake.
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CEng 6506 Earthquake Engineering lecture Notes

Common Failures caused by Irregularities

(Cont’d)
View inside the above building
showing the collapse of the second
story due to shear failure of the
second-floor columns. Note the
significant lateral displacement
(interstory drift to the right) due to
the torsional rotation of the upper
part of the building.

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Common Failures caused by Irregularities

(Cont’d)

Close-up of one of the collapsed

columns of the above slide. Note that the
upper floor has displaced to the right and
dropped, and the top and bottom
sections of the column are now side-by-
side. Although the columns had lateral
reinforcement (ties) these were not
enough and at inadequate spacing to
resist the shear force developed due to
the torsional moment which originated in
the second story.

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CEng 6506 Earthquake Engineering lecture Notes

Common Failures caused by Irregularities

(Cont’d)

Bridge failure Pounding Soft story

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Structural wall Configuration in

structures with dual wall-frame
lateral load resisting systems

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CEng 6506 Earthquake Engineering lecture Notes

Possible Shear wall shapes & arrangements

Eccentric SW Basic SW Shapes

arrangements

Symmetrical SW
arrangements

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Configuration in wall-frame system

Examples for both preferable and

undesirable positioning of major
lateral-force-resisting elements,
consisting of structural walls and
moment resisting frames.

In all cases the distance between

the CM and CR should be reduced
in order to minimize torsional
effects

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CEng 6506 Earthquake Engineering lecture Notes

Uniform Distribution of Mass and

Stiffness

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Distribution of Mass in a Building

 Dynamic response of a structure depend on
distribution of its reactive masses
amount and distribution of the masses
 The smaller the reactive masses, the smaller the
earthquake forces will be
 The use of unnecessary masses should be avoided.

 i.e. reactive masses are masses that will react to the shaking of
the building foundation.

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CEng 6506 Earthquake Engineering lecture Notes

Uniform Mass Distribution (Cont’d)

Damage to a wooden house

due to a heavy roof supported
on a flexible frame. 1971 San
Fernando Earthquake.

Damage to the old portion of the Olive

View Hospital in the 1971 San Fernando
Earthquake. This building had a very
heavy tile roof supported on
unreinforced brick masonry and was
neither designed nor detailed to resist
seismic effects
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Uniform Stiffness Distribution

Olive View Hospital, Psychiatric Unit,

San Fernando, California. 1971 San
Fernando Earthquake. This unit was
a 2-story reinforced concrete
building. The structural system was a
moment resisting frame. However, in
the second story there were masonry
walls that added significantly to the
stiffness of this story.
 Lightweight concrete was used in the construction of this
building. Note that the building collapsed completely at the
first (soft) story and the second floor dropped to the ground
after moving laterally about 2 meters
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CEng 6506 Earthquake Engineering lecture Notes

Uniform Stiffness Distribution (Cont’d)

 Imperial County Services

Building. Overall view of this
modern 6-story reinforced
concrete building. Not the
continuous shear wall at the east
end of the building which was
discontinued (offset) at the second
floor level, resulting in a severe
discontinuity and in a practically
open first story (soft story in the
E-W direction).

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Uniform Stiffness Distribution (Cont’d)

 View of the first story columns

located in the east end of the
building. Note that the explosive type
of failure just above the ground and
the offset between the columns and
the solid shear wall.

 Close-up of the failure at the bottom

of the column at the southeast corner
of the building. The failure occurred in
the zone of the column where there
was not adequate confinement of the
concrete and shear reinforcing steel.

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CEng 6506 Earthquake Engineering lecture Notes

Effects of non-structural components

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Non-structural infill panels and partitions

 Earth quake produces story drift.

 Causes vertical deformations  Change in height
 Any infill panel should be designed to deal with both
these movements either by:
 Integrating (very stiff frame with flexible infill)
 Separating (more preferable for flexible frames)
In the absence of computed
values use the following
minimum separations
20mm for horizontal
40mm for vertical
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CEng 6506 Earthquake Engineering lecture Notes

Cladding, wall finishes, windows and doors

 In flexible buildings, precast concrete
cladding should be mounted on
fixings which ensure separation from
horizontal drift movements of the
structure
 Brittle or rigid finishes should be
avoided or specially detailed Lightweight partition detailed so
 stairwells should be free of material that earthquake hammering by the
which may spall or fall structure will damage limited end
 Window sashes should be separated strips.
from frame action
Detail of external frame showing
separation of spandrel or parapet
from columns to avoid unwanted
interaction.
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Effect of Non-Structural Components

Two-story reinforced concrete building,
Managua, Nicaragua, damaged in the 1972
Managua Earthquake. The slide shows a
reinforced concrete column which was part of
the structural system and which failed due to
its shortening because of the effect of the
masonry wall. The masonry walls were
considered as non-structural elements.

Medical Clinic in El Asnam,

Algeria.Close-up of column failure of
this new 4-story reinforced concrete
building induced by the response of
the building to the 1980 El Asnam
Earthquake.
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CEng 6506 Earthquake Engineering lecture Notes

Multiple Line of Defense

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Multiple defense lines

 A structure should have the largest possible number of internal
and external redundancies. While a high degree of static
indeterminacy is desirable, this is not sufficient. In order that a
building be efficient in resisting severe earthquake shaking, it
should have sufficient ductility, toughness and stable hysteric
behavior under repeated cycles of deformation reversals

 Plan view of the Banco de America,

Managua, Nicaragua. This building generally
performed very well during the 1972
Managua Earthquake. Its excellent
performance can be attributed to the
symmetry and uniformity of distribution of
the masses and structural stiffnesses
throughout the building.

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CEng 6506 Earthquake Engineering lecture Notes

Multiple defense lines (Cont’d)

 The structural system, which can be B. d. America B. Central
considered as a combination of the ductile
walls with a framed tube, is an excellent
system for seismic-resistant design,
providing several lines of defense whereby
the behavior of the whole system can
accommodate the demands of a severe
earthquake.

 View of the core service walls and floor area

at the second story of the Banco de America,
Managua, Nicaragua. Note that few of the
marble tiles that cover the reinforced
concrete shear walls have spalled off. This
was the only visible damage in this story after
the 1972 Managua Earthquake.

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Multiple defense lines (Cont’d)

 Typical floor plan above the fourth floor of
the Banco Central Building, Managua,
Nicaragua. This building had a reinforced
concrete frame as the basic structural
system. Note that the overall configuration
of the reinforced concrete system of the
tower was not symmetric.
 View of the stairway after the 1972 Managua EQ. Most
of the stairs were covered with debris that resulted from
the failure of the hollow tile partitions surrounding the
stairs. The damage (structural and non-structural) and
the protection of the contents of this very flexible
moment resisting frame building were in sharp contrast
with those observed in the taller but symmetric
combined coupled shear wall-tubular frame structural
system of the Banco de America Building. There was
also significant structural damage that resulted in the
need to demolish the tower of this building.
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CEng 6506 Earthquake Engineering lecture Notes

Balanced Stiffness, Strength and

Ductility

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Balanced stiffness, strength and ductility

 “A chain breaks at its weakest link”. It is not worthwhile using

strong, stiff and ductile structural members if they are not
properly connected. Collapse and severe damage of buildings
due to lack of good connections is common.
 Galerie Algerienne Building, El
Asnam, Algeria, 1980 El Asnam
Earthquake. View of the unit of
this four story RC building which
collapsed in the earthquake. Lack
of adequate reinforcement at the
column-girder connections was
one of the reasons for the
collapse of this unit.

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CEng 6506 Earthquake Engineering lecture Notes

Balanced stiffness, strength and ductility (Cont’d)

 Naiguata Beach Club Building, Naiguata,
Venezuela, 1967 Caracas Earthquake. This was
a single-story building (approximately 7 meters
high) with a mezzanine at 3 meters above
ground. This slide shows the damage at the
connection between the column and the girder
supporting the mezzanine

 Mosque Building, El Asnam, Algeria,

1980 El Asnam Earthquake. View
of the first story column and
column-girder connection at the
second floor level of the mosque.

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Balanced stiffness, strength and ductility (Cont’d)

 Four Season Apartment Building, Anchorage,
Alaska, 1964 Alaska EQ. General view of the
building after the EQ. The lateral resistance to
earthquake ground motions was essentially
provided by the two slender vertical reinforced
concrete shafts. These shafts failed at the ground
floor level where all the vertical reinforcing bars
in the shafts were spliced
 Overall view of an Apartment Building,
Anchorage, Alaska, 1964 Alaska EQ. This
14-story RC structure has as a basic lateral-
resisting structural system a series of
slender walls coupled by spandrel girders
that worked as coupling
girders. Unfortunately these spandrel
girders were not designed (detailed) to
work as coupling girders and therefore
suffered significant damage in the EQ.
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CEng 6506 Earthquake Engineering lecture Notes

Desirable features of Structural materials for

Earth quake resistant design
 High ductility
 High strength-to-weight ratio
 Homogeneity
 Ease in making full-strength connections
 Possibility of suppression of brittle failure
modes

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Typical brittle failure modes of common

construction materials
Material of construction Brittle failure mode
Reinforced Concrete Buckling of reinforcement bars
Bond or anchorage failure
Member shear failure
Masonry Out-of-plane bending failure
Global buckling of walls
Sliding shear
Structural Steel Fracture of welds and/of parent material
Bolt shear or tension failure
Member buckling
Member tension failure
Member shear failure
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CEng 6506 Earthquake Engineering lecture Notes

Suitable Construction Material for Moderate to

High EQ Loading

Dorwick 2009
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Basic design guidelines from past EQ

Prof. S. Mahin U C Berkeley

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CEng 6506 Earthquake Engineering lecture Notes

Basic guidelines (cont’d)

Prof. S. Mahin U C Berkeley

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CEng 6506 Earthquake Engineering lecture Notes

27 December 2017 Addis Ababa University (Dr. Adil Z.) 49

Architect – Engineer Relationship

 While the provision of earthquake resistance is accomplished
through structural means, the architectural design and the
decision that create it, play a major role in determining the
building’s seismic performance

 Seismic design is a shared architectural and engineering

responsibility, which stem from the physical relationship
between architectural forms and structural systems.

 The interrelation between issues of engineering and architecture

demand that architect and engineer work together from the
inception of the project.

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CEng 6506 Earthquake Engineering lecture Notes

Architect – Engineer cont’d

 In resistance to gravity loads architectural and

structural decisions may be made independently
of each other. But in resistance to EQ effects,
separating the engineer from the architect is the
formula for disaster.
M. Sozen 1978

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References
1. Dowrick, D. J., “Earthquake Resistant Design,” 2nd Edition, John Wiley &
Sons, 1987.
2. Chen, W-F.; Scawthorn, C., “Earthquake Engineering Handbook”, CRC
Press, 2002
3. Naiem, F., “Seismic Design Handbook” Kluwer Press, 2001
4. Kramer, S., “Earthquake Geotechnical Engineering”, Prentice Hall, 1995
5. Paulay, T., Priestley, M.J.N. “Seismic Design of Reinforced Concrete and
Masonry Buildings,” John Wiley & Sons, 1992.
6. Wolfgang Schueller, “High-Rise Building Structures,” John Wiley & Sons,
Inc New York, 1977.
7. Online material from the site http://nisee.berkeley.edu/

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