SEISMIC DESIGN OF HIGH RISE

BUILDINGS
Lesson 1:
INTRODUCTION
MTYANA, H.J
PhD. Structural Engineering - on progress

Ass. Lecturer
Dept. of Structural and Construction Engineering
College of Engineering and Technology
University of Dar es salaam, Tanzania
Email: hjmtyana@gmail.com
Cell Phone: +255 (0) 655 004212
 Topics to be covered

1.1 Basic Definitions as used in Tall Buildings

1.2 Significance of Tall Buildings

1.3 Historical Development of Tall Buildings

1.4 Tall Buildings Structural Systems

 1.1 Basic Definitions as used in Tall Buildings
 The term “Tall Building” is a relative term depending on the concerned
or respective society:

For a scientist: a tall building is that which its height is affected

be lateral forces due to wind or earthquake actions to an
extent that they play an important role in structural design.

For a fire brigade: When the fire extinguishing equipment can

not reach the upper part of the building, then that building is
termed as Tall.

For a sociologist: For a crippled person, it is obvious that, any

building may be termed as Tall if he/she cannot go up easily
to the next floor.
 Definition
High-rise building:
Emporis Standards defines a high-rise as "A multi-story structure
between 35–100 meters tall, or a building of unknown height
from 12–39 floors." According to the building code of
Hyderabad, India, a high-rise building is one with four floors or
more, or 15 to 18 meters or more in height.
Buildings between 23m and 150m are considered high rises,
while those taller than 150m are considered as skyscrapers.
The Council on Tall Buildings and Urban Habitat (CTBUH)
developed the international standards for measuring and
defining tall buildings, as outlined below, and is recognized as
the arbiter for bestowing designations such as the “World’s
Tallest Building.”

Tall, Supertall & Megatall Buildings

Tall Buildings
 There is no absolute definition of what constitutes a “tall building;” the
definition is subjective, considered against one or more of the
following categories:

 Height Relative to Context

 A 14-story building may not be considered a tall building in a high-rise
city such as Chicago or Hong Kong, but in a provincial European city
or a suburb this may be distinctly taller than the urban norm.
Height Relative to Context
 Proportion
There are numerous buildings that are not particularly high, but
are slender enough to give the appearance of a tall building.
Conversely, there are numerous big/large-footprint buildings
that are quite high, but their size/floor area rules them out of
being classed as a tall building.
 Embracing Technologies Relevant to Tall Buildings
A building containing technologies which may be attributed as
being a product of “tall”.
(e.g., specific vertical transport technologies, structural wind
bracing as a product of height, etc.).
 Supertall & Megatall Buildings

 Tall buildings that

achieve significant
heights are classed
in two additional
sub-groups:
 A “supertall” is a tall
building 300 meters
or taller, and a
 “megatall” is a tall
building 600 meters
or taller.
 Summary of tall building classifications (CTBUH)

Buildings higher than 50m is termed as Tall Building

Buildings higher than 100m is termed as skyscraper

A “supertall” is a tall building 300 meters or taller, and a

“megatall” is a tall building 600 meters or taller

 Measuring Tall Building Height
 Three height categories are recognized. All categories measure the building from: The level1
of the lowest, significant2 open-air3 pedestrian4 entrance to…
 1 Level: finished floor level at threshold of the lowest entrance door.
 2 Significant: the entrance should be predominantly above existing or pre-existing grade
and permit access to one or more primary uses in the building via elevators, as opposed to
ground-floor retail or other uses that solely relate/connect to the immediately adjacent
external environment. Thus, entrances via below-grade sunken plazas or similar are not
generally recognized. Also note that access to car park and/or ancillary/support areas are
not considered significant entrances.
 3 Open-air: the entrance must be located directly off an external space at that level that is
open to air.
 4 Pedestrian: refers to common building users or occupants and is intended to exclude
service, ancillary, or similar areas.
1. Height to Architectural Top
...  the architectural top of the building, including spires, but not
including antennae, signage, flagpoles or other functional-
technical equipment. This measurement is the most widely utilized
and is employed to define the CTBUH rankings of the “World’s Tallest
Buildings.”
 2. Height to Highest Occupied Floor
...the finished floor level of the highest occupiable floor within
the building
 3. Height to Tip
 ...to the highest point of the building, irrespective of material or
function of the highest element
Example: Official Heights of Willis vs. Petronas Towers
Table 1: List of Tall Buildings (over 25 floors) in Tanzania
Source: Council on Tall Buildings and Urban Habitat (CTBUH), 2017
 Table 2: 10 Tallest buildings in the world as at 2019
(Skyscraper Centre, CTBUH)
Rank Bldg Name City, Height Floors Completed Material Use
Country (m)

1 Burj Khalifa Dubai, UAE 828 163 2009 Reinforced Offices ,

concrete, steel, Residential,
aluminum Hotel
2 Shanghai Shanghai, 632 128 2015 Reinforced Hotel and
Tower China concrete, steel Offices
3 Makkah Mecca, 601 120 2012 Steel and Mixed
Royal Clock Saudi Reinforced
Tow Arabia concrete
4 Ping An Shenzhen, 599 115 2017 Steel and Offices
Finance China Reinforced
Center concrete
5 Lotte World Seoul, South 554.5 123 2017 Reinforced Hotel and
Tower Korea concrete, steel Offices
 Table 2: 10 Tallest buildings in the world as at 2019
(Skyscraper Centre, CTBUH)

Rank Bldg Name City, Height Floors Completed Material Use

Country (m)

6 One World New York, 541.3 94 2014 Reinforced Hotel and

Trade Center USA concrete, steel Offices
7 Guangzhou Guangzhou, 530 111 2016 Composite Mixed
CTF Finance China
8 CITIC Tower Beijing, 527.7 109 2018 Composite Offices
(China Zun) China
9 TAIPEI 101 Taipei, 508 101 2004 Composite Offices
Taiwan
10 Shanghai Shanghai, 492 101 2008 Composite Hotel and
World China Offices
Financial
Center
Shanghai Tower
Ping An Finance
Center

Burj Khalifa

Makkah Royal Clock Tow

Lotte World Tower

 Guangzhou CTF
Finance
TAIPEI 101

One World Trade

Center

CITIC Tower Shanghai WFC

 1.2 Significance of tall buildings
Why tall buildings???????? Tall buildings therefore, are
Scarcity of land solutions for density problems
and lack of available of
Increasing demand for business and available land for land
residential space development , sometimes tall
Economic growth buildings more about power,
Technological advancement prestige status.
Innovations in structural systems
Cultural significance and prestige
Human aspiration to build higher
 1.3 Historical Development of Tall Buildings
Where the tall building phenomena started
Vertical habitation isn’t a new trend. It’s one that has been
driven by urbanization and bustling, overpopulated cities for
centuries. While the high-rise buildings that we know today
became possible with the inventions of elevators, newer
building materials and structural engineering systems, multi-
storey construction dates back to the Roman Empire and
vertical cities have been around for centuries.
 Daring engineering feats of the 1800s
In 1852, Elisha Graves Otis built the first ‘fall safe’ hoisting system (the
elevator) allowing vertical transportation of people and goods in
multi-storey buildings. This invention made the construction of
skyscrapers possible and as a result greatly altering the way modern
cities were planned and constructed.
Cincinnati architectural firm Elzner & Anderson, USA designed
(Transit Building) what was considered a daring engineering feat at
the time (people feared the building would collapse under wind
loads or its own weight), but the success of the building led to the
team creating the tallest reinforced concrete structure.
From the 1950s through to the 1970s, great technological
advancements took place that allowed architects and engineers to
aspire to greater heights. Some of these advancements included high-
strength bolts replacing hot-driven rivets, the emergence of glass-metal
curtain wall facades, the use of electric arc welding in shop fabrication
and the compressive strength of concrete catapulting from 40 MPa in
the 1960s to 65 MPa in the 1970s (and eventually 100 MPa+ in the 1990s).
Technological advances, combined with a deeper understanding of
structural behaviour and analysis under environmental loads
(particularly wind loads), led to the emergence of supertall buildings
being built in Chicago during the 1960s and 1970s. These supertall
buildings were conceived by structural engineers as “tubular” schemes
where the entire structure was designed as a cantilevered “tube” (John
Hancock Centre, 1969) or a bundle of tubes (Willis Tower, 1974) resisting
wind loads.
 Table 3: Some Ancient Tall Buildings
Source: Design, Innovation & Eminence,
# Building Name City Height No. of Year Structural Material Use
(m) Floors (completed) System
1 Shibam, 8 16th Century Structural Walls Mud brick Shelter vs
Yemen Bedouin
attacks
2 Home Insurance Chicago, 55 10 1885 Framed Gravity Steel, Office
Building USA System
3 Monadnock Chicago, 60 17 1893 Portal System, Masonry Office
Building USA Masonry Walls
4 The Eiffel Tower Paris, 324 1889 Lattice Tower Wrought- Monument
France Iron
5 The Ingalls Ohio, USA 16 1903 Framed Reinforced Office
Building (Transit Concrete
Building) (fcu <20MPa)
6 Singer Building New York, 186.6 47 1909 Framed Steel, R.C Office
USA
7 Woolworth New York, 241 55 1912 Framed Steel, R.C Office
Building USA
 First
Generation Third Generation
(16th C- 1850 ) (1940 - present)

Buildings in
Shibam, Yemen
16th century

The Woolworth Singer Building The Ingalls Building Eiffel Tower, Paris Home Insurance
Building New York, 1909 Ohio, 1903 1889 Building
New York 1912 Chicago, 1885
Second Generation
(1850 - 1940 )
 Tall Building Characteristics
 Single-function vs. Mixed-use Buildings
A single-function tall building is defined
as one where 85 percent or more of its
total height is dedicated to a single
function.
A mixed-use tall building contains two or
more functions, where each of the
functions occupies a significant
proportion of the tower’s total space

Support areas, such as car parks and mechanical

plant space, do not constitute mixed-use
functions. Functions are denoted on CTB UH
“Tallest” lists in descending order (e.g.,
“hotel/office” indicates hotel function above
office function).
  Building vs. Tower

To be considered a building, at least 50

percent of its height must be
occupiable. Telecommunications or
observation towers that do not meet
the 50 percent threshold are not
eligible for inclusion on CTBUH’s “Tallest”
lists.
 Co-Joined Building
 A building is a single, co-joined building (as opposed to separate buildings
in a complex) when 50 percent or more of the total building height is
connected. Exceptions to this 50 percent rule can be made in cases where
the form of the building creates a coherent arch, creating a singular
architectural expression and thus a co-joined building.
 Number of Floors
 Includes all above-ground floors, including the ground floor itself, and
significant mezzanine floors / major mechanical plant floors, unless they
have a significantly smaller floor are than the major floors below.
Mechanical penthouses or plant rooms above the general roof area are
not counted.

 Note: CTBUH floor counts may differ from other published accounts for
several reasons. Examples include: It is common in some regions of the
world to exclude certain floor numbers (e.g. 4, 14, 24, etc. in Hong Kong); A
building’s owner/marketing team may number floors to meet its own
objectives and are not based on the physical floors present in the building.
 Tall Building Trends in Recent Time
A composite tall building
utilizes a combination of both
steel and concrete acting
compositely in the main
structural elements.

A mixed—structure tall
building is any building that
utilizes distinct steel or
concrete systems above or
below each other.

Structural material usage from 1930 to 2013

 1.4 Classification of Tall Building Structural Systems
According to ‘Council on Tall Buildings and Urban habitat’ there are
four types of structural system:
Type I : Shear Frames
Type II : Interacting Systems
Type III: Partial Tubular Systems
Type IV: Tubular Systems (CTBUH, 1980)

According to Mir M. Ali and Kyoung Sun Moon, Structural systems of tall buildings
can be divided into two broad categories:

1. Interior structures and

2. Exterior structures.

According to material it can be:

1.Concrete type and
2.steel type
 1.4 Tall Building Structural Systems
INTERIOR STRUCTURES
By clustering steel columns and beams in the core, engineers create
a stiff backbone that can resist tremendous wind forces. The inner
core is used as an elevator shaft , and the design allows lots of open
space on each floor

EXTERIOR STRUCTURES
In newer skyscrapers, engineers moved the columns and
beams from the core to the perimeter, creating a hollow,
rigid tube as strong as the core design, but weighing much,
much less.
 INTERIOR STRUCTURAL SYSTEMS

 RIGID FRAME

 Height to roof: 157m

 Floor count: 38 floors
 Structural frame material: Steel

Seagram building
New York, USA  Lateral forces due to wind and seismic
are resisted by beams and columns
 Materials: concrete, steel
 Frames may also be braced to
increase stability
 INTERIOR STRUCTURAL SYSTEMS
 SHEAR WALL STRUCTURE

A shear wall is a structural panel that can resist

lateral forces acting on it.
Lateral forces are those that are parallel to the plane
of the wall, and are typically wind and seismic loads.
 OUTRIGGER STRUCTURES
• Outriggers serve to reduce the overturning moment in the core that would otherwise act as pure
cantilever, and to transfer the reduced moment to the outer columns through the outriggers
connecting the core to these columns.

• The core may be centrally located with outriggers extending on both sides or in some cases
it may be located on one side of the building with outriggers extending to the building
columns on the otherside.

• The outriggers are generally in the form of trusses in steel structures, or walls in concrete
structures.
 OUTRIGGER STRUCTURES

Shanghai World
Financial Centre

Height:
Roof : 487.4m
Tip: 494.3m
Floor count: 101 (3 belowground)
 EXTERIOR STRUCTURAL SYSTEMS
 TUBE SYSTEM
General
 Tube is a system where in order to resist lateral loads, a building is designed to
act like a hollow cylinder cantilever perpendicular to the ground.
 The main idea of tubular system is to arrange the structural elements so that
the system can resist the loads imposed on the structure efficiently particularly
horizontal loads.
 In tubular system the horizontal loads are by columns and spandrel beams at
the perimeter of the tubes.

 Several tube systems exist including:

 Framed tube system
 Braced tube system
 Bundled tube
 Tube in tube
 EXTERIOR STRUCTURAL SYSTEMS
 TUBE SYSTEM
Framed tube system
 One of the most widely used tube systems

 Compared to tube-tube system, it featured a much stiffer exterior tube in this

type system

Allows more open floor plans

 Depending on the structure, the spacing of the column is quite close,
generally 1.5–4.5m spacing.

Spandrel beam depths can range from 0.5 to 1.2 m.

Main disadvantages: High level of workmanship in connecting the core
with perimeter frames, high strength of bolts, shear lag.
 Total area: 6 hectares
Height to top (WTC1): 417m
(WTC2): 415.1m

Floor count: 110 floors

Structural frame material:
Perimeter columns: Steel
tubular sections (vierendeel
trusses), closely spaced to form
wall structure supporting all
lateral loads and sharing the
gravity loads with the core
Structural Layout Plan
World trade centre twin columns
towers, NY USA Core columns: Steel
(1973 - 2001) Spandrel beam: Steel
 EXTERIOR STRUCTURAL SYSTEMS
 TUBE SYSTEM
Braced tube system
Designed to resist wind and earthquake
forces in which members in a braced
frame are not allowed to sway laterally
(which can be done using shear wall or
diagonal steel sections, similar to
trusses). Steel members work effectively
both in tension and compression.

It is an improvement of tubular structure

made by cross bracings frames with X
bracing over many stories. Diagonal of
braced tube are connected to the
columns at each intersection, thus
eliminating the effect of shear lag in the
web and flange.
 EXTERIOR STRUCTURAL SYSTEMS
 TUBE SYSTEM
Braced tube system

Load distribution:
 Axial forces along the flanged frame
columns at one floor is not uniform

 Distribution of shear forces along the web is

not linear

 Along flanges, non-linearity result in the

corner or exterior columns, experience
greater stress than the centre or interior
columns.
Height to top (WTC1): 417m
(WTC2): 415.1m

Floor count: 100 floors

Structural frame material:
Perimeter columns: Steel tubular
sections (vierendeel trusses),
closely spaced to form wall
structure supporting all lateral
loads and sharing the gravity
loads with the core columns
Core columns: Steel
Spandrel beam: Steel
 Onterie Center (Chicago, 58 stories, 174 m)
Architect: Skidmore, Owings & Merril
Braced Frame material /configuration :
CONCRETE

Braced frame
Braced Frame Steel Work on John Hancock Centre
 EXTERIOR STRUCTURAL SYSTEMS
 TUBE SYSTEM
Bundled tube system
A bundled tube is a cluster of individual tubes
connected together to act as a single unit.
Instead of one tube, a building is consists of
several tubes tied together to resist lateral forces.
• For such a structure, the three- dimensional
response of the structure could be improved
for strength and stiffness by providing cross
walls or crossframes in the building.

• Also allowed for wider column spacing in the

tubular walls, which made it possible to place
interior frame lines without seriously compromising
interior space planning of the building.

• It is possible to add diagonals to them to increase

the efficient heightlimit
 Height to top : 527m
Floor count: 110 + 3 basement floors
Floor area: 416,000m2
Structural material:
Steel
Others:
black iodized aluminum
bronze – tinted glass

2 tubes

5 tubes

7 tubes

9 tubes

Wills Towers
Chicago, USA
  TUBE SYSTEMS
 Tube in tube
• The stiffness of a framed tube can also be enhanced by using the core
to resist part of the lateral load resulting in a tube-in-tube system.

• The floor diaphragm connecting the core and the outer tube transfer
the lateral loads to both systems.

• The core itself could be made up of a solid tube, a braced tube, or a

framed tube. Such a system is called a tube-in-tube.

• It is also possible to introduce more than one tube inside the perimeter
tube.

• The inner tube in a tube-in-tube structure can act as a second line of

defense against a malevolent attack with airplanes or missiles.

• Most of the loads are taken by the outer tube because of its
greater strength.
 Inner Tube
(Core)
Outer Tube

• The exterior columns & beams are spaced so

closely that the façade has the appearance of a
wall with perforated window opening.

• The entire building acts as a hollow tube

cantilevering out of the ground.

• The interior core increases the stiffness of the

building by sharing the loads with the facade
tube.
 2. DIAGRID SYSTEM

• With their structural efficiency as a varied version of the tubular systems.

• For diagrid structures, almost all the conventional vertical columns are eliminated.

• This is possible because the diagonal members in diagrid structural systems can
carry gravity loads as well as lateral forces due to their triangulated
configuration in a distributive and uniform manner.

• Efficiently resists lateral shear by axial forces in the diagonal members but have
Complicated joints.
 30 St Mary Axe, also known as SwissRe Triangular steel frame
Building (London, UK, 41 stories, 181 m)
• Steel framed tube type
Material /Configuration: structural system
STEEL • Triangular steel frame
generates the tube
• Beams are supported by
diagonal steel member
• Requires less steel than conventional steel
frame

Triangular grids are exposed in façade

 O-14 Building (Dubai)
Material /Configuration : CONCRETE
 3. SPACE TRUSS STRUCTURE

 Space truss structures are modified

braced tubes with diagonals connecting
the exterior to interior.

 In a typical braced tube structure, all the

diagonals, which connect vertical corner
columns in general, are located on the
plane parallel to the facades.

 However, in space trusses, some diagonals

penetrate the interior of the building.
Bank of China Tower
Height: 367m
Floors; 72 Stories
Status Completed
Country : China
City: Hong Kong
Building Function: Office
Structural Material: Composite
Core: Reinforced Concrete
Columns: Reinforced Concrete
Floor Spanning: Steel
 4. SUPERFRAMES
 A super frame is composed of mega columns comprising braced frames of large dimensions at building
corners, linked by multistory trusses at about every 15 to 20 stories.

 The concept of super frame can be used in various ways for tall buildings, such as the 56-story tall
Parque Central Complex Towers of 1979 in Caracas, Venezuela and the 168-story tall Chicago World
Trade Center proposed by Fazlur Khan in 1982 (Ali, 2001; Iyengar, 1986).

Parque Central
ComplexTowers

Chicago World Trade

Center
 5. EXO-SKELETON
• In exoskeleton structures, lateral load-resisting systems are placed outside the building lines
away from their facades. Examples include Hotel de las Artes in Barcelona.

• Due to the system’s compositional characteristics, it acts as a primary building identifier – one of
the major roles of building facades in general cases.

• Fire proofing of the system is not a serious issuedue to its location outside the building line.

• However, thermal expansion/contraction of the system, exposed to the ever- changing outdoor
weather, and the systemicthermal bridges should be carefully considered during design.
Hotel de las Artes (Barcelona, Spain, 43 stories, 137 m)

Exterior skeloton