Structural system of Buildings(sub-structure+ super structure)

Structural system of Building
Presenting by-
156025
160005
166010
166012
166013
166028
Dept. of Architecture,DUET
1

Foundation:
Foundation is one of the essential parts of the structure. It is defined as that part of the structure that
transfers the load from the structure constructed on it as well as its weight over a large area of soil in
such a way that the amount does not exceed the ultimate bearing capacity of the soil and the
settlement of the whole structure remains within a tolerable limit. Foundation is the part of a structure
on which the building stands. The solid ground on which it rests is known as foundation bed.
Substructure:
The substructure is the part of the
building that is underneath the
ground, while the superstructure is
everything that is above
ground. Substructure. The purpose
of the substructure of a building is
to transfer the loads of the
superstructure to the soil that is
underneath
2
There are two structural parts of a building:
• Sub-Structure
• Super-Structure
SUB-STRUCTURE
Source:Building constraction illustrated,Francis D.K.Ching(4th edition)
page no:80

Why a Foundation is Provided?
Foundation should fulfil the
following objectives:
• Distribute the weight of the
structure over a large area of
soil.
• Avoid unequal settlement.
• Prevent the lateral movement
of the structure.
• Increase structural stability.
Why There are Different Types
As we know that there are
different types of soil, and the
bearing capacity of the soil is
different for each type of soil.
Depending on the soil profile,
size, and load of the structure,
engineers chose different kinds
of foundation.
3
SUB-STRUCTURE
Source : https://civiltoday.com

Types of Foundation
In general, all foundations are divided into two categories, - shallow and deep foundations. The terms
Shallow and Deep Foundation refer to the depth of the soil at which it is placed. Generally, if the width
of the foundation is greater than the depth, it is labelled as the “Shallow Foundation”. If the width is
smaller than the depth of the foundation it is called as “Deep Foundation.” However, deep foundation
and shallow foundation can be classified as shown in the following chart.
4
SUB-STRUCTURE

Shallow Foundations
As the shallow foundation depth is low
and it is economical, it is the most
popular type of foundation for
lightweight structures. Several types of
shallow foundations are discussed
below.
1. Isolated Spread Footing
This is the most widely recognized
and most straightforward shallow
foundation type, as this is the most
economical type. They are typically
utilized for shallow establishments to
convey and spread concentrated
burdens caused, for instance, by
pillars or columns. They are generally
used for ordinary buildings (Typically
up to five stories).
5
SUB-STRUCTURE
page no:87

The followings are the types of spread footing.
6
SUB-STRUCTURE

2. Wall Footing or Strip footing
Wall footing is also known as continuous footing. This type is used to distribute loads of structural or non-
structural load-bearing walls to the ground in such a way that the load-bearing limit of the soil isn't
outperformed. It runs along the direction of the wall. The width of the wall foundation is usually 2-3 times
the width of the wall.
The wall footing is a continuous slab strip along
the length of the wall. Stone, brick, reinforced
concrete, etc. are used for the construction of
wall foundations.
• On account of block walls, the footing
comprises a few courses of bricks, the least
course being generally double the
expansiveness of the wall above.
• On account of stone masonry walls, the
counterbalances could be 15 cm, with the
statues of the course as 30 cm. Along these
lines, the size of footings is marginally more
than that of the block divider footings.
• If the heap on the wall is substantial or the
soil is of low bearing limit, this reinforced
concrete foundation type can be given.
Wall footing is economical when:
• Loads to be transmitted are of small
magnitude.
• It is placed on dense sand and gravel.
7
SUB-STRUCTURE
page no:87

3. Combined Footing
The combined footing is very similar to the isolated footing. When the columns of the structure are
carefully placed, or the bearing capacity of the soil is low and their footing overlap each other, combined
footing is provided. It is fundamentally a blend of different footings, which uses the properties of various
balances in a single footing dependent on the necessity of the structure.
Combined foundations are
economic when:
• The columns are placed close
to each other.
• When the column is close to
the property line and the
isolated footing would cross
the property line or become
eccentric.
• Dimensions of one side of the
footing are restricted to some
lower value.
The foundations which are made common to more than one column are called combined footings. There
are different types of combined footing, including slab type, slab and beam type, rectangular, raft, and
strap beam type. They may be square, tee-shaped, or trapezoidal. The main objective is the uniform
distribution of loads under the entire area of footing, for this is necessary to coincide with the center of
gravity of the footing area with the centre of gravity of the total loads.
8
SUB-STRUCTURE
page no:87

4. Cantilever or Strap Footing
Strap footings are similar to combined footings.
Reasons for considering or choosing strap footing
are identical to the combined one.
In strap footing, the foundation under the
columns is built individually and connected by a
strap beam. Generally, when the edge of the
footing cannot be extended beyond the property
line, the exterior footing is connected by a strap
beam with interior footing.
9
SUB-STRUCTURE
page no:87

5. Raft or Mat Foundation
Raft or Mat foundations are used where other
shallow or pile foundations are not suitable. It is
also recommended in situations where the
bearing capacity of the soil is inadequate, the
load of the structure is to be distributed over a
large area or structure is subjected continuously
to shocks or jerks.
Raft or Mat foundations are economic when:
• The soil is weak and the load has to be
spread over a large area.
• The structure includes a basement.
• Columns are closely placed.
• Other kinds of foundations are not feasible.
• Differential settlement is to be prevented.
Raft or Mat foundations consists of a reinforced
concrete slab or T-beam slab placed over the entire
area of the structure. In this type, the whole
basement floor slab acts as the foundation. The total
load of the structure is spread evenly over the entire
area of the structure. This is called raft because, in
this case, the building seems like a vessel that floats
on a sea of soil.
10
SUB-STRUCTURE

Pile Foundation:
Pile foundation, a kind of deep
foundation, is actually a slender column
or long cylinder made of materials such
as concrete or steel which are used to
support the structure and transfer the
load at desired depth either by end
bearing or skin friction.
Types of Pile Foundation
Pile foundations can be classified based on
function, materials and installation process,
etc. Followings are the types of pile
foundation used in construction:
A. Based on Function or Use
1. Sheet Piles
2. Load Bearing Piles
3. End bearing Piles
4. Friction Piles
5. Soil Compactor Piles
11
SUB-STRUCTURE
B. Based on Materials
and Construction Method
1. Timber Piles
2. Concrete Piles
3. Steel Piles
4. Composite Piles
page no:102

The following diagram is representing pile foundation types discussed above.
12
SUB-STRUCTURE

Classification of Pile Foundation Based on Function or Use
Sheet Piles
This type of pile is mostly used to provide lateral support.
Usually, they resist lateral pressure from loose soil, the flow
of water, etc. They are usually used for cofferdams, trench
sheeting, shore protection, etc. They are not used for
providing vertical support to the structure. They are usually
used to serve the following purpose
 Construction of retaining walls.
 Protection from river bank erosion.
 Retain the loose soil around foundation trenches.
 For isolation of foundation from adjacent soils.
Figure: sheet Pile
13
SUB-STRUCTURE

Load Bearing Piles
This type of pile foundation is mainly used to transfer the vertical loads from the structure to the soil.
These foundations transmit loads through the soil with poor supporting property onto a layer which is
capable of bearing the load.
In this type of pile, the loads pass through the
lower tip of the pile. The bottom end of the pile
rests on a strong layer of soil or rock. Usually,
the pile rests at a transition layer of a weak and
strong slayer. As a result, the pile acts as a
column and safely transfers the load to the
strong layer.
End Bearing Piles
Friction Pile
Friction pile transfers the load from the structure
to the soil by the frictional force between the
surface of the pile and the soil surrounding the
pile such as stiff clay, sandy soil, etc.
In friction pile, generally, the entire surface of
the pile works to transfer the loads from the
structure to the soil.
14
SUB-STRUCTURE
page no:103

Soil Compactor Piles
Sometimes piles are driven at placed closed intervals to increase the
bearing capacity of soil by compacting.
Classification of Piles Based on Materials and Construction Method
On the basis of materials of pile construction and their installation process load-bearing piles can be
classified as follows:
1. Timber Piles
i. Untreated
ii. Treated with Preservative
2. Concrete Piles
i. Pre-cast Piles
ii. Cast-in-pace Piles
3. Steel Piles
i. I-Section Piles
ii. Hollow Piles
4. Composite Piles
15
SUB-STRUCTURE

Timber Piles
Timber piles are placed under the water level. They last for approximately about 30 years. They can be
rectangular or circular in shape. Their diameter or size can vary from 12 to 16 inches. The length of the
pile is usually 20 times of the top width.
They are usually designed for 15 to 20 tons. Additional strength can be obtained by bolting fish plates to
the side of the piles.
Advantages of Timber Piles-
 Timber piles of regular size are available.
 Economical.
 Easy to install.
 Low possibility of damage.
 Timber piles can be cut off at any desired length after
they are installed.
 If necessary, timber piles can be easily pulled out.
Disadvantages of Timber Piles-
 Piles of longer lengths are not always available.
 It is difficult to obtain straight piles if the length is short.
 It is difficult to drive the pile if the soil strata are very hard.
 Spicing of timber pile is difficult.
 Timber or wooden piles are not suitable to be used as end-bearing
piles.
Figure: timber Pile
16
SUB-STRUCTURE

Concrete Piles
The precast concrete pile is cast in pile bed in the
horizontal form if they are rectangular in shape.
Usually, circular piles are cast in vertical forms.
Precast piles are usually reinforced with steel to
prevent breakage during its mobilization from
casting bed to the location of the foundation. After
the piles are cast, curing has to be performed as per
specification. Generally curing period for pre-cast
piles is 21 to 28 days.
Pre-cast Concrete Pile
Cast-in-Place Concrete Piles
This type of pile is constructed by boring of
soil up to the desired depth and then,
depositing freshly mixed concrete in that
place and letting it cure there. This type of
pile is constructed either by driving a metallic
shell to the ground and filling it with concrete
and leave the shell with the concrete or the
shell is pulled out while concrete is poured.
Figure: Pre-cast Concrete Pile
Figure: cast-in-situ Concrete Pile
17
SUB-STRUCTURE

Steel Piles
Steel piles may be of I-section or hollow
pipe. They are filled with concrete. The size
may vary from 10 inches to 24 inches in
diameter and thickness is usually ¾ inches.
Because of the small sectional area, the
piles are easy to drive. They are mostly used
as end-bearing piles.
Combination of different materials in the same of
pile. As indicated earlier, part of a timber pile
which is installed above ground water could be
vulnerable to insect attack and decay. To avoid
this, concrete or steel pile is used above the
ground water level, whilst wood pile is installed
under the ground water level
Composite Piles
Figure: composite pile
18
SUB-STRUCTURE

Classification of pile foundation based on the effect of soil
1. Driven piles
2. Bored piles
3. Screw pile
4. Timber piles
5. Steel piles
Driven piles, also known as displacement piles, are a
commonly-used form of building foundation that provide
support for structures, transferring their load to layers of soil
or rock that have sufficient bearing capacity and suitable
settlement characteristics. Driven piles are commonly used to
support buildings, tanks, towers, walls and bridges, and can
be the most cost-effective deep foundation solution.
1. Driven piles
2. Screw pile
Screw pile foundations are a type of pile foundation with a helix
near the pile toe so that the piles can be screwed into the
ground. The process and concept is similar to screwing into
wood. A screw pile may have more than one helix (also called a
screw), depending on the usage and the ground conditions.
Generally, more helices are specified if a higher load is required
or softer ground is encountered.
Figure: driven pile
Figure: screw pile
19
SUB-STRUCTURE

Pier Foundation
Pier is an underground structure that transmits a more massive
load, which cannot be carried by shallow foundations. It is
usually shallower than piles. The pier foundation is generally
utilized in multi-story structures. Since the base region is
determined by the plan strategy for the regular establishment,
the single pier load test is wiped out. Along these lines, it is
increasingly well known under tight conditions.
Pier foundation is a cylindrical structural member that transfer
heavy load from superstructure to the soil by end bearing.
Unlike piles, it can only transfer load by bearing and by not skin
friction.
Figure: Pier Foundation
Caisson Foundation
Caisson foundation is a watertight retaining
structure used as a bridge pier, construction of
the dam, etc. It is generally used in structures that
require foundation beneath a river or similar
water bodies. The reason for choosing the caisson
is that it can be floated to the desired location
and then sunk into place
Figure: caisson Foundation
20
SUB-STRUCTURE

Caisson foundation is a ready-made hollow cylinder depressed into the soil up to the desired level and
then filled with concrete, which ultimately converts to a foundation. It is mostly used as bridge piers.
Caissons are sensitive to construction procedures and lack construction expertise.
There are several types of caisson foundations.
1. Box Caissons.
2. Floating Caissons.
3. Pneumatic Caissons.
4. Open Caissons.
5. Sheeted Caissons.
6. Excavated Caissons.
21
SUB-STRUCTURE

22
TYPES OF SUPER – STRUCTURAL SYSTEMS:
Super-Structure
Post slab
Slab
Column
without
Beam
Post-
Lintel slab
Slab Beam Column
Wall Slab
Slab Wall
SUPER-
STRUCTURE

POST SLAB
• A reinforced concrete slab supported
directly by concrete
columns without the use of beams.
• Theoretically there is no limit on
maximum length.
• But practically and economically they
are restricted.
Flat slab without drop and column capital
COLUMN
SLAB
• Slab depth: 5’’ to 12’’
• Rule of Thumb:
For slab depth: Span/33
• Suitable for light live to moderate loads
over relatively short spans pf 12’ to 24’.
• Characteristics :
Simplicity of forming.
Lower floor to floor heights.
POST SLAB
Simple flat slab
Flat
slab construction
with column
heads.
Flat
slab construction
with drop panels.
Flat
slab construction
with both column
heads and drop
panels.
• Span:20’ to 40’
23
SUPER-
STRUCTURE
Sources:(book name- building construction illustrated, 4th edition)
Page nO:108

Flat slab with column capital
Fig :Flat Slab With Drop Panel
Page nO:108
COLUMN
COLUMN
CAPITAL
SLAB
Flat slab with drop panel and column capital
COLUMN
SLAB
COLUMN
CAPITAL
DROP PANEL
COLUMN
SLAB
DROP PANEL
Slab:
• Slab depth:6’’ to 12’’
• Rule of Thumb:
for slab depth : Span/36
Drop panel:
• Minimum projection of drop panel =0.25x
slab thickness
• Width:0.33x Span
• Used :resistance to punching shear.
24
SUPER-
STRUCTURE

Uses Of Post Slab
• Post slabs are mostly used in large industrial structures,
parking garages, ramps, warehouse, high rise buildings.
• They are also used where uses of beams are not required.
Major components of flat slab are capital/head, drop panel,
columns strip and middle strips.
Slab Thickness:
Slab without drop panel :125mm
Slab with drop panel :100mm
25
STRUCTURAL ADVANTAGES OF FLAT SLAB
 Economic
 Faster construction
 Prefabricated in standard sizes
 Minimized installation time
 Better quality control
STRUCTURAL DISADVANTAGES OF FLAT SLAB
• Seismic loading is poor
• Flat slab failure in earthquake
• Punching shear
• punching limitation
• Cheek shear diagram
• Each floor should have cantilever.
• Can not punch at column strip.
& FLAT SLAB DESIGN BY O’ROUOKE, CE AND SAMUEL BAKER,
CE(Serial-2754-4), BNBC 2014, (6.5.2.5)

• Slab Supported on wall
• There is no column & beam
Wall Slab
Load Distribution System
Wall slab structure
page no:64
26
SUPER-
STRUCTURE

TYPE OF SLAB BASED ON SUPPORT CONDITION:
 One Way Slab  Two Way Slab
• Slabs supported on Two Opposite side
• rectangular in shape.
• Main reinforcement is provided in short span and
distribution reinforcement is provided in a longer
span.
• Slab thickness is more as compared to the two-way
slab.
• Chajja and Varandha are practical example.
• Slabs supported on four sides.
• Preferred if the shape of slab is close to
square.
• Effective for medium span and heavy loads.
• Used in constructive floors of the building.
 Waffle slab
L
b
L
b
L/b>=2 L/b<2
page no:64
27
SUPER-
STRUCTURE

• Rule of thumb for estimating thickness:
Floor slab : Span/30 (4’’ minimum)
Roof slab: Span/36
• Suitable for light to moderate loads over relatively short
spans of 6’ to 18’.
page no:106,107
One Way Slab
Two Way Slab
• Rule of thumb for estimating thickness:
Slab depth : Span perimeter/180 (4’’ minimum)
• Suitable for carrying intermediate loads over 15’ to 40’
span.
SLAB THICKNESS & SPAN
28
SUPER-
STRUCTURE

To control deflection , ACI Code 9.5.2.1
specifies minimum thickness
Type of one-way
slab
Structural depth Diagram
Simple supported L/20
One end continuous L/24
Both ends continuous L/28
Cantilever L/10
Position of Stair
Wall Support
Wall
Support
t=Thickness of slab
Landing
`
• Landing should be supported by load bearing wall
• The wall in both sides is the main structural
member
• Parallel walls on two sides can also provide
support
One-way slab depth:
29
SUPER-
STRUCTURE

•Masonry Wall: Masonry is the most durable part of any
structure. It allows for unlimited architectural expressions. They
provide strength durability. Masonry wall also helps to control
the temperature in indoor and out. Also, it increases the fire
resistance. Lateral stiffness of the masonry wall is very low.
•Engineering Brick Wall: It uses double open-ended bond beam
blocks. It is built using a mold . Block wall is replaced
horizontally.
•Stone Wall: It is treated as a stone structure. It is kind a
masonry construction. This wall provides structure to a
building and encloses an area.
Types of Load Bearing Walls
Followings are the types of load bearing walls:
•Precast Concrete Wall: This wall is aesthetically pleasing. The
precast wall has superior strength and known for its durability. It
provides excellent protection and is easy to install.
30
SUPER-
STRUCTURE

MINIMUM THICKNESS OF MASONARY WALL:
TYPES OF Load bearing masonry wall Min. thickness
Stone Masonry Wall 16inch
Cavity wall masonry Wall 8inch
Hollow unit Masonry Wall 8inch
Solid Masonry 8inch
Grouted Masonry Wall 6inch
Reinforced masonry Wall 6inch
 Exterior non-bearing walls may be 4’’ less than required for bearing wall , but not
less than 8’’ thick, except where 6’’ walls are permitted in residences.
• Plain (unreinforced)masonry bearing walls must be at
least 12’’ thick for the uppermost 35’ of the wall and
increase 4’’ in thickness for each successive
35’downward from the top.
• For buildings not more than 3 stories or 35’ in height,
masonry walls may ne 8’’ thick.
• One- story solid masonry walls not more than 9’’ high
may be 6’’ thick.
Plain Masonry Bearing Wall
Note: Local building codes to verify the structural requirements for masonry.
page no:131
31
SUPER-
STRUCTURE

MINIMUM THICKNESS OF WALLS IN HIGH WIND REGION:
Type of Wall Minimum thickness (mm)
Unreinforced grouted brick wall 250
Reinforced exterior bearing wall 200
Unreinforced hollow and solid masonry wall 200
Interior non-bearing wall 150
Source:Bangladesh National Building Code-2012(chapter:7)7.4.6
page no6-382,:6-400
• The maximum unsupported height of bearing walls or other masonry walls shall be 3.5 m.
Minimum Thickness of Load Bearing Walls:
The nominal thickness of masonry bearing walls in building shall not be less than 250 mm.
Exception:
• Stiffened solid masonry bearing walls in one‐story buildings may have a minimum effective
thickness of165 mm when not over 3 m in height,
• provided that when gable construction is used an addition1.5 m height may be permitted at the
peak of the gable.
Parapet Wall:
• Parapet walls shall be at least 200 mm thick.
• height shall not exceed 4 times the thickness.
• The parapet wall shall not be thinner than the wall below.
32
SUPER-
STRUCTURE

• SUITABLE FOR SMALLER SCALE CONSTRUCTION.
• SUITABLE FOR SOLID MASS DESIGN.
• ECONOMICAL.
• SUITABLE FOR ARCH , VAULT OPENING.
• EASY TO REPAIR.
• CAN BE USED LOCAL MATERIALS.
• PRODUCE THERMAL COMFORTABLE.
• IT IS MOST SUITABLE WHERE THE BEARING CAPACITY OF SOIL IS HIGH.
DISADVANTAGES
• NOT APPLICABLE IN HIGH RISE BUILDING
• NOT POSSIBLE TO CHANGE IN UPPER FLOOR
• MONOTONOUS STRUCTURE & ELEVATION.
• NOT POSSIBLE TO MAKE AN OPENING ANY WHERE IN THE WALL.
• LOW CAPABILITY OF RESISTING THE EARTH QUAKE.
• LIMITED HEIGHT
• LESS ACCEPTABLE FOR CREATING VOID SPACE.
• SMALLER FLOOR AREA.
ADVANTAGES & DISADVANTAGES OF WALL SLAB
33
SUPER-
STRUCTURE

Waffle slab
• The most technical and economical type of roofs
among conventional systems.
• A waffle slab is flat on top, while joists create a
grid like surface on the bottom.
• The main element in the construction waffle
slabs is waffle formwork.
• Suitable for span of 24’ to 54’, longer span may be
possible with Posttensioning.
Sources:(book name- building construction illustrated, 4th edition
Page:107
SUPER-
STRUCTURE
Square metal or fiberglass dome
Width:19’’ to 30’’
Depth: 8’’ to 20
Rib width : 5’’ to 6’’
Slab depth:3’’ to 4’’
Rule of Thumb: depth=span/24

Waffle slab design
Slab depth is typically 75 mm (3 in) to 130 mm (5 in)
thick.
As a rule of thumb, the depth should be 1⁄24 of the
span.
The width of the ribs is typically 130 mm (5 in) to
150 mm
(6 in), and ribs usually have steel rod reinforcements.
The distance between ribs is typically 915 mm (3 ft).
The height of the ribs and beams should be 1⁄25 of the
span between columns.
The width of the solid area around the column should
be 1⁄8
of the span between columns. Its height should be the
same
as the ribs.
Diagram shows slab and rib width with
rules of thumb formula
Diagram showing waffle slab rib and Beam
Heights rule of thumb formulas
Diagram shows the width of the column head
with rule of thumb formula
Sources:(book name- building construction illustrated, 4th edition
SUPER-
STRUCTURE

POST-LINTEL SLAB:
SLAB
BEAM
COLUMN
GROUND
LOAD
WIDTH DEPTH
Should not be equal or grater
than width of supporting
columns
Rule of Thumb:
depth=span/16
SIZE SUPPORTED AREA
12’’ 2000sf
16’’ 3000sf
20’’ 4000sf
Column spacing=Beam or Slab span
Post -Lintel structures/Frame structure:
Frame structures are the structures having the combination of beam, column and
slab to resist the lateral and gravity loads.
Source:Bangladesh National Building Code-2012(chapter:7)7.4.6
page no:146-148
36
SUPER-
STRUCTURE

TYPES OF POST-LINTEL STRUCTURE :
1.Moment frames
Moment frames resist gravity and lateral load in bending and compression.
They are derived from post-and beam portals with moment resisting beam
to column connections.
Deformation under gravity and lateral lodes are visualized in diagram:
1 Portal with pin joints collapses under lateral load
2 Portal with moment joints at base under lateral load
3 Portal with moment beam/column joint under gravity load
4 Portal with moment /column joint under lateral load
5 Portal with all moment joint under gravity load
6 Portal with all moment joint under lateral load
7 High-rise moment frames under gravity load
8 Moment frames building under lateral load
Source: G G Schierle Architectural structures Excerpts, Chapter-(17-6)
2.Braced frames
Braced frames resist gravity bad in bending and axial compression,
and lateral load in axial compression and tension by triangulation,
much like trusses. The triangulation results in greater stiffness,
an advantage to resist wind bad, but increases seismic forces,
a disadvantage to resist earthquakes.
SUPER-
STRUCTURE

Braced frames as follows:
1 Single portal under gravity and lateral loads
2 A-braced portal under gravity and lateral load
3 V-braced portal under gravity and lateral load
4 X-braced portal under gravity and lateral load
5 Braced frame building without and lateral load
3.Steel framing
Steel framing with wide-flange profiles requires careful orientation of columns
in order to
achieve proper strength and stiffness to resist lateral load in both orthogonal
directions.
Measured by the moment of inertia, typical wide-flange columns have a
stiffness ratio of
about a 3:1 about the x and y-axis, respectively, yet some deep sections have
stiffness
ratios up to 50:1, about strong to weak axes.
1 Front view of moment resisting frame with setback floors on tap
2 Column layout in plan for moment resistance in direction
3 Column oriented for lateral support in width direction
4 Column oriented for lateral support in length direction
SUPER-
STRUCTURE

4.Framed Tube
Framed tubes are a variation of moment frames, wrapping
the building with a "wall" of closely spaced columns and
short spandrel beams. To place the lateral resistance system
on the facade rather then at the interior gives it a broader
base for greater stability as well as improved rotational
resistance.
1 Framed tube without interior core.
2 Framed tube with interior core.
3 Global stress diagram of framed tube.
4 Framed tube with belt and top truss for additional stiffness.
5.Bundled Tube
Bundled tube structures are composed of tubes framed by closely spaced
columns joined
to beams to form moment frames. The bundled tubes resulting from the rows
of columns
add lateral resistance to the structure, transferring shear between exterior
columns
subject to tension and compression under lateral load.
1 Square tube modules.
2 Triangular tube modules
3 Hexagonal tubes would be less effective to reduce shear lag.
4 Farmed tube shear lag.
5 Bundled tube with reduced shear lag.
A Shear lag between connecting shear walls.
B Peak resistance at shear wall.
SUPER-
STRUCTURE

Structural system of Buildings(sub-structure+ super structure)

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