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7/30/2019 Structures in Practice
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STRUCTURESIN PRACTICEEngineering Mechanics - CE101
EN 13522148 | M.K.S.Liyanarachchi
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Engineering Mechanics | CE101 Structures in Practice
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Content
What is a structure? Types of Structures Forces acting on structures Structural Members Hospitality Management Building Engineering Faculty Building Hyatt Regency Colombo
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What is a structure?
A structure is a body or assemblage of bodies in space to form a system capable of supporting
loads
A structure is something that will support an object or a load. A structure must be strong enoughto support its own weight and whatever load is put on it.
Physical structures include man-made and natural arrangements. Buildings, aircraft, soap films,
skeletons, anthills, beaver dams and salt domes are all examples of physical structures
The structure of a building is the part which is responsible for maintaining the shape of the
building under the influence of the forces to which it is subjected.
A building must be designed to safely withstand the most severe combination of forces or loads
likely to be applied during its lifetime.
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Types of Structures
There are three types of structures.
1. Mass Structures2. Frame Structures3. Shell Structures4. Suspension structures5. Arch structures
Mass Structures
Mass Structures are solid structures which rely on their
own weight to resist loads. They are normally made
from low quality materials but the structure is normally
thick. A single brick is a mass structure but so is a large
dam.
Frame structures
Frame structures resist loads due to the arrangement of its members. A house roof truss cansupport a load many times its own weight. A two dimensional frame such as this is known as a
plane frame. The Eiffel Tower is an example of a three dimensional frame structure, known as a
space frame. Electricity pylons are good examples of frame structures
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Shell Structures
Structures, which keep their shape and
support loads, even without a frame, or
solid mass material inside, are called
shell structures. These structures use athin, carefully shaped, outer layer of
material, to provide their strength and
rigidity. The shape of a shell structure
spreads forces throughout the whole
structure, which means every part of the
structure supports only a small part of the
load, giving it its strength.
Examples include: igloos, egg cartons, turtle shell, food or pop cans, or, even bubbles in foam
and cream puffs.
Suspension structures
Suspension structures hold an element by cables held from the top of a tall column. Because of
this, they are often the best bridges that are needed to cover big rivers
Arch structure
Romans invented the arch and their style was the semicircular arch. The stone at the top was
called the key stone. Thegeometry of the arch and its
main load displaces the
force to the sides, so there was a
space under it to span obstacles.
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Forces acting on structures
A structure has forces acting on it all the time. A structure must be able to resist the forces acting
on it without collapsing.
Forces can be:
Static - static forces are usually forces caused by the weight of the structure and anythingwhich permanently attached to it.
DynamicDynamic forces are caused by the things such as wind, waves, people, andvehicles.
Members of structures support external forces or loads that can act in different way. Depending
on the external forces or load acting on a structural member, it can be under different stresses.
Tension: the forces acting on a structural member try to pull it apart. Compression: name given to a force that tries to squash something together. Torsion: name given to a turning or twisting force. Shear: a shear force is created where two opposite forces try to cut something in two. Bending: the force acting on a structural member form a curve on it. The structural
member is stretched and squashed at the same time.
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Structural Members
Members are the different parts of a structure that are interconnected in such a way that so the
structure will support the load put on it.
Structural members are the primary load bearing components of a building. The structure of abuilding constitutes about 30% of the construction cost. A good structural design can result in
cost efficient building.
In any building design, the strength and stability of an overall building and its individual
components must be considered. This involves structural calculations to work out the effects of
all the forces acting on any component in the building and on the building overall. To do this we
need to resolve the forces in the system to see what the overall effects are likely to be.
The type of material used and the shape of a structural member have a significant impact upon its
structural effectiveness
Some of those members are:
Beams Columns Concrete slabs Girder Trusses
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Beams
A beam may be defined as an
element in which one dimension is
much greater than the other two
and the applied loads are usually
normal to the main axis of the
element. Beams and columns are
called line elements and are often
represented by simple lines in
structural modeling.
Cantilevered (supported at one end
only with a fixed connection)
Simply supported (supported vertically at each end; horizontally on only one to withstandfriction, and able to rotate at the supports)
Columns
Columns are elements that carry only axial force - compression - or both axial force and bending
(which is technically called a beam-column but
practically, just a column). The design of a column
must check the axial capacity of the element,
and the buckling capacity.
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Truss
A truss is a structure comprising two types
of structural elements; compression
members and tension members (i.e. struts
and ties). Most trusses use gusset plates to
connect intersecting elements. Gusset
plates are relatively flexible and minimize
bending moments at the connections, thus
allowing the truss members to carry
primarily tension or compression.
Trusses are usually utilized in span large distances, where it would be uneconomical to use solid
beams
Girder
A girder is a support beam used in
construction. Girders often have an I-
beam cross section for strength, but
may also have a box shape, Z shape
or other forms. Girder is the term
used to denote the main horizontal
support of a structure which supports
smaller beams. A girder is
commonly used many times in thebuilding of bridges, and planes.
Concrete slabs
A concrete slab is a common structural element of modern
buildings. Horizontal slabs of steel reinforced concrete,
typically between 100 and 500 millimeters thick, are most
often used to construct floors and ceilings, while thinner
slabs are also used for exterior paving.
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Site Information & Report
Projects going on at SLIIT Malabe Campus Premises (Group Visit) Hospitality Management Building
Location: SLIIT Malabe Campus Premises
Date: 02/04/2013
Group: 01 (Tuesday at 8.30 AM - 10.30 AM)
Lecturer: Dr. Gobithas Tharmarajah
The hospitality management building was visited to study practical about:
Primary Structure Secondary Structure Tertiary Structure Load Path Stability of the Building
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Primary structures
The primary structures are the repeating frames arranged parallel to each other. Two columns,
two beams and a roof are the major components of each primary frame. The columns and beams
are concrete elements. The roof structure is made of steel trusses and steel purlins. The roof is
simply supported at one end, and fixed at the other end.
All Beams in this building is square shaped. Trusses are connected to columns as simply
supported in one end & other end as pin joined. This will reduce the damage that is caused to the
primary structure due to the expansion happen due to heat and also helps to manage vibrational
situations such as earthquakes.
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Secondary Structure
The secondary structures are steel C section purlins. The purlins are fixed perpendicular to the
roof truss and carry the roof structure on them. A plate is used to bolt the purlins with the truss.
In the first floor concrete slab is the secondary structure. Concrete slab is also categorized in the
secondary structure.
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Tertiary structure
Zinc aluminum roof is the tertiary structure. The roof is fixed to the C section steel purlins.
The roof is fixed purlins by bolts.
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Load Path
a) At the roof level: The load from roof is transferred to the purlins as uniformly distributed load.
The purlins transfer the loads to roof truss as point loads. Then the roof trusses distribute it to the
columns as point loads. The columns finally transfer the loads to foundations where foundations
disperse it to the ground.
b) At the first or second floor level: The loads from floors are transferred to the beams as
uniformly distributed load. The beams transfer the loads as point loads on columns where
columns disperse the load to the ground via foundation.
Stability of the Building
Main Frame of the building is the primary structure for stability. The stability of structure at roof
level is taken from the purlins connect all the steel trusses and ensure the stability of the roof
trusses. Also fixed joint of the truss on columns increases the stability of the roof trusses. In
addition, the reinforced concrete walls for lift, staircase and service area provides the additional
stability to the building.
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Engineering Faculty BuildingLocation: SLIIT Malabe Campus Premises
Date: 02/04/2013
Group: 01 (Tuesday at 8.30 AM - 10.30 AM)Lecturer: Mr. Gobithas Tharmarajah
The Engineering Faculty Building is an under construction building at SLIIT
Premises. There are 7 floors and a ground floor in this building.
The site visit to this building is mainly for study in practically about:
Primary Structure Secondary Structure Tertiary Structure
Load Path Stability of the Building
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Primary structure
In the engineering faculty building there are square shaped beams are used instead of truss due to
the high load that will be on the floor on top of it because of heavy tables & equipment used in
labs. They are fixed joint to the column. It is less expensive when compared with using metal
truss.
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Secondary structure
The secondary structure used in the new engineering building is purlins. The purlins are fixed
perpendicular to the concrete beam and carry the upper floor on them. Concrete & steel used to
fix those purlins & Beams.
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Tertiary Structure
In this floor (Third floor), there is no particular tertiary structure. There is the concrete slab on
the concrete purlins. In this level the concrete slab is the tertiary Structure.
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Load path
The loads from floors (slabs) are transferred to the purlin beams as uniformly distributed
load. The purlin beams transfer the loads as point loads on Concrete beams. The concrete
beams transfer the loads as point loads on columns where columns disperse the load to
the ground via foundation.
Stability of the building
Main Frame of the building is the primary structure for stability. The stability of structure
at third level is taken from the purlin beams connect all the columns and ensure the
stability of the primary structure. Also fixed joint of the concrete beams on columns
increases the stability of the beams. In addition, the reinforced concrete walls for lift,
staircase and service area provides the additional stability to the building & special shape
of front section provides more support to the stability of the Building
Reinforced concrete wall
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Hyatt Regency Colombo(Individual visit)Location: Colombo
Date: 20/04/201
The Hyatt Regency Colombo, a 42-floor hotel on Galle Road, one of the arterial roads in the
central business district area, will also have a lobby lounge, an all-day dining, multi-cuisine
restaurant, three specialty restaurants, a bar, eight spa treatment rooms, a fitness center, a
swimming pool, and a Regency Club lounge.
The site visit to this building is mainly for study in practically about:
1. Primary Structure2. Secondary Structure3. Tertiary Structure4. Load Path5. Stability of the Building
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Primary Structure
Almost all beams in this building are square shaped. They are connected to columns as fixed
joints. The concrete beams can handle the massive force better than truss and it is also less
expensive.
There are also truss have been used to support a small roof that comes out.
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Secondary structure
The secondary structures are concrete purlins. The purlins are fixed perpendicular to the concrete
beam and carry the upper floor on them. Concrete & steel used to fix those purlins & Beams
There are small amount of purlins have been used since there wont be much weight put on them.
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Tertiary Structure
Since the building havent yet completed the roof there no clear tertiary structure in the building.
In this level the concrete slab is the tertiary Structure. There is the concrete slab on the concrete
purlins.
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Load Path
The loads from floors (slabs) are transferred to the concrete purlins, and then the load is
transferred to beams by fixed joints. The concrete beams then transfer the load to columns.
Finally load is transfer to the foundation by columns
Stability of the building
Main Frame of the building is the primary structure for stability. The stability of structure at first
level is taken from the concrete beams connect all the columns and ensure the stability of the
primary structure. Also fixed joint of the concrete beams on columns increases the stability of the
beams. In addition, the retaining walls provide the additional stability to the building & special
step shape of the building provides more support to the stability of the Building and also protects
the occupants from the elements.
Since this is a high rising building stability of the building is very importance. The buildingmust be stable enough to handle its own weight, weight of the equipment in the building,
occupants and also massive cross-wind.
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References
Mechanical Science (Third Edition)o By W. Bolton
Structures in Practice CE101 Engineering Mechanics: Semester1o By Gobithas Tharmarajah