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

structures in practice

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