TYPES OF BRIDGES :

How do bridge's work????


Although there are many types of bridges most bridges work by balancing compression and tension. Place a flexible object like an eraser, sponge, or small piece of bread between your thumb and index finger. Press your fingers together. One side of the object will bend inwards and shorten while the other will bend outwards and lengthen. The shorter side has been compressed, while the other side is under tension. Bridge
components experience these tension and compression stresses



ARCH BRIDGE ==>>
Arch bridge are structures in which each span forms an arch. The arch bridge is one of the oldest types of bridges. Early arch bridges were made from stone. The spans range up to about 1700 ft.


GIRDER BRIDGES ==>>

Girder bridges are made of beams called girders. The ends of the beams or girders rest on piers or abutments. The span length of girder bridges ranges up to about 1000 ft.

TRUSS BRIDGE==>>

Truss bridges are supported by frameworks called trusses. Trusses are beams arranged to form triangles.

CANTILEVER BRIDGE==>>

Cantilever bridges consist of two independent beams, cantilevers, that extend from opposite banks of a waterway. Cantilever bridges have spans as long at 1800 ft.

CABLE STAYED BRIDGE==>>

Cable-stayed bridges have roadways that hang from cables. The cables are connected directly to towers.

MOVEABLE BRIDGE==>>

Moveable bridges have roadway that is moved to provide enough clearance for boats or large ships to pass. An example of a moveable bridge is a drawbridge that tilts the roadway upward.

SUSPENSION BRIDGES==>>

Suspension bridges may be the most impressive type of bridge with their long main span and beauty. These bridges have a roadway that hangs from steel cables supported by two high towers. The difference between suspension bridges and cable-stayed bridges is that suspension bridge cables are not directly connected to the towers. The cables of a suspension bridge are not connected to the bridge - the cables pass through a hole in the top of the towers.


A suspension bridge has at least two main cables. These cables extend from one end of the bridge to the other. Suspender cables hang from these main cables. The other end of the suspender attaches to the roadway.


Suspension bridges have the longest spans in the world and are used to cross great distances. These types of bridges are used to cross deep water channels, cannons or gorges, where construction of supporting piers can be difficult. The towers can be placed far apart eliminating the need for multiple towers and piers. Some suspension bridges have a main span longer then 4000 ft. The longest suspension bridge in the world is in Japan (the Akashi- Kaikyo Bridge) and has a span over a mile long. The largest bridges have cables several feet wide which weigh thousands of pounds per foot. For that reason the cables are spun in place.

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==>> MOMENT DISTRIBUTION METHOD'S THEORY IN VERY SIMPLE WAY<<==

                                       ==>> MOMENT DISTRIBUTION METHOD
                                                                         OR
                                                    [HARDY -CROSS METHOD]
                                                                         OR
                                      METHOD OF SUCCESSIVE APPROXIMATION<<==

==>>   It is based on stiffness approach and stiffness is defined as the moment required to produce unit rotation....

FIRST we have to clear all terms which we are going to learn in this method

K=STIFFNESS,
I=MOMENT OF INERTIA,
E=MODULUS OF ELASTICITY
L=LENGTH OF WHOLE SPAN

In this method some formulas are given bellow ==>>

1==>> If the far end is fixed then stiffness is ==>> K= 4EI/L

2==>>If the far end is hinged then stiffness is ==>> K=3EI/L

3==>>If the far end is free then stiffness is ==>> K=0

Here is the example==>>

Fixed far end are==>> OB and OD
Free far end are==>> OF
Hinged far end are==>> OC and OE

Length of each span  OB=L1 ,,, OD=L2 ,,, OF =L3 ,,, OC=L4 ,,, OE=L5

Now we have to calculate individual and total stiffness==>>
Stiffness of OB IS ==>> K1=4EI / L1 [FAR END B IS FIXED]
Stiffness of OD is ==>> K2=4EI / L2  [FAR END D IS FIXED]
Stiffness of OF is ==>> K3=K=0    [FAR END F IS FREE]
Stiffness of OC is ==>> K4=3EI / L4  [FAR END C IS HINGED]
Stiffness of OE is ==>>  K5=3EI / L5  [FAR END E IS HINGED]

Now we have to calculate TOTAL STIFFNESS ,so
TOTAL STIFFNESS ==>>K=K1+K2+K3+K4+K5
K=4EI / L1+4EI / L2+0+3EI / L4+3EI / L5

After this steps we have to calculate RELATIVE STIFFNESS ==>>

RELATIVE STIFFNESS is defined as the individual stiffness/total stiffness

==>>RELATIVE STIFFNESS of all members are==>>

For OB=K1 / K;
For OD=K2 / K;
For OF=K3 / K;
For OC=K4 / K;
For OE=K5 / K;

Some other terms used in MOMENT DISTRIBUTION METHOD are==>>

CARRY OVER MOMENT==>>
If moment M is applied at a joint B then carry over moment is the moment which is develop at the far end..

==>> If any beam fixed at one end and supported at other end ...then moment develop at the fixed end is half of the moment develop at the supported end...

A==>>FIXED END , B==>> SUPPORTED END...
MOMENT AT B= M
Then MOMENT develop in A is = M / 2;

CARRY OVER FACTOR==>> is given by

CARRY OVER MOMENT /  APPLIED MOMENT

MOMENT ABOUT A / MOMENT ABOUT B

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SWAY AND NON-SWAY OF STRUCTURE:

SWAY AND NON-SWAY OF STRUCTURE:

NON-SWAY==>> If structure in stable in any condition then it is non sway condition of structure...

CONDITION FOR NON-SWAY=>

For non - sway structure have same moment of inertia through all members ...loads applied is centric for all members (it may be UDL or may be point load)... Supports are at same level..

                                                                              [1ST]                                  [2ND]

1ST structure ==>> NON-SWAY

2ND structure ==>> SWAY


SWAY==>> If structure is not in stable position ..and structure tilled , then it is called sway of structure..

CONDITION FOR SWAY==>>

=> IF moment of inertia of all members are different then sway come into action ...structure tilled in that side where moment of inertia is less...

=> IF applied load is not in center than sway also come in action.. at which side load is less at that side sway will come..

=>IF supports of structure are not in same level than sway also come in structure...

=>IF all condition are applying in single structure than we consider all condition at same time...

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Wow , after reading about sway and non sway 

you are curious about knowing Bar Bending Schedule, how to calculate those steel , which we use in construction , which are used before occurring of sway and non sway , so here are the article for you 

How to calculate Quantity of steel

If you are searching some important interview questions about cement than this article will boost your  knowledge today. 

Cement : The backbone of construction

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