How To Design a Cross Girder or Floor Beams in Bridges or Railway Bridge.

Cross girder are provided in each panel, joining the corresponding lower panel points of two truss girder.

The design procedure is given by:-

Step 1:-
               Loads:-

Effective span of cross girder = 4 m (say)
The dead load as transformed as the point load at 1 m from the ends of cross girder.
Self weight of cross-girder = 3 kN/m (Assumed), it acts as uniformly distributed.
The cross girder is subjected to maximum live load when both the adjacent spans loaded.
EUDLL (Effective uniformly Distributed Live Load) for 8 m span = 1056 KN (Say)
Impact factor = 0.909 (say)
[Note: - Impact factor is calculated by using this formula = 0.15 + [8 / (6+L)]
So, Impact load is given by,
                                                      = 0.909 × 1056
                                                      = 960 KN
Live Load + Impact Load = 2016 KN
Half of live load and impact load is carried by girder as two point’s loads at 1 m from each end.
Point load due to superimposed dead load {(1/2) × dead load per track for two stringer as calculated in design of stringer}.
Point load due to live load & impact load = [(1/2) × {1/2) × 2016}]
Total point load = sum of two calculated load above in KN
Draw the loading diagram with UDL and point load at 1 m from the edges.
The reactions at the ends = Total point load + UDL span × span length KN

Step 2:-
                Bending Moment at centre:-

M = [(Reaction at each end span / 2) – Point Load × 1 – (UDL load × span) / 2]
Allowable stress in bending = 165 N/mm2.

Step 3:-
               Section Modulus:-
                                                 Z = M / Sigmacbc  ,            
                                                                 Where Sigmacbc = 165 N/mm2
From the Steel Table Select ISWB section having greater than the value of Z as we calculated.

Step 4:-
             Shear stress:-

Vn = Shear force at the end / height of section selected above/ thickness of web tw and it should be less than 100 N/mm2. Otherwise revise the section. Hence, safe.
Provide the details of the section provided.
The connection of stringer with cross girder is designed for end reaction






Comments

Post a Comment

Popular posts from this blog

Lane’s Weighted Creep Theory

Image
Bligh, in his theory, had calculated the length of the creep, by simply adding the horizontal creep length and the vertical creep length, thereby making no distinction between the two creeps. However, Lane, on the basis of his analysis carried out on about 200 dams all over the world, stipulated that the horizontal creep is less effective in reducing uplift (or in causing loss of head) than the vertical creep. He, therefore, suggested a weightage factor of 1/3 for the horizontal creep, as against 1.0 for the vertical creep. Thus in Fig–1,  the total Lane’s creep length (L l ) is given by L l = (d 1 + d 1 ) + (1/3) L 1 + (d 2 + d 2 ) + (1/3) L 2 + (d 3 + d 3 ) = (1/3) (L 1 + L 2 ) + 2(d 1 + d 2 + d 3 ) = (1/3) b + 2(d 1 + d 2 + d 3 ) To ensure safety against piping, according to this theory, the creep length Ll must no be less than C1H L , where H L is the head causing flow, and C 1 is Lane’s creep coefficient given in table –2 Table – 2: V
Read more

What is Soil in Geotechnical Engineering.

Image
Definition of Soil The word ‘soil’ is derived from the Latin word solium which, according to Webster’s dictionary, means the upper layer of the earth that may be dug or plowed; specifically, the loose surface material of earth in which the plants grow. The above definition of soil is used in the field of agronomy (The application of soil and plant sciences to land management and crop production) where the main concern is in the use of soil for raising crops. In geology, earth’s crust is assumed to consist of unconsolidated sediments, called mantle or regolith, overlying rocks. The top soil contains a large quantity of organic matter and is not suitable as a construction material or as a foundation for structure. The top soil is removed from the earth’s surface before the construction of structure. The term ‘ soil ’ in the soil engineering is defined as an unconsolidated material , composed of solid particles , produced by the disintegration of rocks . The void space
Read more

What is Mill bent in Industrial Buildings?

Image
The assembly of roof truss attached to and supported on column at both the ends is known as bent, mill bent or transverse bent . An industrial buildings consists of a series of such transverse bent supporting the roof. The distance between the two adjacent transverse bents is known as bay . The space between the column lines is usually called an aisle.
Read more