Week 10 Challenge

Aim : To calculate the snow load on the bridge using following data.

Given data :

• The snow is settled snow
• Span of bridge is 10 m
• The deck of bridge is flat with β < 30°
• The depth of accumulation of snow is 1250 mm

Theory :

Generally the bridge structure is subjected to snow load, when the bridge is located in a snowy region or cold climatic countries.

• Snow load is calculated as per IS 875 part 4 and the loads are applied in accordance with IRC
• Minimum snow load is considered for design of bridges is 900 Kg/m³

Some of the snowy regions in India are Jammu and Kashmir, Himachal Pradesh, Haryana, Assam.

Calculation:

Depth of snow – 1.25m

Density of settled snow – 3 KN/m³

Flat deck β - 0°

Formula : Snow load, S­­­­­_° = density x area

= 3 x 10 x 1.25

Snow load, S­­­­­_° = 37.5 KN/m

Shape coefficient from I.S 875 part 4

For β < 30^° , µ = 0.8

Design snow load, S = µ x S­­­­­_°

= 0.8 x 37.5

Design snow load, S = 30 KN/m

Aim : To prepare the model in a STAAD Pro and perform the analysis and justify with the results.

Theory : The general steps to be create a STAAD Pro model is given below,

Step 1 : Create the nodes by using the nodes cursor.

Step 2 : Joining the nodes by using the respective beam plate cursor.

Step 3 : Supports given to the nodes whether its pinned or fixed or any other custom supports

Step 4 : specifications given to the respective beams plates

Step 5 : Assign the dead load as per calculation

Step 6 : Save the model and perform the analysis

Step 7 : The results are obtained and discuss with the results

Step 8: Take the print out of report of necessary results.

Creating the nodes by using node cursor.

Open the STAAD Pro window > Select > Node cursor > enter the value with respect to X Y Z axis > click enter

Join the nodes by using beam cursor.

Select > beam cursor > join by dragging the mouse or enter the node numbers > click enter

Deck slab are created by using nodes and plates cursor.

Supports are given to the respective nodes.

Specifications > Supports > select the supports > click enter

Defining the properties to the beam .

Specification > Prismatic > Rectangle > enter dimensions > select the beam > assign the properties to selected beams.

Defining the thickness to the plate.

Specification > plate thickness > enter dimensions > select the plates > assign the properties to selected plates.

properties are assigned.

Defining the load cases .

Loading > Load case detail > select load > Add

Add > plate load > enter the value > ok

Loads are defined.

Select the defined load > select the beam/Plate > Assign to selected beam/plate > click enter

Run analysis > go to post processing mode > Results

The reactions are generated at the end of the nodes .the reaction value is 1080 KN

• The maximum deflection in X direction is 0.004 mm
• The minimum deflection in X direction is -0.004 mm
• The maximum deflection in Y direction is 0 mm
• The minimum deflection in Y direction is -8.97 mm
• The maximum deflection in Z direction is 0.015 mm
• The minimum deflection in Z direction is -0.015 mm

• The maximum shear force in X direction is 188.805 KN
• The minimum shear force in X direction is -2.774 KN
• The maximum shear force in Y direction is 79.407 KN
• The minimum shear force in Y direction is -79.401 KN
• The maximum shear force in Z direction is 12.83 KN
• The minimum shear force in Z direction is -12.833 KN

• The maximum bending moment in X direction is15.958 KN-m
• The minimum bending moment in X direction is -15.958 KN-m
• The maximum bending moment in Y direction is 60.257 KN-m
• The minimum bending moment in Y direction is -60257 KN-m
• The maximum bending moment in Z direction is 34.091 KN-m
• The minimum bending moment in Z direction is -42.046 KN-m

• The maximum shear stress in X direction is 326.496 KN/m²
• The minimum shear stress in X direction is 363 KN/m²

• The maximum shear stress in y direction is 7.801 KN/m²
• The minimum shear stress in y direction is 1097.4 KN/m²
• Reports are taken printout which ever is necessary by using report
• In the report option we obtain the results of section forces, displacement, reactions, plate
• The exact report is to be taken further move to design