Challenge

Week 9 Challenge

AAkash Singh17 Dec 2022

Aim: To determine the wave load acting on bridge and analyze accordingly in Staad.Pro.

Introduction:

The objective is to calculate wave loads from the given data manually and attempt the same in Staad.Pro for the bridge and analyse the results and effects on the structure.

The Illustrated bridge is 12.0 m long in length and width of 9.0 m having I girder beam in order to support deck slab.

Given Data (for calculation):

Span of bridge = 12.0 m

Width of carriage way = 9.0 m

Maximum crest elevation = 3.0 m

Number of Main Girders = 3

Size of I girder = (2.5 x 0.5) x (1.7 x 0.5)

Thickness of deck slab = 2.0 m

Constant r = 5

Coefficient of varying load (Cva) = 3

Storm elevation = 8.5 m

Reduction Coefficient (Cr) = 0.4

Assumption:

Size of Pier = 1.5 m Diameter

Height of Pier = 10.7 m

Size of Cross beam = 1 m x 1.5 m

Ignoring the self-weight of the bridge structure.

It is assumed that datum is provided at the base of the bridge.

Procedure:

By considering all the given data and assumed which are discussed above are rectified in the figure below showing all the necessary dimensions for further calculations.

All the loads are calculated in such a manner as mentioned below,

Maximum elevation of wave crest, η_max = 8.5 + 3 =11.5 m

Depth of Superstructure = 2 + 1.7 = 3.7 m

ΔZh = η_max – Centroid of superstructure = 11.5 – ((3.7/2)+7) = 2.65 m

ΔZv = η_max – elevation of upside of deck =11.5 – (2+1.7+7) = 0.8 m

Number of girders supporting bridge deck (N) = 3

Vertical load (Fv) = r x ΔZv x Av = 5 x 0.8 x (9 x (3.7/2)) = 66.6 KN

Horizontal load (Fh) = r x ΔZh x Ah = 5 x 2.65 x (12 x 3.7) = 588.3 KN

Maximum wave induced vertical load (Fv_max) = Cva x Fv = 3 x 66.6 = 199.8 KN

Maximum wave induced horizontal load (Fh_max) = (1+Cr x (N-1)) x Cva x Fh = (1 + 0.4 x (3-1)) x 3 x 588.3 = 3176.82 KN

Computer Proficiency:

Create a model by putting the necessary inputs as file location, units etc.

Create two nodes (x,y,z) represents as (0,0,0) & (0,10.7,0) Because the height of pier is assumed to be 10.7 m.

Go to Add Beams option and connect the both nodes. And replicate the pier at spacing of 9.0 m in z direction.

Connect the beam at the top of pier by add beams option in order to make cross beam of carriageway.

Go to Properties tab, define the size of piers, cross beam & girder beam as mentioned above and assign all the members accordingly.

Go to supports tab, and create fixed support and assign to end of peirs.

Select the whole assembly and replicate it in 12.0m in x direction and connect top of the piers in order to make the beam girder.

Assign all the missing property element as discussed above. Refer image below.

Divide the outer cross beams into two parts by the insert node tool and replicate the cross beams at spacing of 4.5m. Refer image below.

Go to create mesh, and connect corner node of the panel and create quadrilateral mesh of 0.5 m x 0.5 m.

Assign the thickness of the plate and replicate it into every panel in order to make deck slab.

Go to loading tab, define the wave load as discussed above in both vertical and horizontal direction. Refer image below.

Then Go to Analysis tab, select Analysis command and add the perform analysis command.

14. 3D rendering model view is illustrated below.

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Analytical Results:

Bridge has been analyzed and check for different load combination and different displacement for different scenarios has been record.

Maximum node displacements is recorded as 71 mm.

Maximum Base reactions are recorded axial force as 3799.43 KN and moment as 17811.377 KN-m.

Maximum shear force recorded in beam in Fy direction is 3751.667 KN.

Maximum Bending Moment recorded in beam in Mz direction is 8228.91 KN-m.

Maximum Shear Force in SQX (local) direction for deck slab is recorded as 1165.37 KN/m2.

Maximum Shear Force in SQY (local) direction for deck slab is recorded as 381.093 KN/m2.

Maximum Moment in MX (local) direction for deck slab is recorded as 725.153 KN-m/m.

Maximum Moment in MY (local) direction for deck slab is recorded as 10466.9 KN-m/m.

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Conclusion:

Different results have been found under the water current loads,