Challenge

Week 10 Challenge

NNikhil Agnihotri1 Feb 2023

Aim of The Challenge : To Model & Analyse the Bridge Section which is having span of 10.0m length for Snow Load acting on the bridge having Width of Deck Slab 18.0 m, The deck of the slab is supported by 4 T Beam Girders. Each T Girder is 1.066 m height with a top flange width of 0.8 m. The thickness of web is 0.625 m.

Introduction : As we Know Staad Pro is Designed and Maintained by Bentley Systems Software Company, Staad Pro is used for Structural Analysis and Design Purposes, As the Given Structure is a Bridge of 10m span, we have to analyse the structure for Snow Loads and briefly describe the analysis results.

Procedure :

Calculation of Snow Loads:

Design Snow Load,

S = μ x So

Where,

So - is snow load on the ground.

μ - is Shape Coefficient.

So= Span of the Bridge x Depth of snow x Density of settled snow.

As per IS 875 Part IV code Density of settled snow is 2 -3kN/m3

We taken the value of Density of settled snow is 3 kN/m3

So = 10 x 1.25 x 3

=37.5 kN/m

As per IS 875 Part IV code value of Shape Coefficient for angle B<30 degree is, u = 0.8

S = u x So

=0.8*37.5

=30 kN/m Design Snow Load.

Modeling :

1. Open Staad Pro and Create a new Project and select Metric in Unit, this will allow us to model the structure in metres as shown in the given diagram and get results in Kn.
2. Input the origin node as 0,0,0 Select the node press CTRL C+ CTRL V input 6 in Y and press ok, create beam between two nodes, again select both the nodes and perform Translational Repeat No. of steps 3, Step Spacing - 4m in Z Direction. Now Select all the 4 Beams press CTRL C+ CTRL V input 10 in X and press ok, which creates all the piers. Now Join Left and Right Piers with the beams which acts as Longitudinal Girders. Now Create Cross Girders Select the Corner node of Left piers (x-0,y-6,z-0) press CTRL C+ CTRL V input -3 in Z, again select the Corner node of Left piers (x-0,y-6,z-12) press CTRL C+ CTRL V input 3 in Z. also join the beams between the piers to create the cross girder on the left side select all the beams in the left side press CTRL C+ CTRL V input 10 in X and press ok.
3. Create a Deck Slab Select the corner node of the cross girder press CTRL C+ CTRL V input 0.5 in X press ok. Select both the nodes and press CTRL C+ CTRL V input 0.5 in Z press ok, create a plate inside the 4 nodes, now select the plate and perform Translational Repeat No. of steps 19, Step Spacing - 0.5m in X Direction, again select all the newly created plates perform Translational Repeat No. of steps 35, Step Spacing - 0.5m in Z Direction. which creates our deck slab.
4. Create Crash Barriers at the deck corners, select 2 corner nodes of the deck slab in the left and press CTRL C + CTRL V input 0.5 in Y Direction, create a plate inside these nodes. select this plate and perform Translational Repeat No. of steps 19, Step Spacing - 0.5m in X Direction, again select all the plates and perform Translational Repeat No. of steps 2, Step Spacing - 0.5m in Y Direction. Which creates our crash barrier at one corner, select all the plates in the crash barriers press CTRL C + CTRL V input 0.5 in Z Direction. After all the steps the Model will look like this.
5. Now we can have to Provide Supports in Pier Bottom Select all the bottom Nodes Click on Specification in Upper Tab Create a Fixed Support and Assign the Bottom Nodes to Fixed end Support. After all the steps the Model will look like this.

Assingning Specifications :

1. Click on Specification Tab click on Define click on Circle and input 1m dia click add. Again click on Define click on Rectangle and input YD-0.8 and ZD-0.3, Again Click on Thickness and add a plate of 0.35 m click ok, Again Click on Thickness and add a plate of 0.5 m click ok. Again Click on Define Click on Tee input the values as shown in the image below.

2. Select All the Piers Click on Select click on Parallel under Beams click on parallel to Y which selects all Piers. Assign the Specification having Circle of 1m dia. again Select All the Cross Girders Click on Select click on Parallel under Beams click on parallel to Z which selects all Cross Girders. Assign the Specification having Rectangle and input YD-0.8 and ZD-0.3. again Select All the Longitudinal Girders Click on Select click on Parallel under Beams click on parallel to X which selects all Longitudinal Girders. Assign the Specification having Prismatic Tee Specification. Also Select all the plates except the plates for crash barriers and assign the Specification having plate 0.35 m Configuration. again select all the Crash Barrier Plates and assign the Specification having plate 0.5 m Configuration. After assigning all the properties the model should look like the image provided below.

Adding Snow Load:

1. Click on Load Cases Details Click add write name Snow Load click add. Again click add click Member Load and follow the image below.

2. Click on Load Cases Details Click add write name Snow Load 2 click add. Again click add click Plate Load and select Pressure on Full Plate and follow the image below.