Week 11 Challenge

Aim of The Challenge : To Model & Analyse the Bridge Section which is having span of 9.0m length for Temperature Load acting on the bridge having Width of Deck Slab 7.0 m, The deck of the slab is supported by 3 Box Girders having size 1500x1500mm web thickness 300mm. These Girders Lie on the top of Pier Cap having Width 6m and a Circular Pier having Diameter 2.5m.

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 9m span, we have to analyse the structure for Temperature Loads and briefly describe the analysis results.

Procedure :

Calculation of Temperature Loads:

Max temperature in the location as per IRC 6 Isotherm at the location=47.5°

Min temperature in the location as per IRC 6 Isotherm at the location=-2.5°

Effective Temperature Difference=(47.5-(-2.5)/2)+10

Effective Temperature Difference=35°

Stess due to temperature =α *ΔT*E

α = 11.27 x 10^-6

ΔT = 35°

E = 5000 x sqrt(40)

=11.27x 10^-6 x 35 x 5000 x sqrt(40)

Stess due to temperature =12.47KN/m^2.

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 10 in Y and press ok, create beam between two nodes, again select the top center node and press CTRL C+ CTRL V input 2.45 in Z and press ok, again select the top center node and press CTRL C+ CTRL V input -2.45 in Z and press ok, this will create us nodes for our Longitudinal Box Girders, again select the top center node and press CTRL C+ CTRL V input 3 in Z and press ok, again select the top center node and press CTRL C+ CTRL V input -3 in Z and press ok, this will create a node for our pier cap join these nodes to create a pier cap, perform Translational Repeat No. of steps 1, Step Spacing 9m in X Direction also click link steps and after that delete the bottom node of the pier bottom. The Model Should Look Like the Image Below.

• 3. Now Create a Deck Slab Select the corner node of the Pier Cap press CTRL C+ CTRL V input -0.5 in Z press ok. Select both the nodes and press CTRL C+ CTRL V input 0.5 in X press ok, create a plate inside the 4 nodes, now select the plate and perform Translational Repeat No. of steps 17, Step Spacing 0.5m in X Direction, again select all the newly created plates perform Translational Repeat No. of steps 13, Step Spacing 0.5 m in Z Direction. which creates our deck slab of 7m wide and 9m long.
• 4. Now we 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 :

Creating Groups :

• 1. Click on Utilities and Click on Groups, again click on Create enter name as BOXGIRDERS and type Beam new group has been created, click on select click on Parallel under Beams click on parallel to X which selects all Longitudinal Box Girders Click on associate to selected Geometry. again click on Create enter name as PIERCAP and type Beam new group has been created, click on select click on Parallel under Beams click on parallel to Z which selects both the Pier Caps Click on associate to selected Geometry. again click on Create enter name as CIRCULARPIERS and type Beam new group has been created, click on select click on Parallel under Beams click on parallel to Y which selects Both the Piers Click on associate to selected Geometry. again click on Create enter name as DECKSLAB and type Plate new group has been created, Select all the plates Click on associate to selected Geometry. Hence all the Groups has been Created it is lot easier for us to assign specifications for certain objects.

• Click on Specification Tab click on Define click on Tappered Tube, under type of section select Square and assign these properties mentioned in the image below to create a box girder of 1500x1500mm size having web thickness 300mm.

• Click on Specification Tab click on Define click on Circle and input 2.5 m dia click add this will create specification for Piers. Again click on Define click on Rectangle and input YD-1.1 and ZD-2.1 this will create specification for Pier Cap, Again Click on Thickness and add a plate of 0.55 m click ok this will create specification for Deck Slab.
• Assign different Specifications with the help of groups and the model will look like this.

Adding Temperature Load:

• 1. Click on Load Cases Details Click add write name Temperature Load click add again click add select Temperature Loads and give the values of Temperature Change along Axial Elongation =30 and Temperature Differential from Top to Bottom=41.9. and Add.

Analysis & Results :

• 1. Click on analysis and design click on define commands click add which adds a command for perform analysis, press run analysis, again go to post processing

In Results Tab Displacement Pattern show in the image below

In Results Bending Moments shown in the image below

In Results Shear Stresses are shown in the image below

In Results Plate Stresses in MX Local are shown in the image below

In Results Plate Stresses in MY Local are shown in the image below