Week 8 Challenge

AIM and INTRODUCTION :

• To calculate the centrifugal load for the bridge subjected to a live load of class 70 R loading and to design a bridge for the given data and need to apply calculated centrifugal load in the bridge using staad pro.
• The centrifugal force is an outward pushing force that exerts a load on structural elements of the bridge.
• The centrifugal force which tends to move the vehicle out of the track causes a collision.
• It is given with formula C = w*v*v / 127 R
• c is point load on wheel or udl over the length of the vehicle.
• w is the live load of the vehicle class 70 R loading.
• v is the design speed of the vehicle in km/hr.
• R is the radius of curvature.
• In this challenge, we are going to apply the centrifugal load as a vehicular load using class 70R as a live load.

PROCEDURE :

The step by step procedure :

• The first step is needed to enter the coordinates for node, enter the coordinates as (0,0,0) and (0,10,0), Here the nodes are created for the pier, connect the nodes by using add beam command.

• The pier has been created for a height of 10m, next step is to form the span and carriageway for the bridge.

• Select the pier and use translational repeat command in x-direction at a spacing of 12m and steps as 1, another pier will be created to represent the span of the bridge.

• select the two piers and use translational repeat command in the z-direction, at a spacing of 7m another two piers will be created to form the width of the bridge.

• The bridge of 12m span with a carriageway width of 7m has been designed and the next step is to assign the properties for the structural members of the bridge.

• Add a circular section of dia 1m and select the piers of the bridge, click the assign to selected beam command in the property section tab.

• The next step is to assign the property for the cross beam and longitudinal beams, add a rectangular section of 1m * 0.75m, select the beams and assign the property to the beam by clicking the assign button.

• Add a node in x and z-direction by using repeat command with a spacing of 0.5m, connect the nodes and add a plate by using add plate command, copy the plates in x-direction and z-direction to form the deck slab for the bridge.
• In x-direction repeat the plate for 23 steps and in z-direction for 13 steps at spacing 0.5m each, thus the deck slab has been created.

• Add plate thickness of 0.3m for the deck slab, select all the plates of deck and assign the the property by clicking assign to selected beam.

• The plate thickness has assigned, the structural members are given with required properties, next step is to assign the support .

• click on the specification, select fixed support, after the select the bottom nodes of the pier and then click on assign to selected nodes, the fixed support will be assigned to piers.

• Next step is to give loading to the structure, click on vehicular definitions, define the load enter the calculated value and distance as 3.6m click add.

• Then click on load case details, and enter the no of loads to be generated as 15, then click add to enter the coordinates to place the load.
• enter the load increment value as 1 in x direct then click add, now we need to enter into post processing mode, so click on run analysis command, after analysis select enter in to post processing mode for the structural analysis.

RESULT :

To analyse the structural behaviour of members for the designed bridge for the applied centrifugal load.

• The bending moment along z direction is shown, click on mZ in the post processing tools tab.

• The shear force along y direction is shown, click on FY in post processing tools tab to show the shear force for applied load.

• click on plat stress in post processing tools tab, stress diagram will be shown in contour image, which gives the maximum and minimum value of mY.
• Thus the centrifugal load has calculated using formula and the calculated load is applied on bridge using staad pro.