Week 8 Challenge

AIM OF THE EXPERIMENT: To determine the centrifugal load acting on bridge and perform analysis in Staad.Pro.

THEORY:-

Centrifugual Force:- Centrifugal force is the apparent outward force on a mass when it is rotated. Think of a ball on the end of a string that is being twirled around, or the outward motion you feel when turning a curve in a car. In an inertial frame, there is no outward acceleration since the system is not rotating.

Mathematically:-C= (W x V²) / (127 x R)

Super elevation:- Super elevation is the banking of a roadway along a horizontal curve so motorists can safely and comfortably manoeuvre the curve at reasonable speeds. A steeper super elevation rate is required as speeds increase or horizontal curves become tighter.

Data Given:-

Span of bridge = 12.0 m

Width of carriage way = 7.0 m

Live load on bridge = Class 70R tracked vehicle.

Design Speed of vehicles = 75 km/hr

Radius of curvature = 3 m

Assumption:

Size of Pier = 1.5 m Diameter

Height of Pier = 10.0 m

Size of Girder beam = 2m x 1m

Size of Cross beam = 1m x 1m

Thickness of deck slab = 0.250 m

CALCULATIONS:-

According to IRC 6 code,

Live load of 70R tracked vehicle is 70KN

So, Live load (W) = 70 KN

Radius of curvature (R) = 3 m

Design speed (V) = 75 km/hr

Centrifugal Load (C) = (W x V²) / (127 x R) = (70 x 75²) / (127 x 3) = 1033.5 KN

Procedures in Staad:-

STEP 1:-

Model the bridge as per the given questions and mesh the top slab to get appropriate designed plate values.

STEP 2:-

Assigning of Property to the members and the top deck slab

For Abutments, circular section 1.5m was taken.

For longitudinal girder section, rectangular section of 1m x 2m was taken

Rectangular section of 1m x 1m was taken for cross-girder elements.

Deck Slab of uniform thickness of 0.250m was proposed for analysis

STEP 3:-

Providing fixed supports to the bridge

STEP 4:-

Assigning of DL and Centrifugal loads to the bridge:-

Assignation of Centrifugal loads to the bridge.

Assignation of DL to the structure

STEP 5:-

Analyzing the model structure:-

STEP 6:-

Go to the post processing mode and get the required values

Maximum support reactions of the bridge for DL load case

Maximum Beam Stress values

Plate contour showing MY local