Challenge

Week 5 Challenge

SSmarak Priyaranjan13 Mar 2023

AIM OF THE EXPERIMENT:-

To determine wind load acting on the bridge and perform analysis in Staad Pro.

THEORY:-

Basic Wind Speed is based on peak gust velocity averaged over a short time interval of about 3s and corresponds to mean heights above ground level in an open terrain

Figure 1 gives basic wind speed map of India, as applicable to 10m height above mean ground level for different zones of the country

Design Wind Speed can be calculated as per IS 875:2015 (Part 3); cl 6.3

Vz = Vb x K₁ x K₂ x K₃ x K₄

where,

Vb = Basic Wind Speed

K₁ = Risk Coefficient

K₂ = Terrain, Height Factor

K₃ = Topography Factor

K₄ = Importance Factor for Cyclonic Region

DATA GIVEN:-

Height of bridge above ground level = 9m.

Location = Open terrain with well scattered obstructions of height less than 10m.

Pier size = 1.5m x 1.5m

Site = Mumbai

Size of Girder beam = I Girder

Size of Cross Beam = 1m x 1m

Thickness of deck sheet = 0.3 m = 300 mm

Since, the height of the bridge is 9m it is asumed that the overall height is 10m for determining the wind loads

Procedure:

Basic Wind Speed (V_b) = 44 m/s

K₁ = 1.0

Since location is open terrain with well scattered obstructions having heights generally between 1.5m and 10m. So, assumed Category 2 and Height Z = 10m, then K₂ = 1.0

K₃ = 1.0 [Topographical faction is less than 3^o]

K₄ = 1.3 [Refer cl 6.3.4 of IS 875:2015 (Part 3)]

Vz = K₁ x K₂ x K₃ x K₄ x V_b = 1 x 1 x 1 x 1.3 x 44 = 57.2 m/s

Pz = 0.6 x Vz² = 0.6 x (57.2)² = 3.271kn/m^2

MODELLING AND ANALYSIS IN STAAD PRO.

STEP 1:-

Model the Bridge as per dimension