As per IS: 800, in the case of a plate girder with vertical and horizontal stiffeners, the greater and lesser unsupported clear dimension of a web panel in terms of web thickness t w should not exceed ______________ respectively.
- A180 tw and 85 tw
- B270 tw and 180 twCorrect
- C270 tw and 200 tw
- D400 tw and 250 tw
Solution
Concept
Plate Girder Web Panel Dimensions
Formula
No, this is a code-specified dimensional limit as per IS 800:2007, not a mathematical formula.
Step-by-step solution
1. Refer to IS 800:2007 specifications for web panels with both vertical and horizontal stiffeners. 2. Note that the maximum limit for the greater unsupported dimension is 270 tw and for the lesser dimension is 180 tw. 3. Select Option B (270 tw and 180 tw).
Explanation
According to Indian Standard IS 800:2007 guidelines for designing plate girders, adding both vertical and horizontal stiffeners helps prevent the thin web plate from buckling under heavy shear and bending loads. To ensure safety and structural stability, the code specifies strict maximum limits for the size of the panel formed between these stiffeners: - The greater (maximum) unsupported clear dimension of the panel must not exceed 270 tw. - The lesser (minimum) unsupported clear dimension of the panel must not exceed 180 tw Therefore, 270 tw and 180 tw correctly state the upper =allowable limits for the greater and lesser panel dimensions.
Shortcut
Remember the ratio 3:2 and the base value 90: Multiply 90 by 3 for the greater dimension (270 tw) and by 2 for the lesser dimension (180 tw).
Common mistake
A common mistake is confusing the dimensional limits for web panels stiffened with both vertical and horizontal stiffeners (270 tw and 180 tw) with those having only vertical stiffeners (180 tw and 85 tw), or reversing the order of the greater and lesser dimensions.
Correct answer: B) 270 tw and 180 tw