Spacing rule for vertical (transverse) stiffeners in a plate girder: if d is the clear distance between flange angles (web depth), the spacing should be limited to what range?
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ANot greater than d and not less than 0.20 d
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BNot greater than 1.25 d and not less than 0.33 d
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CNot greater than 1.5 d and not less than 0.33 d
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DNot greater than 2.0 d and not less than 0.50 d
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ENot greater than 2.5 d and not less than 0.50 d
Answer
Correct Answer: Not greater than 1.5 d and not less than 0.33 d
Explanation
Introduction / Context:Transverse stiffeners subdivide the plate girder web into panels and must be spaced to control shear buckling while avoiding unnecessarily close placement that complicates fabrication.
Given Data / Assumptions:
- d = clear distance between flange angles (effective web depth).
- Standard plate girder proportions and mild steel.
Concept / Approach:A common exam rule-of-thumb limits the maximum spacing to about 1.5 d to prevent excessive panel slenderness, while a minimum spacing of roughly 0.33 d avoids crowding and allows practical connections and access.
Step-by-Step Solution:
Compute 1.5 d: set as maximum spacing between vertical stiffeners.Compute 0.33 d: set as minimum practical spacing.Detail stiffeners at or within these bounds and verify web panel shear buckling capacity.Verification / Alternative check:Check web panel aspect ratio and use shear buckling equations for confirmation; adjust spacing or web thickness accordingly.
Why Other Options Are Wrong:Smaller maxima like d may be overly restrictive; larger maxima like 2.0 d or 2.5 d risk slender panels; different minima may not reflect customary practice.
Common Pitfalls:Measuring d as overall depth rather than clear depth; omitting end/bearing stiffeners at supports; failing to align stiffeners with load application points.
Final Answer:Not greater than 1.5 d and not less than 0.33 d