Limit on clear web panel dimension without stiffeners For a web of thickness t, the greater clear dimension should not exceed:

Introduction:
Thin webs in plate girders and built-up members are susceptible to shear buckling. Codes therefore limit the clear panel size between stiffeners in terms of web thickness to ensure adequate stability under shear and combined stresses.

Given Data / Assumptions:

• Unstiffened web panel of thickness t.
• We are selecting the upper limit on the greater clear dimension.
• Elastic buckling considerations govern the limit.

Concept / Approach:
Critical shear buckling stress is inversely proportional to the square of panel aspect ratio and directly to plate thickness. To prevent premature buckling, the greater clear dimension a is restricted to a ≤ 180 t (typical conservative limit), unless intermediate stiffeners are provided or the web is thicker.

Step-by-Step Solution:
1) Identify web as a thin plate subject to shear.2) Apply code-based dimensional limit for panel size.3) Choose a(max) = 180 t to satisfy stability without stiffeners.4) If a larger spacing is needed, provide intermediate stiffeners or use a thicker web.

Verification / Alternative check:
Shear buckling checks or tension-field action design may permit larger panels with stiffeners; without them, 180 t provides a safe bound.

Why Other Options Are Wrong:
200 t, 240 t, 270 t relax the limit and can be unsafe for slender webs without additional stiffening.

Common Pitfalls:
Measuring overall rather than clear distance; ignoring cut-outs and openings that further reduce stability.

Final Answer:
180 t