Riveted joints – definition of joint strength: The strength of a riveted joint (per pitch length) is defined as which of the following?
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APull required to tear the plate across one pitch (P_t)
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BPull required to shear the rivet(s) across one pitch (P_s)
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CPull required to crush the rivet(s) or plate bearing across one pitch (P_c)
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DMinimum of P_t, P_s, or P_c
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ESum of P_t, P_s, and P_c
Answer
Correct Answer: Minimum of P_t, P_s, or P_c
Explanation
Introduction / Context:Designing riveted (and bolted) joints requires identifying the weakest failure mode. Each pitch length of a joint can fail by plate tearing, rivet shear, or bearing (crushing). The safe joint capacity equals the lowest resistance among these competing modes.
Given Data / Assumptions:
- P_t = resistance against plate tearing across the net section per pitch.
- P_s = total shear resistance of all rivets in that pitch length.
- P_c = total bearing (crushing) resistance of rivets and plate in that pitch.
- Load is axial and uniformly distributed over the considered pitch.
Concept / Approach:Structural capacity is governed by the first mode to reach its limit. Therefore, the joint strength equals the minimum of the three resistances. This definition aligns with limit-state design and classical working-stress design philosophies where the weakest link dictates overall strength.
Step-by-Step Solution:
Compute P_t from net plate area: P_t = sigma_t_allow * (p − d) * t (for single row, representative form).Compute P_s from rivet shear capacity: P_s = tau_allow * (number of shear planes) * (pi * d^2 / 4).Compute P_c from bearing capacity: P_c = sigma_b_allow * d * t * (number of rivets).Joint strength = min(P_t, P_s, P_c).Verification / Alternative check:Inspection of failed joints typically shows a clear governing mode (net-section fracture, sheared shanks, or bearing deformation), confirming that the minimum resistance controls.
Why Other Options Are Wrong:
- Any single mode (P_t, P_s, or P_c) may overestimate capacity if another mode is weaker.
- Summing the capacities is non-physical; failure occurs by one mechanism, not all simultaneously in a load-sharing manner.
Common Pitfalls:Ignoring staggered (diagonal) tearing paths, multi-row effects, or double shear where applicable; always evaluate all relevant modes for the given joint configuration.
Final Answer:Minimum of P_t, P_s, or P_c