The Scope Creep on a Seismic Upgrade
You are an applied science technologist supporting a structural engineer on the seismic retrofit of a 1970s three-storey masonry building. Your assignment is to run a drift analysis using the engineer's model and report results. Midway through, you discover the model assumes a diaphragm stiffness the drawings do not support; the existing roof is flexible wood sheathing, not the rigid diaphragm entered in the model. Correcting it changes the computed drift at the second floor from 1.4% to 2.1% of storey height, exceeding the 2.0% limit in the applicable code. The engineer is on vacation for two weeks, and the permit submission is due in five days.
1. What is the technically defensible action, and what limits your authority here?
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The defensible action is to correct the model and report the resulting 2.1% drift, flagging it as exceeding the limit, and to notify the engineer of record immediately rather than waiting for his return. Your authority is bounded: you are competent to identify the modeling error and run the corrected analysis, but the engineering conclusion - whether the exceedance is acceptable, whether an alternate compliance path applies, or what redesign is needed - belongs to the licensed engineer. You should not quietly submit the uncorrected model, and you should not unilaterally redesign. Prepare the corrected results, a short memo explaining the diaphragm assumption and its effect, and options for the engineer to evaluate. Send it by the fastest channel that reaches him. The permit deadline does not license submitting a model you know to be wrong.
2. How do you handle the permit deadline and communicate the issue to the client?
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Treat the deadline as a scheduling problem, not a technical one. Contact the engineer of record first; if he is unreachable, contact his supervisor or principal. In parallel, inform the client that a modeling assumption has been found inconsistent with existing conditions and that the submission may need to be delayed or filed with a clearly disclosed qualification, depending on the engineer's direction. Do not file the uncorrected analysis. If a partial submission is possible, it should be accurate and explicitly note the open item. Document the timeline: when you found the discrepancy, who you notified, and what was decided. The client will be unhappy about a delay but far less unhappy than with a permit issued on a model that understates drift by 50%.