Sealing a Supplier's Shoring Design Under Commercial Pressure
You are a professional engineer in a consulting firm that earns about 40 percent of its fee from one industrial client. The client's logistics contractor has submitted a proprietary modular shoring system, 34 m tall, for facade work on the client's warehouse. The leg-load calculations were produced by the contractor's own engineering technician and show a maximum factored leg load of 190 kN. There is no seal and no independent check.
The firm's project manager has asked you to review and seal the package by the next morning, because the submittal deadline is fixed and the client is threatening to take the work elsewhere. You would have two hours; your firm's normal practice for a system of this height is a three-week independent check, and you have no prior experience with this proprietary system.
While skimming the calculations you notice that the leg load includes no dynamic or impact allowance for the material hoist that will run on the towers. A previous submission from the same contractor, which you saw last year, omitted a 1.15 dynamic factor on hoist loads. The PM says the contractor has done this on many sites and the client will not accept a delay.
1. Identify the professional issues and state what you would do before the deadline.
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There are four separate problems. Competence: a 34 m proprietary shoring system is outside my demonstrated experience, and the consequence of error is collapse with people underneath. Responsible charge: sealing another party's design means I become the engineer of record for it; I cannot do that without the authority, time and control to actually review and approve it, and two hours is not a review. Conflict of interest: a client representing 40 percent of fee income is threatening to leave, which is exactly when judgement is most at risk. And there is already evidence the check is inadequate, because the load case omits hoist dynamics.
Before the deadline I would decline in writing to seal the package by tomorrow. I would tell the PM why, in one short memo, so the reason is recorded rather than verbal. I would offer two constructive alternatives: the firm performs the full independent check on a stated programme, or the firm engages a recognised specialist in that proprietary system to work under the firm's responsibility with my oversight.
What I would not do is seal and hope, or seal with a covering note that limits liability. A limitation of liability does not limit the consequence to the workers on the tower.
2. If the firm does take the work, what must a proper review actually involve?
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Start with a written scope and basis of design: the configuration, the foundation and ground conditions, the tie-backs to the building, the erection and dismantling sequence, and the design standards to be applied. Then define the loads properly. That means dead and live construction loads, wind on a 34 m open structure including the shielding and the temporary condition, the material hoist loads with a dynamic or impact allowance of at least 1.15 on the hoist contribution, and any eccentricity from the hoist mast.
Then check members, bracing, connections and base plates, and the foundation bearing and uplift. Independently verify the contractor's model: boundary conditions assumed pinned versus fixed, effective lengths, the load combinations used, and whether the software's second-order effects were enabled for a structure of this slenderness.
Apply the firm's high-risk temporary works procedure: an independent check by a second engineer, a record of assumptions and of the checks performed, and a sealed calculation set signed by the engineer in responsible charge. Confirm the jurisdictional rules on sealing a design prepared by others before starting, because some boards restrict it. Retain the review notes with the calculation file.
3. What do you do about the missing dynamic factor and the earlier submission that may have been built?
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Raise the current one immediately and in writing to the contractor and the client's project manager, with the arithmetic. If the hoist contribution was omitted, applying a 1.15 factor to the relevant portion raises the maximum leg load above 190 kN, at least to the order of 218 kN if the hoist dominates the leg, which is a 15 percent under-design affecting legs, bracing, base plates and the foundation. The contractor may rebut it, but the query must be documented and answered before the system is erected.
Ask directly whether the earlier submission was constructed and, if so, whether it is still standing or in use. If it was, the owner and the contractor need to know in writing, and if a structure is carrying people under a possibly under-designed system, the authority having jurisdiction should be notified. That notification does not require the client's permission.
The commercial pressure is real but irrelevant to this decision. If the contractor or the client walks away because the concern was raised, the record should show exactly why. A professional engineer's duty is owed to the public who will stand under that shoring, not to the account, and silence now would be far more damaging to the firm than a lost deadline.