The load path in your drawings is not the load path in your structure

A forty-year-old industrial structure has been modified. Not possibly — certainly. Crane rails have been extended, mezzanines added, columns strengthened after a load increase nobody documented, members cut through for a pipe route and never properly reinstated. Some of this appears in the drawing set. Much of it does not.

Why this matters more in demolition than in operation

A structure in service is generally forgiving of undocumented modification, because it is carrying a load it has already proven it can carry. Demolition removes that certainty. The moment you start taking members out, load redistributes through paths that were never analysed — and an undocumented modification that was harmless for thirty years becomes the governing condition in a sequence that assumed it was not there.

The failure mode is specific and it is almost always the same: a member is removed on the assumption that its load transfers to an adjacent frame, when in fact a modification has made it the primary path for something else entirely.

What a proper structural resurvey involves

Reconciling the structure against its records is not a walkthrough. It requires:

• Physical measurement of primary member sections, not reliance on schedule values
• Ultrasonic thickness testing at critical connections in any corrosive-service environment
• Identification and modelling of every modification, extension and repair found on site
• Explicit flagging of areas where records are absent, so they are engineered rather than assumed
• A revised structural model reflecting measured condition, used to generate the sequence

A case from a cement kiln programme

On a preheater tower removal in Rajasthan, the structure had been extended twice. Drawings for the second extension could not be located anywhere in the plant's records. We surveyed and modelled that section from scratch — a two-week investment against a six-month programme.

The model identified a transfer arrangement carrying load from the extension into the original frame through a route that the assumed sequence would have removed at step four. The consequence of proceeding on the assumed sequence would have been serious and it would have occurred with crews at the work front.

Two weeks of survey against six months of programme is not a cost. It is the cheapest insurance available on a demolition project.

The practical recommendation

Treat the drawing set as a starting hypothesis, not as evidence. Budget survey time explicitly rather than absorbing it into mobilisation. And where records are missing, say so in writing and engineer the gap — because the alternative is that someone quietly assumes, and assumption is what puts crews under load paths nobody analysed.