Page 277 - Forensic Structural Engineering Handbook

DESIGN ERRORS, CONSTRUCTION DEFECTS, AND PROJECT MISCOMMUNICATION 8.17

The RFI process is a critical ingredient in the construction communication chain and it
should be encouraged if undertaken for its intended purpose. Unfortunately, the RFI
process is sometimes abused, and used for reasons it was not intended for. The RFIs are
increasingly tied to compensation issues, by owners contractually penalizing designers for
projects that generate RFIs beyond a threshold they deem reasonable; by contractors tying the
number of RFIs generated to substantiating claims of incomplete design documents; by
designers relying on the RFI process to supplement design information that should have been
part of the contract documents. The RFI process is also increasingly becoming less formal and
less coordinated for the sake of expediency. The practicality and expediency of email encour-
ages communication between individuals, sometimes to the point of side-stepping the formal
RFI process and thus by-passing the institutional controls and coordination functions of either
the contractor or the design team. These pressures threaten to subvert the intended purpose of
the RFI process, whether by discouraging communication on one side, or increasing spurious
RFIs on the other, or by bypassing the formal coordination and tracking function.
However, irrespective of these pressures, any uncertainty or doubt the contractor might
have concerning the design intent should be resolved through the RFI process. Questions
need to be voiced, and the temptation to just generate shop drawings based on guesses must
be resisted.
The single most critical failure point where the RFI process proves its life-saving value
is when a contractor encounters field conditions that make a design detail difficult or
impossible to construct. In a recent fatal reinforced concrete building collapse, which
involved an eccentric girder framing into a column, the contractor found it difficult to
engage the girder rebars through the column steel, which he had “necked” within the slab
to splice, so he placed all of the girder steel outside the column reinforcing cage. Slab steel
had also been deemed difficult to place within this congested area and was thus stopped
before engaging the column. Had the concrete contractor used the RFI process to inform
the structural engineer of the condition encountered, this construction collapse would have
certainly been averted.

Engineer Design Changes and Contractor Substitutions

It is critically important that design changes during construction, irrespective of their
source, be communicated clearly as such. Changes in design need to trigger the appropri-
ate structural review not only for “narrow” equivalence to the original design, but also for
effect on the overall structural scheme and for unintended consequences.
Situations that are particularly prone to problems are instances where a pre-engineered,
prefabricated system is proposed to substitute for a cast-in-place design. Pre-engineered
systems come with their own design assumptions and practical connection limitations.
These assumptions might conflict with the load path assumptions underlying the original
system. Care should be taken to re-analyze the structural system based on the proposed
changes and check for changes in load distribution, load path, moment transfers, eccen-
tricities, etc. Prefabricated systems often rely on bearing connections and do not provide
redundancy through continuity redistribution, making them particularly vulnerable to unin-
tended loads or load paths. Even though a contractor substitution requires the contractor’s
representation of equivalence and, if appropriate, his engineer’s seal to certify that the
structural equivalence had been established with the appropriate calculations, it is still
imperative that the structural assumptions and calculations be clearly and completely com-
municated to the Engineer of Record for review. We are aware of a number of instances
where the manufacturers of pre-engineered systems, invoking patents, refused to disclose
the detailed design and calculations of their systems, effectively rendering a complete
review by the Engineer of Record impossible.