Diaphragm Connection Plates.
When diaphragm connection plates are incorrectly fit in a location other than shown on the design plans or approved shop drawings by more than 6” (150mm), an acceptable solution would be to leave the plate in place, fill any holes with bolts, and add a new connection plate at the proper location, depending on an analysis of the situation and the ability to access the location for additional fabrication and with the owners approval. When diaphragm connection plates are incorrectly fit by a small amount, the as fabricated condition may be acceptable upon review by the owner. The diaphragm will not be perpendicular to the girder and may or may not fit without modification. Care should be taken not to buckle or create a situation where buckling in the diaphragm may occur. In any case, the gusset plate should always be in full contact with the connection plate at the bolt locations.
If a diaphragm is to be attached to a bearing stiffener, checks should be made to verify fit between the diaphragm and the non-conforming bearing stiffener.
When holes are mis-located in a diaphragm connection plate, a bearing stiffener, or an intermediate stiffener where a diaphragm will be attached, several options exist:
1) If the stiffener has not been fit to the girder, the option to re-fabricate the piece exists.
2) New gusset plates may be fabricated to match holes already drilled if fit or not fit.
3) New diaphragm to match the plates the diaphragm will be connecting to.
4) Ability to provide positive connection to the tension flange for the connection plate or stiffener if required.
For any of the above conditions, the fabricator should carefully explore all options and weigh those options for cost, design requirements and time to repair and should be able to justify their proposal to the owner/engineer. In any case, a custom diaphragm is fabricated to fit in this location, the shop drawings should be revised and submitted reflecting the “As Fabricated” condition to the owner and the contractor.
As the level of complexity of the structure rises, the required solutions for mis-located stiffeners or connection plates become more difficult. The QC/QA inspectors must contact the owner/design engineer to request a design analysis in the following situations:
1) Diaphragm connection plates that also act as intermediate web stiffeners.
2) Curved structures where the diaphragms must line up to resist the horizontal forces due to curvature.
3) Any situation involving earthquake loads carried by diaphragms or cross frames, or any situation where eccentric loading may cause the diaphragm to buckle.