| Requires | Chapter 4 provides requirements for repairs of existing buildings. The provisions define conditions under which repairs may be made using materials and methods like those of the original construction or the extent to which repairs must comply with requirements for new buildings.
Section 405.2.1 indicates for damage less than substantial structural damage, the element elements shall be permitted to be restored to their predamage condition.
Section 405.2.3.1 indicates that an evaluation of the building shall determine whether the building, if repaired to its predamage state, would comply with the provisions of IBC for load combinations that include wind or earthquake effects.
Section 405.2.3.2 indicates if Section 405.2.3.1 is satisfied, then the damaged elements shall be permitted to be restored to their predamage condition.
|
|---|
| Code Modification or Alternate Requested | The intent of this appeal is to accept the replacement of a gravity-only shallow post footing with a vertical helical pier and concrete pile cap footing (otherwise known Helical Precon) as a Repair, rather than an Alteration, thus requiring the new foundation element to resist existing code loading to restore original gravity load-resisting function (passenger vehicle loading) rather than increasing the capability of this single element to current code-required loading (AASHTO HS-25 axle loads per Building Official Determination 96-01: Elevated Private Driveways).
*Reconsideration Text*
We are proposing to move forward with a reduced vehicle loading for the "altered foundation", using judgment to apply an equivalent to a 26-foot moving truck (AASHTO Class 6 Vehicle) as the design axle load for the replaced foundation element. Plans and calculations have been revised accordingly (attached to this appeal).
|
|---|
| Proposed Design | The portion of project scope in question relates to the replacement of an intermediate post footing at the midspan of an elevated concrete parking slab outside an existing single-family residence. The existing construction is a concrete slab on metal deck spanning between wood 4x10 joists. The wood joists span from a concrete retaining wall (plan south) across an intermediate wood beam and post line (6x10 beam and 6x6 posts), to an existing foundation wall at the exterior of the residence (plan north). One 6x6 post and associated shallow spread footing along the intermediate beam line has experienced vertical settlement and no longer provides adequate support of the elevated slab. Evaluation of the site indicates the settlement was caused by inadequate protection from water runoff, leading to localized erosion and consolidation of the soil surrounding the subject footing. The proposed solution in this area is to remove the existing shallow spread footing and install a precon helical pier in the same location to support the existing 6x6 post and associated load path above, thus providing the same function while resolving the concern of localized surface level erosion and consolidation.
|
|---|
| Reason for alternative | Permit checksheets provided by David Tarries have indicated that since the repair involves installation of a deep foundation element instead of a shallow foundation element, the new system is considered "new construction" and is thus subjected to new loading criteria, which in this case would be AASHTO HS-25 vehicle loading, regardless of the existing design or current/intended use of the existing structure.
We respectfully request that the installation of the precon helical pier in place of the existing shallow footing be classified as a repair under 2021 IEBC Chapter 4 / Section 405, and that the new pier be permitted to be designed for the existing loads, rather than current code-required loads.
Per Section 405.2.1, the minor settlement of the existing spread footing is considered to be less than substantial structural damage.
Per Section 405.2.3.1, upon inspection of the existing elevated parking slab, the intermediate post and beam line in question does not serve as part of the lateral load resisting system. Therefore, the post footing in question is considered to resist gravity loads only, and therefore restoring the foundation to its predamage condition would not impact the structure's ability to resist wind or earthquake loads.
Per Section 405.2.3.2, since Section 405.2.3.1 is satisfied, the damaged element should be permitted to be restored to its predamage condition. We consider this to mean restoring the existing gravity load resisting function intended to be resisted by the existing spread footing.
Per IEBC Chapter 4 Commentary, "In general, structural repairs are simply required to restore the structure in such a manner that will not make the building less complying (with the latest edition of the codes) than it was before the repair was undertaken."
The helical pier restores the original gravity load-resisting function without altering the load path or supporting any new or additional loads. Though the foundation system is changing from shallow to deep, it is a single isolated foundation element where the function remains identical, the structure remains unmodified, the load path remains the same, and the intended use and load-carrying capacity of the remainder of the structure remains the exact same. The existing structure was intended and is presently used for passenger vehicle loading only. The existing structure and the existing load path leading to the proposed footing replacement are not capable of withstanding AASHTO HS-25 vehicle loads; therefore, even if the isolated footing replacement were to be designed for this hypothetical increase in loads, it is unreasonable to assume or expect that these loads will actually be applied to this replaced foundation element. Furthermore, the existing isolated shallow footing could be replaced in like kind with a new isolated shallow footing of the same size, which would meet the provisions of the Existing Building Code, but would not alone resolve the erosion and settlement issue. The proposed solution to install a precon helical pier in its place will exceed the present level of safety by meeting/exceeding the current gravity load-carrying capacity/performance of the existing footing, while also resolving concerns for further localized settlement and erosion at the soil surface. All helical components are ICC code tested and approved, will be installed per manufacturer requirements, and are properly engineered to meet or exceed existing demands.
We believe this scope clearly aligns with the intent and language of the IEBC's repair provisions, and we kindly request approval to proceed on that basis. We would be happy to provide additional documentation or calculations to demonstrate the adequacy of the proposed repair if needed.
*Reconsideration Text*
We are proposing to move forward with a reduced vehicle loading for the "altered foundation", using judgment to apply an equivalent to a 26-foot moving truck (AASHTO Class 6 Vehicle) as the design axle load for the replaced foundation element. Plans and calculations have been revised accordingly (attached to this appeal).
|
|---|
