Soffit Repair in Continuous Drop Panel

Enable · Jul 2, 2021

Wondering what everyone's thoughts are on soffit repair in drop panels? I was recently engaged to design shoring for a repair project, not mine, where there was a bunch of soffit repair in drop panel locations. And for some reason I feel a bit uneasy about the ultimate repair (not the shoring). I suppose my unease comes from the fact that generally when we repair structures we try to restrict our cold joints into low shear areas, which is the exact opposite of drop panel locations.

I guess I am wondering if doing a soffit repair in a continuous drop is doing more harm than good? I am unsure about the ability of the repair to integrate with the parent concrete such that shear capacity is restored across the depth for a couple reasons:

A) propensity of the grout / concrete to shrink from parent concrete
B) inability to install shear dowels or other means of engaging shear friction
C) lack of bar generally at drop panel locations giving the repair even less to hang on to (this is a non seismic zone FYI)
D) just feels wrong

Below is a typical soffit repair detail for those that are not familiar. Basically you chip to the neutral axis and pressure grout from the underside. If the top is accessible sometimes you can core + use SCC. Not a huge fan of them but sometimes they are the only thing you can do.

Am I being silly on this one?

Ingenuity · Jul 2, 2021

I share your concerns about repairs in high-shear areas, and notably punching shear critical areas at drops and capitals.

I think such soffit repairs need to be 'form and pump' from soffit using SCC and with the formwork designed for the increased pumping pressure where the SCC is literally 'squeezed' into the existing prepared substrate. Slide valves to the soffit forms enable the pump pressure to be maintained when the pump pressure is dis-engaged.

You state that your application is a continuous drop panel (I am thinking wide-shallow beam equivalent with/without beam stirrups) - so repairs may be at midspan and at column locations. Depending on the total thickness of the drop + slab, are you able to add additional vertical hooked dowels (adhesive anchored), and/or add a capital at the column locations?

The following is a common 'form and pump' soffit setup when making new column caps, but does not directly address your situation:

Enable · Jul 3, 2021

Thanks ingenuity. Neat idea to add a capital which I'll keep in my back pocket for other projects where I'm the EOR. Additional L dowels would definitively be added if there is little existing bar in the repair. Though on this one I am only the shoring engineer for the contractor and have no real say in the repair program.

However, while my involvement is limited when I saw the repair extents on-site I become mildly concerned for my client. He'll be put into the fire if something bad happens afterwards. See attached picture. Circled areas are approximate extents of soffit repairs. Just seems like they are putting a lot of discontinuities into the drop where it only takes 1/2 not to work as intended for bad things to occur.

The deterioration extent is also interesting. You'd expect adjacent slab areas to exhibit more deterioration as a result of them being much thinner, but they are quite alright. Doesn't appear to be any obvious penetration or crack leading to water infiltration directly through the drop either (waterproofing all intact on the topside). I'm thinking maybe the extra drop caught a bit of snow in the winter during forming and they salted it (not uncommon for Canadian winter construction).

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Soffit Repair in Continuous Drop Panel

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