GeoStructural Response Letterwww.geostructuralengineering.com
7172 Regional St #440~Dublin, CA 94568
Email: andre.hawks@geostructuralengineering.com~Cell: 707-322-3507
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GeoStructural Engineering Inc
March 16, 2021 P. 1 of 7
FROM: Andre Hawks, PE
Principal & Founder
TO: Arnold Hom, PE
Plan Check Engineer, City of Cupertino
RE: 877/879 Miller Ave Cupertino CA Response Letter #1
Plan Check #BLD-2021-0216 & BLD2021-0314
Dear Mr. Hom:
Please find my response to the plan check comments below:
1. Specify the maximum load (in pounds/kips) allowed for each push pier. Specify the test loading
criteria for each push pier and duration used for test loading.
Response: The maximum load capacity of each FP3B bracket is 21.7 kips. The minimum
depth and pressure are specified on the plans. Once the pressure is exceeded or met, it is
held or a minimum of 10 mins and observed for creep.
2. Initial Review: Sheet S0, General Notes 2: Specify the manufacturer’s make and model number
for each device (push pier, and bracket). Specify the ICC/ ESR Report listing number for each
device.
Response: Push Pier Bracket FP3B, Pier Tube FP3T, (Bracket and Pier Tube Assembly p/n
FP3BA) UES Evaluation Report Number: 531. Please see revised Note 2 on Sheet S0.
3. Initial Review: Provide manufacturer’s listing/ cut-sheets for the Push Pier system and the
Brackets. Provide listing approval from a nationally recognized testing agency for the products
(such as an ICC/ ESR Report). Listing must allow this usage for this seismic design category.
Further comments may follow due to lack of information.
Response: Please see attached UES ER 531 Report. Grip-Tite cut sheets are on Sheet S2.
Voluntary Foundation Repair is focused on the below ground issues of settlement to
stabilize an existing concrete foundation which is the focus of the ER Report. There are no
push pier manufacturers that will have Seismic design category C or D in their ESR reports
or will provide documentation saying they allow it. They always defer this decision as
Arnold Hom
05/03/21
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
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discretion of the Engineer-of-Record per project. This project is only to address floor
settlement and is not for life safety. We are not doing any seismic improvements or touching
the existing seismic resisting system. The project site is a single- story building on a flat lot.
Grip-Tite push piers are more than adequate for supporting the loads of this building.
4. Initial Review: Sheet S3 shows brackets that have welding; welding must be done by California
Certified Welding Shop that has been State Certified for Welding Special Inspections, or the
welds shall be inspected by an approved 3 rd Party Special Inspections Agency. See comment 5
regarding welding. See comment 3 regarding listed and approved manufactured product.
Response: All factory welding to meet ER70S per AWS D1.1-2010 with Min Ult Tensile
Stress: Fu=70 ksi. The brackets are sent to the contractor already welded. There is no on-
site welding to observe.
5. Initial Review: Only a 3 rd Party Testing Agency that has been approved by the City of Cupertino
is allowed to perform these inspections. Please provide another Special Inspections Form for the
inspections of the welding. Form is to be signed by all parties and completed; form is available
on-line at cupertino.org. Although Engineer of Record will perform Drilled Pier Inspections
(which is acceptable), welding inspections must be done by a Certified Welding Inspection
Agency/ 3 rd Party Testing Agency that is approved by the City of Cupertino.
Response: See #4 above.
6. Initial Review: Sheet S2: Specify the method of backfilling soil from the exposed cut. Specify
soil parameters for backfill (e.g. specify the type of soil allowed for backfill, compaction
percentage, thickness of each lift of backfill for each compaction). Brackets are not shown to
anchor into the existing foundation and are connected via skin friction; specify mechanical
connection of brackets into the existing foundation. Per sections 1604.8.1 and 1613.1 of the 2019
CBC and ASCE 7-16 section 12.1.
Response: Please see the notes added on revised Sheet S2
7. Initial Review: Sheet S1: Specify a note stating that ‘SHORING METHODS TO BE DONE BY
CONTRACTOR
Response: Please see revised sheet S1 with the note added.
8. Please see revised Sheet S0 and the wind calcs below:
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
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Risk Category = II
Wind Velocity = 92 mph per ASCE 7-10 Figure 26.5.1A
Kd = 0.85 per ASCE 7-10 Table 26.6-1
Exposure Category = C per ASCE 7-10 26.7
Kzt = 1.00 per ASCE 7-10 26.8
G = 0.85 per ASCE 7-10 26.9
GCpi = 0.00 per ASCE 7-10 Table 26.11-1 for open buildings
Kz = 0.94 per ASCE 7-10 Table 27.3-1
qz = 0.00256 x Kz x Kzt Kd x V^2 per ASCE 7-10 27.3.2
qz = 0.00256 x 0.94 x 1.00 x 0.85 x 92^2
qz = 17.31 psf
9. Please see revised Sheet S0 and the seismic calcs below:
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
10. The push piers on this project are being installed to correct settlement and are not being installed
for life safety reasons. A soils report is not necessary because the push piers are installed until load
bearing stratum is reached and is verified by in-situ pressure readings. Every push pier installed is
akin to a soil boring and provides in-situ soil strength data at every location. The minimum pressure
on the plans is calculated based off the building weight. Piers are always driven until ¼” lift is
observed. This is usually around a gauge pressure of 3,000 psi depending on the size of the structure.
If questions arise please contact me via email at andre.hawks@geostructuralengineering.com
Best Regards,
EXP: 3-31-22