22-100822-SF-Planset- 02-24-2022 V1WOLDEN
STRUCTURAL
ENGINEERING, .Lc
Practical Structural Engineering Solutions
February 18, 2022
27T/`, 2 2
CITY OF FEDERAL WAY
('()NIMUNI rV DEELOPMEN F
Tim Wolden, PE, SE
34930 Hwy 53
Nehalem, OR 97131
(541) 915-6389 cell
(503) 368-7962 office
(503) 368-7963 fax
lip p_woldense., com
Re'. Foundation Assessment and Repair Recommendations for the Garage and Rear Comer of
the Howland Family Residence at 3822 SW 321't Street in '176dertil My, Washington
Dear Ken:
I prepared a foundation stabilization plan for the southeast corner of the two car garage at the
Howland Family residence at 3822 iSW 321'st Street in Federal Way, Washington per your
offices' recent request. The purpose of the repair plan was to provide the necessary
information needed to properly lift and stabilize the settled portion of the structure, in particular
at the southeast comer of the two-story home where the existing pad footing was pressed
roughly 2-inches in to the soil. This settlement has cracked the floor slab and east side
foundation to crack and tilt. I have determined that the settled foundation at this corner will be
able to be lifted and permanently stabilized with three (3) helical piers and foundation brackets.
The existing residence was built on this flat residential property in 1967 based on available
online information. This overall home structure is rectangular shaped measuring 60-feet wide
and 50-feet deep from north to south. The two car garage portion at the southeast corner is
roughly 20-foot square, It is my opinion that the settlement is probably due undersized footings
)ns, due to
Front or South Elevation
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View of the Rear or Northeast Garner -- Two Piers here
The pipe pier shafts will be supported for their full length against buckling. They will be installed
in gravelly soil that has no acidic conditions that would deteriorate the steel piers. I anticipate
that a hard bearing layer is probably present about 15 to 20 feet below the footings based on
this being mostly a glacially consolidated marine sediment soil.
I have calculated that the pressure used',to drive the piers should be at least 17,000 pounds of
equivalent torque capacity which is maximum at the east end of the garage header. I used a
snow loading of 25 psf at the roof, 40 psf live loading for the upper floor, and 50 psf at the
garage floor with dead loading consistent with the materials used. The piers along the east
side wall should not be spaced further than 8-feet apart. I have also shown the use of L6x6
angle to be added on top of the various foundation support bracket which increases the width of
bearing.
In conclusion, I found that the southeast corner of the garage and the northwest comer of the
two-story Howland Residence at 3822 SW 321st Street in Federal Way, Washington has
experienced up to 2-inches of settlement. Please refer to my attached repair plan for
stabilization recommendations possible with a total of five hydraulically driven helical piers with
foundation brackets placed under the footings. I have enjoyed working with you on this project.
If qU' an, additional questions, comments, or concerns please feel free to call.
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TABLE 1-FOUNDATION STRENGTH
PRODUCT
NUMBER
DESCRIPTION
PILING DIAMETER
(inch)
LLOWABLE CAPACITY
(kips)
Compression
Tension
Lateral
4021.1
Side load bracket
2 7/a
33.65"
See Table 3A
Note 6
4021,55
Side load bracket
31/2
5.12 ",5
See Table 3A
Note 6
4038.1
Side load bracket
2716
19.701,6
See Table 3A
Note 6
4039.1
Side load bracket
21/a
32.07' Sr-
See Table 3A
Note 6
4075.1
New construction
27/$
See Table 3B
See Table 3C
1.492,1
4077.1
New construction
4Y2
See Table 3B
See Table 3C
2.98425
40791
New construction
2718
See Table 3B
See Table 3C
1 A91,5
4076
New construction
31% (upset)
See Table 3B
See Table 3C
2.0321
31/2 (threaded)
See Table 38
See Table 3C
2.792,5
4093.1
Slab bracket
27/3
See Table
N/A
NIA
4550.2875.1
Tieback assembly
27/8
27.9 @ 20' angle (tension onlyfr,
27.6 @ 30' angle (tension only)5
For S1- I inch = 25.4 mm, I kip (1000 lbf) = 4.48 kN.
'Load capacity is based on full scale load tests per AC358 with an installed V-0" unbraced pile length having a maximum of one coupling per
2018, 2015, 2012 and 2009 IBC Section 1810.2.1 and 2006 IBC 1808,2.9.2. A 4-foot-long guide sleeve must be installed at the top of the shaft
as required in Figures 3, 5 and 7. Side load bracket must be concentrically loaded. Side load bracket plate must be fully engaged with bottom
of concrete foundation. Only localized limit states such as mechanical strength of steel components and concrete bearing have been
evaluated.
21-ateral load capacity is based on lateral load tests performed in firm day soil per Section 4.1.1 of this report. For any other soil condition, the
lateral capacity of the pile must be determined by a registered design professional. The bracket must be installed with minimum embedment
of 3 inches when measured from the bottom of the concrete foundation to the bottom of the bracket plate. Minimum width of footing must be
12 inches.
3The capacities listed in Table I assume the structure is sidesway braced per 2018, 2015, 2012 and 2009 IBC Section 1810.2.2 and 2006 18C
Seaton 1808.2.5.
4Tleback assemblies must be installed in accordance with Section 4.2.5 of this report. Only localized limit states such as mechanical strength
of steel components and concrete bearing have been evaluated. The tieback assembly must be installed to support a minimum 6-inch-thick
concrete wall. Two through bolts are required for connection between bracket sleeve and helical shaft. Bolts must be 3/4-inch diameter
complying with ASTM A325 and installed snug -tight with threads excluded.
5The tabulated values are based on installation with normal -weight concrete having a minimum compressive strength of 2500 psi (17.23 MPa).
sThe lateral load capacity of the side -load brackets must be designed by a registered design professional in accordance with Chapter 18 of the
IBC.
N/A = not applicable.
TABLE 2-MECHANICAL PROPERTIES AFTER CORROSION LOSS IN STEEL THICKNESS OF
2.8764NCH-, 3.64NCH-, AND 4.6-INCH-DIAMETER HELICAL SHAFTS'
MECHANICAL PROPERTIES
SHAFT DIAMETER
(inch)
2.876
3.6
4.6
Steel Yield Strength, F, (ks!)
65
65
65
Steel Ultimate Strength, F,(ksi)
80
76
76
Modulus of Elasticity, E (ksi)
29,000
29,000
29,000
Nominal Wall Thickness (inch)
0.217
0:254
0.237
Design Wall Thickness (inch)
0.1758
0.2102
0.1944
Outside Diameter (inch)
2.8490
3,4740
4.474
Inside Diameter (inch)
2.4974
3.0536
4.085
Cross Sectional Area (inch 2)
1 A8
2.16
2.61
Moment of Inertia, I (inch4)
1.32
2.88
600
Radius of Gyration, r (inch)
0.96
1.16
1.51
Section Modulus, S (inch)
0.93
1.66
2.68
Plastic Section Modulus, Z(inchl)
1.26
2.24
3.56
For SI: I inch = 26.4 mm; I ksi = 6.89 MPa, I ft-lbf =1.36 N-m; 1 lbf =445 N.
'Dimensional properties are based on powder coated steel losing 0.026-inch steel thickness as indicated in Section 3.9 of AC358 fora 50-year
service life.