Mini Caisson Design-Calculations

Pile Design 1

ROBERT SIQECA, PE

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PROJECT: 920 Westchester Ave, BX, NY JOB # CHK'K: RS

ITEM: Pile design DATE:

Foundation Wall Data:

f 'c, grout strength = 5 ksi

f'c_f, footing concrete strength = 4 ksi

f 'y c steel strength casing = 60 ksi

f 'y b steel strength bar = 75 ksi

, strength reduction factor for shear = 0.75

Area grout= = 52 in2

Area bar= = 2.25 in2

(no 14. threaded bar)

Area casing= = 11.9 in2

(HSS 8.625x0.500)

Plunge length= = 5 ft

Dia casing= 8.625 in

Dia bond= = 10 in

RS

1531

1 OF6

8/2/2010

920 Westchester Ave

Pile Design 2

1. Pile Cased Length (Service Load Design)

For strain compatibility between casing and bar, use the following for steel

yield stress:

F y-steel = the minimum of Fy bar & Fy casing= 60 ksi

Tension - Allowable load

Pt -allowable = 0.55 Fy steel x ( Area bar + Area casing)= 424.5 kips

(Note: 0.55 is per AASHTO Table 10.32.1A)

Tension Allowable load :

Fa = Fy-steel/FS . . . . . FS = 2.12

P c -allowable = 0.40fc-grout Area gout + 0.47Fy-steel [Area bar + Area casing]

= 503.03 kips

(Note: 0.40 is per AASHTO 8.15.2.1.1; 0.47 is per AASHTO, i.e. 1/2.12 = 0.47)

2.Pile Uncased Length (Service Load Design)

Cased bond length (plunge length) allowable load = P transfer allowable

= 257,717 lbs

bond nominal strength = geotechnical unit grout-to-ground bond strength= 2000 kpa

= 290 psi

920 Westchester Ave

Pile Design 3

Tension - Allowable load

P t-allowable = 0.55 Fy bar x Area bar + P transfer allowable= 350.5 kips

(Note: 0.55 is per AASHTO Table 10.32.1A)

Compression - Allowable load

P c-allowable = 0.4fc-grout x Area grout + 0.47 Fy bar x Area bar + P transfer allowable=

= 441.0295 kips >> 300 kips ok

(Note: 0.40 is per AASHTO 8.15.2.1.1; 0.47 per AASHTO, i.e 1 /2.12 = 0.47)

920 Westchester Ave

Pile Design 4

3. Pile to Footing Connection

a. bond between the pile casing and the footing concrete:

bond btwn casing & footing= 1.75 Mpa= 253.8 psi

casing embedment= 6 in

P casing bond= (bond btwn casing & footing/FS)x3.14xD casing x Casing embedment

= 20,617 lbs

920 Westchester Ave

Pile Design 5

b. Check if compression load can be transferred through bearing on pile top(figure 5-8) without optional

bearing plate:

Pn, max = 323,159 lbs

Pn, max + Pcasing bond = 343,776 lbs < 300 kips

Detail in Figure 5-8 cannot work.

c.Design for bearing plate without stiffeners

Pu=300kips- P casing bond= 279.38 kips

920 Westchester Ave

Pile Design 6

109.56 in2

Use 11"x11" plate

2.05 in

fp=Pu/ 3.14*Dia casing = 10.316 ksi

tp= 0.803 in

Use 11x11x1" bearing plate

920 Westchester Ave