cn-2011-00466.tif Wickstrom, PE, MBA, and Associates
11056 South Street
BLAIR, NE 68008 -6106
HOME OFFICE PHONE (402) 426 -5467
wickfaa_huntel.net
October 18, 2011
To Whom It May Concern:
Vulcan Industries, Inc.
212 S. Kirlin Street
Missouri Valley, IA 51555
To Whom It May Concern:
The attached calculations for Blair, NE are calculated using wind and seismic calculations per
ASCE 7 -05 as shown in the accompanying drawings. The caisson design is designed per the
reference documents listed at the end of the caisson design report. Embed the windmill column
bottoms a minimum of 18 inches into the concrete caissons. Cargill will verify the 8' windmill
footprint prior to construction. Wickstrom, PE, MBA, and associates Is not responsible for the
windmill steel structure, or any alterations made to It.
SECTIONS FOLLOWING:
A This cover page
B Sketches and hand calculations demonstrating the design factors
C Caisson design with calculations with design calculations
D Spreadsheet Calculations: ASCE -7 Seismic
E Soils report furnished by Cargill
Sincerely,
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President
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R L Sogge PE
Consulting Civil Engineer STRUCTURAL CALCULATIONS
5343 N Via Alcalde
Tucson AZ 85718
ph: (520) 299 - 9336
RLSogge @gmail.com
Project No: 11 -14 Sheet # 1 of 17
PROJECT:
Windmill Foundation
Civil /Structural Engr: Lawrence L'Wick' Wickstrom PE MBA & Associates
11056 South St, Blair NE 68008 (402) 426 -5467 wick @huntel.net
Geotechnical Engr: Olsson Associates, 8720 114th St #107, La Vista NE (402)827 -7220
Approving Agency:
FEATURE: Windmill Pier Foundation System Analysis
Configuration units = ft
# Piers Spacing oc
4 8.0
Foundation consisting of Drilled Shafts placed beneath the 4 tower legs
No Pier Cap (Grade beam at ground) ties the 4 piers together
ITEM: Pier Foundation Structural Analysis Calcs using Service Load Design
(1) Vertical Load Capacity based on soil bearing capacity
(2) Lateral Load Capacity and moment development due to lateral loads
Service Loads
Force Wind Wind Seismic Seismic DL = 0.5 k/pier
Direction ten or comp Horz ten or comp Ho rz LL = 1.0 k/pier
Magnitude 9.841 2,573 1.47 0.28 No applied moment
SOURCE OF DATA:
Wick Wickstrom Windmill load caics email 13 Oct 2011
Wick Wickstrom Windmill dwg email 11 Oct 2011
REFERENCES:
See Calc Sheet #: 17
Calculations by: R L Sogge PE Stamp:
Date: 10/17/2011
pp
�
L
' % jib
Expires June 30, 2013
R L Sogge PE
Consulting Civil Engineer STRUCTURAL CALCULATIONS
5343 N Via Alcalde
Tucson AZ 85718
ph: (520) 299 -9336
RLSogge @gmail.com
Project No: 11 -14 Sheet # 1 of 17
PROJECT:
Windmill Foundation
Civil /Structural Engr: Lawrence L'Wick' Wickstrom PE MBA & Associates
11056 South St, Blair NE 68008 (402) 426 -5467 wick @huntel.net
Geotechnical Engr: Olsson Associates, 8720 114th St #107, La Vista NE (402)827 -7220
Approving Agency:
FEATURE: Windmill Pier Foundation System Analysis
Configuration units = ft
# Piers Spacing oc
4 8.0
Foundation consisting of Drilled Shafts placed beneath the 4 tower legs
No Pier Cap (Grade beam at ground) ties the 4 piers together
ITEM: Pier Foundation Structural Analysis Calcs using Service Load Design
(1) Vertical Load Capacity based on soil bearing capacity
(2) Lateral Load Capacity and moment development due to lateral loads
Service Loads
Force Wind Wind Seismic Seismic DL = 0.5 k/pier
Direction ten or comp Harz ten or comp Horz LL = 1.0 k/pier
Magnitude 9.841 2.573 1.47 0.28 No applied moment
SOURCE OF DATA:
Wick Wickstrom Windmill load calcs email 13 Oct 2011
Wick Wickstrom Windmill dwg email 11 Oct 2011
REFERENCES:
See Calc Sheet #: 17
Calculations by: R L Sogge PE Stamp:
Date: 1011712011
Expires June 30, 2013
R L Sogge PE Project No. 11 -14 Sheet # 2
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/1712011
TABLE OF CONTENTS Sheet
Basis for Design 3
Structural Configuration 3
Loads 6
Structure Strength Properties 7
Concrete & Steel Reinf Material Strength 7
Reinforcing Steel Geometry Properties 7
Concrete Geometrical Strength 9
Soil Strength Properties 11
Vertical Pier Bearing Capacity 12
Design Criteria 12
Allowable Capacity and Deflection 12
Lateral Pier Capacity 13
Design Criteria 13
Finite Element Analysis 13
Subgrade Reaction 14
Analysis Results 14
Allowable Deflections 15
Construction Sequence & Notes 15
Conclusions 16
References 17
FIGURES
Fig 1 Windmill Pier Foundation
Fig 2 Pier Foundations - Plan View
Fig 3 Pier Foundation - Cross - Section A
Fig 4 Pier Foundation - Elevation
Placed at end of report
WSD Moment Capacities of beam -col (P -M Interaction Diagram) Program PMEIX
Fig 5 Pier - 1.5 ft dia
Vertical Bearing Capacity of Drilled Pier Foundations Program Pier- BrgCap5
Fig 6 Pier - 1.5 ft dia
Lateral Loading - Mom, Disp, Soil Pres Program LLP
Fig 7 Pier - 1.5 ft dia
R L Sogge PE Project No. 11 -14 Sheet # 3
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Camp. by: R L Sogge PE 10!17/2011
Basis for Design
Criteria: Service Load Design
Design Spec:
AASHTO (2010), AASHTO LRFD Bridge Design Specifications, 5th Edition
AASHTO (2002), Standard Specifications for Highway Bridges (Service Loads), 17th Edition, 1028 pp_
Chapter Topic Sections
2 General Design and Location Features 2.5.2.6
3 Loads and Load Factors 3.1 - 3.6, 3.10
4 Structural Analysis and Evaluation 4.1-4.6
5 Concrete Structures 5.1 - 5.8, 5.10 - 5.14
10 Foundations 10.1-10.6
11 Abutrnents, Piers and Walls 11.1 - 11.6
12 Buried Structures and Tunnel Liners 12.1 - 12.6, 12.11
Definitions: Pier Shaft Caisson Pile names shall be considered the same
Structural Configuration
Proposed Structural System & Foundation Support:
Ref: Wick Wickstrom Windmill dwg email 11 Oct 2011
• 1 Caisson to support each of the four tower legs
• Tower legs are 8 ft apart
• No grade beam or pier cap to tie caissons together
Piers # dia (ft) pacing oc(ft)
4 1.5 8
0.125
Shaft Configuration Depth below Ht above Total Shaft
Dia (L) A, (L) 1 1 ,(0) Grade (ft) -- Ftg Bot (ft) Length (ft)
in 18 254 5,153 14
ft 1.5 1.8 0.2
To be Determined:
(1) Vertical Load Capacity of caisson with depth
(2) Lateral Load - moment development due to lateral loads
R L Sogge PE Project No. 11 -14 Sheet # 4
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/17/2011
No Pier Cap or grade beam between top of piers
circular Piers below ground elevation
0
Transverse
Spacing = 8
F—
Spacing= 8
0
Fig 2 - Pier Foundations - Plan View
Tap of Pier at Ground Surf'
cA
Spacing oc
8.0
Fig 1 - Windmill Pier Foundation
R L Sogge PE Project No. 11 -14 Sheet # 5
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by_ R L Sogge PE 10/17/2011
8 -#4 * bars evenly distributed
O O
3" cl I O
O # 4 tie bars at 8" o.c.
O lap tie bars min 20" or hook end
1.5 —►�
Fig 3 - Pier Foundation - Cross - Section A
P
1
V El top at existing Grade
No Pier Cap
Pier
Shaft
Caisson
Pile
Mat[ y (pcf) (deg) c (ksf) k (kcf)
Clay 0.098 26 1 200
Sec A
dia
1.5
Fig 4 - Pier Foundation - Elevation
R L Sogge PE Project No. 11 -14 Sheet # 6
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/17/2011
Loads
The following are the load cases that need to be evaluated for the drilled shafts supporting the structure:
DL /pier = 0.5 k
LUpier = 1.5 k
Load Case P (down) P (uplift) V Mtrans
( kips) (kips) (kips) k -ft
Wind 9.841 9.841 2.573 0
Seismic 1.47 1.47 0.28 0
• For each of these cases, the loadings are SERVICE LOADS (unfactored loads) applied to the
drilled shaft at the top of the shaft (bottom of pier cap).
• For the loading cases, "P" is the axial load on the shaft, "V" is the horizontal shear force
in the shaft, and "M" is the bending moment all loads being applied at the mudline.
• El of Ld Application is at ground level
• The maximum of each of these loads do not occur simultaneously
• All loads were computed by Wick wiskstrom PE using ASCE 7 -05
Ref: Wick Wickstrorn Windmill load calcs email 13 Oct 2011
R L Sogge PE Project No. 11 -14 Sheet# 7
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sagge PE 10/17/2011
Structure Strength Properties
Concrete & Steel Reinf Material Strenath
Material Properties - Pier
Type Concrete Reinf* AASHTO
Strength, f,, f (ksi) 3 60 (12.4.2.6)`
Unit Wt (kcf) 0.150 0.490
E. 57,600 "sgrt(f',,), E� =E Es (ksi) 3,155 29,000 (5.4.2.4)
Ec =57,600 *sgrt(f'c) (ksf) 1 454,303 1 4,176,000
Steel rebar shall conform to AASHTO M 31 (ASTM A615), Grade 60 (12.4.2.6)
Reinforcinq Steel Geometry Properties
Balanced Design Reinf Steel (for rectangular beam with tension steel only)
p = 0.85 * B, * f,.' / f * 871(87 +f = 2.14% for tension reinf steel
% of Pb p Wt (Ib /cy) defining p = As /Ag
25% 0.53% 71
50% 1.07% 141
75% 1.60% 212
100% 2.14% 283
Jointing No construction joints within the total pier length are allowed.
Lap Splice Length = Development Length
Do not terminate > 50°% of reinforcing at critical sections (where stress is max) (5.11.1.2.1)
Deformed Bar in Tension
Id (in.) = MAX (1.25 A f I sgrt(f c), 0.4 d f (5.11.2.1.1)
Modification Factors Class C 1.7 used (5.11.5.3.1)
Mod Factor= 0.8 not used (5.11.2.1.3)
Bar # 4 5 6 7 8 9
splice L (in) 20 26 33 44 58 73
x bar dia 41 41 43 51 58 65 min 40 d
#9 - #11 bar dia > bar dia /8
Reinf Steel Cover Area I Area inside effective area, bd, simulated by
Cast against Earth Gross (in 2 ) Gross (in °) Rebar (in) area within outer rebar perimeter
Side (in) 3 254 5153 113 (5.12.3)
Bottom (in) 6
Clear Spc input for >#8
No of Bars Size ( #) at lap (in) A (in) p =A Wt (lb /cy)
longitudinal: 8 4 4.0 1.57 0.62% 81.7 82
okif>6"
transverse - tie rebar 4 8 1 0.59 3.27% 433.0 433.0
514.6
R L Sogge PE Project No. 11 -14 Sheet# 8
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/17/2011
Min Reinforcing Requirements
A. (in'/ft) I p = A /(bd)
• Shr & Tmp: Reinf for surfaces exposed to daily temperature changes - buried structure no AT
As, As' (0.11 / fy) A = 1 0.47 0.18% (12.11.4.3.1 & 5.10.8)
0.0018 A OK
in both transverse & longitudinal directions if thk > 6 in. distribute steel in both face (5.10.8.2)
• Crack Ctrl: Reinf when designed using strut & tie models (Art 5.6.3) - N/A
As > .0.003 A 1 0.76 0.30% 1 controls (5.6.3.6)
in each direction 12" max spacing of orthogonal grid OK
• Min Flexure: As > 0.03 f'c / fy A = 1 0.38 0.15% (5.7.3.3.2)
long direction 0.0015 A 0.38 < As tension OK
Ref: ACI (1999), Building Code Requirements for Structural Concrete and Commentary, ACI 318 -99
ACI specifie.c P = 1.0% of A = 1 2.5 1 1.0% (ACI 10.9)
value can be reduced up to 50 %, if cross - section is larger than reqd for loading
A used = 1.57 in2
R L Sogge PE Project No. 11 -14 Sheet # 9
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by_ R L Sogge PE 10/17/2011
Concrete Geometrical Strength AASHTO
Resistance Factors for strength limit state (5.5.4.2.1)
Flexure & Tension 0.90 Mdesign = * M, wmkba , _ M
Shear & Torsion 0.85 VdesFan = * vnominal
Axial Compression 0.75
Bearing on Concrete 0.70
Shear WSD Allowable Capacity - single shear v de$iy „ ( psi) IShear A(in fides (k)
1.5 lit dia vdeslgn = 1.1 Sgrt(f,) (psi) = 60 113 1 6 (5.8.3.3)
Moment
Bending Stiffness and Moment Capacity of the reinforced beam - column components are derived for the
various sections using the following programs to develop aP -M Interaction Diagram:
PCAcol (1992) - The nominal (ultimate) load capacities used for strength design analysis
are when the component materials reach their ultimate strength
(%= f y , e s > s y , max extreme concrete compression fiber strain,s, = 0.003) (5.7.2)
PCAcol gives essentially the same strength results as from program PMEIX (Reese, 1984)
PMEIX can be used to develop WSD allowable capacities for the sections
• The results of the WSD analyses by program PMEIX are presented in Fig 5
Section Bending Stiffness, El
• El decreases as the section is deformed and moment is developed to the strength limit state
• Modulus values approach E SeC , and effective moment of inertias approach 111,ked, as
the moment capacity reaches its ultimate limit design capacity, Mdeaign = + MP,
• Design sectional properties selected at point where the Ultimate Load Capacity for the section
under load occurs, i.e. bending stiffness represented by El (+ = Mf(EI)) using a linearly elastic
secant modulus value, E and an effective moment of inertia, l e , defined for the section when
the section reach their ultimate load capacities
E - modulus of elasticity
• A nonlinearity in the concrete stress- strain relation, Ec exists
For strength analysis a secant E = 1.0 x Einital is used
R L Sogge PE Project No. 11 -14 Sheet # 10
Consufting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge@gmail.com Ilem: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/17/2011
1- moment of inertia
Cracking of concrete below the neutral axis causes a reduction in the moment of inertia,
At the limit state the section is cracked and the effective moment of inertia of the section = Icracked
• For the circular section the cracked moment of inertia at service loads is determined using
program PMEIX (Reese, 1984) where
Design section flexural rigidity properties, Ell, are determined from the relation El = M1�
Ell decreases as the section is deformed (0 is incremented and moment is developed)
Flexible sections, ones with lower I, have lower moment capacities and transfer load to the soil material
For determining the Euler buckling load P the LRFD spec (and ACI) permit EJ, 12.5 (5.7.4.3 -2)
using 1.0 E, and I.M.0 => 1.00 is used for service loads
• No uncracked section properties used
Cracked Section Properties Allowable Service Load Design Capacity (WSD)
Eencked I. d P M f, < 0.4 f, f = 0.4 f
(ksi ) (in k (k -ft) (ksi (ksi)
3,155 5,153 -9.841 9.5 0.65 24
Program PMEIX output attached provides the Service Load Design Moments + cracked section moduli
Cracked Section Properties Strength Design Capacity (USD)
(El)a.:ed /(EI) Eaec le P Mdes fc fy
ksi
(in 4 ) k ) (k - ft) __� Iksi ksi
3,155 5,153 60
R L Sogge PE Project No. 11 -14 Sheet # 11
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/1712011
Soil Strength Properties
• Design based on values of soil parameters from field & lab testing.
Ref: Olsson Associates, Rpt of Geotechnical Exploration, Cargill Office Building Blair NE, 5/5109, 4009 -0570
Material Properties - Soil Ref page
Summary Borings #1 -9
Depth (ft)
Material )
N -value (SPT) 15
Groundwater Depth (ft) > 6D Not Encountered
E (kcf) 0.098
Friction Angle, � (deg) 26 page 22
Cohesion, c (ksf) 1 page 24
q„ (ksf) 4 page 5
w ( %) 17
S(%) 65
LL ( %) 36
PI (%) 22
Constant of horz subgrade reaction
k, (kcf) 200
Shape exponent, n 0.25
Allowable Lateral Soil Pressure
Sand = 1.5 K depth(ksf) 1 0.7
Clay = 2.5 q„ = 5 coh (ksJ 5
Sand - pier bottom submel 1.9
Lateral Soil Pressure
k = tan (45 - *12) 0.39
Active - k. -( (pcf) 38 pages 20 -22
At -Rest = K y (pct) 55
Passive = K y (pcf) 196
R L Sogge PE Project No. 11 -14 Sheet # 12
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10117/2011
Vertical Pier Bearing Capacity
Design Criteria
• Shaft diameter = 1.5 ft
• Maximum end bearing pressure may not exceed 20 ksf
• A buoyant unit weight is used below the depth even though groundwater was not encountered in the field
investigation
Bearing Capacities are determined from the following equation (Reese & O'Neil, 1988)
such that deflections which occur due to end bearing stresses and skin friction shears are compatible.
Q.11. = ( Qp 13 + Q 9 ) / 1.5
where:
Q p = ultimate pier capacity in end bearing
Q = ultimate pier capacity in skin friction
1.5 = overall factor of safety
The factor 3 is used to lower the end bearing stresses to the point where
deflections equal to those resulting due to skin friction stresses occur.
The ultimate end bearing capacities, q„ lt , are computed using Terzaghi's bearing capacity equation
with coefficients for deep foundations developed by Meyerhoff (Lambe & Whitman, 1969, p 501):
q cN. +ADN +AB /2 N
Allowable Capacity and Deflection
• Plots of the allowable (unfactored) vertical pier and uplift load capacity (kips) versus embedment depth
of the pier for the 1.5 ft dia shaft is presented in Figs 6.
• Total settlement under the pier design loads is approximately equal to 1 % of the pier diameter
Pier D (ft) lVertical Settlement (in)
1.5 0.18
R L Sogge PE Project No. 11 -14 Sheet# 13
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 1 011 7/201 1
Lateral Pier Capacity
Design Criteria
• A Service Load Design using unfactored loads is used to determine
• Computer Program LLP (Sogge, 1992) performs a 2 -d Finite Element Soil- Structure Interaction Analysis
to analyze a circular concrete pier of a given dia, length, and steel reinforcement,
for the moments, deflections and soil pressures associated with the reinforced concrete piers.
• The program idealizes the pier as beam finite elements and the supporting soil as
independent spring elements whose strength is represented
by a coefficient of horizontal subgrade reaction, k (Sogge, 1981).
• The section's moment capacity is compared to this developed moment.
Finite Element Analysis
Model
• 2 -d plane - strain finite element soil - structure interaction model of a transverse section taken
• Discretization of the pier structure and soil continuum has been performed to insure that enough beam
elements & soil springs are used so changes in moment along the pier are adequately determined.
The adequacy of the mesh gradation has been determined by observing
changes in pier moments and deflections with variations in the number of beam elements
(spacing of the springs)
• Tot No of Coord Degrees of Freedom, DoF - Translation (Y), Rotation (0) = 34
Beam Element # = 1 thru 16 Bar Element # = 17 thru 33
DoF # = 2 1 =DoF# Y
1 = Ele # X Pos
4 3
orient X -axis positive, vertically downward
2
6 5
Supt of Spring by roller
vert and horz direction only
Element type - soil Element type - structure
17 - 2 -d spring elements for soil 16 - 2 -d beam bending elements for pier
30 29
15
32 31
16
34 33 Supt at Jt 33 is roller (vert supt only)
R L Sogge PE Project No. 11 -14 Sheet # 14
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/1712011
Assumptions
• The concrete piers are designed to carry the entire lateral and vertical force.
• The lateral analysis decouples the pier response to lateral loads from that to vertical loads.
• Single step loading of the lateral force and moment
• Representation of soil strength by a linear coefficient of horizontal subgrade reaction
• The 2 -d load application assumption is realistic for this 2 -d plane strain soil condition
Verification of Program
• Similar models used by Bowles (1974) and Desai & Kuppusamy (1978)
for laterally loaded pier structure systems in many research and practical problems
Subgrade Reaction
The coefficient of horizontal subgrade reaction, k, varies with depth as follows:
k = k, Z " /B(kcf)
where k, = constant of horizontal subgrade reaction (kcf)
B = shaft width or dia (ft)
Z = depth below grade (or the lowest scour surface) (ft)
n = exponent to describe the shape of strength curve with depth
= 0 if constant with depth (cohesive soils)
= 1 if linearly increasing with depth (granular soils)
For the soil profile the value for the coefficients of horizontal subgrade reaction
prescribed in the above table are applicable (Sogge, 1984)
Analysis Results
• Developed Moment, Displacement and Soil Pressure for the various Lateral Loading cases -
output from the 2 -d Finite Element Analysis Program LIP (1992) is presented in Fig 7
Point of Fixity- Unbraced Length
• If the portion of a bent above the foundation level is to be analyzed alone, rather than including
the foundation and soil properties below grade, it is necessary to determine where fixed
supports should be applied to the columns of the bent superstructure.
• These fixed support points, denoted as points of fixity of the pier foundation system,
can be determined from the results of the analysis of a single pier foundation.
• The point of fixity, located at a distance below the ground that is sometimes denoted as
unbraced length, can be defined as either the point:
• of maximum moment in the pier
• where the pier displacement is equal to zero.
• of inflection where the moment is equal to zero (2nd point if loaded into -M range)
Usually the M,,, definition is employed and the supports are fixed at this location below ground surface.
• The unbraced length derived from these charts is: Oft below grade
for design purposes, at this depth the pier can be considered to be fixed
R L Sogge PE Project No. 11 -14 Sheet# 15
Consulting Civii Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 10/17/2011
Shaft Spacing
• Based on criteria outlined in AASHTO (2002) for laterally loaded drilled shafts,
they may be considered to act individually where the center -to- center spacing is greater than
2.5 diameters in the direction normal to loadings = 0.3125
8 diameters in the direction parallel to loading.= 1 8 24 oc
For shaft layouts not conforming to these criteria, the effect of shaft interaction should be considered
resulting in a reduced lateral capacity for the shafts
• The structural capacity of the shafts should be evaluated for the combined stress state induced
by both axial and lateral force loadings.
Allowable Deflections
• The allowable lateral load shall not be more than 112 of the load that produces a (IBC 2000)
gross lateral movement of 1 inch at the ground surface. sec 1807.2.9.3
• Since the elastic model deformations are directly proportional to load, S „ = 0.5 in.
Since load is in the allowable range, not ultimate, use the following structure properties for deflection
computations: Material: Section:
E = E = Emma, Gross Uncracked
Construction Sequence & Notes
• Drill the piers (shafts) to the depth specified below the exisitng grade.
• Depending on the ability of the soil to maintain an open hole casing may be required for a distance
• Casing should be installed for the full shaft depth if downhole inspection and clean out
of the bottom of the hole is required - usually such inspection and clean out is not necessary
• Set rebar cage into the shaft hole supporting it vertically at the top of the hole and on its sides by spacers
• Promptly after drilling the hole and setting the steel reinforcing cage concrete should be poured
into the hole thru a tremie pipe centered in the middle of the rebar cage
• A one -pour sequence of construction for the piers is possible without a construction joint
• During the pier (shaft) drilling the soil should be inspected by a qualified geotechnical engineer
to verify the suitability of the soil present for the design herein presented.
R L Sogge PE Project No. 11 -14 Sheet # 16
Consulting Civil Engineer Project: Windmill Foundation
Feature: Pier Foundation Design
RLSogge @gmail.com Item: Vertical Bearing & Lateral Ld Capacity
Comp. by: R L Sogge PE 1011712011
Conclusions
• The imposed vertical design loadings are less than the Vertical Bearing Capacities of the piers
presented in Fig 6.
• The moments, shears, displacements and soil pressures presented in Fig 7 show the
response of the entire structure to the various imposed service lateral soil loadings.
• Working Stress Design (WSD) P -M Capacities are presented in Fig 5 for the reinforced concrete pier
section and the deflection and soil pressure criteria for the shafts
• Surnmary of Response of shafts to imp osed vertical and lateral loads
Results - Critical Service Ld Condition
Loading Develo ed Design Capaci
Lateral Pier Loading
Vert P (k) 9.841 L Fig 6 => embedment depth = 14
Lat V (k ) = 2.573
Lat M (k -ft) = 0
Fig 7 => Mdev = 6.5 < 9.5 OK Fig 5
Vd,, = 2.57 < 6 OK
SoilPres ksf = 0.4 < 0.7 OK
Dis (in) 0.18 < 1 OK
• Configuration Shaft Pier Column
Pier Pier Section El bottom of Grade El Depth below Ht' ** above Total
Location Dia (in -) Pier Cap Grade (ft) ** Grade (ft) Length (ft)
Windmill 1.5 1 0 0 14 0 14
*" Embedment Depth below the bottom of adjacent grade
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