SS Gravity Calculations 4.8 Metric

8/12/2019 SS Gravity Calculations 4.8 Metric

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version 4.8 (4/30/13)

visit www.stonestrong.com to check current version

1 The conventional (non LRFD) calculation methodology generally adheres to the AASHTO Standard

Specifications for Highway Bridges (17th Edition, 2002). Additional methods and practices follow the FHWA

Mechinically Stabilized Earth Walls and Reinforced Slopes Design and Construction Guidelines, NHI-00-043.

Specific methods, procedures, equations, and nomenclature can be found in the Gravity Wall DesignMethodology and Example Gravity Calculations in the Engineering Manual and available on the Stone

Stron web site www.StoneStron .com.

2 The end user is res onsible for all hi hli hted in ut values and chan es to unhi hli hted ro ram default

USER NOTES

Stone Strong LLC is the owner of this computer file and retains all common law, statutory, and other reservedrights including the copyright. Limited license is granted to copy, print, or use this spreadsheet as an aid in

performing design calculations for Stone Strong retaining walls. Stone Strong LLC makes no warranties, either

expressed or implied, of merchantability or fitness for any particular purpose, and accept no responsibility for the

accuracy, suitability, or completeness of information contained herein.

Licensee acknowledges that this computer file is the proprietary property of Stone Strong LLC. Licensee certifies

that he/she will maintain this computer file as a confidential trade secret and will not copy or distribute the file to

any person or entity that is not acting under his/her direct supervision and control.

This calculation spreadsheet is provided for general information purposes only. Anyone making use of

this spreadsheet and related information does so at their own risk and assumes all liability for such use.

Site specific design should be performed by a licensed Professional Engineer based on actual site

conditions, materials, and local practices.

values. Properties for soil and other materials should be obtained through testing or from recommendations

by an experienced geotechnical engineer with knowledge of local materials and practices.

3 The backfill height defaults to the total wall height, assuming that the wall is backfilled to the top of any Capunits or Dual Face units. The backfill height may be overwritten where the Cap or Dual Face units are

allowed to project above grade. The total wall height and backfill height are measured from the top of the

base pad, neglecting embedment. The exposed height is the total backfill height less the embedment depth.

N t th t i i t t th t i l t d t i i ti f d l ll



Note that passi e resistance at the toe is neglected per c stomar engineering practice for mod lar all

6 The trial wedge routine will automatically solve complex slope, tier, and surcharge geometry. Sloped

embankments may be defined by entering the slope value (run per foot of rise) or by entering the elevation

change over the defined segment length. Entry method is toggled by entering "slope" or "elevation" in the

entry field in the non-printed space to the right of the slope section. The segment lengths for the zoned

slopes and surcharges are measured successively beginning from the front face of the wall. Up to 4

segments may be entered, and all segment lengths are horizontal. The total defined distance must exceed

the influence distance of the trial wedges, typically beginning at approximatley 30 degrees above horizontal.

The length of segment 1 is measured from the face of the wall, and the lengths of segments 2, 3, and 4 are

measured from the previous segment. Tiers may be entered between segments. For purposes of the trial

wedge analysis, all tiers are assumed vertical. See the Backslope & Surcharge Terminology sketch located

below.

7 A rigid boundary, such as a rock ledge or an embedded structural element, may be modeled by entering a

negative tier height at the location of the rigid boundary. The boundary is assumed to be vertical.

8 Live load surcharges may be entered for individual zone segments. Live load surcharges would include

vehicle loads and other intermittent surcharges. LL surcharges are omitted in seismic analysis (if used).

9 The conventional calculations for overturning and contact pressure use a reduced block base width to

account for rounding of the face (reduced by 2 inches by default). Contact pressure can be reduced by

increasing the thickness of the granular base (see note #14).

10 The recommended design procedure for extended blocks (62HD, 86HD, or 24-ME) or tail extensions is to

determine the maximum gravity height without an extension for the specific soil and loading conditions, and

to use extended blocks or tail extension for at least the entire wall section that exceeds this limiting height.

,

of extended units. Cast in place extensions may be added to individual block courses. For blocks with a

height of 914 mm (24SF units), the extender may be limited to the bottom half by selecting "1/2 H" in the cell

next to the extension width. This feature is disabled for blocks with a height of 457 mm (6SF units).

11 For calculating driving forces applied to the wall, the effective batter of the back of the blocks is taken as the

facing batter when uniform block widths are used. If any extended blocks (62HD, 86HD, or 24-ME) or a cast

in place tail extension is included, the batter on the back of the wall is recalculated following AASHTO



15 The base materials, configuration, and properties are entered to the right of the printable space. Sliding

resistance across the surface of the base is evaluated using a composit friction coefficient based on the

contributory area for each interface combination. The calculated coefficient can be overridden by entering a

composite coefficient in the OVERRIDE entry cell. If ANY value is entered in this cell, it will be used to

calculate the sliding resistence regardless of the other values entered. The sliding resistence routine also

includes evaluation of sliding failure throught the foundation soils below the base, and the lower result is

reported as the sliding resistance Rs.

16 The aggregate base thickness may be adjusted for site and other conditions. The base thickness is typically

set at 225 mm, but may be reduced to 150 mm for shorter walls (1.8 m or less) or for hard and stable

foundation soil conditions. In soft conditions with lower allowable bearing pressures, the contact pressure

may be reduced by increasing the thickness of the granular base. The horizontal dimension of the base

should be set to provide a minimum projection in front of the face equal to 1/2 of the base thickness plus 75to 150 mm inches for construction tolerance. The rear projection of the base behind the tail should provide

at least 75 to 150 mm for construction tolerance.

17 The thickness of a concrete base is typically set at 150 mm unless site conditions dictate a thicker base to

distribute the wall weight over soft soils. When an unreinforced concrete base is used, the front projection of

the footing should be at least equal to the concrete thickness. For calculating the equivalent bearing width

and the contact pressure, a 1:1 distribution is taken through the unreinforced concrete base instead of the

1:2 distribution traditionally used for an aggregate base. If a reinforced concrete footing is used, the front

projection dimension is used to calculate the equivalent bearing width regardless of the thickness.

18 An allowable bearing pressure may be entered if specified by the geotechnical report or other requirements.

This allowable bearing pressure will override the calculation of allowable bearing pressure based on the

entered properties of the foundation soil. If a net allowable bearing pressure is indicated, then the

overburden at the toe will be added to determine the gross allowable bearing pressure. If unsure as to

whether the specified bearing pressure is net allowable, select "gross" to indicate gross allowable

(conservative). If an allowable bearing pressure is not entered, bearing capacity is calculated using the

Vesic equation. The calculation includes the thickness of the aggregate base and the cover depth in theembedment factor D f .

19 Internal stability analysis can be performed at any unit interface within the wall. To switch to internal

analysis select "internal" in cell O10 At a minimum internal stability should be checked at each change in



22 The LRFD version follows the AASHTO LRFD Bridge Design Specification (4th Edition, 2007). Load and

Resistance Factor Design methodology applies separate factors to address the variability of the applied

loads, materials, and design components that provide support. The factored loads must be less than the

factored resistance to satisfy the design requirements. Specific methods, procedures, equations, and

nomenclature can be found in the LRFD Design Methodology and LRFD Example Calculations in the

Engineering Manual and available on the Stone Strong web site www.StoneStrong.com.

23 A table of load and resistance factors used in the LRFD spreadsheet is included on page 2 of the program

output. These are based upon tables 3.4.1-1 and 3.4.1-2 in the AASHTO LRFD specification. Calculations

are provided for relevent load cases - Strength I (a & b variations), Strength II, Strength IV, Extreme Event I

(seismic), Extreme Event II (collision), and Service I. For this type of Precast Modular Block (PMB) system,

load cases Strength I and Extreme Event I (seismic) will typically control design. Results are summarized

for load case Strength I (relevent behaviors from a or b cases) and Extreme Event I (seismic, if applicable).

Detailed calculations for all of the load cases are presented in tabular form below the summary. If these

additional calculations indicate stabiltiy problems, a flag occurs in the Results summary.

24 Lateral loads at the top of the wall are assumed to be guardrail or barrier collision loads in the LRFD analysis

(treated as live loads in conventional analysis). Collision loads are treated in Extreme Event II load case. If

the lateral load is a different type of loading, this may be investigated by editing the load factor CT and load

case designation. Note that the last 2 load case headings and the CT load factor designation are not

protected and can be edited by the user, as can all of the individual load factor values.







STONE STRONG GRAVITY CALCULATIONS - ver 4.8

Project Name: Gravity Retaining Wall Design

Location: Stone Strong, Lincoln, NE

Job#: 08110.00

Section: Trial DataCalc by: Author 7/23/14 19:12

Notes

Wall Configuration setback (mm) block units unit f ill soil wedge CIP Extension

block w (mm) h (m) face tail Wb (kN) xb (mm) Wa (kN) xa (mm) Ws (kN) xs (mm) we (mm) ht

6 1118 0.46 202 202 5.8 685 4.3 799

24 1118 0.91 101 101 10.9 589 8.8 731

24 1118 0.91 0 0 10.9 488 8.8 630

OK! 1118 2.29 202 202 27.7 570 21.8 704 0.0 0

backfill height 2.29 m ω= 6.31 deg






Job#: 08110.00


Page 2 of 2

Analysis Qlh = 0.00 kN e= 0.13 m

Ka = 0.312 Qlv = 0.00 kN ∆K AE = 0.000 Bf ' = 1.04 m

Ph = 16.16 kN Rs = 25.09 kN PIR = 0.00 kN eeq= 0.13 m

Pv

= 1.90 kN qult

= 237 kPa P AEh

= 0.00 kN Bf

'eq

= 1.04 m

Results Overturning: Desired FS = 1.5 Actual FS= 2.46 OK!

Sliding: Desired FS = 1.5 Actual FS= 1.55 OK!

Bearing Capacity: Desired FS = 2 Actual FS= 4.41 OK!

qall = 119 kPa qc = 54 kPa

qall = qc =

Ground Surface & Trial Wedge Plot

14

16

18

7

8






Job#: 08110.00


Notes

Wall Configuration setback (mm) block units unit f ill soil wedge CIP Extension

block w (mm) h (m) face tail Wb (kN) xb (mm) Wa (kN) xa (mm) Ws (kN) xs (mm) we (mm) ht

6 1118 0.46 202 202 5.8 735 4.3 799

24 1118 0.91 101 101 10.9 639 8.8 731

24 1118 0.91 0 0 10.9 538 8.8 630

OK! 1118 2.29 202 202 27.7 620 21.8 704 0.0 0

backfill height 2.29 m ω= 6.31 deg






Job#: 08110.00


Page 2 of 2

Ground Surface &

Trial Wedge Plot

Unfactored LoadsKa = 0.260

Ph = 13.41 kN

Pv = 2.05 kN

Qlh = 0.00 kN

Qlv = 0.00 kN

∆K AE = 0.000

PIR = 0.00 kNP AEh = 0.00 kN

P AEv = 0.00 kN0

2

4

6

8

10

12

14

16

0

1

2

3

4

5

6

7

8

0.0 2.0 4.0 6.0 8.0 10.0 12.0

R e s u l t a n t ( k N )

H e i g h t ( m )

Distance from Face (m)

Load Cases: Strngth Strngth Strngth Extrme Extrme Service

I-a I-b IV I (EQ) II (CT) I

Factored Loading Overturning: 15.3 15.3 15.3 10.2 10.2 10.2 kN-m OK!

Sliding: 20.1 20.1 20.1 13.4 13.4 13.4 kN OK!

Bearing: 56.8 65.9 70.3 48.0 48.0 48.0 kPa OK!

e= 0.20 0.13 0.11 0.10 0.10 0.10 m OK!



Block Library3/1/2013

Block Conc. Wt. Void Vol Length Height Unit Width Lift Align xc xv Special

Type Description (kN) (m3) (m) (m) (mm) (mm) (mm) (mm) (mm) Top

6 6SF unit (6 square feet) 7.12 0.30 1.22 0.46 1,118 483 432 533 597

24 24SF unit (24 square feet) 26.69 1.24 2.44 0.91 1,118 533 432 538 63024-ME 24SF Mass Extender unit 44.48 1.29 2.44 0.91 1,422 533 432 831 655

24-M6 24SF w/ 150mm Mass Extender (check availability) 35.58 1.26 2.44 0.91 1,270 533 432 977 643

24-M18 24SF w/ 450mm Mass Extender (check availability) 53.38 1.29 2.44 0.91 1,575 533 432 1,269 672

24-M24 24SF w/ 600mm Mass Extender (check availability) 62.27 1.31 2.44 0.91 1,727 533 432 1,123 663

62 62HD unit (24 square feet) 30.49 2.15 2.44 0.91 1,575 533 432 739 838

86 86HD unit (24 square feet) 34.22 3.26 2.44 0.91 2,184 533 432 1,016 1,146

Alternate top units (not typically used - regular 24SF top unit is used in most applications, analyzed as regular 24 SF unit)

Cap Cap unit 7.12 0.00 2.44 0.18 813 406 406 406 Yes

DF Dual Face unit 15.57 0.00 2.44 0.46 711 356 356 356 356 Yes

Cast-in-place coping (overhang would be 480 mm less than the Alignment dimension entered - custom coping may be entered below)

300 cp cast-in-place concrete coping 8.75 1.00 0.30 1280 680 640 Yes 450 cp cast-in-place concrete coping 13.12 1.00 0.45 640 Yes

600 cp cast-in-place concrete coping 17.50 1.00 0.60 1280 680 640 Yes

750 cp cast-in-place concrete coping 21.87 1.00 0.75 1280 680 640 Yes

coping custom cast-in-place concrete coping 11.66 1.00 0.40 1280 680 640 Yes

Vertical stack units (modified recess and face to permit construction of a vertical face)

V6 6SF unit (6 square feet) 7.12 0.30 1.22 0.46 1,118 533 533 533 597

V24 24SF unit (24 square feet) 26.69 1.24 2.44 0.91 1,118 533 533 538 630

V24-ME 24SF Mass Extender unit 44.48 1.29 2.44 0.91 1,422 533 533 831 655

V24-M6 24SF w/ 150mm Mass Extender (check availability) 35.58 1.26 2.44 0.91 1,270 533 533 977 643

V24-M18 24SF w/ 450mm Mass Extender (check availability) 53.38 1.29 2.44 0.91 1,575 533 533 1,269 672

V24-M24 24SF w/ 600mm Mass Extender (check availability) 62.27 1.31 2.44 0.91 1,727 533 533 1,123 663

V62 62HD unit (24 square feet) 30.49 2.15 2.44 0.91 1,575 533 533 739 838V86 86HD unit (24 square feet) 34.22 3.26 2.44 0.91 2,184 533 533 1,016 1,146

Green Wall units (increased setback - use for green wall or as isolated planter block)

G6 6SF unit set behind loops (6 square feet) 7.12 0.30 1.22 0.46 1,118 483 -114.0 533 597

G24 24SF unit set behind loops (24 square feet) 26.69 1.23 2.44 0.91 1,118 533 -114.0 538 630

Custom user entered elements below (use for any dealer specific variances from above default dimensions/weights)

Documents

SS Gravity Calculations 4.8 Metric