THE

E M K I NFILES

What is the Mystery of

• Engineers are using software for which limitations have been documented.

• Engineers are designing structures without fully understanding the limitations of the software analysis tools they are using.

THE E M K I N FILES ?

WHY ?

• Many have not listened…

• For more than 29 years, Dr. Leroy Emkin has been telling the story…

WHY ?

For more than 29 years the comparisons have been difficult.

Until Now…

The Emkin Files now brings you two illustrations of some significant differences.

We used the Structural Desktop program to translate files and run them through parallel analysis.

• Original Bracing Layout• A Look at Load Distribution

and Torsion in the 2nd, 3rd & 4th Stories

• Double & Single-Story Bracing Results

• Base Shear Comparison• Limitations of RISAFloor &

RAM Steel Type Programs• Conclusion

14 STORY BUILDING

Double-Story Bracing vs. Single-Story Bracing

GT STRUDL Base Shear Comparison

RISAFloor, GT STRUDL & STAAD Base Shear (Z-dir)

172

244

299

295

147

267

316

307

93

255

260

256

0 50 100 150 200 250 300 350

1

3

7

8

Fram

es

Base Shear (kips)

RISAFloorSTAADGT STRUDL

Frames1378

Average

Frames1378

Average

0.2%15.4%15.0%18.1%

4.2%8.5%

% Dif. Between GT - STAAD Avg. & RISAFloor

42.0%

% Dif. Between GT STRUDL & STAAD14.6%9.6%5.8%

GT STRUDL Base Shear Comparison

RISAFloor, GT STRUDL & STAAD Base Shear (X - direction)

137

222

272

233

233

128

241

278

237

242

140

222

168

164

169

0 50 100 150 200 250 300

2

4

5

6

9

Frame

s

Base Shear (kips)

RISAFloorSTAADGT STRUDL

Frames24569

Average

Frames24569

Average28.9%21.5%

% Dif. Between GT STRUDL & STAAD6.8%8.8%2.3%1.6%

4.6%

% Dif. Between GT - STAAD Avg. & RISAFloor

3.6%

5.9%3.9%

39.0%30.0%

Load Application

• Limitations of RISAFloor and RAM Steel– Inability to account for non-rectangular geometry– Assumes that side wall wind loadings are equal and opposite– Applies the Wind Load in orthogonal directions only– Difficult to account for architectural features, or other exterior

obstructions

• Load Application with GT STRUDL and STAAD.Pro– Engineer can apply loads correctly regardless of geometry– Can handle any shape of structure

– Can account for architectural features and exterior obstructions and distribute the load along the load path of the structure

Conclusions

• Torsion is a cause of unusual story shears due to the 2nd floor weak story (atrium), architectural features, non-orthogonal window wall projections, and the non-symmetric locations of brace frames

• The 2-Story X-Bracing contributed to the unusual loading patterns in the Bracing.

• The ability of RAM Steel / RISAFloor-like programs to model the correct wind loadings is limited to symmetrical / rectangular structures.

• GT STRUDL and STAAD.Pro require more time to create a model, but allow the user to correctly apply wind pressures and other loadings.

Cable Pavilion Structure –

Preliminary Design

• Base ~ 40 meters square

• Tower Height ~ 25 meters

• Comparisons based on selfweight only

Structural Desktop Model

GT STRUDL Model

STAAD.Pro Model

1 1961 100 12 198.878 374.42 24.534 24.4997 9007 100 12 91961 859.54 24.1443 819612 1962 13 81 325.767 347.49 25.378 25.3425 9010 13 81 91962 649.36 25.6387 819623 1963 14 119 505.503 595.65 18.886 18.8596 9013 14 119 91963 1084.88 18.8593 819634 1969 455 14 250.02 300.47 17.372 17.3477 9031 455 14 91969 549.58 17.6147 819695 1972 597 14 356.241 245.36 16.7 16.6767 9040 597 14 91972 631.64 16.3952 819726 1974 195 12 76.314 144.03 15.448 15.4264 9046 195 12 91974 149.96 15.2777 819747 1975 185 13 50.635 151.36 15.845 15.8229 9049 185 13 91975 149.2 15.9463 819758 3444 813 858 567.775 571.37 18.886 18.8596 9055 813 858 93444 1075.55 18.8924 834449 4404 812 13 119.124 79.13 21.536 21.5059 9064 812 13 94404 191.7 21.536 84404

10 4405 811 12 105.843 81.6 21.536 21.5059 9067 811 12 94405 191.7 21.536 8440511 4406 1620 813 296.206 304.12 17.372 17.3477 9070 1620 813 94406 579.14 17.5933 8440612 4409 1371 811 370.916 353.2 25.378 25.3425 9079 1371 811 94409 716.32 25.5946 8440913 4817 1355 812 368.326 351.93 24.534 24.4997 9088 1355 812 94817 898.17 24.1609 8481714 4820 1747 813 284.658 289.87 16.7 16.6767 9094 1747 813 94820 664.28 16.4136 8482015 4929 1387 812 39.135 128.49 15.448 15.4264 9100 1387 812 94929 150.47 15.2747 8492916 4930 1419 811 56.612 150.38 15.845 15.8229 9103 1419 811 94930 150.47 15.9156 84930

17 1959 109 791 134.725 150.99 12.71 12.7020 9001 109 791 91959 255.5 12.7129 8195918 1960 127 798 43.47 49.43 12.893 12.8849 9004 127 798 91960 251.41 12.8784 8196019 1964 127 791 20.889 175.44 12.893 12.8849 9001 109 791 91964 243.15 12.8641 8196420 1965 90 798 190.11 233.99 11.65 11.6427 9004 127 798 91965 248.57 11.6664 8196521 1966 90 799 8.908 10.65 10.65 10.6433 9022 90 799 91966 247.63 10.5471 8196622 1967 456 798 96.342 80.22 11.39 11.3829 9025 456 798 91967 249.74 11.2928 8196723 1968 456 799 78.098 85.5 11.0364 11.0295 9028 456 799 91968 258.27 11.0025 8196824 1970 598 797 140.901 85.89 11.976 11.9685 9034 598 797 91970 259.84 11.8918 8197025 1971 598 796 144.662 25.76 11.707 11.6997 9037 597 796 91971 255.79 11.665 8197126 1973 127 795 308.644 220.13 10.391 10.3845 9043 127 795 91973 250.74 10.3484 8197327 3441 866 1343 49.739 52.59 12.893 12.8849 9052 866 1343 93441 248.64 12.8609 8344128 3445 866 1342 39.452 43.05 12.893 12.8849 9058 866 1342 93445 255.11 12.882 8344529 3454 866 1340 346.034 291.68 10.391 10.3845 9061 866 1340 93454 246.38 10.3545 8345430 4407 1622 1341 103.4 86.2 11.036 11.0291 9073 1622 1341 94407 261.26 11.001 8440731 4408 1622 1342 118.028 84.08 11.39 11.3829 9076 1622 1342 94408 242.99 11.2929 8440832 4410 1379 791 239.971 238.46 11.649 11.6417 9082 1379 791 94410 254.13 11.661 8441033 4816 1363 794 193.619 195.32 12.731 12.7230 9085 1363 794 94816 257.45 12.735 8481634 4818 1748 1344 114.566 95.61 11.707 11.6997 9091 1748 1344 94818 258.5 11.6753 8481835 4821 1748 1343 114.266 83.62 11.98 11.9725 9097 1748 1343 94821 256.47 11.9144 8482136 4931 109 796 24.849 90.05 11.837 11.8296 9106 109 796 94931 258.93 11.7504 8493137 4932 1379 1341 3.147 12.98 10.65 10.6433 9109 1379 1341 94932 244.32 10.5427 8493238 4933 1363 1344 14.924 21.64 11.825 11.8176 9112 1363 1344 94933 258 11.751 84933

STAAD PRO RESULTSUPPER CABLES

CABLE #

CABLE #

Cable Force 2 (kN) (length)

Initial Length (m)

Input Length (m)

CABLE #CABLE # Node 1 Node 2 Cable Force 1 (kN) Node 1 Node 2 Element ID#Cable Force

(kN)Unstress Length

(m)Element ID#

Node 2 Element ID#

BOTTOM CABLES

CABLE # Node 1 Node 2 Cable Force 1 (kN)Cable Force 2

(kN)Initial Length

(m)Input Length

(m)

BOTTOM CABLES

TOP CABLESGT STRUDL RESULTS

Cable Force (kN)

Unstress Length (m)

Element ID#CABLE # Node 1

Upper Cable Comparison

0 200 400 600 800 1000 1200

1

2

34

5

6

7

89

10

11

12

1314

15

16

Cab

le N

um

ber

Axial Force (KN)

STAAD (Length)

STAAD (Tension and Length)

GT STRUDL

STAAD Total Weight: 5161.916 kNGT STRUDL Total Weight: 5988.347 kN

% Diff. 14.82%

Lower Cable Comparison

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

Cab

le N

um

ber

Axial Force (kN)

STAAD (Length)

STAAD (Tension and Length)

GT STRUDL

• TRUST NO ONE

TRUST NO ONE• Our first responsibility is to the public

safety.

• The Stamping Engineer is 100% responsible.

•THE TRUTH IS OUT THERE

THE TRUTH IS OUT THERE

• Good engineering practice is finding the true answer, not just getting an answer.

• Understanding your software is a requirement, not an option.

• All software is NOT created equal.

• I WANT TO BELIEVE

I WANT TO BELIEVE…that the structural engineering profession has the integrity that we must have to fulfill our commitment to the public trust.

The Emkin Files is one means to assist our fellow structural engineers

to accomplish this goal.

Special Thanks to:

Dr. Leroy Emkin Dr. Kenneth (Mac) Will

Michael Swanger Robert Abernathy

The Ramblin’ Wrecks from Georgia Tech

The GT STRUDL Users Group

Hamid Zand

Ben Deaton

And, of course, to:

Joan

“Joan of Tech”

Incrocci