Transcript Document

THE
EMKIN
FILES
What is the Mystery of
THE E M K I N FILES ?
• 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.
WHY ?
• For more than 29 years, Dr. Leroy
Emkin has been telling the story…
• Many have not listened…
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.
14 STORY BUILDING
• 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
Double-Story Bracing vs.
Single-Story Bracing
GT STRUDL Base Shear
Comparison
RISAFloor, GT STRUDL & STAAD Base Shear (Z-dir)
256
8
307
295
260
7
Frames
316
299
255
267
244
3
RISAFloor
STAAD
GT STRUDL
93
1
147
172
0
50
100
150
200
Base Shear (kips)
250
300
350
Frames
1
3
7
8
Average
% Dif. Between GT STRUDL & STAAD
14.6%
9.6%
5.8%
4.2%
8.5%
Frames
1
3
7
8
Average
% Dif. Between GT - STAAD Avg. & RISAFloor
42.0%
0.2%
15.4%
15.0%
18.1%
GT STRUDL Base Shear
Comparison
RISAFloor, GT STRUDL & STAAD Base Shear (X - direction)
169
9
164
6
Frames
242
233
237
233
168
5
278
272
222
4
241
222
RISAFloor
STAAD
GT STRUDL
140
2
128
137
0
50
100
150
Base Shear (kips)
200
250
300
Frames
2
4
5
6
9
Average
% Dif. Between GT STRUDL & STAAD
6.8%
8.8%
2.3%
1.6%
3.6%
4.6%
Frames
2
4
5
6
9
Average
% Dif. Between GT - STAAD Avg. & RISAFloor
5.9%
3.9%
39.0%
30.0%
28.9%
21.5%
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, nonorthogonal window wall projections, and the nonsymmetric 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
CABLE # CABLE # Node 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1961
1962
1963
1969
1972
1974
1975
3444
4404
4405
4406
4409
4817
4820
4929
4930
100
13
14
455
597
195
185
813
812
811
1620
1371
1355
1747
1387
1419
CABLE # CABLE # Node 1
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
1959
1960
1964
1965
1966
1967
1968
1970
1971
1973
3441
3445
3454
4407
4408
4410
4816
4818
4821
4931
4932
4933
109
127
127
90
90
456
456
598
598
127
866
866
866
1622
1622
1379
1363
1748
1748
109
1379
1363
STAAD PRO RESULTS
UPPER CABLES
Cable Force 2 Initial Length Input Length
Node 2 Cable Force 1 (kN)
CABLE # Node 1 Node 2
(kN) (length)
(m)
(m)
12
198.878
374.42
24.534
24.4997
9007
100
12
81
325.767
347.49
25.378
25.3425
9010
13
81
119
505.503
595.65
18.886
18.8596
9013
14
119
14
250.02
300.47
17.372
17.3477
9031
455
14
14
356.241
245.36
16.7
16.6767
9040
597
14
12
76.314
144.03
15.448
15.4264
9046
195
12
13
50.635
151.36
15.845
15.8229
9049
185
13
858
567.775
571.37
18.886
18.8596
9055
813
858
13
119.124
79.13
21.536
21.5059
9064
812
13
12
105.843
81.6
21.536
21.5059
9067
811
12
813
296.206
304.12
17.372
17.3477
9070
1620
813
811
370.916
353.2
25.378
25.3425
9079
1371
811
812
368.326
351.93
24.534
24.4997
9088
1355
812
813
284.658
289.87
16.7
16.6767
9094
1747
813
812
39.135
128.49
15.448
15.4264
9100
1387
812
811
56.612
150.38
15.845
15.8229
9103
1419
811
BOTTOM CABLES
Cable Force 2 Initial Length Input Length
Node 2 Cable Force 1 (kN)
CABLE # Node 1 Node 2
(kN)
(m)
(m)
791
134.725
150.99
12.71
12.7020
9001
109
791
798
43.47
49.43
12.893
12.8849
9004
127
798
791
20.889
175.44
12.893
12.8849
9001
109
791
798
190.11
233.99
11.65
11.6427
9004
127
798
799
8.908
10.65
10.65
10.6433
9022
90
799
798
96.342
80.22
11.39
11.3829
9025
456
798
799
78.098
85.5
11.0364
11.0295
9028
456
799
797
140.901
85.89
11.976
11.9685
9034
598
797
796
144.662
25.76
11.707
11.6997
9037
597
796
795
308.644
220.13
10.391
10.3845
9043
127
795
1343
49.739
52.59
12.893
12.8849
9052
866
1343
1342
39.452
43.05
12.893
12.8849
9058
866
1342
1340
346.034
291.68
10.391
10.3845
9061
866
1340
1341
103.4
86.2
11.036
11.0291
9073
1622
1341
1342
118.028
84.08
11.39
11.3829
9076
1622
1342
791
239.971
238.46
11.649
11.6417
9082
1379
791
794
193.619
195.32
12.731
12.7230
9085
1363
794
1344
114.566
95.61
11.707
11.6997
9091
1748
1344
1343
114.266
83.62
11.98
11.9725
9097
1748
1343
796
24.849
90.05
11.837
11.8296
9106
109
796
1341
3.147
12.98
10.65
10.6433
9109
1379
1341
1344
14.924
21.64
11.825
11.8176
9112
1363
1344
Element ID#
91961
91962
91963
91969
91972
91974
91975
93444
94404
94405
94406
94409
94817
94820
94929
94930
Element ID#
91959
91960
91964
91965
91966
91967
91968
91970
91971
91973
93441
93445
93454
94407
94408
94410
94816
94818
94821
94931
94932
94933
GT STRUDL RESULTS
TOP CABLES
Cable Force Unstress Length
(kN)
(m)
859.54
24.1443
649.36
25.6387
1084.88
18.8593
549.58
17.6147
631.64
16.3952
149.96
15.2777
149.2
15.9463
1075.55
18.8924
191.7
21.536
191.7
21.536
579.14
17.5933
716.32
25.5946
898.17
24.1609
664.28
16.4136
150.47
15.2747
150.47
15.9156
BOTTOM CABLES
Cable Force Unstress Length
(kN)
(m)
255.5
12.7129
251.41
12.8784
243.15
12.8641
248.57
11.6664
247.63
10.5471
249.74
11.2928
258.27
11.0025
259.84
11.8918
255.79
11.665
250.74
10.3484
248.64
12.8609
255.11
12.882
246.38
10.3545
261.26
11.001
242.99
11.2929
254.13
11.661
257.45
12.735
258.5
11.6753
256.47
11.9144
258.93
11.7504
244.32
10.5427
258
11.751
Element ID#
81961
81962
81963
81969
81972
81974
81975
83444
84404
84405
84406
84409
84817
84820
84929
84930
Element ID#
81959
81960
81964
81965
81966
81967
81968
81970
81971
81973
83441
83445
83454
84407
84408
84410
84816
84818
84821
84931
84932
84933
Cable Number
Upper Cable Comparison
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
STAAD (Length)
STAAD (Tension and Length)
GT STRUDL
0
200
400
600
Axial Force (KN)
STAAD Total Weight: 5161.916
GT STRUDL Total Weight: 5988.347
% Diff.
14.82%
kN
kN
800
1000
1200
Lower Cable Comparison
STAAD (Length)
STAAD (Tension and Length)
GT STRUDL
38
37
36
35
34
33
32
31
Cable Number
30
29
28
27
26
25
24
23
22
21
20
19
18
17
0.00
50.00
100.00
150.00
200.00
250.00
Axial Force (kN)
300.00
350.00
400.00
• 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:
The Ramblin’ Wrecks from
Georgia Tech
Dr. Leroy Emkin
Dr. Kenneth (Mac) Will
Michael Swanger
Robert Abernathy
Hamid Zand
Ben Deaton
The GT STRUDL
Users Group
And, of course, to:
Joan
“Joan of Tech”
Incrocci