Power Generation Engineering And Services Company
Department of Civil Engineering
Structural Design Central Group
Modeling of Composite Steel Floors
Using GT STRUDL
A Presentation Submitted to:
GT STRUDL Users Group
24th Annual Meeting & Training Seminar
To Address Application of GT STRUDL for
Structural Analysis of composite steel section
February, 2012
Power Generation Engineering And Services Company
PGESCo.
1)
2)
3)
4)
5)
PGESCo stands for (Power Generation Engineering
Services Company)
Established in 1994
Located in Cairo, Egypt
Focused on EPCM (Engineering, Procurement,
Construction and Management)
Produced more than 20,000MW
Rendered View of a Combined
Cycle Power Plant
CTG / STG
CTG ( Combustion Turbine Generator)/ STG (Steam turbine Generator)
3
Structures in power plants where
composite slabs are used:
1)
2)
3)
4)
5)
Steam Turbine Generator “STG” Building.
Combustion Turbine Generator “CTG” Building.
Control building.
Electrical building.
Circulating Water Electrical Building “CWEB”.
Control building during construction:
5
Control building model using Gtstrudl:
-Model include
structural steel
upper part and the
concrete lower part
(Walls and Slab)
-Concrete slab
is represented by big
horizontal X brace to
simulate rigid
diaphragm action. The
purpose of this study is
how to model the slab
as a diaphragm and a
support for gravity
loads.
6
Models used to simulate Composite
Steel Floor
1- Full model
2- Springs were used to replace beams to
control deflection
3- Plate elements were deleted at corners
only.
4- Plate elements on the girders were
deleted to insure floor was not spanning
between girders.
5- Element has one direction
6- Sequential analysis
7- Rigid element between beam & slab
8- Master & Slave
9- Eccentricity between the centerline of
plate and steel beams.
7
Criteria for the normally used design
model.
• Bending moments in the slab, approach approximate values
obtained using continuous beam analysis results (confirm one
way action),
• Bending moments in beams (confirm transverse beams support
of the concrete slab)
• Bending moment in the Girders (Confirm Girders support of the
transverse beams).
• Lateral deflection ( Confirm rigid diaphragm action by the
concrete slab)
• The above 4 limits will be compared with a MANUAL
calculation
• A simpler structure than the control building will be used
for this case study.
8
Simple structure:
5
x5
4
W2
W2
1x
4
W2
W2
1x
X
W2
44
44
44
4
W2
x1
44
1
5
x5
1x
T5
W2
W10x33
1x
44
W
6.000 M
(19.686 Ft)
W2
1x
W
W10x33
T5
x1
1
1x
4
WT5x11
10.00 M
(32.81 Ft)
• Slab thickness 200mm
• Gravity Load 1.0 metric tons/m2 (200psf)
• Lateral Load 10.0 metric tons (22.0 kips)
• Hinged supports at column bases.
W10x33
X
X
10.00 M
(32.81 Ft)
9
Manual Calculation:
Girder
Column
10.00 M
X
X
W24X55
Filler
beam
W21X44
10.00 M
W21X44
W21X44
W21X44
W21X44
W21X44
W24X55
X
X
5 EQ. SPACS.
10
Manual Calculation:
• For Concrete Slab:-
11
Manual Calculation:
• For steel filler beams:• The steel (filler) beams behave
simply supported on steel girders.
• Steel beam span (L) = 10.0 meters.
•Beam uniform load (w) = slab
uniform load * spacing
=1*2 = 2.0 t/m’
•Maximum bending moment
(M)=2*102/8= 25 m.t (180.8Kip.ft)
•Maximum deflection
(Δ) =
[5*(2*(1000)4]/[(384*2100*35088)]
= 3.53 cm = 35.3 mm (1.39in)
•Reaction =2*10/2=10ton (22.04Kip)
12
Manual Calculation:
• For steel girders:• The steel girders behave simply
supported on steel columns.
• Steel beam span (L) = 10.0 meters.
•Steel girder loads are the reaction of
filler beams
•Maximum bending moment
M=0.6*10*10=60 m.t (433.9 kip.ft)
•Maximum deflection (Δ) =
[(0.063*10*(1000)3]/[(2100*56191)]
= 5.34 cm = 53.4 mm (2.1in)
•Reaction=4*10/2=20 ton (44.1 kip.ft)
13
1-Full model used:
• 10m X 10m X 6m high structure.
• Braced in one direction & frame
action in the other.
• Columns W10X33, and vertical
brace WT5X11
• Girder size of W24X55, and
transverse beams size of W21X44
• Slab thickness 200mm supported by
the steel filler beams.
• Gravity Load 1.0 metric tons/m2 (200psf)
• Lateral Load 10.0 metric tons (22.0 kips)
• Hinged supports at column bases.
14
1-Full model used:
VAL 35.38
LOC 5.000E-02
Moment Z
Load: 1
M-MTON
VAL 35.38
LOC 5.000E-02
Bending in filler
beams & girders
uniformly loaded
VAL 16.02
LOC 9.000E-01
VAL 12.65
LOC 6.500E-01
VAL 16.02
LOC 9.000E-01
VAL 11.16
LOC 1.000E+00
VAL 12.79
LOC 9.500E-01
VAL 11.16
LOC 1.000E+00
15
1-Full model used:
MYY
MID
Load 1
M-METN/M
• Bending in slab
(Neg. mom.= 0.0)
• One way action
does NOT exist
-3.9
-3.2
-2.4
-1.6
-0.8
0.0
0.8
1.6
2.4
3.2
4.0
4.8
5.4
16
1-Full model used:
Y -38.94
Displacements at Joints
Load 1
MM
Y -24.06
178
X
Displacement at joints in
mm under Load 1
176
X
104
X
174
X
Seems like slab is
supporting the filler
beams. Hand
Calculation shows filler
beam max deflection =
35.3 mm (1.39 in)
168
X
170
X
172
X
Y -48.31
Y -48.31
Y
Y -24.06
Z
Y -38.94
X
17
1-Full model used:
• GT results are quite different from the results obtained by the
manual calculation because of the combined action of the slab
and the steel beams.
•Each of the upcoming trials has its own perspective in choosing
the methodology to represent the composite action of floor
beams.
• Each model presented a different set of problems simulating
composite action.
• A comparison of the results will be made with manual
calculation. The results will be evaluated to understand the
reasons for differences of the results from those of manual
calculations.
18
2-Springs used to control deflection
• Solve the beam manually for uniform load W obtained by
multiplying the area uniform load by beam spacing
• Calculate the deflection @ 0.5m intervals(0.5m X 0.5m
Plate elements)
• Multiply the uniform load by 0.5m to get concentrated load
• Divide the concentrated load by the deflection
calculated manually at this point to get stiffness
19
2-Springs used to control deflection
• This stiffness used represents the steel beam.
• In the model the steel beams are replaced by the calculated
spring constants.
This model cannot be used simply because the added springs
generate vertical reactions that are not transmitted to the
columns which generate lower reaction loads at the columns.
20
3-Delete plates at corners only
• Delete elements at
the corners to prevent
the slab from being
directly supported by
the columns
21
3-Delete plates at corners only
VAL 36.01
Moment Z
Load: 1
M-MTON
VAL 16.02
• Bending moment
in the steel beam
VAL 12.65
VAL 16.05
VAL 35.98
VAL 12.67
VAL 10.87
VAL 10.87
22
3-Delete plates at corners only
• Bending moment in the
slab
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
23
4- Delete plate elements on the
girders
•Delete the plate elements that rest on the
girder to force the slab to
transfer the load to the
beams then to the girders
then to the columns
24
4- Delete plate elements on the
girders
VAL 31.53
Moment Z
Load: 1
M-MTON
•Bending moment
in the steel beams
VAL 31.53
VAL 15.30
VAL 12.30
VAL 15.36
VAL 10.81
VAL 12.32
VAL 10.81
25
4- Delete plate elements on the
girders
-0.0
0.0
0.5
1.0
1.5
2.0
2.5
4
•Bending moment in the
slab
MYY
MID
Load 1
M-METN/M
X
3.0
3.5
4.0
4.5
5.0
5.4
26
4- Delete plate elements on the
girders
Displacements at Joints
Load 1
MM
Y -23.03
•Vertical displacement
178
X
176
X
174
X
168
X
170
X
172
X
Y -36.41
Y -23.03
Y -44.81
Y -36.41
Y -44.81
27
5- Element has one direction of
distribution
• PSRR element type are used in modeling
The problem that the PSRR elements do not
permit the consideration of bending stiffness
analysis nor the dynamic analysis
28
6-Sequential analysis
• A thought was discussed that the sequential
analysis will get GTS to differentiate between
the stage when the concrete is wet and the next
stage when the concrete hardens.
• This approach was not what was thought to be
and hence, it was abandoned.
29
7- Rigid elements between beam and
slab
Moment Z
Load: 1
M-MTONON: Z
• This modeling technique did not
produce a good representation
of the bending moment which
can not be explained.
30
8- Use of Master and Slave Joints
Moment Z
Load: 1
M-MTONON: Z
• This also did not produce a good
representation of the bending moment.
31
9- Eccentricity
• Eccentric between the steel member and
the concrete plate elements
32
10
0
9- Eccentricity
X
• Weird Bending
moment diagram
which had no
explanation.
33
9- Eccentricity
MYY
MID
Load 1
M-METN/M
• Bending in
the slab
-3.1
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
1.9
34
Models used to simulate hand calc
till now
1-Full model
2-Springs were used to replace beams to
control deflection
3-Plate elements were deleted at corners
only.
4-Plate elements on the girders were
deleted to insure floor was not spanning
between girders.
5- Element has one direction
6- Sequential analysis
7- Rigid element between beam & slab
8- Master & Slave
9-Eccentricity between the centerline of
plate and steel beams.
35
What to do next???
•None of the above modeling techniques produced a good
representation of the approximate manual approach. So a
combination of the above modeling techniques will be tried to
reach a reasonable representation of the structure with some
modification
• It was suggested to use a combination of the eccentric modeling
approach together with the deleted elements at the corners for:
• Easy to model “applicable for every day work”
• Actual representation of the differences between the steel
beam CL and the concrete slab CL.
• The modification will be by varying one of the following
parameters
• Thickness of the slab
•Young's Modules of the concrete slab
36
Variation in Thickness for the
slab
37
Variation in Thickness for the
slab
38
Variation in E for concrete
39
Variation in E for concrete
40
Variation in E for concrete
•Bending moment
in the steel beam
Moment Z
Load: 1
M-MTON
Case = 0.25% E
VAL 23.50
VAL 57.18
41
Variation in E for concrete
•Bending moment
in the slab
MYY
MID
Load 1
M-METN/M
-0.32
-0.30
-0.24
-0.18
Case= 0.25% E
-0.12
-0.06
0.00
0.06
0.12
0.18
0.24
0.30
0.35
42
Variation in E for concrete
Displacements at Joints
Load 2
MM
•Lateral difflection in Z
direction
101
X
(Braced Dir.)
104
X
Z -0.03885
Y
Z
( Z -0.00152 in)
X
Z -0.03885
( Z -0.00152 in)
43
Variation in E for concrete
Displacements at Joints
Load 3
MM
•Lateral deflection in X
direction
(Moment frame dir.)
101
X
102
X
X -5.884
Y
( X -0.232 in)
X -5.884
Z
X
( X -0.232 in)
44
Verification – Other Software
Comparing results to those obtained by using another software an
other program with a composite beam module built in
45
Verification – Other software
46
Conclusion
•Using the Eccentric model with the deleted shell element at the
corner with a reduction in the E of the concrete slab, produces results
in agreement with the manual calculations. The following table
summarize these results.
47
Questions and Discussion