1. Modeling of Composite Steel Floors Using GT STRUDL
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

2. Power Generation Engineering And Services Company
PGESCo.
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

3. Rendered View of a Combined Cycle Power Plant
CTG / STG
Add notes, Say 1- PGESCO main design activity 2- PGESCo is an engineering firm located in Cairo, Egypt.
CTG ( Combustion Turbine Generator)/ STG (Steam turbine Generator) 3

4. Structures in power plants where composite slabs are used:
Steam Turbine Generator “STG” Building.
Combustion Turbine Generator “CTG” Building.
Control building.
Electrical building.
Circulating Water Electrical Building “CWEB”.

5. Control building during construction:5

6. 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.
Model include structural steel upper part and the lower concrete part (Walls and slab).
The question is there any accurate model rather than the big horizontal brace?? 6

7. 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

8. 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

9. Simple structure: Slab thickness 200mm
Gravity Load 1.0 metric tons/m2 (200psf)
Lateral Load metric tons (22.0 kips)
Hinged supports at column bases. 9

10. Manual Calculation:
Girder
Column
Filler beam 10

11. Manual Calculation:
For Concrete Slab:- 11

12. 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

13. 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

14. 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 metric tons (22.0 kips)
Hinged supports at column bases. 14

15. 1-Full model used: Bending in filler beams & girders uniformly loaded
- Hand calculations: Bending moment in the filler beams = 25 m.t and in the girders equal to the 60m.t which is not equal to the output from the full model. Explain?
- The outer beams carry more than the inner filler beam which is not consistent with one way action of a slab……. This is consistent with the following slide that shows the outer beams supporting the slab, while the inner beams are partly supported by the slab. It also represent the two way action by the slab. 15

16. 1-Full model used: Bending in slab (Neg. mom.= 0.0)
One way action does NOT exist
Explain? 16

17. 1-Full model used: Displacement at joints in mm under Load 1
Seems like slab is supporting the filler beams. Hand
Calculation shows filler beam max deflection = 35.3 mm (1.39 in)
1-Displacements are not equal
2- They are not equal to the manual calculation which is 35.3mm.
3- No deflection reversal. 17

18. 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

19. 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

20. 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

21. 3-Delete plates at corners only
Delete elements at the corners to prevent the slab from being directly supported by the columns 21

22. 3-Delete plates at corners only
Bending moment
in the steel beam 22

23. 3-Delete plates at corners only
Bending moment in the
slab 23

24. 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

25. 4- Delete plate elements on the girders
Bending moment
in the steel beams 25

26. 4- Delete plate elements on the girders
Bending moment in the
slab 26

27. 4- Delete plate elements on the girders
Vertical displacement 27

28. 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

29. 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

30. 7- Rigid elements between beam and slab
This modeling technique did not
produce a good representation
of the bending moment which
can not be explained. 30

31. 8- Use of Master and Slave Joints
This also did not produce a good
representation of the bending moment. 31

32. 9- Eccentricity Eccentric between the steel member and
the concrete plate elements 32

33. 9- Eccentricity Weird Bending moment diagram which had no explanation.33

34. 9- Eccentricity Bending in the slab 34
But at this step we are confidante that the modeling the concrete above the steel or using the eccentric option is the almost right way to model the composite action but still need a lot of enhancement 34

35. 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.
Place this slide before the full model slide. 35

36. 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
This will be deleted. For organization purposes only. 36

37. Variation in Thickness for the slab37

38. Variation in Thickness for the slab38

39. Variation in E for concrete39

40. Variation in E for concrete40

41. Variation in E for concrete
Bending moment
in the steel beam
Case = 0.25% E 41

42. Variation in E for concrete
Bending moment
in the slab
Case= 0.25% E 42

43. Variation in E for concrete
Lateral difflection in Z
direction
(Braced Dir.)
Adjust note as follows: Load 2. Displacement at joints, mm. Add also inches. 43

44. Variation in E for concrete
Lateral deflection in X
direction
(Moment frame dir.) 44

45. Verification – Other Software
Comparing results to those obtained by using another software an other program with a composite beam module built in 45

46. Verification – Other software46

47. 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

48. Questions and Discussion