Power Generation Engineering And Services Company

Modeling of Composite Steel FloorsUsing GT STRUDL

Department of Civil Engineering Structural Design Central Group

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) PGESCo stands for (Power Generation Engineering Services Company)

2) Established in 1994

3) Located in Cairo, Egypt

4) Focused on EPCM (Engineering, Procurement, Construction and Management)

5) Produced more than 20,000MW

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Rendered View of a Combined Cycle Power Plant

CTG / STG

CTG ( Combustion Turbine Generator)/ STG (Steam turbine Generator)

Structures in power plants where composite slabs are used:

1) Steam Turbine Generator “STG” Building.

2) Combustion Turbine Generator “CTG” Building.

3) Control building.

4) Electrical building.

5) Circulating Water Electrical Building “CWEB”.

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Control building during construction:

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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.

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1- Full model2- Springs were used to replace beams to control deflection3- 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 direction6- Sequential analysis7- Rigid element between beam & slab8- Master & Slave9- Eccentricity between the centerline of plate and steel beams.

Models used to simulate Composite Steel Floor

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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.

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Simple structure:

• 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.

WT5

x11

WT5

x11

WT5x11

W10

x33

W10

x33

W10

x33

W24x55

W24x55

W21x44

W21x44

W21x44

W21x44

W21x44

W21x44

XXXX

XXXX

6.000 M

XXXX

10.00 M

XXXX

10.00 M

(19.686 Ft)

(32.81 Ft)

(32.81 Ft)

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Manual Calculation:XXXXXXXX

10.00 M

XXXX

XXXX

10.00 M

XXXXXXXX

5 EQ. SPACS.

W21X44

W21X44W21X44W21X44W21X44

W21X44

W24X55

W24X55

Filler beam

Girder

Column

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Manual Calculation:

• For Concrete Slab:-

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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)

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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)

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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.

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Bending in filler beams & girders uniformly loaded

Moment ZLoad: 1M-MTON

VAL 16.02LOC 9.000E-01

VAL 12.79LOC 9.500E-01

VAL 11.16LOC 1.000E+00

VAL 11.16LOC 1.000E+00

VAL 12.65LOC 6.500E-01

VAL 16.02LOC 9.000E-01

VAL 35.38LOC 5.000E-02

VAL 35.38LOC 5.000E-02

1-Full model used:

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• Bending in slab (Neg. mom.= 0.0)• One way action does NOT exist

1-Full model used:

-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

MYY MIDLoad 1M-METN/M

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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)

X

Y

Z

XX104

XX170

Y -38.94

XX168

Y -24.06

XX172

Y -48.31

XX174

Y -48.31

XX176

Y -38.94

XX178

Y -24.06Displacements at JointsLoad 1MM

1-Full model used:

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• 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.

1-Full model used:

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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

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• 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.

2-Springs used to control deflection

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• Delete elements at the corners to prevent the slab from being directly supported by the columns

3-Delete plates at corners only

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• Bending moment in the steel beam

Moment ZLoad: 1M-MTON

VAL 16.05

VAL 12.67

VAL 10.87

VAL 10.87

VAL 12.65

VAL 16.02

VAL 36.01

VAL 35.98

3-Delete plates at corners only

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• 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

3-Delete plates at corners only

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•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

4- Delete plate elements on the girders

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•Bending moment in the steel beams

Moment ZLoad: 1M-MTON

VAL 15.36

VAL 12.32

VAL 10.81

VAL 10.81

VAL 12.30

VAL 15.30

VAL 31.53

VAL 31.53

4- Delete plate elements on the girders

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•Bending moment in the slab

-0.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.4

4

XX

MYY MIDLoad 1M-METN/M

4- Delete plate elements on the girders

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•Vertical displacement

Displacements at JointsLoad 1MM

XX168

Y -23.03

XX170

Y -36.41

XX172

Y -44.81

XX174

Y -44.81

XX176

Y -36.41

XX178

Y -23.03

4- Delete plate elements on the girders

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• 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

5- Element has one direction of distribution

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• 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.

6-Sequential analysis

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• This modeling technique did not produce a good representation of the bending moment which can not be explained.

Moment ZLoad: 1M-MTONON: Z

7- Rigid elements between beam and slab

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• This also did not produce a good representation of the bending moment.

Moment ZLoad: 1M-MTONON: Z

8- Use of Master and Slave Joints

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• Eccentric between the steel member and the concrete plate elements

9- Eccentricity

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• Weird Bending moment diagram which had no explanation.

100

XX

9- Eccentricity

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• 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

MYY MIDLoad 1M-METN/M

9- Eccentricity

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1-Full model2-Springs were used to replace beams to control deflection3-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 direction6- Sequential analysis7- Rigid element between beam & slab8- Master & Slave9-Eccentricity between the centerline of plate and steel beams.

Models used to simulate hand calc till now

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•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

What to do next???

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Variation in Thickness for the slab

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Variation in Thickness for the slab

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Variation in E for concrete

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Variation in E for concrete

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Variation in E for concrete

VAL 23.50

VAL 57.18

Moment ZLoad: 1M-MTON•Bending moment

in the steel beam

Case = 0.25% E

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•Bending moment in the slab

Case= 0.25% E

Variation in E for concrete

-0.32

-0.30

-0.24

-0.18

-0.12

-0.06

0.00

0.06

0.12

0.18

0.24

0.30

0.35

-0.32

-0.30

-0.24

-0.18

-0.12

-0.06

0.00

0.06

0.12

0.18

0.24

0.30

0.35

-0.32

-0.30

-0.24

-0.18

-0.12

-0.06

0.00

0.06

0.12

0.18

0.24

0.30

0.35

MYY MIDLoad 1M-METN/M

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Variation in E for concrete

X

Y

Z

Displacements at JointsLoad 2MM

XX104

Z -0.03885

XX101

Z -0.03885

•Lateral difflection in Z direction (Braced Dir.)

( Z -0.00152 in)

( Z -0.00152 in)

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•Lateral deflection in X direction (Moment frame dir.)

Variation in E for concrete

X

Y

Z

XX101

X -5.884

XX102

X -5.884

Displacements at JointsLoad 3MM

( X -0.232 in)

( X -0.232 in)

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Verification – Other Software

Comparing results to those obtained by using another software an other program with a composite beam module built in

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Verification – Other software

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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.

Questions and Discussion