This document discusses voided deck slabs and cellular deck slabs. It provides an overview of different types of voided slabs based on span range and material. It also describes analyzing voided slabs using orthotropic plate theory, grillage analogy, or 3D modeling. The document outlines manual analysis steps taken and challenges faced in modeling a sample voided slab in Midas Civil software. It includes diagrams of the sample voided slab plan and cross-section. A schedule outlines the status of analyzing voided and cellular deck slabs using manual and software methods.

1. Analysis of Voided Deck Slab &
Cellular Deck Slab

2. • . 11050
Plan of Voided Slab
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3. Voided Slab Model in Auto-Cadd

4. Voided Slab Deck – Intro.
• Criteria for selection of voided slabs are different in various
Textbook:
Description Span
Range in
meters
Span to
Depth
Ratio
RCC
/PSC
Text Book Remarks
Hollow Slab 25 to 35 20 to 30 RCC Johnson Victor Page 232
Voided Slabs 8 to 15 RCC Bridge Superstructure by
N.RajaGopalan P.145&146
Prestressed
Voided Slab
15 to 30 PSC Bridge Superstructure by
N.RajaGopalan P.145&146
Upto a depth
of 1.2 m
Moderate
Skew Slabs
15 to 25 PSC Bridge Superstructure by
N.RajaGopalan P.145&146
By
Longitudinal
Prestessing

5. • .
Description Span
Range in
meters
Span to
Depth
Ratio
RCC
/PS
C
Text Book Remarks
Voided Slabs 8 to 15 15 RCC Bridge Superstructure by
N.RajaGopalan P.145&146
Simple
Spans
Voided Slabs 8 to 15 20 to 25 RCC Bridge Superstructure by
N.RajaGopalan P.145&146
Continuous
Spans
Prestressed
Voided Slab
8 to 15 25 to 30 PSC Bridge Superstructure by
N.RajaGopalan P.145&146
By Longitudinal
Prestessing
Voided Slab Deck – Intro.

6. Voided Slab Deck - Analysis
• It is used to decrease the overall weight by as much as 35%
when compared to a solid slab of the same capacity.
• 1. The structure shall be analyzed both for longitudinal as well
as transverse structural actions.
• 2. Where the voids conform to the dimensional requirements
an the void ratio(area of the voids to the area of the solid slab)
does not exceed 40% the superstructure may be analyzed as a
solid slab. However, for the purpose of detailing, the presence
of void shall be taken into account. The detailing of
reinforcement should take care to see that the voided portion
is prevented from cracking from inside.
• As per IRC:SP:64-2005 “Guidelines for the analysis and
Design of Cast-in-Place Voided Slab Super Structure”

7. Voided Slab Deck - Analysis
• 3. If the void ratio exceeds 40%, the super structure may be
analyzed by any one of the following methods:
• a. Orthotropic plate method
• b. Grillage Analogy
• c. Three-dimensional continuum
Or By using a Software like
• mIDAS Civil
• 4. If the dimension parameters mentioned under article are not
satisfied the structure cannot be designated as voided slab and the
same has to be separately considered and appropriate method of
analysis may be adopted.

8. Position of Void in Voided Slab
• Void Centre should coincide with the Neutral axis where the
stresses are zero.
• Void centre can be eccentric with the Neutral axis provided
that the reinforcement above and below the void should bear
the loads acting on it and resisting the void area.

9. Manual Analysis
• Assumption:- As a Crude Method I have started Analysis of the
Voided Slab taking I section and Exact section, The stresses at
every 25 metres obtained by above two methods are:-
Y Stress
-400 -268471.012
-375 -251691.573
-350 -234912.135
-325 -218132.697
-300 -201353.259
-275 -184573.821
-250 -167794.382
-225 -151014.944
Void -200 -134235.506
Void -175 -117456.068
Void -150 -100676.629
Void -125 -83897.191
Void -100 -67117.753
Void -75 -50338.315
Void -50 -33558.876
Void -25 -16779.438
Void 0 0.000
Void 25 16779.438
Void 50 33558.876
Void 75 50338.315
Void 100 67117.753
Void 125 83897.191
Void 150 100676.629
Void 175 117456.068
Void 200 134235.506
225 151014.944
250 167794.382
275 184573.821
300 201353.259
325 218132.697
350 234912.135
375 251691.573
400 268471.012
-300000.000
-200000.000
-100000.000
0.000
100000.000
200000.000
300000.000
-400
-375
-350
-325
-300
-275
-250
-225
-200
-175
-150
-125
-100
-75
-50
-25
0
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
Stress Distribution in I Section
1
3
2

10. • .
Manual Analysis – Exact Section
Y Stress
-400 -228945.085
-375 -214636.017
-350 -200326.949
-325 -186017.881
-300 -171708.813
-275 -157399.746
-250 -143090.678
-225 -128781.610
Void -200 -114472.542
Void -175 -100163.474
Void -150 -85854.407
Void -125 -71545.339
Void -100 -57236.271
Void -75 -42927.203
Void -50 -28618.136
Void -25 -14309.068
Void 0 0.000
Void 25 14309.068
Void 50 28618.136
Void 75 42927.203
Void 100 57236.271
Void 125 71545.339
Void 150 85854.407
Void 175 100163.474
Void 200 114472.542
225 128781.610
250 143090.678
275 157399.746
300 171708.813
325 186017.881
350 200326.949
375 214636.017
400 228945.085
-300000.000
-200000.000
-100000.000
0.000
100000.000
200000.000
300000.000
-400 -350 -300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300 350 400
Stress Distribution in Exact Section

11. Plan of Voided Slab Selected
• .

12. Side View of Voided Slab in Midas Civil
• .

13. Model of the Voided Slab in Midas civil
• .

14. Present Work Status
• Presently Learning Midas-Civil Software and searching material to
learn Orthotopic plate theory and Grillage Analysis for completing
manual analysis Part.
• Problems in Midas Civil:-
• Unable to perform Analysis in Midas civil – So I contacted Midas
Civil User Support.
• I have to redo the whole structure as Guided by the support team.

15. Schedule for Project
• .
Sl.
No
Description Duration Status
1 Review of Journals 15 Days Completed
2 Selection of Topic 15 Days Completed
3 Analysis of Voided Deck Slab - Manual 45 Days In Progress
4 Analysis of Voided Deck Slab – Midas Software 45 Days In Progress
5 Analysis of Cellular Deck slab- Manual 45 Days Yet to
complete
6 Analysis of Cellular Deck slab- mIDAS 45 Days Yet to
complete
7 Comparision of Decks for Cost Optimization 45 Days Yet to
complete