Analysis of Voided Deck Slab & Cellular Deck Slab

• . 11050

Plan of Voided Slab

13675

Traffic

Direction

Voided Slab Model in Auto-Cadd

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

• .Description

Span Range in meters

Span to Depth Ratio

RCC/PSC

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.

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”

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 continuumOr 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.

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.

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 -134235.506Void -175 -117456.068Void -150 -100676.629Void -125 -83897.191Void -100 -67117.753Void -75 -50338.315Void -50 -33558.876Void -25 -16779.438Void 0 0.000Void 25 16779.438Void 50 33558.876Void 75 50338.315Void 100 67117.753Void 125 83897.191Void 150 100676.629Void 175 117456.068Void 200 134235.506

225 151014.944250 167794.382275 184573.821300 201353.259325 218132.697350 234912.135375 251691.573400 268471.012

-400

-350

-300

-250

-200

-150

-100 -50 0 50 10

015

020

025

030

035

040

0

-300000.000

-200000.000

-100000.000

0.000

100000.000

200000.000

300000.000

Stress Distribution in I Section

1

3

2

• .

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 -114472.542Void -175 -100163.474Void -150 -85854.407Void -125 -71545.339Void -100 -57236.271Void -75 -42927.203Void -50 -28618.136Void -25 -14309.068Void 0 0.000Void 25 14309.068Void 50 28618.136Void 75 42927.203Void 100 57236.271Void 125 71545.339Void 150 85854.407Void 175 100163.474Void 200 114472.542

225 128781.610250 143090.678275 157399.746300 171708.813325 186017.881350 200326.949375 214636.017400 228945.085

-400

-350

-300

-250

-200

-150

-100 -50 0 50 10

015

020

025

030

035

040

0

-300000.000

-200000.000

-100000.000

0.000

100000.000

200000.000

300000.000

Stress Distribution in Exact Section

Plan of Voided Slab Selected• .

Side View of Voided Slab in Midas Civil

• .

Model of the Voided Slab in Midas civil

• .

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.

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