RCC Slab Bridge Design || Bridge Design As per IRC Codes || Part-1

Deck Slab Bridge Design || Design of Deck Slab Bridge as per IRC|| Part-1

Picture-1: Cross-section of deck slab

At first, you have to collect the Indian Standard Codes which are helpful for Bridge Design. 

Design calculation of Superstructure (Solid slab - span-10.00m)

Location...……...            Ch...…..…..At Km 

Design Data:

1. Type of Super Structure:  RCC Solid Slab(RCC M-25)

2. Type of Abutment:  RCC solid wall type (M-25)

3. Formation Level:  567.50m

4. Length Of Super Structure: 10.00m

5. Overall width of Super Structure: 8.40m

6. Clear Carriageway Width:  7.50m

7.  Thickness of wearing coat: 100mm

8. Material: Concrete: M30 and Steel: Fe415.

Deck Slab Bridge Design : 

 Manually analysis and Design of Deck Slab Bridge as per IRC codes is done here step by step.  The following steps have to follow to Design of Deck Slab Bridge as per IRC codes

1. Calculation for effective depth and effective length: 

The overall length of the bridge is 10.00m. 

Assume the width of the bearing is 400mm.

So, Clear span of the bridge=Lc(10.00m-0.40m-0.40m)=9.20m

Assume the Clear span/Overall depth ratio is 13   (from  IS 456: 2000)

Clear Span(L)/Overall Depth(D)=13

9200/D=13

Drequired=708mm

Provide Overall depth(D)=750mm

So, provide effective depth(d)=750-40(clear cover)-20(Bar dia.)/2=700mm

Calculation of effective length: 

Assume the width of the bearing is 400mm.

Clearspan of the bridge: 9.20m

Simply Supported Beam/Slab: The effective span of a member that is not built integrally with its supports shall be taken as clear span plus the effective depth of slab or beam or center to center of supports, whichever is less. (As per Clause 21.1.a: IS 456 2000:)

Effective span Length of the bridge= 

Smaller value of (a. C/C distance of bearings/support, b. Clear span length  plus effective depth)

a. 9.20m+0.20m+0.20m=9.60m (distance between C/C of support)

b. Clear span + effective depth=9.20m+0.70m= 9.90m

So, the effective span length (Leff) of the bridge will be 9.60m

Bending Moment and Shear Force for Dead Load: 

I. Maximum Bending Moment Calculation for Dead Load:

Find out the unit weight of reinforced concrete, wearing coat (asphalt), and plain cement concrete (See page-8, clause:203, IRC 6: 2017)

A. Dead Load for self weight=0.75x1.0x25 (unit in kN/m) (taking per meter width) 

     =18.75 kN/m

B. Dead load due to wearing coat=0.10x1.0x22 (unit in kN/m)

    =2.2 kN/m

So, total Dead Load=(18.75+2.2)=20.95kN/m/m-width

Picture-2: UDL for Dead Load

Dead load is uniformly distributed throughout the bridge length.

The maximum bending moment due to dead load will be at the mid-span.

So, Maximum bending moment due to dead load (as per udl load)

=WL²/8

=(UDL load (W) X effective length (Leff)^2)/8

B.M(D.L)=20.95X(9.6)^2/8

=241.344 kN.m per meter width.

II. Maximum Shear Force calculation for Dead Load:

We know, The maximum shear force will act at both support due to UDL Dead Load.

So, Reaction at support A and B, 

Ra=Rb=WLeff/2

=(20.95x9.6)/2

=100.56 kN.

You may visit my youtube channel: 

1.  Slab-Bridge-Design-In-Midas-Civil-as Per Indian Code IRC 112

More Posts: 

1. RCC Slab Bridge Analysis And Design Step-By-Step Manually || Part-1

2. Live Load Bending Moment IRC Class 70R Tracked Vehicle for Slab Bridge Design Manually || Part 2

3. Maximum Shaer Force Calculation for IRC Class 70R Tracked Vehicle || Slab Bridge Design Manually || Part 3

4. Bridge Deck Slab Design Example as per IRC || Slab Bridge Design example || LSM Method ||Part 4