Week 11 Challenge

Calculate the temperature load for the RC bridge with M40 grade to be constructed in Delhi.

• The Span of the bridge is 9 m.
• The Box girder dimension is 1500 x 1500 with a web thickness of 300mm.
• The diameter of the circular pier is 2.5m
• The width of Deck slab is 7m and width of pier cap is 6m.
• The Thickness of Deck slab is 550mm.

Calculate the temperature load for the RC bridge with M40 grade to be constructed in Delhi.

• The Span of the bridge is 9 m.
• The Box girder dimension is 1500 x 1500 with a web thickness of 300mm.
• The diameter of the circular pier is 2.5m
• The width of Deck slab is 7m and width of pier cap is 6m.
• The Thickness of Deck slab is 550mm.

1.AIM: Calculate the Temperature Loads as per IS 875-5 and apply the same on given bridge which is located in Delhi. The Bridge shall be model in Staad.pro as per given data and apply the calculated loads to obtain required results.

1.1 Given Data:

Span of the Bridge = 9 m.

Type of super structure = RCC Box girder

Box size = 1.5 m X 1.5m.

Pier type = Circular with 2.5 m dia

Width of deck slab = 7 m

Thickness of deck slab=0.550 m

Width of pier cap = 6 m

Thickness of Pier cap = 1.1 m

Grade of Concrete (F_ck) = 40 N/mm^2.

2.Load Calculation: -

2.2 Temperature Load: The load effects are due to temperature resistant.

The effective of bridge temperature is the temperature for a location of the bridge which can be estimate from Isotherm of shade air temperature. The Temperature Loads can be calculated on the basis of IS 875-5

Maximum Temperature of Delhi=52⁰ C

Minimum Temperature of Delhi =6⁰ C

Effective Temp difference (52-6)/2= 23

Temperature diff is more than 20⁰ C

Avg Temp = 23+10=33⁰C

Temperature stress = αxΔTxE

α= Coefficient thermal Expansion = 12.0X10^-6/⁰C.(IRC 6 clause 215.4)

ΔT= Effective temperature difference=33 ⁰C.

E= Modulus of Elasticity of concrete=5000SQRT(f _ck)

Stress due to temperature =

12.0X10^-6/⁰CX33X 5000XSQRT(40)=12.52 N/mm²

Maximum permissible stress=2/3X0.7XSQRT(40)=2.95 N/mm²

Hence the stress is restricted to 3 N/mm²

Positive temperature difference

Temperature at Top= 52⁰ C

Temperature at Bottom= (2.1/17.8)X52=6.13⁰C

3.Procedure: -

(i) Create a model as per given data in Staad.pro.

(ii) Apply the Temperature Load.

(iii) Analysis.

(iv) Results.

3.1 Create a model in Staad.pro.

Fig 1

Create a node and make a 2 D box of 1.5 m X1.5 m through

translation repeat in X,Y and Z direction as shown in fig 1.

Fig 2.

Make a 3D box length of 9m through translation repeat in X- direction with adding beams as shown in the Fig:2.

Fig3

Messing of 0.5mX0.5m for bottom slab in both x and z-direction and assign of 0.3 m thick plate as per given data.

Fig-4

Messing of wall 0.5mX0.5m for the box with help of beam break and add nodes and assign plate thick 0.3 m with help of thickness of properties.

3D view of both wall and bottom slab of 1.5 mX1.5m (Fig-5).

Make 1.5mx1.5m box cell with messing plate of 0.3 m thick and make another two box cells at Centre-to-centre 2m (Fig-6)

3D-view of triple box as shown fig-7

Create a combine slab of 0.55 m thick over 3 no of box in 3D view

Fig-8.

3D view of super structure Fig-9.

Make end beams for boxes to stiffened the box both ends to distribute the box loads through end beam to bearing pedestal to the pier Cap (Fig-10).

3 D view of end beam with bearing pedestals as below (Fig-11).

Create a pier with circular 2.5 m and pier cap of 6 m length height 1.1m and 3 m wide.

Pier, pier cap, pedestal with end beam as above (Fig-12)

3D view Pier, pier cap, pedestal with end beam as below (Fig-13)

Assign of fixed support for the pier as shown in Fig-14.

3D-view of bridge (Fig-15).

3.2 Some checks to be done before apply of the Load

Check for duplicate node, No duplicate node found

No orphan nodes found.

No duplicate beam found.

No zero-length member found.

3.3 Apply the Temperature Load.

Add and apply temperature Load as calculated above and temperature for axial elongation 52⁰C, Temperature differential from top to bottom 52⁰C.

3.4 Analysis

Analysis of the bridge through Analysis and Design

Perform analysis to be add before run analysis.

No errors and No warnings are found as shown above.

Results: -

Maximum Bending Moment at pier bottom=1.58X10³ KN-m.

Maximum Reaction =58.445 KN.

Maximum Bending Moment at pier cap=126.707KN-m.

Maximum Bending Moment at Bearing pedestals = 119.149.

Maximum Shear Force in the B/pedestal= 77.899 KN.

Maximum BM at bottom slab of Box=67.2 KN-m/m

Maximum BM at bottom slab of Box=54.5 KN-m/m

Maximum BM of deck slab = 146 KN-m/m