bridge deck slab design procedure

IRC 18: 2000This code covers the structural and design aspects  with reference to the use of prestressed concrete (post tensioned) for constructing road bridges.

The scope of this code covers the following areas:

Material properties of cement, aggregates and steel, including there permissible stresses

Minimum dimensions and section properties of various superstructure sections.

Various losses in prestress.Shear and torsion.Minimum reinforcements, end and anchorage

blocks, splay of cables, etc.

DESIGN OF POST-TENSIONED CONCRETE SLAB BRIDGE DECK (DESIGN STEPS)

LOAD AND BENDING MOMENT CALCULATIONS

Selecting material gradesAssume depth of slab, 50 mm per meter spanCalculation of dead load and dead load

bending moments; weight of slab weight of wearing coat

….contd

Calculation of live load bending moments

• Consider IRC load class• Calculate impact factor according to loading

class and span• Calculate average intensity of loading and

maximum bending moment due to live loads• Calculate design shear at support

LOAD POSITION FOR MAXIMUM BENDING MOMENT AND MAXIMUM SHEAR

EFFECTIVE WIDTH OF DISPERSION FOR IRC CLASS AA LOAD

CHECKS TO APPLIED

Check for minimum section modulusMinimum prestressing forceCheck for stresses; 1. at transfer 2. at serviceCheck for ultimate strength 1. failure by yielding of steel 2. failure by crushing of concreteCheck for ultimate shear strength

Supplementry reinforcement: 0.15 % of gross sectional area should be

provided.Design of end block: bursting tension should be computed and

according to that area of steel should be calculated.

Section of Deck Slab at Centre of Span &Longitudinal Section of Deck Slab

CONCLUSION

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