The permissible flexural tensile stress in insitu concrete at contact surface with prestressed element, as prescribed in British code BS: 8110 varies from 3.2 to 5.0n/mm² corresponding to various grades of concrete.

As early as in 1960, Sarkar based on a rigorous computational analysis have reported variations of cost of bridge deck in relation to span and number of longitudinal girders in a tee girder bridge and although cost was more or less spans up to 15m cost increased with increasing number of girders for spans in range of 15 to 35m.

The live load deflection is always estimated using composite properties if precast beam is propped during construction and deflections due to dead weight of in situ concrete is also computed on basis of composite sections.

The ultimate shear resistance is expressed as v_u = (?lb/s) = (1.2x2487x105x80/350x30x95) = 24000n = 24kn, ? = 1.2n/mm².

The horizontal shear force at interface of precast and insitu components due to design ultimate loads is total compression from that part of compression zone above interface calculated from ultimate bending moment.

The dead weight of deck can be considerably reduced by using voids or light weight longitudinal cores in space between precast prestressed units and this light weight concrete for cast in situ slab results in reduced dead loads, leading to economy in overall costs.

The stresses developed in prestressed and cast insitu concrete are computed using simple bending equations until stage of cracking and if precast prestressed unit is unpropped during placing of insitu concrete, stresses that develop in precast unit are sum of stresses due to self weight of members.

For computing live load stresses, effect of different moduli between cast in situ and precast unit is considerable by using modular ratio of precast insitu concrete for calculating area, centroid, second moment of area and second modulus of equivalent composite sections.

The coupling units are used in prestressing steel for coupling units used for joining of high tensile wires should have an ultimate strength of not less than individual strengths of wires or bars being joined and welding is not permitted for joining of high tensile wires or bars.

Portals are slightly more expensive than continuous beams of unequal spans and however for very long spans especially in deep ravines, reinforced concrete arched bridges are more economical and concrete arches are seldom prestressed because prestressing adds very little to natural advantage of thrust in arch design.