Concrete Technology and Design of Concrete Structures
In prestressed concrete

both forces of tension and compres-sion as well as lever arm change
forces of tension and compressions remain unchanged but lever arm changes with the moment
forces of tension and compression change but lever arm remains unchanged
both forces of tension and compres-sion as well as lever arm remain unchanged

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Concrete Technology and Design of Concrete Structures
If the depth of neutral axis for a singly reinforced rectangular section is represented by kd in working stress design, then the value of k for balanced section

depends on aCbC only
is independant of both ast and acbc where d is the effective depth, ast is per-missible stress in steel in tension and ocbc is permissible stress in concrete in bending compression.
depends on both crst and acbc
depends on as, only

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Concrete Technology and Design of Concrete Structures
According to IS : 456-1978, the fiexural strength of concrete is

inversely proportional to compressive strength
directly proportional to compressive strength
inversely proportional to square root of compressive strength
directly proportional to square root of compressive strength

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