stress and strain

huangyhg

stress and strain
when a beam (concrete or steel )subjected to load
which parameter develop first
is it stress or strain or both simultaniously
they exist simultaneously and are related by young's modulus, at least in the linearly elastic region. plasticity makes for a bit of difference, but permanent set (i.e. strain) will have some amount of residual stress associated with it.
though stress and strain occur simultaneously , strain (deformation)is a fundamental physical quantity, observable and measurable, whereas stress is a concept which is only 'felt' or 'reckoned'. stress is defined as force per unit area and its presence is felt and quantified only through the measurement of strain.
stress develops first.when the load is applied stress is developed which in turn strain is developed in the tension side.
liaisoneng and trilinga are correct.  stress and strain goes hand in hand.  i.e. for steel in elastic range, e=es where e=strain, e=young's modulus and s=stress
fyi you can get, and in some cases will get, compressive strain along with tensile strain depending on how your member behave under loading.  ie. in purely compressive loading, your member will undergo compressive straining.  in positive bending (smilie face deflection) your member will undergo compressive straining at the top and tensile straining at the bottom.