Abstract:
Axial shortening of columns in reinforced concrete buildings is a phenomenon that was
commenced from the day of commencement of concrete building construction. However,
this seems to start creating problems only before two or three decades ago. The reason for
this can be argued as the capability of older concrete buildings to withstand the effects
caused by axial deformation of columns. This means the ability of bearing the effects of
axial shortening of columns in modem concrete buildings is lower than that of former
concrete buildings. Reasons for this can be suggested in a glance as the sudden reduction
taken place in member dimensions, specially in columns, in newly constructed concrete
buildings, due to the adoption of high strength concrete in them. Creep, shrinkage and
elastic stresses were identified as the major factors that contributes axial shortening of
reinforced concrete columns. Dimensions of member, properties of material from which
the member is cast, included reinforcement percentage and the surrounding environment
condition can be mentioned as the main factors that influence the amount of creep and
shrinkage. Methods are available from past literature to estimate possible axial
deformation of reinforced concrete columns, taking all above mentioned influencing
factors into account. This report includes recommendations and guidelines, which can be
directly used to specify approximate shortening values those are possible to occur in
different buildings. Special consideration is given throughout the report, to the effect of
relative humidity on axial shortening of columns
