Deformations in Service of Reinforced Concrete Columns


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Title: Deformations in Service of Reinforced Concrete Columns

Author(s): R.N. Swamy and P. Arumugasaamy

Publication: Special Publication

Volume: 55


Appears on pages(s): 375-408

Keywords: age; (supports); deformation; field tests; load transfer; loads forces); multistory buildings; reinforced concrete; reinforcing steels; static loads; strains; stresses; temperature

Date: 8/1/1978

The long-term movements of in-situ reinforced concrete columns in two structures are reported through the construction stage to occupancy and subsequently in service. The columns were extensively instrumented to measure strains, temperature and moisture changes; in addition, a stress meter was incorporated in the second structure at the base of an internal column to relate the field movements and their effects to the load actually carried by the column. The results show that the inelastic movements in concrete cause a gradual load transfer to the steel reinforcement. In one structure steel stresses in excess of the permissible design values were noted. The assumed design dead load components of the working loads were realized in the lower columns of the structure but not in the upper storeys. After nearly five years in service, the concrete in the columns of the second structure were found to carry loads varying from 50% to 80% of the measured load carried by the columns. It is shown that a major proportion of the loads carried by the columns result from dead loads and that only about 10%-20% of the total design loads constitute imposed loads.