Seismic assessment of non-engineered reinforced concrete columns in low to moderate seismic regions

In under-developed rural areas of Asia, a larger portion of the housing facilities is constructed without any intervention of engineer(s). Such non-engineered reinforced concrete (NRC) structures constitute a major portion of the housing in rural areas. The lateral load resisting columns, in these structures, are constructed by locals using poor quality concrete having compressive strength as low as of 5 MPa and the amount of reinforcement may be lower than 1%. In the case of any earthquake activity, the higher population density and vulnerability of NRC structures would result in the loss of precious human life and economic turmoil. This paper investigates the reversed cyclic behavior of such an NRC column in low to moderate seismic regions of Thailand. Four columns, representative of existing NRC structures, were tested under reversed cyclic loading. Two axial load levels were used to study the effect of axial load on the ultimate lateral load and displacement capacity of the NRC column specimens. To investigate the influence of bar type, 9 mm round rebars and 12 mm deformed bars were used to fabricate the specimens. The maximum lateral drift was found to be extremely low (i.e.,1.75%) under a higher axial load level. The type of reinforcement found to influence the extent of damage in these columns. Finally, a newly developed numerical model; to incorporate the axial-flexure-shear phenomenon, is used to simulate the reversed cyclic behavior of the tested specimen and found to be successful in replicating the observed reversed cyclic behavior.