09-25-2010, 05:26 PM
Hi Paladin,
failures during earthquake could happen at column, beam, wall, and beam-column joint. in columns damage, the causes are mainly due to flexural and shear failures at column ends. flexural failure is affected by the level of axial force in column, particularly at the corner exterior columns. the column was experiencing extremely high compression force due to overturning moment of structure, which was leading to flexural compression failure followed by the loss of gravity load carrying capacity. compression failures of shear and flexural could take place near the column ends.
the shear failure at column is propagated because the tensile stress carried by the concrete before onset of significant shear cracking cannot be resisted by shear reinforcement once shear cracks open which then leading to diagonal tension failure.
buckling (flex outward) failure in column is commonly caused by deficiency of ties and excessive compression force. it actually can be occurred at any place of column span where deficiency of ties takes place. earthquake reconnaissance reports show that buckling failures appear at near column ends as well.
for me, it is best to place point of plastic hinge of member at point where the arrangement of longitudinal and shear reinforcements are not identical to get accurately seismic performance result. nevertheless, using member ends (or near) as plastic hinge points are accurately enough based on many modelling studies that referred to experimental testing.
cheers
failures during earthquake could happen at column, beam, wall, and beam-column joint. in columns damage, the causes are mainly due to flexural and shear failures at column ends. flexural failure is affected by the level of axial force in column, particularly at the corner exterior columns. the column was experiencing extremely high compression force due to overturning moment of structure, which was leading to flexural compression failure followed by the loss of gravity load carrying capacity. compression failures of shear and flexural could take place near the column ends.
the shear failure at column is propagated because the tensile stress carried by the concrete before onset of significant shear cracking cannot be resisted by shear reinforcement once shear cracks open which then leading to diagonal tension failure.
buckling (flex outward) failure in column is commonly caused by deficiency of ties and excessive compression force. it actually can be occurred at any place of column span where deficiency of ties takes place. earthquake reconnaissance reports show that buckling failures appear at near column ends as well.
for me, it is best to place point of plastic hinge of member at point where the arrangement of longitudinal and shear reinforcements are not identical to get accurately seismic performance result. nevertheless, using member ends (or near) as plastic hinge points are accurately enough based on many modelling studies that referred to experimental testing.
cheers