Heavy damage to the columns in earthquakes occurs due to the insufficient shear reinforcement.The shear capacity of the columns should be at least greater than the plastic joints and should be kept at a level that can carry the shear forces.According to the regulations foreseen for ductile columns, transverse reinforcement should be placed in accordance with the stirrup spacing and quantity.
The ductility level of the structure, which was slightly and moderately damaged during the earthquake, can be accepted as normal.Between the columns and beams in the appropriate parts of the building, reinforced concrete curtain can be made from the foundation to the roof.Curtains can be of normal or high ductility level, without or with gaps.
While tensile cracks occur in the concrete due to the large bending moment in the delicate columns, depending on the direction affected by the earthquake, crushing occurs in the concrete on the other side.With the change of direction of the earthquake, crushing occurs in the part withtensile cracks.On the other side, concrete is poured with the effect of pulling in the part where the crushing is.The shell part outside the area enclosed by the reinforcement is poured.If stirrup tightening is not done in the column, the damage of theconcrete passes to the inner part surrounded by the reinforcement.
L = Column size, M = Column bending moment, T = Column shear moment, h = Column Width. If stirrups are tightened in delicate columns, there will not be much cracking in the interior.If the bending cracks are widened in the columns, longitudinal reinforcement flows in that area.If the concrete is crushed and the reinforcement is buckled at a later stage, there is severe damage.If the column concrete is damaged excessively, the column becomes unable to bear load.All column reinforcement is buckled and stirrups are opened.Due to theseverely damaged columns, the structure becomes severely damaged, beyond repair.
If the shear force carrying capacity is insufficient in the column, shear cracks inclined at approximately 45 degrees occur in the column.Oblique shear cracks in columns cause brittle fractures due to insufficient stirrups.If the shear cracks are enlarged in the column, the column is severely damaged.If the column longitudinal reinforcement is added in the same place and there is not enough adherence between the concrete and the reinforcement, the concrete shell cracks and falls.The desired capacity in the column will not be reached before the reinforcement flows due to the lack of adherence.Due to the addition of column longitudinal reinforcements in the same place, full adherence cannot be achieved with concrete that cannot enter between the reinforcement.
If the axial load of the column is excessive, earthquake pressure break occurs in the column with more than 50% of the axial load carrying capacity.Pressure rupture in the column becomes brittle and sudden.Pressure rupture in the column, ( before reaching the yield limit of longitudinal reinforcement)occurs as the concrete is crushed and cracked.This type of damage is also seen in columns with low concrete strength.The first symptoms are vertical cracks outside the column and buckling of the reinforcement.
Torsional damage in columns is caused by the torsion moment effect.While diagonal cracks and spills occur in concrete on one side of the column, pressure ruptures and crushing occur diagonally on the other side.In places where there is crushing in the concrete with the effect of the earthquake, the impact of the load, the concrete is broken and poured.
Short column damage is a type of shear fracture.In case the column length is shorter than the length in the project,column stiffness increases in case of strip window gaps left on the partition wall or if elements such as partition wall lintel prevent horizontal deformation of the column.Cutting force occurs more than specified in the calculation,the oblique tensile stresses caused by the shear force cause the column to break with shear fracture, since the shear capacity of the short column is lower than the bending moment capacity.Partition walls that do not continue at the height of the column within the frame, ornamental beams placed close to the upper part of the column on the ground floor also form short columns.
Devran Bilkay
Hello, my name is Devran Bilkay. I live in Turkey. I am a Civil Engineering 4th grade student. Engineering, Earthquake engineering, Structural engineering and Architectural design are my areas of interest in engineering.
LinkedIn: Devran Bilkay