Identification of Cracks
1.
a.
ans: This failure mode occurs when the loads on the beam exceed its flexural capacity. The shear strength of the beam should be greater than its flexural strength otherwise the shear failure would occur before flexural failure.
1. Its a form of flexural failure due to earthquake stress reversal
2. During stress reversal, the upper part of the support is in compression and the lower part is in tension
b.
ans:
Beam-column joint plays an important role in the structural response of reinforced concrete structures, especially when these structures are subjected to cyclic or seismic loads.
1. It is a failure by pulling out the beam due to insufficient development of the length of the reinforcement in the joints
2. During an earthquake, the horizontal movement of the structure aggravates this condition and separates the beam from the column
c.
ans:
In framed structures, both steel and reinforced concrete, beam-column joints play a very crucial role in terms of seismic resistance. Under the effects of high lateral seismic loads, beam-column joints are subjected to high forces and moments and their behavior have a significant influence on the response of the structure.
1. Its a plastic hinge failure
2. At first, the damage occurred only in the joint area
3. Cyclic later loading and reversal of stress in the joints led to the damage
2.
a.
ans:
The development of plastic hinges at column ends accompanied by excessive storey drift in such soft storey is its typical failure mechanism. Several such building failures due to the development of a soft storey mechanism had been observed in past earthquakes.
1. It's a soft storey failure, technically plastic hinge formation
2. Due to the absence of infill Walls on the ground floor, the plastic hinge forms at the top of ground-storey columns during lateral movement
b.
ans:
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.
1. It's a pure shear failure
2. Inadequate share reinforcement forces the concrete to absorb all the shear stresses
c.
ans:
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.
1. It's a short column failure
2. An additional slab or beam connected to a column in mid-height leads to this effect
3. This leads to failure, especially if the connection is unintentional and not considered in the design