How do you solve torsional irregularity?

Compute the average story drift at two ends of the building, then compare with the maximum story drift for that specific mode i.e. Dmax/Dav<1.2 or 1.4 for each mode. Combine all modes using the SRSS or ABS method to determine whether Torsional Irregularity or Extreme Torsional Irregularity is applicable to the model.

What is Plan irregularity?

Plan or vertical irregularity makes structures vulnerable under seismic loading. Torsional irregularity, overturning moment can rise abruptly having irregularity in a structure. Structural irregularities are important factors which decrease the seismic performance of the structures.

What is torsion earthquake?

The torsional motion of such structures during an earthquake is said to be the result of natural torsion. Another factor is the twisting of structure caused by rotational motion of the ground about a vertical axis. The present study deals with both natural and accidental torsion.

What is mass irregularity?

Mass irregularity is considered to exist where the seismic weight of any storey is more than 200 percent of that of its adjacent storey. One regular building with uniform mass is studied with 4 irregular buildings with varying masses for Base shear, Mode shapes, storey drift, story shear, Torsion moment.

What is out of plane offset irregularity?

Unlike the vertical member discontinuity irregularity of the structural system, out of plane-offset irregularity refers to the fact that the vertical members bearing horizontal force are located on another axis rather than its own axis continu- ing along the height of the structure.

What is torsional failure?

When torque applied to a machine by an electric motor is constant, a torsional fatigue failure that requires a varying torque can occur.

What are structural irregularities?

These are irregular design in plan and vertical direction, discontinuity in mass and rigidity distribution, configuration of structural elements on nonparallel axis, height differences between floors, short columns, pounding effects, etc. (Tezcan, 1998).

What is accidental torsion?

nonstructural components, uneven live load distribution, stiffness degradation of parts of the lateral. system, and varying ground motion intensity across the plan of a building, are classified as. ‘accidental torsion’ [1].

What is torsion building?

Torsion is the state of strain in a material that has been twisted by an applied torque. It will occur whenever a structural element is subject to a twisting force. Torsion develops shear stresses and is equivalent to tension and compression at right angles.

What is soft storey failure?

Soft story buildings are vulnerable to collapse in a moderate to severe earthquake in a phenomenon known as soft story collapse. A soft-story building is described as existing wood-frame buildings with soft, weak, or open-front walls and existing non-ductile concrete buildings in the ordinance.

When is a structure torsionally irregular?

Your structure is torsionally irregular if the maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drifts of the two ends of the structure.

What is torsional irregularity in civil engineering?

Torsional irregularity is one such horizontal irregularity which has to be looked upon while designing a structure. Before explaining the term torsional irregularity, one has to be acquainted with the terms drift, story drift, eccentricity and torsion.

How do you check for torsional irregularity?

Therefore the check on torsional irregularity should be based on story drift instead of displacement. If the structure is found to be torsionally irregular, it has the tendency to amplify aby accidental torsion. This is also sometimes referred to as the dynamic amplification of seismic responses.

What is the amplification factor for irregular torsion?

If the structure is found to be torsionally irregular, it has the tendency to amplify aby accidental torsion. This is also sometimes referred to as the dynamic amplification of seismic responses. To empirically account for that amplification, UBC 97 have defined an amplification factor Ax.