Abstract:
Shear wall, commonly used to provide lateral stiffness of buildings, and is an
important element for seismic resistance of a stmcture. Shear walls are frequently
pierced for doors, windows al)d corridor openings. Also provision of parking at
basement or ground level may require opening to be kept at the base of a shear wall.
As the entire lateral load acting in a shear wall is transmitted to the ground through
the base, it is the most critical section of a shear wall. So openings at that level will
affect its overall stiffness as compared to shear wall without opening. [n this research
work, concentration is given to establish the range of base opening that may be
allowed without significantly affecting the strength and stiffness of a structural wall.
The behavior of both planar and box type shear wall (core wall) with varying
percentages of base opening have been studied.
With the above objective, finite element package ANSYS (2000) has been used for
modeling the shear wall and study its behavior in tenns of stress pattem and stiffness
variation due to incorporation of opening at base. The behavior of shear wall for
different opening width have been studied and compared to that of a shear wall
without opening. Three parametric ratios such as deflection ratio, maximum shear
stress ratio and maximum flexural stress ratio have been studied. The ratios are
calculated as the ratio of corresponding values of a shear wall with and without base
opening. A set of non-dimensional graphs have been prepared featuring. important
parameters which will guide the designer to choose appropriate opening width
without hampering the lateral stiffness significantly. An investigation is also
perfonned to show how the degradation of stiffness of shear wall with base opening
can be compensated using additional portion of the shear wall.
It is observed that these three parametric ratios increase with the increase of
percentage of base opening. However, the rate of increase of these ratios has been
found to be relatively low up to 60% base opening. Beyond 60% opening, these ratios
increase rapidly, meaning strength and stiffness degradations are excessive beyond
this limit. It is also observed that, with the introduction of compensating elements, it
is feasible to fully compensate the deflection and flexural stress ratios and also bring
about significant improvement in the shear stress ratio. Based on the findings of the
study, it has been recommended that in high-rise construction a provision of base
opening up to 50% of the length of the wall may be considered as a feasible option.
