Know all about how Architectural features affect buildings during Earthquakes?

Architectural Features

A desire to create an aesthetic and functionally efficient structure drives architects to conceive wonderful and imaginative structures. Sometimes the shape of the building catches the eye of the visitor, sometimes the structural system appeals, and in other occasions, both shape and structural system work together to make the structure a marvel. However, each of these choices of shapes and structure has a significant bearing on the performance of the building during strong earthquakes. The wide range of structural damages observed during past earthquakes across the world is very educative in identifying structural configurations that are desirable versus those which must be avoided.

Size of Buildings

In tall buildings with large height-to-base size ratio, the horizontal movement of the floors during ground shaking is large. In short but very long buildings, the damaging effects during earthquake shaking are many. And, in buildings with large plan area like warehouses, the horizontal seismic forces can be excessive to be carried by columns and walls.

Horizontal Layout of Buildings

In general, buildings with simple geometry in the plan have performed well during strong earthquakes. Buildings with re-entrant corners, like those U, V, Hand + shaped in plan, have sustained significant damage. Many times, the bad effects of these interior corners in the plan of buildings are avoided by making the buildings in two parts. For example, an L-shaped plan can be broken up into two rectangular plan shapes using a separation joint at the junction. Often, the plan is simple, but the columns/walls are not equally distributed in the plan. Buildings with such features tend to twist during earthquake shaking.

Vertical Layout of Buildings

The earthquake forces developed at different floor levels in a building need to be brought down along the height to the ground by the shortest path; any deviation or discontinuity in this load transfer path results in poor performance of the building. Buildings with vertical setbacks (like the hotel buildings with a few stories wider than the rest) cause a sudden jump in earthquake forces at the level of discontinuity. Buildings that have fewer columns or walls in a particular story or with the unusually tall story, tend to damage or collapse which is initiated in that story. Many buildings with an open ground story intended for parking collapsed or were severely damaged in Gujarat during the 2001 Bhuj Earthquake. Buildings on the sloppy ground have unequal height columns along the slope, which causes ill effects like twisting and damage in shorter columns. Buildings with columns that hang or float on beams at an intermediate story and do not go all the way to the foundation have discontinuities in the load transfer path. Some buildings have reinforced concrete walls to carry the earthquake loads to the foundation. Buildings, in which these walls do not go all the way to the ground but stop at an upper level, are liable to get severely damaged during earthquakes.

Adjacency of Buildings

When two buildings are too close to each other, they may pound on each other during strong shaking. With an increase in building height, this collision can be a greater problem. When building heights do not match, the roof of the shorter building may pound at the mid-height of the column of the taller one; this can be very dangerous.

Building Design and Codes

Looking ahead, of course, one will continue to make buildings interesting rather than monotonous. However, this need not be done at the cost of poor behavior and earthquake safety of buildings. Architectural features that are detrimental to the earthquake response of buildings should be avoided. If not, they must be minimized. When irregular features are included in buildings, a considerably higher level of engineering effort is required in the structural design and yet the building may not be as good as one with simple architectural features. Decisions made at the planning stage on building configuration are more important or are known to have made a greater difference than the accurate determination of code specified design forces.