The Non-Structural Components Should be Effectively Isolated from, or Properly Integrated with, the Basic Structural System
Some building components (architectural, mechanical, and electrical) can become very responsive during the earthquake shaking of the building foundation. The effects of the interaction can be grouped into two categories: first, the effect of the response of the structural system on the non-structural components; and second, the effect of the non-structural components on the response of the structural system. The more flexible the basic structural system, the worse the effects of the non-structural components will be.
1. The effect of the response of the structural system on the non-structural components is illustrated in Slides J81 and J82.
Inside
view of a light, flexible, industrial building in Coalinga, California.
This warehouse building has a 100-ft span steel moment-resisting gabled
frame which has cross-bracing in the roof but does not have longitudinal
bracing in the sidewalls.
Outside
view of the structure of Slide J81 after the 1983 Coalinga Earthquake.
While the light metal roof was intact, most of the corrugated asbestos
cement siding suffered significant damage, emphasizing the need for proper
attachment of non-structural components to the structural system.2. The effect of the non-structural components on the response of the structural system is illustrated in Slides J83-J88. Analysis of building performance during earthquakes has shown that numerous building failures result from the fact that basic structural systems are designed neglecting the structural modifications introduced by the non-structural components, particularly by the addition of infills (partitions and walls) as illustrated in the following examples.
Medical
Clinic in El Asnam, Algeria. Close-up of column failure of this new
4-story reinforced concrete building induced by the response of the
building to the 1980 El Asnam Earthquake.The building in Slide J83 exhibited severe stiffness and strength discontinuities at the first story. The corner location of a stiff stairway and a reinforced concrete shear wall contributed to the collapse of the building. Usually stairways are considered as non-structural components in spite of the fact that in most cases they are rigidly attached to the structure of the building, particularly in the case of reinforced concrete buildings. Note how the landing of the stairway is connected rigidly to the column at is mid-height converting it into a short column with a shear resistance demand twice that computed neglecting the stairway. Hence it is not surprising that the column failed in shear. Similar effects have also been observed in steel structures as illustrate in Slides J39 and J40.
Two-story
reinforced concrete building, Managua, Nicaragua, damaged in the 1972
Managua Earthquake. The slide shows a reinforced concrete column
which was part of the structural system and which failed due to its
shortening because of the effect of the masonry wall. The masonry
walls were considered as non-structural elements.
Mene
Grande Building, Caracas, Venezuela, damaged in the 1967 Caracas
Earthquake. This 16-story reinforced concrete frame building has an
H-shape in plan, and has tile walls in the four exterior ends of the
building. The design was conducted neglecting the interaction
effects of these tile walls. During the earthquake, there was not
only considerable non-structural damage to the tile walls in the lower
floors of the building, but also some spectacular failures on most of the
first story corner columns as illustrated in this slide. This
emphasizes the importance of considering the interaction effects of the so
called ‘non-structural’ components. This building was repaired
and retrofitted by adding shear walls and reinforcing the eight corner
columns.
Capri
Residencia Apartment Building, Caracas, Venezuela. This 12-story
reinforced concrete frame building with tile infilled exterior walls at
its corners had a complete open first story for a parking area. The
building suffered considerable non-structural damage during the 1967
Venezuela Earthquake. The tile walls and partitions of the lower
stories shattered and had to be removed as is illustrated in this slide.
Note the very flexible structural system used in this building.
Damage
to the Coral Apartment Building, Caracas, Venezuela, during the 1967
Venezuela Earthquake. This building has a reinforced concrete frame
as a structural system and infilled tile walls were used as exterior
walls. Note the long cantilevers. Some of the tile walls in
the second, third, and fourth stories exploded and fell down. This
explosion of the tile walls resulted also in severe damage to the beams
and columns surrounding these walls. Note the failure of the top of the third story corner column. Just beside this building was the 10-story reinforced concrete San Jose Building that completely collapsed killing 45 occupants. Near the Coral and San Jose Buildings was the Plaza 1 Apartment Building shown in Slide J78 which did not suffer any damage because of its greater lateral stiffness and strength provided by shear walls.
Plaza
1 Apartment Building, Caracas, Venezuela. This is a 12-story
reinforced concrete building with a penthouse and four levels of
underground parking. The building has split-level apartments, and
its structural system is based on the use of reinforced concrete shear
walls in both directions. These shear walls give significant
strength and stiffness to the building, allowing it to survive the 1967
Venezuela Earthquake without any structural or non-structural damage.
Copyright 1997, The Regents of the University of California.
Structural Engineering Slide Library, W. G. Godden, Editor
Set J: Earthquake Engineering, V. V. Bertero