Learning from Earthquakes - Earthquake Engineering for Structural Design - page 83

The structural conformation aspects refer to the lessons to improve the global
behavior of the structure, using appropriate constructional rules.
- Uncertainness on the seismic input and structural response requires a
particular emphasis on conceptual design and detailing aspects rather than
on the analysis issue.
- Well-conformed, well-detailed and well-constructed buildings have the
chance of good performance during large earthquakes, without collapse or
excessive damage, even if the analysis does not consider all the behavioral
aspects in a correct way.
- Well-conformed structure means well-coordinated architectural and
engineering aspects, which requires that the structural engineer should be
involved early in the conceptual design.
- Poor construction practice and lack of quality control can lead to severe
damage or collapse (see 1999 Kocaeli earthquake).
- Building horizontal and vertical conformations on seismic performance are
recognized to be of primary importance. Buildings having irregular in
plane shapes (in L, U or T or corner buildings) and uncontrolled setback
elevations or soft levels generally perform in a poor way. These
irregularities must be avoided or at least minimized (Fig. 3.9) .
- Buildings having no uniform distribution of resistant elements in plan have
shown a bad performance, by experiencing severe tensional effects.
- Special attention must be paid to the horizontal diaphragms (roof and floor
systems) in order to uniformly transfer the seismic forces to all vertical
resistant elements.
- Severe pounding damage can result when adjacent buildings do not have
adequate separation, giving enough space to move independently without
touching. During the Mexico City earthquake a lot of damage was
produced due to these poundings (Fig. 3.10).

- Weak columns and strong beams configuration, resulting for large span

multi-story frames, can give rise to column failure and global structural
collapse.

- Dual structures (moment-resisting frames combined with braced or infilled

frames) generally performed very well during the last earthquakes,
provided that bracings do not create some discontinuities. But in some
cases, when the infilling is not controlled by the designer, due to the
irregularity in distribution, it is preferable to use frames only.