Learning from Earthquakes - Earthquake Engineering for Structural Design - page 84

Figure 3.9 . Collapse of corner buildings; (a) Bucharest RC building; (b) Kobe steel
building (courtesy of Fischinger et al, 1998)

- Discontinuities of mass, stiffness and strength in elevation give rise to
local damages very difficult to avoid. Soft stories create hazardous
conditions. During the Kocaeli (Turkey) earthquake many buildings
having “pilotis structures” (free frames at the first level and rigid walls
above) collapsed (Fig. 3.11).
The conformation of structural element refers to the lessons to improve the
local behavior of the structure.
- The weakest points in building structures are typically the

connectionsamong structural elements. Designing adequate connections is
normally more difficult than providing adequate strength and ductility to
structural members. Many structural failures during 1994 Northridge and
1995 Kobe earthquakes have been caused by inadequate detailing of
connections (Fig. 3.12).

- Overall collapse may occur when local strength and ductility of structural

elements (columns, beams and joints) are insufficient. For steel structures,
the most known case is the Pino Suarez building, collapsed during the
1985 Mexico City earthquake, due to lack of ductility of trusses and
columns (Fig. 3.13) (Gioncu and Mazzolani, 2002).

- Structural redundancy providing redistribution of forces can prevent

collapse when individual members deteriorate during an earthquake. The
complete failure of an element can be produced by local buckling or by
fracture (in case of steel elements) or by crushing (in case of reinforced