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buildings with different concrete strength and steel yield. This comprised keeping the member size
constant and changing the material properties. Moreover, the higher the strength of concrete, the
steeper was the third segment of the model. The above features of that study significantly affected the
results obtained, hence, the conclusions drawn. By keeping the section dimensions and ratio of
reinforcement constant, many of the structures ended up with response typical of 'strength design' as
opposed to 'ductility design', as well as sections being over-reinforced. The consequence is to decrease
the ductility of structures using high yield steel. The feature of using severely dipping descending
branches for concrete lead to the structures behaving in a highly non-ductile fashion. It was noted in
that study that high strength structures exhibit very low levels of ductility and behaviour factors
nearing unity. In common with the current study though, the range of concrete and steel for viable
seismic design was identified. Therefore, the above analytical study represents the expected behaviour
of high strength concrete structures if the confined concrete behaviour is still non-ductile and the steel
stress ratio (ultimate-to-yield) is near unity. Higher levels of ductility would have been obtained
though, if the 'over-reinforced' sections were re-designed.
SCOPE OF WORK ON ANALYTICAL ASSESSMENT
The main objective of this paper is to summarize investigations of the seismic performance of high
nse, high strength, concrete buildings designed according to existing code provisions and undertaken
by the primary author and his co-researchers (Kateinas [1997], Laogan and Elnashai [1999],
Goodfellow [1998] and Elnashai and Goodfellow [2002]) and to employ the conclusions of the
experimental study in structural-level investigations.
Ten, 24-storey structures with the same overall dimension
and geometry, sized according to two equivalence criteria
(Laogan and Elnashai, 1999), were analyzed elastically and
designed according to the provisions of the Uniform Building
Code (1994). The general layout of the frame-wall structures
is shown in Figure 1. The material strength characteristics of
the structures are given in Table 3. Every effort was made to
have realistically designed and detailed structures. A
comparative cost analysis of these structures was performed
to determine their relative cost-effectiveness. Inelastic
analyses were then performed using the program ADAPTIC
(Izzuddin and Elnashai, 1989). Two sets of inelastic analyses
were undertaken: first a static pushover analysis of the
structure was performed, followed by a set of dynamic
analyses using three artificial accelerograms, scaled to the
design ground acceleration (PGA) and twice the design PGA.
Moreover, dynamic analyses up to collapse, for purposes of FIGURE 1
(R ° r q) ' ^ 24-STORY FRAME-WALL
MODEL STRUCTURE