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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
SEISMIC RESISTANCE OF VERY HIGH STRENGTH
HIGH RISE RC BUILDINGS FOR URBAN DEVELOPMENT
A.S. Elnashai 1 and B. Laogan 2
1 Mid-America Earthquake Center, Department of Civil and Environmental Engineering,
University of Illinois, Urbana, Illinois, USA
2 ATR JEngineering, Manila, Philippines
ABSTRACT
High rise buildings have increased in number and geographical spread. This in turn dictates that higher
strength materials are utilized, to keep member sizes at manageable proportions. Whereas the increase
in strength of high strength steel and concrete (steel above 500 MPa yield strength and concrete above
70 MPa compressive strength) results in commensurate increase in member capacity, this does not
necessarily follow when considering the deformational capacity of members hence structures.
Moreover, the increase in cost associated with high strength materials is not necessarily offset by the
reduction in quantities and construction time. Issues of ductility of high strength materials have been
explored by the writer and his co-workers using testing and analysis on the material, member and
structure levels for a number of years. In this paper, after a brief mention of previous studies, ten high
rise frame-wall RC buildings are designed with various combinations of steel and concrete strengths
and equivalence criteria (defined as criteria that render two different designs equivalent in terms of
their fulfilment of a design premise). These structures are then analyzed up to collapse when subjected
to a number of earthquake ground motions. The results for the different strengths and also the different
equivalence criteria are compared from a structural performance as well as from the cost of
construction points of view. It is concluded that there is a limit to the use of high strength materials
dictated by the ductility capacity, energy absorption potential and economics of construction. These
limits are quantitatively established for the class of structure investigated.
INTRODUCTION
The need for higher buildings (due to financial centres and population expansion) naturally leads to the
conclusion that high strength construction materials will be increasingly used in the future, in order
that column sizes are maintained at current dimensions and more effective use is made of floor areas,
especially in the lower stories of high rise structures. Two other performance criteria lend weight to the
necessity of the use of high strength concrete: increased wind and traffic vibration susceptibility
dictates that the modulus of elasticity of the material is as high as possible, in order to delimit small
amplitude elastic displacements. Moreover, the need for rapid construction requires early age strength
gain, a feature that may be offered readily by high strength concrete.