Title: Structural Serviceability Under Dynamic Loading
Author(s): A. Farah
Publication: Symposium Paper
Appears on pages(s): 419-434
Keywords: concrete slabs; dynamic loads; floors; high-rise
buildings; human factors engineering; models; reinforced concrete;
The serviceability of structures such as floors and tall buidlings to dynamic loading is assessed in terms of absorbed power which is the rate of energy dissipation through a standard biomechanical model simulating the human user of the structure. Design formulae and curves were developed to assist the engineer in assessing structural serviceability of existing structures and that of structures at the design stageforperiodic and transient vibration. Abstract: Some structures vibrate perceptibly when subjected to service dynamic loads. The serviceability of such structures which include floors and tall buildings is dependent upon the imposed excitations and the characteristics of the structure such as frequency, stiffness and damping. However, structural design practice has been dominated by deflection requirements limiting the live load deflection or the span to depth ratio of the main girders. These restrictions represent essentially static criteria and thus are not adequate to provide for proper serviceability under dynamic loading. It is to be noted that the loads producing disagreable vibrations are usually different in type and intensity from the design live loads and are only a small proportion of such loads. The objective of this paper is to present 'objective' criteria based on the response of the human user, for evaluating the structural serviceability of floors and tall buildings relative to vibrations in the vertical and fore-and-aft modes. These criteria, developed to deal with periodic and transient vibrations, are expressed in terms of the human response and the major characteristics of the structure. Based on the above criteria, design curves in terms of stiffness, frequency, mass and damping were produced to assist the engineer in arriving at a design satisfying both the strength and serviceability requirements. Furthermore, the serviceability of forty floors and tall buildings was assessed using these criteria. The loading on the floors included impact loads, excitations due to human walking and high-heel impact and the forces resulting from other human activity such as dancing which may produce resonance. The results indicate excellent agreement with the reported sub-jective ratings.