Abstract
AbstractThe seismic vulnerability of old multi‐storey reinforced concrete (R.C.) buildings reinforced with substandard details is assessed as a function of interstorey drift demand imposed by the design earthquake while considering brittle termination of elastic response of the critical members of the structure due to a premature shear failure. Interstorey drift demand is related to column and wall translational stiffnesses which are expressed through analytical derivations in terms of the floor area ratios of gravity and lateral load bearing members in the critical floor. Interstorey drift capacity is related to the available transverse reinforcement and the axial load ratio of the vertical members. The significance of the area ratio of vertical members in the typical floor as an index of vulnerability is explored with reference to the limitations in the value of axial load ratio used in R.C. design in order to secure ductile flexural behavior, and also with reference to the stability index of gravity load bearing members. Interstorey Drift Spectra are derived for the existing R.C. buildings suitable for rapid seismic vulnerability screening but also as a guide for rehabilitation of the existing structures. Lightly reinforced or substandard reinforced concrete buildings that reportedly collapsed during previous earthquakes are used as example case studies in order to calibrate the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.
Highlights
The progress made in earthquake engineering over the last few decades has had such a stunning influence on design and detailing practices in the area of reinforced concrete (R.C.) construction that the level of safety provided by modern structures designed according with the new philosophies bears no relationship with that of structures built in the former years
The proposed methodology is used to investigate the seismic vulnerability of older R.C. buildings, with particular emphasis on buildings that have collapsed during previous earthquakes, in an attempt to test its accuracy as a practical tool for identification of structures that are in dire need of detailed seismic assessment
Member end rotations are related to the interstorey drift magnitude of the storey under consideration, i= i/hi; the relationship is established by the requirement of moment equilibrium at the beam-column joints and depends on the relative stiffness ratio of the nb beams and the nc columns that converge at a typical floor joint: =nbEIb·hc/ncEIc·Lb (Figure 4(e))
Summary
The seismic vulnerability of old multi-storey reinforced concrete (R.C.) buildings reinforced with substandard details is assessed as a function of interstorey drift demand imposed by the design earthquake while considering brittle termination of elastic response of the critical members of the structure due to premature shear failure. Interstorey drift demand is related to column and wall translational stiffnesses which are expressed through analytical derivations in terms of the floor area ratios of gravity and lateral load bearing members in the critical floor. Interstorey drift capacity is related to the available transverse reinforcement and the axial load ratio of the vertical members. The significance of the area ratio of vertical members in the typical floor as an index of vulnerability is explored with reference to the limitations in the value of axial load ratio used in R.C. design in order to secure ductile flexural behavior, and with reference to the stability index of gravity load bearing members.
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