Abstract
The Algerian seismic design code (RPA99) recommends a limit on the elastic period as a governing factor in the design process of low and mid‐rise buildings, function of the structural system regardless of the related ductility level. The recommended limit criterion is evaluated through approximate analytical methods using drift limit. The assignable displacement ductility ratio for the force reduction factor is derived from some well established R‐μ‐Tn expressions. The limit period evaluation procedure (proposed in this paper) agrees with a capacity design approach since it allows for adjusting the required resistance demand level function of a ductility level resulting from code's steel recommendations. This will enhance seismic design procedure based on a target‐period approach such as in the Algerian seismic design code RPA99, to fulfil the minimum required two performance levels or to satisfy three performance levels if a damage control is considered. A critical study is carried out considering three regular earthquake‐resistant concrete framed structures and taking into account the specificity of various types of soils, namely rock, firm and soft. A comparison of the obtained results shows clearly that the RPA99 recommended limit is only valid for nude moment resisting frames.
Highlights
Depending on the earthquake structural system, the Algerian seismic design code RPA99 [1] recommends a limit on the elastic period as a governing factor in the design process
Being a force based design code, the global behaviour factor R specified by RPA99 for a given earthquake resistant system is constant regardless of the relevant global ductility level
The evaluation procedure proposed in this work may serve as a means to control the global behaviour, guaranteing a minimum resistance capacity agreeing with the permissible deformation level necessary for controlling the structural damage
Summary
Depending on the earthquake structural system, the Algerian seismic design code RPA99 [1] recommends a limit on the elastic period as a governing factor in the design process. It is rational and easier to define a period limit on a deformation limit basis rather than by empirical expressions based on a general description of the structural system and its geometry For this reason, the global ductility level (μ) to be assigned for the force reduction factor Rμ = R/Q must be defined by using well established Rμ-μ-Tn relations (Newmark-Hall, Vidic-Fajfar-Fishinger, KrawinklerNasser) [5] and the earthquake response of inelastic systems can be estimated by approximate analytical methods. The work undertaken consists in the evaluation of the period limit by assessing the maximum structural period considering a global drift by using approximate analytical methods estimating inelastic displacement demands of buildings This will certainly contribute to the improvement of the security design level against an eventual deformation exceedance, guarantying by the way an acceptable performance level while preserving human life and limiting the damage state. It should be noted that the relationship has been obtained by considering just
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