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[Design] Can Capacity Based Design based on special provision for seismic design be performed?


Can Capacity Based Design based on special provision for seismic design be performed?



As per Capacity Design it is decided which objects within a structural system will be permitted to yield (ductile components) and which objects will remain elastic (brittle components).

For the special provision of seismic design, from the main menu select Design > Design > RC Design > Concrete Design Code.

Based on the code and structure it is required to select data. In this design approach the structures are designed in such a way so that plastic hinges can form only in predetermined positions and in predetermined sequences. The concept of this method is to avoid brittle mode of failure. This is achieved by designing the brittle modes of failure to have higher strength than ductile modes. Once ductile and brittle systems are decided upon, design proceeds according to the following guidelines:
Ductile components are designed with sufficient deformation capacity such that they may satisfy displacement-based demand-capacity ratio. Brittle components are designed to achieve sufficient strength levels such that they may satisfy strength-based demand-capacity ratio.

When an engineer knows which objects will behave elastically, and which will be permitted to yield, material non linearity need only be modeled for ductile components, while components which will not yield need only consider elastic stiffness properties. Brittle components are redesigned such that strength capacity exceeds that demanded. A level of complexity comes with the redesign of ductile components, however, in that ductile components may satisfy nonlinear demand-capacity criteria through a balance of both strength and deformation capacity. While Capacity Design should lead to more reliable modeling and more accurate results, when too many sources of uncertainty exist, it is up to the designer to best characterize as many behavioral parameters as is practical.

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