Design smartness for tackling unanticipated loads

Abstract

With present day scenario on enviornment and living, unanticipated loads from natural and man-made causes are on the rise, defying any rationality or scientific reasoning for anticipation. This aspect, coupled with the interest in creating slender and sleek structural systems, has assumed greater significance in designing structures with 'smartness' -- either in-built or externally activated or through evolution to a different configuration -- for tackling loads which do not get bracketed in conventional or limit state approaches. The definition of under these circumstances can be termed as the ability to carry unanticipated loads over and above the designed one. Although the design methodology is confined within the boundaries of codal and functional requirements, a needs to be built in the design so that an extra reserve is available over and above that prescribed by normal approach. This might seem misleading and here only the present day computing methods provide the turn-around by shifting the paradigm from design-for-requirement to requirement-from-designs, an Object Oriented Approach. Thus the focus on present paper is on choosing from different to satisfy requirements to bring in smartness in the design choice. Reinforced concrete section under bending is the emphasis to highlight this aspect, even though the concept is expandable. For a given span, and design/ultimate moment, sections are chosen to provide buffer and compared with conventional designs. Nonlinear behavior is modeled so that failure state is kept as the endpoint. From the studies it is observed that for a given span, moment -- either ultimate or design state -- and given strengths, number of smart designs with buffer indications can be generated to satisfy different criteria. This is illustrated with some examples for a typical span and given external moment, modeling either a bridge section or part of a frame member. It was also observed from the studies that there is no unique design that satisfies all parameter simultaneously. A section that performs well in terms of cost and weight may yet fail in terms of buffer or utilization of steel upto its limit. Whereas a section that performs moderately in every one of the parameter may still be a better option. Depending upon the requirement, weightages for performance with respect to resisting moment, cost weight and additional buffer capacity must be specified. The section that best satisfies all the above criteria could be chosen as the ideal section. Section design done by varying other parameters such as grade of steel and concrete can also be studied. Strain hardening in steel can also be investigated to arrive at the greater carrying capacity of the sections. For example, it may even be possible for a structure to be designed purely for dead load and live load. But inherent can be induced to take care of seismic loads either partly or even completely.