A continuous load path in a structure is always the best way to transmit the load from the upper story to the foundation. However, there is a tradition of using irregular shapes of structures nowadays to enhance the aesthetic, make a terrace, or for getting sunlight. This irregular shape disrupts the continuous load path of the structure and there is the formation of a high-stress zone in the structure which may lead to failure in case of extreme events. During the event of an earthquake, a structure that has an irregularity in its mass, stiffness, and strength suffers more damage as compared to its regular counterpart. So, we need to pay more attention while designing the irregular structure so that it can withstand the force acting on it and ensure the safety of people. So, in this thesis, the seismic response of structures with vertical irregularity is studied. For this purpose, the fundamental time periods of the structures with vertical irregularity are studied and compared with their regular structure. The obtained result is compared with the approximate fundamental period, Ta, given by ASCE/SEI 7-16. Also, the location of critical columns which has the highest load ratio is studied and designed.

This study was initiated to quantify the effect of different degrees of irregularity on structures designed for earthquake using simplified analysis. The types of irregularity considered were: (a) Vertical Irregularity • Mass • Stiffness -Strength (b) Horizontal (Plan) Irregularity • Diaphragm Flexibility Simple models were used to allow many analyses to be conducted in a relatively short time. For vertical irregularity studies, simple shear-type structures were designed according to the New Zealand design Standard, NZS1170.5, firstly as regular structures, and then they were redesigned as irregular structures to the same target drift. Both regular and irregular structures were then subjected to a suite of records, and vertical irregularity effects evaluated from the difference in response. For the flexible diaphragm effect study, simple models of structures were developed with: (a) a rigid diaphragm assumption; and (b) a flexible diaphragm assumption. Flexible diaphragm effects were evaluated by conducting time-history analyses and comparing the responses of structures with rigid and flexible diaphragms. A mechanics based approach was developed to quantify flexible diaphragm effects, which was shown to produce consistent results with those from time-history analyses. Relationships between the degree of irregularity and the change in behaviour were developed. This information facilitates designers and plan checkers to rapidly evaluate the likely effect of irregularity on structures. It provides guidance as to: (a) when the effect of structural irregularity can be ignored, and (b) the change in demands for different degrees of structural irregularity. The relations developed also provide a rigorous technical basis for future regularity provisions in the NZS1170.5 and other world-wide seismic design codes.