It has been shown that the strengths specified in the Loadings Standard NZS 4203: 1992 (Standards New Zealand 1992) to resist seismic actions are low when compared with major international design codes (Fenwick and Davidson 1994; Fenwick et al. 2002). Few modifications to these low strengths other than an increase in the minimum permissible base shear have been made in the draft revision of the Standard, NZS 1170.5. Furthermore, the design procedure to allow for higher mode effects in multi-storey structures subject to dynamic forces was developed in the 70's using a limited number of non-linear time-history analyses with a bilinear hysteretic rule and in most cases neglecting P-delta effects. In this work, a four storey, a six storey, and two twelve storey buildings, in which the resistance to lateral forces is provided by concrete moment resisting frame structures were designed and analysed. Through a senes of non-linear time-history analyses using a Takeda hysteretic rule and considering P-delta effects, three main objectives were studied. The first objective was to investigate if the strengths given to beams and columns met the objectives set by the Loadings Standard (Standards New Zealand 1992). The second objective was to examine how well the method of determining column actions from the NZS 3101:1995 (Standards New Zealand 1995) works when using the lateral loading specified in NZS 4203:1992 (Standards New Zealand 1992) and the draft provisions of the proposed Loadings Standard NZS 1170.5 and the third objective was to compare the performance of multi-storey moment resisting frame buildings where columns are modelled as: Elastic responding columns except at the base; Columns designed to meet the minimum requirements as given in NZS 3101: 1995 (Standards New Zealand 1995); and Columns designed to meet the minimum strength requirements as defined in the 2004 draft of NZS 1170.5 where limited protection to plastic hinge formation is given. The influence of the choice of hysteretic rule was assessed and in general, the structures studied performed in a satisfactory manner due to the use of a more realistic hysteretic model. The individual results from the non-linear time-history analyses were very scattered making the structures reach critical performance levels with some of the selected ground acceleration records and poor performance was observed for structures analysed using a 2,500 year return period earthquake. It was also shown that P-delta effects have a significant influence to the response even for the four and six storey structures and concluded that P-delta effects should always be included in the design and analysis of structures.