Risk Analysis of Three-storey Reinforced Concrete Moment-resisting Frame Structures Using Performance-based Wind Engineering

Abstract

This paper discusses the application of concepts of performance-based wind engineering used to determine the effects of changing building design elements to the performance of a structure against severe wind hazards in the Greater Metro Manila Area, Philippines. Only three-storey reinforced concrete moment-resisting frame structures were subject to analysis through computational fluid dynamics. Before assessing the performance of structures, severe wind hazards for the study area was characterized by collecting wind speed data from over 50 years and fitting the data using the Gumbel distribution. The building stock was developed by varying roof pitch and floor aspect ratio values in certain set increments. Roof pitches observed were 15, 30, and 45 along with structures with floor aspect ratios of 1:1, 1:2, and 1:3. The damage to roof and windows, as well as the damage index which gives the ratio of the repair cost to the replacement cost of a building, were identified. Damage for each model was classified according to the Hazard-US Damage State Matrix in order to generate a damage probability matrix. From this damage probability matrix, the probability of exceedance of each damage state was compute by taking the cumulative probabilities. Data points for each damage state were then fitted with a lognormal function. Vulnerability curves were developed by multiplying the probability of exceedance of each damage state to cost percentages adopted from the UPD-ICE Report [2]. Damage indices were computed per wind speed by summing the total damage for damage states. Wind speed versus risk density curves were generated by multiplying values for each data point in the vulnerability curves to the probability density function of the hazard. Risk curves were then obtained by plotting wind speeds against values of damage indices that correspond to said wind speeds. One key observation is that damage percentage increased as roof pitch also increased, having as much as around a 15% difference between structures with roof pitches of 15 and 45. Slender structures whose windward sides were also the long sides had the most damage. For all structures, a top-to-bottom progressive damage trend was observed.