Assessing the oppressive impact of the form of tall buildings on citizens: Height, width, and height-to-width ratio

The tremendous growth in the development of tall buildings has necessitated assessment of their oppressive impact on citizens. Accordingly, this study seeks to assess the oppression caused by changes in the form of tall buildings (i.e. height, width, and height-to-width ratio) on observers at different distances. For this purpose, an assessment framework was developed based on the literature and examined through a case study with the results being compared with the criterion of permissible oppression (a visual weight of 8%) that can be endured by citizens. Finally, the accuracy of the results was evaluated by a survey of people's opinions. The findings indicated a relative correlation between the results of the framework and the participants' opinions, through there were some differences. Based on our survey, the effect of the building's height on oppression was generally more significant than that of the width. In scenarios where the height of the building was fixed, the width of 20 m was a critical point in oppression. If the building's width exceeded 20 m, the oppressive effect on citizens would significantly increase. Given a constant height, changing the height-to-width ratio from 2 to 3 was more effective in reducing oppression than altering it from 3 to 4. In conclusion, tall buildings with a height of 60 m or higher and a width of 15 m or higher on streets which are 30 m wide or narrower impose the highest oppression on the observer which can be mitigated with sufficient vegetation in front of the building.