In structural engineering, slenderness is a measure of the propensity of a column to buckle. It is defined as where is the effective length of the column and is the least radius of gyration, the latter defined by where is the area of the cross-section of the column and is the second moment of area of the cross-section. The effective length is calculated from the actual length of the member considering the rotational and relative translational boundary conditions at the ends. Slenderness captures the influence on buckling of all the geometric aspects of the column, namely its length, area, and second moment of area. The influence of the material is represented separately by the material's modulus of elasticity .
Structural engineers generally consider slender those skyscrapers with a ratio maximum of 1:10 or 1:12. Slim towers require the adoption of specific measures to counter the high strengths of the wind in the vertical cantilever, like including additional structures to endow greater rigidity to the building or diverse types of tuned mass dampers to avoid unwanted swinging.
The most slender residential skyscraper in the world is the Highcliff of Hong Kong which, with 72 floors and a height of 252 metres (827 ft), possesses one of the most extreme slenderness ratios, 1:20. Its extreme slenderness is characteristic of Hong Kong, where there are more pencil-shaped buildings than in any other place in the world.
|111 West 57th Street||New York, NY||82||438||1:24||2018|
|Highcliff||Happy Valley, Hong Kong||73||252||1:20||2003|
|150 North Riverside||Chicago, Illinois||54||228||1:20 at base||2017|
|Collins House (Melbourne)||Melbourne, Australia||61||190||1:16.25||2019 (under construction)|
|432 Park Avenue||New York, NY||85||425.5||1:15||2015|
|One Madison Park||New York, NY||50||188||1:12||2016|
|Sky Hous||55||179||Between 1:12 and 1:17||Proposed|
|785 Eight Avenue||42||158||Between 1:18 and 1:15||Proposed|
- Willis, Carol. "The Skyscraper Museum: SKY HIGH & the logic of luxury WALKTHROUGH". Retrieved 2016-01-24.
- Willis, Carol. "Presented by The Skyscraper Museum". Retrieved 2016-01-24.