In high-rise buildings, the axial deformations of columns cannot be ignored, and special consideration is required for construction and design. In this session, we will cover the construction stage analysis for column shortening. We can also see how midas Gen considers construction stage analysis with creep & shrinkage effect.

Key Point 1: Why construction stage analysis is required?

Live, wind and seismic loads are applied at once to the entire complete structure. However, Dead load is a type of sequential loading as shown in this slide. Since most buildings are constructed by one story or several floor units at a time, we need to consider the construction sequence in analysis. Therefore the actual structural behavior can be significantly different from the conventional analytical behavior.

Key Point 2. Compensation of the differential column shortening

There are 4 reasons which occur column shortening.

–Elastic stresses due to gravity loads

–Creep caused by gravity load

–Drying shrinkage

–Temperature variations of exposed columns

Among those, shortening due to Creep & Shrinkage will be happened only in the concrete buildings.  Due to high stresses, the elastic shortening of the steel column is higher than the shortening of the concrete column. In the concrete columns, the shortening due to shrinkage and creep comprise respectively 36% and 28% of total shortening.