7. Reinforced concrete column design

Columns are structural elements which carry on the loads from girders and distribute them to the foundations. They are designed using the bending moments on both directions and the axial forces.7.1 Internal forcesBeing a main structural element the computation is done in the elastic range and the internal forces for both fundamental and the special loaded cases are chosen from the outputs results using Robot program.The design internal efforts resulted from running the Finite element program are the following

7.2 Checking the maximum displacement of the sectionChecking of the maximum displacements for the seismic action is made for both ULS and SLS.For the SLS the checking is done using the following relation:

Where: - relative displacement under a specific level corresponding to the serviceability limit state; reduction factor which takes into account the period of appearance of an earthquake having the value 0.4; behaviour coefficient; relative displacement of a level ( between first floor and second floor) -maximum value for relative displacement of a level associated with the serviceability limit state;; For the ULS the checking is done using the following relation:

Where: relative displacement corresponding to the ultimate limit state; c- coefficient for amplification of the displacements which takes into account that for periods smaller than the corner period, the seismic displacements computed are higher than the ones corresponding to the elastic seismic response: l where: T-the main period of the building; Tc-corner period taken from P100-2006; q- behavior coefficient; -relative displacement of a level; - maximum allowable relative displacement under a level corresponding to the seismic action corresponding to the ultimate limit state;