Investıgatıon oF Soft Floor Effects On Steel Structures wıth Eccentric and Central Braced wıth Passıve Isolatıon System Under Earthquake Effect

In our country for

residential, car park and business purposes, in order to be able to use the

buildings the basement and ground floors of the buildings as open. The use of

basement and ground floors for this purpose causes the soft floor effect to

occur. In this study, a total of eight four-story steel structures with or

without isolation formed by central or eccentric braced are considered. The

ground floor of these structures is not formed with central or eccentric steel

braced and is designed as a soft floor. Excessive shear force, bending moment

and lateral displacement are expected in the columns of the floors that have

soft story effect during the earthquake of the investigated structures. In soft

floor columns, two types of passive isolation systems are used, namely the

friction pendulum isolation system or the lead-based rubber system passive base

isolation system, in order to reduce these effects and to use these floors for

parking or workplace purposes. In this study, isolation systems were placed

between the foundation and the structure to transmit seismic effects to the

building during an earthquake and to increase the natural dominant period of

the building. Firstly, non-linear analysis in the time domain of non-isolation

structures with soft-fold effect was performed. Later, nonlinear analyzes in

the time domain of the structures with floor insulated soft story effects were

made. A series of results was obtained by comparing the analyzes made.

According to the analysis results, it has been observed that both isolation

systems reduce the shear forces, lateral displacements and bending moments

occurring in the columns of the floor that has a soft floor effect. However, it

has been achieved that in the friction pendulum isolation system, it can absorb

the energy from the earthquake more than the lead-based rubber system isolation

system. In the steel structure formed as an eccentric braced, the soft floor

effect is less prominent than the steel structure formed as a central braced. Since

the tie beams formed by the eccentric steel braces can meet the earthquake

effects, it has been proposed to create a steel structure system with an

eccentric braced in structures with soft story effect. In addition, the use of

passive insulation systems and cross members together will limit the possible

soft story effect on the steel structure.<o:p></o:p>