Article Title

Çelik çerçevelerin enerjiye dayalı tasarımında kat yatay yer değiştirmelerinin etkisi


Earthquake-resistant design methods for the structures are generally force-based and displacement-based. In the force-based methods; internal forces must not exceed the bearing capacity of the structural members under external forces. It is aimed that excessive displacement of the structure under earthquake effects must be prevented in the displacement-based design methods. In the energybased methods; earthquake input energy must be consumed in the structural members with the nonlinear behavior and as a result the structure must remain stable without collapsing. In the study, multi-story steel frames, which are predesigned by considering the Turkish Seismic Design Code (2007), are redesigned according to the different predefined sway displacements and selected yield mechanism using the energy equations which are written at each story level. The effect of sway displacements on the energy-based design of steel frame is studied. The variations in the dimensions of the steel structural systems are searched by choosing different interstory drift ratios in connection with the different sway displacements which correspond to different performance levels. The sway target displacements in the design are compared with the displacement results of the nonlinear static pushover analysis and dynamic time history analyses for chosen earthquake records. Dimensions of the steel profiles that constitute the structural system of the frames decrease with increasing target displacement of the story. It is observed that the sway displacement results of the nonlinear static pushover analyses and dynamic time history analyses do not exceed the target displacement limits which are defined at the beginning of the energy-based design. The design method in the study is for the design of new structures. It is accepted in the study that the stored energy to the steel structures under the effect of an earthquake is calculated using Housner’s input energy equation. Housner’s total input energy is expressed as the sum of the elastic and plastic energies assuming the total energy is consumed by the linear elastic and nonlinear behavior of the structural system. The elastic energy of the system is defined by Akiyama’s elastic energy equation. The plastic energy of the system is obtained from Housner’s total input energy and Akiyama’s elastic energy. The plastic energy equation is obtained by subtracting the elastic energy from the total input energy of the system. Then the plastic energy is obtained again by equating the external and internal works of the plastic hinges of the system. Plastic energies which are defined by different approaches are equated to each other. Energy-based base shear force of the system is obtained from the equation of the plastic energies. Energy-based base shear force expression that is obtained within the study depends on the properties such as yield mechanism, story displacements, period of vibration and story heights, story numbers and story weights of the structures. The effect of story displecements in the energy-based base shear force equation is expressed in terms of interstory drift ratios. After calculating the energybased base shear, beam and column design are performed according to the plastic design concept. Beams are designed writing energy balance equation in the story beam levels. Then columns are designed according to combined both the axial force and bending moment values. In the study, European Norm Profiles are chosen for the steel structural system. Five-story regular steel frames with two bays and three meters story heights are designed taking 1.5%, 2% and 3.5% interstory drift ratios. It is assumed that there is a 30 kN/m total uniformly distributed load in all spans. As a conclusion, the effect of story displacements on the energy-based structural design is searched within the study. Taking different interstory drift ratios or indirectly different story displacements, different base shears are calculated in the design. So; different steel profile dimensions are obtained for different story displacements. Steel profile dimensions decrease with increasing the story displacement values. Nonlinear static pushover analyses and dynamic time history analyses are used to check the results of the energy-based design method. It is seen from the results of nonlinear static analyses and time history analyses for the chosen earthquake effects that the predefined story displacements or interstory drift ratios at the beginning of the energy-based design are not exceeded.