Accuracy of nonlinear static procedures for estimating the seismic performance of steel frame structures

Author(s):  
Kensuke Shiomi

Through the 2011 Tohoku Earthquake or the 2016 Kumamoto Earthquake, much larger earthquakes are considered recently in the seismic designs of large steel-frame structures. When structures are exposed by these severe ground motions, partial destructions in the structures, such as damage or fracture of members could happen. Especially, the low cycle fatigue of steel structures because of the repeated load from these long-term ground motions is a serious problem. However, current seismic performance evaluation method based on nonlinear dynamic analysis considers only elastic and plastic deformation of each member, excluding the fracture of members. If this member fracture happens during earthquakes, there is considered to be many effects on the seismic performance, like the changes of the vibration property, the dynamic response and the energy absorbance capacity of structures. Therefore, the fracture of members is preferably taken into account in the seismic performance evaluation for these large earthquakes. This paper proposes the dynamic analysis method for steel-frame structures which can express the member fracture. Dynamic analyses considering and not considering member fracture under the repeated loads supposing the long-term earthquake are conducted to the FEM model of full-scale structure. By comparing each result, the effects of considering member fracture to the seismic performance such as the dynamic response and the energy absorbance capacity are discussed.


Author(s):  
Kensuke Shiomi

Abstract For steel frame infrastructure facilities like thermal power plants, storage facilities or port facilities, the more advanced seismic performance is needed which not only prevent major damages against assumed design ground motions but also result in the “desirable failure mode” that concerns the recovery works or prevent from resulting in catastrophic failure mode, even under severe ground motions beyond design assumptions in which occurrence of some damages in structures are inevitable. “Seismic structures which can control the locations of failure of structural members inside structures” is one of the examples of this seismic performance. By adding this performance to steel frame structures at the stage of seismic design, the high resilience structures which concern recovery works after earthquakes can be realized. In this research, a basic study on the seismic performance which controls the locations of fractures of steel frame members by adjusting the cross sections of each structural member was carried out. The analytical studies about the design procedure to realize this seismic performance were conducted. Then, by conducting the shaking table tests for simple steel frame structures and confirming the location of fractures under dynamic loads, the possibility of this seismic performance was discussed experimentally.


2021 ◽  
Author(s):  
Emad A. Elhout

Abstract In design steel frames, combining semi-rigid and rigid connections can result in better structural performance, particularly in seismic locations. In this study, the effects of semi-rigid beam-to-column connections located on the seismic performance of steel frame structures are investigated. The analysis uses six and twelve-story moment resisting steel frames (MRSF) with rigid, semi-rigid, and dual beam-column connections. These frames are designed according to the Egyptian design codes. Drain-2Dx computer program and seven earthquake ground motions are used in the non-linear dynamic analysis. The rotational stiffness of beam-to-column connections is indicated through the end fixity factors with a value equal to 0.6. The performances of these frames are evaluated through the roof drift ratio (RDR), the maximum story drift ratios (SDR), and the maximum column axial compression force (MACF). The results indicated that the quantities of fundamental periods, roof drift ratio, the story drift ratio, and the column axial compression force are related to stiffness, rigidity, and the number of semi-rigid connections in steel frames.


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