فهرست مطالب m.h razmkhah

In the process of implementing steel structures with bolted connections, the bolts are temporarily tight by the workers and so-called tightened, in this article, called the initial stage. After performing the connections of several different parts in the form of primary fastening, in the following stages of construction, the bolts of connection are pre-tensioned so that the minimum pre-tensioning force of the regulations is created in them. Therefore, in the process of the construction of steel structures with pre-qualified connections of the steel moment end plate frame, the effects of the construction sequence are important, because during the construction, due to the different construction situations of the project implementation conditions, delays In the secondary fastening of the connections, the lack of completion of the lateral restraint system of the structure and on the other hand the possibility of earthquakes with different magnitudes can lead to local or general damage to the structure and ultimately lead to the imposition of exorbitant costs on the project. In this research, the acceleration records proposed by FEMA-P695 (ATC-63) were used with the nature far field, and then the vulnerability of the BUEEP connection was investigated using the fragility curves. Without implementing the secondary fastener in the structure, the connections have a semi-rigid behavior and the discussion of damping and reducing the seismic demand caused by it is more noticeable. This trend was more visible at lower accelerations. In general, in slight and medium performance levels, the effect of not using the secondary fastener is greater due to the slack of the connections and the need for lower drifts to reach this level of performance.

From experimental researches and analytical studies, it has been fully proven that the resistance and stiffness parameters of elements and structures decline during cyclic loading due to the dynamic nature of seismic excitations. The simultaneous effect of the magnitude of the system response and the number of loading cycles is expressed by cumulative damage laws; In other words, the current deformation of an element or structure depends on the accumulation of damage in all past oscillations that remain in the system's memory. The analysis and design of structures based on performance and the branch of health monitoring of structures has led to having a clear picture of the amount of possible damage at different levels of risk, and in the last few decades, it has drawn the attention of many researchers to this field by developing different evaluation methods. In this research, the evaluation of the cumulative damage of steel structures under far and near field earthquakes has been investigated using Park-Ang and Kratzig damage indices. Two structural systems of special steel moment frame and dual structural system (special steel moment frame and special concentric braced frame) with the number of floors 8, 15 and 23 were studied and investigated. The results of this research show that the Kratzig damage index shows more damage values than the Park-Ang damage index for the same structure under the same earthquake record, and the damage values are reduced by changing the moment frame system to a dual structural system.

In this study, the fragility curves were developed for three-, five-, and eight-story moment resisting steel frame structures with considering soft story and torsional irregularities during the earthquake mainshock to assess the probabilistic effects of irregularities in plan and height of steel structures. These models were designed according to Iranian seismic codes. 3D analytical models of steel structures were created in the OpenSees software platform and Incremental Dynamic Analysis (IDA) was conducted to plot the IDA curves. The maximum value of inter-story drift was selected as the demand parameter and the capacity is determined according to the HAZUS-MH limit states; and finally, the corresponding fragility curves were developed. The results of the 3D nonlinear dynamic analysis indicated that the damage state of the structure due to soft story irregularity was decreased with increasing stories. On the other hand, the damage caused by torsional irregularity in plan was increased by increasing the height of the structure. For example, in the 3-story structure, soft-story effect on damage probability was more dominant than torsional irregularity.