جستجوی مقالات مرتبط با کلیدواژه « steel beam » در نشریات گروه « مهندسی زلزله »

Frames with a Khorjini connections is one of the most commonly used structural systems in Iran. In these frames, the beams are placed on the sides of the pillar and each beams are placed on a lower corridor. The columns are double-skinned and have a relatively long sheet at the Khorjini, so that the lower and upper corners are in place. What makes this type of connection a lot of use is the high speed and ease of execution of sophisticated frames. Several studies have shown that when exposed to the structure, the exposed fire will change its resistance. The purpose of this study is to investigate the behavior of steel beams with Khorjini connections at different temperatures and times. First, after the library studies, the laboratory test was verified by Abacus software. The results of the numerical investigation were compared with the results of the experimental study in the paper, and the results of this comparison showed that the matching of the experimental results and the results of the numerical study with a percentage difference of less than 10 Percentage. In order to develop a numerical model, 17 different models were investigated with temperature variations and exposure time of exposed beams. The results of this study showed that increasing the temperature of the heat in the Khorjini connection reduces the resistance, increases the amount of failure and deformation in the joint area. Other results of the study showed that as the Khorjini connections are exposed to more fire, the resistance will be reduced, the failure rate will increase and the structural deformation will be higher.

The composite RCS moment resisting frame, including concrete columns and steel beams, has some advantages in comparison with the ordinary steel and concrete moment resisting frames. Previous studies have shown that these systems, in case of preserving sufficient strength and needed ductility in seismic condition, could be effective in design and construction. Notwithstanding the previous research, during the 1970s and 1980s, the use of this composite structural system was limited to areas with low seismic hazard in the US, and it was used as a replacement for steel moment resisting frames and high rise buildings. Besides, in Japan, it was used instead of concrete frames in low rise and short span buildings. In the previous research on these structures, studies were made on the frame and RCS connections, but there has not been any study on the seismic assessment of the RCS structure with time history and for the near-fault earthquakes. Investigating the structure behavior under near-fault earthquake, due to the special nature and characteristics of these earthquakes in comparison to the far-fault earthquakes, seems to be essential. In this research, the seismic demand of composite RCS and concrete structures under the near-fault earthquakes are investigated in comparison with the far-fault earthquakes. For this purpose, five composite RCS intermediate moment resisting frames with 4, 7, 10, 15 and 20 stories and five spans were designed, and then, nonlinear dynamic analysis was performed on the structures using the OpenSees software under 10 far-fault and 10 near-fault accelerographs. The obtained results in this research showed that the stories displacement demand due to the far and near-fault earthquakes in composite structures is lower with respect to the stories displacement of concrete structure due to the same record, and by increasing the number of stories, the values of this difference increase. The effectiveness of near-fault records on the composite structures is greater than the ordinary concrete structures. It seems that the assessment of high rise composite structures with respect to high rise concrete structures yields a better displacement response. Finally, the effect of steel beam in reducing displacement due to both of the records is observed.
RESEARCH In this research, the seismic demand of RCS and RC moment frames under the near-fault earthquakes are investigated with respect to the far-fault earthquakes. For this purpose, five RCS and RC intermediate moment resisting frames with 4, 7, 10, 15 and 20 stories and five spans were designed and then nonlinear dynamic analysis was performed on the structures using the OpenSees software. Then, 10 far-fault and 10 near-fault accelerographs were used respectively. All used accelerograms that have been received from the site of Peer, had a view to soil type of III on the basis of regulations of seismic design code of Iran (2800) or dirt Class of D based on the classification guidelines of FEMA. To draw the whole reactionary response, the software of SeismoSignal was used and all accelerograms before scaling had their equal maximum with acceleration (PGA). For nonlinear dynamic analysis on intended frames, OpenSees software was used and the results of story displacement, drift angle and story shear were provided in full paper. Selected records in this study were applied to the models and finally the decision has been made among the obtained responses. For scaling, accelerograms used method for scaling of the Fourth Edition of 2800 guideline. Finally, the effect of steel beam in reducing displacement due to both of the records is observed.
Displacement and drift angle of RC structures under near-fault records was more than far-fault records. However, with increasing the number of stories, drift angle of RC structures under far-fault records was more than near-fault records By an increase in the number of stories, the RCS frame's drift angle due to near records is less than RC frames. The drift angle in RCS tall buildings under near-fault records and in RC tall buildings under far-fault records are more critical. Base shear of RCS structures under near-fault records was more than the base shear under far-fault records and by an increase in number of stories, the difference was reduced. In RCS frames, by an increase in the number of stories, steel beams cause a decrease in effectiveness of drift angle and displacement under near-fault records.