Beam connections with reduced drilled section and slotted web have been presented after the Northridge earthquake (1994). Their new geometrical shapes have been resulted in weakening of beams and subsequently the bette rperformance of connections in the earthquakes. In this research, the advantages of both connections, mentioned above, have been studied in the Slotted Web Drilled Flange (SWDF) composite connections. Accordingly, the effects of different parameters of slot such as length, width and end hole dimension have been assessed as well. Based on the results obtained in this research,energy dissipation is reduced due to the increase of length of slot web in the SWDF connection, exceeded the values recommended in the codes. Besides, the stability of hysteresis curve decreases because of increasing in the width and end hole diameter of web slot.
The ductility and strength of reinforced concrete (RC) columns could be noticeably improved by replacing steel bars with polymeric bars. Despite the previous research on RC columns, most of those studies focused only on the lateral load capacity of this structural member and were mainly costly experimental studies. However, this paper is concentrated on the previously occurred damages to the reinforced columns in the previous earthquakes. Subsequently, finite element analysis has been performed to examine 24 models including the various shapes of RC columns. In employing the plastic behavior of steel, carbon fiber-reinforced polymer (CFRP), and glass fiber reinforced polymer (GFRP) bars, the bilinear hardening has been considered. To capture both compressive and tensile behavior of the concrete, the concrete damage plasticity model has been implemented. Furthermore, the optimization technique is used for CFRP models to compare with other models. In this paper, the parameters of energy, seismic factor, stiffness, and ductility have been computed using the method proposed by the authors. This suggested method is considered to compare the results from each parameter. Finite element results of steel bars are compared with carbon and glass models. The results show the stiffness of models is improved by CFRP bars, while the energy absorption and ductility factor are enhanced with steel bars. Moreover, GFRP bars can enhance the seismic factor. The reduction of column stiffness to almost half would occur in some rectangular cross-section columns.
Reduced Beam Section (RBS) and Drilled Beam Section (DBS) are seismic moment resistant frame connections, introduced after 1994 Northridge earthquake. RBS connection has been tested under cyclic loading and showed acceptable performance. In this paper, seismic behavior of Drilled Beam Section (DBS) connection is studied numerically using finite element method. A drilled beam section of a cantilever H-beam has been subjected to cyclic loading at its free end and studied for its optimal shapes. 62 samples of DBS connections have been modeled and studied under cyclic and pushover loadings. Based on the results obtained in this research, the connection shows its positive seismic behavior if the biggest hole is near the column face and its diameter decreases as the holes move away from the column face. In this research the effects of dimensions, position and number of holes are investigated using Von Mises stress and elastic strain criteria under cyclic and monotonic loadings. In this drilled beam the smaller holes shift plastic hinges out of the connection zone. .
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