الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The lack of ductility and the low shear strength are some of the main problems associated with beam-column precast connection during past earthquakes. The main objective of this thesis is to upgrade the performance of the bolted precast beam-column joint by studying experimentally and analytically the behavior of precast reinforced concrete beam-column external connections subjected to a vertical reversed cyclic loading at the beam tip. In addition, the tested specimens had been numerically modeled by a numerical program based on the nonlinear finite element method, to perform cyclic loading and nonlinear cyclic analyses of this connection type. In the proposed connection system and to enhance the performance of shear resistance, two factors were studied: firstly, introducing a shear key between column and beam in the connection zone, and secondly, studying the effect of adding shear reinforcement to this region. Five external beam-column connection specimens were tested experimentally, including four precast concrete specimens and one monolithic specimen as a reference connection. Three variables were studied in this thesis affecting the proposed beam-column connection behavior, where the presence of shear reinforcement placed in the shear key zone, the grouted beam length, and the location of bolted threaded bars. All specimens were designed according to the concept of a strong column-weak beam, and the scale factor of specimens was two-thirds of a prototype structure based on the ACI building code. All Specimens were manufactured and poured in the Reinforced Concrete Laboratory, Faculty of Engineering, Alexandria University. After curing time, the assembly process was conducted and the specimens were transported and tested in the Reinforced Concrete and Heavy Structures Laboratory, Faculty of Engineering, Tanta University. For all specimens, a constant vertical axial load was applied at the top of the column at the beginning of each test, and the beam tip was subjected to a vertical cyclic loading following a pre-described displacement history. The behavior of the proposed precast and monolithic specimens was evaluated and compared based on the flexural strength capacity, ductility factor, lateral drift capacity, and energy dissipation. The results of the experimental study showed that the bolted precast connections with reinforcement at the shear key region had higher flexural strength and initial stiffness than the similar bolted precast connection without shear reinforcement as well as the monolithic specimen. Also, all precast specimens showed similar ductility behavior as the monolithic connection. In addition, a numerical nonlinear spring model was prepared to simulate the cyclic performance of the precast reinforced concrete beam-column connections. The proposed model was developed based on the nonlinear finite element method with the consideration of the concrete interface friction and the dowel action of reinforcing steel bars using the SeismoStruct program. In this model, beams and columns were modeled using nonlinear fiber elements and were connected at the beam-column joint by zero-length spring elements. The nonlinear model was calibrated with several experimental test results. The numerical study results proved that the nonlinear spring model was able to simulate the cyclic performance of the monolithic and precast connections. Furthermore, it was able to simulate the stiffness degradation and the strength deterioration of different specimens. The comparison between the results of both analytical and experimental tests showed good agreement. Also, a parametric study was performed to investigate the effect of some parameters on the performance of the precast beam-column joint. These studied parameters included the effect of increasing the area of shear reinforcement at the shear key zone and the presence of the concrete shear key, the concrete compressive strength, and the column axial load value. The obtained results from the parametric study results showed that the shear reinforcement in the shear key and the concrete compressive strength are important factors for enhancing the performance of the bolted precast beam-column joints. In addition, the increase of the column axial load level from 5% to 30% of the column capacity provides more confinement for the beam-column joint. Furthermore, the author suggested an equation to evaluate the vertical beam tip load of the precast bolted connection from the vertical beam tip load of the monolithic connection based on the experimental test results and the obtained results from the numerical model and the parametric study.