Development of Innovative Self-Centering Concrete Beam-Column Connections Reinforced using Shape Memory Alloys
Creators: name: Oudah, Fadi
Publisher: name: Graduate Studies
Year: 2015
Subjects: subject: Engineering--Civil
subject: Earthquake
subject: Concrete
subject: Beam-Column Connection
subject: Shape Memory Alloy
subject: Self-Centering
subject: Finite Element Method
subject: Slotted-Connections
subject: Two Distinct Element Shear Theory

description: The use of smart materials in the design of structures is emerging in the research community due to their unique ability to sense the environment and react upon thermal and/or mechanical stimulus. The main objective of this research study is to design innovative self-centering concrete beam-column connections reinforced using Shape Memory Alloy (SMA) bars with relocated plastic hinges. The proposed systems utilize the Psuedoelastic (PE) response of SMA in re-centering the connection after being subjected to earthquake-like motion. The behaviours of the systems are investigated experimentally, analytically, and using finite element simulation. In the first stage of this project, the design of steel-reinforced Single Slotted Beam (SSB) and Double Slotted Beam (DSB) connections with relocated plastic hinges is conducted and validated using experimental testing of large-scale connections. The SSB system includes a vertical slot made into the bottom fibre of the beam member while the DSB system includes vertical slots on both the top and the bottom fibres of the beam member. The location of the plastic hinge, is therefore, relocated by moving the vertical slots away from the face of the column. Test results indicated the efficiency of the newly developed systems in relocating the plastic hinge away from the face of the column, while a relocating distance equivalent to the shear depth of the beam member was found to provide the best seismic performance. The design of SSB and DSB connections reinforced using PE SMA bars at the locations of the plastic hinges was conducted in the second stage of this research. The transfer of forces in the concrete joint is different than in conventional design, and thus, experimental testing of joint-like specimens was conducted to examine the transfer of forces. The test results were also used to validate an analytical strut-and-tie model that was developed to verify the effect of the PE SMA anchorage on the behaviour of joints in beam-column connections. Furthermore, mechanical steelanchors and couplers were modified in the context of this research in order to provide adequate anchorage of the PE SMA bars into the concrete joint and beam members. Experimental testing of large-scale SSB and DSB connections reinforced using PE SMA indicated their superior performance as compared with conventional concrete connections in terms of low permanent deformation and high drift capabilities. Analytical models were developed to predict the load-displacement relationships of the connections in the third stage of this project. The sliding shear behaviour at the location of the vertical slots was also included in the models via a newly developed Two Distinct Element (TDE) shear deformation theory. A parametric study of the PE SMA-reinforced connections was also conducted. It was concluded that changing the concrete hinge depth and the relocation distance have significant effect on the stiffness, ultimate load, and ultimate displacement of the connections. Three-dimensional Finite Element Method (FEM) models of the tested connections were also developed using the ABAQUS software in the third stage. The models were validated with the experimental results in terms of the load-displacement envelopes, beam rotation, strain in bottom reinforcement, and cracking pattern. The models were found to predict the response of the connections reasonably. However, the accuracy is reduced as the vertical slot is moved away from the face of the column by 1.7 times the effective shear depth.