Seismic assessment and strengthening of 3D beam-column joints
Final Report Abstract
The research project investigates the seismic load-bearing behavior of full-scale reinforced concrete (RC) beam-column joint subassemblies, with particular focus on the joint shear behavior. The reinforced concrete beam-column joint subassemblies were non-seismically designed, by providing no transverse reinforcement in the joint core. The effects of missing joint shear reinforcement, as required in current design regulations for the earthquake load case, could be investigated in the experimental and numerical tests with regard to load-bearing capacity, deformation behavior and the type of failure. The influence of transverse beams and slab monolithically connected to the joint was taken into account. Further tests on beam-column joints retrofitted with the Fully Fastened Haunch Retrofit Solution (FFHRS) were conducted. In this solution, steel haunches are post-installed onto column and beam by means of anchors. This project used bonded anchors for the connection. In 1:1 scale component test on two-dimensional (2D) and three-dimensional (3D) beam-column joint specimens with transverse beams and slab, earthquake-like deformations were applied to the test specimens with the aid of two servo-hydraulic test cylinders in displacement-controlled manner. The cyclic load-displacement behavior, failure modes and the influence of transverse beams and slab could be documented. Numerical Finite Element (FE) models were created for further analysis of the load-bearing behavior observed in the test. In this way, important information on the internal load transfer could be obtained. The following basic statements can be made: • The presence of unloaded transverse beams increased the joint shear strength • The diagonal joint shear cracks extended into the transverse beams • The presence of slab increased the stiffness of the beam-column joint subassembly • The slab bars participated under flexure, especially when the slab acted in tension. However, the slab participation diminished once joint shear failure initiates • The presence of transverse beams and slab did not pose any problem during the installation of FFHRS • The seismic performance of all retrofitted specimens improved significantly in terms of stiffness, strength and ductility • At high displacement levels with large flexural crack widths intercepting the anchors, anchorage failure intervened which reduced the efficiency of FFHRS • In the retrofitted specimen, the increased flexural capacity of the beam due to the slab participation made the column shear critical.
Publications
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Influence of the aspect ratio on the shear strength of 3D beam-column joints. Otto-Graf-Journal. 2020; 19
Tonidis M., Sharma A. & Bosnjak J.
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Numerical modeling of 3D beam-column joints. 17th World Conference on Earthquake Engineering, 17WCEE, Sendai, Japan; 2020
Tonidis M., Sharma A. & Bosnjak, J.
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Numerical investigations on the influence of transverse beams and slab on the seismic behavior of substandard beam-column joints. Engineering Structures, 247, 113123.
Tonidis, Margaritis & Sharma, Akanshu
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Detailed 3D FE modeling approach for 2D and 3D beam-column joints retrofitted with fully fastened haunch retrofit solution including anchor behavior. Engineering Structures, 294, 116769.
Tonidis, Margaritis & Sharma, Akanshu
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Experimental investigations on the influence of transverse beams and slab on the seismic behavior of non-seismically designed beam-column joints. CARRS 2023, IIT Hyderabad, India
Tonidis M., Birtel V. & Sharma A.
