Rehabilitation of Seismic-damaged Reinforced Concrete Beam-column Joints with Different Corrosion Rates Using Basalt Fiber-reinforced Polymer Sheets

Influence of the degree of damage and confinement materials on the seismic behavior of RC beam-SRC column composite joints

Due to several reasons as the low resistance of constructed concrete and also change in codes or application of structures, some concrete frames need to be retrofitted. By adding the steel brace to the reinforced concrete, many seismic parameters such as resistance, ductility, stiffness and the resistance reduction coefficient change. This study experimentally investigates the impact of adding the prop, the convergent steel brace and also the convergent steel brace with a ductile ring on resistance, stiffness, ductility and energy dissipation of RC frames. Four samples of RC frames with one span and one story with the same characteristics were constructed and retrofitted by different methods. All frames were subjected to the cyclic loading, and the hysteresis and pushover-displacement graphs of them were plotted. The novelty of the work was using such braces in RC frames. The results obtained from the tests showed that although the frame retrofitted by the X-brace showed a better performance in terms of resistance and stiffness, but the retrofitted frame with a ring also showed a better behavior in terms of resistance and stiffness compared to the RC frame and the sample with the jacket as well as compared to the sample with the X-brace showed more ductility and energy dissipation (with a slight reduction in resistance).

Experimental evaluation of RC frames retrofitted by steel jacket, X-brace and X-brace having ductile ring as a structural fuse

In this study, reinforced concrete beams with insufficient shear capacity were strengthened on both sides of the beam along the shear openings by a novel approach: Mechanical Steel Stitches (MSS). This innovative method facilitates the application of strengthening the beams with a low-cost solution. In this concept, six specimens were experimentally investigated under vertical load. While one of the specimens was tested as a reference, the others were strengthened with MSS application at different ratios (ρMS), ranging from 0.2% to 1% at both the beams’ shear span. MSS were applied with the angle of 90° considering stirrup logic. The diameter, anchorage depth and mechanical properties of the MSSs were kept constant, and their effects on the strengthening of the beams in terms of ductility, strength, stiffness, and energy dissipation capacities were investigated by changing the spacing of the MSSs. The results revealed that increasing MSS ratio caused a dramatic positive change in the behavior in terms of both strength and energy dissipation capacity. MSSs to be made at appropriate intervals ((%1) MSS ratio or (d/5) MSS spacing) significantly improved the shear capacity. However, a 43% loss in stiffness occurred with the increase in ρMS since the MSSs are applied to the beams by drilling and anchoring from the outside.

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Mechanical Steel Stitches: An Innovative Approach for Strengthening Shear Deficiency in Undamaged Reinforced Concrete Beams

Experimental research and finite element analysis on the seismic behavior of CFRP-strengthened severely seismic-damaged RC columns

The experimental and shear strength analytical investigations carried out on seismic-damaged steel reinforced concrete (SRC) columns strengthened with enveloped steel jacket subjected to cyclic loading are presented in this paper. Four 1/2-scale SRC columns were designed and manufactured and the postearthquake damage, enveloped steel jacket-confined, and destructive tests were carried out under lateral cyclic loading. The effects of postearthquake damage degree and enveloped steel jacket-confined on shear capacity and ductility capacity were all well examined. Test results indicate that the ductility of seismic-damaged SRC columns strengthened with enveloped steel jacket increases with the reduction of the postearthquake damage degree. The results indicate that the calculation formula of shear bearing capacity of SRC columns is feasible. Based on GB50010-2010, ACI318-08, and CSA-04, three different shear models were established, and the calculated values of shear capacity are quite different, and the analysis of the shear strength of RC in the strengthened seismic-damaged SRC column cannot be ignored. The formula is verified, and the calculated results are consistent well with the experimental results.

/pdf/experimental-and-theoretical-research-on-shear-strength-of-3m2u9us5co.pdf

Chong C. Wan

Papers

Experimental and Theoretical Research on Shear Strength of Seismic-Damaged SRC Frame Columns Strengthened with Enveloped Steel Jackets