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This article aims to propose a novel seismic strengthening technique for non-seismically detailed beam-column joints of existing reinforced concrete buildings, typical of the pre-1975 construction practice in Turkey. The technique is based on mounting prefabricated SIFCON composite corner and plate blocks on joints with anchorage rods. For the experimental part three 2/3 scale exterior beam-column joint specimens were tested under quasi-static cyclic loading. One of them was a control specimen with non-seismic details, and the remaining two with the same design properties were strengthened with composite blocks with different thickness and anchorage details. Results showed that the control specimen showed brittle shear failure at low drift levels, whereas in the strengthened specimens, plastic hinge formation moved away from column face allowing specimens to fail in flexure. The proposed technique greatly improved lateral strength, stiffness, energy dissipation, and ductility.

Post-earthquake observations revealed that seismic performance of beam-column connections in precast concrete structures affect the overall response extensively. Seismic design of precast reinforced concrete structures requires improved beamcolumn connections to transfer reversed load effects between structural elements. In Turkey, hybrid beam-column connections with welded components have been applied extensively in precast concrete industry for decades. Beam bottom longitudinal rebars are welded to beam end plates while top longitudinal rebars are placed to designated gaps in joint panels before casting of topping concrete in this type of connections. The paper presents the major findings of an experimental test programme including one monolithic and five precast hybrid half scale specimens representing interior beam-column connections of a moment frame of high ductility level. The required welding area between beam bottom longitudinal rebars and beam-end plates were calculated based on welding coefficients considered as a test parameter. It is observed that the maximum strain developed in the beam bottom flexural reinforcement plays an important role in the overall behavior of the connections. Two additional specimens which include unbonded lengths on the longitudinal rebars to reduce that strain demands were also tested. Strength, stiffness and energy dissipation characteristics of test specimens were investigated with respect to test variables. Seismic performances of test specimens were evaluated by obtaining damage indices.

A probabilistic seismic hazard analysis (PSHA) for Western Anatolia is presented using the Gutenberg-Richter (G-R) frequency-magnitude relation. Since the modeling is sensitive to the location of seismotectonics boundaries, to use the information content of the observed earthquake data, as a general rule the borders of the affected area are extended. In this study, the effect of the region's definition on the G-R model is debated on the Western Anatolian region, which is one of the most seismically active and rapidly deforming regions of the world throughout the ages. Calculations are carried out for two subregions and one combined region as a whole using the seismic catalog from 1900 to 2005. The data sets are determined by the region's borders with the parameters computed according to these data sets by the least-squares and maximum likelihood methods, and then future predictions are estimated via these parameters. Comparing the results with historical earthquake records, most appropriate regional borders for Western Anatolia are defined, and for this new region G-R model parameters are obtained.

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