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A novel retrofitting application for pinned beam–column connections in RC precast frames was investigated from experimental and numerical perspectives. The application is based on the insertion of a lead extrusion damper (LED) in regions of beam–column connection of precast RC frames. The bending moment and deformations at the column base tends to decrease with increased damping, and the shear force at the connection of the LED on the structural member increases with the insertion of an LED. Half-scale non-retrofitted and retrofitted specimens were tested on a shake table. In addition, nonlinear dynamic time history analyses were carried out. The structural behaviors of non-retrofitted and retrofitted specimens were compared based on the experimental and numerical results. Ultimate displacement and story drift of the precast frame, the bending moment and plastic deformations at the column base were significantly reduced via the insertion of an LED. Also, the numerical results are in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Past earthquakes showed that infill walls used in RC frames had many advantages in terms of improvements in global stiffness, lateral strength and energy dissipation capacities of the structures when they are placed regularly throughout the structure unless they cause shear failures of columns, (Dolsek and Fajfar 2008). Several experimental researches conducted on infilled RC frames also showed a significant improvement in the overall behavior. Shake table tests on infilled RC frames performed by Hashemi and Mosallam (2006), resulted that the infill walls increased the structural stiffness nearly 4 times, shortened natural period nearly 50% and increased the damping coefficient from 4-6% to 12%. Infill walls during any credible earthquake may experience excessive damage and/or out of plane movement. Retrofitting these walls by CFRP would improve the contribution of infills to the overall seismic behavior of the vulnerable RC building. The aim of the study is to develop an effective seismic retrofit strategy involving the use CFRP sheets. The retrofitting technique consisted of CFRP sheets, surface bonded to the masonry wall, while also anchored to the surrounding concrete frame by means of specially developed CFRP anchors. In order to achive this goal, an experimental investigation was conducted on six 1/3-scaled reinforced concrete RC frames which were built and tested in two groups as infilled frames, and as cross diamond braced retrofitted frames. Bare and retrofitted infilled reinforced concrete frames have been tested pseudodynamically and obtained results have been compared with the quasistatic ones. The specimens were one-bay, one-story and loaded laterally from top of column location. The first specimen of the each group was tested with quasistatic (QS) test method using a drift-based reversed cyclic loading pattern where the second and the third specimens of each group were tested by the pseudo-dynamic testing (PsD) method under the effect of simulated low and high inertial masses. The rationale of this research is to increase effectiveness of the CFRP based retrofitting technique in which intact infill walls of vulnerable midrise reinforced concrete (RC) buildings are turned into a lateral load resisting system. The objective of this study is to determine the seismic performance of in-filled frames through QS and PsD testing methodologies on the response of infilled RC frames in terms of strength, stiffness, energy dissipation capacity and observed damage levels. Energy dissipation capacity is an effective parameter in order to evaluate structural performance. Important findings have been drawn-up from this experimental study. The sectional and global response parameters such as strength, stiffness, energy dissipation capacity and damage observations were compared between the specimens. When two different test methodologies are compared, the energy dissipation of the specimens that was obtained from the PsD testing became more than the one tested with QS test for the same level of story drifts. The maximum restoring force and drift couples that were obtained from PsD tests showed a close behavior pattern, regardless of the level of inertial masses, compared with QS tests. The energy dissipation capacity of the retrofitted specimens increased significantly when compared with the non-retrofitted specimens. Cross diamond braced frame dissipated 1.7 times more than energy than the bare infilled frame. The maximum load carrying capacity increased from 80 kN to 150 kN when the bare infilled frame is retrofitted with CFRP. The crack widths were much more smaller in the retrofitted specimen than the bare infilled frame at the same drift ratios. The performance limits that are obtained from the QS test results may be adjusted according to the PsD response results. In the scope of this study, the experimental results have also been compared with the theoretical ones. The theoretical calculations based on the non-linear static analysis showed a good convergence with the experiments. In order to model the infill wall or retrofitted infill wall in the RC frame, a shearspring is defined which has a initial rigidity and maximum load carrying capacity. The response model of the shear spring is based on the Saneinejad and Hoobs (1995) infill model and the performed infill wall element tests. Both the static and pseudodynamic test results are enveloped with the theoretically obtained capacity curve. [ABSTRACT FROM AUTHOR]

Single-storey precast reinforced concrete (RC) frame type buildings are mainly preferred in manufacturing plants and storehouses. The behaviour of semi-rigid beam-column connections of the buildings is one of the main sources of uncertainty. The common damages observed after credible earthquakes were falling off large-span beams and large plastic deformations at the column base. New generation Lead Extrusion Damper (LED) developed by the authors is utilized in the seismic retrofitting of these buildings in use. This paper discusses the seismic performances of pre- and post-behaviour of the retrofitted buildings and evaluates the efficiency of the applied retrofitting technique. It is exposed that seismic demands are diminished essentially. The relative storey drifts decrease by about 40-90% while the reduction in the strain at the column base section reaches to 70%. • Lead extrusion dampers can be used for the industrial buildings in use. • Structural demands are reduced drastically by the appropriate use of the damper. • The capacities of the structural members are mostly adequate after the retrofitting. • Seismic retrofitting of an industrial building is succeeded with a reasonable cost. [ABSTRACT FROM AUTHOR]