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The seismic retrofitting of existing multi-storey multi-bay reinforced concrete (RC) frame buildings by the conversion of selected bays into new RC infilled walls is the subject of this research work. The contribution of dowels that connect a new RC infill wall to the surrounding existing RC frame members was studied through a parametric study. The parametric study was performed by nonlinear response-history analyses of a finite element (FE) model. A two-dimensional (2D) frame was modeled, and analyses were performed to calibrate it using the experimental results obtained from a full-scale experiment. The description of the experiment, the experimental results, and the FE model simulation of the test specimen are presented in Georgiou et al. (2018), Georgiou et al. (2022) and Kyriakides et al. (2015) along with a comparison between the experimental results and the numerical ones. Based on the experimental results it was concluded that the number of dowels used in the experiment resulted in a monolithic behavior of the RC infilled frame. To complement the experimental results and to study the interaction between RC infills and the bounding frame both at the global and local level, a parametric study was performed by reducing the number of dowels starting from a spacing of 100 mm (monolithic) to no dowels. The numerical results of the parametric study show that the number of dowels used in the experimental study can be reduced significantly making the use of this method more attractive. These results also provide a basis for the development of a general model for the design of RC infills in existing RC frames, particularly regarding the connection details of the new RC infill walls to the existing bounding frame. The parametric study of the number of dowels connecting the wall to the bounding frame is presented and conclusions are drawn regarding, among others, the effect on the stiffness of the frame, the top storey displacement, the base shear, the axial and shear forces in the dowels, as well as the bending moment at the base of the wall and the outer columns. Some observations that can lead to design recommendations are also presented.

Although it is evident that the RC infill wall is an economic and practical way to improve the lateral strength of framed structures and a retrofitting method for existing buildings to withstand earthquake loads, there are still a lot of limitations regarding their application. Codes do not provide any guidance for their design and detailing or specific regulations for their interaction with the bounding frame. Furthermore, specific directions do not exist for the modelling or evaluation of frame bays converted into RC walls, depending on the type and details of the connection. A representation of the real behaviour of the wall and its interaction with the bounding frame during an earthquake is necessary to provide more accurate guiding information. For this aim, numerical models of this structural system were developed and are presented in this paper. The experimental results of the project SERFIN, which was a full-scale four-storey model tested with the pseudo-dynamic method at the ELSA facility of the Joint Research Centre in Ispra, were used to calibrate the numerical models. Two-dimensional (2D) frames were modelled in DIANA FEA, and nonlinear transient analyses were performed to simulate the experimental results obtained from the SERFIN full-scale experiment. In this paper, the FE model simulation of the test specimen is presented along with a comparison between the experimental results and the numerical ones. It was concluded that the developed numerical models capture effectively the behaviour of the studied structural system and can be used for parametric studies to examine the effects of the number of dowels on the behaviour of the system and propose design guidelines based on the results of the parametric study.

The seismic retrofitting of existing multi-storey multi-bay reinforced concrete (RC) frame buildings by the conversion of selected bays into new RC infilled walls is the subject of this research work. The parametric study of the contribution of dowels that connect a new RC infill wall to the surrounding RC frame members was performed through nonlinear dynamic analyses of a numerical finite element (FE) model. The FE model was simulated in DIANA finite element analysis (FEA) software in order to study the effectiveness of the seismic retrofitting of existing structures with the conversion of selected bays into new infilled RC walls for the retrofitting of a multi-storey multi-bay RC frame building. A two-dimensional (2D) frame was modeled, and nonlinear transient analyses were performed to calibrate it using the experimental results obtained from a full-scale experiment found in the literature. The description of the experimental results and of the FE model simulation of the test specimen is provided along with a comparison between the experimental results and the numerical ones. Based on the preliminary results it was concluded that the number of dowels used in the experiment resulted in a monolithic behavior of the RC infilled frame. In order to complement the experimental results and to study the interaction between RC infills and the bounding frame both at the global and local level, numerical simulation experiments were performed by reducing the number of dowels starting from a spacing of 100mm (monolithic) to no dowels. For each scenario, nonlinear response-history analysis was performed and an evaluation of the numerical results of each of these scenarios was subsequently performed. The parametric study of the number of dowels connecting the wall to the bounding frame is presented and conclusions are drawn. The parametric results provide a basis for the development of a general model for the design of RC infills in existing RC frames, particularly regarding the connection details of the new RC infill walls to the existing bounding frame. Member of the committee: Diofantos G. Hadjimitsis, Petros Christou Completed

The effectiveness of seismic retrofitting of multi-storey multi-bay RC-frame buildings by converting selected bays into new walls through infilling with reinforced concrete (RC) was studied experimentally at the ELSA facility of the Joint Research Centre in Ispra (Italy). A fullscale model was tested with the pseudo-dynamic method and consisted of two four-storey (12m tall) three-bay (8.5m long) parallel frames linked through 0.15m slabs with the central bay (2.5m) infilled with a RC wall. The frames were designed and detailed for gravity loads only and are typical of similar frames built in Cyprus in the 1970’s. Different connection details and reinforcement percentages for the two infilled frames were used in order to study their effects in determining structural response. The results of the pseudo-dynamic and cyclic tests performed on the specimen and their analytical simulation are presented, and conclusions are drawn, JRC.G.4-European laboratory for structural assessment

International audience; The effectiveness of seismic retrofitting of RC-frame buildings by converting selected bays into new walls through infilling with RC walls was studied experimentally using a full-scale four-storey model tested with the pseudo-dynamic (PsD) method. The frames were designed and detailed for gravity loads only using different connection details between the walls and the bounding frame. In order to simulate the experimental response, two numerical models were formulated differing at the level of modelling. The purpose of this paper is to illustrate the capabilities of these models to simulate the experimental nonlinear behaviour of the tested RC building strengthened with RC infill walls and comment on their effectiveness. The comparison between the capacity, in terms of peak ground acceleration, of the strengthened frame and the one of the bare frame, which was obtained numerically, has shown a five-fold increase.

The effectiveness of seismic retrofitting of multi-storey multi-bay RC-frame buildings, by converting selected bays into new walls through infilling with RC, was studied experimentally at the ELSA facility at JRC, Ispra, and the results are reported here. The full-scale model tested with the pseudo-dynamic method consisted of two parallel frames, linked through 0.15m slabs, having three bays each (8.5m long), with the central bay (2.5m) infilled with RC wall, and being four storeys tall (12m). The frames were designed and detailed for gravity loads only and are typical of similar frames built in Cyprus in the 1970’s. Different connection details and reinforcement percentages for the two infilled frames were used in order to study the effects of these parameters. The results of the pseudo-dynamic and cyclic testing performed are presented and conclusions are drawn., JRC.G.5-European laboratory for structural assessment