engleski

Performance based seismic design of masonry infilled frames

Reinforced concrete frames with masonry infills are composite structures, dominant in the low and medium high buildings, which achieve its constructive function with infilling concrete frame with masonry wall. Because of the inhomogeneity of components of this composite systems, behavior during earthquake activity is difficult to predict, which often leads with neglecting infill influence in the design of enginnering practice, although its positive effect was observed during the last earthquakes. Experiences from past earthquakes have shown conflicting findings about the influence of infills on buildings responses. With continuous and uniform distribution, infill will increase the strength and stifnness and reduce possible damage of the frame structure. However, uneven distribution of infills in planar or spatial structure can cause both local and global plastic deformation that can result in colaps of part or colaps of entire structure. Some modern regulations state that it is necessary to include infills in design proces with no usable recommendations on the model, but on the other hand certain national codes completely ignore masonry infills defined them as nonstructural part with no influence on the system. Guidance provided by Eurocode 8 commonly accepted only unfavorable contributions of masonry infill, ignoring the positive ones. Despite a big number of experimental tests of reinforced concrete frame with brick infill, with general conclusion of increasing stiffness, strength and energy dissipation compared to bare frames, there is no characterization of parameters with infuence on the phenomenon of behavior that can in real aspects allow proper calibration of mathematical models with the confirmation correlation and compliance. Given the necessity of systematization of experimental data and achieving the relationship between the seismic behavior and material and geometric properties of components of the infilled frames, was formed EDIF experimental database was conducted. EDIF database includes one story one bay reinforced concrete frames with non reinforced masonry infills. Processing ot the data scaled to prototype scale experimental tests was performed using neural networks. An evaluation and calibration of different numerical models of infilled frames, based on the results from the EDIF experimental base, resulted in the best numerical nonlinear model for one story one bay infilled frame structure. Analysis on real models of structures based on experimental results from a number of European projects has proven the suitability and usability of the numerical model that is the base for parametric study in accordance with the expected earthquake response of buildings consisting of a frame with infill. Defined model building sets include different number of storeys, material and geometrical characteristics of the frame and masonry infill, the ratio of inffiled frames area to floor area and different earthquake loads according to the PGA values.Incremental dynamic analysis in accordance with the expected earthquake response was applied in order to obtain the vulnerability curves and discrete probabilities for each observed level of damage and the correlation between the expected level of seismic excitation and response structures with design parameters for a given type of construction. Realization of disertation in applicative methodology for engineering practice in the process of optimal design and analysis of seismic response of new buildings and evaluation of the behavior of existing buildings of reinforced concrete frames with masonry infills in earthquakeprone areas.

peformace-based design; r/c infilled-frames; framed-masonry

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