The behaviour of reinforced concrete frames with masonry wall infills is influenced a lot by the stiffness and strength difference between the frame and the infill, causing early detrimental damage to the infill or to the critical concrete columns. The paper reports the results from shake table seismic tests on a full-scale reinforced concrete (RC) frame building with modified hollow clay block (orthoblock brick) infill walls, within INMASPOL SERA Horizon 2020 project. The building received innovative resilient protection using Polyurethane Flexible Joints (PUFJs) made of polyurethane resin (PU), applied at the frame-infill interface in different schemes. Further, PUs were used for bonding of glass fibre grids to the weak masonry substrate to form Fibre Reinforced Polyurethanes (FRPUs) as an emergency repair intervention. The test results showed enhancement in the in-plane and out-of-plane infill performance under seismic excitations. The results confirmed remarkable delay of significant infill damages at very high RC frame inter-story drifts as a consequence of the use of PUFJs. Further, the PUFJ protection enabled the resilient repair of the infill even after very high inter-story drift of the structure up to 3.7%. The applied glass FRPU system efficiently protected the damaged infills against collapse under out-of-plane excitation while they restored large part of their in-plane stiffness.

Passive control of structures represents practical concept and qualitative change of the design and construction of new seismically resistant structures and strengthening of existing ones. The best distribution obtained by the minimization or maximization of the defined structural responses is achieved by optimal placement of the different types of control devices in structures. In this paper the procedure for optimal placement of viscous damping devices (PDD–Prestressed Damping Device-PDD) (space distributed) in structures for controlling their response due to seismic excitation, will be presented. For the purpose of determination of the PDDs' optimal location, 3D five story steel frame structure has been designed following Eurocode 3 and Eurocode 8 requirements. Nine, previously defined, initial configurations have been used as a starting point in the process of optimization. The desired performance has been defined using the fitness function derived from the inter-story drift and energy dissipated by the PDDs vs. input energy in the structure in two directions x and y. The value of the fitness function has been used to rank and quantify the optimum of the particular solution among all other solutions in the optimization process. Numerous nonlinear analyses have been conducted and a lot of analytical results have been collected in order to confirm the validity and the application of the presented procedure including the fitness function in any steel structure.

The paper presents the results of research on a nearly full-scale, 1-story reinforced-concrete (RC) spatial frame structure with masonry infill walls tested on a shake table. The experiment was conducted in four phases to investigate the in-plane and out-of-plane responses of the infill walls of the specimen. The use of a digital image correlation (DIC) technique with noncommercial analysis system allowed the computation of principal strains for the infill. Two methods of infill-RC frame protection using polyurethane resin (PU) flexible joints (PUFJ) at the RC frame-infill connection and an external innovative fiber-reinforced PU (FRPU) repair system were considered in the research. The test results indicated that the in-plane and out-of-plane infill performance was enhanced under seismic excitations. The PUFJs at the interface of the frame and infill walls helped the infills to withstand dynamic excitation of high intensity with repairable damage. Furthermore, the externally applied glass FRPU repair system efficiently protected the damaged masonry infills against collapse under out-of-plane excitation while restoring a significant portion of their in-plane stiffness. The variable contributions of the RC frame and of the brick infills when protected with innovative joints are evaluated through three-dimensional finite-element models. Externally bonded fiber-reinforced PU composite is prefabricated or constructed on-site repair and strengthening solution, consisting of strengthening fibers and flexible polyurethane matrix. It is capable of carrying high loads and high deformations simultaneously and allows for reducing of stress concentrations and redistributing them over large bonding area, what results in higher load capacity of the composite strengthening systems. This innovative composite solution is dedicated to structures made of brittle materials (concrete, masonry) located in seismic areas. Flexible polyurethane matrix allows working with even low-strength fibers and low-strength brittle substrates, introducing greater strength, ductility, and load-bearing capacity, making it safer in exploitation. This composite strengthening system was examined as emergency strengthening of infill walls damaged by vibrations on a shake table. Repeated seismic excitations of high intensity were unable to cause collapse of the infill walls protected by this innovative composite system, neither in in-plane nor in out-of-plane modes. The tested building specimen of natural scale, protected by the flexible composite system, survived many seismic excitations remaining in good structural shape. This paper presents results of dynamic tests, proving practical efficiency of the composite system examined in more dangerous conditions than are present during strong earthquakes.