The cyclic behaviour of reinforced concrete columns has been object of many experimental studies in the last years, mostly focused on the unidirectional loading of columns under constant axial load ...conditions. In this research work, the existing test on reinforced concrete (RC) columns under biaxial load has been reviewed, underlying their main findings. In general, the experimental results show that the RC columns' response is highly dependent on the loading pattern, and the biaxial loading induces a decrease in the maximum strength and anticipates each damage state. Thus, in columns where demands are expected with large moments in both directions, specific detailing should be provided in their critical regions in order to improve the columns' performance and avoid premature failure.
The poor out-of-plane behaviour of masonry infill-walls (MIW) in recent earthquakes, resulted in several casualties and economic losses. The main objective of this work is to present an experimental ...campaign comprised of four out-of-plane tests of full-scale MIW with the main goal to assess the possible effect of the previous damage, workmanship and test setup in the MIW out-of-plane behaviour. From the results, it was observed that the existence of the prior damage reduced the out-of-plane strength and energy dissipation of about 30% and 70%, respectively. The workmanship can introduce variations in the MIW response from 10% to 30%.
•An experimental campaign of full scale infill masonry walls composed by of three out-of-plane test.•The results are discussed in terms of hysteretic force–displacement, damage evolution, ...out-of-plane displacements profile.•A significant difference was found between the tests’ results, with and without previous in-plane damage.
Infill masonry (IM) walls are considered to be non-structural elements but, when subjected to earthquakes, they tend to interact with the surrounding RC (reinforced concrete) frames, which can result in different failure modes depending on the combination of the in-plane and out-of-plane behaviour. Therefore, the contribution of IM panels should be considered in the structural response analysis of existing buildings, for which an understanding of the out-of-plane non-linear behaviour of IM walls is of paramount importance in order to develop efficient strengthening solutions to prevent collapse and improve their performance in future earthquakes, and consequently reduce their seismic vulnerability. In order to obtain further knowledge of the out-of-plane response of IM panels, a study of full-scale IM walls was carried out with the realization of three experimental (cyclic and monotonic) out-of-plane tests with and without previous in-plane damage. The experiments, material characterization and the test set-up will be described in this paper as well as presenting and discussing the main test results, namely in terms of hysteretic force–displacement curves, damage evolution, stiffness degradation and energy dissipation.
•A review of the experimental testing of strengthening solutions of infill walls was performed.•Different strategies can be adopted: disconnection of the panel from the frame adopting energy ...dissipation or the effective strengthening based on different techniques.•All the techniques revealed interesting results, in terms of increase the deformation capacity of the panels.•All the techniques are effective if the strengthening material is bonded or anchored to the panel and to the surrounding frame.
The masonry infill walls’ seismic behaviour is being characterized by extensive damages and out-of-plane (OOP) collapses due to combined in-plane and OOP loading demands. Several efforts are being made to develop efficient strengthening strategies to reduce their seismic vulnerability and in particular to prevent the panels’ collapse. The present manuscript aims presenting retrofit and strengthening strategies to improve the infill masonry walls seismic performance, with particular attention to the prevention of the OOP collapse. Retrofit and improvement of infill walls seismic behaviour is a complex subject, since it cannot be disconnected from their effect on the overall building response. It is paramount to assume that the strengthening should be effective under seismic actions in the plane of the infill wall and under transverse loadings. A systematic review was carry out focusing the major findings and observations made by each author are presented. For each technique, a summary table is provided containing the details regarding the strengthening strategy adopted, major results and observations.
AbstractThe behavior of reinforced-concrete (RC) elements subjected to axial loading variation in conjunction with cyclic biaxial bending is recognized as a very important research topic with a ...reduced number of experimental results available. Six full-scale RC rectangular columns were tested and analyzed to study the effects of variable axial load on the hysteretic behavior of RC building columns under biaxial horizontal loading. The experimental results are presented and discussed in terms of damage evolution, global hysteretic behavior, stiffness degradation, columns’ capacity, and energy dissipation. The global findings revealed the significant effects of the axial load variation on the hysteretic behavior of RC columns.
This work's primary objective is to present an experimental campaign, comprised of three full-scale in-plane tests. It was assessed the effect of the openings (central window) and of using ...textile-reinforced mortar strengthening. The slenderness is also studied by comparing the results herein obtained with other test existing in the literature. The masonry infill walls were built with horizontal hollow clay bricks. All the tests consisted of applying cyclic (loading-unloading-reloading) history of imposed displacements in the in-plane direction employing a top horizontal load. The mechanical properties of the adopted materials are characterized and presented. The results will be presented in terms of in-plane force-displacement responses, damage evolution and energy dissipation capacity. A literature review of numerical modelling approaches to simulate the masonry infill walls seismic behaviour was provided after that. In the end, the experimental tests were simulated in the software OpenSees through a simplified modelling approach. The openings reduced the in-plane maximum strength and energy dissipation capacity by about 40% and 18%, respectively. On the other hand, the textile-reinforced mortar increased the initial stiffness, maximum peak strength and energy dissipation capacity by about 31%, 15% and 38%, respectively.
•Experimental and numerical assessment of in-plane behavior of masonry infilled walls.•Experimental assessment of the effect of the openings in the in-plane behavior of infilled RC frames.•Experimental assessment of the effect of the textile-reinforced mortar strengthening in the in-plane behavior of infilled RC frames.
► Uniaxial and biaxial cyclic tests on rectangular RC columns were performed. ► Comparison of the energy dissipation for biaxial and uniaxial loading. ► A correlation between the ductility and ...dissipated energy was derived. ► The influence of the load path on the equivalent damping was studied. ► Expressions for the equivalent damping of columns under biaxial loading were proposed.
The hysteretic behaviour of RC columns has been object of many experimental studies over the past years. However, the majority of these studies are focused on unidirectional loading. An experimental program was carried out where 24 columns were tested for different loading histories, under uniaxial and biaxial conditions. The experimental results are presented in this paper and are discussed in terms of global column behaviour, and particularly with regards to energy dissipation and damping capacity. The energy dissipation capacity of the columns was evaluated in terms of cumulative dissipated energy, comparing uniaxial and biaxial test results, and individual cycle dissipated energy. Ultimately, an equation relating the normalised dissipated energy with the displacement ductility is proposed. The equivalent viscous damping was analysed by comparing the uniaxial with biaxial test results, demonstrating the high influence of the load path in the biaxial response of RC columns. Proposals for estimating the equivalent viscous damping given by other authors are compared with the experimental results. Finally, simplified expressions are proposed to estimate equivalent viscous damping in RC columns under biaxial loading.
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