During an earthquake, an interaction between the inplane and outofplane seismic forces occurs and the infilled frames suffer damage in both inplane and outofplane directions simultaneously. Particularly, the outofplane collapse of unreinforced masonry infill walls is critical even for new buildings complying with the modern seismic codes, resulting in high casualties and huge economic losses. However, the outofplane behaviour of infill walls is yet not fully understood. This study is therefore aimed towards characterizing the outofplane seismic capacity of unreinforced masonry infill walls. First of all, available outofplane experimental tests performed on unreinforced masonry infill walls are reviewed with a detailed comparison of the experimental results. The influence of parameters like slenderness ratio, aspect ratio, boundary conditions, openings, vertical load, inplane damage level, the strength of masonry and plaster, and frame stiffness are evaluated, and research gaps are identified. Based on the collected experiments, all available analytical capacity models are checked for their accuracy in the prediction of the outofplane capacity of unreinforced masonry infill walls. In doing so, both types of capacity models are evaluated: Type (I) for the estimation of the outofplane strength in the inplane undamaged state; TypeII for the estimation of outofplane strength reduction factor for the inplane damaged state. Afterwards, the best pairs of models from two groups i.e. Type I and Type II, are coupled and checked with the experimented specimens where the reference infill specimen (specimen tested in outofplane without prior inplane damage) is not available. In addition, the influence of orthotropy of the infill masonry in the outofplane capacity predicted by the capacity models is analysed. The possibility of using the capacity models in the cases of infillbeam gap and infill with openings is also checked. Different available macromodelling techniques are investigated and a simple macroelement model which can simulate the behaviour of unreinforced masonry infill walls under inplane and outofplane loads is developed. The model is validated with different sets of experiments. The model takes into account the decrease in outofplane capacity due to prior inplane damage and is capable to capture inplane/outofplane interaction effects of the seismic forces. From the correlation between the experimental and macromodel results, empirical equations are developed that can be used to calculate the stressstrain parameters required for defining the compressive behaviour of the struts. With the provided strategy, the geometrical and mechanical parameters required for the struts can be easily identified for numerical modelling of the infill wall. Using the model, inplane and outofplane responses of the infill wall in lateral loads can be checked. To enrich the information obtained from the experiments regarding the outofplane behaviour of infill walls, numerical experimentation is performed by using the developed macromodel covering the range of infill’s geometrical and mechanical properties. From the detailed parametric analysis, the outofplane strength of the infill wall is found to be largely influenced by compressive strength, slenderness ratio, aspect ratio, and more importantly by the level of inplane damage. The decay of strength and stiffness due to prior inplane damage is also largely governed by the strength and the slenderness ratio of the unreinforced masonry infill. Based on the numerical results, empirical equations are proposed for the evaluation of the infilled frame’s outofplane capacity under inplane damaged or undamaged conditions. The reliability of the proposed equations is proved by comparisons with experimental results. Finally, a procedure for developing the outofplane fragility functions is proposed by using the developed macromodel. The fragility is calculated assuming the uncertainty in the geometric and mechanical properties of infill walls instead of the uncertainty in the seismic input. The fragility is defined with respect to the position of the infill wall in a lowrise RC building. Experimental data available in the literature are used for the validation of the output. Overall, the results indicated lower vulnerability in the outofplane direction for infill walls without prior inplane damage and high vulnerability when the infill wall is prior damaged in the inplane. The proposed procedure can be extended to other types of infill walls depending on the construction technique of the site of interest, obtaining different and specific fragility curves for perming a largescale risk analysis.
During an earthquake, an interaction between the inplane and outofplane seismic forces occurs and the infilled frames suffer damage in both inplane and outofplane directions simultaneously. Particularly, the outofplane collapse of unreinforced masonry infill walls is critical even for new buildings complying with the modern seismic codes, resulting in high casualties and huge economic losses. However, the outofplane behaviour of infill walls is yet not fully understood. This study is therefore aimed towards characterizing the outofplane seismic capacity of unreinforced masonry infill walls. First of all, available outofplane experimental tests performed on unreinforced masonry infill walls are reviewed with a detailed comparison of the experimental results. The influence of parameters like slenderness ratio, aspect ratio, boundary conditions, openings, vertical load, inplane damage level, the strength of masonry and plaster, and frame stiffness are evaluated, and research gaps are identified. Based on the collected experiments, all available analytical capacity models are checked for their accuracy in the prediction of the outofplane capacity of unreinforced masonry infill walls. In doing so, both types of capacity models are evaluated: Type (I) for the estimation of the outofplane strength in the inplane undamaged state; TypeII for the estimation of outofplane strength reduction factor for the inplane damaged state. Afterwards, the best pairs of models from two groups i.e. Type I and Type II, are coupled and checked with the experimented specimens where the reference infill specimen (specimen tested in outofplane without prior inplane damage) is not available. In addition, the influence of orthotropy of the infill masonry in the outofplane capacity predicted by the capacity models is analysed. The possibility of using the capacity models in the cases of infillbeam gap and infill with openings is also checked. Different available macromodelling techniques are investigated and a simple macroelement model which can simulate the behaviour of unreinforced masonry infill walls under inplane and outofplane loads is developed. The model is validated with different sets of experiments. The model takes into account the decrease in outofplane capacity due to prior inplane damage and is capable to capture inplane/outofplane interaction effects of the seismic forces. From the correlation between the experimental and macromodel results, empirical equations are developed that can be used to calculate the stressstrain parameters required for defining the compressive behaviour of the struts. With the provided strategy, the geometrical and mechanical parameters required for the struts can be easily identified for numerical modelling of the infill wall. Using the model, inplane and outofplane responses of the infill wall in lateral loads can be checked. To enrich the information obtained from the experiments regarding the outofplane behaviour of infill walls, numerical experimentation is performed by using the developed macromodel covering the range of infill’s geometrical and mechanical properties. From the detailed parametric analysis, the outofplane strength of the infill wall is found to be largely influenced by compressive strength, slenderness ratio, aspect ratio, and more importantly by the level of inplane damage. The decay of strength and stiffness due to prior inplane damage is also largely governed by the strength and the slenderness ratio of the unreinforced masonry infill. Based on the numerical results, empirical equations are proposed for the evaluation of the infilled frame’s outofplane capacity under inplane damaged or undamaged conditions. The reliability of the proposed equations is proved by comparisons with experimental results. Finally, a procedure for developing the outofplane fragility functions is proposed by using the developed macromodel. The fragility is calculated assuming the uncertainty in the geometric and mechanical properties of infill walls instead of the uncertainty in the seismic input. The fragility is defined with respect to the position of the infill wall in a lowrise RC building. Experimental data available in the literature are used for the validation of the output. Overall, the results indicated lower vulnerability in the outofplane direction for infill walls without prior inplane damage and high vulnerability when the infill wall is prior damaged in the inplane. The proposed procedure can be extended to other types of infill walls depending on the construction technique of the site of interest, obtaining different and specific fragility curves for perming a largescale risk analysis.
(2022). Out of Plane response of Unreinforced Masonry infills: Comparative analysis of experimental tests for the definition of strategies of macro modelling and fragility prediction.
Out of Plane response of Unreinforced Masonry infills: Comparative analysis of experimental tests for the definition of strategies of macro modelling and fragility prediction
PRADHAN, Bharat
20220223
Abstract
During an earthquake, an interaction between the inplane and outofplane seismic forces occurs and the infilled frames suffer damage in both inplane and outofplane directions simultaneously. Particularly, the outofplane collapse of unreinforced masonry infill walls is critical even for new buildings complying with the modern seismic codes, resulting in high casualties and huge economic losses. However, the outofplane behaviour of infill walls is yet not fully understood. This study is therefore aimed towards characterizing the outofplane seismic capacity of unreinforced masonry infill walls. First of all, available outofplane experimental tests performed on unreinforced masonry infill walls are reviewed with a detailed comparison of the experimental results. The influence of parameters like slenderness ratio, aspect ratio, boundary conditions, openings, vertical load, inplane damage level, the strength of masonry and plaster, and frame stiffness are evaluated, and research gaps are identified. Based on the collected experiments, all available analytical capacity models are checked for their accuracy in the prediction of the outofplane capacity of unreinforced masonry infill walls. In doing so, both types of capacity models are evaluated: Type (I) for the estimation of the outofplane strength in the inplane undamaged state; TypeII for the estimation of outofplane strength reduction factor for the inplane damaged state. Afterwards, the best pairs of models from two groups i.e. Type I and Type II, are coupled and checked with the experimented specimens where the reference infill specimen (specimen tested in outofplane without prior inplane damage) is not available. In addition, the influence of orthotropy of the infill masonry in the outofplane capacity predicted by the capacity models is analysed. The possibility of using the capacity models in the cases of infillbeam gap and infill with openings is also checked. Different available macromodelling techniques are investigated and a simple macroelement model which can simulate the behaviour of unreinforced masonry infill walls under inplane and outofplane loads is developed. The model is validated with different sets of experiments. The model takes into account the decrease in outofplane capacity due to prior inplane damage and is capable to capture inplane/outofplane interaction effects of the seismic forces. From the correlation between the experimental and macromodel results, empirical equations are developed that can be used to calculate the stressstrain parameters required for defining the compressive behaviour of the struts. With the provided strategy, the geometrical and mechanical parameters required for the struts can be easily identified for numerical modelling of the infill wall. Using the model, inplane and outofplane responses of the infill wall in lateral loads can be checked. To enrich the information obtained from the experiments regarding the outofplane behaviour of infill walls, numerical experimentation is performed by using the developed macromodel covering the range of infill’s geometrical and mechanical properties. From the detailed parametric analysis, the outofplane strength of the infill wall is found to be largely influenced by compressive strength, slenderness ratio, aspect ratio, and more importantly by the level of inplane damage. The decay of strength and stiffness due to prior inplane damage is also largely governed by the strength and the slenderness ratio of the unreinforced masonry infill. Based on the numerical results, empirical equations are proposed for the evaluation of the infilled frame’s outofplane capacity under inplane damaged or undamaged conditions. The reliability of the proposed equations is proved by comparisons with experimental results. Finally, a procedure for developing the outofplane fragility functions is proposed by using the developed macromodel. The fragility is calculated assuming the uncertainty in the geometric and mechanical properties of infill walls instead of the uncertainty in the seismic input. The fragility is defined with respect to the position of the infill wall in a lowrise RC building. Experimental data available in the literature are used for the validation of the output. Overall, the results indicated lower vulnerability in the outofplane direction for infill walls without prior inplane damage and high vulnerability when the infill wall is prior damaged in the inplane. The proposed procedure can be extended to other types of infill walls depending on the construction technique of the site of interest, obtaining different and specific fragility curves for perming a largescale risk analysis.File  Dimensione  Formato  

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