Overall structural integrity and load transfer between concrete and reinforcement enabling compos... more Overall structural integrity and load transfer between concrete and reinforcement enabling composite action relies on the bond between concrete and reinforcement. Bond strength determination of reinforced concrete is an essential task that a pullout test can determine. Experimental pullout behaviour can be affected by various parameters, such as concrete and steel strength, boundary conditions, etc. Therefore, a parametric study on pullout tests is time-consuming. In addition, measurements of internal stress-strain components and damages of constitutive materials are also difficult in experimental endeavours. In this context, finite element (FE) models should be developed to perform a parametric study with cost and time-saving. This study proposes a finite element modeling strategy of reinforced concrete under pullout force by using the expected failure mechanism to predict bond-slip behaviour in ABAQUS. In FE models, surface-to-surface cohesive interaction behaviour was used to assign interaction between reinforcement and concrete. The proposed modelling strategy was validated with available experimental data from four reference specimens, having all possible failures (i.e., pullout, splitting, and splitting-pullout) under pullout loading. The finite element analysis showed that the proposed FE modeling strategy performed well in predicting bond-slip behaviour in elastic regions. Additionally, maximum bond stresses were predicted satisfactorily, except for the splitting failure pattern, using the proposed FE modelling strategy.
In developing countries, lateral strengthening of seismically vulnerable masonry infilled RC buil... more In developing countries, lateral strengthening of seismically vulnerable masonry infilled RC buildings is one of the major concerns. In this context, ferrocement can be used as low cost and less labor-intensive strengthening scheme for those buildings. This study aims to experimentally identify major failure mechanisms, and to develop a lateral strength evaluation procedure of ferrocement strengthened masonry infilled RC frame. Mainly four major failure mechanisms (i.e. overall flexural, column punching-joint sliding, diagonal compression, and diagonal cracking-sliding) are identified from the current experimental work and past experimental studies. The strength evaluation procedure, based on the identified failure mechanisms, is proposed and verified with an average calculated to experimental lateral strength ratio of 0.8.
Journal of The Institution of Engineers (India) Series A, 2024
Strengthening of RC columns is necessary to meet the capacity requirement of staged building cons... more Strengthening of RC columns is necessary to meet the capacity requirement of staged building construction, which is a common practice in developing countries. In addition to axial capacity, moment capacity of RC column might also need to be upgraded to address the seismic demand. Therefore, it is important to investigate the effectiveness of strengthening of RC columns under both axial and bending moment domains. In this study, behavior of one of the strengthening methods, i.e., steel angle and strip jacketing of the RC column, has been experimentally studied under several eccentricities (i.e., eccentricity to column depth ratio of 0 to 0.45). In addition, the performance of a capacity prediction model of the steel strengthened RC column, available in literature, has also been investigated using the experimental results of this study and different past experiments. The results of the experiment have shown that the ultimate load capacity of steel jacketed RC columns has been reduced by about 15% for an increase of load eccentricity to column width ratio (e/d) from 0 to 0.45. The observed failure mechanism of the steel strengthened RC columns under eccentric loading is the failure of compression steel angle and subsequent concrete crushing. Further, the analysis result has shown that the capacity prediction model of the steel strengthened RC column can give a fair prediction where the composite action of the steel angle and RC column can be achieved (i.e., escaped from local welding failure and local buckling of the steel angle at the top of the column).
Bulletin of the New Zealand Society for Earthquake Engineering, 2024
Although concrete framed structures are widely used with masonry infills, the contribution of mas... more Although concrete framed structures are widely used with masonry infills, the contribution of masonry infills in structural design is limited to their dead loads only. Therefore, the full-fledged stiffness characteristics of masonry infill are not often considered. However, recent earthquakes showed the impact of masonry infill on the lateral behavior of surrounding RC frames. Moreover, sometimes existing masonry infills are strengthened using Ferrocement (FC), Textile Reinforced Mortar (TRM), Carbon Fiber Reinforced Polymer (CFRP), etc., which might also have a similar impact on surrounding RC frames. The impact includes enhanced shear demand, damage, etc. However, the effect of the enhanced shear demand on RC columns is a relatively less investigated issue. In this context, an experimental program was designed to compare the effect of non-strengthened and FC strengthened masonry infill on the behavior of the surrounding RC frame in terms of lateral strength, hinge formation, shear demand enhancement, and damage to columns. The test specimens, including a bare RC frame, a masonry infilled RC frame, and a FC strengthened masonry infilled RC frame, were subjected to a quasi-static cyclic lateral loads. The experimental result showed that the masonry infill and FC strengthened masonry infill increased lateral strength, on average, by 81% and 244%, respectively, when compared to that of the bare RC frame. Meanwhile, FC strengthening of masonry infill improved the lateral strength, on average, by 90% when compared with the masonry infilled RC frame's lateral strength. In this study, low-strength masonry infill caused the formation of a short column on the tension column of the RC frame. The application of ferrocement to low-strength masonry altered the position of the plastic hinge formed on the tension column of the RC frame when compared to that of the masonry infilled RC frame. Therefore, ferrocement strengthening of masonry eliminated the short column phenomenon in this particular study. Nevertheless, the shear demand (in terms of strain on the column tie) enhancement of the tension column was not substantial due to the ferrocement strengthening of the masonry infill when compared to that of the masonry infilled RC frame. Moreover, the damage concentration on RC columns (i.e., residual crack width) after insertion of masonry infill and ferrocement strengthened masonry infill changed to a smaller extent when compared to the bare RC frame damages, where the residual crack widths were within 1.0 ~ 2.0 mm.
The interaction between the masonry infill wall and the surrounding RC frames and the positive or... more The interaction between the masonry infill wall and the surrounding RC frames and the positive or negative consequences of integrating infill walls into a frame is often ignored for the structural design of the building. The masonry infill walls are usually considered a non-structural element. Researchers illustrate that an infilled frame structure performs better against earthquakes. In this paper, a bare frame and a masonry-infilled RC frame were developed, verified with experimental results of an available specimen in literature, and then analyzed using a finite element software ABAQUS. A perfect convergence of the numerical model with the experimental results in terms of strength and lateral load-drift relationship is achieved from validation. The effect of adding masonry wall in terms of lateral strength and shear demand of columns were analyzed. Finally, a parametric study was done varying the lateral capacity of the masonry panel to understand its local behavior.
Bangladesh which lies in an earthquake-prone region, possesses many seismically vulnerable struct... more Bangladesh which lies in an earthquake-prone region, possesses many seismically vulnerable structures and would need to be strengthened for future usage following the current building code. In this context, assessing the responses of the existing building frames with or without infilled masonry is essential for designing an adequate strengthening scheme that would be suitable for the building. The current study intends to model and simulate one of the available masonry infilled test specimens where the fiber modeling approach of RC member and the multi-strut model of infill masonry have been considered. In addition, the numerically obtained lateral strength has also been compared with analytically evaluated lateral strength. The lateral responses obtained from the numerical analysis showed a fair agreement with the experimental cyclic behavior having a ratio of experimental to the numerical lateral capacity of 0.97. The numerical lateral strength also indicates good conformity with ...
Steel fibers and their aspect ratios are important parameters that have significant influence on ... more Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers...
Overall structural integrity and load transfer between concrete and reinforcement enabling compos... more Overall structural integrity and load transfer between concrete and reinforcement enabling composite action relies on the bond between concrete and reinforcement. Bond strength determination of reinforced concrete is an essential task that a pullout test can determine. Experimental pullout behaviour can be affected by various parameters, such as concrete and steel strength, boundary conditions, etc. Therefore, a parametric study on pullout tests is time-consuming. In addition, measurements of internal stress-strain components and damages of constitutive materials are also difficult in experimental endeavours. In this context, finite element (FE) models should be developed to perform a parametric study with cost and time-saving. This study proposes a finite element modeling strategy of reinforced concrete under pullout force by using the expected failure mechanism to predict bond-slip behaviour in ABAQUS. In FE models, surface-to-surface cohesive interaction behaviour was used to assign interaction between reinforcement and concrete. The proposed modelling strategy was validated with available experimental data from four reference specimens, having all possible failures (i.e., pullout, splitting, and splitting-pullout) under pullout loading. The finite element analysis showed that the proposed FE modeling strategy performed well in predicting bond-slip behaviour in elastic regions. Additionally, maximum bond stresses were predicted satisfactorily, except for the splitting failure pattern, using the proposed FE modelling strategy.
In developing countries, lateral strengthening of seismically vulnerable masonry infilled RC buil... more In developing countries, lateral strengthening of seismically vulnerable masonry infilled RC buildings is one of the major concerns. In this context, ferrocement can be used as low cost and less labor-intensive strengthening scheme for those buildings. This study aims to experimentally identify major failure mechanisms, and to develop a lateral strength evaluation procedure of ferrocement strengthened masonry infilled RC frame. Mainly four major failure mechanisms (i.e. overall flexural, column punching-joint sliding, diagonal compression, and diagonal cracking-sliding) are identified from the current experimental work and past experimental studies. The strength evaluation procedure, based on the identified failure mechanisms, is proposed and verified with an average calculated to experimental lateral strength ratio of 0.8.
Journal of The Institution of Engineers (India) Series A, 2024
Strengthening of RC columns is necessary to meet the capacity requirement of staged building cons... more Strengthening of RC columns is necessary to meet the capacity requirement of staged building construction, which is a common practice in developing countries. In addition to axial capacity, moment capacity of RC column might also need to be upgraded to address the seismic demand. Therefore, it is important to investigate the effectiveness of strengthening of RC columns under both axial and bending moment domains. In this study, behavior of one of the strengthening methods, i.e., steel angle and strip jacketing of the RC column, has been experimentally studied under several eccentricities (i.e., eccentricity to column depth ratio of 0 to 0.45). In addition, the performance of a capacity prediction model of the steel strengthened RC column, available in literature, has also been investigated using the experimental results of this study and different past experiments. The results of the experiment have shown that the ultimate load capacity of steel jacketed RC columns has been reduced by about 15% for an increase of load eccentricity to column width ratio (e/d) from 0 to 0.45. The observed failure mechanism of the steel strengthened RC columns under eccentric loading is the failure of compression steel angle and subsequent concrete crushing. Further, the analysis result has shown that the capacity prediction model of the steel strengthened RC column can give a fair prediction where the composite action of the steel angle and RC column can be achieved (i.e., escaped from local welding failure and local buckling of the steel angle at the top of the column).
Bulletin of the New Zealand Society for Earthquake Engineering, 2024
Although concrete framed structures are widely used with masonry infills, the contribution of mas... more Although concrete framed structures are widely used with masonry infills, the contribution of masonry infills in structural design is limited to their dead loads only. Therefore, the full-fledged stiffness characteristics of masonry infill are not often considered. However, recent earthquakes showed the impact of masonry infill on the lateral behavior of surrounding RC frames. Moreover, sometimes existing masonry infills are strengthened using Ferrocement (FC), Textile Reinforced Mortar (TRM), Carbon Fiber Reinforced Polymer (CFRP), etc., which might also have a similar impact on surrounding RC frames. The impact includes enhanced shear demand, damage, etc. However, the effect of the enhanced shear demand on RC columns is a relatively less investigated issue. In this context, an experimental program was designed to compare the effect of non-strengthened and FC strengthened masonry infill on the behavior of the surrounding RC frame in terms of lateral strength, hinge formation, shear demand enhancement, and damage to columns. The test specimens, including a bare RC frame, a masonry infilled RC frame, and a FC strengthened masonry infilled RC frame, were subjected to a quasi-static cyclic lateral loads. The experimental result showed that the masonry infill and FC strengthened masonry infill increased lateral strength, on average, by 81% and 244%, respectively, when compared to that of the bare RC frame. Meanwhile, FC strengthening of masonry infill improved the lateral strength, on average, by 90% when compared with the masonry infilled RC frame's lateral strength. In this study, low-strength masonry infill caused the formation of a short column on the tension column of the RC frame. The application of ferrocement to low-strength masonry altered the position of the plastic hinge formed on the tension column of the RC frame when compared to that of the masonry infilled RC frame. Therefore, ferrocement strengthening of masonry eliminated the short column phenomenon in this particular study. Nevertheless, the shear demand (in terms of strain on the column tie) enhancement of the tension column was not substantial due to the ferrocement strengthening of the masonry infill when compared to that of the masonry infilled RC frame. Moreover, the damage concentration on RC columns (i.e., residual crack width) after insertion of masonry infill and ferrocement strengthened masonry infill changed to a smaller extent when compared to the bare RC frame damages, where the residual crack widths were within 1.0 ~ 2.0 mm.
The interaction between the masonry infill wall and the surrounding RC frames and the positive or... more The interaction between the masonry infill wall and the surrounding RC frames and the positive or negative consequences of integrating infill walls into a frame is often ignored for the structural design of the building. The masonry infill walls are usually considered a non-structural element. Researchers illustrate that an infilled frame structure performs better against earthquakes. In this paper, a bare frame and a masonry-infilled RC frame were developed, verified with experimental results of an available specimen in literature, and then analyzed using a finite element software ABAQUS. A perfect convergence of the numerical model with the experimental results in terms of strength and lateral load-drift relationship is achieved from validation. The effect of adding masonry wall in terms of lateral strength and shear demand of columns were analyzed. Finally, a parametric study was done varying the lateral capacity of the masonry panel to understand its local behavior.
Bangladesh which lies in an earthquake-prone region, possesses many seismically vulnerable struct... more Bangladesh which lies in an earthquake-prone region, possesses many seismically vulnerable structures and would need to be strengthened for future usage following the current building code. In this context, assessing the responses of the existing building frames with or without infilled masonry is essential for designing an adequate strengthening scheme that would be suitable for the building. The current study intends to model and simulate one of the available masonry infilled test specimens where the fiber modeling approach of RC member and the multi-strut model of infill masonry have been considered. In addition, the numerically obtained lateral strength has also been compared with analytically evaluated lateral strength. The lateral responses obtained from the numerical analysis showed a fair agreement with the experimental cyclic behavior having a ratio of experimental to the numerical lateral capacity of 0.97. The numerical lateral strength also indicates good conformity with ...
Steel fibers and their aspect ratios are important parameters that have significant influence on ... more Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers...
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