PERFORMANCE-BASED ASSESSMENT OF MEDIUM-RISE MASONRY BUILDINGS
Ahmed Mohamed Abd-El Latif Yassin;
Abstract
The main objective of this research was to analyze and predict the seismic performance of medium rise reinforced masonry structural walls having rectangular, flanged and end-confined cross sections. From a structural behavior view point, medium rise masonry walls lies between squat (low rise) walls and slender (high rise) walls and it was observed that these walls are mainly dominated by flexure mode of failure.
This study was divided into three phases, the first of which involved the development and validation of a non-linear finite element model that is capable of simulating the lateral response of two and three story flexural dominated walls and previously tested by other researchers. The model was capable to simulate the stiffness degradation, energy dissipation, pinching and cyclic response for all wall types (rectangular, flanged and end-confined) followed by a parametric study to assess the effect of vertical reinforcement and axial compression on wall behavior. The second phase incorporated the generation of a set of fragility curves for the aforementioned wall types used for the prediction of the seismic performance or the level of damage for the reinforced masonry walls. Fragility curves showed the importance of end confinement zones and end flanges in enhancing the seismic behavior and delaying the structural damage. In the third phase a prototypical of three story building which is composed of a combination of rectangular, flanged and end confined walls was analyzed in order to determine the ductility and response modification factor for the entire building assuming equal displacement approach.
7.2 Conclusions
Analysis and interpretation of the results reached in this study led to the following conclusions:
1- Medium rise masonry walls behave similarly to high rise walls by which both behave mainly in flexure dominated mode of failure and perform with full ductility capacity by which the effect of aspect ratio on ductility of mid-rise still makes it perform in ductile manner.
2- Regarding to wall section type, End confined wall section is the most seismic efficient wall type compared to flanged and rectangular wall sections regarding to strength and ductility capacity for the same vertical reinforcement and axial compression stress.
3- Regarding to aspect ratio, walls having lower aspect ratio (1.5) had higher displacement ductility compared to higher aspect ratio walls (2.2).
4- Yield displacement increases with the increase of vertical reinforcement or axial compression but the effect of vertical reinforcement is more significant.
5- Displacement ductility decreases with the increase of axial compression or vertical reinforcement but the effect of axial compression is more significant than vertical reinforcement.
6- Effect of vertical reinforcement in increasing ultimate capacity is much bigger than the effect of axial compression.
7- Effect of increasing reinforcement on increasing strength is more significant on end confined and flanged walls compared to rectangular walls.
8- Effect of increasing reinforcement on decreasing displacement ductility is more significant on rectangular wall.
9- Flanged and end confined walls are more vulnerable to the second damage state (immediate occupancy, which is considered for the onset of reinforcement yielding) compared to rectangular wall section.
10-Rectangular walls are more vulnerable to the third damage state (life safety, which is considered for vertical cracking at compression toes) followed by flanged walls then end confined walls which seem to be the most reluctant for this damage state.
11-For the fourth damage state (collapse prevention, which is considered for crushing of masonry or buckling of reinforcement) both flanged and end confined provide a better alternative in delaying the occurrence of
This study was divided into three phases, the first of which involved the development and validation of a non-linear finite element model that is capable of simulating the lateral response of two and three story flexural dominated walls and previously tested by other researchers. The model was capable to simulate the stiffness degradation, energy dissipation, pinching and cyclic response for all wall types (rectangular, flanged and end-confined) followed by a parametric study to assess the effect of vertical reinforcement and axial compression on wall behavior. The second phase incorporated the generation of a set of fragility curves for the aforementioned wall types used for the prediction of the seismic performance or the level of damage for the reinforced masonry walls. Fragility curves showed the importance of end confinement zones and end flanges in enhancing the seismic behavior and delaying the structural damage. In the third phase a prototypical of three story building which is composed of a combination of rectangular, flanged and end confined walls was analyzed in order to determine the ductility and response modification factor for the entire building assuming equal displacement approach.
7.2 Conclusions
Analysis and interpretation of the results reached in this study led to the following conclusions:
1- Medium rise masonry walls behave similarly to high rise walls by which both behave mainly in flexure dominated mode of failure and perform with full ductility capacity by which the effect of aspect ratio on ductility of mid-rise still makes it perform in ductile manner.
2- Regarding to wall section type, End confined wall section is the most seismic efficient wall type compared to flanged and rectangular wall sections regarding to strength and ductility capacity for the same vertical reinforcement and axial compression stress.
3- Regarding to aspect ratio, walls having lower aspect ratio (1.5) had higher displacement ductility compared to higher aspect ratio walls (2.2).
4- Yield displacement increases with the increase of vertical reinforcement or axial compression but the effect of vertical reinforcement is more significant.
5- Displacement ductility decreases with the increase of axial compression or vertical reinforcement but the effect of axial compression is more significant than vertical reinforcement.
6- Effect of vertical reinforcement in increasing ultimate capacity is much bigger than the effect of axial compression.
7- Effect of increasing reinforcement on increasing strength is more significant on end confined and flanged walls compared to rectangular walls.
8- Effect of increasing reinforcement on decreasing displacement ductility is more significant on rectangular wall.
9- Flanged and end confined walls are more vulnerable to the second damage state (immediate occupancy, which is considered for the onset of reinforcement yielding) compared to rectangular wall section.
10-Rectangular walls are more vulnerable to the third damage state (life safety, which is considered for vertical cracking at compression toes) followed by flanged walls then end confined walls which seem to be the most reluctant for this damage state.
11-For the fourth damage state (collapse prevention, which is considered for crushing of masonry or buckling of reinforcement) both flanged and end confined provide a better alternative in delaying the occurrence of
Other data
| Title | PERFORMANCE-BASED ASSESSMENT OF MEDIUM-RISE MASONRY BUILDINGS | Other Titles | تقييم سلوك مبانى الطوب متوسطة الأرتفاع على أسس الأدائية | Authors | Ahmed Mohamed Abd-El Latif Yassin | Issue Date | 2014 |
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