Seismic performance of concrete frame structures reinforced with superelastic shape memory alloys

Alam, M. Shahria,Nehdi, Moncef,Youssef, Maged A. Techno-Press 2009 Smart Structures and Systems, An International Jou Vol.5 No.5

Superelastic Shape Memory Alloys (SMAs) are gaining acceptance for use as reinforcing bars in concrete structures. The seismic behaviour of concrete frames reinforced with SMAs is being assessed in this study. Two eight-storey concrete frames, one of which is reinforced with regular steel and the other with SMAs at the plastic hinge regions of beams and regular steel elsewhere, are designed and analyzed using 10 different ground motion records. Both frames are located in the highly seismic region of Western Canada and are designed and detailed according to current seismic design standards. The validation of a finite element (FE) program that was conducted previously at the element level is extended to the structure level in this paper using the results of a shake table test of a three-storey moment resisting steel RC frame. The ten accelerograms that are chosen for analyzing the designed RC frames are scaled based on the spectral ordinate at the fundamental periods of the frames. The behaviour of both frames under scaled seismic excitations is compared in terms of maximum inter-storey drift, top-storey drift, inter-storey residual drift, and residual top-storey drift. The results show that SMA-RC frames are able to recover most of its post-yield deformation, even after a strong earthquake.

Fire performance curves for unprotected HSS steel column

M. Shahria Alam,A.H.M. Muntasir Billah,Shahriar Quayyum,Mahmud Ashraf,A.N.M. Rafi,Ahmad Rteil 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.15 No.6

The behaviour of steel column at elevated temperature is significantly different than that atambient temperature due to its changes in the mechanical properties with temperature. Reported literaturesuggests that steel column may become vulnerable when exposed to fire condition, since its strength andcapacity decrease rapidly with temperature. The present study aims at investigating the lateral load resistanceof non-insulated steel columns under fire exposure through finite element analysis. The studied parametersinclude moment-rotation behaviour, lateral load-deflection behaviour, stiffness and ductility of columns atdifferent axial load levels. It was observed that when the temperature of the column was increased, there wasa significant reduction in the lateral load and moment capacity of the non-insulated steel columns. Moreover,it was noted that the stiffness and ductility of steel columns decreased sharply with the increase intemperature, especially for temperatures above 400°C. In addition, the lateral load capacity and the momentcapacity of columns were plotted against fire exposure time, which revealed that in fire conditions, thenon-insulated steel columns experience substantial reduction in lateral load resistance within 15 minutes offire exposure.

Seismic performance of concrete frame structures reinforced with superelastic shape memory alloys

M. Shahria Alam,Moncef Nehdi,Maged A. Youssef 국제구조공학회 2009 Smart Structures and Systems, An International Jou Vol.5 No.5

Superelastic Shape Memory Alloys (SMAs) are gaining acceptance for use as reinforcing bars in concrete structures. The seismic behaviour of concrete frames reinforced with SMAs is being assessed in this study. Two eight-storey concrete frames, one of which is reinforced with regular steel and the other with SMAs at the plastic hinge regions of beams and regular steel elsewhere, are designed and analyzed using 10 different ground motion records. Both frames are located in the highly seismic region of Western Canada and are designed and detailed according to current seismic design standards. The validation of a finite element (FE) program that was conducted previously at the element level is extended to the structure level in this paper using the results of a shake table test of a three-storey moment resisting steel RC frame. The ten accelerograms that are chosen for analyzing the designed RC frames are scaled based on the spectral ordinate at the fundamental periods of the frames. The behaviour of both frames under scaled seismic excitations is compared in terms of maximum inter-storey drift, top-storey drift, inter-storey residual drift, and residual top-storey drift. The results show that SMA-RC frames are able to recover most of its post-yield deformation, even after a strong earthquake.

Seismic behaviour of repaired superelastic shape memory alloy reinforced concrete beam-column joint

Nehdi, Moncef,Alam, M. Shahria,Youssef, Maged A. Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.7 No.5

Large-scale earthquakes pose serious threats to infrastructure causing substantial damage and large residual deformations. Superelastic (SE) Shape-Memory-Alloys (SMAs) are unique alloys with the ability to undergo large deformations, but can recover its original shape upon stress removal. The purpose of this research is to exploit this characteristic of SMAs such that concrete Beam-Column Joints (BCJs) reinforced with SMA bars at the plastic hinge region experience reduced residual deformation at the end of earthquakes. Another objective is to evaluate the seismic performance of SMA Reinforced Concrete BCJs repaired with flowable Structural-Repair-Concrete (SRC). A $\frac{3}{4}$-scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading, and subsequently repaired and retested. The joint was selected from an RC building located in the seismic region of western Canada. It was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour under reversed cyclic loading of the original and repaired joints, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation, requiring a minimum amount of repair, even after a large earthquake, proving to be smart structural elements. It was also shown that the use of SRC to repair damaged BCJs can restore its full capacity.

Seismic behavior of soft storey mid-rise steel frames with randomly distributed masonry infill

Shahriar Quayyum,M. Shahria Alam,Ahmad Rteil 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.6

In this study, the effect of presence and distribution of masonry infill walls on the mid-rise steel frame structures having soft ground storey was evaluated by implementing finite element (FE) methods. Masonry infill walls were distributed randomly in the upper storey keeping the ground storey open without any infill walls, thus generating the worst case scenario for seismic events. It was observed from the analysis that there was an increase in the seismic design forces, moments and base shear in presence of randomly distributed masonry infill walls which underlines that these design values need to be amplified when designing a mid-rise soft ground storey steel frame with randomly distributed masonry infill. In addition, it was found that the overstrength related force modification factor increased and the ductility related force modification factor decreased with the increase in the amount of masonry infilled bays and panels. These must be accounted for in the design of mid-rise steel frames. Based on the FE analysis results on two mid-rise steel frames, design equations were proposed for determining the over strength and the ductility related force modification factors. However, it was recommended that these equations to be generalized for other steel frame structure systems based on an extensive analysis.

Principal Component and Multiple Regression Analysis for Steel Fiber Reinforced Concrete (SFRC) Beams

Mohammad S. Islam,Shahria Alam 한국콘크리트학회 2013 International Journal of Concrete Structures and M Vol.7 No.4

This study evaluates the shear strength of steel fiber reinforced concrete (SFRC) beams from a database, which consists of extensive experimental results of 222 SFRC beams having no stirrups. In order to predict the analytical shear strength of the SFRC beams more precisely, the selected beams were sorted into six different groups based on their ultimate concrete strength (low strength with fc<SUP>1</SUP><50 MPa and high strength with fc<SUP>1</SUP><50 MPa), span-depth ratio (shallow beam with a/d ≥ 2.5 and deep beam with a/d < 2.5) and steel fiber shape (plain, crimped and hooked). Principal component and multiple regression analyses were performed to determine the most feasible model in predicting the shear strength of SFRC beams. A variety of statistical analyses were conducted, and compared with those of the existing equations in estimating the shear strength of SFRC beams. The results showed that the recommended empirical equations were best suited to assess the shear strength of SFRC beams more accurately as compared to those obtained by the previously developed models.

Erratum to : Principal Component and Multiple Regression Analysis for Steel Fiber Reinforced Concrete (SFRC) Beams

Mohammad S. Islam,Shahria Alam 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.2

Seismic behaviour of repaired superelastic shape memory alloy reinforced concrete beam-column joint

Moncef Nehdi,M. Shahria Alam,Maged A. Youssef 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.7 No.5

Large-scale earthquakes pose serious threats to infrastructure causing substantial damage and large residual deformations. Superelastic (SE) Shape-Memory-Alloys (SMAs) are unique alloys with the ability to undergo large deformations, but can recover its original shape upon stress removal. The purpose of this research is to exploit this characteristic of SMAs such that concrete Beam-Column Joints (BCJs) reinforced with SMA bars at the plastic hinge region experience reduced residual deformation at the end of earthquakes. Another objective is to evaluate the seismic performance of SMA Reinforced Concrete BCJs repaired with flowable Structural-Repair-Concrete (SRC). A ¾-scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading, and subsequently repaired and retested. The joint was selected from an RC building located in the seismic region of western Canada. It was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour under reversed cyclic loading of the original and repaired joints, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation, requiring a minimum amount of repair, even after a large earthquake, proving to be smart structural elements. It was also shown that the use of SRC to repair damaged BCJs can restore its full capacity.