Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC)... more Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC) column deteriorates due to crushing of core concrete and buckling of longitudinal bars. Hence, the need for developing new cross sections and systems for seismic applications is evident. This paper presents the shake-table test of a damage-resistant segmental double skin bridge column with post-tensioned unbounded strands with incorporated replaceable energy dissipaters. The column cross-section is a double skin section composed of an outside glass fiber reinforced polymer tube, an inside steel tube, and concrete cast in between the two. The energy dissipaters consist of mild steel fuses outside the cross-section. The column has the advantages of accelerated bridge construction, self centering due to rocking, energy dissipation, and ease of replacing the dissipaters. The column was subjected to a sequence of scaled near-fault pulse-like ground motions. A reference RC column was also tested for comparison
Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retr... more Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retrofitted. The main structural element that resist earthquakes in these buildings are the old URM walls which were designed to resist mainly gravity loads. This paper presents the experimental results of testing URM wall including a door opening. The wall was tested before and after retrofitting using glass fiber reinforced polymers (GFRP).The test results were compared to two different assessment guidelines namely FEMA 356 (2000) and Lang (2002).
ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of h... more ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of hybrid columns which consists of a layer of concrete sandwiched between an inner steel tube and an outer FRP tube. While a large amount of research has been conducted on the monotonic behavior of this novel form of columns, only a limited amount of work has been conducted on their behavior under cyclic loading. This paper presents the first ever study on the behavior of circular hybrid DSTCs under cyclic axial compression. Results from a series of stub column tests, where the hybrid DSTCs were subjected to cyclic axial compression, are first presented and discussed. The test results show that hybrid DSTCs are very ductile under cyclic axial compression, with the envelope axial load-strain curve being almost the same as the axial load-strain curve of a corresponding DSTC under monotonic compression. It is also shown that repeated unloading/reloading cycles have a cumulative effect on the permanent strain and the stress deterioration of the confined concrete in hybrid DSTCs. The experimental stress–strain curves of the confined concrete in hybrid DSTCs are then compared with predictions from two existing models: (1) a monotonic stress–strain model for the confined concrete in hybrid DSTCs; and (2) a cyclic stress–strain model for the concrete in FRP-confined solid columns. The comparison suggests that the combined use of the two models can give reasonably accurate predictions of the test results.
Australian Journal of Structural Engineering, 2014
ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for... more ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for estimating the in-plane shear strength of partially grouted reinforced masonry (PGM) walls, by comparing them to available experimental results. The shear equations considered are taken from masonry design codes of practice of the United States (MSJC 2011), New Zealand (NZS4230 2004), Canada (CSA S304.1-04) and Australia (AS3700-2011). The experimental results were taken from a data base of 89 wall specimens that displayed shear failure collected from a range of published research. The ability of the code equations to predict shear strength is compared with the experimental results. In addition, a range of parameters that are influential on the shear strength, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied and compared with test results in detail. Both uni-variate and multivariate regression analysis have been employed to investigate the effect of each parameter. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls effectively. In some cases the code predictions were up to three times the actual shear strength determined from the test, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.
ABSTRACT In recent years, a very important environmental issue all over the world is the disposal... more ABSTRACT In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones.
Journal of Structural Engineering-asce, May 1, 2016
AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls ... more AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls (PT-MWs). All walls had identical thickness, height, and length of 190, 2,000, and 1,400Â mm, respectively, and were constructed using concrete masonry units (CMUs) and mortar type N, and were fully grouted. Different horizontal spacing values of 400, 600, and 1,200Â mm were used between the posttensioning bars in the walls. Only Wall W4 had horizontal bonded reinforcement, located in the fourth and seventh courses. Two different levels of posttensioning force corresponding to an average posttensioning compressive axial stress on the masonry of 1.35 and 2.7Â MPa were applied to the walls. Different initial posttension stresses in the bars ranging from 0.32 to 0.63 of the yield stress of each bar were applied to the walls. The walls were subjected to incrementally increasing in-plane lateral displacement cyclic load applied to the top of each wall. The experimental results including damage pattern, force displacem...
Australasian Structural Engineering Conference 2012: The past, present and future of Structural Engineering, 2012
The objective of this paper is to compare the in-plane shear strength of partially grouted masonr... more The objective of this paper is to compare the in-plane shear strength of partially grouted masonry walls (PG-MW) in the Australian code (AS3700-2001) with other codes. This is of high importance because while most of the test experiments have been done recently - and have affected other codes, shear equations in the Australian masonry design code remained relatively unchanged since 1988 (AS3700-1988). Therefore it is important to find out the differences between Australian provisions and provisions in other codes such as MSJC-2011, NZS4230-2004 and S304.1-2004. These codes were selected as they were calibrated against comprehensive test results. In this paper the effectiveness of various parameters that influence the shear strength of PG-MWs is investigated and discussed. The differences between the selected design provisions are also highlighted. The comparison shows significant differences between AS3700-2001 and the other codes' design expressions.
In recent years, a very important environmental issue all over the world is the disposal of waste... more In recent years, a very important environmental issue all over the world is the disposal of waste tires. One possibility being explored is to use rubber from waste tires to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). Recent research on CRC is focusing on using it in structures subject to seismic loads, due to its higher ductility, damping ratio, and energy dissipation compared to conventional concrete. However CRC can have lower compressive strength (Æ’\u27CRC), tensile strength (Æ’\u27TRC), and modulus of elasticity (ERC) when compared with conventional concrete. This paper presents empirical models able to predict the CRC characteristics (Æ’\u27CRC, Æ’\u27TRC, and ERC). The proposed models are verified through the results of 148 CRC mixes as well as compared with two previous models. The proposed models resulted in predictions of the CRC characteristics with only 10.7%, 12.6%, and 11.3% errors in the predictions of Æ’\u27CRC, Æ’\u27TRC, and ERC, respectively. The proposed Æ’\u27CRC model reduced the mean, standard deviation and maximum error percentages by 24.6%, 5.8%, and 20.2%, respectively, compared with the nearest best predictions by previous models. The proposed models can aid structural engineers who are considering CRC as an environmentally-friendly alternative to conventional concrete in structural applications
Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC)... more Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC) column deteriorates due to crushing of core concrete and buckling of longitudinal bars. Hence, the need for developing new cross sections and systems for seismic applications is evident. This paper presents the shake-table test of a damage-resistant segmental double skin bridge column with post-tensioned unbounded strands with incorporated replaceable energy dissipaters. The column cross-section is a double skin section composed of an outside glass fiber reinforced polymer tube, an inside steel tube, and concrete cast in between the two. The energy dissipaters consist of mild steel fuses outside the cross-section. The column has the advantages of accelerated bridge construction, self centering due to rocking, energy dissipation, and ease of replacing the dissipaters. The column was subjected to a sequence of scaled near-fault pulse-like ground motions. A reference RC column was also tested for comparison
Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retr... more Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retrofitted. The main structural element that resist earthquakes in these buildings are the old URM walls which were designed to resist mainly gravity loads. This paper presents the experimental results of testing URM wall including a door opening. The wall was tested before and after retrofitting using glass fiber reinforced polymers (GFRP).The test results were compared to two different assessment guidelines namely FEMA 356 (2000) and Lang (2002).
ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of h... more ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of hybrid columns which consists of a layer of concrete sandwiched between an inner steel tube and an outer FRP tube. While a large amount of research has been conducted on the monotonic behavior of this novel form of columns, only a limited amount of work has been conducted on their behavior under cyclic loading. This paper presents the first ever study on the behavior of circular hybrid DSTCs under cyclic axial compression. Results from a series of stub column tests, where the hybrid DSTCs were subjected to cyclic axial compression, are first presented and discussed. The test results show that hybrid DSTCs are very ductile under cyclic axial compression, with the envelope axial load-strain curve being almost the same as the axial load-strain curve of a corresponding DSTC under monotonic compression. It is also shown that repeated unloading/reloading cycles have a cumulative effect on the permanent strain and the stress deterioration of the confined concrete in hybrid DSTCs. The experimental stress–strain curves of the confined concrete in hybrid DSTCs are then compared with predictions from two existing models: (1) a monotonic stress–strain model for the confined concrete in hybrid DSTCs; and (2) a cyclic stress–strain model for the concrete in FRP-confined solid columns. The comparison suggests that the combined use of the two models can give reasonably accurate predictions of the test results.
Australian Journal of Structural Engineering, 2014
ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for... more ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for estimating the in-plane shear strength of partially grouted reinforced masonry (PGM) walls, by comparing them to available experimental results. The shear equations considered are taken from masonry design codes of practice of the United States (MSJC 2011), New Zealand (NZS4230 2004), Canada (CSA S304.1-04) and Australia (AS3700-2011). The experimental results were taken from a data base of 89 wall specimens that displayed shear failure collected from a range of published research. The ability of the code equations to predict shear strength is compared with the experimental results. In addition, a range of parameters that are influential on the shear strength, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied and compared with test results in detail. Both uni-variate and multivariate regression analysis have been employed to investigate the effect of each parameter. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls effectively. In some cases the code predictions were up to three times the actual shear strength determined from the test, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.
ABSTRACT In recent years, a very important environmental issue all over the world is the disposal... more ABSTRACT In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones.
Journal of Structural Engineering-asce, May 1, 2016
AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls ... more AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls (PT-MWs). All walls had identical thickness, height, and length of 190, 2,000, and 1,400Â mm, respectively, and were constructed using concrete masonry units (CMUs) and mortar type N, and were fully grouted. Different horizontal spacing values of 400, 600, and 1,200Â mm were used between the posttensioning bars in the walls. Only Wall W4 had horizontal bonded reinforcement, located in the fourth and seventh courses. Two different levels of posttensioning force corresponding to an average posttensioning compressive axial stress on the masonry of 1.35 and 2.7Â MPa were applied to the walls. Different initial posttension stresses in the bars ranging from 0.32 to 0.63 of the yield stress of each bar were applied to the walls. The walls were subjected to incrementally increasing in-plane lateral displacement cyclic load applied to the top of each wall. The experimental results including damage pattern, force displacem...
Australasian Structural Engineering Conference 2012: The past, present and future of Structural Engineering, 2012
The objective of this paper is to compare the in-plane shear strength of partially grouted masonr... more The objective of this paper is to compare the in-plane shear strength of partially grouted masonry walls (PG-MW) in the Australian code (AS3700-2001) with other codes. This is of high importance because while most of the test experiments have been done recently - and have affected other codes, shear equations in the Australian masonry design code remained relatively unchanged since 1988 (AS3700-1988). Therefore it is important to find out the differences between Australian provisions and provisions in other codes such as MSJC-2011, NZS4230-2004 and S304.1-2004. These codes were selected as they were calibrated against comprehensive test results. In this paper the effectiveness of various parameters that influence the shear strength of PG-MWs is investigated and discussed. The differences between the selected design provisions are also highlighted. The comparison shows significant differences between AS3700-2001 and the other codes' design expressions.
In recent years, a very important environmental issue all over the world is the disposal of waste... more In recent years, a very important environmental issue all over the world is the disposal of waste tires. One possibility being explored is to use rubber from waste tires to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). Recent research on CRC is focusing on using it in structures subject to seismic loads, due to its higher ductility, damping ratio, and energy dissipation compared to conventional concrete. However CRC can have lower compressive strength (Æ’\u27CRC), tensile strength (Æ’\u27TRC), and modulus of elasticity (ERC) when compared with conventional concrete. This paper presents empirical models able to predict the CRC characteristics (Æ’\u27CRC, Æ’\u27TRC, and ERC). The proposed models are verified through the results of 148 CRC mixes as well as compared with two previous models. The proposed models resulted in predictions of the CRC characteristics with only 10.7%, 12.6%, and 11.3% errors in the predictions of Æ’\u27CRC, Æ’\u27TRC, and ERC, respectively. The proposed Æ’\u27CRC model reduced the mean, standard deviation and maximum error percentages by 24.6%, 5.8%, and 20.2%, respectively, compared with the nearest best predictions by previous models. The proposed models can aid structural engineers who are considering CRC as an environmentally-friendly alternative to conventional concrete in structural applications
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Papers by Mohamed ElGawady