... The FRP lamination schedule for this specimen was similar to the carbon/epoxy strengthened sp... more ... The FRP lamination schedule for this specimen was similar to the carbon/epoxy strengthened specimens described earlier. After applying the composites, the composites material was allowed to cure for at least 72 hours under the laboratory environment. ...
Results of a pilot study on developing structural repair techniques for damaged steel beam-to-col... more Results of a pilot study on developing structural repair techniques for damaged steel beam-to-column connections using both conventional and unconventional systems are presented. The primary repair system developed in this study is in the form of 3-D braided graphite/epoxy composite connectors attached to the flanges of both beams and columns. Two composite repair details were investigated: (i) with high-strength/high-toughness adhesively bonded composite stiffeners, and (ii) with mechanically fastened composite stiffeners. The specimens were tested under both quasi-static and cyclic loading conditions. In addition, a novel adhesively bonded steel stiffener was developed and tested. The results were compared to those obtained from testing the welded control specimens. The adhesive repair system provided several desired features such as: minimum construction time, ease of applications, minimizing the use of heavy equipment, minimizing the use of holes and bolts, and eliminating the use of welding and the associated fire hazards to occupied facilities. Results obtained are encouraging. (a) For the covering entry of this conference, please see ITRD abstract no. E204495.
23rd Annual International Conference on Composites or Nano Engineering (ICCE23), 2015
This paper presents a summary of preliminary results obtained from an experimental investigation ... more This paper presents a summary of preliminary results obtained from an experimental investigation on the behavior of web-flange junctions of pultruded glass fibre-reinforced polymer (GFRP) I-profiles. In particular, the aim of the study is to suggest simple stiffening and strengthening element to improve the axial flexibility and strength of the junctions. Digital image correlation technique was used to capture in plane displacements and strains of the specimens
This paper presents results of an experimental study that focuses on monitoring changes in dynami... more This paper presents results of an experimental study that focuses on monitoring changes in dynamic characteristics of a damaged and retrofitted two-story reinforced concrete (RC) building model with poor detailing. In the study, ambient vibration tests are performed via four test setup protocols in order to monitor changes in dynamic characteristics before and after such setups. The four main test setups are: (i) undamaged (as-built) case (Setup # 1), (ii) damaged cases with different degrees of damages (Setup # 2), (iii) repaired case with different types of repair methods (Setup # 3), and (iv) strengthened case with externally bonded CFRP composite laminates (Setup # 4). In addition, a total of eight ambient vibration tests are conducted in order to assess the effects of degree of damage and associated retrofit systems on building’s dynamic characteristics such as natural frequencies, mode shapes, and damping ratios. The Stochastic Subspace Identification (SSI) Method is used to identify the dynamic characteristics. Experimentally identified dynamic characteristics obtained from all setups are compared with each other in order to detect the effect of damage and repair applications on the structure’s dynamic characteristics. Moreover, Modal Assurance Criterion (MAC) and Coordinate Modal Assurance Criterion (COMAC) are determined to examine the changes of stiffness of each RC building model.
Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete j... more Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete joints of hybrid girder bridges has gained wide popularity among bridge engineers. For a PBL group with multi-row PBLs in tandem arrays, comprehensive interactions exist among the connectors. However, the current design approaches assume that the force transferred by each row of PBL is uniform, resulting in an overestimated shear resistance of the connector group. The main objective of this paper is to introduce a mathematical approach, which accounts for the bonding-friction effects (BF) at the perforated steel plate/concrete slab interfaces and the reinforced concrete dowel (RD) effects by the perfobond hole, to assess the ultimate resistance of PBL group under the RD fracture failure mode. In this study, six push-out specimens for different PBL groups, with varying connectors’ quantity, were evaluated experimentally to determine the key parameters for the proposed analytical model. The experimental results revealed the significant reduction in average resistance of single PBL in a connector group as connector number increased. The proposed approach is validated by an experimental database that includes push-out test results obtained from the previously published studies and afterwards converted to the design load level, which can be extensively applied to the PBL group using normal concrete and ultra-high performance concrete (UHPC). The proposed analytical approach provides an efficient tool for analyzing and designing of PBL group in steel–concrete joints of hybrid girder bridges.
Masonry towers and minarets are slender tall structures and highly vulnerable to strong ground mo... more Masonry towers and minarets are slender tall structures and highly vulnerable to strong ground motions due to their structural and material characteristics. The paper aims to investigate the effect of vertical ground motion on damage propagations of historical masonry slender tall rectangular stone minarets numerically. The Ulu Mosque minaret with height of 42.90 m constructed in 639 in Diyarbakır, Turkey, is selected as an application. Firstly, three dimensional solid and continuum finite element models of the minaret are obtained from the surveys. Since the foundation of the minaret is sitted on the hard soil, soil-structure interaction is not considered in the finite element model. The finite element model of the minaret is updated by modal analyses results and an empirical frequency formulation developed using the measurement results. Mechanical material properties of the masonry unit are determined using the properties of the stone and mortar used in the minaret. Concrete damaged plasticity (CDP) material model adjusted to masonry structures is considered in the nonlinear analyses. The acceleration records of horizontal (N-S) and vertical (V) components of May 1, 2003 Bingöl earthquake (Mw = 6.4), which was recorded in hard soil and occurred in the near region of Diyarbakır city, are chosen as a strong ground motion. Then, linear time history and nonlinear step by step seismic analyses of the minaret are implemented for only horizontal, and combined horizontal and vertical components of the earthquake. The time histories of displacements, minimum and maximum principal strains and stresses, and damage propagations on the minaret are compared for only horizontal, and combined horizontal and vertical load cases including self-weight. It can be stated that consideration of vertical ground motion component in combination with horizontal component affects damage percentages and propagations on slender tall rectangular stone minarets.
Structural health monitoring (SHM) offers the potential to evaluate the safety and integrity of t... more Structural health monitoring (SHM) offers the potential to evaluate the safety and integrity of the civil infrastructure. By obtaining accurate information about the condition of the structure, appropriate preventive measures can be taken to prolong the service life and prevent the catastrophic failure of the structure. Application of effective damage detection strategies can reduce the life-cycle costs as well. Damage reduces the stiffness and modifies the modal properties of a structure. Therefore, changes in modal properties can be used to detect damage in the structure. Although extensive research has been conducted on structural diagnosis by measuring the vibrational signals of structures, more research is still needed for development of reliable and effective damage detection techniques. This paper presents a study on damage detection of a 3-story steel moment-resisting frame structure instrumented by a network of wireless sensors and cable-based accelerometers. Experimental data from shake table testing and numerical results from finite element simulation were used for damage identification through two approaches. In the first approach, the finite element model of the structure was calibrated and used to locate and quantify the elemental stiffness loss on the basis of the experimentally-identified modal parameters. Moreover, a direct search algorithm was used for minimization of an objective function representing the difference between predicted and measured dynamic parameters of the structure. In the second approach, damage identification was performed through application of the Modal Assurance Criterion (MAC) and detection of the changes between undamaged and damaged conditions. Results of this study are indicative of capability and effectiveness of both approaches in identification of damage.
... The FRP lamination schedule for this specimen was similar to the carbon/epoxy strengthened sp... more ... The FRP lamination schedule for this specimen was similar to the carbon/epoxy strengthened specimens described earlier. After applying the composites, the composites material was allowed to cure for at least 72 hours under the laboratory environment. ...
Results of a pilot study on developing structural repair techniques for damaged steel beam-to-col... more Results of a pilot study on developing structural repair techniques for damaged steel beam-to-column connections using both conventional and unconventional systems are presented. The primary repair system developed in this study is in the form of 3-D braided graphite/epoxy composite connectors attached to the flanges of both beams and columns. Two composite repair details were investigated: (i) with high-strength/high-toughness adhesively bonded composite stiffeners, and (ii) with mechanically fastened composite stiffeners. The specimens were tested under both quasi-static and cyclic loading conditions. In addition, a novel adhesively bonded steel stiffener was developed and tested. The results were compared to those obtained from testing the welded control specimens. The adhesive repair system provided several desired features such as: minimum construction time, ease of applications, minimizing the use of heavy equipment, minimizing the use of holes and bolts, and eliminating the use of welding and the associated fire hazards to occupied facilities. Results obtained are encouraging. (a) For the covering entry of this conference, please see ITRD abstract no. E204495.
23rd Annual International Conference on Composites or Nano Engineering (ICCE23), 2015
This paper presents a summary of preliminary results obtained from an experimental investigation ... more This paper presents a summary of preliminary results obtained from an experimental investigation on the behavior of web-flange junctions of pultruded glass fibre-reinforced polymer (GFRP) I-profiles. In particular, the aim of the study is to suggest simple stiffening and strengthening element to improve the axial flexibility and strength of the junctions. Digital image correlation technique was used to capture in plane displacements and strains of the specimens
This paper presents results of an experimental study that focuses on monitoring changes in dynami... more This paper presents results of an experimental study that focuses on monitoring changes in dynamic characteristics of a damaged and retrofitted two-story reinforced concrete (RC) building model with poor detailing. In the study, ambient vibration tests are performed via four test setup protocols in order to monitor changes in dynamic characteristics before and after such setups. The four main test setups are: (i) undamaged (as-built) case (Setup # 1), (ii) damaged cases with different degrees of damages (Setup # 2), (iii) repaired case with different types of repair methods (Setup # 3), and (iv) strengthened case with externally bonded CFRP composite laminates (Setup # 4). In addition, a total of eight ambient vibration tests are conducted in order to assess the effects of degree of damage and associated retrofit systems on building’s dynamic characteristics such as natural frequencies, mode shapes, and damping ratios. The Stochastic Subspace Identification (SSI) Method is used to identify the dynamic characteristics. Experimentally identified dynamic characteristics obtained from all setups are compared with each other in order to detect the effect of damage and repair applications on the structure’s dynamic characteristics. Moreover, Modal Assurance Criterion (MAC) and Coordinate Modal Assurance Criterion (COMAC) are determined to examine the changes of stiffness of each RC building model.
Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete j... more Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete joints of hybrid girder bridges has gained wide popularity among bridge engineers. For a PBL group with multi-row PBLs in tandem arrays, comprehensive interactions exist among the connectors. However, the current design approaches assume that the force transferred by each row of PBL is uniform, resulting in an overestimated shear resistance of the connector group. The main objective of this paper is to introduce a mathematical approach, which accounts for the bonding-friction effects (BF) at the perforated steel plate/concrete slab interfaces and the reinforced concrete dowel (RD) effects by the perfobond hole, to assess the ultimate resistance of PBL group under the RD fracture failure mode. In this study, six push-out specimens for different PBL groups, with varying connectors’ quantity, were evaluated experimentally to determine the key parameters for the proposed analytical model. The experimental results revealed the significant reduction in average resistance of single PBL in a connector group as connector number increased. The proposed approach is validated by an experimental database that includes push-out test results obtained from the previously published studies and afterwards converted to the design load level, which can be extensively applied to the PBL group using normal concrete and ultra-high performance concrete (UHPC). The proposed analytical approach provides an efficient tool for analyzing and designing of PBL group in steel–concrete joints of hybrid girder bridges.
Masonry towers and minarets are slender tall structures and highly vulnerable to strong ground mo... more Masonry towers and minarets are slender tall structures and highly vulnerable to strong ground motions due to their structural and material characteristics. The paper aims to investigate the effect of vertical ground motion on damage propagations of historical masonry slender tall rectangular stone minarets numerically. The Ulu Mosque minaret with height of 42.90 m constructed in 639 in Diyarbakır, Turkey, is selected as an application. Firstly, three dimensional solid and continuum finite element models of the minaret are obtained from the surveys. Since the foundation of the minaret is sitted on the hard soil, soil-structure interaction is not considered in the finite element model. The finite element model of the minaret is updated by modal analyses results and an empirical frequency formulation developed using the measurement results. Mechanical material properties of the masonry unit are determined using the properties of the stone and mortar used in the minaret. Concrete damaged plasticity (CDP) material model adjusted to masonry structures is considered in the nonlinear analyses. The acceleration records of horizontal (N-S) and vertical (V) components of May 1, 2003 Bingöl earthquake (Mw = 6.4), which was recorded in hard soil and occurred in the near region of Diyarbakır city, are chosen as a strong ground motion. Then, linear time history and nonlinear step by step seismic analyses of the minaret are implemented for only horizontal, and combined horizontal and vertical components of the earthquake. The time histories of displacements, minimum and maximum principal strains and stresses, and damage propagations on the minaret are compared for only horizontal, and combined horizontal and vertical load cases including self-weight. It can be stated that consideration of vertical ground motion component in combination with horizontal component affects damage percentages and propagations on slender tall rectangular stone minarets.
Structural health monitoring (SHM) offers the potential to evaluate the safety and integrity of t... more Structural health monitoring (SHM) offers the potential to evaluate the safety and integrity of the civil infrastructure. By obtaining accurate information about the condition of the structure, appropriate preventive measures can be taken to prolong the service life and prevent the catastrophic failure of the structure. Application of effective damage detection strategies can reduce the life-cycle costs as well. Damage reduces the stiffness and modifies the modal properties of a structure. Therefore, changes in modal properties can be used to detect damage in the structure. Although extensive research has been conducted on structural diagnosis by measuring the vibrational signals of structures, more research is still needed for development of reliable and effective damage detection techniques. This paper presents a study on damage detection of a 3-story steel moment-resisting frame structure instrumented by a network of wireless sensors and cable-based accelerometers. Experimental data from shake table testing and numerical results from finite element simulation were used for damage identification through two approaches. In the first approach, the finite element model of the structure was calibrated and used to locate and quantify the elemental stiffness loss on the basis of the experimentally-identified modal parameters. Moreover, a direct search algorithm was used for minimization of an objective function representing the difference between predicted and measured dynamic parameters of the structure. In the second approach, damage identification was performed through application of the Modal Assurance Criterion (MAC) and detection of the changes between undamaged and damaged conditions. Results of this study are indicative of capability and effectiveness of both approaches in identification of damage.
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Papers by Ayman S MOSALLAM