Ammar Ali - Academia.edu (original) (raw)

Papers by Ammar Ali

Research paper thumbnail of Strength and Ductility of Concrete Encased Composite Beams

Maǧallaẗ al-handasaẗ wa-al-tiknūlūǧiyā, Sep 1, 2012

Experimental research was conducted to investigate the structural behavior of concrete-encased co... more Experimental research was conducted to investigate the structural behavior of concrete-encased composite beams. Specimens were tested under lateral loading. The test results indicate that the behavior and failure mode of the beam are greatly affected by the steel beam core. The beams showed highly ductile behavior. The design flexural strength of concrete-encased beams is calculated from both the elastic and plastic stress distribution on the composite section. The deflection at the mid-span of the beam cannot be well predicted using linear elastic theory.

Research paper thumbnail of Prediction of axial capacity of octagonal concrete-filled steel tube columns considering confinement effect

International Journal of Structural Engineering, 2022

Research paper thumbnail of Prediction of Axial Capacity of Hexagonal Concrete-Filled Steel Tube Columns

The present study aims to introduce a new method that gives accurate predictions of the ultimate ... more The present study aims to introduce a new method that gives accurate predictions of the ultimate capacity of hexagonal concrete-filled steel tube columns. Experimental data available in the literature were used to validate the new method. Also, it was used to construct a constitutive model for the core concrete that can be employed in the finite element analysis. This allows testing the model with the available experimental results of the behavior of hexagonal columns under concentric load. An extensive parametric study was carried out to explore the effects of different parameters on the behavior and ultimate capacity of the columns. The effects of the compressive concrete strength, yield strength of steel ratio and depth-to-thickness of the tube ratio were investigated. It is found that these parameters have significant effects on the behavior of the columns, for example a reduction in depth-to-thickness ratio from 33 to 17 gave a 100% increase in ultimate strength.

Research paper thumbnail of Experimental and Theoretical Comparative Study of Circular Steel Tubular Columns Filled with Self-Compacting Concrete under Axial Concentric Loading

DOAJ (DOAJ: Directory of Open Access Journals), Oct 1, 2013

This study presents an experimental and theoretical study on the behavior of circular, concrete-f... more This study presents an experimental and theoretical study on the behavior of circular, concrete-filled, steel tube (CFT) columns filled with self-compacting concrete (SCC) concentrically loaded in compression to failure. Specimens were tested to investigate the ultimate capacity and the load– deformation behavior of the columns. The behavior of these columns in confinement was discussed. The test results for acceptance characteristics of self-compacting concrete (SCC) such as slump flow; V-funnel and L-Box are presented. The experimental study was used to compare with theoretical results based on three different building codes. The codes used were the Eurocode 4 - EN 1994-1-1:2004 (EC4), ANSI/AISC 360:2010 and AIJ. The test specimens were of a length-to-diameter ratio (L / D) of 2.5, 6.25 and 9.375 respectively. The internal core is self -compacting concrete had nominal unconfined cylinder strength of 30 MPa. In general, the code provisions were of different accuracy in the prediction of column capacity. The AISC (1999) was the most conservative, while Eurocode 4 presented the values closest to the experimental results. The slenderness ratio was critical in determining the formation of a local buckle, and those slenderest columns only attained 85.7% of their section capacities.

Research paper thumbnail of Shear Wall Analysis using Framework Method: Comparison with Shell Element Method and Column Analogy

Engineering and Technology Journal

Different techniques are utilized to analyze shear walls like shell elements model or column anal... more Different techniques are utilized to analyze shear walls like shell elements model or column analogy. Framework method (FWM) is used to substitute the shell elements. A rectangular model of rigidly-connected plane framework is adopted here. FWM is found to be more sensitive for mesh size than shell element. Column analogy (CA) is to model the shear wall using the standard wide column analogy between the adjoining columns using beam elements. The column analogy is a simple and efficient method to represent the structure.

Research paper thumbnail of Experimental Behavior of Circular Steel Tubular Columns Filled with Self-Compacting Concrete under Concentric Load

Engineering and Technology Journal

This paper presents an experimental study on the behavior of circular, concretefilled, steel tube... more This paper presents an experimental study on the behavior of circular, concretefilled, steel tube (CFT) columns concentrically loaded in compression to failure. Selfcompacting concrete (SCC) is used here as a filler in order to increase homogeneity of the core and reduce segregation problems. Total six column specimens with different lengths (0.4 m-1.5 m) of constant diameter of 160 mm and wall thickness of 2.8 mm were tested. The purpose here is to investigate the ultimate capacity and the deformation behavior of different slenderness ratio columns. The behavior of these columns in confinement was discussed. Experimental results indicate that the compression force capacity is affected by slenderness ratio of the column. For slender column the overall buckling was observed while for the short columns the crushing and the local buckling is the dominant failure shape.

Research paper thumbnail of Shear behavior of composite girders of zigzag web

8TH ENGINEERING AND 2ND INTERNATIONAL CONFERENCE FOR COLLEGE OF ENGINEERING – UNIVERSITY OF BAGHDAD: COEC8-2021 Proceedings

The purpose of this paper is to investigate the behavior of shear composite girders (flat & zigza... more The purpose of this paper is to investigate the behavior of shear composite girders (flat & zigzag webs). The experimental work involves testing six composite girders to investigate the influence of web height and the effect of using a zigzag web under shear loading. Three web heights (400, 600, and 800 mm) were considered for all specimens. The steel girders were 1800 mm overall length, and the composite concrete slab were 460 mm, and150 mm width and depth, respectively. The resulted are showing in from where of a recorded load of capacity, mid-span deflection, and crack pattern for the girders of composite, and the slip between the deck of concrete and steel girder. Increasing the web height resulted in reduce the vertical deflection, slip, and the cracks were limited at the loading zone. The curves of the load-displacement and stress distribution predicted by the FEM agree well with those obtained from experiments, proving the accuracy of the suggested FEM.

Research paper thumbnail of Serviceability limit state of two-way reinforced concrete slab strengthened with different techniques

MATEC Web of Conferences, 2018

The experimental results for service load of sixteen simply supported two way reinforced concrete... more The experimental results for service load of sixteen simply supported two way reinforced concrete slabs under the action of concentrated patch load were determined based on the amount of permissible deflections and the crack widths.All the slabs had the same overall dimensions and flexural steel reinforcement. Five types of strengthening were adopted. The first and second methods include applying either near surface mounted (NSM) or near reinforcement mounted (NRM) ferrocement layers. While the third method includes applying a concrete layer reinforced with welded wire fabric mesh of various diameters. The fourth and fifth methods include fixing CFRP rods and laminates, respectively, on the bottom surface of slabs. Strengthening techniques were applied on the bottom surface of fifteen slab specimens. In addition, a control slab specimen without any strengthening was used for the purpose of comparison. The calculated results for ultimate loads based on serviceability requirements (de...

Research paper thumbnail of CFRP strengthening of steel plate girders with web openings subjected to shear and bending

IOP Conference Series: Materials Science and Engineering, 2020

The present study illustrates the effect of applying combined shear and bending loading on steel ... more The present study illustrates the effect of applying combined shear and bending loading on steel plate girders having web openings strengthened with CFRP wrap. Five steel plate girders have been tested under the above-mentioned action; one of these plate girders which can be considered as a control specimen has no web opening whereas the other four girders have openings of circular or square cut-outs. Strengthening by attaching CFRP sheets using a type of adhesives has been applied to two of the plate girders, one with square opening and the other with circular web opening. Web opening size is chosen to have a depth equal to 40% of the web depth. In comparison with the reference girders with openings, results have shown that the ultimate load of the strengthened plate girder containing square and circular web openings increased 63.6% and 52.6%, respectively.

Research paper thumbnail of Experimental comparative study of reactive powder concrete: mechanical properties and the effective factors

MATEC Web of Conferences, 2018

Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite... more Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite material generally characterized by high cement content, high durability, low porosity, low water/cement ratio and in most cases contains steel fibers as new types of concrete appears, further investigation for their mechanical properties are needed. This work aims to give a better understanding of RPC behavior by deriving formulas to calculate the modulus of elasticity and the splitting tensile strength in relation with compressive strength and steel fibers content. This study is based on data obtained from the experimental investigation done in this work and from others pervious works. The parametric study is based mainly on the silica fume content which is used in four different ratios (12 %, 15 %, 20 % and 25 %), the use of micro steel fibers 15 mm in length, 0.2 mm in diameter and aspect ratio of 75 added in ratios of (0 %, 1 %, 1.5 % and 2 %), and water/cement in ratios of (16 %, ...

Research paper thumbnail of Behavior of Box Concrete-Filled Steel Tube Columns Considering Confinement Effect

International Journal of Steel Structures, 2021

In recent years considerable attention has been given to estimating the strength of box concrete-... more In recent years considerable attention has been given to estimating the strength of box concrete-filled steel tube (CFST) stub columns. The effect of confining pressures is one of the complexities in determining the ultimate strength of the CFST columns. An experimental database of 188 tested columns has been used to produce two types of formulae: modified and simplified, that can help to predict the ultimate strength of box CFST columns with a wide range of geometrical and material properties. Different code procedures and previous formulae given by other authors were used for verification purposes and to show reliability. The axial load-shortening behaviors of composite columns were plotted using a proposed model of confined concrete adopted in a finite element analysis and compared with the experimental results. It has been found that the present formulae and concrete model have given results that agree quite well with the results of the experimental tests.

Research paper thumbnail of Strength and Ductility of Concrete Encased Composite Beams

Maǧallaẗ al-handasaẗ wa-al-tiknūlūǧiyā, Sep 1, 2012

Experimental research was conducted to investigate the structural behavior of concrete-encased co... more Experimental research was conducted to investigate the structural behavior of concrete-encased composite beams. Specimens were tested under lateral loading. The test results indicate that the behavior and failure mode of the beam are greatly affected by the steel beam core. The beams showed highly ductile behavior. The design flexural strength of concrete-encased beams is calculated from both the elastic and plastic stress distribution on the composite section. The deflection at the mid-span of the beam cannot be well predicted using linear elastic theory.

Research paper thumbnail of Prediction of axial capacity of octagonal concrete-filled steel tube columns considering confinement effect

International Journal of Structural Engineering, 2022

Research paper thumbnail of Prediction of Axial Capacity of Hexagonal Concrete-Filled Steel Tube Columns

The present study aims to introduce a new method that gives accurate predictions of the ultimate ... more The present study aims to introduce a new method that gives accurate predictions of the ultimate capacity of hexagonal concrete-filled steel tube columns. Experimental data available in the literature were used to validate the new method. Also, it was used to construct a constitutive model for the core concrete that can be employed in the finite element analysis. This allows testing the model with the available experimental results of the behavior of hexagonal columns under concentric load. An extensive parametric study was carried out to explore the effects of different parameters on the behavior and ultimate capacity of the columns. The effects of the compressive concrete strength, yield strength of steel ratio and depth-to-thickness of the tube ratio were investigated. It is found that these parameters have significant effects on the behavior of the columns, for example a reduction in depth-to-thickness ratio from 33 to 17 gave a 100% increase in ultimate strength.

Research paper thumbnail of Experimental and Theoretical Comparative Study of Circular Steel Tubular Columns Filled with Self-Compacting Concrete under Axial Concentric Loading

DOAJ (DOAJ: Directory of Open Access Journals), Oct 1, 2013

This study presents an experimental and theoretical study on the behavior of circular, concrete-f... more This study presents an experimental and theoretical study on the behavior of circular, concrete-filled, steel tube (CFT) columns filled with self-compacting concrete (SCC) concentrically loaded in compression to failure. Specimens were tested to investigate the ultimate capacity and the load– deformation behavior of the columns. The behavior of these columns in confinement was discussed. The test results for acceptance characteristics of self-compacting concrete (SCC) such as slump flow; V-funnel and L-Box are presented. The experimental study was used to compare with theoretical results based on three different building codes. The codes used were the Eurocode 4 - EN 1994-1-1:2004 (EC4), ANSI/AISC 360:2010 and AIJ. The test specimens were of a length-to-diameter ratio (L / D) of 2.5, 6.25 and 9.375 respectively. The internal core is self -compacting concrete had nominal unconfined cylinder strength of 30 MPa. In general, the code provisions were of different accuracy in the prediction of column capacity. The AISC (1999) was the most conservative, while Eurocode 4 presented the values closest to the experimental results. The slenderness ratio was critical in determining the formation of a local buckle, and those slenderest columns only attained 85.7% of their section capacities.

Research paper thumbnail of Shear Wall Analysis using Framework Method: Comparison with Shell Element Method and Column Analogy

Engineering and Technology Journal

Different techniques are utilized to analyze shear walls like shell elements model or column anal... more Different techniques are utilized to analyze shear walls like shell elements model or column analogy. Framework method (FWM) is used to substitute the shell elements. A rectangular model of rigidly-connected plane framework is adopted here. FWM is found to be more sensitive for mesh size than shell element. Column analogy (CA) is to model the shear wall using the standard wide column analogy between the adjoining columns using beam elements. The column analogy is a simple and efficient method to represent the structure.

Research paper thumbnail of Experimental Behavior of Circular Steel Tubular Columns Filled with Self-Compacting Concrete under Concentric Load

Engineering and Technology Journal

This paper presents an experimental study on the behavior of circular, concretefilled, steel tube... more This paper presents an experimental study on the behavior of circular, concretefilled, steel tube (CFT) columns concentrically loaded in compression to failure. Selfcompacting concrete (SCC) is used here as a filler in order to increase homogeneity of the core and reduce segregation problems. Total six column specimens with different lengths (0.4 m-1.5 m) of constant diameter of 160 mm and wall thickness of 2.8 mm were tested. The purpose here is to investigate the ultimate capacity and the deformation behavior of different slenderness ratio columns. The behavior of these columns in confinement was discussed. Experimental results indicate that the compression force capacity is affected by slenderness ratio of the column. For slender column the overall buckling was observed while for the short columns the crushing and the local buckling is the dominant failure shape.

Research paper thumbnail of Shear behavior of composite girders of zigzag web

8TH ENGINEERING AND 2ND INTERNATIONAL CONFERENCE FOR COLLEGE OF ENGINEERING – UNIVERSITY OF BAGHDAD: COEC8-2021 Proceedings

The purpose of this paper is to investigate the behavior of shear composite girders (flat & zigza... more The purpose of this paper is to investigate the behavior of shear composite girders (flat & zigzag webs). The experimental work involves testing six composite girders to investigate the influence of web height and the effect of using a zigzag web under shear loading. Three web heights (400, 600, and 800 mm) were considered for all specimens. The steel girders were 1800 mm overall length, and the composite concrete slab were 460 mm, and150 mm width and depth, respectively. The resulted are showing in from where of a recorded load of capacity, mid-span deflection, and crack pattern for the girders of composite, and the slip between the deck of concrete and steel girder. Increasing the web height resulted in reduce the vertical deflection, slip, and the cracks were limited at the loading zone. The curves of the load-displacement and stress distribution predicted by the FEM agree well with those obtained from experiments, proving the accuracy of the suggested FEM.

Research paper thumbnail of Serviceability limit state of two-way reinforced concrete slab strengthened with different techniques

MATEC Web of Conferences, 2018

The experimental results for service load of sixteen simply supported two way reinforced concrete... more The experimental results for service load of sixteen simply supported two way reinforced concrete slabs under the action of concentrated patch load were determined based on the amount of permissible deflections and the crack widths.All the slabs had the same overall dimensions and flexural steel reinforcement. Five types of strengthening were adopted. The first and second methods include applying either near surface mounted (NSM) or near reinforcement mounted (NRM) ferrocement layers. While the third method includes applying a concrete layer reinforced with welded wire fabric mesh of various diameters. The fourth and fifth methods include fixing CFRP rods and laminates, respectively, on the bottom surface of slabs. Strengthening techniques were applied on the bottom surface of fifteen slab specimens. In addition, a control slab specimen without any strengthening was used for the purpose of comparison. The calculated results for ultimate loads based on serviceability requirements (de...

Research paper thumbnail of CFRP strengthening of steel plate girders with web openings subjected to shear and bending

IOP Conference Series: Materials Science and Engineering, 2020

The present study illustrates the effect of applying combined shear and bending loading on steel ... more The present study illustrates the effect of applying combined shear and bending loading on steel plate girders having web openings strengthened with CFRP wrap. Five steel plate girders have been tested under the above-mentioned action; one of these plate girders which can be considered as a control specimen has no web opening whereas the other four girders have openings of circular or square cut-outs. Strengthening by attaching CFRP sheets using a type of adhesives has been applied to two of the plate girders, one with square opening and the other with circular web opening. Web opening size is chosen to have a depth equal to 40% of the web depth. In comparison with the reference girders with openings, results have shown that the ultimate load of the strengthened plate girder containing square and circular web openings increased 63.6% and 52.6%, respectively.

Research paper thumbnail of Experimental comparative study of reactive powder concrete: mechanical properties and the effective factors

MATEC Web of Conferences, 2018

Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite... more Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite material generally characterized by high cement content, high durability, low porosity, low water/cement ratio and in most cases contains steel fibers as new types of concrete appears, further investigation for their mechanical properties are needed. This work aims to give a better understanding of RPC behavior by deriving formulas to calculate the modulus of elasticity and the splitting tensile strength in relation with compressive strength and steel fibers content. This study is based on data obtained from the experimental investigation done in this work and from others pervious works. The parametric study is based mainly on the silica fume content which is used in four different ratios (12 %, 15 %, 20 % and 25 %), the use of micro steel fibers 15 mm in length, 0.2 mm in diameter and aspect ratio of 75 added in ratios of (0 %, 1 %, 1.5 % and 2 %), and water/cement in ratios of (16 %, ...

Research paper thumbnail of Behavior of Box Concrete-Filled Steel Tube Columns Considering Confinement Effect

International Journal of Steel Structures, 2021

In recent years considerable attention has been given to estimating the strength of box concrete-... more In recent years considerable attention has been given to estimating the strength of box concrete-filled steel tube (CFST) stub columns. The effect of confining pressures is one of the complexities in determining the ultimate strength of the CFST columns. An experimental database of 188 tested columns has been used to produce two types of formulae: modified and simplified, that can help to predict the ultimate strength of box CFST columns with a wide range of geometrical and material properties. Different code procedures and previous formulae given by other authors were used for verification purposes and to show reliability. The axial load-shortening behaviors of composite columns were plotted using a proposed model of confined concrete adopted in a finite element analysis and compared with the experimental results. It has been found that the present formulae and concrete model have given results that agree quite well with the results of the experimental tests.