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Magdi Elemam

American University of Sharjah, Civil Enginnering, Faculty Member

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Institut Teknologi Sepuluh Nopember

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Dokuz Eylül University

Indian Institute of Technology Delhi

bhuvaneshwari subramanian

SRM UNIVERSITY

University of Chile

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University of North Carolina at Greensboro

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University of Salamanca

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Papers by Magdi Elemam

Shear Strength and Bearing Capacity of FibreReinforced Sand

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

In this paper, direct shear tests were conducted to evaluate the effect of randomly distributed f... more In this paper, direct shear tests were conducted to evaluate the effect of randomly distributed fibres on the shear strength parameters of dry sand. Polyolefin fibre which is a polymeric produced from a simple olefin (CnH2n) was mixed with dry sand to investigate the improvement of shear strength and effect on volume changes. Specimens with 0.5%, 1%, 1.5% and 2% of fibre contents with different lengths (i.e. 15mm and 30mm) are prepared in repeatable steps and tested in direct shear tests. In addition, two sand types; coarse sand and fin sand were used in this investigation to study the grading size effects on the behaviour of the fiber-reinforced sand. Results indicated that, the inclusion of randomly distributed discrete fibres significantly improved the shear strength of sand. The existence of polymeric fibre inside the sand developed what is called apparent tensile cohesion in addition to the sand normal internal friction angle. The optimum fibre percentage for improving both friction angle and apparent tensile cohesion was about 1%. Adding fibre more than this ratio resulted in a significant reduction in both soil shear strength parameters. The effect of fibre on sand tensile cohesion is more pronounced compared to its effect on the friction angle. A bearing capacity of hypothetical footing resting on ground surface of fibre reinforced sand was estimated and discussed. Finally, quantitative effects of fibre contents on both shear strength and volume changes for sand are presented and discussed.

Strength Properties of Pervious Concrete Made with Locally Produced Recycled Coarse Aggregate

Proceedings of the World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2024

Pervious concrete is a special type of concrete that addresses critical environmental issues and ... more Pervious concrete is a special type of concrete that addresses critical environmental issues and supports green, sustainable construction. In such concrete, little or no sand is employed in the mix in order to allow the formation of considerable void content leading to high permeability. In this study, seven pervious concrete mixes made with recycled coarse aggregate and containing different amount of natural fine aggregate are tested in the laboratory for their strength. The source of the coarse aggregate is demolished old concrete buildings in the United Arab Emirates. One of the mixes contains 100% natural coarse aggregate without natural sand, another 100% recycled coarse aggregate without natural sand, and the remaining 5 mixes include both recycled coarse aggregate and fine natural aggregate such that the amount of fine-to-coarse aggregate is 1.5-11.7%. Results of the study revealed that that the use of recycled coarse aggregate in pervious concrete without fine aggregate reduced the compressive strength by 36% and tensile strength by 57%. Replacing 4.7% of the recycled coarse aggregate with natural sand in such concrete helped in restoring the compressive strength to the level of the control mix that contained natural coarse aggregate. Likewise, replacing 11.7% of the recycled coarse aggregate with natural sand in concrete mix aided in restoring the split cylinder tensile strength to the level of the control mix that contained natural coarse aggregate. There is a relationship between compressive and tensile strengths, of which a lower bound can be reasonably predicted by models proposed for pervious concrete in the literature. The study confirms the feasibility of using recycled aggregate in pervious concrete mixes if about 10% natural fine aggregate is utilized in the mix as replacement of the recycled coarse aggregate.

Plane Strain Sand Properties from Numerical Modelling of Direct Shear Test

Proceedings of the World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2024

Direct shear test is the simplest, inexpensive and the oldest among shear tests in soil laborator... more Direct shear test is the simplest, inexpensive and the oldest among shear tests in soil laboratories. Although such test is commonly used in research and practice, analysis for many long geotechnical structures such as earth pressure and slope stability problems require measurement of plane strain soil properties. Plane strain soil properties are complex and need special skills and equipment to measure in the lab. Therefore, engineers usually rely on empirical relations to predict the plane strain soil properties from direct shear or triaxial test. In this study, a two-dimensional, plane strain finite difference model is employed in the software FLAC to simulate the mechanical behaviour of sandy soil tested in direct shear box. The study showed that the results of the finite element analysis complied with those obtained from laboratory tests conducted with the help of a direct shear box. The plane strain properties of the sandy soil can be back calculated from numerical simulations of direct shear tests with reasonable accuracy. Moreover, the numerical model was able to capture the trend in the experimental results and in most cases gave reasonable estimate of the shear strength and volume change of sandy soil.

Influence of Optimum Particle Packing on the Macro and Micro Properties of Sustainable Concrete

Sustainability

In this research, the possibility of making eco-friendly concrete from available materials in the... more In this research, the possibility of making eco-friendly concrete from available materials in the local United Arab Emirates (UAE) market was investigated. Supplementary cementitious materials, such as ground granulated blast-furnace slag (GGBS) and silica fume (SF), were utilized for decreasing the cement quantity, enhancing the particle size distribution and improving packing. In sum, 130 concrete specimens—cubes, cylinders, and prisms—from 10 different concrete mixes were tested to determine the enhancement levels in the fresh and hard properties of new concrete. The results showed the improved particle packing of the concrete, especially within the region of sizes 100–10,000 microns, produced by the Elkem Materials Mix Analyser (EMMA), closely matching the Andreassen theoretical model. The green concrete incorporating SF and GGBS possessed air content in the range 1.0–1.4% and compressive strength that is on average 11% higher than the well-packed concrete that did not contain S...

Bearing Capacity and Strength of Fibre-Reinforced Sand: Experimental and Parametric Study

International Journal of Civil Infrastructure

Development of Relative Rigidity Measure for Shallow Foundations

International Journal of Civil Infrastructure

Sensitivity of Raft Foundation’s Structural Behaviour to Changes in Geometry and Materials

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

Experimental modeling of strip footing adjacent to non-yielding retaining wall

Innovative Infrastructure Solutions, 2020

A series of reduced-scale models were tested to assess the performance of non-yielding basement w... more A series of reduced-scale models were tested to assess the performance of non-yielding basement wall due to strip footing constructed adjacent to it. Construction design parameters such as strip footing width (B), its distance from non-yielding wall back (a), and footing embedment depth below the backfill surface (d f) have been considered in this study. This paper presents results of five model tests that isolate effects of non-yielding wall on the strip ultimate footing bearing capacity. The opposite effect of the strip footing distance design parameters on the non-yielding wall responses is also investigated. Experimental results revealed that the strip footing load-carrying capacity increased, and the settlement decreased as its distance from the back of non-yielding wall increased. Furthermore, the vertically loaded strip footing imposed significant vertical and horizontal forces at the back of the non-yielding wall. Results also indicate that distance a > 4B between the footing and the back of the wall enabled the strip footing to mobilize ultimate load-carrying capacity comparable to both control strip footing test and value calculated with Terzaghi's equation. Comparison of the measured and predicted lateral forces showed that using elastic theory method together with Jacky formula for at-rest lateral earth pressure coefficient led to about 23-35% underestimation of the measured lateral forces. However, including sand overconsolidation ratio, OCR = 2 resulted in an overestimation of the lateral forces by about 20-29% of the measured value. Finally, results of the experimental program are used to identify sources of conservativeness and non-conservativeness in the current design methodologies used to calculate lateral forces imposed on non-yielding walls due to adjacent strip footing and suggested necessary modifications. Keywords Retaining wall • Strip footing • Model tests • Sand soil • Lateral earth forces List of symbols a Footing-wall back distance B Strip footing width C c Coefficient of curvature C u Coefficient of uniformity d f Footing embedment depth Δσ v(z) Vertical earth pressure any depth (z) Δσ h(z) Lateral earth pressure any depth (z) Δσ v Vertical stress increment Δδ 2 Vertical strain increments δ v-u Vertical settlements measured at q u-T

Strength and Deformation Characteristics of Dune Sand Earth Blocks Reinforced with Natural and Polymeric Fibers

Sustainability

In this paper, we present a strength and deformation evaluation of earth blocks reinforced with d... more In this paper, we present a strength and deformation evaluation of earth blocks reinforced with different types of fiber. A natural palm tree fiber and two other types of synthetic polyolefin fibers were used to improve earth blocks’ strength and stiffness. The soil used to cast the earth blocks was composed of dune sand, which is extensively available in the United Arab Emirates and most Gulf Cooperation Council (GCC) deserts, and clayey silt soil acquired from Al-Ain city, UAE. Sixteen different mixes were prepared for this study. Two identical earth blocks were cast in a wooden mold from each mix to form a total of 32 blocks. After compaction, the blocks were consolidated under pre-specified pressure, air dried, and tested to failure in the compression machine. The main parameters investigated in this study were clay content, fiber types and percentages, and cement content. The results indicate that the addition of natural or polymeric fiber to cast earth blocks significantly imp...

Dynamic Properties of Calcareous Sands from Urban Areas of Abu Dhabi

Applied Sciences, 2022

Abu Dhabi (ABD) has recently developed its national building code that mandates dynamic analysis ... more Abu Dhabi (ABD) has recently developed its national building code that mandates dynamic analysis of large structures to seismic loadings. Large strain dynamic properties such as shear modulus (G) and damping ratio (D) of local undisturbed calcareous sands are not available. Designers are compelled to choose degradation models from studies on calcareous sands of other regions that are usually reconstituted. This research presents for the first time large strain dynamic properties of calcareous sands of urban ABD. Undisturbed samples are collected from different areas of urban ABD and are tested in cyclic triaxial (CT) devices fitted with bender elements (BE). The dynamic properties as functions of confinement are curve fitted with power models, whereas their variation with shear strain level is curve fitted with hyperbolic models. The results are compared with findings of previous studies on calcareous and silica sands. The results indicate that dynamic properties of all samples degr...

Response of Strip Footing Adjacent to Nonyielding Basement Wall

Ground Improvement and Earth Structures, 2017

A series of 1/3-scale experimental model tests were performed at the American University of Sharj... more A series of 1/3-scale experimental model tests were performed at the American University of Sharjah (AUS) to assess the performance of strip footing constructed adjacent to nonyielding basement wall. Different construction design parameters have been considered including the strip footing width (B), its distance from nonyielding wall back (a), and footing embedment depth below the backfill surface (D f). The effects of nonyielding wall proximity to the strip footing were investigated. The experimental results show that the lateral deflection of the nonyielding wall is a major factor in dictating the load carrying capacity of the strip footing. The vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load carrying capacity increased as the footing width decreased, the distance from the wall increased and the embedment depth increased. Meanwhile, the vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The data gathered from this program is used to identify deficiencies in current design methodologies for similar soil structure interaction problems.

Behaviour of Strip Footing in the Vicinity of Non-Yielding Wall

World Congress on Civil, Structural, and Environmental Engineering, 2018

The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and ... more The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and tested at the sand box test facility at the American University of Sharjah (AUS). The objective of the testing program is to quantify the responses of both strip footing and nonyielding wall constructed closer to each other. To achieve this objective, different design construction parameters have been considered including: (1) the strip footing width (B), (2) footing distance from non-yielding wall back (a), and, (3) strip footing embedment depth below the backfill surface (Df). Test results indicated that the location of the strip footing relative to the wall is a major factor in dictating the load bearing capacity of the strip footing, and the maximum lateral deflection of the non-yielding wall. Meanwhile, the vertically loaded strip footing imposed substantial vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load bearing capacity increased as the distance from the wall increased, the footing width decreased, and the embedment depth increased. Data collected from the responses of scaled-physical model test were used to recognize deficiencies in current design approaches for similar soil structure interaction problems.

Seismic Hazard Assessment and Local Site Effects on United Arab Emirates major Cities and their environs: An Overview

This paper summarizes the results of seismic hazard assessment of the United Arab Emirates (UAE) ... more This paper summarizes the results of seismic hazard assessment of the United Arab Emirates (UAE) and the influence of local site effects on the intensities of ground shaking on recently emerged mega projects in UAE major cities including Abu Dhabi, Dubai, Sharjah and their localities. The probabilistic seismic hazard assessment was based on: (1) recently developed new generation of ground motion prediction equations; (2) collection of catalogues of various degrees of completeness that were homogenized for temporal distribution of events; (3) source zones that were delineated based on their seismic activities and tectonics; and (4) activity parameters that were based on doubly bounded magnitude-frequency relationships. The local site effect is based on selected time histories that were chosen based on a target response spectrum. This target response was obtained from the results of the probabilistic seismic hazard assessment stated above. In addition, subsurface geotechnical data fro...

Effect of Water Content, Void Ratio and Clay Content on Sand P-Wave Velocity

Proceedings of the 4th World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2019

The main purpose of the current research is to implement different Geophysical Techniques (GT) in... more The main purpose of the current research is to implement different Geophysical Techniques (GT) in measuring wave velocity at different soil properties. For this purpose, a number of 6-in-diameter specimens have been prepared with different soil properties for index tests. The objective of the small scale models is to study the variation of the compressional wave velocity with different soil parameters. Soil properties that are of high importance to the wave velocity are compaction efforts (void ratio, density, porosity), water content, soil grading size, soil clay content, and the addition of Portland cement. Specially acquired accelerometers are used to measure the P-wave velocity through the soil specimens after manually triggering mechanical waves. Sensitivity tests program is conducted to determine suitable specimen dimensions and the best and right method of attaching the accelerometers to the soil specimen. Index test results indicate that the P-wave velocity decreases as the soil water content and degree of saturation increases up to certain threshold values, which itself increases with the compaction effort. In addition, the wave velocity becomes larger as the soil includes more fine contents. Finally, compressional wave velocity increased as the void ratio of the soil specimen decreased.

Experimental and Numerical Study of At-Rest Lateral Earth Pressure of Overconsolidated Sand

Advances in Civil Engineering, 2011

The paper presents a one-meter-height rigid facing panel, supported rigidly at the top and bottom... more The paper presents a one-meter-height rigid facing panel, supported rigidly at the top and bottom to simulate nonyielding retaining wall system. A set of load cells is used to measure the horizontal force at the top and bottom of the facing panel, which is converted to equivalent horizontal earth pressure acting at the back of the wall. Another set of load cells is used to measure the vertical load at the bottom of the wall facing, both at the toe and the heel. Uniformly graded sand was used as backfill soil. The measured wall responses were used to calibrate a numerical model that used to predict additional wall parameters. Results indicated that the measured horizontal earth force is about three times the value calculated by classical at-rest earth pressure theory. In addition, the location of the resultant earth force is located closer to 0.4 H, which is higher compared to the theoretical value of H/3. The numerical model developed was able to predict the earth pressure distribut...

Behaviour of Strip Footing in the Vicinity of Non-Yielding Wall

Proceedings of the 3rd World Congress on Civil, Structural, and Environmental Engineering (CSEE’18), 2018

The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and ... more The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and tested at the sand box test facility at the American University of Sharjah (AUS). The objective of the testing program is to quantify the responses of both strip footing and nonyielding wall constructed closer to each other. To achieve this objective, different design construction parameters have been considered including: (1) the strip footing width (B), (2) footing distance from non-yielding wall back (a), and, (3) strip footing embedment depth below the back-fill surface (Df). Test results indicated that the location of the strip footing relative to the wall is a major factor in dictating the load bearing capacity of the strip footing, and the maximum lateral deflection of the non-yielding wall. Meanwhile, the vertically loaded strip footing imposed substantial vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load bearing capacity increased as th...

Energy dissipation in engineered sand of large damping ratio

Geomechanics and Geoengineering, 2013

Many geotechnical problems such as seismic resistant designs and machine vibrations require the i... more Many geotechnical problems such as seismic resistant designs and machine vibrations require the installation of dampers or isolators to control the amplitude of vibrations. Engineered fills designed with increased capability of dissipating energy can provide a more economical approach to control excessive vibrations. This study presents a novel technique to increase the damping ratio of sand without affecting its stiffness

Responses of Non-Yielding Basement Walls Adjacent to Strip Footing

by Majid Touqan and Magdi Elemam

Proceedings of the Second International Conference on Infrastructure Management, Assessment and Rehabilitation Techniques, 2016

A series of 1/3-scale experimental model tests were performed at the American University of Sharj... more A series of 1/3-scale experimental model tests were performed at the American University of Sharjah (AUS) to assess the performance of strip footing constructed adjacent to nonyielding basement wall. Different construction design parameters have been considered including the strip footing width (B), distance from nonyielding wall (a), and embedment depth (Df). The interchangeable effects between both strip footing and the wall were investigated. The experimental results show that the stiffness of the nonyielding wall is a major factor in dictating the load carrying capacity of the strip footing. The vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load carrying capacity increased as the footing width decreased, the distance from the wall increased and the embedment depth increased. The data gathered from this program is used to identify deficiencies in current design methodologies for similar soil structure interaction problems.

Local site effects on seismic ground response of major cities in UAE

by Jamal A. Abdalla and Magdi Elemam

This paper investigates the influence of local geotechnical and geological soil conditions on the... more This paper investigates the influence of local geotechnical and geological soil
conditions on the intensity of ground shaking of major cities in United Arab Emirates
(UAE) including Abu Dhabi, Dubai, and Sharjah, and their surrounding areas. Two time
histories for each city were chosen based on the target response spectrum that was obtained
from results of probabilistic seismic hazard analysis conducted in previous study for UAE.
Subsurface geotechnical data from more than hundred different sites were used to evaluate
the effect of local site conditions on ground response during earthquake. Dynamic properties
of soil for selected soil profiles have been generated, and one-dimensional site
response analysis has been conducted. Results are presented in terms of response spectral
accelerations (RSA) for different site classes in each city. RSA results indicated that the
surficial deposits in the studied areas have the ability to amplify earthquake ground motion
significantly with peak amplification at relatively narrow frequency range of 1.5–5 Hz
(0.2–0.67-s period). This frequency range was found to be a representative of the predominant
frequency ranges of the site classes under consideration. At higher frequencies,
slight amplification, and in some cases slight attenuation, is observed. Design response
spectra for each site class in each city were developed based on the results of site response
analysis. The developed design response spectra were compared with spectrum currently
used in each city, and the modified site coefficient is presented.

Probabilistic seismic hazard analysis and spectral accelerations for United Arab Emirates

by Jamal A. Abdalla and Magdi Elemam

In recent years, the United Arab Emirates (UAE) has experienced an unprecedented growth which is ... more In recent years, the United Arab Emirates (UAE) has experienced an unprecedented
growth which is coupled with the increase in seismic activity in the surroundings.
Previous studies presents significant variations in their results whereas some recent studies
although very detailed focus on only few cities. This study reviews the results of previous
studies and presents new findings for the whole of UAE based on the improved source model
and use of next generation attenuation (NGA) equations. The peak ground accelerations,
spectral accelerations and deaggregation of hazard for major cities are presented. Moreover,
the breakdown of the range of mapped spectral accelerations (S0.2 and S1) is proposed to form
the basis for the development of site amplification factors in subsequent studies. The results
of this study indicate almost similar values of ground motion compared to some recently
published studies and smaller values compared to some earlier studies.

Shear Strength and Bearing Capacity of FibreReinforced Sand

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

In this paper, direct shear tests were conducted to evaluate the effect of randomly distributed f... more In this paper, direct shear tests were conducted to evaluate the effect of randomly distributed fibres on the shear strength parameters of dry sand. Polyolefin fibre which is a polymeric produced from a simple olefin (CnH2n) was mixed with dry sand to investigate the improvement of shear strength and effect on volume changes. Specimens with 0.5%, 1%, 1.5% and 2% of fibre contents with different lengths (i.e. 15mm and 30mm) are prepared in repeatable steps and tested in direct shear tests. In addition, two sand types; coarse sand and fin sand were used in this investigation to study the grading size effects on the behaviour of the fiber-reinforced sand. Results indicated that, the inclusion of randomly distributed discrete fibres significantly improved the shear strength of sand. The existence of polymeric fibre inside the sand developed what is called apparent tensile cohesion in addition to the sand normal internal friction angle. The optimum fibre percentage for improving both friction angle and apparent tensile cohesion was about 1%. Adding fibre more than this ratio resulted in a significant reduction in both soil shear strength parameters. The effect of fibre on sand tensile cohesion is more pronounced compared to its effect on the friction angle. A bearing capacity of hypothetical footing resting on ground surface of fibre reinforced sand was estimated and discussed. Finally, quantitative effects of fibre contents on both shear strength and volume changes for sand are presented and discussed.

Strength Properties of Pervious Concrete Made with Locally Produced Recycled Coarse Aggregate

Proceedings of the World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2024

Pervious concrete is a special type of concrete that addresses critical environmental issues and ... more Pervious concrete is a special type of concrete that addresses critical environmental issues and supports green, sustainable construction. In such concrete, little or no sand is employed in the mix in order to allow the formation of considerable void content leading to high permeability. In this study, seven pervious concrete mixes made with recycled coarse aggregate and containing different amount of natural fine aggregate are tested in the laboratory for their strength. The source of the coarse aggregate is demolished old concrete buildings in the United Arab Emirates. One of the mixes contains 100% natural coarse aggregate without natural sand, another 100% recycled coarse aggregate without natural sand, and the remaining 5 mixes include both recycled coarse aggregate and fine natural aggregate such that the amount of fine-to-coarse aggregate is 1.5-11.7%. Results of the study revealed that that the use of recycled coarse aggregate in pervious concrete without fine aggregate reduced the compressive strength by 36% and tensile strength by 57%. Replacing 4.7% of the recycled coarse aggregate with natural sand in such concrete helped in restoring the compressive strength to the level of the control mix that contained natural coarse aggregate. Likewise, replacing 11.7% of the recycled coarse aggregate with natural sand in concrete mix aided in restoring the split cylinder tensile strength to the level of the control mix that contained natural coarse aggregate. There is a relationship between compressive and tensile strengths, of which a lower bound can be reasonably predicted by models proposed for pervious concrete in the literature. The study confirms the feasibility of using recycled aggregate in pervious concrete mixes if about 10% natural fine aggregate is utilized in the mix as replacement of the recycled coarse aggregate.

Plane Strain Sand Properties from Numerical Modelling of Direct Shear Test

Proceedings of the World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2024

Direct shear test is the simplest, inexpensive and the oldest among shear tests in soil laborator... more Direct shear test is the simplest, inexpensive and the oldest among shear tests in soil laboratories. Although such test is commonly used in research and practice, analysis for many long geotechnical structures such as earth pressure and slope stability problems require measurement of plane strain soil properties. Plane strain soil properties are complex and need special skills and equipment to measure in the lab. Therefore, engineers usually rely on empirical relations to predict the plane strain soil properties from direct shear or triaxial test. In this study, a two-dimensional, plane strain finite difference model is employed in the software FLAC to simulate the mechanical behaviour of sandy soil tested in direct shear box. The study showed that the results of the finite element analysis complied with those obtained from laboratory tests conducted with the help of a direct shear box. The plane strain properties of the sandy soil can be back calculated from numerical simulations of direct shear tests with reasonable accuracy. Moreover, the numerical model was able to capture the trend in the experimental results and in most cases gave reasonable estimate of the shear strength and volume change of sandy soil.

Influence of Optimum Particle Packing on the Macro and Micro Properties of Sustainable Concrete

Sustainability

In this research, the possibility of making eco-friendly concrete from available materials in the... more In this research, the possibility of making eco-friendly concrete from available materials in the local United Arab Emirates (UAE) market was investigated. Supplementary cementitious materials, such as ground granulated blast-furnace slag (GGBS) and silica fume (SF), were utilized for decreasing the cement quantity, enhancing the particle size distribution and improving packing. In sum, 130 concrete specimens—cubes, cylinders, and prisms—from 10 different concrete mixes were tested to determine the enhancement levels in the fresh and hard properties of new concrete. The results showed the improved particle packing of the concrete, especially within the region of sizes 100–10,000 microns, produced by the Elkem Materials Mix Analyser (EMMA), closely matching the Andreassen theoretical model. The green concrete incorporating SF and GGBS possessed air content in the range 1.0–1.4% and compressive strength that is on average 11% higher than the well-packed concrete that did not contain S...

Bearing Capacity and Strength of Fibre-Reinforced Sand: Experimental and Parametric Study

International Journal of Civil Infrastructure

Development of Relative Rigidity Measure for Shallow Foundations

International Journal of Civil Infrastructure

Sensitivity of Raft Foundation’s Structural Behaviour to Changes in Geometry and Materials

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

Experimental modeling of strip footing adjacent to non-yielding retaining wall

Innovative Infrastructure Solutions, 2020

A series of reduced-scale models were tested to assess the performance of non-yielding basement w... more A series of reduced-scale models were tested to assess the performance of non-yielding basement wall due to strip footing constructed adjacent to it. Construction design parameters such as strip footing width (B), its distance from non-yielding wall back (a), and footing embedment depth below the backfill surface (d f) have been considered in this study. This paper presents results of five model tests that isolate effects of non-yielding wall on the strip ultimate footing bearing capacity. The opposite effect of the strip footing distance design parameters on the non-yielding wall responses is also investigated. Experimental results revealed that the strip footing load-carrying capacity increased, and the settlement decreased as its distance from the back of non-yielding wall increased. Furthermore, the vertically loaded strip footing imposed significant vertical and horizontal forces at the back of the non-yielding wall. Results also indicate that distance a > 4B between the footing and the back of the wall enabled the strip footing to mobilize ultimate load-carrying capacity comparable to both control strip footing test and value calculated with Terzaghi's equation. Comparison of the measured and predicted lateral forces showed that using elastic theory method together with Jacky formula for at-rest lateral earth pressure coefficient led to about 23-35% underestimation of the measured lateral forces. However, including sand overconsolidation ratio, OCR = 2 resulted in an overestimation of the lateral forces by about 20-29% of the measured value. Finally, results of the experimental program are used to identify sources of conservativeness and non-conservativeness in the current design methodologies used to calculate lateral forces imposed on non-yielding walls due to adjacent strip footing and suggested necessary modifications. Keywords Retaining wall • Strip footing • Model tests • Sand soil • Lateral earth forces List of symbols a Footing-wall back distance B Strip footing width C c Coefficient of curvature C u Coefficient of uniformity d f Footing embedment depth Δσ v(z) Vertical earth pressure any depth (z) Δσ h(z) Lateral earth pressure any depth (z) Δσ v Vertical stress increment Δδ 2 Vertical strain increments δ v-u Vertical settlements measured at q u-T

Strength and Deformation Characteristics of Dune Sand Earth Blocks Reinforced with Natural and Polymeric Fibers

Sustainability

In this paper, we present a strength and deformation evaluation of earth blocks reinforced with d... more In this paper, we present a strength and deformation evaluation of earth blocks reinforced with different types of fiber. A natural palm tree fiber and two other types of synthetic polyolefin fibers were used to improve earth blocks’ strength and stiffness. The soil used to cast the earth blocks was composed of dune sand, which is extensively available in the United Arab Emirates and most Gulf Cooperation Council (GCC) deserts, and clayey silt soil acquired from Al-Ain city, UAE. Sixteen different mixes were prepared for this study. Two identical earth blocks were cast in a wooden mold from each mix to form a total of 32 blocks. After compaction, the blocks were consolidated under pre-specified pressure, air dried, and tested to failure in the compression machine. The main parameters investigated in this study were clay content, fiber types and percentages, and cement content. The results indicate that the addition of natural or polymeric fiber to cast earth blocks significantly imp...

Dynamic Properties of Calcareous Sands from Urban Areas of Abu Dhabi

Applied Sciences, 2022

Abu Dhabi (ABD) has recently developed its national building code that mandates dynamic analysis ... more Abu Dhabi (ABD) has recently developed its national building code that mandates dynamic analysis of large structures to seismic loadings. Large strain dynamic properties such as shear modulus (G) and damping ratio (D) of local undisturbed calcareous sands are not available. Designers are compelled to choose degradation models from studies on calcareous sands of other regions that are usually reconstituted. This research presents for the first time large strain dynamic properties of calcareous sands of urban ABD. Undisturbed samples are collected from different areas of urban ABD and are tested in cyclic triaxial (CT) devices fitted with bender elements (BE). The dynamic properties as functions of confinement are curve fitted with power models, whereas their variation with shear strain level is curve fitted with hyperbolic models. The results are compared with findings of previous studies on calcareous and silica sands. The results indicate that dynamic properties of all samples degr...

Response of Strip Footing Adjacent to Nonyielding Basement Wall

Ground Improvement and Earth Structures, 2017

A series of 1/3-scale experimental model tests were performed at the American University of Sharj... more A series of 1/3-scale experimental model tests were performed at the American University of Sharjah (AUS) to assess the performance of strip footing constructed adjacent to nonyielding basement wall. Different construction design parameters have been considered including the strip footing width (B), its distance from nonyielding wall back (a), and footing embedment depth below the backfill surface (D f). The effects of nonyielding wall proximity to the strip footing were investigated. The experimental results show that the lateral deflection of the nonyielding wall is a major factor in dictating the load carrying capacity of the strip footing. The vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load carrying capacity increased as the footing width decreased, the distance from the wall increased and the embedment depth increased. Meanwhile, the vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The data gathered from this program is used to identify deficiencies in current design methodologies for similar soil structure interaction problems.

Behaviour of Strip Footing in the Vicinity of Non-Yielding Wall

World Congress on Civil, Structural, and Environmental Engineering, 2018

The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and ... more The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and tested at the sand box test facility at the American University of Sharjah (AUS). The objective of the testing program is to quantify the responses of both strip footing and nonyielding wall constructed closer to each other. To achieve this objective, different design construction parameters have been considered including: (1) the strip footing width (B), (2) footing distance from non-yielding wall back (a), and, (3) strip footing embedment depth below the backfill surface (Df). Test results indicated that the location of the strip footing relative to the wall is a major factor in dictating the load bearing capacity of the strip footing, and the maximum lateral deflection of the non-yielding wall. Meanwhile, the vertically loaded strip footing imposed substantial vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load bearing capacity increased as the distance from the wall increased, the footing width decreased, and the embedment depth increased. Data collected from the responses of scaled-physical model test were used to recognize deficiencies in current design approaches for similar soil structure interaction problems.

Seismic Hazard Assessment and Local Site Effects on United Arab Emirates major Cities and their environs: An Overview

This paper summarizes the results of seismic hazard assessment of the United Arab Emirates (UAE) ... more This paper summarizes the results of seismic hazard assessment of the United Arab Emirates (UAE) and the influence of local site effects on the intensities of ground shaking on recently emerged mega projects in UAE major cities including Abu Dhabi, Dubai, Sharjah and their localities. The probabilistic seismic hazard assessment was based on: (1) recently developed new generation of ground motion prediction equations; (2) collection of catalogues of various degrees of completeness that were homogenized for temporal distribution of events; (3) source zones that were delineated based on their seismic activities and tectonics; and (4) activity parameters that were based on doubly bounded magnitude-frequency relationships. The local site effect is based on selected time histories that were chosen based on a target response spectrum. This target response was obtained from the results of the probabilistic seismic hazard assessment stated above. In addition, subsurface geotechnical data fro...

Effect of Water Content, Void Ratio and Clay Content on Sand P-Wave Velocity

Proceedings of the 4th World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2019

The main purpose of the current research is to implement different Geophysical Techniques (GT) in... more The main purpose of the current research is to implement different Geophysical Techniques (GT) in measuring wave velocity at different soil properties. For this purpose, a number of 6-in-diameter specimens have been prepared with different soil properties for index tests. The objective of the small scale models is to study the variation of the compressional wave velocity with different soil parameters. Soil properties that are of high importance to the wave velocity are compaction efforts (void ratio, density, porosity), water content, soil grading size, soil clay content, and the addition of Portland cement. Specially acquired accelerometers are used to measure the P-wave velocity through the soil specimens after manually triggering mechanical waves. Sensitivity tests program is conducted to determine suitable specimen dimensions and the best and right method of attaching the accelerometers to the soil specimen. Index test results indicate that the P-wave velocity decreases as the soil water content and degree of saturation increases up to certain threshold values, which itself increases with the compaction effort. In addition, the wave velocity becomes larger as the soil includes more fine contents. Finally, compressional wave velocity increased as the void ratio of the soil specimen decreased.

Experimental and Numerical Study of At-Rest Lateral Earth Pressure of Overconsolidated Sand

Advances in Civil Engineering, 2011

The paper presents a one-meter-height rigid facing panel, supported rigidly at the top and bottom... more The paper presents a one-meter-height rigid facing panel, supported rigidly at the top and bottom to simulate nonyielding retaining wall system. A set of load cells is used to measure the horizontal force at the top and bottom of the facing panel, which is converted to equivalent horizontal earth pressure acting at the back of the wall. Another set of load cells is used to measure the vertical load at the bottom of the wall facing, both at the toe and the heel. Uniformly graded sand was used as backfill soil. The measured wall responses were used to calibrate a numerical model that used to predict additional wall parameters. Results indicated that the measured horizontal earth force is about three times the value calculated by classical at-rest earth pressure theory. In addition, the location of the resultant earth force is located closer to 0.4 H, which is higher compared to the theoretical value of H/3. The numerical model developed was able to predict the earth pressure distribut...

Behaviour of Strip Footing in the Vicinity of Non-Yielding Wall

Proceedings of the 3rd World Congress on Civil, Structural, and Environmental Engineering (CSEE’18), 2018

The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and ... more The paper presents two-1/3 scale nonyielding wall-strip footing models that were constructed and tested at the sand box test facility at the American University of Sharjah (AUS). The objective of the testing program is to quantify the responses of both strip footing and nonyielding wall constructed closer to each other. To achieve this objective, different design construction parameters have been considered including: (1) the strip footing width (B), (2) footing distance from non-yielding wall back (a), and, (3) strip footing embedment depth below the back-fill surface (Df). Test results indicated that the location of the strip footing relative to the wall is a major factor in dictating the load bearing capacity of the strip footing, and the maximum lateral deflection of the non-yielding wall. Meanwhile, the vertically loaded strip footing imposed substantial vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load bearing capacity increased as th...

Energy dissipation in engineered sand of large damping ratio

Geomechanics and Geoengineering, 2013

Many geotechnical problems such as seismic resistant designs and machine vibrations require the i... more Many geotechnical problems such as seismic resistant designs and machine vibrations require the installation of dampers or isolators to control the amplitude of vibrations. Engineered fills designed with increased capability of dissipating energy can provide a more economical approach to control excessive vibrations. This study presents a novel technique to increase the damping ratio of sand without affecting its stiffness

Responses of Non-Yielding Basement Walls Adjacent to Strip Footing

by Majid Touqan and Magdi Elemam

Proceedings of the Second International Conference on Infrastructure Management, Assessment and Rehabilitation Techniques, 2016

A series of 1/3-scale experimental model tests were performed at the American University of Sharj... more A series of 1/3-scale experimental model tests were performed at the American University of Sharjah (AUS) to assess the performance of strip footing constructed adjacent to nonyielding basement wall. Different construction design parameters have been considered including the strip footing width (B), distance from nonyielding wall (a), and embedment depth (Df). The interchangeable effects between both strip footing and the wall were investigated. The experimental results show that the stiffness of the nonyielding wall is a major factor in dictating the load carrying capacity of the strip footing. The vertically loaded strip footing imposed significant vertical and horizontal forces at the wall top and bottom boundaries. The strip footing load carrying capacity increased as the footing width decreased, the distance from the wall increased and the embedment depth increased. The data gathered from this program is used to identify deficiencies in current design methodologies for similar soil structure interaction problems.

Local site effects on seismic ground response of major cities in UAE

by Jamal A. Abdalla and Magdi Elemam

This paper investigates the influence of local geotechnical and geological soil conditions on the... more This paper investigates the influence of local geotechnical and geological soil
conditions on the intensity of ground shaking of major cities in United Arab Emirates
(UAE) including Abu Dhabi, Dubai, and Sharjah, and their surrounding areas. Two time
histories for each city were chosen based on the target response spectrum that was obtained
from results of probabilistic seismic hazard analysis conducted in previous study for UAE.
Subsurface geotechnical data from more than hundred different sites were used to evaluate
the effect of local site conditions on ground response during earthquake. Dynamic properties
of soil for selected soil profiles have been generated, and one-dimensional site
response analysis has been conducted. Results are presented in terms of response spectral
accelerations (RSA) for different site classes in each city. RSA results indicated that the
surficial deposits in the studied areas have the ability to amplify earthquake ground motion
significantly with peak amplification at relatively narrow frequency range of 1.5–5 Hz
(0.2–0.67-s period). This frequency range was found to be a representative of the predominant
frequency ranges of the site classes under consideration. At higher frequencies,
slight amplification, and in some cases slight attenuation, is observed. Design response
spectra for each site class in each city were developed based on the results of site response
analysis. The developed design response spectra were compared with spectrum currently
used in each city, and the modified site coefficient is presented.

Probabilistic seismic hazard analysis and spectral accelerations for United Arab Emirates

by Jamal A. Abdalla and Magdi Elemam

In recent years, the United Arab Emirates (UAE) has experienced an unprecedented growth which is ... more In recent years, the United Arab Emirates (UAE) has experienced an unprecedented
growth which is coupled with the increase in seismic activity in the surroundings.
Previous studies presents significant variations in their results whereas some recent studies
although very detailed focus on only few cities. This study reviews the results of previous
studies and presents new findings for the whole of UAE based on the improved source model
and use of next generation attenuation (NGA) equations. The peak ground accelerations,
spectral accelerations and deaggregation of hazard for major cities are presented. Moreover,
the breakdown of the range of mapped spectral accelerations (S0.2 and S1) is proposed to form
the basis for the development of site amplification factors in subsequent studies. The results
of this study indicate almost similar values of ground motion compared to some recently
published studies and smaller values compared to some earlier studies.