Ahmed-Waeil Elgamal

Ahmed-Waeil Elgamal
University of California, San Diego | UCSD · Department of Structural Engineering

Professor

About

277
Publications
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8,984
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Publications

Publications (277)
Article
Sustainability has emerged as a paramount concern in the construction and development of built infrastructure. This study delves into the environmental impact and vulnerability of an idealized bridge–foundation–ground system using stone columns as a liquefaction countermeasure, focusing on the seismic response in the transverse direction. For that...
Conference Paper
Full-text available
This paper presents a research study focusing on the impact of liquefaction-induced lateral spreading on pile foundations. Previous earthquakes have demonstrated that such lateral spreading deformations can lead to significant movement and localized plastic demands on the piles. To investigate this phenomenon, the authors conducted a 1g shake-table...
Chapter
Full-text available
Numerical simulations of a liquefiable sloping ground for LEAP-ASIA-2019 centrifuge tests are presented. The simulations are performed using a pressure-dependent constitutive model implemented with the characteristics of dilatancy, cyclic mobility, and associated shear deformation. The soil model parameters are determined based on a series of stres...
Chapter
Full-text available
This chapter presents a summary of Type-B and Type-C numerical simulations submitted by nine numerical simulation teams that participated in the LEAP-ASIA-2019 prediction campaign, with the results of a selected set of centrifuge model tests on the seismic behavior of a uniform-density, 20-m-long, and 5-degree sandy slope. Time histories of respons...
Chapter
Full-text available
This chapter presents a summary of the calibration exercises (i.e., element test simulations) submitted by nine numerical simulation teams that participated in the LEAP-ASIA-2019 prediction campaign. The standard sand selected for the campaign is Ottawa F-65, and researchers have developed several efforts to increase the database of laboratory test...
Book
One-dimensional (1D) equivalent-linear total-stress site response analysis (SRA) is the de facto standard for state department of transportation (DOT) highway facilities at locations where site-specific ground response analyses are conducted. However, many users and various DOTs have concerns about the applicability of equivalent-linear analyses fo...
Article
Carbon footprint considerations have become one of the significant concerns in the construction and rehabilitation of public infrastructure. As such, sustainability metrics using carbon footprint are of particular significance to stakeholders of lifeline infrastructure systems, including bridges, under extreme events. This study aimed to assess the...
Article
Full-text available
Shake table testing was conducted to document the seismic response of a bucket foundation offshore wind turbine (OWT) system. Salient response of the system's soil-structure interaction effects is presented and discussed. Among the observed response characteristics, excess pore pressure fluctuation within and around the soil-bucket domain is thorou...
Article
Full-text available
A practical yet realistic three-dimensional (3D) constitutive model is presented for modeling the cyclic degradation behavior of soil. Such response can be attributed to pore pressure build-up and loss of cementation, among other stiffness and strength degradation mechanisms. Extending an existing multi-yield surface (MYS) plasticity formulation, t...
Article
Traditional deterministic approaches for estimating liquefaction-induced settlement (LIS) do not account for uncertainties associated with earthquake loading and soil spatial variability. A numerical–probabilistic method for evaluating LIS that accounts for these uncertainties is developed. An advanced non-linear soil constitutive model is employed...
Article
Full-text available
Shake table experiments are conducted to assess the potential of the polymer injection technique as a liquefaction countermeasure. A large 2.9 m high (10 ft) laminar soil container on a 3.9×1.85 m (13×6 ft) shake table is employed. Mitigation of liquefaction-induced settlement for a shallow foundation is explored. In a series of two shake table exp...
Article
Full-text available
This paper presents a three-dimensional (3D) multi-surface plasticity model to computationally simulate the behavior of coarse-grained granular soil during seismically-induced liquefaction. The model extends an existing multi-surface plasticity formulation and includes the Lade–Duncan failure criterion as the yield function to more closely capture...
Article
Liquefied soils may induce widespread permanent ground deformation in the vicinity of abutments and cause extensive damage to bridge foundations during earthquakes. As such, it is essential to systematically assess the performance of bridges susceptible to earthquake hazards and associated soil liquefaction. Motivated by details of an actual 18-spa...
Conference Paper
A series of two large-scale shake table tests were performed to investigate the efficacy of the polymer injection technique in remediating liquefaction-induced foundation settlement. In these tests, foundation-ground system response was studied first without and subsequently with polymer injected into the liquefiable stratum, resulting in a set of...
Chapter
Numerical simulations of LEAP-UCD-2017 centrifuge tests are conducted using a multi-surface cyclic plasticity sand model implemented with the characteristics of dilatancy, cyclic mobility and associated shear deformation. This model extends the OpenSees PDMY03 material to include the Lade-Duncan failure criterion as the yield function, thus allowin...
Chapter
Ground slopes with an underlying liquefiable layer are particularly prone to failure due to seismic excitation. For an embedded foundation, the extent of ground deformation at its specific location within the slope, will dictate the level of detrimental consequences. As such, knowledge about the spatial configuration of expected ground deformation...
Article
Full-text available
Considerable bridge-ground interaction effects are involved when evaluating the consequences of liquefaction-induced deformations. Due to seismic excitation, liquefied soil layers may result in substantial accumulated permanent deformation due to the sloping ground near the abutments. Ultimately, global response of the bridge is dictated by soil-st...
Conference Paper
Full-text available
This paper discusses the key findings of the 2018 PEER blind prediction contest based on a large-scale shaking table test that was conducted at the University of California San Diego. The test comprised of a shallow foundation located on top of a three-layer ground model that included a thick liquefiable layer in the middle. The blind prediction co...
Article
Full-text available
Full-scale shake table testing was conducted to evaluate the seismic performance of single and grouped helical piles. Eight circular and one square helical piles with different properties including length, radius and number of helices, as well as one driven circular pile were installed in dry sand enclosed in a laminar soil shear box that was situa...
Article
Recorded earthquake motions from the highly instrumented Eureka Channel bridge-foundation system have been compiled and made available by the California Geological Survey. During eight seismic events, more than 20 data channels have been documenting the seismic response of the bridge, abutments, and adjacent ground surface. Of special interest is t...
Article
Full-text available
This study evaluates the application of helical piles to reduce liquefaction-induced foundation settlement and investigates their seismic performance in liquefiable grounds. Two large-scale shake table test series, one without mitigation and one using helical piles, were conducted using the shake table facility at the University of California, San...
Article
In order to investigate the liquefied soil pressure inposed on an individual pile of pile group, a centrifugal shake table test on a pile-supported wharf on the sloping saturated sand stratum has been designed and implemented in this study. Final test results, including processing results of free-field soil responses as well as lateral displacement...
Article
This paper presents and discusses the measured responses of single and grouped helical piles to strong ground motions during a large-scale shake table testing program. The effects of earthquake characteristics (i.e., intensity and frequency content) on the seismic performance of single and grouped helical piles are evaluated from the measured respo...
Article
Full-text available
Dynamic ground and ground-structure responses are heavily dependent on the soil shear wave velocity. During seismic excitation, soil stiffness inferred from the shear wave velocity (Vs) might change significantly and affect the overall system response. In this study, an instrumentation and analysis framework was developed to allow for continuous es...
Chapter
Global response of bridges is dictated by soil-structure interaction considerations of the entire bridge-ground system. In this study the three-dimensional (3D) longitudinal response of such a bridge-ground system is numerically investigated. A realistic multi-layer soil profile is considered with interbedded liquefiable/non-liquefiable strata. Eff...
Chapter
Current computational platforms allow unprecedented opportunities for conducting seismic soil-structure interaction simulations. In geomechanics, capabilities such as coupled solid–fluid formulations and incremental-plasticity approaches allow for representation of the involved seismic response. Recent research that facilitated such endeavors in te...
Article
This paper presents numerical simulations of a liquefiable sloping ground related to LEAP-UCD-2017 and LEAP-Asia-2019 (Liquefaction Experiments and Analysis Projects) dynamic centrifuge model tests (Type-C phase) conducted by various institutions. The numerical simulations are performed using a pressure-dependent constitutive model implemented with...
Article
Full-text available
The significant damage observed during recent earthquakes resulting from liquefaction of shallow saturated soil deposits beneath structures has illustrated the need for further research in the area of liquefaction-induced ground movement effects. This study used the shake table facility at the University of California, San Diego to evaluate the liq...
Conference Paper
Full-text available
Documented case histories from past earthquakes have exhibited the devastating effects of the liquefaction phenomenon on the performance of buildings that are often presented in the form of excessive settlement of shallow foundations. Example earthquakes include the 1964 Niigata earthquake in Japan, and more recently the 2010-2011 Canterbury Earthq...
Article
This study presents a framework for assessing the seismic performance of a pile-supported wharf at different seismic hazard levels. A refined Three-Dimensional (3D) Finite Element (FE) model is conducted using the open-source computational platform OpenSees. The modeling strategies of the refined numerical model are given in detail, including refin...
Conference Paper
Full-text available
The results from a pilot study performed at the University of California, San Diego to assess potential of the polymer injection technique as a liquefaction countermeasure are presented. Three containers of dimensions about 1.1 m (length) by 0.9 m (width) by 1.0 m (height) are filled with saturated Ottawa F-65 sand at loose, medium-dense and dense...
Article
A three-dimensional (3D) incremental plasticity constitutive model is developed for simulating the strain softening behavior of soil materials. The constitutive model extends an existing multiyield surface (MYS) plasticity formulation with a new strain softening logic. Formulation of the model is presented, and calibration is undertaken to match an...
Article
For large embedded structures, soil-structure interaction (SSI) plays a major role in dictating the overall seismic response. In light of recent strong seismic excitation affecting such structures, three-dimensional (3D) response as well as nonlinear (NL) soil behavior are among the areas of increased interest. As such, this paper presents a series...
Article
Full-text available
Due to seismic response, accumulation of permanent ground deformation (lateral spreading) is an important mechanism of much practical significance. Such deformations typically occur near a ground slope, behind retaining structures such as sheet-pile and quay walls, and in mildly sloping ground. In conducting a shake table test, the generation of pe...
Conference Paper
Full-text available
A shake table testing program is conducted at the University of California, San Diego, to assess the potential of the polymer injection technique in remediating liquefaction induced foundation settlement. A large laminar soil container placed on a shake table is employed. Emphasis is placed on mitigating the liquefaction-induced settlement of a sha...
Conference Paper
Full-text available
This paper presents the results of a class C numerical blind prediction based on a large-scale shaking table test which was recently conducted at UCSD on a shallow foundation located on top of liquefiable soils. The organized blind prediction was focused on predicting the liquefaction-induced permanent settlements at multiple locations at free-fiel...
Article
Considerable bridge‐ground interaction effects are involved in evaluating the consequences of liquefaction‐induced deformations. Due to seismic excitation, liquefied soil layers may result in substantial accumulated permanent deformation of sloping ground near the abutments. Ultimately, global response is dictated by the bridge‐ground interaction a...
Article
Pile-supported wharves may be subjected to severe damage during major earthquakes. As such, efficient strategies for retrofitting wharf systems are needed. In this study, we investigate the seismic performance of a pile-supported wharf retrofitted by the following three conventional slope strengthening strategies: i) improving the ground with a soi...
Chapter
Full-text available
This paper presents comparisons of 11 sets of Type-B numerical simulations with the results of a selected set of centrifuge tests conducted in the LEAP-2017 project. Time histories of accelerations, excess pore water pressures, and lateral displacement of the ground surface are compared to the results of nine centrifuge tests. A number of numerical...
Chapter
Full-text available
This paper describes the numerical sensitivity study requested prior to the December 2017 LEAP workshop. Several but not all of the simulation teams participated in this sensitivity study. The results of the sensitivity study are used to begin to map out the simulation response surfaces that relate residual displacement to PGAeff and relative densi...
Chapter
This paper presents numerical simulations (modified Type-B) related to LEAP-UCD-2017 (Liquefaction Experiments and Analysis Projects) dynamic centrifuge model tests for a liquefiable sloping ground conducted by various institutions. The numerical simulations are performed using a pressure-dependent constitutive model implemented with the characteri...
Chapter
Full-text available
This paper presents a summary of the element test simulations (calibration simulations) submitted by 11 numerical simulation (prediction) teams that participated in the LEAP-2017 prediction exercise. A significant number of monotonic and cyclic triaxial (Vasko, An investigation into the behavior of Ottawa sand through monotonic and cyclic shear tes...
Article
Four large laminar-box shaking table experiments are conducted to document pile response due to the mechanism of liquefaction-induced lateral spreading. Single-pile and pile-group configurations are tested in a mildly inclined ground configuration. Two ground profiles of about 5 m in height are investigated, one with a liquefiable saturated sand st...
Article
A helical pile is composed of a steel shaft and single or multiple helical plates welded to its shaft. This study investigated full-scale seismic soil reactions for helical piles embedded in dry sand. Ten helical and driven piles were installed in sand enclosed in a laminar shear box mounted on a large outdoor shake table. The paper discusses inter...
Article
Dynamic measurements are undertaken on a utility scale wind turbine (900 kW rated power, 55 m hub height, and a 53.6 m rotor diameter) located at Oak Creek Energy Systems near Mojave, California, USA. The acceleration response to wind and other ambient sources is recorded by as many as 81 channels at locations along the height of the tower, on the...
Conference Paper
Full-text available
In this study, a 1-g large-scale shake table test was conducted to investigate the dynamic characteristics of a suction bucket foundation system. A scaled model of a suction bucket wind turbine that simulates a prototype 3.45 Megawatt (MW) offshore counterpart was manufactured and installed in a saturated dense sand stratum. A laminar soil containe...
Article
Full-text available
A full-scale pile testing program was implemented using the large outdoor shake table at the University of California – San Diego. Nine steel helical piles with varying geometry were embedded in dense sand and tested individually and in 2×2 groups, comparing fixed and pinned pile head connections. The test piles were subjected to shake motions rang...
Article
Past seismic events have shown that pile-supported wharves are susceptible to severe damage during earthquakes, and thus it is important to assess the seismic performance of pile-supported wharves. Seismic fragility analysis is recognized as an effective means for seismic performance assessment of infrastructural systems exposed to seismic hazards...
Conference Paper
Full-text available
With the increasing demand on wind power, offshore wind turbines are being increasingly installed in sites where seismic loading must be considered, as it may affect the design of the supporting tower as well as the foundation. Suction caisson is a relatively recent foundation system that has been introduced to support a wide variety of offshore st...
Conference Paper
Full-text available
This paper presents a series of large scale liquefaction-induced lateral spreading shake table tests conducted at the University of California, San Diego (UCSD). A total of 7 different experiments are illustrated with varying heights, inclinations, soil profiles, pile material and cross-sections. The available capabilities discussed are part of ove...
Conference Paper
This paper presents a series of large scale liquefaction-induced lateral spreading shake table tests conducted at the University of California, San Diego (UCSD). A total of 7 different experiments are illustrated with varying heights, inclinations, soil profiles, pile material, and cross-sections. The available capabilities discussed are part of ov...
Article
On the basis of a systematic parametric study, three-dimensional (3D) finite-element (FE) simulations were conducted to evaluate mitigation by the stone column (SC) approach. Mildly sloping saturated cohesionless strata (uniform as well as stratified) were investigated under the action of an applied earthquake excitation. For that purpose, the open...
Article
Full-text available
Recent earthquakes have highlighted the need for safe and efficient construction of earthquake-resilient structures. Meanwhile, helical piles are gaining popularity as a foundation not only for new construction, but also retrofitted structures, owing to their advantages over conventional driven pile alternatives. In addition, several structures sup...
Chapter
Full-text available
This paper discusses a range of geotechnical testing capabilities available at the University of California, San Diego (UCSD). The capabilities discussed are part of overall large-scale UCSD laboratories, one of the largest and most active earthquake engineering laboratories worldwide. Specifically, testing using 2 different shake tables is discuss...
Chapter
Full-text available
On-shore wind turbines are typically founded on shallow gravity-based foundations that are designed to transmit vertical and lateral loads. Improved understanding of the foundation, as well as the over-all system behavior will lead to safe and economical designs. In this study, experimental results of a 55 m in-service Gamesa G52/850 wind turbine t...
Chapter
Full-text available
Past earthquakes demonstrate that lateral spreading induced by liquefaction may cause excessive movement, and significant damage to structures and their underlying pile foundation. A 1-g shake-table series of experiments was conducted to investigate the mechanism of liquefaction-induced lateral spreading effects on pile foundations in mildly inclin...
Article
A constitutive soil model that was originally developed to model liquefaction and cyclic mobility has been updated to comply with the established guidelines on the dependence of liquefaction triggering to the number of loading cycles, effective overburden stress (Kσ), and static shear stress (Kα). The model has been improved with new flow rules to...
Conference Paper
Full-text available
Full scale experiments and laboratory tests are used to illustrate the significantly higher strength of compacted sand with silt (SP-SM) backfill, as compared with typical design assumptions. Two testing phases are conducted inside a large soil container on an outdoor shake table in order to investigate: 1) the passive earth pressure force-displace...
Article
Recorded earthquake motions from the extensively instrumented Samoa Channel Bridge provide valuable information on the mechanisms of structural response during seismic excitation. Using this data, system identification techniques are employed to derive salient response characteristics of the bridge system and its foundations. For that purpose, Fini...
Article
Full-text available
This article presents the main results of the validation phase of the PRENOLIN project. PRENOLIN is an international benchmark on 1D nonlinear (NL) site‐response analysis. This project involved 19 teams with 23 different codes tested. It was divided into two phases; with the first phase verifying the numerical solution of these codes on idealized s...
Conference Paper
Helical piles represent an attractive deep foundation system, which can be used to support wind turbines, solar farms, energy pipelines and telecommunication and transmission towers. This paper investigates the performance of full-scale single helical piles installed in sandy soil and subjected to lateral loads similar in characteristics to those i...
Conference Paper
Full-text available
To simulate the dynamic response of geotechnical models and study soil-structure interaction problems with minimum boundary effects, a new lightweight laminar container has been designed and constructed at the University of California San Diego (UCSD). The container consists of individually-mounted aluminum laminates designed to slide independently...
Article
Considerable three-dimensional (3D) effects are involved in the seismic performance of pile-supported wharves. Such effects include the pile-to-pile interaction mechanisms as dictated by the behavior of the surrounding soil. This interaction might be further affected by potential ground slope settlement/heave, and the constraint of pile connectivit...
Article
A large set of earthquake records from the highly instrumented Samoa Channel bridge-ground system has been compiled and made available by the California Geological Survey. During six seismic events, more than 30 data channels have been documenting the seismic response of the bridge, abutments, and adjacent ground surface. Of special interest is the...