Amr Salah Eldin Elnashai

University of Illinois, Urbana-Champaign | UIUC · Department of Civil and Environmental Engineering

Highrise buildings that have structural irregularities are in general more susceptible to damage from earthquakes. Such damage is primarily due to the coupling of torsional and translational vibrational response whereby the building twists even though it is being excited in translational modes only. For optimal earthquake design and retrofit of suc...

Abstract Our built environment is characterized by large, ever‐expanding and highly complex cities. The spatial extent of the interconnected systems that serve these cities leads to higher vulnerability to disruption. On the other hand, climate change and political instability have noticeably increased the frequency of natural and human‐induced haz...

Structural fragility assessment is a fundamental component of modern performance-based earthquake design and assessment processes. Major advances in fragility functions development and implementation have occurred over the past three decades.

This edited volume on challenges in structural and bridge engineering brings together contributions to this important area of engineering research. The volume presents findings and case studies on fundamental and applied aspects of structural engineering, applied to buildings, bridges and infrastructures in general, and heritage patrimony. The scop...

This edited volume on challenges in structural and bridge engineering brings together contributions to this important area of engineering research. The volume presents findings and case studies on fundamental and applied aspects of structural engineering, applied to buildings, bridges and infrastructures in general, and heritage patrimony. The scop...

This edited volume brings together findings and case studies on fundamental and applied aspects of structural engineering, applied to buildings, bridges and infrastructures in general. It focuses on the application of advanced experimental and numerical techniques and new technologies to the built environment. This volume is part of the proceedings...

Accurate, verifiable, and efficient analytical models for interacting soil and structure systems are still very challenging. While geotechnical software usually has limited capacity for structural analysis in the inelastic response range, the converse is true for structural analysis packages. In this paper, a multi-platform analytical approach is d...

This paper presents hybrid simulations of a three-span R/C bridge among EU, US, and Canada. The tests involved partners located on both sides of the Atlantic with each one assigned a numerical or a physical module of the substructured bridge. Despite the network latency in linking remote sites located on the two sides of the Atlantic the interconti...

Plan-irregular structures are generally more vulnerable to earthquake damage due to torsional response, and they usually need more iterative assessments and adjustments in their structural design. However, in the traditional design process, consistency between design and analysis is not always assured; rather, manual efforts are required to keep th...

ZEUS-NL is the analysis and simulation platform of the MAE Center. It is a state-of-the-art 3D static and dynamic analysis platform specifically developed for earthquake engineering applications. Its extreme efficiency, accuracy, verification and user-friendly graphical user interface has made it easier than ever to undertake inelastic large displa...

Earthquakes occur as a cluster in many regions around the world where complex fault systems exist. The repeated shaking usually induces accumulative damage to affected structures. Damage accumulation in structural systems increases their level of degradation in stiffness and also reduces their strength. Many existing analytical tools of modeling RC...

Hybrid simulation has been effectively utilized to assess structural response subjected to intense dynamic loads. The process comprises dividing the structure into experimental and numerical modules. The experimental modules represent the critical components responses, which cannot be idealized reliably through analytical approaches. The responses...

Analytical methods are frequently utilized for structural assessment due to their simplicity and cost-effectiveness. However, modeling of material inelasticity and geometric nonlinearity under reversed inelastic deformations is still very challenging and its accuracy is difficult to quantify. On the other hand, realistic experimental assessment is...

Hybrid simulation has emerged as a potentially-accurate and efficient tool for the evaluation of the response of large and complex structures under earthquake loading. As an application example, hybrid simulation is applied to semi-rigidly connected frames with different connection strength limits. In the sample study three hybrid simulations were...

Field investigations after the recent Tohoku and Christchurch earthquakes reported failure of structural systems due to multiple earthquakes. In most failure cases the reported damage was mainly due to dramatic loss of stiffness and strength of structural elements as a result of material deterioration due to repeated earthquake loading. This study...

This paper investigates the elongation of the fundamental period of reinforced concrete buildings that occurs during earthquake loading and its correlation with various intensity measures and engineering demand parameters. For this purpose, five buildings designed according to modern seismic codes are studied through equivalent single degree of fre...

SUMMARY Civil engineering structures are often subjected to multidirectional actions such as earthquake ground motion, which lead to complex structural responses. The contributions from the latter multidirectional actions to the response are highly coupled, leading to a MIMO system identification problem. Compared with single-input, multiple-output...

This paper presents the challenges encountered in preparing and conducting hybrid experiments between E.U., U.S. and Canada in the framework of an FP7-funded European project focusing on the study of seismic soil-structure interaction effects in bridge structures. The test involved partners located on both sides of the Atlantic; each one assigned a...

Reinforced concrete (RC) bridge piers are subjected to combined loading conditions resulting from complex earthquake ground motions coupled with irregular geometry and asymmetry of the bridge structure. Furthermore, the influence of the assumptions and simplifications made in modeling irregular and curved bridges on the reliability of their resulti...

Hybrid simulation has emerged as a relatively accurate and efficient tool for the evaluation of structural response under earthquake loading. In conventional hybrid simulation the response of a few critical components is obtained by testing while the numerical module is assumed to follow an analytical idealization. Where there is a much larger numb...

System identification of civil engineering structures are often formulated as Multiple-Input, Multiple-Output (MIMO) problems due to the complexity of loading conditions such as differential ground motion, which is also multi-directional in nature. Such MIMO system identification problems are challenging due to strong coupling between the contribut...

Reinforced concrete bridge piers are subjected to complex loading conditions under earthquake ground motions. Bridge geometric irregularities and asymmetries result in combined actions imposed on the piers as a combination of displacements and rotations in all six degrees of freedom at the pier-deck juncture. Existing analytical tools have proven t...

The Pharos of Alexandria is one of the seven wonders of the ancient world which reflects the glory of ancient engineering and construction skills. It remains the tallest stone tower that stayed intact for more than 15 centuries and survived from more than 20 major earthquakes. This paper describes inelastic dynamic simulations of the response and f...

The behavior of semirigid partial-strength connections has been investigated through either experimental component testing or detailed three-dimensional (3D) finite-element (FE) models of beam-column subassemblies. Previous experiments on semirigid partial-strength connections were conducted under idealized loads and boundary conditions, which do n...

Curved bridges are subject to combined loading conditions resulting from complex earthquake ground motions coupled with irregular geometry and asymmetry of the bridge structure. This paper describes a part of the CABER project that compares the experimental results of a curved bridge under multidirectional earthquake loading with its un-calibrated...

Previous analytical, numerical, and experimental studies have been conducted to assess the behavior of semi-rigid partial-strength beam-column subassemblies and the results showed desirable behavior. However, realistic evaluation of semi-rigid steel frames requires a system-level examination to allow for investigating the effect of local behavior o...

Story drifts, connection rotations and story drift-connection rotation relationships of 6 partial strength/semi-rigid and 2 rigid frames having 7.0m and 9.0m span lengths and four different connection capacities are investigated with nonlinear dynamic analyses. In dynamic analyses 25 real ground motion records with 2 different earthquake levels and...

Unreinforced masonry (URM) structures represent a significant portion of the residential building stock of the central and eastern United States. Fifteen percent of homes in the eight-state region impacted by the New Madrid Seismic Zone are URM buildings. The brittle nature of URM buildings further supports a thorough consideration of seismic respo...

It is desirable to use probabilistic performance targets for decision-making as it relates to intervention methods, because of high uncertainties of structure responses under earthquake loadings. This is based on the probabilistic performance assessment of structures with various retrofit options. Extensive computer simulations to account for the r...

Transportation networks are critical civil infrastructures susceptible to natural hazards such as earthquakes. It is essential to understand and model the travel demand in emergency situation when considering measures to secure traffic function immediately after the earthquake and to restore the performance of transportation networks. Post-earthqua...

The accuracy of fragility functions is critical for regional risk and loss estimations. This paper proposes a two-stage approach to generate improved fragility functions for engineering structures using field measurement and experimental data. In the first stage, the linear and nonlinear parameters of the bridge model are calibrated using measured...

The objective of this paper is to develop a tool for the numerical analysis of full-scale ECC structures. For this purpose, a macroscopic cyclic constitutive model for engineered cementitious composite (ECC) materials is developed based on the response of the material at the stress–strain level under different loading regimes. Various features spec...

This paper presents an experimental study on the performance of a full-scale unreinforced brick masonry (URM) building system tested under quasi-static loading at the Earthquake Engineering Centre, University of Engineering and Technology in Peshawar, Pakistan. The configuration and materials used in the single-story URM building are typical of tho...

The Maule (Chile) earthquake of 27 February, 2010 has caused severe disruption and economic losses. With a magnitude of 8.8, it has been recorded as one of the largest earthquakes of the last century. The ground motion records from large subduction earthquakes, such as the Chile earthquake, are sparse. The number of accelerograms that recorded the...

The behavior of bolted beam-to-column connections in steel and composite frames has a significant effect on their structural response to strong ground motion. Their hysteretic response exhibits highly inelastic characteristics and continuous variation in stiffness, strength and ductility, hence they influence both supply and demand. Therefore, accura...

Substructure hybrid simulation of engineering structures subjected to multiple-support excitation (MSE) is investigated. In time history analysis of MSE problems, the equations of motion are generally posed in relative coordinates (designated EOM-rel), which only require the ground acceleration as an input. However, the suitability of EOM-rel for h...

An online optimization method was proposed in this paper to improve the accuracy of numerical–experimental hybrid simulations of bridges subjected to earthquake forces. The online optimization method aims to solve the problem induced by the inconsistency of the multiple identical bridge piers where only one or a few of them are simulated experiment...

The paper presents an integrated and extensible framework for assessment of the impact of earthquakes on civil infrastructure systems, particularly buildings and bridges. The framework, referred to as NEES Integrated Seismic Risk Assessment Framework (NISRAF), is developed with a focus on improving the reliability of earthquake assessment results....

The bridge network, as part of the critical civil infrastructure, is susceptible to natural and man-made hazards. It is essential that the network retains its traffic-carrying capacity after a disastrous earthquake to ensure efficient evacuation of at-risk population to safe zones and timely dispatch of emergency response resources to the impacted...

The present work assesses the seismic response of reinforced concrete (RC) members subjected to horizontal (HGMs) and vertical (VGMs) ground motions recorded during the 2009 L’Aquila (Italy) earthquake. Normalized axial loads in beam-columns as well as the peak ground acceleration ratios between horizontal and vertical ground accelerations are emph...

Despite the recognition of the need for broad-based integrative education that prepares students for addressing complex problems in the real world, multi-disciplinary course offerings remain rare. The paper describes the development and offering of a multi-disciplinary graduate course covering earthquake loss assessment and mitigation ‘from source...

The Retrofit Yield Spectrum (RYS) is a new spectrum-based device that relates seismic demand of a retrofitted structure with the fundamental design parameters of the retrofit. This is obtained from superposition of Yield Point Spectra with design charts that summarize in pertinent spectrum-compatible coordinates the attributes of a number of altern...

Engineered cementitious composites (ECC) are a fiber-reinforced highperformance material developed as a replacement for conventional concrete. ECC is characterized by high damage tolerance, shear resistance and energy absorption. This paper provides detailed information regarding the hybrid tests performed as a part of a broader experimental progra...

A methodology is developed in this paper for the design and proportioning of interventions for seismic upgrading of substandard reinforced-concrete (RC) buildings. The retrofit approach is presented in the form of a simple design tool that aims toward both demand re-duction and enhancement of force and deformation supply through controlled modifica...

The seismic performance of low-rise frames with energy dissipative semirigid connections is evaluated under far and near field artificial ground motion records. Four different connection capacities are employed in the frames and are characterized by two different moment-hardening ratios and two different hysteresis models. Nonlinear time-history an...

Fragility analyses are conducted in this study to evaluate the relative seismic safety margins of seismic code-designed multi-story reinforced concrete (RC) buildings with varying input motion intensity, ductility level and configuration. Structural variations are accounted for by using twelve buildings [13] with diverse structural systems, heights...

The objective of the research presented in this paper is to investigate, experimentally, the effect of material- and section-level parameters on the structural response of concrete and engineered cementitious composite (ECC) buildings. In addition to testing of columns under monotonic, cyclic, and static-time history loading, hybrid simulation of s...

The life-cycle cost (LCC) of a structure in seismic regions, which includes the initial and the post-earthquake repair cost, is a critical parameter for structural engineers and other stakeholders. The LCC analysis has been gaining prominence in recent years since civil infrastructure sustainability has been identified as one of the grand challenge...

In the early 1800s Central USA has experienced some of the strongest earthquake ground motions observed nationwide. A recurrence of these earthquakes would cause significant social and economic impacts affecting the lives of millions of residents. For instance, it is estimated that more than 60,000 families will need temporary housing assistance in...

In the absence of comprehensive and statistically viable observational damage data, there is a pressing need for simulation-based fragility relationships for populations of structures so as to improve the reliability of earthquake loss assessment studies. In this report, improved fragility relationships for populations of buildings are developed ba...

This paper presents an experimental program aimed at assessing the effect of vertical earthquake ground motion on reinforced concrete bridge piers. The program comprised testing of four large scale piers by utilizing the Multi-Axial Full-Scale Sub-Structured Testing and Simulation (MUST-SIM) facility at the University of Illinois. Two hybrid analyt...

In the aftermath of recent earthquakes there has been substantial field evidence demonstrating that the collapse of several existing structures was caused by the effects of the vertical component of seismic ground motions. Such field evidence has not yet been supported by comprehensive analytical assessment and experimental tests. The present work...

This paper investigates the implications of ground motion spatial variability on the seismic response of an extended highway bridge. An existing 59-span, 2,164-meter bridge with several bearing types and irregularity features was selected as a reference structure. The bridge is located in the New Madrid Seismic Zone and supported on thick layers of...

This paper presents the shake table test of a one-forth scaled model, representing a typical Pakistani three stories confined brick masonry building. The model was constructed following complete model similitude and subjected to a series of sinusoidal base motions of increasing amplitude at a constant frequency equivalent to the predominant frequen...

This paper presents an overview of the damage from the 2010 Chile Earthquake observed by a field reconnaissance team from the Mid-America Earthquake Center. Seismic performances of structures in Santiago, Biobío, and Maule regions in Chile are summarized based on field observations and discussions with researchers and city officials. In addition, p...

Moment-resisting steel frames are used frequently in low-rise and mid-rise buildings located in high seismic areas due to their high ductility and economic solutions. In these type of structures, strong-column weak-beam design requirements result in larger column sections and overdesign in low-rise long-span buildings. To mitigate this problem, mom...

This paper presents the shake table test of a one-forth scaled model, representing a typical Pakistani three stories confined brick masonry building. The model was constructed following complete model similitude and subjected to a series of sinusoidal base motions of increasing amplitude at a constant frequency equivalent to the predominant frequen...

This paper presents the seismic performance of a one-forth scaled model, representing a typical Pakistani three storey confined brick masonry buildings. The structure was evaluated by shake-table testing. This test program is a part of the ongoing research project on seismic impact assessment of Abbottabad city in Northern Pakistan which was affect...

A comprehensive study carried out to assess the seismic response of a 59-span bridge using a refined inelastic modeling approach and considering Soil–Structure Interaction (SSI) is summarized in this paper. The focus is on describing the methodology adopted to idealize the bridge and its foundation system, while only highlights from the extensive e...

Mathematics-based computational mechanics involves idealization in going from the observed behaviour of a system into mathematical equations representing the underlying mechanics of that behaviour. Idealization may lead mathematical models that exclude certain aspects of the complex behaviour that may be significant. An alternative approach is data...

The large-scale and catastrophic impacts of Hurricanes Katrina and Rita in 2005 challenged the efficacy of traditional postdisaster temporary housing methods. To address these challenges, the U.S. Congress appropriated $400 million to the Department of Homeland Security to support alternative housing pilot programs, which encourage innovative housin...

This article presents a novel approach for deriving Retrofit Design Spectra (RDS) that are intended for use in preliminary development and assessment of seismic upgrading scenarios of existing structures. The new spectral representation relates the characteristics of the intervention method chosen as the core of the upgrading strategy, with the duc...

In the aftermath of large-scale natural disasters, emergency management organizations are expected to provide safe temporary housing for a large number of displaced families and to ensure that these housing arrangements are not located in hazardous areas. Potential postdisaster hazards can take many forms such as earthquake aftershocks, landslides,...

Earthquake loss estimation procedures exhibit aleatory and epistemic uncertainty imbedded in their various components; i.e. seismic hazard, structural fragility, and inventory data. Since these uncertainties significantly affect decision-making, they have to be considered in loss estimation to inform decision- and policymakers and to ensure a balan...

In the aftermath of catastrophic natural disasters such as hurricanes, tsunamis and earthquakes, emergency management agencies come under intense pressure to provide temporary housing to address the large-scale displacement of the vulnerable population. Temporary housing is essential to enable displaced families to reestablish their normal daily ac...

The behavior of beam-to-column connections in steel and composite frames strongly influences their stability and strength. This is particularly true in response to sever dynamic actions, where the changes in stiffness and damping influence both supply and demand. This means that it is necessary to accurately model the stiffness, strength and ductil...