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Objective: Coronavirus disease 2019 (COVID-19) is a new disease entity that appeared in late 2019. In this study, we aimed to determine the prevalence of loss of smell and/or taste among patients who tested positive for COVID-19 and identify demographic and clinical differences between patients with and without anosmia/dysgeusia. Methods: The study was performed in a referral center for COVID-19 in Istanbul, Turkey between the months of April and July 2020. The responses from a set of questions in regard to loss of sense of smell and/or taste were collected. None of these patients were exposed to any further examination or testing related to their senses of smell and/or taste. The data in regard to the patients being tested as well as their demographic information and co-morbidities associated with their condition were collected. Results: Twenty patients (10 male, 10 females, mean age 43.3 years) out of 86 patients (49 male, 37 female, median age 49.5 years), who tested positive for COVID-19, declared a loss of smell and/or taste. Nineteen patients (19/20, 95%) had a full recovery, and one (1/20, 5%) had partial recovery at the end of two weeks. Conclusion: Our results indicate that 23.3% of patients who tested positive with reverse transcription-polymerase chain reaction testing for COVID-19 had loss of sense of smell to a certain extent.

Urban infrastructures, to fully take advantage of future investments, must first be recognized as interconnected complex systems of systems. This forum paper describes research and education needs ...

In this paper, we report on the acceleration of protons and oxygen ions from tens of micrometer large water droplets by a high-intensity laser in the range of 1020 W/cm2. Proton energies of up to 6 MeV were obtained from a hybrid acceleration regime between classical Coulomb explosion and shocks. Besides the known thermal energy spectrum, a collective acceleration of oxygen ions of different charge states is observed. 3D PIC simulations and analytical models are employed to support the experiential findings and reveal the potential for further applications and studies.

The use of wireless sensors for bridge assessment has been investigated extensively in the past decades. However, in most field applications, current sensors and sensing systems still rely on wired connectivity for communication and power. This is the case even though tethered sensors require extensive cabling throughout a structure resulting in long installation processes, and their maintenance may increase the total cost of Structural Health Monitoring systems and impede their broader use, especially when rapid infrastructure assessment is needed. One possible explanation of this slow adoption of wireless sensors is the use of sensing units that have not been tested for decades as their wired counterparts. This paper presents a suite of wireless sensors that were developed through the transformation of established wired sensors into wireless units. The objective was to explore whether it was possible to transform such wired sensors into wireless units and then confirm successful transformation with laboratory and field applications. The sensors presented here focus on accurate measurements of displacement, strain, and acceleration with units that are rugged, have a long service life and are used primarily for rapid structural assessment. With this transformation, the authors wanted to accomplish the goal of rapid installation and sensing reuse, and achieve accurate wireless measurements guaranteed by the wired sensors of established sensing vendors. In this study, the wireless sensors were tested first in laboratory conditions along with wired sensors for comparison and then were successfully tested in the field.

The development, characterization and implementation of a water (H 2 O) droplet source for laser–plasma interactions at high-repetition rates are reported. The system is capable of generating a continuous stream of water droplets for several hours and was tested to operate continuously as a target source. Based on glass capillaries, a detailed parameter scan on the automated pulling process is presented, allowing a fine-tuning of the shape of the capillaries and therefore the diameter of the droplets.

Engineered targets are expected to play a key role in future high-power laser experiments calling for joined, extensive knowledge in materials properties, engineering techniques and plasma physics. In this work, we propose a novel patterning procedure of self-supported 10 μm thick Au and Cu foils for obtaining micrometre-sized periodic gratings as targets for high-power laser applications. Accessible techniques were considered, by using cold rolling, electron-beam lithography and the Ar-ion milling process. The developed patterning procedure allows efficient control of the grating and foil surface on large area. Targets consisting of patterned regions of 450 μm × 450 μm, with 2 μm periodic gratings, were prepared on 25 mm × 25 mm Au and Cu free-standing foils, and preliminary investigations of the micro-targets interacting with an ultrashort, relativistic laser pulse were performed. These test experiments demonstrated that, in certain conditions, the micro-gratings show enhanced laser energy absorption and higher efficiency in accelerating charge particle beams compared with planar thin foils of similar thickness.

We study the laser-driven acceleration of electrons from overdense hydrogen clusters to energies of up to 13 MeV in laser forward direction and several hundreds of keV in an outer ring-structure. The use of cryogenic hydrogen allows for high repetition-rate operation and examination of the influence of source parameters like temperature and gas flow. The outer ring-structure of accelerated electrons, originating from the interaction, that is robust against the change of laser and target parameters can be observed for low electron densities of ca 3 × 1016 cm−3. For higher electron densities, an additional central spot of electrons in the laser forward direction can be observed. Utilizing 3D particle-in-cell simulations, it is revealed that both electron populations mainly stem from ponderomotive scattering.

A methodology and its associated tools for the objective condition assessment and reliability evaluation of bridges are discussed. Integrated analytical-experimental research, conducted to explore the serviceability and damageability behavior, is summarized. An effective research and development strategy is described, comprising field and laboratory applications, designed with a structural identification approach.

We present a study on laser-driven proton acceleration from a hydrogen cluster target. Aiming for the optimisation of the proton source, we performed a detailed parametric scan of the interaction conditions by varying different laser and the target parameters. While the underlying process of a Coulomb-explosion delivers moderate energies, in the range of 100 s of keV, the use of hydrogen as target material comes with the benefit of a debris-free, single-species proton acceleration scheme, enabling high repetition-rate experiments, which are very robust against shot-to-shot fluctuations.

We report on a detailed experimental and numerical study on the boosted acceleration of protons from ultra-thin hemispherical targets utilizing multi-Joule short-pulse laser-systems. For a laser intensity of 1 × 1020 W/cm2 and an on-target energy of only 1.3 J with this setup a proton cut-off energy of 8.5 MeV was achieved, which is a factor of 1.8 higher compared to a flat foil target of the same thickness. While a boost of the acceleration process by additionally injected electrons was observed for sophisticated targets at high-energy laser-systems before, our studies reveal that the process can be utilized over at least two orders of magnitude in intensity and is therefore suitable for a large number of nowadays existing laser-systems. We retrieved a cut-off energy of about 6.5 MeV of proton energy per Joule of incident laser energy, which is a noticeable enhancement with respect to previous results employing this mechanism. The approach presented here has the advantage of using structure-wise simple targets and being sustainable for numerous applications and high repetition rate demands at the same time.

An investigation of the electromagnetic (EM) pulse produced by high intensity laser-solid interactions has been carried out by employing the proton probing technique. Laser parameters including energy, pulse duration, and intensity were varied to investigate the influence on the EM pulse amplitude. The data reveal that the amplitude of the EM pulse depends on the incident laser energy and the pulse duration. The optimum pulse length for a given laser energy is found to be close to 100 fs. The net charge associated with the traveling EM pulse has been found to be dependent on the laser intensity, in a good agreement with a semiempirical model. The understanding of the EM pulse is important for the postacceleration of laser driven proton beams.An investigation of the electromagnetic (EM) pulse produced by high intensity laser-solid interactions has been carried out by employing the proton probing technique. Laser parameters including energy, pulse duration, and intensity were varied to investigate the influence on the EM pulse amplitude. The data reveal that the amplitude of the EM pulse depends on the incident laser energy and the pulse duration. The optimum pulse length for a given laser energy is found to be close to 100 fs. The net charge associated with the traveling EM pulse has been found to be dependent on the laser intensity, in a good agreement with a semiempirical model. The understanding of the EM pulse is important for the postacceleration of laser driven proton beams.

With the latest configuration, the Ti:Sa laser system ARCTURUS (Düsseldorf University, Germany) operates with a double-chirped pulse amplification (CPA) architecture delivering pulses with an energy of 7 J before compression in each of the two high-power beams. By the implementation of a plasma mirror system, the intrinsic laser contrast is enhanced up to $10^{-12}$ on a time scale of hundreds of picoseconds, before the main peak. The laser system has been used in various configurations for advanced experiments and different studies have been carried out employing the high-power laser beams as a single, high-intensity interaction beam ( $I\approx 10^{20}~\text{W}/\text{cm}^{2}$ ), in dual- and multi-beam configurations or in a pump–probe arrangement.

The primary objective of this discussion is to argue that the need for innovation in civil engineering practice is becoming more critical, especially as the goals and expectations associated with infrastructure performance expand to include Livability, Sustainability, and Resilience (LSR). Current approaches to assess and characterize constructed infrastructures rely primarily on visual inspection procedures, which largely serve to guard against blatant safety problems. These efforts generally include a thorough documentation of visual appearance guided by heuristics. Unfortunately, the relationship between key limit states (e.g. structural safety, serviceability, functionality, etc.) and visual condition is nebulous and thus decision-makers are often forced to rely on conservatism at the expense of accuracy. Further, documenting visual distresses do not always lend to understanding the root causes. As a result, visual assessment procedures make organizations struggle to design proper and effective maintenance and make prudent asset management decisions. In general completely visual infrastructure evaluation may lead to incomplete diagnoses followed by ineffective prognoses, often leading to highly consequential disruptions impacting LSR. To illustrate this argument further the paper draws upon the authors’ experiences evaluating bridges over the last several decades. More specifically, this paper aims to present an overview of the current highway bridge engineering and management practices in the US and to postulate how technologies may be incorporated to achieve LSR goals. Wherever possible, the authors have tried to present this discussion in sufficiently general terms as many aspects of it may equally apply to other infrastructure nodes and sectors as well.

A high-repetition rate laser-driven proton source from a continuously operating cryogenic hydrogen cluster target is presented. We demonstrate a debris-free, Coulomb-explosion based acceleration in the 10s of kilo-electron-volt range with a stability of about 10% in a 5 Hz operation. This acceleration mechanism, delivering short pulse proton bursts, represents an ideal acceleration scheme for various applications, for example, in materials science or as an injector source in conventional accelerators. Furthermore, the proton energy can be tuned by varying the laser and/or cluster parameters. 3D numerical particle-in-cell simulations and an analytical model support the experimental results and reveal great potential for further studies, scaling up the proton energies, which can be realized with a simple modification of the target.A high-repetition rate laser-driven proton source from a continuously operating cryogenic hydrogen cluster target is presented. We demonstrate a debris-free, Coulomb-explosion based acceleration in the 10s of kilo-electron-volt range with a stability of about 10% in a 5 Hz operation. This acceleration mechanism, delivering short pulse proton bursts, represents an ideal acceleration scheme for various applications, for example, in materials science or as an injector source in conventional accelerators. Furthermore, the proton energy can be tuned by varying the laser and/or cluster parameters. 3D numerical particle-in-cell simulations and an analytical model support the experimental results and reveal great potential for further studies, scaling up the proton energies, which can be realized with a simple modification of the target.

The design and operation of an online energy and spatially resolving detector based on three different scintillators for laser-driven protons are described. The device can be used for a multi-Hertz recording rate. The spatial resolution is

A continuous cryogenic hydrogen cluster-jet target has been developed for laser-plasma interaction studies, in particular as a source for the acceleration of protons. Major advantages of the cluster-jet target are the compatibility with pulsed high repetition lasers and the absence of debris. The cluster-jet target was characterized using the Mie-scattering technique allowing to determine the cluster size and to compare it with an empirical prediction. In addition, an estimation of the cluster beam density was performed. The system was implemented at the high power laser system ARCTURUS and first successful measurements show the acceleration of protons after irradiation by high intensity laser pulses with a repetition rate of five Hertz., Comment: 9 pages, 7 figures

Civil engineeringmaster builders havebeen constructingmasterpieces for millennia, long before the recent advent of systems engineering. However, since the 1950s, the planning, financing, design, construction, operation, and maintenance of civil engineered constructed systems, e.g., buildings, bridges, airports, plants, tunnels, dams, antenna towers, storage tanks, power transmission towers, highways, railroads, and pipelines, became the elements of highly complex, intertwined, and interdependent systems in dense urban areas. Such highly complex and multidomain systems, termed infrastructures, include government, education, healthcare, transportation, water, communication, and energy [U.S. Department of Homeland Security (DHS) 2010]. As urban populations grew, demands for infrastructure services increased. Meanwhile, the engineered elements of infrastructures aged and deteriorated, and their operational and structural capacity started to fall short of the demands. Their fragility was recognized as the failure of one infrastructure element that precipitated cascading consequential failures of additional elements from different infrastructures. Failures of critical infrastructure because of natural or manufactured hazards reiterate this connectivity. For example, on January 2, 1998, “a century-oldwatermain ruptured under lower FifthAvenue in New York City, creating a car-swallowing, curb-to-curb sinkhole andwatery chaos in a bustling neighborhoodwhose streets resembled Venice for a few hours. Then, as the rivers receded, a gas main broke and the crater spewed forth a tower of orange flames. No one was injured . . . but water damaged scores of lobbies, storefronts, and basements for blocks around, 40 residents were evacuated, hundreds of offices and businesses were closed, subways were halted, traffic was rerouted, and gas, water, electric, steam heat, and telephone services were disrupted for many” (McFadden 1998). Three infamous 21st century examples further demonstrate the unexpected cascading consequences of infrastructure failure: • In the case of the World Trade Center collapse on September 11, 2001, while airplane impact was a design consideration for the Towers, the consequential explosion and fire associated with an airplane impact were neglected in the design. Catastrophic and disproportionate collapse of the Towers because of fire in the upper floorswas completely unexpected. TheNIST investigation (NIST 2005) into the collapses led to new code provisions. • In the city of New Orleans on August 31, 2005, the storm surge because of Hurricane Katrina caused more than 50 breaches in drainage canal levees and navigational canal levees and precipitated the worst engineering disaster in the history of the United States. Such an event had been expected, but neither the consequences nor the preparation needed for effective emergency response were properly estimated (ASCE 2007). • An hour after the March 11, 2011 Tohoku earthquake off the coast of Japan, the tsunami wave breached the protective walls at the Fukushima Nuclear Power Plant and destroyed backup diesel power systems, leading to partial meltdowns at several reactors. The diesel generators were situated in a low spot on the assumption that the tsunami walls were high enough to protect against any likely tsunami. Subsequently, ancient stone markers indicating higher tsunami events were reported (Associated Press 2011).

Structural identification (St-Id) of long-span bridges by ambient vibration testing provides a starting point for quantitatively characterizing the actual in-service mechanical characteristics and behaviors of these complex constructed systems. However, various uncertainties involved in the experimental and identification processes impact the reliability of St-Id, especially if vibration testing is the sole experiment. Such uncertainties represent perhaps the most fundamental barrier to more widespread applications of measurements in civil engineering practice. The goal of this paper is to leverage a vibration test of a long-span suspension bridge to illustrate a number of possible strategies for coping with the uncertainties confronted when identifying the dynamic characteristics of large-scale constructed systems. The design and implementation of a field test in the context of St-Id are first presented to illustrate how uncertainties can be mitigated by following a disciplined approach to designing the experiment. Next, data preprocessing strategies including data inspection, time window selection, band-pass filtering, averaging, and windowing are proposed to reduce data errors. Three separate postprocessing methods, including Peak Picking, PolyMAX, and Complex Mode Indicator Function, are executed independently to verify the reliability of the data processing results. Experimental results for both the towers and suspended spans are correlated with simulations from three-dimensional finite-element analysis of the long-span bridge for St-Id.

The objective of this paper is to discuss the limitations in structural identification of large constructed structures. These limitations arise due to the geometric complexity, uncertain boundary and continuity conditions, loading environment, and the imperfect knowledge and errors in modeling such large constructed facilities. In this paper, the writers present their studies on developing a mixed microscopic-structural element level three-dimensional finite-element (FE) modeling of a long-span bridge structure and its structural system identification by integrating various experimental techniques. It is shown that a reasonable level of confidence (50–90%) can be achieved with a model that is calibrated using global and local structural monitoring data with a sufficiently high spatial resolution. The reliability of the global attributes, such as boundary and continuity conditions that may be identified and simulated by means of field-calibrated models using only dynamic test results (globally calibrated m...

The primary goal of this paper is to discuss the state-of-the-art related to the structural identification (St-ID) of constructed systems, and to point out the most pressing needs for research and applications. As a subset of the system identification concept, St-ID aims to develop representative mathematical models of manufactured (mechanical) and constructed (civil) structural systems through the correlation of experimentally measured inputs and outputs. While the concept of St-ID has matured over the past three decades and it is widely and reliably applied to manufactured systems, St-ID for constructed systems remains in its infancy and has enjoyed only sparse implementation in practice, and generally only for signature structures. The authors believe that this delayed progress is principally the result of a lack of appreciation for the inherent distinctions between constructed systems and their manufactured counterparts. Through this paper the authors hope to clearly convey the unique challenges associated with the St-ID of constructed systems and motivate researchers from engineering mechanics to join in the investigation of these issues and to ultimately aid in advancing the art of St-ID of constructed systems.

The most critical issues that have been identified as being needed to implement meaningful and beneficial applications of health monitoring for infrastructure management are discussed. Issues related to infrastructure health monitoring for management can be defined in three overlapping categories. In this context, engineering tools, methods, and knowledge should be developed and utilized to answer societal and educational aspects of the problem while taking advantage of the information tools and methodologies available today. The need for integrated research, education, and practice for infrastructure management is emphasized. The challenges in the integration of intelligent transportation and structural systems concepts within an optimum integrated asset management framework are described and illustrated. Examples from ongoing research on the health monitoring of short-span bridge families and long-span bridges are presented to illustrate the issues.

An ongoing research project involving structural identification of the Commodore Barry Bridge, a major long-span truss bridge over the Delaware River, is described. Structural identification is an approach in which a constructed facility and its loading environment are objectively characterized by field observations, measurements, and controlled experiments in conjunction with an analytical model. This process is a necessary precursor to performing health monitoring of the bridge. Long-span bridges have attributes that make utilization of experimental and analytical techniques on them quite different than for short-span bridges. The concept of structural identification and the methods used in applying it to a long-span bridge are presented and discussed. The structural characteristics of the bridge are described and conceptualized. Development of the three-dimensional analytical model and the model characteristics are summarized. Static and dynamic analyses are conducted to help locate anomalies and errors in the model. The experimental techniques necessary for structural identification of a long-span bridge are defined. A limited-scale health-monitoring system, which integrates operational data with structural performance and loading environment data, was designed and installed on the bridge. Mechanical and electrical characteristics of the monitor system and issues related to management of the data from this system are discussed. The monitoring system currently has over 80 channels of different sensor types collecting various data from the bridge. In addition, data from the system can be viewed from a remote location in real time.

A decommissioned, 40+-year-old reinforced concrete deck on a steel girder bridge was subjected to a series of induced damages, nondestructive field tests, and visual evaluations to compare objective and subjective methods of bridge-condition assessment. Prior subjective evaluations of bridge condition often produced highly variable results. For example, inspectors with different backgrounds and field experience disagreed on how severely certain forms of deterioration and damage influenced bridge behavior and safety so, consequently, different assessments of bridge condition were generated. Furthermore, a load rating of the “as-is” state of the bridge (e.g., the state before any induced damages), according to current Ohio Department of Transportation procedures, indicated that the bridge could only support truckloads of 227 804 N (51,192 lbf). However, the objective data acquired during nondestructive field testing of the bridge, which was subjected to truckloads of 282 130 N (63,400 lbf), revealed maximum superstructure deflections and live-load stresses of 0.190 cm (0.075 in.) and 15 985 kPa (2,320 psi)—values well within AASHTO limits. These values also imply that the bridge can support loads much greater than those indicated in the load rating. Comparing subjective and objective assessments for the induced damage scenarios yielded similar results. Essentially, data revealed that subjective methods of bridge evaluation and assessment were unable to properly characterize intrinsic bridge mechanisms and the influence that such mechanisms have on bridge behavior. Condition assessment of a typical reinforced concrete deck on a steel girder bridge should therefore include objective evaluations of bridge condition and behavior.

A 371-ton (816.7-kip) cooling unit crossed over three steel stringer bridges in Toledo, Ohio. Any bridge damage was compensated if scientifically documented. Researchers predicted the superload responses by using finite element analysis and experimental test results, and then measured the superload responses to establish whether the event caused any damage. Although the conservative results of the finite element model predicted an overbound of critical stresses, experimental results gave closer predictions of the measured response under superload. During the superload crossing, the maximum stress levels at the girders remained at about 34.5 MPa (5 ksi). The cross braces were stressed up to 68.9 MPa (10 ksi), exceeding the girder stresses. The study included questions about the real behavior versus design assumptions regarding cross braces in steel stringer bridges. (Cross braces are the weak links that fail first, causing lateral instability and failure.) Research revealed the possibility of predicting superload responses and behavior quite reliably by using a combination of diagnostic tests and finite element analysis. These tools permit the best design for superload axle configuration, crossing paths and positions on bridges, and possible options for effective bridge strengthening when needed.

The US Federal Reserve Board has concluded that the failure of civil infrastructure systems to perform at their expected level may reduce the national gross domestic product (GDP) by as much as 1%. Intelligent-infrastructure systems and components hold promise for improving performance with an excellent cost/benefit ratio. A recent National Science Foundation (NSF) workshop demonstrated the state of the art in research and applications on intelligent materials and structures in Japan and the US. Major investments have been made by the leading Japanese construction companies into developments for enabling intelligent-structure applications for mitigating earthquake and wind damage. A number of innovative concepts and ideas have been developed by American researchers; however, a lack of applications has also become apparent. This paper reports on the research of a multidisciplinary team working at the University of Cincinnati Infrastructure Institute to conceptualize a wide spectrum of issues in infrastructure condition assessment, health monitoring and intelligent systems by conducting exploratory research on actual operating highway bridges. The writers have made much progress towards developing an intelligent-bridge application. Such an application requires advances in sensors, communication and information technology, global non-destructive evaluation technologies of a rigorous and objective nature and fundamental knowledge on state parameters, loading environments, damage and deterioration mechanisms and performance of actual highway bridges. The writers initiated a strong university-government-industry partnership a decade ago and have explored a global condition assessment methodology based on the structural identification concept. After a decade, they have reached an in-depth realization of the complex multisystem identification and integration which must accompany any `intelligent' systems approach to the infrastructure problem. The writers are currently maintaining three `typical' steel-stringer highway bridge overpasses as generic test-sites for intelligent structures, condition assessment and health monitoring. One of these bridges, which is forty years old, has been decommissioned. This specimen is being tested to understand damage limit-state behavior. Another ten year old specimen has been tested and monitored for five years to understand operating loading environment and behavior at service limit-states. The third bridge is being monitored during its construction to understand the causes and magnitudes of intrinsic forces. After commissioning, this bridge will have a built-in monitor with 300 embedded/attached sensors, a weigh-in-motion scale and sufficient on-site hardware and software to create an intelligent-bridge prototype. By taking advantage of the linkages provided by research at all three test-sites, it has been possible to understand the complete life-cycle spectrum of loading effects and behavior of the medium length steel-stringer bridge type.

A full-scale, active, structural vibration-control system was successfully implemented and tested on an 80-m (250 ft) span, steel-truss highway bridge. More than 90% reduction in global mode response was achieved during testing using random, sinusoidal, and step-release disturbance excitations. Control performance was maintained in the presence of large changes in the dynamic characteristics of the structure due to environmental effects. This study demonstrated the feasibility and reliability of a new approach to active structural vibration-control–adaptive modal filter (AMF) based independent modal space control (IMSC). This work identified and explored many of the practical problems that must be addressed for commercial control installations on civil facilities to be viable.

Present inability to manage large amounts of data properly is a big barrier for a widespread deployment of structural health monitoring, especially when multiparameter data is involved and combined with camera images. Various sensors can measure strain, tilt, temperature, and weather, while live cameras can visualize traffic, and all the data can be registered both statically and dynamically. In order to combine the complex monitored data and make it available for multiple users, which can be the owner/manager of the bridge, researchers, practitioners, or students, a website portal with live data streaming can be a good solution. Historic data can then be consulted using another, “Playback” software package. Both Live Portal and Playback should have embedded algorithms for data visualization, statistical data analysis and reporting. This new solution for data visualization and accessibility, which combines internet omnipresence, computer science, and structural engineering, has been researched, developed and applied on the Tacony-Palmyra Bridge between Pennsylvania and New Jersey and presented in this paper.

The effects of different approaches to rating reinforced concrete slab bridges are explored by using an existing bridge as an example. Nonlinear finite‐element analysis (NLFEA) has been conducted on a field‐calibrated model of the bridge to obtain the ultimate capacity, which is compared with the rating factors obtained from American Association of State Highway and Transportation Officials (AASHTO) guidelines. The demand used to obtain the rating factor depends on how the structure is idealized in the analysis. The capacity can be interpreted at either the local level (material strength or cross‐sectional strength) or at the global level (failure of the structure due to attainment of a collapse mechanism or due to regional shear failure). It is observed that different approaches yield significantly different rating factors and the reasons for the noted differences are discussed.

A bridge-condition assessment method for evaluating the global state of health is formulated based on modal flexibility directly obtained by processing modal test data, complemented by structural identification. The method is proven and the experimental and analytical tools that have been developed for implementation are demonstrated on a three-span reinforced-concrete high-way bridge.

A destructive test was conducted on a decommissioned skew RC slab bridge. This bridge had severely deteriorated shoulder regions, where the top mat reinforcing bars were exposed. The test bridge was loaded using hydraulic cylinders arranged so as to simulate an HS‐20‐44 truck entering the bridge in one lane. The results indicate that the boundary conditions and the geometry of the bridge significantly influence bridge behavior. During the test, changes in the boundary conditions and yielding of the reinforcing bars caused the load path to shift twice. Failure of the slab occurred due to punching shear at a load of 3,200 kN (720 kips), equivalent to the axle load of 22 HS‐20‐44 trucks. Although the deterioration did not appear to affect flexural behavior, it did greatly reduce the punching‐shear capacity. Analysis indicates that simple modeling methods, such as strip models, overestimate structural demand and underestimate structural supply because they do not properly account for additional load‐carrying ...

The objective of this paper is to discuss some relevant aspects of how experimental data (through the process of structural identification (St-Id)) may be used to make rational decisions regarding infrastructure systems. The discussion presented is part of the recently completed state-of-the-art report on St-Id assembled by the ASCE SEI Structural Identification of Constructed Systems Committee.

Modal testing by impact is a practical tool for structural identification, integrity monitoring, and diagnostics of bridges. Typically, nonlinearities in bridge response as well as sensitivity to ambient conditions are observed during modal tests. Therefore, impact tests should be planned and executed so that the effects of nonlinearities are incorporated in estimating modal parameters of a test structure. Furthermore, indexes more reliable than the modal parameters are needed to diagnose local and/or obscure damage. These and other shortcomings in current modal test‐based diagnostic studies are reviewed. A multireference impact testing of a bridge, in which frequency‐response functions (FRF) are measured and a large number of modal parameters are reliably identified, is presented. The mode shape coefficients obtained through processing measured FRF are directly transformed into flexibility of the test bridge without assuming mass. Analytical studies of a calibrated analytical model are presented to demon...

There is a lack of established guidelines for the seismic design of reinforced concrete (RC) walls with nonplanar shapes such as L and T. Inelastic responses of such walls may be governed by biaxial flexure irrespective of the building geometry. A related problem is evaluating the seismic vulnerability of irregular frame-wall construction. Walls may be subjected to bilateral postyield deformations in such buildings. The paper introduces a microcomputer program to practically study 3-D characteristics of RC wall response by utilizing hypoelastic fiber modeling. The program is first verified by correlating simulated and reported experimental responses of RC columns subjected to biaxial flexure. Subsequently, a sensitivity study considering three analytical test specimens of different shapes and flexural reinforcement amount is carried out. Major direction response of barbell walls is not influenced by bilateral displacements unless the displacement along the weak direction is significantly larger than displacement along the strong direction. However, response characteristics of an L-shaped wall may change significantly along different directions of a bilateral displacement path. The effective flexural reinforcement of such walls as they respond along certain bilateral displacement paths may lead to undesirable failure characteristics.

A general constructed facility identification methodology that permits synthesis of localized flexibility coefficients is presented. An application of it to a region of an in-situ concrete bridge is also described. Rigorous analytical investigation and modeling is undertaken first; dynamic testing using low stress level and easily induced impact excitation are executed next. Modal parameters except for damping ratios are identified, then the mass matrix is estimated, and then the flexibility matrix is derived. Model parameters are altered rationally; and a very good match between experimental and model flexibilities is attained. This is accomplished despite the existence of several closely spaced modes and the use of a simple identification algorithm. A static test is conducted to validate the dynamic test–based identification. A very strong agreement is shown between static and dynamic test results. Analytical modeling, field testing, and data reduction are found to be highly interrelated tasks. Remarks on needed further research in each of these areas is presented.