Civil and Environmental Engineering

This paper deals with the formulation, calibration, and validation of the Lattice Discrete Particle Model (LDPM) suitable for the simulation of the failure behavior of concrete. LDPM simulates concrete at the meso-scale considered to be the length scale of coarse aggregate pieces. LDPM is formulated in the framework of discrete models for which the unknown displacement field is not continuous but only defined at a finite number of points representing the center of aggregate particles. Size and distribution of the particles are obtained according to the actual aggregate size distribution of concrete. Discrete compatibility and equilibrium equations are used to formulate the governing equations of the LDPM computational framework. Particle contact behavior represents the mechanical interaction among adjacent aggregate particles through the embedding mortar. Such interaction is governed by meso-scale constitutive equations simulating meso-scale tensile fracturing with strain-softening, cohesive and frictional shearing, and nonlinear compressive behavior with strain-hardening. The present, Part I, of this two-part study deals with model formulation leaving model calibration and validation to the subsequent Part II.

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Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

This paper presents recent results obtained by the Lattice Discrete Particle Model (LDPM) for the simulation of concrete and fiber reinforced concrete behavior. LDPM is a meso-scale model which has been recently formulated at Rensselaer Polytechnic Institute and extensively validated against experimental data. LDPM can accurately predict several phenomena characterizing concrete behavior, including failure under uniaxial, biaxial, and triaxial compression; material compaction under hydrostatic compression; and tensile fracturing.

Real-time monitoring of civil infrastructure provides valuable information to assess the health and condition of the associated systems. This paper presents the recently developed shape acceleration array (SAA) and local system identification (SI) technique, which constitute a major step toward long-term effective health monitoring and analysis of soil and soil-structure systems. The SAA is based on triaxial micro-electro-mechanical system (MEMS) sensors to measure in situ deformation (angles relative to gravity) and dynamic accelerations up to a depth of one hundred meters. This paper provides an assessment of this array's performance for geotechnical instrumentation applications by reviewing the recorded field data from a bridge replacement site and a full-scale levee test facility. The SI technique capitalizes on the abundance of static and dynamic measurements from the SAA. The geotechnical properties and constitutive response of soil contained within a locally instrumented ...

The first-generation time-series synthetic aperture radar interferometry (TSInSAR) technique persistent-scatterer (PS) InSAR has been proven effective in ground deformation measurement over areas with high reflectivity by taking advantage of coregistered temporally coherent pointwise scatterers. In order to increase the spatial density of measurement points and quality of displacement time series over moderate reflectivity scenes, a second-generation TSInSAR called SqueeSAR was developed to extract displacement information from both PSs and distributed scatterers, by taking into account their temporal coherence and their spatial statistical behavior. In this paper, we propose a new second-generation TSInSAR, which is referred to as jointscatterer (JS) InSAR, to measure the line-of-sight surface displacement using the neighboring pixel stacks. A novel goodness-of-fit testing approach is proposed to analyze the similarity between two JS vectors based on time-series likelihood ratios. By taking advantage of the proposed test, a new spatially adaptive filter is developed to estimate the covariance matrix. Based on the estimated covariance matrix, the projection of the joint signal subspace onto the corresponding joint noise subspace is applied to retrieve phase history. With coherence information of neighboring pixel stacks, JSInSAR is able to provide reliable geophysical parameters in the presence of large coregistration errors. The effectiveness of the proposed technique is verified with a time series of high-resolution SAR data from the TerraSAR-X satellite.

Soil and soil structure systems are massive multiphase particulate systems characterized by the development of localized response mechanisms under extreme loading conditions. Identification and analysis of such systems on the basis of inverse boundary value problem formulations and sparse measurements are generally indeterminate. An alternative local inverse problem technique using measurements from the newly developed wireless shape-acceleration array (WSAA) system is presented. Local identification analyses of the constitutive behavior of water-saturated soil and soil structure systems are performed with acceleration and pore pressure records provided by a cluster of closely spaced sensors. The developed novel technique does not require the availability of boundary condition measurements or the solution of an associated boundary value problem. The constitutive behavior at a specific location of a soil or soil structure system is analyzed independently of adjacent response mechanis...

Landslides, lateral spreading and other similar forms of ground failures due to natural disasters, such as heavy rains, floods and earthquakes, continue to be catastrophic events with extreme economic and societal costs, despite our increased understanding of the mechanisms of failure and large ground deformation, primarily because these events occur without much warning. Realtime monitoring programs are essential to develop warning systems of impending danger from active landslides in any site specific or regional hazard program. Unfortunately the current state-of-the-art in real-time monitoring of active slopes is either based on very expensive monitoring systems or on measurement of ground surface displacements. The work presented in this paper is a major step in the direction of establishing autonomous monitoring technology for soil and soil-structure systems. The MEMS-based in-place inclinometer system, ShapeAccelArray (SAA), is capable of simultaneously measuring 3D soil acceleration and 3D permanent ground deformation up to a depth of one hundred meters, with an accuracy of ±1.5mm per 30m. Each sensor array is connected to a wireless sensor node to enable real-time monitoring as well as remote sensor configuration. This paper presents a brief description of the design of this sensor array and results from full-scale liquefaction and lateral spreading testing, as well as preliminary results from field tests of an active slope in California aimed at validating the measured accelerations and displacements.

The integrity and reliability of levees, earthen dams and flood-control infrastructure are essential components of homeland safety. The development of a potentially affordable satellite-based interferometric synthetic aperture radar (InSAR) technique for use in a new health assessment framework to monitor, manage and ensure the safety of levees and other systems of flood-control infrastructure is presented in this paper. To estimate the yearly rate of deformation of both the concrete and grass-covered levee structures with sub-wavelength accuracy, a new InSAR technique referred to as joint pixels InSAR (JPInSAR) is proposed. The corresponding results of applying JPInSAR to TerraSAR-X Stripmap data from February 2009 to October 2011 for widespread settlement monitoring in the New Orleans area are presented herein. The presented data processing chain significantly increases the number of pixels where the deformation-rate can be estimated as compared to the number of pixels that can be processed by the classical persistent scatterer technique. Local measurements from GPS and ShapeAccelArrays (SAAs), which were installed in June 2012, will be integrated with the satellite-based InSAR measurements into a global-local network to monitor the response of flood-control levees.

This paper discusses the preparation and pre-evaluation for the development and implementation of an educational module that integrates major remote research facilities into undergraduate classes. The developed educational module incorporates state-of-the-art experimental tools (geotechnical centrifuge) into the undergraduate education curriculum via web-based technologies that enable real-time video monitoring, tele-control, and shared execution of experiments. The students' activities within the developed module are centered around building a model consisting of a shallow foundation on a sand deposit utilizing the Network for Earthquake Engineering Simulation (NEES) centrifuge facility. The project provides students at three different engineering universities with new educational tools for improving their understanding of various geotechnical engineering concepts. The main goals of this project are: to develop and pilot test educational models utilizing the centrifuge facility at one of these universities; to provide visual observation of the response of soil and soil-foundation systems; and to promote student-based use of instrumentation, interpretation of acquired data, and utilization of the NEES 3D data viewer in order to analyze the measured response. Students were able to access, interpret, evaluate, and exchange relevant technical information via the Internet thereby bringing major experimentation into geotechnical engineering classes. In order to ensure successful development and implementation of the multi-institute educational model, a preliminary implementation was conducted in the fall of 2011 at two of the three universities. Students at one university involved in this trial were undergraduate research students, while those participating at the second one did so as part of a soil mechanics and foundations class. The close interaction with undergraduate research students helped in identifying potential problems at early stages and allowed for timely corrections as the second university's class progressed. This paper presents the results and lessons learned through early implementation. It focuses on explaining centrifuge technology, the tools used to build the model, testing logistics, and methods adopted to resolve obstacles encountered during execution of the module. The student survey indicates that the developed module successfully addresses an important educational gap-students' lack of understanding of the strong relationship between soil laboratory testing, system design, and field performance. The survey also highlighted the fact that students did appreciate the practical nature of the project. The educational module was revised and successfully implemented in the spring of 2012 at the three universities.

Game-based learning has long been heralded as a promise to transform education into a more engaging and experiential paradigm. Its implementation in engineering education has thus far shown that promise, yet more evidence is needed for widespread adoption. Our work focuses on issues of equity, inclusivity, and diversity, thus surfacing the question of whether game-based learning benefits each and every student. To date, these issues have not received much attention in game-based learning educational research landscape, despite its poignancy, given today's global social climate and the systematic lack of equity and diversity in engineering education. With a focus on gender and race/ethnicity we reflect on the outcomes of implementing game-based learning environment in undergraduate geotechnical engineering courses (n = 362). We find evidence that game-based learning supports positive outcomes and provides an equitable learning environment. However, we also note several challenges that are further discussed.

Truck-related crash occurrences in Manhattan, New York City, are analyzed during four time blocks: morning peak (AMP, 6:00 to 10:00 a.m.), midday (MD, 10:00 a.m. to 3:00 p.m.), afternoon peak (PMP, 3:00 to 7:00 p.m.), and nighttime (NT, 7:00 p.m. to 6:00 a.m.). The results of zeroinflated negative binomial models indicate that both the built environment and traffic flows contribute to temporal variation in truck-related crash occurrences. More specifically, tracts with larger populations and higher employment in the finance, insurance, and health care sectors tend to have fewer crashes at night. In contrast, larger household sizes and the retail, professional services, education, and accommodation industry sectors are associated with increased NT crash occurrences. In addition, if 1,000 trucks were shifted from AMP to the NT, the average tract would experience a net increase of truck crashes of 0.2160; the net increase would be 0.1948 if the trucks were shifted from the PMP to the NT. Shifting trucks from the MD to the NT reduces the count by 0.0267; this result suggests that this strategy might provide the best safety benefits. When possible induced nontruck demand is accounted for, even the largest impact on safety (during the PMP) increased crashes by only 3.56%. These findings fill the void of studies that focused on the influence of temporal effects on truck crash occurrences in congested urban settings.

The concept of freight consolidation center (FCC) has emerged in recent years. Although several case studies have indicated that FCCs are beneficial to the operation of urban transportation systems, the implementation of this concept has proven difficult because the construction and operation of a FCC involves the coordination of different, and conflicting, stakeholders. Unlike other traditional approaches, this paper investigates the FCC development issue using experimental economics. First, profit functions are defined for involved stakeholders; based on those profit functions, four players-carriers, operators, government, and residents-bid on rent, financial incentives, and wages to maximize their own profits. Eight scenarios are analyzed and compared to determine potential influential factors and appropriate conditions for FCC decision making. Results show that public-private partnership lowers rent and increases wages, which leads to higher carrier, operator, and resident profits. A central location lowers rent, wages, financial incentives, and all stakeholders' profits. A larger carrier size benefits all stakeholders. In conclusion, the appropriate conditions for FCC development are public-private partnerships in noncentral locations with large carrier sizes.

The traffic fatalities in the U.S. had remained relatively stable between 40,716 and 43,510 from 1994 to 2005. However, according to the Fatality Analysis Reporting System (FARS), the traffic fatalities dropped dramatically from 43,510 in 2005 to 33,808 in 2009. This paper studies fatalities from social-economic perspective and uses an ARIMA model to perform a time-series analysis of fatalities from 1994 to 2009 by controlling unemployment rate, GDP, auto sales and other factors. The results indicate that ARIMA model is appropriate for the analysis and the number of auto sales is significantly related to fatality downturn. Findings from this study will enhance the understanding of traffic safety issues from a macro level and facilitate traffic safety policy design.

The rapid growth of ecommerce brings great changes to the transportation system. However, most existing studies focus on the impact of ecommerce on freight system. Its impact on personal trips is relatively less studied. It is reasonable to argue that online shopping reduces the need of shopping trips by making goods accessible via door-to-door deliveries. On the other hand, online shopping may also create more shopping trips as online shoppers travel to stores to experience, compare or pick up the goods. Understanding the connections between online shopping and shopping trips is critical for transportation planners to prepare for changes that information technology will continue to bring to this nation in the future. Using the 2009 National Household Travel Survey (NHTS) data and a structural equation model (SEM), this paper disentangles the bidirectional connections between online shopping and shopping trips. Results show that online shopping encourages shopping trips while shopping trips tend to suppress the online shopping propensity. Besides, both online shopping and shopping trips are influenced by exogenous factors such as shoppers' demographic features, regional specific factors and household attributes. A closer examination at the state level further confirms model validity while disclosing spatial variation in their relationship.

As a result of the rapid growth of online shopping, more goods and services are delivered directly to residential units. The door-to-door deliveries improve residents' accessibility to retail sector, and at the same time create truck delivery trips. However, partially due to the data limitation, most existing freight research focuses on freight trips generated by business establishments. Little is known about freight trips generated by residential units. As a growing number of urban areas are pushing for dense and mixed development, it is necessary to understand the pattern of truck freight trips directly generated by residential units. This paper uses the U.S. National Household Travel Survey (NHTS) data to investigate the freight trips generated by residential units. The 2009 NHTS provides accurate, comprehensive and timely information on trips, land use, household characteristics and social economic factors. It is the first time that the NHTS data is used to estimate freight trips. A binary choice model and a right-censored negative binomial model are used to identify the impacts of person-related, household-related, and regional-specific variables on home delivery frequency. A case study for the New York State Capital District is then presented. The estimated freight trips generated by residential units are also compared to the freight trips generated by business establishments. Results, although still preliminary and subject to uncertainty, indicate that freight trips generated by residential units have comparable magnitude as the freight trips generated by businesses. Such a study will supplement city logistics studies that traditionally focus on business behavior, helping reconstruct a complete picture of the freight activities in urban areas.