An answer to an important controversy and the need for caution when using simple models to predict inelastic earthquake response of buildings with torsion

This paper presents evidence that the extension of conclusions based on the widely used simplified, one story, eccentric systems of the shear‐beam type, to actual, nonsymmetric buildings and consequent assessments of the pertinent code provisions, can be quite erroneous, unless special care is taken to match the basic properties of the simplified models to those of the real buildings. The evidence comes from comparisons of results obtained using three variants of simplified models, with results from the inelastic dynamic response of three‐ and five‐story eccentric buildings computed with detailed MDOF systems, where the members are idealized with the well‐known plastic hinge model. In addition, a convincing answer is provided on a pertinent hanging controversy: For frame‐type buildings, designed in accordance with the dynamic provisions of modern codes (such as EC8 or IBC2000), which allow reduced shears at the stiff edge due to torsion, the frames at the flexible sides are the critical elements in terms of ductility demands. Copyright © 2009 John Wiley & Sons, Ltd.     

Integrated use of GIS and remote sensing for monitoring landslides in transportation pavements: the case study of Paphos area in Cyprus

This study considers the impact of landslides on transportation pavements in rural road network of Cyprus using remote sensing and geographical information system (GIS) techniques. Landslides are considered to be one of the most extreme natural hazards worldwide, causing both human losses and severe damages to the transportation network. Risk assessment for monitoring a road network is based on the combination of the probability of landslides occurrence and the extent and severity of the resultant consequences should the disasters (landslides) occur. Factors that can trigger landslide episodes include proximity to active faults, geological formations, fracture zones, degree and high curvature of slopes, water conditions, etc. In this study, the reliability and vulnerability of a rural network are examined. Initially, landslide locations were identified from the interpretation of satellite images. Different geomorphological factors such as aspect, slope, distance from the watershed, lithology, distance from lineaments, topographic curvature, land use and vegetation regime derived from satellite images were selected and incorporated in GIS environment in order to develop a decision support and continuous landslide monitoring system of the area. These parameters were then used in the final landslide hazard assessment model based on the analytic hierarchy process method. The results indicated good correlation between classified high-hazard areas and field-confirmed slope failures. The CA Markov model was also used to predict the landslide hazard zonation map for 2020 and the possible future hazards for transportation pavements. The proposed methodology can be used for areas with similar physiographic conditions all over the Eastern Mediterranean region.     

Numerical Modeling of the Long-Term Transport, Dispersion, and Accumulation of Black Sea Pollutants into the North Aegean Coastal Waters

This study investigates the long-term capacity of the North Aegean coastal systems to transport and store conservative pollutants that originate from the Black Sea. Emphasis is placed on modeling the dispersion and accumulation of a passive tracer that represents a Black Sea pollutant (BSP) substance that continuously discharges from the Dardanelles exit into the North Aegean, for a long period of time (16?years). The effects of the Black Sea water (BSW) inflows, meteorological forcing, and seasonal stratification are assessed with a 3D hydrodynamic model (Estuary, Lake and Coastal Ocean Model), after validation with available field data. The salinity, water temperature, and discharge from the Dardanelles Strait are taken to be seasonally varied. According to the authors' best knowledge, the present paper constitutes the first numerical modeling attempt in the literature that apart from the long-term hydrodynamic characteristics that have also been studied in previous works, a suitable tracer is introduced in order to predict the long-term fate, distribution, and accumulation of pollutants that originate from the Black Sea into the North Aegean coastal regions. The overall results of the present investigation indicate that the BSP concentration is very high at the coastal waters of Thassos, Samothraki, and Limnos islands, as well as along the mainland coastal waters between Alexandroupolis and Strymonikos Gulf, during summer and autumn when strong water column stratification occurs. In general, the BSP concentration in the North Aegean surface waters reaches considerable high values (47?C58?% of the initial pollutant concentration at Dardanelles inflow) within 16?years. Even for depths more than 500?m the BSP concentration is still remarkable, slightly increasing with time. The increase of the BSP concentration with respect to time at various depths (from free surface up to 750?m) is also investigated.     

Landfill Base Liners: Assessment of Material Equivalency and Impact to Groundwater

This paper gathered available flow and transport solutions and used them for two composite liners, consisting of geomembrane (GM) overlying either a compacted clay liner (CCL) or a geosynthetic clay liner (GCL). Its aim is to provide a guiding framework for the possible choices of (a) approaches to bottom liner design, (b) respective analytical solutions to flow and transport equations, as well as (c) parameters required for each type of solution. On the basis of the obtained results, the following recommendations are made. When the goal of analysis is to determine material equivalency, leachate flow rate is an adequate key parameter for GM-CCL composite liners. For GM-GCL composite liners, it is necessary to compute contaminant concentration or mass flux, considering (a) transport through defects for inorganic contaminants and (b) diffusion and the contribution of any available attenuation layer for organic contaminants. When the goal of analysis is to assess impact to groundwater, it is advised to calculate both discharge rate and contaminant mass flux regardless of liner type. The critical parameter for the transport calculations is the retardation factor of the contaminant, for the case of CCLs, while the results for GCLs are much less sensitive to this parameter.     

Accidental design eccentricity: Is it important for the inelastic response of buildings to strong earthquakes?

To deal with earthquake-induced torsion in buildings due to some uncertain factors, difficult to account for directly in design, modern codes have introduced the so-called accidental design eccentricity (ADE). This provision has been based primarily on elastic investigations with special classes of multi-story buildings or with simplified, one-story inelastic models. In the present paper, the effectiveness of this provision is investigated using inelastic models, both of the typical one-story, 3-DOF type, and the more sophisticated MDOF, frame idealizations of the plastic hinge type. One, three and five story, realistic, frame buildings with different natural eccentricities were designed for different ADEs, including those specified by the EC8 and IBC codes. The evaluation is made using mean peak ductility factors of the edge frames as measures of their inelastic response, obtained from dynamic analyses for ten pairs of semi-artificial earthquake motions. The simplified models indicate that the accidental design eccentricity is very effective in reducing ductility demands, especially for very stiff systems. However, this is not confirmed by the more accurate and detailed plastic hinge building models, which show that designs accounting for accidental eccentricity do not exhibit any substantial reduction or better distribution of ductility demands, compared to designs in which accidental eccentricity has been entirely ignored. These findings suggest that the ADE provisions in codes, especially the more complicated ones as in the IBC, should be re-examined, by weighting their importance against the additional computational work they impose on designers. In the cases examined herein this importance can be characterized as marginal. Obviously additional studies are required, to include more building types and earthquake motions, in order to arrive at firm conclusions and recommendations for code modifications.     

Relationship between MODIS based Aerosol Optical Depth and PM10 over Croatia

This study analyzes the relationship between Aerosol Optical Depth (AOD) obtained from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and ground-based PM10 mass concentration distribution over a period of 5 years (2008–2012), and investigates the applicability of satellite AOD data for ground PM10 mapping for the Croatian territory. Many studies have shown that satellite AOD data are correlated to ground-based PM mass concentration. However, the relationship between AOD and PM is not explicit and there are unknowns that cause uncertainties in this relationship. The relationship between MODIS AOD and ground-based PM10 has been studied on the basis of a large data set where daily averaged PM10 data from the 12 air quality stations across Croatia over the 5 year period are correlated with AODs retrieved from MODIS Terra and Aqua. A database was developed to associate coincident MODIS AOD (independent) and PM10 data (dependent variable). Additional tested independent variables (predictors, estimators) included season, cloud fraction, and meteorological parameters — including temperature, air pressure, relative humidity, wind speed, wind direction, as well as planetary boundary layer height — using meteorological data from WRF (Weather Research and Forecast) model. It has been found that 1) a univariate linear regression model fails at explaining the data variability well which suggests nonlinearity of the AOD-PM10 relationship, and 2) explanation of data variability can be improved with multivariate linear modeling and a neural network approach, using additional independent variables.     

On the long-term stability of terrestrial reference frame solutions based on Kalman filtering

The Global Geodetic Observing System requirement for the long-term stability of the International Terrestrial Reference Frame is 0.1 mm/year, motivated by rigorous sea level studies. Furthermore, high-quality station velocities are of great importance for the prediction of future station coordinates, which are fundamental for several geodetic applications. In this study, we investigate the performance of predictions from very long baseline interferometry (VLBI) terrestrial reference frames (TRFs) based on Kalman filtering. The predictions are computed by extrapolating the deterministic part of the coordinate model. As observational data, we used over 4000 VLBI sessions between 1980 and the middle of 2016. In order to study the predictions, we computed VLBI TRF solutions only from the data until the end of 2013. The period of 2014 until 2016.5 was used to validate the predictions of the TRF solutions against the measured VLBI station coordinates. To assess the quality, we computed average WRMS values from the coordinate differences as well as from estimated Helmert transformation parameters, in particular, the scale. We found that the results significantly depend on the level of process noise used in the filter. While larger values of process noise allow the TRF station coordinates to more closely follow the input data (decrease in WRMS of about 45%), the TRF predictions exhibit larger deviations from the VLBI station coordinates after 2014 (WRMS increase of about 15%). On the other hand, lower levels of process noise improve the predictions, making them more similar to those of solutions without process noise. Furthermore, our investigations show that additionally estimating annual signals in the coordinates does not significantly impact the results. Finally, we computed TRF solutions mimicking a potential real-time TRF and found significant improvements over the other investigated solutions, all of which rely on extrapolating the coordinate model for their predictions, with WRMS reductions of almost 50%.     

Risk provision using field spectroscopy to identify spectral regions for the detection of defects in flexible pavements

Natural and physical hazards accelerate the deterioration of asphalted surfaces. Climatic factors are unavoidable and can affect the properties of asphalt mixtures, making them weaker and less durable. Thus, continuous monitoring of bituminous surfaces is something that can reduce the risks of public health. Remote sensing techniques have become an effective, noninvasive method for early detection of damaged asphalt pavements. This paper outlines a range of different remote sensing methodologies that can be used to monitor asphalt road pavements. This is complemented by the use of field spectroscopy for the examination of asphalt pavements of varying age and conditions. The results of the study found spectral differences regarding asphalt defects, such as physical cracking, patched cracking and polishing. These spectral changes were examined through “in-band” simulation analysis of the Landsat 7 ETM+ sensor, using appropriate relative spectral response filters, concluding that the ratio band 5/band 1 can be used to distinguish asphalt pavements of different date of construction and condition.     

Bridge health monitoring system based on vibration measurements

A bridge health monitoring system is presented based on vibration measurements collected from a network of acceleration sensors. Sophisticated structural identification methods, combining information from the sensor network with the theoretical information built into a finite element model for simulating bridge behavior, are incorporated into the system in order to monitor structural condition, track structural changes and identify the location, type and extent of damage. This work starts with a brief overview of the modal and model identification algorithms and software incorporated into the monitoring system and then presents details on a Bayesian inference framework for the identification of the location and the severity of damage using measured modal characteristics. The methodology for damage detection combines the information contained in a set of measurement modal data with the information provided by a family of competitive, parameterized, finite element model classes simulating plausible damage scenarios in the structure. The effectiveness of the damage detection algorithm is demonstrated and validated using simulated modal data from an instrumented R/C bridge of the Egnatia Odos motorway, as well as using experimental vibration data from a laboratory small-scaled bridge section.