The effect of soil–structure interaction on the seismic risk to buildings

This paper studies the effect of soil–structure interaction (SSI) on the seismic risk estimates of buildings. Risk, in this context, denotes the probability distribution of seismic monetary loss due to structural and nonstructural damage. The risk analysis here uncovers the probability that SSI is beneficial, detrimental, or uninfluential on seismic losses. The analyses are conducted for a wide range of buildings with different structural systems, numbers of stories, and foundation sizes on various soil types. A probabilistic approach is employed to account for prevailing sources of uncertainty, i.e., those in ground motion and in the properties of the soil–structure system. In this approach, probabilistic models are employed to predict the response, damage, and repair cost of buildings. To properly account for the ground motion uncertainty, a suite of nearly 7000 accelerograms recorded on soil is employed. It is concluded that structures on very soft soils are extremely likely to incur smaller losses due to SSI, which is in line with the common belief that SSI is a favorable effect for such systems. However, the results for buildings on moderately soft soils reveal a considerable probability, up to 0.4, that SSI has an adverse effect on the structure and increases the seismic losses.     

Trophic functioning of macrobenthic fauna in a tropical acidified Bornean estuary (Southeast Asia)

The trophic structure of a community is used to infer ecosystem functioning(e.g. energy transfer and nutrient cycling). Here the trophic structure of the benthic infaunal and epifaunal communities in the Brunei Estuary are characterized, and their distribution along an estuarine pH gradient is analyzed using univariate and multivariate techniques. This analysis revealed that surface deposit feeders(e.g., polychaetes) were numerically dominant within the infaunal communities whereas in the epifaunal communities filter feeders(e.g., bivalves) were highly abundant. Species richness for almost all trophic groups increased toward the lower estuary, except for omnivores in the epifaunal communities, which decreased markedly. Both Analysis of Variance(ANOVA) and Analysis of Similarities(ANOSIM) detected significant differences in the density of respective trophic groups among stations. Within infaunal communities, both Biological and Environmental procedure(BIO-ENV) and Canonical Correspondence Analysis(CCA) showed that trophic shifts were associated with environmental gradients. Surface-deposit feeders and omnivores were the most abundant macrobenthos of the upper estuary characterized by low salinity, low pH, and a higher percentage of mud particles. The proportion of filter feeders and carnivores increased with salinity/pH and sand. A more uniform distribution of trophic structure was found in the lower estuary, with high salinity and pH over sandy habitat. In contrast, within epifaunal trophic groups,the percentage of surface deposit feeders and omnivores declined, but filter feeders remarkably increased toward the sea. The proportion of carnivores remained similar at all stations. Non-Metric Multidimensional Scaling(nMDS) ordination for epifaunal trophic groups clearly demarcated higher salinity/pH stations from lower salinity/pH stations, suggesting different trophic compositions along the estuarine pH gradient.     

Force‐displacement model for solid confined masonry walls with shear‐dominated failure mode

This paper addresses the behavior of confined masonry walls with dominating shear failure mode in walls. For this purpose, failure modes of these walls are classified in details. For each failure mode, complete set of analytical‐based relations for deriving parameters related to backbone curves is introduced. Calibrated finite element analyses are utilized as a benchmark for verification of some of the assumptions. The results of the proposed relations are compared with those of several Iranian and non‐Iranian experimental data. Sensitivity analysis is performed in order to understand the effects of important behavioral characteristics of these walls. The results of this study indicate that the proposed relations can accurately simulate behavior of confined masonry walls with dominating shear failure mode regardless of the failure mode in the ties. Moreover, it is concluded that the detailing limitations given in the Iranian Seismic Code are rationally compatible with the behavioral characteristics of confided masonry walls. The results of this study in terms of backbone curves can be utilized as the complementary part to this code. Copyright © 2017 John Wiley & Sons, Ltd.     

Investigating the ability of periodically correlated (PC) time series models to forecast the climate index

Stochastic Environmental Research and Risk Assessment - Considering the importance of climate change and its effects, especially in recent decades, the forecast of future climate conditions can be...     

Investigating extreme scenarios with multiple-point geostatistics and variance maximization

Stochastic Environmental Research and Risk Assessment - In many geoscience applications, the data extracted from environmental variables are very limited. Multiple-point geostatistical (MPS)...     

Assessing the accuracy of sequential gaussian simulation through statistical testing

Sequential Gaussian simulation is one of the most widespread algorithms for simulating regionalized variables in the earth sciences. Simplicity and flexibility of this algorithm are the most important reasons that make it popular, but its implementation is highly dependent on a screen effect approximation that allows users to use a moving neighborhood instead of a unique neighborhood. Because of this, the size of the moving neighborhood the number of conditioning data and the size of variogram range are important in the simulation process and should be chosen carefully. In this work, different synthetic and real case studies are presented to show the effect of the neighborhood size the number of conditioning data and the size of variogram range on the simulation result, with respect to the reproduction of the model first and second-order parameters. Results indicate that, in both conditional and non-conditional simulation cases, using a neighborhood with <50 conditioning data may lead to an inaccurate reproduction of the model statistics, and some cases require considering more than 200 conditioning data. It also can be understood from the result of example 3 that when the variogram range is beg compared to the simulation domain determination of inaccurate simulation program is harder.     

Simulation of relationship between river discharge and sediment yield in the semi-arid river watersheds

Complex and variable nature of the river sediment yield caused many problems in estimating the long-term sediment yield and problems input into the reservoirs. Sediment Rating Curves (SRCs) are generally used to estimate the suspended sediment load of the rivers and drainage watersheds. Since the regression equations of the SRCs are obtained by logarithmic retransformation and have a little independent variable in this equation, they also overestimate or underestimate the true sediment load of the rivers. To evaluate the bias correction factors in Kalshor and Kashafroud watersheds, seven hydrometric stations of this region with suitable upstream watershed and spatial distribution were selected. Investigation of the accuracy index (ratio of estimated sediment yield to observed sediment yield) and the precision index of different bias correction factors of FAO, Quasi-Maximum Likelihood Estimator (QMLE), Smearing, and Minimum-Variance Unbiased Estimator (MVUE) with LSD test showed that FAO coefficient increases the estimated error in all of the stations. Application of MVUE in linear and mean load rating curves has not statistically meaningful effects. QMLE and smearing factors increased the estimated error in mean load rating curve, but that does not have any effect on linear rating curve estimation.     

Integration of rock physics and seismic inversion for rock typing and flow unit analysis: A case study

Rock typing and flow unit detection are more challenging in clastic reservoirs with a uniform pore system. An integrated workflow based on well logs, inverted seismic data and rock physics models is proposed and developed to address such challenges. The proposed workflow supplies a plausible reservoir model for further investigation and adds extra information. Then, this workflow has been implemented in order to define different rock types and flow units in an oilfield in the Persian Gulf, where some of these difficulties have been observed. Here, rock physics models have the leading role in our proposed workflow by providing a diagnostic framework in which we successfully differentiate three rock types with variant characteristics on the given wells. Furthermore, permeability and porosity are calculated using the available rock physics models to define several flow units. Then, we extend our investigation to the entire reservoir by means of simultaneous inversion and rock physics models. The outcomes of the study suggest that in sediments with homogeneous pore size distribution, other reservoir properties such as shale content and cementation (which have distinct effects on the elastic domain) can be used to identify rock types and flow units. These reservoir properties have more physical insights for modelling purposes and can be distinguished on seismic cube using proper rock physics models. The results illustrate that the studied reservoir mainly consists of rock type B, which is unconsolidated sands and has the characteristics of a reservoir for subsequent fluid flow unit analysis. In this regard, rock type B has been divided into six fluid units in which the first detected flow unit is considered as the cleanest unit and has the highest reservoir process speed about 4800 to 5000 mD. Here, reservoir quality decreases from flow unit 1 to flow unit 6.