Comparison between the indirect approach and kriging with samples of different support for estimation using samples of different length

In this paper we compare two estimation methods to deal with samples of different support: (1) the indirect approach using accumulation and (2) kriging with samples of different support. These two methods were tested in a simple example. The estimates of the two methods were compared against a benchmark scenario. The benchmark consisted of kriging using a complete set of samples on the same support. The effects of the nugget effect, variogram range and type on the weight of long samples, the estimate, and the error variance were assessed. Kriging with samples of different support led to lower error variance and to estimates closer to the estimates of the benchmark scenario. Furthermore, in the case of spatially continuous attributes (low nugget effect), the indirect approach assigns greater weight to long samples than kriging with samples of different support. A cross validation study comparing the two methods with a database from a bauxite deposit was performed. The results of the cross validation study showed that kriging with samples of different support resulted in more precise estimates.     

On the significance of the climate-dataset time resolution in characterising wind-driven rain and simultaneous wind pressure. Part II: directional analysis

Both semi-empirical methods and CFD simulations use real climate datasets as a basis for determining the building facade exposure to wind-driven rain and simultaneous wind pressure. The time resolution of these datasets and the number of variables considered (commonly rainfall intensity, wind speed and wind direction) determine the required calculation effort and the accuracy of the result. Omitting the wind direction, a former article (Part I of this research) has analysed the effect of this time resolution on two scalar exposure indices obtained by semi-empirical methods: driving rain index (aDRI) and driving-rain wind pressure (DRWP). However, the wind direction during precipitation events also causes significant exposure variations between possible facade orientations. Thus, it is also necessary to clarify the influence of the time resolution of the dataset, on the accuracy of the directional semi-empirical calculation of aDRI and DRWP. To meet this challenge, the article examines 10-min climate records collected between 2001 and 2016 at 6 Spanish locations, uses them to obtain hourly, daily, monthly and annual datasets, and analyses the accuracy of the directional exposure indices associated with each time resolution. The results show that a daily dataset would allow identifying the most exposed orientation with an error less than 45°. However, even the hourly datasets cause errors close to 10% in the exposure values identified on each facade orientation. Finally, adjustment relationships that allow estimating the maximum value of directional exposure from simple scalar indices are obtained.

     

Spatial GR4J conceptualization of the Tamor glaciated alpine catchment in Eastern Nepal: evaluation of GR4JSG against streamflow and MODIS snow extent

Snow and glacial melt processes are an important part of the Himalayan water balance. Correct quantification of melt runoff processes is necessary to understand the region's vulnerability to climate change. This paper describes in detail an application of conceptual GR4J hydrological model in the Tamor catchment in Eastern Nepal using typical elevation band and degree‐day factor approaches to model Himalayan snow and glacial melt processes. The model aims to provide a simple model that meets most water planning applications. The paper contributes a model conceptualization (GR4JSG) that enables coarse evaluation of modelled snow extents against remotely sensed Moderate Resolution Imaging Spectroradiometer snow extent. Novel aspects include the glacial store in GR4JSG and examination of how the parameters controlling snow and glacial stores correlate with existing parameters of GR4J. The model is calibrated using a Bayesian Monte Carlo Markov Chain method against observed streamflow for one glaciated catchment with reliable data. Evaluation of the modelled streamflow with observed streamflow gave Nash Sutcliffe Efficiency of 0.88 and Percent Bias of <4%. Comparison of the modelled snow extents with Moderate Resolution Imaging Spectroradiometer gave R² of 0.46, with calibration against streamflow only. The contribution of melt runoff to total discharge from the catchment is 14–16% across different experiments. The model is highly sensitive to rainfall and temperature data, which suffer from known problems and biases, for example because of stations being located predominantly in valleys and at lower elevations. Testing of the model in other Himalayan catchments may reveal additional limitations. © 2016 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.     

Damage mechanics applied to performance‐based design of reinforced concrete columns

Performance‐based design methodology is based on reaching performance objectives that are associated to certain damage conditions. These performance objectives are related to the seismic hazard and to the performance levels. In actual application, reliable tools are required for capturing the evolution of the damage condition as well as for measuring and locating it. Moreover, it is essential to accurately establish the relationship between the damage and the performance levels. This paper shows the application of damage mechanics to performance‐based design. A layered damage mechanics‐based finite element program is presented with a discussion on modeling for prediction of the response of normal‐strength and high‐strength concrete columns subjected to cyclic flexural loading and various axial load levels. The damage indices derived from these analyses were used to elaborate several damage charts expressed as a function of drift and displacement ductility. This makes it possible to establish a relationship between the damage state and the performance levels. Results have demonstrated the ability of the damage mechanics modeling to accurately predict the behavior of the specimens tested. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimal placement of dampers for passive response control

The effectiveness of viscous and viscoelastic dampers for seismic response reduction of structures is quite well known in the earthquake engineering community. This paper deals with the optimal utilization of these dampers in a structure to achieve a desired performance under earthquake‐induced ground excitations. Frequency‐dependent and ‐independent viscous dampers and viscoelastic dampers have been considered as the devices of choice. To determine the optimal size and location of these dampers in the structure, a genetic algorithm is used. The desired performance is defined in terms of several different forms of performance functions. The use of the genetic approach is not limited to any particular form of performance function as long as it can be calculated numerically. For illustration, numerical examples for different building structures are presented showing the distribution and size of different dampers required to achieve a desired level of reduction in the response or a performance index. Copyright © 2002 John Wiley & Sons, Ltd.     

Assessing drought in the drylands of northeast Brazil under regional warming exceeding 4 °C

Natural Hazards - Historically, during periods of extreme drought, food security in the drylands of the semiarid region of Northeast Brazil (NEB) is under severe risk due to agricultural collapse....     

Formulation of elastic earthquake input energy spectra

The object of this paper is to introduce a procedure for the determination of elastic design earthquake input energy spectra taking into account the influence of magnitude, soil type and distance from the surface projection of the fault. Firstly, an accurate selection of a large set of representative records has been realized. Secondly, the construction of the design input energy spectra has required determining the spectral shapes and a normalization factor which measures seismic hazard in terms of energy. This factor, denoted as the seismic hazard energy factor, has been defined as the area under the earthquake input energy spectrum in the period interval between 0·05 and 4·0 s. Finally, due to the importance of the source-to-site distance in the evaluation of the input energy, an investigation into the attenuation of the seismic hazard energy factor has been carried out. © 1998 John Wiley & Sons, Ltd.     

Safety level of damaged RoPax ships: Risk modelling and cost-effectiveness analysis

This paper elaborates on results of a recent risk analysis study for RoPax vessels, carried out as part of the activities of the SAFEDOR Integrated Project, targeting possible improvements on safety levels following large scale flooding. The study is based on a comprehensive analysis of accident statistics for the period 1994–2004, through which a high-level risk model (in the form of event trees) is established. This is then used to determine the current safety level of RoPax vessels (in various risk metrics, such as individual risk, potential loss of life and on an F–N curve), reconfirming that even though safety levels are improving, risk is still “high in the ALARP region”. In search of ways to further improve the situation possible risk control options are examined, by performing a sensitivity analysis on the effects of the Attained Index of Subdivision A onto the safety levels and by evaluating their cost-effectiveness.     

Humic substances in estuarine soils colonized by Spartina maritima

This study characterizes humic substances (HS) from two soils colonized by Spartina maritima at different physiographical positions in estuarine environments on the north-western coast of the Iberian Peninsula: the Villaviciosa site, a stand close to the main tidal channel, and the Ortigueira site, located in the low salt marsh. Humic and fulvic acids were extracted from the soils and characterized qualitatively by the following spectroscopic techniques: Fourier transform infrared spectroscopy, fluorescence spectroscopy and solid-state ¹³C nuclear magnetic resonance.The characterized HS showed a predominance of low humified compounds with a high proportion of aliphatic components and a low degree of aromaticity. The HS composition differed substantially between sites. In the Villaviciosa soil, the large amount of nonpolar aliphatic components and the very low degree of aromaticity may indicate a significant contribution of marine organic matter and/or microbial material to the HS. However, in the HS from the Ortigueira soil, the higher proportion of polysaccharides together with the presence of lignin-derived compounds may indicate greater inputs of vascular plant material. The δ¹³C isotopic composition of the bulk soils highlights the large input of Spartina maritima debris to the Ortigueira site, whereas in the Villaviciosa site, organic contributions from this C4 vascular plant were not so evident.The results indicate that in these soils colonized by Spartina maritima, physiographical position has an important effect on the composition of soil HS and, therefore, must be considered in the study of organic matter characteristics in such estuarine environments.     

The relationship of anchovy and sardine to water masses in the Peruvian Humboldt Current System from 1983 to 2005

The Humboldt Current System (HCS) is dominated by two pelagic species; Peruvian anchovy or anchoveta (Engraulis ringens) and sardine (Sardinops sagax). Using data from 43 acoustic surveys conducted from 1983 through 2005 by the Peruvian Marine Institute (IMARPE), we examined the distribution of these two species relative to water masses. We tested the hypothesis that anchovy was found more frequently in upwelled cold coastal water (CCW) and mixed waters (MCW) than in other water types and that sardine was more associated with more offshore oceanic surface subtropical water (SSW). Surface temperature, salinity, latitude, season and distance to the coast data were used to define water masses. Results using generalized additive models (GAM), modelling sardine and anchovy presence–absence as a function of year, water body, bottom depth and latitude, showed that anchovy were primarily found in CCW and MCS, while sardine were more ubiquitous relative to water masses with some predilection for SSW. These results were supported by various indexes of anchovy and sardine distribution versus water mass as well as temporal and location variables.