Terrain Categories Research Articles

Response in piled raft foundation of tall chimneys under along-wind load incorporating flexibility of soil

The present paper deals with the numerical analysis of tall reinforced concrete chimneys with piled raft foundation subjected to along-wind loads considering the flexibility of soil. The analysis was carried out using finite element method on the basis of direct method of soil-structure interaction (SSI). The linear elastic material behavior was assumed for chimney, piled raft and soil. Four different material properties of soil stratum were selected in order to study the effect of SSI. The chimney elevation and the thickness of raft of piled raft foundation were also varied for the parametric study. The chimneys were assumed to be located in terrain category 2 and subjected to a maximum wind speed of 50 m/s as per IS:875 (Part 3)-1987. The along-wind loads were computed according to IS:4998 (Part 1)-1992. The base moments of chimney evaluated from the SSI analysis were compared with those obtained as per IS:4998 (Part 1)-1992. The tangential and radial bending moments of raft of piled raft foundation were evaluated through SSI analysis and compared with those obtained from conventional analysis as per IS:11089-1984, assuming rigidity at the base of the raft foundation. The settlements of raft of piled raft foundation, deflection of pile and moments of the pile due to interaction with different soil stratum were also evaluated. From the analysis, considerable reduction in the base moment of chimney due to the effect of SSI is observed. Higher radial moments and lower tangential moments were obtained for lower elevation chimneys with piled raft resting on loose sand when compared with conventional analysis results. The effect of SSI in the response of the pile is more significant when the structure-foundation system interacts with loose sand.

Wind induced pressure on 'Y' plan shape tall building

This paper presents a comprehensive study of pressure developed on different faces of a 'Y' plan shape tall building using both numerical and experimental means. The experiment has been conducted in boundary layer wind tunnel located at Indian Institute of Technology Roorkee, India for flow condition corresponding to terrain category II of IS:875 (Part 3) - 1987, at a mean wind velocity of 10 m/s. Numerical study has been carried out under similar condition using computational fluid dynamics (CFD) package of ANSYS, namely ANSYS CFX. Two turbulence models, viz., <TEX>$k-{\varepsilon}$</TEX> and Shear Stress Transport (SST) have been used. Good conformity among the numerical and experimental results have been observed with SST model yielding results of higher magnitude. Peculiar pressure distribution on certain faces has been observed due to interference effect. Furthermore, flow pattern around the model has also been studied to explain the phenomenon occurring around the model.

The Multipurpose New Wind Tunnel STU

Abstract BLWT STU tunnel, which is currently in test mode, will in its two measuring sections allow to prepare measurements with laminar and turbulent wind flow. The front section will fulfill technical parameters of steady flow for testing sectional models and dynamically similar models. In the rear operating section it is necessary to reproduce correctly the roughness of the earth surface covering different terrain categories and to prepare boundary layer suitable for experimental testing. Article deals with the brief description of the preparation and testing laminar flow and boundary layer for the urban terrain, which was simulated with rough elements and barriers of different heights. The attention is focused in getting get at least 1 meter height of boundary layer, which allows to optimize scale similarity of model.

3D Soil–Structure Interaction Analyses of Annular Raft Foundation of Tall RC Chimneys Under Wind Load

Three dimensional soil–structure interaction (SSI) analyses of tall reinforced concrete chimneys with annular raft foundation subjected to wind loads are presented in this paper. Different ranges of height and slenderness ratios of the chimneys and different ratios of external diameter to thickness of the annular raft were selected for the parametric study. To understand the significance of SSI, four types of soils were considered based on the stiffness. The chimneys were assumed to be located in terrain category two and subjected to a maximum wind speed of 50 m/s as per IS:875 (Part 3)-1987. The along-wind and across-wind loads were computed according to IS:4998 (Part 1)-1992. The linear elastic behavior was assumed for the integrated chimney-foundation-soil system and it was analysed using finite element software ANSYS based on direct method of SSI. The radial and tangential moments and settlement of annular raft foundation were evaluated through SSI analysis and compared with that obtained from conventional method of analysis as per IS:11089-1984, assuming foundation system is rigid. From the analysis, it is concluded that the SSI analysis results in higher radial moments and lesser tangential moments as compared to conventional method. All these variations depend on the geometric properties of chimney and annular raft foundations.

Comparing English, Mandarin, and Russian hydrographic and terrain categories

The paper compares hydrographic and terrain categories in the geospatial data standards of the United States, Taiwan, and Russian Federation where the dominant languages used are from different language families. It aims to identify structural and semantic differences between similar categories across three geospatial data standards. By formalizing the data standard structures and identifying the properties that differentiate sibling categories in each geospatial data standard using well-known formal relations and quality universals, we develop a common basis on which hydrographic and terrain categories in the three data standards can be compared. The result suggests that all the three data standards structure categories with a mixture of relations even though most of them are well-known relations in top-level ontologies. Similar categories can be found across all the three standards. Cases of categories from different standards carrying identical meaning are rare. Partial overlaps in the meaning of the similar categories can be a direct result of different quality universals at work in defining and distinguishing these categories, or in the case of these categories being ordered by size, the threshold values for distinguishing the categories are ambiguous and language-dependent. Understanding these differences avoids incorrect mappings of categories in multilingual applications. More importantly, it provides a starting point for more effective mapping between hydrographic and terrain categories between English, Mandarin, and Russian.

Generation of inflow turbulence using the local differential quadrature method

When performing unsteady time-dependent Computational Fluid Dynamics (CFD) calculation to investigate dynamic wind–structure interactions, turbulence whose mean and fluctuating velocity components satisfy the requirements of the Atmospheric Boundary Layer (ABL) of the specified terrain category must be imposed at the inlet of the computational domain at each time step. This paper proposes incorporation of the local Differential Quadrature Method (DQM) and the recycling technique to simulate inflow turbulence for wind engineering applications. Local DQM is utilized to help simulate the high-frequency component of turbulence because of its inherent high accuracy. The recycling technique is utilized to control the mean-velocity profile and boundary layer height. In this paper, local DQM is first described and verified by a numerical simulation of turbulence in a channel. It is then utilized in conjunction with the recycling technique to generate three kinds of turbulent boundary layers with different mean-velocity profiles. The results show that local DQM is a good approach to generation of inflow turbulence, particularly to increase the turbulence energy of high-frequency components.

Observations of late winter Canadian tundra snow cover properties

AbstractTundra snow cover is important to monitor as it influences local, regional, and global‐scale surface water balance, energy fluxes, as well as ecosystem and permafrost dynamics. Observations are already showing a decrease in spring snow cover duration at high latitudes, but the impact of changing winter season temperature and precipitation on variables such as snow water equivalent (SWE) is less clear. A multi‐year project was initiated in 2004 with the objective to quantify tundra snow cover properties over multiple years at a scale appropriate for comparison with satellite passive microwave remote sensing data and regional climate and hydrological models. Data collected over seven late winter field campaigns (2004 to 2010) show the patterns of snow depth and SWE are strongly influenced by terrain characteristics. Despite the spatial heterogeneity of snow cover, several inter‐annual consistencies were identified. A regional average density of 0.293 g/cm3 was derived and shown to have little difference with individual site densities when deriving SWE from snow depth measurements. The inter‐annual patterns of SWE show that despite variability in meteorological forcing, there were many consistent ratios between the SWE on flat tundra and the SWE on lakes, plateaus, and slopes. A summary of representative inter‐annual snow stratigraphy from different terrain categories is also presented. © 2013 Her Majesty the Queen in Right of Canada. Hydrological Processes. © 2013 John Wiley &amp; Sons, Ltd.

Prediction reliability, quantitative differences and spatial variations of erosion models for long-range petroleum and gas infrastructure

The main goal of this study was to assess the prediction reliability, the quantitative differences and the spatial variations of the Morgan––Morgan–Finney (MMF) and the Universal Soil Loss Equation (USLE) erosion prediction models along the 442-km-long and 44-m-wide Right-of-Way of Baku–Tbilisi–Ceyhan oil and South Caucasus gas pipelines. USLE performed better than MMF erosion model by the accurate prediction of 61% of erosion occurrences. Paired-samples T-test with p-value less than 0.05 and bivariate correlation with the Pearson's correlation coefficient equal to 0.23 showed that the predictions of these two models were significantly different. MMF model revealed more clustered patterns of predicted critical erosion classes with a soil loss of more than 10 ton/ha/year in particular ranges of pipelines rather than USLE model with the widespread spatial distribution. The average coefficients of variation of predicted soil loss rates by these models and the number of accurately predicted erosion occurrences within the geomorphometric elements of terrain, vegetation cover and landuse categories were larger in the USLE model. This supported the hypothesis that larger spatial variations of erosion prediction models can contribute to the better soil loss prediction performance and reliability of erosion prediction models.

Method of the Snow Load for Design of the Low Rise Roof Structures in the Different Country Codes

Snow load is very important for the design of the large span roof structures in the cold region. The determine of the snow loads are influenced by many factors, such as wind, shape of the roof , terrain categories and so on, therefore comprehensive consideration of the transport and drift by the strong wind for design of the roof is very complex. Compared with other countries load codes, the China load code don’t detailed consider wind and snow interaction effect, the method of snow load for design has some further improved terms.

Wind tunnel test study on the wind pressure coefficient of claddings of high-rise buildings

The area-averaged most unfavorable wind pressure coefficients (MUWPCs) on various regions of building surfaces and the influence of the side ratio and the terrain category were studied based on wind tunnel test data of scale models of typical high-rise buildings with rectangular cross-sections. The negative area-averaged MUWPCs in the middle-height edge areas generally increased with an increasing D/B side ratio. The areaaveraged MUWPCs can be well fitted with a function of the average area reduced by the square of the building depth, D 2. In addition, no unique pattern was found for the effect of the terrain category on the MUWPCs.

Interference effects of two and three super-tall buildings under wind action

Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings, and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing. In this paper, mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings, especially the three-building configuration, are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements. Furthermore, the present paper focuses on the effects of parameters, including breadth ratio and height ratio of the buildings and terrain category, on the interference factors and derives relevant regression results for the interference factors.

Terrain Characterisation and Design Wind Profiles for Hong Kong

Numerous wind profiles at different locations in Hong Kong have been obtained from topographical model studies undertaken in the CLP Power Wind/Wave Tunnel Facility (WWTF) at the Hong Kong University of Science and Technology (HKUST). The results of these studies confirm that the impact of adjacent buildings and surrounding topography on the site wind profile is noteworthy and support the addition of more representative wind profiles to the current wind code of Hong Kong, Code of Practice on Wind Effects in Hong Kong 2004 (HK Wind Code 2004), so as to more accurately reflect the site wind characteristics in different regions of Hong Kong. Mean wind speed profile and turbulence intensity profile for three terrain categories, namely deep open sea, harbour-front and built-up, are proposed to be adopted in the wind code of Hong Kong. A case study of wind-induced loads on generic tall buildings with a square cross-section and varying heights demonstrated that the proposed wind profiles provide a more accurate ...

Performance improvement of fixed wireless access networks by conjunction of dual polarization and time domain radio resource allocation technique

AbstractThis paper considers the impact of dual polarization adoption on the performance for a fixed wireless access (FWA) network. The major limiting factor of the performance in these systems is co‐channel interference (CCI) originating from intracell and intercell concurrent transmissions. The proposed framework combines an appropriate time domain radio resource allocation technique with a dual polarization pattern to mitigate CCI and enhance the obtained signal to interference plus noise ratio (SINR). Simulation results present the performance of the proposed framework against various terrain categories and sector antenna characteristics. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Long-range Terrain Perception Based on Conditional Random Fields

Based on conditional random fields(CRFs),an online,adaptive,and near-to-far long-range terrain perception approach is proposed.First,the current image is segmented into superpixels,and feature vectors and terrain categories of near-field superpixels are incorporated into terrain database as learning samples.Second,superpixel features and spatial relationships between far-field superpixels are modeled by using conditional random fields and terrain database.Finally,terrain categories of far-field superpixels are inferred based on the on-line learned model parameters.Experimental results show that the proposed approach outperforms other existing methods in terms of accuracy,robustness and adaptability to dynamic environments.

Assessing the Relative Performance of Microwave-Based Satellite Rain-Rate Retrievals Using TRMM Ground Validation Data

Abstract Spaceborne microwave sensors provide critical rain information used in several global multisatellite rain products, which in turn are used for a variety of important studies, including landslide forecasting, flash flood warning, data assimilation, climate studies, and validation of model forecasts of precipitation. This study employs 4 yr (2003–06) of satellite data to assess the relative performance and skill of the Special Sensor Microwave Imager [SSM/I (F13, F14, and F15], Advanced Microwave Sounding Unit [AMSU-B (N15, N16, and N17)], Advanced Microwave Scanning Radiometer for Earth Observing System [AMSR-E (Aqua)], and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) in estimating surface rainfall based on direct instantaneous comparisons with ground-based rain estimates from the TRMM Ground Validation (GV) sites at Kwajalein, Republic of the Marshall Islands (KWAJ), and Melbourne, Florida (MELB). The relative performance of each of these satellite estimates is examined via comparisons with space- and time-coincident GV radar-based rain-rate estimates. Because underlying surface terrain is known to affect the relative performance of the satellite algorithms, the data for MELB were further stratified into ocean, land, and coast categories using a 0.25° terrain mask. Of all the satellite estimates compared in this study, TMI and AMSR-E exhibited considerably higher correlations and skills in estimating–observing surface precipitation. While SSM/I and AMSU-B exhibited lower correlations and skills for each of the different terrain categories, the SSM/I absolute biases trended slightly lower than AMSR-E over ocean, where the observations from both emission and scattering channels were used in the retrievals. AMSU-B exhibited the least skill relative to GV in all of the relevant statistical categories, and an anomalous spike was observed in the probability distribution functions near 1.0 mm h−1. This statistical artifact appears to be related to attempts by algorithm developers to include some lighter rain rates, not easily detectable by its scatter-only frequencies. AMSU-B, however, agreed well with GV when the matching data were analyzed on monthly scales. These results signal to developers of global rainfall products, such as the TRMM Multisatellite Precipitation Analysis (TMPA) and the Climate Data Center’s Morphing (CMORPH) technique, that care must be taken when incorporating data from these input satellite estimates to provide the highest-quality estimates in their products.

Across‐wind dynamic response of high‐rise building under wind action with interference effects from one and two tall buildings

AbstractSystematic studies on the across‐wind dynamic interference effects on two and three tall buildings are presented in this paper. It is found that surrounding and upstream interfering building(s) can significantly affect the across‐wind load on the interfered principal building. Generally speaking, two interfering buildings can cause more adverse dynamic effects on the principal building than a single one does. The results show that the maximum interference factor (IF) among three buildings increases 80% over that between two buildings in terrain category B which has been defined in Chinese load code for design of building structures; a noticeable difference of 29% of IF is also observed in terrain category D. Vortex shedding from the upstream buildings can lead to vortex‐induced resonance, resulting in excessive across‐wind loads on the downstream building. Although interference effects in terrain category D are much smaller than those in exposure category B, the maximum IF is found to be 1·83 in the case of three buildings with the same size in terrain category D and 2·27 in other configurations. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Power Output during the Tour de France

The aim of this study was to evaluate the demands of riding a "Grand Tour" by monitoring both heart rate and power output in 15 professional cyclists. SRM power output profiles (SRM Trainingsystem, Jülich, Germany) were collected during 148 mass start stages during the 2005 Tour de France and analyzed to establish average power, heart rate (HR) and cadence produced in different terrain categories (flat [FLT]; semi-mountainous [SMT]; mountainous [MT]). The maximal mean power (MMP) for progressively longer durations was quantified. Average HR was similar between FLT (133 +/- 10 bpm) and SMT (134 +/- 8 bpm) but higher during MT (140 +/- 3 bpm). Average power output revealed a similar trend (FLT 218 +/- 21 W [3.1 +/- 0.3 W/kg], SMT 228 +/- 22 W [3.3 +/- 0.3 W/kg], and MT 234 +/- 13 W [3.3 +/- 0.2 W/kg]). Cadence during MT was approximately 6 - 7 rpm lower (81 +/- 15 rpm) compared to FLT or SMT. During MT stages, the MMP for 1800 sec. was highest (394 W vs. 342 W) but the MMP 15 was lower (836 W vs. 895 W) compared to FLT. The data document comprehensively the power output demands during the Tour de France.

Automated classifications of topography from DEMs by an unsupervised nested-means algorithm and a three-part geometric signature

An iterative procedure that implements the classification of continuous topography as a problem in digital image-processing automatically divides an area into categories of surface form; three taxonomic criteria–slope gradient, local convexity, and surface texture–are calculated from a square-grid digital elevation model (DEM). The sequence of programmed operations combines twofold-partitioned maps of the three variables converted to greyscale images, using the mean of each variable as the dividing threshold. To subdivide increasingly subtle topography, grid cells sloping at less than mean gradient of the input DEM are classified by designating mean values of successively lower-sloping subsets of the study area (nested means) as taxonomic thresholds, thereby increasing the number of output categories from the minimum 8 to 12 or 16. Program output is exemplified by 16 topographic types for the world at 1-km spatial resolution (SRTM30 data), the Japanese Islands at 270 m, and part of Hokkaido at 55 m. Because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre-set criteria, the resulting classes are undefined and must be calibrated empirically by subsequent analysis. Maps of the example classifications reflect physiographic regions, geological structure, and landform as well as slope materials and processes; fine-textured terrain categories tend to correlate with erosional topography or older surfaces, coarse-textured classes with areas of little dissection. In Japan the resulting classes approximate landform types mapped from airphoto analysis, while in the Americas they create map patterns resembling Hammond's terrain types or surface-form classes; SRTM30 output for the United States compares favorably with Fenneman's physical divisions. Experiments are suggested for further developing the method; the Arc/Info AML and the map of terrain classes for the world are available as online downloads.

Wind Tunnel Study for Estimating Outdoor Ventilation in a Dense Low-Rise Building Area

To accurately estimate the natural ventilation of outdoor spaces surrounded by low-rise buildings using a wind tunnel requires correct representation of the natural wind regime combined with appropriately scaled building models and testing method. Existing outdoor ventilation studies are largely based on wind speed and estimated air change rates. Wind speeds mainly influence: peoples’ comfort, safety in pedestrian areas, the heat transfer between outdoor surfaces and airflow, and evaporation from wet surfaces. Studies of air change rates in outdoor spaces (for regions below surrounding roof height) are mainly related to the dispersion and/or removal of pollutants, moisture and hot air. This paper considers the application of wind tunnel studies to estimate the ventilation of outdoor spaces. It also considers the role of CO2 as a tracer gas for such studies. It concludes that to accurately estimate the ventilation of outdoor areas by means of a wind tunnel analysis, the natural wind properties in the wind tunnel model must be correctly related to the local terrain category. Buildings themselves can be represented by low cost small scale models constructed from expanded polystyrene. The CO2 tracer gas method is a safe, low cost and efficient quantitative test method for estimating the ventilation of outdoor spaces using a wind tunnel.

Sloth bear habitat use in disturbed and unprotected areas of Madhya Pradesh, India

In the North Bilaspur Forest Division in Madhya Pradesh, India, the sloth bear (Melursus ursinus) population is ecologically isolated, and some bears have developed aggressive behavior. Available bear habitat is highly fragmented and degraded and is interspersed with human habitation. In this study we assessed habitat use patterns of sloth bears with the goal of establishing management guidelines to reduce human–bear conflicts. Goodness-of-fit comparisons showed that expected use of each habitat category differed from habitat availability. Bear sign was most frequent in sal forest followed by land near water, sal mixed forest, and mixed forest. However, bear use of terrain categories was not different from expected use. A large number of bear dens were near water and human settlements. Bears regularly used more than 50% of observed den sites. Because of nearness to human settlement and degraded habitat, bears largely depended on villages for food, resulting in frequent human–bear encounters, some of which led to maulings and fatalities. One management priority is to protect highly preferred habitats of sloth bears. Bear population control and translocation of bears from isolated habitat patches to more suitable areas may be carried out simultaneously with education and awareness programs to conserve this species and to mitigate human–bear conflicts on a long-term basis.