Limit Criteria of Post-Tensioned Thin Web Beams

A total of 45 partially prestressed post-tensioned thin web T-be answered tested to investigate their ultimates hear and flexural strengths and the service ability limit so reflection and crack width. The varying para meters included in the study are the amount of prestress, amount of supplementary nonprestressed reinforcements, prestressing tendons being bonded or unbonded, absence or presence of shear reinforcements and width of the web. Astrain compatibility method with the associated bond factors is presented for the ultimate flexural strength analysis of the beams. For prediction of the oreticalloads, material characteristics are taken at their ultimate with no materials safety factor associated

Managing Surged Furrow Irrigation

The behaviour of the infiltration process in an irrigation system is the most important feature that must be determined. Knowledge of soil infiltration, as it is a dominant physical process in surface irrigation, is crucial to the successful implementation of the scheme. This cannot be over-emphasized in surface systems, especially in furrow systems. This paper describes the infiltration behaviour of a furrow irrigation system under the surge flow regime. Infiltration behaviour over the various runs was studied, Suggestions for the implementation of such a management-oriented irrigation practice are discussed. The infiltration characteristics over the various flows are given

Evaluation of Infiltration in Furrow Irrigation Part 1: Recession Flow

Recession flow in a large field can be significant from the point of view of water-use efficiency. This is particularly important in the case where the furrow field is long, thus the receding flow can contribute to the irrigation of crops. Indeed, recession flow is very significant in the surge method of furrow irrigation. In the continuous mode of operation in very long furrows the amount of recession flow can be significant. Herein is presented the mathematical modelling of the recession flow. The analytical procedure is based on the kinematic wave approach used for the simulation of the advance-flow trajectory for furrows. This resulting recession simulation was found to be very useful for the evaluation of the basic infiltration rate in a furrow

Water Use Efficiency in a Furrow System

An existing volumetric balance approach in conjunction with the Kostiakov infiltration equation for determining soil infiltration parameters in a furrow is used to study furrow irrigation in the local environment. Other parameters required include furrow geometry, assumed subsurface profile and flow advance data. A set of adjacent furrows is used to indicate the performance of the field system. The procedure outlined here can be used to evaluate efficiency of continuous mode furrow irrigation. The spatial and temporal variation of infiltration characteristics of a soil are well known. As such, the performance of a furrow irrigation system which uses the soil as a medium of conveyance varies with the ever-changing infiltration behaviour. There is therefore a need for an evaluation procedure to determine water use efficiency which can be followed throughout the irrigation season so as to enable the irrigator to make any necessary changes to improve its performance. This determination of irrigation performance hinges very much on the correct evaluation of the infiltration process, in this case, in dynamic infiltration water flowing overland in small channels. An evaluation example is given

Stochastic Rainfall Model for Irrigation Projects

Stochastic rainfall models are concerned with the time of occurrence and depth of rainfall. Various rainfall models have been using different time scales. Daily rainfall models have gained wide applicability as being appropriate for use in detailed water balance and agricultural and environmental models. In this study a stochastic daily rainfall generation model was adapted for the Besut Irrigation Scheme located in Terengganu, Malaysia. The model simulates the sequence of rainfall occurrence using the method of transitional probability matrices, while daily rainfall amount was generated using a skewed normal distribution. Rainfall data from six meteorological stations located at the Besut Irrigation Scheme were used for this model. The model parameters were estimated from historical rainfall records. The model validation was then performed with a separate set of data. Results obtained showed that the model could be used to generate rainfall data satisfactorily

Decision support tool for water management of double cropping rice system: water allocation

Besut Irrigation Scheme is one of the main rice growing areas in Malaysia. This scheme faces water scarcity especially during pre-saturation period with the traditional water supply. It is necessary to evolve an innovative approach for water distribution and management. A decision support tool was developed to improve decision-making with respect to water release policies and timely water distribution in the large double cropping rice irrigation project. The tool was designed to focus on water allocation and release decisions in rice growing area. The decision support tool includes database management, a model management, a knowledge base, and a user interface. The knowledge base of the decision support tool was developed from the knowledge derived from field experts and from the results of the model management system. This paper presents an integrated decision support tool for generating alternative water allocation based on water availability. Thus, the final output is given in the form of specific water management actions for the irrigated areas

Evaluation of Infiltration in Furrow Irrigation Part 2 : Basic Infiltration Rate

Part 1 of this title was the simulation of the recession flow in a furrow. This part uses the recession simulation further to establish the basic infiltration rate in a furrow and, therefore, the infiltration characteristics in a furrow. Determining infiltration in a furrow is complicated by the dynamic flow nature of irrigation water, as well as the geometric shape of the channel, among other factors. The evaluation of this infiltration in furrows is important in order to evaluate the water use in such irrigation systems. The use of the Kostiakov equation in its extended form has been suggested for the determination of infiltration characteristics in a furrow. This equation, however, depends on the evaluation of the long-term basic infiltration rate, which can be determined practically by a long-term tedious inflow/outflow hydrograph of the irrigation event. An analytical method based on the kinematic wave theory and recession flow data is proposed here to evaluate the long-term basic infiltration rate pertinent to the correct evaluation of the infiltration flow characteristics in a furrow

Estimating earthen tertiary water channel seepage losses as a function of soil texture

Estimation of seepage losses is important in the management of an irrigation scheme because such losses significantly affect the efficiency of water usage. An attempt was made to determine seepage losses as a function of soil texture. Losses were measured three times, with the inflow-outflow method, for each of the 30 channels made of sandy loam, clay, clay loam, silt clay, and silt loam (six channels for each soil texture), and the soil-specific losses were determined. The soil-specific values were validated in terms of computing outflows. The maximum seepage of 294 mm day-1 was found for sandy loam, followed by 200, 185, 144, and 96 mm day-1 for silt loam, silty clay, clay loam, and clay material channels, respectively. Two empirical equations requiring soil type constants were also evaluated-namely, the Moritz formula and the Molesworth and Yennidunia formula. Investigation using these two equations for seepage estimation showed either underestimation or overestimation for the soil textures investigated. Therefore, these equations should be used after calibration, in accordance with channel conditions

Dam Overtopping risk using probabilistic concepts - Case Study: The Meijaran Dam, Iran.

Hydrologic risk assessment and uncertainty analysis by mathematical and statistical methods provide useful information for decision makers. This study presents the application of risk and uncertainty analysis to dam overtopping due to various inflows and wind speeds for the Meijaran Dam in the north of Iran. The procedure includes univariate flood and wind speed frequency analyses, reservoir routing, and integration of wind set-up and run-up to calculate the reservoir water elevation. Afterwards, the probability of overtopping was assessed by applying two uncertainty analysis methods (Monte Carlo simulation and Latin hypercube sampling), and considering the quantile of flood peak discharge, initial depth of water in the reservoir, and spillway discharge coefficient as uncertain variables. The results revealed that rising water level in the reservoir is the most important factor in overtopping risk analysis and that wind speed also has a considerable impact on reservoirs that are placed in windy areas

Measuring the geographic coverage of methadone maintenance programme in Hong Kong by using geographic information system (GIS)

<p>Abstract</p> <p>Objective</p> <p>While access and utilization form core components in assessing the effectiveness of a health service, the concept of coverage is often neglected. In this study we propose to develop a GIS-based methodological framework for the measurement of district-based geographic coverage to examine the service effectiveness of methadone treatment programme (MTP) in Hong Kong on a regular basis.</p> <p>Methods</p> <p>To overcome the incompatibility of spatial units, population data and data of heroin addiction of the year 2001 are interpolated by population-weighted and area-weighted algorithms. Standard overlay and proximity analytical functions are used to delineate altogether 20 accessible zones around each methadone clinic at a fixed 1.5 km Euclidean distance. Geographic coverage here is defined as the percentage of heroin addicts covered by a methadone clinic within the accessible zone by district.</p> <p>Results</p> <p>A total of 6413 out of 11000 reported heroin addicts are found geographically covered. The average geographic coverage in Hong Kong is 44.6%, with the figure varying from 0% to 96% by district. One district having no clinic results in 0% coverage whereas another without a clinic yields 15.3% coverage from the clinic in adjacent district. Maps illustrating district-based geographic coverage are generated.</p> <p>Conclusion</p> <p>As continuous data collection is required for a monitoring system, the simplified approach facilitates the handling of large volume data and relevant data analysis. It is concluded that the number of methadone clinics is as important as their locations. Geographic coverage could become an important consideration for monitoring harm reduction.</p