Analytical solution for buckling of asymmetrically delaminated Reissner's elastic columns including transverse shear

The exact analytical solution of buckling in delaminated columns is presented. In order to investigate analytically the influence of axial and shear strains on buckling loads the geometrically exact beam theory is employed with no simplification of the governing equations. The critical forces are then obtained by the linearized stability theory. In the paper, we limit the studies to linear elastic columns with a single delamination, but with arbitrary longitudinal and vertical asymmetry of delamination and arbitrary boundary conditions. The studies of quantitative and qualitative influence of transverse shear are shown in detail and extensive results for buckling loads with respect to delamination length, thickness and longitudinal position are presented. (c) 2007 Elsevier Ltd. All rights reserved

A proposal for integrated development of the water area\ud of the Brežice HPP\ud

The paper discusses an integrated development scheme of the future HPP Brežice reservoir area.\ud The primary goal of the development is to establish a gravel pit, which would furnish material for\ud the construction of the Lower Sava HPP chain, as the gravel found in the area is well suited for\ud concrete manufacture and embankment construction. Later, the gravel pit could be redeveloped and\ud filled with water to be used as an additional reservoir to the HPP Brežice reservoir, which would\ud significantly improve the siting of the plant by using the area for tourist and recreational purposes.\ud These include the creation of a kayaking trail and the development of forested peninsulas, walking\ud trails, wetlands and other tourist and recreational sites. Besides the development scheme proposal,\ud the study includes estimates on the volume of material extracted from the gravel pit, flow regime in\ud the reservoir during extreme weather changes, and different hydraulic solutions of flow control,\ud along with the calculations. During the construction of the Lower Sava HPP chain, the problem of\ud migration of aquatic organisms impeded by the dams became evident. Fishways are a feasible\ud solution; however, in Slovenia they are still not properly implemented, and they also mean power\ud loss for the HPPs. The paper represents an alternative solution of the fish passage as par

Effects of Changing Surrounding Conditions on the Thermal Analysis of the Moste Concrete Dam

This paper deals with the heat transfer analysis of the 63 years old and 60 metres high Moste concrete arch-gravity dam, located in NW Slovenia, which was performed after a new sophisticated monitoring system had been established, making it possible to perform continuous measurements of the temperatures of the concrete, of the water, and of the surroundings of the dam, i.e. the air temperatures and the amount of solar insolation. An equation defining nonlinear and non-stationary heat conduction in the case of a two-dimensional space, for a homogeneous isotropic solid whose thermal conductivity is independent of temperature, was solved numerically by means of the finite element method, taking into account appropriate boundary conditions. The latter involved the effects of changing conditions of the surroundings (i.e. shading, convection, and solar radiation) during the analysed period of 15 consecutive clear days in the summer. The results show that the measured and calculated temperatures of the concrete at different locations, and at different depths, were in very good agreement

The impact of hydroelectric projects on water regime

The purpose of this paper is to discuss the impacts of hydropower plants of Mavcice and Medvode on the water regime of the plain Kranjsko-Sorško polje, Slovenia. Both hydropower plants are situated on the Sava River between Kranj and Medvode on an aquifer layer of variable thickness. The hydropower plants have changed the river regime into a lake regime. As a result, the infiltration of the Sava into groundwater increased, while sediment transport was cut off. We prepared the water balance of the Sava River, a groundwater model of Kranjsko-Sorško polje using\ud Modflow and a comparison of volume of both reservoirs. We established the flow rate and directions of groundwater flow, a larger inflow at the Medvode hydropower plant, which is a\ud consequence of groundwater drainage downstream from the hydropower plant Mavcice, and\ud considerable volume change in the Mavcice reservoir. Due to sedimentation the infiltration of the\ud Sava is decreasing, which was demonstrated with measurements of piesometric pressures

Testing of Concrete Abrasion Resistance in Hydraulic Structures on the Lower Sava River

The paper deals with the issues of resistance of concrete linings to long-term abrasion loading caused by waterborne particles, particularly for the proposed hydro power plants on the Sava River in Slovenia. The main purpose of the research work was to define the possibility of forecasting the process of concrete lining wear on the Sava River dam structures based on the standard procedures of abrasion resistance testing. Abrasion resistance of concrete has been researched in accordance with the standard ASTM C 1138 and Böhme (DIN 52108) methods. The research work was based on a comparison between laboratory results and measurements of abrasion resistance of concrete under natural conditions by performing test plots in the stilling basin of the Vrhovo HPP. Concrete composites with different mechanical properties have been analysed within the research programme. The analysis showed a qualitative similarity of the level of concrete abrasion between laboratory simulations and measurements in the field, as well as suitability of the ASTM C 1138 laboratory method for the assessment of\ud abrasion resistance of concretes in the spillway of the HPP chain on the Lower Sava River

Historical, Hydrological and Hydraulics Studies for Sustainable Flood Management

Extreme events such as floods can endanger human lives and cause large economic damage. The Savinja River catchment is one of the most frequently flooded areas in Slovenia, Europe. In order to evaluate the impact of the proposed flood mitigation measures on the flood safety in this catchment, the combined hydrological and hydraulic modelling approach was carried out. The hydrological model Hydrologiska Byråns Vattenbalansavdelning (HBV-light) was used to perform hydrological modelling. The hydraulic calculations were carried out using the HEC-RAS 5.0.3 model in order to simulate the combined one- and two-dimensional unsteady flow. Using the calibrated and validated hydrological and hydraulic models, the impact of the proposed measures was assessed in the light of the sustainable flood management. Additionally, with analyses of the historical data and past flood events, we were able to investigate the characteristics of the extreme floods in this area and also downstream at the confluence with the Sava River. Moreover, it was found that the backwater effect has an important role on the water level and flood safety along the river reach, which is often neglected in the aspect of flood management

A Review of Measurement Calibration and Interpretation for Seepage Monitoring by Optical Fiber Distributed Temperature Sensors

Seepage flow through embankment dams and their sub-base is a crucial safety concern that can initiate internal erosion of the structure. The thermometric method of seepage monitoring employs the study of heat transfer characteristics in the soils, as the temperature distribution in earth-filled structures can be influenced by the presence of seepage. Thus, continuous temperature measurements can allow detection of seepage flows. With the recent advances in optical fiber temperature sensor technology, accurate and fast temperature measurements, with relatively high spatial resolution, have been made possible using optical fiber distributed temperature sensors (DTSs). As with any sensor system, to obtain a precise temperature, the DTS measurements need to be calibrated. DTS systems automatically calibrate the measurements using an internal thermometer and reference section. Additionally, manual calibration techniques have been developed which are discussed in this paper. The temperature data do not provide any direct information about the seepage, and this requires further processing and analysis. Several methods have been developed to interpret the temperature data for the localization of the seepage and in some cases to estimate the seepage quantity. An efficient DTS application in seepage monitoring strongly depends on the following factors: installation approach, calibration technique, along with temperature data interpretation and post-processing. This paper reviews the different techniques for calibration of DTS measurements as well as the methods of interpretation of the temperature data.Tento článek shrnuje různé techniky pro kalibraci měření DT

Dynamic monitoring as a part of structural health monitoring of dams

Safety of dams and other hydraulic structures is a complex procedure that must consider the individual characteristics of each structure and provide an insight in the structural health at every stage of the structure’s life cycle. Failures of structures permanently or temporarily retaining water may cause large economic damage, environmental disasters, and loss of lives. An engineering design should, therefore, guarantee maximum security of such structures or maximize their reliability not only in ordinary operating conditions but also under extreme hydrological load. By performing structural heath monitoring (SHM), the safety can be optimized, including the performance and life expectancy of a structure by adopting an appropriate methodology to observe the identified failure modes for a selected dam type. To adopt SHM to hydraulic structures it is important to broaden the knowledge and understanding of the ageing processes on hydraulic structures, which can be achieved by laboratory testing and application and development of novel monitoring techniques, e.g., vibration monitoring. In Slovenia, we are increasingly faced with the problem of ageing of dam structures. At the same time, we are also faced with changes in the environment, especially with the variability in time-dependent loads and with new patterns of operation on dams used for hydropower, with several starts and stops of turbines happening on a daily basis. These changes can lead to a decrease in structural and operational safety of dams. In this paper we propose a methodology where the dynamic response of concrete dams is continuously monitored in few locations on the dam using accelerometers, while all significant structural members are measured in discrete time intervals using portable vibrometers. We focused on run-of-the-river dams, which are a common dam type in Slovenia. The pilot case for the system is lower Sava River with a cascade of 5 dams used for hydropower

A dynamic calibration of optical fiber DTS measurements using PEST and reference thermometers

Temperature measurements are widely used in structural health monitoring. Optical fiber distributed temperature sensors (DTS) are developed, based on Raman spectroscopy, to measure temperature with relatively high accuracy and short temporal and spatial resolutions. DTS systems provide an extensive number of temperature measurements along the entire length of an optical fiber that can be extended to tens of kilometers. The efficiency of the temperature measurement strongly depends on the calibration of the DTS data. Although DTS systems internally calibrate the data, manual calibration techniques were developed to achieve more accurate results. Manual calibration employs reference sections or points with known temperatures and the DTS scattering data to estimate the calibration parameters and calculate temperature along the optical fiber. In some applications, manual calibration is subjected to some shortages, based on the proposed fiber installation configuration and continuity of calibration. In this article, the manual calibration approach was developed using the model-independent Parameters Estimation (PEST), together with the external temperature sensors as references for the DTS system. The proposed method improved manual calibration in terms of installation configuration, continuity of dynamic calibration, and estimation of the calibration parameters