A. Melih Yanmaz

Bridge Scour Risk Assessment and Countermeasure Design

Statistical surveys conducted on investigation of reasons of bridge failures implied that the majority of bridges have failed because of excessive scouring at infrastructural elements. A bridge crossing an alluvial river should therefore be designed properly with special reference to possibility of this action at piers and abutments. On construction of a bridge, its scour criticality should be examined regularly throughout the service life spans to take necessary actions promptly. The Federal Highway Administration (FHwA) developed a methodology and software named HYRISK to evaluate annual risk of scour failure of an existing bridge in monetary values. A case study is carried out for a bridge crossing Fol Creek in the Black Sea region of Turkey using this methodology, which is integrated with additional assessment methods for checking conditions of bridge elements and channel in close vicinity. The scour criticality of the bridge corresponding to existing and possible future conditions is obtained, and a feasible scour countermeasure is designed using HYRISK and an economic analysis.

Uncertainty Quantification of Transient Unsaturated Seepage through Embankment Dams

AbstractSensitivity analysis is conducted to investigate the effects of uncertainty in hydraulic conductivity and van Genuchten parameters on transient seepage. To this end, a random number generator is used to generate random values from probability distributions of each parameter. The generator is coupled with finite-element software that handles seepage analysis in porous media. The Monte Carlo simulation approach is adopted for stochastic seepage analyses. The suggested method is applied on a homogeneous dam made of clayey sand. Uncertainties in each parameter are considered individually in different cases for rapid drawdown and rapid fill conditions. The results show that a variation of hydraulic conductivity has significant effects on transient seepage, and it is suggested that it should be treated as a random variable. However, the effects of the van Genuchten parameters on seepage are found to be insignificant, such that they can be treated as deterministic variables.

A Feasibility Study on Bridge Scour Countermeasures

Many bridges are destroyed or completely failed during floods due to excessive scouring around bridge piers and abutments. Safe bridge design is based on joint consideration of structural, hydraulic, and geotechnical aspects. This paper concerns the feasibility study of various types of countermeasures against scouring at bridge sites. The design criteria of these countermeasures are reviewed in terms of hydraulic, hydrologic, constructional, and economical requirements. Conditions of applicability of these countermeasures are evaluated in a case study and hydroeconomic analyses are performed for a bridge. Based on evaluation of the results of hydroeconomic analyses, combinations of riprap and grout filled bags are found to be appropriate measures for piers and abutments against scouring, respectively, whereas vegetation is observed to be applicable for bank protection.

Flood interaction with river crossings: a case study

A river engineer frequently tackles the problem of interaction of flood waves with river structures. Solutions of flood mitigation problems is usually complicated in these cases, because of considerable variation in hydrologic, topographic, geologic and local socio-economic conditions along the reaches of rivers. River crossings as well as the other river structures should be designed to withstand severe floods. During the rising stage of a flood, piers and abutments of bridges are subject to excessive scour which may result in damages or in complete failure of bridges. Besides, coarse material transported by water flow impacts piers and abutments with considerable dynamic loads. In receding stages of floods, however, floating objects like debris and the coarse bed material may be accumulated in the vicinity of river crossing, which lead to clogging of space between successive piers. In this paper, problems encountered at river crossings during floods and measures taken to increase the resistance and safety of crossings against floods are discussed on the examples from Turkey.

Probabilistic Evaluation of the Effects of Uncertainty in Transient Seepage Parameters

AbstractThis paper investigates the effect of uncertainty in the hydraulic conductivity and van Genuchten fitting parameters used for unsaturated flow modeling of transient seepage through embankme...

Evaluation Study on the Instrumentation System of Cindere Dam

The first hardfill dam in Turkey, Cindere Dam, has recently been constructed and a number of instruments have been installed. The aim of this study is to review the capability of the current instrumentation system and to observe the feasibility of possible alternative measurement systems. To this end, the current instrumentation system has been evaluated as a whole with reference to the parameters measured, instruments, and data acquisition system. Afterward, an alternative instrumentation system was developed by considering additional parameters and instruments to the current system. Furthermore, each instrumentation system equipped with manual and automatic data acquisition systems was considered. The comparison between the current and alternative instrumentation systems was also carried out in terms of technical and economical aspects. Although the current instrumentation system was found to be satisfactory according to the commonly used dam instrumentation practices, it was observed that the alternati...

Stability of Bridge Piers Subjected to a Probable Flood Event Followed by a Probable Seismic Event

AbstractScour-induced reduction in bridge stability can develop vulnerabilities during a probable seismic event. This problem has been typically addressed by researchers as if these two extreme eve...

Computer-Assisted Design of Diversion Weirs

A diversion weir is a headwork facility built across a river to raise water level and to divert water for various purposes, such as irrigation, hydropower generation, etc. In this study, a Windows-based, visual, and user friendly program named WINDWEIR is developed in Visual Basic.NET programming language for the optimum design of a diversion weir with sidewise intakes. The methodology used in the program is developed with reference to the design guidelines reported in the literature and in accordance with the common engineering practice. The program determines the overall dimensions and the total cost of a diversion weir. It also performs stability analyse s. The program is relatively flexible such that a design engineer can assess various dimensions of the structure by performing quick successive test runs to achieve an optimum solution among various al ternatives. An application is presented to demonstrate the use of the program.

Capacity and Benefit-Cost Relation for Concrete Gravity and RCC Dams

The relationship between capacity and total net benefit of concrete gravity and roller compacted concrete (RCC) dams is investigated using benefit-cost analyses. The total capital cost of such dams is equal to the summation of costs of construction, engineering and consultancy services, right of way, and relocation of structures. Operation, maintenance and repair costs are considered as the annual costs during the service life of the structure. Implementation of dams may lead to the achievement of several benefits, such as meeting municipal water demand, irrigation, hydropower, navigation, flood mitigation, water quality control, wildlife and recreational facilities, and positive impacts on the environment. In a case study, benefit-cost analyses have been carried out for 144 different concrete gravity and RCC dam alternatives that can be implemented at Cine Dam site, Turkey. Stability analyses have also been conducted for the proposed alternatives. The information obtained through this study can be used in decision-making for optimum size and type of a gravity dam.