Computation of temporal variation of clear water scour is important for the design of bridge foundations. Previous studies conducted for determining equilibrium scour depth at bridge abutments indicated that very long flow duration was needed to achieve equilibrium scouring situations. However, the corresponding durations in the prototype conditions may yield considerably greater values than time to peak of the design flood. Therefore, there is a need to estimate the temporal variation of scour depth. An experimental study was carried out to observe temporal variation of scour depth and contours around vertical-wall and wing-wall abutments. The results of the experiments have been interpreted. A semi-empirical model has been developed for determining time-dependent variation of clear water scour depth at vertical-wall abutments. This approach is based on the application of sediment continuity equation to the scour hole around the vertical-wall abutment. To this end, time-dependent geometric features of the scour hole were investigated and a recent sediment pickup function was used to formulate the rate of sediment transport out of the scour hole. The results of the proposed model were compared with those of some empirical models. The findings of the model agree well with the experimental results.

Traditionally, destructive methods such as coring are used for the condition assessment of an existing concrete structure. Although these methods may yield valid data about the corresponding concrete section, they are quite expensive and time consuming. More important than these, destructive methods damage the structure being investigated and these points usually become focal points for further deterioration. For all these reasons, only a few samples can be collected from a structure and this results in a poor representation of the complete structure. The impact-echo technique is one of the most suitable non-destructive test methods that may be used on concrete for thickness determination or for investigation of possible delaminations in the internal parts of a concrete structure without damaging the surface. It has been observed that reliable results can be obtained quickly. Unlike pulse-echo tests which are commonly used on steel, testing a heterogeneous material like concrete requires the use of low frequency sound waves as in impact-echo, in order to mitigate the effects of paste-aggregate interfaces or small air voids. This method may be used to locate internal cracks or large air voids existing in concrete. It is known that impact-echo has been used successfully on structures with varying geometries and various purposes such as evaluation of concrete pavements, retaining walls and other reinforced concrete sections. Besides the investigation of the internal state, it may also be used when the other side of the section cannot be reached, as in the case of concrete pavements, in order to find the thickness of the section. This is especially important for quality control and for cost calculations. Research conducted in this thesis study was concentrated on the thickness determination of existing concrete pavement sections, produced in the laboratory with dimensions of 1500 x 2000 mm four and varying thicknesses, and the accuracy associated with these results. In order to correctly determine the sensitivity, several other parameters were investigated and optimum ranges were determined for these to be used while on a field test. Among these factors were the steel impactor size, accuracy related to the data acquisition, distance between the impact point and the transducer and the location of the test point. Finally, the accuracy of the impact-echo method for concrete pavement applications was studied. By observing the large number of data points collected, it was found out that an average error of 1.5% exists for a single impact-echo reading regardless of section thickness, but this value reduces to 0.6% when the average of all test results is used while determining pavement thickness. Results of this study show that the impact-echo technique is reliable and may be used with success for the thickness determination of concrete pavements and for locating internal voids.

Within the scope of this research, factors contributing to the decline and failure in the Turkish construction industry are examined by the aid of a broad literature review and a Delphi Study conducted among respondents selected to be civil engineers who experienced organizational decline and/or bankruptcy throughout their professional lives. Based on the identified factors and their interrelations, Analytical Network Process (ANP) is used to quantify the relative importance of these factors on &ldquo / Organizational Decline/Bankruptcy of the Turkish Construction Companies&rdquo / . Organizational Decline/Bankruptcy evaluation and prediction model to be used by the construction company managers as a decision support tool is constructed. As a result of the ANP analysis, importance of management competency and companies&rsquo / intangible resources such as organizational knowledge and its technical and technological capabilities came out to be the most important factors effective on the fate of the company to success or bankruptcy whereas external factors such as economic and political changes / which are effective on all kind of industries commonly, occurred to be the least effective factors that directly affect business failure.

In construction industry Gantt charts, network methods and Line of Balance (LOB) methods are generally used for planning and control of projects. Networking techniques such as Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT) require technical knowledge and could be difficult to implement without proper scheduling background. Gantt charts and LOB techniques are usually easier to implement, however, similar to network techniques these techniques lack visualization. A graphical based scheduling and progress control method could improve existing techniques with visualization so that schedule information could be understood easily by the project participants. Geographic Information Systems (GIS) can be helpful for improving the traditional scheduling methods by utilizing spatial information. In this study, a prototype Global Positioning System (GPS) and GIS based LOB method is proposed. To illustrate the benefits, the proposed method will be applied to a pipeline project.

In order to evaluate a project as successful or not, initially, the questions of &ldquo / what are the factors affecting the success&rdquo / and &ldquo / according to whom and which criteria should the success be measured&rdquo / should be answered. Both the factors and their influences vary depending on a project&rsquo / s specific characteristics, different environmental factors affecting it, and different parties involved. These factors are not independent of each other and the interrelationship between them should be investigated as a whole in order to model the project success. Moreover, parties involved in a project usually have different objectives and the performance indicators used to measure project success differ according to company priorities, preferences and attitudes. Thus, there exists a need to develop a project success model that contains the interrelationships between factors such as risks, decisions, and strategies, project success criteria, objectives and the relations of the factors with the objectives. A cognitive map (CM) is a strong visual tool to reflect the beliefs and knowledge of people about a situation or domain, identifying the causes, effects and the relations between them. This qualitative technique being enhanced by quantifiable properties makes it appropriate to be utilized to model the project success. As a result, the objective of this study is to demonstrate the application of CMs as a powerful tool for modeling project success. It is hypothesized that CMs can be effectively used to model the factors affecting success of a construction project, to reflect the interrelations between project success factors, to demonstrate the different objectives of parties involved in a project and show how the project success can be defined differently, by different parties. This technique is applied to a real construction project realized in Turkey. CMs of two consortium contractors and client organization involved in the project are constructed and the differences between the perceptions of three parties are revealed by content and structural analyses. Finally, the benefits and shortcomings of using CMs for modeling project success are discussed by referring to case study findings.

Bridge failures are generally resulted from scour of the bed material around bridge piers and abutments during severe floods. In this study, scour phenomenon around bridge abutments and collars, located at abutments as scour countermeasures, were experimentally studied. The experimental study was carried out under clear-water scour conditions with uniform non-cohesive sediment (having a grain size diameter of d50=0.90 mm). The experimental flume is a rectangular channel of 30 m long and 1.5 m wide filled with this erodible bed material. Based on the results of 97 experiments conducted during the study, the efficiency of various sizes of collars, which were used to reduce the local scour depth, located at different elevations around the abutments was determined. The results obtained were compared with previous studies, and the effect of the sediment grain size on the performance of abutment collars was emphasized. It was noticed that when the collar width was increased and placed at or below the bed level, the reduction in scour depth increases considerably. It was also found out that the change of the sediment size did not affect the optimum location of the collar at the abutment, which yields the maximum scour reduction around the abutment.

Fluidized bed combustion (FBC) ashes containing significant amount of free CaO and CaSO4 in addition to valuable inorganic acidic oxide ingredients such as SiO2, Fe2O3 and Al2O3 can be utilized as potential raw materials in the production of nonexpansive belite-rich calcium sulfoaluminate cement which is one of the special cement type of sulfoaluminate-belite cements having performance characteristics similar to those of ordinary portland cement besides lower energy requirements and CO2 emissions during manufacturing. Therefore, in this thesis study, possibility of producing non-expansive belite-rich calcium sulfoaluminate cement by adding FBC ashes in various proportions to the raw meal was investigated. For this purpose, a raw meal composed a mixture of limestone, bauxite, gypsum together with 10 wt % bottom ash and 15 wt % baghouse filter ash was prepared. It was sintered in a laboratory scale muffle furnace at temperatures of 1200, 1250 and 1300 &deg / C for various holding times. The results of chemical and mineralogical analysis as well as microscopic examination reveal that FBC ashes have the potential to be used in the raw meal due to the presence of characteristic mineral phases of this type of cements, i.e. yeelimite, larnite, ferrite and anhydrite, in the sample obtained at optimum sintering temperature of 1250 &deg / C for 60 min.

In recent years, the application of thermal analysis to study the combustion and pyrolysis behavior of fossil fuels has gained a wide acceptance because of its significance for industry and economy. In this thesis, the thermal and kinetic analysis of different origin crude oil samples are performed by two well-known thermal analysis techniques: Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG/DTG). The investigation of combustion and pyrolysis behaviors, kinetic analysis of oil samples and the determination of heating rate effect are the main objectives of this study. Six different crude oils from the Southeastern region of Turkey are analyzed throughout the study. All experiments are performed at different heating rates (5, 10 and 15&ordm / C/min) and air is used for combustion and nitrogen for pyrolysis experiments. In combustion experiments, TGA and DSC techniques indicate that the combustion process of crude oils studied is composed of two main reaction regions. These are low-temperature (LTO) and high-temperature oxidation (HTO) regions. In LTO, huge mass loss occurs (from 69 to 87 %) due to high amount of free moisture and volatile hydrocarbons contained in oil samples. Combustion reactions continue up to 900 K. On DSC curves, two exothermic regions of oxidation regimes are detected. Comparing TG/DTG and DSC curves, it can be understood that the mass loss under combustion is accompanied by exothermic peaks because of the oxidative degradation of crude oil components. As in combustion, two distinct reaction regions are revealed under pyrolysis for all samples. The first region indicates distillation and the second one is due to thermal cracking reactions occur at high temperatures and completed up to 840 K. As expected, lighter crude oils have relatively higher amounts of mass loss in distillation region as compared to heavier ones. Besides, residue amount and burn-out temperatures are higher for heavier oils with higher asphaltene content in cracking region. DSC curves for both reactions show endothermic effects. In combustion and pyrolysis experiments, it is noticed that higher heating rates are resulted in higher reaction regions. Distinguishing peaks of samples shift to higher temperatures with an increase in heating rate. Heat of reaction amount under DSC curves is related to asphaltene content and &amp / #730 / API gravity of crude oils. It is deduced that, when &amp / #730 / API gravity of crude oils decreases, the heat value of this reaction increases. The kinetic parameters are evaluated by different kinetic models and mean activation energies (Em) of samples are obtained. At the end, a correlation is established between Em and &amp / #730 / API gravity of oil samples. It is concluded that heavier oils have higher activation energy and Arrhenius constant values for each reaction region. Besides, it is proved that the activation energy is mostly insensitive to the heating rate.

In this thesis, we present our approach to add dynamism support to simulation environments, which adopts DEVS-based modeling and simulation approach and builds upon previous work on SiMA, a DEVS-based simulation framework developed at TUBITAK UEKAE. Defining and executing simulation models of complex and adaptive systems is often a non-trivial task. One of the requirements of simulation software frameworks for such complex and adaptive systems is that supporting variable structure models, which can change their behavior and structure according to the changing conditions. In the relevant literature there are already proposed solutions to the dynamism support problem. One particular contribution offered in this study over previous approaches is the systematic and automatic framework support for poststructural-change state synchronization among models with related couplings, in a way that benefits from the strongly-typed execution environment SiMA provides. In this study, in addition to introducing theoretical extensions to classic SiMA, performance comparisons of dynamic version with classic version over a sample Wireless Sensor Network simulation is provided and possible effects of dynamism extensions to the performance are discussed.

Traffic accidents which damage the safety of human beings are one of the most important problems due to their material losses and effects to human health. Although continuous improvements are made by the governments / losses of traffic accidents are still a significant issue all over the world. The usual studies realized so far are generally related with the accident prevention models. However, there has not been much research done concerning the situation after the traffic accidents happen. After occurrence of traffic accidents, determination of fault rates for each party involved in the accident is urgently important. The aim of this study is to develop an expert system that uses the knowledge of experts for determination of fault rates in traffic accidents. For this purpose, a detailed literature survey was performed to define the determinants influencing the fault rates of each party. In addition, required data, that is, expert-witness reports were taken from academicians. Classification of these data was done and critical factors affecting fault rates were determined. In light of the defined factors, flowcharts were developed for each type of traffic accident. Moreover questionnaire submitted to experts, was prepared to acquire knowledge of experts. The critical factors affecting fault rates were assessed with a quantitative way in questionnaire. The proposed Traffic Accident Expert System (TAES) is on the basis of the knowledge of experts. Quantification of fault rates can change from one expert to another. An expert system such as the one this thesis will propose will prevent these contradictions. In addition, the expert system quantifies fault rates faster and more consistent as well.