Scientia Iranica
Volume:21 Issue: 3, 2014

Evaluating the performance of a facultative aerated lagoon in a semi-humid region in Iran shows that the design parameters, which were derived from foreign references, used for dimensioning these types of wastewater treatment facilities, do not match the real values. A study conducted by Moradhasseli and Mohamadi proves that the design procedure, including choosing the initial design parameters has affected the performance of wastewater treatment plants in Iran [1]. S.R. et al. reported that the need for determining the exact values of qualitative and quantitative parameters for new design is obvious [2]. Of The need to review those parameters to achieve a more realistic and cost effective design is therefore obvious. In addition to suggesting more reasonable design parameters which may be of benefit while dimensioning these plants in Iran, computing the overall BOD removal rate based on the real qualities of the wastewater, which can be used in a theoretical approach for dimensioning, ensures a more accurate design compared with a design based on an assumed detention time as is currently usual in Iran. Accurately designing the facultative aerated lagoons widely used in Iran leads to cost savings because of decreasing the dimensions of the downstream lagoons, thus the obligation to apply the real quality parameters obtained in this study in new designs is proved.

Estimation of maximum scour depth is an important factor in designing structures that are embedded in rivers. Using a hydraulic model, the mechanism of local scour around bridge piers that are embedded in cohesive soils has been studied. Experiments were performed in a flume of 22m long, 0.77m wide and 0.60 m deep with a pier of 0.1 m in diameter. Also, three types of cohesive soils with different percent clay were used. While changing parameters, such as current velocity, flow depth, initial moisture content, clay percentage, and undrained shear strength in each experiment, the scour depths were measured.The measured data was adjusted by hyperbolic law. Using dimensional analysis, a relationship between the ultimate scour depth and effective parameters was developed. Finally, the ultimate scour depths obtained by experiments were compared with those calculated by empirical equations.

The erosion problem at Nnobi was investigated with a view to determining the types and major factors responsible for accelerated erosion in the area in other to develop a simple prediction model for erosion rate. Severe erosion of ground surface such as the unpaved road shoulders and bare soil surfaces in high density areas of South Eastern Nigeria is a common feature. For many years hydrologist and engineers have been beset with challenge of producing adequate drainage works to check the menace of erosion by overland flow. Six flume experiments were conducted where erosion rates were measured. The rainfall data for the past ten years were obtained and analyzed, a survey of the catchment area for each of the gully sites was carried out and soil samples were obtained from the eroding layers of the gullies. Analysis of the results show that the area experiences rainfall of high intensities, with intensities of up to 80mm/hr being recorded for a duration of 30minutes. The slope of the land is generally steep with slope gradient varying from 15% to 22% and the soil particles with very low organic and clay content, ranging between 0.2 to 0.4 to 1 and 6% respectively. A mathematical model of hill slope overland flow for Nnobi experimental watershed was obtained, using Saburo [1] equation to predict erosion rate,

Prediction of accident frequency based on traffic and roadway characteristics has been a very significant tool in the field of traffic management. The accident frequencies on 185 roadway segments of the City of Mashhad, Iran for the year 2007 were used to develop accident prediction models. Negative Binomial Regression, Zero Inflated Negative Binomial Regression, Support Vector Machine and Back-Propagation Neural Network models were used to fit the accident data. Both fitting and predicting abilities of the models were evaluated through computing errors values. Results show the NBR model, because of its low prediction and fitting error values, is the most effective model to predict the number of accidents. Although, the BPNN model has high fitting capability, but it does not have the prediction ability of the NBR model. Furthermore, the NBR is easy to develop and interpret the role of effective variables, in comparison with the machine learning models which have a black-box form.Marginal effect values for the NBR and ZINBR models and sensitivity analysis of the SVM and BPNN models reveal that volume to capacity ratio (V/C), Vehicle-Kilometers Travelled (VKT) and roadway width are the most significant variables. Increase in V/C and roadway width will decrease the number of accidents, however, increase in VKT and permission of parking on the right lane of the roadway can increase the crash frequency.

Shear connectors are used to avoid potential slipping between steel and concrete and slipping due to deformations on concrete plate. Many materials having different shapes and dimensions are tested as shear connectors. In this study, availability of earthquake resistant steel bars manufactured in the same length as headed studs are investigated. For this purpose, 4 push-out tests accomplished to the composite beams with profiled steel sheeting in which earthquake resistant steel bars are used as shear connector and 4 push-out tests accomplished in which headed studs are used as shear connector. Earthquake resistant steel bar is a steel reinforcement bar used in concrete and produced by a heating process during hot rolling with the ribs on it to increase the adherence between concrete and steel.It is abundantly manufactured in recent years with an increasing use in reinforced concrete constructions due to its advantages in terms of ductility, weldability, adherence, corrosion resistance and strength.In the experimental section, 8 push-out tests performed on 16 slab specimens with different slab height, different number and arrangement of shear connectors. As a result of the tests, earthquake resistant steel can be suggested to be used as an alternative material for the shear connectors.

Agreat number of studies on the vibration of plates subjected to moving loads are available which are gained by the moving force and moving mass modelling frameworks. As a result, evaluating the reliability of approximate simulation of a moving oscillator problem through moving force/mass would be of interest in engineering application. Therefore, in this article, transverse vibration of a thin rectangular plate under a traveling mass-spring-damper system is revealed by eigenfunction expansion method. Both moving force and moving mass modelling approaches are compared with the moving oscillator and various plate fixity cases and load trajectories are involved to present benchmark solutions. The spring stiffness range for which the plate response agrees closely with the corresponding moving force/mass analysis is recommended. The results elucidate that the moving mass can be considerably unrealistic in predicting the contact force of an undamped oscillator. Moreover, errors of orbiting force/mass simplification of the orbiting oscillator in predicting the resonant conditions of the plate vibration are not negligible.

In this paper, a new Hybrid Charged System Search and Particle Swarm Optimization, HCSSPSO, is presented. Although Particle Swarm Optimization (PSO) has many advantages, including directional search, it has also some disadvantages resulting in slow convergence rate and low performance. On the other hand, the Charged System Search (CSS) is a robust optimization algorithm which has been successfully utilized in many structural optimization problems. In this study, the goal is to incorporate the positive features of the PSO in CSS and make it more capable of solving optimization problems. The hybrid CSS and PSO is named HCSSPRO, and it uses the positive features of the PSO to further improve the CSS. In order to show the higher performance of the HCSSPSO, it is implemented and applied to some engineering problems. These structures are benchmark examples which are optimized by many other methods and are suitable for comparison.Results of the present algorithm show its better performance and higher convergence rate for the problem studied.

The present study aims to determine the hydrological change-year by evaluating the homogeneity of average annual stream flow data in Turkey. Pertaining to the years 1936-2005, change-year stream flow data from 74 stream flow gauging stations, which have no regulatory structure on the source side, and possessing a minimum of 39 years of data, from stream flow gauging stations located on 26 stream flow basins in Turkey, have been collected. By using the employed homogeneity tests, it has been attempted to detect the change year. Employed methods are the Buishand test, the Pettitt test, the Standard Normal Homogeneity test and the Von Neumann test. By comparing the results obtained from tests, it is aimed to detect the consistency of the change years in gauging stations. The change year could be detected in 16 gauging stations using three tests each every year, and 18 stations using 2 tests in the same year. It has also been ascertained that change years of stream flow are geographically closer to each other in western Turkey in comparison to the east. The reason for values in the west to be closer, with respect to both location and time, might be attributed to the precipitation characteristics and uniformity of measured data.

Impulsive water waves generated by landslides impose severe damages on coastal areas. Very large mass flows in the ocean can generate catastrophic tsunamis. Preventing damages to dams and coastal structures and saving lives of local people against landslide-generated waves have become increasingly important in recent years. Numerical modeling of landslide-generated waves is a challenging subject in CFD. The reason lies in difficulty of determining the interactions between the moving solids and sea water that causes complicated turbulent regimes around the moving mass and at the water surface. Submarine or aerial types of landslide can further complicate the problem. Up to now a number of numerical approaches have been proposed for predicting the behavior of flow during and after the mass movement. In this study a Lattice Boltzmann Method (LBM) based-code is employed for analyzing and simulating the impulsive water waves generated by landslides. Four experimental cases of submerged and aerial landslides have been modeled to investigate the efficiency and accuracy of the LBM code, and the obtained results are verified against experimental observations. The results indicate the capability of LBM in simulating complicated flow fields and demonstrate its superiority over numerical methods that have been used so far such as SPH and RANS.

The term progressive collapse«has been used to describe the spread of local failure in a manner analogous to a chain reaction that leads to partial or total collapse of a structure. Robustness is de ned as a fundamental property of structural systems to prevent damage propagation and to mitigate the potential of progressive collapse. In this paper, the progressive collapse capacity of steel moment-resisting frames was rst investigated using the alternative load path method, then suggestions are made for assessment of structural robustness, and the robustness of frames is quanti ed. According to the results, the robustness and progressive collapse potential of the frames varied signi cantly, depending on the location of the initial local failure and number of building stories.