International Journal of Engineering
Volume:26 Issue: 2, Feb 2013

In this study, the performance of two aerobic sequencing batch reactors (SBR) in removing carbon and nutrient (N & P) from Faraman’s industrial estate wastewater (FIW) with flocculated and granulated sludge were compared. The comparison study was performed by varying two significant independent variables (aeration time and mixed liquor volatile suspended solids (MLVSS)). The experiments were conducted based on a central composite design and analyzed using response surface methodology (RSM). The region of exploration for the process was taken as the area enclosed by aeration time (6-24 h) and MLVSS (2000-7000 mg/L) boundaries. The results showed that the granulated sludge system was more efficient than the flocculated sludge system in removing the non- biodegradable COD (nbCOD), total nitrogen (TN), total phosphorus (TP) and other sludge characteristics studied. The performance of both systems was almost the same for COD removal in FIW with a maximum removal of about 70 %.

In this study, the elevated temperature flexural strengths of lightweight foamed concrete (LFC) containing fly ash (FA) and polypropylene fiber (PF) was investigated experimentally and statistically. The variables included were the temperature degrees (in a range of 20 to 600°C), LFC densities of 600, 800, 1000, 1200 and 1400 kg/m3 and additive content. Two mixes were made by replacing 15% and 30% of cement mass with FA and in other two series; PF was added to LFC mix, respectively by 0.2% and 0.4% of binder volume, one controlled mixture without additives was also produced. After being subjected to high temperatures, the flexural strengths of LFC have been investigated. The reduction of LFC flexural strength in temperature may be principally due to the formation of micro cracks at temperature above 93°C since the flexural strength is adversely influenced by cracks so that a severe strength loss was observed at 600°C and the flexural strength was only about 40% of its original value. Flexural strength of LFC with higher density achieved a higher value regardless to temperature. LFC flexural strength exposed to high temperature increased by contribution of FA and PF and this relative improvement for all series was the most pronounced for LFC with higher density and higher additive content. In addition, the applicability of some suggested models for normal concrete was examined for the flexural strength prediction of LFC incorporating different percentages of FA and PF at elevated temperature and the most reliable model was recommended for future researches.

Response modification factors (R-factor) are used in current seismic building codes to reduce earthquake forces associated with seismic design level to determine force levels. In recent years, many authors have shown great interest in the development of seismic structural systems and several theoretical and experimental studies have been conducted to investigate performance of dampers but little attention is given to the response modification factors of steel-braced frames equipped whit friction damper. In this study the effect of pall friction damper, as an additional element to the structure, on the parameters of seismic behavior of steel braced frame is evaluated. Along with the pushover analysis, dynamic analysis has been adopted to investigate the components of the behavior factor. For this purpose three steel frames of 5, 8 and 10 stories were analyzed without considering the existence of dampers, then each frame equipped with a friction damper of various slip loads-3, 8, 15, 20, 50 and 100 percentages of weight of the structure- is studied. The results show that behavior factor of chevron braced frame equipped with friction damper depends on its slip load and changing the R-factor can be an appropriate method to design steel frames equipped with friction damper.

In this paper, we have tried to predict earthquake events in a cluster of seismic data on pacific ring of fire, using multivariate adaptive regression splines (MARS). The model is employed as either a predictor for a sequence prediction task, or a binary classifier for a sequence recognition problem, which could alternatively help to predict an event. Here, we explain that sequence prediction/recognition, as two aspects of sequence learning, are not the same in general. We show that while both these approaches are plausible for earthquake prediction, the forecasting results indicate that MARS as a binary classifier outperforms the predictor MARS. The results clearly show how it is important to challenge a single earthquake forecasting problem from an appropriate point of view.

Progressive collapse is a kind of failure in which whole or large part of a structure collapse when a local damage occurs and distributes to other parts. Many researchers focus on the column removal analysis and study of the structure behavior under effect of gravity loads, so these investigations are mostly carried out on the tall building. Earthquake inspections indicate structural element can be damaged during earthquakes and this initial damage distributes to the other parts, so seismic progressive is proposed as a research issue. In this article, seismic progressive collapse of a steel-frame building is investigated. A local damage in a part of the structure was created by weakening a column intentionally so, the initial damage was navigated toward a part of structure then the lateral loads were applied to the model and the structure behavior subjected to seismic progressive collapse is evaluated. In the next step, the effect of differentiating length and numbers of spans in both directions is studied and finally structure failure pattern cased by seismic progressive collapse is obtained.

It is impractical and uneconomic to design a structure that remains elastic throughout severe ground motions. The main design philosophy is that minor structural damages are acceptable as long as the structure does not collapse. Hence, seismic base isolation of structures provides a better alternative in constructing seismic resistant structures. A fixed-base structure designed in accordance to seismic code provisions would be more prone to damage than their seismic isolation counterparts. This paper presents finite element analyses carried out to investigate the feasibility of applying locally produced elastomeric rubber bearing base isolators in seismically isolating non-ductile precast concrete structures from earthquake excitations. The precast wall structures were analyzed in terms of in-plane and out-of-plane isolation effects due to dynamic lateral loads. Ground excitations from three classifications of acceleration history based on different a/v ratios were used in dynamic analyses of the structures. The results showed that although the base isolator had successfully reduced most of the critical structural responses, it also compromised some other less crucial seismic behaviour of the structures. Current design philosophy for seismic base isolation should be urgently revisited. Imperative discussion and review of the feasibility in utilizing base isolators as seismic mitigation plan for seismic prone areas are presented.

Following the Northridge earthquake of 1994, a significant number of steel moment resisting structural systems were damaged. Several studies have been conducted to improve the seismic performance of steel structures and specially their beam-to-column connections. One of the proposed connections for special moment-resisting frames included AISC-358 is Kaiser bolted bracket moment connection, briefly named, KBB. The brackets in these connections are precast steel elements. In this study, the seismic behavior of moment connection KBB has been examined under standard loading history and near-fault loading history according to ATC and FEMA codes. The results show that KBB connection has acceptable seismic performance except for deep beams. In deep beams a high prying force may occurs in upper rows of the bolts. the main reason for such phenomenon is rigidity of the bracket. Moreover use of Tapered Wedge Shims reduces pre-tensioned force in bolts and increases pinch in hysteresis curve of specimens.

An intelligent method based on adaptive neuro-fuzzy inference system (ANFIS) for identifying Manning’s roughness coefficients in modeling of alluvial river is presented. The procedure for selecting values of Manning n is subjective and requires judgment and skill which are developed primarily through experience. During practical applications, researchers often find that a correct choice of the Manning n can be crucial to make a sound prediction of hydraulic problems. In this paper, an ANFIS model was set up to predict the Manning coefficient of alluvial river, with the mean bed particle size, mean flow depth and channel slope as three input parameters. The regression equations are also applied to the same data. Statistic measures were used to evaluate the performance of the models. Based on comparison of the results, it is found that the ANFIS model gives better estimates than the other empirical relationships. Also, a sensitivity analysis showed that mean flow depth has a greater influence on Manning coefficient than the other independent parameters in ANFIS model.

An increase in the flow velocity in flowthrough large porous media and deflection of flow regime from Darcy law causes a nonlinear relationship between hydraulic gradient and pore velocity of media. So many investigations have done previously in such Medias. One of the most important subjects in flowthrough large porous media is relationship between friction coefficient and flow characteristics which previously focused by some of investigators. On the other hands, most of the structures which are generated from such media like detention rockfill dams convey sediment contained flow. Therefore a detailed investigation is needed to study relationship between friction coefficient and flow characteristics in the sediment contained flowthrough. Also in most of previous studies the friction coefficient presented in Darcy-Weibach form which is not so common in the open channel flow between hydraulic engineers like manning coefficient. In this study required data was collected from four different sources. Three series of them were operated in the sediment contained and another one was operated in sediment free flowthrough mood. By using some basic equations about pore velocity and frictional coefficient new relationships were developed and calibrated for estimation of manning coefficient in open channel fowthrough porous media. It was found that modified Wilkins equation has a better estimation for manning coefficient in both of sediment free and contained flow rather than Ergun and Sedghi’s one. Also it was found that general trend of moody diagram for pipe flow is established in flowthrough large porous media such that by increase in the media Reynolds number, the manning coefficient limits to a constant value and become dependent to the media characteristics.

Modeling buildings response to blast and subsequent progressive collapse interested more and more researchers during the past two decades. Due to the threat from extreme loading, efforts have been made to develop methods of structural analysis and design. In this paper, progressive collapse capacity of steel moment frames was first investigated using alternate load path method, then a nonlinear dynamic analysis was carried out to examine dynamic response of the steel frames in blast and sudden column loss scenario. The structural response of the building under sudden loss of column for different scenarios of column removal, with or without external blast loading was assessed in detail. According to results progressive collapse potential are strongly dependent on location of column loss. Loss of column can affect overall response of structure under external blast loading. The obtained results provide better insight into the influence of sudden column loss on dynamic response of steel moment frames under blast loading.

This paper presents a new multi objective job shop scheduling with sequence-dependent setup times. The objectives are to minimize the makespan and sum of the earliness and tardiness of jobs in a time window. A mixed integer programming model is developed for the given problem that belongs to NP-hard class. In this case, traditional approaches cannot reach to an optimal solution in a reasonable time. Thus, we propose an efficient multi-objective hybrid genetic algorithm.we assign fitness based dominance relation and weighted aggregate in the genetic algorithm and local search, respectively.We take a variable neighborhood search algorithm as a local improving procedure in the proposed algorithm to the best individuals in the population of GA every specific number generations. To prove the efficiency of our proposed HGA, a number of test problems are solved. Its reliability based on some comparison metrics is compared with a prominent multi-objective evolutionary algorithm, namely SPEA-II. The computational results show that the proposed HGA outperforms the SPEAII algorithm.