نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و ششم شماره 1 (پیاپی 82، بهار 1395)

An important issue that is the reason of damages and collapses during earthquake is liquefaction of loose and saturated sands. After the reduction of soil strength, piles will behave like unsupported columns. So it seems that behavior of these piles and their analysis method isnt clear and suitable. For a better view a pile group is modeled using FLAC3D software that is connected to each other with a cap. Soil profile has three layers that middle layer is liquefiable while other two layers are not. In this research settlement of pile group in different values for liquefied layer thickness and pile length has investigated. Before the analysis of model, sensitivity analyses are carried out to achieve accurate results in less computing time.

Traditional management of water resources, which is often based on cost and benefit, is not sustainable approach; therefore reassessment of the former approaches seems necessary nowadays. Optimum reservoirs operation is one of the important water resource management problems. Present study has used the non dominated sorting genetic algorithm (NSGA-II) for multi-objective optimization of Sefidrud reservoir in North of Iran. The main goal of the study is to reach sustainable operation of the reservoir by considering these objectives simultaneously: supply of downstream demand, sediment evacuation and hydropower generation

Buildings and bridges on loose to medium dense sands are often built on piles foundation. If sand layer is saturated, liquefaction is likely to occur. In recent earthquakes, liquefaction and its effects have been reported as one of the main reasons for failure of piles and pile-supported structures [1]. When pile foundations are exposed to intense dynamic transverse loads during earthquakes, soil–structure interaction (SSI) plays an important role in allocating the response of pile foundations to lateral excitation [2]. Recent observations after major earthquakes have shown that extensive damages and destructions are still likely to be happened to pile foundations. This problem is significant particularly for pile foundations in loose saturated cohesionless deposits which are vulnerable to liquefaction and lateral spreading during seismic loading. Design procedures that have been developed for evaluating pile behavior under earthquake loading, have many uncertainties to be used for cases involving liquefaction. The performance of piles in liquefied soil layers is much more complex than that of non-liquefying soil layer as a result of the diminishing of stiffness and shear strength of the surrounding soil over time due to the increase of pore water pressure [3].By increasing the density of the soil the probability of liquefaction is reduced liquefaction. Soil compaction increases the soil relative density, modulus of elasticity, the angle of internal friction, and SPT-N of the soil. With regard to the relationships in soil mechanics science increase of relative density causes the bearing capacity of foundation to be increased, improves the soil properties, reduces the inappropriate subsidence, risk of liquefaction, and stabilizes embankments. High relative density is accounted suitable for geotechnical activities and provides the ideal conditions at least for static designs.

In this study, a three-dimensional finite element model of a partial orthotropic steel deck was created by ABAQUS software [1], and fatigue design load was simulated according to the AASHTO LRFD Bridge Design Specification [2]. The stress in points susceptible to fatigue cracks of rib-to-deck joint is investigated in five different cross-sections in model’s middle span and most sensitive region of fatigue cracks was identified. Then, the most sensitive region of fatigue cracks cross-section was simulated with a two-dimensional sub-model by compact meshing and domains of stress intensity factor were calculated with various depths of crack in point susceptible to fatigue crack by the numerical method, finally according to stress results and using the linear elastic fracture mechanics (LEFM) method Fatigue evaluation, including simulation of cracking growth, estimation of loading period and connection fatigue resistance, was done.

In this study, different mixtures containing Zeolite, Metakaolin and their combination with each other have been tested and the results have been compared with the control sample. Experiments include compressive strength, water absorption, water permeability, electrical resistivity, accelerated diffusion (migration) of chloride and corrosion.

Progressive collapse means gradual destruction of a part of a structure resulting from uncommon damage and expansion of this destruction to other parts of the structure. The damage can be caused by an explosion, earthquake, being hit by a vehicle or a sudden collapse etc. The damage is often applied to the structure dynamically and during a short time period. After the destruction of Ronand’s Building and engineers’ focus on progressive collapse, a wave of research on protective methods or reducing the structure’s potential against progressive collapse started. In the beginning the result was in the form of some changes in codes; however, after a few years when a couple of similar happenings occurred, separate codes were set to reduce or protect destruction. Two of these codes which deal with progressive collapse separately are Department of Defense (DOD) [1] and General Service Administration (GSA) [2].

With increasing population and necessity of building construction in the least time, we need to use the precast structures. However, due to some problems, the precast industry has not reached to its whole potential yet. The main problem is due to their precast concrete connections. The reduction factor is an important factor in linear analysis that indicates inelastic behaviors of structure such as resistance and ductility in nonlinear stage. In spite of many studies to obtain reduction factor of monolithic structures, we have a little information about this factor in precast ones. Hence, determining this factor is necessary for this type of structures. In this research, moment resistant precast systems in 4, 6 and 8 stories with 3 and 5 bays were investigated. The effects of two types of typical beam to column connections were evaluated. Nonlinear static pushover in three forms of triangular, uniform and modal was applied. The results indicate that precast concrete moment frames have reduction factor less than equivalent in site moment frames.

Anaerobic baffled reactor (ABR) consists of a series of continuous chambers divided into two upflow and downflow parts by a baffle. ABR could effectively purify high strength wastewater types with negligible surplus sludge and doesn’t need a settlement tank [1]. ABR is a treatment system based on its hydrodynamic characteristics and so, the hydrodynamic study of the current flow is an important issue about it. In this study, the hydrodynamic characteristics of the reactor are investigated. Also, the regime of passing flow is discussed.

The usual hazard of drinking water disinfection methods (by products and drug-resistant strains of bacteria) has prompted research on new methods for disinfection. One of these methods is applications of silver nanoparticles on different surfaces (metal, plastic and polymer). Anti-bacterial effect of silver had been known for a long time, but advances in nanotechnology was improved the efficiency of disinfection with silver. However, due to the harmful effects of silver in water, silver should be non-removable on a coated surface and it leaks into the water should be evaluated [1]. Part of Shiraz drinking water are provided from surface water resources (Doroudzan Dam), but chlorination of water can produce trace amounts of byproducts such as trihalomethanes (THMs). Therefore, it is necessary to use alternative methods such as nanoparticles. In this research, effect of silver nanoparticles which coated on polyurethane foams (PU) in drinking water was investigated. Polyurethane (PU) is one of the most attractive synthetic elastomers and is extensively used in biomedical applications due to its good biocompatibility and mechanical properties [2].