JOURNAL OF CIVIL AND ENVIRONMENTAL ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2013 | Volume:43 | Issue:1 (70)|Papers Count:7

1. IntroductionRepair of concrete is an important aspect of maintenance of concrete structures. Durability of such repair and rehabilitation has become the biggest concern to the repair industry as well as to the end users. Substantial advances have been made in the field of repair materials, while the industry still has an unacceptable high level of defects and failures of concrete repairs. Recent investigations of repairs to bridge decks and other structures have indicated an overwhelming incidence of premature failures resulting from a range of factors. These factors include inappropriate selection of repair materials, poor workmanship, and inadequate characterization of substrate concrete [1].

1. IntroductionThe study of river flow is one of the most important cases in the designing of a water storage structure and management of extreme events such as floods and droughts.The rate of river flow depends on various parameters and the nonlinear relationship between them has caused river behavior to be dynamic, nonlinear and complex.

1. IntroductionDrought indices as important tools for drought monitoring are used to evaluate the performance of water resource systems in most parts of the world [1]. A lot of drought indices are developed at particular geographic and climate condition and given objectives. Consequently, the application of such indices is generally involved with considerable uncertainty in accurate and complete drought characteristic analysis in different places due to inherent complexity of the drought phenomenon and local climate condition.

1. IntroductionEach year, huge amounts of budget are spent for urban transportation projects, in order to improve traffic performance and reduce travel time. In some cases, they may produce adverse impacts on the whole network due to the lack of adequate studies. These adverse effects are in addition to financial and human resource losses and environmental impacts on urban communities. Usually in urban arterial streets, at-grade intersections are changed into grade-separated in order to reduce delays and increase the capacity of the intersection. But experiences have shown that the construction of grade-separated intersections in urban arterial streets may lead to increase travel time and delay in the adjacent network and intersections. Accordingly, deeper and more scientific studies are needed to address this phenomenon and to obtain a reliable criterion for assessing the performance of the network with at-grade or grade-separated intersection.

1. IntroductionNatural processes associated with rivers lead to meandering, degradation of the channel, erosion of banks and the migration of river bends. Bendway weirs are one of the structures which may be used to control these changes. Bendway weirs are generally built from stone and are usually constructed at the outer bank to deflect the flow and to prevent erosion of outer bank of river bends. These structures are straight extending riverwards from the bank that should be protected, but unlike the more familiar spur structures, they are intended to be overtopped by the design flow. The flow over the weir crest is supposed to be directed perpendicular to the plane of the weir, and so by appropriate placement of the weirs, the flow can be directed away from the bank.

1. IntroductionConcrete structures in aggressive environments greatly suffer from corrosion which causes a premature failure in their life span. Persian Gulf region is one of the most aggressive environments in which concrete structures need further attention in order to increase their durability and serviceability as well. In the present investigation, the half-cell potential and corrosion resistance of rebar embedded in concrete with different water to cement ratios (0.35, 0.40, 0.45 and 0.50) exposed to splash zones in Qeshm Island for 18 month ware studied (Fig 1). The results demonstrated that concretes with lower water to cement ratio perform better in terms of corrosion protection and process retardation.

1. IntroductionAging in asphalt mixtures is a phenomenon that starts from the time of construction in the factory and by passing the time, it will progress and finally it leads to stiffening of the asphalt and deterioration of the mixture. Asphalt undergoes hardening primarily due to two factors: loss of volatiles and oxidation of asphalt. The main loss of volatiles occurs in asphalt-aggregate mixtures between the time of mixing and final placement, when the mixture is at elevated temperatures. This is referred to as short-term aging. The longer, never-ending process of oxidation occurs partially throughout the short-term aging time frame, but much more extensively over time, while the mixture is in service and exposed to the environment. This is referred to as long-term aging [1]. Aging does not progress among different types of asphalts at the same rate, and also aggregate types are effective in this phenomenon [2]. Aging is not negative completely, because a small amount of this leads to improvement of the characteristics of the mixture [3].