AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2011 | Volume:42 | Issue:3|Papers Count:12

Concrete shear walls are the most common system resisting against seismic loads in the world. These elements carry the lateral loads by a combination of the axial, shear and flexural responses. Change in the seismic code requirements, subjecting intensive dynamic loads such as explosion or earthquake and other destructive effects make the shear walls weak for continuing service life. In the recent years FRP materials have attracted much interest. FRP application in retrofitting projects is appealing because of their unique properties. Nevertheless, a review on the previous studies shows that despite the squat walls, very limited analytical and/or experimental studies have been conducted on the FRP strengthening of the slender RC shear walls under monotonic loading so far. In this paper it is focused on the strengthening of boundary elements with FRP and it's effect on the wall behavior. The finite element software is calibrated and verified using available experimental data. Nonlinear finite element analysis of reinforced concrete walls is performed using damage plasticity model and tension stiffening effects. Results of the current study show the superior effectiveness of strengthening FRP composite layers on the behavior of the concrete shear walls.

Fluid flow simulation through a natural fracture is one of the most important and complex problem in Geomechanics. In general, various analytical and numerical methods are used to model fluid flow in fractures. Cellular automata method has been known as a powerful tool for simulation of complex phenomena such as fluid flow, fault movement and fracture production and propagation in a media. As a result, it can have predominant role on simulation of fluid flow in rock fractures.In this study, the modeling of fluid flow in ideal fracture has been carried out employing cellular automata method. For this purpose, a computer program has been developed and used in Fortran Power Station Domain. In this paper, the cellular automata method has been introduced and its application in fluid flow modeling described. The method of fluid flow simulation has also been presented and the results compared with available analytical solution.

Local site effects play a very important role in characterizing seismic and design ground motions because they may strongly amplify (or deamplify) seismic motions before reaching the ground surface.The purpose of this paper is to evaluate local ground response in ABASBAD region (around the TEHRAN MOSALLA). To perform dynamic analysis, soil layers dynamic characteristics is determined from seismic down-hole tests performed at 6 borehole stations. Bedrock Seismicity characteristics is evaluated and 15 accelerograms from various earthquakes around the world is selected. Considering the local topography and soil conditions, one dimensional equivalent linear analysis is performed and results is presented in form of microzonation maps of maximum ground acceleration and velocity, maximum amplification and site specific design spectra. The results indicate that presence of stiff shallow granular soil layers has no considerable affect on bedrock seismic motions and using Iranian earthquake code (2800) normalized design spectra for this site, is conservative at long periods.

In recent years, the use of nanoclays in different projects are reported. However, there has been very little attention on the application of nanoclays in geo-environmental projects. In this paper the possibility of application of nanoclays for retention of heavy metal (HM) contaminant were investigated. To achieve this objective a series of experiments were performed on bentonite, kaolinite and nanoclays samples. The buffering capacity, retention properties and XRD experiments show that among Cation Exchange Capacity (CEC), specific surface area, and carbonate, the main factor that controls the soil-HM interaction is carbonate phase. The CEC is the second important factor. Furthermore, after interaction of soil samples with HM the intensity of basal spacing of minerals in XRD decreased. In Cloisite 15A which had the minimum interaction with HM, the minimum reduction in peak intensity was observed (200 Cps). In addition, the contaminant retention of soil samples are in accordance to following order: Bentonite>CloisiteÒNa+>Kaolinite>CloisiteÒ30B>CloisiteÒ20A>CloisiteÒ15A.

In this paper, seismic performance of steel moment frames is investigated. Linear static and nonlinear static and dynamic of time history analysis have been performed on the usual and special steel moment resistant of 5, 10, 15 stories frames according to third addition of 2800 certification and new seismic rules and the performance of the members have bring under consideration. In the time history analysis, scaled seismographs of Northridge, Lomaprieta and Imperial valley earthquakes are used. At the end, special moment frames that were designed according to new seismic rules, have been designed on performance, has placed on limitation of certification goals.

This paper presents the results of experimental study on the effect of natural pozzolans: Jajrood Truss, Eskandan Pumice, Abyek Tuff, and Khash Pumice, on the ordinary structural concrete durability in chloride corrosion. Concrete specimens were made of three pozzolan replacements, and Rapid Chloride Penetration test, Electrical Resistance test, Half-Cell Potential test, water permeability test, and water adsorption test were conducted in different ages.Generally, the results indicate that natural pozzolans have positive effects on concrete specimen resistance to the chloride ions penetration and bars corrosion in comparison with concretes containing ordinary cement.

Bridge performance and health monitoring can be obtained from numerical models, site load test or combination of both. Load test approach illustrates bridge behavior with minimum inaccuracy without taking into account the assumptions and simplified approaches of structure analysis. In this research, the structure of Qale Morqi bridge was investigated in order to identify the bridge performance and defects that cause vibration to be induced into surrounding buildings. Numerical models of bridge were made and bridge model was loaded according to bridge Design codes. Bridge was instrumented with more than a hundred sensors, and then loading was implemented in static and dynamic steps. It was observed that the bridge vibrates intensively and instead of bending pattern, the first mode shape was torsional. Due to proximity of bridge first mode with peripheral building first mode, resonance is probable. In conclusion, some strategies for decreasing bridge vibration or preventing resonance in peripheral building are presented.

Numerical solution of depth averaged equations is one of the best ways for describing of two dimensional horizontal flow and behavior of flow around circular piers. In this paper, governing equations of turbulent shallow water flow are converted to discrete form using overlapping finite volume method on triangular unstructured mesh. The equations include to the depth average equation of continuity and motion for flow model and K-e equation for turbulence model. For simulation of scouring in cohesive bed, the results of the flow solver model are combined with the empirical relations obtained from the E-SRICOS bed scouring method which is a laboratory base method for determining rate of flow induced scouring.

The application of Reactive Powder Concrete for the construction of strategic structures such as shelters is under investigation by many researchers, because of their extremely high compressive strength. In this paper, the impact resistance of Reactive Powder Concrete and Steel Fiber Reinforced Reactive Powder Concrete has been studied by using the repeated drop-weight impact test, recommended by ACI Committee 544. The results have been analyzed using statistical methods.Results show that despite the very high compressive strength of Reactive Powder Concrete, its impact resistance is very low. The impact resistance of Reactive Powder Concrete is substantially increased by application of steel fibers. Kolmogorov–Smirnov test indicated that despite large variability of the results, impact resistance of Reactive Powder Concrete and Steel Fiber Reinforced Reactive Powder Concrete obtained from the repeated drop weight test had the normal distribution.