Journal of Numerical Methods in Civil Engineering
Volume:3 Issue: 4, Jun 2019

In this article, a parallel computer program is implemented, based on Finite Element Method, to speed up the analysis of hollow circular cylinders, made from Functionally Graded Materials (FGMs). FGMs are inhomogeneous materials, which their composition gradually varies over volume. In parallel processing, an algorithm is first divided to independent tasks, which may use individual or shared data. Such tasks could be simultaneously executed. In this paper, a parallel Finite Element software is developed to perform the analysis on a multiprocessor system. The software parallelizes every time-consuming task of the algorithm, if possible. As an application, the analysis of a thick hollow cylinder, made from FGM, is performed to evaluate the capability of the software. The results show not only the software is authoritative of analyzing large-scale problems, but also it is 2.4 times faster than the serial version. Although such speedup is achieved using eight processors, the number of processors could be increased utilizing computer networks. According to the results, it could be concluded that the speedup increases when the number of processors increases. However, because of some technical limits and overheads such as data traffic among the processors, the speedup approaches its maximum for a certain number of processors.

This paper aims to investigate the effects of motion duration on the structural seismic demands, seeking potential correlations between motion durations and structural responses at several seismic intensity levels. Three seismic intensity levels with 100years, 475years, and 2475years earthquake return periods (RPs) are first considered for correlation computations. Spectrally matched ground motions are employed to isolate the contribution of duration from the effects of ground motion amplitudes and response spectral shape. Four single degree of freedom systems derived from four real reinforced concrete structures are studied, where both degrading and non-degrading equivalent SDOF systems are included for structural modeling. Results show a low positive correlation between motion duration and structural displacement demand, but this correlation increases with an increase in earthquake RP. It is also investigated whether or not this insignificant positive correlation has an impact on the incremental dynamic analysis curves. The spectrally matched ground motions are divided into two distinct groups in this case: short  and long duration ground motions. The comparison of incremental dynamic analysis of these two groups at the collapse limit reveals that long-duration ground motions can cause up to a 20 percent decrease in the spectral acceleration demand of considered structural systems.

According to the geographical location of Iran, it enjoys both arid and semi-arid weather, which has been the cause of water shortage problems. Therefore, water has been one of strategic importance in Iran. When the population dramatically increased in ancient Iran, the demand for supplying water also increased simultaneously and brought about the need for the invention of a new way for supplying water from the ground by using gravity. This invention was named Qanat, and it has an important role for managing groundwater in arid and semi-arid areas like Isfahan. Qanat is a sustainable way for water supply in many regions. As qanat is a cultural heritage which is still prevalent in some regions of the country, it has been of great importance not only in the history of Iran but also recognized around the world as an unprecedented invention. The unparalleled source of this ancient invention and its popularity has led to their preservation in Iran and also made it famous around the world. In this article, due to the importance of its cultural heritage, attempts have been made to find the routes of the qanat in Isfahan using available spatial layers such as flood way, stream, ditch, watercourse, bush, etc. based on fuzzy logic method. To this regard, three different scenarios of fuzzy logic rules are proposed and consequently three paths are obtained for each group of fuzzy rules. Then, the explored routes are compared with the qanat route that was found by geophysics institute in Iran. The similarity of the most desirable map with the actual one was 73 percent.

The prediction of groundwater level fluctuations is one of the most remarkable issues in water resources management, especially in arid and semiarid regions. The present study uses a numerical meshless method, named meshless local Petrov-Galerkin, to predict the groundwater level over a ten-year period. This method makes up for the shortcomings of mesh-dependent methods and increases modeling accuracy significantly. The study site is the unconfined aquifer of the Birjand plain with 190 groundwater discharge wells. The groundwater head is predicted based on two scenarios. The first scenario is defined as the discharge rate increased by 10% compared to the year before. Due to this scenario, the groundwater level in the aquifer is significantly reduced, especially in the central part (in the location of piezometer No. 8) and southwestern part (in the location of piezometer No. 5) of the aquifer, where groundwater table experiences 11.74 m and 35.80 m drawdown, respectively over a 10-year period. In that area, the high density of groundwater wells is the main reason for the depletion of the aquifer. Within the second scenario, the effect of rainfall rate is assessed by decreasing it by 20% and increasing discharge rate of groundwater wells by 5% compared to the year before. The results of this scenario show that the declines of groundwater level in the southwestern and central parts of the aquifer around 14.81 m and 5.05 m, respectively during the considered ten-year period.

Using fiber reinforced Polymer composite materials (FRP) in the rehabilitation schemes of vulnerable structural members is becoming more popular over the past decades. From the analytical point of view, the lack of numerical acceptance criteria in attaining the desired performance goal is a major restriction in employing this retrofitting method. The major parameter to control the seismic performance of frame members in nonlinear behavior is plastic hinge rotation angle (PHRA) especially for deformation-controlled actions. To predict accurate performance of RC columns, strengthened with externally-bonded FRP, there is an urgent need to discover PHRA as the acceptance criteria in a nonlinear static procedure stipulated in ASCE/SEI 41-13 standard. As indicated, the parameters such as FRP thickness to section diameter ratio (aspect ratio), the relative height of FRP and the FRP material properties have significant influence on the behavior of the members strengthened with FRP under combineed cyclic axial-flexural loading. For easy to use, analytical formulation is calibrated to evaluate PHRA as the function of the aforementioned triple parameters. An attempt has been made to simulate the RC columns with FRP laminate with general-purpose finite element software ABAQUS. Verification of the numerical method has been done by comparing numerical results versus existing experimental tests.

Recycling of waste materials has significant environmental and economic advantages. Plastic containers and steel slag waste solids were incorporated in Stone Mastic Asphalt (SMA) and the rutting performance of modified asphalt mixtures was investigated. Slab specimens with three percentage of Polyethylene Terephthalate (PET) including 3, 5 and 7 percent in two forms (PET particles and PET fibers) were prepared and wheel tracking test was performed. For various samples, rutting profiles were modeled by the Zhou model in the MATLAB environment. It was found that modified samples had better capability to resist permanent deformation. Induced rutting depth was the lowest for specimens modified with 5 percent PET followed by 7 and 3 percent, respectively. Moreover, adding PET in the form of fiber was more effective and exhibited the lowest damage ratio. Based on the obtained results, modified samples with 5 percent PET fiber caused 35 percent less rutting. According to life cycle ratio analysis, in average S-5P-F lasted 3.35 times more than the slag control sample.