Ferdowsi Civil Engineering
Year:2016 | Volume:27 | Issue:1|Papers Count:13

Coupled- shear walls are one of lateral load resisting systems in high and medium rise reinforced concrete buildings. The lateral structural response is exactly dependents on the shear walls behavior; therefore these elements must response well whenundergodifferent load conditions. The structures located in near- source region behave differently compared to those in near-source sites when subjected to earthquake. Therefore, it is very important to study the behavior of these walls under near-field seismic loads. To do this, after validation of the finite element model with experimental sample; coupled-shear walls in 10 and 20 story buildings with l/h ratio (l=span length and h =beam height) of 2/0.7, 2/1, 2/1.75 and were modeled in Abaqus computer software. The nonlinear time history analysis were carried out using two coupled near and far fault records and then the performance of walls were studied under near- field earthquake. The results show that the structural demands are higher for structures in near-field area in comparison to those for far- field. Besides, the effects of near- fault earthquake decrease when the coupled beam height and structural natural period increase.

In this research an algorithm based on Monte Carlo simulation is introduced to assess the risk of fire following earthquake in residential, industrial, educational, and governmental land- uses in district No. 20 of Tehran. The proposed algorithm consist of different modules including hazard analysis, vulnerability assessment, leak and break analysis of damaged pipeline, ignition probability analysis of the damaged pipeline, gas flow analysis of pipeline, ignition and consequence analysis. Based on the results of this research in the extreme state, four leaks, one break, and two ignitions were estimated. In addition, the total affected area of the four mentioned occupancies includes 25233 square meters and the total affected population of 146 people was acquired. By applying proposed mitigation measure, the mentioned results in the case of leak could be reduced by 75%, in the case of break reduced by 100%, and in the case of ignition it was reduced by 100%.

According to high height and weak tensile strength of materials in minarets, it is necessary to study the structural behaviour of minarets under earthquake loading. Therefore nine historical brick masonry minarets in Isfahan have been modelled and analysed by applying the nonlinear finite element method for two cases: 1) the whole minaret, and 2) only the outer shell. Results show that all minarets fail due to inclined tensile cracks in bricks and bearing of materials under scaled ground motion records based on the 2800 code. Parametric study has been done to find situations in which the minarets do not undergo failure. Parameters have been the height of minarets, tensile and compressive strengths of materials, failure criterion, and damping ratio. Conventional variation of the parameters does not prevent the failure of minarets due to earthquakes.

Due to increasing rate of flood risk throughout the world, including Iran, it is necessary to identify and prioritize flood- contributing areas for flood control activities. In this study, a new approach on Unit Flood Response method called "Flood Reduction method" was introduced which is applicable to prioritization of sub-basins for flood control activities. It was used to prioritize upstream sub-basins of Kardeh dam in Khorasan Razavi province. To conduct the study, the entire basin was divided into 24 sub-basins and physical characteristics of the basin and sub-basins were extracted using HEC-GeoHMS extension in ArcGIS. HEC-HMS model was calibrated using a rainfall-runoff event data and then, the 50- year design storm was simulated by this calibrated model. Prioritization of flood source areas was performed using the Unit Flood Response method and the Flood Reduction method was used to prioritize flood control activities. For the basin under study, the results showed that the sub- basin which has higher flood contribution is not necessarily the most appropriate sub-basins for flood control activities. In general, the prioritization results of the Flood Reduction method and those of the Unit Flood Response method were significantly different. The effect of rainfall duration on sub-basins prioritization was also studied. The results showed that rainfall duration has a significant effect on the sub- basins prioritization.

Many experimental studies have been conducted on development of the scour hole as a result of vertical jet impaction. Research has shown that aeration of the nappe flow in the model is much weaker than that in the prototype. Therefore, the influence of aeration on scour holes needs further study. Experimental investigation of the effects of air entrainment and tail water depth on the scour hole developed by a vertical submerged jet impaction is carried out in this study. The scour holes with and without air entraining conditions were investigated while hydraulic parameters like jet velocity and tail-water depth were kept constant. The results showed that air entrainment effectively reduces the scour depth and dimension. Variation of maximum relative depth and length of scouring i.e. ds/htw and Ls/htw versus tail- water Froude number parameter, i.e. Frtw were analyzed. By increasing the air concentration, maximum relative depth and length of scour hole reduced. The changes in scour hole dimension has a threshold. Results indicated that for Frtw more than 8.78, no meaningful effect on maximum scour hole depth (ds/htw) and length (Ls/htw) was seen for air concentration of less than 3.25 percent.

Recognizing of river flow pattern, deposition and erosion areas in meanders is highly important. Despite the limitations of the physical models in laboratory investigation of flow pattern in meanders, mathematical models can be helpful. In this research, RSM and LES turbulence models have been compared on sharp river bend of a laboratory flume using Fluent Software. The Laboratory flume is a sharp river bend established in hydraulic laboratory of EPFL. In order to investigate turbulence models, depth-averaged parameters were used. Moreover, to quantitatively examine those models, some longitudinal velocity profiles were selected and compared with measured ones. Results of longitudinal depth averaged velocities showed that RSM model is not able to precisely determine the important flow points. This model shows flow separation region within 85 degree and maximum width of 40 percent, though measurements indicated it was located in the region with maximum width of 60 percent of total width and approximately 75 degree. On the contrary, LES model suitably shows separation region. Besides, it better determines maximum measured depth averaged velocity situations rather than RSM model. Investigation of transversal depth-averaged velocity distinguished LES model from RSM as the better model and finally quantitative comparison of velocity profiles showed LES model is more accurate and presents more valid authentic results.

Application of structures of flow pattern modification is one of the erosion control methods in bends. Triangular vanes (triangular weirs) are among these structures which provide less scour depth compared to the other techniques such as spur dike. Since little information on erosion and sedimentation pattern around triangular vanes are available, this study was conducted to study the effect of structure effective length variations on erosion and sedimentation pattern. Therefore a triangular vane with different effective lengths (23.3, 17.5, 14 and 10 cm) was tested under different hydraulic conditions (Froude numbers 0.194, 0.214, 0.233 and 0.253). For all experiments, single triangular vane was installed with an angle of 30° relative to the upper bank and outside bend of flume in the 72° location which maximum scour depth is usually occurs. For all tests, flow depth was kept constant equal to 13 cm. At the end of each test bed topography was measured and from that the geometry of scour hole and point bar was measured. The results showed that maximum scour depth has been reduced by reducing of vane effective length. Variations of scour depth for low Froude numbers (0.194 and 0.214) was found to be more than high Froude numbers (0.233 and 0.253). Eroded sediments were transported downstream of vane and accumulated closed to the outer bank. The results showed that, in effective length 10 cm point bar distance from the beginning of vane was almost 0.8 times the effective length of vane for Froude number 0.233 and in effective lengths 14 and 10 cm was respectively, 1 and 2 times the effective length of vane for Froude number 0.253. In addition, minimum point bar distance from the outer bank has been reduced by reducing of vane effective length. For effective lengths of 14 and 10 cm the point bar distance from the outer bank was almost 1.5-2 percent width of the flume.

In this paper, a Fully Informed Particle Swarm (FIPS) algorithm is proposed for solving the Multi-mode Resource- Constrained Project Scheduling Problem (MRCPSP) with minimization of project makespan as the objective subject to resource and precedence constraints. In the proposed FIPS, A random key and the related mode list (ML) representation scheme are used as encoding schemes and the multi-mode serial schedule generation scheme (MSSGS) is considered as the decoding procedure. In particular, a new fitness function which reduces the average deviation from optimality and CPU- time is presented. Comparing the results of the proposed FIPS with other approaches using the well- known benchmark sets in PSPLIB validate the effectiveness of the proposed algorithm to solve the MRCPSP.

The mechanism of flow and sediment transport in channel bend is much complex. Because of secondary current, the sediment moves away from outer bank toward inner bank and therefore outer bank of the bend is one of best positions for lateral diversion. In this paper, the mechanism of sediment transport was simulated with SSIIM software in the U shape channel with lateral intake. In order to verify the numerical model results used in Montaseri's lab studies, The position of injection was upstream of bend and sediment injection rate was approximately is equal to 250 gr/min and Frude number is equal to 0.32. The SSIIM numerical model solves the Navier- Stokes equations with the k-e model on a three- dimensional. The bed load can be calculated Van Rijn' formula. The numerical model has been implemented at various times to see how the formation and development of bed forms in the U shape channel with lateral intake. The numerical results show that the prediction of development of bed forms, mechanism of sediment entry to intake, location of intermittent dune and location of sediment accumulation are in fairly good agreement with experimental data and the maximum error occurred in front of intake.

A transversely isotropic half- space with axis of material symmetry perpendicular to the free surface supports a flexible circular plate. The contact area of the plate and the half- space is considered to be both frictionless and unbonded (tensionless). The foundation is affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems is the target of this paper. With the use of ring load Green’s functions for both the plate and the continuum half- space, dual integral equations accompanied with some inequalities are obtained to model the complex boundary value problem. With the incorporation of the ring- shape finite element method, where its size gradually varies, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular plate and half- space. Some new illustrations are presented to portray the aspect of the anisotropy of the half- space.

In this paper, nonlinear behavior of composite steel plate shear wall systems, in which steel infill plate is strengthened by fiber reinforced polymer (FRP) layers, are experimentally investigated. Tests are designed to evaluate the effect of glass- FRP layers, layers number of GFRP and orientation of GFRP layers on the stiffness, shear strength, cumulative dissipated energy and other seismic parameters in the composite steel plate shear wall. Experimental models are scaled one-story steel shear panel model, with hinge type connections of boundary elements at four corners. In the first test, unstiffened steel infill plate is used for test. In the next four tests, strengthened steel infill plates are being used with different number and orientation of GFRP layers. Each test was performed under fully reversed cyclic quasi-static loading in the elastic and inelastic response zones of the specimens, in compliance with ATC-24 (1992) test protocol. The experimental results indicate that by strengthening infill steel plate yield strength, ultimate shear strength and cumulative dissipated energy can be significantly increased.

In this study, stability of geosynthetic reinforced soil retaining walls investigated using PLAXIS code that is based on finite element method. The effects of axial stiffness, length and vertical space between geosynthetic layers, internal friction angle of soil wall and cohesion of foundation on deformations of wall and maximum axial force of geosynthetic have been investigated. Results of analyses indicated that horizontal displacements and settlements of wall reduce with increase in axial stiffness, length and decrease of vertical space between reinforcement layers but there is a critical value for axial stiffness, length and number of geosynthetic layers which increase more than this certain value has not significant effect on reduction of settlements and horizontal displacements of wall. Also vertical and horizontal deformations of wall reduce with increase in internal friction angle of soil wall and cohesion of foundation but effect of these two factors on reduction of deformations for values more than a critical value are almost constant.

The two main approaches for estimating PMP are the synoptic and statistical techniques that their results are often different and selection of the appropriate option is difficult. In the most previous researches the frequency factor in the statistical method has been considered equal to 15 which this is the ultimate limit of frequency factor and the corresponding PMP is became too large. In the present research the PMP for 1 to 7 days durations in the Bakhtiari Dam basin was calculated using statistical and synoptic techniques, and the frequency factors in Statistical technique were properly determined. Results showed that the appropriate factor frequency in statistical technique for this area is about 6.1 which in this case, its results are almost the same as synoptic techniques. Based on the results of synoptical PMP and statistical PMP with factor frequency 6.1 at different durations, about 55 percent of the PMP have been observed, while for factor frequency 15, less than 30% of statistical PMP has been observed.