2024-03-28T13:27:21Z
https://ijstc.shirazu.ac.ir/?_action=export&rf=summon&issue=189
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
The joint probability method of determining the flood return period of a tidally affected pond
In this paper a method is presented to determine the return period of flood levels within detention ponds used to store surface water runoff for affected coastal catchments. A simulation method is proposed in probability space based on derivation of the joint probability of occurrence of pond levels by combining the probability of the rainfall inflow hydrograph and peak tidal amplitudes. Each combination of events is then analyzed and the overall pond level statistics of the site produced. The results are to be used in an attempt to produce a rational approach to the problem of the design of detention ponds in coastal regions. The technique was applied to an existing tidally affected pond in Newport in the United Kingdom that is surcharged at the outlet due to the occurrence of tidal fluctuations. The results prove that traditional design assumptions that the peak inflow occurs at the peak high tide are pessimistic and lead to overdesigned systems
Rainfall
inflow hydrograph
peak tidal amplitude
detention pond
joint probability
2013
03
03
599
610
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Winter rainfall in iran: enso and aloft wind interactions
The effect of the El Oscillation (ENSO) phenomenon on winter rainfall in Iran was explored for the period 1951-1995. The interactions between this phenomenon, aloft wind in Tehran and the rainfall were also investigated. Positive and significant (at 1% level) correlations between the Troup Southern Oscillation Index (SOI) and February rainfall data were found for Bandaranzali and Noushahr located over the western half portion of the Caspian sea coastal strip. In February, the aloft wind velocity was observed in association with SOI. It was found that, in January, an increase (decrease) in wind velocity (500 to 200 hPa levels), generally, corresponds with less (more) than usual rainfall over the eastern half of the Caspian sea shores. The velocity data (in February) are also exhibited a meaningful relationship with the corresponding rainfall in various parts of the country. On a seasonal scale, winter rainfall in Iran tends to be slightly more (less) than normal for the episodes that SOI is positive (negative). Compared to the warm ENSO phase, the SOI-rainfall relationships were found to be stronger during cold periods. For most parts of the country, more (less) than usual winter rainfall has occurred during intense La (El ) events. Exceptional spells in which contrary effects of the ENSO events were observed were also identified.
Iran
ENSO
aloft wind
winter rainfall
2013
03
03
611
624
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
An investigation into the risk of piping at dams in the Urmia region, Iran
Six diversion dams in Shar-Chai, Nazlu-Chai, and Baranduz-Chai rivers in Urmia plain, Urmia, Iran, were selected to investigate their safety against piping. The analytical model was based on a PIPING code based on Sellmeijer’s design formula and a propabilistic method. A sensitivity analysis was undertaken using collected prototype and laboratory data to investigate the model’s compatibility and accuracy. The model produced reasonable results at the end of this analysis. The selected diversion dams were then analyzed for their probability of failure due to piping. The results were compared with the predetermined target probabilities of failure and showed safe configurations for most of the selected dams.
The partial safety factors for Sellmeijer’s design formula were calculated to be used when designing water-retaining structures for piping in Urmia region. The comparison of the Sellmeijer’s method with the empirical methods of Bligh and Lane showed that the Sellmeijer’s method requires a shorter seepage length and produces a more economical design for water retaining structures.
Piping
diversion dams
seepage length
probability of failure
safety factors
2013
03
03
625
634
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
An improved numerical algorithm to simulate the interaction of nonlinear water waves with a fixed large cylinder
The diffraction of nonlinear water waves around a fixed large surface-piercing body of arbitrary shape is solved in three-dimension numerically using second order perturbation theory. A time domain panel method is applied using uniform distribution of sources and doublets on each panel. Based on the above method, a computer program was developed in MATLAB environment and FORTRAN language. A simple radiation boundary condition was proposed by considering constant celerity for the scattered first and second order waves. Numerical results are presented for surface-piercing vertical circular cylinder on a flat bed with initial conditions corresponding to a Stokes second order wave field in the domain. Applying proposed radiation condition made the algorithm simpler and faster, so it reduced the memory storage and CPU time by factors of 1.5 and 1.1, respectively. Employing an efficient cylindrical panelization also reduced the number of panels by a factor of 4.8 relative to ordinary rectangular type panelization. The above modifications have reduced the computer memory storage and CPU time by factors of 14.5 and 7.4, respectively.
Nonlinear diffraction theory
perturbation methods
water waves
offshore hydrodynamics
2013
03
03
635
652
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Autographic rain-gage network design for iran by kriging
Autographic rain-gage networks are designed to provide the density and distribution of stations so that characteristics of the rainfall events both in time and over the region concerned can be determined with sufficient precision. The conventional rain-gage network design is simple random sampling, correlation of functions, and regression techniques. All procedures in generalized and theoretical approaches require some knowledge for the spatial correlation of rainfall processes. In this regard Kriging method, may fully define this spatial correlation. Therefore, the location(s) of the additional rain-gage(s), in an existing network, can be optimized on the basis of the estimated variance. The intensity-duration-frequency (IDF) curves from 64 autographic rain-gage stations in Iran were used in this study. One-hour (60 min) duration, ten-year recurrence , a key entry to IDFcurves, was used to analyze the adequacy of the present autographic rain-gage network. The results showed that at least six more rain-gages are needed for reducing the relative CVfrom the initial value of 100% to 40%. Three of them must be added in Isfahan, two in Kerman, and the last one in Sistan-Baluchestan provinces. Application of this procedure for the other entry of verified the adequacy of the new proposed network. However, the performance of these six additional rain-gages needs to be evaluated over time, using their real IDF curves
Geostatistics
spatial variability
variogram
intensity
Duration
frequency curves
2013
03
03
653
660
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Finite element modeling of flows in open-channel transitions
To analyze flows in channel expansions and contractions, two-dimensional, depth-averaged, unsteady flow equations are solved by using the two-step Taylor-Galerkin scheme. The 2-D, depth-averaged equations are written in a fully conservative form. The solution algorithm is based on an explicit time integration procedure which exploits the conservative properties of the governing equations. The unsteady flow model is used to obtain steady flow equations by treating the time variable as an iteration parameter and letting the solution converge to the steady state. The results of the mathematical model are compared with experimental data and other models. The capability of the model for handling mixed super- and sub-critical flows in a channel transition is demonstrated
Open channel flow
finite element
Taylor-Galerkin scheme
Unsteady flow
channel expansion and contraction
2013
03
03
669
680
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Prediction of sediment transport in littoral zones
In this paper, the longshore sediment transport in littoral zones is investigated. For investigation of sediment transport in the nearshore zone, the effects of waves, currents and topographical conditions of the coast, are considered. Linear wave theory is used for investigation of wave behavior. Governing equations of littoral current are continuity and momentum, and for calculating the concentration profile of suspended sediments at depth, convection-diffusion equation must be solved. A computer program called “PLSTP” (Prediction of Littoral Sediment Transport Program) is developed for investigation of sediment transport process in littoral zones. The finite difference method is used for solving the governing equations. The results show a good agreement between this model and existing measurements.
Sediment
longshore transport
wave
current
sediment concentration
2013
03
03
681
689
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Use of a self-cementing fly ash as a soil stabilization agent
The increasing trend towards electrical power generation through coal combustion has aggravated the problems associated with disposal of the fly ash produced as a by-product. Due to the pozzolanic properties of fly ash, it can be utilized as a soil stabilizer. In this study, the calcareous expansive soil in Cyprus has been stabilized with different percentages of fly ash and the results are discussed. Scanning electron micrographs (SEM) show that the new tobermorite minerals formed from the gelatinous reaction products are responsible for the long-term strength development of soils. Due to its mineralogical composition, unlike to the expected soil behavior, the long-term strength development of this soil is obtained below lime modification optimum (LMO). Increasingly, granular nature of the stabilized soils with time, results in a reduced water sorption potential. The use of fly ash with a small percentage of lime produces even more dramatic results. The risk of lime and fly ash treatment of sulfate-bearing clay soils is discussed. The findings encourage the consideration of fly ash as a possible alternative for the stabilization of calcareous expansive soils.
Calcareous
cementation
fly ash
lime
semi-arid
stabilization
strength
swell
2013
03
03
691
698
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Relating the usda and isss soil particle size distributions
Different systems are in use for texture classification of soils. The two most common systems originated with the International Soil Science Society (ISSS) and the United States Department of Agriculture (USDA). These systems use different particle size cutoff limits to define sand percentages, namely, 0.02mm to 2mm in the ISSS and 0.05mm to 2mm in the USDA. To merge data sets with soil properties reported in the ISSS with those reported in the USDA system, it is necessary to convert the ISSS particle size distribution (PSD) to the USDA PSD or vice versa. Previous research converted sand or silt of a soil sample but allowed the PSD statistics of the whole sample to change. We developed an approach that held the sample PSD statistics, the geometric mean particle diameter and the geometric particle standard deviation, constant in the ISSS and USDA systems. The standard errors of the difference between the two approaches were ±2.21% and ±4.14% for clay and sand conversions, respectively, and the error of conversion in the present method was ±0.2%.
particle size distribution
conversion
ISSS
USDA
2013
03
03
699
708
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Vertical and horizontal seismic microzonation by microtremor asurement
One of the methods by which one can state the dynamic characteristics of the soil of an area, is by the measurement and analysis of microtremors. In this paper microtremors have been measured on 143 sites located in the city of Tabriz, Iran. These sites were chosen on profiles that covered the city in two orthogonal directions. Three components of the microtremors were measured on sediments and associated rock sites. Spectral amplification with respect to rock has been implemented in addition to Nakamura method for HS/VSto interpret the results of measurements for calculation of the natural period of the ground due to horizontal dynamic loadings. Due to the importance of the vertical component of earthquakes, the vertical component of the microtremors has been also studied. On such basis a method was proposed to study the natural period of deposits for vertical ground vibrations.
Seismic microzonation
microtremores
vertical ground motion
site effects
2013
03
03
709
715
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Buckling modes of plate assemblies with variable thickness
A semi analytical procedure based on the bubble finite strip method for the elastic buckling problems of thin-walled structures with variable cross section thickness is presented. The method is programmed to investigate instability phenomena of plate assemblies with tapered-thickness cross sections. Numerical studies are included, including tapered plates in compression and shear, L-sections and channels with variable thickness under bending, compression and shear, and a tapered thickness stiffened plate under compression. The results computed by this method show the accuracy and efficiency of the method for the instability phenomena of thin-walled structures with variable thickness.
Bubble finite strip method
buckling modes
thin walled structures
variable thickness
2013
03
03
717
727
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2001
25
4
Uncertainty in the design and simulation of reservoirs
Insufficient information associated with historical data may require utilization of time series techniques, which in turn would result in record generation with sources of uncertainty. This type of effect can be evaluated by incorporation of parameter uncertainty into the data generation process. In this research the effects of parameter uncertainty incorporation and sequential reduction of record length on reservoir storage-demand and efficiency parameters (failure and total shortfall) were studied. The SPIGOT package was used for data generation for two reservoirs with high and low inflow variances. Based on the results, record length reduction had minimal effect on the storage of reservoir with low inflow variance, while failure and shortfall increased. Also incorporation of parameter uncertainty was more effective than 100% reduction of the record length. For the case of the reservoir with high inflow variance an irregular trend was observed in all cases
Uncertainty
data generation stream flow variance
reservoir design
reservoir simulation
2013
03
03
729
736