2019-05-25T15:46:53Z
http://ijstc.shirazu.ac.ir/?_action=export&rf=summon&issue=186
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Fuzzy logic methodology to evaluate the service level of freeways basic segments
Based on fuzzy logic, a <span style="font-size: x-small;">methodology is developed</span>to evaluate the level of service of the basic segments of freeways. For this purpose, the four most important parameters known as the “characteristic parameters for evaluating the freeway service level” are being used. In this study, according to the approaches given in Highway Capacity Manual (HCM), as well information obtained by some highway transportation experts, some primary values of the parameters based on the corresponding membership functions are chosen. The methodology developed herein can be used as a basic approach in order to evaluate the service level of freeways. As a numerical study, three freeways are chosen. In order to show the effect of some important parameters such as speed, density, and so on, on the service level of freeways, parametric studies are carried out. It is found that the freeway service level significantly depends on the density of the traffic.
Fuzzy Logic
highway
freeway
service level
2013
01
25
281
288
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Repair and maintenance models for highway traffic control devices
The maintenance of highway traffic control devices faces problems based on the conventional and experimental methods. To resolve the above mentioned complexity, this paper sets forth mathematical models which can provide an optimum interval for non-operational devices, considering the financial limitations. For the optimized selection of various marking materials another model has also been presented.
<span style="font-size: x-small;">This paper has also tried to propose an appropriate management system for the maintenance of traffic control devices, along with the development of computer software for control devices, identifying the necessary procedure, time, tools, and manpower. The computer software and the mathematical models presented leads to optimization of the repair and maintenance operations</span>
Management
maintenance
repair
traffic control devices
signs
marking
2013
01
25
289
299
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Pullout behaviour of geogrids
In this study a comprehensive set of pullout tests were conducted on geogrid. Apart from measuring the interface properties (i.e., the internal friction angle and dilatancy angle) between the geogrid and two soils, some interesting results concerning the mechanisms behind the behavior of reinforcement in pullout tests were obtained.
Geogrid
pullout test
pullout resistance
Bearing capacity
punching shear failure
2013
01
25
301
310
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Prediction of the modulus of elasticity of high strength concrete
The prediction of the mechanical characteristics of concrete according to its components’ properties has been of great interest. In the current study, attempts have been made to extract some experimental models to predict the modulus of elasticity of high strength concrete based on some known characteristics of the concrete mix. To do so, 45 mix proportions including 5 different ratios of silica fume, i.e., SF/CM = 0, 5, 10, 15 and 20 percent, 3 water to cementitious materials ratios, i.e., W/CM = 0.24, 0.3 and 0.4, and 3 types of coarse aggregates, i.e., limestone, quartzite and andesite were selected. 540 cylindrical specimens were cast, cured and tested after 7, 28 and 91 days. Regarding different ratios of silica fume and different ratios of W/CM, the relationship of modulus of elasticity of coarse aggregate and concrete at different ages was discussed and some empirical equations were proposed. Special emphasis was paid on two proposed models, the comprehensive model and the simple model. The credibility of the models was verified using some independent experimental data.
high strength concrete
model
modulus of elasticity
silica fume
2013
01
25
311
321
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Modeling structure-actuator systems by neural networks
Neural networks are used for identification and solving the coupled equations of motion of a structure and its actuators. First, a neural network is trained to learn the behavior of the structure under study. Second, other neural networks are trained to learn the behavior of the actuators. Third, the trained neural networks of the structure and its actuators are interconnected to form a modular neural network which can be used in the analysis and/or in predicting the future response of the structure-actuators system. Such a modular neural network is called here the "neuro-modeler" or the "neuro-analyzer" of the system. The method is especially advantageous when it is desired to model the structure-actuators system based on laboratory data, and is applicable to both linear and non-linear structure-actuator problems. However, as a first study of the method, the emphasis of this paper is on linear problems. The method is tested on a SDOF frame with one actuator. The robustness of the neuro-analyzer is tested too.
Neuro-modeler
neuro-analyzer
structure
frame
actuator
linear
Non-linear
Control
emulator
2013
01
25
323
332
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
A new investigationon on the performance of rainfall IDF models
Rainfall intensity at different durations and frequencies (IDF curves) are widely needed in nearly all water projects, e.g., culverts, urban drainage, etc. However, IDF curves are reported at discrete durations and frequencies. To avoid subjective decisions, however, IDF models have been developed and are used universally. In this article, the performance of five commonly used IDF models is analyzed for three synoptic stations in Iran. The results show that there is an overall acceptable performance for all models, as far as the prediction of rainfall intensity from duration and frequency is concerned. However, from a probabilistic point of view, the non-negativity of a cumulative distribution function is not satisfied. Therefore, the non-negativity concept was added as a constraint. Consequently for this case, the performance of the models decreased considerably. It seems that all IDF models currently in use are not efficient, yet more efficient models must be developed to take into account all characteristics of the phenomena.
IDF models
CDF
Iran
2013
01
25
333
342
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Application of geostatistics for potential evapotranspiration estimation
This paper compares the evaluation of three geostatistical interpolation methods including ordinary kriging, residual kriging and cokriging for the interpolation of long-term monthly and yearly reference crop potential evapotranspiration (ET<sub>o</sub>). This study has been conducted in a region including Fars, Booshehr, Hormozgan, and Kohgilooye-Boyrahmad provinces. Long-term mean values of monthly and yearly ET<sub>o</sub> were computed from recorded meteorological variables at 119 weather stations using the Hargreaves-Samani method. ET<sub>o</sub> estimates and estimation errors were evaluated at 19 validation stations. In general, estimates were in good agreement with observed values for residual kriging and cokriging methods. Based on mean absolute error (MAE), mean square error (MSE), mean error percent (MEP) and root mean square interpolation error (RMSIE), the best method for Farvardin (April) is kriging and for Khordad (June), Tir (July), Aban (November), and Azar (December) is cokriging. For other months and for mean annual ET<sub>o</sub> the best method is residual kriging. It should also be noted that MAE, MSE, and MEP for Mordad (August), Mehr (October), Dey (January), and Bahman (February) are very similar for cokriging and residual kriging. With the exception of Farvardin (April), Ordibehesht (May), and Shahrivar (September), for the other months and for annual ET<sub>o</sub>, the deviation of cokriging estimations from a 1:1 line is less than kriging and residual kriging. In other words, the points from these methods are more spread out around the 1:1 line, but the band of the deviation in cokriging is less than the two other methods. Therefore, the best method for estimation of monthly and yearly ET<sub>o</sub>is cokriging, except in Farvardin (April), Ordibehesht (May) and Shahrivar (September).
Reference crop potential evapotranspiration
Ordinary kriging
residual kriging
Cokriging
2013
01
25
343
355
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
Estimating storm erosion index in southern region of I. R. Iran
A universal soil loss equation is used for predicting soil erosion. Rainfall erosivity (EI) in this equation is related to storm type, amount, and intensity, so it should be calculated from rainfall characteristics. In the present research, data of 13 recording rain gauge stations at the southern region of the Islamic Republic (I.R.) of Iran were analyzed and single storm, daily, monthly and annual erosion indices (MJ.mm.ha<sup>-1</sup>.h<sup>-1</sup>) were calculated and estimated by different simple models. For a single storm erosion index, the model EI=a P<sub>e</sub><sup>b</sup>/D<sup>g</sup>was modified. A coefficient of a for stations without snowfall and with an elevation of less than 1000 m, or higher than 1000 m, and b for stations without snowfall were 0.51, 0.21 and 2.0, respectively. The values of a and β for stations with snowfall and g for both types of stations may be determined based on the station elevation using the proposed equations. For a daily erosion index, a power function (EI=ahb) was derived (h is daily rainfall, mm). The value of a was dependent on station conditions, but an average value of 1.61 was obtained for b. For monthly erosion index, a simple model was proposed as
<span style="font-size: x-small;">where H is the elevation (m), and P<sub>m24</sub> is monthly, maximum daily rainfall (mm). The coefficients of the Arnoldus model were modified for the study region to estimate the annual erosion index using annual maximum daily rainfall (P<sub>a24</sub>, mm), monthly (P<sub>i</sub>, mm) and annual rainfalls (P, mm) as follows: </span>
<span style="font-size: x-small;"> </span>
<span style="font-size: x-small;">Using simple available rainfall data for 65 weather stations throughout the study region, the annual erosion indices were calculated by the above equation and an iso-erosivity map for the study region was prepared. </span>
Rainfall event EI30
daily EI30
monthly EI30
annual EI30
2013
01
25
357
363
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2005
29
3
The initiation of sediment motion in fixed bed channels
The transport of sediment in open channels is a complex process, and the physics of this phenomenon have not been completely explored. The majority of research work on sediment transport has been concentrated on beds formed of the same mobile sediment and only a few researchers have been concerned with sediment motion over fixed bed. This paper reviews the state of the problem and focuses on some practical points. Sediment threshold experiments were conducted in the two types of V-shaped bottom channels. Sand and gravel particle movements were considered and the relationship between flow discharge and bed shear stress, as well as channel bed slope were found at the threshold condition. Some practical and design equations were found to be more appropriate. It may be found that the effect of cross sectional shape on sediment threshold in fixed bed channels should be examined
sediment particles
incipient motion
fixed bed
V-shaped channel
boundary shear stress
2005
06
25
365
372
http://ijstc.shirazu.ac.ir/article_790_47faba0c99ddd944772390e5549cf31c.pdf