جستجوی مقالات مرتبط با کلیدواژه "riprap" در نشریات گروه "عمران"

Hydraulic phenomena are generally studied in the laboratory, so it seems necessary to use a method that reduces the number of experiments and saves time and time with good accuracy, and Taguchi method is one of these methods. In this regard (Dalir et al., 2021), Taguchi method and response level in the laboratory model of the pond were used to evaluate the efficiency of trapping and sedimentation and introduced the effective parameters. (Ranjbar-Zahedi et al., 2021) To reduce local scouring around bridge piers and to minimize the number of experiments, they used the 27 proposed Taguchi experiments to determine the optimal size and location of the structure (Atarodi et al., 2020) for Design of decomposition geometric parameters using Taguchi and Taguchi-GRA methods. In this study, in addition to the Taguchi property in reducing the number of studies in the study of the stable size of the riprap around the bridge piers (in the experimental part the number of experiments and in the neural network the number of responses), the optimization and prediction of Taguchi (a property that is less studied Taken.) Be used. Then, for validation, the results of Taguchi prediction were compared with the results of artificial neural network.

Taguchi method was studied as one of the experimental design methods based on reducing the number of experiments and proposing different but limited compounds for studies. Also, the analysis of the results has been examined using the mean mean graph and the signal to noise ratio (S/N) and the best combination of parameters has been introduced. Also, using the ANOVA table, the effect of the levels of each parameter and finally the effective parameters have been determined. In order to evaluate the results, the results of Taguchi method with the results of ANN artificial neural network were evaluated using the predictive property. It should be noted that Taguchi method has been used to adjust the adjustable parameters of the neural network for the phenomenon of stone crushing failure. In designing the stable size of the riprap around the bridge piers to protect against scour, 145 research laboratory data (Karimaei Tabarestani and Zarrati., 2013) have been used and according to these data, four parameters including flow rate in six levels, rock size, ratio The length to the width of the bridge pier and the angle of the pitch relative to the flow direction were examined at three levels. Also, the adjustable components of the neural network, including the four components of the number of neurons in the first and second hidden layers, the training function and the transmission function in each layer were examined at three levels. Finally, the results of the neural network were compared with the results of the Taguchi prediction.

In designing a stable size of riprap around bridge piers to protect against scouring, the Taguchi method with a reduction of 87 and 89%, respectively, compared to the results (Karimaei Tabarestani and Zarrati., 2013) and the complete factorial method, reduces the number of tests and saves time and money. have been. In the analysis of the results using Taguchi, it was found that the maximum flow depth for crimping stability will occur when the flow rate is 0.06 m3 / s, d50 is 0.00205 m, L is 35 m and θ = 20 is 20 Degree and in this regard the most effective parameter Q was introduced. Also, the best ANN artificial neural network based on the optimal combination introduced by Taguchi based on S/N diagram analysis, with three layers and correlation coefficient (R) equal to 0.971, will occur when the first and second hidden layers each contain 7 The neuron is a training function of trainlm and the transmission function of each layer is tansig. Also, according to ANOVA analysis, the most effective factor with a high rate of 95.07% participation is the transfer function. Finally, the Taguchi-assisted neural network with a detection coefficient of 0.94 performed better than the Taguchi method with a detection coefficient of 0.79 in predicting the results of designing a stable size of riprap around bridge piers to protect against scouring.

The results of the present study show that by using the Taguchi orthogonal array table and analyzing its results in the experimental section, the optimal combination of parameters can be determined with only a small number of experiments and the optimal solution can be predicted. Also, Taguchi method is a more suitable alternative to trial and error method for adjusting neural network parameters, and the results obtained from designing neural network parameters with Taguchi method are of good accuracy.

Scour at the shallow abutment foundation during floods is a common cause of bridge failure. In some cases, the bed is reinforced with riprap. There are several advantages and disadvantages of using this method. One of the disadvantages of using flush riprap aprons with the bed is that heterogeneous roughness (riprap versus native bed materials) alters the flow and manifesting as strong secondary currents. This flow can increase the shear stress and the scour depth in the unprotected bed. To study the subject, a conceptual model for determining the shear stress ratio in the unprotected bed in both with and without riprap has been investigated. In developing the conceptual model, numerical simulation tests in a flexible bed have been used. Then, the validation of Flow3D numerical model is presented and the mentioned model is used to simulate the flow in two cases with and without riprap in the rigid bed. In a rigid bed compare to flexible bed, computational and hardware costs are significantly reduced. The shear stress ratio in the unprotected bed is calculated and the quadratic polynomial equation is fitted for different roughness ratios. The coefficient of determination in each case indicates the appropriate correlation of the stress ratio in the two modes of flexible and rigid bed.

Scouring control in the downstream of the ski jump spillway is one of the most important issues faced by hydraulic engineers. In this study, an experimental investigation was done to evaluate the reduction of the maximum scour volume due to the combination of six-legged concrete elements (A-Jacks) in different hydraulic conditions. These elements were placed in the downstream of the ski jump spillway. The experiments included a single size of concrete element and two sizes of riprap with five discharges and three different tail-water depths. The change in depth of tail-water resulted in the spillway having free, semi-submerged and submerged states. The results showed that as the scour depth increased, the scour rate is reduced significantly. The simultaneous presence of concrete elements and riprap amid different hydraulic conditions caused a 100% decrease to the maximum scour volume when compared to the control tests. The use of A-Jacks when equated to riprap covered structures in a 100 m2 area indicated a 10% reduction in bed protection costs ( By use of Price list ).