نشریه مهندسی عمران فردوسی
سال سی و یکم شماره 4 (زمستان 1397)

In this study the experimental study was performed to determine the scour hole dimensions due to falling jets at the downstream of storage reservoir. The geometry of the scour hole depend to many parameters such as outflow discharge of gates (Qj), medium diameter of sediment (D50) and the confluence angle of jets at horizontal plane ( . In this study the effect of these parameters were investigated. Water jet falls from pipes with circular section and diameter of 1.25 inch into the downstream pound. The drop height was 95 cm. The downstream pound filled with 20 cm of non-cohesive sediments with medium diameter of 1.7 mm, 3.2 mm and 6.75 mm.  Experiments were carried out with different discharges at the range of 1.32 to 5.14 l/s. The results of this study shows that for all experiments a scour hole created at the downstream of the reservoir and with increasing discharge the scour depth (ds) increased. The sensitive analysis of the proposed general equation showed that when jet discharge, sediment diameter and the confluence angle of jets at horizontal plane (  changed ± 20%, the relative scour depth changed 12.33, 6.23 and 34.03 %, respectively.

This paper aims to design a special active control system based on the proposed genetic algorithm for active control of structures. In this trend, by connecting the actuator to the structure’s freedom degrees and using the proposed method to find the proper control forces, the structure’s movement is controlled and minimized. The nodal displacements are calculated by solving the dynamic equations of motion at each time step. By evaluating these responsese and utilizing the proposed cost function, the proper actuator’s forces are determined during the prediction-correction process of the genetic algorithm. Moreover, due to the nature of the prediction-correction of the genetic algorithm method, the effect of time delay on the control scheme is mentioned. To illustrate the effectiveness of the proposed method for controlling the oscillations of the structure, three numerical examples are solved and the results are compared with the linear differential equation (LQR) method. Accordingly, the proposed method has a very good ability to control the oscillations of the structure.

In this study, according to the high value of stone architecture in Iran, an investigation to improve mechanical properties on a type of limestone (Sandy limestone) used in Pasargadae were done by Nano Silicate (SiO2) as a consolidation material. Thus, some mechanical properties such as water absorption, water vapor permeability, porosity and resistance to against aging tests have studied by using UNE-EN standards and Ultrasonic velocity as well as changes in superficial strength by Micro-drilling. Results show the rate of water absorption and water drying decrease about %11 and water capillarity slightly changed. In contrast, water vapor permeability remained almost the same. But, the porosity of stone decreased %14 as well as %20 increasing the superficial resistance. Hence the improving two properties of the stone (porosity and superficial resistance) by applying Nano Silicate are the advantages of this kind of material in order to increase sandy limestone durability used at Pasargadae World Heritage Site.

Damages or cracks change the natural frequencies and the mode shapes of the structures. Therefore, the modal parameters could be used in damage detection or structural health monitoring techniques. Based on the knowledge of the authors, most researches in this field have been focused on one-dimensional problems, e.g. beams, trusses, columns, and frames. It seems that the main reason for the lack of comprehensive researches is the huge computational cost for two or three- dimensional problems involved with the finite-element modeling. In order to reduce the costs, two distinct techniques have been utilized here. Firstly, instead of using the genetic algorithm method, the particle swarm optimization (PSO) technique has been applied for finding the best solution. Secondly, instead of applying the fine meshes for calculation of the modal parameters in the finite- element modeling, the course meshes are used. In this paper, the combination of the frequencies and the mode shapes as an objective function has been applied in the optimization procedure for damage detection of two-dimensional plane stress type problems. For this purpose, the finite-element computer program has been developed in MATLAB environment for the required calculations. The results show that non- gradient-based optimization techniques such as GA and PSO have been successfully detected the existence, location and the intensities of the pre-defined damage scenarios.

In this paper, a laboratory study of the Bored Pile Retaining Wall with Anchorage Bracing in sandy soils has been conducted. To this end, the physical modeling in laboratory condition was used. The results of the experiments suggest that the ratio of maximum lateral displacement of wall to the depth of excavation () is in the range of 0.145% to 0.51%. Also, the ratio of maximum ground surface settlement to the depth of excavation () is estimated in the range of 0.11% to 0.76. Furthermore, this study investigated the location of maximum lateral displacement of the walls, the ground surface settlement pattern to be used in laboratory studies and determination of the depth of penetration pile.

In this study, a new method called M5, was employed to derive ground-motion prediction equations (GMPEs). Peak ground acceleration (PGA) and peak ground velocity (PGV) was formulated by seismic parameters including earthquake magnitude, earthquake source to site distance, average shear-wave velocity and faulting mechanisms with The Pacific Earthquake Engineering Research Center (PEER) database. For verification, the proposed model was compared with three well-known models by Correlation Coefficient, Root Mean Square Error and Mean Absolute Error. A sensitivity analysis and a parametric analysis was carried out to determine the contributions of the parameters affecting model and sensitivity of the models to the variations of the influencing parameters. The equations are remarkably simple and can reliably be used for pre-design purposes.

One of the most important factors affecting the serviceability of structures is the deflection of concrete members. In this paper, short-term deflection of reinforced concrete (RC) beams with FRP and steel bars were studied by modeling in ABAQUS software. For different types of steel and FRP bars, twelve RC beams have been analyzed and the effective moment of inertia and deflection of the results were compared with the ACI 440.1R-15 and proposed equations. After analysis, it was found that to prevent sudden failure of RC beams with FRP bars, it is better to design a concrete beam with over reinforced sections. According to load-deflection curves of RC with FRP bars, the use of carbon FRP (CFRP) bars are the suitable alternative for steel bars in the corrosive environment. It is concluded that the use of Bischoff- Scanlon, and Bischoff- Gross equations in RC beams with glass FRP (GFRP) and aramid FRP (AFRP) with the error of less than 2% and 10%, respectively, are appropriate for determining deflection in these beams. Results indicate that any of the proposed relations for all different types of FRP rebar does not provide satisfactory results and in terms of used reinforcement special equations should be used.

In the history, Earthquakes have been a major source of many damages and human losses and there has always been a lot of concern about the destruction of large structures such as dams due to significant financial losses and casualties caused by it as well as the uncontrolled release of water in the towns and villages located downstream. Seismic risk analysis, one of the most important methods to deal with earthquake hazards. In this study a type of seismic risk analysis in dams is discussed and used and seismic hazard analysis is conducted for the Chah Nimeh Zabol dam. Semi-quantitative risk analysis for Chah Nimeh Zabol dam by seismic hazard analysis for the location of the dam was conducted which placed it in the medium risk category and there is no requirement to redesign or reinforce the dam body. The results can be used as a guide for seismic risk of the dams.

Experimental investigation of six RC cantilever beam made with High Performance Fiber Reinforced Cementitious Composite (HPFRCC) with two different fiber percentage and two different stirrup configuration (compact and non-compact) under monotonic loading is conducted in this paper. The results showed that the fiber role was more effective in specimens reinforced without compacted stirrups and energy absorption increasing, the rupture creation delay, and crack width and distribution decreasing have been observed. The ductility and load capacity of the HPFRCC specimens were 200 to 233 and 2 to 17.5% more than those of the Reference beams.

One of the important issues in the design of chute spillway is to study the flow characteristics in the chute path because the flow is supercritical. In this study, the hydraulic characteristic of flow in the chute spillway of Surk dam has been investigated using both physical and numerical modeling. The plexiglass physical model was made with a geometry scale of 1:50 and FLUENT software was used for mathematical modeling. The experiments were carried out at 5 different discharges and the parameters of pressure, velocity and depth of flow were measured in the central axis and at the side of the wall. The results showed that among the measured parameters of FLUENT model, the velocity parameter was simulated with the lowest average error rate (4.3%) and the depth parameter with the highest average error rate (16.9%). Also, the Nash-Sutcliff coefficient and the correlation coefficient for the parameters, indicated that FLUENT software has a good ability to simulate flow characteristics over the chute spillway with a suddenly change slope. Regarding the RMSE and NRMSE criteria, FLUENT model have had the highest accuracy in calculating the flow parameters by using finite volume numerical method, turbulent model k-e, RNG, SIMPLE pressure correction method and VOF two-phase method.