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Factors such as improper performance of gates, their failure, and inappropriate design of gate dimensions are likely to be followed by dangerous dam overtopping. In this article, the nonlinear equations expressing the flow rate through the dam bottom gate or intake as well as the water head inside the reservoir were converted into linear equations in the state space. Based on these linear equations, the inlet and outlet hydrographs of the dam were plotted and the equilibrium point of the diagrams duly determined. Upon adjusting the equilibrium point between the inlet and outlet hydrographs and the height (head) and volume of the reservoir water, the bottom gate or intake dimensions were calculated. The inflow and outflow flood hydrographs fully overlap in case the smart prediction and flood control system along with the pulse method is used for routing of the flood to the reservoir, such that the difference between the two is negligible. Therefore, the proposed smart system offers sufficient accuracy. Then, the digital controllers and other electronic devices were built using microcontrollers, sensors, ultrasonic distance meters, and radio wave transmitters and receivers. Different programming languages were employed in the design building of systems. The proposed flood prediction and control system is equipped with alarm systems to inform the operators in the case of emergencies. After their design and building, the systems were repeatedly used and tested in the laboratory and open channels. The results were favorable and of high accuracy. This is a simple, useful, and reliable method, and can be a suitable substitute for previous ones.

In the present paper, the efficiency of combined tuned liquid damper (CTLD) in controlling the dynamic responses of offshore jacket platforms under the earthquake and sea wave excitation is investigated. This type of damping system consists of one or more tanks containing a fluid, generally water or oil, which can be installed on the topside (superstructure) of the platform. During the excitation, hydrodynamic action induced by the sloshing of the water in the tank acts as a resistant force against the vibration and controls the structural response. In fact, due to the oscillation of the structure, the fluid inside the tank begins to oscillate in the opposite direction. During this process, most part of the fluid has a wave-like oscillatory motion, while the part adjacent to the tank’s floor experiences a rigid-type displacement and exerts impact pressures to the tank’s walls. In order to attain maximum decrease in the structural response, the oscillation frequency of the fluid inside the tank should be near the natural frequency of the structural free vibration which can be determined by performing a modal analysis. Hence, one of the objectives of the present study is to adjust the frequency of fluid’s oscillation based on the natural frequency of the jacket structure. In other words, the aim is to find a frequency range in which the maximum decrease can be achieved in the amplitude of structural responses. In this research, using the FE software ANSYS, a jacket-type platform having dimensions appropriate for the Persian Gulf climate (case study: SPD1 platform) was modeled and then dynamically analyzed by the modal and time-history approaches subjected to the records of El Centro and Tabas earthquakes as well as 10 cases of wave loading with different height and period. The CTLD system was optimally designed and after the verification of FE results, the dynamic responses of the jacket-type platform with and without CTLDs were compared.

Spillway gates are used to increase water depths on power generating turbines, regulate the flow passing the spillway and augment the safety of the dam and its installations during flooding.Inappropriate performance, inaccuracy in determining the proper dimensions and sudden opening of the spillway gate(s) causes vibration, overtopping, instability in the dam, and also damages to the dam's body, its installations and even downstream areas. Regarding the rainfall reduction, adjusting reservoir level, increasing water pressure on power generating turbines and proper use of water inside the reservoir, determining the accurate dimensions of the gate and making smart spillway gate(s)  are required. Using the technique of linearizing the equations of discharge passing spillway and water level inside the reservoir and the point of equilibrium of the incoming and outgoing discharge hydrograph, the dimensions of the spillway gate are carefully designed and constructed in accordance with the environmental conditions and its installation site. By smarting the spillway gate and determining its precise dimensions, it will be possible to control floods remotely, manage water consumption, save manpower and reduce visual error.

The main aim of the present paper is numerical investigation of the tsunami wave forces on coastal structures using the commercial software FLOW-3D. Verifications of the simulation results using experimental data and empirical formula showed that the present numerical model is capable of modeling the aforesaid problem with good accuracy. Several numerical simulations have been conducted in the framework of this work to study different parameters affecting the forces induced by tsunami waves on coastal structures. Four empirical equations have been introduced to estimate nonbreaking tsunami wave forces on coastal structures. Based on our results, quantity of exerted forces by breaking waves over curved structures and gradient structures with 45 degree was 20 and 35 percent of exerted forces over caisson structures, respectively.

In the present paper, the effectiveness of Tuned Liquid Damper (TLD) in controlling the dynamic responses of offshore jacket platforms under earthquake excitation is investigated. This type of dampers consisting of one or more fluid (generally water) containers can be installed on the platform’s deck. Hydrodynamic actions induced by the tilting of the water surface in the container act as resistant forces against vibration controlling the structural response. In this research, using FE-based software package ANSYS, a jacket structure having dimensions appropriate for the Persian Gulf climate (case study: SPD1 platform) was modeled and then dynamically analyzed by the modal and time-history approaches subjected to the records of Tabas, El Centro, and Kobe earthquakes. The TLDs were optimally designed and after the verification of FE results, the dynamic responses of the jacket-type platform with and without TLDs were compared.

Methods of estimating the remaining life of cracked tubular joints in offshore jacket-type platforms are based on fracture mechanics (FM) approach. The accuracy of FM approach depends on the accurate estimation of the stress intensity factors (SIFs). In the present paper, effects of geometric parameters on the results of SIFs for tubular X-joints are investigated. In this study, FE models were generated using ABAQUS and to evaluate the SIFs, J-integral method was used. Numerical SIF results were validated against available experimental data. Results showed that the J-integral method is suitable for the calculation of SIFs. The increase of the γ (= D / 2T) and/or β (= d / D) leads to the decrease of the SIFs. Moreover, the increase of the τ (= t / T), c / a ratio and/or a / T ratio results in the increase of the SIFs; where D, d, T, t, a, and c are the chord diameter, brace diameter, chord thickness, brace thickness, crack depth, and half of crack length, respectively.

Because of random nature of many dependent variables in coastal engineering, treatment of effective parameters is generally associated with uncertainty. Numerical models are often used for dynamic analysis of complex structures, including mechanical systems. Furthermore, deterministic models are not sufficient for exact anticipation of structure’s dynamic response, but probabilistic models are far more efficient in modelling uncertainties. To determine the uncertainty effect on dynamic characteristics, the laboratory samples of a pier structure were created. Stochastic finite element method was used for numerical study of pier’s dynamic behavior. For this purpose, the concept of variable distributions of Gaussian and Wishart random matrices for modeling dynamic characteristics of the system was used. At last, by comparing the output frequency response function obtained from empirical experiments and numerical simulation of stochastic finite element method, it is shown that probability density function of Wishart matrix evaluates and tracks uncertainty parameters in system’s dynamic response far better than Gaussian matrix.

Although there exist advanced models which predict beach profile for natural beaches, the behavior of the beaches in front of seawalls still suffers from the lack of appropriate theoretical models and sufficient measured data. In this paper, following the results obtained from the measurements, a beach profile evolution model is developed, using the measured probability distribution of the near-bed horizontal velocities as input, to predict the short-term bed level changes in the vicinity of a partially reflective seawall. The present model introduces a new approach in which based on integrating the probability density functions of the near-bed horizontal velocities, the sediment displacements and consequently bed level changes are calculated in front of a partially reflective structure. The results obtained from the model in comparison with the experiments are promising and encouraging for further developments of the proposed model.

Tubular KT-joints are quite common in offshore structural design and despite the crucial role of stress concentration factors (SCFs) in evaluating the fatigue performance of tubular joints. However, the SCF distribution in internally ring-stiffened KT-joints have not been investigated and no design equation is currently available to determine the SCFs for this type of joint. In the present paper, results of experimental and numerical investigations of the SCF distribution in internally ring-stiffened tubular KT-joints are presented. In this research, experimental study has been followed by a set of parametric stress analyses for 118 steel ring-stiffened KT-joints subjected to balanced axial loads. The analysis results are used to present the general remarks on the effect of geometrical parameters on the SCF distribution along the weld toe and to establish a new set of SCF parametric equations for the fatigue design of internally ring-stiffened KT-joints.

During their service life, marine pipelines continually accumulate damage as a result of the action of various environmental forces. Clearly, the development of robust techniques for early damage detection is very important to avoid the possible occurrence of a disastrous structural failure. Most of vibration-based damage detection methods require the modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties, such as natural frequencies and mode shapes are not adequate sensitive indicators of structural damage. In this paper, structural damage was identified based on a new method called Detail Signal Energy Rate Index (DSERI). Damage localization of offshore pipeline was then based on Continuous Wavelet Transform (CWT) and Discrete Wavelet Transform (DWT). For modeling the damage, the stiffness of 1 and 2 elements were reduced in three models and the dynamic signals were measured by finite element analysis. The dynamic signals were analyzedby applying discrete and continuous wavelet transforms. Then, by using Daubechies wavelet, a peak was clearly evident and the exact damage location was identified by the peak with the maximum absolute value in the plots of the detail signal calculated with the DWT and CWT. To eliminate the effects of the boundary conditions on the wavelet-based damage, the authors proposed a new DSERI. Component energies were then calculated and used for damage assessment. The results showed that the DSERI were good candidate indices sensitive to structural damage. These component energies could be used for damage assessment including identifying damage occurrence and location of damage. Wavelet coefficient was a good candidate for structural damage identification when damage occured at the middle of pipeline but not sensitive for damaged elements near to supports.

Failure of the quay walls due to earthquakes results in severe economic loss. Because of hazards threatening such inexpensive nodes of national and international transportation networks، seismic design of quay walls is still an evolving topic in marine structural engineering. This study investigates the sensitivity of the gravity-type quay wall stability respect to uncertain soil and seismic properties using ultimate limit-sate pseudo-static design process. Stability is defined in terms of safety factor against sliding (sfs)، overturning (sfo) and exceeding bearing capacity (sfb). In order to assess the forces exerting on quay walls، to be more accurate، pore water pressure ratio، horizontal and vertical inertia forces، fluctuating and non-fluctuating components of hydraulic and soil pressure were considered. It was found that the increase of water depth in front of the quay، vertical and horizontal seismic coefficients، and pore water pressure ratio play important roles in reduction of all mentioned safety factors. Increase of specific weight of the rubble mound، backfill and foundation soil، friction angle of wall-foundation/seabed interface and wall back-face/backfill interface and friction angle of backfill soil، lead safety factors to magnify. A comprehensive sensitivity analysis was also performed using the tornado diagrams. Results of this study could give designers insights into the importance of uncertain soil and seismic factors، in order to choose geometry of the design in a way that its analysis and assessment is less relied on severely uncertain parameters and to introduce more reliable and economic quay walls.

Regarding to increase in cities population, the amount of internal trips enlarged. To provide suitable facilities on these movements, construction of urban railways has been adopted. Deportation of massive materials containing stone and soil in tunnel excavation causes stress variation in region around the tunnel and consequently settlement in ground surface. Therefore, to prevent probable damages in adjacent structures, assessment of settlement amount has to be considered before tunnel construction. Settlement amount due to excavation depends on different factors such as, soil type, ground water level and parameters refer to shield operation. Considering a lot of effective factors in settlement and also great distance of excavation, a large amount of calculations and studies are necessary to settlement estimation. In this field, the black box models can be used as a powerful method, because of their ability, independent performance of physical parameters and their relation among them. In this paper, we used two types to networks, feed forward back-propagation neural network and wave-net. Feed forward neural network is the most popular neural network. To construct wave-nets, sigmoidal activation functions of hidden layers in feed forward neural network are substituted with appropriate wavelet functions. In this paper, studies on the measurement of subway project in Bangkok have been done. In the Bangkok MRTA project, data on ground deformation and shield operation were collected. The tunnel sizes are practically identical and the subsurface conditions over long distances are comparable, which allow one to establish relationships between ground characteristics and EPB-operation on the one hand, and surface deformations on the other hand. At first, the impact of every parameter on the settlement was observed individually and then effective input data was determined for training of the network. Thirteen parameters were determined as inputs and surface settlement was output parameter of networks. Networks were trained and optimal models of networks were determined and then analysis results of ANN and wave-net were compared together. Analysis results demonstrate both networks capability. Furthermore, reduction in errors for wave-net shows its high accuracy in comparison to neural network.

Natural phenomena usually seem irregular at the first glance, however, with changing the scale and the noise they can become regular and therefore it is possible to predict their behaviors. This idea is the main base of the Chaos Theory that deals with studying of unstable and non-periodic behavior of nonlinear and swinging dynamic systems. The time series of drought, as a major natural disaster, has a dynamic nature. and therefore the Chaos Thero can play a significant role in capturing the detailed changes. Refinement of the indicators, standardized precipitation index (SPI) is now widely used in the world. The obtained SPI data are noisy, and therefore the predictions made based on this data are not very accurate. Wavelet algorithm is able to describe a signal in time and frequency domain and also analyze a signal locally. Hence in this study, it is used in order to de-noise time series of SPI of Tabriz city for the past 40 years. The nature of the chaotic time series was evaluated using the Lyapunov exponent and correlation dimension parameters. The results indicated a very chaotic time series behavior for the studied data. The behavior of the system is non-random, and then the time series are not portion of the stochastic and the noise process. To predict the SPI values by the Chaos Theory, the algorithm of the false nearest neighbors is used. Validation of the results indicated the high accuracy of the predictions of the Chaos Theory. According to the proposed method the severity of the droughts and the SPI of the Tabriz city are predicted for the next 3 years.