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The significant wave height is a critical parameter in the design and analysis of marine structures, as well as in their operational use. Consequently, predicting this parameter greatly contributes to improving the design and analysis of marine structures. Various modeling approaches for wave characteristics include numerical, empirical, and artificial intelligence models. This study employs the SWAN model, which is a third-generation model for the simulation and estimation of wave characteristics. Furthermore, soft computing models, including individual and hybrid artificial intelligence models such as Adaptive Neuro-Fuzzy Inference System (ANFIS), Support Vector Machine (SVM), and Emotional Artificial Neural Networks (EANN), have been utilized for wave height prediction, using data from the Amirabad buoy for validation purposes. In this research, the model inputs consist of wind speed, while the outputs are the wave heights. The analysis of the different models was carried out using statistical metrics, including bias, root mean square error, coefficient of variation, and coefficient of determination. The evaluation of the models using these statistics indicates an acceptable agreement between the significant wave heights estimated by the SWAN model and the buoy data. Additionally, each of the three artificial intelligence models mentioned demonstrates a relatively accurate capability in predicting wave height. A comparison of the results from the artificial intelligence models revealed that the Support Vector Machine model exhibited higher accuracy than the others. The Support Vector Machine model serves as an alternative method to the SWAN model or other numerical techniques, enhancing modeling outcomes when wave height data is unavailable or lacks the necessary statistical quality.
 

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Abstract In this paper the effect of two types of common initial geometric imperfections on the reliability of steel frames is investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most finite element reliability analyses in past literature neglect this source of uncertainty. For this purpose static nonlinear pushover structural analysis is used from which reliabilities are estimated based on FORM and Monte Carlo sampling methods. Furthermore to investigate the importance of uncertain parameters, reliability sensitivity analysis is performed by use of the direct differentiation method which has been implemented in the object oriented software framework Open Sees. It is demonstrated that some of these geometric imperfections have significant influence on reliability assessment of steel frames.

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Abstract: The effect of two types of common initial geometric imperfections on the reliability of steel frames was investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most of the finite element reliability analyses in the past haveneglect this source of uncertainty. For this purpose, static non-linear pushover structural analysis was used in the present work from which reliabilities were estimated based on the FORM and Monte Carlo sampling methods. Furthermore, to investigate the importance of uncertain parameters, reliability sensitivity analysis was performed by the use of direct differentiation method, which was implemented in the object oriented framework of OpenSees software. It was demonstrated that some of these geometric imperfections have significant influence on the reliability assessment of steel frames.

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In this paper, crack detection possibility in an arch dam structure is investigated by wavelet transform analysis. An arch dam is a solid concrete dam, curved upstream in plan. In addition to resisting part of the pressure of the reservoir by its own weight, it obtains a large measure of stability by transmitting the remainder of the water pressure and other loads by arch action into the canyon walls. The complete necessity of high safety, economical design, complex of designing and its application increase the importance of concrete arch dams. Successful arch action is dependent on a unified monolithic structure, and special care must be taken in the construction of an arch dam to ensure that no structural discontinuities such as open joints or cracks exist at the time the structure assumes its water load. According to the principles of theory of structures, there is a relationship between the dynamic and static responses and, consequently, the stiffness. Any sudden change in stiffness leads to dynamic and static response variation. This condition will help to estimate the damage and to investigate the structural response before and after the failure. Wavelet analysis has recently been considered for damage detection and structural health monitoring (SHM). It provides a powerful tool to characterize local features of a signal. The basis function in wavelet analysis is defined by two parameters: scale and translation. This property leads to a multi-resolution representation for stationary signals. It has high ability in analysis of static and dynamic response signals. Staionary wavelet transform (SWT) can show the location of frequency changes. That these locations are the points that they have been damaged. The case study is the concrete curvature arch of KAROON-1 (Shahid Abbaspour) dam with the height of 200 m. This dam is considered as one of the most complex dams because of different external and internal radia and angles, as well as asymmetrical center of the external and internal archs in different levels. Using the geometrical dimensions of the above-mentioned dam- from respective design sheetsand its mechanical and physical properties, the dam with and without crack was modeled by the ABAQUS FE software package. After frequency analysis of the dam by ABAQUS for both safe and cracked models in the same frequency mode, displacement responses at the cracked level (crest) were extracted along the reservoir’s longitudinal axis. Afterwards, the responses were used for the wavelet analysis by the wavelet toolbar of the MATLAB software and the detection of crack in the dam structure was investigated with SWT. The results of wavelet analysis showed that the graphs have considerable rise at or around the crack location. But there was no noise or any harmony in the graphs of the safe dam. Hence, detecting the location of crack in dam structures is possible with wavelet transform.

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Corrosion in spiral steel prestressed wires tensioned around core are one of the major weaknesses of prestressed concrete pipes which their untimely detection can cause sudden failure and damages. To date, these kinds of pipes are used and produced in Iran and their abrupt failure due to corrosion has been experienced. In this study acoustic emission monitoring in prestressed concrete was used to investigate the corrosion. An approximately full-scale experimental sample pipe is made in Middle East Technical University laboratory. The pipe is loaded by internal water pressure and accelerated corrosion applied to the sample and the resulted acoustic emission signals are recorded using piezoelectric sensors during corrosion. The sample is tested under wetting and drying cycles frequently for corrosion detection in which during the experiment, pipe inside pressure was fluctuated and Kaiser Effect was studied in different conditions. Experimental results show significant changes in some gained acoustic emission parameters as the pipe work pressure increases to higher amounts. It is shown that the changed AE parameters can be used for damage prediction, condition assessment and corrosion detection of prestressed concrete pipelines.

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Adding fresh concrete to old concrete is a common method for repairing or strengthening structures. In this research, in order to evaluate the shear and tensile strength of the joint of old and new concrete under successive cycles of freezing and thawing of new concrete with cement grades of 300, 350 and 400 kg/m3 and three water-to-cement ratios of 0.4, 0.45, 0.5 and bubble-making materials with amounts of 0.0, 0.1, 0.2, 0.3 and 0.4 of the weight of cement used. Then, 300 consecutive cycles of freezing and thawing were performed on the samples after 3, 7 and 28 days of processing period. Freezing and thawing periods include lowering the temperature of the samples from 4°C to -18°C and raising it from -18°C to 4°C, which is done alternately and in a period of 4 hours for each thawing-freezing cycle. The samples were frozen for 3 hours and placed in water for 1 hour for the thawing process. The results of this research show that the effect of freezing and thawing cycles on the shear strength is more than the tensile strength of the bond and the increase in the weight percentage of the bubble-making material has the greatest effect on the shear stress during the 28-day processing period, and with the increase in the weight percentage of the bubble-making material from zero to 0.4, the difference in the amount of shear stress in the conditions with and without the freezing and thawing cycle decreases. The maximum decrease in the shear strength of the joint bond after the application of the temperature cycle is zero in the amount of bubble-making material, so that for a 28-day concrete sample, the shear strength decreases by 93% on average in the ratio of water to cement and different grades of cement. According to the results of this research, with the increase in the weight percentage of bubble-making materials from zero to 0.4, for concrete with 300, 350 and 400 kg/m³ grade, the amount of shear stress for different water-cement ratios and different processing periods decreases on average by 15%, 14% and 11%, respectively. But for laboratory conditions with freezing and thawing cycles, the amount of shear stress increases significantly with the increase in the weight percentage of bubble-making materials, so that for concrete with 300, 350 and 400 kg/m³ grade in the 28-day processing period and the ratio of water to cement 0.45, with the increase in the weight percentage of bubble-making materials from zero to 0.4, the amount of shear stress reaches from a very small value of 0.42, 0.45 and 0.47 to 2.59, 2.91 and 2.99 MPa. With the increase of water-cement ratio in conditions without freezing and thawing cycle, the amount of shear strength decreases, but in conditions with freezing and thawing cycles, the shear strength first increases and then decreases, so that the highest value of shear strength occurs in the water-cement ratio of 0.45.  Also, the highest bond strength after applying freezing and thawing cycles in the samples, after 3 days of processing in water to cement ratio of 0.4, grade of 400 kg/m3 and using 0.4% of cement weight used as bubble material occurs.
 

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Abstract
Steel shear walls have been used in various buildings as a system to resist lateral loads. The special advantage of this type of wall is its good malleability, high initial hardness, and high energy consumption power. But due to its special geometry, the steel shear wall undergoes buckling in the elastic range. To prevent steel sheet buckling in steel shear walls, there are two general solutions: using metal stiffeners or using concrete cover that is connected to steel sheet through shears. Based on this research, a solution has been proposed to improve the seismic performance of modern steel-concrete composite shear walls. The composite steel shear wall is a modern lateral bearing system consisting of a steel sheet with a reinforced concrete cover, which is connected to the sheet from one side or both sides by clips. In the composite steel shear wall, the reinforced concrete cover, by restraining the steel sheet and preventing its buckling, increases the shear capacity of the steel shear wall to the point of yielding in shearing inside the plate instead of tension in the direction of the tensile field. The composite steel shear wall, while increasing the shear capacity of the system, increases the resistance of the panel against destructive factors such as corrosion, fire, impact, explosion, and other cases and causes a reduction of more than 25 to 50 percent in the consumption of steel in medium and large buildings. In the new composite steel shear wall system, a distance is created between the concrete cover and the boundary beams and columns. Tests on conventional and modern composite steel shear walls show that the modern system has little damage compared to the conventional system. From nonlinear static analysis using the finite element method and with the help of ABAQUS software, the influence of the geometric characteristics of steel stiffeners on the seismic performance of the modern steel-concrete composite shear wall has been investigated. After modeling the steel-concrete composite shear wall and validating the numerical model with laboratory results, the effect of parameters such as the number of stiffeners, the type of arrangement, including vertical, horizontal, diagonal, and combined, on the maximum bearing capacity of the composite shear wall, ductility coefficient, additional strength, energy consumption, compressive damage of the concrete hardener, and failure modes have been investigated. The results of this research show that the use of T-shaped steel stiffeners and their arrangement have a significant effect on the bearing capacity of steel-concrete composite shear walls and cause the overall buckling of the steel sheet to become local buckling between the stiffeners. The use of diagonal stiffeners increases the capacity of steel shear walls by 25%. The ductility factor and added strength factor of the steel frame with diagonal stiffeners are about 39 and 124% higher than the ductility factor and added strength factor of the base sample without the use of stiffeners, respectively. The use of diagonal stiffeners in composite shear walls compared to composite shear walls without steel stiffeners increases energy consumption by about 18%. The use of T-shaped steel diagonal stiffeners in composite shear walls compared to composite shear walls without steel stiffeners causes a significant reduction in the damage and failure of the concrete stiffener.