نشریه مهندسی عمران مدرس
سال بیستم شماره 6 (بهمن و اسفند 1399)

Surface deformation of the earth due to earthquake fault dislocation is very important for predicting ground motions. There are many studies on kinematic modeling of earthquake faults in both analytical and numerical methods. However, suitable investigations on improving usefulness and efficiency of those numerical methods are still necessary for relevant researchers. In this paper, displacement fields for free surface of the earth due to fault dislocation in homogeneous elastic half-space have been investigated by finite element method. Boundary conditions have significant effects on the results of finite element method, especially when the domain of the problem has infinite boundaries (half-space). Therefore, appropriate cares should be taken to increase the efficiency and accuracy of this method. In order to achieve a comprehensive study on this topic, boundaries have been modeled by two approaches here. The first approach uses common elements for infinite boundaries, while the second one uses infinite elements for those boundaries. To verify the results, each problem has been examined by several meshes and numerical solutions have been compared to Okada’s analytical solutions. In addition to the effects of the boundary modeling, the discretization effects have been investigated in order to find a suitable approach to reduce computational efforts and to increase the accuracy and efficiency of finite element method. In the modeling process, contact elements have been employed to impose fault dislocation. Three numerical examples have been provided for these finite element analyses. Each example includes four analyses without infinite elements and three analyses with infinite elements which are also compared together. The results show that not only infinite elements are necessary for quasi-static fault dislocation problems, but also they improve the performance of finite element method, so that with finer meshes and smaller dimensions of a domain, analytical solutions can be captured by numerical solutions with suitable accuracy.

Soils, which show a large amount of volume reduction and cause a series of sudden settlements on the surface of the earth, due to the increase of moisture, are referred to as collapsible soils. In many different countries, the immediate settlements of these soils, especially in warm and arid areas, have caused the formation of subsidence and sinkhole. These soils always create inappropriate conditions for the construction of structures such as buildings, road projects, foundations, water channels and other civil engineering projects. The occurrence of such sinkholes in parts of Iran and other parts of the world is one of the geotechnical problems of the above problematic soils. Several sink holes have formed in the northern sector of Hamedan. The soil types in this area include sandy and clayey soils which have low dry density. Generally, collapsible behaviour of soils can be evaluated by the use of odometer test. According to the ASTM standard (D5333-03), the collapse index (Ie) is used to determine the magnitude of collapsible possibility during saturation at 200 kPa in a simple odometer device. The purpose of this study was to investigate the effect of changing the order of clay and sand layers on the collapsible behavior mechanism of collapsible soils and on the changes in the collapse index. To achieve the above mentioned objective, the sandy soil was used from the northern areas of Hamadan and kaolinite clay (Super Zenouz of Tabriz) used to make the samples in three single-layer, two-layer and three-layer systems in specific molds made to a height and diameter of 5 cm in the odometer apparatus. Accordingly, in the present laboratory study on these two types of soil, considering the different arrangements of clay and sandy layers, at each stage of the specimen preparation, specimens were prepared in three different series with a dry unit weight of 1.3, 1.5 and 1.7 g per cubic centimeter in a odometer metal molds. By carrying out a series of odometer experiments, it was found that the sandy soils of the study area alone did not have a high percentage of the collapse index. However, with the presence of clay layers in such soils, the collapse index increases, so that collapse index at a unit weight of 1.3 g per cubic centimeter in the sample made in a single-layer system (fine-grained sand sample) reached from 3.8% to 8.7% in the sample made in the presence of a clay in the two-layer system, (the lower layer of the fine-grained sand and the upper layer of clay). Based on the results obtained from this study, the mechanism of collapse can significantly being influenced by the order of layering in that with increasing dry unit weight, the effect of the ordering of the layers on the value of the collapse index decreases. The results of this paper shows that in specimens made with a density of 1.7 g per cubic centimeter, the collapse index of all samples are almost similar values. In other words, the collapsible behaviour of soils is a function of soil dry density.

In addition to the stiffness, strength, and ductility, that are the main requirements of earthquake-resistant buildings, the necessity of reversibility is also essential, and one of the ways to meet this demand is to use materials with high elasticity and low residual strain, such as shape memory alloys (SMAs). The purpose of this study is to determine the seismic fragility curve of steel moment eccentric diagonal bracing frames in 3, 6, 9, 12, 15 and 20-story structures using HAZUS guidelines using incremental dynamic analysis and determining the amount of reduction in the residual displacement of structures with the SMA performing time history dynamic analysis. Survey the fragility curves of the partial failure level of alloyed structures in different stories, it was concluded that the rate of damage reduction for 3 and 6 stories structures was 23 and 18% and for structures with more stories, it was limited to 4 to 9%. At the level of average failure, the same reduction between structures with different classes using this type of alloy has been seen by an average of 30%. On the other, the reduction was about 40% in the area of ​​extensive damage for short and medium-sized structures, while this reduction was limited to 15% for structures of 12 to 20 stories. Besides, in the level of general failure, the use of SMA has not had much effect in reducing damage, especially in high-rise structures. On the other hand, the reduction in residual displacement for high-rise structures with alloys has been between 80 and 95% of the residual displacement of structures without alloys. Therefore, in terms of reducing damage at different levels, the presence of shaped memory alloy in short-rise structures is more effective than high-rise structures. In terms of reversibility, the use of these materials can be a positive point in reducing damage due to residual displacement in operating time for high-rise buildings.

Concrete is extensively used in the construction industry. To reduce the production of cement and subsequently reduce air pollution due to the release of  gas into the atmosphere and also to increase the strength of concrete, cement additives can be used. One of the additives that can be used in concrete is biochar from agricultural waste during the pyrolysis process. Pyrolysis is the process in which wastes are decomposed in the absence of oxygen and at high temperatures. Agricultural wastes are pyrolyzed before being added to concrete. It produces biofuels that can replace fossil fuels, and pyrolysis residues can be used as cement additive in concrete. In this study, the possibility of using biochar of rice husk and sugarcane bagasse treated with hydrochloric acid as an additive to replace cement at the values of 0, 5 and 10% was investigated. Sulfuric acid with pH = 1 was used to simulate the wastewater environment. In order to evaluate the effects of acidic environment on the properties of concrete samples, weight loss, compressive strength and tensile strength of the samples were measured and SEM and EDS instrumental analyzes were performed on the samples immersed in acid after 28 days.  The results showed that pretreatment of rice husk and sugarcane bagasse with dilute hydrochloric acid could improve the pozzolanic properties of the samples by reducing the amount of potassium and calcium in the composition. The results of compressive strength showed an increase in compressive strength of samples containing 5% of treated rice husk biochar and sugarcane bagasse biochar by 35.9% and 54%, respectively, compared to non-pozzolan sample (control). The changes in tensile strength of the samples containing pozzolan compared to the control sample were not significant, compared to the compressive strength. The weight and compressive strength of concrete samples decreased in the vicinity of sulfuric acid. The weight loss of all samples was less than the control, but the comparison of the compressive strength of the samples containing pozzolan with the control showed that only the compressive strength of the concrete sample containing 5% biochar of treated rice husk was higher than that of control by 16%. Tensile strength of concrete samples containing 5% biochar of treated rice husk and treated bagasse increased by 12% and 13%, respectively, compared to the control. In general, the results showed the positive effect of biochar pozzolan on the mechanical properties of concrete.

Understanding the exact real performance of rigid connections in steel moment frames is very important. Not paying enough attention in connection design process may lead to not only local connection damages but also other structural memberschr('39') failure or even building collapse. According to seismic requirements of the tenth topic of national building regulations of Iran, clear span to depth ratio of beam (L/D) in the prequalified bolted flange plate moment connection shall be limited to 7 and 9 or greater respectively for intermediate moment frames and special moment frames and the beam flange thickness shall be limited to 30 millimeters too. Although the beam depth is limited to 1000 millimeters in this type of prequalified moment connection, due to architectural limitations and urbanism requirements, it is usually unacceptable to design such deep beam in the conventional residential buildings. So, in spite of its wide use and practical utility because of exceeding the clear span to depth ratio or beam flange thickness limitations, applying this kind of moment connection in steel moment frame structures is sometimes impossible specially in big span structures. To study the effect of these limitations on cyclic behavior of aforementioned rigid connection towel samples in L/D of 6, 7, 9, 12 and beam flange thickness of 20, 30, 35 were considered and modeled in a finite element software. First of all, the moment connection designed to have enough strength. Then, in term of ductility, the moment connection acceptance criterion is to count the rotation corresponding to related inter story displacement of 0.04 and 0.02 in special moment frames and intermediate moment frames respectively. The results show that applying this type of connection in special moment frames in L/D of 7 and beam flange thickness up to 35 millimeters provides required ductility, and thus, is acceptable. In addition, the moment connection in L/D up to 12 which itchr('39')s flange thickness limited to 30 millimeters has enough ductility to pass seismic requirements of the tenth topic of national building regulations. In intermediate steel moment frames, applying bolted flange plate connection in clear span to depth ratio of beam up to 12 and the beam flange thickness up to 35 millimeters fulfills the seismic requirements. Comparison between models was shown that although by increasing the beam flange thickness and decreasing clear span to depth ratio of beam, the strength of connection is improved up to 37%, the connection ductility is reduced and so, the connection capacity is decreased. The von Mises stress distribution in samples show that the plastic hinges are almost located on the last row of bolts from column faces. The maximum stress in beams which observed in distance range of 20 to 100 centimeters from column faces has exceeded the yield stress and shows protected zone. As expected, the beams failure mode is top or bottom plate buckling. As a research suggestion, it seems that it is possible to combine these three limitations (clear span to depth ratio of beam, beam section flange thickness, and beam section depth) to gain a more comprehensive and useful phrase.

As a result of progressing of industries and population growth, new chemical contaminants have entered to natural water resources that in order to protect the environment and promote hygiene, they should be purified. Acetaminophen is the most widely used chemical pharmaceutical compound. In this study has been tried to omit acetaminophen from water solutions by cyclic biologic procedures. This kind of procedures are friendly environment. The CBR process is a modification of the sequential split reactor (SBR) process. However, instead of the wastewater being injected into the reactor, the contaminant is injected into the process using a continuous drip pump, thus the possibility of shock to the reactor. The purification process is reduced. This treatment system can be used for treatment of various types of municipal and industrial wastewater. In this study synthetic sewage includes acetaminophen, in laboratory scale, has been treated. The first phase of the test involved the adaptation of acetaminophen-degrading microorganisms that lasted for 50 days. Secondary settling sludge from a pharmaceutical company was used for primary seeding. Then the effect of cycle time (6-24 hours), hydraulic retention time (10.03-27.30 hours), density of inlet contaminant (100-1000 mg/L), density of inlet COD (360-7600 mg/L), and temperature (14-30°C), on the reactorchr('39')s performance was investigated. The pH value has been checking and setting on 7 at all stages. At the end of study, the performance of the two CBR and SBR reactors was compared. During the tests, the concentration of ACT was measured by UV-Vis set. The other parameters were measured based on the standard procedures. The results showed the reactor had the best performance in 18 hourschr('39') cycle. The average of removal efficiency of COD and ACT in during this period was 94.70% and 94.97%, respectively. In the phase of control of the concentration of inlet contaminant, the result showed in density of inlet acetaminophen 500 mg/L, hydraulic retention time 44.38 hours, and the 16 hourschr('39') aeration cycle, the reactor can remove more than 99% of acetaminophen and 97% of COD in the contaminants. In the same condition and concentration of inlet acetaminophen up to 1000 mg/L, removal efficiency of ACT and COD was more than 96% and 94%, respectively. Also temperature changes had a great effect on the reactor performance, so that with increasing temperature up to 30°C, COD removal efficiency decreased by 16% to 78%. Whereas with the change of temperature from 14° to 30°C the ACT mean removal was 97.8%. The results of comparing the performance of the two CBR and SBR reactors were also significant, so that, in the same condition, in the SBR, the removal efficiency of COD and ACT were decreased 15% and 10%, respectively. Since the cyclic biological reactor is injected by stepwise process, the results show foodstuffs are more rapidly absorbed by microorganisms, because microorganisms are more than foods. This feature increases the removal efficiency of organic matter in this system over continuous flow systems. Also, due to this feature, the reactor is highly resistant against of load shock. Given that all the phases, settling and discharging processes, take place in one storage, without worrying about leaving MLSS through the effluent, it can be greatly increased.

The need to solve the complex, nonlinear, and variable problems grows with time. Conventional mathematical models perform linear and constant analysis effectively. Although techniques that work on a particular model, capable of analyzing complex nonlinear and time-varying problems, however, they also face some limitations. Combining these with other issues such as decision making, etc., has inspired the development of intelligent techniques such as fuzzy logic, neural networks, genetic algorithms, and expert systems. Intelligent systems mainly employ a combination of these techniques to solve very complex problems. Although both fuzzy logic and artificial neural networks have been very successful in solving time-varying nonlinear problems, each has its own limitations which reduces their use in solve of many of these problems. The roof global ductility, is a comprehensive reflection of various engineering demand parameters (EDP), such as story-drift, plastic rotation at member ends, roof displacement, etc. Careful estimation of this parameter will certainly lead to greater accuracy in the design of structural members. One of the methods which establish a good estimate of the nonlinear seismic response is the using of EDP parameters and measuring the seismic intensity index. The main purpose of this paper is to establish an accurate intelligent model related to the geometrical characteristics of the structure, performance level, the behavior factor and global ductility in eccentrically steel frames, under earthquakes near-fault. For this purpose, genetic algorithm is used. Initially a wide database consisting of 12960 data with 3-, 6-, 9-, 12-, 15- and 20- stories, 3 column stiffness types, and 3 brace slenderness types were designed, and analyzed under 20 pulse-type near-fault earthquakes for 4 different performance levels. To generate the proposed model, 6769 training data were used in the form of adaptive-neural fuzzy inference system(ANFIS). Subtractive clustering and FCM methods have been used to generate the purposed model. The results showed that Subtractive clustering provides more accurate results than the other FIS. To validate the proposed model, 2257 test data were used to calculate the mean squared error of the model. The proposed model is an intelligent model in the range of data used, and can be used to estimate the global roof ductility of EBFs. To evaluate the efficiency and performance of the model, correlation coefficient and common error calculation criteria including RMSE and MARE were used. The correlation coefficient for the Subtractive clustering method was 0.888, based on intelligent model in the test data. In the other hand, the developed intelligent model can be used as a precise alternative to prediction of (μR) for EBFs under near-earthquakes. To evaluate the model’s efficiently and accuracy, various error criteria including Error, Mean Error, RMSE, MARE% and R were used between model values and real values, in the test data. From the results of this study, it can be pointed out that, the developed intelligent model can be used as an accurate substitute method to predict the (μR) for EBF structures, under near-fault earthquakes. The results of correlation analysis of the proposed model show that the proposed intelligent model has high accuracy.

Bridges are one of the most important river structures that have been used for many years. With the construction of bridges, the natural width of the river decreases and this results in a barrier in water flow. This causes the depth of water upstream of the bridge to exceed the normal depth and this increase in depth is called afflux, which is an important factor to consider when designing bridges. In this present study, two kinds of bridge piers of different shapes were used; circular and semicircular nose and tail. Using laboratory modeling and the two types of bridge piers, the effect of Froude number, the amount of flow path narrowing (σ), and the effect of the angle of bridge pier with respect to flow direction, pier shape, and ratio of length to thickness of the bridge pier were examined. Experiments were done in a flume with 15 m length, 30.9 cm width, and a 45 cm height.  Results show that when Froude number is increased, afflux is increased as well. However, these changes are not the same in the two different bridge pier shapes. By examining Froude number in different path narrowing, it was found that generally, the amount of afflux is directly related to the Froude number. This survey also investigated the length-thickness ratio (L/t) effect of piers. For this purpose, different dimensions of piers, with widths of 3.8 cm and lengths of 15.2, 26.6, and 38 cm were investigated. For circular shape bridge piers, 3.8 cm diameter piers were used. When Froude number is constant, afflux is increased by increasing the number of piers across the channel. Results indicate that the amount of water rising is different in the two kinds of bridge piers (in circular shape and semicircular nose and tail piers). Additionally, changing the direction of piers also affects the formation of this phenomenon (afflux). Usually, piers are installed so that their mounting degree with flow direction is 90 degrees, but sometimes it is necessary to install them in another degree. Therefore, the use of skewed bridge piers with various angles can be important for the design. In this study, it was shown that , the angle of the pier, strongly affects the amount of afflux. It was illustrated that afflux increases more when changes are among higher degrees. For instance, when  is changed from 15 to 20 compared to changing from 10 to 15, the increase in afflux is greater. According to results, afflux is higher in semicircular nose and tail piers than in circular shapes with the same Froude number. Also, as Froude number increases, the slope of the afflux curve of circular piers becomes smaller than that of the semicircle nose and tail piers.Investigation of the length-thickness ratio (L/t) effect of piers on afflux shows that this parameter is negligible in  (when pier direction is parallel to flow direction). However, as  is increased, this parameter affects afflux more. Finally, by considering all the parameters, the experimental relationships for estimating the amount of afflux were developed for both bridge pier shapes utilized in the study.

Damage detection is a necessary part for structural health monitoring (SHM), being beneficial to SHM and determining the severity of damage. Application of statistical pattern recognition methods for SHM has gained considerable attention to detect changes in a structure. One of the advantages of these methods is that only data from undamaged state is needed in training phase (unsupervised learning) as opposed to supervised learning where data from both undamaged and damaged conditions is required to train the model. There are different approaches used by researchers and the success of a certain one may depend on the type of structure or structural changes. Most of studies focused on the application of statistical pattern recognition methodologies for SHM utilize the time series analyses for extracting damage-sensitive features. These features are statistical properties of time series models that directly depend on damage. Extracting damage-sensitive features is a fundamental step in damage detection process because pattern recognition algorithms can identify the state of structure unless these features are just dependent on damage.  The change in an environmental and operational condition during the data acquisition process is one of the problems that causes damage features to be depended on factors besides existence of damage. This can lead to incorrect structural state identification. On the other hand, after extracting damage-sensitive features, the application of a statistical novelty detection methodology for decision making on structural state is a significant topic in SHM. This paper proposes a new application of random decrement (RD) technique in order to choose appropriate and accurate damage features which are independent from environmental and operational conditions of structure. The RD technique transforms time series data of the structural response to free decay vibration form that only consist of dynamic properties information by averaging them at specific time. Moreover, a novel statistical method named as Bhattacharyya measure is applied as a robust method for damage diagnosis. The Bhattacharyya measure determines the discrepancy between damage features from different structural states through partitioning data and utilizing numerical information of each partition. Herein, before extracting damage features, time series data are averaged through RD technique. Then the Autoregressive-Autoregressive with exogenous output model (AR-ARX) is used to fit a mathematical model to the averaged time series data and the residuals are considered as damage features. The Bhattacharyya measure is utilized for damage identification and localization. The data obtained from an experimental study on a three-story frame structure model are exploited to validate the accuracy and reliability of the proposed algorithm. Random excitation is applied by varying amplitude level of the input force, simulating various environmental and operational conditions. Damage is induced at two different locations. The proposed algorithm is conducted on data from various environmental and operational conditions at two different locations. A comparative study is also carried out to demonstrate the superiority of the proposed algorithm over some exiting techniques. Results show that the application of random decrement technique reduces the influence of operational and environmental condition due to averaging and normalizing data and correctly determines the state of structure. In addition, using Bhattacharyya measure improves the structural health monitoring results in damage identification and localization.

Landslide is one of the types of mass movements involving the jogging of rock, earth or aggregate both on the downward slope affected by gravity. This is one of the natural disasters that causes huge loss of life and financial loss in different countries every year. Therefore, it is important to investigate the factors affecting the occurrence of this phenomenon and to determine landslides. The purpose of the present study is to develop a forecast-area rate chart for landslide hazard zoning. Landslide zoning is one of the ways in which the critical areas can be identified in terms of slope stability and the zoning maps obtained in sustainable development planning. Zoning is the division of land into several zones and the classification of these zones according to the degree of actual or potential risk of a phenomenon. Landslide hazard zoning maps can be used as a useful tool for managers and decision makers to determine suitable locations for the development of residential areas and critical arteries. Landslide studies in the past have mostly been done to stabilize instability in natural slopes and to carry out specific projects, and engineers have developed techniques in this field to design structures to control slope instability. Extensive variations in geotechnical properties of materials, internal friction angle (Փ) and adhesion coefficient (C), heterogeneity of natural environments at regional and regional scales compared to homogeneity in local and expensive models, and time-consuming exploration techniques. The desert makes old ways inappropriate. Because this seems unreasonable given the cost to profit ratio, especially in the early stages of decision making in engineering projects. To address this problem, taking into account that landslide risk assessment should be based on a careful study of the natural conditions of an area and all possible parameters involved in slope instability should be analyzed seriously in the area of ​​landslide hazard zoning. Was Initial measures in this area should be based on field studies and analysis of instability relationships in slopes and natural and geographical conditions. The results of engineering geological and geomorphological surveys that pay particular attention to minor landslide issues are generalized to the entire study area with no instability observed in its natural slopes and to sites that are naturally occurring. And geographies of landslide conditions are being searched. For this purpose, after defining a descriptive and conceptual model including landslide hazard zoning, all the features that could be used as suitable criteria were identified and collected in a target model. Then, by analyzing different information layers and weighting those using logistic function, control maps and weighted prediction were obtained. In this regard, for the first time to weighted landslide hazard maps, weighted maps were produced continuously, without classifying and simplifying the data into different parts, as well as minimizing expert judgment. It was also identified using the Prediction - Area chart of each layer and identifying the most important factor affecting landslide occurrence for the first time without expert judgment. Finally, all the weighted maps were integrated using the data-driven overlay index method.It was also able to identify 55% of the landslide points in 45% of the total area. Application of the developed model in the Oshvand-Nahavand watershed proved that modeling the above method can optimally reduce the studied areas and reduce the objectives. Identify for further field surveys.

A suitable design is one design can achieve to its aims with minimum cost and needing to less computing time. In civil engineering due to survey of large scale structures and large number of design variables, it is so hard achieving to such design only based on experience and therefore optimization methods came to help designer as useful tools in order to find an economic and efficient design. Structural optimization can be defined as a process of dealing with the optimal design of various structures. Ausual objective function is the weight of the structure. In general, there are three main categories in structural optimization applications, namely, size, topology and geometry (shape) optimization.Cellular automata (CA) is a computationally efficient and robust tool to simply implement complex computations. As CA is simple to be implemented and can deal with complex problems without extensive mathematical computations, it is widely used in various fields of science and engineering.In recent years, various meta-heuristic inspired optimization methods have been developed.Almost all of metaheuristic algorithms come up with an idea of employing a particular process or event in nature as a source of inspiration for the development of optimization algorithm. The Cuttlefish algorithm is inspired based on the color changing behavior of cuttlefish to find the optimal solution. The patterns and colors seen in cuttlefish are produced by reflected light from different layers of cells including (chromatophores, leucophores and iridophores) stacked together, and it is the combination of certain cells at once that allows cuttlefish to possess such a large array of patterns and colors.In this article, cuttlefish algorithm (CFA)combined with cellular automata (CA) and were used for optimization truss structures.First, cellular automata and the Moor neighboring cells are defined and to the number ofsquares of the cell number ofcellular automata lattice( )is selected from the  best population. Then, the variables vector and their objective function of selected population are placed in each cell of the cellular automata.In a Moor neighboring, nine cells are compared to each other and the best answer ( )is selected and that is used to create new population.Finally, the best person in thenew population will be selected and itreplacedwith the worst person in the cellular automata, and thus the cellular automatais updated. Some benchmark numerical examples were solved using the CFA and CA-CFA algorithms, and the results of the numerical examples showed that the enhanced algorithm performancesbetter in size and topology optimization of truss structures than cuttlefish algorithm and other methods introduced in the literature. Finally, it can be concluded that the convergence speed of the improved algorithm compared with previous approaches is higher and its ability to achieve the desired values is better too.

One of the main causes of damage to dams, especially earth dams is the overtopping which may cause huge human losses and financial damages. Fuse plug is used as a safety valve to protect dams against catastrophic damages of overtopping. The increasing outbreak of floods and their huge and sometimes irrecoverable damages has incentivized dam experts and designers for more studies on the most effective and economical spillway construction. The attempt is towards letting higher amounts of water run through spillways. One approach is using an auxiliary spillway beside the main spillway. Fuse plug can be used as an economical auxiliary or emergency spillway. Fuse plug structure consist of embankment body and pilot channel. Fuse plugs are designed with the same details and ingredients of many earth and rockfill dams. In terms of the material of their body, fuse plugs are categorized as either homogeneous or non-homogeneous. As a result of the embankment erosion, the waterway opens up. When the flood is over, the embankment is reconstructed. The fuse plug operation is totally automatic and does not require human intervention. At other times, fuse plug should be stable and have reliability coefficients equal to those of earth dams. In this experimental research, the effect of the body grain size of embankment fuse plug on the failure and washout mechanism of non-cohesive homogeneous fuse plug is evaluated. The water level upstream of fuse plug is kept constant throughout the overtopping and failure processes, the tests thereby simulating the failure of embankment fuse plug impounding a very large upstream reservoir. The failure trend and mechanism, rate of embankment sediment washout and the output hydrograph of overtopping are addressed. The breach shape and failure mechanism can be used as a guide to interpret the extent of grain size effect and failure progress. The mechanisms of embankment breach due to overtopping can be categorized into 2D and 3D processes. 3D mechanism consists of both lateral and vertical erosions, whereas 2D mechanism only consists of vertical erosion. In this research, both types of erosions were observed. Initially 3D mechanism is observed and breach expansion continued until the breach reached the flume walls. Then after the 2D mechanism failure was observed. Also the equation obtained for describing non-dimensional embankment crest in 2D process by non-dimensional time and non-dimensional grain size. The mean rate of washout in test No.2 is the highest and an analysis similar to the mean rate of washout materials can be generalized to the washout period, which given the uniformity of the total volume of materials, is a rational generalization. The important point in the optimal performance of the fuse plug during the time of destruction is the volume of more outlet water in a shorter time period at the level desired by the designer. The material used in the embankment body with d* equal to 0.004, taking into account the results obtained, including the minimum water level behind the structure, reducing drained water, preventing structural instability due to the piping and the higher total erosion rate is an appropriate choice for building an embankment plug fuse in the range of test parameters.

In design of structures using force-based methods applied in current seismic codes, to obtain the nonlinear displacements of structures under the design earthquake, deflection amplification factor (Cd) is applied. In other words, the displacements obtained from elastic analyses under the reduced seismic forces are amplified by Cd to obtain the inelastic displacements under the design earthquake. Research studies showed that using a constant coefficient for estimating the inelastic displacements may lead to considerable overestimation or underestimation of the displacements in different stories of structures. Generally, in regular structures the inelastic maximum interstory drift ratio (IMIDR) occurs in lower stories. Investigating the seismic performance of structures with irregularity in their heights showed that the inelastic responses of these types of structures can differ significantly from the inelastic responses of regular structures. The present study investigates Cd for estimating IMIDR and inelastic maximum roof drift ratio (IMRDR) for steel special moment resisting frames (SMRFs) with vertical mass irregularity under the design earthquake. In addition, the variation of Cd with the variation of the location of the heavier story in the structural height, and mass ratio (i.e., the ratio of the mass of the heavier story to the mass of the adjacent story) is studied. For producing a heavier story, the dead and live loads of the story are multiplied by 2.0 and 3.0. Three different locations (i.e., bottom, mid-height and top story) for the heavier story, are assumed. For investigating the effects of mass irregularity, two regular 5- and 10-story structures are also considered. Therefore, 14 structures (i.e., two mass ratios × two building heights (5 and 10 stories) × three locations for the heavier story + two regular structures) are considered. To perform nonlinear dynamic analyses, 67 ground motion records are applied. The records are scaled such that the mean of the pseudo acceleration response spectra exceeds the design response spectrum for the period range of 0.2T1 to 1.5T1. The results show that using Cd = 5.5 recommended by Standard No. 2800 and ASCE 7 for steel SMRFs underestimates the IMIDR in most of the structures considered and their stories, under the design earthquake. When the heavier story is located in the first story, the lowest mean Cd is obtained in the first story. Because, increasing the mass of the story leads to an increment in the stiffness and strength demand of the story. When the heavier story is located at the roof, the lowest mean Cd is obtained for the top story. While the mean Cd in the first story increases significantly. Moreover, it is shown that Cd = 5.5 underestimates the IMRDR in the structures considered. Investigating the consideration of different values for Cd shows that using Cd = 7.5 leads to the lowest error in the estimation of IMIDR in the structures considered. In the case of estimating IMRDR, the displacement amplification factor is termed Cd Roof, and it is shown that using Cd Roof = 6.5 leads to the lowest error in the estimation of IMRDR. Therefore, Cd = 7.5 and Cd Roof = 6.5 are respectively proposed for more precisely estimating IMIDR and IMRDR in steel SMRFs with vertical mass irregularity.

Seismic retrofit of concrete columns with FRP composites is a well-known method for enhancing their strength and ductility. Behavior of rectangular concrete columns confined with FRP composites depends on several parameters, including unconfined concrete strength, confinement level, aspect ratio of cross-section (defined as the depth /width of the cross-section), and the sharpness of the section corners. For proper design of rectangular concrete columns confined with FRP composites, a good understanding of the stress–strain behavior of FRP-confined concrete prism under axial monotonic compression is necessary. In recent years many design oriented stress-strain models with simple closed-form expressions have been developed for FRP-confined concrete columns. Also some analysis oriented models are proposed in which the stress-strain behavior of circular columns is generated with an incremental process. But to the best knowledge of authors, there is not an analysis oriented stress-strain model for FRP-confined rectangular columns in the literature. Thus in this paper a base model for actively confined concrete is used to develop a new analysis stress-strain model for rectangular concrete columns confined with FRP. This model considers all parameters that affect behavior of rectangular columns. The procedure for generation of analysis oriented stress–strain curves for FRP–confined concrete based on active confinement model is as follows:1) For a given axial strain, find the corresponding lateral strain according to the lateral-to-axial strain relationship; (2) based on force equilibrium and radial displacement compatibility between the concrete core and the FRP jacket, calculate the corresponding lateral confining pressure provided by the FRP jacket; (3) use the axial strain and the confining pressure obtained from steps (1) and (2) in conjunction with an active-confinement base model to evaluate the corresponding axial stress, leading to the identification of one point on the stress–strain curve of FRP–confined concrete; (4) Repeat the above steps to generate the entire stress–strain curve.      It is obvious from above procedure that the main relations in analytical modeling are the lateral-to-axial strain relationship, lateral confining pressure provided by the FRP jacket, peak axial stress on the stress–strain curve of actively confined concrete, axial strain at peak axial stress, and stress–strain equation. Thus in this paper these relations for rectangular sections are presented and when these relations be defined, the stress-strain curve can be generated using above mentioned procedure. In this paper an experimental database containing 167 axial compression test results of externally confined rectangular columns is assembled and used for stress-strain modeling. The proposed model considers different parameters that can affect the behavior of rectangular columns, including aspect ratio, corner radius, confinement ratio, and unconfined concrete strength. Also both the strain hardening and strain softening behavior of rectangular columns can be modelled by the proposed formulation. Comparison between experimental results and those of model predictions indicates that the proposed model provides good predictions for different parts of stress-strain curve such as compressive stress and strain also ultimate stress and strain. Also the shape of predicted stress-strain curve is in a good agreement with the test results.