Journal of Rehabilitation in Civil EngineeringJournal of Rehabilitation in Civil Engineering
http://civiljournal.semnan.ac.ir/
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http://civiljournal.semnan.ac.ir/
Feed provided by Journal of Rehabilitation in Civil Engineering. Click to visit.Innovations in Sustainable Earthquake Resisting Rocking Wall-Frames
http://civiljournal.semnan.ac.ir/article_2645_344.html
This paper introduces a novel design concept for the development of efficient, sustainable Rocking-Wall Moment Frames (RWMFs) under seismic conditions. The proposed concepts lead to a novel structural configuration with provisions for Collapse Prevention (CP), Self-Centering (SC), reparability, performance control (PC), damage reduction, and energy based seismic analysis. It introduces the merits of design led analysis (DLA) over the traditional methods of approach, followed by the development of a lateral resisting system that is more efficient than its conventional counterparts. The fundamental idea behind the proposed methodology is that seismic structural response is mainly a function of design and construction, rather than numerical analysis. In design led analysis the rules of mechanics and structural design are induced rather than followed .The new system is a combination of grade beam restrained moment frames and articulated shear walls, tied to each other by means of post tensioned (PT) stabilizers and Gap Opening Link Beams (GOLBs).Tue, 31 Jul 2018 19:30:00 +0100Effect of Pile Scouring on the Structural Behavior of a Fixed Jacket Platform with ...
http://civiljournal.semnan.ac.ir/article_2634_344.html
In offshore structures, most of failures are caused by the lack of sufficient piles strength. Scour phenomena affects the load transition and the pile strength. The necessity of the consideration of scouring phenomena amplifies when the scour depth becomes remarkable, which can endanger the jacket stability. In this paper, a new method is used to consider the pile scouring using nonlinear pushover analysis with SACS software. A recently-built existing jacket platform namely SPD 19C is selected as a case study. Results show that Reserve Strength Ratio (RSR) of the jacket platform decreases when scour depth increased in the both aged and recently-built cases. RSR decreasing becomes more sensible as scour depth increases. According to API RP2A collapse will be occurred in the range of RSR< 1.6. It is shown at RSR=1.6, collapse will be occurred in the scouring depth of 13.5m and 11m for recently-built and aged platform respectively, which both have approximately 27% lower RSR than their original state. So scour protection methods should be addressed in vulnerable areas as preventive alternatives.Tue, 31 Jul 2018 19:30:00 +0100Modeling of Resilient Modulus of Asphalt Concrete Containing Reclaimed Asphalt Pavement using ...
http://civiljournal.semnan.ac.ir/article_2638_0.html
Reclaimed asphalt pavement (RAP) is one of the waste materials that highway agencies promote to use in new construction or rehabilitation of highways pavement. Since the use of RAP can affect the resilient modulus and other structural properties of flexible pavement layers, this paper aims to employ two different artificial neural network (ANN) models for modeling and evaluating the effects of different percentages of RAP on resilient modulus of hot-mix asphalt (HMA). To this end, 216 resilient modulus tests were conducted for establishing the experimental dataset. Input variables for predicting resilient modulus were temperature, penetration grade of asphalt binder, loading frequency, change of asphalt binder content compared to optimum asphalt binder content and percentage of RAP. Results of modeling using feed-forward neural network (FFNN) and generalized regression neural network (GRNN) model were compared with the measured resilient modulus using two statistical indicators. Results showed that for FFNN model, the coefficient of determination between observed and predicted values of resilient modulus for training and testing sets were 0.993 and 0.981, respectively. These two values were 0.999 and 0.967 in case of GRNN. So, according to comparison of R2 for testing set, the accuracy of FFNN method was superior to GRNN method. Tests results and artificial neural network analysis showed that the temperature was the most effective parameter on the resilient modulus of HMA containing RAP materials. In addition by increasing RAP content, the resilient modulus of HMA increased.Tue, 31 Jul 2018 19:30:00 +0100Ultra-Low Cycle Fatigue Fracture Life of a Type of Buckling Restrained Brace
http://civiljournal.semnan.ac.ir/article_2643_344.html
Buckling restrained braced frames (BRBFs) for seismic load resistance have been widely used in recent years. One of the key requirements for a buckling restrained brace is to sustain large plastic deformations under severe ground motions. The core of a buckling restrained brace is prone to fatigue fracture under cyclic loading. The earthquake induced fracture type of the core plate in a buckling restrained brace can be categorized as ultra-low cycle fatigue fracture. This paper investigates the ultra-low cycle fatigue fracture life of a type of composite buckling restrained brace previously tested. The newly developed cyclic void growth model was adopted to theoretically predict the fracture and crack initiation in the core. In addition, the Coffin-Manson fatigue damage model was applied to estimate the fracture life of the brace. A FEM model of the BRB developed in ABAQUS was used to evaluate the fatigue life. The analysis results showed that the cyclic void growth model is capable to nearly predict the fracture life of the core in buckling restrained brace.Tue, 31 Jul 2018 19:30:00 +0100Time-Dependent Structural Behavior of Repaired Corroded RC Columns Located in a Marine Site
http://civiljournal.semnan.ac.ir/article_2724_0.html
The chloride corrosion of reinforcing steel in reinforced concrete (RC) structures is a significant reason for premature deterioration and failure of RC structures in aggressive environments such as Persian Gulf region. This is one of the most important sources of engineering and economic problems in developed countries. So, the repair and maintenance of RC structures exposed to corrosive environments are very important for optimizing the service life and life cycle cost of these structures.In this research, a finite element model is applied to assess the time-dependent capacity of corroded RC structures using nonlinear analysis; this includes the impact of corrosion on inelastic buckling and low-cycle fatigue degradation of reinforcements. In this analysis, the influence of a number of repair or rehabilitation methods on the performance of a corroded square RC column due to chloride-induced corrosion are investigated and compared, including concrete surface coatings used on the external surface of concrete, and shotcrete repair after the initial cracking of concrete cover. So that, to investigate the surface coating influence on the corrosion percentage of reinforcements and structural performance due to corrosion, two surface coatings as repair methods are simulated as the equivalent concrete cover thickness. The equivalent concrete cover thickness is considered on the initial concrete cover at crack initiation time that decreases the corrosion current density and corrosion percentage after this time. Moreover, the equivalent concrete cover thickness is calculated based on experimental data of chloride diffusion into concrete specimens with surface coating located in south of Iran.Mon, 30 Oct 2017 20:30:00 +0100Prediction of Lightweight Aggregate Concrete Compressive Strength
http://civiljournal.semnan.ac.ir/article_2641_344.html
Nowadays, the better performance of lightweight structures during earthquake has resulted in using lightweight concrete more than ever. However, determining the compressive strength of concrete used in these structures during their service through a none-destructive test is a popular and useful method. One of the main methods of non-destructive testing in the assessment of compressive strength of concrete in the service is ultrasonic pulse velocity test. The aim of this study is predicting the compressive strength of lightweight aggregate concrete by offering a suitable mathematical formulation. Many samples of lightweight aggregate concrete, made by expanded clay, have been produced and tested. After determining the actual compressive strength and indirect ultrasonic pulse velocity for each sample, a relationship was presented to predict the compressive strength through Gene Expression Programming (GEP). The results show the presented equation has high accuracy in estimating the compressive strength of samples and that experimental results are perfectly compatible with the test results.Tue, 31 Jul 2018 19:30:00 +0100Experimental investigation of octagonal partially encased composite columns subject to ...
http://civiljournal.semnan.ac.ir/article_2725_0.html
Partially Encased Composite (PEC) column is one of the recent achievements in the field of composite columns. This paper presents a combined experimental and theoretical study on the mechanical performances of six octagonal PEC columns subjected to axial compressive and bending moment loading. The major different between them was the concrete reinforcement details. The parameters studied in the experimental and numerical study were the type of reinforcement details and the failure mode. The results were presented as load-deformation and moment-rotation curves. In the analytical phase, the experimental results in the compressive loading were compared with those obtained from CSA S16-14 and EN 1994-1-1 equations. The comparison of the code equations given in CSA S16-14 and EN 1994-1-1 revealed that the equation in CSA S16-14 underestimates the capacity. Also, theoretical relationships were used to estimate the compressive capacity and the behavior of laboratory models in order to find the confinement coefficient of concrete.Mon, 30 Oct 2017 20:30:00 +0100Nonlinear Finite Element Modeling of Different Cross-Sectional Shapes of Slender RC Columns ...
http://civiljournal.semnan.ac.ir/article_2644_344.html
In the present study, non-linear finite element analyses are carried out on the slender reinforced concrete columns wrapped using CFRP composite with different cross-sectional shapes having the same area. Thickness of the CFRP wraps, concrete compressive strength, corner radius, loading condition, slenderness ratio and column size are the main parameters of this study. According to this, four different eccentricity-to-section-height ratios, four different levels of the CFRP thicknesses in the strengthened specimens, the slenderness ratio of the length to the section-height (l/h) from 6 to 12, three various types of column size, concrete compressive strength values from 20 MPa to 50 MPa and corner radius from 10 to 40 mm are considered. This paper presents a comparison of a numerical simulation using ABAQUS software, with the results of experimental tests by previous researchers to validate finite element models. It is shown that the predicted results by this numerical study are in reasonable agreement with the results of experimental studies. The results of this investigation also represented a considerable enhancement on the performance of strengthened columns with CFRP compared to unstrengthened columns.Tue, 31 Jul 2018 19:30:00 +0100Cross Section Effects on Convergence-Confinement Method in Multi Stage Tunnel Excavation
http://civiljournal.semnan.ac.ir/article_2726_0.html
Dimensionless coefficient () in convergence confinement method shows the relaxation of stress in the wall of the tunnel at different excavation movements. This factor is considered a constant number in previous studies and tunnel geometric characteristics (such as depth, cross-section shape, radius, soil material, etc.) are not included in its determination; however, ignoring these effects can cause significant errors in the analysis of tunnels. In this study, the effect of excavation pattern and tunnel cross section shape on stress reduction factor has been investigated. For this purpose, at first, by considering the conventional cross sections of the tunnel (circular, horseshoe, and double arch), using finite difference numerical simulation software FLAC 2D and FLAC 3D, the type of excavation (full face and multi face) was investigated in estimating the stress reduction factor by considering depth, radius, and different points around the tunnel. Finally, studies were carried out between the 2D and 3D analyses and the experiments conducted at Karaj Subway to verify the results obtained from the above 2D analyses. The results of this study show the important effect of tunnel cross-section on determining stress reduction factor. Using variable stress reduction factor in the all-around of tunnel cross section can lead to more realistic simulations of complex behavior of tunnels during the excavation. Moreover, this method can be used for the analysis and design of tunnel due to its time saving nature and at the same time sufficient accuracy.Mon, 30 Oct 2017 20:30:00 +0100Soil Structure Interaction Effects on Hysteretic Energy Demand for Stiffness Degrading Systems ...
http://civiljournal.semnan.ac.ir/article_2640_344.html
This paper aims to study the influence of soil-structure interaction on plastic energy demand spectra directly derived from the energy-balance equations of soil-shallow-foundation structure with respect to an ensemble of far-field strong ground motions obtained from Pacific Earthquake Engineering Research (PEER) database and recorded on alluvium soil. The superstructure is modeled as a single-degree-of-freedom (SDOF) oscillator with Modified Clough stiffness degrading model resting on flexible soil. The soil beneath the superstructure is considered as a homogeneous elastic half space and is modeled through the concept of Cone shallow foundation Models. A parametric study is carried out for 2400 soil-structure systems with various aspect ratios of the building as well as non-dimensional frequency as a representative of the structure-to-soil stiffness ratio having a wide range of fundamental fixed-base period and target ductility demand values under a family of 19 earthquake ground motions. Results show that generally for the structure located on softer soils severe dissipated energy drop will be observed with respect to the corresponding fixed-base system. The only exception is for the case of short period slender buildings in which the hysteretic energy demand of soil-structure systems could be up to 70% larger than that of their fixed-base counterparts. Moreover, dissipated energy spectra are much more sensitive to the variation of target ductility especially for the case of drastic SSI effect.Tue, 31 Jul 2018 19:30:00 +0100Leak detection in water collection and transmission networks using minimum nodal pressure ...
http://civiljournal.semnan.ac.ir/article_2727_0.html
Leak has always been one of the problems in water distribution networks, whose preventing not only results in saving of water sources, but also has profound effects on maintenance cost of networks. In present paper, a new method is applied for leak detection in water collection and transmission network. In this method, detection of leak location is performed by pressure difference analysis at junctions and by the help of relative index of leak. In this regard, at least two nodes have to be selected for pressure measurement within the network, in order to monitor the pressure changes in with and without leak cases. The investigated network in this research includes 7 wells with approximate length of 7800 m located in North Western city of Mashhad. A real leak with a rate of 7.57 l/s is created at one of the network nodes whose amount is measurable by a volume counter. Finally, this leak is identified by the proposed method via 3 nodal pressure measurementsMon, 30 Oct 2017 20:30:00 +0100Determining the Effective Distance of Wind Shelter Index by Defining Innovative Index Named ...
http://civiljournal.semnan.ac.ir/article_2635_344.html
The wind’s effectiveness was compared in different points of a watershed using a quantity called The Wind Shelter Index.The wind’s effectiveness was compared in different points of a watershed using a quantity called The Wind Shelter Index. It is necessary to choose a distance called the effective distance in the process of this index determination. The criterion already used for this purpose was only usable in snowy places. According to the wind shelter index usability in some phenomena that are not in snowy areas, the use of this index will be applied. This study uses observational data of snow surveys from 258 points in Samsami Basin to introduce a new index called “Virtual Wind Shelter” that can be used to choose the effective distance of the area applicable in snowy and non-snowy places. The results showed that the index introduced in this study has the capability of replacement with the correlation of wind shelter index with snow depth criterion.Tue, 31 Jul 2018 19:30:00 +0100Impact of Loading Protocol on the Performance of the Steel Moment Frame Connections
http://civiljournal.semnan.ac.ir/article_2728_0.html
Today, for the moment frame structures, seismic provisions of the structural engineering design codes depend on the inelastic deformation as well as inelastic capacity of the connections. A cyclic loading protocol is normally exercised for measuring such capability. This paper investigates the deformation capacity of steel moment resisting frame’s connections subjected to different loading protocols. To evaluate the performance of the connections subjected to various cyclic loads, behavior of three types of connections is studied. Behavior and capacity of each connection are assessed subjected to different loading protocols; namely ATC, FEMA and SAC. The results from this research indicate that the ATC and FEMA loading make greater demands on the connections; while SAC basic loading shows a better agreement with the target values of the loading protocol. A loading protocol has been developed taking some criteria into account in order to match the target values presented in SAC study for steel moment connection’s bam to column sub-assemblies. Then the connections were subjected once again to the proposed loading protocol and results compared to those of other loading protocols. The results reveal that the connections subjected to the proposed loading protocol provide greater deformation and strength capacity. Also, lower equivalent plastic strain and lower dissipated energy were observed when the connection is subjected to the proposed loading protocol.Mon, 30 Oct 2017 20:30:00 +0100Application of soft computing techniques to Predict of hydraulic jump length on rough beds
http://civiljournal.semnan.ac.ir/article_2729_0.html
A hydraulic jump phenomenon serves a variety of purposes, for instance, to dissipate the energy of flow to prevent bed erosion and aerate water or to facilitate the mixing process of chemicals used for the purification of water. In the current study, three artificial intelligence approaches, namely artificial neural networks (ANNs), two different adaptive-neuro-fuzzy inference system with grid partition (ANFIS-GP), and gene expression programming (GEP) were applied to forecast developed and non-developed hydraulic jump length. Four different GEP, ANFIS-GP and ANN models comprising various combinations of Froude number, bed roughness height, upstream and downstream flow depth based on measured experimental data-set were developed to forecast hydraulic jump length variations. The determination coefficient (R2) and root mean square error (RMSE) statistics were used for evaluating the accuracy of models. Based on the comparisons, it was found that the ANN, ANFIS-GP and GEP models could be employed successfully in forecasting hydraulic jump length. A comparison was made between these artificial intelligence approaches which emphasized the superiority of ANNs and ANFIS-GP over the other intelligent models for modeling developed and non-developed hydraulic jump length, respectively. For non-developed hydraulic jump, the R2 and RMSE values obtained as 0.87 and 2.84 for ANFIS-GP model.Wed, 01 Nov 2017 20:30:00 +0100Reliability and Sensitivity Analysis of Structures Using Adaptive Neuro-Fuzzy Systems
http://civiljournal.semnan.ac.ir/article_2730_0.html
In this study, an efficient method based on Monte Carlo simulation, utilized with Adaptive Neuro-Fuzzy Inference System (ANFIS) is introduced for reliability analysis of structures. Monte Carlo Simulation is capable of solving a broad range of reliability problems. However, the amount of computational efforts that may involve is a draw back of such methods. ANFIS is capable of approximating structural response for predicting probability of failure, allowing the computation of performance measures at much lower cost. In fact, ANFIS derives adaptively an explicit approximation of the implicit limit state functions. For this purpose, a quasi sensitivity analysis based on ANFIS was developed for determination of most influential design variables, used for predicting the limit state function, led to the approximation of the structural failure probability. Preparation of ANFIS however, was preceded using a relaxation based method developed by which the optimum number of training samples and epochs was obtained. That was introduced to more efficiently reduce the computational time of ANFIS training. To assess the effectiveness of the proposed methodology, some illustrative examples are considered.Wed, 01 Nov 2017 20:30:00 +0100A two-step method for damage identification and quantification in large trusses via wavelet ...
http://civiljournal.semnan.ac.ir/article_2731_0.html
In the present study, a two-step approach for damage prognosis in long trusses is suggested in which the first step deals with locating probable damages by wavelet transform (WT) and static deflection derived from modal data with the intention of declining the subsequent inverse problem variables. Then, in the second step, optimization based model updating method using Artificial Bee Colony (ABC) algorithm will be employed to quantify the predicted damages within an inverse problem. Interestingly, it is shown in the paper that the two-step method greatly aids in declining the number of variables of the model updating process resulting in more precise results and far less computational effort. Besides, the method is found considerably effective especially for damage prognosis of large trusses. In this regard, two numerical examples including noisy data are considered to assess the efficacy of the method for real practical problems. Additionally, the validity of the second step results is investigated using other optimizers namely Invasive Weed Optimization (IWO) and Particle Swarm Optimization (PSO).Wed, 01 Nov 2017 20:30:00 +0100Comparison of Seismic Input Energy Based on the Characteristics of Structural Hysteretic Behavior
http://civiljournal.semnan.ac.ir/article_2733_0.html
The variation of earthquake input energy with characteristics of various structural systems, particularly in hysteretic states, has not been studied to such extent that creates enough con-fidence for proposing energy-based design criteria. In this paper, at first, based on a somehow new insight into the concept of earthquake input energy, two concepts of ‘Received Energy’ (ERec) and ‘Returned Energy’ (ERet) have been discussed. Then, by using various hysteretic mod-els for expressing the behavior of structures, including elasto-plastic, bilinear, Wen, Clough, and Takeda models, and two strength levels for the structure, variations of the ‘Total Input Energy’ (ETot) and also ERec and ERet with respect to the structural specifications have been investigated, by a series of Non-Linear Time History Analyses (NLTHA). Several earthquake accelerograms with various frequency contents from low to high, and peak ground acceleration values have been used for NLTHA. Results show that in some cases the amount of seismic input energy varies remarkably with the hysteretic specifications of the structure, particularly its strength. On this basis, it can be claimed that the hysteretic specifications can be used as measures for limiting the amount of earthquake input energy, and accordingly the level of overall damage to the structure.Sat, 11 Nov 2017 20:30:00 +0100Experimental comparison of sacrificial piles and submerged vanes as scour countermeasures ...
http://civiljournal.semnan.ac.ir/article_2834_0.html
An experimental study has been conducted on the effectiveness of two types of flow-altering countermeasures placed around a cylindrical pier under clear water condition, which include sacrificial piles and submerged vanes. Their arrangements follow the optimal configurations recommended in the published articles with some modification. The temporal evolution of maximum scour depth and its equilibrium amount around the pile without and with two scour countermeasures were recorded; scour depth reduction rates and changes in bed topography were then calculated. It can be said that according to the result which has been earned from the experiments of this study, submerged vanes had better performances compare with the sacrificial piles in all of investigated aspects. By using submerged vanes 75% of the scour only occurred in first 5 minute. Presence of submerged vanes played more efficient role in reducing scour depth as subjected scour depth reduction was 17% more than one subjected to sacrificial piles. The length of changes downstream the pier (L) were 12, 13.2 and 6 times of pier diameter (D) corresponding to pier with no protection, sacrificial piles and submerged vanes respectively, which showed the effectiveness of submerged vanes in reducing the area affected by pier scour. Also the maximum changes of bed level were -6.9 cm to 3.9 cm in unprotected pier test, -4.4 to 3.5 cm in protection by sacrificial piles test and -3 to 3.2 cm in protection by submerged vanes.Sun, 04 Feb 2018 20:30:00 +0100Effect of the frequency content of earthquake excitation on damage detection in steel frames
http://civiljournal.semnan.ac.ir/article_2835_0.html
In this study, the effect of earthquake frequency content and noise effects on damage detection has been investigated. For this purpose, the damage was defined as nonlinear behavior of beams and columns, and several ground motion records were scaled so that some elements yield under the applied excitation. Then the acceleration response data of each floor obtained using the nonlinear dynamic analysis. Using the discrete wavelet analysis, the occurrence and time of damage in a frame can be detected based on the spikes appearing in the wavelet details plots obtained from discrete wavelet decomposition. The mean period (Tm) was used to determine the frequency content of earthquakes. The implications of this parameter for the analyses with different ground motion records were investigated and the results showed that the records with low Tm are more suitable for structural damage detection. To investigate the effect of noise or measurement errors on damage detection process, the discrete wavelet analysis was repeated with a noise introduced to the acceleration response data.Sun, 04 Feb 2018 20:30:00 +0100New Lateral Force Distribution for Seismic Design of Structures Based on Seismic Demand Ratio
http://civiljournal.semnan.ac.ir/article_2836_0.html
The design of earthquake-resistant buildings starts with defining the maximum lateral earthquake forces or their resultant. The amount of these forces depends on various factors, including coefficient of system behavior which depends on overstrength and its ductility. In this study, a method is presented for designing an earthquake-resistant system in which the distribution of lateral forces is adjusted based on equal distribution of the seismic demand ratio in structural elements for the optimum use of seismic capability of the structure. To this end, three types of 4-, 7-, and 10-story structures are used. First, the above-mentioned structures are designed based on gravity loads and then analyzed based on linear and nonlinear dynamic analyses, using the accelerograms of some major earthquakes. Following that, the average loading ratio to the allowed capacity of the elements of each story in linear analysis and the average ratios of plastic rotations to the allowed capacity of elements in nonlinear analysis are applied as the modified shear ratio in the Iranian National Seismic Code. Therefore, the new lateral loading distribution is measured and identified. Based on this new distribution, the above-mentioned structures are designed and their seismic behaviors are identified, using linear and nonlinear dynamic analyses of the same accelerograms. The findings indicate an improved seismic behavior of the beams and the columns. Moreover, the distribution of the seismic demand ratios attains more uniformity along the height of the structures.Sun, 04 Feb 2018 20:30:00 +0100An experimental and numerical study on the bearing capacity of circular and ring footings on ...
http://civiljournal.semnan.ac.ir/article_2837_0.html
This paper presents the results of a series of small-scale model tests and numerical analyses conducted on circular and ring model footings located near geogrid reinforced sand slopes. Layers of geogrid were used as reinforcement. For numerical analyses Finite Element Method (FEM) was used. The effects of reinforcement depth, size, number of layers, and the horizontal distance between reinforcement and the slope surface were experimentally investigated. Additionally, the effects of other parameters such as slope angle, the distance of the footing from the slope crest (for circular footings) and the ratio of inner to outer diameters (for ring fittings) were also investigated, numerically. The results of numerical analyses were compared with the laboratory test results and found to be in fair agreement. Optimum bearing capacity values were found for some studied parameters. The results indicate that if the reinforcement layers are implemented correctly, the bearing capacity of circular and ring footings over slopes would significantly increase.Sun, 04 Feb 2018 20:30:00 +0100On the Local Scour around Group Piers in Series by Experimental Tests
http://civiljournal.semnan.ac.ir/article_2838_0.html
In this research a physical model is presented. A trapezoidal shape of channel with 1.45 m width, 1 meter depth and banks slope of 1H: 1.5V was used. Circular piers (6, 8 and 10cm diameter) were tested under three different flow discharges of 50, 65 and 80 lit/s and three different median bed material sizes equal to 0.94, 1.31 and 2.12 mm. Seven different longitude distance to pier diameter ratios (1, 1.5, 2, 2.5, 3, 4 and 5) were tested. Measurement of scour depth (upstream, around and downstream of pier) was accomplished in 10, 15, 20, 30, 60, 120, 240 and 360 minutes from the beginning of each test. The results showed that 30% to 40%, 55% to 65% and more than 90% of local scour occurs at first two minutes, at first 10 minutes and 120 to 200 minutes from the beginning of test respectively. The effect of different parameter especially the distance between piers on scour depth at group piers in series was evaluated and the results were compared to other investigators. It was found that our results is best fitted with the general form of well known Sheppard et al. (2004)’s equation.Sun, 04 Feb 2018 20:30:00 +0100Testing and numerical modelling of Steel-Concrete-Steel with stud bolts connectors subject to ...
http://civiljournal.semnan.ac.ir/article_2839_0.html
Steel-concrete-steel (SCS) sandwich panels are composed of two steel plates with low thicknesses and high densities and strengths and one thick layer between both plates with low strength and density known as core that is composed of concrete. Cohesive material-epoxy resin or shear connectors are usually used to connect the plates to the concrete core. SCS sandwich composites are being developed to be used in offshore structures and buildings. Stud bolt is one of the shear connectors and their interlayer shear behavior is studied in the present study. To investigate the effect of parameters on interlayer shear behavior of steel-concrete-steel sandwich structure with stud bolt connectors, push-out test is performed under progressive loading.According to the tests performed, relations are proposed to predict ultimate shear strength and load-slip behavior of samples with stud bolt shear connectors.Then, numerical model of push-out test is presented on the basic component of Steel-Concrete-Steel sandwich structure (SCS) with stud bolt connectors. The results showed that finite element model is consistent with test results using mass scaling in Explicit Solver with a suitable analysis speed. Using the regression analysis on the results of 80 numerical models of push-out test,a relation was proposed for shear strength of push-out samples with stud bolt connectors.Sun, 04 Feb 2018 20:30:00 +0100Evaluating the Performance of the Buckling Restrained Braces in Tall Buildings with ...
http://civiljournal.semnan.ac.ir/article_2840_0.html
In recent years, seismic design of structures has been undergoing significant changes due to increasing demand for optimization and minimizing the level of damage and reducing the cost of structural repairs. Development of analytical methods and remarkable improvements of computer performance have been among the factors which influenced the design of structures. A lot of research has been conducted on the development of braces with perfect elastoplastic behaviour. The invention and development of the buckling restrained braces have been the results of these researches. In this study, the performance of the Buckling Restrained Environmental Braces (BRB) in high-rise buildings were evaluated using nonlinear time-history dynamics analysis with three pairs of acceleration and compared with the conventional concentrically braced frame (CBF). The studied structures are 20, 40, and 60 stories building in which braces were utilized peripherally. The obtained results illustrate that the use of Buckling Restrained Brace Frames (BRB) instead of conventional braces frame (CBF) in high-rise steel buildings improves hysteresis behavior of the braces and reduces lateral displacements and also increase the capacity of base shear.Sun, 04 Feb 2018 20:30:00 +0100Seismic Rehabilitation of Liquid Storage Tanks using Friction Pendulum Base Isolation subjected ...
http://civiljournal.semnan.ac.ir/article_2841_0.html
Cylindrical liquid storage tanks are considered as vital structures in industrial complex whose nonlinear dynamic behavior is of crucial importance. Some of these structures around the world have demonstrated poor seismic behavior over the last decades. There are several methods and techniques for rehabilitation and reducing damages in these structures which among them passive control devices, in particular seismic base isolators, are noticeable. Friction Pendulum System (FPS) is the most popular base isolation system. In this paper, the effectiveness of FPS is studied on reducing the seismic responses of base isolated liquid storage tanks as well as the impact effect of slider to the side restrainer. To this end, the whole mass of liquid storage tank is considered as three lumped masses known as convective mass, impulsive mass which is connected to tanks with corresponding spring, and rigid mass which is connected rigidly. By means of state space method the time history analysis is done using 60 earthquake records to obtain dynamic responses under the different hazard levels i.e. SLE, DBE and MCE ground motions. The results show that the normalized base shear force in squat tank decreased 59%, 62% and 33% respectively under SLE, DBE and MCE ground motions. The reduction of normalized base shear force in slender tank is 53%, 49% and 35% under the aforementioned hazard levels. Examining the effect of side restrainer’s stiffness on the maximum responses show that the impact effect must be considered particularly when the system is excited by MCE’s ground motions.Sun, 04 Feb 2018 20:30:00 +0100Extraction of model parameters for reactive solute transport
http://civiljournal.semnan.ac.ir/article_2842_0.html
In the present study, tried to examine the reactive solute relationships for transport and degradation processes through the rockfill media. By applying the analytical solution of reactive transport, the 1st to 3rd theoretical temporal moments have been extracted then, by using two methods of curve fitting and temporal moment matching, the coefficients of dispersion and degradation have been exploited. Two rock diameter, two operating discharges and five instantly injection mass have been used as the variables of experiments. The EC sensors with operation software were installed inside the rockfill media and then the experimental breakthrough curves with intervals of 4 seconds have been extracted. It is concluded that both methods are suitable for application of transport and degradation processes inside the media. It was observed that by increasing inflow discharges, pore velocity, and media diameters the dispersion coefficient decreases and with a decrease in media diameter or with increase in injection mass the decay rate decreases. The sensitivity analysis on the derived moment equation and also skewness coefficient equation indicated that the velocity and degradation are the most and less effective parameters on the moment equations respectivelySun, 04 Feb 2018 20:30:00 +0100A laboratory investigation on the potential of computational intelligence approaches to ...
http://civiljournal.semnan.ac.ir/article_2843_0.html
The piano key weir (PKW) is a type of nonlinear control structure that can be used to increase unit discharge over linear overflow weir geometries, particularly when the weir footprint area is restricted To predict the outflow passing over a piano key weir, the discharge coefficient in the general equation of weir needs to be known. This paper presents the results of laboratory model testing of a piano key weir located on the straight open channel flume in the hydraulic laboratory of Bu-Ali Sina University. The discharge coefficient of piano key weir is estimated by using four computational intelligence approaches, namely, feed forward back-propagation neural network (FFBPN), an extension of genetic programming namely gene-expression programming (GEP), least square support vector machine (LSSVM) and extreme learning machine (ELM). For this purpose, 70 laboratory test results were used for determining discharge coefficient of piano key weir for a wide range of discharge values. Coefficient of determination (R2), Nash-Sutcliffe efficiency coefficient (NS), root mean square error (RMSE), mean absolute relative error (MARE), scatter index (SI) and BIAS are used for measuring the models’ performance. Overall performance of the models shows that, all the studied models are able to estimate discharge coefficient of piano key weir satisfactorily. Comparison of results showed that the ELM (R2=0.997 and NS= 0.986) and LSSVM (RMSE=0.016 and MARE=0.027) models were able to produce better results than the other models investigated and could be employed successfully in modeling discharge coefficient from the available experimental data.Sun, 04 Feb 2018 20:30:00 +0100Assessing Seismic Performance of The Elliptic Braced Moment Resisting Frame through Pushover Method
http://civiljournal.semnan.ac.ir/article_2844_0.html
The seismic performance of elliptic braced moment resisting frame (ELBRF) is assessed here and is found that the structural behavior is improved and is of free of architectural space. The demand for seismic performance of ELBRF is estimated through conventional pushover methods of 3, 5, 7, and 10-story ELBRF frames and they are compared with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. The effective parameters in the seismic design of structures, like the ductility, overstrength and response modification factors are evaluated. The response modification factor for ELBRF in the design by ultimate limit state and allowable stress methods is proposed as 10 and 14.4, respectively. Finally, the process of forming plastic hinges in ELBRF is assessed and it is found that an increase in height makes the plastic hinges to be transmitted to the upper stories, allowing the structure to collapse at higher stories.Sun, 04 Feb 2018 20:30:00 +0100Evaluation of Dynamic Shear Rheometer Test parameters and Effect of Carbon Black Particles ...
http://civiljournal.semnan.ac.ir/article_2845_0.html
Using 100% of recyclable materials in road construction, protecting the environment, is an influential factor in the decision-making process for road projects. As one of the most important elements in nature and an original basis for the formation of life on earth, Carbon has been used in many different industries for its high surface area and porosity. Because of asphalt binder rheology characteristics, asphalt layers tend to return to their initial conditions after traffic flow but some of these deformations return in elastic form and some not return in plastic form. In this research, the Dynamic Shear Rheometer (DSR) test was used to analyze asphalt Binder performance Grade. Carbon Black particles processed from agricultural waste recycling (walnut skin) with specific weight percentages of 3, 5, 7 and 10, were used for asphalt binder rehabilitation. According to the results, the use of Carbon Black particles derived from the recycling of agricultural waste improves asphalt binder performance Grade from PG64 to PG74 for modified asphalt binder with 7% carbon black and rheological parameters like complex modulus increased 1.7 times and phase angle decreased approximately 0.85 times.Sun, 04 Feb 2018 20:30:00 +0100An optimal semi-active thermal exchange-Fuzzy logic Controller for Structural Dynamic Control ...
http://civiljournal.semnan.ac.ir/article_2846_0.html
The effect of intelligent semi-active thermal exchange-fuzzy controller in structural rehabilitation by attenuating seismic responses of structural systems is investigated. In the suggested control system, MR dampers and sensors are employed as a semi-active controller. Resultant control forces of MR damper are administrated by providing external voltage supply, during the earthquakes and high intensity winds. Moreover, a novel evolutionary algorithm of thermal exchange (TE) is utilized to optimize the placement and the number of MR dampers and sensors in the sense of minimizing resultant vibration magnitude. An optimal semi-active thermal exchange-Fuzzy logic Controller (TE-FLC) is introduced to manage MR damper intelligently. Results of numerical simulations illustrate the efficiency of suggested control system. The TE-FLC can determine the optimal control arrangement and forces during a reasonable number of iterations. In comparison of the performance of various control strategies, the TE-FLC demonstrates that economical cost and rehabilitation properties of the building could be optimized simultaneously. The TE-FLC managed the optimal control forces online during strong ground motion, to attenuate the excessive responses in several rehabilitated buildings. Hence, the TE-FLC could improve the reliability of rehabilitated structure in comparison with passive and offline controllers. The significant efficiency of optimal arrangement of dampers and sensors over uniformly distribution of damper and sensors is also illustrated.Sun, 04 Feb 2018 20:30:00 +0100