Pub Date : 2018-06-01DOI: 10.7508/CEIJ.2018.01.011
H. Mortezaie, Freydoon Rezaie
Since the structure and foundation are built on soil, the soil is the major platform by which seismic vibrations are transmitted to the structure, and has noticeable effects on the response and behavior of structure during earthquakes. In this research, the recently introduced Performance-based plastic design (PBPD) and its modified Performance-based plastic design (MPBPD) method in which soil and structure interaction effect has been considered underwent the seismic evaluation. In order to do evaluation, a twenty-floor concrete structure with MPBPD method and conventional PBPD was designed and analyzed in accordance with the time history of the 22 far-field quake records. In this study, cone model is employed for modeling the soil and foundation. With a detailed three-dimensional finite element model of a twenty-story high-rise structure constructed and exploited in the OpenSees software, it is attempted to consider a more realistic behavior of the structure. The results of six related parameters with the maximum response of the structure demonstrate the efficiency and performance of the MPBPD method for the purpose of considering the SSI effect, compared with the conventional method of PBPD. The Results show that, in the MPBPD design method, maximum displacement, acceleration, inter-story drift and shear force dropped leading to a better distribution of energy in the structure compared to the PBPD method.
{"title":"Seismic Behavior and Dissipated Plastic Energy of Performance-Based-Designed High-Rise Concrete Structures with Considering Soil–Structure Interaction Effect","authors":"H. Mortezaie, Freydoon Rezaie","doi":"10.7508/CEIJ.2018.01.011","DOIUrl":"https://doi.org/10.7508/CEIJ.2018.01.011","url":null,"abstract":"Since the structure and foundation are built on soil, the soil is the major platform by which seismic vibrations are transmitted to the structure, and has noticeable effects on the response and behavior of structure during earthquakes. In this research, the recently introduced Performance-based plastic design (PBPD) and its modified Performance-based plastic design (MPBPD) method in which soil and structure interaction effect has been considered underwent the seismic evaluation. In order to do evaluation, a twenty-floor concrete structure with MPBPD method and conventional PBPD was designed and analyzed in accordance with the time history of the 22 far-field quake records. In this study, cone model is employed for modeling the soil and foundation. With a detailed three-dimensional finite element model of a twenty-story high-rise structure constructed and exploited in the OpenSees software, it is attempted to consider a more realistic behavior of the structure. The results of six related parameters with the maximum response of the structure demonstrate the efficiency and performance of the MPBPD method for the purpose of considering the SSI effect, compared with the conventional method of PBPD. The Results show that, in the MPBPD design method, maximum displacement, acceleration, inter-story drift and shear force dropped leading to a better distribution of energy in the structure compared to the PBPD method.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49350561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.7508/CEIJ.2018.01.002
َAmin Amiri, M. M. Toufigh, Sina Sadeghi Janat Abadi, V. Toufigh
Vertical drains and stone columns which have been used in infrastructure construction for highways, ports, coastal regions, etc., provide significant benefits for improving soil characteristics such as reducing the drainage length and accelerating the consolidation process. So the investigation of the radial consolidation is inevitable. Soils may be subjected to cyclic loading such as silos, tanks, etc. This paper presents semi-analytical solutions for radial consolidation and investigates the consolidation behavior under three types of cyclic loading. Consolidation under cyclic loads was calculated using the superimposition rule. Barron (1948) and Olson (1977) have presented theories for calculating radial consolidation under static and ramp load respectively. In this study, by using a set of continuous static loads or a series of infinite ramp loads, with alternatively positive and negative signs, we have extended these theories for rectangular, triangular and trapezoidal cyclic loads. The obtained analytic results demonstrate that the average degree of consolidation at the steady state depends on the integral of the load-time curve for each cycle and it increases with increase of the integral and the results indicate that change in cycle period of time does not effect on the time of getting steady state. Radial and vertical consolidation under rectangular cyclic loading have also compared and the effect of the distance between vertical drains on the time of getting steady state have investigated.
{"title":"Comparison of Radial Consolidation Behavior of Clay under Three Types of Cyclic Loading","authors":"َAmin Amiri, M. M. Toufigh, Sina Sadeghi Janat Abadi, V. Toufigh","doi":"10.7508/CEIJ.2018.01.002","DOIUrl":"https://doi.org/10.7508/CEIJ.2018.01.002","url":null,"abstract":"Vertical drains and stone columns which have been used in infrastructure construction for highways, ports, coastal regions, etc., provide significant benefits for improving soil characteristics such as reducing the drainage length and accelerating the consolidation process. So the investigation of the radial consolidation is inevitable. Soils may be subjected to cyclic loading such as silos, tanks, etc. This paper presents semi-analytical solutions for radial consolidation and investigates the consolidation behavior under three types of cyclic loading. Consolidation under cyclic loads was calculated using the superimposition rule. Barron (1948) and Olson (1977) have presented theories for calculating radial consolidation under static and ramp load respectively. In this study, by using a set of continuous static loads or a series of infinite ramp loads, with alternatively positive and negative signs, we have extended these theories for rectangular, triangular and trapezoidal cyclic loads. The obtained analytic results demonstrate that the average degree of consolidation at the steady state depends on the integral of the load-time curve for each cycle and it increases with increase of the integral and the results indicate that change in cycle period of time does not effect on the time of getting steady state. Radial and vertical consolidation under rectangular cyclic loading have also compared and the effect of the distance between vertical drains on the time of getting steady state have investigated.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44089017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.7508/CEIJ.2018.01.006
Farrokh Kianmofrad, E. Ghafoori, M. Motavalli, M. Rahimian
Trapezoidal prestressed unbonded retrofit (TPUR) systems have been recently developed and tested. The authors have already developed a comprehensive and accurate analytical solution for the TPUR system that takes many system parameters into account. The main aim of this paper is to develop a simplified analytical solution for predicting the behavior of metal beams that have been strengthened with the TPUR system. The developed analysis method can be useful to engineers because of its simplicity. An energy approach based on Castigliano’s theorems is used to study the flexural behavior of a steel beam retrofitted with the TPUR system. A parametric study was performed and the comparative results showed that the results using Castigliano’s first theorem are in agreement with the results using the flexibility approach.
{"title":"Analytical Solutions for the Flexural Behavior of Metal Beams Strengthened with Prestressed Unbonded CFRP Plates","authors":"Farrokh Kianmofrad, E. Ghafoori, M. Motavalli, M. Rahimian","doi":"10.7508/CEIJ.2018.01.006","DOIUrl":"https://doi.org/10.7508/CEIJ.2018.01.006","url":null,"abstract":"Trapezoidal prestressed unbonded retrofit (TPUR) systems have been recently developed and tested. The authors have already developed a comprehensive and accurate analytical solution for the TPUR system that takes many system parameters into account. The main aim of this paper is to develop a simplified analytical solution for predicting the behavior of metal beams that have been strengthened with the TPUR system. The developed analysis method can be useful to engineers because of its simplicity. An energy approach based on Castigliano’s theorems is used to study the flexural behavior of a steel beam retrofitted with the TPUR system. A parametric study was performed and the comparative results showed that the results using Castigliano’s first theorem are in agreement with the results using the flexibility approach.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47121293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.7508/CEIJ.2018.01.001
M. Mohammadian, M. S. Zadeh
The only way to test the ability of concrete plants to produce high quality concrete is to test their final products. Also, the process of testing and controlling concrete quality is time consuming and expensive. In this regard, having a quick, cheap and efficient way to predict the readiness of concrete plants to produce high quality concrete is very valuable. In this paper, a probabilistic multi-attribute algorithm has been developed to address this problem. In this algorithm, the goal is to evaluate readiness of concrete plants to produce high quality concrete based on the error rate of concrete compressive strength. Using past information and data mining techniques, this algorithm predicts the readiness level of concrete plants by similarity of their production factors to past information. Readiness alternatives for plants are ranked using data mining techniques for order preference based on their production factors (PF) and by evaluating the similarity/difference of each PF to past information. A case study of 20 concrete plants is used to illustrate the capability of the new algorithm; with results showing that the algorithm generated nondominated solutions can assist plant managers to set efficient production plan, a task both difficult, cost and time-consuming using current methods. In the case study, lab test totally confirm the algorithm outcomes thus it has been successfully verified.
{"title":"Evaluation of Concrete Plants Readiness to Produce High Quality Concrete for Municipal Constructions Using Past Information","authors":"M. Mohammadian, M. S. Zadeh","doi":"10.7508/CEIJ.2018.01.001","DOIUrl":"https://doi.org/10.7508/CEIJ.2018.01.001","url":null,"abstract":"The only way to test the ability of concrete plants to produce high quality concrete is to test their final products. Also, the process of testing and controlling concrete quality is time consuming and expensive. In this regard, having a quick, cheap and efficient way to predict the readiness of concrete plants to produce high quality concrete is very valuable. In this paper, a probabilistic multi-attribute algorithm has been developed to address this problem. In this algorithm, the goal is to evaluate readiness of concrete plants to produce high quality concrete based on the error rate of concrete compressive strength. Using past information and data mining techniques, this algorithm predicts the readiness level of concrete plants by similarity of their production factors to past information. Readiness alternatives for plants are ranked using data mining techniques for order preference based on their production factors (PF) and by evaluating the similarity/difference of each PF to past information. A case study of 20 concrete plants is used to illustrate the capability of the new algorithm; with results showing that the algorithm generated nondominated solutions can assist plant managers to set efficient production plan, a task both difficult, cost and time-consuming using current methods. In the case study, lab test totally confirm the algorithm outcomes thus it has been successfully verified.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45064002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.004
M. Rezaiee-Pajand, M. Yaghoobi
In this paper, a plane quadrilateral element with rotational degrees of freedom is developed. Present formulation is based on a hybrid functional with independent boundary displacement and internal optimum strain field. All the optimality constraints, including being rotational invariant, omitting the parasitic shear error and satisfying Fliepa’s pure bending test, are considered. Moreover, the static equilibrium equations are satisfied in this scheme. Authors’ element has only four nodes and twelve degrees of freedom. For the boundary displacement field, Alman’s second-order displacement function is employed. The validities of the proposed element are demonstrated by eleven numerical examples: thick curved beam, thin cantilever beam, Cooke’s skew beam, thin curved beam, cantilever beam with distortion parameter, high-order patch test, cantilever beam with five and four irregular mesh, Mc Neal’s thin cantilever beam and cantilever shear wall with and without openings. When utilizing the coarse and irregular meshes, numerical tests show the high accuracy, rapid convergence and robustness of the suggested element. Less sensitivity to distortion is another property of the new element.
{"title":"A Hybrid Stress Plane Element with Strain Field","authors":"M. Rezaiee-Pajand, M. Yaghoobi","doi":"10.7508/CEIJ.2017.02.004","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.004","url":null,"abstract":"In this paper, a plane quadrilateral element with rotational degrees of freedom is developed. Present formulation is based on a hybrid functional with independent boundary displacement and internal optimum strain field. All the optimality constraints, including being rotational invariant, omitting the parasitic shear error and satisfying Fliepa’s pure bending test, are considered. Moreover, the static equilibrium equations are satisfied in this scheme. Authors’ element has only four nodes and twelve degrees of freedom. For the boundary displacement field, Alman’s second-order displacement function is employed. The validities of the proposed element are demonstrated by eleven numerical examples: thick curved beam, thin cantilever beam, Cooke’s skew beam, thin curved beam, cantilever beam with distortion parameter, high-order patch test, cantilever beam with five and four irregular mesh, Mc Neal’s thin cantilever beam and cantilever shear wall with and without openings. When utilizing the coarse and irregular meshes, numerical tests show the high accuracy, rapid convergence and robustness of the suggested element. Less sensitivity to distortion is another property of the new element.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44939485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.011
A. Miyamoto, Hiroyoshi Asano
A practical Bridge Management System has been developed by the author, which is referred to as the Japanese Bridge Management System (J-BMS) for existing concrete bridges. This paper introduces a newly developed bridge management system for the prestressed concrete (PC) bridges (J-BMS PC version) which is integrated with the PC bridge rating expert system (PC-BREX). The proposed system is able to predict the deterioration process of the existing PC bridge superstructure components as well as assess a broad array of optional corrective strategies. The system also has the capability to search and retrieve from a J-BMS database system (J-BMS DB), the necessary information, carry out suitable analyses to arrive at some recommendations that would help users to optimize their decisions based on engineering aspects, cost and economic issues and bridge management policies. A comparison of the results of applying the system to some actual in-service PC bridges with a special designed survey form to experts shows that optimal maintenance planning as well as bridge rating can be predicted accurately by using the system.
{"title":"Development and Practical Application of a Lifetime Management System for Prestressed Concrete Bridges","authors":"A. Miyamoto, Hiroyoshi Asano","doi":"10.7508/CEIJ.2017.02.011","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.011","url":null,"abstract":"A practical Bridge Management System has been developed by the author, which is referred to as the Japanese Bridge Management System (J-BMS) for existing concrete bridges. This paper introduces a newly developed bridge management system for the prestressed concrete (PC) bridges (J-BMS PC version) which is integrated with the PC bridge rating expert system (PC-BREX). The proposed system is able to predict the deterioration process of the existing PC bridge superstructure components as well as assess a broad array of optional corrective strategies. The system also has the capability to search and retrieve from a J-BMS database system (J-BMS DB), the necessary information, carry out suitable analyses to arrive at some recommendations that would help users to optimize their decisions based on engineering aspects, cost and economic issues and bridge management policies. A comparison of the results of applying the system to some actual in-service PC bridges with a special designed survey form to experts shows that optimal maintenance planning as well as bridge rating can be predicted accurately by using the system.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42866199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.001
G. Abdollahzadeh, E. Jahani, Zahra Kashir
This study introduces, two models based on Gene Expression Programming (GEP) to predict compressive strength of high strength concrete (HSC). Composition of HSC was assumed simplified, as a mixture of six components (cement, silica fume, super-plastisizer, water, fine aggregate and coarse aggregate). The 28-day compressive strength value was considered the target of the prediction. Data on 159 mixes were taken from various publications. The system was trained based on 80% training pairs chosen randomly from the data set and then tested using remaining 20% samples. Therefore it can be proven and illustrated that the GEP is a strong technique for the prediction of compressive strength amounts of HSC concerning to the outcomes of the training and testing phases compared with experimental outcomes illustrate that the.
{"title":"Genetic Programming Based Formulation to Predict Compressive Strength of High Strength Concrete","authors":"G. Abdollahzadeh, E. Jahani, Zahra Kashir","doi":"10.7508/CEIJ.2017.02.001","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.001","url":null,"abstract":"This study introduces, two models based on Gene Expression Programming (GEP) to predict compressive strength of high strength concrete (HSC). Composition of HSC was assumed simplified, as a mixture of six components (cement, silica fume, super-plastisizer, water, fine aggregate and coarse aggregate). The 28-day compressive strength value was considered the target of the prediction. Data on 159 mixes were taken from various publications. The system was trained based on 80% training pairs chosen randomly from the data set and then tested using remaining 20% samples. Therefore it can be proven and illustrated that the GEP is a strong technique for the prediction of compressive strength amounts of HSC concerning to the outcomes of the training and testing phases compared with experimental outcomes illustrate that the.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41891633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.003
R. Chenari, Behroo Behfar
The soil is a heterogeneous and anisotropic medium. Hydraulic conductivity, an intrinsic property of natural alluvial deposits varies both deterministically and randomly in space and has different values in various directions. In the present study, the permeability of natural deposits and its influence on the seepage flow through a natural alluvial deposit is studied. The 2D Finite Difference code, FLAC 5.0, is used for modeling permeability as a random variable with lognormal distribution and correlated structure. Effect of spatially varying permeability on the seepage flow through deposit is investigated for both isotropic and anisotropic conditions. Results show that in isotropic condition, the mean discharge flow rate calculated from stochastic analyses is less than the equivalent deterministic value and this reduction depends on the coefficient of variation, COV of permeability and the correlation length. The directionality of permeability introduced as mechanical anisotropy was also studied along with the heterogeneity. It was found that increasing the anisotropy ratio of permeability leads to the formation of horizontal flow canals and increasing the seepage flow consequently at a constant vertical permeability. Variation of permeability coefficient was found to have almost no impact on mean discharge flow rate for anisotropic fields in comparison to the isotropic condition.
{"title":"Stochastic Analysis of Seepage through Natural Alluvial Deposits Considering Mechanical Anisotropy","authors":"R. Chenari, Behroo Behfar","doi":"10.7508/CEIJ.2017.02.003","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.003","url":null,"abstract":"The soil is a heterogeneous and anisotropic medium. Hydraulic conductivity, an intrinsic property of natural alluvial deposits varies both deterministically and randomly in space and has different values in various directions. In the present study, the permeability of natural deposits and its influence on the seepage flow through a natural alluvial deposit is studied. The 2D Finite Difference code, FLAC 5.0, is used for modeling permeability as a random variable with lognormal distribution and correlated structure. Effect of spatially varying permeability on the seepage flow through deposit is investigated for both isotropic and anisotropic conditions. Results show that in isotropic condition, the mean discharge flow rate calculated from stochastic analyses is less than the equivalent deterministic value and this reduction depends on the coefficient of variation, COV of permeability and the correlation length. The directionality of permeability introduced as mechanical anisotropy was also studied along with the heterogeneity. It was found that increasing the anisotropy ratio of permeability leads to the formation of horizontal flow canals and increasing the seepage flow consequently at a constant vertical permeability. Variation of permeability coefficient was found to have almost no impact on mean discharge flow rate for anisotropic fields in comparison to the isotropic condition.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41883470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.010
S. Madani, Mohammad Kooshafar
Nanosilicas have been known as super-pozzolanic materials and compared to silica fume, these materials have higher purity of silica and finer particles. However, in contrast to silica fume, nanosilicas are produced by various methods, leading to different morphologies and agglomeration statuses in their initial form. On the other hand, due to several mechanisms such as the bridging effect of calcium ions between particles, double layer compression at a high ionic concentration, and dehydration of silica surfaces, nanosilica particles are destabilized in the pore solution environment of cement mixtures. Thus, the behavior of these materials is different from that of silica fume. In this research, considering the recent studies, a comprehensive investigation has been carried out on the influence of nanosilicas on the mechanical, durability and microstructural characteristics of cement composites. This study investigates the mechanisms that influence the performance of nanosilica in cement-based materials. Based on these mechanisms, several applications have been suggested and discussed. Some of these applications include viscosity-modifying agent in self-compacting concrete, enhancing the cohesion of cement composites, increasing the adhesion capacity of repair mortars and shotcrete to the substrate surface, accelerating the cement hydration, developing low-alkali cements and fast early-strength cements.
{"title":"Influential Mechanisms and Potential Applications of Nano-Silicas in Cement Composites","authors":"S. Madani, Mohammad Kooshafar","doi":"10.7508/CEIJ.2017.02.010","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.010","url":null,"abstract":"Nanosilicas have been known as super-pozzolanic materials and compared to silica fume, these materials have higher purity of silica and finer particles. However, in contrast to silica fume, nanosilicas are produced by various methods, leading to different morphologies and agglomeration statuses in their initial form. On the other hand, due to several mechanisms such as the bridging effect of calcium ions between particles, double layer compression at a high ionic concentration, and dehydration of silica surfaces, nanosilica particles are destabilized in the pore solution environment of cement mixtures. Thus, the behavior of these materials is different from that of silica fume. In this research, considering the recent studies, a comprehensive investigation has been carried out on the influence of nanosilicas on the mechanical, durability and microstructural characteristics of cement composites. This study investigates the mechanisms that influence the performance of nanosilica in cement-based materials. Based on these mechanisms, several applications have been suggested and discussed. Some of these applications include viscosity-modifying agent in self-compacting concrete, enhancing the cohesion of cement composites, increasing the adhesion capacity of repair mortars and shotcrete to the substrate surface, accelerating the cement hydration, developing low-alkali cements and fast early-strength cements.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45893729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-01DOI: 10.7508/CEIJ.2017.02.009
M. Amiri, J. V. Amiri, B. Ganjavi
The determination of structural and nonstructural damage under earthquake excitations is usually considered as a key factor in performance-based seismic design (PBSD) methods is In this regard, various damage indices have been developed in recent years to quantitatively estimate structural damage. The aim of this study is to develop a simple method to evaluate performance levels of zipper-braced frame (ZBF) structures by using damage indices based on the results of nonlinear static and dynamic analyses. To this end, 5, 7, 10, 12 and 15 story zipper-braced frames (ZBF) are modeled and undergone to twenty different synthetic ground motion records and their damage values have been computed. In dynamic damage analysis procedure, the performance levels of the ZBF models have been computed based on the FEMA-356 standard. Considering the results of the nonlinear dynamic analyses, the correlation between FEMA-356 performance levels and damage indices has been investigated and some simplified formula is presented. On the other side, in static damage analysis approach, by using pushover analysis the performance points of ZBF models have been estimated based on capacity spectrum method (CSM) provided by ATC-40 standard. Then, the correlation between ATC-40 performance levels and some static damage indices has been investigated and some simple equations have been proposed. These relations can be utilized to estimate the performance levels of structures from damage indices. Finally, tables are represented for determination of the structural damage index values for assumed performance levels of the ZBF structures based on static and dynamic damage analysis.
{"title":"Evaluation of Performance Levels of Zipper-Braced Frames Using Structural Damage Index","authors":"M. Amiri, J. V. Amiri, B. Ganjavi","doi":"10.7508/CEIJ.2017.02.009","DOIUrl":"https://doi.org/10.7508/CEIJ.2017.02.009","url":null,"abstract":"The determination of structural and nonstructural damage under earthquake excitations is usually considered as a key factor in performance-based seismic design (PBSD) methods is In this regard, various damage indices have been developed in recent years to quantitatively estimate structural damage. The aim of this study is to develop a simple method to evaluate performance levels of zipper-braced frame (ZBF) structures by using damage indices based on the results of nonlinear static and dynamic analyses. To this end, 5, 7, 10, 12 and 15 story zipper-braced frames (ZBF) are modeled and undergone to twenty different synthetic ground motion records and their damage values have been computed. In dynamic damage analysis procedure, the performance levels of the ZBF models have been computed based on the FEMA-356 standard. Considering the results of the nonlinear dynamic analyses, the correlation between FEMA-356 performance levels and damage indices has been investigated and some simplified formula is presented. On the other side, in static damage analysis approach, by using pushover analysis the performance points of ZBF models have been estimated based on capacity spectrum method (CSM) provided by ATC-40 standard. Then, the correlation between ATC-40 performance levels and some static damage indices has been investigated and some simple equations have been proposed. These relations can be utilized to estimate the performance levels of structures from damage indices. Finally, tables are represented for determination of the structural damage index values for assumed performance levels of the ZBF structures based on static and dynamic damage analysis.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43045039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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