Pub Date : 2020-05-01DOI: 10.22075/JRCE.2019.17441.1329
A. A. Mazloum, M. A. Afshar
In this paper, in addition to introduce a hybrid structural system contained local isolators and dampers, its behavior and functional capabilities were studied on a conventional structure. For this purpose, an RC frame building with six-story was designed based on valid codes and then, in four cases based on the number of spans, it was split into two separate adjacent frames. Base isolation was done underneath the columns of one frame, while the bottom connections of the other frame’s columns were remained fixed and viscous dampers provided the connection of two adjacent frames on the same floors. Nonlinear time history analysis (NTHA) under three near-fault and three far-fault earthquakes and frequency-domain analysis are performed. Displacement, drift, acceleration and shear forces of the stories in the four proposed hybrid cases with two limited cases, full base-isolated and full base-fixed frames, as well as nonlinear hysteresis behavior of a damper and an isolator are assessed. The results showed that using the novel hybrid control method in most cases can mitigate deteriorating effects of all types of seismic motions observed in the conventional structural systems. However, among them, two cases (2 isolated columns -5 fixed columns and 3 isolated columns -4 fixed columns) had the best significant influence on seismic performance and structural response reduction. Furthermore, frequency response functions of displacement and acceleration with respect to ground acceleration demonstrated that the two proposed cases further suppress the responses of the limited cases, over a wide range of frequencies including all natural frequencies. Due to decrease about 50-70% in the number of base isolators (compared to full isolation) lead to considerable construction cost savings. In spite of the limitation of ASCE7-10 code on separately using base isolators and dampers on structure, applying the proposed combination technique of these two dissipating devices can overcome the limitation.
{"title":"Study and Comparison of Seismic Behaviour of Isolator-Damper Hybrid Control System with Conventional Structural Systems","authors":"A. A. Mazloum, M. A. Afshar","doi":"10.22075/JRCE.2019.17441.1329","DOIUrl":"https://doi.org/10.22075/JRCE.2019.17441.1329","url":null,"abstract":"In this paper, in addition to introduce a hybrid structural system contained local isolators and dampers, its behavior and functional capabilities were studied on a conventional structure. For this purpose, an RC frame building with six-story was designed based on valid codes and then, in four cases based on the number of spans, it was split into two separate adjacent frames. Base isolation was done underneath the columns of one frame, while the bottom connections of the other frame’s columns were remained fixed and viscous dampers provided the connection of two adjacent frames on the same floors. Nonlinear time history analysis (NTHA) under three near-fault and three far-fault earthquakes and frequency-domain analysis are performed. Displacement, drift, acceleration and shear forces of the stories in the four proposed hybrid cases with two limited cases, full base-isolated and full base-fixed frames, as well as nonlinear hysteresis behavior of a damper and an isolator are assessed. The results showed that using the novel hybrid control method in most cases can mitigate deteriorating effects of all types of seismic motions observed in the conventional structural systems. However, among them, two cases (2 isolated columns -5 fixed columns and 3 isolated columns -4 fixed columns) had the best significant influence on seismic performance and structural response reduction. Furthermore, frequency response functions of displacement and acceleration with respect to ground acceleration demonstrated that the two proposed cases further suppress the responses of the limited cases, over a wide range of frequencies including all natural frequencies. Due to decrease about 50-70% in the number of base isolators (compared to full isolation) lead to considerable construction cost savings. In spite of the limitation of ASCE7-10 code on separately using base isolators and dampers on structure, applying the proposed combination technique of these two dissipating devices can overcome the limitation.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83380900","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 : 2020-05-01DOI: 10.22075/JRCE.2019.15596.1291
M. Alhassan, M. M. Alhaji
Pavement maintenance and rehabilitation have been neglected in Nigeria for a very long time and has resulted to maintenance backlog. Design agencies in Nigeria still use California Bearing Ratio (CBR), even though the method is outdated. An introduction of Dynamic Cone Penetration Test (DCPT) was pertinent, even though the method is relatively old in some developed countries, it has not gain much prominence in Nigeria. A flexible pavement, constructed from Bida to Mokwa,, Nigeria, was Rehabilitated after 22 years of construction. This was done by placement of stone base course in one section and lateritic base course in the other. The stretch of the road was then overlaid with asphalt surfacing. Before commencement of the rehabilitation, DCPT tests were conducted on the road to evaluate performance of the pavement base and subgrade. Two years after the rehabilitation, an evaluation was carried out at five selected positions (two at crushed stone base and three at lateritic base) to evaluate the performance of the two base courses. The evaluation was carried out by coring the asphalt concrete and DCPT test below the hole created by corer to indirectly estimate the in-situ CBR of the base and subgrade courses. The results from both the stone base and lateritic base sections satisfy the minimum specifications based on standard. The study also showed that pavement failure along the road is not as a result of the materials used in the base course, but as a result of the excessive axle loads experienced by the road.
{"title":"Performance Evaluation of a Trunk-A Road in North Central Nigeria","authors":"M. Alhassan, M. M. Alhaji","doi":"10.22075/JRCE.2019.15596.1291","DOIUrl":"https://doi.org/10.22075/JRCE.2019.15596.1291","url":null,"abstract":"Pavement maintenance and rehabilitation have been neglected in Nigeria for a very long time and has resulted to maintenance backlog. Design agencies in Nigeria still use California Bearing Ratio (CBR), even though the method is outdated. An introduction of Dynamic Cone Penetration Test (DCPT) was pertinent, even though the method is relatively old in some developed countries, it has not gain much prominence in Nigeria. A flexible pavement, constructed from Bida to Mokwa,, Nigeria, was Rehabilitated after 22 years of construction. This was done by placement of stone base course in one section and lateritic base course in the other. The stretch of the road was then overlaid with asphalt surfacing. Before commencement of the rehabilitation, DCPT tests were conducted on the road to evaluate performance of the pavement base and subgrade. Two years after the rehabilitation, an evaluation was carried out at five selected positions (two at crushed stone base and three at lateritic base) to evaluate the performance of the two base courses. The evaluation was carried out by coring the asphalt concrete and DCPT test below the hole created by corer to indirectly estimate the in-situ CBR of the base and subgrade courses. The results from both the stone base and lateritic base sections satisfy the minimum specifications based on standard. The study also showed that pavement failure along the road is not as a result of the materials used in the base course, but as a result of the excessive axle loads experienced by the road.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74555888","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 : 2020-05-01DOI: 10.22075/JRCE.2020.15624.1292
B. Peymanian, R. Dabiri
Nowadays, new materials are widely used for improving the bearing capacity of the soils and geosynthetics include the type of these materials which are utilized in this regard. In addition, the geofoam panel type of geosyntethic materials is useful and an alternative for backfill in retaining wall or pavement layers. The present research mainly aimed to investigate sthe effects of geofoam particles (0.2, 0.5, & 1%) on improving the bearing capacity of the clay-sand mixture. To this end, dune sandy soil (passed from sieve No.30 and residue on sieve No.50) was provided from Shore of the Lake Urmia and mixed with kaoline industrial clay at 15, 30, and 50 percentages. Then, compaction, uniaxial in three loading speed (0.5, 1, & 1.5 mm/min), direct shear (in vertical stresses 1, 2, & 3 kg/cm2), and falling head permeability tests were performed to evaluate the influence of geofoam particles on geotechnical properties of the mixed soil. The results showed that maximum dry density and elastic modulus increased by a 0.5% increase in the geofoam in the soil mixture. Meanwhile, the shear strength of the specimens increased as well. Finally, permeability and the drainage condition improved by adding geofoam to the specimens.
{"title":"Effects of Geofoam Particles on Geotechnical Properties of Clay-dune Sand","authors":"B. Peymanian, R. Dabiri","doi":"10.22075/JRCE.2020.15624.1292","DOIUrl":"https://doi.org/10.22075/JRCE.2020.15624.1292","url":null,"abstract":"Nowadays, new materials are widely used for improving the bearing capacity of the soils and geosynthetics include the type of these materials which are utilized in this regard. In addition, the geofoam panel type of geosyntethic materials is useful and an alternative for backfill in retaining wall or pavement layers. The present research mainly aimed to investigate sthe effects of geofoam particles (0.2, 0.5, & 1%) on improving the bearing capacity of the clay-sand mixture. To this end, dune sandy soil (passed from sieve No.30 and residue on sieve No.50) was provided from Shore of the Lake Urmia and mixed with kaoline industrial clay at 15, 30, and 50 percentages. Then, compaction, uniaxial in three loading speed (0.5, 1, & 1.5 mm/min), direct shear (in vertical stresses 1, 2, & 3 kg/cm2), and falling head permeability tests were performed to evaluate the influence of geofoam particles on geotechnical properties of the mixed soil. The results showed that maximum dry density and elastic modulus increased by a 0.5% increase in the geofoam in the soil mixture. Meanwhile, the shear strength of the specimens increased as well. Finally, permeability and the drainage condition improved by adding geofoam to the specimens.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88837051","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 : 2020-05-01DOI: 10.22075/JRCE.2019.14856.1279
B. Hamedmirjafari, J. B. Bazzaz, S. Abrishami
Even though steel bar is a conventional reinforcement in soil stabilization systems, the problem of corrosion of steel may lead to vast damages especially in aggressive environments. In the past decades, Fiber Reinforced Polymer (FRP) materials have offered an effective solution to overcome the corrosion problem. Despite numerous bond stress-displacement models for reinforcements in concrete, there is a lack of models for FRP nails in grout. In this paper, the usability of four bond stress models (Malvar, EPB, CMR and Soroushian) of reinforcements in concrete was evaluated to predict the bond stress of FRP nails in grout. For this purpose, the results of several experimental pullout tests were used to calibrate the reinforcement-concrete bond stress models and the constant parameters were obtained. To evaluate the accuracy of the calibrated models, four statistical criteria of R2, SSE, RMSE and MAPE have been also determined for each model. Results showed that Malvar model with R2 of 0.94 and MAPE of %21 was deemed suitable for the prediction of bond stress of GFRP nails while CMR model is not recommended.
{"title":"Calibration of bar-Concrete Bond Stress Relationships for Bond Stress Prediction of GFRP Soil Nails Using Experimental Pullout Tests","authors":"B. Hamedmirjafari, J. B. Bazzaz, S. Abrishami","doi":"10.22075/JRCE.2019.14856.1279","DOIUrl":"https://doi.org/10.22075/JRCE.2019.14856.1279","url":null,"abstract":"Even though steel bar is a conventional reinforcement in soil stabilization systems, the problem of corrosion of steel may lead to vast damages especially in aggressive environments. In the past decades, Fiber Reinforced Polymer (FRP) materials have offered an effective solution to overcome the corrosion problem. Despite numerous bond stress-displacement models for reinforcements in concrete, there is a lack of models for FRP nails in grout. In this paper, the usability of four bond stress models (Malvar, EPB, CMR and Soroushian) of reinforcements in concrete was evaluated to predict the bond stress of FRP nails in grout. For this purpose, the results of several experimental pullout tests were used to calibrate the reinforcement-concrete bond stress models and the constant parameters were obtained. To evaluate the accuracy of the calibrated models, four statistical criteria of R2, SSE, RMSE and MAPE have been also determined for each model. Results showed that Malvar model with R2 of 0.94 and MAPE of %21 was deemed suitable for the prediction of bond stress of GFRP nails while CMR model is not recommended.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72915281","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 : 2020-05-01DOI: 10.22075/JRCE.2018.13348.1242
S. S. Kourehli
In this paper, a new method proposed for structural damage detection from limited number of sensors using extreme learning machine (ELM). One of the main challenges in structural damage identification problems is the limitation in the number of used sensors. To address this issue, an effective model reduction method has been proposed. To condense mass and stiffness matrices, the second-order approximation of Neumann series expansion (NSEMR-II) has been used. Mode shapes and frequencies of damaged structures and corresponding generated damage states used as input and output to train extreme learning machine, respectively. To show the effectiveness of presented method, three different examples consists of a truss structure, irregular frame and shear frame have been studied. The obtained results show the ability of the proposed approach in identifying and estimating different damage cases using limited numbers of installed sensors and noisy modal data.
{"title":"Damage identification of structures using second-order approximation of Neumann series expansion","authors":"S. S. Kourehli","doi":"10.22075/JRCE.2018.13348.1242","DOIUrl":"https://doi.org/10.22075/JRCE.2018.13348.1242","url":null,"abstract":"In this paper, a new method proposed for structural damage detection from limited number of sensors using extreme learning machine (ELM). One of the main challenges in structural damage identification problems is the limitation in the number of used sensors. To address this issue, an effective model reduction method has been proposed. To condense mass and stiffness matrices, the second-order approximation of Neumann series expansion (NSEMR-II) has been used. Mode shapes and frequencies of damaged structures and corresponding generated damage states used as input and output to train extreme learning machine, respectively. To show the effectiveness of presented method, three different examples consists of a truss structure, irregular frame and shear frame have been studied. The obtained results show the ability of the proposed approach in identifying and estimating different damage cases using limited numbers of installed sensors and noisy modal data.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82488523","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 : 2020-05-01DOI: 10.22075/JRCE.2019.17478.1331
S. K. Badroodi, M. Keymanesh, G. Shafabakhsh
The present research aims to conduct laboratory assessment on fatigue phenomenon in warm mix asphalt modified with nano-silica and including reclaimed asphalt pavement materials by the aid of review on self-healing behavior and measurement of validity of laboratory results by modeling via neural artificial network in neutral network of SPSS software. For this purpose, 2% weight of sasobit and 3, 5 and 7 % weights of base bitumen-to-bitumen (85-100) were added and they were stirred up by high-cut mixer. Then, the specimens of four-point flexural test were made by the reclaimed bitumen samples. The quantities of 0, 70 and 100% of reclaimed asphalt materials were utilized for aging simulation process in warm mix asphalt to build four-point flexural tested slabs. The findings indicate that adding nano-silica may essentially affect rising self-healing level in warm mix asphalts. The current study intends to present a model based on neural artificial network technique to predict behavior of warm asphalt specimens including different nano-material contents and to compare them with the laboratory results for measurement of validity of the given model. The given results show high precision of the model at level of 0.951.
{"title":"Laboratory Study and Investigation on Significance Level of Fatigue Phenomenon in Warm Mix Asphalt Modified with Nano-Silica","authors":"S. K. Badroodi, M. Keymanesh, G. Shafabakhsh","doi":"10.22075/JRCE.2019.17478.1331","DOIUrl":"https://doi.org/10.22075/JRCE.2019.17478.1331","url":null,"abstract":"The present research aims to conduct laboratory assessment on fatigue phenomenon in warm mix asphalt modified with nano-silica and including reclaimed asphalt pavement materials by the aid of review on self-healing behavior and measurement of validity of laboratory results by modeling via neural artificial network in neutral network of SPSS software. For this purpose, 2% weight of sasobit and 3, 5 and 7 % weights of base bitumen-to-bitumen (85-100) were added and they were stirred up by high-cut mixer. Then, the specimens of four-point flexural test were made by the reclaimed bitumen samples. The quantities of 0, 70 and 100% of reclaimed asphalt materials were utilized for aging simulation process in warm mix asphalt to build four-point flexural tested slabs. The findings indicate that adding nano-silica may essentially affect rising self-healing level in warm mix asphalts. The current study intends to present a model based on neural artificial network technique to predict behavior of warm asphalt specimens including different nano-material contents and to compare them with the laboratory results for measurement of validity of the given model. The given results show high precision of the model at level of 0.951.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89336905","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 : 2020-04-07DOI: 10.22075/JRCE.2020.17989.1345
N. Mahdavi, M. Salimi, M. Ghalehnovi
In recent years, Concrete Filled Tube (CFT) columns have been very much taken into consideration due to the many advantages of the instrument. In experimental studies, the focus has been on compressive loading. Although in many cases the eccentric loading (the presence of a bending moment) has also been investigated, further research is needed in this regard. Therefore, in this study, the steel columns filled with concrete with a regular octagonal cross section were studied under the influence of pressure axial load with eccentricity. The parameters studied in this study include bearing capacity, coefficient of ductility and energy absorption. To test and compare the stated parameters, specimens of 150 cm height, which were filled with plain concrete and fiber reinforced concrete were tested. The compressive axial load has been applied to the specimens by the eccentricity of 50, 100 and 150 mm. The results show that at pure compressive loading, the increase in concrete core capacity increases the load bearing capacity of the specimens so that by increasing the concrete compressive strength by 50%, the bearing capacity of the cross section increases by about 15%. Also, based on the results, the average ductility coefficient for specimens was 7.4, and it seems that this value is independent of the type of loading. The use of concrete with intermediate grade resistance can increase the energy absorbed. However, according to the results, it seems that by increasing the bending moment the positive effects of the concrete core are greatly reduced.
{"title":"Experimental study of octagonal steel columns filled with plain and fiber concrete under the influence of compressive axial load with eccentricity","authors":"N. Mahdavi, M. Salimi, M. Ghalehnovi","doi":"10.22075/JRCE.2020.17989.1345","DOIUrl":"https://doi.org/10.22075/JRCE.2020.17989.1345","url":null,"abstract":"In recent years, Concrete Filled Tube (CFT) columns have been very much taken into consideration due to the many advantages of the instrument. In experimental studies, the focus has been on compressive loading. Although in many cases the eccentric loading (the presence of a bending moment) has also been investigated, further research is needed in this regard. Therefore, in this study, the steel columns filled with concrete with a regular octagonal cross section were studied under the influence of pressure axial load with eccentricity. The parameters studied in this study include bearing capacity, coefficient of ductility and energy absorption. To test and compare the stated parameters, specimens of 150 cm height, which were filled with plain concrete and fiber reinforced concrete were tested. The compressive axial load has been applied to the specimens by the eccentricity of 50, 100 and 150 mm. The results show that at pure compressive loading, the increase in concrete core capacity increases the load bearing capacity of the specimens so that by increasing the concrete compressive strength by 50%, the bearing capacity of the cross section increases by about 15%. Also, based on the results, the average ductility coefficient for specimens was 7.4, and it seems that this value is independent of the type of loading. The use of concrete with intermediate grade resistance can increase the energy absorbed. However, according to the results, it seems that by increasing the bending moment the positive effects of the concrete core are greatly reduced.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81977157","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 : 2020-02-06DOI: 10.22075/JRCE.2020.19167.1362
H. Saberi, Vesam Kolmi Zade, A. Mokhtari, V. Saberi
In this study, the co-operation of steel and concrete in composite columns is considered. Using numerical modeling to study the behavior of these sections, a new type of sections, namely Concrete Filled Double-Skin steel Tubular (CFDST) columns, is introduced. The parameters and techniques that influence the numerical simulation that bring this modeling closer to the laboratory conditions are determined by varying the dimensions and geometry as well as the properties of materials such as the compressive strength of concrete and width to thickness ratio on the strength of circular section columns at internal and external skins are investigated by the ABAQUS finite element software. The purpose of this paper is to investigate the effect of concrete compressive strength on the axial performance of CFDST columns. In this paper, the effects of concrete with different compressive strength, concrete confinement, bearing capacity and width-to-thickness ratio on the overall strength of tubular cross-section columns in their inner and outer skins are investigated. The results of the study indicated that the bearing capacity of CFDST columns under axial pressure increases by increasing the concrete compressive strength in the inner skin and decreases by increasing width to thickness ratio (D/t).Also, studies have shown that with increasing cross-sectional area, the bearing capacity in circular columns decreases by about 3%.
{"title":"Investigating of the Effect of Concrete Confinement on the Axial Performance of Circular Concrete Filled Double-Skin Steel Tubular (CFDST) Long Columns","authors":"H. Saberi, Vesam Kolmi Zade, A. Mokhtari, V. Saberi","doi":"10.22075/JRCE.2020.19167.1362","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19167.1362","url":null,"abstract":"In this study, the co-operation of steel and concrete in composite columns is considered. Using numerical modeling to study the behavior of these sections, a new type of sections, namely Concrete Filled Double-Skin steel Tubular (CFDST) columns, is introduced. The parameters and techniques that influence the numerical simulation that bring this modeling closer to the laboratory conditions are determined by varying the dimensions and geometry as well as the properties of materials such as the compressive strength of concrete and width to thickness ratio on the strength of circular section columns at internal and external skins are investigated by the ABAQUS finite element software. The purpose of this paper is to investigate the effect of concrete compressive strength on the axial performance of CFDST columns. In this paper, the effects of concrete with different compressive strength, concrete confinement, bearing capacity and width-to-thickness ratio on the overall strength of tubular cross-section columns in their inner and outer skins are investigated. The results of the study indicated that the bearing capacity of CFDST columns under axial pressure increases by increasing the concrete compressive strength in the inner skin and decreases by increasing width to thickness ratio (D/t).Also, studies have shown that with increasing cross-sectional area, the bearing capacity in circular columns decreases by about 3%.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77488961","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 : 2020-02-01DOI: 10.22075/JRCE.2019.15637.1293
M. F. Marfavi, S. Basirat, S. Sadeghi
One of the major factors in deliberating the depth of foundations in structures adjacent to the water flow is the scouring phenomenon; the scouring is a phenomenon caused by the interactions between water flow and erodible bed materials, which causes the removal of sediments where hydraulic structures are located, including bridge piers. Every year, a great number of bridges are damaged as a result of local scoring of their piers and foundations. In this paper, the geotechnical study of Malahide viaduct failure due to scouring was carried out applying Plaxis 2D software. For this purpose, the Malahide viaduct, which was damaged in 2009 due to bed scouring of one of its piers, was selected and the necessary simulations were carried out in consonance with the bridge specifications, and the conditions of the bridge underlying bed was investigated. Simulations results revealed that the cause of scouring in the bed of collapsed pier was the high shear strains of the bed, bed shear strength parameters (i.e. angle of internal friction and cohesion) reduction and as a result, reducing the bed resistance to the scouring. Moreover, it was found that by using the micropile group below the foundation of bridge pier as a solution to reduce the scouring effect, the bed maximum scour depth is significantly reduced compared to the shallow foundations without micropiles; Furthermore, by using the micropile group, the shallow foundation thickness can be reduced, provided that after foundation thickness reduction and micropiles application, the structure safety factor remains in the stable range.
{"title":"Bridge Bed Strengthening, Disaster Prevention due to Scouring","authors":"M. F. Marfavi, S. Basirat, S. Sadeghi","doi":"10.22075/JRCE.2019.15637.1293","DOIUrl":"https://doi.org/10.22075/JRCE.2019.15637.1293","url":null,"abstract":"One of the major factors in deliberating the depth of foundations in structures adjacent to the water flow is the scouring phenomenon; the scouring is a phenomenon caused by the interactions between water flow and erodible bed materials, which causes the removal of sediments where hydraulic structures are located, including bridge piers. Every year, a great number of bridges are damaged as a result of local scoring of their piers and foundations. In this paper, the geotechnical study of Malahide viaduct failure due to scouring was carried out applying Plaxis 2D software. For this purpose, the Malahide viaduct, which was damaged in 2009 due to bed scouring of one of its piers, was selected and the necessary simulations were carried out in consonance with the bridge specifications, and the conditions of the bridge underlying bed was investigated. Simulations results revealed that the cause of scouring in the bed of collapsed pier was the high shear strains of the bed, bed shear strength parameters (i.e. angle of internal friction and cohesion) reduction and as a result, reducing the bed resistance to the scouring. Moreover, it was found that by using the micropile group below the foundation of bridge pier as a solution to reduce the scouring effect, the bed maximum scour depth is significantly reduced compared to the shallow foundations without micropiles; Furthermore, by using the micropile group, the shallow foundation thickness can be reduced, provided that after foundation thickness reduction and micropiles application, the structure safety factor remains in the stable range.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86272169","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 : 2020-02-01DOI: 10.22075/JRCE.2019.16080.1302
A. Anvarsamarin, F. Rofooei, M. Nekooei
The existence of torsion, as well as consideration of the Soil-Structure Interaction (SSI), increase the natural periods of the structure resulting from a subsequent decrease in the seismic demand of the system. This paper summarizes the probabilistic assessment for evaluation of collapse fragility curves in concrete moment resisting structure with different mass center eccentricities. A 12-story, 3-D, moment resisting concrete structure with fixed-base and considering SSI, both types of one- and two-way eccentricities is employed to estimate the collapse fragility curve by the IM-based approach. According to the obtained results, increasing the torsion due to shifting the mass centers decreases the median of the collapse fragility curve. In addition, it was observed that the SSI consideration for soil type D with shear wave velocity of 180m/s to 360m/s leads to reduction of the median of collapse capacity by in the presence of torsion effect due to one- and two-way mass center eccentricities in range of 0-20% of the building's plan dimensions respectively. In other words, the fixed-base assumption overestimates the median of collapse capacity and leads to unsafe design. Moreover, shifting the mass centers of all the stories up to 20% of the building's plan dimensions, with or without the consideration of the SSI, decreases the median of collapse capacities and increases the seismic vulnerability of the building. Accordingly, the fixed-base assumption can be underestimated the dispersion range of the collapse fragility curve. The result shows that the mentioned differences cannot be neglected.
{"title":"Torsion Effect on the RC Structures using Fragility Curves Considering with Soil-Structure Interaction","authors":"A. Anvarsamarin, F. Rofooei, M. Nekooei","doi":"10.22075/JRCE.2019.16080.1302","DOIUrl":"https://doi.org/10.22075/JRCE.2019.16080.1302","url":null,"abstract":"The existence of torsion, as well as consideration of the Soil-Structure Interaction (SSI), increase the natural periods of the structure resulting from a subsequent decrease in the seismic demand of the system. This paper summarizes the probabilistic assessment for evaluation of collapse fragility curves in concrete moment resisting structure with different mass center eccentricities. A 12-story, 3-D, moment resisting concrete structure with fixed-base and considering SSI, both types of one- and two-way eccentricities is employed to estimate the collapse fragility curve by the IM-based approach. According to the obtained results, increasing the torsion due to shifting the mass centers decreases the median of the collapse fragility curve. In addition, it was observed that the SSI consideration for soil type D with shear wave velocity of 180m/s to 360m/s leads to reduction of the median of collapse capacity by in the presence of torsion effect due to one- and two-way mass center eccentricities in range of 0-20% of the building's plan dimensions respectively. In other words, the fixed-base assumption overestimates the median of collapse capacity and leads to unsafe design. Moreover, shifting the mass centers of all the stories up to 20% of the building's plan dimensions, with or without the consideration of the SSI, decreases the median of collapse capacities and increases the seismic vulnerability of the building. Accordingly, the fixed-base assumption can be underestimated the dispersion range of the collapse fragility curve. The result shows that the mentioned differences cannot be neglected.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79085701","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：