Pub Date : 2020-08-01DOI: 10.22075/JRCE.2020.18723.1354
F. T. Komishani, S. F. Saghravani, M. Jalali
This paper investigated the effects of seawater curing of concrete made by Micro-Nano Air Bubbles (MNAB) on compressive, flexural and tensile strengths of the concrete. This product will be applicable for rehabilitation or repair of coastal RC structures. In this research, the effect of different combinations of concrete ingredients including 0-100, 25-75, 50-50, 75-25, and 100-0 percent seawater and MNAB, respectively, on compressive strength of concrete was investigated. A total of 93 specimens were experimentally examined to study the compressive, flexural and tensile strength of MNBA concrete (MNABC) through ASTM Standard for cube, cylinder, and beam samples. The samples were cured for 1, 7, 28 and 90 days. Results revealed that MNABC cured in seawater had about 30 % higher compressive strength at ages 7 and 28 days, but it decreased in longer periods. The flexural strength of MNABC slightly increased, about 6%, after 28 days of curing in seawater. In general, the mechanical properties of MNABC at an early age revealed a considerable increase, whereas, in the longer period of time, they were decreased gradually.
{"title":"Effect of Seawater on Micro-Nano Air Bubbles Concrete for Repair of Coastal Structures","authors":"F. T. Komishani, S. F. Saghravani, M. Jalali","doi":"10.22075/JRCE.2020.18723.1354","DOIUrl":"https://doi.org/10.22075/JRCE.2020.18723.1354","url":null,"abstract":"This paper investigated the effects of seawater curing of concrete made by Micro-Nano Air Bubbles (MNAB) on compressive, flexural and tensile strengths of the concrete. This product will be applicable for rehabilitation or repair of coastal RC structures. In this research, the effect of different combinations of concrete ingredients including 0-100, 25-75, 50-50, 75-25, and 100-0 percent seawater and MNAB, respectively, on compressive strength of concrete was investigated. A total of 93 specimens were experimentally examined to study the compressive, flexural and tensile strength of MNBA concrete (MNABC) through ASTM Standard for cube, cylinder, and beam samples. The samples were cured for 1, 7, 28 and 90 days. Results revealed that MNABC cured in seawater had about 30 % higher compressive strength at ages 7 and 28 days, but it decreased in longer periods. The flexural strength of MNABC slightly increased, about 6%, after 28 days of curing in seawater. In general, the mechanical properties of MNABC at an early age revealed a considerable increase, whereas, in the longer period of time, they were decreased gradually.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77837829","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 : 2020-08-01DOI: 10.22075/JRCE.2020.17929.1343
A. Kheyroddin, M. Hajforoush, A. Doustmohammadi
The main purpose of this study is to numerically assess the effect of boundary elements with different types of steel and concrete materials on nonlinear performance of composite steel–reinforced concrete wall (CSRCW) by employing ABAQUS software. Two types of common steel profiles including box and I-shaped sections, located at the middle and extremities of the wall, were used to assess ultimate strength of the CSRCW. In addition, effects of concrete confinement on boundary elements were investigated for fully and partially encasement degrees. Following this, steel materials with three yield stresses of 300, 400 and 500 MPa, and concrete in two grades with compressive strengths of 30 and 40 MPa were considered. The theoretical results demonstrated that numerical models can predict the fracture zones similar to experimental observations where the failure modes of CSRCWs appeared to have ductile mechanisms. Based on the numerical outputs, the presence of I-shaped steel section in the middle of CSRCW participated to effectively distribute the stress throughout the shear wall, which was found to be 6.5% higher than that conventional shear wall. Furthermore, using steel boundary elements with higher yield strengths caused the highest amount of ultimate strength for the CSRCW to be 397.1 kN.
{"title":"Numerical Investigation of Composite Shear Walls with Different Types of Steel and Concrete Materials as Boundary Elements","authors":"A. Kheyroddin, M. Hajforoush, A. Doustmohammadi","doi":"10.22075/JRCE.2020.17929.1343","DOIUrl":"https://doi.org/10.22075/JRCE.2020.17929.1343","url":null,"abstract":"The main purpose of this study is to numerically assess the effect of boundary elements with different types of steel and concrete materials on nonlinear performance of composite steel–reinforced concrete wall (CSRCW) by employing ABAQUS software. Two types of common steel profiles including box and I-shaped sections, located at the middle and extremities of the wall, were used to assess ultimate strength of the CSRCW. In addition, effects of concrete confinement on boundary elements were investigated for fully and partially encasement degrees. Following this, steel materials with three yield stresses of 300, 400 and 500 MPa, and concrete in two grades with compressive strengths of 30 and 40 MPa were considered. The theoretical results demonstrated that numerical models can predict the fracture zones similar to experimental observations where the failure modes of CSRCWs appeared to have ductile mechanisms. Based on the numerical outputs, the presence of I-shaped steel section in the middle of CSRCW participated to effectively distribute the stress throughout the shear wall, which was found to be 6.5% higher than that conventional shear wall. Furthermore, using steel boundary elements with higher yield strengths caused the highest amount of ultimate strength for the CSRCW to be 397.1 kN.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82159852","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 : 2020-07-29DOI: 10.22075/JRCE.2020.20195.1401
A. Hosseinnezhad, Amin Golizad
Long-span bridges, as vital structures, play a very important role in economic development. Furthermore, the results of several earthquake-damaged bridges showed that their seismic behavior was different from that predicted under uniform excitation and in some cases the responses were more than predicted results. Therefore, the damaged bridges under non-uniform excitations were re-analyzed and the obtained results were in good agreement with the recorded outcomes. It is clear that almost all of them ignored it and just the Euro Code 2008 prepared some recommendations. It is found that the main reason of the differences in results from uniform and non-uniform excitations is the spatial variation of earthquake ground motions. Based on the papers three phenomena were introduced for spatial variability of ground motion: the wave-passage, the incoherence, and also the site-response effects. The responses of structures under non-uniform excitations obtained from the superposition of dynamic and pseudo-static components. This paper investigated the seismic behavior of a long-span structure under non-uniform movements to evaluate the most undesirable conditions. So, different soils and load combinations considered and soil-structure effects included. The effect of wave-passage, incoherence, and site-response on the structure was measured and the results were compared with the uniform excitation. The results indicate that the variation in soil condition significantly affects the seismic responses under non-uniform excitations. Also, it is found that the results from uniform excitations with considering soil-structure interactions are remarkably increased. Moreover, the outcomes showed that ignoring the spatially varying ground motions may lead to a non-conservative design.
{"title":"Investigating the effect of pseudo-static components on bridge structures under multiple support excitations using conditional simulated records","authors":"A. Hosseinnezhad, Amin Golizad","doi":"10.22075/JRCE.2020.20195.1401","DOIUrl":"https://doi.org/10.22075/JRCE.2020.20195.1401","url":null,"abstract":"Long-span bridges, as vital structures, play a very important role in economic development. Furthermore, the results of several earthquake-damaged bridges showed that their seismic behavior was different from that predicted under uniform excitation and in some cases the responses were more than predicted results. Therefore, the damaged bridges under non-uniform excitations were re-analyzed and the obtained results were in good agreement with the recorded outcomes. It is clear that almost all of them ignored it and just the Euro Code 2008 prepared some recommendations. It is found that the main reason of the differences in results from uniform and non-uniform excitations is the spatial variation of earthquake ground motions. Based on the papers three phenomena were introduced for spatial variability of ground motion: the wave-passage, the incoherence, and also the site-response effects. The responses of structures under non-uniform excitations obtained from the superposition of dynamic and pseudo-static components. This paper investigated the seismic behavior of a long-span structure under non-uniform movements to evaluate the most undesirable conditions. So, different soils and load combinations considered and soil-structure effects included. The effect of wave-passage, incoherence, and site-response on the structure was measured and the results were compared with the uniform excitation. The results indicate that the variation in soil condition significantly affects the seismic responses under non-uniform excitations. Also, it is found that the results from uniform excitations with considering soil-structure interactions are remarkably increased. Moreover, the outcomes showed that ignoring the spatially varying ground motions may lead to a non-conservative design.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85726016","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 : 2020-07-29DOI: 10.22075/JRCE.2020.19819.1385
M. K. Sichani, A. Keramati, F. Behzadinia
The potential of buckling in compressive members has been considered as a disadvantage when using steel members in the construction industry. In spite of the progress made in this regard, buckling is still considered as a challenge in the analysis and design of compressive steel structural members. Such a challenging phenomenon can be controlled by strengthening of compressive members. Stiffened compressive members can control the weakness of steel members in the global buckling. In this paper, elastic buckling behavior of three-segment symmetric steel members with pinned ends is investigated. The differential stability equation for non-prismatic three-segment members is solved numerically. Critical load parameter for stiffened members is calculated considering different stiffened length and moment of inertia ratios. Based on a wide range of the calculated data, the buckling load could be accounted as a safe measure to be used in the design formulas. Evaluation of the effects of various parameters on the buckling load shows that the desired buckling load value can be achieved by a partially stiffened member. By constant increase of a member’s weight, the shorter the length of the variation in the cross-section, the higher moment of inertia is essential in the stiffened segment; and the maximum critical load parameter is achieved by a stiffened length ratio between 0.4 and 0.6.
{"title":"Modification of the Euler load for the stiffened compressive members and determination of the optimal stiffening for the maximum buckling load","authors":"M. K. Sichani, A. Keramati, F. Behzadinia","doi":"10.22075/JRCE.2020.19819.1385","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19819.1385","url":null,"abstract":"The potential of buckling in compressive members has been considered as a disadvantage when using steel members in the construction industry. In spite of the progress made in this regard, buckling is still considered as a challenge in the analysis and design of compressive steel structural members. Such a challenging phenomenon can be controlled by strengthening of compressive members. Stiffened compressive members can control the weakness of steel members in the global buckling. In this paper, elastic buckling behavior of three-segment symmetric steel members with pinned ends is investigated. The differential stability equation for non-prismatic three-segment members is solved numerically. Critical load parameter for stiffened members is calculated considering different stiffened length and moment of inertia ratios. Based on a wide range of the calculated data, the buckling load could be accounted as a safe measure to be used in the design formulas. Evaluation of the effects of various parameters on the buckling load shows that the desired buckling load value can be achieved by a partially stiffened member. By constant increase of a member’s weight, the shorter the length of the variation in the cross-section, the higher moment of inertia is essential in the stiffened segment; and the maximum critical load parameter is achieved by a stiffened length ratio between 0.4 and 0.6.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89757414","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 : 2020-07-29DOI: 10.22075/JRCE.2020.19431.1367
E. Naderi, A. Asakereh, M. Dehghani
There can be many reasons for engineers to place the footings near a slope such as leakage of suitable sites or architectural considerations. One of the approaches to increase the amount of bearing capacity, especially in soft soils, is adding stone columns to the soil. In this research, the behavior of a strip footing placed near a stone column reinforced clayey slope was investigated. For this purpose, some small-scale model tests were performed on a clayey slope reinforced with stone columns. The effects of the length of the stone column and the length of encasement on the footing were studied. Additionally, vertical encased stone columns in a group arrangement were investigated. Some numerical analyses were also performed using the Midas GTS NX finite element software, and the factor of safety was studied. Results show that the optimum length was equal to four times the diameter of stone columns. It was observed that by increasing the length of encasement, the bearing capacity of strip footing was also increased. The safety factor of slope showed an increase when stone columns were added to the slope, but the maximum influence on the factor of safety appeared when the stone column was in the upper middle of the slope.
{"title":"Numerical and physical modeling of soft soil slope stabilized with stone columns","authors":"E. Naderi, A. Asakereh, M. Dehghani","doi":"10.22075/JRCE.2020.19431.1367","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19431.1367","url":null,"abstract":"There can be many reasons for engineers to place the footings near a slope such as leakage of suitable sites or architectural considerations. One of the approaches to increase the amount of bearing capacity, especially in soft soils, is adding stone columns to the soil. In this research, the behavior of a strip footing placed near a stone column reinforced clayey slope was investigated. For this purpose, some small-scale model tests were performed on a clayey slope reinforced with stone columns. The effects of the length of the stone column and the length of encasement on the footing were studied. Additionally, vertical encased stone columns in a group arrangement were investigated. Some numerical analyses were also performed using the Midas GTS NX finite element software, and the factor of safety was studied. Results show that the optimum length was equal to four times the diameter of stone columns. It was observed that by increasing the length of encasement, the bearing capacity of strip footing was also increased. The safety factor of slope showed an increase when stone columns were added to the slope, but the maximum influence on the factor of safety appeared when the stone column was in the upper middle of the slope.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83949000","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 : 2020-07-29DOI: 10.22075/JRCE.2020.17829.1342
P. Tehrani, F. Mahmoudi
Moment resisting frames as one of the conventional lateral load resisting systems in buildings suffer from some limitations including code limitations on minimum span-to-depth ratio to ensure the formation of plastic hinges with adequate length at beam ends. According to seismic codes, in ordinary steel moment resisting frames the minimum span-to-depth ratios should be limited to 5 and in special steel moment resisting frames this ratio should not be less than 7, which is typically difficult to achieve in some cases. For instance, framed-tube structures typically have moment resisting frames with span-to-depth ratios lower than the above mentioned ranges. Therefore, existing buildings with low span-to-depth ratios may exhibit poor seismic performance when subjected to seismic excitation. In this paper, a method is presented to rehabilitate such moment resisting frames. The novelty of this rehabilitation method is that it can be used not only for intact structures, but also for damaged moment resisting frames after earthquakes to enhance their remaining strength and ductility capacity. While most of the available rehabilitation methods focus on improving the system strength and stiffness, the proposed rehabilitation in this paper is based on the weakening the mid span of the beam which causes the formation of the shear plastic hinge in middle of the beam instead of the two beam ends. Numerical evaluation is conducted to show the efficacy of this method, and the results indicate that the use of the proposed rehabilitation method significantly increase the ductility capacity of the system during subsequent earthquakes.
{"title":"A Technique for Seismic Rehabilitation of Damaged Steel Moment Resisting Frames","authors":"P. Tehrani, F. Mahmoudi","doi":"10.22075/JRCE.2020.17829.1342","DOIUrl":"https://doi.org/10.22075/JRCE.2020.17829.1342","url":null,"abstract":"Moment resisting frames as one of the conventional lateral load resisting systems in buildings suffer from some limitations including code limitations on minimum span-to-depth ratio to ensure the formation of plastic hinges with adequate length at beam ends. According to seismic codes, in ordinary steel moment resisting frames the minimum span-to-depth ratios should be limited to 5 and in special steel moment resisting frames this ratio should not be less than 7, which is typically difficult to achieve in some cases. For instance, framed-tube structures typically have moment resisting frames with span-to-depth ratios lower than the above mentioned ranges. Therefore, existing buildings with low span-to-depth ratios may exhibit poor seismic performance when subjected to seismic excitation. In this paper, a method is presented to rehabilitate such moment resisting frames. The novelty of this rehabilitation method is that it can be used not only for intact structures, but also for damaged moment resisting frames after earthquakes to enhance their remaining strength and ductility capacity. While most of the available rehabilitation methods focus on improving the system strength and stiffness, the proposed rehabilitation in this paper is based on the weakening the mid span of the beam which causes the formation of the shear plastic hinge in middle of the beam instead of the two beam ends. Numerical evaluation is conducted to show the efficacy of this method, and the results indicate that the use of the proposed rehabilitation method significantly increase the ductility capacity of the system during subsequent earthquakes.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87860182","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 : 2020-07-29DOI: 10.22075/JRCE.2020.19792.1383
B. Behzadfar, A. Maleki, M. L. Yaghin
Spacious experimental and numerical investigation has been conducted by researchers to increase the ductility and energy dissipation of concentrically braced frames. One of the most widely used strategies for increasing ductility and energy dissiption, is the use of energy-absorbing systems. In this regard, the cyclic behavior of a chevron bracing frame system equipped with multi-pipe dampers (CBF-MPD) was investigated through finite element method. The purpose of this study was to evaluate and improve the behavior of the CBF using MPDs. Three-dimensional models of the chevron brace frame were developed via nonlinear finite element method using ABAQUS software. Finite element models included the chevron brace frame and the chevron brace frame equipped with multi-pipe dampers. The chevron brace frame model was selected as the base model for comparing and evaluating the effects of multi-tube dampers. Finite element models were then analyzed under cyclic loading and nonlinear static methods. Validation of the results of the finite element method was performed against the test results. In parametric studies, the influence of the diameter parameter to the thickness (D/t) ratio of the pipe dampers was investigated. The results indicated that the shear capacity of the pipe damper has a significant influence on determining the bracing behavior. Also, the results show that the corresponding displacement with the maximum force in the CBF-MPD compared to the CBF, increased by an average of 2.72 equal. Also, the proper choice for the dimensions of the pipe dampers increased the ductility and energy absorption of the chevron brace frame.
{"title":"Improved Seismic Performance of Chevron Brace Frames Using Multi-Pipe Yield Dampers","authors":"B. Behzadfar, A. Maleki, M. L. Yaghin","doi":"10.22075/JRCE.2020.19792.1383","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19792.1383","url":null,"abstract":"Spacious experimental and numerical investigation has been conducted by researchers to increase the ductility and energy dissipation of concentrically braced frames. One of the most widely used strategies for increasing ductility and energy dissiption, is the use of energy-absorbing systems. In this regard, the cyclic behavior of a chevron bracing frame system equipped with multi-pipe dampers (CBF-MPD) was investigated through finite element method. The purpose of this study was to evaluate and improve the behavior of the CBF using MPDs. Three-dimensional models of the chevron brace frame were developed via nonlinear finite element method using ABAQUS software. Finite element models included the chevron brace frame and the chevron brace frame equipped with multi-pipe dampers. The chevron brace frame model was selected as the base model for comparing and evaluating the effects of multi-tube dampers. Finite element models were then analyzed under cyclic loading and nonlinear static methods. Validation of the results of the finite element method was performed against the test results. In parametric studies, the influence of the diameter parameter to the thickness (D/t) ratio of the pipe dampers was investigated. The results indicated that the shear capacity of the pipe damper has a significant influence on determining the bracing behavior. Also, the results show that the corresponding displacement with the maximum force in the CBF-MPD compared to the CBF, increased by an average of 2.72 equal. Also, the proper choice for the dimensions of the pipe dampers increased the ductility and energy absorption of the chevron brace frame.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86548695","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 : 2020-07-12DOI: 10.22075/JRCE.2020.19420.1368
S. Khaksefidi, M. Ghalehnovi
Ultra-high performance concrete (UHPC) is a developing concrete and today is increasing to interest using it in structures due to its advantages such as high-compressive strength, modulus of elasticity, highly durability and low-permeability. Therefore, it is necessary to provide models for prediction of nonlinear behavior of this material. This study is aimed to investigate the tension-stiffening phenomenon for UHPC and to propose a model for the post-cracking behavior of the reinforced concrete members under tension. For this purpose, in this study, 24 cylindrical concrete specimens reinforced with a rebar in its center were prepared using UHPC and Two rebar types including steel and GFRP (Glass Fiber Reinforced Polymer). Three specimen diameters (65 mm, 100 mm, and 125 mm), and two rebar diameters (12 mm and 16 mm) were considered. All specimens were tested under direct tension. According to the experimental data, a tension-stiffening model was proposed for UHPC. The proposed model has suitable correlation with experimental results.
{"title":"Effect of Reinforcement Type on the Tension Stiffening Model of Ultra-High Performance Concrete (UHPC)","authors":"S. Khaksefidi, M. Ghalehnovi","doi":"10.22075/JRCE.2020.19420.1368","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19420.1368","url":null,"abstract":"Ultra-high performance concrete (UHPC) is a developing concrete and today is increasing to interest using it in structures due to its advantages such as high-compressive strength, modulus of elasticity, highly durability and low-permeability. Therefore, it is necessary to provide models for prediction of nonlinear behavior of this material. This study is aimed to investigate the tension-stiffening phenomenon for UHPC and to propose a model for the post-cracking behavior of the reinforced concrete members under tension. For this purpose, in this study, 24 cylindrical concrete specimens reinforced with a rebar in its center were prepared using UHPC and Two rebar types including steel and GFRP (Glass Fiber Reinforced Polymer). Three specimen diameters (65 mm, 100 mm, and 125 mm), and two rebar diameters (12 mm and 16 mm) were considered. All specimens were tested under direct tension. According to the experimental data, a tension-stiffening model was proposed for UHPC. The proposed model has suitable correlation with experimental results.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79178661","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 : 2020-06-27DOI: 10.22075/JRCE.2020.19626.1375
A. Sharifzadeh, S. Tariverdilo
Rebar fracture in boundary elements of lightly reinforced shear walls in recent earthquake motivated research on the minimum longitudinal reinforcement applicable to shear walls. These researches lead to change in the ACI 318-19 requirement for minimum longitudinal reinforcement in boundary elements. New ACI 318 requirement increase minimum longitudinal reinforcement ratio for boundary elements of shear walls with low demand, that could have economic burden. This study experimentally investigates is it possible to avoid this increase in minimum rebar by debonding rebars in lightly reinforced shear walls. Tests includes specimens with bonded and debonded rebars, which are tested under monotonic and cyclic loading. Load protocol to account for failure types of low reinforcement shear walls is unsymmetric. Test results show that out of plane buckling of specimens with debonded rebars initiates at lower axial strains that could be attributed to reduction in lateral stiffness due to use of debonding. On the other hand debonding resulted in reduction of local strain demand on rebar. It could be concluded that larger minimum dimension for boundary elements will be required when debonding is employed
{"title":"Effect of Debonding of Rebars on the Seismic Response of Boundary Elements of Lightly Reinforced Shear Walls","authors":"A. Sharifzadeh, S. Tariverdilo","doi":"10.22075/JRCE.2020.19626.1375","DOIUrl":"https://doi.org/10.22075/JRCE.2020.19626.1375","url":null,"abstract":"Rebar fracture in boundary elements of lightly reinforced shear walls in recent earthquake motivated research on the minimum longitudinal reinforcement applicable to shear walls. These researches lead to change in the ACI 318-19 requirement for minimum longitudinal reinforcement in boundary elements. New ACI 318 requirement increase minimum longitudinal reinforcement ratio for boundary elements of shear walls with low demand, that could have economic burden. This study experimentally investigates is it possible to avoid this increase in minimum rebar by debonding rebars in lightly reinforced shear walls. Tests includes specimens with bonded and debonded rebars, which are tested under monotonic and cyclic loading. Load protocol to account for failure types of low reinforcement shear walls is unsymmetric. Test results show that out of plane buckling of specimens with debonded rebars initiates at lower axial strains that could be attributed to reduction in lateral stiffness due to use of debonding. On the other hand debonding resulted in reduction of local strain demand on rebar. It could be concluded that larger minimum dimension for boundary elements will be required when debonding is employed","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84520872","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 : 2020-06-08DOI: 10.22075/JRCE.2020.20000.1394
S. Mollaei, M. Babaei, M. Jalilkhani
In the current study, the effect of the extreme lateral loading on the square and circular Reinforced Concrete (RC) columns with and without retrofitting was investigated. 3D finite element modeling of the columns and impact loading condition was performed using the ABAQUS/Explicit software. The data of a real scale blast test carried out in our previous study were used to verify the modeling accuracy. The effect of secondary moments due to axial load, different geometrical characteristics of the steel jacket, compressive strength of the concrete, and the longitudinal reinforcement on the explosive capacity of the column and its residual axial strength were studied. Results showed that the circular columns perform better under the sudden lateral pressure than equivalent square ones. Also, steel jacketing increased the explosive capacity of the column, which was more effective in the circular columns than the square ones. The results also indicated that steel jacketing with less buckling capacity had the least improvements on the column capacity. It was found that the effects of the initial axial force in the column were significant on its behavior under explosive loading condition, which should be taken into account in any modeling approaches. In general, the P-δ phenomenon had less effect on the circular columns than the square ones. Also, the use of a high-strength concrete and a higher percentage of longitudinal reinforcement further influenced the retrofitted columns than unretrofited (normal) ones, which was more evident in the circular columns in comparison with square columns.
{"title":"Assessment of Damage and Residual Load Capacity of the Normal and Retrofitted RC Columns against the Impact Loading","authors":"S. Mollaei, M. Babaei, M. Jalilkhani","doi":"10.22075/JRCE.2020.20000.1394","DOIUrl":"https://doi.org/10.22075/JRCE.2020.20000.1394","url":null,"abstract":"In the current study, the effect of the extreme lateral loading on the square and circular Reinforced Concrete (RC) columns with and without retrofitting was investigated. 3D finite element modeling of the columns and impact loading condition was performed using the ABAQUS/Explicit software. The data of a real scale blast test carried out in our previous study were used to verify the modeling accuracy. The effect of secondary moments due to axial load, different geometrical characteristics of the steel jacket, compressive strength of the concrete, and the longitudinal reinforcement on the explosive capacity of the column and its residual axial strength were studied. Results showed that the circular columns perform better under the sudden lateral pressure than equivalent square ones. Also, steel jacketing increased the explosive capacity of the column, which was more effective in the circular columns than the square ones. The results also indicated that steel jacketing with less buckling capacity had the least improvements on the column capacity. It was found that the effects of the initial axial force in the column were significant on its behavior under explosive loading condition, which should be taken into account in any modeling approaches. In general, the P-δ phenomenon had less effect on the circular columns than the square ones. Also, the use of a high-strength concrete and a higher percentage of longitudinal reinforcement further influenced the retrofitted columns than unretrofited (normal) ones, which was more evident in the circular columns in comparison with square columns.","PeriodicalId":52415,"journal":{"name":"Journal of Rehabilitation in Civil Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77524249","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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