Pub Date : 2020-12-28DOI: 10.22059/CEIJ.2020.292705.1629
Saman Rashidyan, A. Maji, T. Ng
Nondestructive Testing (NDT) methods have extensively been used to assess the conditions of civil infrastructure in the recent decades. Among various NDT techniques, Impulse Response (IR) has a vast application due to its simplicity and low cost. However, factors such as reflections from changes in impedance along the investigated members can adversely influence the success of the method. Numerous numerical and experimental studies have already been performed to evaluate the effect of change in mechanical impedances such as bulging, necking and similar anomalies. In this study, the effect of the presence of joints connecting the investigated members to other members, as another source of impedance change, is demonstrated. A three-story steel-concrete composite column of a building was selected for testing and IR tests were conducted. The obtained mobility graphs were clear, and the height of the column was easily measured with an acceptable error. The results of this study show that although the joints located between the top and bottom of the tested member are sources of change in mechanical impedance, they do not result in concealing the resonant frequencies from the wave reflected from the bottom of the member. Thus, IR method seems to be applicable in determining the length of prismatic members with intermediate joints such as piles of unknown bridge foundations with bracing and columns of buried buildings.
{"title":"Performance of Impulse Response Testing on Prismatic Members with Intermediate Joints","authors":"Saman Rashidyan, A. Maji, T. Ng","doi":"10.22059/CEIJ.2020.292705.1629","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.292705.1629","url":null,"abstract":"Nondestructive Testing (NDT) methods have extensively been used to assess the conditions of civil infrastructure in the recent decades. Among various NDT techniques, Impulse Response (IR) has a vast application due to its simplicity and low cost. However, factors such as reflections from changes in impedance along the investigated members can adversely influence the success of the method. Numerous numerical and experimental studies have already been performed to evaluate the effect of change in mechanical impedances such as bulging, necking and similar anomalies. In this study, the effect of the presence of joints connecting the investigated members to other members, as another source of impedance change, is demonstrated. A three-story steel-concrete composite column of a building was selected for testing and IR tests were conducted. The obtained mobility graphs were clear, and the height of the column was easily measured with an acceptable error. The results of this study show that although the joints located between the top and bottom of the tested member are sources of change in mechanical impedance, they do not result in concealing the resonant frequencies from the wave reflected from the bottom of the member. Thus, IR method seems to be applicable in determining the length of prismatic members with intermediate joints such as piles of unknown bridge foundations with bracing and columns of buried buildings.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45027075","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 : 2020-12-28DOI: 10.22059/CEIJ.2020.283701.1592
H. Teymouri, A. Khojasteh, M. Rahimian, R. Pak
In this paper, an analytical method is developed for the axisymmetric dynamic response of a finite thickness liquid layer overlying a transversely isotropic porous solid half-space due to body waves. Potential functions and integral transforms are used together to handle the equations of wave motion in two media. The time-harmonic excitation with axisymmetric shape is assumed to be distributed in the interface of liquid and porous media. Green’s functions of stress and displacement are derived as closed-form integral expressions. Demonstration of the effect of the liquid thickness, degree of material anisotropy, and frequency of excitation on the dynamic response is considered here. Numerical results for a uniform distributed disk load are comprised with the existing elastic and poroelastic solutions to illustrate the quality of the method. The results of the current paper can be used in analysis and modelling the rigid or flexible foundations in marine structures.
{"title":"An Analytical Solution of Wave Motion in a Transversely Isotropic Poroelastic Half-Space Underlying a Liquid Layer","authors":"H. Teymouri, A. Khojasteh, M. Rahimian, R. Pak","doi":"10.22059/CEIJ.2020.283701.1592","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.283701.1592","url":null,"abstract":"In this paper, an analytical method is developed for the axisymmetric dynamic response of a finite thickness liquid layer overlying a transversely isotropic porous solid half-space due to body waves. Potential functions and integral transforms are used together to handle the equations of wave motion in two media. The time-harmonic excitation with axisymmetric shape is assumed to be distributed in the interface of liquid and porous media. Green’s functions of stress and displacement are derived as closed-form integral expressions. Demonstration of the effect of the liquid thickness, degree of material anisotropy, and frequency of excitation on the dynamic response is considered here. Numerical results for a uniform distributed disk load are comprised with the existing elastic and poroelastic solutions to illustrate the quality of the method. The results of the current paper can be used in analysis and modelling the rigid or flexible foundations in marine structures.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68426942","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 : 2020-12-28DOI: 10.22059/CEIJ.2020.291426.1623
Homira Agah, A. Saleh, M. Jalili
This study is the first investigation to assess the variations of physical and chemical characteristics and biodiversity of planktons in offshore water column and chlorophyll-a and b, during the two monsoons at Chabahar Bay, to evaluate the water quality. To this end, 27 surface water samples in pre-monsoon (May, 2012) and totally 60 surface and deep water samples in post-monsoon (December, 2012) were collected from 9 and 10 stations at depths between 3.8 to 13.6 m in Chabahar Bay, respectively. The results showed that water salinity and pH with low variations were relatively higher in post-monsoon. The averages of water alkalinity levels in pre- (2.42±0.02 mmol H+/kg) and post- (2.44±0.01 mmol kg-1) monsoons were comparable to that of oceanic surface water (2-2.5 mmol H+/kg). In this study, 66 phytoplankton genus and species belonging to 13 groups were identified in pre-monsoon. Results demonstrated that nutrients were at higher levels inside the Chabahar Bay. Moreover, the physicochemical parameters of water samples were investigated and compared with international standards and data from other marine ecosystems. The results indicated that the water quality falls within the stipulated range of acceptability and sampling area can be classified as a good, stable, and healthy aquatic ecosystem.
{"title":"Assessment of Environmental Parameters in Pre- and Post-Monsoons at Chabahar Bay, Gulf of Oman","authors":"Homira Agah, A. Saleh, M. Jalili","doi":"10.22059/CEIJ.2020.291426.1623","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.291426.1623","url":null,"abstract":"This study is the first investigation to assess the variations of physical and chemical characteristics and biodiversity of planktons in offshore water column and chlorophyll-a and b, during the two monsoons at Chabahar Bay, to evaluate the water quality. To this end, 27 surface water samples in pre-monsoon (May, 2012) and totally 60 surface and deep water samples in post-monsoon (December, 2012) were collected from 9 and 10 stations at depths between 3.8 to 13.6 m in Chabahar Bay, respectively. The results showed that water salinity and pH with low variations were relatively higher in post-monsoon. The averages of water alkalinity levels in pre- (2.42±0.02 mmol H+/kg) and post- (2.44±0.01 mmol kg-1) monsoons were comparable to that of oceanic surface water (2-2.5 mmol H+/kg). In this study, 66 phytoplankton genus and species belonging to 13 groups were identified in pre-monsoon. Results demonstrated that nutrients were at higher levels inside the Chabahar Bay. Moreover, the physicochemical parameters of water samples were investigated and compared with international standards and data from other marine ecosystems. The results indicated that the water quality falls within the stipulated range of acceptability and sampling area can be classified as a good, stable, and healthy aquatic ecosystem.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44634618","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.271426.1532
M. Tajdini, Yaser Khalaji Zadeh, Hamidreza Nokhbeh Zaeim, Omid Rasouli Ghahroudi, M. Jalili
Soil-cement is a mixture of Portland cement, soil and water, which are bonded together due to the cement hydration and compaction. It have durability, low permeability and resistance against wear. Water to cement ratio, cement content and type have been commonly investigated as the most effective factors on the compressive strength of soil-cement. This study aims at the investigation of the effects of some other factors, such as Sand Equivalent (SE), Plasticity Index (PI), and gradation of the soil on the compressive and flexural strength of soil-cement. Results show that the compressive and flexural strength of soil-cement increases with increasing the sand equivalent and decreasing the plasticity index of the soil.
{"title":"Experimental Investigation of the Effective Parameters on the Strength of Soil - Cement","authors":"M. Tajdini, Yaser Khalaji Zadeh, Hamidreza Nokhbeh Zaeim, Omid Rasouli Ghahroudi, M. Jalili","doi":"10.22059/CEIJ.2020.271426.1532","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.271426.1532","url":null,"abstract":"Soil-cement is a mixture of Portland cement, soil and water, which are bonded together due to the cement hydration and compaction. It have durability, low permeability and resistance against wear. Water to cement ratio, cement content and type have been commonly investigated as the most effective factors on the compressive strength of soil-cement. This study aims at the investigation of the effects of some other factors, such as Sand Equivalent (SE), Plasticity Index (PI), and gradation of the soil on the compressive and flexural strength of soil-cement. Results show that the compressive and flexural strength of soil-cement increases with increasing the sand equivalent and decreasing the plasticity index of the soil.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46769649","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 : 2020-12-01DOI: 10.22059/CEIJ.2019.283206.1588
Saman Rashidyan, A. Maji, T. Ng
The long-term effects of scour have been identified as one of the primary reasons for bridge failure. To evaluate the performance of the bridges against scour, it is essential to assess the conditions of the bridge foundation including the depth of the piles. Sonic Echo (SE) has been a favorable nondestructive method to evaluate the condition of unknown bridge foundations in the recent decades. Previous studies have shown that the results obtained from SE tests can be affected by a variety of factors such as the pile-to-soil stiffness ratio, length-to-diameter ratio of the pile, presence of defects and anomalies near the pile head, striking method, and hammer type. Although previous studies have discussed such affecting factors, there is a lack of comprehensive investigation regarding the effect of striking method and hammer tip type specific to wood piles supporting bridge decks. In the current study, the effect of striking method and hammer type on the success of SE tests conducted on wood piles has been scrutinized by investigating various options of striking methods and hammer tip types. After comparing different options, superior ones were identified and recommendations for better conducting the SE tests on unknown wood bridge foundations were presented. Numerical simulations were also performed to support some of the conclusions.
{"title":"Study of the Effect of Source Application on Sonic Echo Tests in Timber Piles","authors":"Saman Rashidyan, A. Maji, T. Ng","doi":"10.22059/CEIJ.2019.283206.1588","DOIUrl":"https://doi.org/10.22059/CEIJ.2019.283206.1588","url":null,"abstract":"The long-term effects of scour have been identified as one of the primary reasons for bridge failure. To evaluate the performance of the bridges against scour, it is essential to assess the conditions of the bridge foundation including the depth of the piles. Sonic Echo (SE) has been a favorable nondestructive method to evaluate the condition of unknown bridge foundations in the recent decades. Previous studies have shown that the results obtained from SE tests can be affected by a variety of factors such as the pile-to-soil stiffness ratio, length-to-diameter ratio of the pile, presence of defects and anomalies near the pile head, striking method, and hammer type. Although previous studies have discussed such affecting factors, there is a lack of comprehensive investigation regarding the effect of striking method and hammer tip type specific to wood piles supporting bridge decks. In the current study, the effect of striking method and hammer type on the success of SE tests conducted on wood piles has been scrutinized by investigating various options of striking methods and hammer tip types. After comparing different options, superior ones were identified and recommendations for better conducting the SE tests on unknown wood bridge foundations were presented. Numerical simulations were also performed to support some of the conclusions.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45328440","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.285244.1598
M. Hajiazizi, Z. Mirzazadeh
The creep of earth slopes is an important challenge of the long-term stability of slopes. This paper develops a limit equilibrium method (LEM)-based analytical approach for calculating the shear displacement of creep-induced failure surface in 2D state for all slices where both force and moment equilibrium equations are simultaneously satisfied as a new research. The relation between shear displacement and creep time is obtained with regard to visco-elastoplastic creep model. The overall safety factor is first calculated for the slip surface using Spencer method. Then, the shear displacements of all slices are obtained based on vertical displacement of crown and using displacement compatibility relation exists between slices. By combining force and moment equilibrium equations and assuming a zero resultant for inter-slice forces, the vertical displacement at crown is determined using visco-elastopastic creep model. A numerical model was developed to calculate slope displacement by the proposed method. Force and moment equilibrium equations are simultaneously satisfied by iteration technique. The proposed method is verified through two numerical examples comparing the new approach and conventional finite element method.
{"title":"Determination of Creep-Induced Displacement of Soil Slopes Based on LEM","authors":"M. Hajiazizi, Z. Mirzazadeh","doi":"10.22059/CEIJ.2020.285244.1598","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.285244.1598","url":null,"abstract":"The creep of earth slopes is an important challenge of the long-term stability of slopes. This paper develops a limit equilibrium method (LEM)-based analytical approach for calculating the shear displacement of creep-induced failure surface in 2D state for all slices where both force and moment equilibrium equations are simultaneously satisfied as a new research. The relation between shear displacement and creep time is obtained with regard to visco-elastoplastic creep model. The overall safety factor is first calculated for the slip surface using Spencer method. Then, the shear displacements of all slices are obtained based on vertical displacement of crown and using displacement compatibility relation exists between slices. By combining force and moment equilibrium equations and assuming a zero resultant for inter-slice forces, the vertical displacement at crown is determined using visco-elastopastic creep model. A numerical model was developed to calculate slope displacement by the proposed method. Force and moment equilibrium equations are simultaneously satisfied by iteration technique. The proposed method is verified through two numerical examples comparing the new approach and conventional finite element method.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42875681","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.275720.1549
M. Sharbatdar, Norouz Ali Mohazen
FRC concretes with high strength are practical material for strengthening existing particularly damaged concrete structures and able to dissipate seismic energy. The main purpose of this paper was to using high strength-FRC concrete for strengthening the damaged and undamaged frames. The five experimental specimens were loaded laterally and vertical gravity loads, simultaneously. The first specimen was a reference without strengthening, but the second same specimen was strengthened. The other three specimens were initially were loaded up to 55, 75, and 100% of the maximum capacity of the reference specimen and prepared as damaged specimens. The damaged specimens were laterally and vertically loaded. The test results showed that ductility of the undamaged strengthened frame was 2.2 times that of the reference specimen, while these amounts for three strengthened specimens (55, 75, and 100%) were up to 110, 60, 15 increase compared to the reference. The maximum lateral capacity of second undamaged, third fourth, and fifth damaged specimens were 38 and 35, 16, 9% more than that of reference; while the significant increase of energy absorption from 1.28 to 2.37 times reference was observed.
{"title":"Experimental Strengthening of Damaged and Un-Damaged RC Frames with Ultra-FRC Composite Layers","authors":"M. Sharbatdar, Norouz Ali Mohazen","doi":"10.22059/CEIJ.2020.275720.1549","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.275720.1549","url":null,"abstract":"FRC concretes with high strength are practical material for strengthening existing particularly damaged concrete structures and able to dissipate seismic energy. The main purpose of this paper was to using high strength-FRC concrete for strengthening the damaged and undamaged frames. The five experimental specimens were loaded laterally and vertical gravity loads, simultaneously. The first specimen was a reference without strengthening, but the second same specimen was strengthened. The other three specimens were initially were loaded up to 55, 75, and 100% of the maximum capacity of the reference specimen and prepared as damaged specimens. The damaged specimens were laterally and vertically loaded. The test results showed that ductility of the undamaged strengthened frame was 2.2 times that of the reference specimen, while these amounts for three strengthened specimens (55, 75, and 100%) were up to 110, 60, 15 increase compared to the reference. The maximum lateral capacity of second undamaged, third fourth, and fifth damaged specimens were 38 and 35, 16, 9% more than that of reference; while the significant increase of energy absorption from 1.28 to 2.37 times reference was observed.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47078186","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.281338.1582
H. Taherkhani, Farid Noorian
This research aimed to use response surface methodology (RSM) for investigating the Marshall Stability (MS), flow and Voids in Mineral Aggregates (VMA) of asphalt concrete containing different percentages of Reclaimed Asphalt Pavement (RAP) and rejuvenated by different percentages of waste cooking and engine oil. Variables of RAP content in 3 different levels of 25, 50 and 75% (by the weight of total aggregates) and waste oils content in 3 different levels of 5, 10 and 15% (by the weight of total binder) were selected. Quadratic and linear two factor interaction models were well fitted to the experimental results. Analysis of variance showed that the models were capable to well predict the MS, flow and VMA of the mixtures, and the terms of oil and RAP content and type of oil are significant. MS, flow and VMA increased with increasing RAP content and decreased with increasing oil content. Results also reveal that higher MS, flow and VMA values are resulted by using WEO than using WCO. Some interaction effects were found between RAP content, oil content and type of oil on the responses. Optimization analysis showed that using 10.6% of WCO and 15% of WEO, allows a maximum RAP incorporation of 75 and 51.77%, respectively, by which the properties are similar to control mix. Use of the rejuvenators allows using high RAP content without sacrificing the properties of the mixtures.
{"title":"Investigating the Marshall and Volumetric Properties of Asphalt Concrete Containing Reclaimed Asphalt Pavement and Waste Oils Using Response Surface Methodology","authors":"H. Taherkhani, Farid Noorian","doi":"10.22059/CEIJ.2020.281338.1582","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.281338.1582","url":null,"abstract":"This research aimed to use response surface methodology (RSM) for investigating the Marshall Stability (MS), flow and Voids in Mineral Aggregates (VMA) of asphalt concrete containing different percentages of Reclaimed Asphalt Pavement (RAP) and rejuvenated by different percentages of waste cooking and engine oil. Variables of RAP content in 3 different levels of 25, 50 and 75% (by the weight of total aggregates) and waste oils content in 3 different levels of 5, 10 and 15% (by the weight of total binder) were selected. Quadratic and linear two factor interaction models were well fitted to the experimental results. Analysis of variance showed that the models were capable to well predict the MS, flow and VMA of the mixtures, and the terms of oil and RAP content and type of oil are significant. MS, flow and VMA increased with increasing RAP content and decreased with increasing oil content. Results also reveal that higher MS, flow and VMA values are resulted by using WEO than using WCO. Some interaction effects were found between RAP content, oil content and type of oil on the responses. Optimization analysis showed that using 10.6% of WCO and 15% of WEO, allows a maximum RAP incorporation of 75 and 51.77%, respectively, by which the properties are similar to control mix. Use of the rejuvenators allows using high RAP content without sacrificing the properties of the mixtures.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47497919","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.285125.1596
Charles Chinwuba Ike
The cosine integral transform method is applied to find the expressions for spatial variations of displacements and stresses in the Westergaard continuum under vertical concentrated loading, and distributed loadings acting over lines and geometric areas on the surface. The half-space is considered to be horizontally inextensible and the displacement field reduces to the vertical displacement component. The paper derives a displacement formulation of the equation of equilibrium in the vertical direction. Cosine integral transformation is applied to the formulated equation and the Boundary Value Problem (BVP) is found to simplify to Ordinary Differential Equation (ODE). The general solution of the ODE is obtained in the cosine integral transform space. The requirement of bounded solutions is used to obtain one integration constant. Inversion of the bounded solution gave the solution in the real problem domain space. The stress fields are obtained using the stress-displacement equations. The requirement of equilibrium of the vertical stress fields and the vertical point loading at the origin is used to determine the remaining integration constant, and thus the vertical deflections and the stresses. The solutions obtained are kernel functions employed to derive the expressions for solutions for line, and uniformly distributed loads applied over given geometric areas such as rectangular and circular areas. The vertical stresses are expressed in terms of dimensionless vertical stress influence factors and tabulated. The vertical displacements and stresses obtained are identical with Westergaard solutions obtained by stress function method. The solutions agree with results obtained by Ike using Hankel transform method.
{"title":"Cosine Integral Transform Method for Solving the Westergaard Problem in Elasticity of the Half-Space","authors":"Charles Chinwuba Ike","doi":"10.22059/CEIJ.2020.285125.1596","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.285125.1596","url":null,"abstract":"The cosine integral transform method is applied to find the expressions for spatial variations of displacements and stresses in the Westergaard continuum under vertical concentrated loading, and distributed loadings acting over lines and geometric areas on the surface. The half-space is considered to be horizontally inextensible and the displacement field reduces to the vertical displacement component. The paper derives a displacement formulation of the equation of equilibrium in the vertical direction. Cosine integral transformation is applied to the formulated equation and the Boundary Value Problem (BVP) is found to simplify to Ordinary Differential Equation (ODE). The general solution of the ODE is obtained in the cosine integral transform space. The requirement of bounded solutions is used to obtain one integration constant. Inversion of the bounded solution gave the solution in the real problem domain space. The stress fields are obtained using the stress-displacement equations. The requirement of equilibrium of the vertical stress fields and the vertical point loading at the origin is used to determine the remaining integration constant, and thus the vertical deflections and the stresses. The solutions obtained are kernel functions employed to derive the expressions for solutions for line, and uniformly distributed loads applied over given geometric areas such as rectangular and circular areas. The vertical stresses are expressed in terms of dimensionless vertical stress influence factors and tabulated. The vertical displacements and stresses obtained are identical with Westergaard solutions obtained by stress function method. The solutions agree with results obtained by Ike using Hankel transform method.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43666203","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 : 2020-12-01DOI: 10.22059/CEIJ.2020.287804.1609
A. Baghban, A. Karamodin, H. Kazemi
In this paper, the artificial intelligence is employed to design a Fault-Tolerant Controller (FTC) for structural vibrations. The FTC is designed to reduce the probability of damage considering sensor fault. For this purpose, Neural Networks (NNs) are used as fault detection and accommodation and fuzzy logic is used as a controller. This control strategy requires two groups of neural networks. The first group of neural networks finds the faulty sensor by estimating the structural responses and comparing them with the responses obtained from the sensors. The second group has the task of estimating the response of the faulty sensor using data obtained from healthy sensors. To evaluate this method, the time history analysis of a 3-story benchmark building equipped with accelerometers and active actuators has been used. This evaluation is based on determining the probability of structural damage and the generation of fragility curves under forty ground motions. To develop fragility curves, the criteria specified in the FIMA 356 (IO, LS and CP) for the moment frame based on the inter-story drift are used. This study show that in the absence of the neural networks, sensor fault reduces the performance of the fuzzy controller and it is even possible to increase the structural responses compared to the structure without the controller. In addition, results demonstrate that the proposed control strategy can rectify the deterioration of sensor faults and decrease the probability of failure.
{"title":"Fault-Tolerant Damage Control of Nonlinear Structures Using Artificial Intelligence","authors":"A. Baghban, A. Karamodin, H. Kazemi","doi":"10.22059/CEIJ.2020.287804.1609","DOIUrl":"https://doi.org/10.22059/CEIJ.2020.287804.1609","url":null,"abstract":"In this paper, the artificial intelligence is employed to design a Fault-Tolerant Controller (FTC) for structural vibrations. The FTC is designed to reduce the probability of damage considering sensor fault. For this purpose, Neural Networks (NNs) are used as fault detection and accommodation and fuzzy logic is used as a controller. This control strategy requires two groups of neural networks. The first group of neural networks finds the faulty sensor by estimating the structural responses and comparing them with the responses obtained from the sensors. The second group has the task of estimating the response of the faulty sensor using data obtained from healthy sensors. To evaluate this method, the time history analysis of a 3-story benchmark building equipped with accelerometers and active actuators has been used. This evaluation is based on determining the probability of structural damage and the generation of fragility curves under forty ground motions. To develop fragility curves, the criteria specified in the FIMA 356 (IO, LS and CP) for the moment frame based on the inter-story drift are used. This study show that in the absence of the neural networks, sensor fault reduces the performance of the fuzzy controller and it is even possible to increase the structural responses compared to the structure without the controller. In addition, results demonstrate that the proposed control strategy can rectify the deterioration of sensor faults and decrease the probability of failure.","PeriodicalId":43959,"journal":{"name":"Civil Engineering Infrastructures Journal-CEIJ","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41732561","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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