Nowadays,education and teaching have become a hot topic,and teaching in colleges and universities is facing a brand-new development direction.Principles of Concrete Structure Design,as one of the main courses,transmit...Nowadays,education and teaching have become a hot topic,and teaching in colleges and universities is facing a brand-new development direction.Principles of Concrete Structure Design,as one of the main courses,transmits professional knowledge for students,enhances the students’professional ability,and further carries out in-depth research on the course to bring a better teaching effect for students.The article mainly focuses on the research of the principles of concrete structure design course,conducts an analysis of the teaching characteristics of the principles of concrete structure design course,and reasonably sets the teaching content from the optimization of the course teaching objectives;innovative course teaching methods can deepen the effect of knowledge understanding;reform of experimental practice teaching can lay down the effect of the internalization of knowledge,etc.The in-depth description and discussion of the relevant aspects of the research aim to provide guidelines for related research.展开更多
The inherent teaching approach can no longer meet the demands of society.In this paper,current issues within the teaching landscape of architectural engineering technology in higher vocational colleges as well as the ...The inherent teaching approach can no longer meet the demands of society.In this paper,current issues within the teaching landscape of architectural engineering technology in higher vocational colleges as well as the policies and teaching demands that formed the basis of this model were analyzed.The study shows the importance of the implementation of the teaching model“promoting teaching and learning through competitions.”This model puts emphasis on the curriculum and teaching resources,while also integrating the teaching process and evaluation with competition.These efforts aim to drive education reform in order to better align with the objectives of vocational education personnel training,while also acting as a reference for similar courses.展开更多
This paper proposes a hybrid peridynamic and classical continuum mechanical model for the high-temperature damage and fracture analysis of concrete structures.In this model,we introduce the thermal expansion into peri...This paper proposes a hybrid peridynamic and classical continuum mechanical model for the high-temperature damage and fracture analysis of concrete structures.In this model,we introduce the thermal expansion into peridynamics and then couple it with the thermoelasticity based on the Morphing method.In addition,a thermomechanical constitutive model of peridynamic bond is presented inspired by the classic Mazars model for the quasi-brittle damage evolution of concrete structures under high-temperature conditions.The validity and effectiveness of the proposed model are verified through two-dimensional numerical examples,in which the influence of temperature on the damage behavior of concrete structures is investigated.Furthermore,the thermal effects on the fracture path of concrete structures are analyzed by numerical results.展开更多
The rapid development of science and technology puts forward higher requirements for new building construction,especially in civil engineering construction.The construction quality of construction engineering is the c...The rapid development of science and technology puts forward higher requirements for new building construction,especially in civil engineering construction.The construction quality of construction engineering is the core management and the testing link.The Concrete structure is an important safety and quality guarantee in the project and is the top priority in the civil engineering.In civil engineering,the concrete structure has an important social impact on the continuous research and development,and application of construction technology.This paper,discuss the advantage and disadvantage of using concrete in building construction.展开更多
Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures.The accurate and timely monitoring of crack development plays a significant role in the saf...Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures.The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering.The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack.Based on this,a novel crack-identification method for underwater concrete structures is presented.This method uses water irrigation to generate seepage at the interface of a crack;then,the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack.Crack information can be identified by monitoring the cooling law and leakage flow near cracks.The proposed mobile crack-monitoring system consists of a heating system,temperature-measurement system,and irrigation system.A series of tests was conducted on a reinforcedconcrete beam using this system.The crack-discrimination indexψwas defined,according to the subsection characteristics of the heat-source cooling curve.The effects of the crack width,leakage flow,and relative positions of the heat source and crack onψwere studied.The results showed that the distribution characteristics ofψalong the monitoring line could accurately locate the crack,but not quantify the crack width.However,the leakage flow is sensitive to the crack width and can be used to identify it.展开更多
A Fe_(2)O_(3)-MWNTs(multi-walled carbon nanotubes)composite with a reinforced concrete structure was fabricated employing a two-step method which involves a sol-gel process followed by high-temperature in situ sinteri...A Fe_(2)O_(3)-MWNTs(multi-walled carbon nanotubes)composite with a reinforced concrete structure was fabricated employing a two-step method which involves a sol-gel process followed by high-temperature in situ sintering.This Fe_(2)O_(3)-MWNTs composite,intended to be used as an anode material for lithium-ion batteries,maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%.The rate capabilities of the Fe_(2)O_(3)-MWNTs composite,evaluated using the ratios of capacity at 100,200,500,1000,2000 and 100 mA/g after every 10 cycles,were determined to be 904.7,852.1,759.0,653.8,566.8 and 866.3 mA·h/g,respectively.Such a superior electrochemical performance of the Fe_(2)O_(3)-MWNTs composite is mainly attributed to the reinforced concrete construction,in which the MWNTs function as the skeleton and conductive network.Such a structure contributes to shortening the transport pathways for both Li+and electrons,enhancing conductivity and accommodating volume expansion during prolonged cycling.This Fe_(2)O_(3)-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.展开更多
According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,wh...According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,which was suitable for China. Furthermore,a visual service life prediction program of concrete structure was developed by optimized Monte Carlo method. Meanwhile,Life 365 program was compared,indicating reliability of the prediction program. Finally,the validity of prediction model was verified in JinTang Bridge of Zhoushan Island Mainland Linkage Project.展开更多
Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced co...Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature(SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.展开更多
This paper presents an application of strut-and-tie model(STM) to design the interior anchorage zone(IAZ) in the post-tensioned concrete structure.The STM theory and range of IAZ are introduced.Then,based on the finit...This paper presents an application of strut-and-tie model(STM) to design the interior anchorage zone(IAZ) in the post-tensioned concrete structure.The STM theory and range of IAZ are introduced.Then,based on the finite element analysis,a series of simplified equations to calculate internal forces in IAZ are presented.Finally,the STM model for IAZ is given.In the proposed STM model,internal forces in ties vary with the dimension ratio and the eccentricity of load.The U-turn of internal forces is suggested to allocate rebar to resist bearing flexural tensile force.Compared with the FIP(International Federation for Prestressing) model,the proposed STM model is more reasonable and applicable.展开更多
In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the ...In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the composite structure.Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls.The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves.When a layer of air was added,the effect of blast waves was exaggerated,while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.展开更多
This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fi...This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fiber reinforced concrete is suited for use in load-bearing members. Despite excellent material properties, the use of glass fibers in a concrete matrix is carried out so far only in non- structural elements or as a modification for the prevention of shrinkage cracks. The aim of re- search at the University of Applied Sciences in Leipzig is the use of alkali-resistant macro glass fibers as concrete reinforcement in structural elements as an alternative to steel fiber reinforcement. Slabs on ground, as an example for structural members, provide a sensible application for the new material because they can be casted as load bearing and non-load bearing and are mostly made of steel fiber reinforced concrete. In the future, structural glass fiber reinforced concrete shall provide a simple and visually appealing alternative to conventional steel bar or steel fiber reinforced concrete. The glass fibers can also be used in combination with conventional reinforcing bars or mat reinforcements. Initial investigations have announced some potential.展开更多
The demand for defect diagnoses is gradually gaining ground owing to the growing necessity to implement safe inspection methods to ensure the durability and quality of structures.However,conventional manpower-based in...The demand for defect diagnoses is gradually gaining ground owing to the growing necessity to implement safe inspection methods to ensure the durability and quality of structures.However,conventional manpower-based inspection methods not only incur considerable cost and time,but also cause frequent disputes regarding defects owing to poor inspections.Therefore,the demand for an effective and efficient defect-diagnosis model for concrete structures is imminent,as the reduction in maintenance costs is significant from a long-term perspective.Thus,this paper proposes a deep learning-based image objectidentification method to detect the defects of paint peeling,leakage peeling,and leakage traces that mostly occur in underground parking lots made of concrete structures.The deep learning-based object-detection method can replace conventional visual inspection methods.A faster region-based convolutional neural network(R-CNN)model was used with a training dataset of 6,281 images that utilized a region proposal network to objectively localize the regions of interest and detect the surface defects.The defects were classified according to their type,and the learning of each exclusive model was ensured through test sets obtained from real underground parking lots.As a result,average precision scores of 37.76%,36.42%,and 61.29%were obtained for paint peeling,leakage peeling,and leakage trace defects,respectively.Thus,this study verified the performance of the faster RCNN-based defect-detection algorithm along with its applicability to underground parking lots.展开更多
The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in...The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in Sikkim,was triggered by an intraplate source on the overriding Eurasian plate.Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program.In this paper,near-field and far-field ground motions from this earthquake were analyzed to evaluate their key characteristics and examine their time-frequency features by employing Fast Fourier Transforms(FFTs)and Continuous Wavelet Transforms(CWTs).A comparison between the ground motion parameters of near-field and far-field seismic waves highlights the distinct characteristics of near-field ground motions.Additionally,the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated.The results from the non-linear time history analyses indicate that the roof displacements,drift ratio and strain induced in the frame elements are less than the code-prescribed maximum limits.Further,the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios.The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the nonengineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.展开更多
The column-to-beam flexural strength ratio(CBFSR)has been used in many seismic codes to achieve the strong column-weak beam(SCWB)failure mode in reinforced concrete(RC)frames,in which plastic hinges appear earlier in ...The column-to-beam flexural strength ratio(CBFSR)has been used in many seismic codes to achieve the strong column-weak beam(SCWB)failure mode in reinforced concrete(RC)frames,in which plastic hinges appear earlier in beams than in columns.However,seismic investigations show that the required limit of CBFSR in seismic codes usually cannot achieve the SCWB failure mode under strong earthquakes.This study investigates the failure modes of RC frames with different CBFSRs.Nine typical three-story RC frame models with different CBFSRs are designed in accordance with Chinese seismic codes.The seismic responses and failure modes of the frames are investigated through time-history analyses using 100 ground motion records.The results show that the required limit of the CBFSR that guarantees the SCWB failure mode depends on the beam-column connection type and the seismic intensity,and different types of beam-column connections exhibit different failure modes even though they are designed with the same CBFSR.Recommended CBFSRs are proposed for achieving the designed SCWB failure mode for different types of connections in RC frames under different seismic intensities.These results may provide some reference for further revisions of the SCWB design criterion in Chinese seismic codes.展开更多
In order to study the feasibility of strengthening of segmental tunnel linings by using steel-concrete composites(SCC),a three-dimensional(3D)finite element(FE)model is proposed in this paper.The nonlinear mechanical ...In order to study the feasibility of strengthening of segmental tunnel linings by using steel-concrete composites(SCC),a three-dimensional(3D)finite element(FE)model is proposed in this paper.The nonlinear mechanical behavior of concrete is described by a plastic-damage model.The nonlinearity,resulting from the interface of the SCC and reinforced concrete(RC)segments,is simulated with the help of a system of springs.The analysis results are compared with those obtained from a full-scale test of a tunnel segment.Their agreement validates the usefulness of the 3D FE model.Numerical re-analysis of the test shows that the interfacial connectors govern both the strengthening effect of SCC and the failure pattern of the strengthened segments.Thus,the force-transmitting capacity of the interfacial connectors should be concerned in design activities.As regards the circular segments,the interfacial connectors refer to both the shearing and the stripping connectors.The composite effect of the SCC and RC segments increases with the increasing number of these connectors.The latter,therefore,results in the increases of the bearing capacities and stiffnesses of the strengthened segments.Those increases become insignificant as the number of these connectors is sufficient to ensure a perfect composite effect of the SCC and RC segments.In addition,the numerical simulations show that using high-performance steel shell(HPS)or/and ultra-high-performance concrete(UHPC)is an effective way to increase the strengthening effect of SCCs.展开更多
Today,the most commonly used civil infrastructure inspection method is based on a visual assessment conducted by certified inspectors following prescribed protocols.However,the increase in aggressive environmental and...Today,the most commonly used civil infrastructure inspection method is based on a visual assessment conducted by certified inspectors following prescribed protocols.However,the increase in aggressive environmental and load conditions,coupled with the achievement of many structures of the life-cycle end,has highlighted the need to automate damage identification and satisfy the number of structures that need to be inspected.To overcome this challenge,this paper presents a method for automating concrete damage classification using a deep convolutional neural network.The convolutional neural network was designed after an experimental investigation of a wide number of pretrained networks,applying the transfer-learning technique.Training and validation were conducted using a database built with 1352 images balanced between“undamaged”,“cracked”,and“delaminated”concrete surfaces.To increase the network robustness compared to images in real-world situations,different image configurations have been collected from the Internet and on-field bridge inspections.The GoogLeNet model,with the highest validation accuracy of approximately 94%,was selected as the most suitable network for concrete damage classification.The results confirm that the proposed model can correctly classify images from real concrete surfaces of bridges,tunnels,and pavement,resulting in an effective alternative to the current visual inspection techniques.展开更多
This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operato...This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operator from the genetic algorithms (GAs), namely MOSAMO1, MOSAMO2 and MOSAMO3. The procedure is applied to three objective functions: the economic cost, the reinforcing steel congestion and the embedded CO 2 emissions. Additional results for a random walk and a descent local search multi-objective algorithm are presented. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to a typical bridge pier of 23.97 m in height. This example involved 110 design variables. Results indicate that algorithm MOSAMO2 outperforms other algorithms regarding the definition of Pareto fronts. Further, the proposed procedure will help structural engineers to enhance their bridge pier designs.展开更多
In recent years,great attention has focused on the development of automated procedures for infrastructures control.Many efforts have aimed at greater speed and reliability compared to traditional methods of assessing ...In recent years,great attention has focused on the development of automated procedures for infrastructures control.Many efforts have aimed at greater speed and reliability compared to traditional methods of assessing structural conditions.The paper proposes a multi-level strategy,designed and implemented on the basis of periodic structural monitoring oriented to a cost-and time-efficient tunnel control plan.Such strategy leverages the high capacity of convolutional neural networks to identify and classify potential critical situations.In a supervised learning framework,Ground Penetrating Radar(GPR)profiles and the revealed structural phenomena have been used as input and output to train and test such networks.Image-based analysis and integrative investigations involving video-endoscopy,core drilling,jacking and pull-out testing have been exploited to define the structural conditions linked to GPR profiles and to create the database.The degree of detail and accuracy achieved in identifying a structural condition is high.As a result,this strategy appears of value to infrastructure managers who need to reduce the amount and invasiveness of testing,and thus also to reduce the time and costs associated with inspections made by highly specialized technicians.展开更多
This article offers a demonstration of a novel technology that uses hydro and solar power combined with battery storage to generate electricity for deployment off coastal regions.Called the coastal power plant(CPP),su...This article offers a demonstration of a novel technology that uses hydro and solar power combined with battery storage to generate electricity for deployment off coastal regions.Called the coastal power plant(CPP),such an installation has a multistorey water reservoir that draws in seawater that is then pumped up in vertical stages by geyser pumps into an overhead tank,from which it is released into a hydropower plant to generate electricity.The ocean surface is utilized to install a floating solar plant for photovoltaic energy generation.The intermittent renewable source is combined with a battery energy storage system to meet peak demands.Offshore oil industry technologies are utilized in fabricating the structures on shore and towing them to the site.The potential and cost effectiveness of a 201-MW CPP are also analyzed.Results demonstrate the effectiveness of the new design in terms of investment and operation/maintenance costs.These compare favorably with other renewable energy technologies.展开更多
文摘Nowadays,education and teaching have become a hot topic,and teaching in colleges and universities is facing a brand-new development direction.Principles of Concrete Structure Design,as one of the main courses,transmits professional knowledge for students,enhances the students’professional ability,and further carries out in-depth research on the course to bring a better teaching effect for students.The article mainly focuses on the research of the principles of concrete structure design course,conducts an analysis of the teaching characteristics of the principles of concrete structure design course,and reasonably sets the teaching content from the optimization of the course teaching objectives;innovative course teaching methods can deepen the effect of knowledge understanding;reform of experimental practice teaching can lay down the effect of the internalization of knowledge,etc.The in-depth description and discussion of the relevant aspects of the research aim to provide guidelines for related research.
文摘The inherent teaching approach can no longer meet the demands of society.In this paper,current issues within the teaching landscape of architectural engineering technology in higher vocational colleges as well as the policies and teaching demands that formed the basis of this model were analyzed.The study shows the importance of the implementation of the teaching model“promoting teaching and learning through competitions.”This model puts emphasis on the curriculum and teaching resources,while also integrating the teaching process and evaluation with competition.These efforts aim to drive education reform in order to better align with the objectives of vocational education personnel training,while also acting as a reference for similar courses.
基金the financial support received from the National Natural Science Foundation of China(11872016)National Key Laboratory of Shock Wave and Detonation Physics(JCKYS2021212003)+1 种基金Fundamental Research Funds for the Central Universities(DUT20LAB203)Key Research and Development Project of Liaoning Province(2020JH2/10500003).
文摘This paper proposes a hybrid peridynamic and classical continuum mechanical model for the high-temperature damage and fracture analysis of concrete structures.In this model,we introduce the thermal expansion into peridynamics and then couple it with the thermoelasticity based on the Morphing method.In addition,a thermomechanical constitutive model of peridynamic bond is presented inspired by the classic Mazars model for the quasi-brittle damage evolution of concrete structures under high-temperature conditions.The validity and effectiveness of the proposed model are verified through two-dimensional numerical examples,in which the influence of temperature on the damage behavior of concrete structures is investigated.Furthermore,the thermal effects on the fracture path of concrete structures are analyzed by numerical results.
文摘The rapid development of science and technology puts forward higher requirements for new building construction,especially in civil engineering construction.The construction quality of construction engineering is the core management and the testing link.The Concrete structure is an important safety and quality guarantee in the project and is the top priority in the civil engineering.In civil engineering,the concrete structure has an important social impact on the continuous research and development,and application of construction technology.This paper,discuss the advantage and disadvantage of using concrete in building construction.
基金This work was supported by the Natural Science Foundation of Sichuan Province(No.2022NSFSC0422)China and the Fundamental Research Funds for the Central Universities,China.
文摘Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures.The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering.The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack.Based on this,a novel crack-identification method for underwater concrete structures is presented.This method uses water irrigation to generate seepage at the interface of a crack;then,the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack.Crack information can be identified by monitoring the cooling law and leakage flow near cracks.The proposed mobile crack-monitoring system consists of a heating system,temperature-measurement system,and irrigation system.A series of tests was conducted on a reinforcedconcrete beam using this system.The crack-discrimination indexψwas defined,according to the subsection characteristics of the heat-source cooling curve.The effects of the crack width,leakage flow,and relative positions of the heat source and crack onψwere studied.The results showed that the distribution characteristics ofψalong the monitoring line could accurately locate the crack,but not quantify the crack width.However,the leakage flow is sensitive to the crack width and can be used to identify it.
基金National Natural Science Foundation of China(Nos.21471100,21704066)Guangdong Basic and Applied Basic Research Foundation,China(No.2021A1515010241)Shenzhen Natural Science Fund,China(the Stable Support Plan Program)(No.20200813081943001).
文摘A Fe_(2)O_(3)-MWNTs(multi-walled carbon nanotubes)composite with a reinforced concrete structure was fabricated employing a two-step method which involves a sol-gel process followed by high-temperature in situ sintering.This Fe_(2)O_(3)-MWNTs composite,intended to be used as an anode material for lithium-ion batteries,maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%.The rate capabilities of the Fe_(2)O_(3)-MWNTs composite,evaluated using the ratios of capacity at 100,200,500,1000,2000 and 100 mA/g after every 10 cycles,were determined to be 904.7,852.1,759.0,653.8,566.8 and 866.3 mA·h/g,respectively.Such a superior electrochemical performance of the Fe_(2)O_(3)-MWNTs composite is mainly attributed to the reinforced concrete construction,in which the MWNTs function as the skeleton and conductive network.Such a structure contributes to shortening the transport pathways for both Li+and electrons,enhancing conductivity and accommodating volume expansion during prolonged cycling.This Fe_(2)O_(3)-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.
文摘According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,which was suitable for China. Furthermore,a visual service life prediction program of concrete structure was developed by optimized Monte Carlo method. Meanwhile,Life 365 program was compared,indicating reliability of the prediction program. Finally,the validity of prediction model was verified in JinTang Bridge of Zhoushan Island Mainland Linkage Project.
文摘Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature(SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.
基金the National High Technology Research and Development Program (863) of China(No. 2006AA09A103)the Shanghai Leading Academic Discipline Project (No. B208)
文摘This paper presents an application of strut-and-tie model(STM) to design the interior anchorage zone(IAZ) in the post-tensioned concrete structure.The STM theory and range of IAZ are introduced.Then,based on the finite element analysis,a series of simplified equations to calculate internal forces in IAZ are presented.Finally,the STM model for IAZ is given.In the proposed STM model,internal forces in ties vary with the dimension ratio and the eccentricity of load.The U-turn of internal forces is suggested to allocate rebar to resist bearing flexural tensile force.Compared with the FIP(International Federation for Prestressing) model,the proposed STM model is more reasonable and applicable.
文摘In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the composite structure.Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls.The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves.When a layer of air was added,the effect of blast waves was exaggerated,while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.
文摘This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fiber reinforced concrete is suited for use in load-bearing members. Despite excellent material properties, the use of glass fibers in a concrete matrix is carried out so far only in non- structural elements or as a modification for the prevention of shrinkage cracks. The aim of re- search at the University of Applied Sciences in Leipzig is the use of alkali-resistant macro glass fibers as concrete reinforcement in structural elements as an alternative to steel fiber reinforcement. Slabs on ground, as an example for structural members, provide a sensible application for the new material because they can be casted as load bearing and non-load bearing and are mostly made of steel fiber reinforced concrete. In the future, structural glass fiber reinforced concrete shall provide a simple and visually appealing alternative to conventional steel bar or steel fiber reinforced concrete. The glass fibers can also be used in combination with conventional reinforcing bars or mat reinforcements. Initial investigations have announced some potential.
基金a grant(19CTAP-C152020-01)from Technology Advancement Research Program(TARP)funded by the Ministry of Land,Infrastructure and Transport of the Korean government.
文摘The demand for defect diagnoses is gradually gaining ground owing to the growing necessity to implement safe inspection methods to ensure the durability and quality of structures.However,conventional manpower-based inspection methods not only incur considerable cost and time,but also cause frequent disputes regarding defects owing to poor inspections.Therefore,the demand for an effective and efficient defect-diagnosis model for concrete structures is imminent,as the reduction in maintenance costs is significant from a long-term perspective.Thus,this paper proposes a deep learning-based image objectidentification method to detect the defects of paint peeling,leakage peeling,and leakage traces that mostly occur in underground parking lots made of concrete structures.The deep learning-based object-detection method can replace conventional visual inspection methods.A faster region-based convolutional neural network(R-CNN)model was used with a training dataset of 6,281 images that utilized a region proposal network to objectively localize the regions of interest and detect the surface defects.The defects were classified according to their type,and the learning of each exclusive model was ensured through test sets obtained from real underground parking lots.As a result,average precision scores of 37.76%,36.42%,and 61.29%were obtained for paint peeling,leakage peeling,and leakage trace defects,respectively.Thus,this study verified the performance of the faster RCNN-based defect-detection algorithm along with its applicability to underground parking lots.
文摘The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in Sikkim,was triggered by an intraplate source on the overriding Eurasian plate.Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program.In this paper,near-field and far-field ground motions from this earthquake were analyzed to evaluate their key characteristics and examine their time-frequency features by employing Fast Fourier Transforms(FFTs)and Continuous Wavelet Transforms(CWTs).A comparison between the ground motion parameters of near-field and far-field seismic waves highlights the distinct characteristics of near-field ground motions.Additionally,the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated.The results from the non-linear time history analyses indicate that the roof displacements,drift ratio and strain induced in the frame elements are less than the code-prescribed maximum limits.Further,the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios.The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the nonengineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.
基金National Key R&D Program of China under Grant No.2017YFC1500601National Natural Science Foundation of China under Grant Nos.51678541 and 51708523Scientific Research Fund of the Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2016A01。
文摘The column-to-beam flexural strength ratio(CBFSR)has been used in many seismic codes to achieve the strong column-weak beam(SCWB)failure mode in reinforced concrete(RC)frames,in which plastic hinges appear earlier in beams than in columns.However,seismic investigations show that the required limit of CBFSR in seismic codes usually cannot achieve the SCWB failure mode under strong earthquakes.This study investigates the failure modes of RC frames with different CBFSRs.Nine typical three-story RC frame models with different CBFSRs are designed in accordance with Chinese seismic codes.The seismic responses and failure modes of the frames are investigated through time-history analyses using 100 ground motion records.The results show that the required limit of the CBFSR that guarantees the SCWB failure mode depends on the beam-column connection type and the seismic intensity,and different types of beam-column connections exhibit different failure modes even though they are designed with the same CBFSR.Recommended CBFSRs are proposed for achieving the designed SCWB failure mode for different types of connections in RC frames under different seismic intensities.These results may provide some reference for further revisions of the SCWB design criterion in Chinese seismic codes.
基金supported by the National Natural Science Foundation of China(Grant Nos.52078376,51908424,and 52038008)the Shanghai Rising-Star Program(Grant No.22QB1405000)the State Key Laboratory for Hazard Reduction in Civil Engineering of Tongji University(Grant No.SLDRCE19-B-39).
文摘In order to study the feasibility of strengthening of segmental tunnel linings by using steel-concrete composites(SCC),a three-dimensional(3D)finite element(FE)model is proposed in this paper.The nonlinear mechanical behavior of concrete is described by a plastic-damage model.The nonlinearity,resulting from the interface of the SCC and reinforced concrete(RC)segments,is simulated with the help of a system of springs.The analysis results are compared with those obtained from a full-scale test of a tunnel segment.Their agreement validates the usefulness of the 3D FE model.Numerical re-analysis of the test shows that the interfacial connectors govern both the strengthening effect of SCC and the failure pattern of the strengthened segments.Thus,the force-transmitting capacity of the interfacial connectors should be concerned in design activities.As regards the circular segments,the interfacial connectors refer to both the shearing and the stripping connectors.The composite effect of the SCC and RC segments increases with the increasing number of these connectors.The latter,therefore,results in the increases of the bearing capacities and stiffnesses of the strengthened segments.Those increases become insignificant as the number of these connectors is sufficient to ensure a perfect composite effect of the SCC and RC segments.In addition,the numerical simulations show that using high-performance steel shell(HPS)or/and ultra-high-performance concrete(UHPC)is an effective way to increase the strengthening effect of SCCs.
文摘Today,the most commonly used civil infrastructure inspection method is based on a visual assessment conducted by certified inspectors following prescribed protocols.However,the increase in aggressive environmental and load conditions,coupled with the achievement of many structures of the life-cycle end,has highlighted the need to automate damage identification and satisfy the number of structures that need to be inspected.To overcome this challenge,this paper presents a method for automating concrete damage classification using a deep convolutional neural network.The convolutional neural network was designed after an experimental investigation of a wide number of pretrained networks,applying the transfer-learning technique.Training and validation were conducted using a database built with 1352 images balanced between“undamaged”,“cracked”,and“delaminated”concrete surfaces.To increase the network robustness compared to images in real-world situations,different image configurations have been collected from the Internet and on-field bridge inspections.The GoogLeNet model,with the highest validation accuracy of approximately 94%,was selected as the most suitable network for concrete damage classification.The results confirm that the proposed model can correctly classify images from real concrete surfaces of bridges,tunnels,and pavement,resulting in an effective alternative to the current visual inspection techniques.
基金supported by the Spanish Ministry of Science and Innovation(No. BIA2011-23602)the European Community with the European Regional Development Fund (FEDER), Spain
文摘This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operator from the genetic algorithms (GAs), namely MOSAMO1, MOSAMO2 and MOSAMO3. The procedure is applied to three objective functions: the economic cost, the reinforcing steel congestion and the embedded CO 2 emissions. Additional results for a random walk and a descent local search multi-objective algorithm are presented. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to a typical bridge pier of 23.97 m in height. This example involved 110 design variables. Results indicate that algorithm MOSAMO2 outperforms other algorithms regarding the definition of Pareto fronts. Further, the proposed procedure will help structural engineers to enhance their bridge pier designs.
文摘In recent years,great attention has focused on the development of automated procedures for infrastructures control.Many efforts have aimed at greater speed and reliability compared to traditional methods of assessing structural conditions.The paper proposes a multi-level strategy,designed and implemented on the basis of periodic structural monitoring oriented to a cost-and time-efficient tunnel control plan.Such strategy leverages the high capacity of convolutional neural networks to identify and classify potential critical situations.In a supervised learning framework,Ground Penetrating Radar(GPR)profiles and the revealed structural phenomena have been used as input and output to train and test such networks.Image-based analysis and integrative investigations involving video-endoscopy,core drilling,jacking and pull-out testing have been exploited to define the structural conditions linked to GPR profiles and to create the database.The degree of detail and accuracy achieved in identifying a structural condition is high.As a result,this strategy appears of value to infrastructure managers who need to reduce the amount and invasiveness of testing,and thus also to reduce the time and costs associated with inspections made by highly specialized technicians.
文摘This article offers a demonstration of a novel technology that uses hydro and solar power combined with battery storage to generate electricity for deployment off coastal regions.Called the coastal power plant(CPP),such an installation has a multistorey water reservoir that draws in seawater that is then pumped up in vertical stages by geyser pumps into an overhead tank,from which it is released into a hydropower plant to generate electricity.The ocean surface is utilized to install a floating solar plant for photovoltaic energy generation.The intermittent renewable source is combined with a battery energy storage system to meet peak demands.Offshore oil industry technologies are utilized in fabricating the structures on shore and towing them to the site.The potential and cost effectiveness of a 201-MW CPP are also analyzed.Results demonstrate the effectiveness of the new design in terms of investment and operation/maintenance costs.These compare favorably with other renewable energy technologies.
