Damage smear method(DSM)is adopted to study trans-scale progressive rock failure process,based on statistical meso-damage model and finite element solver.The statistical approach is utilized to reflect the mesoscopic ...Damage smear method(DSM)is adopted to study trans-scale progressive rock failure process,based on statistical meso-damage model and finite element solver.The statistical approach is utilized to reflect the mesoscopic rock heterogeneity.The constitutive law of representative volume element(RVE)is established according to continuum damage mechanics in which double-damage criterion is considered.The damage evolution and accumulation of RVEs are used to reveal the macroscopic rock failure characteristics.Each single RVE will be represented by one unique element.The initiation,propagation and coalescence of meso-to macro-cracks are captured by smearing failed elements.The above ideas are formulated into the framework of the DSM and programed into self-developed rock failure process analysis(RFPA)software.Two laboratory-scale examples are conducted and the well-known engineering-scale tests,i.e.Atomic Energy of Canada Limited’s(AECL’s)Underground Research Laboratory(URL)tests,are used for verification.It shows that the simulation results match with other experimental results and field observations.展开更多
Large structures,such as bridges,highways,etc.,need to be inspected to evaluate their actual physical and functional condition,to predict future conditions,and to help decision makers allocating maintenance and rehabi...Large structures,such as bridges,highways,etc.,need to be inspected to evaluate their actual physical and functional condition,to predict future conditions,and to help decision makers allocating maintenance and rehabilitation resources.The assessment of civil infrastructure condition is carried out through information obtained by inspection and/or monitoring operations.Traditional techniques in structural health monitoring(SHM)involve visual inspection related to inspection standards that can be time-consuming data collection,expensive,labor intensive,and dangerous.To address these limitations,machine vision-based inspection procedures have increasingly been investigated within the research community.In this context,this paper proposes and compares four different computer vision procedures to identify damage by image processing:Otsu method thresholding,Markov random fields segmentation,RGB color detection technique,and K-means clustering algorithm.The first method is based on segmentation by thresholding that returns a binary image from a grayscale image.The Markov random fields technique uses a probabilistic approach to assign labels to model the spatial dependencies in image pixels.The RGB technique uses color detection to evaluate the defect extensions.Finally,K-means algorithm is based on Euclidean distance for clustering of the images.The benefits and limitations of each technique are discussed,and the challenges of using the techniques are highlighted.To show the effectiveness of the described techniques in damage detection of civil infrastructures,a case study is presented.Results show that various types of corrosion and cracks can be detected by image processing techniques making the proposed techniques a suitable tool for the prediction of the damage evolution in civil infrastructures.展开更多
Since the similarity in size distribution of earthquakes and acoustic emissions (AE) was found in the 1960s, many laboratory studies have been motivated by the need to provide tools for the prediction of mining fail...Since the similarity in size distribution of earthquakes and acoustic emissions (AE) was found in the 1960s, many laboratory studies have been motivated by the need to provide tools for the prediction of mining failures and natural earthquakes. This paper aims, on the one hand, to draw an outline of laboratory AE studies in the last 50 years, which have addressed seismological problems. Topics include the power laws in which the similarity between AEs and earthquakes is involved and progress that has been made in AE technology and laboratory AE study. On the other hand, this study will highlight some key issues intensively discussed, especially in the last three decades, such as aspects related to the pre-failure damage evolution, fault nucleation and growth in brittle rocks and discuss factors governing these processes.展开更多
The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit dia...The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit diagram(FFLD)was transformed into a stress-based(σ-FFLD)and effective plastic strain(EPS)vs triaxiality(η)plot to remove the excess dependency of fracture limits over the strains.For the prediction of fracture limits,seven different damage models were calibrated.The Oh model displayed the best ability to predict the fracture locus with the least absolute error.Though the experimentally obtained fracture limits have only been used for the numerical analysis,none of the considered damage models predicted the fracture strains over the entire considered range of stress triaxiality(0.33<η<0.66).The deep drawing process window helped to determine wrinkling,safe and fracture zones while drawing the cylindrical cups under different temperature and lubricating conditions.Further,the highest drawing ratio of 2 was achieved at 673 K under the lubricating condition.All the numerically predicted results of both stretch forming and deep drawing processes using the Hill 1948 anisotropic yielding function were found to be good within the acceptable range of error.展开更多
There are always some local damages in spatial steel structures induced by strong earthquakes, such as welding cracks of steel nodes,anchor loose of supports etc.If these local damages of spatial steel structures occu...There are always some local damages in spatial steel structures induced by strong earthquakes, such as welding cracks of steel nodes,anchor loose of supports etc.If these local damages of spatial steel structures occur,there will be serious dangers to the structural safety.In order to detect the position of local damage under earthquake quickly and accurately,the method of support damage diagnosis of spatial steel structures under earthquakes is studied by using wavelet packet decomposition,data fusion and cluster analysis.Furthermore,a scale model of spatial steel structure was tested on a seismic simulation shaking table to detect the position of damaged support.Results show that the damaged support position can be detected accurately by using the method proposed in this paper,which has practical applications to the damage detection of spatial steel structures.展开更多
This paper establishes a 3D numerical model for 15# hydropower house of the Three Gorges Project (TGP) and performs a nonlinear static and dynamic damage analysis. In this numerical model, a coupling model of finite a...This paper establishes a 3D numerical model for 15# hydropower house of the Three Gorges Project (TGP) and performs a nonlinear static and dynamic damage analysis. In this numerical model, a coupling model of finite and infinite elements for simulating infinite foundation of hydropower station is adopted. A plastic-damage model based on continuum damage mechanics, which includes the softening and damage behavior under tension is considered for the concrete material. The dynamic equilibrium equations of moti...展开更多
In this paper, using discontinuous deformation analysis, we simulate numerically the processes of the 1975 Haicheng earthquake and the 1999 Xiuyan earthquake in the tectonic environment of North China where blocks res...In this paper, using discontinuous deformation analysis, we simulate numerically the processes of the 1975 Haicheng earthquake and the 1999 Xiuyan earthquake in the tectonic environment of North China where blocks restrict each other by DDA+FEM. Based on the research on the distribution of foreshocks and recent aftershocks of Xiuyan earthquake and the results from our study and other study on Haicheng earthquake, we present a tectonic block model of Haicheng and Xiuyan earthquakes. The results from numerical simulation include the variation of principal stress field released by these two earthquakes, contour patterns of maximum shear stress change, variation patterns of displacement vectors before and after the earthquakes and variation of the earthquake fault slip with time, which agree basically with the focal mechanisms, macroscopic isoseismal and horizontal displacement characters from observations.展开更多
Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics con...Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics concepts. The parameter is used to modify the beam element at the cracked or damaged location. Soil samples were obtained from the site of the pile and were subjected to laboratory tri-axial tests to obtain shear strength parameters c and . Other soil parameters such as Young’s modulus E and Poisson’s ratio were also obtained from the tri-axial tests. These were used to calculate shear strength and sub-grade modulus k for the soil. The parameters , E, and k were later used together with the damage parameter in the finite element simulation of the strength of the damaged pile using Eigen value analyses. The layered soil modulus is approximated by taking the mean value and is denoted by . The discrete element matrices are assembled into a system Eigen-value equation, the solution of which provides the stability or instability loads for the damaged pile. The results obtained for a pile without damage, that is, when =0 , are in good agreement with those published in the literature. It has also been found that higher soil resistance is needed to support the damaged pile. It is concluded that the proposed model is a good candidate for use in the analysis and repair of damaged piles due to earthquake overload by soil stabilization methods.展开更多
Japan has experienced many large-scale natural disasters, such as earthquakes, typhoons accompanied by heavy rain, and landslides. Based on data for the damage caused by four recent major earthquakes in Japan, we inve...Japan has experienced many large-scale natural disasters, such as earthquakes, typhoons accompanied by heavy rain, and landslides. Based on data for the damage caused by four recent major earthquakes in Japan, we investigate the trends in the number of evacuees and evacuation centres after these disasters as well as the restoration processes for public utilities such as electricity, gas, water, and communication lines. We compare the restoration speeds and trends of the damaged infrastructure systems. We also propose various mathematical models to approximate the recovery trends using both evacuee-related data and damage recovery process data. These results can be used to design natural disaster mitigation policies not only in Japan, but also in other countries. The results of various statistical data analyses and mathematical modelling techniques are applied to provide policy suggestions.展开更多
The Ms8.0 Wenchuan earthquake in 2008 caused huge casualties, economic losses, and building damages , which are analyzed. The results show that damages of houses designed according to the current seismic code were sig...The Ms8.0 Wenchuan earthquake in 2008 caused huge casualties, economic losses, and building damages , which are analyzed. The results show that damages of houses designed according to the current seismic code were significantly smaller than those without such design, suggesting that the code has achieved the desired goal of seismic fortification. Buildings of different kinds of structures showed large differences in damages : Houses with steel-frames and shear walls or steel structures suffered the least damages ; those with frames or with brick-and-concrete structures suffered more; old cottages, the most.展开更多
Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunn...Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunnel,which is located in a seismic region of China,three-dimensional seismic analysis is conducted to investigate the dynamic response of a tunnel portal subjected to earthquake waves with different vibration directions.In order to simulate the mechanic behavior of slope rock effectively,an elastoplastic damage model is adopted and applied to ABAQUS software by a self-compiled user material(UMAT)subroutine.Moreover,the seismic wave input method for tunnel portal is established to realize the seismic input under vertically incident earthquake waves with different vibration directions,e.g.,S waves with a vibration direction perpendicular or parallel to the tunnel axis and P waves with a vibration direction perpendicular to the tunnel axis.The numerical results indicate that the seismic response and damage mechanisms of the tunnel portal section are related to the vibration direction of the earthquake waves.For vertically incident S waves running perpendicular to the tunnel axis,the hoop tensile strain at the spandrel and arch foot and the hoop shear strain at the vault and arch bottom are the main contributors to the plastic damage of the tunnel.The strain is initially concentrated around the tunnel foot and spandrel,before shifting to the tunnel vault and bottom farther away from the tunnel entrance.For vertically incident S waves running parallel to the tunnel axis,very large hoop shear strain and plastic damage appear at the tunnel haunches.This strain first increases and then decreases with distance from the tunnel entrance.For vertically incident P waves running perpendicular to the tunnel axis,the maximum damage factor of the slope rock and the maximum plastic strain of the tunnel are significantly lower than for S waves.Moreover,with increasing distance from the tunnel entrance,the plastic damage to the tunnel lining rapidly decreases.展开更多
On the 2011 off the Pacific Coast of Tohoku Earthquake, gymnasium buildings exhibited the unexpected structural damages, which prevented a use as evacuation shelters in during- and post-disaster periods. The major fai...On the 2011 off the Pacific Coast of Tohoku Earthquake, gymnasium buildings exhibited the unexpected structural damages, which prevented a use as evacuation shelters in during- and post-disaster periods. The major failure occurr<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ing</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> on the connection between the RC column top and steel roof as well as the cracks in the RC column base w</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">as</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> observed during the emergent inspection. According to the earlier studies, it was implied that the presence of the slotted hole possibly deteriorates the seismic capacity;however, the length of slotted hole was fixed at a certain value. Facing this concern, this research attempts to clarify the influence of the slotted hole length through a comprehensive parametric study by pushover and seismic response analyses. In conclusion, it has been discovered that the slotted hole deteriorates the seismic capacity for the connection failure up to almost 50% of that without slotted hole. Moreover, the discrepancy of characteristics obtained by the static and dynamic analyses is originated by means of the presence of slotted hole. This slotted hole effect should be noted by structural engineers and researchers to provide the adequate seismic diagnosis and strengthening.</span></span></span>展开更多
Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interact...Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interaction(SSI)significantly affects the responses of OWT under environmental loads. However, there is few systematic research about the difference in the dynamic response of different SSI models under environmental loads. In order to solve the problem, the OWT is modeled by shell element, and several SSI models are built. The wind, wave and earthquake loads are taken into account. Moreover, the dynamic response, fatigue and buckling analysis are performed by ANSYS. The results indicate that SSI cannot be ignored in the dynamic response of the OWT under wind and wave loads. The SSI can decrease the displacement response of the OWT by 19% under wind and wave loads and reduce the fatigue damage of the pile. Multi-layer SSI can strongly influence the OWT's dynamic response under wind and wave loads or earthquake-only load. The vertical earthquake load increases the dynamic response in three directions.Besides, in order to simulate real environment, multi-layer SSI, soil damping and vertical SSI must be considered to evaluate the displacement response of the OWT under wind, wave and earthquake loads. The earthquake and gravity loads can cause more obvious response of the OWT than that of only wind and wave loads. The top and bottom of the tower are prone to occur buckling.展开更多
基金supported in part by the National Natural Science Foundation of China (Grant Nos.51679028 and 51879034)Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology (Grant No. SKLGDUEK1804)the Fundamental Research Funds for the Central Universities (Grant No.DUT18JC10)
文摘Damage smear method(DSM)is adopted to study trans-scale progressive rock failure process,based on statistical meso-damage model and finite element solver.The statistical approach is utilized to reflect the mesoscopic rock heterogeneity.The constitutive law of representative volume element(RVE)is established according to continuum damage mechanics in which double-damage criterion is considered.The damage evolution and accumulation of RVEs are used to reveal the macroscopic rock failure characteristics.Each single RVE will be represented by one unique element.The initiation,propagation and coalescence of meso-to macro-cracks are captured by smearing failed elements.The above ideas are formulated into the framework of the DSM and programed into self-developed rock failure process analysis(RFPA)software.Two laboratory-scale examples are conducted and the well-known engineering-scale tests,i.e.Atomic Energy of Canada Limited’s(AECL’s)Underground Research Laboratory(URL)tests,are used for verification.It shows that the simulation results match with other experimental results and field observations.
基金Part of the research leading to these results has received funding from the research project DESDEMONA–Detection of Steel Defects by Enhanced MONitoring and Automated procedure for self-inspection and maintenance (grant agreement number RFCS-2018_800687) supported by EU Call RFCS-2017sponsored by the NATO Science for Peace and Security Programme under grant id. G5924。
文摘Large structures,such as bridges,highways,etc.,need to be inspected to evaluate their actual physical and functional condition,to predict future conditions,and to help decision makers allocating maintenance and rehabilitation resources.The assessment of civil infrastructure condition is carried out through information obtained by inspection and/or monitoring operations.Traditional techniques in structural health monitoring(SHM)involve visual inspection related to inspection standards that can be time-consuming data collection,expensive,labor intensive,and dangerous.To address these limitations,machine vision-based inspection procedures have increasingly been investigated within the research community.In this context,this paper proposes and compares four different computer vision procedures to identify damage by image processing:Otsu method thresholding,Markov random fields segmentation,RGB color detection technique,and K-means clustering algorithm.The first method is based on segmentation by thresholding that returns a binary image from a grayscale image.The Markov random fields technique uses a probabilistic approach to assign labels to model the spatial dependencies in image pixels.The RGB technique uses color detection to evaluate the defect extensions.Finally,K-means algorithm is based on Euclidean distance for clustering of the images.The benefits and limitations of each technique are discussed,and the challenges of using the techniques are highlighted.To show the effectiveness of the described techniques in damage detection of civil infrastructures,a case study is presented.Results show that various types of corrosion and cracks can be detected by image processing techniques making the proposed techniques a suitable tool for the prediction of the damage evolution in civil infrastructures.
基金financial support by the Japan Science Promotion Society(JSPS 21246134)
文摘Since the similarity in size distribution of earthquakes and acoustic emissions (AE) was found in the 1960s, many laboratory studies have been motivated by the need to provide tools for the prediction of mining failures and natural earthquakes. This paper aims, on the one hand, to draw an outline of laboratory AE studies in the last 50 years, which have addressed seismological problems. Topics include the power laws in which the similarity between AEs and earthquakes is involved and progress that has been made in AE technology and laboratory AE study. On the other hand, this study will highlight some key issues intensively discussed, especially in the last three decades, such as aspects related to the pre-failure damage evolution, fault nucleation and growth in brittle rocks and discuss factors governing these processes.
基金Science and Engineering Research Board,Government of India(ECR/2016/001402)BITS-Pilani,Hyderabad Campus。
文摘The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit diagram(FFLD)was transformed into a stress-based(σ-FFLD)and effective plastic strain(EPS)vs triaxiality(η)plot to remove the excess dependency of fracture limits over the strains.For the prediction of fracture limits,seven different damage models were calibrated.The Oh model displayed the best ability to predict the fracture locus with the least absolute error.Though the experimentally obtained fracture limits have only been used for the numerical analysis,none of the considered damage models predicted the fracture strains over the entire considered range of stress triaxiality(0.33<η<0.66).The deep drawing process window helped to determine wrinkling,safe and fracture zones while drawing the cylindrical cups under different temperature and lubricating conditions.Further,the highest drawing ratio of 2 was achieved at 673 K under the lubricating condition.All the numerically predicted results of both stretch forming and deep drawing processes using the Hill 1948 anisotropic yielding function were found to be good within the acceptable range of error.
基金supported by the National Science and Technology Support Program Subproject Foundation of China(2006BAJ13B03)
文摘There are always some local damages in spatial steel structures induced by strong earthquakes, such as welding cracks of steel nodes,anchor loose of supports etc.If these local damages of spatial steel structures occur,there will be serious dangers to the structural safety.In order to detect the position of local damage under earthquake quickly and accurately,the method of support damage diagnosis of spatial steel structures under earthquakes is studied by using wavelet packet decomposition,data fusion and cluster analysis.Furthermore,a scale model of spatial steel structure was tested on a seismic simulation shaking table to detect the position of damaged support.Results show that the damaged support position can be detected accurately by using the method proposed in this paper,which has practical applications to the damage detection of spatial steel structures.
基金Supported by National Natural Science Foundation of China (No.50679009)Key Laboratory for Scientific Research of Department of Education in Liaoning Province (No.2008S045)
文摘This paper establishes a 3D numerical model for 15# hydropower house of the Three Gorges Project (TGP) and performs a nonlinear static and dynamic damage analysis. In this numerical model, a coupling model of finite and infinite elements for simulating infinite foundation of hydropower station is adopted. A plastic-damage model based on continuum damage mechanics, which includes the softening and damage behavior under tension is considered for the concrete material. The dynamic equilibrium equations of moti...
基金National Natural Science Foundation of China (40174011 and 40274029).
文摘In this paper, using discontinuous deformation analysis, we simulate numerically the processes of the 1975 Haicheng earthquake and the 1999 Xiuyan earthquake in the tectonic environment of North China where blocks restrict each other by DDA+FEM. Based on the research on the distribution of foreshocks and recent aftershocks of Xiuyan earthquake and the results from our study and other study on Haicheng earthquake, we present a tectonic block model of Haicheng and Xiuyan earthquakes. The results from numerical simulation include the variation of principal stress field released by these two earthquakes, contour patterns of maximum shear stress change, variation patterns of displacement vectors before and after the earthquakes and variation of the earthquake fault slip with time, which agree basically with the focal mechanisms, macroscopic isoseismal and horizontal displacement characters from observations.
文摘Instability of a damaged pile due to a statically or dynamically applied overload is studied in this work using the finite element method. A damage parameter from such a pile is calculated using fracture mechanics concepts. The parameter is used to modify the beam element at the cracked or damaged location. Soil samples were obtained from the site of the pile and were subjected to laboratory tri-axial tests to obtain shear strength parameters c and . Other soil parameters such as Young’s modulus E and Poisson’s ratio were also obtained from the tri-axial tests. These were used to calculate shear strength and sub-grade modulus k for the soil. The parameters , E, and k were later used together with the damage parameter in the finite element simulation of the strength of the damaged pile using Eigen value analyses. The layered soil modulus is approximated by taking the mean value and is denoted by . The discrete element matrices are assembled into a system Eigen-value equation, the solution of which provides the stability or instability loads for the damaged pile. The results obtained for a pile without damage, that is, when =0 , are in good agreement with those published in the literature. It has also been found that higher soil resistance is needed to support the damaged pile. It is concluded that the proposed model is a good candidate for use in the analysis and repair of damaged piles due to earthquake overload by soil stabilization methods.
文摘Japan has experienced many large-scale natural disasters, such as earthquakes, typhoons accompanied by heavy rain, and landslides. Based on data for the damage caused by four recent major earthquakes in Japan, we investigate the trends in the number of evacuees and evacuation centres after these disasters as well as the restoration processes for public utilities such as electricity, gas, water, and communication lines. We compare the restoration speeds and trends of the damaged infrastructure systems. We also propose various mathematical models to approximate the recovery trends using both evacuee-related data and damage recovery process data. These results can be used to design natural disaster mitigation policies not only in Japan, but also in other countries. The results of various statistical data analyses and mathematical modelling techniques are applied to provide policy suggestions.
基金supported by the Institute of Seismology,China Earthquake Administration ( IS200826056)
文摘The Ms8.0 Wenchuan earthquake in 2008 caused huge casualties, economic losses, and building damages , which are analyzed. The results show that damages of houses designed according to the current seismic code were significantly smaller than those without such design, suggesting that the code has achieved the desired goal of seismic fortification. Buildings of different kinds of structures showed large differences in damages : Houses with steel-frames and shear walls or steel structures suffered the least damages ; those with frames or with brick-and-concrete structures suffered more; old cottages, the most.
基金support from the Beijing Natural Science Foundation Program(JQ19029)the National Natural Science Foundation of China(41672289+1 种基金U183920151421005).
文摘Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunnel,which is located in a seismic region of China,three-dimensional seismic analysis is conducted to investigate the dynamic response of a tunnel portal subjected to earthquake waves with different vibration directions.In order to simulate the mechanic behavior of slope rock effectively,an elastoplastic damage model is adopted and applied to ABAQUS software by a self-compiled user material(UMAT)subroutine.Moreover,the seismic wave input method for tunnel portal is established to realize the seismic input under vertically incident earthquake waves with different vibration directions,e.g.,S waves with a vibration direction perpendicular or parallel to the tunnel axis and P waves with a vibration direction perpendicular to the tunnel axis.The numerical results indicate that the seismic response and damage mechanisms of the tunnel portal section are related to the vibration direction of the earthquake waves.For vertically incident S waves running perpendicular to the tunnel axis,the hoop tensile strain at the spandrel and arch foot and the hoop shear strain at the vault and arch bottom are the main contributors to the plastic damage of the tunnel.The strain is initially concentrated around the tunnel foot and spandrel,before shifting to the tunnel vault and bottom farther away from the tunnel entrance.For vertically incident S waves running parallel to the tunnel axis,very large hoop shear strain and plastic damage appear at the tunnel haunches.This strain first increases and then decreases with distance from the tunnel entrance.For vertically incident P waves running perpendicular to the tunnel axis,the maximum damage factor of the slope rock and the maximum plastic strain of the tunnel are significantly lower than for S waves.Moreover,with increasing distance from the tunnel entrance,the plastic damage to the tunnel lining rapidly decreases.
文摘On the 2011 off the Pacific Coast of Tohoku Earthquake, gymnasium buildings exhibited the unexpected structural damages, which prevented a use as evacuation shelters in during- and post-disaster periods. The major failure occurr<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ing</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> on the connection between the RC column top and steel roof as well as the cracks in the RC column base w</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">as</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> observed during the emergent inspection. According to the earlier studies, it was implied that the presence of the slotted hole possibly deteriorates the seismic capacity;however, the length of slotted hole was fixed at a certain value. Facing this concern, this research attempts to clarify the influence of the slotted hole length through a comprehensive parametric study by pushover and seismic response analyses. In conclusion, it has been discovered that the slotted hole deteriorates the seismic capacity for the connection failure up to almost 50% of that without slotted hole. Moreover, the discrepancy of characteristics obtained by the static and dynamic analyses is originated by means of the presence of slotted hole. This slotted hole effect should be noted by structural engineers and researchers to provide the adequate seismic diagnosis and strengthening.</span></span></span>
基金supported by the National Natural Science Foundation of China (Grant Nos. 51976131, 52006148, and 52106262)。
文摘Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interaction(SSI)significantly affects the responses of OWT under environmental loads. However, there is few systematic research about the difference in the dynamic response of different SSI models under environmental loads. In order to solve the problem, the OWT is modeled by shell element, and several SSI models are built. The wind, wave and earthquake loads are taken into account. Moreover, the dynamic response, fatigue and buckling analysis are performed by ANSYS. The results indicate that SSI cannot be ignored in the dynamic response of the OWT under wind and wave loads. The SSI can decrease the displacement response of the OWT by 19% under wind and wave loads and reduce the fatigue damage of the pile. Multi-layer SSI can strongly influence the OWT's dynamic response under wind and wave loads or earthquake-only load. The vertical earthquake load increases the dynamic response in three directions.Besides, in order to simulate real environment, multi-layer SSI, soil damping and vertical SSI must be considered to evaluate the displacement response of the OWT under wind, wave and earthquake loads. The earthquake and gravity loads can cause more obvious response of the OWT than that of only wind and wave loads. The top and bottom of the tower are prone to occur buckling.