The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)fr...The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)frame buildings,and masonry buildings.The near-field region is known to be tectonically highly active,and the local intensity level is the highest,that is,0.4g peak ground acceleration(PGA)for the design basis earthquake,in the Chinese zonation of seismic ground motion parameters.The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy.The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings.It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement.Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field.However,careful forensic analyses are needed before any conclusive judgment can be made.展开更多
A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used ...A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used to predict fatigue crack initiation and the fatigue life until failure.Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present.The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8%to 2.4%.Microscopically,the adjacent grain arrangements and their interactions account for the stress concentration.In addition,different sets of grain orientations with the same total grain numbers of 150 were generated using the present model.Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale,although little effect is found on the macroscopic length-scale.展开更多
Cracking failure of cement-treated base(CTB)has always been the concern of highway constructors.Mesoscale cracking analysis is an important means to study the damage degradation mechanism,which is difficult to be char...Cracking failure of cement-treated base(CTB)has always been the concern of highway constructors.Mesoscale cracking analysis is an important means to study the damage degradation mechanism,which is difficult to be characterized by experimental techniques alone.The objective of this paper is to develop a random aggregate modelling method to simulate the mesoscopic cracking of CTB material.A minimum rectangle area method was proposed to calculate the polygon aggregate size,which is closer to the sieving analysis than the average radius method.A buffer zone method was proposed to determine the distance between randomly generated polygon aggregates.Based on the proposed random algorithm,finite element method(FEM)was adopted to build the mesoscopic model of CTB including aggregate,mortar,interfacial transition zone(ITZ)and air voids.Laboratory tests were conducted to validate the numerical model.Then the sensitivity analyses were conducted to study the influencing factors on cracking behavior.The simulation results indicate that the higher aggregate content and the finer gradation lead to the increase of ITZ,thus reducing the cracking resistance of the CTB material.Low porosity content is able to significantly reduce the stress concentration and thus improves the cracking resistance.The research results of this paper could be used to guide the crack resistant design of CTB material.展开更多
基金the Natural Science Foundation of China(52122811).
文摘The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)frame buildings,and masonry buildings.The near-field region is known to be tectonically highly active,and the local intensity level is the highest,that is,0.4g peak ground acceleration(PGA)for the design basis earthquake,in the Chinese zonation of seismic ground motion parameters.The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy.The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings.It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement.Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field.However,careful forensic analyses are needed before any conclusive judgment can be made.
基金supported financially by the National Natural Sciene Foundation of China(Nos.51725503 and 51575183)111 Project+4 种基金Zhang XC is also grateful for the support by Shanghai Pujiang ProgramYoung Scholar of the Yangtze River Scholars ProgramShanghai Technology Innovation Program of SHEITC(No.CXY-2015-001)financial supports by Coventry University through the Early Career Researcher-Outgoing Mobility Awardthe East China University of Science and Technology through 111 Project to facilitate this international research collaboration.
文摘A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used to predict fatigue crack initiation and the fatigue life until failure.Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present.The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8%to 2.4%.Microscopically,the adjacent grain arrangements and their interactions account for the stress concentration.In addition,different sets of grain orientations with the same total grain numbers of 150 were generated using the present model.Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale,although little effect is found on the macroscopic length-scale.
基金This work was supported in part by the National Natural Science Foundation of China under Grants No.51978163 and 52208439the Jiangsu Nature Science Foundation under Grant No.BK20200468.
文摘Cracking failure of cement-treated base(CTB)has always been the concern of highway constructors.Mesoscale cracking analysis is an important means to study the damage degradation mechanism,which is difficult to be characterized by experimental techniques alone.The objective of this paper is to develop a random aggregate modelling method to simulate the mesoscopic cracking of CTB material.A minimum rectangle area method was proposed to calculate the polygon aggregate size,which is closer to the sieving analysis than the average radius method.A buffer zone method was proposed to determine the distance between randomly generated polygon aggregates.Based on the proposed random algorithm,finite element method(FEM)was adopted to build the mesoscopic model of CTB including aggregate,mortar,interfacial transition zone(ITZ)and air voids.Laboratory tests were conducted to validate the numerical model.Then the sensitivity analyses were conducted to study the influencing factors on cracking behavior.The simulation results indicate that the higher aggregate content and the finer gradation lead to the increase of ITZ,thus reducing the cracking resistance of the CTB material.Low porosity content is able to significantly reduce the stress concentration and thus improves the cracking resistance.The research results of this paper could be used to guide the crack resistant design of CTB material.
