Liu Jiyuan Shakes Hands with Armstrong

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Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Rock slope with horizontal-layered fractured structure(HLFS)has high stability in its natural state.However,a strong earthquake can induce rock fissure expansion,ultimately leading to slope failure.In this study,the dynamic response,failure mode,and spectral characteristics of rock slope with HLFS under strong earthquake conditions were investigated based on the large-scale shaking table model test.On this basis,multiple sets of numerical calculation models were further established by UDEC discrete element program.Five influencing factors were considered in the parametric study of numerical simulations,including slope height,slope angle,bedding-plane spacing and secondary joint spacing as well as bedrock dip angle.The results showed that the failure process of rock slope with HLFS under earthquake action is mainly divided into four phases,i.e.,the tensile crack of the slope shoulder joints and shear dislocation at the top bedding plane,the extension of vertical joint cracks and increase of shear displacement,the formation of step-through sliding surfaces and the instability,and finally collapse of fractured rock mass.The acceleration response of slopes exhibits elevation amplification effect and surface effect.Numerical simulations indicate that the seismic stability of slopes with HLFS exhibits a negative correlation with slope height and angle,but a positive correlation with bedding-plane spacing,joint spacing,and bedrock dip angle.The results of this study can provide a reference for seismic stability evaluation of weathered rock slopes.

Seismic performance evaluation of water supply pipes installed in a full-scale RC frame structure based on a shaking table test

As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete(RC)frame structure.Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance.Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions.A seismic fragility study of displacement demand is conducted based on numerical simulation.The acceleration response and displacement response of different combinations are compared.The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.

Experimental study on seismic reinforcement of bridge foundation on silty clay landslide with inclined interlayer

A shaking table test for a bridge foundation reinforced by anti-slide piles on a silty clay landslide model with an inclined interlayer was performed.The deformation characteristics of the bridge foundation piles and anti-slide piles were analyzed in different loading conditions.The dynamic response law of a silty clay landslide with an inclined interlayer was summarized.The spacing between the rear anti-slide piles and bridge foundation should be reasonably controlled according to the seismic fortification requirements,to avoid the two peaks in the forced deformation of the bridge foundation piles.The“blocking effect”of the bridge foundation piles reduced the deformation of the forward anti-slide piles.The stress-strain response of silty clay was intensified as the vibration wave field appeared on the slope.Since the vibration intensified,the thrust distribution of the landslide underwent a process of shifting from triangle to inverted trapezoid,the difference in the acceleration response between the bearing platform and silty clay landslide tended to decrease,and the spectrum amplitude near the natural vibration frequency increased.The rear anti-slide piles were able to slow down the shear deformation of the soil in front of the piles and avoid excessive acceleration response of the bridge foundation piles.

Study on a conical bearing for acceleration-sensitive equipment

Seismic isolation effectively reduces seismic demands on building structures by isolating the superstructure from ground vibrations during earthquakes.However,isolation strategies give less attention to acceleration-sensitive systems or equipment.Meanwhile,as the isolation layer’s displacement grows,the stiffness and frequency of traditional rolling and sliding isolation bearings increases,potentially causing self-centering and resonance concerns.As a result,a new conical pendulum bearing has been selected for acceleration-sensitive equipment to increase self-centering capacity,and additional viscous dampers are incorporated to enhance system damping.Moreover,the theoretical formula for conical pendulum bearings is supplied to analyze the device’s dynamic parameters,and shake table experiments are used to determine the proposed device’s isolation efficiency under various conditions.According to the test results,the newly proposed devices have remarkable isolation performance in terms of minimizing both acceleration and displacement responses.Finally,a numerical model of the isolation system is provided for further research,and the accuracy is demonstrated by the aforementioned experiments.

A novel control strategy for reproducing the floor motions of high-rise buildings by earthquake-simulating shake tables

To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.

Fundamental Study on Response Properties of Structures Constructed on Lunar Regolith

The Artemis Program, for constructing the lunar base, is in progress. How to design and construct architectural and civil engineering structures in the lunar environment has become an important issue. The lunar surface is covered with soft sand, called regolith, and it is required to protect lunar bases and structures, as well as internal precision equipment, against vibrational disturbances such as moonquakes and meteorite collisions. Therefore, in this study, the static and cyclic triaxial compression tests of the regolith simulant were conducted. The reference strain and equivalent damping factor of the regolith simulant were smaller compared to sandy soil on Earth. In addition, a shaking table test using model specimens was conducted on the response properties of regolith ground alone and structures set on regolith ground. The buried foundation and pile foundation notably suppressed the horizontal response attributed to the rocking component compared to a direct foundation.

Analysis on kinematic and inertial interaction in liquefiable soil-pile-structure dynamic system

The dynamic pile-soil interaction in a liquefied site was investigated by means of numerical simulation and shaking table tests in this study.Based on the results from the shaking table experiment,the cross-correlation analysis of the soil displacement-pile bending moment and superstructure acceleration-pile bending moment was performed to study the influence of kinematic interaction and inertial interaction on the seismic response of piles.A relatively reasonable and accurate finite difference numerical analysis model of liquefiable soil-pile group-superstructure dynamic system was established.Through numerical simulation,the understanding of kinematic interaction and inertial interaction in the shaking table test was verified.The mass,damping and period of the superstructure were selected as variables to carry out parameter analysis to further study the influence of inertial interaction on the pile-structure failure mechanism.The results show that the influence of kinematic interaction on the pile was much greater than that of inertial interaction.The mass of the superstructure was the most important parameter of inertial interaction,and dynamic characteristics of the superstructure also had an effect on inertial interaction.The effect of inertial interaction on the part near the pile tip was more significant,indicating that the failure near the pile tip is closely related to inertial interaction.

Experimental studies on liquefaction and reliquefaction potential of saturated ground subjected to repeated incremental acceleration loading with varying shaking duration

Past research has focused on the factors that influence liquefaction under normal shaking conditions.However,studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shaking events are limited.In this study,an attempt has been made to examine the influence of acceleration amplitude and shaking duration on liquefaction and reliquefaction potential under repeated shaking conditions is conducted.1-g uni-axial shaking table experiments were performed on saturated ground prepared with 40%and 60%relative density.The prepared ground was subjected to alternate longer and shorter shaking durations(40 and 20 s)of repeated incremental 0.1 g,0.2 g,0.3 g and 0.4 g acceleration loading,respectively.The variation in density,excess pore water pressure(EPWP),cyclic resistance ratio(CRR)and surface settlement were estimated.The results showed that due to repeated incremental shaking events,reliquefaction was observed on the prepared ground.During longer shaking duration,the post-liquefied soil showed density improvement with improved soil resistance.However,the application of shorter duration loading followed by longer shaking reduced the beneficial effect of density improvement by disturbing the densified ground.Due to this,the ground was found to be more susceptible to reliquefaction in the subsequent incremental longer shaking event.

The impacts of ambiguity in preparation of 80% sulfuric acid solution and shaking time control of calibration solution on the determination of transparent exopolymer particles

The quantification of transparent exopolymer particles(TEP) by colorimetric method is of large error and low repeatability,one major reason of which is related to the absence of clear definition and evaluation for part steps of the original method.It is obscure that the 80% sulfuric acid solution,acted as the extraction solution in the determination of TEP,is prepared based on a volume ratio or mass ratio.Furthermore,the change of solubility of recently available Gum Xanthan(GX) from the market means that the original protocol is no longer applicable,and the grinding of GX stock solution with a tissue grinder is replaced by shaking with a rotating shaker in the study to prevent the excessive dissolution of GX.We found that different preparation techniques could result in the varied concentrations of 80% H_(2)SO_(4).The duration of shaking during the preparation of standard solution significantly affected the slope of the calibration curve,which caused different correction results of TEP.The impacts of different extraction solution concentrations and shaking time of GX solution on the quantification of TEP were investigated based on the field sampling and laboratory analysis.The extraction capacities of H_(2)SO_(4) with different concentrations for Alcian Blue were distinct,but had limited effect on the final measuring result of TEP.The change of the standard curve slope came along with the variation of shaking time,which markedly altered the detection limit and calibration result,and the extended shaking time was in favor of the determination of low-concentration TEP.It was suggested that the extraction solution concentration,shaking time and filtration volume of standard solution are required to be well controlled and selected to obtain more accurate results for TEP with different concentrations.

Effects of non-liquefiable crust layer and superstructure mass on the response of 2×2 pile groups to liquefaction-induced lateral spreading

In this research,two shake table experiments were conducted to study the effects of non-liquefiable crust layer and superstructure mass on the responses of two sets of 22 pile groups to liquefactioninduced lateral spreading.In this regard,an inclined base layer overlain by a very loose liquefiable layer was constructed in both models;while only in one model,a non-liquefiable crust layer was built.A lumped mass,being representative of a superstructure,was attached to the cap of one pile group in both models.The models were fully instrumented with various sensors,including acceleration,displacement,and pore water pressure transducers.Also,the piles were instrumented with pair strain gauges to measure pure bending moments induced by cyclic and monotonic loadings associated with ground shaking and lateral spreading,respectively.The results showed that the existence of the non-liquefiable crust layer increases both the maximum and residual soil displacements at the free field and also the maximum bending moments in the piles.The results of the experiments indicated that the crust layer induces a high kinematic lateral soil pressure and force on the piles which are not present in the crustless case.The crust layer increases the pile cap displacement before liquefaction,albeit decreases it after liquefaction,due to the elastic rebound of the piles in the liquefiable layer.The crust layer postpones both liquefaction triggering and dissipation of excess pore water pressure.The existence of the superstructure mass on the pile caps decreases the acceleration amplitude of the pile caps,while increases their maximum displacement.

Earthquake response of wrap faced embankment on soft clay soil in Bangladesh

A wrap-faced embankment model on soft clay soil subjected to earthquake motion was investigated in this study.The study was conducted both experimentally using a shaking table and numerically using PLAXIS 3D software.The amplification of acceleration,displacement,pore water pressure,and strain response were measured while varying input accelerations and surcharge pressures.Time histories of the Kobe record of the 1995 Hanshin earthquake were used as the input seismic motion.The input acceleration was 0.05 g,0.1 g,0.15 g,and 0.2 g,and different surcharge pressures were 0.70 kPa,1.12 kPa,and 1.72 kPa with relative density of Sylhet sand fixed to 48%.The output data from the shaking table tests and the numerical analysis performed through the PLAXIS 3D software were compared,and these findings were also compared with some earlier similar studies.The acceleration amplification,displacement,pore water pressure,and strain(%)changed along the elevation of the embankment and acceleration response increased with the increase in base acceleration.The increase was more noticeable at higher elevations.These findings enrich the knowledge of predicting the dynamic behavior of wrap-faced embankments and enable the design parameters to be adjusted more accurately.

Fever glove hand-shake method safe blood collection from children's fingertips in COVID-19 fever clinic

BACKGROUND During the coronavirus disease 2019(COVID-19)epidemic,the fever clinic is an important link for screening and diagnosing whether a patient is infected with the novel coronavirus.Blood collection from children’s fingertips is a commonly used detection method;however,in children,the blood collection process may cause discomfort and resistance.To address this problem,the use of heating gloves combined with hand swinging can be considered for fingertip blood collection in children.AIM To explore the application of fever gloves with the handshaking method for fingertip blood collection from children in fever clinics during the COVID-19 epidemic.METHODS A total of 100 children were selected for fingertip blood collection at the fever clinic of our hospital from June 2022 to June 2023 and were divided into two groups using a randomized numerical table method,with 50 cases in each group,including the control and observation groups.The patients in the control group followed the doctor's instructions to cooperate with the routine fingertip blood collection method,and the patients in the observation group followed the doctor's instructions to cooperate with the static fever gloves with the shaking hands method of children's fingertip blood collection.The level of the six blood routine and collection indexes,and the satisfaction of the examination of the patients in the peripheral blood group and the fever gloves with the shaking hands method of the children's fingertip blood collection group were compared.RESULTS The red and white blood cell count,hemoglobin,and red blood cell pressure volume in the observation group were higher than those in the control group(P<0.05);the platelet count in the control group was lower than that in the observation group(P<0.05);the number of times of squeezing the fingertip,the average time of blood collection,and the score of puncture pain in the observation group were significantly better than those in the control group(P<0.05);and satisfaction with the routine blood examination in the observation group was greater than that in the control group.CONCLUSION The application value of the fever gloves with shaking hands method for children's fingertip blood collection was better,the accuracy of examination indexes was higher,and patient satisfaction with the examination was greater.

Shaking table test and cumulative deformation evaluation analysis of a tunnel across the hauling sliding surface

To explore the cumulative deformation effect of the dynamic response of a tunnel crossing the hauling sliding surface under earthquakes,the shaking table test was conducted in this study.Combined with the numerical calculations,this study proposed magnification of the Arias intensity(MIa)to characterize the overall local deformation damage of the tunnel lining in terms of the deformation characteristics,frequency domain,and energy.Using the time‐domain analysis method,the plastic effect coefficient(PEC)was proposed to characterize the degree of plastic deformation,and the applicability of the seismic cumulative failure effect(SCFE)was discussed.The results show that the low‐frequency component(f1 and f2≤10 Hz)and the high‐frequency component(f3 and f4>10 Hz)acceleration mainly cause global and local deformation of the tunnel lining.The local deformation caused by the high‐frequency wave has an important effect on the seismic damage of the lining.The physical meaning of PEC is more clearly defined than that of the residual strain,and the SCFE of the tunnel lining can also be defined.The SCFE of the tunnel lining includes the elastic deformation effect stage(<0.15g),the elastic–plastic deformation effect stage(0.15g–0.30g),and the plastic deformation effect stage(0.30g–0.40g).This study can provide valuable theoretical and technical support for the construction of traffic tunnels in high‐intensity earthquake areas.

Activation of Nrf2 alleviates Parkinson’s disease-like pathology:a new strategy targeting the C/EBPβ/α-Syn pathway

Parkinson’s disease(PD)is a prevalent neurological disorder around the globe,currently affecting over 6 million people globally[1].It is estimated that by 2040,this number may double to more than 12 million[2].Aging is strongly associated with PD,as it is a significant risk factor for its development[3].Clinically,PD presents with various motor and non-motor signs.Movement-related issues mainly consist of slowed motion,involuntary shaking at rest,stiff muscles,and balance difficulties.At the same time,non-movement-related issues include impaired sense of smell,sleep disturbances,bowel irregularities,feelings of sadness,and problems with the body’s automatic functions[4].The typical pathological features of PD patients include the gradual loss of dopaminergic neurons within the substantia nigra pars compacta,coupled with the buildup ofα-synuclein(α-Syn)in neurons,the aggregates of which form inclusions known as Lewy bodies[5].The A53T mutant of humanα-Syn has a propensity to aggregate,a characteristic closely associated with the neurotoxicity seen in familial PD[6].A synthesis of both in vitro and in vivo research indicates that the misfolding and aggregation ofα-Syn are key pathogenic mechanisms in the development of PD[7-9].

Sharing Opportunities

Chinese and African traders will soon meet at a great gathering where they can sit down and talk face to face about their future plans after shaking off the impact of the COVID-19 pandemic.The third edition of the biennial China-Africa Economic and Trade Expo(CAETE)is scheduled to open on 29 June to 2 July.About 50 African countries will come to the host city of Changsha in central China’s Hunan Province to exhibit their products and services that they hope could enter the Chinese market.

新一代土层地震反应分析方法

剖析了当今国际上频域等效线性化和时域非线性求解土层地震反应分析方法的典型代表SHAKE2000与DEEPSOIL,对目前其他学者FDM改进方式的可行性进行评判,采用新的直频法动剪模量阻尼比求解技术,提出新一代一维土层地震反应计算方法和程序SOILQUAKE,并用四种类别和巨厚场地实际记录检验了新程序。结果表明:SHAKE2000与DEEPSOIL在一类、二类场地上基本一致且结果可靠,三类和四类场地上两程序计算反应谱"矮粗胖"现象严重,与实际情况相差甚远;现有考虑频率相关性的FDM改进方式,其基本出发点存在定性错误;对硬场地和中硬场地,SOILQUAKE与SHAKE2000和DEEPSOIL结果大致相似,但在高频部分表现比SHAKE2000更加合理,与DEEPSOIL基本一致;对软场地和巨厚场地,SOILQUAKE克服了SHAKE2000和DEEPSOIL严重低估场地放大效应的缺点,模拟结果与实测记录较为接近,在软场地上优势显著,在巨厚软场地上优势十分显著。SOILQUAKE首先攻克现有软土层地震动计算结果"矮粗胖"和硬土中等效线性化方法缺少高频分量求解难点,具备了作为新一代一维土层地震反应计算方法的能力,将在http://www.soilquake.com或http://www.soilquake.cn上提供共享服务。

现有等效线性化分析程序在实际软场地计算结果方面的比较

SHAKE2000和LSSRLI-1分别是目前国外和国内广泛使用的两种一维等效线性化土层地震反应分析程序，分析二者之间的异同性及其与实测记录的差异程度，可为改进土层地震反应分析方法提供基础。收集整理了日本KiK-net台网中17个软场地（Ⅲ、Ⅳ类场地）39次地震的基岩及地表地震动记录，其中基岩加速度峰值在6∽214Gal之间，土层非线性取3种情况，采用SHAKE2000和LSSRLI-1两种程序分别进行了土层地震反应计算，从地表峰值加速度、加速度反应谱、加速度反应谱谱值比以及土层最大剪应变4个方面进行了对比计算。研究表明：当土体非线性不强时，SHAKE2000和LSSRLI-1计算出的PGA结果差异多数可忽略，计算出的土体剪应变最大值误差也多数小于20％；当土体非线性较强时，仅有少数差异可忽略，计算出土体剪应变最大值误差则多数大于20％；SHAKE2000的结果和LSSRLI-1与实测峰值加速度和反应谱多数情况下差异较大，土体弱非线性下LSSRLI一1结果稍好于SHAKE2000的结果，土体非线性较强时SHAKE2000的结果要好一些。

人体运动建模的实时逆运动学算法

人体运动的虚拟仿真及建模是当今计算机图形学研究的一个热点,而逆向运动学方法则是求解人体运动的一项关键技术.为了实现人体运动建模,提出一种新颖的基于人体关节约束的实时逆向运动学算法.首先基于骨骼长度改进了传统的循环坐标下降(CCD)算法,使其生成的运动效果更加流畅自然;然后引入生物分子运动模拟中的SHAKE算法,使短距离运动建模效果更加高效、鲁棒.在此基础上,提出了模拟多个节点同时运动的解析算法,以获得在多个关节点共同作用下的人体运动仿真效果.同运动捕捉的实测数据相比,采用文中算法所得的结果与在视觉效果上非常接近,并通过实验证实了其应用价值.

应用动态复合震源模型模拟汶川M_w 7.9地震强地面运动

2008年5月12日中国汶川地区发生M_w7.9地震,震中位置103.4°E,31.0°N.主要发震断层空间展布长达300多公里,由南西方向到北东方向呈现明显的分段性,汶川—映秀段逆冲为主兼有少量的右旋走滑分量;安县—北川段为逆冲-右旋走滑的断层错动;青川段以右旋走滑为主兼有少量逆冲分量.采用改进后的复合震源强地面运动预测模型,建立了长为320km,宽为20km的断层破裂运动学模型,实现了断层分段、空间倾角、滑动方向连续变化的动态设定.数值模拟结果给出了近断层两侧(上、下盘)的地面加速度的分布特征,并同卧龙、郫县走石由及绵竹清平强震观测记录进行了对比分析.模拟加速度时程曲线无论在波形、持续时间、频率分量、峰值大小同观测记录都具有较好的相似性.利用现有83个已知经纬度台站的强震实测数据及数值模拟的结果同Boore等的新一代衰减关系(NGA)进行比较,对比模拟与实际观测水平峰值加速度的一致程度.近断层峰值加速度分布特征则进一步显示了在汶川、北川和青川附近明显的高值分布区域,同野外地质调查相一致.进一步的分析结果也表明,汶川—映秀段逆冲为主的断层上盘的运动量远大于断层下盘,在距离断层地表出露位置5km处,峰值加速度N-S、E-W及UP方向分量的比值分别为1.72:1、2.5:1及1.77:1.本文中给出的动态复合震源模型和近断层区域强震模拟的计算方法,对大震强地面运动的预测及实现近实时强地面运动分布特征的圈定(Shaking Map)有着重要的实际意义.