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Seismic performance and resilience of composite damping self-centering braced frame structures

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Fundamental Research 2024年第3期4卷 603-610页

作者： Longhe Xu Xingsi Xie Zhongxian Li School of civil Engineering Beijing Jiaotong UniversityBeijing 100044China key laboratory of coast civil structure safety of China ministry of education Tianjin UniversityTianjin 300072China

A magnetorheological self-centering brace(MR–SCB)has been proposed to improve the energy dissipation capability of the brace.In this paper,a 15-story MR–SCB braced frame is numerically analyzed to examine its seismic performance and resilience.The MR–SCB provides higher lateral stiffness than the buckling restrained brace and greater energy dissipation capability than the existing self-centering brace.The brace also exhibits a reliable recentering capacity.Under rare earthquakes,the maximum average residual deformation ratio of the structure is less than the 0.5%limit.Under mega earthquakes,the maximum average interstory drift ratio of the structure does not exceed the 2.0%elastoplastic limit,and its maximum average floor acceleration ratio is 1.57.The effects of mainshock and aftershock on the structural behavior are also investigated.The interstory drift and residual deformation of the structure increase with the increase of the intensity of the aftershock.Under aftershocks with the same intensity as the mainshocks,the maximum increment of the residual deformation ratio of the structure is 81.8%,and the average interstory drift ratios of the 12^(th),7^(th),and 3^(rd)stories of the structure are increased by 13.4%,9.2%and 7.5%,respectively.The strong aftershock may significantly cause increased damage to the structure,and increase its collapse risk and residual deformation.

关键词： Braced frame structure Self-centeringbrace Magnetorheological fluid Disc spring Seismic performance Seismic resilience Mainshock-aftershock

Surface Motion of Alluvial Valley in Layered Half-Space for Incident Plane P-Waves

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Transactions of Tianjin University 2011年第3期17卷 157-165页

作者：巴振宁梁建文 School of civil Engineering Tianjin University key laboratory of coast civil structure safety of ministry of education

The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.

关键词：层状半空间平面P波冲积入射运动间接边界元法共振频率直接刚度法

Integrated multi-scale approach combining global homogenization and local refinement for multi-field analysis of high-temperature superconducting composite magnets

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 747-762页

作者： Hanxiao GUO Peifeng GAO Xingzhe WANG key laboratory of Mechanics on Western Disaster and Environment of ministry of education Key Laboratory of Special Function Materials and Structure Design of Ministry of EducationCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China

Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting applications.With respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic fields.Traditional numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally demanding.Herein,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake coils.This approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic scale.We then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic scale.The results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and efficient.The proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.

关键词： epoxy-impregnated high-temperature superconducting(HTS)magnet multi-scale method global homogenization(GH) local refinement(LR) multi-field analysis

Experimental study on the size effect on the equation of state of concretes under shock loading

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Defence Technology（防务技术） 2024年第3期33卷 160-167页

作者： Mei Li Jian Cui Yanchao Shi Baijian Tang Xin Chen key laboratory of coast civil Structural safety of the ministry of education Tianjin UniversityTianjin 300072China School of civil Engineering Suzhou University of Science and Technology1701 Binhe RoadSuzhou 215011JiangsuChina School of civil Engineering Tianjin UniversityTianjin 300072China

Adopting the classical theory of hydrocodes,the constitutive relations of concretes are separated into an equation of state(EoS)which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of concrete.The experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations,especially for the specimen size effect on the EoS.Although some researchers investigate the shock properties of concretes by fly-plate impact tests,the specimens used in their tests are usually in one size.In this paper,the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete materials.The mechanical background of the size effect on the shock properties are revealed,which is related to the lateral rarefaction effect and the deviatoric stress produced in the specimen.According to the tests results,the modified EoS considering the size effect on the shock properties of concrete are proposed,which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.

关键词： Concrete Equation of state Size effect Shock wave Fly-plate impact test

Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

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Defence Technology（防务技术） 2024年第2期32卷 496-509页

作者： Shan Liu Chunyuan Liu Yifei Hao Yi Zhang Li Chen Zhan Li key laboratory of coast civil structure safety of ministry of education Tianjin UniversityTianjin 300072China Tianjin key laboratory of Prefabricated Buildings and Intelligent Construction Hebei University of TechnologyTianjin 300400China Institute of Defense Engineering AMSPLABeijing 100850China Engineering Research Center of safety and Protection of Explosion&Impact of ministry of education Southeast UniversityNanjing 211189JiangsuChina State key laboratory of Disaster Prevention&Mitigation of Explosion&Impact Army Engineering University of the PLANanjing 210007JiangsuChina

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

关键词： Engineered geopolymer composites Fiber optimization Strengthening material Blast resistance Masonry wall Reinforced AAC panel Plain concrete slab

Three-dimensional limit variation analysis on the ultimate pullout capacity of the anchor cables based on the Hoek-Brown failure criterion

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Journal of Mountain Science 2024年第3期21卷 1036-1047页

作者： ZUO Shi ZHAO Lianheng HU Shihong College of civil Engineering Changsha UniversityChangsha 410022China Hunan Provincial key laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering structure Key Laboratory of Heavy-Haul Railway Engineering StructureMinistry of EducationCentral South UniversityChangsha 410075China College of civil Engineering Central South UniversityChangsha 410075China

Only simplified two-dimensional model and a single failure mode are adopted to calculate the ultimate pullout capacity(UPC)of anchor cables in most previous research.This study focuses on a more comprehensive combination failure mode that consists of bond failure of an anchorage body and failure of an anchored rock mass.The three-dimensional ultimate pullout capacity of the anchor cables is calculated based on the Hoek-Brown failure criterion and variation analysis method.The numerical solution for the curvilinear function in fracture plane is obtained based on the finite difference theory,which more accurately reflects the failure state of the anchor cable,as opposed to that being assumed in advance.The results reveal that relying solely on a single failure mode for UPC calculations has limitations,as changes in parameter values not only directly impact the UPC value but also can alter the failure model and thus the calculation method.

关键词： Anchor cable Ultimate pullout capacity(UPC) Failure model Variation analysis Hoek-Brown failure criterion

Stability analysis of intermittently jointed rock slopes based on the stepped failure mode

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Journal of Mountain Science 2024年第3期21卷 1019-1035页

作者： LI Dejian FU Junwen LI Hekai CHENG Xiao ZHAO Lianheng ZHANG Yingbin PENG Xinyan School of civil Engineering Southwest Jiaotong UniversityChengdu 610031China Institute for Disaster Management and Reconstruction College of Architecture&EnvironmentSichuan UniversityChengdu 610065China School of civil Engineering Key Laboratory of Heavy-Haul Railway Engineering StructureMinistry of EducationHunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering StructureCentral South UniversityChangsha 410075China

In practical engineering,due to the noncontinuity characteristics of joints in rock slopes,in addition to plane failure,stepped sliding failure may occur for intermittently jointed rock slopes.Especially for intermittently bedding jointed rock slopes,the correlation and difference in strength parameters between joints and rock bridges,along with the various failure modes and intermittency of rock bridges,contribute to the complexity of stepped failure modes and the unpredictability of failure regions.Based on the upper-bound limit analysis method and multi-sliders step-path failure mode,considering the shear and tensile failure of rock bridges and the weakened relationship between the strength parameters of rock bridges and jointed surfaces,by introducing the modified M-C failure criterion and the formula for calculating the energy consumption of tensile failure of rock bridges,two failure mechanisms are constructed to obtain the safety factor(F_(s))of intermittently jointed rock slopes.The sequential quadratic programming method is used to obtain the optimal upper-bound solution for F_(s).The influence of multiple key parameters(slope height H,horizontal distance L,Slope angleβ,shear strength parameters of the rock bridgeφr and cr,Dimensionless parameter u,weakening coefficients of the internal friction angle and cohesion between the rock bridges and joint surfaces Kφand Kc)on the stability analysis of intermittently jointed rock slopes under the shear failure mode of rock bridges as well as under the tensile failure mode is also explored.The reliability of the failure mechanisms is verified by comparative analysis with theoretical results,numerical results,and landslide cases,and the variation rules of F_(s)with each key parameter are obtained.The results show that F_(s) varies linearly withφr and cr of the rock bridge and with K_(φ)and K_(c),whereas F_(s)changes nonlinearly with H and L.In particular,with the increase in Kφand Kc,Fs increases by approximately 52.78%and 171.02%on average,respectively.For rock b

关键词： Jointed rock slopes Stepped sliding failure Weakening characteristics Modified M‒C failure criterion

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

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Earthquake Research Advances 2024年第1期4卷 67-75页

作者： Yuteng Cao Zhe Qu Xiaodong Ji key laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbin150080China key laboratory of Earthquake Disaster Mitigation Ministry of Emergency ManagementHarbin150080China key laboratory of civil Engineering safety and Durability of China education ministry Department of Civil EngineeringTsinghua UniversityBeijing100084China

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.

关键词： Shake table test Nonstructural element High-rise building Open-loop IDCS algorithm Off-line iteration

Loading capacity and emulsification phenomena of HREE extraction by dialkylphosphinic acids with different β,γ,δ-substituents

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Journal of Rare Earths 2024年第1期42卷 191-199,I0007页

作者： Junlian Wang Guodong Xu Wen Xu Jianguo Cui Yufu Chen Ziyong Chang School of civil and Resource Engineering University of Science and Technology BeijingBeijing100083China key laboratory of ministry of education for Efficient Mining and safety of Metal Mines Beijing100083China State key laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization Baotou Research Institute of Rare EarthsBaotou014030China

The relationship between dialkylphosphinic acid structure and their loading capacity for HREEs and emulsification phenomena has rarely been studied.In this paper,we took Lu extraction as an example to study the effect of β,γ,δ-substituents of dialkylphosphinic acids on their loading capacity and anti-emulsification performance for HREEs.To discuss conveniently,the dialkylphosphinic acids were classified into two groups:β-substituent group(P208,INET-1,P218,USTB-1 and P227)and γ,δ-substituent group(P218,P2132 and Cyanex 272).For β-substituent group extractants,their loading capacities are in the order P208(299.7 mg/L)≈INET-1(299.5 mg/L)>P218(270.8 mg/L)>>USTB-1(163.1 mg/L)>P227(151.4 mg/L),while their anti-emulsification/gelation performances are just in the opposite order P227>USTB-1>P218>P208≈INET-1 under the studied conditions.For γ,δ-substituent group extractants,their loading capacities are in the order P218(270.8 mg/L)>P2132(192.3 mg/L)>Cyanex272(131.7 mg/L),while the anti-emulsification performance of P218 is better than those of P2132 and Cyanex 272.The loading capacity data given in the parentheses are obtained through repeatedly extracting Lu from ~4×10^(-4)mol/L of Lu aqueous feed solution with initial pH of 2.40 by 0.01 mol/L extractant at phase ratio A/O of 1:1.

关键词： Heavy rare earth element Dialkylphosphinic acid Extraction Loading capacity Emulsification