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Resilience-incorporated seismic risk assessment of precast concrete frames with“dry”connections

Earthquake Engineering and Engineering Vibration 2024年第2期23卷 403-425页

作者： Wu Chenhao Tang Yuchuan Cao Xuyang Wu Gang Key Laboratory of concrete and Prestressed concrete Structures of the Ministry of Education Nanjing 211102China Department of Civil and Environmental Engineering University of CaliforniaLos AngelesCA 90095USA School of Civil Engineering Southeast UniversityNanjing 211102China College of Civil and Transportation Engineering Hohai UniversityNanjing 210024China

A resilience-incorporated risk assessment framework is proposed and demonstrated in this study to manifest the advantageous seismic resilience of precast concrete frame(PCF)structures with“dry”connections in terms of their low damage and rapid *** framework integrates various uncertainties in the seismic hazard,fragility,capacity,demand,loss functions,and post-earthquake *** this study,the PCF structures are distinguished from ordinary reinforced concrete frame(RCF)structures by characterizing multiple limit states for the PCF based on its unique damage ***,probabilistic story-wise pushover analyses are performed to yield story-wise capacities for the predefined limit *** the seismic resilience analysis,a step-wise recovery model is proposed to idealize the functionality recovery process,with separate considerations of the repair and non-repair *** recovery model leverages the economic loss and downtime to delineate the stochastic post-earthquake recovery curves for the resilience loss *** such,contingencies in the probabilistic post-earthquake repairs are incorporated and the empirical judgments on the recovery parameters are largely *** proposed framework is demonstrated through a comparative study between two“dry”connected PCFs and one RCF designed as alternative structural systems for a prototype *** results from the risk quantification indicate that the PCFs show reduced loss hazards and lower expected losses relative to the ***,the PCF equipped with energy dissipation devices at the“dry”connections largely reduces the expected economic loss,downtime,and resilience loss by 29%,56%,and 60%,respectively,compared to the RCF.

关键词： precast concrete frame non-emulative precast system seismic resilience seismic risk functional recovery

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On the Preparation of Low-Temperature-Rise and Low-Shrinkage concrete Based on Phosphorus Slag

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Fluid Dynamics & Materials Processing 2024年第4期20卷 803-814页

作者： Jianlong Jin Jingjing Ding Long Xiong Ming Bao Peng Zeng China Construction Ready Mixed concrete Co. Ltd.Wuhan430000China

The effects of different contents of a MgO expansive agent and phosphorus slag on the mechanical properties,shrinkage behavior,and the heat of hydration of concrete were *** slump flow,setting time,dry shrinkage,and hydration heat were used as sensitive parameters to assess the response of the considered *** shown by the results,in general,with an increase in the phosphorus slag content,the hydration heat of concrete decreases for all ages,but the early strength displays a downward trend and the dry shrinkage rate *** 90-d strength and dry shrinkage of concrete could be improved with a phosphorus residue content between 0%-20%,with the best performances in terms of mechanical properties and shrinkage characteristics being achieved for a content of 20 kg/m^(3).On the basis of these results,it can be concluded that appropriate amounts of phosphorus slag and MgO expansive agent can be used to improve the compressive strength of concrete in the later stage by reducing the hydration heat and dry shrinkage rate,respectively.

关键词： Phosphorus slag MgO expansion agent mass concrete hydration heat

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Frequency-dependent Electrical Capacitance and Resistance of Ultra-high Performance concrete and Their Responses to Compressive Strain

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 968-978页

作者：吴瑜孙明清 ZHU Lutao SONG Qiulei CHEN Jianzhong Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics School of ScienceWuhan University of TechnologyWuhan 430070China School of Civil Engineering and Architecture Hubei University of Arts and ScienceXiangyang 441053China Suzhou concrete and Cement Products Research Institude Co. LtdSuzhou 215026China

The frequency-dependent electrical properties and strain self-sensing behaviour of ultra-high performance concrete(UHPC)as cement-based stress/strain self-sensing(CBSS)smart materials were investigated in the frequency range from 100 Hz to 300 *** using the electrical parameters of the equivalent electric circuit model,the quantitative relations of capacitance and conductance of CBSS with the measurement frequency were *** capacitance and the conductance exhibit power-law type dependence on the measurement *** calculated capacitance values at frequencies beyond 2 kHz and conductance values are consistent with the experimental *** sweep-frequency test and the fixed-frequency test were performed to examine effects of the excitation frequencies on strain self-sensing properties of *** fractional change in capacitance(FCC)and resistance(FCR)of CBSS are frequency-dependent in the frequency range from 100 Hz to the f_(B),but frequency-independent in the frequency range from the f_(B)to 300 *** f_(A)and the f_(B)are 1.7-4.0 kHz and 11-78 kHz depending on the fiber dosages,*** and FCR reach their maximum at the f_(A)and 100 Hz,*** responses of capacitance and resistance of CBSS to strain show good repeatability during cyclic *** the fiber dosage increases,capacitance-based sensitivity to strain increases initially and then decreases at the f_(A),and resistance-based sensitivity to strain of CBSS increases with increasing fiber contents.

关键词： UHPC strain self-sensing capacitance-based frequency-dependent

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Failure mechanism of full-size concrete filled steel circle and square tubes under uniaxial compression

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Science China(Technological Sciences) 2015年第10期58卷 1638-1647页

作者： CAI JingMing PAN JinLong SHAN QiFeng Key Laboratory of concrete and Pre-stressed concrete Structures of Ministry of Education Southeast University

In this paper, the failure mechanisms of full-size concrete filled steel tubes(CFST) under uniaxial compression were investigated with nonlinear finite element method. Existing experimental results were employed to verify the validity of the finite element models of CFST specimens. Then, the numerical analysis was further conducted to study the mechanical behaviors of full-size CFST columns with circular and square cross sections under uniaxial compression. The simulation results indicate that the distribution of the contact pressure between circular steel tube and core concrete is much more uniform than that between square steel tube and concrete, resulting in much higher confinement and more efficient interaction between steel tube and core concrete in circular CFST columns, as well as ultimate load capacity and ultimate displacement. Extensive parametric analysis was also conducted to examine the effect of various parameters on the uniaxial compression behaviors of circular and square CFST columns.

关键词： CFST uniaxial compression finite element analysis interaction mechanism

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Behavior and strength of headed stud shear connectors in ultra-high performance concrete of composite bridges

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Frontiers of Structural and Civil Engineering 2019年第5期13卷 1138-1149页

作者： Jianan QI Yuqing HU Jingquan WANG Wenchao LI Key Laboratory of concrete and Prestressed concrete Structures of the Ministry of Education School of Civil EngineeringSoutheast UniversityNanjing 211189China

This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.

关键词： ultra-high performance concrete studs shear strength FE analysis push-out test

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Mechanical Behavior of Rectangular Steel-Reinforced ECC/concrete Composite Column under Eccentric Compression

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Transactions of Tianjin University 2015年第3期21卷 269-277页

作者：潘金龙鲁冰顾大伟夏正昊夏天阳 Key Laboratory of concrete and Pre-stressed concrete Structures of Ministry of Education Southeast University

In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.

关键词： engineered cementitious composite (ECC) steel-reinforced concrete ECC/concrete composite column eccentric compression behavior ultimate load-carrying capacity

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Mechanical Behavior and Failure Criterion of High Performance concrete Under Biaxial Tension-Compression Loading Condition

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Journal of Beijing Institute of Technology 2018年第3期27卷 433-441页

作者： Jinlong Pan Dan Wu Changyu Qi Key Laboratory of concrete and Pre-stressed concrete Structures of Ministry of Education Southeast University

The mechanical behavior and failure criterion of high performance concrete(HPC)subjected to biaxial tension-compression loading conditions were investigated experimentally with a real triaxial testing *** failure modes,ultimate strength and stress-strain curves of HPC under biaxial tension-compression loading conditions were ***,mechanical behavior of HPC under different stress ratios were ***,based on the Kupfers strength criterion for conventional concrete and test results,a novel failure criterion was proposed for HPC under biaxial tension-compression loading conditions.

关键词： high performance concrete(HPC) biaxial tension-compression failure mode failure criterion

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Numerical study on flexural behaviors of steel reinforced engineered cementitious composite(ECC) and ECC/concrete composite beams

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Science China(Technological Sciences) 2014年第3期57卷 637-645页

作者： YUAN Fang PAN JinLong WU YuFei Key Laboratory of concrete and Prestressed concrete Structures of Ministry of Education Southeast University Department of Civil and Architectural Engineering City University of Hong Kong

Engineered cementitious composite(ECC)is a class of high performance cementitious composites with pseudo strain-hardening behavior and excellent crack control *** of concrete with ECC can largely reduce the cracking and durability problems associated with brittleness of *** this paper,a simplified constitutive model of the ECC material was applied to simulate the flexural behaviors of the steel reinforced ECC and ECC/concrete composite beams with finite element *** simulation results are found to be in good agreement with test results,indicating that the finite element model is reasonably accurate in simulating the flexural behaviors of the steel reinforced ECC flexural *** effects of the ECC modulus,ECC tensile ductility,ECC thickness and ECC position on flexural behaviors in terms of ultimate moment,deflection and the maximum crack width of the steel reinforced ECC or ECC/concrete composite beam are hence evaluated.

关键词： engineered cementitious composite(ECC) constitutive model flexural behavior finite element

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Experimental study on mechanical behavior of high performance concrete under multi-axial compressive stress

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Science China(Technological Sciences) 2014年第12期57卷 2514-2522页

作者： ZHOU Jia Jia PAN Jin Long LEUNG Christopher Kin Ying LI Zong Jin Key Laboratory of concrete and Prestressed concrete Structures of Ministry of Education Southeast University Department of Civil and Environmental Engineering Hong Kong University of Science and Technology

Experimental investigation was conducted to characterize the responses of high performance concrete(HPC) subjected to multiaxial compressive stresses. The HPC specimens were prepared with three different mix proportions, which corresponds to three different uniaxial compressive strengths. The cubic specimens with size of 100 mm for each edge were tested with servo-hydraulic actuators at different stress ratios. The principal stresses and strains of the specimens were recorded, and the failure of the cubic specimens under various stress states was examined. The experimental results indicated that the stress states and stress ratios had significant influence on the strength and deformation of HPC under biaxial and triaxial compression, especially under triaxial compression. Failure criteria were proposed for the HPC specimens under biaxial and triaxial compressive loading. The test results provided a valuable reference for obtaining multi-axial constitutive law for HPC.

关键词： high performance concrete (HPC) biaxial compressive stress triaxial compressive stress failure criterion stress-straincurve

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Deflection analysis of reinforced concrete beams strengthened with carbon fibre reinforced polymer under long-term load action

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第8期13卷 571-583页

作者： Mykolas DAUGEVIIUS Juozas VALIVONIS Gediminas MAR IUKAITIS Department of Reinforced concrete and Masonry Structures Vilnius Gediminas Technical University

This paper presents the results of an experimental research on reinforced concrete beams strengthened with an external carbon fibre reinforced polymer(CFRP) layer under long-term load action that lasted for 330 *** describe the characteristics of deflection development of the beams strengthened with different additional anchorages of the external carbon fibre composite layer during the period of *** conducted experiments showed that the additional anchorage influences the slip of the external layer with respect to the strengthened ***,concrete and carbon fibre composite interface stiffness decreases with a long-term load ***,the proposed method of analysis based on the built-up-bars theory can be used to estimate concrete and carbon fibre composite interface stiffness in the case of long-term load.

关键词： Carbon fibre composite Beam strengthening Beam deflection Long-term load Bending stiffness concrete and carbon fibre composite interface stiffness Effective inertia moment

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