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Wetting effects and strength degradation of swelling shale evaluated from multistage triaxial test

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Underground Space 2019年第2期4卷 79-97页

作者： Hayder Mohammed Salim Al-Maamori M.Hesham El Naggar Silvana Micic Civil and Environmental Engineering Department The University of Western Ontario1151 Richmond St.LondonOntario N6A 5B9Canada Geotechnical Research Centre Civil and Environmental Engineering DepartmentThe University of Western Ontario1151 Richmond St.LondonOntario N6A 5B9Canada

The multistage triaxial compression test was mainly utilized in this research to investigate the degradation in the strength of swelling shale under different wetting *** samples were tested in four different conditions:(1)under their natural moisture content denoted as intact,and after soaking in,(2)water,(3)polymer solution,and(4)bentonite solution,*** experimental results showed that a considerable decrease in the shale’s strength was noted after soaking in water and the lubricant fluids(LFs).The polymer solution caused the least decrease in the strength compared to other *** envelopes of the tested shale were constructed for intact and soaked *** envelopes showed fair agreement between the single stage and the multistage triaxial compression test results,indicating suitability of the multistage triaxial compression test for the tested swelling shale.

关键词： Multistage Triaxial compression Swelling shale strength degradation strength envelopes

Structural strength degradation Model Based on Non-stationary Gamma Process

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Journal of Donghua University(English Edition) 2015年第6期32卷 946-949页

作者：孙道明安宗文 School of Mechatronics Engineering Lanzhou University of Technology

strength degradation is a stochastic and irreversible *** process is an independent nonnegative increment process which can be used to describe the characteristics of strength *** is unreasonable to choose a linear function to describe the strength degradation trend considering that the degradation rate may change over ***,a non-linear power law is proposed to describe the strength degradation trend based on preliminary *** is more general compared with the linear one and the inadequacy of strict linear assumption is ***,the model parameters of non-stationary Gamma process are estimated based on the maximum likelihood ***,it is proved that the non-stationary Gamma process can accurately reflect the strength degradation law through comparative analysis of a real example.

关键词： strength degradation non-linear power law non-stationary Gamma process maximum likelihood estimation

The degradation of Particleboard strength

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Journal of Forestry Research 1997年第1期8卷 59-60页

作者：王逢瑚戴芳天 Northeast Forestry University Harbin China

A number of references about the degradation of particleboard strength were reviewed. Evidencesindicae that PF adhesives are hydrolytically stable and yet particleboards bonded with these resins still degrade. The maincauses of degradation of PF bonded particleboard are the reversal of densification and the development of glue linestresses.

关键词： Particleboard strength degradation PF and UF adhesives

Numerical simulation of triaxial compression test for brittle rock sample using a modified constitutive law considering degradation and dilation behavior

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Journal of Central South University 2015年第8期22卷 3097-3107页

作者：谭鑫 KONIETZKY H FRüHWIRT T College of Civil Engineering Hunan University Geotechnical Institute TU Bergakademie Freiberg

The understanding of the rock deformation and failure process and the development of appropriate constitutive models are the basis for solving problems in rock engineering. In order to investigate progressive failure behavior in brittle rocks, a modified constitutive model was developed which follows the principles of the continuum damage mechanics method. It incorporates non-linear Hoek-Brown failure criterion, confining pressure-dependent strength degradation and volume dilation laws, and is able to represent the nonlinear degradation and dilation behaviors of brittle rocks in the post-failure region. A series of triaxial compression tests were carried out on Eibenstock(Germany) granite samples. Based on a lab data fitting procedure, a consistent parameter set for the modified constitutive model was deduced and implemented into the numerical code FLAC3 D. The good agreement between numerical and laboratory results indicates that the modified constitutive law is well suited to represent the nonlinear mechanical behavior of brittle rock especially in the post-failure region.

关键词： progress failure strength degradation dilation Hoek-Brown criterion numerical simulation brittle rock

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 439-448页

作者： Yan Changwang Jia Jinqing School of Mining and Technology Inner Mongolia University of Technology Huhhot 010062 China State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

关键词： cyclical test axial load ratio volumetric stirrup ratio ductility strength degradation stiffness degradation steel reinforced ultra high strength concrete beam-column joint

Seismic vulnerability evaluation of axially loaded steel built-up laced members II:evaluations

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Earthquake Engineering and Engineering Vibration 2008年第2期7卷 125-136页

作者： Kangmin Lee Michel Bruneau Department of Architectural Engineering Chungnam National University Department of Civil Structuraland Environmental EngineeringUniversity at BuffaloState University of New York

The test results described in Part 1 of this paper （Lee and Bruneau, 2008） on twelve steel built-up laced members （BLMs） subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. strength capacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessments of hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of the specimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFD Specifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture, while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, EC/ET and the normalized compressive strength degradation, Cr″/Cr of BLMs typically decrease as normalized displacements δ/δb,exp increase, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similar trends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio, b/t, experienced a larger number of inelastic cycles than those with larger ratios.

关键词： seismic vulnerability built-up compression member strength capacity ductility capacity energy dissipation strength degradation

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Effect of eccentricity in reinforced concrete beam-column-slab connection under cyclic loading

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Frontiers of Structural and Civil Engineering 2021年第2期15卷 390-398页

作者： Rooh ULLAH Amjad NASEER Muhammad FAHIM Mohammad ASHRAF Eid BADSHAH Civil Engineering Department University of Engineering&Technology Peshawar KPKPeshawar25000Pakistan

Beam-column connections are one of the most critical elements of reinforced concrete structures,especially in seismically active regions,and have been extensively evaluated experimentally and ***,very limited experimental studies about eccentric reinforced concrete connections including the effect of connected slabs are *** study presents the experimental results of two half-scale eccentric beam-column-slab connections subjected to quasi-static cyclic *** horizontal eccentricity(eh)is maintained at 12.5%and 25%of column width(bc)for specimens 1 and 2,*** damage pattern,performance levels,displacement ductility(μD),energy dissipation,and connection strength and stiffness are compared for both specimens,and the effect of eccentricity is *** is concluded that the eccentricity has no significant effect on the lateral load carrying capacity;however,the overall strength degradation increases with the increase in ***,the elastic stiffness of specimen 2 decreased by 14%as the eccentricity increased from 12.5%to 25%;however,the eccentricity had no significant effect on the overall stiffness degradation.μD decreased by 43%,and the energy dissipation capacity decreased by 40%in specimen 2 with higher *** story drifts corresponding to the performance levels of the life safety(LS)and collapse prevention(CP)were found to be 28%lesser in specimen 2 than in specimen 1.

关键词： corner connection eccentricity strength degradation stiffness degradation energy dissipation performance levels

Reliability Analysis of Slope Stability Considering Temporal Variations of Rock Mass Properties

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Computers, Materials & Continua 2020年第4期63卷 263-281页

作者： Xin Gu Lin Wang Fuyong Chen Hongrui Li Wengang Zhang Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqingChina School of Civil Engineering Chongqing UniversityChongqingChina National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas Chongqing UniversityChongqingChina

Temporal variation of rock mass properties,especially the strength degradation due to drying-wetting cycles as well as the acidic wetting fluid(rainfall or reservoir water)is crucial to stability of reservoir rock *** on a series of drying-wetting cycling and experiments considering the influences of pH values,the degradation degree models of the reduced cohesion𝑐𝑐′,friction angle𝜑𝜑′are developed.2D stability analysis of the slope is subsequently carried out to calculate the factor of safety(Fs)via limit equilibrium method(LEM)and a predictive model of Fs is built using multivariate adaptive regression splines(MARS),revealing the effect of the drying-wetting cycles and pH *** reliability analysis by Monte Carlo simulation is performed to rationally consider the uncertainty and the temporal variation of the shear strength parameters of rock *** indicate that the MARS-based model can estimate the Fs *** Fs and the reliability indexβdecrease with increase of drying-wetting cycles,and the temporal variation of rock mass properties has significant influence on the slope *** the temporal variation of rock properties may overestimate the Fs and reliability indexβin the longer term.

关键词： Reservoir slope stability pH value reliability analysis temporal variation strength degradation

Reliability Analysis Based on a Nonlinear Fatigue Damage Accumulation Model

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Journal of Donghua University(English Edition) 2014年第6期31卷 741-743页

作者：袁容李海庆 School of Mechanical Electronic and Industrial Engineering University of Electronic Science and Technology of China

A modified nonlinear fatigue damage accumulation model based on the Manson-Halford theory was presented,and the new model was developed for fatigue life prediction under constant and variable amplitude loading, which took the effects of the load interactions and the phenomenon of material's strength degradation into account. The experimental data of the 30 Cr Mn Si A and the LY-12 cz from literature were used to verify the proposed model. And from the good agreement between the experimental data and predicted results,we can see it clear that the proposed method can be applied to predicting fatigue life under different loadings.

关键词： fatigue damage accumulation Manson-Halford theory load interactions strength degradation