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Considering that the rubber isolation bearing of buildings is exposed to the air will be, respectively, subjected to the freeze–thaw cycles in the wintertime period, the isolation effect of the bearing is very likely to be affected. To this end, the freeze–thaw cycle tests of natural rubber (NR) materials were carried out, with the aim of investigating how the performances of NR bearings in northern China change under freeze–thaw cycles in winter and the mechanical properties of NR materials with time were studied. The results show that after the freeze–thaw cycle test, the appearance of the rubber sheet did not have an obvious change. However, the sealing plate and steel plate layer of the rubber bearing had brown rust spots and the colour of the rubber layer was still dark. After the freeze–thaw cycle, the vertical compression stiffness and the horizontal equivalent stiffness of the rubber isolation bearing showed a decreasing trend. After freeze–thawing cycles, the Mooney–Rivlin constitutive model constant C10 of rubber material showed a decreasing trend with the test time while C01 showed an increasing trend. Under the action of freeze–thawing cycles, the stiffness of basic mechanical properties of rubber isolation bearings will decrease as time increases. Among them, the vertical compression stiffness has decreased by 10.24% and the horizontal equivalent stiffness has decreased by 2% after 50 years under the freeze–thaw cycles based on the prediction equation of the test values, while the vertical compression stiffness has decreased by 5.73%, and the horizontal equivalent stiffness has decreased by 8.7% after 50 years under the freeze–thaw cycles based on the prediction equation of the simulation value. The above research results can provide a basis for the study of the degradation law of the rubber isolation bearing and the evaluation of the life cycle performance of the isolation projects. [ABSTRACT FROM AUTHOR]

In view of the long-term durability problem of coated reinforced magnesium oxychloride cement concrete (CRMOCC) has not been studied. Combined with the environment of salt lake and saline soil in western China, the degradation law of CRMOCC's long-term durability was studied by solution immersion test. After soaking of different periods, electrochemical test, ultrasonic test, quality test and microscopic test were used to investigate the durability performance of specimens. long-term durability of CRMOCC was evaluated by relative corrosion evaluation parameters (ω1), relative dynamic elastic modulus evaluation parameters (ω2) and relative quality evaluation parameters (ω3). The results show that after 2 160 d of immersion, taking ω1 as the durability evaluation index, the bare steel has reached the state of corrosion, while the coated steel is still in the state of no corrosion. when ω2 and ω3 are used as the durability evaluation index, both coated steel and bare steel specimens are in the state of corrosion but no damage, and the durability degradation of coated steel specimens is slower than that of bare steel specimens. It shows that the coating has a good protection effect on the steel bars. Taking ω1, ω2 and ω3 as degradation parameters, CRMOCC reliability curve fails zero at 25 000 d, 2 000 d and 18 000 d. [ABSTRACT FROM AUTHOR]

Copyright of Chemistry & Industry of Forest Products is the property of Chemistry & Industry of Forest Products Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Concrete in saline or coastal settings exposed to freezing temperatures is frequently affected by coupling actions of sulfate assault and freeze–thaw degradation, reducing the service life of concrete structures significantly. This study conducted an accelerated freeze–thaw cycle test in pure water and Na2SO4 solution with a mass proportion of 5% to examine the coupling impact of sulfate freeze–thaw on the frost resistance of composite limestone powder (CLP) concrete. Combined with SEM and XRD methods, the performance degradation mechanisms of composite limestone powder (CLP) concrete in coupling sulfate freeze–thaw conditions were analyzed with a microscopic point of view. The findings demonstrated that limestone powder has a filling effect but the activity is low. When the content is 10~20%, the chemical response is higher than the physical response. The pozzolanic effect of fly ash and slag can improve the pore structure and improve the compactness of concrete. The "superposition effect" of limestone powder, fly ash, and slag can improve the frost resistance of CLP concrete. The scenario of salt freezing cycles has negative effects that are worse than those of water freezing cycles on the antifreeze performance of CLP concrete, including apparent morphology, mass loss, relative dynamic modulus of elasticity, and compressive strength. Sulfate's activation effect boosts slag's activity effect, which significantly promotes the antifreeze performance of concrete subjected to salt frozen cycles over water frozen cycles. The freeze–thaw damage model of CLP concrete under coupling sulfate freeze–thaw is established through theorem analysis and experiment statistics, laying a theoretical framework for the popularization and use of this concrete. [ABSTRACT FROM AUTHOR]

Simply supported prestressed concrete (PC) box girders have been widely adopted in high-speed railway bridges. In complex climatic environments, the corrosion of the prestressing strands always occurs and deteriorates the flexural behavior of PC box girders. In the present study, six T-shaped scaled beams were designed and fabricated according to the specifications for a high-speed railway PC box girder. The corrosion process of the prestressing strand in scaled beams was experimentally simulated by using the constant current accelerated corrosion method. The flexural behavior of corroded high-speed railway simply supported PC box girders was then investigated through four-point bending tests and theoretical investigation. The experimental results showed that strand corrosion significantly decreased the flexural behavior of the test beams. When the mass loss was 12.30%, the cracking load, ultimate load, and ductility decreased by 27.8%, 29.9%, and 11.5%, respectively. The effect of strand corrosion on flexural stiffness displayed a difference before and after concrete cracking. The failure mode changed when strand mass loss was above a critical value (7%). The flexural bearing capacity degradation law of corroded PC beams could be divided into two distinct stages. A strand mass loss of less than 7% could lead to a linear degradation law with a relatively slight reduction. As mass loss increased, it exhibited an exponential and sharp declining trend. An analytical model including the effects of strand cross-section reduction, strand property deterioration, and concrete cracking was also proposed to predict the flexural behavior of corroded PC beams. By comparison with the experimental data, it was found that the model could predict the cracking moment, flexural bearing capacity, and failure mode well. [ABSTRACT FROM AUTHOR]

In order to study the variation of mechanical properties of steel under acid rain corrosion conditions in northern China, monotonic tensile tests were conducted on Q235 steel with a thickness of 3.0 mm and 4.5 mm using a method of artificially prepared simulated acid rain solution for indoor accelerated corrosion. The results show that the failure mode of corroded steel standard tensile coupon includes normal fault and oblique fault. The failure patterns of the test specimen show that the thickness of the steel and corrosion rate affected the corrosion resistance. Larger thicknesses and lower corrosion rates will delay the failure mode of corrosion on steel. The strength reduction factor (Ru), deformability reduction factor (Rd) and energy absorption reduction factor (Re) decrease linearly with the increasing corrosion rate from 0% to 30%. The results are interpreted also from the microstructural point of view. The number, size, and distribution of the pits are random when the steel is subjected to sulfate corrosion. The higher the corrosion rate, the clearer, denser, and more hemispherical the corrosion pits. The microstructure of steel tensile fracture can be divided into intergranular fracture and cleavage fracture. As the corrosion rate increases, the dimples at the tensile fracture gradually disappear and the cleavage surface gradually increases. An equivalent thickness reduction model is proposed based on Faraday's law and the meso-damage theory. [ABSTRACT FROM AUTHOR]

Concrete in saline or coastal settings exposed to freezing temperatures is frequently affected by coupling actions of sulfate assault and freeze–thaw degradation, reducing the service life of concrete structures significantly. This study conducted an accelerated freeze–thaw cycle test in pure water and Na2SO4 solution with a mass proportion of 5% to examine the coupling impact of sulfate freeze–thaw on the frost resistance of composite limestone powder (CLP) concrete. Combined with SEM and XRD methods, the performance degradation mechanisms of composite limestone powder (CLP) concrete in coupling sulfate freeze–thaw conditions were analyzed with a microscopic point of view. The findings demonstrated that limestone powder has a filling effect but the activity is low. When the content is 10~20%, the chemical response is higher than the physical response. The pozzolanic effect of fly ash and slag can improve the pore structure and improve the compactness of concrete. The “superposition effect” of limestone powder, fly ash, and slag can improve the frost resistance of CLP concrete. The scenario of salt freezing cycles has negative effects that are worse than those of water freezing cycles on the antifreeze performance of CLP concrete, including apparent morphology, mass loss, relative dynamic modulus of elasticity, and compressive strength. Sulfate’s activation effect boosts slag’s activity effect, which significantly promotes the antifreeze performance of concrete subjected to salt frozen cycles over water frozen cycles. The freeze–thaw damage model of CLP concrete under coupling sulfate freeze–thaw is established through theorem analysis and experiment statistics, laying a theoretical framework for the popularization and use of this concrete.

Harmonic reducer is widely used in robot and aerospace fields. Transmission efficiency is one of the important indexes to characterize its transmission performance. The transmission efficiency evaluation model of double wave cam harmonic reducer with thin wall bearing is established, and the influence and sensitivity of ambient temperature, rotational speed, load, and reduction ratio on transmission efficiency are discussed. The law of decline of transmission efficiency of harmonic drive is studied, and it is pointed out that harmonic drive has failed when the performance index of transmission efficiency drops below the threshold value, and a failure evaluation model based on transmission efficiency degradation is established. The validity of the efficiency evaluation model was verified by comparing the numerical simulation results with the experimental results. The results provide a theoretical basis for slowing down the decline rate of transmission efficiency and guiding the design of long-life harmonic reducer. [ABSTRACT FROM AUTHOR]

Simply supported prestressed concrete (PC) box girders have been widely adopted in high-speed railway bridges. In complex climatic environments, the corrosion of the prestressing strands always occurs and deteriorates the flexural behavior of PC box girders. In the present study, six T-shaped scaled beams were designed and fabricated according to the specifications for a high-speed railway PC box girder. The corrosion process of the prestressing strand in scaled beams was experimentally simulated by using the constant current accelerated corrosion method. The flexural behavior of corroded high-speed railway simply supported PC box girders was then investigated through four-point bending tests and theoretical investigation. The experimental results showed that strand corrosion significantly decreased the flexural behavior of the test beams. When the mass loss was 12.30%, the cracking load, ultimate load, and ductility decreased by 27.8%, 29.9%, and 11.5%, respectively. The effect of strand corrosion on flexural stiffness displayed a difference before and after concrete cracking. The failure mode changed when strand mass loss was above a critical value (7%). The flexural bearing capacity degradation law of corroded PC beams could be divided into two distinct stages. A strand mass loss of less than 7% could lead to a linear degradation law with a relatively slight reduction. As mass loss increased, it exhibited an exponential and sharp declining trend. An analytical model including the effects of strand cross-section reduction, strand property deterioration, and concrete cracking was also proposed to predict the flexural behavior of corroded PC beams. By comparison with the experimental data, it was found that the model could predict the cracking moment, flexural bearing capacity, and failure mode well.

In order to study the variation of mechanical properties of steel under acid rain corrosion conditions in northern China, monotonic tensile tests were conducted on Q235 steel with a thickness of 3.0 mm and 4.5 mm using a method of artificially prepared simulated acid rain solution for indoor accelerated corrosion. The results show that the failure mode of corroded steel standard tensile coupon includes normal fault and oblique fault. The failure patterns of the test specimen show that the thickness of the steel and corrosion rate affected the corrosion resistance. Larger thicknesses and lower corrosion rates will delay the failure mode of corrosion on steel. The strength reduction factor (Ru), deformability reduction factor (Rd) and energy absorption reduction factor (Re) decrease linearly with the increasing corrosion rate from 0% to 30%. The results are interpreted also from the microstructural point of view. The number, size, and distribution of the pits are random when the steel is subjected to sulfate corrosion. The higher the corrosion rate, the clearer, denser, and more hemispherical the corrosion pits. The microstructure of steel tensile fracture can be divided into intergranular fracture and cleavage fracture. As the corrosion rate increases, the dimples at the tensile fracture gradually disappear and the cleavage surface gradually increases. An equivalent thickness reduction model is proposed based on Faraday’s law and the meso-damage theory.

As the key member that connects the column and steel beam of steel–reinforced concrete (SRC) frame structures, the T-shaped SRC column–steel beam joints should have good hysteretic characteristics under earthquakes, which has an important influence on the safety and stability of the structures. To describe the degradation law of joints, a tri-linear skeleton curve model was developed to study the seismic characteristics of this type of joint based on the experimental results. An improved Bouc-Wen-Baber-Noori (BWBN) model was established for T-shaped steel SRC column–steel beam joints by combining the BWBN model and hysteresis characteristics. The parameters of the hysteresis model were obtained using a genetic algorithm and nonlinear regression analysis. Based on the Visual Studio platform, the improved BWBN model was embedded and developed in the OpenSees software, and a numerical simulation analysis was conducted to verify the accuracy of the numerical simulation method. The results show that the hysteresis curve obtained via the simulation is in good agreement with the test curve. The improved BWBN model effectively represents the actual degradation characteristics of this type of structural member under seismic loads. • An improved BWBN model of T-shaped steel concrete column-steel beam joints was established. • The parameters of model was obtained by genetic algorithm and nonlinear regression analysis. • The improved BWBN model was embedded and developed in the OpenSees. [ABSTRACT FROM AUTHOR]

Anisotropic theoretical fatigue damage model for concrete material based on rigorousness degradation law of continuum damage mechanics theory of concrete materials due to tensile strain increment reflected as a newly proposed theory for quantification of fatigue damage is developed by utilizing the Helmholtz Free Energy (HFE) related to the thermodynamics and micromechanics concept. A strain which is taken as the main domain for initiation of microcracks, microvoids, and microfracture is taken as the main diagnosis tools for fatigue damage prediction as a form of governing constitutive theoretical equations is developed to carry out the stiffness dilapidation, diminution in the Young's Modulus of springiness, injury growth consistent with regularized life, accretion, decease in axial strain, loss in strength, increase in the transverse strain as well as Poisson's ratio, cyclic behavior in elastic damage process, stress reduction and strain-based theoretical fatigue damage model are well developed. The theoretical results thus obtained are validated through the experimental results of the author [Benard Isojeh et al. (2017)], [5].

Based on the mechanism of stray current generation in underground structures, the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate. The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microstructure of corroded concrete was observed to determine the phase composition of erosion products. The damage performances such as quality, strength, and dynamic elastic mode of corroded concrete were performed. The experimental results show that, under the action of stray current, the products of sulfate-eroded concrete are mainly gypsum, ettringite, and thaumasite; the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate; when the concrete pores are filled with the erosion product, there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus; and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Limited by the current power battery technology, electric vehicles show extremely poor duration performance and potential risk at low temperature, which is mainly caused by poor charging performance of lithium‐ion batteries. To explore the impact of charging process on cycle degradation at low temperatures, a cycle aging experimental scheme with different charging C‐rate (0.3C and 0.5C) under −10°C and −20°C was designed for the commercial LiFePO4 battery. The experimental batteries showed severe degradation after a few of cycles. The phenomenon of reduced internal resistance and up‐shift of the charging curve was found during the early cycle stages (0th‐20th cycle). The influence of low‐temperature cycle on battery was analyzed by the increment capacity analysis (ICA); the fast decreasing intensity of ①*II showed sharp loss of lithium ions. Those lithium ions mainly transformed into lithium plating and built up dendrites instead of reintercalating into the anode crystal structure, causing the further degradation of capacity and ohmic resistance. Degradation law was obtained by curve regression analysis in the end. [ABSTRACT FROM AUTHOR]

In this paper, the stress corrosion and monotonic tensile test of corroded steel wire were carried out. The effects of different corrosion ages and stress levels on failure modes, stress-strain curve and mechanical properties of corroded steel wire were discussed. Then, a finite element model of steel wire considering real surface morphology was established, and the surface stress distribution and the failure of steel wire under different corrosion degrees were compared. The relationship between stress triaxiality and critical equivalent plastic strain to different corrosion parameters was given. Finally, the degradation model of mechanical properties of corroded steel wires was established. The results showed that the failure patterns of steel wires with different degrees of corrosion were mainly divided into three types: cup cone shape, milling cutter shape and splitting shape. The shear lip zone of fracture section basically disappeared with the increase of stress corrosion, and the location of fiber area was transferred from the inside to the surface of steel wire. The decrease in strength and elastic modulus of the specimen under stress corrosion was four times and three times greater than that under non-stress corrosion, respectively. In addition, the crack position of specimen changed from the inside of section to the location of corrosion pit with the increase of corrosion degree. The fracture equivalent plastic strain decreased gradually, while the stress triaxiality increased. When the degree of corrosion reached 19.53%, the fracture equivalent plastic strain decreased by 55.41% from 0.314 to 0.140, and the stress triaxiality increased by 23.53% from 0.390 to 0.510. The influence of uniform thickness loss on the stress triaxiality was less than that of pit depth-width ratio. The larger the depth-width ratio, the larger the maximum stress triaxiality corresponding to the failure element. The constitutive model proposed in this paper could reflect the degradation law of mechanical properties of corroded steel wires. • The effect of corrosion ages and stress levels on the mechanical properties of corroded steel wire was discussed. • The stress distribution and failure of steel wire under different corrosion degrees were compared. • The degradation model of mechanical properties of corroded steel wires was established. [ABSTRACT FROM AUTHOR]

270 steel bars with different diameters of 12, 14 and 16 are accelerated to corrode in 5% chloride solution, 5% sulfate solution and 5% halogen solution by DC voltage stabilization. A different age periods, the quality is weighed by high precision balance, the steel bar is stretched by electronic universal testing machine, and the corrosion rate, yield strength, ultimate tensile strength and elongation are measured. The test data show that the chloride solution in the three solutions has the strongest corrosion, and the corrosion rate of 15% is the critical point of yield strength. When it exceeds the critical point, the yield platform disappears, showing obvious brittleness, and the elongation decreases. On the basis of the mechanism of steel corrosion, the mathematical model of the thickness of steel corrosion layer, the constitutive relationship of the three-stage theory and the two-stage wheel of steel corrosion are obtained. At the same time, the linear relationship between elongation, corrosion rate and ultimate tensile strength of steel bar is found, and the degradation law of mechanical properties of corroded steel bar is further obtained. [ABSTRACT FROM AUTHOR]

This study aimed to explore the rule of degradation of dietary proteins by identifying chyme proteins in different segments of the digestive tract of growing pigs, using proteomics techniques. Six growing pigs were fed a corn-soybean meal-based diet for 7 days. The feedstuff and chyme proteins were separately extracted and separated with SDS-PAGE. 2D LCMS/MS combined with protein database searching identified 1,513 proteins in different segments of the gastrointestinal tract, the number of identified exogenous proteins gradually decline from the stomach to colon, with large amounts in the duodenum to the large intestine. More corn proteins than soybean proteins were identified both in the feedstuff and chyme, and these were significantly decreased after digestion in the stomach. More membrane proteins than non-membrane proteins were identified in whole digestive tract. These results regarding the profiles of chyme proteins in different segments of the gastrointestinal tract would provide useful information for optimizing feed formula in pigs. [ABSTRACT FROM AUTHOR]

Normal adhesive wear process in tribological components is characterized by a non-linear behavior during the transient running-in stage followed by a constant rate of steady-state wear. Even though the running-in stage of wear has an imperative significance in defining the component's long-term performance, its characteristics have been largely overlooked in the literature. In general, many of the available predictive models do not consider the contact temperature and the variation in the friction coefficient with time. The present work is an endeavor to propose a complete integrated wear model using the principles of thermodynamics. In this regards, an integrated degradation coefficient is proposed which correlates the time-dependent wear rates (at both running-in and steady-state stage), friction coefficient, and the contact temperature. The efficacy of the proposed degradation coefficient compared to established wear coefficient is demonstrated by considering test results using a vertical pin-on-disk apparatus. Results reveal that the degradation coefficient provides a realistic measure of wear during running period. [ABSTRACT FROM AUTHOR]

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a 60 Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO 2 was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments. [ABSTRACT FROM AUTHOR]

• A more accurate mathematical model of harmonic reducer backlash is established. • The sensitivity analysis of different influencing parameters of reducer backlash is carried out. • The inner wall of the flexspline is the key position that affects the transmission precision of harmonic reducer. • The backlash degradation law of harmonic reducer is investigated. Harmonic gear drive mechanism has been widely used in space mechanism, robot and other precision actuators. Based on the theory of probability and statistics, this paper establishes a mathematical model of harmonic gear transmission error considering the assembly and wear among components, and conducts sensitivity analysis and normalization of factors affecting harmonic gear transmission error model. Through Kriging model and Monte Carlo method, reliability degradation law of transmission accuracy is obtained by transmission error function and reliability analysis. Some suggestions are given in the design of harmonic gear drive in the future. [ABSTRACT FROM AUTHOR]

• The relationship between stress, confining pressure and creep parameters is established. • A concrete creep model considering the dual effects of confining pressure and stress is established. • A simple and feasible model parameter identification method is proposed. The MTS815.03 rock test system is used to carry out mechanical property and triaxial compression creep tests on concrete specimens of the same specification under different confining pressure conditions to study the creep characteristics of concrete structures in deep high-stress level areas. The relationship between the creep strain rate of the concrete specimen and the stress level and the creep characteristics of the concrete specimen in the high-stress level area are analyzed. Based on the establishment of a creep damage model in the high-stress level zone of a concrete specimen, a method for determining creep parameters is proposed on the basis of the characteristics of the creep test curve. The degradation law of creep parameters under different stress levels is analyzed, and the relationship between creep parameters and stress is constructed. Finally, the expressions between each creep parameter and stress are substituted into the creep damage model, and an improved creep damage model is obtained. The correctness of the established model is verified by comparing the test curve and the model curve. Result shows that the agreement between the established creep model curve and the accelerated test curve is higher than that between the traditional Nishihara model curve and the accelerated test curve. The established creep damage creep model can be used to predict the deformation trend of surrounding concrete over time after chamber or tunnel excavation and provide theoretical basis for concrete support and lining construction. [ABSTRACT FROM AUTHOR]

High-temperature material properties are the most important input parameters for the study of the fire resistance of steel structures. Meanwhile, the structural failure of steel structures might occur during compartment fires. This paper presents steady-state experiments on Q345 cold-formed steel (CFS) during the rising and falling temperature periods. The results show that whether in the rising or falling temperature periods, the material properties of Q345 CFS decrease as the load testing temperature increases. Meanwhile, the difference between the test results of the rising and falling temperature periods can not be ignored. Under the same load testing temperatures, the differences in the elastic modulus reduction factors of Q345 CFS between the rising and falling temperature periods are within −0.16 to 0.057; meanwhile, the differences in the yield strength reduction factors between the rising and falling temperature periods are within −0.009 to 0.142. For the fire resistance design, if the material properties during the rising temperature period are used to replace those during the falling temperature period, the calculation results of the fire-induced deformation for Q345 CFS members may be conservative, but the corresponding high temperature bearing capacity will be over-predicted. In addition, the differences in the reduction factors of material properties for Q345 CFS caused by the maximum temperature are significantly lower than those for G550 CFS. Finally, a maximum temperature influence coefficient is introduced and unified expressions are put forward, which can be appropriately used to predict the material properties and stress-strain curves of Q345 CFS during full-range compartment fires. Unlabelled Image • Steady-state tests of Q345 CFS were conducted during the rising and falling temperature periods. • The effects of rising and falling temperatures were discussed. • The difference in the degradation law between Q345 and G550 CFS was analyzed. • The results of bearing capacity of CFS might be over-predicted in compartment fires. • A maximum temperature influence coefficient is introduced and unified expressions are proposed. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of sedimentary rocks, such as carbonates, are highly sensitive to the influence of water. In carbonate-rich regions, rock failures induced by water corrosion have been widely reported, such as the collapse of cliffs and rockslides. In this study, a 2D model was built to investigate the time-dependent strength degradation of carbonate rocks under the influence of water. First, degradation laws for two types of bonds were derived based on the different behaviors of depositional and diagenetic cements in water. Then, via developing customized code using the Fish language, the degradation laws were coupled with UDEC to build the numerical procedure. Finally, the ability of the proposed model to reproduce the macroscopic short- and long-term behaviors of carbonate rocks under the influence of water was validated by comparing the numerical results with the lab observations and measurements. The results show that the presented procedure is capable of simulating the strength properties of carbonate rocks submerged in water for different time periods (uncoupled tests), as well as the lifetime (time-to-failure) of rocks in a chemo-mechanically coupled condition. [ABSTRACT FROM AUTHOR]