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An energy‐based isotropic elastoplastic damage model is developed for investigating the elastoplastic damage responses and stress–strain relationships of nano‐silica incorporated concrete. The formulation employs a multiscale micromechanical framework to determine the effective elastic properties of composites at different scales. The stress–strain constitutive relation is derived by splitting the strain tensor into "elastic‐damage" and "plastic‐damage" parts while introducing the homogenized free potential energy function and the undamaged potential energy function. The elastoplastic damage response of the material is further characterized by elastic–plastic‐damage coupling. To construct realistic 3D three‐phase concrete mesostructures in numerical simulations, this paper introduces an encapsulation placement method that avoids particle overlap checking when placing aggregates. This methodology allows adjustments for the aggregate compactness as needed and enhances computational efficiency in concrete mesostructure construction. The numerical results of the modeling show good agreement with the experimental values in the open literature. Further, the influence of nano‐silica addition contents and ITZ (interfacial transition zone) thicknesses on the elastoplastic damage response of nano‐silica incorporated concrete are quantitatively and qualitatively investigated for the optimization of nano‐silica incorporated cementitious composites. The proposed model facilitates simulating and optimizing the mechanical characteristics of nano‐silica incorporated concrete and enhances the computational efficiency of 3D concrete modeling with the introduced encapsulation placement method. [ABSTRACT FROM AUTHOR]

For steel framed structures with small geometric nonlinearity, the conventional first-order plastic hinge method (FPHM) estimates rapidly the failure mode and ultimate strength of frames according to the proportionality property. However, it ignores the combined action of multiple internal forces on the development of plastic hinge, leading to mistakes in estimating the failure mode and ultimate strength of frames. Though the second-order plastic hinge method (SPHM) and the refined plastic hinge method (RPHM) overcome this problem, they lose the FPHM's proportionality property and the high efficiency of computation as well. In this paper, the generalized plastic hinge method (GPHM) featuring proportionality property is proposed for steel framed structures to overcome the drawbacks of the conventional FPHM, the SPHM and the RPHM. Firstly, a linearly elastic analysis is performed on the steel framed structure between the formation of any two plastic hinges; then the strength reduction factor is developed by means of the generalized yield criterion (GYC) for modification of the sectional strength of frame component under multiple internal forces during loading process. Secondly, the element bearing ratio (EBR) is defined on the basis of the homogeneous generalized yield function and is in proportion to the loading, so that the position of generalized plastic hinge and the corresponding load increment are determined for each loading step according to this proportional property. Furthermore, the balance vector is developed by means of the GYC and the slope-deflection relation to modify the result of the calculated load increment. Finally, several examples are presented to validate the much higher computational efficiency and accuracy of the proposed method by comparing it with the plastic zone analysis (PZA), the SPHM and the conventional FPHM. [ABSTRACT FROM AUTHOR]

The alternate load path method for progressive collapse analysis ignores the cause and mechanism of member failure and its influence on the dynamic effect of the remaining structures. It must assume the location of member failure, which is unsuitable for grid structures with many members. In this paper, by using the double broken line follow-up strengthening model and the proposed VUMAT material constitutive model, taking the member instability and material failure as the member failure criteria and considering the geometric nonlinearity and material nonlinearity, the instantaneous member removal method for deleting the failure member in real time was proposed. On this basis, nonlinear dynamic analysis for a three-layer space truss was used to compare the effects of different member failure criteria on the structural responses, such as the member failure sequence and the occurrence time of the continuous structural collapse. The results show that when considering the instability of members, the initial member failure and the final progressive collapse occur earlier than when using the material failure criterion, which is more similar to the actual situation. Furthermore, the proposed VUMAT material constitutive model can apply to study the progressive collapse behavior of space truss structures. [ABSTRACT FROM AUTHOR]

Self-healing concrete that employs microencapsulated healing agents has been proven to be an effective method for microcrack repairment in the concrete structure. However, there is a lack of efficient tools to evaluate the effect of the parameters of microcapsules on the mechanical behavior of the self-healing concrete. In this paper, the evolution of the damage-healing process of microencapsulated self-healing concrete subjected to tensile loading is numerically analyzed from a microscopic perspective by using a 2D micromechanical model. Based on the deformation and propagation evolution mechanism of microcracks, the contribution of microcracks to the total compliance tensor of microencapsulated self-healing concrete under tensile loading is deduced at various stages. According to the calculated total compliance tensor, the stress-strain and compliance-strain relations of microencapsulated self-healing concrete are discussed with special attention to the stress dropping and strain softening stages. Finally, parametric analysis was conducted using the constructed model to investigate the influence of size and content of microcapsules, the types of healing agent and the initial damage of the concrete on the mechanical behaviors of microencapsulated self-healing concrete. The constructed 2D model is significantly useful for the reasonable selection of the optimal parameters of microencapsulated self-healing concrete. [ABSTRACT FROM AUTHOR]

This article investigates the size effect of segmental tunnel linings on the deformation behavior and the damage evolution mechanism using the Finite Element Method (FEM). A series of models with different diameters are established under the same loading condition to control the variable. The bolts and the rebar apply the elastic-plastic model. The Concrete Damage Plasticity model has been considered for the concrete lining. The vertical convergence deformation, internal force of these models, and damage to the segment body are selected for comparison. The number and location of the yielded bolts are explored for the analysis of the overall structure stiffness and damage evolution mechanism. In terms of plastic hinge theory, an extended discussion is carried out to explain the differences in damage evolution mechanisms in different-sized linings. The results show the large-diameter lining rings have a relatively greater increasing rate of convergence deformation. Furthermore, fewer plastic hinges emerged in large-scale lining rings before the structures reached their ultimate strength. According to the experimental results, we can know that the failure of large-diameter has the characteristic of more brittle damage than that of small-diameter one and these large-size structures are prone to become unstable geometry. [ABSTRACT FROM AUTHOR]

Characterizing the bond properties of the steel fiber/matrix interface plays an important role in describing the crack bridging effect in steel fiber-reinforced cementitious composites (SFRCC). In this paper, a new interface law considering the residual shear stress is proposed to interpret the slip-softening effects of the steel fiber/matrix interface. Accordingly, a micromechanical crack bridging model for SFRCC is formulated by combining the single steel fiber pullout model with the image analysis-based fiber orientation distribution. Comparisons with the experimental data and the existing models show that the proposed model can well predict SFRCC's tensile softening behavior. Meanwhile, the decrease rate of the bridging stress, the composite fracture energy, the peak bridging stress and the corresponding peak crack opening displacement (COD) are employed to quantitatively evaluate the crack bridging curves. Finally, the effects of the residual shear stress ratio, the interfacial softening coefficient and the fiber orientation distribution on the crack bridging relation are discussed with the proposed framework. [ABSTRACT FROM AUTHOR]

The sulfate attack (SA) of cementitious materials widely exists, which severely reduces the mechanical properties and durability of cementitious materials. However, few numerical SA damage models of cementitious materials have been comprehensively developed. The understanding and simulation of the chemo-mechanical behavior of cementitious materials are beneficial to better modeling, predictions and designs of underground structures. In this research, a numerical chemo-micromechanical damage model under the SA and loading is proposed to explore the cracking process of the cementitious materials based on the discrete element method (DEM). Some inherent characteristics of the chemical attack can be well considered in the proposed numerical model. The local damage effect can be simulated, as well as the sulfate corrosion degree and the material component. The performance of this proposed model is confirmed and validated by available experimental results. We examine the dependence of the strength and the elastic moduli of the cementitious material on: (a) the content of ettringite, (b) the distribution of ettringite, (c) the mechanical properties of the cementitious matrix, (d) the void ratio of the cementitious materials, (e) the confining pressure, and (f) the expansion coefficient of sulfate corrosion products. The softening and fluctuating phenomena are witnessed in the stress-strain curves. The failure mode of cementitious materials with the SA is different from that of specimens without the SA. The damage parameters of cementitious materials under the SA are examined in depth. The numerical results reveal that the proposed damage model is feasible and valuable in the modeling, predictions, applications and durability of chemo-mechanical sulfate attack problems in cementitious materials. [ABSTRACT FROM AUTHOR]

Collapses are the most sensational types of events and frequently the ones that cause the most serious consequences in tunneling operations. It often occurs because of insufficient geological studies and the limitations of experience-based decision-making. To cope with those problems, we proposed a data-driven model based on the tunnel boring machine operational data and the in situ geological information to forecast tunneling-induced ground collapse. In the proposed model, we offered a general data process flow diagram to process engineering data. Three machine learning classifiers, k-nearest neighbors, support vector classifier, and random forests were adopted for collapse prediction. The performance of the three classifiers was verified based on the data from the Yinsong water conveyance tunnel. The results illustrated that the proposed data-driven model was sufficient for the studying task with 90% of the collapsed zones being identified on average. The contributions of this paper are to provide a reliable data process flow diagram to process engineering data and offer an accurate and robust model for identifying collapses. [ABSTRACT FROM AUTHOR]

The current research on the progressive collapse resistance of space grid structures mainly used the alternate path method, without considering the failure causes or mechanism of brace and the dynamic performance on residual structure, which cannot accurately evaluate the progressive collapse resistance of space grid structures. In this paper, a special brace is proposed for accurately distinguish asymmetric responses under compression and tensile loading. The material constitutive model of the special brace considering its buckling is implemented in FEM codes based on the explicit user materials subroutine (VUMAT). Then, the dynamic nonlinear analysis on a large-span space grid structure utilizing special braces was carried out to study the failure sequence of braces and the progressive collapse resistance of the structure. The analysis results show that when special brace is adopted, the occurrence of the initial failure of brace and the final collapse of the structure are earlier than the previous structure. The ultimate bearing capacity of the dynamic progressive instability of the whole structure caused by the buckling of local compression braces is significantly lower when compared with the alternate path method, which better reflects the collapse process of the actual structure and can be applied to the progressive collapse analysis of the space grid structure. [ABSTRACT FROM AUTHOR]

Welding technology is widely used in the steel structure forming process. After welding, there is uneven residual deformation in the structure, resulting in welding residual stress. In this paper, the damage process of beam-column joints in steel frames under ultra-low cycle fatigue loading was simulated by ABAQUS software. The crack initiation position of the joints was obtained. On this basis, the influence of welding residual stress on the development of tensile and bending fatigue damage of beam-column joints in steel frames was analyzed. In parallel, the effect of welding residual stress on the fatigue damage process of joints with different loading modes and different beam flange widths was discussed. The results show that during ultra-low cycle tensile and bending fatigue, cracks are both initiated at the welding holes of the beam flange, but the cycle number required for crack initiation is different, and the cycle number to failure of bending fatigue is greater. The residual stress can accelerate crack initiation and advance approximately two cycles. For bending fatigue damage, the crack first originates from the flange in tension first, and the average cycle number to failure of the flange is 12.85% more than that of the other flange. With the flange width decreasing from 150 to 130 mm, the cycle number to failure affected by residual stress rises from 5.30 to 13.56%. With the increase in cycle number, the damage development of a single cycle is more affected by the residual stress, the increasing trend of the fracture index remains unchanged, and the growth rate becomes faster. [ABSTRACT FROM AUTHOR]

When subjected to fires, cementitious composites can be seriously damaged. However, the mechanical behavior of nanoscale calcium silicate hydrate (C–S–H) grains, which are the main binder of cementitious composites, exposed to elevated temperatures under shear deformations remain poorly investigated. In this paper, considering different calcium/silicate (C/S) molar ratios (i.e., C/S = 1.10, 1.33, and 1.64), the shear behavior of the C–S–H grain after exposure to different high-temperature levels (i.e., 300 K, 500 K, 700 K, 900 K, and 1000 K) is studied by conducting series of reactive molecular dynamics simulations. Results reveal that the C–S–H grain exhibits good plasticity under shear deformation. Furthermore, the shear modulus of the C–S–H grain is between 14 GPa and 17 GPa and exhibits a decrease with the calcium/silicon (C/S) molar ratio at ambient temperature. While the shear strength is around 1.0 GPa and reaches the lowest value at C/S = 1.64. Interestingly, we report that heating can lead to the increase of the shear modulus and shear strength due to the evaporation of the interlayer water which generally acts as the lubricant. Additionally, we show that heating has no clear influence on the shear strain corresponding to the onset of yielding when the C/S ratio is high but can indeed improve the shear strain corresponding to the shear strength. Furthermore, the yielding area of the C–S–H grain under the shear deformation can be enlarged. Finally, factors affecting the strength degradation of cementitious composites after being heated to different temperature levels are further discussed based on the simulation results. [ABSTRACT FROM AUTHOR]

In order to study the failure process of a large-scale spherical bearing, the finite element simulation method was used to establish the full-scale finite element model of the spherical bearing by using ABAQUS software, and the whole failure processes of the bearing under tension and tension-shear action when the upper bearing plate had different initial inclination angle were simulated, respectively. The overall failure mode of the bearing was analyzed, the effects of wedge-shaped part position, initial inclination angle and shear direction on the local failure of wedge-shaped part were discussed, and the failure characteristics of local wedge-shaped parts were obtained. The research results show that the wedge-shaped part of the upper bearing plate of the spherical bearing is destroyed first under tension or tension-shear action. Moreover, the wedge-shaped part at the raised side along the initial inclination direction is the first to be destroyed and the wedge-shaped part at the sunk side is the last to be destroyed. As the initial inclination angle increases, the overall bearing capacity of the wedge-shaped part decreases, and the overall bearing capacity of the bearing also decreases. Under the action of tensile force and shear force in the same direction as the initial inclination direction, the overall bearing capacity of the wedge-shaped part and the overall bearing capacity of the bearing are both reduced compared with that under only the tensile force; Under the action of tensile and shear forces opposite to the initial inclination direction, the overall bearing capacity of the wedge-shaped part and the overall bearing capacity of the bearing are both improved compared with that under only the tensile force. The direction of shearing force has little effect on the local bearing capacity of the wedge-shaped parts 1 and 3 perpendicular to the initial inclination direction, the shearing force reduces the local bearing capacity of the wedge-shaped part to which it points and increases the local bearing capacity of the wedge-shaped part that is directed opposite to it. [ABSTRACT FROM AUTHOR]

In this study, a refined finite element model of concrete-filled steel tubular column was established, and its dynamic response under impact axial load was explored. By extracting the axial stress changes of the steel tube and the core concrete at different positions of the member, the stress and strain characteristics of the concrete-filled steel tubular column under impact load were obtained for the respective impact loads. It is found that the steel tube and the core concrete basically met the deformation compatibility conditions in the same sections. The whole stress wave velocity of the concrete-filled steel tubular column was between elastic stress wave velocity values of the steel tube and the core concrete. Under the smaller impact load, the axial deformation of the column was close to elastic, whereas under larger impact loads, it underwent significant plastic deformation. [ABSTRACT FROM AUTHOR]

This paper presents the effect of residual welding stress on the ultimate stability bearing capacity of the box-section steel column. FEM method is employed to investigate the stability characteristics of box section steel column whose whole length is under high temperature. Firstly, the distribution of the initial longitudinal welding residual stress of the column is calculated. Secondly, the effect of high temperature along the whole column length due to fire on the residual welding stress is investigated. The results indicate that the increase in temperature could cause the relaxation of the longitudinal seam residual stress. When the temperature is less than 244°C, the residual stress relaxation could not decrease the ultimate load-carrying capacity. The ultimate load-carrying capacity could decline remarkably as the temperature increases while the temperature is higher than 244°C. In addition, the initial geometric defects weakly affect the ultimate stability bearing capacity, and the reduction factor of the column gradually declines as the slenderness ratio increases. [ABSTRACT FROM AUTHOR]

In a recent companion paper, a three-dimensional isotropic elastic micromechanical framework was developed to predict the mechanical behaviors of the innovative asphalt patching materials reinforced with a high-toughness, low-viscosity nanomolecular resin, dicyclopentadiene (DCPD), under the splitting tension test (ASTM D6931). By taking advantage of the previously proposed isotropic elastic-damage framework and considering the plastic behaviors of asphalt mastic, a class of elasto-damage-plastic model, based on a continuum thermodynamic framework, is proposed within an initial elastic strain energy-based formulation to predict the behaviors of the innovative materials more accurately. Specifically, the governing damage evolution is characterized through the effective stress concept in conjunction with the hypothesis of strain equivalence; the plastic flow is introduced by means of an additive split of the stress tensor. Corresponding computational algorithms are implemented into three-dimensional finite elements numerical simulations, and the outcomes are systemically compared with suitably designed experimental results. [ABSTRACT FROM AUTHOR]

Recent research does not fully identify the causes of surface volume loss that occur at the tunnel level in sand, as related to the excavation of a pressurized-face tunnel boring machine (PTBM). This paper focuses on the face stability of PTBM tunneling, and the response of sandy soil to the inadequate face pressure is evaluated. Data presented are from tests of a model using reduced-scale PTBM tunneling operations in dry sand. Ground displacement and the evolution of ground stress were analyzed. The relationship between the load factor at the face and the volume loss at surface was examined. The effects of soil density and tunnel depth were considered. An empirical formulation was provided allowing determination of the expected volume loss as a function of load factor (LF), cover-to-diameter ratio (C/D) and soil density (I d). Thus providing a valuable basis for establishing relationship between volume loss associated with tunnel face advancement and face pressures in sandy soil. The results show that instability of the face is accompanied by the triggering of secondary deformation mechanisms at the surface. The volume loss at surface is complicated by the combined effects of soil arching and the dilative/contractive behavior of the soil. The variation of volume loss is sudden prior to face collapse, especially at dense sand, which is different from the progressive variation of volume loss in clays. The size of destressed zone ahead of cutter head is less dependent on C/D in loose soil than in dense soils. [ABSTRACT FROM AUTHOR]

Field measurements and laboratory tests were carried out to study the mechanical behaviors of soil in response to earth pressure balance (EPB) shield tunneling in mixed-face conditions, i.e., layers of granite and sand. Specifically, an experimental investigation was carried out using a laboratory-scale model to replicate the EPB tunneling operations in such ground conditions. The effects of the ratio of rock/sand at the tunnel face (Tr/Ts) and the cover-to-diameter ratio (C/D) on the soil pressure in the chamber, ground displacement, and volume loss were examined. The results show that the soil's response to the mixed-face conditions differs significantly from that in the homogenous ground and highly depends on the ratio of rock/sand, especially for relatively shallow tunnels. As the ratio of rock/sand at the tunnel face increased, the pressure gradient in the chamber became more inconsistent. The translated cumulative curve does not always provide a good fit in the mixed-face conditions, particularly in cases when the rock/sand ratios are high. A smaller width of settlement trough has been observed for cases with a large rock/sand ratio compared to that in clay and cohesionless soil. [ABSTRACT FROM AUTHOR]

Strain hardening behavior can be observed in steel fiber reinforced concretes under tensile loads. In this paper, a statistical micromechanical damage framework is presented for the strain hardening steel fiber reinforced concrete (SH-SFRC) considering the interfacial slip-softening and matrix spalling effects. With a linear slip-softening interface law, an analytical model is developed for the single steel fiber pullout behavior. The crack bridging effects are reached by averaging the contribution of the fibers with different inclined angles. Afterwards, the traditional snubbing factor is modified by considering the fiber snubbing and the matrix spalling effects. By adopting the Weibull distribution, a statistical micromechanical damage model is established with the fracture mechanics based cracking criteria and the stress transfer distance. The comparison with the experimental results demonstrates that the proposed framework is capable of reproducing the SH-SFRC's uniaxial tensile behavior well. Moreover, the impact of the interfacial slip-softening and matrix spalling effects are further discussed with the presented framework. [ABSTRACT FROM AUTHOR]

Innovative pothole patching materials reinforced with a high-toughness, low-viscosity nanomolecular resin, dicyclopentadiene (DCPD, C10H12), have been experimentally proven to be effective in repairing cracked asphalt pavements and can significantly enhance their durability and service life. In this paper, a three-dimensional micromechanical framework is proposed based on the micromechanics and continuum damage mechanics to predict the effective elastic-damage behaviors of this innovative pothole patching material under the splitting tension test (ASTM D6931). In this micromechanical model, irregular coarse aggregates are approximated and simulated by randomly allocated multi-layer-coated spherical particles in certain representative sizes. Fine aggregates, asphalt binder (PG64-10), cured DCPD (p-DCPD), and air voids are formulated into an isotropic elastic asphalt mastic matrix based on the multilevel homogenization approach. The theoretical micromechanical elastic-damage predictions are then systemically compared with properly designed laboratory experiments as well as three-dimensional finite elements numerical simulations for the innovative pothole patching materials. [ABSTRACT FROM AUTHOR]

The moisture content in cement pastes influences their mechanical properties and durability. However, the complex, multiscale nature of cement pastes makes it challenging to isolate the contributions of each scale to their macroscopic water sorption isotherms. In particular, the contribution of the calcium–silicate–hydrate gel (the binding phase of cement pastes) remains only partially understood. Here, we introduce a density functional theory lattice model describing water sorption in calcium–silicate–hydrate, which properly reproduces experimental water sorption isotherms in cement pastes. Based on this model, we deconstruct the contribution of each pore scale (interlayer spacing, gel pores, and capillary pores) to the total sorption isotherm. We show that, when the relative humidity is below 80%, the calcium–silicate–hydrate gel accounts for more than 90% of the moisture content adsorbed in cement pastes. In turn, we find that the contribution of the interlayer space within the calcium–silicate–hydrate grains is governed by the competition between the rate of interlayer space opening and the increasing propensity for water to fill larger pores upon increasing relative humidity. Overall, our results highlight the key role played by the calcium–silicate–hydrate in governing the sorption isotherms of cement pastes. [ABSTRACT FROM AUTHOR]

It is essential to explore the corrosion cracking of concrete under sulfate attack to predict the service performance and durability of concrete structures. The damage degree of concrete caused by sulfate attack is quantitatively investigated. Based on the damage mechanism of the local cracking stage, a chemo-micromechanical damage model of sulfate attack of concrete is established by elasto-damage mechanics. The progressive degradation behavior of concrete under sulfate attack is divided into three zones, including the chemical corrosion zone, the damaged concrete zone by expansive stress, and the intact concrete zone. The proposed chemo-micromechanical damage model can quantitatively determine the effects of chemical sulfate corrosion on mechanical properties of concrete. In addition, the present model considers the interaction among corrosion products, the damaged concrete, the intact concrete and uncorrupted hydration products. The comparison between the calculation results and the available experimental data shows that the proposed model is feasible for corrosion cracking analysis. Based on the proposed model, the influencing factors of concrete damage are discussed. With the increase of corrosion degree, the content of corrosion products, the expansion coefficient of corrosion products and the initial radius of corrosion products, the elastic moduli of concrete decrease after sulfate attack. When the tensile strength and rigidity of concrete matrix reduce, the effective elastic moduli of concrete after sulfate attack also deteriorate. The numerical results exhibit that the proposed chemo-micromechanical model is of notable significance to the application of the chemo-mechanical coupling problems of cementitious composite materials. [ABSTRACT FROM AUTHOR]

When subjected to high temperatures, cement-based materials can dehydrate, which, in turn, affects the mechanical property of the main binding phase (calcium silicate hydrate) at the atomic scale. However, the effects of high temperature on the tensile and compressive behavior of calcium silicate hydrate (C−S−H) grains under uniaxial loading remains poorly understood. In this work, based on reactive molecular simulations, the tensile strength, compressive strength, and stress-strain relations of C−S−H grains with four calcium/silicon (C/S) ratios (1.10, 1.33, 164, and 1.80) both under and after (residual properties) high temperatures are investigated. It is shown that C−S−H grains can shrink due to the water loss induced by high temperature, and a low C/S ratio can lead to a thermo-stable molecular structure. Meanwhile, the residual tensile strength can be enhanced, particularly the tensile strength in the z -direction. Upon the residual compressive strength, in the x and y directions, high temperature can decrease the residual compressive strength for C/S = 1.10 or 1.33 but has no apparent effect for C/S = 1.64 or 1.80. While in the z -direction, the residual compressive strength can be enhanced due to the reduction in the interlayer space. In addition, high temperature can improve the residual tensile ductility but has no obvious effect on the residual compressive stress-strain relations. As for the mechanical properties under high temperature, both the tensile and compressive strengths can be weakened except that the tensile strength in the z -direction can undergo an increasing trend when the temperature is below 800 K due to significant shrinkage in the z -direction. Moreover, high temperature can make stress-strain curves exhibit good plasticity. Discussion indicates that the strength degradation of C−S−H gels or cement paste exposure to high temperatures is likely caused by the increasing porosity and coarsening of the void or defect size. [ABSTRACT FROM AUTHOR]

The electrochemical deposition method is a promising approach to repair the deteriorated concrete in the aqueous environment. In this paper, a continuum damage-healing framework is presented for the electrochemical deposition method based on the multi-field coupling growth process of the electrochemical deposition products. The ion transportation and the electrode reactions are characterized by employing the Nernst-Planck equation and the current conservation equation. The level set method is adopted to capture the growth of the deposition products. Based on the deposition process, a new empirical healing law is presented, with which a new continuum damage-healing framework is presented for electrochemical deposition method. Numerical examples are conducted by applying the presented framework to the damaged cementitious composite under the tensile loadings. The presented framework is compared with the classic continuum damage-healing theory and the experimental data. The results show that the presented models can describe the electrochemical deposition method induced damage-healing for the cementitious composite. Furthermore, the effects of the healing time, the solution concentration and the external voltage on the damage-healing behaviors are investigated based on our proposed framework. [ABSTRACT FROM AUTHOR]

This paper presents a study on the face stability of earth pressure balance (EPB) shield tunnels in dry granular soils using the discrete element model (DEM) method to replicate realistic excavation processes of the EPB machine. Analyses were conducted at different buried depths to determine the limit face pressures and the face failure model induced by the EPB shield machine with varying open ratios and rotation speeds of the cutterhead. The failure kinematics of the soil and the soil arching effect were also determined. The results showed that both the open ratio and the rotation speed of the cutterhead have significant effects on the stability of the face in terms of the failure kinematics, limit face pressures, and the soil arching effect. The failure zone was highly dependent on the open ratio, but it depended less on the rotation speed of the cutterhead. The stability of the face is overestimated when the excavation is conducted with a cutterhead that has a large open ratio, but it is underestimated when the excavation is conducted with a cutterhead that has a smaller open ratio. Ignoring the effect of the configuration of the cutterhead and the rotation speed results in unexpected and unrealistic results. [ABSTRACT FROM AUTHOR]

The self-healing materials have become more and more popular due to their active capacity of repairing the (micro-) damages, such as the (micro-) cracks, the (micro-) voids and the other defects. In this paper, the thermodynamic based damage-healing framework is presented for the hydration induced self-healing composite with a compatible healing variable. The new variable is incorporated to consider the time-dependent properties of the hydration products, with which a new damage healing law is proposed. The hydration kinetics are employed to describe the healing process. The properties of the hydration products are arrived with the multiscale and multilevel homogenization scheme. The presented damage-healing model is applied to an isotropic cementitious composite under the tensile loading histories. The presented framework is compared with the classic continuum damage-healing theory and the experimental data. The results show that the presented damage-healing model is capable of describing the hydration induced self-healing of the cementitious composite. It can describe the behavior of the partially and fully healed concrete material. The effects of the healing time and the compatible healing variables on the damage-healing results are investigated based on our proposed framework. [ABSTRACT FROM AUTHOR]

To proactively assess the losses caused by the deterioration of metro tunnels during the operational period, a new method, the cloud model‐based random forests (CRFs), is proposed to discuss the inconsistencies induced by mapping the monitoring data into the health rate of the metro tunnels. On top of the CRF, a self‐training framework is introduced to improve the predictive accuracy and the stability of the CRF by adding more unlabeled data. The main contribution of this paper is proposing a novel CRF model along with a semisupervised approach to overcome the inapplicability of the random forests algorithm in an inconsistent small database, and to reduce the substantial time and cost for expert annotation. The results indicate that (1) the proposed CRF achieves higher accuracy and stability than random forests in predictions; (2) the CRF outperforms the other state‐of‐the‐art methods even in a small database; (3) the self‐training improved CRF keeps highly precise when the ratio of labeled to unlabeled data is no less than 1:11.4. In this study, the suggested ratio of labeled and unlabeled data is no lower than 1:5.7 to reduce the risk of wrongly forecasting a seriously damaged tunnel section as a slightly damaged tunnel section. [ABSTRACT FROM AUTHOR]

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A dynamic experiment of progressive collapse constitutes the basis of a collapse-resistant analysis. To achieve broad applicability and avoid superfluous influencing factors, two representative substructures extracted from long-span single-layer spatial grid structures were tested using a quick-loading system. The strain and displacement results of the specimens were analyzed, as well as the collapse-resistant mechanisms. The dynamic performance of a full-scale Kiewitt dome was investigated using the hybrid finite-element (FE) model. Finally, a novel cable-reinforced Kiewitt dome is proposed to improve the collapse resistance of Kiewitt domes. The results show that the tests and associated analyses contribute to establishing a database of benchmark models for collapse-resisting simulation of long-span single-layer spatial grid structures. The FE results are well-validated by the test results. The time history of the loading with a suddenly applied load of 1,000 kg for S-10 is similar to the time history of the resistance in a compression mechanism. Owing to the geometric nonlinearity, the time history of the resistance for the catenary mechanism is asymmetrically distributed based on the final equilibrium state. The dynamic performance of long-span single-layer spatial grid structures is significantly affected by the duration of the suddenly applied load. The maximum displacement of the novel cable-reinforced Kiewitt dome is substantially reduced, and the maximum stress is smaller than the yield stress of steel. The superiority of the cable-reinforced Kiewitt dome is therefore demonstrated. [ABSTRACT FROM AUTHOR]

Measurements of the time evolution of neutral hydrogen gas filling capillary tubes were performed by interferometry. Time-resolved gas density evolution was observed by following the temporal variation of the interference pattern, while the spatial distribution of gas in the stationary state was obtained by numerical fluid simulation. It was found that for a 178 μm diameter and 30 mm long capillary tube, the gas flow reaches a stable state at around t=34 ms regardless of the value of the reservoir pressure in the range of 100-500 mbar. The gas density filling the capillary tube is measured to be 81±3% of the reservoir density; the density drop is attributed to losses along the filling line and gas leaks from the capillary in the background vacuum. [ABSTRACT FROM AUTHOR]

By incorporating the interface energy effect into a classical micromechanics framework, effective elastic moduli of a composite material containing randomly distributed nanosized prolate spheroidal inhomogeneities are investigated in this paper. The effect of interface energy, which is usually neglected in classical micromechanics theories, becomes important when the size of the reinforcement phase in the composite enters the nanometer range. The interface energy effect is simulated by inducing interface stress on the zero-thickness membrane interface between the matrix and the inhomogeneities. The interfacial stress discontinuity equations are formulated in accordance with the equilibrium conditions on the idealized interface, from which the interfacial strain discontinuity is solved. Subsequently, the effective elastic moduli are derived based on the classical micromechanics homogenization approaches. Comparisons are made of the effective moduli under the current nanomechanical framework and under classical micromechanical theory. The effective moduli are shown to be dependent upon the size of the inhomogeneities and the interface properties when the interface energy effect is considered. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the association between trabecular bone score (TBS) and new bone formation in ankylosing spondylitis (AS) patients, and to investigate whether TBS is independently associated with new bone formation.Method: Sixty-eight patients with AS underwent spinal magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry of the lumbar spine to measure TBS and bone mineral density at baseline. Lateral radiographs of the cervical and lumbar spine (baseline and 2 years) were assessed for new bone formation (syndesmophyte formation and/or growth combined), and spinal MRIs were assessed for the presence or absence of fat metaplasia (FM) at the first to fourth lumbar vertebrae. The factors associated with new bone formation were analysed at the patient level and the vertebral level.Results: New bone formation had developed in 17 patients (25%) at 2 year follow-up. Patients with new bone formation had a higher prevalence of FM and lower TBS at baseline than patients without new bone formation (p = 0.013 and p = 0.041). At the patient level, FM on MRI and low TBS (< 1.23) were significantly associated with new bone formation. At the vertebral level, new bone formation had developed in 25 out of 231 vertebrae (11%) after 2 years. Vertebrae with both FM on MRI and low TBS tended to have more new bone formation (p < 0.001). Syndesmophytes and low TBS (< 1.23) independently increased the risk of new bone formation at the level of individual vertebrae.Conclusion: At both patient and individual vertebral levels, low TBS was associated with new bone formation independently of FM on MRI. [ABSTRACT FROM AUTHOR]

Marine actinobacteria particularly from marine environments are believed to be inexhaustible sources of biologically active molecules for biomedical and industrial applications. We isolated 126 strains of marine actinomycetes from marine invertebrates such as corals, sponges and gastropod molluscs from Daya Bay and Nansha Islands. The chemical diversity of the metabolites from the isolated strains was evaluated using HPLC-UV fingerprinting and their antibacterial activity was estimated. Preliminary chemical screening and antibacterial activity clearly illustrate that the marine invertebrates-associated actinomycetes are a rich source of novel biologically active compounds. Among the isolates, strain SCSIO-PTE-L054 was further investigated for its unique metabolic profile and antibacterial activity. The bioassay-guided isolation rendered a polycyclic tetramate macrolactam (PTM) as a major chemical constituent with potent antibacterial activity. Our results revealed that the Streptomyces sp., strain SCSIO-L054 is a new source of PTMs which could pave a way to isolation of new series of PTMs with a broad spectrum of activity. In summary, the present investigation makes it possible to select marine actinomycetes from Daya Bay and Nansha Islands as new potential sources to produce potent compounds for a wide range of applications in future drug discovery. [ABSTRACT FROM AUTHOR]

A Legendre polynomial-based stochastic micromechanical framework is proposed to quantify the unbiased probabilistic behavior for the unsaturated concrete repaired by the electrochemical deposition method (EDM). By following the authors' previous works, a deterministic micromechanical model with new multilevel homogenization scheme for the repaired unsaturated concrete is presented based on the material's microstructures. With the stochastic descriptions for the microstructures of the repaired unsaturated concrete, the deterministic framework is extended to stochastic. The unbiased probabilistic behavior of the repaired concrete is reached by incorporating the Legendre polynomial approximations and the Monte Carlo simulations. The predictions herein are then compared with the available experimental data, existing models and the commonly used probability density functions, which indicate that the presented stochastic micromechanical framework is capable of characterizing the EDM healing process for unsaturated concrete considering the material's random microstructure. Finally, the statistical effects of the deposition products and unsaturated pores are discussed. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of different amounts of hydrophilic polymer, in three green roof substrates, on the growth of Salvia elegans. Coir dust and perlite were mixed in ratios of 80% to 20% (C4P1), 50% to 50% (C1P1), and 20 to 80% (C1P4) at a substrate depth of 20 cm. Hydrophilic polymer were added to three substrates in the amounts of 0, 0.25, 0.5, 1.0, and 2.0 kg·m-3. The survival rate and visual quality of Salvia elegans were positively associated with hydrophilic polymer content in the three substrates. Although the growth of Salvia elegans was the greatest under the C4P1 substrate when measured in June (dry season), the greatest growth under the C1P4 substrate was in August (rainy season). Therefore, C4P1 and C1P1 substrates with high coir dust materials is not recommended for Salvia elegans because the plants showed low growth and chlorophyll contents in the rainy season and poor flowering with these substrates. Thus, perlite-based C1P4 amended with hydrophilic polymer at a level of > 1.0 kg·m-3 should be considered for the optimal substrate for Salvia elegans during droughts as well as rainy seasons on green roofs. [ABSTRACT FROM AUTHOR]

The effect of radiation on silica has attracted significant attention due to its potential application where radiation exists. However, the nature of the atomistic defects of quartz formed during the radiation-induced damage at high temperatures has not been fully elucidated. Molecular dynamics is adopted to investigate the damage-healing behavior of the quartz at high temperatures in this research. The ensuing diffusion and recovery of point defects in the irradiated specimen at high temperatures are simulated. The high temperature reduces the number of point defects. At 1400 K, all point defects are removed, while only some point defects are erased at 700 K. It is illustrated that the over-coordinated atoms are the main source of point defects at 300 K and 700 K. The temperature influences the configuration of point defects. The healing variable of the molecular dynamics model is subsequently developed to describe the healing process. The healing mechanisms of the irradiated specimen at high temperatures are summarized by analyzing the trajectories of atoms in detail. These results are helpful to understand the nature of radiation damage in quartz at high temperatures. [ABSTRACT FROM AUTHOR]

A stochastic micromechanical framework is proposed to quantitatively characterize the probabilistic behavior of the mechanical performance of the saturated concrete healed by the electrochemical deposition method. Micromechanical model for the healed saturated concrete is presented based on the material microstructures, and new multilevel homogenization procedures are proposed to quantitatively predict the effective properties of the repaired concrete considering the inter-particle interactions. The evolutions of the deposition products are characterized by non-stationary random process, which is represented by Karhunen–Loeve approximations with limited random variables. The probabilistic behavior for the effective properties of the repaired concrete is reached by incorporating the maximum entropy principle and Monte Carlo simulations. The predictions obtained by the proposed stochastic micromechanical framework are then compared with the available experimental data, existing models, and commonly used probability density functions, which indicate that the presented stochastic micromechanical framework is capable of describing the electrochemical deposition method healing process, considering the inherent randomness of the material microstructures. Finally, the influences of the deposition products on the probabilistic behavior of the repaired concrete are discussed on the basis of the proposed models. [ABSTRACT FROM AUTHOR]

Streptococcus iniae is a pathogenic and zoonotic bacterium responsible for human diseases and mortality of many fish species. Recently, this bacterium has demonstrated an increasing trend for antibiotics resistance, which has warranted a search for new approaches to tackle its infection. Glutamate racemase (MurI) is a ubiquitous enzyme of the peptidoglycan synthesis pathway that plays an important role in the cell wall integrity maintenance; however, the significance of this enzyme differs in different species. In this study, we knocked out the MurI gene in S. iniae in order to elucidate the role of glutamate racemase in maintaining cell wall integrity in this bacterial species. We also cloned, expressed, and purified MurI and determined its biochemical characteristics. Biochemical analysis revealed that the MurI gene in S. iniae encodes a functional enzyme with a molecular weight of 30 kDa, temperature optimum at 35°C, and pH optimum at 8.5. Metal ions, such as Cu2+, Mn2+, Co2+ and Zn2+, inhibited the enzyme activity. MurI was found to be essential for the viability and cell wall integrity of S. iniae. The optimal growth of the MurI-deficient S. iniae mutant can be achieved only by adding a high concentration of D-glutamate to the medium. Membrane permeability assay of the mutant showed an increasing extent of the cell wall damage with time upon D-glutamate starvation. Moreover, the mutant lost its virulence when incubated in fish blood. Our results demonstrated that the MurI knockout leads to the generation of S. iniae auxotroph with damaged cell walls. [ABSTRACT FROM AUTHOR]

In this paper, the effects of inhomogeneous material deformation and fatigue caused by meso-mechanical inhomogeneity are investigated. A representative volume element is constructed for pure copper as a material model which features a polycrystalline Voronoi aggregation consisting of a number of crystal grains. The Chaboche model with random parameters is adopted to reflect inhomogeneous cyclic plastic behavior of grains. Key simulations are performed to model the experimental cyclic evolution of strain fatigue under symmetrical tensile–compressive loading. The simulation results show that, although the macroscopic material hysteresis curve keeps stable, the mesoscopic deformations become increasingly inhomogeneous and the statistic differences keep growing. Accordingly, further research on the underlying relation between inhomogeneous deformation and fatigue is conducted, and a systematic methodology to predict the low-cycle fatigue life is revealed. [ABSTRACT FROM AUTHOR]

A multi-scale micromechanical model is proposed to predict the damage degree of hybrid fiber-reinforced concrete under or after high temperatures. The thermal degradation of hybrid fiber-reinforced concrete is generally composed of the damage of the cement paste caused by thermal decomposition and thermal incompatibility, the deterioration of aggregates and fibers, and the interfacial damage between aggregates and the matrix. In this multi-scale model, four levels of hybrid fiber-reinforced concrete structures are considered when the thermal damage degree is derived; namely, the equivalent calcium silicate hydrate (C–S–H) product level, the cement paste level, the concrete level, and the hybrid fiber-reinforced concrete level. At the cement paste level, thermal decompositions of C–S–H product and calcium hydroxide are taken into account. In addition, a dimensionless parameter of the crack density is introduced to represent the thermal cracking of the matrix. At the concrete level, the interfacial damage of aggregates is simulated by a spring–interface model, in which the interfacial parameters are assumed to be functions of temperature. Moreover, at the cement paste level and the hybrid fiber-reinforced concrete level, a sub-stepping homogenization method is proposed to determine the effective properties. Comparisons between previously published experimental data and predictions and discussions illustrate the feasibility of the proposed multi-scale model in predicting thermal damage of concrete and hybrid fiber-reinforced concrete. [ABSTRACT FROM AUTHOR]

Quasistatic measurements of room-temperature anelastic relaxation were used to characterize the properties of shear transformation zones (STZs) in amorphous Al86.8Ni3.7Y9.5 in the dilute limit. Using a combination of nanoindenter cantilever bending and mandrel bend relaxation techniques, anelastic relaxation was measured over times ranging from 1 s to 3 × 107 s. Direct spectrum analysis yields relaxation-time spectra, which display seven distinct peaks. The results were analyzed using a linear dashpot-and-spring model, combined with transition-state theory, to yield several STZ properties. These reveal a quantized hierarchy of STZs that differ from each other by one atomic volume. Potential STZs occupy a large volume fraction of the solid. They access their ergodic space, with the ratio of forward-to backward jump rates ranging from 1.03 to 4.3 for the range of stress values used. [ABSTRACT FROM AUTHOR]

In this study, rectangular prismatic coarse-grain granites were analyzed through an application of a modified true-triaxial rockburst testing system. Various loading rates were considered in a process in which one face was kept free and loading conducted on the other five faces. Using a proposed surface energy per unit area measurement method, the energy dissipation due to the formation of rock fragments during the rockburst process was quantitatively analyzed. The experimental results show that rockburst occurrence depends on several conditions, including — specifically the tangential loading rate exceeding a certain threshold, the presence of considerable amounts of stored strain energy, the dissipation of energy through rock splitting on the free face, and the shear failure in the potential rockburst pit. With increases in the loading rate from 0.5 to 4.0 MPa/s, the fragmentation and energy dissipation of fragments decline linearly. Lamellar coarse fragments are found to be primarily induced by tension failure from the rockburst pit surface. Blocky medium, fine fragments and white powdery tiny particles are mainly induced by shear failure from the rockburst pit interior. Under various loading rates, the dissipated energy of fragments induced by shear is more than 90% of the total dissipated energy. [ABSTRACT FROM AUTHOR]

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A novel damage model based on micromechanics is proposed for hybrid fiber reinforced cementitious composites under uniaxial compression. In this model, a multilevel homogenization method is presented to predict the overall elastic properties of hybrid fiber reinforced cementitious composites. To account for the contribution of microcracks on its macrocompliance under compression, hybrid fiber reinforced cementitious composite is considered equivalent to the microcrack-weakened solid, whose overall compliance consists of the compliance of the matrix and the additional compliance by sliding, propagating and kinking cracks. The bridging effects of hybrid fibers on restraining crack growth are simplified based on the reality that the average sliding displacement of microcracks is much less than the length of reinforcing fibers. The evolutional domains of microcrack growth under loads where the microcracks are sliding, propagating and kinking are discussed in detail. In addition, the weakening effects of fibers upon compressive behavior are captured by introducing two functions, which consider the influences of fiber geometrical parameters, the microcrack density and the distance between two nearest microcracks with the same oriented angle. Simulation results by our evolutionary damage model render reasonable agreements with available experimental data of fiber reinforced cementitious composites and hybrid fiber reinforced cementitious composites with various fiber contents. The new micromechanical damage model would be beneficial to elucidating the strengthening and weakening mechanisms of hybrid fiber reinforcement. [ABSTRACT FROM AUTHOR]

Dynamic disturbance is regarded as one of the most significant factors that induce rockburst around the boundary of underground excavation, particularly in high confining pressure conditions. In the present study, three types of dynamic loading tests are conducted to investigate the dynamically triggered rockburst behavior of a rock wall with double free faces. The three types of dynamic loading considered are the large stress single-pulse loading (mild-disturbance), the middle stress low-frequency cyclic loading (modest-disturbance), and the small stress high-frequency cyclic loading (weak-disturbance). The experimental results are analyzed and the damage evolution process during the dynamic disturbances is described. The tests reveal that the failure strain (i.e., the strain at unstable failure) of the dynamically triggered rockburst is greater than that of the self-initiated rockburst. The intensity of rockburst depends not only on the initial static stress level but also on the dynamic disturbance type. The rockburst induced by the mild-disturbance is mainly related to large amounts of disturbance energy imported. The rockburst caused by the modest-disturbance is contributed by the disturbance degradation of ultimate energy-storage capacity of specimen. The rockburst in a weak-disturbance specimen is primarily due to the disturbance aggravation of the damage in specimen and the elastic strain energy release. In particular, the rockburst hazard from the double free faces is more likely to be triggered and its result more serious than that of the rock structure with only one free face because the increasing free face decreases the rock strength. The fragmentation of the dynamically induced rockburst is larger than that of the self-initiated rockburst. With increasing time of dynamic loading, the damage induced by the modest-disturbance and the weak-disturbance first increases continually, subsequently increases steadily, and finally increases drastically. By contrast, the damage of the specimen under the mild-disturbance condition has a linearly increasing trend. [ABSTRACT FROM AUTHOR]

A micromechanics-based equivalent elastoplastic damage model for both notch-sensitive and multiple cracking hybrid fiber reinforced composite is proposed in this study. In this model, the elastic modulus, first cracking strength, and ultimate strength are estimated based on micromechanics. To quantify strain after matrix cracks, a novel characteristic length is defined based on the damage mechanics. The effects of the fiber length, diameter and modulus, and interfacial bond stress on the characteristic length of hybrid fiber reinforced composite are presented. In order to avoid the difficulty of determining the traditional damage and plastic potential function, this model is developed from the behavior of single fiber at mesolevel to the response of hybrid fiber reinforced composite at macrolevel. Then the calculated results are verified with several published experimental results of fiber reinforced composites and hybrid fiber reinforced composite, including notch-sensitive cracking fiber reinforced composite, multiple cracking fiber reinforced composite, and multiple cracking hybrid fiber reinforced composite reinforced with two types of fibers (steel fiber and polyethylene fiber). A parametric study has been performed to investigate the effects of the fiber properties, including the fiber volume fraction, length, diameter, and interfacial bond stress, on the tensile performance of hybrid fiber reinforced composite reinforced with steel fiber-like and polyethylene fiber-like fibers. The results indicate that enhancement of the tensile performance can be achieved more effectively by improving the polyethylene fiber-like fiber than steel fiber-like fiber. [ABSTRACT FROM AUTHOR]

Wolbachia influence the fitness of their invertebrate hosts. They have effects on reproductive incompatibility and egg production. Although the former are well characterized, the mechanistic basis of the latter is unclear. Here, we investigate whether apoptosis, which has been implicated in fecundity in model insects, influences the interaction between fecundity and Wolbachia in the planthopper Laodelphax striatellus. Wolbachia‐infected females produced about 30% more eggs than uninfected females. We used the terminal deoxyribonucleotidyl transferase (TDT)‐mediated dUTP‐digoxigenin nick end labeling staining to visualize apoptosis. Microscopic observations indicated that the Wolbachia strain wStri increased the number of ovarioles that contained apoptotic nurse cells in both young and aged adult females. The frequency of apoptosis was much higher in the infected females. The increased fecundity appeared to be a result of apoptosis of nurse cells, which provide nutrients to the growing oocytes. In addition, cell apoptosis inhibition by caspase messenger RNA interference in Wolbachia‐infected L. striatellus markedly decreased egg numbers. Together, these data suggest that wStri might enhance fecundity by increasing the number of apoptotic cells in the ovaries in a caspase‐dependent manner. Our findings establish a link between Wolbachia‐induced apoptosis and egg production effects mediated by Wolbachia, although the way in which the endosymbiont influences caspase levels remains to be determined. [ABSTRACT FROM AUTHOR]

Some herb plants can be adapted to green roof systems when provided with better growing conditions such as irrigation. The aim of this study was to determine the effects of different amounts of water retentive, hydrophilic polymers used in green roof substrate mixtures, on the growth of Agastache rugosa. Coir dust and perlite were mixed at a ratio of 80 to 20% (coir dust to perlite, v/v) (termed C4P1), 50 to 50% (C1P1) or 20 to 80% (C1P4) at a substrate depth of 20 cm. Hydrophilic polymer was added to the substrate mixtures at 0 (polymer: medium (w/v), dry weight basis) (control), 0.25, 0.5, 1.0 or 2.0 kg·m-3. Our study indicated that Agastache rugosa can withstand extended dry conditions experienced in green roofs. Substrates C4P1 and C1P1 with high coir dust matter are not suitable for Agastache rugosa because of the low growth and poor ornamental quality observed in these plants, especially during the summer rainy season. For the determination of difference in growth, flower development and overwintering of Agastache rugosa among the different substrate conditions, Duncan's multiple range test was conducted. It was found that the addition of 1.0 kg·m-3 hydrophilic polymer to C1P4 significantly increased the number of inflorescences and resulted in good growth and ornamental quality during both drought and rainy seasons. Moreover, higher overwintering rate was associated with lower coir dust and hydrophilic polymer content. These results indicated that addition of 1.0 kg·m-3 hydrophilic polymer to C1P4 was optimal for the growth of Agastache rugosa in green roofs under dry and rainy seasons. [ABSTRACT FROM AUTHOR]