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This paper investigates the influence of multi-components strong motion duration on seismic performance of high concrete-faced rockfill dams (CFRDs) by fragility analysis based on the method of incremental dynamic analysis (IDA). The contributions of all compositions of earthquake excitations are considered by the definition of integrated duration based on the concept of significant duration. The nonlinear finite element model of a 2D 200-m-high CFRD is established as a case study and the vertical and horizontal displacements are selected as damage measures. Fragility curves and probabilities of two sets of 23 and 25 spectrally equivalent as-recorded bi-directional long-duration and short-duration motions are determined under different failure grades and intensities. The results show that the duration of vertical component has a certain effect on correction between strong motion duration and deformation of the dam and fragility analysis indicates that the ground motions with long duration can make more risk of failure of high CFRDs than short duration motions. Therefore, the seismic performance of high CFRDs will be reformed by taking the effect of ground motion duration into seismic design and risk assessment consideration. [ABSTRACT FROM AUTHOR]

The slope instability brought on by earthquakes frequently results in significant property damage and casualties. At present, the research on displacement response of a slope under earthquake has mainly emphasized the action of the mainshock, without accounting for the impact of an aftershock, and the spatial variability of material parameters is often neglected. The spatial variability of parameters is fully accounted for in this paper, and dynamic reliability of permanent displacement (DP) of a slope produced by the mainshock–aftershock sequence (MAS) is studied. A slope reliability analysis method is proposed based on the Newmark displacement method and the generalized probability density evolution method (GPDEM) to quantify the effect of the spatial variability of materials parameters on dynamic reliability. Firstly, the parameter random field is generated based on the spectral representation method, and the randomly generated parameters are assigned to the finite element model (FEM). In addition, the random simulation method of MAS considering the correlation between aftershock and mainshock is adopted based on the Copula function to generate the MAS. Then, the DP of slopes caused by the MAS considering the spatial variability is calculated based on the Newmark method. The impacts of the coefficient of variation (COV) and aftershock on the DP of slope is analyzed by means of mean values. Finally, the effect of COV and aftershock on the reliability of DP is explained from a probabilistic point of view based on the GPDEM. The results revealed that with the increase in the COV, the mean of the DP of the slope shows a trend of increasing gradually. The DP of slope is more sensitive to the coefficient of variation of friction angle (COVF). The mean DP of the slope induced by the MAS is larger compared to the single mainshock, and the PGA has a significant impact on the DP. [ABSTRACT FROM AUTHOR]

Thermal expansion of a member can affect structural bearing capacity when one or more members are subjected to fire. To explore the developmental rule of member internal force in latticed shell structure, a computation method of member sensitivity is presented based on the alternate path method. Taking a K8 single-layer latticed shell structure as the analysis object, finite element models are established by ANSYS, applying temperature loads on radial and circumferent ribs, calculating the sensitivity of each member during heating, and exploring the rule of member sensitivity at different temperatures. It is revealed from the numerical results that when one member is in fire, member sensitivity is proportional to temperature and inversely proportional to the distance from the member subjected to fire. Taking the member sensitivity coefficient as an index, the internal force will be transmitted along the member with high sensitivity, the rule of load path and internal force redistribution is given when the latticed shell structure is under elevated temperature. [ABSTRACT FROM AUTHOR]

To eliminate the limitations of the deterministic analysis approach currently used for seismic safety evaluation of dams, this paper introduces a novel framework for analyzing the safety of high dams based on probability and reliability. This framework incorporates the randomness nature and impact of aftershocks in simulating main-aftershock sequences. Then, an improved generalized plastic model (GPM) is adopted to perform static-dynamic deformation analysis of the dam, which is achieved by only one set of parameters. Lastly, the non-invasive stochastic finite element method (SFEM), combined with the direct probability integral method (DPIM), is adopted. This method yields probability density functions (PDFs) for each seismic response moment, ensuring both efficient and accurate assessment of dynamic time-varying reliability. The new framework was employed to evaluate the deformation reliability and slope stability of Lianghekou dam. Results demonstrate its superior efficiency compared to conventional methods, verifying its suitability for stochastic dynamic analysis of large and complex nonlinear structures. The study suggests that the variable impact of aftershocks on dam stability depends on design requirements, emphasizing the necessity to consider such effects in dam safety assessments. • A novel mainshock-aftershock sequences generation method is adopted. • A stochastic dynamic analysis framework of dams subjected to seismic sequences is proposed. • Stochastic seismic analysis is conducted by the noninvasive SFEM based on DPIM. • The effect of aftershocks on the reliability and response probability of the dam is analyzed. [ABSTRACT FROM AUTHOR]

The failure mechanism of MSE (mechanically stabilized earth) walls was studied via numerical analysis with the finite element strength reduction method, which was verified as an effective technique by simulating the experimental results reported in previous papers. The finite element program was applied to explore the effects of reinforcement, geometry, and seismic parameters on failure mechanism control at the design stage of MSE walls to avoid the unavoidable errors experienced in common numerical analysis caused by the assumptions of the failure mode and complex input parameters. The research parameters included the wall height, length, and spacing of the geogrid-reinforced retaining wall and seismic load. The results indicated that the wall height and reinforcement length play a major role in failure mode change. When the reinforcement length is less than 2 m, overturning failure could occur, which was unrelated to the other parameters in all cases studied in this paper. In this paper, the parametric study results were presented by evaluating the critical reinforcement length, generating the failure surface pattern, and summarizing design recommendation. [ABSTRACT FROM AUTHOR]

Reliability analysis provides a more effective method for slope stability evaluations and design because it can reflect the uncertainties of slopes. In this study, a generalized probability density evolution method (GPDEM) is proposed to evaluate the system stability reliability of multi-parameters complex slopes. This method is completely different with the traditional random reliability analytical method, which can combine a set of stochastic analysis and currently advanced deterministic slope stability analysis method using finite element method. The proposed method has great adaptability to complex slope cases with implicit perform functions and multiple parametric variables, and can directly reflect the reliability. In addition, a newly Galerkin finite element method based on Streamline-Upwind/Petrov–Galerkin (SUPG) scheme is proposed for the numerical solution of the GPDEM to increase the convergence rates. Several representative study cases of slope system reliability analysis are selected to certify the high precision and validity of GPDEM over the Monte Carlo simulation (MCS) and other simulation methods. The results demonstrate the novel method is promising for geotechnical engineering in terms of precision and efficiency, and can be used to analyze the failure probability of large and complex geotechnical engineering structures. [ABSTRACT FROM AUTHOR]

At present, there are two problems in 3D slope reliability analysis: (1) the slope stability analysis method; (2) how to effectively extend the reliability analysis method from 2D to 3D slopes. This paper combines the advantages of the finite element method and the limit equilibrium method, develops a 3D slope stability analysis finite element sliding surface stress method program, and introduces the radial basis function network (RBFN) intelligent response surface method, which has the characteristics of strong adaptability, high fault tolerance, greater flexibility, and strong nonlinearity. With the response surface function built for the general framework for an intelligent response surface methodology for the reliability analysis of a 3D slope system, the reliability analysis of a slope is extended from 2D to 3D. The process involves generating samples, creating an intelligent response surface, and calculating the failure probability of the 3D slope system. Through the reliability analysis of typical examples and a comparison with Monte Carlo simulation (MCS) method results, the accuracy, feasibility, and superiority of the proposed intelligent response surface methodology for application to the reliability analysis of a 3D slope system were verified. A comparison with the analysis results of the 3D slope shows that the 2D slope stability calculation is too conservative and seriously overestimates the probability of slope instability. Furthermore, 3D analysis can consider the true stress state of a slope and is able to specify a definite range for a sliding body, thereby providing a basis and reference for determining reinforcement regions. [ABSTRACT FROM AUTHOR]

This article proposes a new type of discrete connected precast reinforced concrete diaphragm floor system that consists of precast flat slabs and slab joint connectors. An experimental investigation of discrete connected new-type precast reinforced concrete diaphragm under a vertical distributed static load was conducted, and the effect of slab joint connectors on the load-bearing capacity was evaluated. Then, a finite element analysis of discrete connected new-type precast reinforced concrete diaphragm, precast reinforced concrete floors without slab connectors, and cast-in-situ reinforced concrete floor were performed to understand their working mechanism and determine the differences in load-bearing behavior. The results indicate that the load-bearing capacity and stiffness of discrete connected new-type precast reinforced concrete diaphragm increase considerably as the hairpin and cover plate hybrid slab joint connectors can efficiently connect adjacent precast slabs and enable them to work together under a vertical load by transmitting the shear and moment forces in the orthogonal slab laying direction. The deflection of discrete connected new-type precast reinforced concrete diaphragm in orthogonal slab laying direction is mainly caused by the opening deformation of the slab joint and the rotational deformation of the precast slabs. This flexural deformation feature can provide reference for establishing the bending stiffness analytical model of discrete connected new-type precast reinforced concrete diaphragm in orthogonal slab laying direction, which is vitally important for foundation of the vertical bearing capacity and deformation calculation method. The deflection and crack distribution patterns infer that the discrete connected new-type precast reinforced concrete diaphragm processes the deformation characteristic of two-way slab floor, which can provide a basis for the theoretical analysis of discrete connected new-type precast reinforced concrete diaphragm. [ABSTRACT FROM AUTHOR]

• A non-intrusive seepage analysis framework for high dams is proposed. • Seepage safety of high dams considering the spatial variability is studied. • The low failure probability of seepage safety is effectively evaluated. • The sensitivity of random parameters was analyzed by grey relational analysis. Seepage failure of high earth-rockfill dams have devastating consequences, and its safety analysis is of great importance in the design phase. However, the highest safety standards in high dams pose a challenge to the calculated efficiency of safety assessment. To address this problem, a random seepage safety assessment method which can consider the spatial variability of hydraulic parameters is proposed. Firstly, the spatial variability of the hydraulic parameters in the impervious materials is simulated using the covariance matrix decomposition under the framework of the non-intrusive finite element method. Then, according to the safety index of critical hydraulic gradient, the seepage stability formula is established to evaluate the safety state. Finally, considering that the highest safety standards in high dams make the probability of seepage hazard small (low failure probability event), it may require more than 10,000 deterministic calculations to complete the assessment process. Therefore, an efficient method based on subset simulation is proposed to optimize the computational efficiency. After the seepage safety evaluation of a 315 m high dam, the results show that the hydraulic conductivity of the core wall has the greatest influence on the seepage safety of the dam, and even under the influence of strong parameter spatial variability, its seepage failure probability is lower than 10-3. Compared with Monte Carlo simulation, the proposed method requires only 1/11 of the computation time at the 10-3 failure level. In addition, the results of grey relational analysis show that the coefficient of variation and correlation distance have obvious effects on seepage safety, and the autocorrelation distance has a greater effect. [ABSTRACT FROM AUTHOR]

This paper presents a rapid static parameter inverse method for concrete-faced rockfill dams based on displacement data using an improved cloud surrogate model and the Jaya optimization algorithm. The improved cloud surrogate model (ICSM), which evolved from the uncertainty cloud theory, is used rapidly to establish a nonlinear relationship between static parameters and displacement. The Jaya optimization algorithm, which is proficient in recognizing the extreme value of the objective function, is selected for parameter identification. To verify the performance of the proposed method, an inverse analysis of two numerical models and a real engineering project is considered, and a comparative study with the BP neural network as the surrogate model is conducted. Study results demonstrate that ICSM has an extremely high prediction accuracy, with a mean relative error that is always under 1 %. The prediction accuracy does not increase too much even under complex nonlinear conditions or when dealing with sparse training data. Moreover, Jaya-ICSM maintains high computational efficiency throughout the entire inverse analysis, saving more than 98 % of the time compared to another inverse method and proving to be much better than direct inversion based on the finite element method. This enables real-time inverse analysis and state feedback of complex engineering. The results also illustrate that the Jaya-ICSM is promising in parameter recognition and superior in supporting the displacement evaluation of earth-rock dams. Therefore, the proposed method can be an effective tool for engineers to evaluate the safety of earth-rockfill dams and ensure their long-term stability. [ABSTRACT FROM AUTHOR]

• An innovative precast steel-concrete composite tube (SCCT) shear wall with middle horizontal joints is proposed. • Five full-scaled models of SCCT shear walls and one cast-in-situ RC shear wall (SW) were tested. • The precast SCCT shear walls had high strength, stiffness, ductility and energy dissipation. • An analytical model was established to calculate the normal section bearing capacity of the SCCT shear walls. • The finite element analysis (FEA) models of the SCCT shear walls were proposed. An innovative precast steel–concrete composite tube (SCCT) shear wall with horizontal joints is proposed, in which the horizontal joints are arranged in the middle of shear walls, the thin-walled steel tube, piercing bars and cover concrete provide restraint for the concrete inside the tube to improve the strength and deformation capacity of internal concrete, and the internal and outer concrete, piercing bars are used to avoid the out-of-plane deformation of the thin-walled steel tube. The experimental program was conducted on five full scale models of SCCT shear walls and one cast-in-situ RC shear wall (SW) subjected to cyclic loading. The results revealed that the precast SCCT shear walls with horizontal joints had high strength, stiffness, ductility and energy dissipation, verifying the reliability of the horizontal joints. Moreover, the horizontal joints had little impact on the overall seismic performance of the SCCT shear walls. In addition, two types of failure modes were observed in the SCCT shear walls, where type A was the ideal failure mode making full use of the steel materials and type B with the characteristics of brittle failure should be avoided. Based on the test results, an analytical model was established to calculate the normal section bearing capacity of the SCCT shear walls, and the proposed model was validated using the test results. Finally, finite element analysis (FEA) models of specimens were proposed based on a multilayer shell element, and a parameter study based on the proposed FEA model was conducted to investigate the influence of critical parameters on the mechanical performance of the SCCT shear walls. [ABSTRACT FROM AUTHOR]

A notable prerequisite for state assessments of earth-rockfill dams is a reasonable and accurate description of the deformation. However, due to the complexity of rockfill, its mechanical properties are often difficult to fully describe using the forward finite element method (FEM). The result of FEM depends on the constitutive model and its parameters' selection usually obtained empirically or from indoor tests. In this paper, the improved Jaya optimization algorithm (iJaya) is combined with the advanced cloud surrogate model (ACSM) to perform inverse analysis, which has great advantages in computational speed and accuracy. The generalized plastic model (GPM) is chosen for simulation and its parameters are analyzed. Finally, the deformation field of the Zipingpu Dam is reconstructed. The results show that the ACSM can greatly replace the FEM even using GPM, achieving high prediction accuracy and reduced computation time. iJaya-ACSM can also identify the parameters of the GPM quickly and correctly. The deformation of ERDs can be well simulated based on the inverted parameters, which could help to know the state of the whole dam body. In conclusion, the proposed inverse method is promising in analyzing the deformation of ERDs. [ABSTRACT FROM AUTHOR]

Seismic reliability analysis of actual slopes considering the spatial variability of soil materials is crucial. However, for the discretization of large-scale random fields, high-precision finite element analysis and analysis of small failure probability events, the random analysis of slopes under seismic loads is inefficient. To address this situation, this study proposes a collaborative reliability analysis framework based on the modified linear estimation method (MLEM) and optimized subset simulation (OSS). First , the random field of the uncertain parameters of the Jinping-I left bank slope model is efficiently discretized by the MLEM, and a sensitivity analysis is carried out. Then , considering the adoption of different degrees of cross-correlation of the sensitive random parameters, the OSS method is used to perform random finite element analysis on the coarse mesh model. Finally , the fine mesh samples are obtained according to the response conditioning method (RCM). The MLEM is used to ensure the consistency of the two sets of random fields, and the seismic failure probability and reliability index of the slope under different cross-correlation coefficients of uncertain parameters are obtained. The results suggest that the degree of cross-correlation of parameters has a great influence on the seismic reliability of the slope. Considering that the shear strength parameters of geotechnical materials are often negatively correlated, the fine analysis based on a fine model is necessary. [ABSTRACT FROM AUTHOR]

• A series of earthquake time history samples with given probabilities was generated. • The seismic stability was analysed in light of time history dynamic analysis. • The seismic stability reliability assessment was performed at two levels SL-1 and SL-2. • The stochastic dynamic responses in unreinforced and reinforced situation were considered. • A novel dynamic reliability method was proposed to obtain the abundant probability information. Bank revetments are built near nuclear power plant sites and are used to protect nuclear power plants from potential damage due to incoming water, such as from flooding or large waves. However, the uncertainty of earthquake behavior can make it difficult to adequately design the bank revetments against seismic activity. In earthquake prone areas, such a situation is dangerous, especially when near bodies of water. Thus, when designing the safety of a nuclear power plant near large bodies of water, the seismic behavior of the bank revetments should be taken into consideration. This paper discusses the development and implementation of a probability density evolution method (PDEM) that can be used to predict the effect of stochastic seismic ground motion on the dynamic stability and reliability of nuclear power plant bank revetments. The probability density equation of a bank revetment is derived through performing a set of deterministic, dynamic finite element analyses and stability analyses. The analyses are supported by second-order statistical analysis of the safety factor of two levels of seismic activity: SL-1 (operational safety earthquake) and SL-2 (ultimate safety earthquake). Then, the probability information is obtained at the two levels by solving the probability density evolution equation. The results demonstrate that the required safety factor can depend on the nature of the seismic excitation. Through the above procedures, the reliability assessment of bank revetments under SL-1 and SL-2 loading can be accomplished. In a comparative case study, the seismic responses of unreinforced and reinforced bank revetments to stochastically generated seismic excitation under SL-2 levels correctly indicates that reinforcement can significantly increase the reliability of the bank revetment. [ABSTRACT FROM AUTHOR]

A novel simulation approach based on the isogeometric analysis (IGA) and scaled boundary finite element method (SBFEM) is proposed in this paper for bending and buckling analyses of cylindrical shells resting on elastic foundation. The proposed formulation is derived from the 3D theory of elasticity. By using the cylinder axis as the scaling center, the cylindrical shell is reduced into 2D plane. The Non-uniform rational B-splines (NURBS) used in the Computer-aided Design (CAD) model are employed as the basis functions to describe the geometry and approximate the unknown fields in an isoparametric fashion. The present technique offers several major advantages over many other numerical methods, namely: only the in-plane dimension of the degenerative 2D plane required to be discretized into IGA elements, this effectively reduces the number of degrees of freedom (DOFs) and cuts down the computational costs; The physical fields along the thickness direction are described analytically, consequently the shear locking phenomena can be eliminated naturally without any special treatment; Due to the higher-order continuity and the locally supported properties of the NURBS, the present model can exactly represent arbitrary complex geometries at any level, which leads to superior accuracy and robustness; The intrinsic flexibility of the NURBS elements dramatically contributes to the excellent adaptability of the present approach on irregular meshes. Several numerical examples are carried out to evaluate the high performance of the present IGSBFEM on accuracy, efficiency and applicability. • First comprehensive investigation of cylindrical shells resting on elastic foundation using IGSBFEM. • Excellent adaptability on arbitrary complex geometries. • High accuracy and robustness for cylindrical shells with or without elastic foundation. • Computational cost is significantly reduced by using 2D IGA elements. • Shear locking phenomena can be eliminated naturally without any special treatment. [ABSTRACT FROM AUTHOR]