Effect Of Self-weight Research Articles

Centrifuge model tests on performance of MSE walls with different facing types

The role of wall facing is crucial in the design of MSE walls. This study employed two centrifuge model tests specifically designed to analyze walls with two distinct facing types: full-height panel facing and modular block facing. Additionally, surcharge loads were applied to these MSE walls to simulate real-world conditions. The findings from these tests revealed that MSE walls with full-height panel facing exhibited superior performance under the combined effects of self-weight and surcharge loads. The measured maximum horizontal displacements in walls with full-height panel facing and modular block facing were about 55% and 85% of those predicted from current design guidelines at EOS3, respectively. The influence of the surcharge loads on the reinforcement loads was found to be substantial for both wall types, especially for the case of model wall with modular block facing, where the reinforcement loads in the upper half of the wall increased by about 30% from EOS2 to EOS3. The insights garnered from this study contribute to a deeper and more nuanced understanding of the impact of facing types on the practical construction and design of MSE walls, offering valuable guidance for future engineering applications.

Post-buckling behavior of variable-arc-length elastica pipe conveying fluid including effects of self-weight and pressure variation

This paper investigated the post-buckling behaviors of a variable-arc-length (VAL) elastica pipe caused by internal transporting fluid motion, accounting for the effects of the self-weight and variation of internal fluid pressure. Both weak-form and strong-form formulations of the VAL elastica pipe were developed. The weak-form formulation was derived by the virtual work principle, and later solved using the nonlinear finite element method (FEM). The strong-form formulation was derived using equilibrium of the force and moment equations, the geometrical relationship of the differential pipe segment, and the energy conservation of the transported fluid. Because of the large displacement analysis, the variation in the internal pressure inside the pipe was considered, which was taken into account by energy conservation based on the Bernoulli principle. Then, the set of nonlinear governing first-order differential equations, corresponding to the two-point boundary value problem, was conveniently solved using the shooting optimization method (SOM). The numerical results obtained from the presented FEM and SOM analyses independently verified each other, with good agreement between these two methods. The parametric study considered the effects of gravity load (pipe and fluid self-weights) and internal fluid pressure on the post-buckling characteristics of the VAL pipe. The numerical results showed that without the pipe and internal fluid weights, the transporting fluid exerted an axial compressive force on the pipe, causing post-buckling phenomena. Beyond the critical state, the support rotation and the length of the VAL pipe increased as the internal fluid velocity decreased. Finally, by including the effect of self-weight, the mode exchange of the odd buckling modes (1st and 3rd modes) was found from the load-displacement path.

Mechanical Behavior of Secondary Lining in Super Large-Span Tunnels Considering Temperature Effects

Temperature stress has a significant impact on the structural stress of (super) large-span tunnel lining, which can easily lead to structural fatigue damage and premature cracking. With the increasing scale and quantity of super large-span tunnels, the issue of temperature stress in secondary lining has attracted widespread attention. Previous studies have paid little attention to the influence of temperature stress on the structural internal forces of ordinary small–medium-span tunnels, but this influence cannot be ignored for super large-span tunnels. We take the Letuan Tunnel (a double-hole eight-lane tunnel) of the Binzhou-Laiwu expressway renovation and expansion project in Shandong Province as a case study and analyze the mechanical response of the secondary lining through on-site measurement. Moreover, a numerical simulation was conducted to evaluate the effects of self-weight and temperature stress on the secondary lining of the case tunnel. The results indicate that: the stress of the secondary lining concrete and steel bars is greatly affected by seasonal temperature changes. The compressive stress of the concrete and steel bars is significantly greater in summer than in winter, and the tensile stress is greater in winter than in summer. Furthermore, multiple measurement points have shown a phenomenon of transition between tensile and compressive stress states. The stress of concrete and steel bars fluctuates periodically with a sine function over time, with a fluctuation period of one year. The structural stress increases with the increase of summer temperature and decreases with the decrease of winter temperature. The fluctuation amplitude of stress in the inner side of the lining concrete and steel bars is greater than that on the outer side. Among them, the stress amplitudes of the inner and outer sides of the concrete are between 0.77–1.75 MPa and 0.44–1.07 MPa, respectively, and the stress amplitudes of the inner and outer steel bars are between 5–31 MPa and 7–13 MPa, respectively. The safety factors in summer are lower than those in winter. The minimum safety factors for secondary lining in summer and winter are 3.4 and 4.6, respectively, which can meet the safety requirements for service. The average axial forces of the secondary lining under the coupling effects of self-weight and temperature in winter and summer are 528 MPa and 563 MPa, respectively, which are significantly greater than the combined axial forces under their individual effects. The bending moment distribution of the secondary lining at the tunnel vault, inverted arch, wall spring and other positions under the coupling effect of self-weight and temperature is different from or even opposite to the bending moment superposition result under the two individual actions. The achieved results reveal that the influence of temperature stress on the service performance of the lining structure cannot be ignored, and the research results can provide useful reference for similar tunnels and related studies.

Structural Design with Self-Weight and Inertial Loading Using Simulated Annealing for Non-Gradient Topology Optimization

This paper explores implementation of self-weight and inertial loading in topology optimization (TO) employing the Simulated Annealing (SA) algorithm as a non-gradient-based technique. This method can be applied to find optimum design of structures with no need for gradient information. To enhance the convergence of the SA algorithm, a novel approach incorporating the crystallization factor is introduced. The method is applied in a benchmark problem of a cantilever beam. The study systematically examines multiple scenarios, including cases with and without self-weight effects, as well as varying point loads. Compliance values are calculated and compared to those reported in existing literature to validate the accuracy of the optimization results. The findings highlight the versatility and effectiveness of the SA-based TO methodology in addressing complex design challenges with considerable self-weight or inertial effect. This work can contribute to structural design of systems where only the objective value is available with no gradient information to use sensitivity-based algorithms.

Numerical Investigation of Cracks at Girder Ends of Prefabricated Post-Tensioned Prestressed Concrete I-Girders

Prefabricated post-tensioned prestressed concrete (PTC) girders with high degrees of prestressing have been developed continuously in recent bridge designs to reach longer spans, higher quality, and larger load-bearing capacity. However, during the prefabrication process, several inclined and horizontal cracks were observed at the ends of a new style post-tensioned concrete girder, which could have a negative impact on the girders' longevity. In this study, a nonlinear finite element analysis technique was utilized to illustrate how concrete reacts and the mechanisms behind typical cracking patterns during the actual post-tensioning sequence. The prestressing load of a PTC girder was simulated with an improved cooling temperature method that accounts for immediate prestress losses. The field of principle tensile strain patterns and primary strain trajectories explained the overall mechanism underlying typical cracking behaviors. The results showed that the horizontal cracks under the anchorage plate (behavior 1) were generated by the bursting force, whereas the inclined cracks (behavior 2) and the horizontal cracks between the strands N1 and N2 anchor plates (behavior 3) were caused due to the spalling force. The effects of self-weight, girder end forms, as well as the transfer length of the prestressing strands, were discussed. The result demonstrates that both the self-weight and girder end shapes have a considerable effect on the behaviors of the anchorage zone. It is suggested that the transfer length of the anchor head be greater than 26 times of strand diameter to achieve the same effective stresses as the theoretical values.

Plastic shrinkage of 3D printed concrete under different self-weight of upper layers

The material properties of 3D printed concrete determine its fragility in preventing plastic shrinkage cracking due to the presence of restraint. Residual friction at the bottom that is positively related to the self-weight of the upper layers is a potential source of constraint that may cause cracking. The present study investigates the effect of self-weight of upper layers on plastic shrinkage of bottom printed concrete at early age. The corresponding surface moisture, bleeding rate, evaporation rate, capillary pressure development, and plastic shrinkage strain of printed concrete specimens under different upper self-weight are determined. It is found that increased self-weight of upper layers can significantly yield more early-age surface moisture and higher bleeding rate of the concrete at the bottom. The increased self-weight of upper layers can induce water to migrate and accumulate on the sides of the printed elements. However, as the self-weight of upper layers reduces the equivalent pore radius, the self-weight of upper layers would still facilitate the development of capillary pressure and further causes larger free plastic shrinkage strain. And when there is friction at the bottom, the horizontal plastic shrinkage is significantly limited by the constraint of the self-weight of upper layers, and the restraint strain increases with the upper self-weight. The maximum principal tensile stress results are calculated by two-dimensional plane strain field on the observation surface, which indicates that the specimen bears a greater risk of plastic shrinkage cracking with larger self-weight of upper layers.

A Deterministic Method for Evaluating Safety Factor of Deep Excavation Stability against Groundwater Inrush Equivalently Considering Soil Uncertainty

In current design specifications for deep excavation, the determination of safety factors against groundwater inrush only considers the self-weight effect of soil mass at the bottom. However, the shear strength and its spatial variability in a cement-solidified bottom layer also plays an important role in safety factor estimation. Based on that, in this study, the strength reduction method was introduced into reliability analysis of deep excavation engineering, and the influence of shear strength and its spatial variability of cement-solidified soil on the stability of deep excavation is studied. Furthermore, a deterministic analysis method that can equivalently consider soil uncertainty is proposed and verified.

Dynamic analysis of the effects of self-weight induced structural and damping nonlinearity on the performance of an origami-inspired vibration isolator

Origami-inspired structure has shown strong nonlinearity on its force response during morphing process between phases. When the origami-inspired structure is applied as vibration isolation system, the structural weight is rare to be considered and discussed in the modelling and analysis of vibration isolation system. The effects of the structural self-weight on the dynamic behaviour of the isolation system is not yet fully understood. Thus, this study aims to investigate the influence of the self-weight induced structural and damping nonlinearity on the dynamic performance of an origami-based vibration isolator. A three-mass body, which includes the payload mass, top facets’ mass and bottom facets’ mass, with multiple degree-of-freedom (DOF) motion is proposed to describe the vibration isolation system. First, a quasi-zero-stiffness feature is designed and its static performance is discussed for a set of specifically selected system parameters. Then, the equation of motion for such three-mass body with spring damping considered is derived by using the harmonic balance method (HBM) on its Lagrange's formulation, where the effects of strong nonlinearity on its dynamic performance can be investigated. The analytical expression is verified with the numerical solutions, which are obtained using the Newmark numerical integration method. The influences of each important system parameter on the dynamic nonlinearity are also discussed. It is expected that this study would provide valuable insights to the effects of structural self-weight in a quasi-zero-stiffness isolation system.

Optical performance evaluation of a large solar dish/Stirling power generation system under self-weight load based on optical-mechanical integration method

Solar dish concentrator system is an optical device that provides high quality thermal source for thermodynamic devices such as Stirling heat engine, the structural deformation caused by self-weight load leads to change of mirror shape and receiver position, reducing its optical performance to affect the safe and efficient operation. In this paper, a previously developed large-scale 38 kW dish/Stirling system with 17.7 m diameter (XEM-Dish system) is used as object, an optical-mechanical integration model of XEM-Dish system is established by combining finite element method and ray-tracing method, which is used to evaluate the effects of self-weight on its optical performance at different elevation angles, including the results of mirror slope error and flux distribution, etc. A method of measuring the deformation of XEM-Dish system using Leica TS30 total station combined 360° prism is presented for validating the correctness of finite element model. Results show that the mirror slope error components SDx and SDy both increase with increase of elevation angle when only concentrator is deformed; mirror slope error increases with its deformation, but their distribution laws in different. The excellent optical efficiency 87% and flux distribution are maintained for XEM-Dish system under self-weight load, with SDx around 0.58 mrad at 0°–60° elevation angle.

Analysis of the most efficient horizontal drainage position in the large strain consolidation considering the self-weight effect

To study the large-deformation settlement of soft soil foundations, an analysis of the large-strain consolidation of soil in a Lagrangian coordinate system based on continuum mechanics is performed, and the control equations with the displacement gradient are obtained in this paper. Based on the nonlinear permeability and compressibility of soft soil foundations, the equation of large-strain nonlinear consolidation is established. Then, the finite difference method is used to solve the governing equations. Under the condition of two-sided drainage while considering the soil self-weight stress, it is found that the distribution of excess pore pressure is not symmetric along the depth of the foundation. The position of the maximum excess pore pressure appears below the midpoint of the soil foundation. The deviation degree increases with increasing foundation thickness and semilogarithmic compression index Cc value, and it decreases with increasing semilogarithmic permeability index Ck value. The calculations show that setting the drainage layer position close to the position of maximum excess pore pressure can effectively improve the drainage ability of the upper and bottom soil layers, which is beneficial to consolidation, and that the deviation distance is related to the Cc and Ck values.

Shaping by Internal Material Frustration: Shifting to Architectural Scale.

Self‐morphing of thin plates could greatly impact the life if used in architectural context. Yet, so far, its realizations are limited to small‐scale structures made of model materials. Here, new fabrication techniques are developed that turn two conventional construction materials—clay and fiber composites (FRP)—into smart, self‐morphing materials, compatible with architectural needs. Controlled experiments verify the quantitative connection between the prescribed small‐scale material structure and the global 3D surface, as predicted by the theory of incompatible elastic sheets. Scaling up of desired structures is demonstrated, including a method that copes with self‐weight effects. Finally, a method for the construction of FRP surfaces with complex curvature distribution is presented, together with a software interface that allows the computation of the 3D surface for a given fiber pattern (the forward problem), as well as the fiber distribution required for a desired 3D shape (the inverse problem). This work shows the feasibility of large‐scale self‐morphing surfaces for architecture.

Simulations of 10MW wind turbine under seismic loadings

In this study, a shell-based finite element model based on Technical University of Denmark 10MW reference wind turbine (DTU 10 MW RWT) is used to study its dynamic responses under seismic loads. The natural vibration frequencies of blades and wind turbines from this study and the results from the literature Bak et al. (2013) are compared. The difference in natural vibration frequencies of the blades arises from simple assigned orientation in composites blades in Bak et al. (2013). The differences in natural vibration frequencies of the wind turbines are suggested to be due to shell elements used in this study whereas beam elements are used in Bak et al. (2013). The built shell-based finite element model of DTU 10MW reference Wind Turbine is then subject to artificially generated earthquake converted from codes of European union earthquake response spectrum. The simulation results show that the foundation has a significant impact on the responses of DTU 10 MW RWT. That is, the DTU 10 MW RWT suffers less stress in the flexible foundation than in the more rigid foundation . The results also show that neglecting the self-weight effect could significantly underestimate the dynamic responses of wind turbines under seismic loadings. This study suggests that shell-element based model should be used in company in the process for certification.

Seismic Performance Evaluation of Agricultural Reservoir Embankment through Shaking Table Tests

In this study, shaking table tests were performed to compare and analyze the acceleration response, displacement behavior, and pore-water pressure behavior of reservoirs with parapets installed to prevent overtopping of deteriorative homogeneous reservoirs. During the shaking table tests, the experimental conditions were divided into four cases considering the range and magnitude of seismic acceleration according to national standards. The vibration-type waveform (Gongen) and shock-type waveform (Minogawa) were applied as input waveforms. The acceleration amplification ratios of both vibration- and shock-wave types were the largest in the dam crest, and the amplification ratio decreased as the design earthquake acceleration increased. In addition, the horizontal displacement was maximum on the upstream slope, owing to the influence of seepage water, and the vertical displacement was maximum on the dam crest, owing to the self-weight effect of the parapet structure. A comparison of the waveform results indicates that the vibration-type waveform may exhibit a more significant effect on the embankment zone displacement than the shock-type waveform. However, when the safety standards for the horizontal displacement, settlement ratio, and excess pore-water pressure ratio were applied, the embankment was stable within the allowable range in both the shock-type and vibration-type waveforms. Therefore, the parapet structure is expected to influence the overflow resistance and stability of embankments positively.

Illustrating Membrane-Dominated Regimes in Pressurized Thin Shells

Pressurized thin-wall structures cover a broad range of applications, including storage tanks, pressurized rubber flood barriers, and large span enclosures. To accurately model such structures, the analyst must select the appropriate mechanical formulation (e.g.membrane vs shell). Membranes are assumed to have negligible bending stiffness and respond to compression by wrinkling; shells resist axial compression (before buckling) and bending efficiently. While theoretical research on these differences is vast, this study aims to explicitly clarify the consequences of this choice and permit a comparison of error between membrane and shell formulations. Therefore, this paper presents a parametric study of canonical pressurized thin-wall structural geometries (i.e.semi-cylinder, hemisphere) to illustrate the transitions between membrane and bending dominant behavior. The mathematical models of a pneumatic 5-parameter shell and membrane are presented and employed to quantify the effects of variables such as thickness and geometry on the amount of membrane, bending, and shear energy. The effects of inflation pressure, self-weight, and hydrostatic loads are also considered. The graphical results, presented in terms of dimensionless quantities in the design space, are general and should be of interest to the theorist and practitioner alike.

Spatial distribution model of the filling and diffusion pressure of synchronous grouting in a quasi-rectangular shield and its experimental verification

Considering that the particular geometric shape of a quasi-rectangular shield, the grout flowing law and its motion process are more complicated than those of a conventional circular shield. To interpret the grouting mechanical ehaviour in the special-shape shield tail void, the filling and diffusion mechanism of synchronous grouting was analysed. The grout flowing is separated into two independent motion processes, which contains a circumferential filling and a longitudinal diffusion. The theoretical model of the grout pressure spatial distribution was derived based on the principle of fluid mechanics. Then, the pressure distributions in the two directions were obtained using a case study and compared with the field measured data to verify the validation of the model. Although the overall spatial pattern of grout pressure distribution on the tunnel profile show a change trend dominated by the self-weight effect mostly, its local fluctuation characteristics is very abnormal relative to that of a circular shield tunnel. Moreover, the important factors in the model were analysed, including the grout material parameters, the grouting construction parameters, and some geometry parameters. The results show that the pressure loss along this way is positively correlated with the grout flow velocity and is sensitive to the shear yield stress of the grout. The pressure loss along the circumferential direction is the most sensitive to the thickness of the ring cake, and the value range suitable for the model should be 0.02–0.03 m. The pressure loss along the longitudinal diffusion direction is the most sensitive to the size of the tail void. The research results can provide a theoretical basis for the control of special-shape shield construction.

Buckling of Tapered Heavy Columns with Constant Volume

This paper studies the buckling of standing columns under self-weight and tip load. An emphasis is placed on linearly tapered columns with regular polygons cross-section whose volume is constant. Five end conditions for columns are considered. The differential equation governing the buckling shapes of the column is derived based on the equilibrium equations of the buckled column elements. The governing equation is numerically integrated using the direct integration method, and the eigenvalue is obtained using the determinant search method. The accuracy of the method is verified against the existing solutions for particular cases. The effects of side number, taper ratio, self-weight, and end condition on the buckling load and mode shape are investigated. The contribution of self-weight acting alone to the buckling response is also explored. For a given column volume, especially, the buckling length and its stress distribution of the columns with different geometries and end conditions are estimated.

Gravity and anisotropy effects in the volume determination of Si spheres for the kilogram realisation

The counting of 28Si atoms plays a fundamental role in the realisation of the unit of mass in terms of stipulated values of fundamental physical constants. In this realisation, the measurement of the volume of a 28Si sphere is a fundamental step. This paper reports a finite element analysis of the self-weight effect on the volume determination, taking the crystal anisotropy into account. The sphere volume might be overestimated from 0.3 × 10−9 to 5.1 × 10−9 (relative terms), depending on the crystal orientation and measurement procedure.

Flat oval duct deflection—finite-element analysis

Finite-element models were developed to predict the deformation of unreinforced spiral flat oval ducts when subjected to a range of positive/negative internal gauge pressures. The models included the effects of duct self-weight. Deflection predictions resulting from a linear analysis and a nonlinear analysis were contrasted. This study also compared finite-element model predictions to experimentally derived spiral flat oval duct deflections, as well as duct deformations derived from a curve fit analysis reported previously in the literature. Close agreement between these results was obtained, thereby corroborating the nonlinear finite-element models that were generated in this study. This investigation emphasized the importance of utilizing nonlinear finite-element modeling to estimate the deflection of spiral flat oval ducts.

Charts for the mining-induced deflection of buildings

This study investigates the flexural deformations of buildings induced by mining-related subsidence. A two-stage solution (previously applied to the tunnelling problem) is used. Buildings are modelled as a beam founded on an elastic continuum that is subjected to ground subsidence. A tensionless soil–structure interface is employed. The effects of both building stiffness and self-weight on the building deflection are considered. The proposed formulation is compared with analytical solutions and empirical envelopes from previous research. A parametric study is conducted for both perfect soil–foundation bond and gap formation to relate deflection ratio modification factors and the limit radius of the greenfield settlement curve (associated with the gap formation) to relative structure–soil stiffness, building weight, foundation shape, and greenfield ground curvature (hogging or sagging) by means of dimensionless groups. Finally, a simple case study is used to demonstrate the proposed procedure. The given framework is more comprehensive than design charts provided by previous mining-related works and can be used for rapid preliminary risk assessment.

On the strength and stability of elliptic toroidal domes

The thin toroidal shell offers exciting possibilities as a lightweight enclosure for working and recreational spaces. In this paper, we use shell theory to investigate the strength and stability of thin toroidal domes of prolate elliptic cross-section. We assume the shell is provided with membrane-type supports so that bending effects at the edges of the shell are insignificant. Focussing attention on the effects of self-weight and the weight of any cladding that may be attached to the shell, we derive the membrane stress resultants for arbitrary values of the shell geometrical parameters, and explore the influence of these parameters on the distribution of stresses in the shell. We then conduct a linear eigenvalue buckling analysis of the shell using a finite-element programme, in order to gain some insight on the stability behaviour of the shell. The main conclusions are that stresses due to gravitational loads are very small in toroidal domes of the type in question, while for the range of geometric parameters (ratio a/b of semi-axes of the toroid; ratio a/A of horizontal semi-axis to mean radius of the toroid) likely to be encountered in practice, buckling is unlikely to govern the design of the shell.