Lateral Deformation Research Articles

Lateral Convergence Deformation Prediction of Subway Shield Tunnel Based on Kalman Model

In order to optimize the structure of a subway shield tunnel, minimize injuries, and avoid potential safety hazards, the lateral convergence deformation of subway shield tunnels should be predicted. In terms of accuracy and stability, existing prediction models perform poorly in obtaining the lateral convergence deformation value of a non-stationary small-sized sample of a subway shield tunnel. In this paper, a lateral convergence model of a subway shield tunnel based on the Kalman algorithm is constructed based on Kalman filtering theory. The model is efficient, adaptive, and robust and can accurately predict the lateral convergence deformation of a subway shield tunnel. Taking the horizontal diameter of a 200-ring shield segment in the interval section of a subway tunnel as an example, we have proved that the residuals of the Kalman prediction model are small, the residual distribution conforms to the normal distribution, and the prediction effect is great. The model is suitable for the prediction of more than five periods of data, and the prediction accuracy of the model improves with an increase in the number of data periods. In addition, in this paper, we compare the Kalman model with the GM(1,1) model and the GM–Markov model, and the RMSE, NRMSE, MAPE, and R2 are used as evaluation indices. The results show that the Kalman model has a higher prediction accuracy and is more suitable for predicting the lateral convergence deformation of a subway shield tunnel.

Endurance time analysis for seismic performance of underground structures subjected to mainshock–aftershock sequences

The seismic response analysis of subway underground structures only considers the impact of a single mainshock, ignoring the aftershocks, which may cause more serious secondary damage within a short time after strong earthquakes. To investigate the seismic performance of underground structures under sequential earthquakes and improve the understanding of aftershocks, we analyzed the dynamic response of subway station structures under mainshock–aftershock sequences. A typical two-story and three-span subway station was selected as the prototype, and a finite element model of a soil–underground structure interaction was established. Based on the basic concept of endurance time and design response spectrum of relevant seismic standards in China, an endurance time acceleration function was generated, and nine mainshock–aftershock sequences were constructed. Thereafter, the seismic responses of subway stations under the action of mainshock–aftershock sequences, such as lateral deformation characteristics and damage failure law, were discussed and analyzed. The results show that the endurance time method can be used as a new and efficient method to study the seismic performance of underground structures subjected to mainshock–aftershock sequences. The effects of aftershocks on the damage and lateral displacement of underground structures were preliminarily revealed. The structural deformation response of each layer varies greatly due to the different damage states of the mainshock. The maximum story drift θ of the structure increases with the increase of loading seismic intensity. From the perspective of seismic damage and relative deformation, the structural dynamic response, considering the effect of sequential earthquakes, is greater than that of the mainshock alone, which reflects the disadvantage of aftershocks in seismic design. The results provide a reference for seismic analysis and damage assessment of structures under sequential earthquakes.

Research on lateral buckling of eccentrically compressed H-shaped section aluminum alloy perforated members

Aluminum alloy members are widely used in various engineering fields because of the light weight and corrosion resistance. However, the existing research on the stability of the aluminum alloy beam-column with web openings is insufficient. This study carried out the eccentrically compressed tests for 60 H-shaped section aluminum alloy perforated members, taking the opening number, opening diameter, slenderness ratio, and eccentricity distance around major axis as main variables. The tested specimens showed obvious lateral buckling. The effects of web openings on buckling mode, stability bearing capacity, longitudinal deformation, lateral deformation, and strain development of the member are studied. The influence of each variable on the mechanical properties is studied, which provides the basis for design of the structure members. Several main parameters are analyzed in depth using verified finite element model. Based on the results of test and FEA, the design method for lateral stability bearing capacity of H-shaped section aluminum alloy perforated members is proposed with reference to existing specifications.

Dynamics of the Deformable Fluid Interface Interacting with an Approaching Solid under the Electrostatic Field.

A theoretical model was developed to describe the dynamics of a deformable fluid interface interacting with an approaching solid without contact by both the attractive electrostatic and van der Waals (i.e., vdW) interaction, analogous to the situation in the experiments by electric force microscopy (i.e., EFM) or electric-surface force apparatus (i.e., E-SFA) involved in the soft fluid interface. On the basis of this model, a numerical study of the deformation of the fluid interface, the force-vs-separation behavior, and the critical limiting conditions of contact has systematically been carried out. Our results show that the surface pressure induced by the electrostatic interaction plays a more prominent role in the deformation of the fluid interface than the vdW interaction does, and there exists a principal length scale associated with the relative strength of the electrostatic field to the surface tension, affecting the fluid interface shape under the electrostatic field. It was also shown that both the force-distance curves and the corresponding curves of fluid interface deformation peak versus distance for various electrostatic fields satisfy the universal scaling power law. Moreover, an analytical solution to the Euler-Lagrange differential equation governing the deformation of the fluid interface under the external electric field is obtained, and two extended formulas for explicitly describing the principal length scales that respectively characterize the lateral and longitudinal deformations of the fluid interface were determined.

A fast actuated soft gripper based on shape memory alloy wires

The application of shape memory alloy (SMA) actuated soft grippers is limited by their slow recovery speed. In order to further expand their application range, as one of the solutions to address this limitation, this paper proposes a fast actuated soft gripper based on SMA wire active heat dissipation and elastic rib combination to meet the rapid actuation and recovery. The structure primarily consists of a heat dissipation module capable of winding SMA wire and a soft structure resembling a scorpion tail with embedded supper elastic SMA wire. The geometric structure model, dynamics and SMA constitutive model and finite element model of the soft gripper are established, and the lateral deformation of soft bionic scorpion tail end is analyzed through simulations and experiments. In addition, the force in designed soft gripper tip and its ability to grasp different objects are also studied through experiments. The results show that the addition of a cooling fan increased the recovery rate by about 25%, and the force in soft bionic scorpion tail end can reach about 0.12 N. The designed soft gripper can successfully grasp objects with different softness, shape, size and weight. It lays a theoretical foundation and technical support for the development of soft grippers actuated by SMA in the future.

Exploring key factors affecting the ultimate compression capacity of Unbonded Steel-mesh-reinforced Rubber Bearings

To address bearing-sliding damage in highway bridges during seismic events, the Unbonded Steel-mesh-reinforced Rubber Bearing (USRB) was developed. This novel bearing employs flexible, high-strength steel wire meshes as reinforcement, enhancing lateral deformation capacity and reducing bearing-sliding risk. Recent seismic specifications increased the bearings' vertical design load to 30 MPa, where existing bearings with flexible reinforcements (e.g., fiber-reinforced bearings) fail to meet this standard. Hence, for the first time, our study thoroughly investigated the ultimate compression capacity of USRBs and the key factors influencing the capacity. Through ultimate compression tests on full-scale prototypes, we demonstrated that USRBs can comply with heightened seismic requirements, with primary failure attributed to the tensile failure of the steel mesh reinforcement. These tests were complemented by 3D finite element modeling in ANSYS, employing the LINK180 elements for mesh reinforcement and defining the ultimate capacity as the point at which reinforcement stress reached tensile strength. This particular modeling approach, validated against experimental data, can accurately predict the ultimate compression capacity and the force-deformation response of USRBs. A comprehensive parametric analysis, using the validated modeling approach and an advanced statistical method LHS-PRCC, was conducted to identify the key factors influencing the compressive capacity, including bearing geometric parameters (i.e., bearing width, the second shape factor, and rubber layer thickness), steel-mesh configuration characteristics, and steel-mesh material properties. Our findings emphasize the significance of rubber layer thickness, steel mesh weight, and steel wire tensile strength and strain in influencing the USRBs' ultimate compression capacity. Based on these key factors, an empirical equation for the ultimate compression capacity of USRBs was established to guide the optimization design of USRBs. This study not only fills the gap in USRB's performance under extensive compression but also provides a foundation for future optimization of these bearings to enhance their performance in bridge engineering.

Compression performance of FRP bar-reinforced seawater sea-sand concrete encased FRP-wrapped steel tube columns

This paper developed a new type of composite column made of fibre-reinforced polymer (FRP) bar-reinforced seawater sea-sand concrete (SWSSC)-encased FRP-wrapped steel tubes, which is suitable for maritime engineering. In this composite form, the inner steel tube was isolated to the chloride ions by wrapping with an FRP sheet, and FRP bars were employed to reinforce the exterior SWSSC. To avoid/delay the occurrence of internal steel tube buckling, two measures were implemented, that is, filling with ordinary concrete, and bundling and welding using four hollow small-sized steel tubes. The compression performance was explored by axial compression and eccentric compression tests, and three experimental variables were set, including the steel tube thickness (2.5 mm and 5 mm), number of steel tubes (0, 1 and 4), and eccentricity (20 mm, 40 mm and 60 mm). The test results showed that increasing the thickness of the steel tube could improve the bearing capacity and lateral deformation of specimens (e.g., from 32.66 MPa to 36.99 MPa), whereas the number of steel tubes had a minor positive effect on the specimens. Meanwhile, the bearing capacity of the specimens decreased with increasing eccentricity of the eccentric compression test from 41.51 MPa to 36.99 MPa. Finally, a calculation method was proposed to predict the peak eccentric strength of specimens, which can provide a reference for the design of this kind of composite column.

Experimental research on lateral performance of CLT shear walls with novel dissipative angle brackets and hold-downs

Cross-laminated timber (CLT) structures offer a prospective solution to mid- and high-rise buildings. This paper reports experimental research on the lateral performance of CLT shear walls with novel dissipative angle brackets and hold-downs adopting soft-steel bracket and rubber. Quasi-static tests were performed on seven full-scale walls, comprising five walls with dissipative connections, one with in-situ replaced dissipative connections on already used CLT panels, and one with conventional metal connections, to investigate the influence of vertical load distributions, aspect ratios, and reparability. Failure modes, mechanical properties, and energy dissipation capacity were obtained and analyzed. The results show that the damage of the walls with dissipative connections primarily occurred at the connections, and these walls have excellent lateral deformation capacity, whose inter-story drift ratio can be up to 4.35%. Compared with the conventional metal connections, the walls with dissipative connections exhibit 26% higher ductility, 37.6% greater energy dissipation capacity and higher equivalent viscous damping ratios. Meanwhile, the repaired CLT shear walls maintained similar mechanical properties as the original wall, showing satisfactory reparability. Furthermore, non-linear numerical models were established to predict the walls’ lateral behavior, and the analytical hysteresis curves agree well with the test results.

Study on the shear and deformation characteristics of geogrid-reinforced gravelly soils based on large-scale triaxial tests

Geogrid reinforcement has a limiting effect on the lateral deformation and thus improves the shear strength of the soil, the overall strength of the soil and the overall stability of the corresponding geotechnical structure. In this study, large-scale triaxial tests without and with geogrid reinforcement were conducted on three typical gravelly soils in Xinjiang using a large-scale triaxial apparatus. The shear strength and deformation characteristics of gravelly soils with different particle shapes and the stress-strain relations, strength characteristics, damage patterns, and reinforcement effects of gravelly soils with and without reinforcement were investigated. Geogrid reinforcement effectively enhances the strength of the soil; the internal friction angle remained relatively constant with and without reinforcement, whereas the cohesive force increased significantly. The reinforcement effects interpreted from the results obtained from the triaxial tests were discovered when a certain deformation or relative displacement with the reinforcement materials of the soil occurred. Under uniform test conditions, the volumetric strain of the samples of gravelly soil with reinforcement significantly decreased with increasing confining pressure, and the difference in volumetric strains with and without reinforcement was greater when the confining pressure was higher. The highlight of this study is its significance in explaining the reinforcement mechanism in gravelly soils and in selecting engineering design parameters.

Curved Damper as Structural Retrofitting Element to Improve the Performance of Steel Truss Bridge

The curved damper can control the structure movement by a physical approach to reduce the lateral deformation under the earthquake, which previously proved to be a significant improvement when applied on a moment-resisting frame in a laboratory scale experiment. With the same idea, a curved damper is considered a passive control to reduce the excessive deformation for a single span of a steel truss bridge, which is analyzed by finite element modeling to evaluate the role of the curved damper in a complex structure. The study of curved dampers applied in this typical bridge showed that mid-span deformation can be mitigated by up to 62% under an earthquake. Hence, a structure with a curved damper is recommended for application in high seismic locations.

Seismic behavior of irregular underground structures in saturated sand

Sand liquefaction is one of the leading causes of severe earthquake damage. In this study, shaking table tests were carried out to investigate the dynamic interaction between the saturated sand and the irregular subway stations. In this test, a method for the preparation of a liquefiable foundation based on a flexible sensing chain combined with water sedimentation was proposed. Typical test results were interpreted, including the development and spatial distribution of pore pressure, surface subsidence, acceleration, deformation, and dynamic earth pressure. Results show that the spatial distribution of excess pore water pressure is changed by the irregular underground structure, and the liquefiable soil below the bottom plate of the structure can be divided into I, II, and III areas based on the degree of liquefication. The surface subsidence is significantly related to Arias intensity and is concentrated within the range of 5 %–95 % of the intensity. The structural floating is synchronized with the liquefaction of the saturated sand, and the uneven floating and inclination of the underground structure are remarkable, anti-flotation design of underground structures should take into account differences in section forms. During the liquefaction of saturated sand, the foundation soil has conspicuous lateral deformation, especially in the deep soil layer. The shape of the dynamic earth pressure increments turns from triangular to linear, when the foundation soil changes from non-liquefied to liquefied. Compared with the limiting values of the elastic inter-story drift ratio, the maximum inter-story drift ratio of the structure is smaller. The tensile strain responses on the columns, particularly in the lower layer, are more prominent than those at the slabs and side walls.

Seismic Damage Assessment of Reinforced Concrete Slab-Column Connections—Review of Test Data, Code Provisions and Analytical Models

Reinforced concrete slab-column connections are vulnerable to punching shear failure when subjected to combined gravity and lateral loadings during earthquakes. Over the years, many experimental campaigns have been conducted and assessed the seismic performance of flat slabs. The experimental findings were used to derive empirical equations for the design provisions. The paper aims to provide a detailed description of the code development for seismic punching shear. Two current code provisions (ACI 318-19, EC 2 & EC 8-2004) for seismic punching shear are presented and discussed. Relevant and updated experimental data of interior slab-column connections without and with shear reinforcement are selected and assessed against the current design provisions with a focus on key response parameters such as the drift ratio and the gravity shear ratio. The ACI 318-19 limit drift line is considered to assess the lateral deformation demand for the connections with respect to the updated database. The gravity shear ratio is shown to have a considerable impact on the limit drift ratio of slab-column connections without shear reinforcement. The majority of the test specimens with no shear reinforcement experienced punching shear failure, followed by the specimens which showed a combined flexure–punching failure. Punching shear failures occurred for a range of gravity shear ratios of 0.2 to 0.9, while all combined flexure–punching shear failures occurred for gravity shear ratio values below 0.5. The shear-reinforced concrete slab-column connections can achieve much higher drift ratios. Most of the slabs were reinforced with shear studs, particularly in the range of gravity shear ratios of 0.4 to 0.6. Most test specimens failed by flexure for gravity shear ratio values of 0.1 to 0.7, followed by the specimens which failed in combined flexure–punching for gravity shear ratio values that ranged from 0.3 to 0.9. Finally, the available numerical and analytical models for seismic punching shear are presented with the objective of observing their potential strengths and limitations.

Seismic Performance of Infilled Reinforced Concrete Frame with Crumb Rubber Mortar Wall Panel

In this paper, the seismic performance of reinforced concrete (RC) frames with crumb rubber mortar wall panels is reported. The tests of the crumb rubber mortar were conducted to obtain model parameters for equivalent diagonal compression struts. With a higher percentage of sand replacement by crumb rubber, the unit weight, the compressive strength, the tensile strength, and the modulus of elasticity of the crumb rubber cement mortar are decreased. Nonlinear pushover analysis of a simple frame shows that the RC frame with a wall panel with less crumb rubber demonstrates lower lateral deformation ability. The failure modes are affected by the amount of crumb rubber and are dependent on the modeling choice of the equivalent compression strut as the wall panel representative. Finally, the seismic performance of the RC building was studied by the equivalent static approach to explore the influence of the crumb rubber mortar wall panels on internal forces and deformations of the frame. With a higher percentage of crumb rubber, the weight of the infill wall panels and the overall weight of the building are reduced, which meets lower seismic base shear demand. This benefit is, however, traded off with higher lateral deformation and also higher inter-story drift of the studied building frames. Doi: 10.28991/CEJ-2024-010-02-09 Full Text: PDF

Mechanical properties of rock under uniaxial compression tests of different control modes and loading rates

To study the influence of control mode and loading rate on mechanical property of rock, uniaxial compression tests of four types of rocks (gray sandstone, red sandstone, mudstone and granite) are carried out under axial strain control mode and lateral strain control mode respectively. The characteristics of complete stress and strain curves, strength, brittleness and failure modes are analyzed. The results show that control mode has little influence on the pre-peak deformation, stress thresholds, while it has a greater impact on post-peak stress and strain curve, which makes the post-peak deformation stable and controllable, and shows the feature of Class II behavior. With lateral loading rates decrease, post-peak stress and strain curves appear more and more obvious fluctuations in the post-peak stage, and the time required for rock failure increases sharply, but the lateral control rate has little effect on the brittleness of rock. The failure mode of rock samples under axial strain control mode is mainly splitting failure, while that under lateral strain control is gradually changed to shear failure. The smaller the lateral loading control rate is, the more obvious the characteristics of shear failure is. Compared with uniaxial compression tests, under high confining pressure, the lateral dilation deformation is restricted, so peak strength is larger and stress redistribution can be better adjusted and stress fluctuation reduced accordingly in post-peak stage. The research results are an effective supplement to rate-dependent property of rocks and can provide some reference for deformation and strength characteristics research of brittle rock under lateral control mode.

Modeling of rigidly-constrained pure shear dielectric elastomer actuators: electromechanical coupling network method

The rigidly-constrained pure shear dielectric elastomer actuator (PS-DEA) has become one of the critical configurations in linear soft actuator design due to its excellent uni-directional actuation performance and convenient preparation process. However, the theoretical analyses are primarily conducted by employing ideal models and lack consideration of the lateral necking deformation of PS-DEA, which has an essential impact on the performance evaluation and optimal design of PS-DEA. Therefore, in this paper, a user subroutine that describing the behavior of the electromechanical behavior of DE in terms of the Gent free-energy model is developed, and then a parametric model of the PS-DEA is established. Different combinations of actuator parameters are obtained by Latin hypercube sampling, and the actuator’s performance under the parameters is simulated by the finite element method. The finite element results are taken as a sample set, and a BP neural network with three hidden layers is employed to train the samples and obtain a PS-DEA network prediction model, which is experimentally analyzed to validate its accuracy and effectiveness. The prediction model explores the influence of geometric and pre-stretching parameters on the actuator’s performance and obtains the difference between the ideal theoretical and the network prediction model under various parameters. The method in this paper provides a new design methodology and theoretical basis for developing high-performance DE actuators.

Stress–strain characteristics of FRP–PVC confined spontaneous combustion gangue concrete columns

A total of 40 fiber reinforced polymer (FRP) and polyvinyl chloride (PVC) confined spontaneous combustion gangue coarse-aggregate concrete (SAC) specimens were subjected to axial compression tests and theoretical studies. The main analysis focused on the impact of the replacement rate of spontaneous combustion gangue (SCG), the type of CFRP confinement, and the number of CFRP layers on the axial compression performance of CFRP–PVC confined SAC (CFRP–PVC–SAC). The results show that CFRP–PVC confinement can effectively enhance the axial compressive capacity, axial deformation, and lateral deformation of the components. The increase in strength ranges from 1.68 to 3.48 times, while the increase in strain ranges from 5.21 to 11.98 times. The crack patterns and expansive behavior of the coal gangue concrete under confinement exhibit significant differences compared to ordinary concrete. In addition, based on the framework of the existing FRP-confined plain concrete model, a modified model is established to facilitate prediction of stress–strain relationships for short columns of CFRP–PVC–SAC, with the calculated results in good agreement with experimental values.

Modeling extrusion process and layer deformation in 3D concrete printing via smoothed particle hydrodynamics

We developed a computational framework to simulate the intricate processes of extrusion and layer deformation in 3D concrete printing (3DCP). A novel two-dimensional (2D) virtual printing scheme is proposed that enables direct prediction of cross-sectional shape, releasing simulations from the constraint of rectangular nozzles inherent in traditional 2D models. The proposed scheme accurately captures significant lateral deformation, previously ignored by conventional 2D models. It is noteworthy that, for the first time, the effect of time-dependent yield stress on layer deformation is considered by introducing the structuration rate. Further, to leverage advantages in avoiding mesh generation and additional interface tracking, a weakly compressible smoothed particle hydrodynamics (SPH) method incorporating the regularized Bingham model is equipped in the proposed framework. The simulated cross-sectional shapes exhibit excellent consistency with experimental results and outperform existing numerical results across various nozzle heights, printing velocities, and extrusion velocities. Our exploration of rheological parameters reveals that the final layer deformation is influenced by the yield stress, while its deformation rate is affected by the plastic viscosity. The proposed virtual printing framework emerges as a promising tool for enhancing predictability and efficiency in the printing process.

Experimental investigation of global-distortional interaction buckling of stainless steel C-beams

This work reports the test data for press-braked stainless steel C-beams subjected to global-distortional (G-D) interaction. The chemical constituents of austenitic S30408 used in the tests were proved to meet the European (EN 10088–1:2014) and Chinese (GB/T 3280–2015) codes. The tensile test of the material was performed to determine the mechanical properties of the flat and corner areas of the press-braked C-beams. Initial imperfections of each specimen were assessed before conducting the bearing capacity tests. A total of 10 specimens consisting of 20C-beams were subjected to four-point bending. All specimens first underwent distortional buckling and then global buckling. The vertical displacement at the mid-span and the loading points, support rotation, distortional deformation, lateral deformation, strain at the boundary of the upper flange as well as strain of the lower flange were meticulously recorded and analyzed. Based on the observed test phenomena, the recorded displacement and strain data, the failure mechanism of G-D interaction and the development of the buckling waves were unveiled. The test data was employed to evaluate the accuracy of the design methods in accordance to the Direct Strength Method (DSM), EN 1993-1-4, AS/NZS 4673 and ASCE 8–22. All codes are found to account for distortional buckling by employing the Effective Width Method (EWM) to reduce the compression plate area. The evaluation results revealed that DSM could safely and stably make a prediction of the ultimate capacity for G-D interaction in stainless steel beams, while EWM have a lower performance in prediction.

Inertial and kinematic demands of isolated pile-supported wharves in liquefiable soils: Centrifuge tests

Pile-supported wharves in liquefiable soils are prone to severe damage during earthquakes. This study employs seismic isolation techniques to adapt for wharf construction, evaluating their seismic performance under lateral ground deformation due to liquefaction. Experimental and numerical analyses are necessary for confirming the efficiency of the isolation in decreasing the requirements for pile-supported wharves. The study initially tests two pile-supported wharves under geotechnical centrifuge conditions, one reinforced by isolation bearings and the other without. The objective is to simulate the force characteristics of isolated pile-supported wharves in liquefiable soils and to analyze the impact of isolation on reducing the seismic response of these wharves. Subsequent analysis delves into the interaction between inertia and kinematics for two types of pile-supported wharves, providing crucial insights. The development of plastic hinges for two kinds of pile-supported wharves under inertia and kinematics is also analyzed. Quantifiable thresholds are established to study the influence of isolation on the resistance of wharves to seismic disruptions, thus preventing pile-supported wharves damage.

Study on the dynamic construction mechanics of side piles in metro station using the pile-beam-arch method

Based on the Tianhe East Station in Guangzhou Metro Line 11 engineering, this paper analyzes the formation mechanism of soil arching effect (SAE) of station by pile-beam-arch (PBA) method in the excavation process and studies the mechanics and deformation laws of side piles in different construction stages under different pile spacing conditions. The results show that the formation, development and destruction of SAE between piles are closely related to construction process. Both too large and too small pile spacings are not conducive to the development about SAE between piles; when it is located between them, the SAE between piles exerts greatly. In the form of composite lining system, supporting piles as well as SAE between piles play an effective role in supporting soil behind piles. The lateral deformation of pile body is most significant in the completion of buckle arch to the excavation of first soil layer, which is the critical construction phase to reduce lateral deformation of side pile. The axial forces of side pile increase gradually with the excavation of station, and the change is the most drastic at the excavation for first soil layer. The influence of pile spacing on vertical settlement and axial force of side piles is much greater than that of horizontal displacement and bending moment.