scholarly journals Three-Dimensional Nonlinear Seismic Response of Shield Tunnel Spatial End Structure

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yijing Lu ◽  
Yongsheng Song ◽  
Yanzhen Wang ◽  
Jiale Yuan
Keyword(s):  
Stress Concentration ◽  
Seismic Response ◽  
Three Dimensional ◽  
Global Model ◽  
Structural Deformation ◽  
Shield Tunnel ◽  
Flexible Joints ◽  
Seismic Motion ◽  
Cohesive Models ◽  
Frequency Components

The stiffness mutation of shield tunnel-shaft junction makes the tunnel structure affected by the differential displacement and forms a complex spatial effect. Taking the subsea shield tunnel crossing under the Shantou Gulf, China, as a case study, a three-dimensional finite element global model and a refined local spatial end submodel are established. The nonlinear dynamic behaviors of the seabed soil and concrete, the simulation of the bolt joints between ring segments by using cohesive models and the SMA shape memory alloy flexible joints, and the input ground motions produced by scaling from the high-level earthquake records are considered in detail. The results show that the shield tunnel spatial end structure increases nonlinearly in response to the increase of seismic motion intensity. The opening width and the deformation between ring segments at the vault and the outside spandrel are larger, and serious seismic damage and stress concentration exist at the conjugate 45° directions of shaft. The seismic responses of the tunnel-shaft junction subjected to the seismic motions with rich low-frequency components are much stronger than those of seismic motions with rich high-frequency components. Adding SMA flexible joints, the structural deformation caused by seismic motion propagation can be induced to the preset flexible joint, and the structural damage and stress concentration can be effectively reduced. The seismic response characteristics of shield tunnel spatial end structure calculated by the global model are consistent with those calculated by the submodel, while the seismic response of the submodel is greater than that of the global model.

scholarly journals Conductive GelMA–Collagen–AgNW Blended Hydrogel for Smart Actuator

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1217
Author(s):  
Jang Ho Ha ◽  
Jae Hyun Lim ◽  
Ji Woon Kim ◽  
Hyeon-Yeol Cho ◽  
Seok Geun Jo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Umbilical Vein ◽  
Three Dimensional ◽  
Silver Nanowire ◽  
Structural Deformation ◽  
Rheological Analysis ◽  
Sem Image ◽  
Smart Actuator ◽  
Umbilical Vein Endothelial Cells ◽  
Electrical Stimuli

Blended hydrogels play an important role in enhancing the properties (e.g., mechanical properties and conductivity) of hydrogels. In this study, we generated a conductive blended hydrogel, which was achieved by mixing gelatin methacrylate (GelMA) with collagen, and silver nanowire (AgNW). The ratio of GelMA, collagen and AgNW was optimized and was subsequently gelated by ultraviolet light (UV) and heat. The scanning electron microscope (SEM) image of the conductive blended hydrogels showed that collagen and AgNW were present in the GelMA hydrogel. Additionally, rheological analysis indicated that the mechanical properties of the conductive GelMA–collagen–AgNW blended hydrogels improved. Biocompatibility analysis confirmed that the human umbilical vein endothelial cells (HUVECs) encapsulated within the three-dimensional (3D), conductive blended hydrogels were highly viable. Furthermore, we confirmed that the molecule in the conductive blended hydrogel was released by electrical stimuli-mediated structural deformation. Therefore, this conductive GelMA–collagen–AgNW blended hydrogel could be potentially used as a smart actuator for drug delivery applications.

Reduction of Free-Edge Stress Concentration

1985 ◽  
Vol 52 (4) ◽  
pp. 801-805 ◽  
Author(s):  
P. R. Heyliger ◽  
J. N. Reddy
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Free Edge ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Interlaminar Shear ◽  
Three Dimensional Elasticity

A quasi-three dimensional elasticity formulation and associated finite element model for the stress analysis of symmetric laminates with free-edge cap reinforcement are described. Numerical results are presented to show the effect of the reinforcement on the reduction of free-edge stresses. It is observed that the interlaminar normal stresses are reduced considerably more than the interlaminar shear stresses due to the free-edge reinforcement.

Influence of Slope Gradient on Distribution Rule of Geostress Field in River Valleys

2013 ◽  
Vol 404 ◽  
pp. 365-370 ◽  
Author(s):  
Qi Tao Pei ◽  
Hai Bo Li ◽  
Ya Qun Liu ◽  
Jun Gang Jiang
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Principal Stress ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Slope Gradient ◽  
Bank Slope ◽  
Distribution Rule ◽  
River Valleys ◽  
Gradient Change

During the construction of hydropower station, the change of slope gradient in river valleys often takes place. In order to study influence of slope gradient change on distribution rule of geostress field, the three dimensional unloading models under different slope gradients were established by finite difference software (FLAC3D). After numerical simulation, the results were as follows: (1) The phenomenon of stress concentration at the bottom of river valleys was obvious, which appeared the typical stress fold. Both the depth of stress concentration zone and the principal stress values significantly increased with the increment of slope gradient. (2) Maximum principal stress values increased less in shallow part of upper bank slope (low stress zone) but increased more in the nearby slope foot with the increment of slope gradient, causing great difference in geostress field of bank slope. (3) There was some difference in released energy of bank slope due to slope gradient change in river valleys. In order to distinguish the difference, stress relief zone was further divided into stress stably released zone and stress instability released zone. Finally, take Ada dam area of the western route project of South-to-North Water Transfer as an example, the results by numerical simulation were reliable through comparing the distribution rule of geostress field for the dam, which could provide important reference for stability of the design and construction of steep and narrow river valleys.

Effect of Pile-Soil-Structure Interaction on the Cable-Stayed Bridge in Response to the Earthquake

2014 ◽  
Vol 539 ◽  
pp. 731-735 ◽  
Author(s):  
Yu Chen
Keyword(s):  
Finite Element ◽  
Seismic Response ◽  
Soil Structure ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Finite Element Software ◽  
Cable Stayed Bridge ◽  
Three Dimensional Finite Element

In this thesis, based on the design of a 140+90m span unusual single tower and single cable plane cable-stayed bridge, free vibration characteristics and seismic response are investigated; three dimensional finite element models of a single tower cable-stayed bridge with and without the pile-soil-structure interaction are established respectively by utilizing finite element software MIDAS/CIVIL, seismic response of Response spectrum and Earthquake schedule are analyzed respectively and compared. By the comparison of the data analysis, for small stiffness span cable-stayed bridge, the pile-soil-structure interaction can not be ignored with calculation and analysis of seismic response.

scholarly journals Viscoelastic Boundary Conditions for Multiple Excitation Sources in the Time Domain

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Chen Xia ◽  
Chengzhi Qi ◽  
Xiaozhao Li
Keyword(s):  
Finite Element ◽  
Seismic Response ◽  
Time Domain ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Seismic Loads ◽  
Element Analysis ◽  
Artificial Boundaries ◽  
The Time Domain ◽  
Transmitting Boundaries

Transmitting boundaries are important for modeling the wave propagation in the finite element analysis of dynamic foundation problems. In this study, viscoelastic boundaries for multiple seismic waves or excitations sources were derived for two-dimensional and three-dimensional conditions in the time domain, which were proved to be solid by finite element models. Then, the method for equivalent forces’ input of seismic waves was also described when the proposed artificial boundaries were applied. Comparisons between numerical calculations and analytical results validate this seismic excitation input method. The seismic response of subway station under different seismic loads input methods indicates that asymmetric input seismic loads would cause different deformations from the symmetric input seismic loads, and whether it would increase or decrease the seismic response depends on the parameters of the specific structure and surrounding soil.

Decomposition of Event-Related Brain Potentials into Multiple Functional Components Using Wavelet Transform

2001 ◽  
Vol 32 (3) ◽  
pp. 122-138 ◽  
Author(s):  
Tamer Demiralp ◽  
Ahmet Ademoglu
Keyword(s):  
Wavelet Transform ◽  
Three Dimensional ◽  
Experimental Session ◽  
Brain Potentials ◽  
Time Frequency ◽  
Similar Characterization ◽  
Component Identification ◽  
Frequency Components ◽  
Neurophysiological Mechanisms ◽  
Functional Components

Event related brain potential (ERP) waveforms consist of several components extending in time, frequency and topographical space. Therefore, an efficient processing of data which involves the time, frequency and space features of the signal, may facilitate understanding the plausible connections among the functions, the anatomical structures and neurophysiological mechanisms of the brain. Wavelet transform (WT) is a powerful signal processing tool for extracting the ERP components occurring at different time and frequency spots. A technical explanation of WT in ERP processing and its four distinct applications are presented here. The first two applications aim to identify and localize the functional oddball ERP components in terms of certain wavelet coefficients in delta, theta and alpha bands in a topographical recording. The third application performs a similar characterization that involves a three stimulus paradigm. The fourth application is a single sweep ERP processing to detect the P300 in single trials. The last case is an extension of ERP component identification by combining the WT with a source localization technique. The aim is to localize the time-frequency components in three dimensional brain structure instead of the scalp surface. The time-frequency analysis using WT helps isolate and describe sequential and/or overlapping functional processes during ERP generation, and provides a possibility for studying these cognitive processes and following their dynamics in single trials during an experimental session.

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