Research on Seismic Reduction and Isolation Measures for Urban Underground Station Structure

2020 ◽  
pp. 2150012
Author(s):  
Guobo Wang ◽  
Feng Ba ◽  
Xianfeng Ma ◽  
Jielin Zhao ◽  
Yifei Yue
Keyword(s):  
Underground Structure ◽  
Reaction Force ◽  
Wave Impedance ◽  
Internal Force ◽  
Finite Element Models ◽  
Isolation Layer ◽  
Dimensional Finite Element ◽  
Reduction Effect ◽  
Underground Station ◽  
Station Structure

Based on a rectangle underground station structure, two-dimensional finite element models are established in this study to explore the effectiveness of different seismic reduction and isolation measures for underground structure, where Davidenkov model is adopted to consider the soil nonlinearity and the underground structure is considered elastic. The performances of the seismic reduction and isolation measures are evaluated by assessing the structure internal force and deformation responses. Depending on the ratio of wave impedance between the isolation layer and the structure, the isolation layers are divided into rigid and flexible types. The effects of the length and elastic modulus of rigid isolation layer as well as that of the thickness and shear modulus of flexible isolation layer are investigated. The results show that the seismic reduction effect of rigid isolation layer is better with the increase of stiffness, and the effect of flexible isolation layer is more obvious with the decrease of stiffness, which are consistent with the classical impedance theory. Furthermore, the middle column of subway station is usually the most vulnerable during seismic shakings, and one viable way to improve its seismic behavior is to reduce the column end constraints. Therefore, different column constraints consisting of swing, hinge, sliding connection and isolation bearing are considered. The numerical results suggest that among the different column end constraints considered, the sliding connection is comparatively more favorable, which can effectively limit the lateral deformation of column while imposing no horizontal reaction force.

scholarly journals Seismic Response Study of Tunnels Running underneath a Subway Station in Parallel

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Fuxue Sun ◽  
Guo-bo Wang ◽  
Xiang-jun Peng ◽  
Zhou-zhou Jin ◽  
Xiao-chun Li ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Underground Structure ◽  
Internal Force ◽  
Underground Structures ◽  
Plane Model ◽  
Metro Station ◽  
Soil Response ◽  
The Impact ◽  
Station Structure ◽  
Range Of Influence

A tunnel passing below a metro station is taken as the object of our study, and a two-dimensional plane model is established to study the effects of their dynamic interaction to seismic excitation. Comparative analysis is used to obtain the influence law between the underground structures and on the soil. The results show that (1) the influence of the underground structure on the soil response is related to structure depth. The range of influence of the station structure on the surface is approximately five times the width of the station, and the surface response is obviously significant within this range. (2) The existence of the tunnel is conducive to reducing the acceleration of the column in the station. It increases the displacement difference between the stations, but the impact on the internal force of the station is not significant. (3) The influence of the station on the dynamic response of the tunnel is consistent with regard to tunnel acceleration, difference in displacement between the top and bottom of the tunnel, and internal force. The presence of the station will reduce the dynamic response of the tunnel.

scholarly journals Internal Force on and Deformation of Steel Assembled Supporting Structure of Foundation Pit under Thermal Stress

2021 ◽  
Vol 11 (5) ◽  
pp. 2225
Author(s):  
Fu Wang ◽  
Guijun Shi ◽  
Wenbo Zhai ◽  
Bin Li ◽  
Chao Zhang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Bending Moment ◽  
High Strength ◽  
Element Model ◽  
Internal Force ◽  
Foundation Pit ◽  
Dimensional Finite Element ◽  
Influence Of Temperature On ◽  
Scale Experiment ◽  
Three Dimensional Finite Element

The steel assembled support structure of a foundation pit can be assembled easily with high strength and recycling value. Steel’s performance is significantly affected by the surrounding temperature due to its temperature sensitivity. Here, a full-scale experiment was conducted to study the influence of temperature on the internal force and deformation of supporting structures, and a three-dimensional finite element model was established for comparative analysis. The test results showed that under the temperature effect, the deformation of the central retaining pile was composed of rigid rotation and flexural deformation, while the adjacent pile of central retaining pile only experienced flexural deformation. The stress on the retaining pile crown changed little, while more stress accumulated at the bottom. Compared with the crown beam and waist beam 2, the stress on waist beam 1 was significantly affected by the temperature and increased by about 0.70 MPa/°C. Meanwhile, the stress of the rigid panel was greatly affected by the temperature, increasing 78% and 82% when the temperature increased by 15 °C on rigid panel 1 and rigid panel 2, respectively. The comparative simulation results indicated that the bending moment and shear strength of pile 1 were markedly affected by the temperature, but pile 2 and pile 3 were basically stable. Lastly, as the temperature varied, waist beam 2 had the largest change in the deflection, followed by waist beam 1; the crown beam experienced the smallest change in the deflection.

Novel and simplified optimisation pathway using response surface and design of experiments methodologies for dental implants based on the stress of the cortical bone

2021 ◽  
pp. 095441192110253
Author(s):  
João PO Freitas ◽  
Bruno Agostinho Hernandez ◽  
Paulo J Paupitz Gonçalves ◽  
Edmea C Baptista ◽  
Edson A Capello Sousa
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Design Of Experiments ◽  
Cortical Bone ◽  
Response Surface ◽  
Dental Implants ◽  
Finite Element Models ◽  
Long Term Treatment ◽  
Dimensional Finite Element ◽  
Surrounding Bone

Dental implants are widely used as a long-term treatment solution for missing teeth. A titanium implant is inserted into the jawbone, acting as a replacement for the lost tooth root and can then support a denture, crown or bridge. This allows discreet and high-quality aesthetic and functional improvement, boosting patient confidence. The use of implants also restores normal functions such as speech and mastication. Once an implant is placed, the surrounding bone will fuse to the titanium in a process known as osseointegration. The success of osseointegration is dependent on stress distribution within the surrounding bone and thus implant geometry plays an important role in it. Optimisation analyses are used to identify the geometry which results in the most favourable stress distribution, but the traditional methodology is inefficient, requiring analysis of numerous models and parameter combinations to identify the optimal solution. A proposed improvement to the traditional methodology includes the use of Design of Experiments (DOE) together with Response Surface Methodology (RSM). This would allow for a well-reasoned combination of parameters to be proposed. This study aims to use DOE, RSM and finite element models to develop a simplified optimisation analysis method for dental implant design. Drawing on data and results from previous studies, two-dimensional finite element models of a single Branemark implant, a multi-unit abutment, two prosthetic screws, a prosthetic crown and a region of mandibular bone were built. A small number of combinations of implant diameter and length were set based on the DOE method to analyse the influence of geometry on stress distribution at the bone-implant interface. The results agreed with previous studies and indicated that implant length is the critical parameter in reducing stress on cortical bone. The proposed method represents a more efficient analysis of multiple geometrical combinations with reduced time and computational cost, using fewer than a third of the models required by the traditional methods. Further work should include the application of this methodology to optimisation analyses using three-dimensional finite element models.

Analytical Study of Fatigue Cracking in Coped Stringers of Steel Bridges

2019 ◽  
Vol 2673 (10) ◽  
pp. 239-246
Author(s):  
Alireza Mohammadi ◽  
Walid S. Najjar
Keyword(s):  
Tensile Stress ◽  
Stress Reduction ◽  
Analytical Study ◽  
Three Dimensional ◽  
Fatigue Cracking ◽  
Hole Drilling ◽  
Finite Element Models ◽  
High Concentration ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Typical coped stringers of streel bridges are prone to fatigue cracking as a result of the high concentration of tensile stress in the cope zone. This stress concentration is caused by a combination of geometric discontinuity at the cope radius and end-connection rigidity. Few retrofit methods are available for mitigating this cracking; they include hole drilling at a crack tip, and top-rivet removal from a stringer-floorbeam connection. Three-dimensional finite element models of a typical stringer with coped web were developed and analyzed to evaluate (i) cope geometry and load configuration parameters and (ii) the effectiveness of these two retrofit methods. The studied geometry parameters were cope radius and cope length. Variations in the cope-zone stress distribution for each parameter and between an original and a retrofitted condition are presented in this paper. Tensile stress reduction was associated with increased cope radius. Although hole drilling resulted in significant stress reduction along the cope edge, this method was associated with increased tensile stress at the bottom of the drilled hole, which could result in further crack propagation. This finding is consistent with existing studies. Removal of a top rivet resulted in significant reduction of tensile stress.

Use of Sub-Modeling Techniques to Calculate Peak Stresses in Bolt Head-to-Shank Fillet Radius

2008 ◽  
Author(s):  
Richard E. Smith ◽  
Stephen J. Speicher
Keyword(s):  
Three Dimensional ◽  
Structural Response ◽  
Peak Stress ◽  
Finite Element Models ◽  
Stress Concentrations ◽  
Sufficient Detail ◽  
Structural Details ◽  
Modeling Techniques ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

There is an ever-increasing use of three-dimensional finite element models in the field of structural analysis to simulate structural response of complex geometries. Although these models are effective in simulating gross structural behavior, they are oftentimes not able to include sufficient detail to simulate small structural details where stress concentrations can occur. To overcome this limitation, sub-models can be used to calculate stresses in areas of peak stress. This paper discusses the process involved in calculating peak stresses in bolt head-to-shank interfaces using sub-modeling methods.

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