scholarly journals Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

2021 ◽  
Vol 11 (4) ◽  
pp. 7386-7392
Author(s):  
T. Nagao ◽  
R. Tsutaba
Keyword(s):  
Seismic Design ◽  
Evaluation Methods ◽  
Bottom Surface ◽  
Seismic Load ◽  
Subgrade Reaction ◽  
Design Code ◽  
Element Analysis ◽  
Resistance Moment ◽  
Embedded Foundations ◽  
Rotational Resistance

In a seismic design of embedded foundations, the vertical Subgrade Reaction (SR) acting on a foundation bottom surface and the Rotational Resistance Moment (RRM) generated by the SR are calculated using an SR Modulus (SRM). The SRM and RRM depend on both ground rigidity and Foundation Width (FW). However, the SRM and RRM calculation methods adopted in design codes might not properly consider their FW dependency. In this study, SRM and RRM evaluation methods for embedded foundations subjected to a seismic load were examined by conducting a two-dimensional finite element analysis under the condition where ground rigidity and FW were changed considering the nonlinearity of the ground. The results show that when the seismic load is large and the nonlinearity of the ground appears, the SR distribution is different from the assumption in the design code. The FW dependency of the SRM was lower than the assumption of the design code. Furthermore, methods to calculate the SRM and RRM in accordance with the FW and ground rigidity are proposed.

scholarly journals An Experimental Study on the Way Bottom Widening of Pier Foundations Affects Seismic Resistance

2020 ◽  
Vol 10 (3) ◽  
pp. 5713-5718 ◽  
Author(s):  
T. Nagao
Keyword(s):  
Flexural Rigidity ◽  
Inertial Force ◽  
Lateral Spreading ◽  
Seismic Resistance ◽  
Subgrade Reaction ◽  
Spreading Pressure ◽  
Reaction Coefficient ◽  
Resistance Moment ◽  
Rotational Resistance ◽  
The Way

The resistance of a pier to horizontal loads, like seismic loads, is due to the flexural rigidity of its foundations and the horizontal subgrade reaction. In the event of a massive earthquake, the latter becomes very small because of the softening of the ground, while the structure may experience a large inertial force and lateral spreading pressure. Therefore, structures with high seismic resistance are required in areas with high seismicity. When a wide caisson is used as a pier foundation, a rotational resistance moment caused by the vertical subgrade reaction acting on the foundation bottom can be expected. Although this rotational resistance moment increases if the foundation is widened, in design practice the subgrade reaction coefficient is evaluated as being low under such circumstances. Therefore, even if the foundation is widened, the rotational resistance moment does not increase greatly. Rotational resistance commensurate with the increased construction cost due to foundation widening cannot be expected. In the present study, horizontal loading experiments were performed at one pier with a normal foundation and at one with widened at the bottom foundation, and the way that the widening affected the seismic performance was examined. The results show that compared with the normal foundation, the bottom-widened one experienced far less displacement and offered higher earthquake resistance.

Character Analysis of Balance and Imbalance of Varying Rigidity of Rigid Pile Composite Foundation under Seismic Load

2014 ◽  
Vol 1065-1069 ◽  
pp. 19-22
Author(s):  
Zhen Feng Wang ◽  
Ke Sheng Ma
Keyword(s):  
Finite Element ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Element Model ◽  
Composite Foundation ◽  
Seismic Load ◽  
Seismic Loads ◽  
Element Analysis ◽  
Rigid Pile ◽  
Rigid Pile Composite Foundation

Based on ABAQUS finite element analysis software simulation, the finite element model for dynamic analysis of rigid pile composite foundation and superstructure interaction system is established, which selects the two kinds of models, by simulating the soil dynamic constitutive model, selecting appropriate artificial boundary.The influence of rigid pile composite foundation on balance and imbalance of varying rigidity is analyzed under seismic loads. The result shows that the maximum bending moment and the horizontal displacement of the long pile is much greater than that of the short pile under seismic loads, the long pile of bending moment is larger in the position of stiffness change. By constrast, under the same economic condition, the aseismic performance of of rigid pile composite foundation on balance of varying rigidity is better than that of rigid pile composite foundation on imbalance of varying rigidity.

Preliminary Parametric Assessment of a Bolted Endplate Joint under Combined Axial Force and Cyclic Bending Moment

2011 ◽  
Vol 255-260 ◽  
pp. 718-721
Author(s):  
Z.Y. Wang ◽  
Q.Y. Wang
Keyword(s):  
Finite Element Analysis ◽  
Axial Force ◽  
Seismic Design ◽  
Axial Load ◽  
Failure Modes ◽  
Bending Moment ◽  
Element Analysis ◽  
Cyclic Behaviour ◽  
Joint Behaviour ◽  
Steel Joints

Problems regarding the combined axial force and bending moment for the behaviour of semi-rigid steel joints under service loading have been recognized in recent studies. As an extended research on the cyclic behaviour of a bolted endplate joint, this study is performed relating to the contribution of column axial force on the cyclic behaviour of the joint. Using finite element analysis, the deteriorations of the joint performance have been evaluated. The preliminary parametric study of the joint is conducted with the consideration of flexibility of the column flange. The column axial force was observed to significantly influence the joint behaviour when the bending of the column flange dominates the failure modes. The reductions of moment resistance predicted by numerical analysis have been compared with codified suggestions. Comments have been made for further consideration of the influence of column axial load in seismic design of bolted endplate joints.

Earthquake Damage and Design Requirement of Stair in Frame Structure

2013 ◽  
Vol 438-439 ◽  
pp. 1461-1465 ◽  
Author(s):  
Yuan Bing Cheng ◽  
Kang Wang ◽  
Yong Qiang Ren
Keyword(s):  
Seismic Design ◽  
Earthquake Damage ◽  
Frame Structure ◽  
Seismic Load ◽  
Specific Calculation ◽  
Rescue Work ◽  
Design Requirements ◽  
Serious Injury ◽  
Death Investigation ◽  
Current Code

In building structure, staircase is more complex and relatively weak. As an important emergency routes when earthquakes and other emergencies (such as fire, explosion, etc.) take place, stairs subject highly evacuation live or seismic load, destruction of the stair caused delay of evacuation and affected the commencement of rescue work, and produced serious injury or death. Investigation of Wenchuan earthquake damage also finds that many stairs broken before the main structure. In the current code for seismic designof building, seismic design advice of stairs was only given instructionally, and specific calculation methods and construction requirements were lacked. Based on the analysis of earthquake destroy of stairs in frame structure, this paper proposes some design requirements of stair.

Numerical Analysis on Influence of Cross Section Shape on Earthquake Resistant Capability of Shallow-Buried Tunnel

2013 ◽  
Vol 405-408 ◽  
pp. 1292-1296 ◽  
Author(s):  
Hong Tao Xie
Keyword(s):  
Cross Section ◽  
Strong Motion ◽  
Seismic Load ◽  
Element Analysis ◽  
Seismic Region ◽  
Cross Section Shape ◽  
Section Shape ◽  
Earthquake Resistant ◽  
Internal Forces ◽  
Shallow Buried Tunnel

Taking portal segment in some shallow-buried tunnel in seismic region with strong motion as objects of study, the finite element analysis method was used to compare and assess the seismic behavior of the tunnel with different cross section shape. The results show that the linings displacement response of the tunnel with different cross section shape differs very minor under seismic load. Meanwhile there exists obvious difference in the lining internal forces of the tunnel with different cross section shape. Among all the tunnel with different section shape, the mechanics situation of the tunnel with triple arched sections is the best. While the section of the tunnel is closer to circular in shape, the mechanics situation of the lining can be effectively improved under seismic load.

scholarly journals Analysis of Forming Limits in Sheet Metal Forming with Pattern Recognition Methods. Part 2: Unsupervised Methodology and Application

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1892 ◽  
Author(s):  
Christian Jaremenko ◽  
Emanuela Affronti ◽  
Andreas Maier ◽  
Marion Merklein
Keyword(s):  
Pattern Recognition ◽  
Sheet Metal ◽  
Optical Measurement ◽  
Unsupervised Classification ◽  
Evaluation Methods ◽  
Time Dependent ◽  
Measuring System ◽  
Forming Limit ◽  
Element Analysis

The forming limit curve (FLC) is used in finite element analysis (FEA) for the modeling of onset of sheet metal instability during forming. The FLC is usually evaluated by achieving forming measurements with optical measurement system during Nakajima tests. Current evaluation methods such as the standard method according to DIN EN ISO 12004-2 and time-dependent methods limit the evaluation range to a fraction of the available information and show weaknesses in the context of brittle materials that do not have a pronounced constriction phase. In order to meet these challenges, a supervised pattern recognition method was proposed, whose results depend on the quality of the expert annotations. In order to alleviate this dependence on experts, this study proposes an unsupervised classification approach that does not require expert annotations and allows a probabilistic evaluation of the onset of localized necking. For this purpose, the results of the Nakajima tests are examined with an optical measuring system and evaluated using an unsupervised classification method. In order to assess the quality of the results, a comparison is made with the time-dependent method proposed by Volk and Hora, as well as expert annotations, while validated with metallographic investigations. Two evaluation methods are presented, the deterministic FLC, which provides a lower and upper limit for the onset of necking, and a probabilistic FLC, which allows definition of failure quantiles. Both methods provide a necking range that shows good correlation with the expert opinion as well as the results of the time-dependent method and metallographic examinations.

Seismic Design for Offshore Wind Farms – Lessons Learnt From the ACE Joint Industry Project

2021 ◽  
Author(s):  
Marcus Klose ◽  
Junkan Wang ◽  
Albert Ku
Keyword(s):  
Seismic Design ◽  
Wind Turbines ◽  
Wind Farms ◽  
The United States ◽  
Offshore Wind ◽  
Seismic Load ◽  
Support Structures ◽  
Offshore Wind Farms ◽  
Asian Pacific Region ◽  
The Impact

Abstract In the past, most of the offshore wind farms have been installed in European countries. In contrast to offshore wind projects in European waters, it became clear that the impact from earthquakes is expected to be one of the major design drivers for the wind turbines and their support structures in other areas of the world. This topic is of high importance in offshore markets in the Asian Pacific region like China, Taiwan, Japan, Korea as well as parts of the United States. So far, seismic design for wind turbines is not described in large details in existing wind energy standards while local as well as international offshore oil & gas standards do not consider the specifics of modern wind turbines. In 2019, DNV GL started a Joint Industry Project (JIP) called “ACE -Alleviating Cyclone and Earthquake challenges for wind farms”. Based on the project results, a Recommended Practice (RP) for seismic design of wind turbines and their support structures will be developed. It will supplement existing standards like DNVGL-ST-0126, DNVGL-ST-0437 and the IEC 61400 series. This paper addresses the area of seismic load calculation and the details of combining earthquake impact with other environmental loads. Different options of analysis, particularly time-domain simulations with integrated models or submodelling techniques using superelements will be presented. Seismic ground motions using a uniform profile or depth-varying input profile are discussed. Finally, the seismic load design return period is addressed.

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