FLAC modeling of shallow tunnels under seismic action

The steel–concrete hybrid wind turbine tower is characterized by the concrete tubular segment at the lower part and the traditional steel tubular segment at the upper part. Because of the great change of mass and stiffness along the height of the tower at the connection of steel segment and concrete segment, its dynamic responses under seismic ground motions are significantly different from those of the traditional steel tubular wind turbine tower. Two detailed finite element models of a full steel tubular tower and a steel–concrete hybrid tower for 2.0 MW wind turbine built in the same wind farm are, respectively, developed by using the finite element software ABAQUS. The response spectrum method is applied to analyze the seismic action effects of these two towers under three different ground types. Three groups of ground motions corresponding to three ground types are used to analyze the dynamic response of the steel–concrete hybrid tower by the nonlinear time history method. The numerical results show that the seismic action effect by the response spectrum method is lower than those by the nonlinear time history method. And then it can be concluded that the response spectrum method is not suitable for calculating the seismic action effects of the steel–concrete hybrid tower directly and the time history analyses should be a necessary supplement for its seismic design. The first three modes have obvious contributions on the dynamic response of the steel–concrete hybrid tower.

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Three-dimensional face stability analysis of shallow tunnels using numerical limit analysis and material point method

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2021.103904 ◽

2021 ◽

Vol 112 ◽

pp. 103904

Author(s):

Fabricio Fernández ◽

Jhonatan E.G. Rojas ◽

Eurípedes A. Vargas ◽

Raquel Q. Velloso ◽

Daniel Dias

Keyword(s):

Stability Analysis ◽

Limit Analysis ◽

Three Dimensional ◽

Material Point Method ◽

Material Point ◽

Point Method ◽

Face Stability ◽

Shallow Tunnels ◽

Dimensional Face

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Near-Fault Seismic Response Analysis of Bridges Considering Girder Impact and Pier Size

Mathematics ◽

10.3390/math9070704 ◽

2021 ◽

Vol 9 (7) ◽

pp. 704

Author(s):

Wenjun An ◽

Guquan Song ◽

Shutong Chen

Keyword(s):

Seismic Response ◽

Bending Moment ◽

Expansion Method ◽

Response Analysis ◽

Seismic Action ◽

Transient Wave ◽

Cross Sectional ◽

Displacement Response ◽

Near Fault ◽

Continuous Girder Bridge

Given the influence of near-fault vertical seismic action, we established a girder-spring-damping-rod model of a double-span continuous girder bridge and used the transient wave function expansion method and indirect modal function method to calculate the seismic response of the bridge. We deduced the theoretical solution for the vertical and longitudinal contact force and displacement response of the bridge structure under the action of the near-fault vertical seismic excitation, and we analyzed the influence of the vertical separation of the bridge on the bending failure of the pier. Our results show that under the action of a near-fault vertical earthquake, pier-girder separation will significantly alter the bridge’s longitudinal displacement response, and that neglecting this separation may lead to the underestimation of the pier’s bending damage. Calculations of the bending moment at the bottom of the pier under different pier heights and cross-sectional diameters showed that the separation of the pier and the girder increases the bending moment at the pier’s base. Therefore, the reasonable design of the pier size and tensile support bearing in near-fault areas may help to reduce longitudinal damage to bridges.

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Case Study of a Heavily Damaged Building during the 2016 MW 7.8 Ecuador Earthquake: Directionality Effects in Seismic Actions and Damage Assessment

Geosciences ◽

10.3390/geosciences11020074 ◽

2021 ◽

Vol 11 (2) ◽

pp. 74

Author(s):

Luis A. Pinzón ◽

Luis G. Pujades ◽

Irving Medranda ◽

Rodrigo E. Alva

Keyword(s):

Damage Assessment ◽

Strong Motion ◽

Response Spectra ◽

Seismic Action ◽

Damage State ◽

Ground Acceleration ◽

Intensity Measures ◽

Capacity Curves ◽

Building Orientation

In this work, the directionality effects during the MW 7.8 earthquake, which occurred in Muisne (Ecuador) on 16 April 2016, were analyzed under two perspectives. The first one deals with the influence of these effects on seismic intensity measures (IMs), while the second refers to the assessment of the expected damage of a specific building located in Manta city, Ecuador, as a function of its azimuthal orientation. The records of strong motion in 21 accelerometric stations were used to analyze directionality in seismic actions. At the closest station to the epicenter (RRup = 20 km), the peak ground acceleration was 1380 cm/s2 (EW component of the APED station). A detailed study of the response spectra ratifies the importance of directionality and confirms the need to consider these effects in seismic hazard studies. Differences between IMs values that consider the directionality and those obtained from the as-recorded accelerograms are significant and they agree with studies carried out in other regions. Concerning the variation of the expected damage with respect to the building orientation, a reinforced concrete building, which was seriously affected by the earthquake, was taken as a case study. For this analysis, the accelerograms recorded at a nearby station and detailed structural documentation were used. The ETABS software was used for the structural analysis. Modal and pushover analyses were performed, obtaining capacity curves and capacity spectra in the two main axes of the building. Two advanced methods for damage assessment were used to obtain fragility and mean damage state curves. The performance points were obtained through the linear equivalent approximation. This allows estimation and analysis of the expected mean damage state and the probability of complete damage as functions of the building orientation. Results show that the actual probability of complete damage is close to 60%. This fact is mainly due to the greater severity of the seismic action in one of the two main axes of the building. The results are in accordance with the damage produced by the earthquake in the building and confirm the need to consider the directionality effects in damage and seismic risk assessments.

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Seismic rocking effects on a mine tower under induced and natural earthquakes

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00221-7 ◽

2021 ◽

Vol 21 (2) ◽

Author(s):

Piotr Adam Bońkowski ◽

Juliusz Kuś ◽

Zbigniew Zembaty

Keyword(s):

Seismic Response ◽

Ground Motion ◽

Ground Surface ◽

Tall Buildings ◽

Earthquake Ground Motion ◽

Seismic Action ◽

Seismic Effects ◽

Copper Ore ◽

Rotational Components ◽

Natural Earthquakes

AbstractRecent research in engineering seismology demonstrated that in addition to three translational seismic excitations along x, y and z axes, one should also consider rotational components about these axes when calculating design seismic loads for structures. The objective of this paper is to present the results of a seismic response numerical analysis of a mine tower (also called in the literature a headframe or a pit frame). These structures are used in deep mining on the ground surface to hoist output (e.g. copper ore or coal). The mine towers belong to the tall, slender structures, for which rocking excitations may be important. In the numerical example, a typical steel headframe 64 m high is analysed under two records of simultaneous rocking and horizontal seismic action of an induced mine shock and a natural earthquake. As a result, a complicated interaction of rocking seismic effects with horizontal excitations is observed. The contribution of the rocking component may sometimes reduce the overall seismic response, but in most cases, it substantially increases the seismic response of the analysed headframe. It is concluded that in the analysed case of the 64 m mining tower, the seismic response, including the rocking ground motion effects, may increase up to 31% (for natural earthquake ground motion) or even up to 135% (for mining-induced, rockburst seismic effects). This means that not only in the case of the design of very tall buildings or industrial chimneys but also for specific yet very common structures like mine towers, including the rotational seismic effects may play an important role.

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Predictions and observations of convergence in shallow tunnels: case histories in Greece

Engineering Geology ◽

10.1016/s0013-7952(01)00094-1 ◽

2002 ◽

Vol 63 (3-4) ◽

pp. 333-345 ◽

Cited By ~ 37

Author(s):

Villy A Kontogianni ◽

Stathis C Stiros

Keyword(s):

Case Histories ◽

Shallow Tunnels

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Vertical oscillations of a basin with a fluid during seismic action

Soviet Applied Mechanics ◽

10.1007/bf00885000 ◽

1980 ◽

Vol 16 (10) ◽

pp. 930-935

Author(s):

V. M. Seimov ◽

A. N. Trofimchuk

Keyword(s):

Seismic Action

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Damage to Shallow Tunnels under Static and Dynamic Loading

Procedia Engineering ◽

10.1016/j.proeng.2016.12.171 ◽

2017 ◽

Vol 173 ◽

pp. 1322-1329 ◽

Cited By ~ 5

Author(s):

Swapnil Mishra ◽

K.S. Rao ◽

N.K. Gupta ◽

Ankeh Kumar

Keyword(s):

Dynamic Loading ◽

Shallow Tunnels ◽

Static And Dynamic Loading

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Dynamic Response of Frame Structure with Different Stiffness in Two Horizontal Directions under Oblique Seismic Action

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.368-370.1644 ◽

2013 ◽

Vol 368-370 ◽

pp. 1644-1647

Author(s):

Zhen Bao Li ◽

Hai Teng Wang ◽

Li Fei Liu ◽

Wen Jing Wang

Keyword(s):

Dynamic Response ◽

Ground Motion ◽

Structure Design ◽

Frame Structure ◽

Maximum Response ◽

Seismic Action

The ground motion is multidimensional, random and uncertain in directions when earthquakes occur, so dynamic response under oblique seismic action needs to be considered in the structure design. A frame structure with different stiffness in two horizontal directions was analyzed under seismic action with different input angles. The maximum response of beams and columns was obtained. The seismic mechanism of structures under oblique seismic action was discussed.

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