Assessment Spectra for Structures Subject to Passing Underground Trains

2011 ◽  
Vol 82 ◽  
pp. 784-789
Author(s):  
Farhad Behnamfar ◽  
Razieh Nikbakht
Keyword(s):  
Structural Damage ◽  
Ground Surface ◽  
Soil Types ◽  
Moving Loads ◽  
Soil System ◽  
Time Histories ◽  
Structural Responses ◽  
Velocity Spectra ◽  
Vibration Time ◽  
Moving Train

Underground trains passing below structures may produce vibrations harming occupants and nonstructural elements, though they do not usually result in structural damage. This is a problem of more importance when assessing buildings such as libraries, hospitals, laboratories, museums, etc. To prepare simple tools to fulfill design needs, in this paper assessment spectra for various underground trains moving with different velocities are calculated. Using these spectra, without resorting to the time consuming and costly analysis of a tunnel-soil system under moving loads, the maximum structural responses can be calculated rapidly. To make this end, the soil-tunnel interaction is modeled using a 3D finite difference scheme under the standard moving train loads. The dynamic analysis of such a system results in the ground surface vibration time histories at different distances from the tunnel axis. Then the maximum values of velocity responses are calculated for an SDF dynamical system. The above calculations are accomplished for different train velocities, tunnel depths, distances from tunnel, and soil types, and are presented as assessment velocity spectra.

RESPONSE OF SOFT CLAY STRATA AND CLAY-PILE-RAFT SYSTEMS TO SEISMIC SHAKING

2007 ◽  
Vol 01 (03) ◽  
pp. 233-255 ◽  
Author(s):  
SUBHADEEP BANERJEE ◽  
SIANG HUAT GOH ◽  
FOOK HOU LEE
Keyword(s):  
Soft Clay ◽  
Ground Surface ◽  
Model Tests ◽  
Pile Foundations ◽  
Kaolin Clay ◽  
Natural Period ◽  
Soil System ◽  
Centrifuge Model ◽  
Inertial Loading ◽  
Centrifuge Model Tests

The behavior of pile foundations under earthquake loading is an important factor affecting the performance of structures. Observations from past earthquakes have shown that piles in firm soils generally perform well, while the performance of piles in soft or liquefied ground can raise some questions. Centrifuge model tests were carried out at the National University of Singapore to investigate the response of pile-soil system under three different earthquake excitations. Some initial tests were done on kaolin clay beds to understand the pure clay behavior under repetitive earthquake shaking. Pile foundations comprising of solid steel, hollow steel and hollow steel pile filled with cement in-fill were then embedded in the kaolin clay beds to study the response of clay-pile system. Superstructural inertial loading on the foundation was modeled by fastening steel weight on top of the model raft. The model test results show that strain softening and stiffness degradation feature strongly in the behaviour of the clay. In uniform clay beds without piles, this is manifested as an increase in resonance periods of the surface response with level of shaking and with successive earthquakes. For the pile systems tested, the effect of the surrounding soft clay was primarily to impose an inertial loading onto the piles, thereby increasing the natural period of the piles over and above that of the pile foundation alone. There is also some evidence that the relative motion between piles and soil leads to aggravated softening of the soil around the pile, thereby lengthening its resonance period of the soil further. The centrifuge model tests were back-analyzed using the finite element code ABAQUS. The analysis shows that the simple non-linear hypoelastic soil model gave reasonably good agreement with the experimental observations. The engineering implication arising from this study so far is that, for the case of relatively short piles in soft clays, the ground surface motions may not be representative of the raft motion. Other than the very small earthquakes, the raft motion has a shorter resonance period than the surrounding soil.

An analysis of the particle trajectories in spherical blast waves reflected from real and ideal surfaces

1981 ◽  
Vol 59 (10) ◽  
pp. 1380-1390 ◽  
Author(s):  
J. M. Dewey ◽  
D. J. McMillin
Keyword(s):  
High Speed ◽  
Ground Surface ◽  
Blast Waves ◽  
Particle Trajectories ◽  
Shock Interactions ◽  
Pressure Time ◽  
Time Histories ◽  
Particle Velocities ◽  
Spherical Shock ◽  
Fixed Times

High speed photogrammetry has been used to measure the particle trajectories in the flows resulting from the interaction of two identical explosively produced spherical shock waves. It is postulated that the interaction simulated the reflection of a spherical shock from an ideal nonenergy-absorbing surface. The "ideal" reflections were compared with reflections from two types of ground surface. From the observed particle trajectories the particle velocities, gas densities, and hydrostatic, dynamic, and total pressures in the complex air flows behind the shock interactions have been computed. These flows are described as two dimensional fields at fixed times and as time histories at fixed locations. The Mach stem shocks at the ground surfaces were weaker than those at corresponding positions near the interaction planes, but the magnitudes of the flow properties in these waves decreased more slowly and, at later times, became greater than those in the waves at the interaction planes. Computed pressure–time histories were compared to measurements made using electronic transducers and good agreement was found.

Modification of seismograph records for effects of local soil conditions

1972 ◽  
Vol 62 (6) ◽  
pp. 1649-1664 ◽  
Author(s):  
P. Schnabel ◽  
H. Bolton Seed ◽  
J. Lysmer
Keyword(s):  
San Francisco ◽  
Ground Surface ◽  
Soil Conditions ◽  
Local Soil ◽  
Geological Conditions ◽  
Soil Deposits ◽  
Time Histories ◽  
Seismic Records ◽  
Local Soil Conditions ◽  
Good Agreement

abstract A procedure for modifying the time histories of seismic records for the effect of local soil conditions is presented. The method is based on a conventional one-dimensional wave-propagation approach with equivalent linear soil properties, extended to practical use for transient motions through the Fast Fourier technique. The validity of the approach is tested against the motions recorded at four soil sites and one rock site during the 1957 San Francisco earthquake. The good agreement between the computed and recorded values indicates that rock motions can be computed from motions recorded on soil deposits, and that the computed rock motions in turn can be used to predict the motion that would have been recorded under different soil and geological conditions. The method is also used to evaluate the probable rock motions in the vicinity of El Centro in the earthquake of 1940 and the ground surface motions that could have been developed on various soil conditions in the same general area.

Experimental research on the dynamic response characteristics of the transition subgrade induced by heavy-haul train passage

2019 ◽  
Vol 233 (9) ◽  
pp. 974-987 ◽  
Author(s):  
Huihao Mei ◽  
Wuming Leng ◽  
Rusong Nie ◽  
Renpan Tu ◽  
Yafeng Li ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Repeated Loading ◽  
Moving Loads ◽  
Response Characteristics ◽  
Heavy Haul Train ◽  
Condition Evaluation ◽  
Heavy Haul ◽  
Variation Characteristics ◽  
Heavy Haul Railway ◽  
Moving Train

The dynamic response of the subgrade under moving train loads provides information on subgrade settlement prediction, condition evaluation, and so forth. This paper presents the field dynamics tests on the transition subgrade in the Shuo-Huang heavy-haul railway in China. The variation characteristics of the peak dynamic displacements along the track and subgrade slope were analyzed, and the random distribution characteristics of the peak dynamic displacements at the subgrade shoulder were studied. The response characteristics of the subgrade during the train passage were investigated, and the attenuation regularities of vibration along the subgrade slope were identified. The results indicated that the action of the train moving loads on the subgrade has obvious periodicity, and two bogies in the adjacent wagons should be considered as one loading unit. The peak dynamic displacements at the subgrade shoulder obey normal distribution under the repeated loading of the loading unit. The subgrade bed is dramatically influenced by the dynamic loadings of the trains, and the moving train loads have little influence on the part below the subgrade bed. The results of the research provide the basis for the evaluation of instantaneous and long-term dynamic stability of the subgrade and offer guidance for simulating train moving loads in the model test and numerical analysis to study the dynamic response of the subgrade.

Tank Car Top Fittings Protection: Evaluation of Derailment Failure Risks — A Conceptual Study

2016 ◽  
Author(s):  
Barbara Di Bacco ◽  
Christopher Kirney ◽  
Anand Prabhakaran ◽  
Graydon F. Booth ◽  
Florentina M. Gantoi ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Conceptual Development ◽  
Ground Surface ◽  
Protective Structure ◽  
Damage And Failure ◽  
Structural Capacity ◽  
Velocity Spectra ◽  
Conceptual Study ◽  
Future Work ◽  
The Impact

Top fittings devices on tank cars are subject to damage and failure under derailment conditions, potentially leading to the release of hazardous lading. This paper describes the conceptual development of an objective methodology for evaluating the risk of fittings protection failure and the potential reduction in that risk when mitigating strategies such as improved fittings protective structure are deployed. The methodology captures several key elements that affect fittings survival, including: the speed of derailment initiation, the impact velocity/force spectrum experienced by the fittings protective structure during the event, the strength/structural capacity of the protective structure, and the rigidity of the ground surface. Detailed finite element modeling efforts were employed to capture derailment dynamics and corresponding impact velocity spectra, as well as the strength of multiple protective designs. Future work, including validation, is planned to extend the concept into a detailed methodology.

Experimental Investigation of the Modal Response of a Rail Span during and after Wheel Passage

2020 ◽  
Vol 2674 (12) ◽  
pp. 15-24
Author(s):  
Korkut Kaynardag ◽  
Giuseppe Battaglia ◽  
Chi Yang ◽  
Salvatore Salamone
Keyword(s):  
Field Tests ◽  
Dynamic Responses ◽  
Modal Parameters ◽  
Moving Loads ◽  
Additional Information ◽  
Time Histories ◽  
Propagation Parameters ◽  
Displacement Force ◽  
Force Time ◽  
Comparison Of The Results

This paper examines the vibrations of a rail span (rail section between two consecutive sleepers) during and after the passage of a rail car’s wheel as well as under impact hammer excitation. In literature, the dynamic response of railway tracks under moving loads has been studied extensively. Many of these studies focus on the responses in relation to displacement/force-time histories and wave propagation parameters. These responses are investigated for the time instants when rail car wheels transverse over the rail spans of interest. In this context, an investigation of responses in relation to modal parameters during and after moving loads might provide additional information. Such information can be used to examine how the loading and additional masses induced by the moving wheels affect the dynamic responses. To this end, field tests were carried out at Transportation Technology Center Inc. (TTCI) facility in Colorado, U.S. First, to find the flexural modes of a rail span under no loading, data was collected from three accelerometers placed on the span under vertical impact hammer excitation. Next, the accelerometers were placed underneath the rail span, and data was collected while a rail car traveled over the span. The signal segments corresponding to during and after a wheel passage were analyzed for the identification of modal parameters. The comparison of the results demonstrated that the frequencies of the rail span increased as the loading induced by the wheel increased.

Prediction of floor responses to crowd bouncing loads by response reduction factor and spectrum method

2020 ◽  
pp. 136943322097556
Author(s):  
Jun Chen ◽  
Jingya Ren ◽  
Vitomir Racic
Keyword(s):  
Structural Damage ◽  
Response Spectrum ◽  
Field Measurements ◽  
Reduction Factor ◽  
Response Reduction Factor ◽  
Long Span ◽  
Single Person ◽  
Vibration Serviceability ◽  
Concert Halls ◽  
Structural Responses

Bouncing is a typical rhythmic crowd activity in entertaining venues, such as concert halls and stadia. When the activity’s frequency is close to the natural frequency of the occupied structure, the corresponding bouncing loads can cause intense structural vibrations resulting in vibration serviceability problems, even structural damage. This study suggests a method for prediction of vibration response due to crowd bouncing by a response reduction factor (RRF) in conjunction with a previously established response spectrum approach pertinent to a single person bouncing. The RRF is defined as a ratio between structural responses with and without taking into account synchronization of body movements of individuals in a bouncing crowd. The variations of RRF with number of persons, structural frequency, bouncing frequency and structural damping ratios have been studied using experimental records of crowd bouncing loads. Based on the findings a practical design curve for RRF has been proposed. Application of the proposed method has been validated on numerical simulations and field measurements of a long-span floor subjected to crowd bouncing loads.

scholarly journals A Procedure to Select Earthquake Time Histories for Deterministic Seismic Hazard Analysis: Case Studies of Major Cities in Taiwan

2017 ◽  
Author(s):  
Duruo Huang ◽  
Wenqi Du
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Surface ◽  
Strong Motion ◽  
Response Spectra ◽  
Dynamic Responses ◽  
Motion Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Deterministic Seismic Hazard

Abstract. In performance-based seismic design, ground-motion time histories are needed for analyzing dynamic responses of nonlinear structural systems. However, the number of strong-motion data at design level is often limited. In order to analyze seismic performance of structures, ground-motion time histories need to be either selected from recorded strong-motion database, or numerically simulated using stochastic approaches. In this paper, a detailed procedure to select proper acceleration time histories from the Next Generation Attenuation (NGA) database for several cities in Taiwan is presented. Target response spectra are initially determined based on a local ground motion prediction equation under representative deterministic seismic hazard analyses. Then several suites of ground motions are selected for these cities using the Design Ground Motion Library (DGML), a recently proposed interactive ground-motion selection tool. The selected time histories are representatives of the regional seismic hazard, and should be beneficial to earthquake studies when comprehensive seismic hazard assessments and site investigations are yet available. Note that this method is also applicable to site-specific motion selections with the target spectra near the ground surface considering the site effect.

scholarly journals Behaviour of cable-stayed bridge’s girder to multi-support excitation

2019 ◽  
Vol 276 ◽  
pp. 01037
Author(s):  
Masrilayanti ◽  
Aryanti Riza ◽  
Kurniawan Ruddy ◽  
Siregar Zakpar
Keyword(s):  
Structural Analysis ◽  
Ground Motion ◽  
Response Spectra ◽  
Analysis Software ◽  
Significant Discrepancy ◽  
Small Magnitude ◽  
Cable Stayed Bridge ◽  
Time Histories ◽  
Structural Responses ◽  
Support Excitation

This paper describes the behaviour of the longitudinal and cross girder of cable-stayed bridge due to multi-support excitation. Cablestayed bridges should be analysed by different support accelerations since generally they have long spans. In this research, an 800 m long cablestayed bridge was assessed by giving different support accelerations. The method used is by arranging simulation using structural analysis software. The displacement time histories are obtained by converting the response spectra using MathCAD. The structural responses were then compared to the application of single support excitation. Results show that there is a significant discrepancy between the two analyses. Single support excitation causes lower responses if the ground motion magnitudes are similar to the small magnitude of the multi-support excitation, and it yields to a higher responses if the magnitudes are similar to the greater value of the multi-support excitation.

Experimental Study on Moving Train Loads Identification from Bridge Responses

2010 ◽  
Vol 143-144 ◽  
pp. 32-37
Author(s):  
Yi Wang ◽  
Wei Lian Qu
Keyword(s):  
Genetic Algorithm ◽  
Experimental Studies ◽  
Steel Beam ◽  
Beam Model ◽  
Moving Loads ◽  
Simply Supported ◽  
Simulated Annealing Genetic Algorithm ◽  
Bridge Responses ◽  
Moving Train ◽  
Moving Speed

This paper describes a method for multi-axle moving train loads identification based on simulated annealing genetic algorithm by minimizing the errors between the measured displacements and the reconstructed displacements from the identified moving loads. Experimental studies were carried out to investigate the effect of the proposed method on moving loads identification. A simply supported steel beam model and a model train with three carriages were constructed in laboratory. A series of comparative researches for moving loads identification have been conducted. Effects of moving speed and measurement station numbers on the accuracy of the proposed method are investigated. The results show that the proposed method is accurate and feasible for multi-axle moving train loads identification.

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