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振动台实验和动态响应地震后的钢筋混凝土建筑英文文献和中文翻译

时间:2020-05-23 10:51来源:毕业论文
Abstract: This paper presents the results from shaking table tests of a one-tenth-scale reinforced concrete (RC) building model. The test model is a protype of a building that was seriously damaged during the 1985 Mexico earthquake. The inpu

Abstract: This  paper presents the results from  shaking table tests  of  a one-tenth-scale reinforced concrete (RC) building model. The  test model is a protype of a building that was seriously damaged  during the 1985 Mexico  earthquake. The input ground excitation used during the test was from the records obtained near the site of the prototype building during the 1985  and 1995 Mexico earthquakes.  The tests showed that the damage pattern of  the test model  agreed well with that of the prototype building. Analytical prediction of  earthquake response has been  conducted for the prototype building using a sophisticated49404
  3-D frame model. The input motion used for the dynamic analysis was  the shaking table test measurements with similarity transformation.  The comparison  of  the analytical results and the shaking table test results indicates that the response of  the RC building to minor and the moderate earthquakes can be predicated well. However, there is difference between the predication  and the actual response to the major earthquake. Keywords: RC building; shaking table test; seismic response; inelastic dynamic analysis 1  Introduction Both  shaking  table  tests  and  nonlinear  response analysis  are  important  approaches  in  earthquake engineering  research  and  design  of building  structures. The results of shaking table tests are affected by the size and the similarity design of  the test model, the properties of model  materials,  the  input  and  control  of vibration, the  data  acquisition  and  treatment,  and  other  similar factors.  Thus,  it  is  difficult to  evaluate  the  test  results. Nonlinear  response  analysis  plays  a  very  important role  in  seismic  design  of  building  structures.  The newly  issued  "Code  for Seismic Design  of  Buildings (GB50011-2001)" (Chinese National  Standard,  2001) emphasizes  the necessity of nonlinear response  analysis for high-rise buildings. As  is  well-known,  the results obtained  from  inelastic  dynamic  response  analysis are  highly  dependent  on  many  factors, such  as  the structural modeling, the evaluation of structural member behaviors,  the  input of earthquake  ground motions,  the numerical methods  and  so  on.  Hence,  the  reliability of Correspondence  to:  Ye  Xianguo, Hefei  University of Tech- nology, Hefei 230009, China Tel: 0086-0551-3441036 E-mail: yexiang@mail.hf.ah.cn *Professor; ~Doctor Supported by: National Natural Science Foundation of China Under Grant No.59978013 Received date: 2003-11-04; Accepted  date: 2004-10-24 the  nonlinear  dynamic  response  analysis  needs  to be examined carefully, which can be done by comparing  it  to the real structural seismic response or  to the shaking  table test results from the model structure. The actual structural seismic response  under  strong  ground motion may  not be easy to obtain from instrumented buildings during the actual  earthquake; however,  shaking  table  tests  can  be used  to  provide  valuable data  for  evaluation  purposes. This  paper  describes  a  shaking  table  test  program of  a  building  model  in  reduced  scale.  The  structural prototype  of  the  model  was  a  10-story  reinforced concrete  (RC)  building(Ye,  1996)  made  in  one-tenth scale.  The test  was  carried  out  by  using  the  three- directional  shaking  table  facility  in  the  State  Key Laboratory for Disaster Reduction at Tongji University, Shanghai, China, and a  total of 11  runs of shaking table tests were conducted. For  comparison  purposes,  an  inelastic  dynamic response  analysis of the prototype building  structure by using a 3-D model was performed. The acceleration time- history  records  obtained  on  the  shaking  table  surface were used as the  input to the numerical analysis. 2  Overview  of  shaking  table  tests Shaking  table  tests  of a  reduced-scale  RC building model were conducted under  recorded  three-directional input  seismic  motions.  The  main  objectives  were  to: (1)  simulate  the  seismic  damage  to  a  real  RC building to  validate  current  shaking  table  test  technology;  (2) comprehensively  understand  the  nonlinear  dynamic performance of RC building structures under earthquakes of different  intensities; and  (3)  verify  the  reliability  of earthquake  response  predication  by means  of  inelastic dynamic response analysis. 2.1  Test  model The  structure  prototype  of  the  test  model  is  a 10- story  RC  frame-wall  official  building  in  Mexico  City, constructed  in  1970.  It had  a  regular  rectangular  shape consisting  of  five  frames  spanning  9.0  meters  in  the longitudinal  direction  (X-direction),  and  four  frames with  the  bay  of  6.0m  in  the  transverse  direction  (Y- direction).  In  the  transverse  direction,  four  shear-walls were  symmetrically  placed  in  the  two  end-frames.  The total  height  of  the  building  was  39.05m.  The  building was  designed  for  a  base  shear  coefficient  of  0.078  in the  longitudinal  direction and 0.104  in  the  transverse direction.  The material  strength  was  about  24 MPa  for concrete  in  cubic  compression  and  400 MPa  for  steel bars  in  tension  yielding  respectively. The  building  was damaged  in  the  1985  Mexico  Michoacan  earthquake. The  peak  acceleration  of  the  earthquake  was only 0.171  g,  but  it  lasted  about  180s  with  peak  velocity of  61  cm/s, and  its  predominant  vibration  period  was 2s. The  fundamental  period  of the building was  1.2s  in the  longitudinal X-direction.  The  performance  of  the building  in  the  1985 Mexico earthquake  is described  in Meli  (1992).  It was characterized  by  plastic hinging  at the ends  of several  longitudinal  beams,  from  the  first to the sixth floors. The concrete was crushed at the top and bottom of  the section and the  longitudinal  reinforcement buckled  in  several  cases.  Some  diagonal  cracking  in the  columns  from  the  third  to  the  sixth  floors and  some evidence  of hinging  at  the  column  bases  of the  ground floor were  found  in  the  longitudinal  direction.  No  sign of damage  attributable  to  the  shaking  in  the  transverse direction could be found. Due  to  the  limited  capacity  of  the  shaking  table facility,  the  specimen  had  to  be  designed  at  a  reduced 1/10  scale and  the maximum weight could not meet  the requirement  of  similarity  of artificial  mass.  Therefore, the  test  model  was  designed  according  to  the  general similitude  law  (Zhang,  1997)  that  considers  the  effect of the  short of artificial  mass. Table  1 lists  the similarity ratios based on the general  similitude  law. The specimen weighed  5.8t,  and  the  base  plate  was  2.8t.  Iron  pieces were evenly  distributed  on  each  floor  slab  to  serve as  additional  artificial  mass.  The  total  weight  of  the test  model  was  15t.  Fig.  l(a) shows  the  view  of  the specimen on the table. Figure  l(b) shows the floor plan and the arrangement of beam-column-shear wall members  of the  test model. The  cross-section  of  columns  was  50mmx80mm, 50mmx90mm,  50mmx70mm  and  50mmx60mm,  and the  cross-section  of  beams  was  40mm•  and 30mm•  The  thickness  of  the  shear-walls  was altered from 40mm  to 25mm. The  floor slab was made in thickness of 20mm  instead of 10mm  in the one-tenth scale  model.  The  unmatched  slab  thickness  was  for the  feasibility  of  reinforcement  detailing  and  for  the capacity to support the artificial mass. The base plate of the  test model was  attached firmly to  the  shaking table surface with bolts. The  specimen was  cast  using  fine  gravel  concrete and  galvanized  steel  wires.  Generally,  #8  steel  wires were  used  for columns, #10  for beams,  #12  for walls, #14  for floor slabs, and #16 used as hoops bars of beams and  columns.  Samples  of  the  concrete  and  steel  wire were  retained during  the  construction of the  specimen and were  tested  to  obtain  their mechanical  properties. Table  2  lists  the material properties of the concrete and steel wire.  The  reinforcement details of the  test model were as similar as possible with the prototype building. Construction of  the test model was executed story by story using  the  following procedures:  (1)  arranging the reinforcement; (2) molding;  (3)  concrete  casting filling vertically; (4) natural curing for three days; and (5)  de- molding. The construction  joint was  on  the  top of each of  the floor slabs. The .galvanized steel wires  in columns were extended 120mm  above the floor slab  and banded with the wires from the upper story columns for the next story  construction.  The  construction  was  completed within one month. The  test was carried out two months later. 2.2  Excitation  program The  three-directional  acceleration  records  SCT85 and  SCT95,  obtained  near  the  site  of  the  prototype building during the 1985 and 1995 Mexico earthquakes, given in Table 3, were used as the input seismic motion. The duration of SCT85  and SCT95  were compressed to 23.94s  and 27.66s,  respectively,  to achieve  the  similarity ratio S, for the shaking table test excitation. The SCT85 input  was  repeated,  increasing  the  acceleration  peak value  gradually.  This  was  done  to  study  the  dynamic response and performance of  the model in a wide range from elastic to elasto-plastic. The excitations in the series are shown in Table 4. The major excitation direction was in X  direction  to  study the  seismic performance of the RC  frames.  Before  and  after  each  seismic  excitation, white  noise  waves  at  low  peak  acceleration  were inputted, to monitor the changes in  the natural vibration characteristics of  the model. 2.3  Response measurement The responses of  the specimen during shaking were measured  using acceleration sensors  and displacement transducers.  The  points  of  the  sensors/  transducers installed are  shown  in  Fig.1.  There were  a  total  of 33 measurement points  including 31  for accelerations and 2  for  displacements.  Three  sensors  were  placed  on the  table  surface  and  every  two  floor  levels  including the  roof  to  measure  the  acceleration  response  in  the X,  Y and  Z  directions,  respectively,  and  two  sensors were mounted on  each  level of the  rest of the  floors  to detect  the  acceleration  in X  and  Y directions. The  two transducers were  installed on  the  table  surface  and  on the roof  to measure the displacements only when the X- direction vibration tests  were performed. 3  Test  results 3.1  Crack  development  and  failure  mode As the peak acceleration of  excitation  increased from 0.15g  to 0.4g (SCT85-1  to SCT85-6),  very small cracks appeared at the construction  joints of the columns from the  first  to  fourth  stories  in  the  exterior  line 44-frame, as well  as  some  cracks  at  the  end  of the X-directional beams.  During  this  stage,  only  a  slight  change  in  the natural period was found. This  indicated that the model performed basically in the elastic state. As  the amplitude of the excitation was  increased  to 0.6g  (SCT85-7  and SCT85-8)  in the  longitudinal frame direction  (X-direction),  obvious  cracks  due  to  bending and  shear  developed  at  the  ends  of many  beams  and at  the  top  of lower story columns,  and diagonal cracks appeared  in  most  beam-column  joints.  Meanwhile, small  cracks  extended  into  the  connection  area  of  the floor  slabs  with  the  transverse  beams  and  shear walls. Furthermore, concrete crushes began  at  the base  of the first-story columns. Also, fine cracks were  found at  the end of some coupling beams between the shear walls The excitation was  increased and reached the target PGA at  the  run  of SCT85-10  after  two  attempts using SCT85-8  and  SCT85-9  (see Table  4). At  this  stage,  the test  model  was  subjected  to  severe  damage  in  the X- directional frames. Diagonal shear cracks on lower-story columns and  some beam-column joints were  observed. Flexural yielding also occurred at X-directional beams in all  stories  from the first to  the sixth floor level. At the base  of the  first-story columns,  cover  concrete  spalled off,  core  concrete  crushed  and  steel  wires  buckled. This  also  happened  at  the middle-height or  top-end  of some  middle-story columns where  diagonal  or  incline cracks appeared.  As the cover concrete spalling  off, the damage to the beam-column  joints increased. In  the  final run  of the  excitation SCT95-11,  almost no further damage was found. This was attributed to the relatively low intensity of  the excitation. The  above  damage pattern  generally conformed to the observed  seismic damage to  the prototype building (Meli,  1992). 3.2  Natural  frequency  and  vibration  mode Table  5  lists  the  natural  frequencies  of  the  model measured  during  the  test.  The  natural  frequency decreased  with  the  development  of  damage  to  the model.  Under  low  excitation  up  to  0.4g  (SCT85-1- SCT85-6),  the natural  frequency only changed slightly. Apparent  changes  in  the  natural  frequency  were observed  after  the  SCT85-8  and  SCT85-9  excitations. This  confirmed  the  damage  and  the  severe  damage  to the  test model,  respectively.  Figure  2  ( where f0 (i=1, 2, 3 and 4)  denotes the  initial natural  frequency) shows the  changes  in  the  first  four  natural  frequencies  with increasing  excitation  intensity.  The  changes  in  the  first vibration mode  shape  of the  test model  (in X-direction) is shown  in Fig.3  for the cases after each excitation. The mode  shape  also  changed  gradually  as  the  excitation intensity increased. 3.3  Measured  acceleration  time  histories The  difference  between  the  target  input  and  the measurement of the  excitation  PGAs  was  noticed,  and attributed  to  the  limited  precision  of  the  shaking  table facility. The  acceleration  time  history  curves  measured on  the  roof and the 6th floor level  can be observed from Fig.4-Fig.7, which show the measured values pided by the similarity factor Sa (for comparison to  the analytical simulation). The  ratio  of peak  response  acceleration  to  the  input PGA  at  selected floor  levels  is  shown  in  Fig.  8.  The change  of  the  ratio  (peak  response  acceleration/peak ground  acceleration,  that  is,  PRA/PGA)  corresponded well with  the  observed  damage. That  is,  in  the  severely damaged X-direction,  the  ratio  of PRA/PGA  obviously was  reduced  in  the  strong  input  SCT85-10,  while  in the  Y-direction,  the  response was  almost elastic  and  the PRA/PGA ratio remained unchanged. 4  Dynamic  response of the  prototype  buiHing and  comparing  with  the  test  results To  verify  the  reliability  of  earthquake  response prediction,  a  time  history  analysis  of  the  prototype building  was  performed.  The  predicted  response was  compared  with  the  shaking  table  test  results. For  comparability,  the  earthquake  response  analysis of  the  prototype  building  used  the  input  of  the  test measurements based on the similitude ratio. The analysis was carried out by using the computer program CANNY, which  has  been  reliable  in  predicting  the  earthquake response  and  damage  of  RC  building  structures (Li  et al.,  1999).  The  program  accepts  input  from  multiple components of earthquake excitation  in  two  horizontal directions  and  in  the  vertical  direction.  It  offers many options  in  modeling  structures  for  analysis;  including various  types  of structures  using  line  elements  (beam, column,  shear wall,  cable,  truss  and  spring  element, as well as special elements such as  isolators and dampers), and  the  interactions  among  multi-axial  loads.  A  rich collection of hysteresis models available in the program makes  it  convenience  to  simulate  the  mechanical properties of structural members of concrete and metal materials in various loading conditions. 4.1 Analysis model A 3-D  frame structural model, which was based on nonlinear  moment-rotation  relationships  of  inpidual structural  members,  was  adopted  to  carry  out  the dynamic response prediction of the prototype building. The  structural members (beam, column and shear wall) were idealized as line elements, and the floor slabs were treated  as  a  rigid  diaphragm  having  three  degrees  of freedom;  that  is,  two  horizontal  translations  and  one rotation in the slab horizontal plane. Beams and columns were considered rigidly connected. Each structural node was  considered as  having  six  displacement degrees of freedom;  that  is,  three  translational  displacements  and three  rotations.  The  two  lateral  translations  of  nodes were determined by the rigid movement of  the floor slab and  the  one  rotation  of nodes  was  determined by  the rotation  in  the  slab  plane.  The mass was  concentrated at  the  structural  nodes.  The  effect of  the  gravity  load on  the  lateral displacement (P-D  effect) was  taken  into account  in  the  analysis.  Fixed  support was  assumed at the first-story column base, consistent with the boundary condition of  the shaking table test. To  account  for  the  interactions  between  the bidirectional  bending  and  the  axial  load  fluctuation  in exterior columns and  shear walls, a multi-spring model (MS  model) was  used  to  idealize  columns  and  shear walls.  Every  steel bar  in  columns and  shear walls was treated as a steel spring, and the concrete of  the element section  was  represented  by  a  fairly  large  number  of concrete springs.  The  spring  properties were based  on the material stress-strain relationships. The beam element had uniaxial bending in the frame plane  and  was  idealized  in  a  one-component rotational spring  model.  The  nonlinear  hysteresis  model  of moment-rotation  relationships had the aspects of  strength deterioration, stiffness degradation and pinching effect,  as shown in Fig.9. The columns and the shear walls had the flexural and axial deformation  idealized  by  the MS model, and were based on the material stress-strain  relationships of concrete and steel. The nonlinear shear behavior of all elements was considered  to be proportional to the  flexural stiffness  degradation.  By  this  simplification,  the  shear deformation was assumed  to be elastic. More information on the details of  the analysis models and assumptions can be found from  in Li et al.  (1999). 4.2  Input for analysis To  ensure comparability, the  input  for  the  dynamic analysis of the prototype building was  the  acceleration time history recorded on  the shaking  table surface. The acceleration values  of the  records were pided by  the similarity ratio 5.659  and the duration was  timed by the similarity ratio 7.522  (see Table 1). The observed results from the  11  shaking  table  tests were combined to  form the  input  acceleration  time  history  in  a  long  duration of 2048s  (the  acceleration X-component shown  in  Fig. 10). Therefore,  the  dynamic  analysis  could  be  carried out once to cover all  11  shaking table  tests.  In this way, the  accumulation effect of nonlinear structural  damage was  reproduced  by  the  analysis.  The  input  directions were taken as the same as the shaking table test in three components  of  two  horizontal  directions  and  vertical direction. The  input PGA for the analysis was  1.099 g / 5.659  or 0.194  g in the X-direction. 4.3  Numerical methods In  the  dynamic  analysis,  step-by-step  numerical integration  in  the  Newmark  b-method  was  employed to  solve  the  equations  of motion.  The  integration was carried  out  at  a  time  interval  of  1/200s  against  the fundamental  period  of  1.2s  of  the  prototype  building in  the  X-direction.  The  mass  and  stiffness  matrices proportional  damping  assumed  a  damping  constant  of 5%. 4.4  Comparison of calculated  and measured  results The  acceleration  response  results  measured  from the  reduced-scale model and  those  from  the  calculated responses of  the prototype building were compared over a  corresponding vibration  time period. The comparison is shown in Fig.4-Fig.7  for the model  building roof, and the 6th floor  level in the Xand Ydirections. The measured results shown in the figures  are the transformed results, that is, they were pided by the similarity factor S. The results  are  shown  in  different scales  and with  the peak response acceleration (PRA)  indicated in the figures for easy comparison. For  input  in  relatively lower peak  accelerations (up to  SCT85-6),  the analytical simulation achieved results similar  to  the  actual  tests.  That  is,  the major  response was  in  the X-direction  and  minor  in  the  Y-direction. Moreover,  the  analysis  indicated  no  cracks  under  the lower  input  up  to  SCT85-3  excitation  (PGA  0.025 g), which  agreed with  the  test  observation. The  results showed  that  the  structure  was  basically  in  the  elastic stage,  and  the  calculated  acceleration responses were close  to  the measured  results  both  in  the wave  shape and amplitude. However,  considerable  differences  could  be  seen between the calculated and the measured results during the  strong  振动台实验和动态响应地震后的钢筋混凝土建筑英文文献和中文翻译:http://www.lwfree.com/fanyi/lunwen_52376.html
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