Effect of vertical ground motions on shear demand and capacity in bridge columns.

Details

• Creators:
  Lee, Hyerin ; Kumar, Pardeep ; Gunay, Selim ; Mosalam, Khalid ; Kunnath, Sashi K.
• Corporate Creators:
  University of California, Berkeley ; University of California, Davis. Dept. of Civil and Environmental Engineering
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Columns
  • Axial loads
  • Shear strength
  • Shaking table test
  • Earthquake resistant design
  • Seismicity
  • Bridges
  • Bearing capacity
• Publication/ Report Number:
  UCD-UCB-SESM-12-01
• Resource Type:
  Tech Report
• Geographical Coverage:
  California
• Corporate Publisher:
  California. Dept. of Transportation. Division of Research and Innovation
• Abstract:
  The objective of this project was to examine the effects of axial force variation in bridge columns due to strong vertical ; ground motions and the influence of these axial force fluctuations on shear strength degradation. ; Two quarter scale specimens (SP1 and SP2) with different transverse reinforcement ratios were constructed and tested on ; the UC-Berkeley shaking table at the Richmond Field Station. As a result of an extensive numerical investigation and ; preliminary fidelity tests, the 1994 Northridge earthquake acceleration recorded at the Pacoima Dam was selected as an ; input motion for the shaking table study. The chosen ground motion was applied to the test specimens at various intensity ; levels ranging from 5% to 125% of the actual recorded motion. ; As part of the computational modeling, a new shear spring model which incorporates shear strength estimations based on ; ACI and Caltrans SDC equations is developed and implemented in the computational platform, OpenSees 28. The models ; are reasonably successful in capturing the shear-force and displacement histories measured during the tests. ; The study indicates that strong vertical excitations can induce axial tension in the column which causes marginal degradation ; of the shear strength (mainly due to the degradation of the concrete contribution to shear strength). The degradation did not ; adversely affect the performance of the column. Since the vertical frequency of bridge columns is much higher than the ; transverse or longitudinal frequency, the imposed axial tension is sustained for very short durations. ; The present study of a single column bent suggests that ignoring the concrete contribution to shear capacity when the ; column is in tension is conservative. Given the fact that the shear capacity expression in SDC is specified to deal with cases ; of sustained axial tension, attention should be paid to the use of SDC expression in cases where axial tension occurs only ; due to vertical excitation.
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• Format:
  PDF
• Funding:
  59A0688
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27017/dot_27017_DS1.pdf
• File Type:
  [PDF - 4.56 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:341a67e67f45ac8d5dc6dbb89f7255c24dcc497cb062087294deb9ccb1bc6349