SEISMIC PERFORMANCE OF REINFORCED CONCRETE FRAME BUILDINGS IN SOUTHERN by nrg44159

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									                        SEISMIC PERFORMANCE OF REINFORCED CONCRETE FRAME BUILDINGS IN SOUTHERN CALIFORNIA IN THE
                                             MAGNITUDE 7.8 SHAKEOUT SCENARIO EARTHQUAKE
                                                                                                                               Abbie B. Liel, Kathryn P. Lynch, Kristen Rowe
                                                                                                         Dept. of Civil, Environmental, and Architectural Engineering, University of Colorado




                                                                     OBJECTIVE                                                                                                                                                                                                                                                                                                          SIMULATION RESULTS

To evaluate the performance and safety of reinforced concrete (RC) frame                                                                                                                                                                                                                                                                                                                                      Nonductile RC Frame Buildings
structures in Southern California due to the Magnitude 7.8 Shakeout scenario
earthquake.                                                                                                                                                 Older Nonductile RC Frames
                                                                                                                                                             Building Information Period
                                                                                                                                                                                                                       Collapse Results
                                                                                                                                                                                                                      No. of                                   Avg.
                                                                                                                                                                                                                                                                                               Non-Collapse Results
                                                                                                                                                                                                                                                                                              Avg. Floor Avg. Column
                                                                                                                                                                                                                                Sacol(T1)/                                                                           Sacol(T1)/
                                                                                                                                                                                                                                                                                             Acceleration
                                                                                                                                                             Stories Frame                      ID #           (sec) Collapses SD(T1)                                    IDR                               PHR (rad)  SD(T1)
                                                                                                                                                                                                                                                                                                  (g)
                                                                                                                                                                          4     Perimeter 3003                   1.0            104       0.99           0.004                                   0.22        0.0012    0.195
                                                                                                                                                                          4       Space 3004                     2.0            245       1.5            0.012                                   0.12        0.0031    0.240
                                                                                                                                                                          8       Space 3016                     2.2            190       2.0            0.014                                   0.15        0.0014    0.340
                                                            RESEARCH APPROACH                                                                                                                                                                                                                                                                              <VALUE>
                                                                                                                                                                                                                                                                                                                                                             0.00 - 0.012                                         0.00 - 0.021                                      0 .00 - 0.0 12
                                                                                                                                                                                                                                                                                                                                                             0.012 - 0.024
                                                                                                                                                            Modern RC Frames                                           Collapse Results                                                        Non-Collapse Results                                          0.024 - 0.036
                                                                                                                                                                                                                                                                                                                                                                                                                  0.021 - 0.024
                                                                                                                                                                                                                                                                                                                                                                                                                  0.024 - 0.036
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    0 .01 2 - 0. 02 4
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    0 .02 4 - 0. 03 6
                                                                                                                                                                                                                                                                                                                                                             0.036 - 0.048
                                                                                                                                                             Building Information                            Period   No. of                                   Avg.                           Avg. Floor Avg. Column                                         0.048 - 0.06
                                                                                                                                                                                                                                                                                                                                                                                                                  0.036 - 0.048                                     0 .03 6 - 0. 04 8


                                                                                                                                                                                                                                Sacol(T1)/                                                                           Sacol(T1)/                              0.06 - 0.072
                                                                                                                                                                                                                                                                                                                                                                                                                  0.048 - 0.06                                      0 .04 8 - 0. 06


                                                                                                                                                                                                                                                                                             Acceleration                                                    0.072 - 0.084
                                                                                                                                                                                                                                                                                                                                                                                                                  0.06 - 0.072                                      0 .06 - 0.0 72


                                                                                                                                                             Stories Frame                      ID #           (sec) Collapses SD(T1)                                    IDR                               PHR (rad)  SD(T1)                                 0.084 - 0.096
                                                                                                                                                                                                                                                                                                                                                                                                                  0.072 - 0.084                                     0 .07 2 - 0. 08 4
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    0 .08 4 - 0. 09 6


•Ground Motions: Broadband ground motion simulations developed by researchers at                                                                                          4     Perimeter 1003                0.96*              13       2.0            0.005
                                                                                                                                                                                                                                                                                                  (g)
                                                                                                                                                                                                                                                                                                 0.25        0.0018    0.420
                                                                                                                                                                                                                                                                                                                                                             0.096 - 0.108
                                                                                                                                                                                                                                                                                                                                                             0.108 - 0.12
                                                                                                                                                                                                                                                                                                                                                                                                                  0.084 - 0.096
                                                                                                                                                                                                                                                                                                                                                                                                                  0.096 - 0.108
                                                                                                                                                                                                                                                                                                                                                                                                                  0.108 - 0.12
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    0 .09 6 - 0. 10 8
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    0 .10 8 - 0. 12




SCEC (Graves et al. 2008) for more than 700 evenly-spaced sites in Southern California                                                                                    4       Space 1008                  0.94*              21       1.9            0.005                                   0.24        0.0022    0.414
                                                                                                                                                                          8       Space 1012                   1.8*              73       3.0            0.009                                   0.20        0.0049    0.623
                                                                                                                                                            * Modern building period values vary due to site-specific design

•Buildings: 1 to 20-story modern and older RC frame buildings, which are representative
of RC office buildings commonly found in California                                                                                                                            250                                                                                                 9




                                                                                                                                                                                                                                                 Normalized Specral Acceleration
                                                                                                                                                                                                                                                                                   8




                                                                                                                                                              # of Collapses
                                                                                                                                                                               200                                                                                                 7
                                                                                                                                                                                                                                                                                         Max
                                                                                                                                                                                                                                                                                                                            ND 4-S

                                                                                                                                                                               150                                              Non-ductile                                        6                                        ND 4-P

•   Analysis Models: Nonlinear building models created in OpenSees                                                                                                                                                              RC Frames                                          5
                                                                                                                                                                                                                                                                                                                            ND 8-S

                                                                                                                                                                               100                                                                                                                                          M 4-S
                                                                                                                                                                                                                                Modern RC                                          4
                                                                                                                                                                                                                                                                                                                            M 4-P
                                                                                                                                                                               50                                               Frames                                             3                                        M 8-S

•Seismic Response: Predicted for each building at each site. Structural collapse is                                                                                             0
                                                                                                                                                                                                                                                                                   2
                                                                                                                                                                                                                                                                                       Avg
                                                                                                                                                                                                                                                                                                                            Average

                                                                                                                                                                                                                                                                                   1
predicted directly from nonlinear simulation models when dynamic instability occurs.                                                                                                 4s           4p           8s                                                                  0
                                                                                                                                                                                                                                                                                             Min
                                                                                                                                                                                                                                                                                                                                                                Non-Collapsed                                         Non-Collapsed
                                                                                                                                                                                                                                                                                                                                                                                                                                                                       Non- Collapsed

                                                                                                                                                                                                                                                                                                                                                                                                                                                                       Collapsed
                                                                                                                                                                                                                                                                                                                                                                Collapsed                                             Collapsed

Peak interstory drifts, floor accelerations, and plastic hinge rotations in beams and                                                                                   Collapse Performance of Simulation                                                                         Spectral Values at Which Collapse
columns are taken as measures of structural damage.                                                                                                                          Buildings (out of 736 sites)                                                                             Occurred normalized by SDT1                                                                                          Modern (Ductile) RC Frame Buildings
                                                                                                                                                                                                                               COLLAPSED BUILDINGS

                           Approximately 700 Sites                                    20 RC Frame Structures                                                 • On average, collapse occurred at 178 (24%) of the sites for
                                                                                                                                                             nonductile (pre-1976) RC frames, while collapse occurred at an
                                                                                                                                                             average of only 36 (4.8%) ductile (modern) building sites.
                                                                                                                                                             • The collapses predicted for modern frames are along the San                                                                                                                                      0.00 - 0.012                                     <VALUE>
                                                                                                                                                                                                                                                                                                                                                                                                                   0.00 - 0.012
                                                                                                                                                                                                                                                                                                                                                                0.012 - 0.024

                                                                                                                                                             Andreas Fault. This area is unlikely to contain the types of RC                                                                                                                                    0.024 - 0.036
                                                                                                                                                                                                                                                                                                                                                                0.036 - 0.048
                                                                                                                                                                                                                                                                                                                                                                                                                   0.012 - 0.024
                                                                                                                                                                                                                                                                                                                                                                                                                   0.024 - 0.036
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 0 - 0.01 2
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 12 - 0 .0 24
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 24 - 0 .0 36
                                                                                                                                                                                                                                                                                                                                                                                                                   0.036 - 0.048                                   0.0 36 - 0 .0 48
                                                                                                                                                             buildings in this study.                                                                                                                                                                           0.048 - 0.06
                                                                                                                                                                                                                                                                                                                                                                0.06 - 0.072
                                                                                                                                                                                                                                                                                                                                                                0.072 - 0.084
                                                                                                                                                                                                                                                                                                                                                                                                                   0.048 - 0.06
                                                                                                                                                                                                                                                                                                                                                                                                                   0.06 - 0.072
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 48 - 0 .0 6
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 6 - 0.07 2
                                                                                                                                                                                                                                                                                                                                                                                                                   0.072 - 0.084
                                                                                                                                                             • The older, nonductile buildings produced collapses mainly in                                                                                                                                     0.084 - 0.096
                                                                                                                                                                                                                                                                                                                                                                0.096 - 0.108
                                                                                                                                                                                                                                                                                                                                                                                                                   0.084 - 0.096
                                                                                                                                                                                                                                                                                                                                                                                                                   0.096 - 0.108
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 72 - 0 .0 84
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 84 - 0 .0 96
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.0 96 - 0 .1 08


                                                                                                                                                             the areas between los Angeles and Long Beach, the I-10
                                                                                                                                                                                                                                                                                                                                                                0.108 - 0.12                                       0.108 - 0.12                                    0.1 08 - 0 .1 2




                                                                                                                                                             corridor from east L.A. to San Bernardino, and along the San
                                                                                                                                                             Andreas Fault.
             Source: Graves                                                                                                                                  • The modern buildings collapsed at an average spectral
             et al. (2008)                                                                                  Structural Response                              acceleration of 2.3 times SD(T1 ). The older buildings collapsed
                                                                                                                                                             at an average Sa of 1.5 times SD(T1).

                                                                              Input Ground
                                                                                 Motions                                                                                                        DAMAGED (NON-COLLAPSED) BUILDINGS

                                                                                                                                                             • Average Interstory Drift Ratio: Nonductile 0.01, Modern 0.007.                                                                                                                                    Non-Collapsed                                      N on-Coll apsed
                                                                                                                                                                                                                                                                                                                                                                                                                    C ollap sed
                                                                                                                                                                                                                                                                                                                                                                                                                                                                         Non-Col lapsed
                                                                                                                                                                                                                                                                                                                                                                                                                                                                         Coll apsed
                                                                                                                                                                                                                                                                                                                                                                 Collapsed

                                                                                                                                                             These IDRs represent slight-to-negligible damage.
                                                                                                                                                                                                                                                                                                                                                                                 4-Story Space Frame                                  4-Story Perimeter Frame                             8-Story Space Frame
                                                                                                                                                             • Average Floor Acceleration: Nonductile 0.16g, Modern 0.23g.
       Nonlinear Analysis Model
                                                                                                                                                                                                                                                                                                                                                                      Maps of Interstory Drift Ratio Variation (top) and Collapse Sites (bottom) for each Simulation Building


    Santa Monica                 Glendale                   Los Angeles
    • Low /moderate              • Low /moderate            - Low to significant              PERFORMANCE OF NONDUCTILE REINFORCED CONCRETE BUILDINGS                                                                                                                                                           Case study buildings represent                                                                                                       FUTURE WORK
                                 collapse risk              collapse risk                                                                                                                                                                                                                                      approximately 100 4-story and 30
    collapse risk
                                                                                                                                                                                                                                                                                                                 8-story NDRC buildings in LA
    • Max. I DR: 0.03 – 0.04     • Max. I DR: 0.02 – 0.06   - Max. I DR: 0.02 – 0.1

                                                                       San Bernardino                                                                                                                  Nonductile Concrete Building
                                                                                                                                                                                                                                                                                                                       Future work to reflect approx.
                                                                                                                                                                                                                                                                                                                       275 2-storyNDRC buildings and
                                                                                                                                                                                                                                                                                                                                                                                           • Buildings: Complete simulations for 1, 12, and 20 story modern RC frames and 2 and
                                                                       - Significant collapse risk
                                                                       - Max. I DR approx. 0.08 – 0.1
                                                                                                                                                                                                       Performance Predicted from                                                                                     60 12-story NDRC buildings in LA
                                                                                                                                                                                                                                                                                                                                                                                           12-story nonductile RC frames.
                                                                                                                                                                                                               Simulations:
                                                                       Riverside                                                                                                                        4-Story (1 of 2) Collapsed                                                                                                                                                         • Simulations: Conduct simulations for a set of closer spaced sites in the Los Angeles
                                                                       • Moderate/significant                                                                                                              8-Story No Collapse
         Approx. Number of                                             collapse risk                                                                                                                                                                                                                                                                                                       and San Fernando valley regions.
            Nonductile                                                                                                                                                                                   4-Story (1 of 2) Collapsed
         Concrete Buildings
                                                                       • Max. I DR: 0.03 – 0.1
                                                                                                                                                                                                              8-Story Collapsed                                                                                                                                                            • ASCE-41: Predict exceedance of ASCE-41 Limit-State Criteria in nonductile RC
                                                                       Fullerton
              2
              3
                                                                       •Moderate/significant                                                                                                                                                                                                            Source: Concrete              Buildings designed
                                                                                                                                                                                                                                                                                                                                                                                           frames at simulation sites.
              4-5                                                      collapse risk                                                                                                                                                                                                                     Coalition (2009)             according to 1967
              6 - 60                                                   • Max. I DR: 0.07 – 0.1 4-Story No Collapse                                                                                           4-Story No Collapse                                                                                                       Uniform Building
                                                                                                                                                                                                             8-Story No Collapse                                                                                                             Code
              61 - 70
                                                                                                8-Story No Collapse
                                                                       Calabasas
              70- 160
                                                                       • Low collapse risk
              161- 1500
                                                                       • Max. I DR: approx. 0.03                                                                                                                                                                                                                                                                                                                                              ACKNOWLEDGEMENTS
                                                                                                                                                                                                     4-Story Collapsed
               Partial inventory of older                                                                             Subset of Nonductile Concrete Buildings
                                                                                                                                                                                                     8-Story Collapsed
                                                                                                                                                                                                                                                                                                                                                                                           This project is supported by the Southern California Earthquake Center. Rob Graves (URS)
     (Pre-1980) Concrete Buildings in Southern                                                                                    in Los Angeles                                                                                                                                                                                                                                           provided ground motion simulations for the ShakeOut Scenario Earthquake. Thanks to Christine
    California with Summary of Simulation Results
                                                                                                                                                                                                                                                                                                                                                                                           Goulet (URS) and Craig Comartin for Concrete Coalition data. Modern RC models were
              for 4 and 8-Story Buildings                                                                                   Source: Anagnos et al.,14 WCEE (2008)
                                                                                                                                                                                                                                                                                             Distribution of 1800 Nonductile Concrete                                                      provided by Curt Haselton (CSU Chico).
                          Source: Concrete Coalition (2009)                                                                                                                                                                                                                                           Buildings in Los Angeles

								
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