SEISMIC PERFORMANCE OF REINFORCED CONCRETE FRAME by benbenzhou

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									   SEISMIC PERFORMANCE OF REINFORCED CONCRETE
FRAME BUILDINGS IN SOUTHERN CALIFORNIA DUE TO THE
       MAGNITUDE 7.8 SHAKEOUT EARTHQUAKE
               KATHRYN PHILLIPS LYNCH
                B.A. Colby College, 2005




                      A report submitted to the
                 Faculty of the Graduate School of the
              University of Colorado in partial fulfillment
                 of the requirement for the degree of
                           Master of Science
   Department of Civil, Environmental, and Architectural Engineering
                                 2009
Introduction

Evaluation of building performance during a scenario earthquake event provides
predictions of building damage, business disruption and casualties that can be used
to assess a community’s seismic vulnerability. Past seismic events, such as the 1971
San Fernando and 1994 Northridge earthquakes, demonstrated the susceptibility of
certain types of buildings in southern California to strong ground motions, including
older (nonductile) reinforced concrete (RC) structures. By combining advanced
ground motion simulations of possible earthquakes with engineering analysis of
structural performance, results can provide structural loss and vulnerability
estimates valuable to both emergency planners and building owners.

This study uses broadband ground motion simulations of the magnitude 7.8
ShakeOut earthquake, developed by Graves et al. (2008), at 735 sites along the
southern San Andreas Fault to assess the performance of reinforced concrete
buildings in the southern California region. We utilize nonlinear response
simulation models of reinforced concrete frame structures to predict building
damage, indicated by floor accelerations, interstory drift ratios, column plastic hinge
rotations, and collapses when dynamically subjected to ground motions from the
ShakeOut earthquake. A total of 20 reinforced concrete frames are analyzed,
ranging from 1 – 20 stories, and including models of both older (pre-1975) and
modern (2003) RC office buildings, typical of those found in California. The models
include both space and perimeter frame configurations. The number of buildings
considered allows for the evaluation of how factors, such as height, lateral resisting
system and reinforcement detailing, affect seismic performance, if this scenario
earthquake were to occur.

The outcome of this study provides a set of measures of building safety, relating
seismic collapse and damage resistance to seismic hazard in the Los Angeles region.
The seismic performance of older and modern buildings is examined, verifying the
need for mitigation of vulnerable nonductile RC frames. The results of this study for
each of the 735 sites are mapped to locate regions of high collapse risk. The collapse
data is combined with inventory data of nonductile RC frames (Concrete Coalition
2009) to determine an estimate of affected buildings. The ShakeOut scenario
provides an important case-study, presenting specific regional information about
possible losses associated with a vulnerable type of building. Through the
collaboration between engineers and seismologists, susceptible communities and
specific structures can be identified and deficiencies can be addressed, before the
next big earthquake.




                                                                                     1
  Ground Motion Simulations

  This study utilizes broadband ground motion simulations developed by Graves et al.
  (2008) for the U.S. Geological Survey (USGS) ShakeOut Scenario (Jones et al. 2008).
  The ShakeOut earthquake is modeled on a magnitude 7.8 earthquake occurring
  between Salton Sea and Lake Hughes, on the southernmost 200 miles of the San
  Andreas Fault. This seismic event was chosen for both the likelihood of occurrence
  and proximity to large population centers, which would enable a full-scale analysis
  of earthquake emergency preparedness in Southern California cities (Jones et al.
  2008).

  Physics-based simulations of rupture and wave propagation are used to generate
  broadband ground motion predictions at a total of 25,000 sites along the southern
  San Andreas Fault for the given rupture scenario (Graves et al. 2008). Ground
  motion intensity and frequency content depend on three first-order effects:
  magnitude of the earthquake, proximity of location to fault line and soil
  characteristics. Second-order factors include directivity and radiation pattern,
  which are determined by the orientation of the fault and rupture direction (Jones et
  al. 2008). Multiple rupture scenarios were considered in the ShakeOut scenario,
  with the south-north rupture used in this study. This situation is most likely the
  worst case for the heavily populated Los Angeles basin.

  A subset of 735 ground motions, spaced at approximately 10 km, are used to assess
  the seismic vulnerability of concrete buildings in Southern California in this study.
  The ground motion information for each site includes ground acceleration time
  history at 0.25-second time-steps in two orthogonal directions: N-S and E-W. The N-
  S and E-W components were applied to the two-dimensional analysis models
  (described below); the worst-case in the two orthogonal direction represents the
  expected damage state of the real (three-dimensional) building. Therefore, 1470
  separate ground motion components were applied to each model, with the
  controlling case analyzed at each of the 735 sites. Figure 1 (a) displays the ground
  motion sites used in the study for building analysis. The sites covered include the
  populated regions of Los Angeles, Riverside, San Diego, Orange, Ventura and Santa
  Barbara counties.

(a)                                             (b)




                                                      Legend
                                                      <VALUE>
                                                          0 - 0.5
                                                          0.5 - 0.8
                                                          0.8 - 1
                                                          1 - 1.1
                                                          1.1 - 1.2
                                                          1.2 - 1.3
                                                          > 1.3

  Figure 1. Maps of (a) Study Ground Motion Sites and (b) Sa(1sec)/MCE.



                                                                                     2
Spectral acceleration, at a period of 1 second, values are normalized by the
maximum considered earthquake (MCE) values, defined by ASCE 7-05 in Figure 1
(b), to illustrate how the intensity of the ShakeOut ground motions compare to the
MCE values used in design. MCE values in the mapped region range from 0.24 to
1.60 g. The ShakeOut earthquake produces large ground motions throughout most
of Southern California, with particularly sizeable motions along the fault line, the
Coachella Valley, and the I-10 corridor.

Analysis of ShakeOut ground motion simulations by Star et al. (2008) finds that, in
general, the intensities and variation predicted are consistent with Next Generation
Attenuation ground motion prediction equations. However, Graves et al. (2008)
determined that synthetic ground motions attenuate faster with distance from the
fault and may underestimate the variation in real ground motions for an individual
event.


Buildings Considered

Structural and Architectural Design

The focus of this study is on RC frame structures, including both modern (2003) RC
special moment-resisting frame structures and existing, so-called “nonductile”, RC
frames constructed in California before approximately 1975. In order to obtain an
accurate assessment of the seismic vulnerability of reinforced concrete structures,
models of 20 buildings were analyzed at each site, including 1, 2, 4, 8, 12 and 20-
story modern buildings and 2, 4, 8, and 12-story older structures.1 Among the 20
study buildings, both space and perimeter frame systems are considered. Each
model is based on a RC office building typical of those found in California and is
designed and detailed according to relevant building code provisions. Table I
summarizes the archetype buildings used in the study.

Table I. Design characteristics of archetype buildings used in study.
    Building     Governing Design       Number of        Lateral Frame
    Number          Provision              Stories          System
                                       2, 4, 8 and 12      Space and
      1- 8            1967 UBC
                                           stories     Perimeter Frames
                                        1, 2, 4, 8, 12     Space and
     9 - 20           2003 IBC
                                       and 20 stories Perimeter Frames




11-story nonductile RC frames are not considered because the performance characteristics of 1 and
2-story buildings should be very similar. The 1967 UBC required ductile detailing in RC structures
with heights greater than 160 feet (IBCO 1967), therefore prohibiting construction of a 20-story
building with the type of non-ductile detailing considered.



                                                                                                     3
 Modern RC frame buildings meet the requirements of ASCE 7-05, IBC 2006 and ACI
 318, including special seismic detailing (Haselton et al. 2009). Older RC frame
 buildings are designed according to the strength and detailing requirements of the
 1967 Uniform Building Code (ICBO 1967), which pre-dated major changes to design
 and detailing for RC structures in seismic regions, by Liel et al. (2009). The
 structures are intended to be broadly representative of RC buildings found in
 Southern California. Earthquake loads are assumed to dominate the lateral loads in
 design and wind load is not considered (Liel and Deierlein 2008; Haselton 2006).
 Plan and elevation views of a typical perimeter frame building design are shown in
 Figure 2. All of the structures have an 8-inch slab floor system and no torsional
 irregularities (Liel and Deierlein 2008).

 Since the entire study region lies within zone 3 of the 1967 UBC, the older RC
 structures’ design is the same at all sites considered in the assessment. The modern
 buildings were modified according to ASCE 7-05 current site-specific design
 requirements in order to present more realistic results. The original buildings were
 designed for the spectral values SDS of 1.0 g and an SD1 of 0.6 g. The site design
 values for SDS and SD1 ranged from 0.33 to 1.8 g and 0.17 to 1.1 g, respectively. This
 large range in design values indicates the need for site-specific modifications to the
 models to obtain an accurate assessment of modern RC frame performance when
 subjected to the study ground motions. In order to modify the current design and
 models of modern RC frames, the strength and stiffness of columns and beams were
 adjusted based on the ratio of the design spectral values used in the original design
 and those at each site. Modification factors differed for space and perimeter frame
 systems, and for buildings of different heights, recognizing the relative dominance of
 gravity and lateral loading for different buildings.

(a)              Lateral Resisting System
                                                       (b)



 125 ft.




                                              25 ft.

                                                        13 ft.

                                                        15 ft.
                                                                              25 ft.
                        125 ft.
 Figure 2. (a) Plan view of representative 8-story nonductile RC perimeter frame and (b) elevation of
 frame lateral resisting system. 8 and 12-story buildings have the same footprint, whereas 2 and 4-
 story buildings are larger in plan (125 ft. x 175 ft.). Space frames (not shown) have beams along
 every column line. Modern RC frame buildings have 20 ft. column spacing and floor plans of 120 ft x
 120 ft. (buildings with 8 stories and above) or 120 ft. x 180 ft. (1,2, and 4-story buildings). Source:
 Liel and Deierlein (2008)

 Older, nonductile RC frame buildings have been consistently identified as being
 particularly vulnerable to significant damage from seismic activity and may present


                                                                                                      4
a life safety hazard (e.g. Liel et al. 2009). Reinforced concrete moment frames are a
prevalent type of building construction and, among office buildings, represent a
significant investment by Southern California business owners. By applying the
ground motions to the various models, this study can show regions of collapse risk
and susceptibility were a large earthquake to occur in this region.


Nonlinear Analysis Models

This study utilizes nonlinear dynamic analysis to assess engineering demands in
each building, i.e. story drifts and floor acceleration at each site. The analysis
utilizes robust models capable of capturing the strength and stiffness deterioration
as a structure collapses under seismic loads such that collapse may be directly
simulated at sites where ground motions are very large (Liel and Deierlein 2008).
The building models are implemented in the OpenSees analysis platform, with each
structure modeled in two-dimensions (2D) and including both lateral and gravity
systems.

Each 2D model incorporates a three-bay representation of the five-bay frame
structure. Three bays is the minimum number of bays that still encompass the
behavior of both interior and exterior beams, columns and joints. The contribution
of the slab-column gravity system in perimeter frames to seismic resistance is
accounted for by adding an additional column line to the model to represent gravity
system stiffness and flexural strength. Added stiffness and flexural strength were
tuned to represent the expected increase in strength associated with the gravity
system (Haselton et al. 2008). Damage in beams, columns and joints is predicted
from element models capable of capturing material nonlinearities at large
deformations. Beams and columns are modeled using lumped plasticity elements,
with elastic beam-columns and moment-rotation plastic hinges at regions of
maximum moment. The properties of the plastic hinges have been calibrated to
experimental data by Haselton et al. (2008). Strength, stiffness, deformation
capacity and energy dissipation capacity of modeled RC members depends on
design characteristics, particularly whether the beam, column or joint is expected to
have nonductile or ductile detailing. Damage is also modeled in the joint shear
panel.

The model parameters incorporate expected rather than nominal values for
material strength and loading. To account for damping, Rayleigh damping is
utilized, with 5% damping at the first and third modes. Geometric nonlinearities are
taken into account by adding a P- column (Liel and Deierlein 2008).




                                                                                        5
Assessment Approach

Structural collapse is predicted directly from nonlinear simulation models when
dynamic instability (i.e. runaway interstory drifts) occurs. For non-collapsed
structures, peak interstory drifts, peak floor accelerations, and peak plastic hinge
rotations in beams and columns are taken as predictors of structural damage.
Building collapse can be caused by a global sidesway collapse mechanism or due to
two possible local collapse modes: loss of vertical carrying capacity (LVCC)
associated with shear failure in columns in the older RC frames or punching shear
failure in the slab-column connection of older perimeter frame buildings. Sidesway
collapse is simulated directly in the analysis models and produced by the creation of
a flexural plastic hinge in the columns or beams or shear-failure in beam-column
joints.

The modern buildings are designed to have adequate shear reinforcement, and
therefore, by design, prevent shear failure. Loss of gravity-load bearing capacity due
to column shear failure in the older buildings is based on post-processing of
dynamic analysis results, using criteria that depend on column drift, axial load and
column detailing to identify whether this failure mode has occurred (Aslani 2005;
Liel and Deierlein 2008). Lastly, since large gravity loads are transferred directly
from the slab to interior columns in nonductile perimeter frames, large drifts in the
column can lead to punching shear failure in the slab-column connection. Using
data and fragility models from Aslani (2005), it is estimated that slab-column
connections with moderate gravity loads and nonductile detailing experience
punching shear and lose vertical carrying capacity at an interstory drift of 2%
(Aslani 2005).

ASCE/SEI 41 and its 2007 supplement provide guidelines for determination of
building damage performance levels for reinforced concrete columns, defined by
column plastic hinge rotation. The performance level parameters were evaluated
for the older buildings using typical reinforcement and axial load ratios. These
limits describe damage levels in the buildings as Immediate Occupancy (IO), Life
Safety (LS), Collapse Prevention (CP), and finally Collapse (CO). These designations
help depict nonductile RC frame seismic performance. The use of robust nonlinear
analysis models and scenario-specific ground motion simulations distinguishes this
study from past studies of scenario earthquake events. Kircher et al. (2006)’s
assessment of a possible repeat of the 1906 San Francisco earthquake in the Bay
Area used HAZUS-fragility functions and ground motion intensity estimates for the
earthquake to assess seismic performance. The approach taken in this study to
assess RC frame buildings is similar to that used by Krishnan et al. in evaluating the
seismic performance of tall steel moment frame buildings in Southern California.




                                                                                     6
Results

General Results

This study assesses the vulnerability of twenty reinforced concrete frame structures
subjected to the ShakeOut earthquake, with damage and collapse characterized by
the performance of beams, columns and joints. Table II lists performance and
building attributes for the buildings considered in this study. Average values of
floor acceleration, column plastic hinge rotation and interstory drift ratios, at non-
collapsed sites for each building type convey trends in building performance and
characteristics between both older and modern buildings, and space and perimeter
frames. Additionally, the Sa Ratio is provided, which is defined as the ratio of
spectral acceleration to the spectral design value, both at one second. The Sa Ratio is
used here to quantify ground motion intensity so that buildings of different periods
can be easily compared.

Table II. Summary of Results for (a) Older and (b) Modern RC Frames
 Older Nonductile RC Frames          Collapse Results             Non-collapse Results
  Building Information              Period    Collapses    Avg. Sa                      Avg.    Avg. Floor   Avg. Column Avg. Sa
 Stories Frame ID #                  (sec) Number      %    Ratio                        IDR Acceleration (g) PHR (rad)   Ratio
    2        P    3002               0.452   57     7.76% 0.804                        0.0027     0.257        0.0012     0.187
    2        S    3001               1.08    130    17.69% 1.003                       0.0064     0.122        0.0028     0.177
    4        P    3003               0.996   111    15.10% 0.988                       0.0036     0.220        0.0012     0.194
    4        S    3004               1.98    237    32.24% 1.478                        0.014     0.126        0.0016     0.253
    8        P    3015               1.60    167    22.72% 1.622                       0.0052     0.224        0.0054     0.263
    8        S    3016               2.20    230    31.29% 1.515                        0.011     0.146        0.00092    0.254
   12        P    3022               2.10    146    19.86% 2.215                       0.0060     0.231        0.0018     0.374
   12        S    3023               2.26    205    27.89% 1.641                        0.010     0.173        0.00092    0.288
Modern RC Frames                                Collapse Results                                 Non-collapse Results
  Building Information              Period    Collapses      Avg. Sa                    Avg.    Avg. Floor   Avg. Column Avg. Sa
 Stories Frame ID #                  (sec) Number       %     Ratio                      IDR Acceleration (g) PHR (rad)   Ratio
    1        P    2069               0.42*   11      1.50%     0.96                    0.0043     0.256         0.0017    0.196
    1        S    2061               0.42*    4      0.54%     1.45                    0.0030     0.288         0.0016    0.202
    2        P    2064               0.49*    8      1.09%     1.04                    0.0035     0.318         0.0011    0.224
    2        S    1001               0.63*    8      1.09%     1.48                    0.0044     0.296         0.0020    0.260
    4        P    1003               0.96*   13      1.77%     1.52                    0.0054     0.250         0.0018    0.262
    4        S    1008               0.94*   21      2.86%     1.56                    0.0050     0.239         0.0022    0.252
    8        P    1011               1.52*   32      4.35%     2.38                    0.0076     0.239         0.0047    0.375
    8        S    1012               1.8*    73      9.93%     2.31                    0.0091     0.198         0.0049    0.363
   12        P    1013               1.82*   21      2.86%     2.76                    0.0076     0.245         0.0030    0.415
   12        S    1014               2.14*   84      11.43% 2.46                       0.0089     0.200         0.0035    0.413
   20        P    1020               2.51*   10      1.36%     4.33                    0.0074     0.262         0.0022    0.610
   20        S    1021               2.36*   48      6.53%     2.97                    0.0079     0.235         0.0019    0.498
* Modern building period values vary due to site-specific design. The periods given are at a site with S DS = 1.0g and SD1 = 0.6g




The main indicator of building collapse performance is the number of sites, out of
the 735 total, that experienced collapse for each building type. Collapse results are


                                                                                                                                    7
listed in Table II, and Figure 3 is a plot of the number of collapses versus the number
of stories for modern and older space and perimeter frames. Each older building
had significantly more collapsed sites than its modern counterpart, collapsing at, on
average, 82% more of the evaluated sites. The range of collapsed sites for older
buildings spanned from 57 to 237 and 4 to 84 for the older and modern buildings,
respectively. Additionally, Table III lists the distribution of collapse mechanisms
within the total predicted collapses for the nonductile RC frames. The results also
indicate a trend in increased collapse resistance of the perimeter over space frames.
This resistance is most likely attributed to the additional lateral resistance of the
gravity systems in perimeter frames, which are not typically included in the seismic
design, but were accounted for in these models.

Table III. Distribution of predicted collapse modes for older RC Frames
   Building Information                                                   Collapse Mechanisms
 Stories Frame       ID #                         Sidesway       Shear Local Failure  Punching Shear         Total
    2        P      3002                         47      6.39%      0        0.00%     10      1.36%    57        7.76%
    2        S      3001                        129     17.55%      1        0.14%      0      0.00%   130       17.69%
    4        P      3003                        104     14.15%      0        0.00%      7      0.95%   111       15.10%
    4        S      3004                        209     28.44%      28       3.81%      0      0.00%   237       32.24%
    8        P      3015                        135     18.37%      3        0.41%     29      3.95%   167       22.72%
    8        S      3016                        230     31.29%      0        0.00%      0      0.00%   230       31.29%
   12        P      3022                        105     14.29%      0        0.00%     41      5.58%   146       19.86%
   12        S      3023                        205     27.89%      0        0.00%      0      0.00%   205       27.89%


Looking at the non-collapse results (Table II), the modern buildings withstood
higher ground motion intensity (represented by the Sa Ratio), floor accelerations
and column plastic hinge rotation before collapse. Similarly, the average Sa Ratio
values for the collapsed sites are typically smaller for the older buildings than for
the modern structures. By using the non-collapsed parameters as indicators of
seismic performance, it is clear that in general, the perimeter frames performed
better in the study than their corresponding space frame.

                         250


                         200
   Number of Collapses




                                                                      Non-ductile RC
                         150                                          Perimeter Frames
                                                                      Non-ductile RC Space
                         100                                          Frames
                                                                      Modern RC Perimeter
                          50                                          Frames
                                                                      Modern RC Space
                           0                                          Frames
                               1   2       4      8    12   20

                                       Number of Stories

Figure 3. Plot of Number of Collapses (out of 735 possible sites) vs. Number of Stories for Modern
and Older RC Frames



                                                                                                                      8
      ArcGIS is used to examine geographic trends in the seismic vulnerability of
      buildings. Appendix I includes maps of collapse and interstory drift ratios for all 20
      study buildings, while those for the 4-story (Fig. 4) and 8-story (Fig. 5) modern and
      older space frames are shown below.

      The older (nonductile) 4-story space frame fared much worse in the ShakeOut
      earthquake than the modern 4-story structure, producing both sidesway collapse
      and local collapse due to column shear failure at sites along the length of the fault
      rupture and the Los Angeles Basin (Fig. 4 (b)). This study predicted 21 collapsed
      sites for the modern space frame, with all collapses along the fault-line, particularly
      near Palmdale, San Bernardino and the Coachella Valley (Fig. 4 (a)). Interstory drift
      ratios are indicative of building damage levels and ultimately collapse, as shown in
      Figures 4 (c) and (d). Colors indicate the level of interstory drift, with red including
      collapsed buildings.


   (a)                                                (b)



                                                          older 4-story space frame
                                                            Older 4-Story Space Frame
         Legend
                                                            Failure
         Modern 4-Story Space Frame                               No Collapse
         Failure
                                                                  Collapse
               No Collapse

               Collapse                                           Column Shear Local Failure




   (c)                                                (d)


            Modern 12-Story Space Frame                        Modern 12-Story Space Frame
                            <VALUE>                                             <VALUE>
                                0 - 0.01                                            0 - 0.01

                                0.01 - 0.02                                         0.01 - 0.02
                                0.02 - 0.03                                         0.02 - 0.03

                                0.03 - 0.04                                         0.03 - 0.04
Modern 12-Story Space Frame - 0.05
                         0.04
                                                   Modern 12-Story Space Frame- 0.05
                                                                            0.04
         <VALUE>                0.05 - 0.06                 <VALUE>                 0.05 - 0.06
              0 - 0.01          0.06 - 0.07                       0 - 0.01          0.06 - 0.07
              0.01 - 0.02       0.07 - 0.08                       0.01 - 0.02       0.07 - 0.08
              0.02 - 0.03       0.08 - 0.09                       0.02 - 0.03       0.08 - 0.09
              0.03 - 0.04       0.09 - 0.1                        0.03 - 0.04       0.09 - 0.1
              0.04 - 0.05       Collapse                          0.04 - 0.05       Collapse

      Figure 4. Seismic performance predictions for 4-story modern, (a) and (c), and older, (b) and (d),
              0.05 - 0.06

              0.06 - 0.07
                                                                  0.05 - 0.06

                                                                  0.06 - 0.07

      space frames indicated by collapses and interstory drift ratios
              0.07 - 0.08                                         0.07 - 0.08

              0.08 - 0.09                                         0.08 - 0.09

              0.09 - 0.1                                          0.09 - 0.1


      Similar observations are made for the collapse trends of the 8-story space frame
              Collapse                                            Collapse




      buildings shown below in Figure 5. The modern (ductile) 8-story space frame had
      significantly fewer collapsed sites than the older structure, which produces a similar
      collapse risk pattern to the nonductile 4-story space frame. Although the older 8-
      story building produced a similar number of total predicted collapses to that of the
      older 4-story space frame (230 and 237 collapses respectively), it exhibited no


                                                                                                           9
      column shear failures; it failed only in sidesway. It appears that the column design
      of the older 8-story space frame had relatively more shear reinforcement than the 4-
      story building due to the larger design base-shear design for the taller, more
      massive structure. This detailing prevented local shear failure in the columns and
      subsequent vertical collapse of the 8-story building. The interstory drift ratio maps
      in Figure 5 (c) and (d) once again demonstrate the correlation between building
      drift and performance. The modern 8-story space frame exhibited 12 predicted
      collapse sites in the Los Angeles Basin, along with 57 (out of 735) predicted
      collapses along most of the San Andreas Fault.


    (a)                                               (b)




          Legend                                          Legend
          Modern 4-Story Space Frame                      Modern 4-Story Space Frame
          Failure                                         Failure
                No Collapse                                      No Collapse

                Collapse                                         Collapse



    (c)                                               (d)

             Modern 12-Story Space Frame                      Modern 12-Story Space Frame
                             <VALUE>                                          <VALUE>
                                 0 - 0.01                                         0 - 0.01

                                 0.01 - 0.02                                      0.01 - 0.02
                                 0.02 - 0.03                                      0.02 - 0.03

                                 0.03 - 0.04                                      0.03 - 0.04
Modern 12-Story Space Frame - 0.05
                         0.04
                                                   Modern 12-Story Space Frame- 0.05
                                                                            0.04
          <VALUE>                0.05 - 0.06                <VALUE>               0.05 - 0.06
               0 - 0.01          0.06 - 0.07                    0 - 0.01          0.06 - 0.07
               0.01 - 0.02       0.07 - 0.08                    0.01 - 0.02       0.07 - 0.08
               0.02 - 0.03       0.08 - 0.09                    0.02 - 0.03       0.08 - 0.09
               0.03 - 0.04       0.09 - 0.1                     0.03 - 0.04       0.09 - 0.1
               0.04 - 0.05       Collapse                       0.04 - 0.05       Collapse

      Figure 5. Seismic performance predictions for 8-story modern, (a) and (c), and older, (b) and (d),
               0.05 - 0.06

               0.06 - 0.07
                                                                0.05 - 0.06

                                                                0.06 - 0.07

      space frames indicated by collapses and interstory drift ratios
               0.07 - 0.08                                      0.07 - 0.08

               0.08 - 0.09                                      0.08 - 0.09

               0.09 - 0.1                                       0.09 - 0.1

               Collapse                                         Collapse




      Modern Buildings

      The predicted performance of the modern RC frames subjected to the ShakeOut
      ground motions was far superior to that of the older, nonductile buildings. A map of
      collapse risk in Southern California, indicated by the fraction of modern buildings
      that collapsed at each site, and weighted by building height distribution, is shown
      below in Figure 6. The building distribution by height for modern buildings is
      assumed to be the same as that determined by Anagnos et al. (2008) for nonductile
      RC buildings, shown in Figure 10. The shorter RC buildings collapsed at fewer sites
      (Table II) but account for a significant proportion of inventory; 1 and 2 story
      buildings comprise approximately 47% of the buildings in Figure 10. By weighting


                                                                                                           10
collapse rates by height distribution, a reasonable map of predicted collapse risk is
presented. The colors on the map span from green to red, with red indicating that
all of the simulated modern buildings collapsed subjected to the ShakeOut scenario
earthquake at an isolated number of sites. The main regions of significant collapse
risk are located along the San Andreas Fault, mainly in areas where very few RC
buildings exist, with the exception of San Bernardino. Additionally, the area in the
East Los Angeles valley, are shown in green and yellow, designating low to moderate
collapse risk, with approximately a predicted 17 to 50% collapse rate for the
simulated buildings.




Figure 6. Map of predicted collapse risk for modern RC frame buildings with weighted fraction of
collapsed buildings at each site spanning from none (green) to all models (red).

Among the 12 modern buildings, the 8 and 12-story structures had substantially
more collapses than the other buildings, which can be explained by the
characteristics of the ground motions simulated in the Los Angeles region and the
increased resistance of the 20-story buildings. The design of 20-story buildings is
governed by the minimum base shear requirement in ASCE 7-05, which probably
increases their strength, relative to mid-height buildings. Figures 4 and 5 illustrate
an increased vulnerability to collapse in the Los Angeles region for modern RC
frames with 8 stories as opposed to 4. The results of this study indicate this trend is
generally observed in all of the modern buildings with 8 or more stories (Appendix
I). By comparing response spectra at various study sites, it is clear that the Los
Angeles basin contains an increased energy at periods greater than 1.5 seconds. The
average period of the 8-story modern buildings is 1.74 seconds, which is consistent
with the increased energy in Los Angeles for 8-story buildings and thus, number of
predicted collapses in the region. The 4-story building has an average period of 0.95


                                                                                                   11
seconds. In this study, the Los Angeles basin demonstrated an increased risk for
buildings of certain periods, which corresponded to a substantial increase in energy
content and potentially attributing to the number collapsed sites. A map of peak
ground velocity (PGV) is shown below in Figure 7. The ShakeOut earthquake
produces large peak ground velocities in both the Los Angeles basin and along the
fault, potentially attributing to collapse risk in the region (Jones et al. 2008).




Figure 7. Map of peak ground velocity produced in the ShakeOut earthquake. Source: Jones et al.
2008

Older Buildings

Historically, older nonductile reinforced concrete frames tend to be more
susceptible to collapse in strong ground motions, and this proves to be true in the
ShakeOut scenario earthquake. The results from this study can be used to depict an
overall evaluation of the collapse risk of nonductile RC frames in Southern
California. Similar to the collapse risk map for modern buildings in Figure 6, Figure
8 below shows the weighted fraction of collapsed buildings at each site, with regions
of no collapsed buildings shown in green and those with 100% (8 of 8 buildings)
collapsed in red. From the map, it is evident that the sites with the most collapses
fall along the San Andreas Fault, the Coachella Valley and in the Los Angeles basin.
Additionally, inventory data of older, pre-1980, RC buildings provided by the
Concrete Coalition (2009) are included in Figure 8. The cities shown are those for
which the Concrete Coalition has gathered inventory data on the number of pre-
1980 RC frame buildings. 1980 is used given the fact that jurisdictions adopted the
1976 UBC provisions at different times, and this year is employed to ensure that all
nonductile RC frames are considered. Reinforced concrete frames constructed
before 1980 are highly likely to include detailing indicative of nonductile design and
thus, this inventory is provided in order to relate the collapse date from this study to
actual regions of nonductile RC construction.



                                                                                                  12
For each city marked on the map (Fig. 8), the number of inventoried older RC
buildings is indicated by a blue circle, which is sized based on the number of
buildings. San Bernardino is in a region of significant collapse risk; virtually all
simulated buildings collapsed. However, there are only 5 nonductile RC buildings
located in San Bernardino. The cities of Riverside and Fullerton both demonstrate
moderate to significant collapse risk, while Santa Monica and Glendale indicate low
to moderate risk. Fullerton, Santa Monica and Glendale all contain sizable numbers
of susceptible structures, with inventory ranging from 60 to 160. Los Angeles varies
from low to significant risk, but contains a considerably larger amount of RC
structures: approximately 1500 buildings (Concrete Coalition 2009). The collapse
risk in Los Angeles is considered in more detail below (Fig. 9). The smaller cities of
Solana Beach and Calabasas show very low risk of collapse and also have the least
amount of nonductile RC frames.




Figure 8. Map of collapse results for older building models with partial inventory of older (pre-
1975) concrete buildings in Southern California. Source: Concrete Coalition (2009).



The results of this study are combined with a detailed map showing locations of
nonductile concrete buildings in Los Angeles in order to provide a comprehensive
analysis of the region. In Figure 9, a satellite map of Los Angeles with locations of
nonductile RC buildings (Anagnos et al. 2008) is shown with yellow stars marking
the location of sites from this study. Five of our study sites are included in the map,
and a graph of the weighted percentage of collapsed buildings from the scenario
simulations is shown for each site. Downtown Los Angeles and Hollywood have the
highest concentration of nonductile concrete buildings, and the sites located within
these areas had 38% and 32% collapse rates respectively, with the breakdown
between perimeter and space frames shown in Figure 9. The case study buildings
are designed to represent typical older RC frame buildings. As such, the existing


                                                                                                    13
building stock likely contains buildings that will perform better (because of
additional overstrength in the design) or worse (because of vertical or torsional
irregularities which increase collapse risk).




Figure 9. Subset of nonductile concrete buildings in Los Angeles, showing results of this study at
sites located within the region. Source: Anagnos et al., 14 WCEE (2008)



The distribution of buildings by number of stories is shown in Figure 10. The eight
study buildings are 2, 4, 8 and 12 stories and thus, represent approximately 480
(36%) of the older RC building stock.




Figure 10. Distribution of nonductile concrete buildings in Los Angeles by number of stories.
Source: Anagnos et al., 14 WCEE (2008)

In order to further quantify the performance of the older RC buildings in the
ShakeOut earthquake, each building model was evaluated by the number of sites in
each of the ASCE 41 performance levels – Immediate Occupancy (IO), Collapse
Prevention (CP), Life Safety (LS) and Collapse (CO). Updated performance-levels
defined by the ASCE/SEI 41 Supplement (ASCE 2007) were used to avoid some of
the conservatism in previous versions of limit state definitions (Elwood et al. 2007).


                                                                                                     14
These levels are defined by values of column plastic hinge rotation and vary based
on column transverse reinforcement and axial load ratios in each building. Figure
11 displays the breakdown of performance levels, in both percentage of sites and
number, by building type. For all buildings, a majority of the sites were predicted to
fall in the Immediate Occupancy performance level. A relatively smaller number of
the sites fell into either the life safety or collapse prevention limit states. The
percentages of sites in each performance level were compared to the results
predicted for older and modern 20-story steel buildings subjected to the ShakeOut
earthquake determined by Muto and Krishnan (2008). The combined percentages
of buildings in the Red-Tagged (RT) and Collapse (CO) limit states were predicted at
30 and 19.6% for the older and modern steel buildings respectively (Muto and
Krishnan 2008). The percentage of collapsed sites in this study ranged from 7.8 to
32.2% (older) and 5.4 to 11.4% (modern). These values are consistent with those
for steel buildings. The percentages of sites in the lower limit states (IO and LS)
tended to be greater for the concrete buildings than steel.

The number of buildings in the Collapse (CO) limit state, based on ASCE 41 plastic
hinge definition, can be compared to those identified to collapse in this study. The
absolute value of percent difference in number of collapsed sites predicted by
ASCE41 versus collapses found in the study ranged from 0.42% to 65.4%, with an
average of 17.5%. It is clear from the results below that the perimeter frames had
more sites within the Immediate Occupancy level and fewer collapsed sites than
space frames with the same number of stories, which is consistent with the findings
in this study.


                100%
                       64          110                      112
                90%    324 215                  208                      176
                                    49
                                      1   238         245       12 218
                80%                                          62
                                                                            6
                70%          8                  14                  10 2 45
                             74           294   91     15 5
   % of Sites




                60%
                                                                                CO
                50%
                40%    635                                                      CP
                                   575                      549
                                          464         470         505   507
                30%          438                422                             LS
                20%                                                             IO
                10%
                 0%
                       2P    2S    4P     4S    8P     8S   12P   12S   Avg.

                                           Building Type

Figure 11. Distribution of sites in each of the ASCE/SEI 41 performance levels by building type,
including the average value for each performance level.

Comparison to ShakeOut NDRC Frame Predictions

The results of this study can be compared to the initial estimates for nonductile RC
frames presented for the ShakeOut Study by Taciroglu and Khalili-Tehrani (2008).


                                                                                                   15
As a preliminary assessment of the seismic resistance of nonductile reinforced
concrete buildings subjected to the ShakeOut Scenario, their study used the
historical performance of nonductile RC frames in previous earthquakes and ran
nonlinear static pushover analyses on a model of a 5-story concrete building
containing deficiencies typical of nonductile construction (Taciroglu and Khalili-
                                                                                 Legend

Tehrani, 2008). On the basis of this analysis, the authors predict that roughly 10 –Events
                                                                                 Data$
                                                                                 Pre80ConcBldg
100 buildings in Riverside, San Bernardino, and Los Angeles counties will collapse,   2

with a slightly larger number experiencing heavy damage (red-tagged). The             3

remaining buildings will be operational, but may be damaged and require some 4 -- 5   6 60
repair. Additionally, most nonductile RC frames in Palm Springs will be at least 61 - 70
heavily damaged with a significant portion, perhaps on the order of 10%, partially - 160
                                                                                      71
                                                                                      161 - 1500
or completely collapsed (Taciroglu and Khalili-Tehrani, 2008).                   CollapseRast
                                                                                             <VALUE>
                                                                                                 0
                                                                                                 0.125
                                                                                                 0.25
                                                                                                 0.375
                                                                                                 0.5
                                                                                                 0.625
                                                                                                 0.75
                                                                                                 0.875
                                                                                                 1
                                                                                                 World Street Map




Figure 12. Predicted collapse risk from study with regions of interest for comparison to Taciroglu
and Khalili-Tehrani (2008).

These numbers are combined with the building inventory provided by the Concrete
Coalition to evaluate the predicted collapse rates determined in this study. There
are approximately 1510 nonductile buildings in L.A., Riverside and San Bernardino
(Concrete Coalition 2009). Taciroglu and Khalili-Tehrani (2008) predict a collapse
rate of 0.66 to 6.6% for older concrete structures in this region. Figure 12 exhibits a
higher incidence of collapse among the study buildings. For these three cities, the
collapse rate of the study nonductile frames range from roughly 25 to 100%,
indicating that the initial performance predictions are much lower than those found
in this report. The estimated collapses for Palm Springs appear to be more
consistent with those found in this study. Palm Springs is southeast of San
Bernardino, just south of I-10, in the Coachella Valley. From Figure 12 above, Palm
Springs is located in a region of high collapse risk; the study buildings in the area
experienced a collapse rate on the order of 50%, which is consistent with the
findings of Taciroglu and Khalili-Tehrani. The buildings analyzed in both studies
are approximated by models with design typical of nonductile construction, but the
buildings have not been tested. Therefore, we expect some real buildings to
perform better and some to perform worse; the collapse rates noted above do not


                                                                                                  16
encompass the performance of all older RC frames, but are indicative of a generally
high risk of collapse in these regions.

Conclusions

This report investigates the performance of reinforced concrete frame structures
subjected to the simulated magnitude 7.8 ShakeOut earthquake. Synthetic ground
motion time histories for 735 sites were applied to twenty nonlinear dynamic
models in order to obtain a thorough assessment of collapse risk and damage of RC
frames in southern California due to the next possible big earthquake. Results from
the study indicate that older, nonductile, RC frames are much more susceptible to
collapse than those designed to current code provisions. Although results varied
according to height and framing system, on average, the older RC buildings were
predicted to collapse at 160 of 735 sites, compared to 28 (of 735) sites for the
modern buildings. The analysis also provides insight into the relative vulnerability
of different buildings. In general, for buildings of the same height, the perimeter
frames experienced fewer predicted collapse than space frames, probably due to the
increased lateral resistance of their gravity frame systems. Also, the collapse results
indicate highest collapse risk for the mid-height range of buildings (4 and 8 stories
for older buildings and 8 and 12 stories for modern buildings) in the scenario
earthquake.

By mapping the fraction of collapsed buildings at each site, weighted by building
height distribution, regions of high seismic risk were identified for both modern and
older RC frame structures. The modern RC buildings exhibited moderate collapse
risk within the Los Angeles basin and significant collapse risk in regions along the
fault including San Bernardino and the Coachella Valley. These regions do not have
a large number of this type of structure. Predicted areas of significant seismic risk
for older RC frames extend along the entire fault line, with moderate collapse risk
projected for the cities of Riverside, Glendale, and Fullerton. For the Los Angeles
valley, collapse risk varied from low to significant, depending on the location and
the type of building.

The results from this study are based on models of older and modern reinforced
concrete office buildings, designed with typical detailing and regular plan. Thus, the
predicted collapses due to the ShakeOut ground motions are not indicative of
seismic performance for all reinforced concrete structures. Depending on the level
of detailing and configuration, real RC frames may have superior or inferior
performance than the archetype buildings used here. Furthermore, due to the large
spacing of ground motions sites (approximately 10 km), it is difficult to determine a
detailed collapse assessment of cities or focused regions. This is particularly of
interest in Los Angeles, where the collapse risk ranges widely and there is a large
inventory of nonductile RC buildings. Future work could combine collapse results
from a finer mesh of ground motions at sites spaced at two kilometers within the
Los Angeles area and the detailed building inventory to pinpoint areas of greatest



                                                                                    17
seismic concern. Computational models for building performance and ground
motion simulation are a topic of ongoing verification.

This study assesses the collapse risk of reinforced concrete buildings in southern
California subjected to the ShakeOut scenario earthquake. The results of the study
provide useful data loss estimation and emergency preparedness. Similar analysis
can be applied to different ground motion simulations and building models to both
quantify the resiliency of susceptible communities and identify priority regions and
buildings for mitigation.




                                                                                  18
References

Anagnos, T., Comerio, M. C., Goulet, C., Na, H., Steele, J., and Stewart, J. P., 2008. Los Angeles
      Inventory of Nonductile Concrete Buildings for Analysis of Seismic Collapse Risk
      Hazards. 14th World Conference on Earthquake Engineering, October 12-17, Beijing,
      China.

ASCE 7-05, 2005. Minimum Design Loads for Buildings and Other Structures. American
       Society of Civil Engineers, Reston, VA.

ASCE/SEI 41, 2007. Seismic Rehabilitation of Existing Buildings. American Society
      of Civil Engineers, Reston, VA.

Aslani, H., 2005. Probabilistic Earthquake Loss Estimation and Loss Disaggregation in
        Buildings. Ph.D. Dissertation, Department of Civil and Environmental Engineering,
        Stanford University.

Concrete Coalition. http://www.concretecoalition.org.

Elwood, K. J., Matamoros, A. B., Wallace, J. W., Lehman, D. E., Heintz, J. A., Mitchell, A. D.,
      Moore, M. A., Valley, M. T., Lowes, L. N., Comartin, C. D., and Moehle, J. P., 2007.
      Update to ASCE/SEI 41 Concrete Provisions. Earthquake Spectra 23, 493-523.

Graves, R. W., Aagaard, B. T., Hudnut, W., Star, L. M., Stewart, J. P., and Jordan, T. H., 2008.
        Broadband simulations for Mw 7.8 southern San Andreas earthquakes: Ground
        motion sensitivity to rupture speed. Geophysical Research Letters 35.

Haselton, C. B., 2006. Assessing Seismic Collapse Safety of Modern Reinforced Concrete
       Moment Frame Buildings. Ph.D. Dissertation, Department of Civil and Environmental
       Engineering, Stanford University.

Haselton, C. B., Goulet, C. A., Mitrani-Reiser, J., Beck, J. L., Deierlein, G. G., Porter, K. A.,
       Stewart, J. P., and Taciroglu, E., 2008. An Assessment to Benchmark the Seismic
       Performance of a Code-Conforming Reinforced Concrete Moment-Frame Building.
       PEER Report 2007/12.

Haselton, C. B., Liel, A. B., Deierlein, G. G., Dean, B. S., and Chou, J. , 2009 (expected). Seismic
       Collapse Safety of Reinforced Concrete Buildings: I. Assessment of Ductile Moment
       Frames. Submitted for publication in Journal of Structural Engineering 2009.

ICBO, 1967. Uniform Building Code. Pasadena, CA.

Jones, L. M., Bernknopf, R., Cox, D., Goltz, J., Hudnut, K., Mileti, D.,
        Perry, S., Ponti, D., Porter, K., Reichle, M., Seligson, H., Shoaf, K.,
        Treiman, J., and Wein, A., 2008. The ShakeOut Scenario. U.S. Geological Survey Open
        File Report 2008-1150, California Geological Survey Preliminary Report 25.




                                                                                                   19
Kircher, C. A., Seligson, H. A., Bouabid, J., and Morrow, G. C., 2006. When the
       Big One Strikes Again - Estimated Losses due to a Repeat of the 1906 San Francisco
       Earthquake. Earthquake Spectra 22, S297-S339.

Krishnan, S., Chen, J., Komatitsch, D., and Tromp, J., 2006. Performance of Two 18-Story
       Steel Moment-Frame Buildings in Southern California During Two Large Simulated
       San Andreas Earthquakes. Earthquake Spectra 22, 1035-1061.

Krishnan, S., Ji, C., Komatitsch, D., Tromp, J., Muto, M., Mitrani-Reiser, J., and Beck, J. L., 2008.
       Simulation of an 1857-like Mw 7.9 San Andreas Fault earthquake and the response
       of tall steel moment frame buildings in southern California – A prototype study. 14th
       World Conference on Earthquake Engineering, October 12-17, Beijing, China.

Liel, A. B., Haselton, C. B., Deierlein, G. G., 2009 (expected). Seismic Collapse Safety of
         Reinforced Concrete Buildings: II. Comparative Assessment of Non-Ductile and
         Ductile Moment Frames. Submitted for publication in Journal of Structural
         Engineering 2009.

Liel, A. B., and Deierlein, G. G., 2008. Assessing the Collapse Risk of California's Existing
         Reinforced Concrete Frame Structures: Metrics for Seismic Safety Decisions. Blume
         Center Report No. 164.

Muto, M., and Krishnan, S., 2008. Response of Tall Steel Buildings in Southern California to
       the Magnitude 7.8 ShakeOut Scenario Earthquake. Inaugural International
       Conference of the Engineering Mechanics Institute, May 18-21, Minneapolis, MN.

Star, L. M., Stewart, J. P., Graves, R. W., and Hudnut, K. W., 2008. Validation against NGA
         Empirical Model of Simulated Motions for M7.8 Rupture of San Andreas Fault. 14th
         World Conference on Earthquake Engineering, October 12-17, Beijing, China.

Taciroglu, E., and Khalili-Tehrani, P., 2008. M7.8 Southern San Andreas Fault Earthquake
       Scenario: Non-Ductile Reinforced Concrete Building Stock. Prepared for the U. S.
       Geological Survey, Pasadena, CA.




                                                                                                  20
Appendix I. (a) Seismic performance predictions for older buildings indicated by
collapses and interstory drift ratios




Legend

Failure                                     0 - 0.01      0.06 - 0.07

      No Collapse                           0.01 - 0.02   0.07 - 0.08

                                            0.02 - 0.03   0.08 - 0.09
      Collapse
                                            0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                            0.04 - 0.05   Collapse
      Punching Shear Local Collapse         0.05 - 0.06

Building ID: 3002 2-Story Perimeter Frame




Legend

Failure                                     0 - 0.01      0.06 - 0.07

      No Collapse                           0.01 - 0.02   0.07 - 0.08

                                            0.02 - 0.03   0.08 - 0.09
      Collapse
                                            0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                            0.04 - 0.05   Collapse
      Punching Shear Local Collapse         0.05 - 0.06

Building ID: 3001 2-Story Space Frame




Legend

Failure                                     0 - 0.01      0.06 - 0.07

      No Collapse                           0.01 - 0.02   0.07 - 0.08

                                            0.02 - 0.03   0.08 - 0.09
      Collapse
                                            0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                            0.04 - 0.05   Collapse
      Punching Shear Local Collapse         0.05 - 0.06

Building ID: 3003 4-Story Perimeter Frame




Legend

Failure                                     0 - 0.01      0.06 - 0.07

      No Collapse                           0.01 - 0.02   0.07 - 0.08

                                            0.02 - 0.03   0.08 - 0.09
      Collapse
                                            0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                            0.04 - 0.05   Collapse
      Punching Shear Local Collapse         0.05 - 0.06

Building ID: 3004 4-Story Space Frame



                                                                                   21
Legend

Failure                                      0 - 0.01      0.06 - 0.07

      No Collapse                            0.01 - 0.02   0.07 - 0.08

                                             0.02 - 0.03   0.08 - 0.09
      Collapse
                                             0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                             0.04 - 0.05   Collapse
      Punching Shear Local Collapse          0.05 - 0.06

Building ID: 3015 8-Story Perimeter Frame




Legend

Failure                                      0 - 0.01      0.06 - 0.07

      No Collapse                            0.01 - 0.02   0.07 - 0.08

                                             0.02 - 0.03   0.08 - 0.09
      Collapse
                                             0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                             0.04 - 0.05   Collapse
      Punching Shear Local Collapse          0.05 - 0.06

Building ID: 3016 8-Story Space Frame




Legend

Failure                                      0 - 0.01      0.06 - 0.07

      No Collapse                            0.01 - 0.02   0.07 - 0.08

                                             0.02 - 0.03   0.08 - 0.09
      Collapse
                                             0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                             0.04 - 0.05   Collapse
      Punching Shear Local Collapse          0.05 - 0.06

Building ID: 3022 12-Story Perimeter Frame




Legend

Failure                                      0 - 0.01      0.06 - 0.07

      No Collapse                            0.01 - 0.02   0.07 - 0.08

                                             0.02 - 0.03   0.08 - 0.09
      Collapse
                                             0.03 - 0.04   0.09 - 0.1
      Loss of Vertical Carrying Capacity
                                             0.04 - 0.05   Collapse
      Punching Shear Local Collapse          0.05 - 0.06

Building ID: 3023 12-Story Space Frame




                                                                         22
 (b) Seismic performance predictions for modern buildings indicated by collapses
 and interstory drift ratios




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

                                             0.03 - 0.04   0.09 - 0.1
     No Collapse
                                             0.04 - 0.05   Collapse

     Collapse                                0.05 - 0.06

 Building ID: 2069 1-Story Perimeter Frame




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 2061 1-Story Space Frame




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 2064 2-Story Perimeter Frame




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 1001 2-Story Space Frame



                                                                                   23
                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 1003 4-Story Perimeter




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 1008 4-Story Space Frame




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 1011 8-Story Perimeter Frame




                                             0 - 0.01      0.06 - 0.07

                                             0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame               0.02 - 0.03   0.08 - 0.09

     No Collapse                             0.03 - 0.04   0.09 - 0.1

                                             0.04 - 0.05   Collapse
     Collapse                                0.05 - 0.06

 Building ID: 1012 8-Story Space Frame




                                                                         24
                                              0 - 0.01      0.06 - 0.07

                                              0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame                0.02 - 0.03   0.08 - 0.09

     No Collapse                              0.03 - 0.04   0.09 - 0.1

                                              0.04 - 0.05   Collapse
     Collapse                                 0.05 - 0.06

 Building ID: 1013 12-Story Perimeter Frame




                                              0 - 0.01      0.06 - 0.07

                                              0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame                0.02 - 0.03   0.08 - 0.09

     No Collapse                              0.03 - 0.04   0.09 - 0.1

                                              0.04 - 0.05   Collapse
     Collapse                                 0.05 - 0.06

 Building ID: 1014 12-Story Space Frame




                                              0 - 0.01      0.06 - 0.07

                                              0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame                0.02 - 0.03   0.08 - 0.09

     No Collapse                              0.03 - 0.04   0.09 - 0.1

                                              0.04 - 0.05   Collapse
     Collapse                                 0.05 - 0.06

 Building ID: 1020 20-Story Perimeter Frame




                                              0 - 0.01      0.06 - 0.07

                                              0.01 - 0.02   0.07 - 0.08
Modern 1-Story Perimeter Frame                0.02 - 0.03   0.08 - 0.09

     No Collapse                              0.03 - 0.04   0.09 - 0.1

                                              0.04 - 0.05   Collapse
     Collapse                                 0.05 - 0.06

 Building ID: 1021 20-Story Space Frame




                                                                          25

								
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