Instrumented Moment Frame Steel Buildings Models Erol Kalkan, PhD California Geological Survey PEER-GMSM First Work Shop, Berkeley Oct

PEER GMSM2 Moment Frame Existing Steel Buildings  Analytical Model in Two-Dimension  6-Story Building [Burbank, CA]  13-Story Building [Los Angeles, CA]  Analytical Model in Three-Dimension  19-Story Building [Los Angeles, CA]

PEER GMSM3 6-story Instrumented Moment Frame Steel Building at Burbank, CA  Moment resisting steel frames on perimeter walls.  Designed in 1976 as per the 1973 UBC requirements

PEER GMSM4 Structural Details  The structural system is essentially symmetrical.  Moment continuity of each of the perimeter frames is interrupted at the ends where a simple shear connection is used to connect to the weak column axis. Moment resisting connection Simple hinge connection

PEER GMSM5 Analytical Modeling in OpenSEES  One half of the total building mass was applied to the frame distributed proportionally to the floor nodes.  The simulation of special features such as local connection fracture did not accounted for; consequently, the modeling of the members and connections was based on the assumption of stable hysteresis derived from a bilinear stress-strain model with 3 percent strain hardening.  The columns were assumed to be fixed at the base level.  A force-based nonlinear beam-column element that utilizes a layered ‘fiber’ section is utilized to model all components.  Centerline dimensions were used in the element modeling.

PEER GMSM6 Recorded Earthquake Data from 6-Story Building The building performed well in all these earthquakes with no visible signs of damage. Recorded data indicates an essentially elastic response in each case.

PEER GMSM7 Dynamic Characteristics of 6-Story Building Dominant Higher ModeDominant First Mode

PEER GMSM8 13-story Instrumented Moment Frame Steel Building at Los Angeles, CA  Moment resisting steel frames on perimeter walls.  Located in South San Fernando Valley.  It was built in 1975 on a design based on the 1973 UBC code designed in 1976 as per the 1973 UBC requirements

PEER GMSM9 Structural Details  The exterior frames of the building are the moment resisting frames and interior frames are for load bearing.  The foundation consists of piles, pile caps and grade beams.  The corner columns of outer frames are composed of box sections. Moment resisting connection Simple hinge connection

PEER GMSM10 Analytical Modeling in OpenSEES  One half of the total building mass was applied to the frame distributed proportionally to the floor nodes.  The simulation of special features such as local connection fracture did not accounted for; consequently, the modeling of the members and connections was based on the assumption of stable hysteresis derived from a bilinear stress-strain model with 2 percent strain hardening.  The columns were assumed to be fixed at the base level.  Raleigh damping of 5 percent for the first and third vibration modes was utilized.  A force-based nonlinear beam-column element that utilizes a layered ‘fiber’ section is utilized to model all components.  Centerline dimensions were used in the element modeling.

PEER GMSM11 Recorded Earthquake Data from 13-Story Building Approximately 12% of the connections on the west perimeter of the North-South frame fractured during the Northridge earthquake.

PEER GMSM12 19-story Instrumented Moment Frame Steel Building at Los Angeles, CA  The building was design in  Has 19 stories above ground and 4 parking levels below ground.  Instrumented in 1992 with 15 accelerometers on 5 levels in the building. Structure has 4 ductile frame along E-W and 5 X-braced frame in N-S direction.

PEER GMSM13 Structural Details  Moment resisting steel frames in the longitudinal and X-braced steel frames in the transverse direction.  The diagonal members of the cross frames are composed of built-up steel sections of two or four back-to-back angles.  Pin connections fasten the diagonal members of the cross frames to the columns.  The foundation consists of 72 ft (21.9 m) long, driven, steel I-beam piles.

PEER GMSM14 Analytical Modeling in OpenSEES  Rigid diaphragm was assumed.  Centerline dimensions were used in the element modeling.  Mass was distributed proportionally to the floor nodes.  The modeling of the members and connections was based on the assumption of stable hysteresis derived from a bilinear stress-strain model with 3 percent strain hardening.  The columns were assumed to be fixed at the base level.  Raleigh damping of 3 percent for the first and third vibration modes was utilized.  3D Model was created in OpenSEES including 19+4 stories.  Braces were modeled as truss elements.  A force-based nonlinear beam-column element that utilizes a layered ‘fiber’ section was utilized to model all beam and columns.

PEER GMSM15 Recorded Earthquake Data from 19-Story Building  After Northridge earthquake, no structural damage was reported.  A more accurate match of the recorded response was obtained with both lateral components of the earthquake applied simultaneously.

PEER GMSM16 Nonlinear Transient Analyses  The following response parameters are recorded: Peak and residual roof displacements Peak and residual interstory drift ratios Floor accelerations Beam plastic rotations (interior/exterior) Column plastic rotations (interior/exterior) Time steps of non-convergence (if exist)