Seismic Behavior, Analysis and

Transcription

1 UNIVERSITY of ILLINOIS NEES Small-Group Research Project: Seismic Behavior, Analysis and Design of Complex Wall Systems (NSF Grant CMMI ) Laura Lowes, Dawn Lehman, Jake Turgeon, Anna Birely, Joshua Pugh, UW Dan Kuchma, Chris Hart, Ken Marley, UIUC

2 Research Objective Establish the seismic performance of modern reinforced concrete walls and develop the response and damage-prediction models required to advance performancebased design of these systems Photo courtesy of MKA Seattle

3 Research Activities to Date Experimental testing: Testing of four planar walls completed in 2008 Testing of a planar coupled wall completed Jan Testing of three c shaped walls to be completed dby April 2012 Simulation: development, calibration and evaluation of Elastic, effective stiffness models Fiber type beam column models w/ and w/o flexure shear interaction Two and three dimensional continuum models Performance prediction models: Development of data relating damage and demand Development of fragility functions for walls

4 Experimental Test Program Prototype structure Experimental test matrix Core Wall under Construction (Courtesy of MKA, Seattle)

5 Experimental Testing of a Coupled Wall

6 Objective: To investigate the seismic behavior of a modern coupled wall Background Numerous tests of coupling beams with different reinforcement layouts, ratios and confinement details. Only seven (7) coupled wall tests found in the literature. Previously tested coupled wall test specimens are not representative of current design practices. Specimen Design Review inventory of modern coupled walled buildings to establish typical configuration and design details (17 buildings with coupled core wall systems designed for construction in CA or WA in last 10 years). Basic geometry and strength th is consistent twith planar walls tested t as part of the project. Design coupled walls following the recommendations of the IBC Seismic Design Manual Vol. III, using ASCE 7 05, and meeting requirements of ACI The progression of yielding and failure mechanism for the initial design was evaluated via continuum finite element analysis using VecTor2. The initial design was revised (increased coupling beam flexibility and wall long. reinforcement ratio) to ensure yielding of coupling beams and wall piers.

7 Coupled Wall Specimen (1/3 scale) 120 in. 48 in. 24 in. Boundary Element long = 3.7% trans = 1.6% 6 in. thick. 12 in.(typ.) 48 in. Web long = 0.27% horz = 0.27% 0.54% 48 in. 156 in. 48 in. Coupling beams: aspect ratio = 2.0 diag = 1.3% V n = 6.2 f A c g confinement per ACI in.

8 Testing of the Coupled dwlls Wall Specimen F z,total M y,total x,f x,total

9 Loading Protocol

10 Validation of the Loading Protocol Compare simulated response of 10 story prototype and 3 story laboratory test specimen 3 rd story load versus displacement response prototype specimen

11 Validation of the Loading Protocol Compare simulated response of 10 story prototype and 3 story laboratory test specimen Principal concrete compressive strain field at 0.75 in. lateral displacement bottom 3 stories of 10-story prototype 3-story test specimen

12 Force/Disp. Control History Force Control Load Steps Base Moment [ kip-ft ] Target Disp Base Shear [ kips ] Target Forces 10 0kips 20 0kips % % % % % % % 225% Drift History t [ in ] Disp. Control ] 3 rd Story Displacement rd Story Drift [ % kips 20 kips 0.128% 0.192% 0.321% 0.50% 0.75% 1.00% 1.50% 2.25% -2.5

13 Coupled Wall Performance

14 Response: Force versus Displacement Base Shea ar [ kips ] rd Story Drift [ % ]

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17 Wall Piers: +/ 2.27% failure sequence -2.20% -2.27% -2.00% -2.10% 1.80% 2.00% 2.20% 2.27%

18 Wall Piers: Out of plane displacement W WP Failure E WP Failure

19 CB: +/ 2.27% Drift All coupling beams exhibited moderate damage Spalling at beam ends Wide cracks at beam ends Max crack width > i in. (CB2) Shear crack < 1/16 in. No sliding CB3 CB1 CB2

20 Following Loss of Lateral Strength: Axial Load Test

21 Data Analysis: Can explain the performance? How do we predict the observed performance?

22 Instrumentation String pots: measure global displacements (38) Linear pots: measure relative displacements (84) Strain gauges: reinforcement and concrete (200) Krypton: LED targets track displacement (128) Photogrammetric: camera track disp. (158) LVDT: measure relative disp. at base (4) Inclinometers: measure rotations at a point (8)

23 Instrumentation: t ti Photogrammetric t Still camera & MATLAB Metris (Krypton)

24 Metris Data: Strain Fields Prior to Failure Max. comp. strain Coupled wall test: (2.0% drift) Max. shear strain Planar wall test: (1.0% drift cycle) cle)

25 Strain Gauge Data: Yielding at 2.25% 25% Gauges Yielded in Tension Gauges Yielded in Compression

26 Deformation Mechanisms 3 rd floor shear 2 nd floor shear 1 st floor shear 3 rd floor flexural 2 nd floor flexural 1 st floor flexural Base rotation Base slip West Pier - Tension East Pier - Compression

27 Wall Pier Demands N.A. depth determined from strain gauge data. Axial forces at the base of the wall piers determined from coupling beam shears. Coupling beams assumed to have zero axial lload. Concrete areas: Gross, compression region w/ cover, compression region w/o cover Demands West Pier East Pier (W ) (E+) 19.3 in in. 48 in kip 617 kip core 95.5 kip kip

28 Coupling Beams: Demands and Performance CB1 CB2 CB3

29 Conclusions Brittle, compressive failure at 2.27% drift. Design and evaluation need to consider local demands in wall pier compression regions. Coupling beams experienced rotation demands of ~4% and performed well.

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