Development of a Real-Time Test Method for Structures
Application of Pushover Analysis to the Design of Structures Containing Dissipative Elements Martin S. Williams1 and Denis E. Clment2 University of Oxford, UK 2 Thomas Jundt Civil Engineers, Geneva, Switzerland 1 13th World Conference on Earthquake Engineering Vancouver, August 2004 Outline Introduction to knee braced frames Modelling using Drain-2DX Five and ten-storey frame designs Pushover and time-history analyses Results Conclusions and future work Introduction to knee braced frames (KBFs) Seismic energy dissipated through hysteresis of short, replaceable knee elements: Cross brace Knee element Knee elements can be designed to: Yield early, maximizing protection to main frame Yield in web shear rather than flexure Remain stable under large non-linear excursions Modelling a knee element using Drain-2DX An assemblage of standard truss and beam elements was used to represent observed shear, flexural and axial behaviour:
Short cantilever shear stiffness Brace Brace Connecting bracket Knee element Connection stiffness Rigid offset Truss element axial stiffness Beam element flexural stiffness Hysteresis response of model Element properties chosen semi-empirically Comparison with full-scale cyclic test data: 600 Force (kN) 300 0 -300 Physical test Drain-2DX -600 -20 -10 0 Deflection (mm) 10
20 Frame designs Designed to EC8, PGA = 0.35g Five-storey frame designed as KBF: Ten-storey frame designed as ductile MRF, then retrofitted: PLAN: PLAN: Knee braced bay 5.2m ELEVATION: 5.2m ELEVATION: 5.2m 6m 6m 6m Pushover analysis EC 8: F modal and uniform load patterns simplify pushover curve to elastic-perfectly plastic d FEMA 356:
other load patterns (e.g. adaptive) permitted, but not used here simplify to bi-linear with post-yield stiffness equal to initial stiffness ATC 40: capacity spectrum method Modal pushover (Chopra and Goel, 2002): combine results of pushovers using first few modal load patterns F d Time history analyses 30 time-histories generated using SIMQKE Compatible with EC8 Type 1 spectrum, soil type C Analysed using DRAIN-2DX (Newmark implicit integration scheme) Comparison with EC8 spectrum, TH1-5 Typical EC8 spectrum-compatible time history 3 0.5 0 -0.5 -1 0 5 10 15 20 Acceleration (g)
Accn (g) 1 EC8 TH1 TH2 2 TH3 TH4 TH5 1 Time (s) 0 0 1 2 Period (s) 3 Pushover curves Results shown for 5-storey frame Post-yield stiffness ~16% of elastic stiffness As a result, EC8 under-estimates initial stiffness Modal load pattern 1500 Uniform load pattern 1500 1000 1000
10-storey MRF FEMA Uniform ATC Modal ATC Uniform Multi-modal 5-storey KBF 0.8 1 1.2 1.4 1.6 Roof disp from pushover Mean roof disp from TH analyses 1.8 Element yielding In 5-storey frame, all knee elements yielded and all main elements remained elastic under design earthquake In 10-storey retrofitted frame, limited plasticity occurred in main frame under design earthquake e.g. 5-storey frame - EC8 pushover analysis under modal loading: 0.15g 0.35g Yielded knee element 0.5g Plastic hinge Element yielding 5-storey frame EC8 pushover analysis under uniform loading: 0.15g
0.35g Yielded knee element 0.5g Plastic hinge Time history analyses: first knee element yield at around 0.08g no hinges in main frame elements below 0.56g Inter-storey drifts under design earthquake 5-storey KBF EC 8 FEMA 356 ATC 40 5 5 5 4 4 4 3 3 3 2 2 2
1 1 1 0 0 0 0.5 1 Storey drift (%) 0 0 0.5 Storey drift (%) 1 0 0.5 Storey drift (%) Time history analysis: Mean Mean +/- st. dev. Pushover analysis: Uniform Modal
1 Drift (%) Time history analysis: Mean Mean +/- st. dev. Pushover analysis: Uniform Modal 2 Conclusions A Drain-2DX knee element model capable of representing shear, flexural and axial behaviour has been developed and validated. Pushover analyses of 5 and10-storey knee braced frames showed that they possess high ductility (~6) and post-yield stiffness (~16%). In time-history analyses, knee elements began to yield at just 0.08g but remained stable up to 0.56g. Use of pushover analysis does not necessarily lead to optimal design. Multi-modal pushover offers some advantages in this respect. In comparison with time-history analyses, FEMA 356 pushover approach gave most consistent results, EC8 approach appears highly conservative for this type of structure.
This presentation is solely for viewing. No part of it may be circulated, quoted, or reproduced for distribution without prior written approval from BHARAT Financial Inclusion Limited. BFIL's . lowest interest . rate benefits 50 . lakh . women ....
5.2 Congruent Polygons. What We Will Learn. Identify and use corresponding parts. Use Third Angles Thm. Needed Vocab. Corresponding parts: same location on different polygons. Ex. 1 Identifying Corresponding Parts. Write congruence statement for the triangle and the corresponding parts.
Queen Elizabeth I. Julius Caesar Similar to Elizabethan England. Her reign was drawing to a close and she did not have any successors to throne. People were concerned about peaceful transition of power because there were threats of rebellion.
Low-level structure. The bulk of the algorithm lies in general subroutines such as graph connectivity. Implementation of the triconnectivity algorithm was greatly assisted by reuse of a library developed during earlier work on biconnectivity (PMAM '12).
Research Team: Eileen Baldry, Melissa Clarence, Leanne Dowse and Phillip Snoyman ARC Linkage Project * PD Conf 2010 * * People with mental health disorders and cognitive disabilities (MHDCD) are over-represented across the criminal justice system (CJS). Over 40 000...
Acid-Base Behavior and Chemical Structure Factors That Affect Acid Strength Consider H-X. For this substance to be an acid we need: H-X bond to be polar with H + and X - (if X is a metal then the bond...
Contact your CUPE Local for support. If incidents of workplace violence continue to happen, keep reporting every incident (even several times a day!)Remember you have a right to refuse unsafe work! 2. Parent/Community to Staff ... Violence in the workplace...
USPOSTAVA REGIONALNIH CENTARA KOMPETENTNOSTI ZA STRUKOVNO OBRAZOVANJE U TURIZMU I UGOSTITELJSTVU. Ministarstvo znanosti i obrazovanja je objavilo Javni poziv osnivačima za kandidiranje ustanova za strukovno obrazovanje za imenovanje regionalnim centrima kompetentnosti
Ready to download the document? Go ahead and hit continue!