Improved drift assessment approach for steel moment frames under realistic earthquake loading

Improved Drift Assessment Approach for
Steel Moment Frames under
Realistic Earthquake Loading
BORJAN PETRESKI, MIHAIL GAREVSKI
OPENSEES DAYS EUROPE 2017,
1ST EUROPEAN CONFERENCE ON OPENSEES,
PORTO, PORTUGAL, 19–20 JUNE 2017
University of Ss. Cyril and Methodius - Skopje
Institute of Earthquake Engineering and
Engineering Seismology - IZIIS

Eurocode Steel Structural
Types
Concentrically Braced Frames Eccentrically Braced Frames
OpenSees Days Europe 2017, 1st European Conference on OpenSees, Porto, Portugal, 19–20 June 2017

Types - MRF
 Most ductile -> large deflections
 Possess large number of dissipative zones in beams and columns
 Large inter-storey drifts -> damage to the non-structural elements

Types - MRF
 One research suggests that “EC8 requirements for drift - a lot more
rigorous than the provisions in other earthquake design codes -
stability factor (θ). It can often govern the design, resulting in over-
strength which reduces the ductility demand of the structure and
affects the loads acting on it, especially if a high ductility factor is
adopted” - Elghazouli (2010)
 Another implies that “EC8 provisions are highly conservative while
the US provisions seem to under-predict the global and maximum drift
modification factors. Also, an oversimplified nature of drift demand
criteria is adopted in the design codes, particularly in the European
codes of practice” - Kumar (2013)
Conclusion: Significant enhancement - by adopting improved models
that can capture the influence of the key structural and loading
characteristics

Plasticity modelling
approaches
Distributed plasticity Lumped plasticity
Image source: Deierlein, Reinhorn & Willford, 2010

Performance based
assessment
Scenario based
•Medium hazard scenario – Type 1,
Soil C - EC8 design spectrum, PGA
= 0.25g
•High hazard scenario –Type 1, Soil
C - EC8 design spectrum, PGA =
0.35g
Intensity based
•100% - design level earthquake
(Limit State of Significant Damage)
•175% - near collapse level
earthquake (Limit State of Near
Collapse)
•350% - 2 x LS of NC

Structural characteristics
3 bays x 6 metres
HFS = 4.5m, HOS = 3.5m
Rigid joints
S355, γov =1.25, E = 210 GPa,
ν = 0.3, 0.25% strain hardening
q = 6.5

Modified Ibarra –
Krawinkler model
Image source: Lignos & Krawinkler, 2010

Rigid vs. Hysteretic plastic
hinges

Floor drift demands (MH)
Model Total frame drift (%) Total frame displacement (m)
Distributed 1.19921857 0.264
Lumped 1.24870571 0.275
Distributed 0.89700814 0.197
Lumped 0.94172257 0.207

Floor drift demands (MH)
Distributed 2.71226000 0.597
Lumped 3.02523857 0.666

Residual drift demands
(MH)

Floor drift demands (HH)
Distributed 1.00233800 0.221
Lumped 1.08395857 0.238
Distributed 1.58467571 0.349
Lumped 1.63203286 0.359

Floor drift demands (HH)
Distributed 2.79344400 0.615
Lumped 3.04388600 0.670

Residual drift demands (HH)

Conclusions
In general, the lumped plasticity model experiences greater drift
demand
Main difference - at greater levels of inelasticity (3% roof drift)
Compliance of the models with previous study parameters and
design codes
General compliance with previous research regarding the
distribution over height
Lumped model tends to match the distributed model’s response at
lower intensity levels and deviates from it largely after the
deterioration of the material takes place

References
ATC. (2011) Seismic Performance Assessment of Buildings, 90% Draft. ATC-58-1
Deierlein, G. G., Reinhorn, A. M. & Willford, M. R. (2010) Nonlinear structural analysis for seismic
design
Elghazouli, A. (2010) Assessment of European seismic design procedures for steel framed
structures
Geschwindner, L. F. (2002) A practical look at frame analysis, stability and leaning columns
Gupta, A. & Krawinkler, H. (1999) Seismic Demands for the Performance Evaluation of Steel
Moment Resisting Frame Structures
Ibarra, L. F. & Krawinkler, H. (2005) Global collapse of frame structures under seismic excitations
Ibarra, L. F., Medina, R. A. & Krawinkler, H. (2005) Hysteretic models that incorporate strength
and stiffness deterioration
Kumar, M., Stafford, P. & Elghazouli, A. (2013) Influence of ground motion characteristics on drift
demands in steel moment frames designed to Eurocode 8
Lignos, D. G. & Krawinkler, H. (2012) Development and utilization of structural component
databases for performance-based earthquake engineering.
Lignos, D. G. & Krawinkler, H. (2010) Deterioration modeling of steel components in support of
collapse prediction of steel moment frames under earthquake loading

Improved drift assessment approach for steel moment frames under realistic earthquake loading

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