Authors: Brisid Isufi, Ildi Cismasiu, António M. P. Ramos, Válter J. G. Lúcio

1. MODELLING OF A SHEAR REINFORCED FLAT SLAB
BUILDING FOR SEISMIC FRAGILITY ANALYSIS
Brisid Isufi, Ildi Cismasiu, António M. P. Ramos and Válter J. G. Lúcio
FIRST EUROPEAN CONFERENCE ON OPENSEES
​​JUNE 19-20, 2017
PORTO, PORTUGAL

2. Contents
• Introduction
• Experimental work
• Modeling in OpenSees
• Some results and conclusions
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS 2

3. Introduction
experimental test of a flat slab-column assembly
prototype building
preliminary
fragility curves
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS 3
OpenSees

4. Experimental work
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1.85m (6.1feet)
thickness: 150mm
(5.9inch)
-Reversed lateral cyclic loading
-Constant gravity loading = 50% Gravity Shear Ratio
-Reinforcement Ratio = 0.96%
-Concrete fcm,cube=44.24MPa
-Shear Studs
Failure: at 4% drift ratio, outside the shear reinforced zone

6. Prototype building
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS 6

7. Slab-column connection models
Kang, Wallace, Elwood (2009)* In this presentation: Joint2D element**
Spring 1 to 4  rigid
Central Spring  “Pinching4” material
undeformed real deformed
shape
for analysis
purposes
Scissor model:
These models are focused on unbalanced moment transfer
*Kang, Thomas H-K., John W. Wallace, and Kenneth J. Elwood. "Nonlinear modeling of flat-plate systems." J.of str. Eng. 135.2 (2009): 147-158.
**Altoontash, Arash. Simulation and damage models for performance assessment of reinforced concrete beam-column joints. Diss. Stanford
University, 2004.

8. Slab-column connections: model & calibration
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS
Joint2D (Altoontash, 2004) element & Pinching4 (PEER 2003/10) uniaxial material
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9. Derivation of Fragility Curves
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS 9
Simple local damage index:
-Variables:
-concrete strength ~Normal(48MPa; 7.2MPa)
-reinforcement yield strength ~LogNormal(550MPa; 33MPa)
-gravity load in the critical punching perimeter ~Normal(196.37kN; 19.64kN)
Damage states based on
the observed damage
during the testrotation
unbalancedmoment
Global Damage Index  weighted based on energy dissipation
- Damage in the flat slabs
Work is currently under progress to improve the DI and representation of variables.
For Gravity Shear Ratio fixed at 50%, the gravity load indirectly accounts for the
uncertainties in the rotational behavior of the slab-column connection

10. Derivation of Fragility Curves: Seismic actions
MODELLING OF A SHEAR REINFORCED FLAT SLAB BUILDING FOR SEISMIC FRAGILITY ANALYSIS 10
Ground motion was represented by means of
artificial accelerograms generated using the
program SeismoArtif.
64 accelerograms (8 for each level
of ground acceleration)
Artificial accelerograms with target spectrum: Eurocode 8, Type 1, Ground Type C

11. Derivation of Fragility Curves: procedure
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Incremental Dynamic Analysis
in which each single accelerogram is
used 30 times under a set of
random variables.
Sampling technique: Latin Hypercube

12. Results
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Roof displacements Max. interstorey drifts
Global pushover (average values of vars.) Damage Indices
assumed global
failure
GLOBAL SLAB-SPECIFIC

13. Fragility Curves & Conclusions
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-OpenSees: very suitable for the
purposes of this study;
-for this building:
-global structural failure is not
governed by punching of the flat
slabs;
-punching failures occurred at
large drifts, in which the capacity
of the other elements was
exhausted;
-punching shear reinforcement
with shear studs contributed in
the limitation of damage to the
flat slabs.

14. OpenSees > Thank you!
FIRST EUROPEAN CONFERENCE ON OPENSEES
​​JUNE 19-20, 2017
PORTO, PORTUGAL
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