evaluation of structural response under exceptional ... · evaluation of structural response under...

Evaluation of structural response

under exceptional seismic actions

Matej Fischinger1, Gaetano Della Corte2

1 Faculty of Civil and Geodetic Engineering

University of Ljubljana

2 Department of Structural Engineering

University of Naples “Federico II”

Urban Habitat Constructions under Catastrophic Events

Naples, Italy,16-18 September 2010

Extreme conditions occur when both loading and structural resistance are combined in such a way to reduce the safety level below acceptable values.

This situation may arise either when the loading is larger than expected (foreseen by the codes existing at the time of the design of the structure) or when the provided capacity was lower than anticipated by the modern standards.

Exceptional seismic actions

Research on structural response under exceptional seismic events

To support the development of the PBD procedures

As a basis for the seismic risk studies

To gain information about innovative structural systems

To provide data for seismic rehabilitation of the systems

designed prior to the development of modern seismic

design principles

To enhance the ability of structures to withstand impact

and explosion loads

Overview

State of the art

Contributions from COST members

Experimental studies – through collapse

Analytical studies

RC structures

Steel structures

Masonry structures

RC structures - Precast structures (contribution from COST members)

PRECAST project (Fischinger et al. 2008,

Toniolo 2007 )

Large rotations of columns (up to 10%)

Ibarra’s model (2005) was modified at UL

Modified Ibarra model

RC structures – Precast structures

(contribution from COST members)

Risk studies on RC precast structures with

strong connections (Fischinger at al. 2008) –

PEER methodology

Other vulnerability studies on RC structures

Kappos (2007)

RC structures - Precast structures (contribution from COST members)

How the connections behave in such

conditions?

SAFECAST project - Response of connections

at large rotations of columns

Experiments on dowel connections (COST26 final

conference – Fischinger et al.) – large rotations

RC structures – Walls

(contributions from COST members)

Seismic response of

lightly reinforced

walls - Fischinger et

al. 2008

Pushover

investigation of 3D

wall systems with

flexible foundation

using capacity

spectrum method –

Apostolska et al.,

2008

Blind prediction of the response of 7-story wall, tested at UCSD

MVLEM

RC structures(contributions from COST members)

Experimental investigation of existing RC

buildings sesimically upgraded by means of

several innovative techniques (e.g. FRP,

eccentric braces and buckling restrained braces)

- Mazzolani et al., 2007

Controventi

con leghe a

memoria di

forma

Materiali

Compositi(C-FRP)

Controventi

Eccentrici(EB)

Controventi

ad instabilità impedita

(BRB)

Isolamento con

isolatori in gomma

(BI)

Prova di spinta sulla

struttura in c.a.

Pannelli

a taglio

(SSP)

5 64321


Full scale experimental tests on a real masonry-

infilled reinforced concrete two story frame

building- Mazzolani et al., 2007


Modelling of upgraded RC structures (non-

ductile mechanisms of the original structure as

well as response of strengthen structure):

Mazzoalni et al., 2007: advanced model for RC in

real masonry infilled building

Bordea et al., 2007: modelling of enhacement of

ductility of RC columns strengthen by FRP

Landolfo et al. 2008: Experimental and analytical studies of typical European steel beams up to severe strength degradation

Strength and stiffness degradation was measured in the range of large plastic rotation demand

Empirical formulas for characterization of ductility and plastic overstrength were proposed

Steel structures

(contributions from COST members)

D’Aniello et al. 2008: Tests on buckling restrained braces subjected to large displacements that far exceed the design values

Design alternatives were proposed to maximize the brace capacity under the extremly large deformations.

Steel structures(contributions from COST members)

Stratan and Dubina 2008: Nearly full scale tests of eccentricaly braced bare steel frames with removable steel shear links

An appropriate detailing of end connections essential for good performance

Steel structures(contributions from COST members)

Landolfo et al. 2006, Della Corte et al. 2006, Dubina et al. 2007: Incremental dynamic analysis of different types of steel structures to investigate near-collapse response

Dogariu et al. 2007: Test on masonry pannels under monotonic and cyclic load

Results can be used as the baseline to evaluate the effectiveness of the retrofiting interventions

Informations can be used for development of the analytical model suitable for analysis of masonry shear pannels up to complete failure

Masonry structures(contributions from COST members)

Krstevska et al. 2007: Large scale test of historical mosque with a minaret

Test on the original bare masonry model, with a small intensity earthquake to produce small, repairable, damage

Tests on the repaired and strengthened model, until collapse of the minaret

Tests on the strengthened mosque until collapse. The strengthening systems were based on FRP materials



Two FEM numerical models of the original and strengthen structure

FEM models successfully used for the comparison of two structuresCalibration with large-scale model steel needed

De Matteis et al. 2008: Experimental and analytical investigations of the cental part of Fossanova gothich church

tests on the bare masonry, to produce moderate, repairable, damage; 2) tests on the strengthened model (transverse FRP rods) , until severe damage (close to the collapse)

Original structure PGA =0,14g, strengthen structure 0.4g


Until a decade ago very few experimental and analytical studies of the structural behaviour up to the collapse. Recently the interest has shifted towards near-collapse behaviour.

Impressive (full-scale) experiments were performed near to the collapse providing suitable data for the development of the adequate analytical models.

Conclusions and recommendations (1)

Empirical calibrated macro-models are prevailing. Although rather simple in concept they provide goodphysical understanding and consequently goodcontrol of the highly complex near-collapse mechanisms. Works performed within the COST C26 action have considerably contributed to these results.

Since each collapse mechanism of a particular structural element or structural system is so specific, general solutions are not to be expected. Long term solution is to perform sufficient experiments

Conclusions and recommendations (2)

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