assessment and improvement of structural safety under ... · nodo danneggiato dal sisma: a) vista...

Department of Civil, Environmental and Architectural Engineering – DICEA Via F. Marzolo 9, 35131 – Padua, Italy. www.dicea.unipd.it

29 November 2015, Beer Sheva, Shamoom College

R.C. STRUCTURES: LESSONS LEARNED FROM THE PAST EARTHQUAKES:

DAMAGE CATALOGUES AND INTERPRETATION

Prof. Eng. Claudio Modena [email protected]

Assessment and improvement of structural safety under seismic actions of existing constructions:

Historic Buildings and R.C. Structures.SEMINAR

LIMITS OF THE EXISTING TOOLS FOR THE ANALYSIS OF STRUCTURAL RESPONSE TO STATIC AND DYNAMIC ACTIONS

2Seismic assessment of R.C. structures

- Ultimate Limit State : a seismic event with areturn period many times greater than servicelife of the structure is considered; thestructure should not collapse under groundshaking , but it may have sustained such alevel of damage that it could not be possibleto economically repair it following theearthquake. Inelastic behaviour

- Serviceability Limit State : a seismic event with a return period comparable to the servicelife of the structure is considered; there should be no damage requiring repair, and normaloperations of the structure should not be significantly affected. Elastic behaviour

Seismic codes aims to provide performance-based guidance for design and assessment ofstructures.

The performance of the structure is defined in relation to “limit states“. Beyond the limitstate condition the structure no longer meets the needs for which it was designed. There aretwo distinct levels of performance in seismic design:


3

R.C. structures should exhibit an adequate (possibly great) capability ofdissipate energy during inelastic response (DUCTILITY).

Energy dissipation should occur without a significant loss of RESISTENCE toboth vertical and horizontal actions.

• Elastic Stiffness: k=Fy/Δy

Quantity that correlates displacements and forces of a structural element within linear-elastic limits. Stiffness is relevant in limiting structural damage caused by seismic events of low to medium intensity (small elastic displacements).

• Resistance : Fy

Maximum force that a structural element (or the entire structure) can withstand responding elastically. Resistance is relevant in limiting structural damage caused by seismic events of low to medium intensity (inelastic response is prevented).

• Ductility: Δ/Δy

Ratio between current displacement Δ and yield displacement Δy. Ductility allows the structure to reach great displacements without collapsing (even though severe damage could occur).

3curated byIng. G. Tecchio [email protected]

Seismic assessment of R.C. structures


4

• Basic criterion for a building structure in a seismic zone is REGULARITY, intended both as PLAN and ELEVATION REGULARITY

• REGULARITY implies several requisites: compactness, symmetry, uniformity

• PLAN REGULARITY produce pure lateral motions

– regular distribution of masses and lateral load resisting elements eliminates large eccentricities leading to torsional effects

– to achieve plan regularity:• compactness and symmetry

• avoid or limit plan set-backs

• subdivide the building into separate independent units using seismic joints

• strengthen those parts of the building that experience largest displacements/forces

Earthquake-resistant buildings


5

• ELEVATION REGULARITY implies that the first eigenmode is predominant and that eigenmodesshapes in both direction can be considered as linear

– avoid sensitive zones where concentrations of stress or large ductility demands increase damage susceptibility

– to achieve elevation regularity:• nearly constant stiffness and mass distributions

• continuous bracings over total height

• avoid interruptions of the lateral stiffness over height by e.g. soft stories

• All lateral load resisting systems, such as cores, structural walls, or frames, shall run without interruption from their foundations to the top of the building or, if setbacks at different heights are present, to the top of the relevant zone of the building



6

• Vertical lateral load resisting elements shall give rise to– comparable lateral stiffnesses– evenly distributed horizontal forces resisting

elements– symmetric distributed system of resisting elements

in both directions

• In general the positions of centre of gravity and centre of stiffness shall be coincident: thereby building has only pure lateral motions and torsional effects are avoided– Centre of gravity position is determined by mass

distribution– Centre of stiffness position is determined by plan

position of lateral resisting elements (frames and walls)



7

• Rigid diaphgrams for floor levels• Continuous load path of horizontal forces down to the foundations.• Structural regularity in mass, stiffness and resistance distribution to achieve

– reduction of global torsional effects– reduction of local concentrations demands in terms of resistance or capacity– reduction of soft storey collapse probability

• Redundancy of structural elements, which permits– bending moment redistribution behaviour– to postpone structural collapse

• Limited masses and adequate stiffness to achieve low displacements and– reduction of second order effects– reduction of non-structural elements damage

• Flexural collapse mechanism• Absence of fragile failure modes (shear failure)



8L’ Aquila 2009 earthquake

- The L’Aquila earthquake occurred the 6th April 2009 and was characterized by a Magnitude of 6.3 Mw.

- Significant damages were observed to cultural heritage and residential buildings, in particular referring to framed structures, most of which designed according to the seismic code of the time of construction (late sixties-early seventies)

STRUCTURAL DAMAGES TO RC STRUCTURES


9Accelerograms of 06/04/09 earthquake, l’ Aquila

Report by Masi & Chiauzzi, available at: http://www.reluis.it

PGA-X: 0,63gPGA-Y: 0,60gPGA-Z: 0,42g

L’AQUILA

http://www.reluis.it/


10

Pseudo-acceleration response spectra (5% equivalent damping)

Report by Masi & Chiauzzi, available at: http://www.reluis.it

Sa-max: 1,61g; T=0,10sSa-max: 1,47g; T=0,16sSa-max: 1,24g; T=0,04s

L’AQUILA

Response spectra of L’ Aquila earthquake



11Factors influencing damage mechanisms in frame buildings

• Conceptual design

• Construction details

• Quality of materials

SOME EXAMPLES

Building close toVia XX Settembre,

L’Aquila


12

Hotel Duca degli Abruzzi, Via Giovanni XXIII (AQ)

“Soft-Storey” mechanism – ground floor


13

Building in Pettino (AQ)



14

- Structural Damages Observed



15

Building in Pianola (AQ)

“Soft-Storey” mechanism – upper floors


16Pounding of adjacent structures or insufficient joints

L’ Aquila, 2009


17L’Aquila, 2009

Pounding of adjacent structures or insufficient joints


18

Building in Pettino (AQ)foto Ferretti D.

Asymmetric bracing and plan irregularity


19

foto Ferretti D.


L’Aquila, 2009


20

Ing. Danilo Ranalli Vile XXV Aprile 11, Sulmona - Tel./Fax.: 0864 201012 - Cell.: 3470329085 - 3470935165

RAPPORTO DI PROVA

OGGETTO: INDAGINI DIRETTE ED INDIRETTE PER LA CARATTERIZZAZIONE

STRUTTURALE DI UN EDIFICIO MULTIPIANO

LOCALITÀ: COMUNE DI L’AQUILA

INDIRIZZO: VIA AVEIA N°2

DATA ESECUZIONE PROVE: 10/12/2009 & 22/12/2009

CONSULENTI RESPONSABILI: Ing. RANALLI Danilo _______________________

Ing. SCOZZAFAVA Marco _______________________

Ing. ARETUSI Nicola _______________________

LUOGO E DATA: L’Aquila, 20.01.2010

NUMERO PAGINE: 48

20


L’Aquila, 2009


21

Buildings in L’Aquila, (dx: Via Vicentini)

Lack of “capacity design”in the conceptual design phase


22

Buildings in Pianola and L’Aquila

In-plane and out-of-plane damage to infill walls


23


Masonry infills out-of-plane damages



24


Masonry infills out-of-plane damagesMasonry infills in-plane damages



25- Infill in-plane Damages

Shear damages



26

Friuli, 1976School building in via Duca degli

Abruzzi, L’Aquila

Partially infilled frames


27

Stair in a building in L’Aquila

Short-column effect


28

Building in Pianola (AQ)

foto Ferretti D.

Construction details and quality of materials


29

Buildings in and close by L’Aquila

Damage to structural joints and construction details


30- Structural Damages Observed

Steel bars instabilities

Damage to structural joints and construction details


31

Shear failure of column-of beams, insufficient stirrups

Buildings in L’Aquila



32

Collaps due to failure of non-confined corner joint


14

2.1. Danni ai nodi di strutture in c.a.

(a) (b)

Figura 1. Nodo danneggiato dal sisma: a) lesione pseudo-orizzontale all’attacco pilastro-pannello; b) lesione diagonale nel pannello (by O.S. Bursi, T. Dusatti, R. Pucinotti)

(a) (b)

Figura 2. Nodo danneggiato dal sisma: a) vista d’insieme; b) particolare del nodo trave-pilastro (by O.S. Bursi, T. Dusatti, R. Pucinotti)


Damage to beam-column joints

15

(a) (b)

Figura 3. Nodo danneggiato dal sisma: a) vista d’insieme; b) particolare del nodo trave-pilastro (by O.S. Bursi, T. Dusatti, R. Pucinotti)

(a) (b)

Figura 4. Nodo danneggiato dal sisma: a) vista d’insieme; b) particolare di uno dei nodi trave-pilastro (by I.Iervolino, A.Prota, P.Ricci, G.M. Verderame)


33

Castelnuovo di San Pio delle Camere (AQ)

Site effects


34

Province building, L’Aquila

Acqueduct in Paganica (AQ) Residential buildings in Pianola (AQ)

Damage to parapets, façade elements, celeings, installations


35

35

Polo Didattico di via G. Di Vincenzo, Università dell’Aquila: griglia di sospensione metallica e

pannelli in fibra minerale 60x60cm

Macerie di pannelli in fibra minerale. (Foto di G. Magliulo)

Caserma della Guardia di Finanza di Coppito (AQ), sala conferenze: griglia di sospensione

metallica e pannelli in fibra minerale 60x60cm

Danneggiamento e collasso dei pannelli (Foto di G. Magliulo)

© Reluis 2009www.reluis.it


Caserma della Guardia di Finanza di Coppito (AQ), padiglione circolo permanenti: griglia di

sospensione metallica e pannelli in lamierino di acciaio 60x60cm

Caduta dei correnti e danneggiamento dei pannelli e dei corpi illuminanti (Foto di G. Magliulo)

Caserma della Guardia di Finanza di Coppito (AQ), padiglione circolo permanenti: griglia di

sospensione metallica e pannelli in lamierino di acciaio 60x60cm

Particolare del danneggiamento del pannello (Foto di G. Magliulo)



Caserma della Guardia di Finanza di Coppito (AQ), edificio mensa: controsoffittatura a

doghe in lamierino di acciaio Collasso delle doghe per perdita di appoggio. (Foto di G. Magliulo)

Caserma della Guardia di Finanza di Coppito (AQ), edificio mensa: controsoffittatura a

doghe in lamierino di acciaio

Danneggiamento e pericolo di collasso delle doghe. (Foto di G. Magliulo)



Ospedale San Salvatore dell’Aquila: controsoffittatura a doghe in lamierino di acciaio

Collasso delle doghe. (Foto di G. Magliulo)

Ospedale San Salvatore dell’Aquila: controsoffittatura a doghe in lamierino di acciaio

Particolare della griglia di sospensione delle doghe. (Foto di G. Magliulo)



Damage to parapets, façade elements, celings, installations



36

INDUSTRIAL RC AND PRC BUILDINGS

http://www.reluis.it/ > Terremoto Emilia 2012 > rapporti tecnici

Structural damages in the recent Emilia earthquake (20-29 May 2012)



37

The recent earthquakes that struck the region of Emilia-Romagna in May 2012 revealed the enormous structural weaknesses of the industrial buildings and, more generally, the RC prefabricated buildings.

The construction systems typical of these structures (most of times of single-storey buildings) are characterized by isostaticschemes, free of redundancies, with floors without in-plane stiffness (no diapraghmaction, in which the resistant function is reduced to a simple system of "inverted pendulum" represented by the single pillar.

One-story industrial buildings typologies


38One-story industrial buildings typologies

Flat Roof(10-15%)

Period: 1960-2000PRC HORIZONTHAL STRUCTURESRC AND PRC VERTICAL ELEMENTS

Double T beams

FLAT ROOF:

Main beams: I section, L=10-15mSecondary beams: Double T, L=10-25m

Double slope(10-15%)


39

Main beams:I section, L=10-15m

Shed roof, Beam h=cost.L= 12-16m, i=6-15mInclined roof = RC secondary beams with enlightments

Secondary beams: ShedL=15-30m



40

Cast on site structuresShed

Rc concrete-brick vaults

Period : 1930-60



41


Typical main beam span : L=10-15m

Multi-story industrial buildings typologies

TWO STORIES

Offices level


42


Multi-story industrial buildings typologies


43Deficiencies in prefabricated rc industrial buildings

43

Typical one-story systems, designed and dimensioned essentially for vertical loads only (modest horizontal actions-wind load), without redundancies.The roof structure is not rigid ( no possible forces redistribution due to diaphragm action), with prchorizontal secondary elements simple laid over beams, and beams connected with hinges to the column top. The 3-d global system is reconducted to a series of simple "inverted pendulum" system constituted by the single pillar (which has no interactions with the rest of the structure, as in a frame structure) behaving like a cantilever.The following "chain" of vulnerabilities is determined:

Roof: loss of support of secondary element or main beamsBeam-column node: low reinforcement percentage (bars and stirrups), no reliable transmittal of horizontal forcesPillars: reinforcement bars and stirrups dimensioned according to lower bound Code limits ( 0.3% longitudinal percentage, stirrups of small diameter with excessive pitch). Reduced element ductility at ULS and insufficient resistance.Infills: out of plane overturningColumn-plinth node: pillar inserted in the prefabricated plinth (low reinforcement, does not guarantee adequate resistant moment and shear transfert at the base )Plinth (foundation beam): foundation dimensioned only for gravity loads, possibile sliding, overturinig…


44Weak points-conections

44

5. 4.

3.

2.

1.


45Structural damages in the recent Emilia earthquake(20-29 May 2012)

Epicenters distribution


46Time evolution of the earthquake sequence

Structural damages in the recent Emilia earthquake (20-29 May 2012)


47

Chemical factory,Paganica (AQ)

Connections in prefabricated buildings


48

Out-of-plane damage of upper panels

Rapporto dei sopralluoghi su edifici industriali prefabbricati danneggiati dal terremoto dell’Abruzzo del 6/04/2009

Figura 25- Velette fuori piano in sommità dell’edificio nelle facciate orientate est-ovest (foto dell’ing. A. Zambrano).

Figura 26 - Velette fuori piano in sommità dell’edificio nelle facciate orientate est-ovest vista dall’interno(foto

dell’ing. F. Giordano).

Rapporto dei sopralluoghi su edifici industriali prefabbricati danneggiati dal terremoto dell’Abruzzo del 6/04/2009

Figura 25- Velette fuori piano in sommità dell’edificio nelle facciate orientate est-ovest (foto dell’ing. A. Zambrano).

Figura 26 - Velette fuori piano in sommità dell’edificio nelle facciate orientate est-ovest vista dall’interno(foto

dell’ing. F. Giordano).

48

Industrial buildings



49

Industrial buildings in Emilia, 2012



50

Damage to fork connection due to pounding of main transverse beam




51

Loss of bearing area for shed roof structures



52

LOSS OF SUPPORT



53Construction details & materials in prefabricatedbuildings

Inadequate reinforcement and concrete quality



54

Shelf damage(and industrial mezzanine)

Damage to secondary elements



55

Images from Structural Engineering Reconnaissance of the August 17, 1999 Earthquake: Kocaeli (Izmit), Turkey-PEER 2000

curated byIng. G. Tecchio [email protected]

55

Settlements caused by soil liquefaction - Kocaeli Earthquake 1999

Soil liquefaction - Niigata Earthquake 1964

Damage to foundations

56

Thanks for your attention!

[email protected] of Civil,

Environmental and ArchitecturalEngineering

[email protected]

assessment and improvement of structural safety under ... · nodo danneggiato dal sisma: a) vista...

Documents