Verifica di capacità portante di fondazioni dirette in fase sismica

Tratto dalla Rivista IoRoma o dal suo allegato Quaderno che è consultabile al sito: http://rivista.ording.roma.it

a cura di 3F9: : .H?G9DIBG 3F9: : 2>99JIDJ commissione !IGEIBFJBH visto da: 3F9: : ): %0)<<DI=G 3F9: ,: G;;IEEJ

VERIFICA DI CAPACITÀ PORTANTE DI FONDAZIONI DIRETTE IN FASE SISMICA "H 7IDJ<JBH @J BH?HBJE+ ?GDEHFEI @J <GF@H;JGFJ @JDIEEI JF <HAI AJA=JBH6 BG=I DJB4JIAEG @HCCI * .-// 6 FIBIAAJEH C0H@G;JGFI @J G??GDE>FI <GD=>CI A7J8 C>??HEI H ?HDEJDI @H JF@H9JFJ A?IDJ=IFEHCJ I AE>@J EIGDJBJ B4I EIF9HFG BGF8 EG @I9CJ I<<IEEJ @ICC0H;JGFI AJA=JBH A>C AJAEI=H EIDDIFG8<GF@H;JGFI: Premessa , BH>AH @ICCI <GD;I @J JFID;JH JF@GEEI @HC AJA=H FIC EIDDIFG HC @J AGEEG @ICCH <GF@H;JGFI @JDIEEH AJ ?> =HFJ<IAEHDI >FH DJ@>;JGFI @IC BHDJBG CJ=JEI: ,C =G=IFEG CH FGD=H FGF <GDFJABI IA?CJBJEH JF@JBH8 ;JGFI A> &>HCI =IEG@G >EJCJ;;HDI ?ID CH 7IDJ<JBH @J BH?HBJE+ ?GDEHFEI JF <HAI AJA=JBH6 CHABJHF@G @J8 ABDI;JGFHCJE+ HC ?DG9IEEJAEH: 3F CIEEIDHE>DH BG=?HJGFG @J7IDAJ =IEG@J EDH B>J J =IEG@J @J .HABGFI6 HGC>BBJ IB ID6 H>9IDJ I 2JB4HD@A B4I 7IDDHFFG EDHEEHEJ JF AI9>JEG:

Verifiche agli stati limite ultimi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

2%3*) %)!"3 3*!)!*)23 %)"", 2 3*.3, %3 2 ,

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

Definizione dellâ&#x20AC;&#x2122;azione sismica secondo la normativa vigente ,C ?HDH9DH<G :55: : :5 * .-// 6 A>CCH AJB>DI;8 ;H @IC BG=?CIAAG <GF@H;JGFI8EIDDIFG6 AJ HB8 BIFFH HCCH valutazione della resistenza con approcci pseudo-statici se la determinazione delle azioni discende da unâ&#x20AC;&#x2122;analisi pseudostatica: "H .JDBGCHDI F: 5 @IC -// HC ?HDH8 9DH<G :55: : :5 EDHEEH JC EI=H @ICCI <GF@H;JGFJ A>?ID<JBJHCJ JF BGF@J;JGFJ AJA=JB4I JFEDG@>BIF@G J EI=J @J JFEIDH;JGFI JFID;JHCI I BJFI=HEJBH @IC AJAEI=H EIDDIFG8AED>EE>DH8ICI7H;JGFI( lâ&#x20AC;&#x2122;azione del sisma si traduce in accelerazioni nel sottosuolo (effetto cinematico, Khk ) e nella fondazione, per lâ&#x20AC;&#x2122;azione delle forze dâ&#x20AC;&#x2122;inerzia generate nella struttura in elevazione (effetto inerziale, Khi ).

"H .JDBGCHDI &>JF@J @JAEJF9>I @>I BGI<<JBJIFEJ AJA=JBJ GDJ;;GFEHCJ I @I<JFJABI JF <>F;JGFI @J BG8 AH BHCBGCHDCJ( Khi BG=I DH??GDEG # ' I CI9H Khk HJ 7HCGDJ @J FGD=HEJ7H A?IBJ<JBHEJ ?ID J ?IF@JJ I &>JF@J HC BGI<<JBJIFEI @J DIH;JGFI GDJ;;GFEHCI @IC EIDDIFG kh B4I H A>H 7GCEH @J?IF@I @H A #BGI<<J8 BJIFEI @J DJ@>;JGFI @ICC0HBBICIDH;JGFI =HAAJ=H HEEIAH HC AJEG ?ID J ?IF@JJ' I @H H=H #HBBICIDH8 ;JGFI GDJ;;GFEHCI =HAAJ=H HEEIAH HC A>GCG':

"H .JDBGCHDI ?DGAI9>I <GDFIF@G JF@JBH;JGFJ A>J ?HDH=IEDJ @H =G@J<JBHDI FIC BHCBGCG @IC BHDJBG CJ=JEI #?HDH9DH<G :55: : :5': Metodo di Cascone J1CJG9DH<JBH=IFEI6 JC =IEG@G B4I ?J AJ H77JBJ8 FH H &>HFEG @IABDJEEG FICCH .JDBGCHDI &>ICCG @J .HABGFI B4I IA?CJBJEH @>I <HEEGDJ BGDDIEEJ7J @H H??CJBHDI HC BGI<<JBJIFEI * @J BH?HBJE+ ?GDEHF8 EI AEHEJBG: effetto cinematico effetto inerziale

Tabella 1 - Coefficienti parziali R per le verifiche agli stati limite ultimi STR e GEO di muri di sostegno (tab. 6.5.I NTC2008) VeriďŹ ca

CoefďŹ ciente parziale (R1)

CoefďŹ ciente parziale (R2)

CoefďŹ ciente parziale (R3)

.H?HBJE+ ?GDEHFEI @ICCH <GF@H;JGFI

2 $ 5:/

2 $ 5:/

2 $ 5:

BGDDJ=IFEG

2 $ 5:/

2 $ 5:/

2 $ 5:5

2IAJAEIF;H @IC EIDDIFG H 7HCCI

2 $ 5:/

2 $ 5:/

2 $ 5:

Tabella 2 - Coefficienti parziali R per le verifiche agli stati limite ultimi di fondazioni superficiali (tab. 6.4.I NTC2008) VeriďŹ ca .H?HBJE+ ?GDEHFEI BGDDJ=IFEG

CoefďŹ ciente parziale (R1) 2 $ 5:/

CoefďŹ ciente parziale (R2) 2 $ 5:

CoefďŹ ciente parziale (R3) 2 $ -:

2 $ 5:/

2 $ 5:5

2 $ 5:5

Altri metodi di calcolo della capacitĂ portante di fondazioni dirette in condizioni sismiche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etodo di Paolucci e Pecker 3C =IEG@G EJIFI BGFEG @I9CJ I<<IEEJ BJFI=HEJBG I JFID;JHCI >AHF@G >F H??DGBBJG BJFI=HEJBG #FG8 EG BG=I yield design theory' I BGFAJ@IDH CH BH8 ?HBJE+ ?GDEHFEI JF BH=?G AJA=JBG ?DG@GEEG @IC 7HCGDI JF BH=?G AEHEJBG I @J EDI BGI<<JBJIFEJ <>F8 ;JGFI @HC BHDJBG GDJ;;GFEHCI @IDJ7HFEI @HCCH AG8 7DHAED>EE>DH6 @HCC0JFID;JH @IC EIDDIFG I @HCC0IB8 BIFEDJBJE+ @IC BHDJBG:

@G7I( BHDJBG GDJ;;GFEHCI @HCCH AG7DHAED>EE>DH(

JFID;JH @IC EIDDIFG @J <GF@H;JGFI(

IBBIFEDJBJE+ @IC BHDJBG(

.GF@J;JGFI FIBIAAHDJH ?ID >EJCJ;;HDI vi B4I AJH kh<tan : %H 7HDJI HFHCJAJ @IC =IEG@G6 AJ I7JFBI B4I C0I<8 <IEEG BJFI=HEJBG =G@IAEG DJA?IEEG H9CJ I<<IEEJ JFID;JHCJ @G7>EJ HCCI H;JGFJ AJA=JB4I EDHA=IAAI @HCCH AG7DHAED>EE>DH: Metodo di Maugeri HCI =IEG@G AEHEG GEEIF>EG @H >FH AIDJI @J HFHCJAJ F>=IDJB4I BGF@GEEI BGF H??DGBBJG ?AI>8 @G8AEHEJBG BGFAJ@IDHF@G AJH C0I<<IEEG BJFI=HEJBG B4I JFID;JHCI: >IAEI HFHCJAJ 4HFFG @IEID=JFHEG J <HEEGDJ @J BH?HBJE+ ?GDEHFEI AJA=JBJ ?ID G9FJ BGFEDJ1>EG I DH??GDEHF@GCJ BGF J DJA?IEEJ7J 7HCGDJ AEHEJBJ 4HFFG ?GDEHEG HCCH 7HC>EH;JGFI @IJ EDI BGI<<JBJIFEJ BGDDIEEJ7J hgf, hcf, hqf @H H??CJBHDI HJ <HEEGDJ @J BH?HBJE+ AEHEJBH AIBGF@G CH AI9>IFEI <GD=>CH;JGFI(

J9>DH 5( Dati iniziali per il dimensionamento della fondazione nel caso in esame.

@G7I( <HEEGDI @J ABGDDJ=IFEG(

<HEEGDI @J BGIAJGFI(

<HEEGDI @J AG7DHBBHDJBG(

3 BGI<<JBJIFEJ 6 .6 %6 )6 I 3 AGFG <>F;JGFJ @J tan : Metodo di Richards !CJ H>EGDJ 4HFFG DJBH7HEG CI IA?DIAAJGFJ @I9CJ HF9GCJ ,) I ) B4I @I<JFJABGFG CI ;GFI @J A?JF8 EH HEEJ7H I ?HAAJ7H FIC =IBBHFJA=G @J DHF@EC I J BGI<<JBJIFEJ @J A?JFEH HEEJ7H I ?HAAJ7H ,) I ) JF <>F;JGFI @ICC0HF9GCG @0HEEDJEG @IC EIDDIFG6 @ICC0HF9GCG @J HEEDJEG EIDDIFG8?HDIEI I @ICCI HB8 BICIDH;JGFJ AJA=JB4I 7 I 4: 3 BGI<<JBJIFEJ @J BH8 ?HBJE+ ?GDEHFEI ?GAAGFG &>JF@J <GD=>CHDAJ BGF(

J9>DH -( Variazione della larghezza B della fondazione e del coefficiente di sicurezza FS in funzione del metodo adottato nei due approcci considerati.

Esempio numerico 3F &>IAEG ?HDH9DH<G 7JIFI H<<DGFEHEG >F BHAG @J ?DHEJBH ?DG9IEE>HCI JFIDIFEI JC @J=IFAJGFH=IFEG @ICCH <GF@H;JGFI @JDIEEH @ICCH A?HCCH @J >F AGEEG8 ?HAAG6 BGF<DGFEHF@G J =IEG@J ?DIBI@IFEI=IFEI

J9>DH ( Confronto dei risultati ottenuti dallâ&#x20AC;&#x2122;applicazione dei vari metodi nei due approcci considerati per la determinazione della larghezza B della fondazione dellâ&#x20AC;&#x2122;esempio in esame.

2%3*) %)!"3 3*!)!*)23 %)"", 2 3*.3, %3 2 ,

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abella 1 A?IBJ<JBH ?ID CI 7IDJ<JB4I H9CJ AEHEJ CJ=JEI >CEJ=J 2 I !) @IJ =>DJ @J AG8 AEI9FG: *ICCI EH1ICCI I FIJ 9DH<JBJ AJ DJ?GDEHFG J @HEJ @ICC0IAI=?JG I J DJA>CEHEJ GEEIF>EJ H??CJBHF@G J @J7IDAJ =IEG@J IA?GAEJ FIJ ?HDH9DH<J ?DIBI@IFEJ HCCI @J7IDAI BG=1JFH;JGFJ6 BGFAJ@IDHF@G >FH <GF@H;JGFI FHAEDJ<GD=I JC B>J ?JHFG @J ?GAH H 56 = @HC ?JHFG BH=?H9FH: ID AI=?CJBJE+ AJ BGFAJ@IDH 7$/: # J99:56-6 ':

Conclusioni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

Per ulteriori articoli della presente pubblicazione IoRoma, consultare il sito: http://rivista.ording.roma.it

2%3*) %)!"3 3*!)!*)23 %)"", 2 3*.3, %3 2 ,