Influence of buckling of longitudinal reinforcement in columns on seismic response of existing reinforced concrete bridges

doctoral thesis

Andrej Anžlin (Avtor), Tatjana Isaković (Mentor), Matjaž Mikoš (Član komisije za zagovor), Miha Tomaževič (Član komisije za zagovor), Matjaž Dolšek (Član komisije za zagovor), Matija Gams (Član komisije za zagovor), Yasin Fahjan (Komentor)

Povzetek

Experimental and analytical studies of the in uence of the buckling in the longitudinal reinforcement on the seismic response of existing concrete bridge columns were performed. Based on the previous tests of typical I-shaped bridge piers the design of new cyclic tests of rectangular columns was performed. The impact of the inappropriate seismic detailing and the in uence of the concrete cover on the drift and load-carrying capacity as well as on the buckling of bars was analysed. After the literature review the data of 63 experimental tests of RC columns were collected in which the collapse of the element was mainly navigated by the local or global buckling of bars. They were all included into newly established `buckling' database. With the aid of the new database the new analytical form for the estimation of the post-capping stifiness of rectangular columns was introduced. All columns from the `buckling' database were analysed with existing engineering macro models, which are usually used for the seismic analysis of RC structures. It was concluded, that for the rectangular RC columns with inadequate seismic detailing many times principal assumptions were not fulflled. Therefore, their improvement was proposed. New procedure for estimation of the inappropriate hook angles of lateral reinforcement and buckled bars on confnement efiectiveness was analytically derived. It based with several detailed FE analyses of concrete columns with diferent reinforcement detailing configurations. The experimental tests of the strengthened RC columns were performed. At first, the efciency of strengthening of the typcal I-shape bridge pier with substandard reinforcement was verified by means of CFRP wrap. It was concluded, that due to the unfavourable aspect ratio of the section anges the conventional strengthening is rather inefective. Based on these findings improved strengthening of substandard rectangular columns was considered. The columns was jacketed with pre-stressed CFRP fibres, the concrete cover was removed and smoothed with epoxy resin, the column corners were rounded to largest possible level. In this way, the deformation capacity of columns was increased for more than 70 %. The strengthened columns with defcient structural details were analysis with similar numerical models as previously described columns. For this type of RC members the modifications of the existing numerical models were also proposed.

Ključne besede

Built Environment;civil engineering;doctoral thesis;buckling of the longitudinal reinforcement;effective confinement;bridge columns;substandard transverse reinforcement;I- shaped columns;rectangular columns;seismic strengthening;

Podatki

Jezik:	Angleški jezik
Leto izida:	2017
Tipologija:	2.08 - Doktorska disertacija
Organizacija:	UL FGG - Fakulteta za gradbeništvo in geodezijo
Založnik:	[IA. Anžlin]
UDK:	624.012.45:624.042.7:624.075.2:624.21(043)
COBISS:	8079713
Št. ogledov:	2052
Št. prenosov:	1301
Ocena:	0 (0 glasov)
Metapodatki:

Ostali podatki

Sekundarni jezik:	Slovenski jezik
Sekundarni naslov:	Vpliv uklona vzdolžne armature stebrov na potresni odziv obstoječih armiranobetonskih mostov
Sekundarni povzetek:	V okviru disertacije so bile opravljene eksperimentalne in analitične raziskave vpliva uklona vzdolžne armature na potresni odziv armiranobetonskih mostnih stebrov. Na osnovi obstoječih testov tipičnih mostnih stebrov I oblike so bili zasnovani ciklični preizkusi pravokotnih pasnic mostnih stebrov oz. pravokotnih stebrov. Analiziran je bil vpliv neustreznih konstrukcijskih detajlov, vpliv krovne plasti na nosilnost in duktilnost elementov ter na uklon vzdolžne armature. Po pregledu literature so bili zbrani podatki o 63 eksperimentih, v katerih je bil dokumentiran globalni ali lokalni uklon vzdolžne armature. Vsi so bili uvrščeni v novo zgrajeno t.i. `uklonsko' bazo podatkov, s pomočjo katere je bil predlagan tudi analitičen izraz za ocenitev postkritične togosti armirano betonskih stebrov. Vsi stebri iz `uklonske' baze so bili analizirani z obstoječimi inženirskimi modeli, ki se običajno uporabljajo za potresno analizo konstrukcij. Ugotovljeno je bilo, da v stebrih s pomanjkljivimi konstrukcijskimi detajli dostikrat niso izpolnjene temeljne predpostavke teh modelov, zato so bile za primer pravokotnih stebrov predlagane njihove izboljšave. Izpeljan je bil nov postopek za določitev vpliva uklona vzdolžne armature in stremen z neustreznimi konstrukcijskimi detajli na efektivnost objetja jedra betona. V ta namen so bile narejene analize z bolj podrobnimi modeli končnih elementov. Izvedene so bile tudi eksperimentalne raziskave utrjenih stebrov. Najprej je bil ciklično testiran tipičen I mostni steber, ki je bil utrjen s karbonskimi vlakni. Ugotovljeno je bilo, da je zaradi neugodnega razmerja višine in širine prečnega prereza pasnic običajna pasivna utrditev neučinkovita. Zaščitna plast betona se sorazmerno hitro zdrobi in objetje iz karbonskih vlaken postane neefkasno. Na osnovi teh zaključkov je bila zasnovana bolj učinkovita potresna utrditev pravokotnih stebrov. Steber je bil objet s prednapetimi karbonskimi vlakni, odstranjena je bila krovna plast betona, izravnana s slojem epoksidne smole in v največji možni meri so bili zaokroženi robovi prereza. Na ta način je bila povečana deformacijska kapaciteta stebra za več kot 70%. Utrjeni stebri s pomanjkljivimi detajli so bili analizirani s podobnimi numeričnimi modeli kot predhodni stebri. Tudi za primer takih stebrov so bile predlagane primerne spremembe obstoječih numeričnih modelov.
Sekundarne ključne besede:	Grajeno okolje;gradbeništvo;disertacije;uklon vzdolžne armature;efektivno objetje;mostni stebri;neustrezni konstrukcijski detajli;I stebri;pravokotni stebri;potresna utrditev;
Vrsta dela (COBISS):	Doktorsko delo/naloga
Komentar na gradivo:	Univ. v Ljubljani, Fak. za gradbeništvo in geodezijo
Strani:	LXIV, 329 str., [7] pril.
ID:	10841595