Seismic behaviour of porous concrete buildings

U radu je opisano ispitivanje provedeno na potresnoj platformi dvaju troetažnih i jednog četveroetažnog modela zgrada izrađenih od porastoga beton. Zabilježeno je tipično ponašanje posmičnog zida s dijagonalnim pukotinama u smjeru uzbuđivanja i katnim mehanizmom ponašanja pri rušenju. Analizirani su odnosu između oštećenja, otpornosti i katnih pomaka za pojedina granična stanja, dana je ocjena za proračunske parametre, kao što su kapacitet pomaka i faktor ponašanja konstrukcije.The testing conducted on seismic platform to determine behaviour of porous concrete buildings, using two three-storey building models, and one four-storey building model, is described in the paper. Typical behaviour of shear wall with diagonal cracks in the direction of excitation, and with storey-based mechanism of behaviour during collapse, has been noted. Relationships between the damage, resistance and storey drift are analyzed for individual limit states, and an estimation of design parameters, such as the drift capacity and structural behaviour factor, is given

Seismic rehabilitation of existing masonry structures

Razmatraju se osnovni kriteriji za protupotresnu obnovu zidanih zgrada u potresnim područjima. Za poboljšanje otpornosti potrebno je osigurati cjelovitost zidane konstrukcije, te poboljšati postojeće ziđe. Iako se obično zahtijeva primjena istih kriterija seizmičke otpornosti za obnovu postojećih i gradnju novih građevina, ipak se u nekim slučajevima proračunsko seizmičko opterećenje može smanjiti. Daju se preporuke za određivanje karakterističnih vrijednosti svojstava materijala.Basic criteria for seismic rehabilitation of masonry buildings in earthquake-prone areas are considered. To increase resistance, uniform behavior of the masonry structure must be ensured and the existing masonry walls must be improved. Although similar seismic resistance criteria are usually applied for renewal of the existing and construction of new structures, there are cased in which design seismic load may be reduced. Recommendations for determinig typical values for material properties are given

Influence of boundary restraints at testing of seismic behaviour of unreinforced masonry walls

V prispevku so predstavljene obsežne eksperimentalne raziskave obnašanja večetažnih zidanih strižnih sten z odprtinami pri potresni obtežbi. Preiskali smo odziv 3-etažnega preizkušanca v naravnem merilu na potresno obtežbo, s katero smo preučevali odziv tipične 5-etažne zidane stavbe, grajene na območju Slovenije in njene širše okolice v času pred letom 1964 (pred prvimi potresni predpisi). Vzporedno smo opravili osem cikličnih strižnih preiskav posameznih zidov pri štirih tipih robnih pogojev. Z analizo rezultatov obsežnih meritev sil in deformacij na površini večetažnih strižnih sten smo ovrednotili vpliv vertikalnih in horizontalnih elementov strižne stene na posamezni slop ter iskali najustreznejši tip robnih pogojev za simulacijo potresnega odziva v preiskavi posameznega zidnega slopa

Seismic response of multistorey plain masonry walls and efficiency of strengthening with composites

večetažnih sten, sezidanih iz modularnih zidakov, s poudarkom na opazovanju mehanizmov odziva in porušitve, ki se razvijejo v večetažnih stenah z odprtinami. Druga tema je osredotočena na raziskave utrjevanja takšnega zidovja z malto, armirano z mrežicami iz steklenih vlaken. Za raziskave smo na Zavodu za gradbeništvo Slovenije zgradili in preiskali posamezne zidove in večji trietažni preizkušanec v naravni velikosti. V cikličnem strigu pri konstantnem tlaku smo preizkusili več referenčnih in utrjenih zidov ter trietažni model dimenzij 4 x 4 m v tlorisu in višine 6,7 m. Trietažni model smo najprej obremenili do večjih, a popravljivih poškodb. Zatem smo poškodovani preizkušanec utrdili s kompozitnimi oblogami iz malte, armirane s steklenimi vlakni (GFRP), ter ga ponovno preiskali, tokrat skoraj do porušitve. V obeh primerih je bil odziv modela na vodoravno obtežbo s t. i. etažnim mehanizmom, pri katerem se večina poškodb skoncentrira v zidovih najšibkejše etaže. V zidovih smo opazili tipične strižne poškodbe z diagonalnimi razpokami. Potresno obnašanje posameznih zidov je bilo zelo podobno odzivu zidnih slopov večetažnega preizkušanca. Rezultati kažejo, da je mogoče z ustreznim načinom utrjevanja zidov doseči občutno izboljšanje potresnega obnašanja.Two topics are presented in the paper. The first one deals with seismic behaviour of multistorey masonry shear walls with openings built from hollow clay units. Special attention is given to the response and failure mechanisms. The second one deals with strengthening of such masonry with fibre reinforced mortar coatings. To study these topics, full scale walls as well as a full scale three storey model were built and tested at Slovenian National Building and Civil Engineering Institute. Reference and strengthened walls as well as the three storey building model with plan dimensions 4 m x 4 m and height of 6.7 m were tested in cyclic shear under constant compressive load. First, the multistorey model was tested in its original state until major but still repairable damage. Then, the damaged model was strengthened with glass fibre (GFRP) mesh reinforced mortar and re-tested to near collapse. In both cases the response to horizontal loads was with storey mechanism, with the majority of damage concentrated in the walls of the weakest storey. The dominant damage was of the diagonal shear type. The seismic response of individual walls tested in cyclic shear was very similar to what was observed in the walls of the multistorey model. Results show that seismic response of masonry structures can be significantly improved by an appropriate strengthening method