Search

At the end of August 2016 an earthquake with a magnitude of 6.2 Mw hit Central Italy, followed by many strong aftershocks, which caused nearly 300 casualties and extensive damage. Less than two months later we had the opportunity to visit part of the affected area and see the seismic damage live. The majority of the affected buildings, seen in the field, were stone masonry buildings; there were almost no modern buildings in the area. Almost all of the buildings in the affected villages, which belong to the region Arquata del Tronto, are more or less damaged, while the village Pescara del Tronto is almost completely ruined. The damage observed is typical for stone and poorly connected buildings, dominated by shear damage. It turned out that buildings with r.c. columns behaved better than those without them. The article presents the earthquake data, typical earthquake damage of brick buildings, damage of two skeletal reinforced concrete structures and shows possible methods for interventional supporting of strongly damaged buildings. Konec avgusta 2016 je osrednjo Italijo prizadel potres z magnitudo 6,2 Mw in več močnimi popotresnimi sunki; povzročil je skoraj 300 žrtev in večjo gmotno škodo. Slaba dva meseca po potresu smo dobili priložnost, da obiščemo del prizadetega območja in si poškodbe ogledamo v živo. Glavnina prizadetih stavb je bila kamnitih zidanih, sodobnih stavb je bilo na obiskanem območju zanemarljivo malo. V prizadetih vaseh, ki sestavljajo naselje Arquata del Tronto, so skoraj vse starejše stavbe tako ali drugače poškodovane, vas Pescara del Tronto pa je skoraj v celoti uničena. Poškodbe so tipične za kamnite in slabo povezane stavbe, prevladujejo strižne poškodbe; stavbe z vezmi so se obnašale bolje kot tiste brez. V prispevku so podatki o potresu, predstavitev tipičnih poškodb zidanih stavb, poškodbe dveh skeletnih armiranobetonskih konstrukcij in prikaz načinov interventnega popotresnega opiranja močno poškodovanih stavb.

The paper presents an experimental study of seismic resistance of reinforced concrete columns for the purpose of analysing the influence of uncertainty of material characteristics and uncertainty in manufacture. In order to cover all of the considered sources of uncertainty, 12 columns were manufactured in three different companies. The same plan and nominally the same materials were used in the production of the columns. In addition to the material characteristics, the influence of lapping of longitudinal reinforcement on the seismic response of columns was analysed as well. The columns were tested with cyclic horizontal load, which was increased until collapse. The research has shown that there are big differences in the manufacture of the columns, which is observed in the seismic response after reaching the maximum capacity. The biggest influence on the ductility can be attributed to the detailing of the stirrups. The research has also confirmed some already well-known dependences and demonstrated that one of important parameters of the seismic resistance of columns might be the location of the first stirrup above the foundation. V članku so prikazane eksperimentalne preiskave potresne odpornosti armiranobetonskih stebrov, ki so bile opravljene na Zavodu za gradbeništvo Slovenije (ZAG) z namenom, da se določi vpliv negotovosti oz. razpršenosti materialnih karakteristik in izvedbe na potresni odziv stebrov. Da bi zajeli kar se da veliko virov negotovosti, smo naročili izdelavo 12 stebrov, ki so jih izdelala tri različna podjetja na podlagi istega načrta in nominalno enakih materialov. Poleg materialnih karakteristik smo analizirali vpliv preklopa vzdolžne armature na potresni odziv stebrov. Stebre smo preizkusili s ciklično horizontalno obtežbo, ki smo jo povečevali do porušitve. Raziskave so pokazale, da so med proizvajalci v resnici velike razlike, ki pa so opazne predvsem pri odzivu stebrov po doseženi največji nosilnosti. Največji vpliv na duktilnost ima izvedba armaturnega detajla stremen. Z raziskavo smo potrdili tudi nekatere že znane odvisnosti in opazili, da bi lahko bil pomemben parameter potresne odpornosti tudi lokacija prvega stremena nad temeljem.