Utrjevanje stavb s križno lepljenimi lesenimi ploščami : doktorska disertacija

Šušteršič, Iztok (avtor), Kilar, Vojko (mentor), Tomaževič, Miha (komentor)

Doktorsko delo obravnava protipotresno utrjevanje obstoječih konstrukcij s sistemom obložnih križno lepljenih lesenih (CLT) plošč. Izvedena je bila serija monotonih preiskav upogiba križno lepljenih plošč v ravnini, kvazistatičnih cikličnih preiskav neutrjenih in utrjenih zidov iz nearmirane opečne zidovine ter dinamične preiskave neutrjenega in utrjenega dvoetažnega armiranobetonskega (AB) okvirja z ali brez opečnih polnil na potresni mizi. Slednji je bil dimenzioniran v skladu s pravilnikom o protipotresnem projektiranju iz leta 1981 in je bil v osnovi že potresno odporen. Testi opečnih zidov so pokazali, da je možno z mehanskim pritrjevanjem CLT plošč na konstrukcijo povečati nosilnost do 34 %, mejni pomik pa za 165 %. Testi AB okvirja z opečnimi polnili so pokazali, da so CLT ojačitve povrnile nihajne dobe poškodovane konstrukcije v prvotno stanje, zmanjšale so tudi torzijsko podajnost objekta. Delež utrditve je bil sicer dokaj velik v primerjavi z osnovnim objektom. Izdelani so bili numerični modeli ter izračunana potresna odpornost testiranih vzorčnih primerov. Ugotovljeno je bilo, da je s predlaganim sistemom obložnih CLT plošč možno zmanjšati obseg poškodb na testiranih AB okvirju in AB okvirju z opečnim polnilom. Na numeričnem 2D modelu večje stene iz nearmirane opečne zidovine (del fiktivnega dvoetažnega objekta), ki ni izpolnjevala kriterijev za mejna stanja omejevanja poškodb in stanja na meji porušitve, smo po namestitvi ojačilnih plošč, sidranih v medetažno konstrukcijo, povečali njeno potresno odpornost. Obenem je bila izvedena parametrična študija vpliva robnih pogojev na obnašanje konstrukcij iz križno lepljenih plošč z različnimi metodami % modalno analizo s spektri odziva, potisno analizo z N2 metodo ter nelinearno dinamično analizo. Prikazali smo, kako različna togost, nosilnost in duktilnost spojev vpliva na potresno odpornost konstrukcij iz CLT plošč, pomembnost upoštevanja vertikalne obtežbe na stene ter vpliv trenja. Analizirali smo tudi vpliv geometrije sten, ki so lahko sestavljene iz enega večjega ali več manjših kosov. Predlagali smo še postopek za izračun nadomestnih horizontalnih togosti in nosilnosti v ravnini križno lepljenih sten, v kombinaciji z upoštevanjem vertikalne obtežbe, trenja in spojev med lesenimi stenami in medetažami, ki je primeren za inženirsko prakso in omogoča definiranje togosti konstrukcije za modalno analizo s spektri odziva.

• Jezik: Slovenski jezik
• Ključne besede: grajeno okolje, gradbeništvo, disertacije, eksperimentalna analiza, križno lepljene lesene plošče, potresna analiza, utrjevanje stavb, potresna sanacija, nearmirano zidovje, armiranobetonske konstrukcije, opečna polnila
• Vrsta gradiva: Doktorsko delo/naloga
• Tipologija: 2.08 - Doktorska disertacija
• Organizacija: FGG - Fakulteta za gradbeništvo in geodezijo
• Kraj izida: Ljubljana
• Založnik: [I. Šušteršič]
• Leto izida: 2017
• Št. strani: XLVIII, 374 str.
• PID: 20.500.12556/RUL-100060
• UDK: 624.011.1:624.073.5:624.042.7:699.841(043)
• COBISS.SI-ID: 8300641
• Datum objave v RUL: 02.03.2018

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Strengthening of buildings with cross-laminated timber plates : doctoral thesis

Izvleček

The doctoral thesis deals with the seismic strengthening of existing structures with a cladding system of cross laminated timber (CLT) plates. An experimental series of monotonic in-plane bending tests of cross laminated timber plates was performed, a quasi-static cyclic testing series of unstrengthened and strengthened unreinforced masonry walls and a series of dynamic tests on a shaking table where a two-story unstrengthened and strengthened reinforced concrete frame with and without masonry infill was analysed. The later was designed according to the demands of the 1981 seismic guidelines and was basically already seismic resistant. The masonry wall tests showed that by using a mechanically connected CLT plate the load bearing capacity can be increased by 34 % and ultimate displacement by 165 %. The RC frame tests with masonry infill showed that the CLT strengthening plates caused the vibration periods of an already damaged structure to return back to their initial state, the building%s torsional flexibility was also decreased. However, the proportion of the strengthening was quite large compared to the basic structure. Numerical models of the tested structures were made, their seismic resistance was calculated. It was found that the proposed CLT cladding strengthening system can reduce the extent of damage on the tested RC frame and frame with masonry infill. A 2D numerical model of a larger unreinforced masonry wall (part of a fictional case study building) that didn%t meet the damage limitation and near collapse limit states, showed that after the instalment of the CLT plates anchored into the floor structure the wall%s seismic resistance was increased. In addition, a parametric study of the influence of boundary conditions on the seismic behaviour of cross laminated timber buildings is performed with different analysis types % a modal analysis with elastic spectrum response, a pushover analysis with the N2 method and a nonlinear dynamic analysis. We have demonstrated how different stiffness, strength and ductility of connections influences on the seismic resistance of CLT structures, the importance of taking the vertical load acting on walls into account as well as the influence of friction. We have also analysed the influence of wall geometry that can be built from either one larger or several smaller pieces. Also, a procedure for the calculation of a wall%s in plane substitute stiffness and strength considering the influence of the vertical load, friction and connections among timber walls and floors is proposed, which is suitable for the engineering practice and allows the definition of a structure%s stiffness for the modal analysis with the response spectra.

• Ključne besede: building environment, civil engineering, thesis, experimental analysis, cross-laminated timber plates, seismic analysis, building strengthening, seismic retrofit, unreinforced masonry, reinforced concrete structures, masonry infill