Performance based experimental and numerical assessment of multi-leaf stone masonry walls : doctoral dissertation

Kržan, Meta (author), Bosiljkov, Vlatko (mentor)

V sklopu naloge je bilo študirano obnašanje troslojnih kamnitih zidov, in sicer obnašanje pri tlačnih obremenitvah in pri strižnih obremenitvah v ravnini zidov. Izvedene so bile obsežne eksperimentalne preiskave; tlačni in strižni testi skupaj 18 zidov ter spremljajoče preiskave konstituentov (malte in kamna). Preskušani kamniti zidovi so značilni predvsem za reprezentativne starejše objekte, ki pogosto predstavljajo pomemben del naše kulturne dediščine. Za testiran tip zidov je bil sistematično analiziran vpliv morfologije zidov (sestave po prerezu), različnih nivojev pred-obremenitev ter robnih pogojev vpetja na različne karakteristike obnašanja zidov. Poleg nosilnosti je bil poudarek na analizi pomikov ter poškodovanosti zidov v karakterističnih stanjih obnašanja. V odvisnosti od robnih pogojev je pri strižnih testih prišlo do različnih porušnih mehanizmov zidov; upogibnega, mešanega in diagonalnega strižnega, pri čemer v nasprotju s pričakovanji izven-ravninski mehanizem ni bil merodajen. Do slednjega je prišlo bolj opazno pri višjih pred-obremenitvah zidov v fazi mehčanja zidov. Za testirani tip zidov povezovalni kamni preko prereza zidu niso prispevali ne k večji nosilnosti ne k večjim mejnim pomikom. Eksperimentalni rezultati nosilnosti in mejnih zasukov so bili primerjani z analitičnimi modeli. Strižno nosilnost se zadovoljivo oceni z obstoječimi modeli za porušitve, do katerih je pri testih dejansko prišlo. Doseženi mejni pomiki zidov so bili pri testih veliko večji, kot so dovoljeni mejni pomiki v standardih (EN 1998-3 in FEMA 306). Ker je pri objektih kulturne dediščine poleg same konstrukcije pogosto v interesu ščititi tudi različne poslikave, je bil na zidove nanesen apneni omet, ki je služil študiju obnašanja umetnostih elementov zidov. Določene so bile vrednosti mejnih zasukov zidov za 4 stanja poškodb ometov, ki so uporabne za oceno potresne odpornosti objektov s stališča poškodovanosti ometov. Drugi del naloge obravnava utrjevanje poškodovanih troslojnih kamnitih zidov. Ker je navadno pri utrjevanju historične zidove zahtevana uporaba kompatibilnih materialov, reverzibilnost ukrepov, itd., je bil v sklopu naloge razvit nov sistem utrjevanja. Poškodovani zidovi so bili injektirani s cementno-apneno injekcijsko mešanico in dodatno utrjeni s stekleno vrvico, s podaljšano apneno malto vgrajeno v horizontalne maltne spojnice, ter z vrvico tudi prečno povezani. Skupaj je bilo z različnimi kombinacijami ukrepov utrjenih in dodatno testiranih 10 zidov. Injektiranje se je izkazalo kot primeren sanacijski ukrep, vrvice v spojnicah pa so povečale duktilnost zidov ter v določenem primeru tudi nosilnost. Rezultati testov neutrjenih zidov so bili aplicirani na dejanski objekt. Na primeru Vile Vipolže je bil numerično analiziran vpliv predpostavke mejnih pomikov zidov na potresno obnašanje objekta, računano z nelinearno statično analizo konstrukcije na modelu z ekvivalentnimi okvirji. Glede na rezultate (nezanemarljivo povečanje odpornosti v primeru povečanja pomikov) bi bilo za bolj duktilno zidovino, kot je navadno zgodovinska, smiselno dodatno preučiti smotrnost povečanja mejnih vrednosti zasukov v predpisih.

• Language: English
• Keywords: civil engineering, thesys, multi-leaf stone masonry, historic masonry, seismic behaviour, recompression tests, in-plane shear tests, drift limits, plaster damage, grouting, NSM, glass cord, transversal connecting of the wall
• Work type: Dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [M. Kržan]
• Year: 2015
• Number of pages: LII, 304 str.
• PID: 20.500.12556/RUL-80038
• COBISS.SI-ID: 7320929
• Publication date in RUL: 05.01.2016

KRŽAN, Meta, 2015, Performance based experimental and numerical assessment of multi-leaf stone masonry walls : doctoral dissertation [online]. Doctoral dissertation. Ljubljana : M. Kržan. [Accessed 15 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=80038

Secondary language

• Language: Slovenian
• Title: Eksperimentalne in numerične preiskave za določitev kontroliranega odziva večslojne kamnite zidovine

Abstract

In the thesis, the behaviour of three-leaf stone masonry walls under compression loading and in-plane shear loading is studied. An extensive experimental campaign was conducted on 18 walls, accompanied by tests on masonry constituents (mortar and stone). The type of the tested masonry is typical for older representative buildings, which often present important cultural heritage assets. Influence of morphology, level of pre-compression and boundary conditions on various characteristics of the walls behaviour was systematically studied. Besides the strength, the greatest emphasis was on the analysis of the displacement capacity and damage of the walls at characteristic stages of their response. Due to various boundary conditions, different failure mechanisms developed; rocking, mixed and diagonal shear. Leaf separation and the out-of-plane mechanism of the wall was not critical as expected. It developed more evidently in the post-peak phase of the tests for specimens with higher pre-compression. The presence of connecting stones had no influence neither on the obtained shear strength nor on the displacement capacity of the walls. The experimental results were compared to results of analytical models for prediction of shear resistance. For the tested type of masonry, shear strength can be adequately estimated with existing models for the failure mechanisms that developed in the tests. Drift capacity of the walls was however significantly higher than drift capacity allowed in the code provisions (EN 1998-3 in FEMA 306). In heritage buildings also various artistic assets in the form of painted walls are often present. Lime plaster was applied to the walls in order to study its performance during cyclic shear loading. Reference drift values for walls at 4 different characteristic plaster damage states were determined. They can be used for performance based seismic assessment of historic buildings. The second part of the thesis deals with strengthening of the damaged three-leaf stone masonry walls. For monumental buildings there are usually strict demands upon the use of materials compatible to existing materials, reversibility, etc., therefore a new strengthening system was developed. Walls were retrofitted along the cracks with lime-cement grout, additionally strengthened with near surface mounted (NSM) glass cords and transversally connected; 10 walls were strengthened with various combinations of measures and re-tested. Grouting successfully retrofitted the walls, while NSM glass cords increased the displacement capacity and, in one case, also shear resistance substantially. Finally, the results of tests of the un-strengthened walls (drifts) were adopted for the numerical analysis of the seismic performance of an actual building (mansion Vipolže). Nonlinear static analyses using equivalent frame model were conducted. The influence of the assumed drift limits on the seismic resistance was analysed. The increase of seismic performance with increasing drift limits of walls is evident and it would be reasonable to further study the prospect of increasing the drift limits in the code provisions for types of masonry, which are more ductile (historical masonry).

• Keywords: gradbeništvo, disertacije, večslojni kamniti zidovi, historični zidovi, potresno obnašanje, tlačne preiskave, strižne preiskave v ravnini, mejni zasuki, poškodbe ometov, injektiranje, urjevanje v fugah, steklena vrvica, prečno povezovanje zidov