Analysis of prestressed cross-laminated timber plates

The present work focuses on the analysis of cross laminated timber plates, with external prestressing. Analysis is done on a system with a 13,5 m span and a 90 mm thick plate. In the first part of the analysis several different mathematical models are presented. First different models done with the use of finite element software SAP2000 and than also a simpler mathematicall analysis. Two different types of construction are analysed – with one and five deviators. Besides models of the complete structure, details in which stress concentrations accur are also analysed – again with finite element software and with simpler mathematical procedures. On the result basis prestress losses in steel cables are estimated. In the second part of the analysis two 1 : 1 scale experiments are done – detail of the deviator and attachment of the cable. In the end there is a comaparison between diferent models – mathematical and experimental and a plan for the experiment of the complete 1 : 1 scale structure. I

SEISMIC DESIGN METHODS – ENERGY-BASED DESIGN

U radu je dan kratak osvrt na trenutno projektiranje konstrukcija otpornih na potres. U ovom radu prikazane su i sažete najnovije spoznaje u pogledu proračuna potresno otpornih građevina, s najosnovnijim primjerima i kritičkim osvrtom na trenutno stanje propisa i budućnosti projektiranja na potres. Fokus rada bio je prikazati novije metode kao što su metode zasnovane na trošenju energije. Predstavljeni su trenutačni zahtjevi i problemi pri proračunu konstrukcija energetskim metodama te predstavljeni dijagrami toka vezanim za spomenutu metodu.This paper gives a brief overview of the current design of earthquake resistant structures. The paper presents and summarizes the latest insights regarding the design of earthquake resistant buildings, with the most basic examples and a critical review of the current state of regulations and the future of seismicdesign. The focus of the paper was to present newer methods such as energy-based design. Current requirements and problems in the design of structures by energy-based design are presented. Shown flow-diagrams serve to understand the procedures more clearl

Strengthening of buildings with cross-laminated timber plates

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.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

Artist Talk

Okrogla miza o umetnosti v širšem družbenem kontekstu. Galerija Loža, Koper, 11. 4. 2019. Del cikla "SPEKULA - Na prelomu upodobitve/At the edge of the depiction", raziskovalno, kulturno-umetniških dogodkov, ki jih organizira Pedagoška fakulteta Univerze na Primorskem.

Restrained swelling deformation of densified wood dowel in dowel-laminated-timber (DLT)

Funder: Republic of Slovenia; Slovenian Research Agency ARRS (J4-3087); CT WOOD</p

Adhesive- and Metal-Free Assembly Techniques for Prefabricated Multi-Layer Engineered Wood Products: A Review on Wooden Connectors

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes

Adhesive- and Metal-Free Assembly Techniques for Prefabricated Multi-Layer Engineered Wood Products: A Review on Wooden Connectors

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes.Validerad;2023;Nivå 2;2023-02-13 (hanlid);Funder: Republic of Slovenia;  Slovenian Research Agency ARRS (J4-3087); CT WOOD, Luleå University of Technology</p

Restrained swelling deformation of densified wood dowel in dowel-laminated-timber (DLT)

Funder: Republic of Slovenia; Slovenian Research Agency ARRS (J4-3087); CT WOOD</p