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Expressions for the calculation of ductility index for concrete girders with different ratios of prestressed and classical reinforcement were proposed using load–displacement, load–strain and load–curvature relation. The results of previous experimental static tests of several large-scale concrete girders with different ratio of prestressed and classical reinforcement are briefly presented. Using the proposed expressions, various ductility index of tested girders were calculated and discussed. It was concluded that the ductility of girders decreases approximately linearly by increasing the degree of prestressing. The study presents an expression for the calculation of the average ductility index of classical and prestressed reinforced concrete girders, which are similar to the analysed experimental test girders.

U ovom radu je prikazan postupak proračuna potpornih zidova prema Europskim normama za dinamičko opterećenje uzrokovano potresom. Prvo su izložene teorijske osnove, a zatim je na praktičnom primjeru armiranobetonskog konzolnog potpornog zida visine 4.40 m proveden proračunski postupak prema EN 1997-1 i EN 1998-5. Na kraju su dati zaključci sa općenitim komentarima primjene Europskih normi.

The paper presents the results of experimental tests with numerical comparison of some typical composite elements. Two different kinds of elements were tested: composite steel-concrete andcomposite wood-concrete elements (Fig. 1) [2]. Deflections at mid-span of simply supported beams under monotonously increasing static load were measured (Fig. 2). The influence of different types of composite joints on the results was analysed. Fig. 1 Some girders prepared for testing Fig. 2 Comparasion of experimental and calculated mid-span deflection for the wood-concrete element In numerical tests, the main structure was modeled with two-dimensional plane elements [1]. The composite surface was modeled with two-dimensional interface elements for the continuous connection simulation and modified beam elements for the discrete connection simulation. The applied material models include the most important nonlinear effects of concrete, steel and wood behavior, as well as nonlinear behavior of the composite at the connection surface. The numerical results of developed numerical model were compared with the experimental test results.

The paper briefly presents experimental tests for omnia slabs and comparison with results of numerical model. Six types of reinforced concrete (omnia) slabs with various types of connection constraints were tested, while deflections in the middle of the span, under different level of load are measured. The achieved test results were compared with the results obtained through the developed numerical model and are evident very good accordance between developed algorithm and test results.

The paper shortly presents numerical model developed for simulation of composite structures. The main structure is modeled with two-dimensional plane elements, while the composite surface is modeled with two-dimensional interface elements for continuous connection simulation and modified beam elements for discrete connection simulation. The applied material model was used for the purpose of simulation of reinforcing concrete structures. It includes the most important nonlinear effects of reinforced concrete behavior: yielding in pressure and opening and propagation of cracks in tension with tensile and shear stiffness of cracked concrete, as well as nonlinear behavior of reinforced steel. It also includes nonlinear behavior of composite surface and connection elements (dowels). The model was confirmed on experimental tests of composite concrete (Omnia) slabs, which are common in usage. The obtained test results were compared with the results obtained through the numerical model.

The paper shortly describes calculation of formwork and scaffold for reinforced concrete dome of sports hall Višnjik in Zadar. The big size and complexity of the structure requires control of all critical elements of formwork and scaffold in all construction phases which are established through building technology. Moreover, the size of the project and relatively long construction period dictate some additional analyzing of load acting on formwork and scaffold during construction.

The paper shortly describes the building technology of reinforced concrete dome sports hall Višnjik in Zadar. Chosen technology is monolithic construction, on spot concreted on fixed formwork and scaffold. Since the structure is double curved, so placing of formwork and scaffold is extremely complex because each part of formwork and scaffold is unique. Furthermore, the (big) size and complexity of the structure require additional analyzing and detail time plan diagram preparing for setting and removing formwork and scaffold, as well as for concreting, aiming to optimally use exploit equipment and human resources. Moreover, some architectural and functional requests cause additional difficulties in connections design, concreting joints and other constructions details which all must be resolved through designed technology.

U ovoj je knjizi ukratko prikazana problematika spregnutih konstrukcija, s posebnim osvrtom na sprezanje čelika i betona, drva i betona te betonai betona. Naglasak je stavljen na razvoj jednog numeričkog modela za simulaciju ravninskih spregnutih konstrukcija izloženih kratkotrajnom mirnom opterećenju.

Prikazani su rezultati eksperimentalnih ispitivanja efikasnosti sprezanja montažnih omnia ploča i monolitnog betona s adekvatno oblikovanim moždanicima od betonskog čelika. Prikazani su rezultati mjerenja progiba u sredini raspona pod monotono rastućim statičkim opterećenjem ploča različitih načina sprezanja. Istražen je utjecaj načina sprezanja na progibe ploče. Predlaže se hrapavljenje gornje plohe omnia ploče i premazivanje čime se postiže visoki stupanj sprezanja.

U radu je prikazan numerički model simulacije ravninskih spregnutih konstrukcija pod statičkim monotono rastućim opterećenjem, te odgovarajući proračunski program za praktičnu primjenu. Prostorna diskretizacija sustava se bazira na metodi konačnih elemenata. Uključena je materijalna nelinearnost konstrukcije, uključujući i simulaciju nelinearnog ponašanja na plohi sprezanja. Korišten je model materijala, prvenstveno namijenjen simulaciji armiranobetonskih konstrukcija opterećenih kratkotrajnim statičkim opterećenjem. Uporabljeni model simulira najvažnije nelinearne efekte ponašanja armiranog betona: tečenje u tlaku i razvoj pukotina vlaku, promjenu vlačne i posmične krutosti ispucanog betona, te nelinearno ponašanje armature. Izloženi model, varijacijom paramatara se može uspješno koristiti i za simulaciju drugih gradiva (čelik, drvo itd.). Za simulaciju spoja elemenata (sprega) korišteni su kontaktni elementi i modificirani štapni elementi. Dan je inženjerski osvrt na spregnute konstrukcije sustava čelik-betona, drvo-beton i beton-beton. Ukratko je prikazan proračun spregnutih konstrukcija iz čelika i betona prema Eurocodu-4. Opisana su provedena eksperimentalna ispitivanja spregnutih konstrukcija iz čelika i betona, drva i betona i betona i betona. Dana je i usporedba dobivenih eksperimentalnih rezultata s rezultatima numeričkog modela. Također su izvedeni određeni zaključci i dani pravci daljnjih istraživanja.

Knjiga je prvenstveno namijenjena studentima i kao takva u potpunosti obuhvaća gradivo iz predmeta Osnove betonskih konstrukcija na Preddiplomskom sveučilišnom studiju građevinarstva te iz predmeta Betonske Konstrukcije 1 i Betonske Konstrukcije 2 na Preddiplomskom stručnom studiju građevinarstva FGAG Split. Djelomično se odnosi i na gradivo u okviru predmeta Betonske Konstrukcije 1 i Betonske Konstrukcije 2 na Sveučilišnom diplomskom studiju građevinarstva te gradivo predmeta Nosive konstrukcije 1 na Sveučilišnom preddiplomskom studiju arhitekture i urbanizma FGAG Split. Intencija je autora da se materija ne prikazuje na detaljistički i u širinu, već da se na jasan i koncizan način predstave osnove proračuna, dimenzioniranja i oblikovanja armirano betonskih konstrukcija. Kako je nastajala u dužem razdoblju, materijali su pratili i razvoj normi za proračun betonskih konstrukcija, od PBAB-a, preko europske prednorme, do najnovije europske norme za beton: HRN EN 1992-1-1:2013/A1:2015 (EC-2). Navedena norma, važeća u Republici Hrvatskoj te po kojoj je ovo izdanje knjige usklađeno, danas u svijetu nesumnjivo predstavlja jednu od najmodernijih normi za proračun, dimenzioniranje i oblikovanje armirano betonskih konstrukcija.