Stiffnes and bearing testing of the polyethylene inspection pit

U radu su prikazane metode i rezultati ispitivanja polietilenskih okana (šahtova) na obodni pritisak i vertikalno opterećenje. Iz rezultata ispitivanja izračunana je krutost okna, dopušteno vertikalno opterećenje i pritisni modul elastičnosti. Rezultati i analize ovih ispitivanja mogu se koristiti pri izradi preporuka za ugradnju i uporabu polietilenskih okana.The paper presents the methods and results of testing of linear low-density polyethylene inspection pits to peripheral pressure and vertical load. From these results stiffness of the pit was calculated as well as permissible vertical load and modulus of elasticity in compression. The results and analysis of these tests are usefull in developement of recommendations for installation and exploitation of inspection pits

RADNI DIJAGRAM I UTJECAJ PARAMETARA ISPITIVANJA NA REZULTATE VLAČNIH ISPITIVANJA

Tensile steel-coupon testing qualifies as one of the more commonly used experiments for determination of basic parameters for structural design. Such tests are usually performed to determine technical stress–strain relationships of tested materials. Technical stress–strain curves are not suitable for various numerical material models that exploit the plastic region of behavior, owing to the necking effect and accompanying change in coupon area being neglected during stress determination. Material ductility is influenced by the choice of gauge length, which may cause different researchers to differently interpret coupon tests of the same material. The proposed research utilizes benefits offered by an optical system for deformation monitoring to track changes in surface area and implement them during stress calculations until fracture. The possibility of adjusting the gauge length the same sample the ability to study its effect on obtained results. Based on analyzed data, these influences were evaluated and possible errors identified.Vlačno ispitivanje čeličnih epruveta je jedan od češćih eksperimenata, za praktične i znanstvene svrhe, prvenstveno jer daje osnovu za određivanje baznih varijabli koje su potrebne prilikom dimenzioniranja. Uobičajeni rezultat vlačnog ispitivanja je tehnički radni dijagram naprezanje - relativna deformacija. Međutim, on nije pogodan za različite numeričke modele materijala pomoću kojih se iskorištava plastično područje ponašanja, vezano uz činjenicu da se učinak suženja i pripadne promjene površine poprečnog presjeka epruvete zanemaruju pri određivanju naprezanja. Duktilnost je pod utjecajem odabrane mjerne duljine, što kao posljedicu može imati da različiti istraživači tumače rezultate vlačnog ispitivanja istog materijala na različite načine. Provedeno istraživanje iskorištava prednosti optičkog sustava za prostorno snimanje deformacija, tako da se prate promjene ploštine poprečnog presjeka i uzimaju u obzir pri proračunu naprezanja, sve do loma. Mogućnost promjene mjerne duljine na uzorku omogućila je proučavanje tog učinka na rezultate. Na temelju analize dobivenih podataka, navedeni utjecaji su procijenjeni i utvrđene su moguće pogreške

Konferencija o sadašnjim i budućim trendovima u projektiranju, gradnji i održavanju mostova, Peking, 17.–18. rujna 2007.

Dana je vijest o održanoj konferenciji o sadašnjim i budućim trendovima u projektiranju, gradnji i održavanju mostova, Peking, 17.–18. rujna 2007

Ductility analysis of laminated timber beams of small section height

Svrha je rada analizirati odnosno utvrditi primjenjivost modela koji uzimaju u obzir duktilnost drvenih elemenata pri savijanju. Ispitani su i prikazani gredni elementi male visine, dakle elementi kod kojih je raspon višestruko veći od visine. Osim ispitivanja grednih elemenata, dani su rezultati ispitivanja mehaničkih karakteristika osnovnog materijala i prikazana su ispitivanja provedena metodom konačnih elemenata (numerički modeli). Numerički modeli napravljeni su u programskom paketu Abaqus.The purpose of this paper is to analyze and determine the applicability of the models that take into account the ductility of timber elements in bending. Beam elements whose span is many times higher than the height are experimentaly tested. In addition to the tested beam elements, paper presents the mechanical properties of the timber material and the results obtained by finite element method (numerical models). Numerical models are made in the software package Abaqus

Measurement of bridge dynamic displacements and natural frequencies by RTS

U radu je prikazana primjena RTS-a za mjerenje pomaka na željezničkom mostu "Sava" tijekom pokusnog opterećenja nakon rekonstrukcije mosta, s posebnim naglaskom na određivanje pomaka pri dinamičkom djelovanju opterećenja te vlastitih frekvencija mosta. Rezultati mjerenja su uspoređeni s rezultatima numeričkog proračuna i s rezultatima vlastitih frekvencija određenih operacionalnom modalnom analizom (OMA).The use of RTS for measuring displacements at the Sava railway bridge during load testing after bridge rehabilitation is presented in the paper, and a special emphasis is placed on the determination of displacements when the bridge was subjected to dynamic load and natural frequencies. Measurement results are compared to numerical analysis results and to natural frequency results obtained by the Operational Modal Analysis (OMA)

Centrifugally-cast concrete poles with non-metallic reinforcement

U radu se prikazuje ispitivanje stupova namijenjenih elektrodistribuciji, koji se proizvode postupkom centrifugiranja, od betona vrlo visoke tlačne čvrstoće i koji su prednapeti šipkama od polimera armiranog ugljičnim vlaknima (Carbon Fibre Reinforced Polymer - CFRP). Prikazani rezultati ispitivanja stupova savijanjem do sloma upućuju na mogućnost primjene ovog građevnog proizvoda, napose u okolišu u kojemu dolazi do pojačane korozije konvencionalne čelične armature. Dio ispitanih stupova imao je posmičnu armaturu u obliku ovijene mrežice od polimera armiranog staklenim vlaknima (Glass Fibre Reinforced Polymer - GFRP), a dio je uzoraka bio bez posmične armature, ali je betonska matrica ojačana sintetičkim makro vlaknima. Dan je osvrt na dosadašnja ispitivanja sličnih proizvoda, na metode proračuna, kao i naznaka smjernica za daljnja istraživanja.The article describes the testing of poles for electric power transmission lines, which are made of centrifugally-cast concrete and ultra-high strength concrete, and which are prestressed with Carbon Fibre Reinforced Polymer tendons (CFRP). The presented results of pole ultimate load testing suggest the potential for usage of this construction product, particularly in aggressive environments with high probability of steel corrosion. Part of the tested poles had shear reinforcement in the form of confined Glass Fibre Reinforced Polymer (GFRP) grid, while one share of samples had no shear reinforcement, but the concrete matrix was strengthened with synthetic macro fibres. A review is given on similar product testing, calculation methods, and guidance is provided for further research

Dynamic analysis of cable-stay and suspension bridges

Dinamička ispitivanja zavješenih i visećih mostova prikazana su na primjerima Mosta Franja Tuđmana u Dubrovniku i pješačkog mosta u Osijeku. Kako je utjecaj dinamičkih djelovanja na zavješene i viseće mostove veći nego na druge tipove mostova veća je i potreba za njihovu eksperimentalnu verifikaciju. Prikazani su rezultati eksperimentalno određenih dinamičkih parametara (vlastitih frekvencija i prigušenja) prikupljenih u različitim vremenskim intervalima te njihove usporedbe.The dynamic analysis of cable-stay and suspension bridges is presented through case studies of the Franjo Tuđman Bridge in Dubrovnik, and the pedestrian bridge in Osijek. As the impact of dynamic actions on cable-stay and suspension bridges is greater when compared to other bridge types, the need for their experimental verification is also greater. The results of experimentally defined dynamic parameters (eigenfrequency and damping), measured at various time intervals, are presented and compared

The Impact Analysis of Lateral Restraint on the State of Stress and Strain in the Thin-Walled Z-Section Beam

The behaviour of thin-walled Z-section beam subjected to gravity load for different variants of lateral restraints is analyzed. For the basic variant of the laterally restrained beam the one defined in Eurocode 3 (EN 1993-1-3:2006) is taken. The Z-section beam which is laterally restrained along the flange by trapezoidal steel sheeting is observed, shown as a Z-section beam laterally restrained with linear stiff connection and rotary elastic connection. Variant of laterally restrained Z-section beam with a linear stiff connection, a variant of laterally restrained Z-section beam with rotary elastic connection and beam without lateral restraints are analyzed. Based on the research, analysis and comparison of the results for individual variants of thin-walled Z-section beams, with and without lateral restraints, is conducted