Skolioza je trodimenzionalna deformacija kralježnice u frontalnoj, sagitalnoj i transverzalnoj ravnini. Prema etiologiji, može biti primarna (idiopatska) i sekundarna (najčešće neuromuskularna), a ...češće se javlja kod djevojčica u adolescenciji. Osim estetskog poremećaja skolioza može uzrokovati dorzalgiju, a progresivne skolioze s Cobbovim kutom većim od 50° izazivaju ireverzibilno oštećenje respiratorne funkcije i indikacija su za operativno liječenje. Ostale skolioze liječe se konzervativno specifičnim vježbama za skoliozu, a kod Cobbova kuta većeg od 20° u kombinaciji s ortozom. Unatrag dvadeset godina brojni su radovi dokazali da je konzervativno liječenje skolioze specifičnim vježbama i ortozom uspješno te da može zaustaviti progresiju i korigirati kut skolioze. Liječenje provodi tim posebno educiranih članova koji čine liječnik (ortoped ili fizijatar), ortotičar i fizioterapeut. U liječenju posebnu pažnju treba posvetiti suradnji oboljeloga i osigurati potporu obitelji i okoline.
The behaviour of fibre reinforced polymer (FRP)-confined concrete in circular columns has been extensively studied, but much less is known about concrete in FRP-confined square columns, in which the ...concrete is non-uniformly confined and the effectiveness of confinement is much reduced. The present paper deals with the analysis of experimental results in terms of load-carrying capacity and strains, obtained from tests on square prismatic concrete column, strengthened with external glass fibre composite. The parameters considered are the number of composite layers and the corner radius for a square shape. A total of twenty-one prisms of size 100 × 100 × 300 mm were tested under strain control rate of loading.
The ductility of reinforced concrete beams is very important, since it is essential to avoid a brittle failure of the structure by ensuring adequate curvature at the ultimate limit state. One of the ...procedures used to quantify ductility is based on curvatures, namely, curvature ductility. It is necessary to know the curvature ductility of singly reinforced high-strength concrete (HSC) sections for determining a maximum permissible tensile reinforcement ratio or a maximum depth of the concrete compression area in design codes. The requirements of several codes and methods of prediction of the curvature ductility are based on the experimental results of normal strength concrete (NSC). The rules derived for NSC sections may not be appropriate for HSC sections, and verifications and modifications may be required for the evaluation of curvature ductility of HSC sections. In this study, the major factors affecting the curvature ductility of a singly reinforced HSC beam section are investigated. Based on numerical analyses, a parametric study has been carried out to evaluate the effects of various structural parameters on the curvature ductility of reinforced HSC beam sections.
U Republici Hrvatskoj uveden je 2010. godine jedinstveni koordinatni sustav poprečne Mercatorove projekcije Hrvatski terestrički referentni sustav 1996 (HTRS96/TM). Dotadašnja dva sustava zamijenjeni ...su jednim, sa srednjim meridijanom 16° 30’. Zbog svojstva poprečne konformne cilindrične projekcije, problem linearne deformacije dolazi do izražaja na rubnim dijelovima projekcije. Udaljavanjem od srednjeg meridijana raste linearna deformacija koja prelazi dopuštenu vrijednost (1 dm/1 km). U ovome radu objašnjena je problematika redukcija i korekcija mjerenih duljina s fizičke površine Zemlje u ravninu projekcije HTRS96/TM. Prikazani algoritam za izračun redukcija i korekcija upotrijebljen je u izradi računalnog programa ReducDist. Kód za navedeni računalni program napisan je u programskom jeziku C# korištenjem razvojnog okruženja .NET framework i softvera za Razvoj Windows aplikacija Visual Studio.
U radu je prikazano delovanje sile prednaprezanja na armiranobetonski ram (u daljem tekstu AB ram). Posmatrani sistem je statički neodređen sa dva ukleštenja. Na njega deluje opterećenje ...prednaprezanje kablom silom Nk=600 kN, kao i sopstveno opterećenje. Visina rama je 6.00 m, a osovinski razmak 20.00 m. Opterećenje od sopstvene težine elemenata je od rigle i stuba. Opterećenje konstrukcije usled prednaprezanja spada u unutrašnja opterećenja, koja zamenjujemo ekvivalentnim opterećenjem koje predstavlja spoljašnje opterećenje. Proračun je izvršen metodom sila i metodom deformacija, kao i u softverskom programu 'Tower'. Metodom sila se uklanja ukleštenje i preseku se omogućava obrtanje. Statički neodređena veličina tada je moment ukleštenja. Kod metode deformacije sve statičke i deformacijske veličine izražavaju se putem izvesnog broja međusobno nezavisnih deformacijskih veličina, koje su određene iz uslova ravnoteže sistema. Broj nezavisnih deformacijskih neodređenih veličina predstavlja deformacijsku neodređenost nosača. Sve deformacijski neodređene veličine mogu se svrstati u dve grupe: prvu grupu čine uglovi obrtanja na krajevima kruto vezanih štapova, a drugu grupu komponente pomeranja čvorova. / The effects of prestressing forces on a reinforced concrete frame are shown in the paper. The structure is a statically indeterminate frame with two fixed supports. The load is due to tendon prestressing with Nk = 600 kN and due to self-weight of columns and beam. The columns height is 6.00 m and the beam span is 20.00 m. Effects of prestressing can be replaced by an external equivalent load. Calculations are performed by the force method, by the direct stiffness method and using the 'Tower' software. The rotational restraints are released at fixed supports and the restraint moments are calculated by the force method. The direct stiffness method uses the members' stiffness relations for computing member forces and displacements in structures. The unknown nodal rotations and translations are obtained by solving a system of equations. The considered tendon profile is without eccentricity above the columns. 'Tower 7' is software for static and dynamic structural analysis and for design of concrete elements. It enables overall structural analysis of plane and three-dimensional structures. Automated, integrated tools allow fast and reliable design or the verification of the results obtained by standard methods. Version 7 is a professional tool with high performance. Three different calculation methods have given close results, with minor differences.
In the short term, the Euorocode-based techniques will be implemented as the main design specifications for structural engineers from the member-states of the European Union instead of the national ...standards. Therefore, it is of primary importance draw attention to the observed inaccuracies, particularly, in predicting non-linear creep strains according to EC-2. The analysis performed was mainly focused on an inconsistency elimination observed in the original EC-2 approach, when transition from the linear to non-linear creep laws for a constant compressive stress is required. A recent CEN corrigendum eliminating the observed inconsistency was also discussed in detail.
In this context, similar techniques which were reported in the literature for predicting the creep non-linearity function were analysed to account for the results obtained. It was particularly demonstrated that the recent CEN amendment results in an extremely enhanced creep strain for low strength concrete. A comparison of the creep non-linearity functions with experimental test results was also considered.
Na furnirima su provedeni kompresijski testovi u smjeru njihove debljine. Uspoređene su dobivene krivulje naprezanja-deformacije furnira s drugim poznatim krivuljama naprezanja-deformacija. Na osnovi ...mikroskopske studije tijekom kompresije furnira moguće je opisati deformacije furnira i objasniti odstupanje od dosad poznatih, tipičnih krivulja naprezanja-deformacija. Istraživanja su pokazala da se zbog valovitosti listova furnira i uzoraka velik dio deformacija pojavljuje pri ispravljanju furnira već uz relativno nisku razinu naprezanja.
In the second half of the previous century, analysis of deformations became a highly interesting subject of research and practical application in industry. The presented approach was developed in ...British Columbia, Canada, for the determination of potential deformations on several dams and landslide areas. Original measurements were obtained via standard surveying observation of distances and directions for horizontal positioning, and elevation differences for vertical positioning. GPS vectors were added some years later. The geodetic measurements of several epochs were adjusted with the parametric model of the method of least squares with minimum datum constraints. The deformation analysis was made with the successive application of the Helmert transformation.
Studies on deformation characteristics of early-age Jointed Plain Concrete Pavements (JPCP) due to environmental effects have drawn significant interest over the years. However, the complex nature of ...the problem arising from interacting environmental factors has resulted in difficulties in predicting the JPCP deformation characteristics. This study introduces a simplified approach for predicting the early-age deformation of JPCP due to environmental factors using an equivalent temperature difference concept. A newly constructed JPCP section on highway US-30 near Marshalltown, Iowa was instrumented to monitor the pavement response to variations in temperature and moisture during the first seven days after construction. Based on the collected field data, the total equivalent linear temperature difference (ΔT
teltd
) corresponding to the actual deformation was quantified using Finite Element (FE) based approach, namely ISLAB 2000. The FE-based calculations were compared with the field measured slab deformation properties. Better predictions were obtained when employing a simplified equivalent temperature difference (ΔTteltd) concept for FE based primary response model.
The behaviour of steel structure components within a high temperature field depends not only on the absolute temperature, but also on the temperature vs time function and on the heating rate, dT/dτ. ...The research objective is the determination of the heating rate impact on selected strength parameters of structural steels. Tests were performed under conditions of a linear temperature increase with different heating rates and with a constant stress value, σ/f
y
. After strength tests, the samples were subjected to metallography. Test results proved that the heating rate makes a significant impact on parameters that determine the steel structure bearing capacity at higher temperatures and that the heating rate should be accounted for in the strength analysis of steel structures exposed to high temperatures.
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