This paper presents general principles of managing the reliability of steel chimneys according to Eurocodes EN 1990 and EN 1993-3-2. It discusses the basis for static calculations and dimensioning and compares Eurocode guidelines to the requirements of old Polish Standards. The use of standard procedures is illustrated by an example of static calculations and dimensioning of a steel chimney shell.
PL
W artykule przedstawiono ogólne zasady zarządzania niezawodnością kominów stalowych wg Eurokodów EN 1990 i EN 1993-3-2. Omówiono podstawy ich obliczeń statycznych i wymiarowania, a także porównano wytyczne Eurokodu z wymaganiami stawianymi przez stare polskie normy. Sposób wykorzystania procedur normowych zilustrowano przykładem liczbowym obliczeń statycznych i wymiarowania powłoki komina stalowego.
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The paper presents an analysis of the guidelines of the European standards on procedures for the calculation of shell structures. The analysis is illustrated with examples concerning three types of structures of the type i.e.: a chimney, a silo and a tank.
PL
W artykule przedstawiono analizę wytycznych norm europejskich dotyczących procedur obliczeniowych konstrukcji powłokowych. Analiza zilustrowana została przykładami obliczeniowymi dotyczącymi trzech konstrukcji, czyli komina, silosu i zbiornika.
Omówione w artykule problemy wynikają z różnego rodzaju błędów projektowych, wieloletnich zaniedbań w kwestii remontów kładek oraz z klęsk żywiołowych. Doskonalsze metody analizy i projektowania pozwalają współcześnie wyeliminować typowe dla dawniej wznoszonych konstrukcji błędy. W nowo projektowanych kładkach odchodzi się od zbyt wiotkich przęseł; dosztywnia się też w czasie remontów starsze konstrukcje.
EN
There are many footbridges in southern Poland. It is a mountainous region, with fastflowing rivers. Because of this, many of the footbridges are suspension, cable-stayed and ribbon footbridges. Four types of operating problems are analysed in the paper: incorrect design – sometimes no professional designers took part in construction; correct estimation of wind load and dynamic effects of wind and moving pedestrians; long period without any repairs (many footbridges are damaged after several dozen years of use); floods. A few footbridges were severely damaged or destroyed during the flood in 2010. At present, the new footbridges have a stiffer span than the older ones. Many old structures have been rebuilt. The missing bracings are added.
W artykule przedstawiono ogólne zasady zarządzania niezawodnością stalowych spawanych zbiorników na ciecze wg eurokodów EN 1990 i EN 1993-4-2 oraz podano podstawy ich obliczeń i wymiarowania w stanie zniszczenia plastycznego ze szczególnym uwzględnieniem imperfekcji montażowych i spawalniczych. Przeprowadzono weryfikację współczynników nośności plastycznej krajowych wyrobów hutniczych wyprodukowanych w latach 1963-1968 oraz 1976-1980. Sposób wykorzystania procedur normowych w stanie plastycznym zilustrowano przykładem liczbowym obliczeń statycznych i wymiarowania powłoki stalowego zbiornika stokażowego przeznaczonego do magazynowania wody amoniakalnej.
EN
The paper presents general rules for the management of structural reliability of weld steel tanks for liquids according to Eurocodes EN 1990 and EN 1993-4-2. Basis of design in plastic limit state, including assembly and welding imperfections, are presented too. Verification of the national partial safety factor for plastic limit state of steel products produced in the years 1963-1968 and 1976-1980 was achieved. Calculations of steel tank for ammonia water are example of design of structures in plastic limit state according to Eurocode rules.
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Conductometric titration (CT) is used as a complementary, non-specific technique against potentiometric (pH) titration (PT). The CT + PT procedure is applied to binary-solvent systems: HmL + Z/A + B (or HmL + Z/W + B) formed of a weak acid HmL and a pH-modifying agent Z (e.g. NaOH, NH3 or HCl), and totally miscible organic solvents A and B (or W = H2O and B) chosen as co-solvents, where acid-base equilibria are considered. The solvent composition in such systems is expressed by the mole fraction x of B. Concentrations of solutes: HmL and Z are the same in the solution titrated (titrand, D) and in titrant (T) and changes in pH value resulted only from differences in acid-base properties of solvents applied in D and T. On the basis of results obtained from PT and CT, the functional relationships related to the solutions of weak acids HmL (m = 1, 2, ...) were formulated, namely: (1) pKi = pKi(x) for acidity parameters; (2) Lp = Lp(x) for molar conductivities, related to the species formed by di- and triprotic acids. For this purpose, the Kohlrausch law on the independence of migrating ions has been applied. The pKi = pKi(x) relationships were formulated for diprotic and triprotic acids on the basis of enderson.Hasselbalch functions and modeled with use of polynomial functions. The pKi(1) and Lp(1) values were obtained by extrapolation. The approach suggested is the essential novelty in contemporary literature related to the subject in question. This way, the paper provides a new methodology, a new dimension (x-scale) to the problems known hitherto. In the experimental part, the pK1 = pK1(x) relationships were formulated for results of mutual pH titrations: HmL/B . HmL/W or HmL/B . HmL/A, obtained for the systems not involving Z. The systems were modeled with the use of Redlich.Kister (R.K) and orthogonal (normal, shifted) Legendre polynomials. Asymmetric functions by Myers.Scott (M.S) and by Michałowski were also suggested for this purpose. It was stated that all approximating functions fit the experimental data very well. The asymmetric functions are applicable for modeling of more bended relationships pK1 = pK1(x), particularly when referred to the limiting x-values in the interval < 0, 1 >. A software that enables to formulate the relationships pKi = pKi(x) according to different approximating functions after introducing the experimental data {(Vj, pHj) | j = 1, ..., N} obtained from PT, was also prepared, together with statistical evaluation of pKi(0) and pKi(1) values, obtained by extrapolation. The results thus obtained are presented in tables and figures. Some criteria of validity of the results obtained according to PT for pK1(0) and pK1(1) are also presented. The first criterion testifying about reversibility of indications of the measuring system is a position of the point of intersection of the plots obtained in the mutual titrations. The second criterion stems from comparison of results obtained from three pH titrations: (1) HmL/B Ť HmL/W, (2) HmL/B Ť HmL/A and (3) HmL/A Ť HmL/W. The convergence of the related plots at x = 0 and x = 1, where x = xB in (1) and (2) and x = xA in (3) testifies on account of the calibration procedure applied for glass electrode.