In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 8 No. 3 September 2002


Investigation of masonry arches; 147–161

Réka Macskási

Abstract. A method for computing masonry arches consisting of rigid brick voussoires and deformable mortar layers is presented. The brick elements are allowed to move and rotate relative to each other, according to the material model of the mortar. Non-linear constitutive law is applied to eccentric compression and the shear behaviour is determined by both the shear and normal stresses. The applied mathematical method produces the global equilibrium path. The proposed algorithm is appropriate for analysing arches of arbitrary geometry subjected to arbitrary static loads. Some examples which show the influence of the various shape and material parameters are given.

Key words: masonry arch, non-linear constitutive law, sliding, equilibrium path, third-order theory.

Residual stresses in different thermal spray coatings; 162–173

Harri Lille, Jakub Kõo, Priit Kulu, and Toomas Pihl

Abstract. By testing a thin-walled ringed coated specimen, we determined the through-thickness residual stress distribution, the modulus of elasticity, and the coefficient of thermal expansion of different flame sprayed Cu-, Ni- and Ni-Al-based powder coatings, flame spray coatings, fused self-fluxing NiCrSiB alloy based coatings, and a high velocity oxy-fuel (HVOF) sprayed tungsten carbide WC-17Co coating. Residual stresses were, as a rule, slightly larger on the outer surface than at the coating–substrate interface, where they were close to adhesion strength. The highest residual compressive stresses were found in HVOF sprayed coatings which have high impact erosion wear resistance. The values of the moduli of elasticity were lower or close to the corresponding values of the basic substance of the powder used for producing the coatings, while the coefficients of thermal expansion were close to those of the basic substance.

Key words: thermal spraying, powder coating, ring specimen, strain gauge, residual stress.

Unstiffened thin-walled girder under uniform loading; 174–188

Priit Vilba and Siim Idnurm

Abstract. The paper focuses on the stresses and deformations of welded plate girders subjected to uniformly distributed edge loading. The critical load parameters of the web plate under the action of edge loading, shear, bending, and compressive stresses are determined. The horizontal edges of the web plate are considered to be elastically restrained, with vertical edges simply supported. The post-buckling behaviour of this web plate is analysed. In the post-buckling situation, the parts of the web plate are assumed to be simply supported and the edge load balanced by shear stresses on the adjacent edges. Numerical results of the continuous analytical and the finite element method are compared with results obtained from the Eurocode 3 formulas and with the test results.

Key words: plate girder, buckling load, post-buckling behaviour, ultimate load, Eurocode.

Flow modelling in the Pärnu Bay and the Kihnu Strait; 189–203

Ülo Suursaar, Tiit Kullas, and Mikk Otsmann

Abstract. Flow features are studied in the NE part of the Gulf of Riga using a 2D hydrodynamic model forced by the wind and sea level data of 1999 as well as by some constructed stationary winds. Two flow patterns dominate in the Pärnu Bay. The most frequent of them has an inflow along the Liu and Tahkuranna coasts and an outflow along the trunk zone of the bay. Eastward motions predominate both in the Kihnu Strait and Valgerand. High flow velocities, participating (along with storm waves) in coastal erosion events, act 1-2 m above the average waterline and about half of the year’s summary work of the flow by charging the coast is done during the 2-3 most stormy days of the year in the Pärnu Bay.

Key words: currents, storm surge, hydrodynamic model, water circulation, coastal engineering, Baltic Sea.

Instructions to authors; 204–206

Copyright Transfer Agreement; 207