A technique for simultaneous topology, shape, and sizing optimization of tall guyed masts is presented in this paper. The typical scheme of telecommunication masts that are triangular in plan and supported by a certain number of guys' levels is examined. The objective function is the total mass of the mast, including the mass of the guys. The mast structure is optimized for self-weight and wind loading that is evaluated according to Eurocodes. The nonlinear behaviour of the guyed mast is simplified idealizing the nonlinear guys as approximate boundary conditions for the mast. A comparison of the simplified solution with the results of nonlinear analysis with Ansys shows small discrepancies that are on the safe side. The constraints involve all strength, local and global stability, and slenderness requirements. The optimization problem is solved using evolutionary algorithm with original genome repair procedure. As an example, a typical 96 m guyed broadcasting antenna for mobile-phone networks was designed employing the proposed optimization technique and taking up to 10 guys' levels. It is shown that the optimal mast is supported by 3-5 guys' levels. The optimal ranges of all remaining design variables were also obtained.
IntroductionIn order to reduce the costs and consequently the material consumption, the construction of recent bridges is dominated by slender structures. Taking into account a sufficient load carrying capacity and durability, reduction of the bridges' costs can be achieved only by optimizing the bridge structures. This work is dedicated to the overall optimization of network tied arch structures for pedestrian bridges of moderate span. A network arch bridge is one of the most slender bridge schemes. Intersecting incline hangers are optimal for uneven or changing external loads, leading mainly to the axial internal forces in the members of bridge. Scheme of tied arch with vertical hangers leads to a substantially heavier design.The behaviour and design of network arch bridges were investigated in details by Tveit [1]. The main his conclusion is, an optimal network arch will remain the world's most slender bridge. Teich [2] in his dissertation tackled the development of optimal structure for network arch. Teich recommends using up to 50 hangers since their efficiency reduces significantly above 50. An essential parameter is the arrangement of hangers. Teich analysed five different arrangement types and concluded that the radial arrangement and arrangement with constantly decreasing slope of hangers are the best choices. Teich also suggests designing the arch of elliptical shape or arch with double radii, and of height 1/5 to 1/7 of the span length. On the contrary, Brito [3] asserts that for a bridge of 100 m span and of 17 m arch rise the variable hanger slope configuration is the least efficient arrangement scheme. However, in these works the influence of different parameters to the objective function (i.e., the cost of the structure or its equivalent form -the mass of structure) was studied independently.Mathematically, optimization of bridge scheme is constraint optimization problem with numerous discrete and continuous design parameters. For large-scale optimization problems, the high-dimensional design space contains usually numerous local minima scattered throughout the space. Common gradient optimization methods find the local minima close to the starting position, and are not suitable for larger optimization problems, and only the stochastic global optimization methods can
Anotacija. Straipsnyje yra analizuojama apmokamų vaiko priežiūros atostogų politika, aptariamas teisinis reglamentavimas, paramos šeimai sistema Lietuvoje ir bei pateikiamas apmokamų vaiko priežiūros atostogų sistemos vertinimas. Apžvelgiama naujausia ir aktualiausia mokslinė literatūra palankios šeimos politikos ir apmokamų vaiko priežiūros atostogų srityje. Remiantis Lietuvos statistikos departamento bei socialinio fondo valdybos (SODRA), darbo jėgos tyrimo duomenimis (Eurostat LFS), atskleidžiamos tėvų, turinčių vaikus dalyvavimo darbo rinkoje tendencijos bei motinų ir tėvų apmokamų vaiko priežiūros atostogų pasirinkimai ir vertinimas. Atlikto tyrimo rezultatai atskleidė, kad Lietuvoje egzistuojanti apmokamų vaiko priežiūros atostogų sistema iš esmės orientuota tik į prarastų pajamų kompensavimą tėvams, bet nesudaro lygių galimybių tolygiam abiejų tėvų įsitraukimui į vaikų priežiūrą bei dalyvavimą darbo rinkoje. Tai patvirtina ir statistiniai duomenys, kad du kartus daugiau moterų nei vyrų naudojasi apmokamomis vaiko priežiūros atostogomis, o moterų, turinčių mažamečių vaikų dalyvavimo darbo rinkoje rodikliai ženkliai mažėja. Motinų ir tėvų apsisprendimą išeiti vaiko priežiūros atostogų pirmiausiai nulemia finansiniai motyvai, sąlygoti mažesnių išmokų dydžių motinoms. Raktažodžiai: apmokamos vaiko priežiūros atostogos, apmokamų vaiko priežiūros atostogų sistemos vertinimas, palanki šeimai politika
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