Static behaviour analysis of masts with combined guys

The purpose of this study was to develop a new type of guyed mast that incorporates a complex guy cable system with a particular focus on the effect of static loading on the response mast behaviour. The intension of such solution is to increase a number of elastic supports for the mast shaft that will impact on its stability under loading. The static analysis of a one‐level guyed mast has been undertaken. The effects of geometrical and physical design parameters on the displacements of the mast were determined. The analysis is illustrated with two‐guyed masts: the bending moments and lateral displacements were determined for a typical guyed mast and guyed mast with combined guys. Stiebų, turinčių mišriąsias atotampas, statinė elgsenos analizė Santrauka Aptariama originali plieninio stiebo konstrukcinė sandara, kurioje vietoje įprastinių vientisų atotampų taikomos mišriosios, turinčios atšakas, atotampos, sutelkiant dėmesį į statinės apkrovos įtaką stiebo elgsenai. Pagrindinis šio sprendinio privalumas – paslankiųjų atramų kiekio kamiene padidinimas, kas tiesiogiai daro įtaką stiebo stabilumui esant apkrovai. Statinės analizės metu buvo išnagrinėta pagrindinių komponuojamųjų geometrinių ir fizinių parametrų įtaka vieno atotampų lygio kamieno ruožo paslankiųjų atramų poslinkiams. Atlikta įprasto ir naujo tipo stiebo poslinkių ir įrąžų lyginamoji analizė. Reikšminiai žodžiai: stiebas, mišriosios atotampos, statinė apkrova, geometriniai ir fiziniai parametrai, elgsenos modeliavimas. First Published Online: 14 Oct 201

Some insights on the optimal schemes of tall guyed masts

The article presents the technique for simultaneous topology, shape and sizing optimisation of tall guyed masts under wind loadings and self-weight using simulated annealing. The objective function is the mass of the mast structure including guys, while the set of design parameters may consist of up to 10 parameters of different nature. The constraints are assessed according to Eurocodes and include the local and global stability constraints, limitations on the slenderness in mast elements, and strength constraints. The proposed optimisation technique covers three independent parts: the optimisation algorithm, meshing pre-processor that yields computational scheme of mast depending on the design parameters, and finite element program evaluating the objective function and constraints via penalisation technique. As an example the results of optimisation of a typical 60 m tall guyed telecommunication mast with different antenna areas are presented. On the basis of these results, the authors try ascertaining the approximate optimal diapasons of geometry and topology parameters such as the width of the shaft, distance of the guy foundation from the mast axis, heights of the guy attachment levels and so on. The authors hope, this will be helpful for constructors as an initial design of mast topology, shape and element sizing

Regulation of guyed mast stresses

Development of mobile communications and their networks in Lithuania produced an essential influence on high telecommunications structures design activities. In its turn it has stimulates their research and innovations of such structural systems. One of the most efficient systems of telecommunication structures is guyed mast. It should be indicated that the behaviour of prestressed structures systems has been thoroughly examined in many investigations. But recently the increase of economical efficiency of guyed masts becomes undoubtedly actual. The development of such structures in many cases is directed to the selection in the mast elements scheme and their cross-sections. It should be underlined that geometric and physical parameters have a decisive moment on prestressed structures. An exact parameters choice allows to obtain in the mast rational distribution of bending moments, predetermining a project solution closely connected with the mass criteria. The diagram of bending moment’s distribution in guyed mast is considered rational when negative and positive moment values are absolutely equal. In the present research, analytical expressions for rational bending moments determining are presented. Above mentioned non-linear expressions estimate an influence of axial force for the bending moments. When solving the task of rational bending moments in a guyed mast, it is necessary to select suitable (i.e. rational) guyed mast bending spans. In the article is described the calculations of the guys fastening altitudes when guy level number is known. It should be noted that it is necessary to use the way of gradual approximation. The sequence of calculations is interrupted, when the sum of guyed mast spans corresponds to the exactness selected. The decisive part in mast behaviour is played by guys. The main parameters of them are pretension and cross-section area. In the article the equations are presented for determining the above-mentioned parameters. It should be stressed that after making uniform stresses of the guys on the different level of each of them it is possible to minimise some steel quantities. In the article a numerical experiment is presented for determining the technical-economical effectiveness of stress regulation. For the analysis, a standard three edged lattice guyed mast with cross-section parameters was selected in a usual way. By the suggested beam composition methods the design of the shaft was performed, and the results obtained were compared to a standard guyed mast shaft. For determining the stresses of beam elements Robot Millennium software was used; its reliability was demonstrated by earlier investigations. The results of numerical experiment that the maximal bending moment of composed guyed mast is three times less than that of a standard maximal one. An applied regulation of stresses has allowed to lessen much of the cross-section of guy rope. By applying the suggested methods it was possible to diminish the steel expenditure of shaft by more than 30%. Plieninių stiebų įrąžų reguliavimas Santrauka Straipsnyje aptariama plieninių stiebų projektavimo metodika, paremta įrąžų reguliavimu. Pateikiamos analitinės išraiškos racionaliems lenkiamiesiems momentams bet kuriame kamieno tarpsnyje nustatyti. Šiose netiesinėse išraiškose vertinama ašinės jėgos, veikiančios kamiene, įtaka racionalių lenkiamųjų momentų reikšmėms. Straipsnyje aptariamas ir atotampų tvirtinimo prie kamieno racionalių koordinačių (altitudžių) apskaičiavimas, taip pat ir pačių atotampų išankstinio įtempimo bei jų skerspjūvio ploto nustatymas. Atliktas skaitinis tipinio tribriaunio spragotinio plieninio stiebo eksperimentas parodė, kad siūloma įrąžų reguliavimo metodika leido ne tik sumažinti atotampų skerspjūvio plotą, bet ir bendrąsias sąnaudas. First Published Online: 16 May 2013 Reikšminiai žodžiai: plieninis stiebas, racionalūs lenkiamieji momentai, įrąžų reguliavimas, geometriniai ir fizikiniai parametrai, elgsenos modeliavima

Mast behaviour analysis and peculiarities of numerical modelling/Stiebų elgsenos analizė ir skaitinio modeliavimo ypatumai

Paper is assigned to numerical analysis peculiarities of masts applying specialised computer‐aided design packages. Mast's deformable behaviour is described as non‐linear one. The test problem of mast is solved by two widely applied in Lithuania computational packages STAADpro and Robot Millennium and the specialised programme for mast design SUDM. A corrected analytical method for mast guy analysis, taking into account a force component, acting along the guy supports. A performed numerical experiment is aimed to clarify the possibilities of the above‐mentioned numerical analysis instruments for geometrical non‐linear modelling of structure. The accuracy errors when determining the mast stress and strain fields by numerical analysis packages comparing with the ones obtained by a corrected analytical method are indicated. Possibilities of employing the considered computer‐aided design programming packages for practical design of masts are discussed. Santrauka Straipsnyje aptariami stiebų kaip netiesiškai deformuojamų konstrukcinių sistemų skaičiavimo ypatumai naudojant kompiuterinio projektavimo specializuotus programinius paketus. Sprendžiamas stiebo elgsenos analizės ir skaičiavimo uždavinys pasitelkiant dvi plačiai Lietuvoje taikomas statybinių konstrukcijų kompiuterinio projektavimo programas STAADpro ir Robot Millennium bei specializuotą stiebų skaičiavimo programą SUDM. Straipsnyje pateikiama ir patikslinta analizinė stiebo atotampos skaičiavimo metodika, rodanti apkrovos komponentę, veikiančią išilgai atotampos atramų. Remiantis atliktu skaitiniu eksperimentu, yra sprendžiama apie minėtųjų kompiuterinio projektavimo programinių paketų galimybes modeliuoti geometriškai netiesinės sistemos elgseną. Nurodomos šių programinių paketų stiebų elementų įrąžų bei poslinkių apskaičiavimo lyginant su patikslinta analizine skaičiavimo metodika paklaidos, aptariamos minėtųjų kompiuterinio projektavimo programų praktinio taikymo stiebams skaičiuoti galimybės. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: stiebai, kabamasis lynas, netiesinė analizė, skaitinis modeliavimas

Design and analysis of combined plane steel guyed tower-mast

One of the most effective and widely used high-rise telecommunication structures are steel towers and guyed masts. The behaviour, analysis and application fields are exhaustively discussed in a number of scientific publications. The main advantages of tower structures are low building area, however, from the point of view of steel consumptions, such structures are not effective enough. For technical-economic efficiency not only the rational types of cross sections for typical mast elements are selected, but also various combined structural systems are developed and implemented. Flat tower-masts are also known. They are combined from a single plain truss supported out of its plane by guys. In this case, such mixed system is able to carry acting loads and actions in one direction like a tower and in other direction – like a mast. From a technicaleconomic point of view, such system stands in the intermediate position between the guyed mast and the tower. The major weakness of such framework is relatively great depth and the cross sectional area of the chords of the tower truss which is caused by the relatively high values of the bending moment in the chord acting in the plane of guys and the large buckling length of the chord out of truss plane. It must be stressed that wind action on the investigated structure directly depends on the dimensions of the chord cross section. This paper deals with the new combined plain tower-mast structure the chords of which out of plane are stiffened by and inserted between the guys connecting joints and the double-sided strut members. These members are pre-stressed to avoid compression induced by transverse loading. The analysis of the behavior of a separate strut system under transversal loading is performed and analytical expressions for determining internal forces and displacements in its members with and without pre-stressing are provided. The minimum values of the required pre-stressing in ties of the strut system are described. It is proved that a proper choice of the parameters of structural components gives a possibility of obtaining a favorable distribution of bending moments in the chord. On the basis of numerical experiments, a comparison between the results defined analytically and ones determined by the means of the Autodesk Robot Structural Analysis program is performed. The accuracy of the proposed analytical method is discussed. For defining the behaviour peculiarities of the new combined structural system and for estimating its technical-economic efficiency, the numerical experiment by the means of FEM program (Autodesk Robot Structural Analysis) was carried out. Analysis was performed using 98 meter high ordinary and new guyed tower-mast structures with guys fixed at four levels. The member sections of the analyzed structures designed according to the values of the defined acting internal forces are presented. It is estimated that using strut members helps in considerably reducing (about 4,8 times) the maximum values of bending moments in the chords of tower truss. It was estimated that depth between the chords in a new combined system was 2 times lesser than that in the ordinary tower – mast system. It is shown that in case of the same cross section and value of the pre-stressing force, the value of the vertical reaction of the new strutted tower-mast system on foundation was 1,65 time lesser than that in the ordinary system. Conclusions and recommendations are provided. Kombinuoto plieninio plokščiojo bokšto-stiebo konstravimas ir skaičiavimas Santrauka Straipsnyje aptariama nauja kombinuota plokščiojo bokšto-stiebo konstrukcijų sistema, kurios juostos sustandintos iš bokšto santvaros plokštumos dvipusiais paspyriniais iš anksto įtemptais elementais, išdėstytais tarp atotampų tvirtinimo mazgų. Analizuojama atskiros paspyrinės sistemos dalies elgsena veikiant skersinei apkrovai, pateikiama inžinerinė metodika jos elementų įrąžoms ir poslinkiams apskaičiuoti. Atlikto skaitinio eksperimento pagrindu nustatytas parengtos inžinerinės skaičiavimo metodikos tikslumas. Pasitelkus baigtinių elementų programą aptarti naujos kombinuotos konstrukcinės sistemos elgsenos ypatumai. Parodyta, kad paspyrinių elementų naudojimas leidžia gerokai sumažinti maksimalius lenkiamuosius momentus bokšto-stiebo santvaros juostose. Parodyta, kad siūloma nauja kombinuota paspyrinė bokšto-stiebo sistema pagal masės kriterijų yra kur kas efektyvesnė už analogišką tradicinę bokšto-stiebo sistemą. First Published Online: 16 May 2013 Reikšminiai žodžiai: plieninis bokštas-stiebas, paspyrinė sistema, išankstinis įtempimas, elgsenos modeliavima

Technical and economical effectiveness of the combined guys mast

This article presents the investigation of a new structure of the guyed mast with combined guys. Technical and economical effectiveness based on material saving criteria of this structure is analysed. Formulas and recommendations are given for determining the rational bending moments distribution in the mast and the coordinates of the guy attachment points. Numerical simulation shows that the new guy cable system allows reducing the quantity of materials for steel masts. Article in Lithuanian. Plieninio stiebo su kombinuotosiomis atotampomis techninis ekonominis veiksmingumas Santrauka. Straipsnyje aptariama nauja plieninio stiebo konstrukcija, kurioje taikomos kombinuotosios atotampos. Analizuojamas šios naujos konstrukcijos techninis ekonominis veiksmingumas pagal medžiagų sąnaudų kriterijų. Pateikiamos analizinės išraiškos racionaliems stiebo kamieno lenkiamiesiems momentams apskaičiuoti ir rekomendacijos atotampų tvirtinimo koordinatėms nustatyti. Atliktu skaitiniu eksperimentu parodyta, kad naujų kombinuotųjų atotampų taikymas leidžia sumažinti bendrąsias stiebo medžiagų (plieno) sąnaudas. Reikšminiai žodžiai: plienines stiebo konstrukcijos, kombinuotosios atotampos, racionalūs lenkiamieji momentai, konstrukcines schemos geometriniai parametrai, techninis ekonominis veiksmingumas. First Published Online: 21 Oct 201

Optimal Design of Lattice Towers Made Up of Solid Round Steel Bars

The article discusses rational design, considering the mass criterion, of a lattice steel tower made up of solid round steel bars affected by the static load. The spacing between the tower truss chords and the inclination of the bracing members are set as the main variables. A mathematical model of tower structure was prepared using MathCad 14.0 software. The conditions of the marginal safety state of the tower’s members were assessed. The numerical experiment was used as a basis to present the dependence of the tower’s optimum width and the optimum inclination of its struts on the tower’s height, wind load intensity and steel strength. Recommendations were provided as well

Optimization of rigidly supported guyed masts

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