•The vibrations of axially loaded thin-walled beams are studied.•The influence of bimoment due to initial stress is investigated.•The thin-walled beams with Z cross-sections and different boundary ...conditions are analyzed.•Bimoment induced by axial loads has significant influence on natural frequencies.
The objective of the paper is to analyze the influence of bimoment induced by constant axial loads on the free motion of thin-walled beams with point-symmetric open cross-section. For various boundary conditions, a closed-form solution for natural frequencies of free harmonic vibrations was derived by using a general solution of governing differential equations of motion based on Vlasov's theory. In order to investigate the effect of the bimoment on natural frequencies, the numerical examples with symmetric Z cross-section are given. The obtained results, verified using an ANSYS finite element model, demonstrate that the influence of the bimoment is important in the assessment of torsional natural frequencies.
In this paper the influence of the bimoment induced by external axial loads on the elastic torsional buckling of thin-walled beams with open cross-section is studied. The governing differential ...equations of a deformed thin-walled beam consistent with Vlasov's classical assumptions are derived applying the principle of virtual displacements. It is shown that in the cross sections with lack of symmetry the bimoment can considerably affect the torsional buckling load. The obtained results are verified using ANSYS finite element software.Original Abstract: U clanku je proucen utjecaj bimomenta na stabilnost tankostjenog stapa s otvorenim poprecnim presjekom uslijed vanjskog aksijalnog opterecenja. Primjenom principa virtualnih pomjeranja izvedene su diferencijalne jednadzbe deformiranog tankostjenog elementa u skladu s klasicnim pretpostavkama Vlasova. Pokazano je da kod poprecnih presjeka koji nemaju os simetrije bimomenat moze znacajno utjecati na u vojnu kriticnu silu. Dobiveni rezultati su provjereni primjenom programa ANSYS.
Problems involving contact are of great importance in industry related to mechanical and civilengineering, but also in biomechanics and other applications. The contact interaction betweensurfaces and ...different bodies like in a bolted splice connection joint or area in which a tire interactswith the soil is not known a priori, leading to a nonlinear boundary value problem. Due to the rapidimprovement of modern computer technology, one can today apply the tools of computationalmechanics to analyze contact problems with required accuracy, depending on design requirements.However, even now most of the standard finite element software is not fully capable of solvingcontact problems, including friction, with robust algorithms. The aim of this paper is to present somebasic concepts of Contact Mechanich.
Progress and demands of all types of constructions imposed the need for the development of modernstructures that are lightweight, but at the same time have high damping capacity and stiffness. ...Theconsequences of these requirements are increased dynamic problems related to vibrations anddissipative processes in structure connection joints. Structural joints are the main reason for thesignificant reduction of the level of energy dissipation and source of structural damping so thereforethey have become a subject of interest to many researchers. The aim of this paper is to present someproblems regarding research of structural damping and the importance of study Contact Mechanicsto better understand the problem of structural damping.
A field load testing is an effective method for understanding the behavior and fundamental characteristics of cable-stayed bridges. This paper presents results of the behavior of the reconstructed ...cable-stayed bridge over river Danube in Novi Sad under test load. The bridge was built between 1976 and 1981 and in 1999 was heavily damaged by two Tomahawk missiles. In 2003 process of the reconstruction began and at the end of 2005 Faculty of Civil Engineering, University of Belgrade was invited to test reconstructed bridge structure. The results of static load testing presented herein include displacements, rotations and strains of the 351 m long main span. Vibrations of the bridge were obtained by impact load produced by heavy truck passing the bridge and the time history response of vertical accelerations was recorded. The frequency content of the signals was determined using Fourier transformation and five flexural natural periods were extracted. The geological structure and engineering properties of the soil are also given. A finite element model of the bridge was made and a good agreement is achieved between the experimental and analytical results. These results have shown that the bridge is in the elastic state under the code-specified serviceability load, which indicates that the bridge has adequate load-carrying capacity and can be put safely into service. Keywords: cable-stayed bridge, experimental analysis, numerical analysis Ispitivanje ovjesenih mostova opterecenih probnim opterecenjem je efikasan nacin za sagledavanje ponasanja i odredivanje glavnih karakteristika takvih mostova. Ovaj rad prikazuje ponasanje rekonstruiranog ovjesenog mosta preko Dunava u Novom Sadu. Most je izgraden izmedu 1976. i 1981. godine, a 1999. godine bio je tesko ostecen kada su ga pogodile dvije Tomahawk rakete. Godine 2003. pocela je rekonstrukcija mosta, a krajem 2005. godine Gradevinski fakultet Sveucilista u Beogradu bio je pozvan ispitati rekonstruiranu konstrukciju mosta. U ovom radu prikazani su rezultati koji se odnose na pomake, rotacije i deformacije glavnog nosaca konstrukcije duljine 351 m. Vibracije mosta izazvane su udarnim opterecenjem uslijed prolaska teskog kamiona preko mosta, pri cemu su odredena vertikalna ubrzanja glavnog nosaca. Potrebne funkcije u frekventnoj domeni odredene su primjenom Fourier-ove transformacije i na taj nacin je izdvojeno prvih pet perioda osciliranja. U radu su prikazane geoloske karakteristike terena. Formiran je numericki model mosta na bazi metode konacnih elemenata i dobiveno je dobro slaganje eksperimentalnih i numerickih rezultata. Ovi rezultati pokazuju da se most ponasa elasticno pod utjecajem probnog opterecenja, sto ukazuje da konstrukcija ima odgovarajucu nosivost i da se sigurno moze pustiti u promet. Kljucne rijeci: ovjeseni most, eksperimentalna analiza, numericka analiza
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