Nelinearno ponašanje i granična nosivost limenih nosača opterećenih lokalizovanim opterećenjem

Abstract: The subject of the thesis is the analysis of steel girders behavior (welded steel I beam) under the influence of the localized load. The girders without longitudinal stiffeners were tested, as well as the girders with the longitudinal stiffeners in the vicinity of the loaded area. The influence of the length of uniform distributed load on the loaded flange, in the plane of the web, known as patch loading was analyzed as well as the behavior of the girder in the non-linear area, as well as the ultimate load which is manifested by buckling in the load application zone. During the bridge assembly procedures, when the bridge is being launched to its definite position over the temporary and permanent supports, the influences which occur may exceed the load of the structure in certain points due to the patch loading. Because of its extreme complexity, a complete theoretical solution for the problem has not been found yet. The solution procedure requires the combination of experiments and numerical analysis. Because of the importance of the numerical simulation of the girders, in this thesis, a special attention was paid to the theoretical foundations and solutions which would contribute to the improvements of efficiency of software packages concerning the onset of singularity points during the simulation. The developed software packages are based primarily on the application of Finite Element Method (FEM) and Boundary Element Method (BEM). In these procedures, algebraic and/or logarithmic problems with singularities of often occur, and one of the goals was to give a contribution towards a more efficient solution of these problems. The research comprised application of numerical procedures where FEM was implemented using most up-to-date software packages; many improvements were made using the analytical methods referring to the singularity problems. Theoretical basis and solutions elaborated here can include an occurrence of singularities, so that it contributes to improving the efficiency of software packages, i.e., it gives a faster and more accurate solution of the problem. A special class of Gaussian quadrature formulas is V derived and it provides improved solutions of certain more complex problems with algebraic and/or logarithmic singularities. An alternative approach with Gaussian quadratures for Müntz systems, developed by Milovanović and Cvetković (SIAM J. Sci. Comput. (2005)) is also mentioned. In the existing literature up to now this area has not been paid due attention. In addition to these solutions and the general theoretical fundamentals, direct answers to the problems of patch loading are provided by presenting the compatible developed numerical model in the software package ANSYS Workbench 15, after the experimental research performed. A large number of the results of the experiments, performed during research, conducted at the Faculty of Civil Engineering in Belgrade under the direction of N. Marković [70], served as a basis for the research and creation of the compatible model in the computer simulation. The goal numerical simulation was to determine the ultimate load and monitor development of deformations and stresses. The actual models for numerical simulation of girder behavior allow inclusion of initial deformations-imperfections into the calculation on the basis of the actual girder model. In the numerical simulations of the model, the form, character and course of deformation process as well as the buckling were identical as in the experiments with actual models, for each concrete sample. Numerical simulations tested the girder model behavior, and the values of the ultimate load of the girder was determined for six material models, and the quantitative analysis of those results was performed. The behavior curve corresponding to the multi linear curve according to EN1993-1-5 [28] gave a very good approximate value of the ultimate load. Because of the topicality of this field, a review of the state-of-affairs is provided, as well as the main course of research in this field. The existing experimental results and standard statistical method, common for these issues were used, for the purpose of result verification, as well as contemporary methods of numerical approximation. The results of the research are applied for the structural design, particularly for the design of steel bridges constructed by launching over the temporary or permanent supports, and in the new versions of the national codes for steel structures design. VI The impact of actual imperfections of the beam web plate was included, and a comparison with the beams without imperfections was performed within the numerical simulation, for the purpose of observing the stress development. The cases of research of impact of actual imperfections on the magnitude of the limit load are present in the literature to some small extent. This thesis contributes to a more realistic modeling of the girders, which provides opportunities for new behavior tests of such or different girder models using numerical simulation. The tests carried out in this way, facilitate beam analyses which would indirectly contribute to the adoption of correct approaches in obtaining the theoretical results

Numerical Modelling of Y Joints of Trusses Made of Steel Hollow Sections

The use of welded structural hollow sections in civil engineering is relatively new. Constructing and dimensioning joints of steel trusses made of welded structural hollow sections requires a more specified approach, compared to traditional joints, achieved by gusset plates. Stress and local deformations at the contact between elements are non-linear and very complex. In this paper, the FEM modelling of the Y-joint was performed, accounting for the non-linear behaviour of steel. The ultimate bearing capacities of the joint were determined numerically, by applying different failure criteria. The results showed very good agreement with the experimental data

COMPARATIVE ANALYSIS OF USING DEGREE OF RIGIDITY AND ROTATIONAL STIFFNESS OF CONNECTIONS IN STRUCTURAL DESIGN

Using classical formulation of stiffness method, impact of semi-rigid connections on the stresses and strains can be analyzed by the degree of rigidity or by rotational stiffness of connections. In this paper, functional dependence between the degree of rigidity and rotational stiffness of connections is formulated and the comparative analysis of these two approaches in the analysis of semi-rigid connections behavior of members in real structures, is implemented

Analysis of material non-linearity of steel girders subjected to patch loading

U radu se daje analiza ponašanja limenih nosača (nosači od zavarenog čelika I) pod lokalnim opterećenjem. Koncentrirano ili jednoliko raspoređeno opterećenje na maloj udaljenosti od prirubnice i u ravnini mreže, poznato je kao lokalno opterećenje (patch loading). Analiziralo se ponašanje nosača u nelinearnom području kao i učinak kritičnog opterećenja, koji se manifestira izvijanjem. Za modeliranje nosača primijenjen je softver ANSYS Workbench 15 [1]. U skladu s važećim propisima EN 1993-1-5 [2] i BSK 07 [3], tijekom numeričke analize korišteno je šest različitih modela materijala. Dobiveni rezultati uspoređeni su s eksperimentalno dobivenim rezultatima.The paper presents an analysis of behaviour of plate girders (welded steel I girders) under patch loading. Concentrated or uniformly distributed loading on a short length of the flange, and in the plane of web is known as patch loading. Behaviour of the girder in non-linear area, as well as the ultimate load capacity, which is manifested by buckling in the loaded zone were analysed. Girder modelling was performed in ANSYS Workbench 15 software [1]. In accordance with the standing regulations EN 1993-1-5 [2] and BSK 07 [3], in the course of the numerical analysis, six different material models were employed. The obtained results were compared to the experimentally obtained results

Nelinearno ponašanje i granična nosivost limenih nosača opterećenih lokalizovanim opterećenjem

Abstract: The subject of the thesis is the analysis of steel girders behavior (welded steel I beam) under the influence of the localized load. The girders without longitudinal stiffeners were tested, as well as the girders with the longitudinal stiffeners in the vicinity of the loaded area. The influence of the length of uniform distributed load on the loaded flange, in the plane of the web, known as patch loading was analyzed as well as the behavior of the girder in the non-linear area, as well as the ultimate load which is manifested by buckling in the load application zone. During the bridge assembly procedures, when the bridge is being launched to its definite position over the temporary and permanent supports, the influences which occur may exceed the load of the structure in certain points due to the patch loading. Because of its extreme complexity, a complete theoretical solution for the problem has not been found yet. The solution procedure requires the combination of experiments and numerical analysis. Because of the importance of the numerical simulation of the girders, in this thesis, a special attention was paid to the theoretical foundations and solutions which would contribute to the improvements of efficiency of software packages concerning the onset of singularity points during the simulation. The developed software packages are based primarily on the application of Finite Element Method (FEM) and Boundary Element Method (BEM). In these procedures, algebraic and/or logarithmic problems with singularities of often occur, and one of the goals was to give a contribution towards a more efficient solution of these problems. The research comprised application of numerical procedures where FEM was implemented using most up-to-date software packages; many improvements were made using the analytical methods referring to the singularity problems. Theoretical basis and solutions elaborated here can include an occurrence of singularities, so that it contributes to improving the efficiency of software packages, i.e., it gives a faster and more accurate solution of the problem. A special class of Gaussian quadrature formulas is V derived and it provides improved solutions of certain more complex problems with algebraic and/or logarithmic singularities. An alternative approach with Gaussian quadratures for Müntz systems, developed by Milovanović and Cvetković (SIAM J. Sci. Comput. (2005)) is also mentioned. In the existing literature up to now this area has not been paid due attention. In addition to these solutions and the general theoretical fundamentals, direct answers to the problems of patch loading are provided by presenting the compatible developed numerical model in the software package ANSYS Workbench 15, after the experimental research performed. A large number of the results of the experiments, performed during research, conducted at the Faculty of Civil Engineering in Belgrade under the direction of N. Marković [70], served as a basis for the research and creation of the compatible model in the computer simulation. The goal numerical simulation was to determine the ultimate load and monitor development of deformations and stresses. The actual models for numerical simulation of girder behavior allow inclusion of initial deformations-imperfections into the calculation on the basis of the actual girder model. In the numerical simulations of the model, the form, character and course of deformation process as well as the buckling were identical as in the experiments with actual models, for each concrete sample. Numerical simulations tested the girder model behavior, and the values of the ultimate load of the girder was determined for six material models, and the quantitative analysis of those results was performed. The behavior curve corresponding to the multi linear curve according to EN1993-1-5 [28] gave a very good approximate value of the ultimate load. Because of the topicality of this field, a review of the state-of-affairs is provided, as well as the main course of research in this field. The existing experimental results and standard statistical method, common for these issues were used, for the purpose of result verification, as well as contemporary methods of numerical approximation. The results of the research are applied for the structural design, particularly for the design of steel bridges constructed by launching over the temporary or permanent supports, and in the new versions of the national codes for steel structures design. VI The impact of actual imperfections of the beam web plate was included, and a comparison with the beams without imperfections was performed within the numerical simulation, for the purpose of observing the stress development. The cases of research of impact of actual imperfections on the magnitude of the limit load are present in the literature to some small extent. This thesis contributes to a more realistic modeling of the girders, which provides opportunities for new behavior tests of such or different girder models using numerical simulation. The tests carried out in this way, facilitate beam analyses which would indirectly contribute to the adoption of correct approaches in obtaining the theoretical results

Stress Analysis of Steel Plate Girders Subjected to Patch Loading in Elastoplastic Domain

This paper considers the stress analysis of steel I girders subjected to patch loading for different lengths of load. Behavior of the girders under the patch loading or uniformly distributed load on the flange and in the plane of web represents complex stability and elastic-plastic problem. The geometric and material non-linearities that exist, also affect the behavior of the girder. A better knowledge of girder behavior is important in order to achieve a more economical and a safer design. In addition to the limit load analysis, the stress analysis is of particular interest. The results from the experiment were used and were compared with the results obtained by modeling the girders in the ANSYS software

MODELIRANJE PEŠAČKOG OPTEREĆENJA U ANALIZI GRANIČNOG STANJA UPOTREBLJIVOSTI PEŠAČKIH MOSTOVA

The last few decades new trends in the design of pedestrian bridges have resulted in lighter and more slender structures. This leads to a reduction in natural frequencies and increased flexibility, and thus a greater possibility for structures to become more exposed to excessive vibrations caused by pedestrians. The lager amplitudes of vibrations occur if the pace frequency of excitation load approaches one of natural frequency of footbridge. The vibration of high proportions may cause pedestrians to feel uncomfortable, sick or unsafe while crossing the bridge. In modern pedestrian bridge design, human-induced vibrations have become an important issue. Footbridge vibrations occur in vertical, lateral and longitudinal direction, and torsion of the bridge deck is also possible. The main types of pedestrian action on the bridge are walking and running, while jumping, bouncing, swaying are considered to be intentional, or sometimes even vandal excitation. Pedestrian-induced loads are difficult to model since pedestrians may have different weight, various number in the groups randomly distributed over the bridge deck. Also, the walking velocity may vary from a pedestrian to a pedestrian. The load models appropriately set up are of great importance for understanding the response of the bridge. Principles of modeling of the human-induced load and some characteristic models of pedestrian loads, described in proposals and codes, are presented in this paper. Some results of Serviceability Limit State analysis, in terms of human-induced vibration, of the pedestrian bridge over the Nišava River in Niš, are also presented.Novi trendovi u projektovanju pešačkih mostova, koji uglavnom proizilaze iz zahtevnih estetskih kriterijuma i mogućnosti korišćenja savremenih građevinskih materijala, doveli su do vitkih i fleksibilnijih konstrukcija. Kao posledica toga, lagani pešački mostovi su skloniji da vibriranju sa amplitudama velikih proporcija i na taj način izazivaju nelagodnost kod pešaka. S toga je dinamička analiza pešačkih mostova postala neizbežna, a određivanje modela opterećenja je neophodno za njeno sprovođenje. U radu su date osnove modeliranja vremenski zavisnog opterećenja pešaka korišćenjem Furijeove transformacije i prikazana je njihova upotreba u važećoj regulativi. Treba naglasiti da je opsežno istraživanje na ovu temu još uvek u toku, kako bi se poboljšali postojeći i predložili pouzdaniji modeli dinamičkog opterećenja. Prikazan je i deo analize graničnog stanja upotrebljivosti pešačkog mosta preko Nišave u Nišu. Pokazano je da je odziv konstrukcije za opterećenje izazvano kretanjem pešaka u granicama preporučenim važećom regulativom

PRIMENA OBRADE ABRAZIVNIM VODENIM MLAZOM U GRAĐEVINARSTVU (GRAĐEVINSKOM INŽENJERSTVU)

Water jet processing techniques can be successfully applied in many fields of civil engineering, such as: structural engineering, structural reconstruction, renovation, demolition and recycling. The problem of cutting difficult-to-machine materials led to the development and application of today the most attractive method for contour cutting - Abrasive Water Jet Cutting (AWJC). It is a high-tech technique that provides unique capabilities compared to conventional machining processes. This paper, along the theoretical derivations, provides a study on use of water jet in construction and civil engineering. The particular part of this paper deals with the results of the original experimental research on granite and aluminum cutting.Tehnika obrade vodenim mlazom može se uspešno primenjivati u mnogim oblastima građevinskog inženjerstva, kao što su: strukturalno inženjerstvo, rekonstrukcija konstrukcija, renovirenje, rušenje i u potupcima reciklaže. Problem sečenja teško obradivih materijala doveo je do razvoja i primene, danas naj atraktivnije metode za konturno sečenje materijala abrazivnim vodenim mlazom. To je visoko tehnološki postupak koji poseduje jedinstvene karakteristike u odnosu na uobičajene postupke obrade materijala. U ovom radu su, pored teorijskog osvrta, predstavljene mogućnosti primene ove tehnike u građevinskom inženjerstvu, dok su u delu rada predstavljeni rezultata ispitivanja na uzorcima od granita i aluminijuma

On the Optimal Design of Steel Shells with Technological Constraints

This paper is concerned with determining the optimum conditions of steel cylindrical shells with technological limitations and one behavioral constraint, related to a specific constitutive law for limiting load-carrying capacity. The optimum structural design in the plastic range of circular cylindrical full shells composed of rings of variable thickness is given. A numerical procedure for determining the optimal dimensions of shell rings is given. A shell collapse mechanism is assumed in the kinematic part, which satisfies requirements. Within the optimum conditions, the power of the dissipation energy of rings assuming the hexagon Hodge condition of plasticity are derived. A series of numerical solutions and results of optimal structural designs for a shell that is simply supported at the ends are presented. In one example of optimally calculated shells, the length X1 of one ring was varied

On the Optimal Design of Steel Shells with Technological Constraints

This paper is concerned with determining the optimum conditions of steel cylindrical shells with technological limitations and one behavioral constraint, related to a specific constitutive law for limiting load-carrying capacity. The optimum structural design in the plastic range of circular cylindrical full shells composed of rings of variable thickness is given. A numerical procedure for determining the optimal dimensions of shell rings is given. A shell collapse mechanism is assumed in the kinematic part, which satisfies requirements. Within the optimum conditions, the power of the dissipation energy of rings assuming the hexagon Hodge condition of plasticity are derived. A series of numerical solutions and results of optimal structural designs for a shell that is simply supported at the ends are presented. In one example of optimally calculated shells, the length X1 of one ring was varied