Аnalysis and estimation of seismic performance of gird reinforced concrete bridges

U EN1998-1 i EN1998-2 su propisane metode za određivanje seizmičkih uticaja koje koriste linearno-elastične modele u modalnoj analizi sa spektrima odgovora. Za regularne konstrukcije, se može primeniti i ekvivalentna statička metoda u slučaju da ne postoji značajan doprinos viših tonova na odgovor sistema. U EN1998-2 su propisane, kao alternativa linearno-elastičnim metodama analize, nelinearna statička analiza i nelinearna dinamička analiza. U ovom radu su primenjene linearne i nelinearne statičke i dinamičke analize armiranobetonskih grednih mostova sa različitim kombinacijama dužina stubova u cilju procene seizmičkih performansi.The EN 1998-1 and EN1998-2 prescribed methods for the determination of seismic action using linear-elastic models for modal analysis with response spectrum. For regular structures, can be applied to the equivalent static method in the action that there is a significant contribution to higher modes on the response of the system. The EN1998-2 are prescribed as an alternative to linear-elastic methods of analysis, nonlinear static analysis and nonlinear dynamic analysis. This study applied linear and nonlinear static and dynamic analysis of reinforced concrete girder bridges with different combinations of length piers in order to assess the seismic performance

Аnalysis and estimation of seismic performance of gird reinforced concrete bridges

U EN1998-1 i EN1998-2 su propisane metode za određivanje seizmičkih uticaja koje koriste linearno-elastične modele u modalnoj analizi sa spektrima odgovora. Za regularne konstrukcije, se može primeniti i ekvivalentna statička metoda u slučaju da ne postoji značajan doprinos viših tonova na odgovor sistema. U EN1998-2 su propisane, kao alternativa linearno-elastičnim metodama analize, nelinearna statička analiza i nelinearna dinamička analiza. U ovom radu su primenjene linearne i nelinearne statičke i dinamičke analize armiranobetonskih grednih mostova sa različitim kombinacijama dužina stubova u cilju procene seizmičkih performansi.The EN 1998-1 and EN1998-2 prescribed methods for the determination of seismic action using linear-elastic models for modal analysis with response spectrum. For regular structures, can be applied to the equivalent static method in the action that there is a significant contribution to higher modes on the response of the system. The EN1998-2 are prescribed as an alternative to linear-elastic methods of analysis, nonlinear static analysis and nonlinear dynamic analysis. This study applied linear and nonlinear static and dynamic analysis of reinforced concrete girder bridges with different combinations of length piers in order to assess the seismic performance

Assessment of RC Frames for SD Limit State Using Nonlinear Methods of Analysis According to EN 1998-3

Design of structures in seismically active areas according to EN 1998-1 includes a choice between two ductility classes, medium or high, without conditioning by other parameters or favouring any of them. The behaviour factor q is applied as a global reduction factor of internal forces that would develop in the structure in the event of elastic response. According to EN 1998-3 a seismic assessment is determined by comparing the demands with the corresponding capacities. For ductile element, seismic demand and capacity are expressed in terms of chord rotation. The research in this paper was focused on the study of influence of the design ductility classes, as well as of the design seismic actions and the number of frames storeys, on seismic response of reinforced concrete frames designed according to European codes. Seismic performance evaluation of newly designed code-conforming structures is of interest, in order to identify any potential weaknesses and deficiencies in new structures that are designed with appropriate acceptable level of structural damage in the event of a design earthquake. The considered frames were evaluated for the significant damage limit state, for which the return period corresponds to the designed seismic actions. Nonlinear methods of analysis were used, which are the reference methods for assessing seismic performance. The frames designed for high class ductility manifested more favourable seismic performance and the frames designed for lower seismic action had lower values of demand/capacity ratio

The estimation of seismic performances of reinforced concrete girder bridges using nonlinear dynamic analysis

varijantama konstrukcija grede mosta jeste kontinuirni nosač sa četiri polja (35 m + 50 m + 50 m + 35 m) i zglobno je oslonjena na vrhove stubova i krajnje oporce. Stubovi su potpuno uklješteni u tlo sa dužinama 7 m, 14 m i 21 m, tj. analizirano je 18 različitih kombinacija dužina stubova. Geometrijska nelinearnost se obuhvaća preko P–Δ efekta, a materijalna nelinearnost se uključuje u analize kroz vlaknaste modele plastičnih zglobova. Procjena seizmičkih performansi je izračunata na osnovu zahtijevane lokalne duktilnosti i kapaciteta lokalne duktilnosti koje posjeduju kritični poprečni presjeci u stubovima analiziranih varijanti mostova. Za nelinearne dinamičke analize upotrebljeni su umjetno (sintetički) generirani i realni zapisi zemljotresa.The paper applies nonlinear dynamic analysis to estimate seismic performances of reinforced concrete girder bridges. In all analysed variations, the structure of the beam implies the continual girder with four fields (35 m + 50 m + 50 m + 35 m) hinged to the pier tops and the abutments. The piers are completely fixed to the ground with the lengths of 7 m, 14 m and 21 m; hence, 18 diverse combinations of pier lengths have been analysed. Geometric nonlinearity is included via the P–Δ effect, while the material nonlinearity is included into the analyses using the fibre models of plastic hinges. The estimation of seismic performances has been calculated on the basis of the demanded local ductility and the local ductile capacity of the critical cross-sections in the piers of all bridge analysed variations. Artificially (synthetically) generated and recorded earthquake accelerograms have been utilized for nonlinear dynamic analyses

The program "ST method" for determining the Strut-and-Tie models of RC plane members

U radu je predstavljen prijedlog za određivanje Strut-and-Tie modela armiranobetonskih ravninskih nosača primjenom diskretne topološke optimizacije koja podrazumijeva rešetkasti sustav za proračun stanja naprezanje-deformacija nosača. Strut-and-Tie model se može koristiti pri analizi dijela ili cijelog nosača, a posebno je pogodan na mjestima naglih promjena statičkih veličina i/ili geometrijskih karakteristika nosača. Na osnovu prikazanog prijedloga, razvijen je program "ST method" pomoću kojeg se može automatski odrediti konačan oblik Strut-and-Tie modela, izvršiti kontrola naprezanja u elementima modela i odrediti potrebna količina armature. Također, u radu je prikazana i optimizacija Strut-and-Tie modela prema potrebnoj količini armature.The paper presents a proposal for determining the Strut-and-Tie models of reinforced concrete plane members using the discrete topology optimization, which involves the truss system for calculation of the stress-strain state of a real member. Strut-and-Tie model can be used for the analysis of both a single part and the entire member, and is particularly suitable for application in cases where an abrupt change of static values and geometrical properties of the member occurs. Based on the presented proposal, the program "ST method" is developed and can automatically determine the final shape of the Strut-and-Tie model, stress control of the model elements and the required amount of reinforcement. Moreover, the reinforcement amount optimization of the Strut-and-Tie models is presented in the paper

Investigation of large-diameter flange joint with soft-gasket

U središtu je interesa ovog rada ponašanje spojeva prirubnice i mekane gumene brtve koja je tipična vrsta brtve za isparivače. Montirana konstrukcija ispitala se prema normi EN 13445-3, a naprezanja su se mjerila tenzometrima. Numerička analiza u programskom paketu ABAQUS obuhvaćala je nekoliko modela s različitim detaljima. Ti su modeli bili podešeni u skladu sa zabilježenim podacima iz ispitivanja. U radu su prikazane i dokumentirane preporuke koje se tiču složenosti modela koji je potreban kako bi se postigla zadovoljavajuća razina predviđanja nelinearnog ponašanja spojeva prirubnica.This study focuses on behaviour of the flanged joint with a soft rubber gasket, which is a common type of gasket for evaporator structures. The assembled structure is tested according to EN 13445-3, and strain values are measured using strain gauges. The numerical analysis in ABAQUS comprises several models with different levels of detail. These models are calibrated according to test data. Recommendations regarding the model complexity that is required to obtain satisfactory prediction of non-linear behaviour of flange joints are presented and documented

A Methodology Proposal for Selecting the Optimal Location for Small Hydropower Plants

The hydropower potential in the Republic of Serbia, as the most important renewable energy source, has been estimated at around 17000 GW·h per year, where approximately 2000 GW·h could be obtained from small hydropower plants (SHP). Small hydropower plants in Serbia currently produce 150 GW·h. Accordingly, the share of the electricity production from small hydropower plants in the total electricity production in Serbia is too small. The paper presents a model for the selection of optimal locations for small hydropower plants, which includes an ecological criterion, along with technical and economic criteria. The ecological criterion is eliminatory, i.e. those parts of the watercourse that border on or pass through protected natural assets are not taken into account when considering potential optimal locations for SHPs. All technical and economic criteria are included in the calculation of the weighted arithmetic mean with the aim of determining the optimal position for the construction of small hydropower plants. The model is implemented in the SHPOP software and its application is demonstrated on five watercourses in Southeastern Serbia

Physicomechanical properties of concrete mixtures for construction of pavements at bus stations

A detailed research of three concrete mixtures, used in construction of pavements at bus stations in Novi Sad, is presented in the paper. The mixtures differ by aggregate content, quantity and type of cement, as well as by the type and quantity of additives used for the preparation of concrete mixtures. After examination of physicomechanical properties of concrete, it was established that all mixtures meet the requirements for construction of concrete pavements at bus stations. The obtained results show that the analysed mixtures are also favourable for construction of concrete pavements on roads