Pushover analysis of bridges including soil-structure interaction effects

This paper deals with the effects of soil-structure interaction (SSI) on the displacement capacity of multi-span RC bridge founded on shallow foundations. Modal pushover analyses are carried out in transverse direction. Target displacement of the monitoring point is calculated using N2 method The SSI is considered through boundary springs according to NEHPR Two different soil properties are considered according to EN1998-1. Analyses are carried out using SAP2OOO, considering fixed- and flexible-base models. The obtained results are discussed

Influence of Soil-Structure-Interaction on Nonlinear Time History Seismic Response of RC Frames

Modern regulations require from engineers to take into account a non-linear behavior and the appearance of plastic hinges in the selected structural elements during the earthquake. Also, regulations more insist on considering the soil-structure interaction (SSI) in the computation of dynamic response of buildings. In this paper, the nonlinear time history analysis of multi-storey RC frame structure is carried out taking into account SSI according to the Eurocode 8 and FEMA 450 recommendations. In order to illustrate the impact of the SSI, the response of the structure is calculated with and without the influence of the soil. Nine accelerograms are selected to correspond to the frequency spectra defined in EC8. Two standard types of soil, (ie. type B and C) according to the EC8, are adopted. The appropriate conclusions and recommendations for further work in this area are carried out

Finite element dynamic analysis of soil-structure interaction

Predmet ovoga rada je linearna analiza dinamičkog sadejstava tla i objekta pri zemljotresu, primenom metode konačnih elemenata (MKE). Za rešenje odgovora rotaclono-simetričnog sistema je korišćena metoda podstruktura. Dinamičke paramétré tla za krut kružni temeij fundiran ria tlu iznad osnovne stene smo odr edili primenom MKE. Tlo je idealizovano podelom na osno-simetriene konačne elemente uz primenu graničnih uslova po silama koje omogućavaju transmisiju seizmiòkih talasa iz zone temei ja u okolni slojevit, v iskoelast ičan poluprostor. Dobijena rešenja su uporedena sa teorijskim. U okviru toga, detaljno je analiziran problem odgovora sistema slojeva za talase u ravni, upravno na ravan i u ci 1indričnim koordinatama. Za sva tri slucaja je formulisana tzv. prenosna granica (transmitting boundary). Na mode lu zgrade nuklearnog reaktora prikazani su neki aspekti interakc i je tla i objekta primenom ekvivalentne metode i metode koncentrisanih masa.A substructure method for earthquake analysis of soil-structure interaction is presented. The procedure is applied to the analysis of axisymmetr ic systems. Dynamic stiffness coefficients of rigid disk resting on layer built in at its base, are determinated by a finite element method. The transmitting boundary between the finite element "core" region and viscoelastic soil layers of infinite horizontal extent are superimposed. The core region is discretized by means of axisymetric finite element. A series of parametric studies of dynamic stiffness coefficients are presented. The substructure method is applied to simplified nuclear containment structural model founded on the "hard" and the "soft" layer. The interaction systems are analysed by equivalent method and lumped mass method

Finite element dynamic analysis of soil-structure interaction

Predmet ovoga rada je linearna analiza dinamičkog sadejstava tla i objekta pri zemljotresu, primenom metode konačnih elemenata (MKE). Za rešenje odgovora rotaclono-simetričnog sistema je korišćena metoda podstruktura. Dinamičke paramétré tla za krut kružni temeij fundiran ria tlu iznad osnovne stene smo odr edili primenom MKE. Tlo je idealizovano podelom na osno-simetriene konačne elemente uz primenu graničnih uslova po silama koje omogućavaju transmisiju seizmiòkih talasa iz zone temei ja u okolni slojevit, v iskoelast ičan poluprostor. Dobijena rešenja su uporedena sa teorijskim. U okviru toga, detaljno je analiziran problem odgovora sistema slojeva za talase u ravni, upravno na ravan i u ci 1indričnim koordinatama. Za sva tri slucaja je formulisana tzv. prenosna granica (transmitting boundary). Na mode lu zgrade nuklearnog reaktora prikazani su neki aspekti interakc i je tla i objekta primenom ekvivalentne metode i metode koncentrisanih masa.A substructure method for earthquake analysis of soil-structure interaction is presented. The procedure is applied to the analysis of axisymmetr ic systems. Dynamic stiffness coefficients of rigid disk resting on layer built in at its base, are determinated by a finite element method. The transmitting boundary between the finite element "core" region and viscoelastic soil layers of infinite horizontal extent are superimposed. The core region is discretized by means of axisymetric finite element. A series of parametric studies of dynamic stiffness coefficients are presented. The substructure method is applied to simplified nuclear containment structural model founded on the "hard" and the "soft" layer. The interaction systems are analysed by equivalent method and lumped mass method

Pushover analysis for seismic assessment of RC Nišava Bridge

Contemporary structural design implies nonlinear behavior of ductile members for design seismic action. Therefore, the application of nonlinear analysis in the aseismic design of structures is required. Nonlinear static (pushover) analysis has become a very popular tool for the seismic assessment of structural performance during a particular earthquake due to the lower computational cost and less time consuming in comparison to the nonlinear time-history analysis. The standard pushover analysis (SPA) has been extended to the modal pushover analysis (MPA) of buildings in order to consider higher modes effects. Since the higher modes usually play an important role in the seismic bridge analysis, the MPA has been adopted for the seismic assessment of bridges. In the paper, the MPA of the Nišava Bridge structure (233.2m long 7-span continuous bridge, curved in plan with R=540m and prestressed 13.75m wide bridge deck) has been performed in transverse direction, for two levels of excitation which are 2 and 3 times higher than the design level (a g =0.1g). For the horizontal component of the seismic action, elastic response spectrum, Type 2 for soil type B, according to EN1998-1 has been selected. Analyses considering different levels of excitation and different monitoring points are carried out using the SAP2000 commercial software package. The seismic demands of the structure (peak displacements of the deck in transverse direction), subjected to the monotonically increasing lateral forces have been calculated, considering five dominant transverse modes. Hinge distribution within the structure has been determined, too, for the target displacement obtained from the MPA. The overall performance of the bridge was very satisfactory. Neither local nor global failure was predicted, even under seismic actions that three times exceed the design level. The performed analysis showed that the fundamental transverse mode shape contributes to the final response significantly. The influence of higher modes is more pronounced for higher level of excitation

Sustainable development of cities: Effects of traffic induced vibration on humans

Traffic induced vibrations can hardly cause the damages of buildings but can caused the disturbances and annoying affects of their occupants. This phenomenon has been the object of investigations in many countries due to the rapid urbanization of the modern cities and due to the demand of sustainable development. In this paper presented is the assessment of vibrations on humans in buildings caused by the traffic in Belgrade, Serbia. Due to the luck of national standard for evaluation of effects of vibrations on humans, the German standard DIN 4150-Part 2 was implemented. The results of evaluations are presented and discussed

Development of dynamic stiffness method for free vibration analysis of plate structures

In the paper, an overview of the development of the dynamic-stiffness-method-based computational model for the free vibration analysis of plates has been presented. Starting from several formulations of the so-called dynamic stiffness elements, formulated at the Institute for Numerical Analysis and Design of Structures (INP) at the Faculty of Civil Engineering, University of Belgrade in the last decade, a novel software framework FREEVIB has been developed and validated. FREEVIB is object-oriented software in Python environment, designed to predict free vibration characteristics in a wide range of possible structural problems (stepped, stiffened and folded plate structures, implying isotropic or orthotropic material formulations). The presented methodology still serves as a strong basis for further improvements through the extensive research efforts of authors, their collaborators and students

Dynamic stiffness method in the vibration analysis of circular cylindrical shell

In this paper the dynamic stiffness method is used for free vibration analysis of a circular cylindrical shell. The dynamic stiffness matrix is formulated on the base of the exact solution for free vibration of a circular cylindrical shell according to the Flügge thin shell theory. The matrix is frequency dependent and, besides the stiffness, includes inertia and damping effects. The derived dynamic stiffness matrix is implemented in the code developed in a Matlab program for computing natural frequencies and mode shapes of a circular cylindrical shell. Several numerical examples are carried out. The obtained results are validated against the results obtained by using the commercial finite element program Abaqus as well as the available analytical solutions from the literature.U ovom radu korišćena je metoda dinamičke krutosti za analizu slobodnih vibracija kružne cilindrične ljuske. Dinamička matrica krutosti formulisana je na osnovu tačnog rešenja sistema diferencijalnih jednačina problema slobodnih vibracija po Flügge-ovoj teoriji ljuski. To je frekventno zavisna matrica koja u sebi, pored krutosti, sadrži uticaj inercije i prigušenja. Izvedena dinamička matica krutosti implementirana je u za tu svrhu napisani Matlab program za određivanje sopstvenih frekvencija i oblika oscilovanja kružne cilindrične ljuske. Urađen je niz primera. Rezultati dobijeni primenom dinamičke matrice krutosti upoređeni su s rezultatima dobijenim pomoću komercijalnog programa zasnovanog na metodi konačnih elemenata Abaqus, kao i sa dostupnim analitičkim rezultatima iz literature

Models related to the moving load problems

In this paper different mathematical models of the vehicle load are presented, depending on the one of the moving load types. In general, vehicle load models can be classified into two types: static and dynamic moving load models. Static moving load model is model with nonvarying load value and shape in time. Dynamic moving load model is defined by differential equations of motion where the road roughness function affects the solution. Due to this influence some of the differential equations cannot be solved analytically and the numerical approach has to be performed. Therefore, in this work Matlab Simulink models have been developed to solve this problem. Validation of Simulink models is carried out and presented for all analysed dynamic moving load models

Development of dynamic stiffness method for free vibration analysis of plate structures

In the paper, an overview of the development of the dynamic-stiffness-method-based computational model for the free vibration analysis of plates has been presented. Starting from several formulations of the so-called dynamic stiffness elements, formulated at the Institute for Numerical Analysis and Design of Structures (INP) at the Faculty of Civil Engineering, University of Belgrade in the last decade, a novel software framework FREEVIB has been developed and validated. FREEVIB is object-oriented software in Python environment, designed to predict free vibration characteristics in a wide range of possible structural problems (stepped, stiffened and folded plate structures, implying isotropic or orthotropic material formulations). The presented methodology still serves as a strong basis for further improvements through the extensive research efforts of authors, their collaborators and students