The rail dampers are mechanical devices which work as dynamic absorbers to reduce the rail vibration and rolling noise. The paper shows the experimental results from the functionality and performance testing of an experimental demonstrative rail damper. The vibration attenuation takes the highest values, namely 6-22 dB, between 160 and 1000 Hz.
Arch bridges are slender structures and can be efficiently used in the range of medium to large spans. These structures have an improved aesthetic aspect and in the same time a low construction height, with obvious advantages regarding reduced costs in the infrastructuers and their foundations.
For this type of structures usually composite or orthotropic decks are used. Lately, innovative solutions have been used in designing arch bridges, especially discarding the top wind bracing system. The level of axial forces and bending moments in the arches and tie imply the design of sections with sufficient stiffness and strength in both directions in order to ensure the general stability of the arches, without the need for top wind bracing. Moreover, the cross section of the arches is not constant, but shifts in accordance with the variation of the bending moments, in order to ensure their lateral stability.
This paper studies a road bridge with parallel Bowstring arches, with a span of 108m and a carriageway 7.00m wide, sustained by a deck made up of crossbeams 2m apart and a concrete slab. The main beams are held by ties arranged in the Langer system, 10 to 14m apart from each other. The sag of the arches is 18m high.
The analyzed structure was proposed for construction in the city of Oradea and is used for crossing the “Crişul Repede” river, between Oneştilor street on the left bank and the Sovata, Fagului and Carpaţi streets on the right bank.
The performed analyses have the following two main objectives: to establish the critical load for which the failure of the arches occurs by instability and to underline the influence of different wind bracing systems on the bridge’s collapse loads respectively.
Cable-stayed bridges are complex structures and for their design, the traditional calculation methods are hard, even impossible to use for a global analysis. Separate analyses for the each component of the bridge in a simplified manner can be conducted, but in this case the concurrence of the elements into the structure is not taken into account, leading to errors in estimating the structural response. For these structures, the construction method and the presence of the stays, which are elements having a nonlinear behaviour, implies to consider a nonlinear staged analysis including the second order effects in order to transmit form one stage to the other the stress-strain state.
In the present time, thanks to the evolution and development of the calculation methods and computer analysis, cable-stayed bridges can be accurate analysed so that the obtained response is close to the behaviour of the structure during erection and later, in service.
The aim of this paper is to present the results obtained using one of the finite element models and nonlinear staged analysis of the bridge at km 0+540 over Danube-Black Sea Canal near Agigea. Inside the paper, results related to the evolution of stress-strain state in principal structural elements of the bridge - pylons, stays and deck - during the execution and in final stage, in service are to be presented.
The paper focuses on the experimental verification of the results derived from numerical simulations, based on a model of the bogie-track system, where the vertical track irregularities are introduced in the form of a pseudorandom function. This function comes from an original method of synthesizing the vertical track irregularities, depending on the geometric quality of the track and on the velocity. To verify the method, the root mean square (RMS) of the simulated accelerations in the axles and the bogie frame against each axle is compared to the experimental accelerations within the frequency range of wavelengths of the track vertical irregularities from 3 to 120 m. The results have shown a good correlation between the simulated RMS accelerations for a low quality track and the measured RMS accelerations.
Dynamic testing of bridges has as target to establish their response on pulse forces between the wheels and unevenness of road surface. Generally, during the tests, real time accelerations or deformations are to be measured and which through successive processing methods lead to other data as velocities, displacements, dynamic impact factor, but also the damping ratio. In order to validate the bridge response following testing, the measured data are compared both with allowable limits existing in standards and with the results obtained using analytical or numerical models.
In Romania, the dynamic testing of bridges is recommended by the current standards, only for important bridges, erected in complex or special solutions and also for large span bridges.
The aim of this paper is to outline the results obtained from the on-site measurements during dynamic testing of a viaduct placed on the motorway A1, sector Orăştie-Sibiu. The bridge superstructure is a composite one, continuous girder on 12 spans: 40+10×60+40 m, the substructure consisting in 11 piers with lamellar elevations and variable height in the range 8.50-24m.
In the paper a finite element model is also presented which was used for time-history analyses using an impulse type load. Finally, the results obtained on the site and using the numerical model are compared and discussed.
This paper presents a new type of seismic isolator that uses the principle of electromagnetic attraction and repulsion, to control the friction force between two electromagnets during earthquakes. The two electromagnets are used in conjunction with a secondary high friction dissipating and damping mechanism composed from a 10mm thick neoprene ring layer and two steel surfaces coated with Si3N4 that are used to dissipate the kinetic energy in the bridge deck at some maximum ground accelerations. The isolator utilizes tri-axial accelerometers embedded in the abutments, high current rechargeable batteries and an automated controlling unit. The presented isolator was developed specifically for a concrete bridge deck with a span of 36 meters and simple supported on two abutments, using time history electromagnetic and structural analyses. The paper presents the advantages of using this active seismic isolation system, compared to classical passive devices and the important results obtained in terms of decreasing internal forces on the substructure elements cross sections together with the reduction of relative displacements between the two electromagnets.
Road bridges with steel arches are used efficiently for medium and large spans. These solutions show advantages determined by the arches geometry, by the number and distributions of hangers and by the form and type of the arches bracing system.
The appearance of the welding as standard connection procedure for steel bridges, for road bridge decks two solutions are mainly used:
- the solution with a concrete slab acting together with the stringers and cross beams (the composite solution);
- the solution with orthotropic deck (the orthotropic deck consists in a network formed by the continuous longitudinal stiffeners and cross beams connected at the upper part by a steel plate).
In this paper a comparative study of the strength and fatigue checks performed on the new road bridge over river Argeşel near Mioveni in Argeş county is presented. The results are obtained using the Romanian standards STAS 1844-75 and SR 1911-1998 and the European norms SR EN 1990, SR EN 1993 and SR EN 1994. The deck was designed with two parallel steel arches, which are sustaining through vertical hangers a concrete slab connected with steel girders at the way level.
The aim of the paper is to outcome the safety factors obtained from checks performed on steel hangers using the Romanian standards with respect with those obtained using Eurocodes.
This paper is intended to show the design of two composite bridges along the Orastie- Sibiu motorway, from the basic concepts, applied without the need for a clause-by- clause checking of codes and standards, to the construction methods.
The bridges are seismically isolated in the longitudinal direction, while transversally the seismic action is distributed among the piers.
Calculations have been carried out through state of the art procedures, taking into account form effect of the cross section. For this reason, different FE models have been set up to study different aspects of the behavior, with increasing degrees of approximation. For example, “beam” elements have been utilised to investigate global effects both in the linear and non linear range, while more accuate 2D and 3D elements have been used for refined cases such as stress checks and local buckling analyses.
The present paper goes into detail in particular for what concerns some of the most interesting parts of the design process for the specific case. Namely, time dependent properties of the materials have been considered, and extensive “staged construction” analyses have been carried out to ensure safety in each phase of the complex life of the bridges, while at the same time guaranteeing significant cost savings.
The carrying structure of the bridge over the Jiu River at Aninoasa consists in two parallel concrete arches with variable height of the cross section, sustaining a concrete deck through vertical concrete hangers. In the time period passed since the bridge was erected, some structural elements shown damages. In order to establish the technical state of the bridge, a technical appraisement was performed and according to this, the most exposed elements to the risk of failure are the hangers.
The purpose of this paper is to present briefly both, the method used to test the actual bridge carrying capacity in situ and the finite element model developed for the static and dynamic analysis of the structure.
In order to estimate the state of the structural elements, two ways were followed. In the first stage, a test project was carried out and in the second stage, a complete 3D finite element model was developed to analyze the bridge structure.
The test project has foreseen the loading of the bridge by heavy unloaded trucks, disposed in some positions on the deck and the measurements of the deck and arches displacements. The positions of the trucks were established in order to obtain the maximum values both for arches transverse displacements and vertical displacements of the deck. Using electro-resistive transducers the hangers elongations and strains values on their cross section were also measured. These measured values were compared with those obtained from the numerical calculations performed by using the complete finite element model. By means of the finite element model, also the response of the structure following the dynamic action of vehicles was investigated.
In this paper, a rail joint model consisting of three Euler-Bernoulli beams connected via a Winkler foundation is proposed in order to point out the influence of the joint gap length upon the stiffness of the rail joint. Starting from the experimental results aiming the stiffness of the rail joint, the Winkler foundation stiffness of the model has been calculated. Using the proposed model, it is shown that the stiffness of the rail joint of the 49 rail can decreases up to 10 % when the joint gap length increases from 0 to 20 mm.