Towards dynamic property control of bridge spans

Regulation of the dynamic properties of bridge spans is a priority field of this research, which solves the problem of increasing the obsolescence and physical periods of bridge structures manifested both at the design stage of the load redistribution in the load bearing and during long-term operation.Over the past 40 years, technical bridge diagnostics has shown that the durability and safe long-term operation can be ensured by the improved calculations, operation and stress and strain control under the excess and over-calculated live loads.The aim of this work is to control the dynamic deformation and amplitude-frequency characteristics of bridge spans under harmonic random (non-stationary) oscillations of the span-vehicle system due to changes in the energy and stress state of the structure. The dynamic behavior of the span-vehicle system is based on the control for the amplitude-frequency characteristics of random oscillations by averaged values, the required spectral density being provided.The use of dynamic dampers for the system element control and the rigidity of junctions provide antiphase oscillations of the bridge span elements such as beams and decks, that leads to the unaccounted inertial forces.Another important element of the joint work imbalance of the bridge span elements during the dynamic load, are various defects, both in the deck design and load-bearing elements. It is assumed that the deck is a transfer layer (element) of vibrations induced by a vehicle in the beams. It is shown that the control for the dynamic properties is required in the case of a coincidence between the vehicle and beam stiffness and mass at the center of the system rigidity.The attention is paid to the conditions and dependencies between the dynamic load parameters and the stress-strain state of the bridge beams at the elastic and elastoplastic stages, with respect to the additional inertia of the system. This approach is the pilot in the Russian and foreign bridge construction in terms of experimental studies and testing of bridges for continuous random traffic.The dynamic testing of bridge spans for random traffic flow contributes to the creation of vibration diagnostic express laboratories necessary for the operation and maintenance of bridges.

Force control in girder-cable systems

The object of the study is the forces in the beam-cable systems. The introduction of these systems in construction is associated with the task of creating a pre-stress in order to regulate the stress-strain state of the beam-cable system as a whole. Prestressing will make it possible to rationally use high-strength materials in the structure, and to design the structure economically. When designing girder-cable-stayed structures of bridge spans, it is necessary to determine the sequence of stresses of the structural elements-shrouds in order to regulate the forces in the beam element of the structure. This problem is considered in this article. The dynamic programming method is used to regulate the stress-strain state of the system by pulling the shrouds in the optimal sequence. To solve the problems, formulas for the output value and the optimality criterion, as well as the matrix, are given. As a result, the values of the output values of interest at all stages of the tension of the shrouds are found.

NUMERICAL SIMULATION OF AERODYNAMIC STABILITY OF LONG-SPAN BRIDGES

Statement of the problem. The aim of the work is to simulate the resonant vibrations of the continuous beam span of the bridge in the direction perpendicular to the wind flow by the finite element method. The article deals with a non-standard situation that arose on May 20, 2010 on the bridge over the Volga River in the city of Volgograd.Results. As a result, an effective algorithm for calculating the aerodynamic stability of large-span bridge structures was developed using one of the most widespread software systems in Russia and neighboring countries - "Lira-SAPR". Recommendations for the selection and modeling of dampers are given. Conclusions. The developed algorithm makes it possible to numerically describe the disturbing force of periodic breakdown of wind flow vortices, which causes resonant oscillations of bridge spans, to apply this force to the design model in Lira-SAPR, and to obtain parameters that make it possible to assess the stress-strain state of the system during oscillations and to select the optimal characteristics of the damping devices.

Grand Avenue Traverse: Uniting Accessibility, Utilities and Economy Into a New Experience

<p>The Grand Avenue Pedestrian Bridge spans 85m from a park and residential neighborhood to a developing waterfront district that is 24m below. The bridge carries sewer, storm, and water utilities over rail lines and a highway while passing under power lines. The bridge’s east landing is on a landslide prone steep slope. On the west the bridge lands on a new concrete stair and elevator tower that rests on soil that is regularly infil- trated with seawater.</p><p>The design concept uses the constraints of the project to create a unique moment that is both utilitarian and unexpected. By sloping the truss to drop 4.8% towards the west, a set of accessible ramps are created on the top, side, and interior of a box-truss style bridge. Traversing 7m of elevation through accessible paths allowed the design team to minimize the height of the elevator and therefore moment into the foundations, critical for a site that is seismically active and located in seawater infiltrated soil.</p><p>Material choices for the bridge and throw barrier were based on considerations of durability and mainte- nance. Weathering steel is used for the primary truss members, painted steel for members located under the deck, and bare aluminum panels with a custom CNC cut perforation form the guardrail and throw barrier. All of the elements come together as a unified experience.</p>

Challenges in Procurement, Design and Construction of the Erasmusrand Pedestrian Bridge

<p>The new Erasmusrand Pedestrian bridge replaced the previously severely damaged pedestrian bridge spanning across the National Route N1 highway in Pretoria, South Africa, for the South African National Roads Agency SOC Ltd (SANRAL). The structure consists of a steel arch supporting a composite steel/concrete deck with inclined square hollow steel struts. The bridge spans 73m across a 10-lane dual carriageway freeway providing access to a local school from the suburbs. Several challenges were presented in the project with procurement, design and construction.</p>

The Ołowianka Bascule Footbridge in Gdansk – A Bridge That Makes the Difference

<p>In the city of Gdansk in Poland, in the very centre of the Baltic capital, on 17 June 2017, a new draw footbridge was ceremoniously opened to the public. The Ołowianka footbridge represents the long-time much-needed link between the highly tourist-visited historical old town and Ołowianka Island, where further cultural, tourist and recreation facilities are located. The bridge spans a very busy navigable channel of the Motława River, leading inward towards other city channels, a harbour for many tourist ships and the Gdansk Marina. Being the main navigable entrance to the city centre, the Motława is constantly under nautical traffic, so the Ołowianka footbridge operates 24/7, according to a 30-minute schedule. The Ołowianka footbridge is an extraordinary acquisition for the city of Gdansk, which immediately became a new landmark and much more in the already very picturesque historic city centre. Not just its design, but also its carefully chosen location and its realisation at the right moment, has made this bridge indispensable to the inhabitants, visitors and the administration of the city of Gdansk, decisively contributing to further development in the Ołowianka Island area and its surroundings.</p>

Structural health monitoring of bridge spans using Moment Cumulative Functions of Power Spectral Density (MCF-PSD) and deep learning

This article proposes a new parameter in evaluating mechanical behaviors of defected bridge spans. It is Moment Cumulative Function of Power Spectral Density (MCF-PSD) based on changes in shape of power spectrum and trained via cumulative function of spectral moment value by deep learning model. This new parameter allows evaluating stiffness attenuation along time, thereby helps to forecast the workability of bridge span. It can identify risky positions in not only a bridge span but also various spans of the same bridge, which proves its sensitivity to the structure’s behavior change over time. This study reveals that training MCF-PSD using cumulative function algorithm has gained outstanding results in comparison with previous studies in structural quality assessment. Therefore, it fulfills criteria of evaluating the damage level in a structure and also fosters new development of defect diagnosis and forecast. Conclusions from this study show that the change of this function is the basis to evaluate difference among measurement positions in the same span or among different spans of the same bridge and behaviors at different positions in the same span. Therefore, MCF-PSD is more sensitive than other parameters in evaluating the structure’s stiffness attenuation.

Somers Town Bridge

<p>The Somers Town Bridge crosses the Regents Canal in central London and was opened in 2017. It is a bridge of extreme simplicity - almost impossibly slender – but meeting the structural demands with the very minimum of materials.</p><p>Designed for cyclists and pedestrians to cross from Camley Street into the King’s Cross development; a landmark redevelopment project by the developer client, Argent (on behalf of King’s Cross Central Partnership Ltd); the bridge spans 38m and is only 1100mm deep at mid-span and 400mm deep at the ends. In keeping with the Victorian heritage of the area, the bridge is unadorned and streamlined, focusing attention on extremely detailed and precise craftsmanship and high-quality materials.</p><p>With such a slender deck form this bridge would normally be sensitive to pedestrian induced vibrations, but for the inclusion of 3 sets of tuned mass dampers at mid-span that are hidden by a cover plate that provides the bridge identification number – 34B.</p><p>This paper presents the story of the bridge development and its response to several challanges.</p>