Features of assessing the condition and behavior of low-water bridges

The article describes features of operation and monitoring of low-water bridges, which are found on highways of regional, intermunicipal and local importance. Vibrations of the bridge span are considered in detail, taking into account its interaction with other structural elements and the environment. As a characteristic, the change of which takes into account the change in the state of the bridge structure, it is proposed to use the frequency of natural vibrations. To simulate the dynamic effects of transport and the dynamic behavior of individual elements and the entire structure as a whole, it is proposed to use viscoelastic elements of the Kelvin–Voigt type. When solving the problem, an approach has been implemented that makes it possible to take into account the anisotropic properties of the superstructure associated with various reinforcement along and across the roadway of the bridge, and to present the design scheme of the span not in the form of a beam supported at the edges with the help of hinges or viscoelastic dampers, but in the form of a plate, which can have different fxing conditions along the entire contour. The use of the proposed model and approach will make it possible to obtain the necessary data on the state of low-water bridges, for which there is often no possibility of visual inspection or instrumental inspection from the lower side of the bearing part of the superstructure. By the values of the frequency of natural vibrations, it is possible to estimate the water level above the low-water period and predict food situations, during which the roadway of the low-water bridge may be fooded.

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.

AERODYNAMIC STABILITY OF BRIDGES WITH VARIOUS LEVELS OF STRUCTURAL DAMPING

Introduction: Structural damping is one of the most important parameters affecting the aerodynamic stability of bridge structures. Purpose of the study: We aimed to assess the effect that structural damping of a bridge structure has on its stability in a wind current. Methods: In the course of the study, we performed experimental studies of the aerodynamic stability in typical girder bridge structures (with two and four main girders) with different levels of structural damping, facilitated by a unique experimental unit: Large Research Gradient Wind Tunnel, courtesy of the National Research Moscow State University of Civil Engineering (NRU MGSU). Results: The results of the experimental studies show that, despite the general trend towards the decrease in the amplitude of bridge span structure oscillations as the structural damping level increases, the dependence between these parameters is nonlinear. When providing R&D support in the design of real-life structures, in case it is necessary to increase the aerodynamic stability of the superstructure by increasing the level of structural damping (changing the type of joints in structural elements, using mechanical damping devices), it is recommended to conduct experimental studies in wind tunnels to assess the effectiveness of a given solution.

Effects on a Nearby Bridge of Dismantling Temporary Lining During Excavation of a Shallow-Buried Rectangular Tunnel

It is almost inevitable that when a tunnel is excavated in an urban area, it will pass under an existing bridge. During tunnel excavation, a temporary lining is installed and subsequently removed. However, dismantling temporary lining may affect the stability of a nearby bridge. A numerical model was created and tests were conducted on a large-scale physical model to investigate the effects of dismantling temporary lining on a nearby bridge structure. A novel method of modeling the restraining force at the top of a pier was introduced to make the model more accurate in representing the physical situation. Analysis of the results led to the following conclusions and suggestions. 1. The process of removing temporary lining can have a significant impact on surface settlement and structural deformation of the bridge. 2. The effect of removing the second half temporary lining is greater than that of removing the first half. The key range of the tunnel where this phenomenon is principally observed contains one section of tunnel ahead (i.e., in the direction of tunnel advance) of the bridge span and the two sections to the rear. 3. A 6 m–3 m–6 m mixed dismantling method is recommended for use in the key range, and a rigid cap-connection method is proposed to counteract the considerable effects of dismantling temporary lining.

Experimental dynamic analysis of the arch road bridge

The paper presents an experimental dynamic analysis of the existing road bridge across the Labe river at Valy village in the Czech Republic. The observed structure is a bridge with 6 spans 23.1 m, 31.5 m, 84.0 m, 31.5 m and 23.1 m long. The horizontal load-bearing structure is a composite structure with two main steel girders and a lower reinforced concrete deck. The load-bearing structure is reinforced in the main span by the arch, this structural system is also called the Langer beam. The experiment was realized in three stages. The first one was performed in May 2020 before its opening, the second stage of the described experiment was realized in August 2020 and the third one was carried out in April 2021. The main purpose of the first stage was to determine in detail the natural frequencies and mode shapes of the whole bridge horizontal load-bearing structure also including the arch. The electrodynamic shaker, that was located on the bridge deck in the quarter of the main bridge span, was used for excitation of the bridge vibration. The measured characteristics of the natural vibration were compared with the calculated ones. Based on this comparison, the theoretical bridge model was verified. Basic objective of the second experiment stage was to verify new approach to dynamic response measurement – radar interferometry realized by two synchronized radars. The vibrations of the bridge caused by the standard road traffic and also by pedestrians were observed concurrently by both radar interferometry and classical approach realized by high sensitive piezoelectric accelerometers. The experiment was focused on the main span of the bridge only and the levels of forced vibration were observed primarily. However, the fundamental natural frequencies were also evaluated. The third stage was carried out by classical approach only. Again, the bridge vibration caused by the usual road traffic and pedestrians were measured in the main bridge span only because this section of the bridge was the most dynamically sensitive. Again, the levels of forced vibration were observed and the fundamental natural frequencies were determined. The evaluated natural frequencies from all three experiment stages were consequently compared.

Evaluating the Dynamic Response of the Bridge-Vehicle System considering Random Road Roughness Based on the Moment Method

The bridge-vehicle interaction (BVI) system vibration is caused by the vehicles passing through the bridge. The road roughness has a great impact on the system vibration. In this regard, poor road roughness is known to affect the comfort of the vehicle crossing the bridge and aggravate the fatigue damage of the bridge. Road roughness is usually regarded as a random process in numerical calculation. To fully consider the influence of road roughness randomness on the response of the BVI system, a random BVI model was established. Thereafter, the random process of road roughness was expressed by Karhunen–Loeve expansion (KLE), after which the moment method was used to calculate the maximum probability value of the BVI system response. The proposed method has higher accuracy and efficiency than the Monte Carlo simulation (MCS) calculation method. Subsequently, the influences of vehicle speed, roughness grade, and bridge span on the impact factor (IMF) were analyzed. The results show that the road roughness grade has a greater impact on the bridge IMF than the bridge span and vehicle speed.

Analysis of Pre-Stressed Box Girder Bridge under Different Standard Codes: A Comparative Study

Pre-stressed concrete bridge analysis is completely dependent on the standards and design criteria. Herein, the current study compares like a pre-stressed concrete bridge under the effect of two different loading standards and specifications. The two different loading standards considered herein are IRC 6: 2000 and AASHTO-LRFD standards. Further, the pre-stressed box girder bridge is modelled and analysis in MIDAS CIVIL. On carrying out analysis, the primary structural analysis parameters which are important for the design of structure, are studied. These parameters are shear force, bending moment and torsion in the bridge elements along its length. It became observed that AASHTO standards are uneconomical than IRC standards, due to consideration of heavy weight vehicle load moving on the bridge span. Thus, it might be said that pre-stressed box girder bridge analysis and design should be carried out effectively and optimistically using IRC standards and specifications.

REUSE OF BRIDGE GIRDERS AS BRIDGE SPAN STRUCTURES OF TEMPORARY BRIDGES

Introduction. This article presents the results of study of the quality of girders that were used for the construction of temporary road bridge. In the bridge construction practice there is a need to use girders in the construction of road bridges on local roads that can be reused in temporary bridges construction. It is important when using such structures to determine their reliability for long-term operation. The cost of bridge girders is up to 60% of the cost of a new bridge, so the reuse of utilizedsed girders is economically feasible. Utilized girders can be reused on local roads and temporary bridges. Problem statement. To determine the usability of utilized girders in temporary bridges construction and provide recommendations for the girders reuse and possible bridge design structures. Materials and methods. The following works were performed during the inspection: visual inspection of the girders at places of their storage after dismounting; measurement of the basic sizes of girders; determination of concrete strength by non-destructive test method; determination of the number of working reinforcement and the protective layer thickness; measurements of pH of concrete of a protective layer were performed; registration of existing defects was performed. The following measurements were performed during the tests: general displacements and deformations of structural elements of the structures; relative deformations of cross sections; local deformations (displacements in joints). Results. According to the results of tests and calculations, the bearing capacity of the bridge span structure was determined. After analyzing the results of experimental and theoretical studies, conclusions were made regarding the operational performance of the girders of the bridge span structure. Conclusions. Girders in the 1st, the 2nd and the 3rd technical state can be considered suitable for bridge span structures unreservedly. Girders in the 4th technical state, need repairing and reinforcement for reuse in bridge span structures. They cannot be used without repairing. Girders in the 5th technical state cannot be used in the span structures of road bridges. They can be used, for example, as transition slabs, or for pedestrian bridges and crossings, or can be used for testing the technology of bridge structures repairing. Thus, tests of bridge girders and full-size joints testify that the accepted design decision provides the needed bearing capacity of girders and of the bridge span structure as a whole. This confirms the sufficient reliability of utilized girders in the further work. Practice shows that it is also needed to pay great attention to the following: firstly- to the methods of dismantling the girders without damage; secondly — to the proper storage of girders after dismantling.

Estimation of the Load-Carrying Capacity of the Constructions of the Cultural Heritage Object «The Oldenburg’s Complex. Lovers Bridge. 1900»

Постановка задачи. Многолетняя бесконтрольная эксплуатация моста привела его несущие конструкции к аварийному состоянию. Для дальнейшей его безопасной эксплуатации требуется конструктивное укрепление практически всех элементов. Так как их прямое упрочнение невозможно без нарушения подлинного облика, авторы поставили перед собой задачу косвенного усиления конструкций путем подбора на математической и физической моделях допустимых схем и предельных значений нагрузок на пролетное строение. Результаты. Для решения поставленной задачи проведены и проанализированы результаты качественных и количественных теоретических исследований объекта культурного наследия «Комплекс Ольденбургских. Мост влюбленных. 1900 г.». Осуществлено инструментальное освидетельствование памятника, выполнена и испытана лабораторная модель подлинного сооружения. Выводы. Полученные в результате всесторонних исследований данные позволили оценить ресурс несущей способности конструкций объекта культурного наследия, проанализировать возможности загружений пролетного строения моста и сделать заключение о его надежной эксплуатации в современных условиях. Statement of the problem. Many years of uncontrolled operation of the bridge led its supporting structures to an emergency condition. For further safe operation of the bridge, structural strengthening of almost all elements is required. Since their direct strengthening is impossible without violating the original appearance, we set the task of strengthening the structures indirectly by choosing permissible schemes and limit values of loads on the span on mathematical and physical models. Results. To solve this problem, we carried out and analyzed the results of qualitative and quantitative theoretical studies of the object of cultural heritage «The Oldenburg’s complex. Lovers Bridge. 1900». We carried out an instrumental inspection of the monument, designed and tested a laboratory model of the original structure. Conclusions. The data obtained as a result of comprehensive studies made it possible to assess the load-bearing capacity of the structures of the cultural heritage object, analyze the possibilities of loading the bridge span and make a conclusion about its further safe operation in modern conditions.