Seismic Performance Assessment of Deteriorated Two-Span Reinforced Concrete Bridges

This paper presents a nonlinear analysis procedure for the seismic performance assessment of deteriorated reinforced concrete bridges using a modified damage index. A finite-element analysis program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze deteriorated two-span simply supported reinforced concrete bridges. The new nonlinear material models for deteriorated reinforced concrete behaviors were proposed, considering corrosion effects as shown in a reduction in reinforcement section and bond strength. A modified damage index aims to quantify the seismic performance level in deteriorated reinforced concrete bridges. Several parameters of two-span simply supported deteriorated reinforced concrete bridge have been studied to determine the seismic performance levels. The newly developed analytical method for assessing the seismic performance of deteriorated reinforced concrete bridges is verified by comparison with the experimental and analytical parameter results.

Defects systematization of reinforced concrete bridges of ukrainian railways as the result of their inspection

Visual inspection is the important part of the bridges management. Many defectscan be detected that determine the traffic conditions, service life, and operation cost. Thedeterioration of bridges calls for effective methods for condition evaluation and maintenance as wellas suitable methods of their repair and recovery. This article aims defects systematization ofreinforced concrete bridges to define the effective method for recovering of their technical state. Morethan 100 reinforced concrete bridges in Ukrainian railways were inspected from 2017 to 2021.Ultrasonic pulse velocity, penetration resistance, reinforcement corrosion tests, and rebar locatingwere performed on beams, bed block, and piers of reinforced concrete bridges. It is shown that themost probable reasons of defects are natural impacts (freezing-thawing, moisturizing-drying),technogenic factors (train vibration, leakage current), and technological disadvantages(unsatisfactory production or setting). During the inspection, there are three categories of defectswere defined. The first one does not influence the train traffic (for example, deficient protectiveconcrete layer). The second one can limit the train traffic (for instance, crack width more than 0.3mm). The third category endangers the safe railway operation (such as an intense leaching of cementstone at an area more than 2 m2). It is made a proposal to match external signs of damage withreasons their appearance and methods of recovery. Three main types of repairs are used in Ukrainianrailways: torkret process, steel hooping, waterproof layer. However, the relationship between thetype of defect and the method of recovery has not been estimated before. It is important that themethods of repair and protection will be assigned according to their operation state (a disabled staterequires immediate recovery of the structures) as well as the reasons of appearance (destructiveacts). These methods must prevent a future destruction or protect of the structures.

STUDY OF THE BRIDGES BUILT IN UKRAINE IN 1998 AND 2001, THAT WERE DESTROYED BY LONG-TERM OPERATION AND FLOODS

Purpose. The aim of the work is to summarize design errors, construction defects and shortcomings and bridge defects after long-term operation on the basis of real field studies and analysis of scientific and technical sources. Methodology. To achieve this goal, an inspection of scientific and technical sources and regulations on the technical condition of transport facilities in Ukraine was conducted. In particular, it is a bridge in the city of Khust, built in 2000 on the site destroyed by floods in 1998 and a monolithic frame-cantilever bridge on the highway Mukachevo-Rogatin km 92 +700, built in 2001 on the site of partially destroyed in March 2001. The authors also took part in the construction, testing for static and dynamic loads of six steel-reinforced concrete bridges in Kobiletska and Kosivska Polyana, which were erected in 2000 on the site of those destroyed by the 1998 flood, as well as overpasses and bridges of long-term operation, – this is the Beregovsky bridge in the city of Mukachevo and the overpass in the village of Vistova. The results of the analysis and synthesis of the above studies became the basis for establishing the corresponding design errors, defects and shortcomings in construction and shortcomings in the operation of bridges and overpasses. Results. The analysis of domestic and foreign scientific and technical sources regarding the technical condition of the constructed reinforced concrete, steel-reinforced concrete bridges and bridges and overpasses of long-term operation is carried out. The analysis and synthesis of the problems of ensuring the reliability and durability of transport structures in the conditions of their operation in the air, soil and water environment. It is established on real examples of design errors, defects and shortcomings in construction, shortcomings in operation. The possibility of restoring the bearing capacity using modern materials and technologies is shown. Scientific novelty. As a result of the analysis of transport structures, scientific and technical sources and a number of studies of reinforced concrete and steel-reinforced concrete structures of bridges built after the floods in 1998 and 2001 and bridges (overpasses) of long-term operation, it was possible to summarize the main reasons that significantly affect the degradation of the structures of these bridges and overpasses. The possibility of restoring their bearing capacity and durability using modern materials and technologies is shown. In particular, it was found that in addition to power factors, factors of the air, soil and water environment also significantly affect. Practical significance. On the basis of these data, and observing the indicated objects for 20 years, it was possible to generalize and establish design errors, defects and shortcomings in construction and shortcomings of long-term operation. This makes it possible to propose areas of theoretical and experimental research and calculation methods, to take them into account in the design and operation of such structures. In particular, on the basis of these data, a technique was created and tested on real objects, which makes it possible to significantly increase the durability and reliability of such structures, using modern materials and technologies for repair and restoration work.

PROSPECTS FOR THE USE OF STRUCTURAL MATERIAL BASED ON LOW-VALUE SOFT HARDWOOD WOOD FOR BRIDGES ON HARVESTING ROADS

Russia has significant reserves of low-value soft deciduous wood (birch, aspen, alder, poplar), which are practically not processed, the wood rots in the forest and in the lower warehouses. Wood is a good and widespread building material. Due to the significant strength, low volume weight, ease of processing, ease of manufacturing and assembly of structures, wood has long been used for the construction of bridges. At present, despite the widespread use of reinforced concrete bridges, in the forest-rich northern and eastern regions of Russia, wooden bridges can be very useful on logging roads. But wooden bridges have a number of significant drawbacks: they have a short service life, are subject to rot, are not fire-resistant, and do not meet the requirements for passing modern loads. In order to ensure the safe and uninterrupted transport of timber on logging roads, special attention should be paid to the construction material for the construction of bridges. The proposed construction material is based on low-value soft hardwood, has high performance characteristics. To improve the performance of the wood, it is necessary to impregnate it-giving it the desired properties and compress it-thereby increasing the density, hardness and strength. We have developed a technology that combines three main technological operations of wood modification: impregnation, pressing and drying, while allowing us to obtain a structural material with increased performance characteristics, suitable for the manufacture of load-bearing supports, as well as beams of wooden bridges on logging roads.