MODERN STEEL-CONCRETE SPAN STRUCTURES OF SMALL AND MEDIUM-SPAN BRIDGES

The paper reviews the most common reinforced concrete girder structures of modern bridges used in Ukraine and other countries. The scope, advantages and disadvantages of reinforced concrete structures are considered. The peculiarities of the use of reinforced concrete structures in European countries are reviewed. The most common typical structural solutions of reinforced concrete girder structures used worldwide are given. Options for facilitation of reinforced concrete structures without significant loss of load-bearing capacity are also highlighted. Options for facilitation of structures are presented in the article by lightening the metal load-bearing elements and reducing the weight of the reinforced concrete slab of the carriageway. Reducing the weight of metal elements can be obtained through the use of perforated elements, which can be performed by waste-free technology. To reduce the cost of materials and reduce the weight of the reinforced concrete slab, it is designed lightweight – hollow or ribbed. When removing concrete from the stretched zone, only the ribs of the width required to accommodate the welded frames and ensure the strength of the panels on an inclined cross section are retained. In this case, the plate in the span between the ribs work on the bend as beams of T-section. The top shelf of the plate also works on the local bend between the ribs. During the inspection, the article presents a new design of reinforced concrete girder structure, using perforated box metal elements, made by waste-free technology, and lightweight reinforced concrete slab of the carriageway with hollow formers. Metal blocks are connected to each other by bolts. Metal blocks are made of perforated sheet elements made of waste-free technology. Each block consists of two main beams, transverse diaphragms and a lower plate. The upper belt of the main beams is implemented with the device of horizontal shelves along the entire length of the beams, performing the function of a supporting element for the reinforced concrete slab. Combining all structural elements into a single finished unit is carried out in the factory by automatic welding, which, in turn, allows us to achieve the high factory readiness. The diaphragms of the block are made with a comb along the upper border, on which a profiled steel sheet is placed, which is a fixed formwork for a reinforced concrete slab. The plate is made of non-removable formwork. To ensure the joint operation of the metal part and the reinforced concrete slab, a system of discrete-continuous connections in the form of rigid stops connected in the longitudinal and transverse directions by reinforcing rods is proposed.

COMPOSITE REINFORCED CONCRETE BRIDGE GIRDERS FOR POST-CONFLICT RECONSTRUCTION OF THE DESTROYED TRANSPORT INFRASTRUCTURE

Purpose. The purpose of this work is to analyze the existing composite reinforced concrete girder structures of bridges, determine their advantages and disadvantages, study of stress changes in the elements of the girder structure and its deflections caused by the coupling of metal beams and reinforced concrete roadway, the possibility of using these structures in post-conflict reconstruction. Methodology. Examination of the data covered in the literature. Studying the experience of design and construction of reinforced concrete girder structures of bridges in our country and abroad. Construction of the calculation model, its loading, change of thickness of a reinforced concrete plate, the analysis of results. Findings. The result of this work is collected data on the advantages and disadvantages of reinforced concrete girder structures of bridges under the railway, the impact on stress in the elements of the girder structure and on its vertical deflections by the joint work of metal beams and concrete slab, analysis of the possibility of using such girders for fast resumption of train traffic. Originality. It lies in that for the rapid and high-quality restoration of destroyed transport infrastructure, including railways, it is proposed to use metal beams of long-term storage (mobilization reserve), which are made on standard projects in the middle of last century, combined with reinforced concrete slab included in joint work, thereby obtaining composite reinforced concrete girder structures. This will allow rational use of the available reserve of materials, high recovery rates and reliable recovery of train traffic. Practical value. Based on the obtained data, it is possible to conclude that the method of combining the long-term stored metal beams and reinforced concrete slabs of the carriageway increases the load-bearing capacity of the obtained girder structures, so the use of these structures can ensure the effective restoration of war-torn railway structures in a short time.

Determination of stresses and dynamic coefficients when testing railway overpasses

This paper presents some results of instrumental measurements of dynamic coefficients and fiber stresses of reinforced concrete girder spans of railway overpasses under mobile load. The results obtained can be used for further monitoring of similar structures on the main railway lines of the Republic of Kazakhstan, to identify damage in the structures of bridges.

Geometric characteristics, local site and curvature radius effects on seismic vulnerability of multi-span concrete girder bridge

Horizontally curved concrete girder bridges have complex dynamic characteristics because of their asymmetry and non-uniform mass and stiffness distribution. Their seismic behaviour is considerably affected by various such as structural characteristics, radius of the superstructure curvature and local site conditions. The computational, three-dimensional (3D) bridge models consisting of concrete girders with concrete deck, single pier columns and caps were created in OpenSees analyzing a representative, three-, four- and five-span continuous curved concrete girder bridges in N. Macedonia. Different seismic hazard levels and soil conditions were chosen in order to perform site-specific hazard calculations to investigate the effect of critical curved bridge parameters on the seismic response using a group of representative bridges. Two levels of capacity were considered: damage and collapse limit state (DLS and CLS). The results from the performed extensive nonlinear analyses including uncertainties were used to estimate the influence of the number of spans, deck width, pier height, deck horizontal curvature radius and local site effects on the bridge performance. The influence of soil conditions and superstructure curvature are significant for the seismic vulnerability of girder bridges, especially those with more spans. With the increase of the superstructure curvature radius, the bridges become more vulnerable, particularly if they have more spans and are founded on soil of weaker characteristics. The difference in the probability of damage occurrence to bridges with smaller number of spans, regardless the curvature radius, is small if these are founded on a good base. In the case of CLS, such probability differs extensively, particularly in multi-span bridges founded on weak soil. Regardless the curvature radius and the soil characteristics, the width of the superstructure has a favorable effect upon the seismic response of the selected type of bridges. Bridges with piers of a greater height and greater curvature radius exhibit considerably less favorable seismic behavior than bridges of smaller curvature radius founded on better soil.