The article discusses the results of the analysis of the stress-strain state of the junction of the column and the beam of a monolithic reinforced concrete frame - in particular, the cornice nodes of the outer columns, which have an L-shape. In these nodes, part or all of the tensile (upper) reinforcement of the beam, bending along a certain radius R, passes into the column. The subject of the study is the stress state of concrete in the frame node, as well as the features of the operation of the curvilinear section of the tensile reinforcement. The study of the features of the concrete operation was carried out by setting up a computational experiment. Modeling was performed in the Lira-SAPR software package. The characteristics of the model (finite element scheme) and the main results of the calculation are given - the distribution and numerical values ​​of stresses. To assess the actual work of the tensile reinforcement of the node, an analysis was made of the influence of the loading history of the reinforcement bar - its plastic bending to give the required outline. It was established that the stress state of concrete of a bisecting section differs fundamentally from the stress-strain state of concrete in normal cross-sections of a beam and a column. Taking into account the loading history of the reinforcing bar (preliminary inelastic bending) allowed us to conclude that, with the same tensile force, the deformations of a pre-bent bar exceed the deformations of a rectilinear bar. Obviously, this circumstance leads to an increase in the crack opening width.

Keywords: ramny node, reinforced concrete, reinforcement, stresses, deformations, bisector section, normal section, plastic bending, bending radius, loading history, finite element, Lira-SAPR

the work is devoted to a comparative analysis of various calculation and mathematical models among themselves. The calculation of the frame joint of reinforced concrete structures is performed: a pylon and a cantilever beam. Three methods for performing the calculation of this joint are proposed: an analytical method, a rod FEM model and a volumetric FEM model. The analysis of the calculation results is performed: a comparison of internal forces and calculated reinforcement. The consequences of a superficial analysis of the structure and simplification of calculation models are shown using the example of damage to a real structure under the action of operational loads.

Keywords: reinforced concrete console, structure calculation, node calculation, Lira 10, Russian software, optimal design of reinforced concrete structures, reinforcement analysis

The work is devoted to the search for an optimal design solution for columns of a 16-storey monolithic reinforced concrete residential building with a minimum cost of materials. The modern approach to the constructive solution of high-rise buildings assumes multipolarity at the design stage. Meeting modern requirements determined by human needs, durability and functionality of housing and other parameters, the essential importance of economic indicators is also noted. A special approach to the design stage as an attempt to consider in detail the preparatory stage (the choice of the section and class of concrete columns in buildings made of monolithic reinforced concrete) is justified by the relevance of the problem considered in the article.

Keywords: Reinforced concrete columns, frame calculation, Lira-SAPR, concrete class variation, optimal design of reinforced concrete structures, calculation of a 16-storey building

The calculation of a multi-storey monolithic building of a wall structural scheme for resistance to progressive collapse is considered. Calculations of the building were made for various operating conditions: normal and extreme (emergency impact — destruction of part of the load-bearing walls of the first floor). Recommendations are given for building protection in case of emergency impacts. It is determined that for buildings with a cross-wall system, the appropriate method of protection against progressive collapse is the method of reserving the strength of load-bearing elements. The increase in the cost of materials is about 2 %. Comparison of technical and economic indicators of buildings of wall and frame structural schemes showed that the cost of protection from progressive collapse of buildings with a wall structural scheme is significantly lower than that of frame

Keywords: progressive collapse, emergency impact, strength reservation, cross-wall design scheme, Lira-SAPR, building design model

In this article the comparative analysis of reinforcement of monolithic reinforced concrete plate under various conditions of calculation is made: without seismic actions, with design earthquake and with maximum design earthquake. It was found that taking into account the seismicity of 9 points without the use of methods of active seismic protection leads to an increase reinforcement to 28 % when taking into account the design earthquake and 81 % when calculating the maximum design earthquake. In addition, the analysis of the tool "Consumption of concrete and reinforcement" in the Lira-SAPR is made. The correction factor for the transition from theoretical to real reinforcement was obtained: it ranged from 2.4 to 3.0

Keywords: seismic impact, Lira-SAPR, maximum design earthquake calculation, frame calculation, slab, reinforced concrete, specific consumption of reinforcement

To date, the construction of the new techniques of construction of buildings and structures, as well as the most advanced durable and lightweight materials with high performance characteristics. All this allows you to build cost-effective, high-quality and aesthetically attractive houses. Depending on the materials used in the construction of multi-storey buildings was considered the effectiveness of ribbed coffered floors. Calculation of the 18-storey monolithic building was made in the program complex "Lira-CAD-2013". Floor slab typical floor is considered in the following schemes: buildings with a step of columns 6m and 12 m, the ceiling is flat and coffered with a 200mm plate 50mm, different beam cross-sections (200х400мм and 200х450мм), step 900х900 mm. analysis of the results showed that the most advantageous use of coffered ceilings in the building with a column grid of 12 m, with the use of high-strength concrete and reinforcement steel class A500.

Keywords: caisson ceiling, slab, beam, reinforcement, concrete, analysis, consumption, reinforcement, step columns, the cost of construction, structural scheme

The article deals with the effectiveness of high-strength concrete for the design of concrete columns on the example of 20-storey residential building in Rostov-on-Don. The results of the ground floor columns calculations for different types of concrete strength are presented. The columns are presented in two variations. The first variation is 600x600 B25 from the second underground floor to the tenth floor and 500x500 B25 from the eleventh to twenty-fifth floor. The second one is 500x500 B60 from the second underground floor to the seventh floor, 400x400 B60 from the eighth to the eleventh and 400x400 B25 from the twelfth to the twentieth floor. The analysis of the study results showed the technical and economic efficiency of the use of high-strength concrete (in particular, concrete class B60) due to increasing the strength characteristics of the compressed elements. This is also due to reducing the cross-sectional size and weight of the columns, saving reinforcement, causing a reduction in the cost of elements as a whole.

Keywords: high-strength concrete, compressed elements, construction of tall buildings, columns, Lira-SAPR, calculation of structures

The calculation of multi-storey reinforced concrete frame building, consisting of apartments, offices and underground parking, against progressive collapse is presented in the paper. Two different ways of simulation of reinforced concrete building against progressive collapse are suggested, needed for estimation of survivability of building structures. The technique, which allows to carry out the stability of reinforced concrete structure to resist progressive collapse, is presented. This method is based on a nonlinear analysis of framed structures under the special load combination and includes dead and live loads, implying that the loading process modeling is fulfilled on the basis of the adjusted step method. The last one is of great importance for simulation of the processes in the whole life cycle of structures. The obtained results show that the offered strength calculation method of the framed structure against progressive collapse considers both geometric and material nonlinearity and also allows to assess survivability of the construction under conditions of emergency events and its stability to resist against progressive collapse. The step method of solving nonlinear problems, applied for modeling of collapse process, is shown to be more appropriate for these cases. We conclude that applying the proposed method of calculation results in more economic use of materials, giving evidence of its effectiveness.

Keywords: progressive collapse, survivability of building structures, computer simulation, structural elements, nonlinear analysis, stability, geometric and material nonlinearity, the step method

The market in Russia is common formwork caisson ceilings SkyDome system.In the article the question of the effectiveness of ribbed caisson ceilings in multi-storey monolithic buildings compared to with .flat slab floor. The program complex "Lira-CAD 2013" calculated the 18-storey residential buildings with monolithic framework. Consider in detail the reinforcement floors typical floor in two versions: a flat of 200 mm and a caisson plate of 50 mm and beams with a section of 200х350 mm with a step of 900х900 mm. Analysis of the results showed that in a building with columns a step of about 5 m difference in cost of materials for the manufacture of the overlap was about 1%. Efficiency gains are expected by increasing the span up to 8 ... 10 m

Keywords: caisson, flat slab floor,monolithic framework, modular falsework of SkyDome, structural calculation, LIRA-CAD

The article deals with the calculation of prestressed reinforced concrete cylindrical tank with capacity of 200,000 m3 to store liquefied natural gas (LNG). The calculation is performed by using the finite element program complex "Lira-SAPR." For the purpose of considering the peculiarities of the work of such structures calculation was conducted in three phases: the initial phase was carried out a preliminary definition of the area of pre-stressed tendons and pitch of their arrangement on the height of the wall. Then - the preliminary determination of the intensity of the reinforcement ring beam coating with prestressed reinforcement. And in the end - the final calculation of prestressed concrete structures with the adjustment of the previous reinforcement. According to the results of calculating is obtained the reinforced concrete structure of the tank, which in the empty state, and in the stage of operation (filling LNG) stresses in the concrete does not exceed: in the compressed zones – the cylinder compressive strength, and in the stretched areas – tensile strength of concrete.

Keywords: tank, reinforced concrete constructions, calculation, Lira for Windows, prestressed reinforcement, liquefied natural gas

This article provides an account tsentrenno and eccentrically compressed reinforced concrete columns of high-strength concrete on the deformed pattern in SP 63.13330.2012. Compares the results of the calculation of the bearing capacity of the columns with the set experimental data. Proposed adjustments in the form of the coefficients in the formulas for the curvature tsentrenno compressed columns j and eccentrically compressed yb.

Keywords: high-strength concrete, physical experiment, prism strength, lateral reinforcement, concrete counters, deformation correction factor

This paper studies the dependence of the ratio of prismatic strength (Rb) from cube strength (R) for high-strength concrete of classes B70 ... B110. Experiments were carried on the concrete cubes with an edge of 150 mm and prisms with a base 150x150 mm and a height 600 mm. The tendency to reduce the ratio Rb / R with increasing strength of the concrete is founded. A new relationship Rb = f (R) is offered

Keywords: high-strength concrete, physical experiment, prismatic strength, cube strength, the coefficient of the prismatic strength

The paper proposes a new relationship for the analytical description of the diagram «b–b» for high-strength concrete of classes C55/67 ... C90/105. The formula developed on the basis of the accepted in EU relation of Sargin and agrees well with the experimental data. A new relation of the ultimate relative deformation of concrete from the strength is developed

Keywords: high-strength concrete, physical experiment, state diagram of concrete, the stress-strain dependence in concrete, the ultimate relative deformation of concrete

The article presents the results of calculations of reinforced concrete columns of high-strength concrete on the SNiP and SP. Compared the results with experimental data. The proposed adjustment formulas used with correction factors k and w resulting standard deviation of the bearing capacity of the columns from the experimental reduced more than four times.

Keywords: high-strength concrete, physical experiment, the correction factor calculation scheme undeformed