Changes and additions of SP LIRA 10.10 R2.5
Changes and additions of SP LIRA 10.10 R2.4
Changes and additions of SP LIRA 10.10 R2.3
Changes and additions of SP LIRA 10.10 R2.2
Changes and additions of SP LIRA 10.10 R2.1
Changes and additions of SP LIRA 10.10 R2.0
Changes and additions of SP LIRA 10.10 R1.1
 Implemented import and export into sdnf format
 Implemented connection with Revit 2020
 Implemented saving of previously entered parameters when importing floor plans from dxf files
 Implemented ability to specify cross sections, materials, loads, etc. automatically through layer names when importing threedimensional model from dxf file (similar to importing of floor plans) Design and graphical environment
 Implemented ability to consider damping properties of material for elements in Dynamics+ problems
 Implemented ability to solve the dynamic problem from disassembling elements for linear and physically nonlinear problems
 Added ability to specify stiffness reduction coefficients for bar and plate elements
 Implemented ability to specify nonlinear parameters for hinges assigned to linear bar FE (as part of a nonlinear problem)
 Consideration of elastic foundation Cx acting along the axis of bar elements, as well as consideration of elastic foundation Cx and Cy acting in the plane of plate elements, have been added
 Implemented FE of multilayer shell (up to 10 layers)
 Implemented ability to manage axes of internal forces calculation (DCL, DCF) for bar elements
 For linear problems it has been implemented decomposition of linear equations system by the Cholesky method
 Implemented ability to specify minimum percentage of modal mass contribution for factoring in natural forms in dynamics problems
 Implemented ability to specify userdefined and automatic DCL in assemblage problems
 Implemented architectural element for modeling the work of piles
 Implemented interactive wind load that allows to determine the average component for wind action on structures automatically by given parameters in accordance to: SNIP 2.01.0785* (changes 1.2, 1987), SP 20.13330.2016 (changes 1, 2), DBN V.1.22:2006 (change 1), EN 199114:2005, DSTU  N B EN 199114:2010
 Implemented interactive snow load that allows to determine snow cover weight on structures automatically by given parameters in accordance to: SNIP 2.01.0785* (changes 1.2, 1987), SP 20.13330.2016 (changes 1, 2), DBN V.1.22:2006 (change 1), EN 199114:2005
 Added ability to specify eccentricity when specifying force loads on plate elements
 Implemented new types of loads applied to architectural elements: concentrated and distributed along the line or part of the area
 Implemented algorithm that allows to perform conversion of FE grid fragment into architectural elements
 Added ability to set the maximum file size in autosave settings, upon reaching which the function will be disabled
 The ability to automatically delete calculation results files for batch of the problems has been implemented
 In triangulation using quadrangular FE the Smoothing algorithm by Laplace has been implemented (for combined networks)
 The automatic transfer of moments of inertia from already specified cross sections has been added in the utility for determining the effective lengths of metal bars
 Implemented ability of automatic adjustment of the coordinates of nodes of the design scheme in accordance with the deformed scheme from DCL or loading, or buckling modes (indicating scale factor) Reinforced concrete structures
 Implemented cross sections with steel core based on guncrete cross sections (round and rectangular pipe). The core may take the form of: filled pipe, empty pipe, cross made of angles, ibeam, ibeam made of channel bars, cross made of ibeams, composite ibeam
 Reinforcement proportioning in plates according to the method of SP 63.13330.2012/SP 63.13330.2018
 Implemented proportioning and check of required reinforcement according to SP 63.13330.2018 Concrete and Reinforced Concrete Structures
 Modernized the mode of displaying of the results of reinforcement proportioning and check Steel structures
 Implemented ability to calculate structures with slender wall for cross sections of symmetric/asymmetric ibeams and RHS
 Implemented check of steel elements of variable cross section according to SNIP, SP, DBN
 Implemented proportioning and check of bar elements’ cross sections according to EN 199311 and EN 199315 Soil
 New modeling capabilities for piles (FE57) have been added Application utilities
 Seismogram by accelerogram and accelerogram by seismogram
 Unit converter
 Scientific calculator
 Interpolation of data
 Calculation of pile's stiffness
 Calculation of bedding values
 Local calculation of reinforced concrete bar
 Local calculation of reinforced concrete plate
 Columns' effective length
Contants
Import/ExportImport/Export
SDNF format (Steel Detailing Neutral File) is used for import/export of 3D models when working with such CAD software, as AutoCAD, Bocad3D, Tekla Structures etc. In the SP LIRA 10.10, it became possible to import/export models from this format.
SDNF format describes such structural elements as bars and plates, as well as loads on them, information about materials etc. Ability to work with SDNF format is implemented both for version SDNF 2.0 and the more modern version — SDNF 3.0.
 Plugin allowing import/export between SP LIRA 10 and Revit has been implemented for Revit 2019 and Revit 2020.
 Added the ability to save and load the results of reinforcement proportioning, transferred to Revit. In addition to isofields/diagrams, the saved data include legend settings.
 The buttons that trigger plugin functions are moved from the dropdown list “External tools” to the Revit ribbon.
Saving of input data when importing floor plans has been implemented. Selected units of measurement are saved for all categories, as well as a scale factor.
Additional analysis of layer name, which was implemented for files of floor plans, is now implemented for freestanding files of *.dxf format. This additional analysis includes all types of loads, cross section geometry and materials.
Design and graphical environment
To achieve the required accuracy of dynamic calculation of buildings and structures, it is very important to ensure correct accounting of damping forces, which have a significant effect on general oscillatory process. When calculating building structures for dynamic effects, the great importance is a choice of a model, describing internal friction in a material.
General damping matrix in SP LIRA 10.10 is written as
(1)
where
– matrix of concentrated dampers,
matrixes of masses and stiffness of the calculation model,
multipliers to the matrixes of masses and stiffness of the calculation model,
number of finite elements with nonzero multipliers to the matrixes of masses and stiffness of the element,
matrixes of masses and stiffness of the finite element,
multipliers to the matrixes of masses and stiffness of the finite element.
Multipliers and to the matrixes of masses and stiffness of the calculation model are set in the loading “Damping”, where you can also specify concentrated dampers for the matrix .
Multipliers and to the matrixes of masses and stiffness of finite element are set in the Material Editor.
Special finite elements do not have multipliers and .
Instant failure (malfunction) of one of the elements of the supporting structure is usually associated with the problem of progressive (avalanchelike) collapse. The origin of the “progressive collapse” term is connected to the tragic event in London on May 16, 1968. The 22 story Ronan Point apartment tower, which was built according to the LarsonNielsen system, suffered due to a natural gas explosion. As a result of the explosion, a loadbearing end wall as well as not bearing external wall of the corner apartment on the 18th floor were destroyed. Having lost their support, end walls and floor slabs of overlying floors collapsed. Also the impact of weight and impact of falling elements caused the destruction of the walls and floors of the corner of the building to the lowest floor.
Calculation of stability against progressive collapse is performed in quasistatic or dynamic settings. In practice, in most cases, quasistatic calculation is used with a dynamic factor equal to 2. This value of the dynamic factor follows from the theoretical solution of a single mass elastic system without damping at constant load.
A sudden destruction of an element corresponds, for example, to an explosion, fire or emergency overload. At the same time, the dynamic response of the structure to damage should be considered. Instant failure is modeled by replacing the reactions of the destroyed elements to the opposite direction. Considering the high failure rate, the dependence of the force on time can be taken as bilinear.
In SP LIRA 10.10, to protect against progressive collapse with local destruction of loadbearing structural elements, the following opportunity was implemented. For assembly dynamic problem, both linear and nonlinear, for the last assemblage stage, you can indicate the elements that will be dismantled in a dynamic setting.
For dynamic loading you can specify the graph of changes in the reactions with the opposite sign of disassembled elements.
After the end of the calculation, the full range of results is available at any time for the studied period. In addition, the possibility of analyzing graphs of the changes in time of accelerations, speeds, displacements, forces, stresses, etc.
So, for the considered problem, dismantling the elements of the diaphragm of the first floor incremented the vertical deformation of the central node of the diaphragm in a static setting to 38.24 mm, and in a dynamic setting — to 68.37 mm. Thus, for this problem, the dynamic coefficient is .Based on the entered coefficients, the stiffness characteristics, used by the calculation processor when compiling the stiffness matrix of design model, can be edited. This feature, in particular, allows you to take into account the recommendations of the normative documents, namely section 6, SP 521032007 “Reinforced concrete monolithic building structures” on decrease in stiffness of plates and columns.
For bars you can specify the coefficients for each of the seven stiffnesses (EF, EIY, EIZ, GKR, GFY, GFZ, EIW), by which they multiply when constructing a stiffness matrix and taking into account temperature loads.
For plates you can specify the coefficients, by which the elements of elasticity matrixes of plane stress state, bending and shear are multiplied (when constructing a stiffness matrix and taking into account temperature loads).
Coefficients to stiffnesses show, how many times the calculated values of stiffness characteristics differ from the values, which will be calculated. By default, stiffness coefficients are taken equal to 1.0.
The hinge indicates the yielding adjoining of the element to the structure's node. We will call the hinge elastic or linear, if the stiffness of its yielding bracing does not depend on the internal forces in the element. An ideal hinge, which is a special case of elastic, has the stiffness of its yielding bracing equal to zero. Implementation algorithm of elastic hinges is based on the method of jordan eliminations and detailed in [1], Annex А.
For nonlinear hinge the dependency between movement and internal force at yielding bracing, satisfying the following condition, is set
the stiffness of yielding bracing is equal to .
Elasticplastic hinges can be used for modeling nonlinear work of structural elements, modeling of structural failure mechanisms, in calculations on extreme load, in calculation of resistance to progressive collapse, for Pushover analysis, as well as to analyze the dynamic behavior of the structure.
It is assumed that the material of the bar finite element itself works in elastic stage, i.e elasticplastic hinges are implemented in the initial and final cross sections 7 and 10 of finite elements. For nonlinear hinges it’s possible to specify elasticplastic with hardening and ideal elasticplastic (fig. 1) work graphs.
Figure 1. Ideal elasticplastic work graph
Figure 1 shows the graph, corresponding to bending. Here: — ultimate moment of bar's cross section, — rotation angle corresponding to ultimate moment
In most cases nonlinear hinges are set only according to the angular degree of freedom, but in general case it is possible to use the plasticity hinge with components for normal strength, torque, transverse forces and bending moments in two planes.
Figure 2. Setting the work diagram of a nonlinear hinge to the elements of design scheme
The problem with nonlinear hinges is solved by iterative method [2]. Consideration of node's yielding can significantly affect the stressstrain behavior of the structure due to redistribution of internal forces.
 Perelmuter A. V. Design models of structures and the possibility of their analysis/ A. V. Perelmuter, V. I Slivker. – K: Steel, 2002. – 597 p.
 Gorbovets A. V. Approximate schemes for stationary and nonstationary problems with oneway restrictions / A. V. Gorbovets , I. D. Evzerov // Computing technology. – 2000. – T. 5, №6. – P. 3335.
To consider elastic foundation along the bar, the following term is added to the potential energy functional for bar
where — contact area perimeter, — coefficient of elastic foundation along the bar.
And the following term is added for plates
where and — coefficients of elastic foundation, accordingly, along the local axes and of the plate.
The added terms have the same form as the standard elastic foundation and are implemented (when constructing a stiffness matrix and calculating reactions) similarly.
Consideration of elastic foundation along the bar is needed for the correct modeling of piles with a chain of bars. Such modeling became possible in the version 10.10 of SP LIRA.
Assignment, control and display of assigned values are implemented for the added elastic foundation components.
Multilayer plates and shells are widely used in various fields of industry and construction. These are elements of space, aviation, shipbuilding equipment, protective structures of NPP, reservoirs and tanks for chemical production, structures of industrial, civil and transport construction, power engineering equipment etc.
Due to widespread use of multilayer shells in engineering practice, the study of stress behavior of the separate layers becomes more relevant. The current implementation ensures work compatibility for the whole multilayer package of composite construction. For each layer (allowed no more than 10 layers) you can specify: thickness, density, Young’s modulus, Poisson’s ratio, and coefficients of thermal expansion.
All the values necessary for the calculation are determined by the throughthickness integration. At the same time, it’s assumed that loads are applied to the middle surface of cross section. Coefficients of thermal expansion are calculated as cross section averages.
In previous versions of the software package LIRA, internal forces in bar elements were calculated exclusively in the main axes of bar’s cross section. In SP LIRA 10.10 the ability to specify axes for calculation internal forces for bar elements has been added. Coordinate system for internal forces calculation in bar elements uses the following rule: local axis , as always, is directed from the first node to the second, a user sets the vector, parallel to the local axis , which may not coincide with the main axis of inertia, local axis forms the right triple with the axes and . In this coordinate system hinges, rigid inserts and local loads are specified.
Results Tables on bar elements in the new version of SP LIRA 10.10 can be obtained both in the axes of internal forces alignment, and in the main axes of inertia.
Cholesky decomposition method was first proposed by a French military geodesist of Polish descent AndreLouis Cholesky at the end of World War I, shortly before his death in a battle in August 1918. The idea of decomposition has been published in 1924 by Benoit (who was a coworker of Cholesky). The decomposition was first used by T. Banashevich in 1938. In Soviet mathematical literature it is also called square root method. This name is associated with the characteristic operations, absent in the related Gauss decomposition.
For sparse matrixes, Cholesky decomposition is widely used as a direct method for solving linear systems.
In the version 10.10 of SP LIRA, the decomposition method using CSC (Compressed Sparse Column) format has been implemented: when only nonzero matrix elements and their coordinates are stored (row and column numbers). This storage scheme has minimal memory requirements and at the same time it’s very convenient for operations on sparse matrices.
The figure shows the representation of the matrix in the CSC format.
This implementation has significantly accelerated decomposition of the stiffness matrix of the design scheme. So, for processors Intel (R) Core(TM) i7 8700 CPU @ 3.20GHz, 6 physical cores, 12 logical cores, with a cache of the third level 12 MB, RAM 16 GB, the acceleration is from 1.3 to 5.
For example, the decomposition procedure of the stiffness matrix of a frame building (3,661,779 unknown values) using the above mentioned computer took less than 2 minutes.
Modal mass is a mass fraction of the structure , involved in a dynamic reaction by the certain form of oscillations
where
— mass matrix of design model,
— st mode of natural oscillations,
— direction vector of foundation’s seismic movement by nodes.
In previous versions of the software package LIRA 10, for consideration of modes of natural oscillations in dynamic reaction of building or structure, contribution in modal masses of the corresponding natural mode should have been at least 1%.
In the version 10.10 of SP LIRA, users are given the opportunity to specify a minimum percentage of contribution in modal masses, after overcoming which the mode of natural oscillations will be taken into account in the dynamic response of a building or structure.
In the version 10.10 of software package LIRA, the calculation of design combinations of loadings (DCL) for ASSEMBLAGE system has been implemented. Both userdefined and automatic combinations are available for forming.
When forming Automatic combinations, one restriction is imposed:
only one stage of erection can have a nonzero coefficient in the history of erection.
Software package LIRA 10.10 provides an opportunity to calculate buildings and structures on a pile basis. It can be either a calculation of the generalized characteristics of piles (FE 57) or modeling of piles with a chain of bars (architectural singlenoded element “Pile”).
For architectural singlenoded element “Pile”, the “Pile (Elastic Restraint)” cross section is assigned, in the parameters of which the opportunity to specify the reinforcement arrangement has appeared for its subsequent proportioning.
After the “Pile (Elastic Restraint)” cross section has been assigned to the architectural singlenoded elements “Pile”, they are displayed with the length specified in the cross section, and when are shown taking into account the assigned cross sections — they are also displayed with a given configuration of the cross section contour.
Modeling of piles with a chain of bars can be implemented in two ways:
 by the method of “elastic supports”
 by the method of “elastic bar”
The idea of the method of “elastic supports” is that elastic links (FE 56) are created in the nodes of the bar with stiffnesses in horizontal and vertical directions. Stiffnesses by directions are obtained as the product of the bedding values of soil foundation and the corresponding area: for horizontal directions — area of cross section’s bearing on soil, for vertical direction — half area of the lateral surface of adjoining elements. In addition, under the tip of the pile for vertical direction, a value equal to the product of the stiffness of the foundation and the crosssectional area of the pile is added to the stiffness.
The idea of the method of “elastic bar” is that sectors of pile’s bars are modeled by bars on an elastic foundation. Bedding values of soil foundation by horizontal directions are calculated according to the Annex V, SP 24.13330.2011 Pile foundations. In the vertical direction, the work of the pile is provided by the resistances along the lateral surface of the soil layers and creating an elastic hinge on the tip of the pile with stiffness that is equal in vertical direction to the product of the stiffness of the base and the area of cross section.
In the version 10.10 of SP LIRA, the idea of the method of “elastic bar” has been iplemented, because this method is independent of the fragmentation step to finite elements and allows to get smooth diagrams of longitudinal and transverse forces, what better matches the actual work of the pile than the results by the method “elastic supports”.
For correct modeling of piles with a chain of bars in the SP LIRA 10.10, the accounting of the elastic foundation along the bar has been implemented, that is, the following term has been added to the potential energy functional for the bar
where — contact area perimeter, — coefficient of elastic foundation along the bar. When modeling horizontal load operation, the accounting of soil foundation is performed using elastic foundation coefficients and .
When indicating to the architectural singlenode elements “Pile” that the characteristics of the foundation should be specified according to the soil model, elastic foundation coefficients are assigned automatically according to the layers pierced by the pile.
Two methods for determining soil base coefficients along the bar have been implemented:
 by the results of field testing
 by the results of calculation of bearing capacity and settlement
In case of using architectural singlenode elements “Pile”, the diagrams of internal forces (, , , , ) along the length of the pile will be obtained in the results of calculation.
And if the structural design parameters were specified for piles, then there is a possibility to perform check or reinforcement proportioning.
In the design scheme, both single piles and pile clusters, as well as artificial foundation, made of FE 57 or architectural singlenoded element “Pile” can simultaneously be present.
In the version 10.10 of SP LIRA, besides the calculation of “Driving piles, jacked piles of all types and shell piles, embedded without soil excavation”, the calculation of “Castinsitu piles, bored piles and shell piles, embedded with soil excavation” of rectangular or round cross section, with widening of pile toe or without it has been added.
Visualization of mosaic of bedding value of soil foundation along the pile , as well as the perimeter of the pile (relevant for piles with widening of pile toe) has been added.
Annex B “Calculations of pile’s bearing capacity, interacting with rocky and semirocky soils along the lateral surface” has been implemented.
Determination of bearing capacity for a driven pile, shell pile, castinsitu pile and bored and castinsitu pile, rockbased, that is for column piles has been performed.
Provisions of changes №2 and №3 of SP 24.13330.2011 Pile foundations have been added in the new version of SP LIRA.
Rigid and hinge adjoining of the pile head to the foundation slab both for FE 57 and for a chain of bars have been implemented.
To specify and calculate the static components of the wind load for buildings and structures of various types, the calculation of wind load on surface has been added in SP LIRA 10.10. Currently, a scheme with freestanding flat solid structures has been implemented in the program. Depending on the case, wind load can be transferred to the design model through nodes, bars or plate elements. The load value may vary from the following parameters: aerodynamic coefficient, safety factor, level of ground surface (z), current height of load application (z_{i}). 
Design pressure can be presented in a more abstract form, when the specifyed parameters are visualized using a graph. Thus, the user can set all the parameters he needs and find the value of the load at a given height without using the main scheme.
To calculate full snow load on the horizontal projection of the roofs of buildings and structures, the calculation of snow load on surface has been added in SP LIRA 10.10. Snow load can be transferred to the design model through nodes, bars or plate elements. Depending on the selected regulations, the load value may vary from the following parameters: thermal factor; safety factor; coefficient that takes into account removal of snow from building roofs due to wind or other factors. Load regularity in directions X/Y is accounted by form factor μ, which makes the transition from weight of snow cover on the ground surface to snow load on the roof. 

In SP LIRA 10.10 the following regulatory requirements have been implemented:


For all local plate loads, except temperature, the eccentricity of their application relative to the middle plane is specified. This allows to take into account the moments from the forces acting in the plane of the plate.
Abilities to set static loads applied to architectural elements have been enhanced in the SP LIRA 10.10. Loads can be set both as concentrated and distributed for the part or for the whole element. Also the load is implemented distributed along the line and applied to the architectural plate. Points to which loads are attached do not participate in the triangulation of architectural elements. It allows to generate highquality finite element networks even in case of a large number of such loads.
SP LIRA 10.10 allows you to import or create design models using FE meshes, or architectural elements, or their combination. Using of architectural elements significantly simplifies the process of variant design and allows you to achieve results in the shortest possible time. In SP LIRA 10.10 the function, allowing to transform the selected FE mesh area into architectural elements for further geometry editing and calculation, has been implemented. During the transformation process, the bar or plate architectural elements, as well as architectural elements modeling piles, can be formed. When combining FE into architectural elements, previously assigned cross sections, materials, structural design parameters, and information about including of FE into the unification groups can be taken into account.
When working with large design schemes, autosaving of the project might require significant time. To eliminate negative effects, associated with unexpected “freezing” of the interface, the ability to disable autosave, when a certain volume of the initial data file is reached, has been implemented.
After continuous working, especially with big problems, quite a large number of files with no longer needed calculation results can be accumulated on the disk. “Manual” clearing of a disk may take much time.
In the SP LIRA 10.10, the function of quick view of calculations has been implemented for the calculations, stored in subfolders of a given directory, with sorting by the amount of disk space and the ability to permanently delete all result files for selected design model. In this case, the files describing the input data will not be affected.
In order to improve the final quality of finite element grid using quadrangular FE, the iterative algorithm Laplacian smoothing for internal triangulation nodes has been implemented.
In the new version of SP LIRA, the interaction with the utility of determination of effective lengths has been improved. The user will no longer have to memorize or copy multivalued values of moments of inertia. It’s because SP LIRA 10.10 allows to choose in the dialog box of determination of effective lengths moment of inertia of the cross section created in the current task.
Buttons invoking the dialog box where you can choose a cross section for specifying moment of inertia
Dialog box where you can choose a cross section for specifying moment of inertia
SP LIRA 10.10 analyzes the type of cross section being constructed and cross sections already created in the project. If there are matches, SP LIRA 10.10 forms a list of cross sections, otherwise, the button invoking the dialog box will be absent.
List of cross sections available for selection when determining effective lengths
Для задания начальных несовершенств реализована возможность корректировки геометрии конечноэлементной модели в соответствии с деформированной схемой (от загружения или РСН) или формой потери устойчивости.
Reinforced concrete structures
For the most complete coverage of standards of SP 63.13330.2012 and SP 63.13330.2018, the ability to calculate plate elements according to the chapter «Calculation of plane reinforced concrete elements of slabs and walls by strength» has been implemented in the program.
The standards describe the procedure for checking reinforcement in elements of shells, plates and walls. The calculation is performed in accordance with pp.8.1.538.1.59 SP. Calculation on resistance to cracking (formation and opening of the crack normal to the longitudinal axis of the element) is performed in accordance with section 8.2.
In LIRA 10.10 the new normative document SP 63.13330.2018 Concrete and reinforced concrete structures has been implemented.
In accordance with the updated edition of SP 63.13330.2018, the calculation of the specified reinforcement in bar and plate elements of a given section on proportioning and check is performed.
To consider the provisions of SP 296.1325800.2017 (Buildings and structures. Special impacts) in case of special impacts, additional conditions of use factors have been added to the resistance characteristics of materials of reinforced concrete structures.


Checking on strength excluding oblique sections and considering oblique sections is performed by introducing additional conditions of use factors according to p. 5.15 SP 14.13330.2018 (instead of SP 14.13330.2014). 
For the convenience of displaying graphical information by results of proportioning of:
longitudinal reinforcement,
transverse reinforcement,
crack opening width,
both in plate and in bar reinforced concrete elements of the structure, the sum checkbox has been added. If you select this checkbox, it allows you to display the sum of selected reinforcement or crack opening width on the scheme’s elements, as you can see on the figures below:
Reinforcement proportioning results As1X in plate elements 

Reinforcement proportioning results of total reinforcement in plate elements


Reinforcement proportioning results Au1 in bar elements


Reinforcement proportioning results of total reinforcement in bar elements 



Selected checkbox allows you to display the sum of selected parameters to view verification results:
 on strength, on internal forces N, M, Qx, Qy, Mx (bars)
 by crack opening width, from the effect of loads of continuous and shortterm action:
Reinforcement proportioning results in plate elements on internal force N 

Reinforcement proportioning results in plate elements on total internal forces 

Reinforcement proportioning results in bar elements on internal force N 

Reinforcement proportioning results in bar elements on total internal forces 



Steel structures
In the software package LIRA 10.10, the calculation of steel elements of variable cross section in accordance with the regulations of SNiP, SP, DBN has been implemented. Welded Ibeam cross sections (symmetrical or asymmetrical), as well as welded RHS, are available for calculation. In particular, it is accepted that the wall’s height and the shelves’ width change linearly, moreover, in one section both walls and shelves can change.
Figure 1. Singlespan traditional frame with variable cross section elements.
Wall’s height change linearly, chords of uniform cross section
Figure 2. Twospan frame with variable cross section elements
Wall’s height change linearly, chords of uniform cross section
Figure 3. Singlespan doublepitch frame with variable section elements.
Wall of uniform cross section, chords’ width changes linearly
ᅠ
The main problem when calculating such elements in accordance with the regulations SNiP, SP, DBN is the determination of the effective length when checking general stability of compressedbent elements upon flexural and flexuraltorsional modes.
In the software package LIRA 10.10, the calculation of general stability of variable cross section elements, based on the assumption of their variable effective length, has been implemented.

Critical force according to Euler's formula is: This formula shows that with variable stiffness EI of the current element, its effective length is also variable. The ratio of the effective lengths in various cross sections of this element is expressed by the condition: 

Each cross section of such an element in the design scheme is characterized not only by its internal forces, but also by its effective length.
If the value of the effective length of the element (basic) is known at a certain value of the moment of inertia , then the effective length of the element anywhere else with the current coordinate х (in the local axis of the bar) can be determined:
– at constant longitudinal force N within the considered element of variable cross section from the formula:
– for elements, for which the compressive force N varies in length, the ratio of the effective lengths in different sections of the element will be:
Such an element, for example, is an oblique crossbar or beam, in which the pitched component of the distributed vertical loads gives a continuous change in longitudinal compressive force N along the element’s length.
To specify a variable cross section, the user sets the section sizes at the beginning and at the end of the element.
Figure 4. Selection of steel cross sections of variable stiffness.
Intermediate values are determined by linear interpolation.
Figure 5. Specifying of steel cross sections of variable stiffness
Specifying structural design parameters, the user must set the effective length in both major planes:
Figure 6. Design of steel cross sections of variable stiffness
In this case, the designer has a choice: set the effective length constant over the entire length of the element or use a variable effective length. In the last case, the base effective length should be given and the place should be specified, where this value is true. As the designed place can be indicated:
Figure 7. Specifying the place of base effective length
To determine the base effective length in some standard cases, reference literature may be used, for example the formula (48) [1], or table extrapolation 6.1 [2]. In this case, the base effective length is given in the place of maximum stiffness.
We recommend to use the «Stability» subsystem to determine the effective lengths. This is a universal method that can be used for various, including nonstandard design schemes. In this case, the effective length is given in the middle of the variable element.
Literature:
1. V.V. Katyushin. Buildings with framework from steel frames of variable cross section (calculation, design, construction). Moscow, Stroyizdat, 2005.
2. V.V. Gorev, B.Yu. Uvarov, V.V. Filippov and others. Metal constructions. In 3 volumes. Volume 1. Elements of structures, Volume 2. Building structures. Tutorial for architectural universities. – 3rd ed., stereotyped. High school, Moscow, 2004.
For cross sections, made of asymmetric Ibeams, the ability to calculate structures with a flexible wall has been implemented. If the actual flexibility of the wall exceeds the permissible one in accordance with p. 9.4.2, 9.4.3 SP 16.13330.2011, it is allowed to exclude the part of the wall from work and perform basic checks of strength and general stability for a decreased (reduced) cross section. The calculation is carried out according to the instructions of p. 9.4.6 and p. 7.3.6.
Figure 1
In this case, the program displays a warning (see fig. 1), and the reduced area Ad is used in these checks (instead of the actual area А) determined by formulas (31), (34) of specified regulations (see fig. 2).
Figure 2
The requirements of Eurocode for steel structures in accordance with EN 199311 and EN 199315 have been implemented in the SP LIRA 10.10.
In accordance with Eurocode, there are four classes of cross sections depending on the stressstrain behavior. Unlike usual national norms, the first cross section class is expressed as a full plastic hinge, second and third cross section classes — with the possibility of developing plastic deformations, fourth class is either SFMB or cross sections with «thin» Ibeam walls. In the SP LIRA 10.10, automatic determination of the class of both individual parts of the cross section, and the cross section of the rolled or welded element entirely have been implemented. These cross section classes are displayed in the graph of results. (fig. 1.1). 
Figure 1.1 
Materials are implemented in accordance with the nomenclature of Eurocode (fig. 1.2). Compared to national regulations, the columns «Normative resistance of rolled metal» and «Design strength of rolled metal» are absent. In these tables, only the characteristic values of the material resistance are displayed, since the transition to the calculated value is carried out directly during each individual check.
Figure 1.2. Material from database
Figure 1.3. Checking by normal stresses 
At the moment, the software package is performing checks by normal, tangent, residual stresses. A basic check of the strength by normal stresses is performed in accordance with the formulas 6.44 and 6.2: (6.44) (6.2) 
Elements’ bearing capacity in terms of stability is checked upon flexural, torsional, flexuraltorsional modes and upon plane bending mode (fig. 1.4). Compressedbent (eccentric compressed) elements of uniform cross section have to be tested for overall stability in accordance with the formulas 6.61 and 6.62:
(6.61)
(6.62)
Figure 1.4. Displaying results
If you want to delve into the features of the calculation, it is worth noting that this formula is universal for stability checking for all existing tests, since in the case of the presence of one term and the equality of the coefficients to zero we get the basic formulas for all existing buckling modes. The calculation of these coefficients is given in the Annexes of EN 199311. There are two alternative methods for calculating these coefficients. For Ibeam, RHS and other symmetrical cross sections, the first method is recommended (Annex A). Since the asymmetrical cross sections are currently under development, the second method is also not presented in this release.
Figure 1.5. Calculation by Eurocode
Calculation of elements, the cross section of which belongs to the 4th class, is presented in EN 199315. This regulatory document, as mentioned earlier, is implemented. In accordance with the theoretical foundations, when calculating the sections of the 4th class, the reduced areas of cross sections should be considered. For more accurate calculation results, shear delay consideration has been implemented. If there is a section of the 4th class, for Ibeam cross sections it is often necessary to apply transversal ribs. For this case, the calculation is carried out in accordance with the norms.
Soil
In the software package LIRA 10.10, pile modeling capabilities (FE57) have been replenished with the following types:
 by the method of deepening into the soil, castinplace piles, bored piles and shell piles embedded with soil excavation and filled with concrete have been added to the friction driven piles and jacked piles (classification corresponds to the table 7.6 СП 24.13330.2011),
 rack piles and bored piles have been added to the calculation methods for determining the bearing capacity. When calculating the bearing capacity, rockbased friction piles are considered as rack piles.
The changes 13 to SP 24.13330.2011 have been added into the program. As a result, the calculation of bearing capacity of friction piles and rack piles is allowed to perform for the cases of interacting with rocky soils along pile skin.
Soil classification that is used in the calculation of single pile in local calculation and Soil Editor has been replenished by rocky soils and their calculated resistances along pile skin and under the tip of the pile. The provisions of the chapter 7.2 and Annex B SP 24.13330.2011 have been implemented to make possible calculations of piles in presence of rocky soils.
Capabilities of calculations in Soil Editor have been replenished by soil foundation characteristics to make possible calculation of bored castinsitu piles and rack piles, including those with partial immersion and support on rocky soils.
The ability to create report based on results of calculating a single pile is added:
Application utilities
Figure 1.1. Utilities of SP LIRA 10.10

Some utilities, not requiring the full functionality of SP LIRA 10.10 were duplicated and combined into an independent program (Utils) (fig. 1.1). Programs included in Utils provide the ability to make calculations of many special problems, that arise in the process of work and which usually do not fit into the structure of SP LIRA 10.10. Thus, the user can use the necessary utilities without downloading the main program. So, for example, the utility for converting records of seismic motion of soil, which was previously available with special loading and selecting the corresponding load on the node, can be run separately using Utils (fig. 1.2). Its functionality will remain the same; conversion from given seismogram is available for accelerogram, and on the contrary, conversion from given accelerogram is available for seismogram. 
Utility gives the ability to read data and then to visualize them with a graph. The user can also get a response spectrum and Fourier transformation from input seismogram/accelerogram. And in doing so, the entire result can be imported both visually and as numerical data.
Figure 1.2. Using the program Utils
A number of auxiliary programs have also been added into separate utilities, which were used in the calculations, but could be launched separately. Among them is unit converter, engineering calculator from LIRA, as well as a utility for tabular and linear data interpolation. Unit converter (fig. 1.2) allows you to convert units from one system to another. The categories implemented in the program are listed in the figure 1.1. 
Figure 1.1. Available unit categories 
Figure 1.2. Unit converter
Engineering calculator (fig. 1.1) is designed to calculate the values of expressions specified by the user in the formula bar. To enter expressions in the calculator, you can use both as algebraic and trigonometric functions, and previously saved constants and variables. 
Figure 1.1. Engineering calculator 
In the Utils program, it is also possible to calculate rigidity of a single pile: the user can specify the characteristics of the pile, pile driving method, type of construction to which it consists, and other necessary parameters (fig. 1.1).
On the «Geology» tab, the user can specify soil layers and their corresponding characteristics. And on the «Parameters» tab, it’s possible to specify norms and parameters for piles calculating: seismicity / occurrence frequency, pile's burial depth into the soil, safety factors, vertical and horizontal load etc.
Figure 1.1. Calculation of the rigidity of a single pile
Also an opportunity to perform local calculation of the bedding values (coefficients) for foundation slabs (С_{1} and С_{2}) has appeared in the SP LIRA 10.10 (fig. 56.1). In the physical sense, these coefficients determine the value of the internal force in the tonneforce, which must be applied to 1 м^{2} of the surface of the foundation, so that the foundation settles on 1 m.
When developing the utility, the requirements of the following regulatory documents were taken into account:
 SNiP 2.02.0183. Bases of buildings and structures.
 SP 501012004. Design and arrangement of bases and foundations of buildings and structures.
 SP 22.13330.2016. Foundations of buildings and structures.
 DBN V.2.110:2009. Bases and foundations of buildings and structures.
Figure 1.1 Calculation of bedding values С1 and С2
Local calculation of reinforced concrete bar utility is designed to determine the area of reinforcement in the bar elements. The calculation is performed in accordance with the following regulatory requirements:
 SNIP 2.03.0184*. Concrete and reinforced concrete structures
 SP 63133302012 (SNIP 52012003). Concrete and reinforced concrete structures. Basic provisions
 SP 63133302018. SNIP 52012003 Concrete and reinforced concrete structures. Basic provisions
 SP 295.1325800.2017. Concrete structures reinforced with fibrereinforced polymer bars. Design rules
 Eurocode 2. Design of concrete structures. Section 11. General rules and regulations for buildings
 DBN V.2.698:2009. Concrete and reinforced concrete structures. Basic provisions
 DSTU B.V.2.6156:2010. Concrete and reinforced concrete structures made of heavy concrete. Design rules
 DSTUN B.V.2.6185:2012. Guide for the design and construction of concrete structures with nonmetallic composite reinforcement based on basalt and fiberglass
 ACI 31811. Building code requirements for reinforced concrete
 Eurocode 2 (Republic of Belarus) (TPK EN 1992112009*)
 Eurocode 2 (Kazakhstan) (SN RK EN 199211:2004/2011).
In the Local calculation of reinforced concrete you can repeatedly change the parameters of cross section, the geometric characteristics of the element, the specified reinforcement of cross section, information about the materials, internal forces/combinations and perform reinforcement proportioning.
Calculation is performed by Ultimate Limit State and Serviceability Limit State (cracking resistance) in accordance with the selected regulatory document. 
The utility is designed to reinforcement proportioning from the following force impacts:

There are permissible section shapes: rectangle, Tbeam (with flange above and below), Ibeam, channel bar, RHS, CHS, cross, and angle. To specify the location of the reinforcement and grouping it by diameters, three types of reinforcement are implemented: asymmetrical, symmetrical (relative to local axes of cross section y_{1}, z_{1}), userdefined. Local calculation of reinforced concrete bar utility relies on the regulatory base which contains the calculated and regulatory characteristics of materials. 
When calculating, the following structural features of the elements are possible: bar, beam, column. As a result of the reinforcement proportioning, the following data will be displayed: longitudinal reinforcement — areas of longitudinal reinforcement (cm2) and percentage of reinforcement, transverse reinforcement — areas of transverse reinforcement (cm2), selected when the step of stirrup is 100 cm, opening width of extended and short cracks. The layout and area of fitted reinforcement will be displayed on the screen, showing cross section materials and table with internal forces values in selected cross sections. 
The tool for analysis and control of results is the View mode tab – neutral axis, diagrams. The following values are displayed in tabular and graphical form: relative deformations and stresses in reinforcement and concrete, angle between the neutral axis and the axis y1, compressed area height. 
Utility Local calculation of reinforced concrete plate is designed to determine the area of reinforcement in plate reinforced concrete elements with complicated stress behavior. Calculation is made in accordance with the following regulatory requirements:
 SNiP 2.03.0184
 SP 63133302012 (SNiP 52012003)
 SP 63133302018
 SP 295.1325800.2017
 Eurocode 2
 DBN V.2.698:2009, DSTU B.V.2.6156:2010
 DSTUN B.V.2.6185:2012; ACI 31811
 Eurocode 2 (Republic of Belarus) (TPK EN 1992112009*)
 Eurocode 2 (Kazakhstan) (SN RK EN 199211:2004/2011)
In the utility Local calculation of reinforced concrete plate you can repeatedly change cross section’s parameters, element’s geometrical characteristics, redefine reinforcement location, materials, internal forces / combinations and perform reinforcement proportioning.
Reinforcement proportioning (longitudinal and transverse separately) is performed taking into account the action of a given number of combinations (per meter): Nx, Ny, Txy, Mx, My, Mxy, Qx, Qy — for shells; Mx, My, Mxy, Qx, Qy — for slabs.
The utility is designed to determine the reinforcement for thinwalled reinforced concrete elements (shell elements), where the torsional and bending forces, axial and shearing forces act. It also can be used to determine the reinforcement for plane reinforced concrete elements (slab elements), where the torsional and bending forces, as well as shearing forces act.
To specify the location of the reinforcement and logical groups of reinforcement inserts, two types of reinforcement have been implemented: By Default, Userdefined. Choosing the «By Default» item allows you to perform proportioning of reinforcement in the most common case of its location, where twolevel reinforcement is implemented (lower and upper) with the averaged attachments of the center of gravity to each level.
Utility Local calculation of reinforced concrete plate is based on the regulatory framework, which contains the design and regulatory characteristics of materials of structural elements.
When calculating the reinforcement of plate elements according to all regulatory documents, the following calculation methods are used: analytical, method of equivalent moments Wood&Armer, SP 63.13330.2012 / SP 63.13330.2018 (for SP 63.13330.2012 / SP 63.13330.2018). Reinforcement proportioning is performed taking into account the work of reinforcement in the orthogonal directions.
The calculation is performed for Ultimate Limit State (strength) and for Serviceability Limit State (resistance to cracking) in accordance with the selected regulatory document. The resulting information after reinforcement proportioning is the following: when selecting longitudinal reinforcement — area per linear meter (cm^{2}) and percentage of cross section’s reinforcement, when selecting transverse reinforcement — area per linear meter (cm^{2}), as well as the width of the opening of prolonged and short cracks. The screen displays the layout and the area of the selected reinforcement, indicating cross section materials and tables of stresses. 
To check the overall stability by flexural and flexuraltorsional modes, it is necessary to use the effective length of the column. This utility allows you to automatically determine the value the effective length of the column in accordance with regulatory and reference documents for the following design cases:
 Сolumns of constant cross sections (Table 31 SP 16.13330.2017).
 Stepped columns (Table 28 of «Handbookto SNiP II2381*»).
 Columns with undercoupling (according to the classical theory based on the displacement method using influence functions).
 Branches of twomember columns (p. 10.1.2 SP, Table 26 of «Handbookto SNiP II2381*»).
Figure 1.1. Utility defining the effective length of the сolumns of constant cross sections
Figure 1.2. Utility defining the effective length of the stepped columns
Figure 1.3. Utility defining the effective length of the columns with undercoupling
Figure 1.4. Utility defining the effective length of the branches of twomember columns