Pile field modeling in scad. Calculation and examination of the workshop building constructive solutions

09.01.2022 Floriculture

What all our users have been waiting for for a long time has finally come true: in SP LIRA 10.6 there is a new end element 57 - "Pile", which implements the provisions of JV 24.13330.2011 "Pile foundations". The appearance of this finite element significantly expands the capabilities of the software package, when calculating buildings on pile foundations, it allows you to make such calculations faster and more accurately. Previously, SP LIRA users had to model FE 56 piles, while their rigidity was calculated either in third-party programs or manually, now the program will do everything, you just need to enter the initial data.

Implementation

The following calculation situations are implemented in SP LIRA 10.6:

Single pile (clauses 7.4.2 - 7.4.3, SP 24.13330.2011);

Pile bush (clauses 7.4.4 - 7.4.5, SP 24.13330.2011);

Conditional foundation (clauses 7.4.6 - 7.4.9, SP 24.13330.2011);

In this case, the following assumptions are made:

It is conventionally assumed that the bearing capacity of the pile is ensured; - The soil on which the pile rests is considered as a linearly deformable half-space; - The following ratio is fulfilled: (l - length, d - reduced diameter of the pile shaft).

The following types of piles are implemented (Fig. 1):

Shell;

Rectangular;

Square.

In this case, the end of the pile can be either pointed or club-shaped.

Rice. 1. Types of piles. SP LIRA 10.6

Single pile calculation

For each pile, whether it is single or as part of a bush / conditional foundation, the following parameters are set (Fig. 2):

Pile length

The number of subdivisions - the larger this number, the more accurate the calculation is

The modulus of elasticity of the trunk is a characteristic of the material from which the pile is made;

Poisson's ratio of the material;

The depth from the earth's surface, at which the soil resistance along the lateral surface is not taken into account (during seismic actions).

Volumetric weight of the pile material.

Rice. 2. Setting the parameters of the pile. SP LIRA 10.6

The calculation parameters for a single pile are set by pressing the button "Calculate the stiffness of a single pile" (Fig. 3).

Rice. 3. Parameters for calculating the stiffness of the pile. SP LIRA 10.6

In this case, the lateral bed coefficient on the pile surface is calculated by the formula:

Where K is the coefficient of proportionality, taken depending on the type of soil surrounding the pile (Appendix B, Table B.1); γс - coefficient of soil working conditions. For a single pile γс = 3.

The settlement of a single pile is calculated in accordance with SP 24.13330.2011: for piles without broadening according to clause 7.4.2 a, for piles with broadening according to clause 7.4.2 b.

Calculation of the pile bush

To create a pile cluster, you need to call the "Pile groups" command, which is located on the toolbar or in the "Assignments" menu item. To define a pile cluster, select a group of piles that will be included in the cluster and click on the "Add pile cluster" button (Fig. 4).

Rice. 4. The task of the pile bush. SP LIRA 10.6

The method for calculating the pile cluster corresponds to clauses 7.4.4 - 7.4.5 SP 24.13330.2011. In this case, the stiffness characteristics of the pile are calculated automatically in the Soil Editor, for which in the latter, the table for setting the physical and mechanical characteristics has been supplemented with four columns (Fig. 5):

The index of fluidity "IL" for silty-clayey soils;

Porosity coefficient "e" for sandy soils;

The proportionality coefficient "K", which can be set numerically, or interpolated by selecting a soil from the column "Soil type for a pile foundation";

Type of soil for the pile foundation (table B.1 SP 24.13330.2011). It is used to interpolate the "K" values according to the given yield index "IL" or the porosity coefficient "e" of the soil.

Rice. 5. Table of physical and mechanical characteristics of IGE. SP LIRA 10.6

A new tab has appeared in the calculation parameters (Fig. 6) - "Piles", in which the parameters necessary for the calculation are indicated:

k is the depth coefficient under the heel (clause 7.4.3 SP 24.13330.2011);

γ c - coefficient of working conditions for calculating piles for the combined action of vertical and horizontal forces and moment (p. B.2, Appendix 2, SP 24.13330.2011);

γ with a is the coefficient of soil compaction when driving the pile, taken into account to reduce the proportionality coefficient K when the piles operate as part of a cluster (p. B.2, Appendix 2, SP 24.13330.2011).

Rice. 6. Pile calculation tab. SP LIRA 10.6

The settlement of the Pile bush is calculated in accordance with clauses 7.4.4 - 7.4.5 SP 24.13330.2011. When calculating the settlement of a group of piles, their mutual influence is taken into account. The calculation of the coefficient of bedding Cz of the soil on the lateral surface of the pile, taking into account the effect of the piles in the cluster, is carried out as for a single pile, but the coefficient of proportionality K is multiplied by the reduction coefficient αi.

The mutual influence of the settlement of pile clusters is taken into account in the same way as when calculating conditional foundations. The calculation of the stiffness of the piles in the pile bushes is carried out according to the same method as for single piles, but taking into account their mutual influence both in the cluster and between the bushes.

Calculation of the conditional foundation

Setting a conditional foundation from a pile cluster differs only in that in the "Group of piles" the item "Conditional foundation" is selected. It is also necessary to additionally set Аcf - the area of the conditional foundation and the method of placing the piles - ordinary or staggered.

Geological conditions, as well as physical and mechanical characteristics of base soils, are set in the Soil Editor.

The total settlement of the foundation pile field is determined by the formula:

Where: - draft of the conditional foundation,

Additional settlement due to punching of piles at the level of the base of the conditional foundation,

Additional settlement due to compression of the pile shaft.

Additional settlement due to compression of the pile shaft is calculated by the formula:

Finding the settlement of a conventional foundation, as well as calculating the mutual influence of groups of piles (including pile clusters) can be performed by analogy with slab foundations using 3 different methods:

Method 1 - the Pasternak foundation model,

Method 2 - Winkler-Fuss base model,

Method 3 - modified Pasternak model.

If the calculation is carried out in the Soil module, it is necessary, as for the calculation of lamellar elements, to assign an initial load to the piles, which can then be refined using the function of converting the results into initial data (Fig. 7). This is done in the "Elastic Base" command.

Rice. 7. Assigning the initial load to the piles. SP LIRA 10.6

After the calculation in the Soil module, by calling the "Model Analysis" function, you can track settlements, stiffness, and other parameters of piles and soil (Fig. 8).

Fig. 8. Calculation visualization. SP LIRA 10.6

Thus, we have considered a new function that appeared in SP LIRA 10.6, which allows calculating buildings on pile foundations.

An engineer, faced with the calculation of the frame of a building, one of the load-bearing elements of which is a column, will come to the need to calculate a free-standing foundation. For the calculation in the SCAD computer complex, the developers have provided almost complete functionality for determining the bearing capacity according to all the criteria for checking the foundation.

So, having completed the construction of a frame, for example, a metal frame, you will need to calculate free-standing foundations. To do this, in the computing complex SCAD, it is necessary to indicate the nodes that are fixed against displacement in the given directions and angles of rotation (it is in these nodes that the reaction of the supports can be calculated). Most often, the vertical, horizontal and moment in the plane of the structure's work are analyzed. The SCAD computer complex displays reactions for all nodes marked by the user, as a rule, three combinations of loads are considered for:

Rz max, Rx acc., Ruy acc.

Rz acc., Rx max., Ruy acc.

Rz acc., Rx acc., Ruy max

Fig. 1 The considered frame of the building (vertical reaction) in the computing complexSCAD

It is not easy to visually determine the maximum values with a heavy workload of the circuit, you can use the "documentation" tool, where the necessary cells of numbers are filtered by displaying a table of all values from the SCAD computing complex in MS Excel.

The resulting combinations of values must be further used when calculating a free-standing foundation. The calculation of free-standing foundations can also be performed manually; for this, the pressure under the foot of the foundation is calculated.

Due to the moment that occurs, the pressure is uneven. The calculation of the boundary values is carried out according to the formula

The next step in calculating a free-standing foundation is to determine the design soil resistance. Calculations are made according to SP 22.13330.2011 "Foundations of buildings and structures", formula 5.7. For the calculation, geotechnical surveys of the soil layers of the construction site under consideration (or directly under a free-standing foundation) are required.

Calculations of the design soil resistance for a free-standing foundation can also be performed using the ZAPROS program (satellite of the SCAD computer complex). The program implements the calculation according to SP 22.13330.2011 "Foundations of buildings and structures".

The resulting R value must necessarily be greater than the pressure P. Otherwise, a decrease in ground pressure is required, for example, by increasing the area of a free-standing foundation. The area of the foundation and the moment of resistance of the section of the foundation are in the denominator of the formula for finding the pressure P, which forces the pressure indicator to decrease.

When calculating a free-standing foundation, one should also not forget about calculating the foundation slab for punching and calculating the bearing capacity. The base plate for bearing capacity is calculated as a two cantilever beam, the load on which is equal to the pressure on the ground (Newton's III law). The result of the calculation is the installation of the working "lower" reinforcement of the slab section.

The force on the slab from the column is very significant, therefore, when calculating for punching, it may be necessary to install additional steps for a free-standing foundation.

Punching, as well as the calculation of two cantilever beams, can be performed by the ARBAT program (satellite of the SCAD computer complex).

When performing all of the above algorithm, the calculation of a free-standing foundation can be considered completed.

Now let's go back to the building frame diagram. Any foundation on a soil foundation (except for rock) sags under the influence of a particular load. The resulting additional deformation of the circuit contributes to a change in the redistribution of efforts already in the circuit elements. Hence, it becomes necessary in some cases (the most responsible) to establish not a rigid pinching, but an elastic connection, at the place where the column adjoins to a free-standing foundation. The computer complex SCAD does not automatically calculate the stiffness of an elastic connection, but you can perform this operation manually. The stiffness of the elastic connection at vertical displacement is equal to the ratio of the bearing capacity of a detached foundation to its draft, the resulting value is measured in t / m. The draft can be calculated using the ZAPROS program (satellite of the SCAD computer complex).

By calculating free-standing foundations, we get a more accurate picture of the deformation of the building, and therefore more accurate efforts in the finished elements.

Fig. 2 Deformed building frame diagram.Computing complexSCAD

So, with the help of the SCAD computer complex, the user will be able to perform the required calculation of free-standing foundations, select the required base area, perform a punching shear calculation, determine the inclination of the building, and also take into account the redistribution of efforts depending on the resulting structural settlement.

Keywords

PILOT-PLATE FOUNDATION / LINEAR DEFORMABLE BASE / WINKLER AND PASTERNAK MODEL/ SCAD OFFICE / SMATH STUDIO / PILE-AND-SLAB FOUNDATION / LINEARLY ELASTIC FOUNDATION / WINKLER AND PASTERNAK GROUND BASE MODELS

annotation scientific article on construction and architecture, the author of the scientific work - Nuzhdin L.V., Mikhailov V.S.

A detailed overview of the main methods for constructing analytical and numerical models is given. pile-slab foundations in accordance with the requirements of the current norms in the calculation complex SCAD Office. The ratios of the results of analytical methods with numerical ones for two cases of foundation are demonstrated: with a pliable grillage and a rigid grillage reinforced by the walls of the basement. The analysis is performed on a homogeneous soil base, excluding soil watering. On the example of seven solved problems, the authors consider three analytical methods for modeling a pile foundation in accordance with the provisions of SNiP 2.02.03-85 and SP 24.13330.2011, as well as two numerical methods for modeling an elastic half-space based solely on the use of the finite element method in a linear formulation. The implementation of analytical calculation models, regulated by regulatory documents, was performed in the SMath Studio mathematical package in addition to the standard functionality of the SCAD Office calculation complex. The complete calculation technology assumes the use of the standard functionality of the mathematical package for importing and exporting data in general data exchange formats in a structured form, available for import and export to the SCAD analytical complex. The article describes in detail the technologies for performing the calculation, indicating the limits of applicability of the models under consideration and recommendations for their use in a static setting. All considered examples demonstrate the convergence of the calculation results sufficient for practical purposes, with the exception of the Pasternak foundation model. The scientific and applied nature of the research and its results may be of interest to design engineers, graduate students and undergraduates.

The text of the scientific work on the topic "Numerical modeling of pile foundations in the computational and analytical complex SCAD Office"

L.V. Nuzhdin, V.S. Mikhailov Numerical modeling of pile foundations in the computational and analytical complex SCAD Office // Bulletin of PNRPU. Construction and architecture. - 2018. - No. 1. - P. 5-18. DOI: 10.15593 / 2224-9826 / 2018.1.01

Nuzhdin L.V., Mikhaylov V.S. Numerical modeling of pile foundations in the structural analysis software SCAD Office. Bulletin ofPNRPU. Construction and Architecture. 2018. No. 1. Pp. 5-18. DOI: 10.15593 / 2224-9826 / 2018.1.01

BULLETIN OF PNRPU. CONSTRUCTION AND ARCHITECTURE No. 1.2018 PNRPU BULLETIN. CONSTRUCTION AND ARCHITECTURE http: //vestnik.pstu. ru / arhit / about / inf /

DOI: 10.15593 / 2224-9826 / 2018.1.01 UDC 624.154.1

NUMERICAL MODELING OF PILE FOUNDATIONS IN THE SCAD OFFICE ANALYTICAL COMPLEX

L.V. Nuzhdin1, 2, V.S. Mikhailov1

1 Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, Russia 2 Perm National Research Polytechnic University, Perm, Russia

ANNOTATION

Keywords:

pile-slab foundation, linear deformable foundation, Winkler and Pasternak model, SCAD Office, SMath Studio

A detailed review of the main methods for constructing analytical and numerical models of pile-slab foundations in accordance with the requirements of the current norms in the calculation complex SCAD Office is given. The ratios of the results of analytical methods with numerical ones for two cases of foundation are demonstrated: with a pliable grillage and a rigid grillage reinforced by the walls of the basement. The analysis is performed on a homogeneous soil base, excluding soil watering. On the example of seven solved problems, the authors consider three analytical methods for modeling a pile foundation in accordance with the provisions of SNiP 2.02.03-85 and SP 24.13330.2011, as well as two numerical methods for modeling an elastic half-space, based solely on the use of the finite element method in a linear formulation.

The implementation of analytical calculation models, regulated by regulatory documents, was performed in the SMath Studio mathematical package in addition to the standard functionality of the SCAD Office calculation complex. The complete calculation technology assumes the use of the standard functionality of the mathematical package for importing and exporting data in general data exchange formats in a structured form, available for import and export to the SCAD analytical complex. The article describes in detail the technologies for performing the calculation, indicating the limits of applicability of the models under consideration and recommendations for their use in a static setting. All considered examples demonstrate the convergence of the calculation results sufficient for practical purposes, with the exception of the Pasternak foundation model.

The scientific and applied nature of the research and its results may be of interest to design engineers, graduate students and undergraduates.

Leonid V. Nuzhdin - Ph.D. in Technical Sciences, Professor, e-mail: [email protected] Victor S. Mikhaylov - Postgraduate Student, e-mail: [email protected]

NUMERICAL MODELING OF PILE FOUNDATIONS USING SCAD OFFICE STRUCTURAL ANALYSIS SOFTWARE

L.V. Nuzhdin1, 2, V.S. Mikhaylov1

Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, Russian Federation Perm National Research Polytechnic University, Perm, Russian Federation

ARTICLE INFO ABSTRACT

The analytical modeling, which is regulated by standards, is carried out using the mathematical package SMath Studio. It is supposed that the complete analysis technology will use a standard mathematical package for import and export to and from the common data interchange format (DIF) in a structured view, which is acceptable for import and export in the SCAD system. A detailed description of the calculation technology is presented by the authors, thus indicating the applicability limits of these methods and recommendations for their use in static conditions. The demonstrated example testifies a fine precision of the considered methods.

The research could be of great interest for designing engineers, university postgraduates and undergraduates.

The actual problem in the design is the choice of the methodology for solving the problem, as closely as possible reflecting the behavior of the analyzed foundation structure. Modern computational systems include many numerical tools for creating foundation models both in a linear (elastic) and nonlinear elastic or elastoplastic formulation. If taking into account the physically nonlinear properties of the soil is a more complex task that requires extended engineering and geological surveys, then the solution of the calculation problem in an elastic formulation in accordance with the requirements of the standards is generally accepted in engineering practice based on standard surveys. This is due to the fact that most modern normative documents are based on two base models: the Winkler contact model with one constant bed coefficient and a linearly deformable half-space in the analytical representation, either in the form of a two-parameter Pasternak contact model, or in numerical form with volumetric finite elements ...

For columnar and strip foundations in the normative methods of calculation, the stiffness of the pile foundation is described by the contact one-parameter Winkler keypad model, which does not take into account the distribution effect of the foundation. In SNiP 2.02.03-85, the Winkler model with one bed coefficient is also the main one when calculating hanging piles in a bush as a conditional foundation. This approach to calculating the settlement of pile

pile-and-slab foundation, linearly elastic foundation, Winkler and Pasternak ground base models, SCAD Office, SMath Studio

damages excludes taking into account the mutual influence of piles. Deformations of the pile cluster according to the Winkler model are ensured by assigning to each individual pile the same constant stiffness C1, kN / m3, in the form of a distributed coefficient over the area of the slab grillage, or by introducing into the finite element model in each lower node of the pile the same single-node bonds of the final stiffness Cz1, kN / m, which is equal to the ratio of the load on one pile to the total foundation settlement:

where - is the total average normative-long-term pressure at the base of the slab grillage, kPa; ^ - average settlement of the pile-slab foundation, as conditional; N - normative-long-term load transmitted to one pile, kN.

Indeed, with an increase in the rigidity of the grillage uniting the piles to infinitely large values, for example, as part of a monolithic columnar foundation on a pile foundation under a single column, the grillage tends to a rigid stamp with synchronous deformations of the piles. Nevertheless, the bearing capacity of each pile does not remain the same and decreases towards the center of the grillage due to the inclusion of a common near-pile soil as the stresses in the soil increase in the place of a higher concentration of piles. When calculating pile foundations, the current normative document SP 24.13330.2011 "Pile foundations", in comparison with the original edition of SNiP.02.03-85, offers two more accurate methods for taking into account the mutual influence of piles in a group. The first analytical method takes into account the noted effect of reducing the bearing capacity of piles in a cluster in accordance with the linear deformable base model and regulates the calculation in paragraphs. 7.4.4-7.4.5 according to the technique, which was first presented in the works of V.G. Fedorovsky, S.N. Levacheva, S.V. Kurillo and Yu.M. Kolesnikov. The implementation of this method when calculating the supports of a bridge crossing together with the calculation complex SCAD is considered in detail by G.E. Edigarov. The principles of constructing a discrete model of a pile cluster, taking into account the stiffness of the grillage, are considered in the monograph by D.M. Shapiro.

The second analytical technique, implemented in SP 24.13330.2011 in paragraphs. 7.4.6-7.4.9, is intended for calculating a large pile field by the cell method, taking into account the pliability of the grillage as a conditional foundation on a natural foundation, but unlike the previous edition of SNiP, it takes into account the additional settlement from punching piles in the soil mass, taking into account the density of the pile field, and also settlement due to deformation of the pile shaft. The solution to this problem was proposed in the monograph by R.A. Mangusheva, A.L. Gotman, V.V. Znamensky, A.B. Ponomareva, N.Z. Gotman. The calculation is recommended to be performed according to the “load - settlement” graphs or according to simplified formulas in the center of gravity of the symmetrical trapezoidal sections of the slab.

As research methods, the authors chose mathematical modeling based on analytical and numerical solutions to the problem. The table shows seven considered numerical and numerical-analytical models, on the basis of which the analysis of the settlement and the stress-strain state of the pile foundation was carried out. For all realized models, a comparison is made of the slump of the flexible slabs.

a single grillage (Index "1" in the first column of the table) and a grillage reinforced by the walls of the basement (Index "2"), The introduction of ribs in the form of monolithic walls increases the overall rigidity of the grillage and reduces the difference in sediment,

The first five models under consideration are numerical-analytical due to the introduction into the finite element model of the stiffness of the base, determined by analytical calculation in accordance with the current standards, Models No. 1 and No. 2 differ only in the method of setting the stiffness and are based on the first analytical method according to SNiP 2.02 , 03-85, in which the pile-slab foundation is considered as conditional on a natural basis, Model No. 3 of the pile cluster is based on the analytical method of SP 24,13330,2011, in which the foundation is considered as a rigid stamp with variable bearing capacity of a group of piles in the cluster, Model No. 4 describes the analytical method of SP 24,13330,2011 for calculating large pile fields, Model No. 5 is an extended method of the pile field with the introduction of variable stiffness of the pile foundation, The last two models, No. 6 and No. 7, use exclusively numerical tools implemented in SCAD Office for a linear deformable base in the form of a contact two-pair a three-dimensional model and in the form of a model of an elastic half-space from volumetric finite elements,

Comparative analysis of calculation results for models of pile-and-slab foundation

Model number Base type and model name Max, draft s, cm Min, draft s, cm Average draft s, cm As,% Mmax, kNm Longitudinal reinforcement, t

1.1 The Winkler model. Conditional foundation according to SNiP 2.02.03-85 with bonds of final stiffness 14.96 14.39 14.68 0.6 146 13.8

1,2 14,77 14,64 14,71 0,1 61 13,8

2.1 The Winkler model. Conditional foundation according to SNiP 2.02.03-85 with bedding ratio on the slab 14.7 14.7 14.7 0 0 13.8

2,2 14,7 14,7 14,7 0 0 13,8

3.1 LDO. Pile bush according to SP 24.13330.2011 pp. 7.4.4-7.4.5 17.90 7.02 12.46 11 3 557 148.7

3,2 16,65 10,19 13,42 6,5 2 463 192,8

4.1 LDO. Pile field SP 24.13330.2011 p. 7.4.6-7.4.9 Ksh * 11.93 11.93 11.93 0 0 13.8

4,2 11,93 11,93 11,93 0 0 13,8

5.1 Winkler model. Pile-slab foundation SP 24.13330 pp. 7.4.6-7.4.9 s Quag 11.06 9.81 10.43 1.2 457 19.1

5,2 10,73 10,35 10,538 0,4 153 14,2

6.1 Pasternak's model. Conditional foundation on an imaginary slab of low rigidity 6.53 4.51 5.52 1.1 538 36.1

6,2 6,06 5,66 5,26 0,8 287 17,7

7.1 LDO. Pile-slab foundation with a base in the form of OKE 14.98 12.07 9.16 5.8 1 525 67.0

7,2 13,27 12,13 10,99 19 782 91,4

First of all, when calculating pile foundations, a relatively simple analytical method should be considered for determining the stiffness of piles as part of a foundation by assessing their settlement as a conditional foundation in accordance with the requirements of the previously valid SNiP 2.02.03-85. This calculation is carried out for models No. 1 and No. 2 by determining the settlement of the conditional foundation as an absolutely rigid columnar foundation on a natural basis in the "REQUEST" satellite program with the subsequent

analysis of deformations in the calculation complex SCAD. Such a simple calculation should always be performed as an estimate at a preliminary stage before moving on to more complex analytical and numerical models.

As part of models No. 3 and No. 4, the technology used by the authors for calculating piles in a group in accordance with normative analytical methods is built on the integrated application of the analytical and analytical system SCAD Office and the freely distributed mathematical package SMath Studio. The main calculation is carried out on the basis of the finite element method in the calculation complex SCAD. In the mathematical package SMath Studio, an additional clarifying calculation of the mutual influence of piles in a group is performed in accordance with two methods regulated by SP 24.13330.2011 based on data on the geometry and stress-strain state of structures in SCAD Office. In model No. 3, the results of the refinement calculation in the mathematical package are exported in the form of a simple computational subcircuit for the SCAD design complex with nodes at the lower ends of the piles and additional efforts calculated in each node, which make it possible to obtain deformations in the linear deformable model in the form of a common sedimentary funnel of the pile field with taking into account the mutual influence of neighboring piles.

In the mathematical package in problem No. 4, the analytical method SP 24.13330.2011 is also implemented based on the cell method for a pile field with a pliable slab grillage. In SCAD, finite-stiffened pile bar elements at the bottom ends are replaced by a distributed bed coefficient applied directly to the slab grillage. Model No. 5 introduces an additional difference from model No. 4, in which the first constant bed coefficient K0 is applied in the center of the slab, and the variable coefficients Kx and Ky are applied along the strip areas of constant pitch along the perimeter of the slab grillage.

The verification of the settlement obtained by analytical calculations according to SP 24.13330.2011, with a sufficient degree of correlation, is carried out by numerical methods based on the strength characteristics of the soil under the assumption of its linear deformation. The first numerical method for model No. 6 involves the creation of a conditional foundation on an elastic Pasternak half-space in the form of an imaginary slab with two assigned constant proportionality coefficients for C1 compression and C2 shear. The application of the KROSS program with the Fedorovsky bilinear model with variable bedding coefficients was not considered, since it is intended for wide slabs. The second numerical method in SCAD in problem no. 7 is a linear deformable base (LBO) model using volumetric finite elements.

Let us give examples of solving problems using the previously described analytical and numerical methods. The object of the study is a pile-slab foundation with a grillage size of 26.6 ^ 17.3 m and a depth of 2 m from the planning surface. Two groups of models are considered. In the first group, only the stiffness of a flexible slab grillage 1000 mm thick made of B20 grade concrete is taken into account, modeled by lamellar four- and three-node finite elements of types 44 and 42. In the second group, the stiffness of the foundation increases due to the introduction of 400 mm thick monolithic walls made of B20 concrete. The pile field is represented by square piles with a side of 300 mm and a length of 10 m made of B20 grade concrete, modeled by universal rod finite elements of the 5th type or, in model No. 7, isoparametric volumetric finite elements of the 34th type. The spacing of the piles in both directions is 1.075 m with a symmetrical arrangement

nii. A conventionally homogeneous subsoil is composed of soft-plastic loams with the following characteristics: y = 19.1 kN / m3, φ = 14 °, c = 0.012 MPa, E = 10.0 MPa. There is no groundwater. Average standard pressure on the foundation and weight of piles ozp is 294 kPa, household pressures from the weight of soil ozg = 229.2 kPa.

Let's consider the solution of the first problem according to the SNiP 2.02.03-85 method. In the ZAPROS program as a part of the SCAD Office computational complex, the section "Settlement of the foundation" is intended for this task under the conditional assumption of the operation of the pile field as a foundation on a natural foundation. When entering the above parameters, the foundation settlement s is 147 mm, the depth of the compressible strata is 11.6 m. A similar calculation of the depth of the compressible strata by the layer-by-layer summation method according to SP 24.13330.2011 gives a similar result of -11.38 m. C1, equal to 2001 kN / m3 when applied to the slab grillage, or Oz1, equal to 2300.9 kN / m when applied to the lower nodes of meter fragments of pile heads. Transferring the stiffness parameters of the pile foundation calculated by the first method to the SCAD design scheme allows taking into account the work of the above-foundation structures with the foundation in strict accordance with SNiP 2.02.03-85. If the bedding coefficient C1 = 2001 kN / m3 is applied to the slab grillage, the bedding coefficient C1 = 2001 kN / m3 is almost uniform and corresponds to the value s = 147 mm calculated in the "REQUEST" (Fig. 1, 1).

When the Winkler bedding coefficient is applied to the lower ends of one-meter fragments of piles, the settlement becomes heterogeneous due to a slight difference in the load areas of the extreme piles and the deformability of the heads of the pile rod elements themselves under the influence of bending moments increasing from the center of the grillage to its edges. Nevertheless, the differences in the settlement of different points of the slab do not exceed ± 3 mm from the average value, and they can be neglected (Fig. 1, 2).

The precipitation of the reinforced grillage, secured by vertical monolithic walls of the basement, in the case of a constant bed coefficient over the area also remains homogeneous (Fig. 1, 3). When the bedding coefficients are applied to the lower nodes of the piles, the grillage settlements turn out to be inhomogeneous, however, due to the increase in rigidity, their variability decreases six times - to ± 0.5 mm (Fig. 1, 4). The model with increased rigidity of the grillage, by introducing vertical walls as reinforcing ribs, clearly demonstrates that the compliance becomes negligible within 0.002% in the direction of the greatest length of the foundation and its lower rigidity. This implies the validity of the calculation of the pile foundation according to the method of SP 24.13330.2011 (clauses 7.4.4-7.4.5) for a pile cluster on the assumption that the grillage works as an absolutely rigid stamp.

The mathematical model No. 4 within the framework of the analytical method SP 24.13330.2011 for the pile field was developed in strict accordance with paragraphs. 7.4.6-7.4.9. This technique, like the first two models, No. 1 and No. 2, is based on the assumption of the behavior of the pile foundation as conditional with a base at the level of the lower ends of the piles and uses the Winkler base model with a single proportionality coefficient C0 (Fig. 1, 5, 7). The difference between this technique and the conditional foundation is the consideration of additional averaged settlement of piles from pushing the soil and compression of the pile shaft. Model No. 5 is of great interest, in which only one bed coefficient Oi is also considered, but with a variable value depending on the distance of the piles from the center of the slab. The proportionality coefficient in the center of the slab C0 is assumed to be the same as in the previous model No. 4. Distribution of the calculated values of the proportionality coefficient and de-

The formation for model no. 5 with flexible and reinforced grillage walls is shown in fig. 1, 6 and fig. 1, 8, respectively. In the case of a single bed coefficient, the model receives only the averaged draft. In the case of a variable bed coefficient, a slight deflection of the slab appears.

Rice. 1. Settlement of the slab grillage (mm) with the reduced stiffness of the pile foundation to the lower surface of the slab according to the Winkler model: 1 - model 1.1; 2 - model 2.1; 3 - model 1.2;

4 - model 2.2; 5 - model 4.1; 6 - model 5.1; 7 - model 4.2; 8 - model 5.2 Fig. 1. Pile-slab settlement (mm) of Winkler subgrade model: 1 is model 1.1; 2 is model 2.1; 3 is model 1.2; 4 is model 2.2; 5 is model 4.1 .; 6 is model 5.1 .; 7 is model 4.2 .; 8 is model 5.2

Let's move on to considering discrete models of pile foundations (Fig. 2). When constructing such finite element models, the first step is to assign bedding coefficients along the lateral surface of the piles, in order to describe the horizontal stiffness of the foundation, which increases with depth as the degree of compaction of the piles by soil increases. Accounting for the influence of piles in a group horizontally is based on the works of K.S. Zavrieva. Calculation of the horizontal resistance of the soil along the lateral surface of the piles in the framework of the study

This is done in SMath Studio. First, the reduction coefficient is calculated according to the formula B.5 SP 24.13330.2011. Then the values of the bedding coefficients Cz on the side faces are calculated according to Appendix B.2.

Rice. 2. Settlement of slab grillage (mm) with a discrete foundation model: 1 - bed coefficient along the lateral surface of the piles (kN / m3); 2 - initial vertical ties of final stiffness along the lower nodes of the piles (kN); 3 - calculated inhomogeneous decrease in stiffness along the tips of the piles with mutual influence along the vertical with the application of additional nodal forces (kN); 4 - model 3.1; 5 - model 3.2; 6 - model 6.1; 7 - model 6.2; 8 - model 6.1; 9 - model 6.2 Fig. 2. Pile-slab settlement (mm) with a discrete subgrade model: 1 is the lateral surface coefficient of subgrade reaction on piles (kN / m3); 2 are the vertical elastic constraints in lower pile nods (kN); 3 is the estimated non-uniform reduction of stiffness along the edges of the piles under the mutual effect of vertically applied additional nodal efforts (kN); 4 is model 3.1 .; 5 is model 3.2 .; 6 is model 6.1 .;

7 is model 6.2 .; 8 is model 6.1 .; 9 is model 6.2

The calculation of the reduction coefficient a is carried out according to the empirical formula with refined coefficients given in Appendix B.5 of SP 24.13330.2011. For the case under consideration, with a symmetrical distance of the adjacent piles by 1.075 m, the required coefficient of reduction in the bearing capacity and with the perception of horizontal loads due to work in a group is 0.1. The bed coefficients are calculated for the rod finite elements of the piles along the directions of the local axes Y1 and Z1 with the indication of the pile width in the field "Support area width" (Fig. 2, 1).

The initial vertical boundary conditions are assigned at the second step of the calculation and at first without taking into account the mutual influence of the piles in the group. Calculation of the preliminary vertical stiffness of the piles is carried out in accordance with clause 7.4.2. SP 24.13330.2011. Since the example adopted a homogeneous soil, the calculations of the averaged characteristics are simplified. The shear modulus G1 of the soil layers cut by the piles is calculated based on the averaged modulus of deformation E1 and Poisson's ratio v1 of the layers cut by the piles. Similarly, the shear modulus G2 is calculated for soil layers located under the lower ends of the piles. The deformation modulus E2 of soil layers located under the pile is taken to be averaged within a depth equal to half the pile length of 0.5L, or equal to 10d of the reduced pile diameters from the lower ends of the piles. Poisson's ratio v2 is set directly on the layer below the base of the conditional foundation. In the considered case of a homogeneous soil, we have uniform values of deformation moduli - E1 = E2 = 10 MPa, shear moduli - G1 = G2 = 3620 kN / m2 and Poisson's ratios - v = v1 = v2 = 0.38.

The initial bond of the final stiffness kz, kN / m, introduced into the lower end of single piles to take into account the interaction with the surrounding soil in the finite element method, without taking into account the mutual influence of neighboring piles in the vertical group, is determined by the formula

k7 = = 52 800 kN / m, (3)

where ß "is the coefficient of the rigid pile, ß" = 0.17ln [(kv G L) / G2 d] = 0.686; kv is an intermediate coefficient for calculating ß ", kv = 2.82 - 3.78v + 2.18v2.

The multiple excess of the initial value of the vertical stiffness in comparison with the SNiP method according to the Winkler model is explained by the fact that the final stiffness will decrease as a result of iterative refinement during the next stage in calculating the mutual influence of piles in a group with joint vertical deformations with the formation of a common sedimentary funnel. This calculation requires data on the coordinates of the lower nodes of the piles in the pile field and the values of the acting loads. This information can be displayed in the "Reactions in special elements" postprocessor, for which, at the moment of starting the linear calculation in the SCAD calculation complex, the "Calculate reactions in links" option should be checked in the parameters. In the postprocessor "Reactions in special elements", the scheme is fragmented along the lower nodes of the piles and the vertical reactions Rz from the normative combinations of constant and long-term loadings for the color scale of the visible fragment are analyzed (Fig. 2, 2).

When analyzing small design schemes, data on the coordinates of the lower nodes of the piles in the horizontal plane and the values of the calculated reactions from normative-long-term effects can be entered directly into the SMath Studio mathematical package in the form of a matrix or a numerical series. In case of large pile fields, direct import is required

into the mathematical data package from the calculation complex SCAD. The easiest way to transfer data is in Excel format. With a visible fragment of the diagram containing only the nodes of the lower ends of the piles, on the table panel on the Nodes tab, press the button to export all nodes currently visible to a separate Excel file. The file must be saved to a directory created on the hard disk at the address that will be specified later when executing the command to import data in Excel format into the SMath Studio mathematical package. Similarly, in the SCAD interface on the table panel, you go to the tab “Efforts in special. elements ”and the button for exporting the efforts in the currently visible links of the final stiffness under the ends of the piles is pressed. In the mathematical package using linear programming tools, the array with the imported coordinates of the pile nodes is transformed into two numerical series with coordinates X and Y. Based on the coordinates of the lower nodes of the piles, the next step is to form a common matrix "a" of the relative position of the piles in the cluster in the form of calculated distances between the piles ... The size of the square matrix corresponds to the number of piles in the foundation. Based on the relative position of the piles, the matrix "5" of the vertical mutual influence of the piles in the cluster is calculated according to the theory of elastic half-space. This is ensured by performing a multiple calculation of each member of the matrix in accordance with the formulas of SP 24.13330.20111 (clause 7.4.4), which provide for the zeroing of the coefficient of mutual influence of one pile on another when a certain distance between them is exceeded. In our case, this distance is 8.5 m. The last step is the calculation of additional forces ANh, which are the sum of the vertical reactions Nh in closely spaced piles, taking into account the mutual influence coefficient 5. The resulting forces ANh should be entered manually into each corresponding lower pile node or in an automated mode, form a corresponding subcircuit with nodes and efforts, which can be inserted into the general design scheme in SCAD. These efforts are necessary for the appearance in the design scheme of additional deformations in the lower node of each pile and the formation of a common sedimentary funnel (Fig. 2, 3). Consequently, in the area where the largest number of piles is located within the circumference of 8.5 m, additional settlements will be greater. In the edge areas of the grillage (and especially at its corners), the concentration of piles within this circle will decrease, which will provide a shallower depth of the sedimentary funnel. In fig. 2, 4 and fig. Figures 2, 5 show the settlements of the pliable and ribbed grillage, taking into account the mutual influence of the piles in the group with the redistribution of loads and the formation of a funnel.

In problem No. 6, due to the fact that the bed coefficients in the Pasternak model are assigned only to plate elements, it is necessary to build an imaginary slab of low rigidity under the lower ends of the piles. In addition, it is recommended to provide at least one additional row of nodes around the outer perimeter of the pile field. For this outer row of nodes, two- and one-node outline elements will be built. An imaginary slab of low stiffness should not have intermediate nodes that do not belong to the ends of the piles in the inter-pile space, otherwise these nodes will receive excessively high deformations. Along the perimeter of the conditional pile foundation in the form of an imaginary slab based on Pasternak, there should be no internal corners for the correct use of outline elements. Such angles should be described by diagonal sections, adding additional nodes between adjacent external nodes. After specifying the necessary nodes along the external office, a finite element mesh is generated on the plane and a mesh is created from shells with the stiffness of the underlying soil only at the specified nodes with a thickness of 1 mm.

On the resulting mesh of triangular and quadrangular lamellar finite elements, the bed coefficients C1 and C2 are assigned, which in the example under consideration are 1560 kN / m3 and 14500 kN / m3, respectively. To complete the Pasternak model, two-node and one-node contour elements with the same bedding coefficients are set along the contour of the imaginary slab. The horizontal stiffness along the lateral surface of the piles is assumed to be identical to model No. 3. For single-node contour elements, it is required to set the corresponding sector angle. Finally, the vertical stiffness of the bonds of finite stiffness should be removed or reduced by six orders of magnitude so that they are turned off from work and vertical deformations are perceived over the entire area of the imaginary slab in the elastic half-space (Fig. 2, 6 and Fig. 2, 7).

The last considered method for calculating a pile-slab foundation in the form of a spatial foundation model is useful in connection with the possibility of a visual visual analysis of the joint deformation of a soil massif and structures of reinforced concrete piles, united by a monolithic slab grillage. In this numerical method, it is recommended to model piles in the form of six- or eight-node isoparametric volumetric elements of type 32 or 36 in order to reduce stress concentrations. The size of the subgrade is taken in height in accordance with the previously determined depth of the compressible strata. The width of the modeled area from the boundaries of the slab grillage should be at least twice the depth of the compressible thickness. Absolutely rigid constraints along all six degrees of freedom at the base of the soil massif and limitation of only horizontal translational deformations along the lateral faces (X, Y) are taken as boundary conditions. The results of calculating model No. 7 are shown in Fig. 2, 8 and Fig. 2, 9.

From the results of the comparative analysis presented in the above table, it can be seen that the foundation models, made using the one-parameter Winkler model, allow the averaged precipitation determined by analytical methods to be transferred with a sufficiently high accuracy to the numerical model of the finite element method. At the same time, there is no redistribution of forces at the Winkler base, as a result of which a characteristic sedimentary funnel does not form and bending moments do not arise in the slab grillage. The longitudinal reinforcement of the grillage will be minimal under distributed loads. With concentrated loads from the columns, the slab in the span will receive a reverse bend, oriented with a bulge upward, which will lead to an unjustifiably overestimated upper reinforcement. Winkler's models are applicable only for the control of average settlements, and can also be useful when taking into account the dynamic stiffness of the soil for the analysis of above-foundations.

The results of calculating the deformations of the grillage according to the mathematical model No. 3 of a pile cluster on a linearly deformable base, implemented by the authors in SMath Studio, in accordance with the analytical method SP 24.13330.2011 according to pp. 7.4.4-7.4.5 turned out to be close to the calculation of the model from volumetric finite elements. At the same time, the nature of deformations in the form of a sedimentary funnel on the surface of the base also has a great similarity due to the use of a unified theory of elastic half-space in the two models. In both cases, extreme stress values are observed in the extreme piles, at which it is necessary to take into account the "edge pile effect" and the transition of the base to the elastoplastic state by lowering the soil deformation modulus.

Model of pile-slab foundation No. 4, also implemented in a mathematical package in accordance with SP 24.13330.2011 pp. 7.4.6-7.4.9, has a constant stiffness

area of the slab and is based on the Winkler model. This model can be used to estimate the average settlement of a structure. The next model - No. 5 - with variable bedding coefficients allows obtaining insignificant bending moments, but relatively small compared to models No. 3 and No. 7 on an elastic half-space. The authors consider the possibility of further refinement of this model by taking into account not the averaged pressures in each pile of the pile-slab foundation, but their actual values calculated in each pile in the finite element model.

Model no. 6 with an imaginary slab in Pasternak's two-parameter contact model showed unjustifiably underestimated precipitation, which indicates the need to analyze other available techniques with two bed coefficients. In contrast to the contact models of Winkler or Pasternak, model No. 7 of a linearly deformable half-space made of volumetric finite elements in a joint design of a structure with a foundation allows a more detailed analysis of the stress-strain state of the soil in the basement. However, it should be noted that the lack of taking into account the plastic properties of the foundation soils allows only a qualitative assessment in order to identify the need for changes in design solutions to exclude areas of high stress concentrations. On the other hand, the LDR model made of volumetric finite elements has an overestimated distribution capacity, as a result of which it may be necessary to refine the depth of the compressible strata by the method of successive iterations based on the results of other previously described calculations to achieve compliance with the average settlements. Thus, this method can only be considered as an additional one, useful for improving the quality of analysis of the stress-strain state. It should also be noted that the deformations of the nodes of the piles of the LDO model occur parallel to the surface of the sedimentary funnel, which does not correspond to reality and the deformations in model No. 3, in which the rigidity should increase with increasing depth due to the compaction of the pile with soil (see Fig. 2, 1) ... Elimination of this problem is possible by taking into account the quasi-anisotropic properties in the volumetric finite elements of the base.

Bibliographic list

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7. Shapiro D.M. Theory and design models of foundations and geotechnical objects. - M .: Publishing house ASV, 2016 .-- 180 p.

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9. Handbook of geotechnics. Bases, foundations and underground structures / under total. ed. V.A. Ilyicheva, R.A. Mangusheva. - M .: Publishing house ASV, 2016 .-- 1040 p.

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13. The effect of the edge pile and its accounting when calculating the slab grillage. Petrukhin, S.G. Bezvolev, O. A. Shulyat'ev, A. I. Harichkin // Urban Development and Geotechnical Construction. - 2007. - No. 11. - S. 90-97.

14. Mikhailov V.S., Busygina G.M. Determination of the roll and joint settlement of slab foundations // Polzunovsky Almanac. - 2016. - No. 3. - S. 141-145.

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3. Tsudik E. Analysis of structures on elastic foundations. FL, J. Ross Publ., 2013, 585 p.

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9. Spravochnik geotekhnika. Osnovaniia, fundamenty i podzemnye sooruzheniia. ... Eds. V.A. Il "ichev, R.A. Mangushev. 2nd ed. Moscow, ASV, 2016, 1040 p.

10. Tomlinson M., Woodward J. Pile Design and Construction Practice. New York, Taylor & Francis, 2008, 566 p.

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14. Mikhaylov V.S., Busygina G.M. Opredelenie krena i sovmestnykh osadok dvukh plitnykh fundamentov. Polzunovskii almanac, 2016, no. 3, Barnaul, Altaiiskii gosudarstvennyi technicheskii universitet, pp. 141-145.

15. Mikhailov V.S., Teplykh A.V. Uchet kharakternykh osobennostei razlichnykh modelei osnovaniia pri raschete vzaimnogo vliianiia zdanii na bol "shikh fundamentnykh plitakh s ispol" zovaniem raschetno-analiticheskoi sistemy SCAD Office. VI Mezhdunarodnyi simpozium. Aktual "nye problemy komp" iuternogo modelirovaniia konstruktsii i sooruzhenii. Vladivostok, 2016, pp. 133-134.

As a basis for calculating the settlement of pile foundations, the technology proposed by SergeyKonstr in this topic was adopted: "OFZ for joint venture 24.13330.2011", on dwg.ru, revised to the best of his understanding, for his own tools and capabilities.

SP 24.13330.2011: S = Sef + Sp + Sc

where, S is the settlement of the pile, Sef is the settlement of the conditional foundation, Sp is the settlement from punching, Sc is the settlement due to compression of the pile shaft.
The technology is as follows:

1. I calculate the scheme as on a natural basis in (SCAD + Cross) I get the average draft (Sef)
2. I place the piles on the plan. I create an additional design scheme that includes only the foundation slab and piles. In order to load the slab with a single load (1T / m2), and find out the load area of the placed piles, or "pile cell area", which is needed to calculate the punching settlement. There is a catch - what area to take for extreme and corner piles? I just for intuitive reasons, added a coefficient to the area of the cell equal to 2 and 4
4. Sc is not a problem to calculate, knowing the load on the pile and its parameters.
5. Knowing Sef, Sp, Sc, I get the stiffness of the piles and perform several iterations of the calculation.

I decided to use universal rods for modeling the piles. It is much more convenient to work with them in SCAD than, for example, with bonds of finite stiffness.
With the help of SPDS Graphics, the parametric object "Pile", "table for calculations" was developed. All calculations are performed inside this object, we just need to set the initial parameters to it:
1. We set the parameters (section, length) and soil parameters (E1, Mu1, E2, Mu2,) to the piles
2. Set the load on the pile (as a first approximation, the total vertical load on the building / number of piles).
3. We assign the piles the draft of the conditional foundation, calculated using the SCAD + Cross, and the depth of the subsidence strata. Here is the isofield of the settlement of my slab, respectively, the Sef was set to the piles, depending on which field they fell into.

4. We set the load areas (reaction in the pile from a single load).
5. The parametric object, receiving all these parameters, calculates the total draft, and accordingly the stiffness (E = N / S), and builds a vertical bar with a length equal to 1000 / E.

6. Actually, we dissect these objects, leave only the vertical bars, and import them into the SCAD, where we assign stiffness EF = 1000 to all bars.
7. It is unrealistic to assign each pile a draft, load, etc. in a large pile field. The assignment of data to the piles is done using Excel - SPDS Table. But this is possible only if the pile numbers in the SCADA correspond to the pile numbers on the plan in AutoCAD. Therefore, the piles in the autocad are sorted by X, Y and numbered using a table. Before importing bars into the SCAD, they must be rebuilt in the same order as the piles. Users Nanocada can take advantage macro who designed swell (d) ... It is also possible to apply for this purpose the PC Lira, which is able to renumber the rods depending on their coordinates along X, Y.

The SCAD software complex, in addition to the computational module of finite element modeling, includes a set of programs capable of solving more specific problems. Due to its autonomy, the set of satellite programs can be used separately from the main calculation module SCAD, and it is not prohibited to perform joint calculations with alternative software packages (, Robot Structural Analysis, STARK ES). In this article, we will look at several examples of calculation in SCAD Office.

An example of the selection of reinforcement in the rib of a prefabricated slab in the SCAD program

The slab will be pivotally mounted on the construction site, for example on brick walls. I consider it impractical to model the entire slab, part of the building, or the entire building for such a task, since labor costs are extremely disparate. The ARBAT program can come to the rescue. The rib is recommended to be calculated by the norms as a T-section of reinforced concrete. The menu of the SCAD software complex is intuitive: for a given section, reinforcement and force, the engineer receives a result about the bearing capacity of the element with reference to the clauses of the normative documents. The calculation result can be automatically generated in a text editor. It takes about 5-10 minutes to enter data, which is much less than the formation of a finite element model of a ribbed floor (let's not forget that in certain situations the calculation by the finite element method gives more design possibilities).

An example of calculating embedded products in SCAD

Now let's remember the calculation of embedded products for fastening structures to reinforced concrete sections.

I often meet designers who set parameters for design reasons, although it is quite simple to check the bearing capacity of mortgages. First, you need to calculate the shear force at the attachment point of the embedded part. This can be done manually by collecting loads from the load area, or from the Q plot of the finite element model. Then use the special design side of the ARBAT program, enter the data on the structure of the embedded part and the forces, and as a result, get the percentage of using the bearing capacity.

With another interesting example of calculation in SCAD engineer may face: determination of the load-bearing capacity of a timber frame. As we know, for a number of reasons, the FEM calculation programs (finite element method) do not have in their arsenal modules for calculating wooden structures according to Russian regulatory documents. in this regard, the calculation can be done manually or in another program. The SCAD software package offers the DECOR program to the engineer.

In addition to the data on the section, the DECOR program will require the engineer to enter the design forces, which will be obtained by SP LIRA 10. Having assembled the design model, you can assign the parametric section of the tree to the rods, set the elastic modulus of the tree and obtain the efforts according to the deformation scheme:

In this example of the calculation in SCAD, the flexibility of the element turned out to be a critical value, the margin for the limiting moment of the sections is "solid". The information block of the DECOR program will help you to recall the limiting value of the flexibility of wooden elements:

An example of calculating the bearing capacity of a foundation in SCAD

An integral part of pile-slab foundation modeling is the calculation of the bearing capacity and settlement of the pile. To cope with a task of this kind, the program REQUEST will help the engineer. In it, the developers have implemented the calculation of foundations in accordance with the norms of "foundations and foundations" and "pile foundations" (you will not find such possibilities in the FEM calculation programs). So, to model a pile, you need to calculate the stiffness of a single-node finite element. Stiffness is measured in tf / m and is equal to the ratio of the bearing capacity of the pile to its settlement. It is recommended to perform modeling iteratively: at the beginning, set the approximate stiffness, then refine the stiffness value according to the calculated pile parameters. The constructed model for calculating by the finite element method will allow us not only to accurately find the load on the pile, but also to calculate the reinforcement of the grillage:

After calculating the structure, the user of SP LIRA 10 will be able to calculate the required load on the pile based on the output of the mosaic of forces in a single-node finite element. The resulting maximum force will be the required design load on the pile, the bearing capacity of the selected pile must exceed the required value.

The type of pile (boring, driven), the parameters of the pile section and soil conditions according to the geological survey data are entered as the initial data into the ZARROS program.

An example of calculating nodal connections in SCAD

The calculation of nodal connections is an important part of the analysis of the bearing capacity of buildings. However, designers often neglect this calculation, the results can be extremely disastrous.

The figure shows an example of the lack of ensuring the bearing capacity of the wall of the upper chord of the truss truss at the point of attachment of the truss truss. According to the Joint Venture Steel Structures, such calculations are made without fail. You will not find such a calculation in the program of calculation by the method of finite elements either. The way out of the situation can be the COMET-2 program. Here the user will find the calculation of nodal connections in accordance with the current regulatory documents.

Our node is a truss and to calculate it, you need to select an advisory item in the program. Next, the user shaves the outline of the belt (our case is V-shaped), the geometric parameters of the panel, the efforts of each rod. The forces are usually calculated in the FEM calculation programs. Based on the entered data, the program generates a drawing for a visual representation of the assembly structure and calculates the bearing capacity for all types of verification in accordance with regulatory documents.

An example of constructing an MCI calculation in SCAD

The construction of finite element analysis models is not complete without the application of loads, manually calculated values are assigned in the FEM calculation programs per element. The WEST program will assist the engineer in collecting wind and snow loads. The program includes several calculation modules that allow for the entered construction area and the outline of the building contour calculates the wind and snow load (the most common calculation modules of the WEST program). So, when calculating the canopy, the designer must indicate the height of the ridge, the angle of inclination and the width of the slope. According to the obtained diagrams, the load is entered into the calculation program, for example, SP LIRA 10.4.

As a conclusion, I can say that the SCAD software complex and its satellites allow the user to significantly reduce labor costs when calculating local problems, as well as form accurate calculation models, and also contain reference data necessary for the work of civil engineers. The autonomy of the programs allows designers to use them in combination with any computational complexes based on the calculation by the finite element method.

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