LTA Manual Enu

Manual

Lattice towers analysis - LTA

Nemetschek Scia - Scia Engineer

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Information in this document is subject to change without notice. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic or mechanical, for any purpose, without the express written permission of the publisher.

SCIA Software is not responsible for direct or indirect damage as a result of imperfections in the documentation and/or software.

© Copyright 2011 SCIA Group. All rights reserved.


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Manual – LTA

Calculation of high voltage lattice towers

Scia Engineer 2011


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Content

Content ............................................................................................................ 4

1. High voltage lattice towers analysis ..................................................... 5

2. Project templates .................................................................................... 2

3. User blocks .............................................................................................. 1

4. Load Generators ..................................................................................... 6

5. Appendix ................................................................................................ 19

6. Wind Load .............................................................................................. 55


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1. High voltage lattice towers analysis

This document serves as a user guide to the calculation of lattice towers through the program Scia Engineer. The document will provide information on:

- Preparation for the lattice powermasts analysis

- Operation of the program

o the data entry

o the analysis;

o the results.

This document is designed so that the issues are treated in the chronological order of use.

This document will only describe things specific for lattice powermasts. Besides this document, please read the following:

Scia Engineer general manual Here the general operations of the program are

explained. ESA Steel instructions all items related to steel fabrication (thickness, voltage,

stability, relative deformations, fire control) are present here.

ESA Connections manual In this document all options regarding connections era

explained. Getting started for Calculating Lattice powermast Step-by-step tutorial for modeling, the parameterization,

analysis, checks and documentation. Installation Note for This document explains how Users Blocks must be user blocks installed and how you can make them by yourself


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To be able to calculate lattice powermasts, the following modules are required: esa.00 - Base modeller esa.06 - Productivity Toolbox esa.08.x – Language module esa.11 - Parametric input esa.16 - Blocks for high voltage powermasts esas.00 - 2D Linear statics esas.01 - Linear statics 3D extension esas.33 - Wind load, load construction, maintenance load and load SBS esasd.10.03 - Steel code check-NEN50341 1-15 esasd.06 - Frame Connections - Bolted diagonal

The preparation Before lattice powermasts can be calculated, at first the program, the user blocks and the project templates have to be installed. These steps are described below.

Installing the program Scia Engineer program is needed as a basis for modeling and calculation of structures. See Installation Guide for information about installing the program.

Installation the user blocks User blocks are structural components that the mast can be built of. For modeling of lattice powermasts are several user building blocks already made by Scia. The files of the blocks must be placed in the user folder on the hard disk.

Installation of project templates For modeling and calculation of lattice powermasts are already prepared templates available. These templates include the predefined projects of lattice powermasts. These templates are therefore especially designed for that purpose. The files of the templates must be placed in the templates folder on the hard disk.

Program operation A number of specific issues are in Scia Engineer for modeling and calculation of lattice powermasts. The table below lists a brief overview.

The project templates In the project templates the reusable typical items for further use are defined. Do these while creating the project which will be used several times.

User Blocks The user blocks will accelerate the structural model creation.

Load generators With the module, the wind, construction services and maintenance loads are automatically generated on the mast.

Calculation The calculation takes into account the connections stiffness and also a special function is designed to calculate the foundation forces.

Results The calculated results can be viewed. Checks The steel and connection checks are made in

accordance with EN 50341-1 and EN 50341-3-15. Optimization The special profile optimization and connection

optimization functionality are available, the entire structure could be quickly and carefully optimized.

Document The complete input, results and checks including pictures are documented.

In the following chapters, all the points discussed above and corresponding operation will be explained. It is possible to refer to other manuals if subject of the matter is part of the operation of the overall program.


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2. Project templates

It is possible, and in practice it often happens that some elements are used in any project where a user is working. Therefore, efficient and time-saving when the user is given an opportunity to store repeated elements and quickly load them when needed in a new project. In Scia Engineer it can be achieved using templates. Generally speaking, a common template is a project that contains all of the necessary information stored in the file.

For modeling and calculation of powermasts there are a number of project templates created which enables a user to use a lot of predefined high-voltage powermasts projects. With regard to the differences between the mast types, the following templates are created.

Support tower

Tension or End tower

Below is shown a project template in Scia Engineer.


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Each project template, includes the following parts:

Parameters There are a number of parameters defined by the load factors unique among others. See section Parameters.

Load cases and combinations The load cases and combinations necessary to analyze are already defined. See chapter Load cases, combinations.

Section List This list contains groups of cross sections that can be used in the sectional optimization. See Section Optimization.

Bolt Diameter - Diameter relationship The list includes the relationship between the diameter and bolt diameter will be used in connection calculation. See section Connection Control

Quality standard bolt Steel service under Command> Connections> Settings, tab Bolted diagonals enables a standard bolt-quality set. This project templates set the quality standard on 8.8 bolt.

The various components will be explained in the following sections.

Parameters The following parameters are created in a project template:

The meaning of the various parameters:


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sw_extra Shows the percentage of extra weight again serving plates, bolts, etc. This parameter is used to determine the combined load factor for the case Weight. gGneg, gGpos, gG Parameter for the combined load factor for the case Dead weight. In "gGneg" ("neg" for negative), the weight has a negative (adverse) effect. In "gGpos" ("pos" for positive), the weight has positive (beneficial) effect. With "gG", only the extra percentage for plates, bolts, etc. will be charged. t Reference period. Based on the safety class, the reference period is determined. To have more influence on the calculation, class safety is not parameterized, but the reference period is. This value affects the combination factor for variable loads (γqw, γqi). IceRegA Check this option if the mast is in ice region A. If the option is checked, the value "1". IceRegB Not applicable. IceReg The ice affects the parameter "a" in the formula for the combination factor. Using the value of parameter IceRegA get this parameter value. If IceRegA> 0 then the value of this parameter "a". a Coefficient by the grouping factor and l_qi l_qi_s affected. gQw-1a, gQqi, gQw-1b, gQw-3, gQw-4 Combination of factors for ULS combinations. gQw-1a-s-s-1b gQw, gQw-3-s, gQw-4-s,-s GQI Combination Factors for SLS combinations. Beta factor for the charging of additional effect on the conductor to the conductor if it is absent. This factor is used in combinations.

Load cases, combinations Load represents probably the most important part of the model. The user should always give attention to the proper definition of loads to which construction is exposed. Scia Engineer comes with a set of tools that facilitate this very important task. The program provides not only different types of loads (point load, linear torque load, thermal load, etc.), but also load groups, load cases, load combinations and result classes. Load Groups


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Load Groups define "how the individual load cases can be combined together" when you enter them in a load combination. In Scia Engineer select in the main tree service Load cases, combinations > Load Groups. The appendix Load Groups is a summary of the load groups in the project templates for powermasts defined.

Load Cases Individual loads are not "free", they are placed in the load cases. The load case manager manages the load cases. It provides the basic operations with load cases: creating a new load case, editing of existing load cases, removal of existing load case, the information on existing load case, printing, storing and reading of existing load cases from an external file. The load case manager can be opened by using menu function Tree > Load cases, combinations>Load Cases, Load cases in the Annex describe the summary of the load groups in the project templates for powermasts defined.

Note

1.) Temperature effects are not reported as separate load case. The effects are incorporated in the combination of factors. 2.) The security case is not specified as a separate one. The effects are incorporated into the ULS combination '5 '. Load Combinations Load cases defined in the project can be combined in load combinations. The combination can then be used for evaluating the results and code check. Combinations may be of various types. Each type is used for various checks. However, all types can be used for an initial evaluation of results (see the calculated internal forces). The determination of the basic design formula for combinations is done according to EN 50341-1, Art. 3.7.3. In addition, to determine the right combination factor, using BS EN 50341-3-15 4.2.11/NL.1 table and table 4.2.11/NL.3. The following combinations are created in the project templates: Tension or End tower


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Support tower

The combinations in which the name "p" is used behind the permanent means positive effect(positive). Where no "p" is used behind the permanent means negative effect (unfavorable). Only the combinations without "-p" after the name will all be explained in the Annex Load combinations. Result Classes Result classes represent a very powerful and useful tool for assessing outputs. They allow the user to combine in one class several results for selected load cases and load combinations. The program treats the class as an envelope of results for individual load cases and combinations. Appendix summarizes the results made classes in the project templates for powermasts.

3. User blocks

Scia Engineer allows the user to create a library of his/her project elements which can be used again. These blocks may at any time be included in a newly created project, or in a previously created and edited current project.

User blocks not only define the geometry, but also include another necessary data -hinges, profile rotations and buckling systems. They are also parameterized. This means that the geometry of the powermasts can be changed quickly by a change of the value of several parameters. The user blocks for powermasts are bundled in the module ESA.16. Because the user blocks Esa are not related to the special projects and there are no hidden functionalities, you can open, view and customize them to your needs.

Below is an overview of the currently available user blocks.

Vertical tower shaft AB = A-box AF.B = AF-box (piece trouser) No.B = no braces TT = top mast VB = V-box XB = X-box SBS # = number of struts of bracing relevant subject + # + # # = Number of struts of bracing top, middle and subject to relevant subject Horizontal frames Tower console BA 1 + # = Traves type 1, with # of existing fields under control. BA 1 + #. H1 = 0 = Traverse type 1, # fields from existing under control and height traverse end is zero. BA 2 + # = Traverse type 2, with # of existing fields under control. BA 3 - (# + #) = Traverse Type 3 from existing fields with # under control. BA 4 = Type 4.


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Note

1) Users blocks are defined in a special layer. After importing the design, check the selected bars if in the desired layer so that the wind generation conform regularly. 2) Users blocks are defined with the appropriate buckling system. Yet it is wise for some specific rods to check the lengths defined.

Saving to a library and inserting a user block to the construction is described in the General Manual, chapter Introduction of user blocks (pages 251 and 252).

When inserting a block user parameters must be defined. The following parameters are used: Horizontal frame Bx The width of the horizontal frame in the direction of the x-axis. By the width of the horizontal frame in the direction of the y-axis. Css HM The profile type of the horizontal frame. Css CM The profile type of the cross elements of the horizontal frame. Css DM The profile type of the diagonal elements of the horizontal frame. Example of parameters:


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Vertical tower shaft Bx The width of the box at the bottom in the direction of the x-axis. By The width of the box at the bottom in the direction of the y-axis. H The height of the box. dx The slope (distance in mm per 1m height) of the peripheral rods in the

direction of the x-axis. dy The slope (distance in mm per 1m height) of the peripheral rods in the

direction of the y-axis. d The slope d (distance in mm per 1m height) of the peripheral rods in the

direction of the x-and y-axis. Put The profile type of the edge bars. Bracing The profile type of the bracing diagonals. AF The profile type of the rear link. CSS HM The profile type of the horizontal edge bar. CSS DM The profile type of the diagonal of the horizontal link. CM CSS The profile type of the cross of the horizontal link. CSS The profile type of the respective bars. SBS The profile type of the strut of the bracing. SBS-top The profile of the type strut of the bracing top. SBS-profile The profile type of the strut of the bracing middle. SBS bott The profile of the type strut of the bracing below. SBS spec The profile type of the special strut of the bracing. Example of parameters:


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Tower console L2 Distance from center of pole to top of rim traverse rod below. L_1 ... L_7 knikverkorters spacing in the wall. L3 Distance from center of pole to top of rim traverse rod above. H1 Height to tip traverse. H2 height crossbar for pole body (where border rod ends). H3 height crossbar for pole body (where ereikt traverse pole body). Css Bott profile type of the edge bars below. Top CSS profile type of edge over bars. Css Diag profile type of the diagonals in the wall. Css Vert Her profile type of the verticals in the wall. WB The width of the traverse at the end on the bottom. WT The width of the traverse at the end on top. WTB The width of the passageway in the pole body at the bottom. WTT The width of the passageway in the body to the mast top. Example of parameters:


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Exceptions of parameter names of the type BA-3 L1 Distance from center of pole to top of rim traverse rod below. L2 Distance from bottom of pole body to break point. L3 Distance from lower border of pivot to tip. L4 Distance from center of pole to top of rim traverse rod above. H1 Height of the crossbar for pole body (where traverse pole body reached). H2 Height traverse to end. WTE The width of the traverse at the end on top.

Exceptions of parameter names of the type BA4 H1 Height traverse of horizontal to bottom. H2 Height difference between bottom and top at end of traverse. L4 Distance from edge of intersection with bottom edge to end of traverse.


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4. Load Generators Load generators represent a tool which can be used for simplified input of the loads. They ensure the transformation of the plane loads to the members. The load generators are used for two load cases, namely:

- Wind loads; - Construction loads.

Wind and construction loads The wind generator allows the user to apply the effect of the wind to the structure according to BS EN50341-3-15. This item is not described in the general instructions and will be discussed here. wind Type The type of wind load can be adjusted in the Project Settings dialog tabs.

The settings can be changed using the [...] button.


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General Reference Action time of the wind load in years. Informative, default is 50 years. terrain Elevation Indicates the height of the terrain compared to the reference plane. This value influences the wind thrust. Default is 0m. Average structure width The average width of the structure influences the structural resonance factor GT. Default value is 3.5m. Basic dynamic wind pressure wind Field The wind region determines the wind speed. reference wind speed The reference wind speed of the wind region can be changed. roughness Parameter Roughness length (z 0). Influenced the reference wind speed and turbulence intensity of the wind pressure. Distance between fields Enter the distance in meters between two wind areas. On this basis, the wind pressure is interpolated between the two areas. Air density The density of air affected the wind pressure.

Development Buildings left, right, Buildings, Construction front, rear Construction For 4 directions in the global coordination system there can be indicated if there is a construction around the structure or not. This affects the wind pressure.

Wind directions The four corners where the wind loads can be generated. Wind from left load in the positive x-direction Wind from right load in the negative x-direction Wind for load in the positive y direction Wind from behind load in the negative y direction


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Dynamic magnification factor Lowest natural frequency The lowest natural frequency affects the dynamic magnification factor G ST. The default is 60 / h. damping Size The damping also affects the dynamic magnification size. Default value 0.01. wind Factors calculation Structural parameters and resonance factor GT Form Factor CT can be determined in three ways: automatic The parameters are automatically determined by the different layers in the model, the size of the structure and the profile properties. Manual for all objects For all objects the value can be set. Manually for each object Separately for each object the value can be set.

The wind and structural load generator Step 0: The wind generation possible – selection of the type of the wind load When the load generator will be used, the user must indicate this fact on the Functionality tab of the Project Settings dialog. The mast section and item - Load cases to be selected in the function list. Then the type of wind Load tab is selected and the correct settings are made. Step 1: The function start The wind generator can be started via the main function in the service menu. Step 2: The subjects for load generation specification When step 1 is complete, click the Select dialog box for load generation on the screen. All layers are displayed here. You can now choose which layers will be taken into account in wind load generation and which layer will be assigned to the generator. You must ensure that the bars are in the right order, so the wind load is correctly generated.


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Move selected layers to the generator.

Remove the selected layers from the generator.

Select all the layers.

Deselects all layers. Step 3: The generated load cases After step 2 is performed, the dialogue will be confirmed by [OK] button and the load generation will start. Step 4: Load generation After the load generation a calculation report is displayed.


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When confirmed by OK button the loads are applied to the structure. conductor Load Input of the conductor tension is a function specifically designed for D & C Engineering BV (Netherland). Conductor tension forces can be transmitted through the Main Load Service menu> Load conductor insulators. Load conductor insulators Defining the conductor load isolators can be done for insulators supported by 1, 2 or 3 supports. You choose what type to use.

name The name of the insulator. Number of conductor supports Based on the selected conductor type there is the number of supports of the insulator defined. While converting the conductor load to the load case, the value is divided by this number. Instead of conductor This indication is used for SLS and broken wire combinations. Load component mast G rep The weight of the conductor and the connecting accessories in the z direction. The load is generated in Load case "6C". Q ijs, rep The conductor in tension plus ice on the conductor Q onderhoud; rep This property represents the maintenance burden of 1kN on the insulator. The load case "4M" is generated. Q w; rep


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The property Q w; rep consists of eight directions, each an input admittance of a load in x-and y-direction. The loads are generated in the Load cases' WI_ {direction} ". Q w(ijs); rep consists of eight directions, each an input admittance of a load in x-and y-direction. The loads are generated in the load cases' WI_ {direction} ". Conductor tension ULS Conductor in tension for various combinations of ULS , temperature can be entered here. Defines the conductor line angle line angle of the conductor with respect to the x-axis. Rotation of the x-axis to the y-axis is positive. 1a conductor in tension together with wind and temperature (wind 10 ° C) 1b conductor in tension together with wind and temperature (wind -20 ° C) 3 conductor in tension together with wind, ice and temperature (wind + ice -5 ° C) 4 conductor in tension together with maintenance 5a conductor in tension together with torsion 6 conductor in tension together with permanent load The loads are generated in load cases: Tuls-{combination number-position }, f.e. Tuls-5a-site Conductor tension SLS Conductor in tension for various combinations of SLS , temperature can be entered here. Defines the Conductor line angle line angle of the conductor with respect to the x-axis. Rotation of the x-axis to the y-axis is positive. 1a conductor in tension together with wind and temperature (wind 10 ° C) 1b conductor in tension together with wind and temperature (wind -20 ° C) 3 conductor in tension together with wind, ice and temperature (wind + ice -5 ° C) 4 conductor in tension together with maintenance The loads are generated in load cases: Tsls-{combination number-position }, f.e. Tsls-1a-site

Maintenance load The maintenance load is defined as 1 kN placed on each bar with an angle less than 30 degrees, according to BS EN50341-3-15: 2001, article 4.2.6, paragraph 5 4.2.6/NL.1 table, load case name is 4M. The characteristics of the load case follows.


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The load is generated during the linear calculation. The load itself cannot be viewed, but has the consequences for the internal forces in Results.

Strut bracing The special load for the design of strut bracing to NEN-EN50341-3-15: 2001, Art. 7.3.5.4 (NL.8) are placed in the load case SBS. During the steel beams checks of the compressive force the impact is calculated (NB, r, d). The characteristics of the load case follows:

This means that all the bars of the type of the vertical bracing should be loaded by additional load of 1% of the force from the support bar, based on the All UGT.

Calculation When the calculation is started, at first the wind generation is performed, in addition, all conductor tension forces are generated. During calculation, the strut bracings are not checked for stiffness, if they satisfy the requirement of EN 50341-3-15, Art. 7.3.5.4 (NL.8). It is assumed that the strut bracings always meet this requirement. The program applies following assumptions:

- All strut bracings members are of the type: vertical bracing (bracing wall).

- For all of these members the hinge is realized at the beginning of the member: o Phiy = Fri, phiz = Fri

- For all of these members the hinge is realized at the end of the member: o Phiy = Fri, phiz = Fri, phiz = Fri, ux = Fri

In addition, the strut bracings members weight is taken into account.


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It is also a special calculation of tower shaft done to determine the forces on the foundation supports. The way how this result is achieved is described in Annex Response Support (foundation forces). The results of this calculation can be viewed in the same way as the other results with respect to reaction forces.

Results Results service can be accessed after the calculation has been successfully completed. For detailed description of the results refer to the general Scia Engineer manual, chapter Results.

Checks Before the user can perform check procedures, certain specific conditions have to be met.

- The complete model of the structure must be properly defined. - The boundary conditions and loads respecting the real conditions of the structure

must be specified. - The model of the analyzed structure must be calculated, in other words, the internal

forces and deformations must be known.

Steel stress checks The procedure used for performing the steel stress checks is analogous to the procedure for evaluating the results. It can be summarized by the following points:

1. Opening the desired service. 2. Selection of members to be checked. 3. Selecting the load case or load combination. 4. Adjusting the screen parameters. 5. Selecting the values that should be displayed. 6. Showing the results of the check.

Extremes can be chosen so that only the extreme results per cross-section are shown. For detailed description of the Steel Control refers to the Scia Engineer Steel guide.

Connection Control The connections are automatically defined for any section in the Data Connection Library. The connection information is already reflected in the user blocks but can be adjusted if desired.


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Depending on the diameter, the bolt diameter edge distance is retrieved from the bolt diameter relationship library. The bolt quality is retrieved from the general settings of steel connections> Connections> Settings, tab Bolted diagonals. If desired, a Double Leg connection could be set. Then the minimum number of bolts is automatically set to 4. For this type of the connection also an even number of bolts can be introduced. When the number of bolts is increased to 2 or more, then the buckling system automatically select the "braced elements are adequately supported" according to BS EN50341-3-15: 2001, Art. 7.3.5.4 (NL.9). This applies to members of the type:, wall bracing, diagonal lattice. After the design and calculation, the connection check is returned with the standard Steel Control. For a detailed output the 'Detailed LTA' can be chosen.


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For a description of the parameters displayed on exports refer to the Scia Engineer Connection Guide.

Optimization When a structure is designed and calculated, there is an option to make an optimization of the original design. Scia Engineer provides a powerful tool for this task. The optimization of the applied profiles can be done automatically or semi-automatically. The process of optimization results in an economical and effective solution.

Principle of optimization Optimization represents generally a complex task. A full, complete and true "optimal" optimization would usually result in a long process. Scia Engineer therefore implemented a kind of compromise. One optimization step considers a single cross section It is possible to simultaneously optimize a cross-section. The user selects one from the list of all the cross sections that are used in the construction. One optimization step considers only "selected" bars It is possible to limit the optimization process to only a selected number of bars. The user can decide to specify which beams should be considered for the optimization calculations. One optimization step considers only "selected" cross sections It is possible to optimize the process to prepare instead of a cross section several sections simultaneously optimized. The user selects the cross-section from a list of all sections that are used in construction. When the optimized cross section is found, it is applied to ALL bars in the structure that belong to the specified diameter. It is irrelevant that the optimized calculation is limited to a selected number of bars or not. The final effect of the optimization is that the original cross section is easily replaced by a new, optimized, cross section. If the options described in connection control is enabled then the diameter of the bolt used to connect the hinge system and adjusted if necessary.

General optimization Step 1: Define General Optimization Through calculation, Net> Optimization can optimize the overall set. This is detailed in the General Manual, chapter Calculation, Optimization. Step 2: Lower Specifically for power pylons for each section indicated a lower limit for the optimization is set.


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This lower limit is fixed to the cross section at the time of adding to the general optimization. If the lower limit should be changed, then it must be changed before this section can again be added to the general optimization. During subsequent optimization iterations, the diameter both above and below are optimized, however it can never go below the lower limit. Step 3: Start of optimization routine After entering the desired parameters, the optimization starts by clicking [Optim.Routine]

This optimization routine will automatically perform the optimization, followed by the calculation, optimize again, so calculating in the cycle. The desired number of iterations for the optimization can be set in two ways:


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- Determine automatically: This is after an optimization round to see if there were intersected altered. If no profiles have been modified, then stop the optimization, otherwise start with a subsequent calculation / iteration.

- Limit number of iterations: It allows the user to set a limit. After an optimization

round to see whether there were intersected altered. If no profiles have been modified, then stop the optimization, otherwise start with a subsequent calculation / iteration until the set limit is reached.

During the optimization, first the sections optimized. If any section changed, then the change is automatically adjusted to the new data of the bolt diameter. Consequently the number of bolts is optimized. Step 4: Evaluation of the General Optimization After completing the optimization, a window is shown, where for each iteration the change in cross sections, unity check, number of bolts, ...etc. is displayed

Document The document is part of Scia Engineer that provides output documents creation. The final document may include:

- Separate tables, - Embedded tables, - Images - Captions of the user, - Associated external files, - Etc.

The document contains three parts, which are closely linked:


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Document window The Document window is the tool used for making the above mentioned output document parts. Preview Window The Preview window enables the user to navigate to different parts of the model in document style to look like. Table composer The composer creates the formatting tables in both Document and Preview windows. The process of inserting the result table with the foundation forces into their document will not be discussed here because it goes in the same way as any other document tables. For a technical description of the results table, see the annex Support Response (foundation forces). In the Steel check the table of layers with each layer results is shown.

For detailed description of the document refer to the General Scia Engineer manual, Document Section.


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5. Appendix

Load Groups In the project templates for powermasts, the following load groups created:

The naming of the Load Group has the following meaning. Perm The permanent loads. Ice The loads in this group are linked to the icing. WindIce The wind load taking into account ice will be linked to this group. Maint The maintenance loads will be linked to this group. SBS The loads in this group are linked to the strut bracings. LTA WIND The wind loads will belong to this load group. Construction The construction loads will be linked to this group. 5a_CI Safety loads related to cable break will be linked to this group. By default, taking into account phase 6 wire and 3 wire lightning. sls The special circumstances in which groups of conductors are absent be linked to this load group. For Tension and End Towers.


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Note

The load groups LTA WIND and Construction generated by the program should not be altered or removed. If these load groups are changed or removed than the generation of wind loads and the content of various combinations could be incorrect. The type of the Load Group can be: standard This option provides the user with sorting capabilities. It allows the user to sort the load cases to be easy managed, but does not affect the process of generation of load combinations. exclusive Two load cases of the same load group of this type will not appear in the same combination. Only one load case is selected from all of the load cases in this group. together Two or more load cases of the same load group of this type will always appear in the same combination. Load of the Coeff2 Group can be: Cat. A: Household Psi0 = 0.7, = 0.5 Psi1, Psi2 = 0.3 These coefficients are set using the Main Service Menu, select Project tab combinations. These coefficients are only used when the combination of the standard is defined (e.g. EC - GGT complex rare). In such a case, the combination of the factors is multiplied by a psi-factors (see Appendix Load combinations). Defining a new load group, for example, considering more guide wires, is explained in the General Manual, Chapter Loads, Load Groups, Define a new Load group.

Load cases Individual loads are placed in the load cases. The following chapters discuss the load cases created in the project templates of power masts. The load case manager is a standard Scia Engineer library manager. It provides basic operations with load cases. More about this topic is written in the General manual, Load cases chapter.

Wind The following load cases are used during the generation of wind loads. The meaning of the names is following: {abbreviation} _ {ind} direction. For example: + W_x wind is positive x-direction (ie, wind from the left). These load cases cannot be renamed or put in another load group. The program checks the name and load group, to be able to place the load in an existing load case. Changing


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the name or group or putting the load case into the another load group before the load generation will cause these loads unavailable for combinations.

Ice While entering the conductor tension forces, loads (Q ice, rep) are taking ice into account..

Wind + ice The following load cases are used during the generation of wind loads and when entering the conductor tension forces. Conductor tension forces in the section (Q w (ijs); rep) are placed in the following load cases.

Maintenance The maintenance load of 1 kN on each bar with an angle less than 30 ° is through tax case (4M) is defined. The characteristics of the load case follows.


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After setting the parameters, the load is automatically generated during the linear calculation.

The construction load of 1 kN at the end of each console to appear is generated simultaneously with the wind loads and the load cases 4C {number}. Two loads are also generated on each console. This sequence may vary from project to project. By default there are 12 predefined load cases. This means that there are three cross members on each side of the mast. Also more load cases and loads could be generated, however, these additional load cases are not processed in the combinations. These can be added manually.

Self weight The self weight of the structure is placed in load case 6T. The self weight is automatically calculated during the linear calculation. The self weight of the conductor is in 6C. While entering the conductor tension (G rep) then the conductor definition is converted to load and it is placed into this load case.


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Conductor Resistance strengths While entering the conductor tension (Tuls - {combinatie_nummer}) then the conductor definition is converted to load and it is placed into this load case.

For Support towers also the conductor tension for combination 5 can be entered. If the conductor definition is converted to load, this load is placed in the load cases:

The loads are shared across different load cases. This allows to take in the combination of load cases into account the wire breakage situation. By default it is assumed that a maximum of 4 conductors on one side of the mast placed on the top. If more conductors are used, the combination is not automatically updated. This must be done manually. In the template "Support Pole 30" the number of conductors is assumed up to 7 on one side and a placed on the top (so 30 in total). While entering the conductor tension forces, load case (T-{sls combinatie_nummer} - {position}) representing the conductor tension for the BMA combination is created. A distinction is made on each side (left front, left rear, right, on the right). These cases apply only to Tension and End towers.


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Strut bracing The special load for the design of strut bracing to NEN-EN50341-3-15: 2001, Art. 7.3.5.4 (NL.8) are placed in the load case SBS. During the steel beams checks of the compressive force the impact is calculated (NB, r, d). The characteristics of the load case follows:

The characteristics of the load case follows:

This means that all the bars of the type of the vertical bracing should be loaded by additional load of 1% of the force from the support bar, based on the All UGT.

Load Combinations Load cases defined in the project can be combined in load combinations. The combination can then be used for evaluating the results and code check. The combination load case manager is responsible for all operations with combinations of load cases. More about this topic is written in the General, section, Load combinations.


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ULS combinations 1a The combination is an envelope and includes the following extreme cases.

The following linear combinations are considered combination with the envelope.

Note

The parameters in the column are described in chapter Parameters coeff.


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1b The combination is an envelope and includes the following extreme cases.


Note

The parameters in the column are described in chapter Parameters coeff.


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3 The combination is an envelope and includes the following extreme cases.



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4 The combination is an envelope and contains the following cases.

The following linear combinations are considered combination within the envelope.


30


31


32


33


34


35


36


37

5 a The combination is an envelope and includes the following cases.


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The combination is designed so that the conductor is always in tension and combined with the maintenance loads. There is a guide created for each combination absence. The serial number of the combination indicates which conductor is absent. The opposite is the value of the beta coefficient. It is assumed that the conductors 1-2, 3-4, 5-6, etc. belong together. Conductor that has been absent a guide 2 the coefficient beta and vice versa. 6 The combination is linear and includes the following extreme cases.

SLS combinations For Tension or Corner towers must also be viewed special limit state combinations. These will be explained in this chapter. The combinations starting with sp (short for "special") have four cases each with 6 variations. The cases are: 1a, 1b, 3 and 4 and represent the combination wind, wind and cold, wind and ice, and maintenance. Each variant represents the particular fact that one group of conductors again absent. the variants are: LF, RF, LR, RR, R and F. The combination name indicates which group is absent, e.g. sp1aLF: the guides left front (front left) are absent for combination 1a (wind).


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Because the "wind" load cases are the "exclusive" type and the conductor tension cases are the "together" type, the maintenance loads are combined with the wind load cases and with all of the tension forces in the conductor. Because this system is the same for all of the combinations, only the linear combination sp1aLF is shown. SP1a The combination SP1a is an envelope and consists of 12 different combinations. Below is a list of the 12 combinations showing sp1aLF content.



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sp1b The combination is an envelope and consists of 12 very different combinations. Below is a list of the 12 combinations showing sp1bLF content.


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sp3 The combination is an envelope and consists of 12 different combinations. Below is a list of the 12 combinations showing sp3LF content.

sp4 The combination is an envelope and includes the following cases.


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Result classes Result classes represent a very powerful and useful tool for assessing the results. They allow the user to define a series (one class) of the results for selected load cases and load combinations. The program treats the class as an envelope of results. The Result class manager is a standard Scia Engineer library manager. It provides basic operations with results. More about this topic is written in the General manual, section Results. The table below describes the results of classes defined in the project templates of power masts.


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List of cross sections When optimizing the structure, the profile can be chosen from a limited set of profiles. The following cross section lists are created:


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45


46

Bolt Diameter - diameter relationship


47


48


49


50


51


52


53


54


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6. Wind Load The wind loads are calculated according to EN 50341-3-15.

Dead weight The weight is calculated as follows.

With l rod length

A cross section γ specific gravity This formula does not take into account an increase of the weight due to connection plates, bolts and other extra material. This is done in combinations. In the combination, the weight is increased by the percentage of plates, screws, etc., as set in the parameters of the project template.

Wind load on the subjects The wind load is calculated following the formula:

With qh The dynamic wind pressure, depending on the wind zone (see fig. 2).

Gq "The gust response" factor

GT The constructive resonance factor CT The form factor GST The dynamic resonance factor A The effective surface of the elements in a box (see Figure 3) for wind

in one of the main direction The total load is distributed among the 8 nodes that are at the end of each block there. The basic dynamic wind pressure q qh * G is equal to the value of pw NEN6702. The structural resonance Gt factor is determined as follows:


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With g =3.5

l(z) =

B = z 0.1 m for a wind field

0.2 m for wind field 2 0.3 m for wind zone 3

h Mast height b average width of the mast

The shape factor C T is determined as follows:

For a mast with a square base and made of steel angle. With Χ Sealing class

A effective surface area of the elements in a section perpendicular to the projected view. Props and strut bracings from the adjacent compartments must be disregarded.

h, b1, b2 see Figure 2 The dynamic resonance factor G ST intensive washing as follows:

With:


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z height above ground box z 0 = 0.1 m for a wind field

= 0.2 m 2 area for wind = 0.3 m for wind zone 3

h Mast height b average width of the mast

D = 0.01 (default) fe First natural frequency (Hz)

The default is 60 / h (Hz)


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Figure 1 - wind areas in the Netherlands


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Front view Top view Figure 2 - Effective area for box and traverse

Wind load on console The wind load on the crossbars for all the consoles is given. The total wind load is determined as follows:

With:

qh·Gq The basic dynamic wind pressure., Depending on the wind field (see Figure 1)

GT the structural resonance factor Ctc the form factor for the wind to traverse perpendicular to the

longitudinal axis of the traverse. Atc Effective are of the console – see Figure 2

Φ the angle between the wind direction and the longitudinal axis of the console - see Figure 2

Gst the dynamic resonance factor. (This value is added at the request of D & C Engineering – it is not a standard)


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The total load is distributed over the bars in proportion to the share of the effective surface of the considered member. The load is divided by 4 per member and the end nodes of the members on the front and back positions.

Support Reaction (foundation forces) Calculating the support reactions, the foundation forces is performed in a special way. The program provides supports for the selected node, select the load case , combination or class:

- The minimum and maximum response support for Rx, Ry and Rz. - For the above reactions, the following values are calculated:

o Horizontal = Sqrt (Rx ^ 2 + Ry ^ 2)

o Resultant = Sqrt (horizontal ^ 2 + Rz ^ 2)

o Slope = Rz / horizontal

A positive value means that the foundation is under pressure.

o diagonal angle t.o.v.

With the diagonal line through GCS (0,0,0) and the corresponding support intended.


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Calculate the positive or negative angle to diagonal. If there are more combinations with equal support reaction, the resultant combination with the largest value is displayed.

LTA Manual Enu

Documents

program scia engineer

scia software

scia group

calculation of lattice

esa connections manual

analysis o

user blocks

high voltage powermasts