<
From version < 38.1 >
edited by Hamid Richard Allili
on 2019/11/27 12:00
To version < 39.1 >
edited by Hamid Richard Allili
on 2019/11/27 12:01
>
Change comment: There is no comment for this version

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5 5  
6 6  ----
7 7  
8 -The calculation of CLT panels is based on the laminated shell theory, which is a general way of calculating any kind of laminated shells, regardless of the material of the components. However, in the civil engineering practice the most popular application area is definitely the timber shells. Keeping in mind this, on FD user interface the CL(T) feature strictly connects to timber panels, including the possibility for both analysis (internal forces/stresses) and design options. Moreover, to make the best of the applied mechanical theory, general composite laminated shells are also implemented, with any kind of constituent material. As the design of these general composite shells are not supplemented by the standard, only analysis results are available for them.
8 +Analysis of laminated type shell structures become available by a new mechanical model implemented into FEM-Design, based on the laminated shell theory. From civil engineering point of view, the most popular field of application is the cross laminated timber (CLT) panel, although the theory in itself is more general, it is applicable for any kind of laminated composite surface structure. As the main purpose of this feature is to calculate and design CLT panels, the currently existing Timber plate and Timber wall tools are supplemented with this calculation model.
9 9  
10 -= Definition =
11 11  
11 +[[image:1574851449204-676.png]]
12 12  
13 -For the definition of CLT panels the currently existing //Timber plate// and //Timber wall// tools are used:
14 14  
15 -[[image:1574678804425-887.png]]
14 +Although, the theory used for the calculation of displacements and stresses is general, the application data (e.g. deformation factor, service class, etc.) and design methods for CLT panels are very specific and standard dependent. In order to preserve the possibility of general application, two new options are added to the original mechanical model used for the calculation of timber shell structures (Orthotropic shell): Cross laminated timber and General laminated composite (GLC).
16 16  
17 -All the tool window options (Define, Properties, Hole, Edge connection, Physical extent, Panels) are valid and applied for both original and CLT timber panels.
18 18  
19 -[[image:1574679210030-270.png]][[image:1574679223883-632.png]]
17 +[[image:1574852042766-929.png]]
20 20  
21 -On the General tab of Properties dialog //Eccentricity// is also modified (improved). So far it was only a display option, without any effect on the calculation. This limitation has no real technical obstacles, thus it will be the choice of the User with a new checkbox here.
22 22  
23 -On the Material tab , we can set the mechanical model of the plate. The original orthotropic shell model is supplemented with two new types, so User can select from the following options:
20 +For CLT panels, both analysis results (displacements and stresses) and design calculations are available, while for GLC panels only the first one is provided. These panel types are stored in different libraries, but their definition is very similar, we can define them layer by layer. In case of CLT, adding a new layer is possible by clicking on the material cell of the table, by this the original timber material library pops up, where we can select the constituent material of the current layer. After the selection, the program automatically fills all necessary data of the current layer, including mechanical properties (for analysis results) and limit stresses (for design calculations).
24 24  
25 -1. Orthotropic shell
26 -1. Cross laminated timber
27 -1. General laminated composite
22 +[[image:1574852438069-859.png]]
28 28  
29 -For the sake of uniformity, //Display stiffness// is available for all three kinds of mechanical models. This matrix is calculated to the middle surface of the element (independently on the eccentricity of the General tab), it should be noted in the tooltip of this button.
24 +It is very important that among the required layer data, there are some properties not specified by the Eurocode, these can be assumed based on the existing ones according to the following (in case the manufacturer does not specify different values for them):
30 30  
31 -[[image:1574680093243-258.png]]
26 +• G,,yz,, (G,,rolling,,) = G,,mean,, / 10
32 32  
33 -Independently on the selected type, the //General//, //Border// and //Panel// tabs are the same for all the three options, only the Material tab changes according to the selection.
28 + nu,,xy,, = 0.2
34 34  
35 -== Orthotropic shell ==
30 +• f,,Rk,, = f,,vk,, / 2
36 36  
37 -Within this feature, there is not change on the Material tab of orthotropic timber shell (picture taken after the separation of creep factors and library displaying change to tree view item)
32 + f,,xyk,, = f,,vk,,
38 38  
39 -[[image:1574680193460-990.png]]
34 +Of course, every value can be overwritten by demand. Besides the layers, the default deformation factors by service classes and stiffness reduction factors also need to be specified for a CLT library element. The new cross laminated timber library is filled up with the products of many famous manufacturers by default, new elements can be easily created based on them. The definition of GLC library elements is very similar, except that only the mechanical properties are necessary to define. For all the three mechanical type a display stiffness option is available to see the element stiffness matrix (refer to mid-plane) of the panels used in the calculations (and/or check its singularity), including the "B" submatrix responsible for the coupling effect.
40 40  
41 41  
42 -== Cross laminated timber (CLT) ==
43 -
44 -CLT panels consist of individual timber layers. As there are several typical panels, they need a new  library, which can be managed from the Material tab, similarly to the orthotropic shells. For the analysis and design the following parameters are necessary:
45 -
46 -* mechanical properties: E,,x,,, E,,y,,, G,,xy,,, G,,xz,,, G,,yz,, (G,,rolling,,), nu,,xy,,, Unit mass, Alpha
47 -* limit stresses: f,,b0k,,, f,,b90k,,, f,,t0k,,, f,,t90,,, f,,c0k,,, f,,c90k,,, f,,xyk,,, f,,vk,,, f,,Rk,,
48 -
49 -It is assumed by default that the grain runs in x direction. The directions by the layers for the CLT panels are: 0 or 90 degrees. As the constituent layers are not general timber materials (in the specification of producers it is stated that the timber material properties are taken according to EN338, but they clearly use different values), a new timber library should be created as constituent materials for CLT panels. According to these specifications even the E,,0,mean,, value can be different for C24 types, the library should differentiate them by producers. This library needs to store the following data:
50 -
51 -[[image:1574680241509-998.png]]
52 -
53 -There are some values which are not specified by the Eurocode, these can be assumed from the existing ones according to the following (if producer does not give exact values for them):
54 -
55 -* G,,rolling,, = G,,mean,, / 10
56 -* nu,,0.90,, = 0.2
57 -* f,,Rk,, = f,,vk,, / 2
58 -* f,,xyk ,,= f,,vk,,
59 -
60 -The Material tab of the CLT plate/wall with the existing library (left) elements and necessary application data (right):
61 -
62 -[[image:1574680319005-894.png]]
63 -
64 -The library elements are grouped by the producers. CLT library elements can be created/edited by the //New/Modify// buttons:
65 -
66 -[[image:1574680418376-297.png]]
67 -
68 -The library elements are basically consisting of a list of Timber materials (Timber library elements). User can add a new layer by clicking to an empty Material cell (or change one by clicking on the filled row’s cell Material). By this, the new special Timber library pops up. After selecting one (e.g. C24), the row is automatically filled with the Mechanical properties and Limit stresses, only the Thickness and Alpha angle should be defined by the User (the mechanical properties and limit stresses are NOT modifiable in the table). If Limit stresses is selected at the top, the table is changing according to the following:
69 -
70 -[[image:1574682424822-795.png]]
71 -
72 -
73 -The preview and Information sections are automatically updated after inserting/modifying/deleting a layer. On the preview picture, layers with the same Alpha are filled with the same colour, moreover layers with 0 angle are displayed with sign of grain direction.
74 -
75 -== General laminated composite ==
76 -
77 -As these composite shells are general and can be made of any material, they are strictly for analysis purpose only, they are not supported with design calculations (User get displacement, internal force and stress results for them). As in case of CLT, the //General//, //Border// and //Panel// tabs are the same, only the //Material// tab is different:
78 -
79 -[[image:1574682570789-660.png]]
80 -
81 -
82 -Because of this generality, a new library is needed for these laminated composite shells, which has similar appearance as CLT library, with slight modifications:
83 -
84 -[[image:1574682706755-534.png]]
85 -
86 -
87 -In this case, only mechanical properties are needed for a library element (as there is no design for them), and these values should be manually defined by the User.
88 -
89 89  = Results =
90 90  
91 91  == Analysis ==
... ... @@ -123,6 +123,7 @@
123 123  * All layer maximum by stress type (e.g. All layer, Sigma x+): search for the combination which results the largest positive x directional normal stress along all the layers at the selected point, on all the five stress figures the result of this combination is displayed
124 124  * Layer maximum by stress type (e.g. 2. layer, Sigma x+): search for the combination which results the largest positive x directional normal stress in the second layer at the selected point, on all the five stress figures the result of this combination is displayed
125 125  
74 +
126 126  ===== //Shell based stress detailed result// =====
127 127  
128 128  Due to the numerous options, finding maximum stresses by components on the shell can be quite time consuming, especially in case of complex loading of the structure. In order to overcome this difficulty and make the maximum finding process much easier a shell based option is also implemented, where User only has to select a shell.
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