How to Archives – Consteel

Software version: ConSteel 17 Build 3303

Keywords: Modeling; Analysis; Design; Lattice girder; Getting started;

Model examples

Design objective, choice of design standard

This design guide is intended for novice ConSteel 17 users and provides a step-by-step guide for designing a simply supported lattice girder. The geometry of the lattice girder to be designed is known from the architectural conceptual design, (Figure 1). According to the concept, the lattice girder chords are made of hot-rolled sections of HEA120, while the lattice bars are made of cold-formed SHS80x4 sections. The design of the connections is not included in this guide.

Figure 1. Geometric design of the lattice girder to be designed

(based on conceptual design) — Figure 1. Geometric design of the lattice girder to be designed
(based on conceptual design)

It is well known that structural design is always carried out according to a certain standard or its version. The selection of the standard can be made from the Design Standard menu when creating a new model in the Project Center, or it can be modified later in the Standards tab [S1] selection panel (Figure 2).

Figure 2. Choosing a design standard.
(S1: access standards; S2: select applicable standard; S3: select standard content; S4: display standard parameters).

The desired design standard can be selected from the list on the left of the panel. In this case, we select the EN Recommended option [S2]. The parameters applied by the selected standard can be accessed by selecting the corresponding row of the middle table [S3] of contents in the right-hand table [S4]. In Figure 2, the combination factors corresponding to Table 1.1 of the EC0 standard have been selected, whose parameters are shown in the right-hand table.

Setting the grid raster editor

First, let’s set the size of the raster according to the span of the structure by using the corresponding button [1] of the tool group on the left, which will bring up the Grid and Coordinate System adjustment panel (Figure 3).

Figure 3. Setting the editor raster
(1: set raster grid and coordinate system; 2: set raster occupancy size; 3: select view)

For example, for the 19.6m long support, the Size window can be set to 20000 millimeters [2]. To update the setting, press Enter. With the above setting, the raster will be 20m wide in X and Y directions, the raster line density will be 1000mm, and the step spacing will be 250mm. It is convenient to add the grid support model in the X-Z global coordinate plane, so the raster editor will be rotated to the X-Z plane. To do this, select the XZ plane option [3].

Loading initial cross-sections

One fundamental characteristic of general structural analysis programs is that they can only work with specifically defined cross-sections. Therefore, the first step is to choose the initial cross-sections for the task, according to the conceptual design. This may seem contradictory to the simple manual methods taught in basic statics courses, where the specific dimensions of the cross-section were often irrelevant information (e.g. calculation of internal forces). When using computer programs, however, we need to provide specific cross-sections even if their dimensions do not affect the static quantities to be calculated (e.g. in the present case, the normal forces of a truss beam). Nevertheless, we should aim to select cross-sections that match the geometrical size of the structure. In this case, the preliminary design served this purpose.

Initially, the section library for the current model is empty, so we first need to select the appropriate cross-sections. To do this, go to the Structure Members tab [4] and select the Section Administration option [5] on the left side of the horizontally positioned tool group, then select the “From Library…” button [6] in the panel that appears (Figure 4).

Figure 4. Selecting the type of cross-section.
(4: picking up structural elements; 5: calling up the section control panel;
6: Select section type)

Figure 5 shows the loading of the HEA120 section, compliant with the European standard, which will be assigned to the chords. We select the region of the cross-section standard (European) and then its type (H profiles). From the list that appears, we can select the type of section (HEA) [7] and then the height of the section (120) [8]. By pressing the Load button [9], the program learns the cross-section, and from then on it knows everything about the cross-section and can work with it. Repeat the procedure as many times as you need different sections. Finally, the window is closed by pressing the Close button [10].

Figure 5. Selection of cross-section type and size (for European HEA120 profile).
(7: select section type; 8: select section size; 9: scan selected section; 10: end loading process)

In our case, also a CF-SHS 80×4 closed section (from Library/Hollow sections – cold formed/CF-SHS/CF-SHS 80×4) was loaded for the bracing members (Figure 6).

Figure 6. Contents of the current cross-section store.

Later on, you can obtain all the information about the cross-section using the Section module. To do this, select the cross-section in the table by clicking on the corresponding row and then click on Properties… to display all the properties of the cross-section, such as type data; cross-section characteristics, etc. The program works with two cross-section mechanical models in a dual manner. The GSS (General Solid Section) model [11] is used for static calculations and the EPS (Elastic Plate Segment) model [12] for standard design operations (Figure 7). The cross-sectional properties (surface area, moments of inertia, etc.) can be displayed by pressing the button [13].

Figure 7. Display of cross-sectional properties.
(11: Open GSS general section model; 12: Open EPS elastic plate segment model;
13: open cross-sectional properties table)

gate

Did you know that Consteel already supports most of the countries which have adopted Eurocode design standard? If your country would still be missing, no problem, you can create your own NA settings. This is useful also in the case when you want to customize the recommended settings based on your own preference.

If you haven’t tried Consteel yet, request a trial for free!

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Geometry definition

Geometry in Pangolin can be described by lines or circular arcs and polygons made up of the former two. The relevant components are the simplest ones, acting as converters from the native Grasshopper geometry types, with the possibility of specifying a Consteel Layer.

Section definition

The geometry definition of the sections is more refined since Consteel uses detailed section models composed of solid representation for analysis and thin-walled representation for standard design checks. There are two options to create sections in Pangolin: use a predefined section from the section bank or create custom sections by predefined parametric macros.

Predefined sections from section bank

7000+ different profiles can be defined from the section bank (hot-rolled, cold-fromedetc.). This workflow contains two steps: 1. Getting the section preview from the bank. 2. Getting the actual section from the preview. (The reason for this is the performance, as in Pangolin sections are real objects, loading all the 7000+ sections from our bank would take minutes even on a powerful pc.) The section bank component provides various filtering options, to help select the section. After the desired section preview is selected, you can create a real section from it along with a material, and check the cross-section surface in Rhino.

Custom sections based on predefined macros

This workflow consists of placing a section macro component, selecting a base macro, and defining the macro parameters.

One of the most important unique features of Consteel is its advanced analysis and design calculations for members with cold-formed sections having various stiffeners. Correspondingly Pangolin makes it possible to create custom cold-formed sections, with custom stiffeners parametrically:

As you can see, the components help in building complex sections with available default values providing a wide range of parameters to be customized.

Structural member definition

Defining beams is as easy as pulling the reference edges and the beam section into the Beam component:

In the example above we also defined a haunch on the beam ends, another unique feature of Consteel, which will be taken accurately into account during analysis and design.

To make modelling easier, Pangolin also provides several useful implicit data conversions, like in the picture above: at the start, we have the IPE 300 beams, and just connecting them into a Grasshopper Plane parameter, the beams get converted to their local coordinate systems. This plane can be directly connected with the Z purlins section direction parameter to correctly lay them upon the main beams.

Structural details

Let us stop at the purlins for a moment! Pangolin also provides a detailed linking of structural objects through Consteel’s link elements which can be rather important in order to consider accurately the lateral restraint effect on the beam provided by the purlins.

The definition of link elements includes setting the interface position, the direction, and the stiffness attributes of the connection. Defining supports for the model is also helped by automatic conversions, where you can directly ask a beam’s endpoint, and place the support there, instead of manipulating with indexes through a complex definition.