Did you know that you could use Consteel to include in your model a wide range of cold-formed macro sections?
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Did you know that you could use Consteel to perform structural analysis at room and elevated temperatures as part of design process for fire resistance?
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Introduction
In ConSteel, there are three options for designing reinforced concrete columns: the Manual Nominal Curvature Method, the Automatic Nominal Curvature Method, and the Nominal Stiffness Method.
Each method has its advantages and disadvantages and should be used in different situations. We will now briefly review these methods and show how they can be used. Example models and a flowchart guide is also available at the end of the overview.
You can find the related chapters within the Online Manual about how to access these features in the Structural design and Structural modeling chapters.
Summary table
The following table summarizes the most important information about the three methods. Click on the table to see it in full screen.
We will now illustrate the application of these methods with a few short examples.
Examples
Manual Nominal Curvature Method
Create section
Define structure without imperfections
Define reinforcement
Define design parameters
First order analysis
Design
Automatic Nominal Curvature Method
Only the steps presented, which are different from the Manual Nominal Curvature Method.
Imperfections
Design parameters
First order analysis – with imperfections
gateDid you know that you could use Consteel to design simple supported, continuous and over-lapped purlins systems, considering shear and rotational stiffness of attached roof sheeting?
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Did you know that you could use Consteel to determine the critical temperature of a steel beam protected against fire with intumescent painting?
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Did you know that you could use Consteel to design a hot-rolled crane beam considering the effect of code-prescribed load eccentricities?
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Consteel offers a range of load combination filtering options, which can be applied based on limit states, load cases, and analysis and design results. By applying different series of filters, designers can streamline their workflow and reduce calculation time.
Filtering options
Filtering is realized through the Load combination set definition window.
Filtering by limit states and by load cases are handled together with the checkboxes under the Limit states and Load cases buttons.
The 3-state checkboxes affect each other as they are not only used for selection but also for indication of the content. They can be manually set only to checked or unchecked. The middle state only appears when other filters are applied.
Filtering by limit states or load cases does not require any calculation results.
Filter by rules, on the other hand,is based on the actual analysis and/or design results. Different types of rules can be applied one by one or at the same time to select the desired load combinations.
When a rule is applied, all the load combinations that are selected on the Load combination set definition dialog- either with filtering by limit states/load cases or checked in manually- are examined at every position the rule indicates. Load combinations that meet the rule’s criteria are selected (remain checked in), while those that do not, become unchecked.
- With analysis rules, load combinations can be selected based on deformations or internal forces at either every finite element node or only at the member ends. This last one is included specifically for connection design. Deformations are checked in SLS combinations, internal forces are checked in ULS combinations only.
- With buckling rules, those ULS load combinations can be selected which have the elastic critical load factor (first buckling eigenvalue) less than the given limit.
- With design rules, load combinations can be selected based on utility ratios checked in every finite element node of the chosen portion. Utilizations are available from several design checks: dominant results and detailed verifications for steel elements such as general elastic cross-section check, pure resistances, interactions and global stability. Only ULS combinations can be filtered with design rules.
Interaction of the different filter types
Filtering by limit states, load cases, and rules can be used together, with rules being applied only to load combinations that are checked in and have the necessary calculation results.
Let’s see an example.
It is a simple 2D frame model, with 27 load combinations of various limit states generated. Analysis and design results are calculated for all load combinations.
If applying design rule to select only those load combinations which result dominant utilization over 50%,
4 load combinations will be selected (Load combination set 1):
But if ULS Accidental limit state is turned off before applying the same 50% filter,
only one load combination is selected (see Load combination set 2).
Application of multiple rules
Applying multiple rules together results in the sum of the lists that would have been created separately.
gateThis paper discusses a combination of best practices and procedures from recent work in Europe and the US, providing rational and economical calculations addressing the complexities associated with frame design using nonprismatic members. Recommendations are provided in the context of US design practice. A primary objective is to achieve maximum simplicity, transparency, and design speed while facilitating rigor of the underlying calculations. The paper provides several focused examples illustrating the recommended design verification procedures.
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GATEIn Consteel 16, we introduced the function of load combination filter. Filtering is possible based on the load combinations’ limit state, load cases, and corresponding analysis and design results. The goal is to create different sets for the different steps of the optimization and reduce calculation time while making sure that all the relevant load combinations are considered. Let’s see what a conscious design workflow looks like in practice!
Description
It is a significant problem in almost all structural design projects that the standards define many possible load cases and combinations to evaluate. Although most of these load combinations are never relevant or provide decisive design situations, it is usually not evident which ones might be neglected safely, especially when considering, that different load combinations can be relevant for different parts of the structure, like primary or secondary structure, connections, etc. Accordingly, the optimization process is overloaded by a large amount of unnecessary calculations.
With the load combination filter function, a reduced list of load combinations aka a load combination set can be created and saved for the different steps of the optimization.
The optimal workflow for the filter may vary for the different purposes the sets are created for, but there is a recommended general process that can serve as the basis for all of them. First, run the simplest calculations and use the results for a rough selection which will already decrease the number of load combinations noticeably. Then one can increase the complexity of the calculations and further reduce the list of combinations by using stricter filters. If needed, this step can be repeated. This iterative process allows us to avoid complex and time-consuming calculations for all the thousands of load combinations.
1 – all load combination, no filter;
2 – initial set with broad filter;
3 – working set with strict filter
Detailed process
Modeling
The base of all optimization processes is a correctly built structural model. So, the first step is geometrical and structural modeling and load definition. It is advisable to run a first-order analysis for only one or two load cases and diagnostics to find possible modeling errors. Load combinations can be created after that. Every limit state that will be used during the whole design of the structure, should be defined. Consteel’s automatic load combination generation function is an efficient tool to do it.
Calculation and filter
On the Load combination set definition dialog, it is possible to create load combination sets by selecting the combinations based on their limit state and/or the load cases they contain. But usually, filtering on specific analysis or design results will likely be more effective in reducing the number of combinations. Using the above-described general workflow, the steps are as follows:
gateThe practical use of the ‘General method’ of EN 1993-1-1 6.3.4 for the buckling design of global structural models is still a challenging issue requiring several problems to solve. In this paper we propose a fully developed methodology presenting solutions for the application topics such as the suitable FE model, specific modeling issues to capture the true 3D behavior of the members and the whole model and the final evaluation of the design parameters. The presented methodology consistently uses a unique model for the evaluation of all analysis and design parameters and results and yields a fully automatic design process controlled solely by the properly created structural model.
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