Mitsubishi Heavy Industries Technical Review Vol. 60 No. 1 (March 2023)
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Development of Automatic Optimum Design System"M-FRAME" for Frame Steel Structure

MASAKI SHIMONO*1

MOTOKI KATO*2

TOMOAKI KASAHARA*3

Reference source: MHI's website
https://power.mhi.com/products/conventional

Mitsubishi Heavy Industries, Ltd. (MHI) has developed a steel frame cross-section
minimizing method for the structural design of a frame steel structure, which enables economic
design through simultaneous minimization of the weights of multiple steel frame members. With
this method, however, there are issues that the data input and output are not automated and thecalculation takes a lot of time, only the constraint conditions for strength and deformation are
considered in the calculation and the other conditions that should be considered in design are nottaken into account. Therefore, the method has been applied to limited products. To solve theseissues, we created a program that automatically delivered the input and output in each calculation
process on the server and developed a system using a Web browser as the user interface. We also
added a function of calculating the cross-section of a frame steel structure with consideration given
to assimilability of members in addition to the constraint conditions for strength and deformation.
This report describes the overview of the developed system and a verification example forapplication effects.

|1. Introduction
MHI has numerous plant products and there are various sizes of frame steel structures tosupport them, from small ones composed of several tens of members to large ones composed ofseveral thousands of members for main plant equipment such as large turbines and boilers. Thefunction of these frame steel structures is to securely support plant equipment, and they must be
robust enough to ensure safety and security without collapsing in natural disturbances such as
earthquakes and storms. On the other hand, there is a need for weight reduction of steel frame
materials from the aspect of the rise in material costs and the reduction of environmental load. In
the previous report(1), we described the steel frame cross-section minimizing method which enabled
a rational design that improved both seismic resistance and economic efficiency. In the method,
however, there are issues that the data input and output in the calculation must be manuallyconducted, it takes a lot of time and since the design conditions with consideration for theassemblability of members, such as size adjustment at joints of members, are not taken intoaccount, adjustment to the optimization calculation results must be made. Therefore, the method
has only been applied to a limited number of products. MHI deals with various plant products, andthere is a need for weight reduction of the frame steel structure of each product. In order to expand
the scope of application of this method, we developed a system responding to the above issues.

|2. Overview of the frame steel structure design method
In Japan, the structural design of frame steel structures is mostly conducted according to theBuilding Standards Act, and the structure is designed so that the responses (stress, deflection, etc.)
of all steel frame members to loads such as seismic force do not exceed the allowable values. In theprevious report, we developed the steel frame cross-section minimizing method, M-FRAME*1Strength Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

*2

Project Manager, Strength Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

*3

EPI Department, Digital Innovation Headquarters, Mitsubishi Heavy Industries, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 60 No. 1 (March 2023)
2(Mitsubishi-Frame weight Reduction Algorithm for Multiple Elements), which enabledsimultaneous minimization of the cross-sections of multiple members constituting a frame steel
structure. By this method, a frame steel structure that minimizes the weight can be automaticallyderived while the above-described constraint conditions (stress, deflection, etc.) are satisfied.
As described in this report, we newly improved and expanded the functions of theM-FRAME and as a result, in addition to the above-described steel frame cross-section
minimization calculation, the preparation work for calculation (such as creation of a model andsetting of conditions) and the adjustment of the cross-sections of members with consideration forassemblability (Chapter 4) became automatically executed. Furthermore, the data input and output
in individual work processes became automated (Chapter 3) and a series of frame steel structuredesign works can be automatically executed in a consistent and integrated manner.

|3. Development of an automated frame steel structure designsystem
In order for the method to be applicable to more frame steel structure products, we created aprogram that allowed the data input and output in each calculation process to be automaticallydelivered on the server and developed a system using a Web browser as the user interface toautomate the data input and output in each design process and make the system versatile. Figure 1
shows the conventional design flow in the case the M-FRAME is not applied and the design flowin the case the developed system is applied. Each design process is automated to shorten the designtime. The target scope of the development in the previous report was the "cross-section
optimization" process in the figure and only the cross-section design in the conventional design
flow was automated.

Figure 1

Comparison of design flows

When the developed system is applied, the processes from creation of a structural analysis
model to calculation of an optimal cross-section can be automatically conducted in aconsistent and integrated manner and the design time becomes shorter than the conventional
design time.

In order to implement the frame steel structure cross-section design in a consistent andintegrated manner, we made a system that enabled automatic execution of the cross-section design
processes using the M-FRAME of "creation of a structural analysis model --> setting ofoptimization conditions --> optimization of cross-section --> adjustment of assimilability -->visualization of design result" and automatic data input and output and data delivery in eachprocess. We selected the major design processes in the frame steel structure cross-section designusing the M-FRAME and developed a system composed of a total of 10 applications.
The main function of the developed system is the "cross-section optimization" application,by which a cross-section that minimizes the weight under the constraints on strength (such asMitsubishi Heavy Industries Technical Review Vol. 60 No. 1 (March 2023)
3stress) is calculated. The algorithm used in the method of the previous report was improved toshorten the calculation time and adopted as the optimization algorithm. We also developed theapplications such as a "model creation" application for reading the information (nodes, elements,load data, etc.) entered in the prescribed form and automatically creating a structural analysis
model, an "assemblability adjustment" application for modifying the cross-section withconsideration for assemblability and a "graph generation" application for outputting graphs ofcomparison results of frame steel structure weights, etc.

|4. Design method with consideration for assemblability
From among the developed applications, the method for "assemblability adjustment" isdescribed. In the design method of the previous report, a cross-section with consideration for
constraints such as strength and deformation could be calculated, but the assemblability ofmembers were not considered in the calculation and adjustment to the calculation result wasrequired. Therefore, we developed a method in which a column-to-beam joint or a beam-to-beamjoint as shown in Figure 2 could be adjusted. For adjustment of a column-to-beam joint, thecross-sectional size of the column is increased according to the cross-sectional dimensions of thebeam. For adjustment of a beam-to-beam joint, the cross-sectional heights of the beams areautomatically changed so that "the beam to be attached < the support beam" can be achieved (thecross-sectional height of the support beam is increased). As a result, the cross-sections are modified
with consideration for connection so that "a girder (connecting a column and a column) > a major
beam (connecting a girder and a girder) > a minor beam to be attached to a major beam" isachieved. In addition, adjustment of a column-to-column joint (the cross-section of the column inthe upper layer < the cross-section of the column in the lower layer) and adjustment of acolumn-to-vertical brace joint (the column width > the vertical brace width) can be made.

Figure 2

Example of assemblability adjustment

For a column-to-beam joint or a beam-to-beam joint, the cross-section of the column or beam
is automatically changed so that the members can be assembled.

In the design method of the previous report, a change of the cross-section should be made foreach element, but in the actual system, the same members were designed to have the samecross-section. Therefore, if several elements need to have the same cross-sectional shape, thecross-sections of the elements must be manually adjusted to make them uniform. In the developed
method, as shown in Figure 3, adjustment is automatically made so that the predetermined groupof elements have the same cross-section. The cross-sections are made uniform to match thecross-section of the element in the group that delivers the best cross-sectional performance (theMitsubishi Heavy Industries Technical Review Vol. 60 No. 1 (March 2023)
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highest bending strength, for example, in the case of beam members in which bending is critical) sothat it has no problem with the constraint on strength.

Figure 3 Adjustment of elements with the same cross-sectional shape
For the elements that should have the same cross-sectional shape, their different
cross-sectional shapes are automatically changed to the same cross-sectional shape.

|5. Frame steel structure design example
We performed a verification calculation to confirm the weight reduction effect and the design
time shortening effect of the developed application. The target structure is shown in Figure 4. The
target structure is a simplified model prepared for the verification.

Figure 5

Weight reduction effect

The weight was reduced by the application of the developedsystem.

Figure 4 Target structure forverification calculation
The developed system was applied to asimplified model for the verification and a seriesof verification design processes from thecreation of a model to the optimization of thesteel frame cross-section were conducted.

Figure 6

Change of stress ratio

Change of the number of members having the stress ratio(generated stress/allowable stress) of 0.8 to 1.0. After theapplication of the developed system, the number ofmembers having the stress ratio of 0.8 to 1.0 increased.

Mitsubishi Heavy Industries Technical Review Vol. 60 No. 1 (March 2023)
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Figure 5 shows the comparison of the initial weight and the weight after the developed
system was applied. Figure 6 shows the comparison result for the stress ratio (generatedstress/allowable stress) from among the constraint conditions. As shown in Figure 6, after thedeveloped system was applied, the number of members with the stress ratio of 0.8 to 1.0 increased.
This shows that the calculated structure has no waste. As a result, as shown in Figure 5, the weightof the frame steel structure in the verification model was reduced. Thus, we confirmed that a frame
steel structure cross-section for minimizing the weight could be calculated by the developedsystem.
Figure 7 shows the comparison of the design time using the conventional design procedureby a designer and the design time using the developed system for the simplified verification model.
As shown in the figure, the design time was reduced. The effectiveness of the developed system in
improving the design efficiency was also confirmed.

Figure 7

Design time shortening effectWith the application of the developed system, the design time wassubstantially reduced compared to the conventional manual designby human.

|6. Conclusion
We developed a design automation system, M-FRAME, which includes the frame steelstructure cross-section optimization method and an adjustment function with consideration forassemblability for steel structures such as frame steel structures. By the use of this system, theframe steel structure design processes from creation of a model to design of the cross-section canbe automatically conducted in a consistent and integrated manner, and the design time issubstantially shortened. As a result, it becomes easy to conduct highly economical structural designfor frame steel structures and thereby becomes possible to apply them to many products.
Furthermore, since the weight of a frame steel structure is reduced (the materials used are reduced),an environmentally friendly design becomes possible. In the future, we will sequentially apply thedeveloped system to a variety of our products.

References(1)

Motoki Kato et al., Development of Rational Design Technique for Frame Steel Structure Combining
Seismic Resistance and Economic Performance, Mitsubishi Heavy Industries Technical Review, Vol.52
No.1 (2015)