Applicability of Hybrid Built-Up Wide Flange Steel Beams

Round 1

Reviewer 1 Report

General: I received a copy of the paper with pdf-comments of the authors in the column to the right, as if it was a working version. Please next time send a cleaned version.

Line 28: It is common to weld tmcp steel to hot rolled steel. What exactly is the background of the tests? This should be explained in the introduction. As I understand, tmcp steel is a low-C steel with its strength depending heavily on the heat treatment. If welded, the controled heat treatment is lost around the weld. That's how I understand the intention of getting a closer look to the effects of welding. 
Do I see that correctly? The background should be made more clear in the introduction.

Line 34: this comparison "price per weight" between concrete and steel is completely unrealistic. If, at all, it should be "price per load carrying capacity" but still this would not consider that concrete always needs reinforcing steel. Furthermore, not considered are the load type influence and furthermore external costs, lifetime cost analysis etc. Such a low-level comparison should not be included in a scientific paper.

 

Line 36: "High-performance steel" should be defined. Mostly, "high performance" is used for high strength. In the paper, a sm490tmc is compared to a sm490a or b. Both have a yield strength of 490MPa, why is the tmcp-steel high-performance?

Line 39: To explain cost-reduction, a comparison is needed. Do you compare the cost of the suggested system to a welded profile with tmcp steel in the web, or do you compare to tmcp rolled I-profiles, or to non-tmcp steel profiles?

Line 63: How can with a Charpy Notch test the hybrid section be tested? This could be an interesting approach, but in section 3.3, only separate tests for both plates are mentioned.

Table 1: very confusing, why is the C-content given in the first column and the last, what is the difference? Why is the last column of tmcp steel stuffed with 5 values? Format must be optimized. The Charpy notch impact work is necessarily combined with the test temperature (-20°C?), please add.

Is "charpy abortion energy" the right technical term?

section 2.1: This section is very important! Maybe could be better placed earlier in the paper, before introducing the steel type.

Line 124: Usually, a K-groove weld is considered fully penetrated. Figure 2 cannot be considered a K-groove weld.

I stopped reading at that point. I suggest to rewrite the paper thoroughly and resubmit it after major improvement. Since I did not read the full paper: My comments can be a starting points, but the whole paper must be checked for scientific soundness. In principle, the test project on the welding between the two steel types is of scientific and practical interest, so that a publication of these test results could be supported from my side.

Author Response

 ■ GENERAL COMMENTS

I received a copy of the paper with pdf-comments of the authors in the column to the right, as if it was a working version. Please next time send a cleaned version.

 

Response:

The authors appreciate your effort in reviewing the submitted manuscript and the feedback from the reviewer. The authors’ responses to the reviewer’s comments described below show the details of how the authors have addressed the reviewer’s comments in the revised version of the manuscript. The copy of the paper in pdf that you received is a version of the first revision and the markings in the right column have done by the editorial board, not by the authors, according to their policy. Please understand it.

 

■ SPECIFIC COMMENTS AND SUGGESTIONS FOR AUTHORS

1. Line 28: It is common to weld tmcp steel to hot rolled steel. What exactly is the background of the tests? This should be explained in the introduction. As I understand, tmcp steel is a low-C steel with its strength depending heavily on the heat treatment. If welded, the controled heat treatment is lost around the weld. That's how I understand the intention of getting a closer look to the effects of welding. Do I see that correctly? The background should be made more clear in the introduction.

 

Response:

TMCP has been introduced to the construction field as a structural material because an enhanced welding performance can be expected when the TMCP is used for a built-up wide flange section. From the performance point of view, the TMCP is preferred by engineers, but it’s not easy to secure price competitiveness. The purpose of this study is to introduce an alternative of conventional TMCP built-up steel member with a modified welding method. Furthermore, the structural performance is verified by experimental and analysis studies. The background of this study was well described in the introduction chapter of the submitted manuscript.

 

2. Line 34: this comparison "price per weight" between concrete and steel is completely unrealistic. If, at all, it should be "price per load carrying capacity" but still this would not consider that concrete always needs reinforcing steel. Furthermore, not considered are the load type influence and furthermore external costs, lifetime cost analysis etc. Such a low-level comparison should not be included in a scientific paper.

 

Response:

The “price per weight” is not the main purpose of this study, however, a structural design company for which one of the authors is working for, thoroughly compared several alternatives with the typical TMCP section case. The unit price of the alternative, SM490 is much cheaper than TMCP. Thus, in this study, the structural performance of the hybrid type steel beam was investigated in various methodologies, so that the target steel beam can be used in practice. Of course, the verification parts included the load-carrying capacity of the steel beams and the authors believe that the results can replace the “price per load carrying capacity” the reviewer commented.

 

3. Line 36: "High-performance steel" should be defined. Mostly, "high performance" is used for high strength. In the paper, a sm490tmc is compared to a sm490a or b. Both have a yield strength of 490MPa, why is the tmcp-steel high-performance?

 

Response:

As you can find in table 2 and figure 3, the material test showed that the measured yield strength of TMCP is much higher than that of SM490A. Besides, the superior welding performance of TMCP is well known, Thus, the TMCP as a structural material is typically called high-performance steel.

 

4. Line 39: To explain cost-reduction, a comparison is needed. Do you compare the cost of the suggested system to a welded profile with tmcp steel in the web, or do you compare to tmcp rolled I-profiles, or to non-tmcp steel profiles?n.

 

Response:

As aforementioned in the response to “Comment 2”, the exact price estimate is not the main purpose of this study, however, a structural design company for which one of the authors is working for, thoroughly compared several alternatives with the typical TMCP section case and the structural performance of the hybrid type steel beam was investigated in various methodologies as the main purpose of this study. As shown in Figure 1 in the submitted manuscript, the typical TMCP built-up wide flange was replaced with SM490A for the web part. The unit price of the SM490 is much cheaper than TMCP and the modified welding detail was also introduced to reduce welding effort by simplifying the detail, thus it can be considered that the economic feasibility is secured enough compared to the existing typical built-up wide flange steel beam.

 

5. Line 63: How can with a Charpy Notch test the hybrid section be tested? This could be an interesting approach, but in section 3.3, only separate tests for both plates are mentioned.

 

Response:

As described in the manuscript, Grade SM490B, SM490C or TMCP steel is preferred in the current practices of BWS members, and thus the impact performance (or toughness) of Grade SM490A should be verified for the application of the hybrid BWS section. The Charpy impact test is for validating the resisting performance to impact load at the welding joint. The hybrid steel beam consists of SM and TMCP steels by welding joint, not directly to each other steel parts as shown in Figure 11. Thus, the impact performance is determined at the lower performance which would be the joint between welding and a steel part whose performance resisting the impact is lower, which would be the test result of SM steel as a conservative capacity of the hybrid steel beam section.

 

6. Table 1: very confusing, why is the C-content given in the first column and the last, what is the difference? Why is the last column of tmcp steel stuffed with 5 values? Format must be optimized. The Charpy notch impact work is necessarily combined with the test temperature (-20°C?), please add.

 

Response:

The carbon in the first column is the carbon content in each steel grade and the last column shows the upper limit. The criteria for TMCP consist of 4 factors, not 5, and you can refer to the footnote of the table to find the meaning of each criterion.

 

7. Is "charpy abortion energy" the right technical term?

 

Response:

The “Charpy abortion energy” is a typo, so it has been corrected as “Charpy absorption energy” in the revised manuscript.

 

 

8. section 2.1: This section is very important! Maybe could be better placed earlier in the paper, before introducing the steel type.

 

Response:

The authors appreciate the considerable recommendation from the reviewer. The paper submitted was written focused on the hybrid built-up wide flange and the point securing efficient structural steel members. The welding detail is also accompanied to enhance the workability and efficiency to fabricate the hybrid member. So, the plot was composed to achieve this point. The authors believe that the flow is organized enough to follow the point of the paper.

 

9. Line 124: Usually, a K-groove weld is considered fully penetrated. Figure 2 cannot be considered a K-groove weld.

 

Response:

The figure 2 shows the simplified welding detail suggested in this study, not the K-groove welding detail. As mentioned by the reviewer, the K-groove welding should be done fully penetrating the welding joint, which could be simplified by the suggested welding detail if the performance at the welding joint remains as good enough as the K-groove welding. The investigation on this point is what this study is addressing.

 

10. I stopped reading at that point. I suggest to rewrite the paper thoroughly and resubmit it after major improvement. Since I did not read the full paper: My comments can be a starting points, but the whole paper must be checked for scientific soundness. In principle, the test project on the welding between the two steel types is of scientific and practical interest, so that a publication of these test results could be supported from my side.

 

Response:

The authors appreciate the reviewer's valuable comments and tried to reflect all the comments. your effort reviewing the submitted manuscript and the feedback from the reviewer. The authors are looking forward to the positive comments from the reviewer.

 

Reviewer 2 Report

The topic is interesting and the reseach activity is well organized.

I think that this paper can be useful, especially because both scientific and technological details are provided.

I have minor comments that I suggest to account for in the revision of the manuscript.

Please improve the state of the art and the relevant discussion. In particular, regarding the rotatio capacity ad flexural overstrength of steel beams there are several studies. I suggest to refer and discuss the following that are devoted to the quantification of rotation capacity and flexural overstrength:

D’Aniello M., Landolfo R., Piluso V., Rizzano G. (2012). Ultimate Behaviour of Steel Beams under Non-Uniform Bending. Journal of Constructional Steel Research 78 (2012) 144–158. doi:10.1016/j.jcsr.2012.07.003

Güneyisi E.M., D'Aniello M., Landolfo R., Mermerdaş K. (2013) A novel formulation of the flexural overstrength factor for steel beams. Journal of Constructional Steel Research 90 , pp. 60-71

Güneyisi E.M., D'Aniello M., Landolfo R., Mermerdaş K. (2014) Prediction of the flexural overstrength factor for steel beams using artificial neural network. Steel and Composite Structures, An International Journal, Vol. 17, No. 3, September 2014, pages 215-236 DOI: http://dx.doi.org/10.12989/scs.2014.17.3.215

 

Did the Authors a sensitivity study on the quality of the nesh? Please clarify this aspect and motivate the choice.

 

Author Response

 

■ GENERAL COMMENTS

The topic is interesting and the research activity is well organized. I think that this paper can be useful, especially because both scientific and technological details are provided. I have minor comments that I suggest to account for in the revision of the manuscript.

 

Response:

The authors appreciate all the positive feedback from the reviewer. The authors’ responses to the reviewer’s comments described below show the details how the authors have addressed the reviewer’s comments in the revised version of the manuscript.

 

■ SPECIFIC COMMENTS AND SUGGESTIONS FOR AUTHORS

1. Please improve the state of the art and the relevant discussion. In particular, regarding the rotation capacity and flexural overstrength of steel beams there are several studies. I suggest to refer and discuss the following that are devoted to the quantification of rotation capacity and flexural overstrength:   D’Aniello M., Landolfo R., Piluso V., Rizzano G. (2012). Ultimate Behaviour of Steel Beams under Non-Uniform Bending. Journal of Constructional Steel Research 78 (2012) 144–158. doi:10.1016/j.jcsr.2012.07.003   Güneyisi E.M., D'Aniello M., Landolfo R., Mermerdaş K. (2013) A novel formulation of the flexural overstrength factor for steel beams. Journal of Constructional Steel Research 90 , pp. 60-71   Güneyisi E.M., D'Aniello M., Landolfo R., Mermerdaş K. (2014) Prediction of the flexural overstrength factor for steel beams using artificial neural network. Steel and Composite Structures, An International Journal, Vol. 17, No. 3, September 2014, pages 215-236 DOI: http://dx.doi.org/10.12989/scs.2014.17.3.215

 

Response:

The authors appreciate the valuable recommendations from the reviewer. The authors have reviewed the papers recommended by the reviewer, and those are added in the revised manuscript, as follows:

“According to the research devoted to the quantification of flexural performance [24-26], the rotation capacity is an important factor to estimate the flexural performance of a beam member.”

 

2. Did the Authors a sensitivity study on the quality of the mesh? Please clarify this aspect and motivate the choice.

 

Response:

The authors have conducted mesh size-sensitivity checks, based on which the mesh size was determined as 20 mm for the specimens, which can be considered small enough. According to several analyses, it revealed that the reponses were not sensitive to the thickness of the steel plate. Upon request from the reviewer, the following description has been added in the revised manuscript.

“To determine the proper mesh size, mesh sensitivity should be considered. In this study, the size of the mesh was determined as 20 mm based on several analyses with various element sizes, and the same mesh size was applied to loading and support parts as well, which generated a total of 7499 hexahedral 3D solid elements. However, for the explicit dynamic analysis, a tetrahedral 3D solid element with an auto meshing method, in which the maximum size of the mesh was 100 mm, was applied to make the analysis optimized considering the time-dependent characteristic of the analysis. The boundaries followed the simply supported conditions.”

Reviewer 3 Report

To improve level of the paper this remarks should be satisfied, added or comment at least:
1)
The hybrid steel beams are quite common in practise already. The use of web from the “less performance” steel is well known solution in bridge engineering several decades. Therefore more references should be studied and referred, as well.
2)
There are several well-known things within the paper that should be described in shorter way – e.g. 2 page space for uniaxial tests of 9 specimens seems to be really useless
3)
The height of the tested beam taken as 1/8 of its span is out of common practical application. Why?
4)
It would be interesting, if author reflect to lateral-torsional buckling. Why they used lateral supports in the middle to prevent of lateral stability? Some comments should be therefore added.
5)
The authors implemented some residual stresses into the ANSYS model, but what about other types of imperfections, especially geometrical ones. Were they taken into account in nonlinear analyses?

 

Author Response

 

■ GENERAL COMMENTS

To improve level of the paper this remarks should be satisfied, added or comment at least:

 

Response:

The authors appreciate all the comments and recommendations from the reviewer to improve the quality of the manuscript. The authors’ responses to the reviewer’s comments and recommendations described below show the details how the authors have addressed the reviewer’s comments in the revised version of the manuscript.

 

■ SPECIFIC COMMENTS AND SUGGESTIONS FOR AUTHORS

1. The hybrid steel beams are quite common in practise already. The use of web from the “less performance” steel is well known solution in bridge engineering several decades. Therefore more references should be studied and referred, as well.

 

Response:

The authors appreciate the valuable comments and recommendations from the reviewer. The authors have found out that there is previous research related to the topic of the submitted manuscript. Thus, the following references have been added to the relevant description in the revised manuscript.

Jun, S.C.; Lee, C.H.; Han, K.H.; Kim, J.W. Flexural Behavior of High-Strength Steel Hybrid Composite Beams. Journal of Constructional Steel Research. 2018, 149, 269-281.

Ke, K.; Yam, M.C.H. A Performance-Based Damage-Control Design Procedure of Hybrid Steel MRFs with EDBs. Journal of Constructional Steel Research. 2018, 143, 46-61.

 

 

2.  There are several well-known things within the paper that should be described in shorter way – e.g. 2 page space for uniaxial tests of 9 specimens seems to be really useless

 

Response:

As the reviewer’s comment, the uniaxial test results might be well known. However, in this study, the uniaxial tension test results should be provided, and it is also required to compare the test results with those obtained from the direct tensile testing at the welding joint. The test results are also the basis of the structural behavior of flexural specimen. Thus, this point has been shortly delivered in the revised manuscript, as follows:

“The uniaxial tension test results are compared with the direct tensile test at the welding joint to validate the proposed welding performance, and the structural behavior would be based on the uniaxial tension test results unless the welding performance is inferior to that with the existing method.”

 

3.  The height of the tested beam taken as 1/8 of its span is out of common practical application. Why?

 

Response:

The plate girder specimens investigated in this study were scaled down from their actual size of target building located in South Korea shown below, where the capacity of loading equipment was also considered. However, the ratio of bending moment to shear force was kept to be the same between testing and actual plate girder. Due to those reason, the specimen size was determined, and this size is not biased from the practice of plate girder design usually done in Korea.

Fig. A – Parc 1 building in Seoul

4.  It would be interesting, if author reflect to lateral-torsional buckling. Why they used lateral supports in the middle to prevent of lateral stability? Some comments should be therefore added.

 

Response:

The specimen was not designed to have lateral restraint, but the stiffeners were placed at the loading and supporting points according to the AISC specifications to prevent the specimen from the premature failure due to any unexpected excessive local deformation. As a result, the lateral-torsional buckling commented by the reviewer was precluded and not observed. Thus, this constraint was modeled in the analysis. The relevant description has been added as follows:

“The beam specimens were designed with stiffeners according to the AISC specification, and those showed stable flexural behaviors without any sign of lateral-torsional buckling. Thus, the analysis was conducted with a model where the lateral constraint is assigned to exclude unexpected buckling behavior in the analysis.”

 

5.  The authors implemented some residual stresses into the ANSYS model, but what about other types of imperfections, especially geometrical ones. Were they taken into account in nonlinear analyses?

 

Response:

In the analysis study, the authors considered geometric and material nonlinearity with residual stresses, however, there is no consideration of initial imperfection because the target specimens are a simply supported beam subjected point loading (i.e., no axial compression), and the purpose of this study is to verify the structural performance of the plate girder with a simplified welding method.

Round 2

Reviewer 2 Report

The revised manuscript is suitable for publication. The article is interesting and well organized