Local, Story, and Global Ductility Evaluation for Complex 2D Steel Buildings: Pushover and Dynamic Analysis
, Alfredo Reyes-Salazar *, Eden Bojorquez, Juan Bojorquez, Arturo Lopez-Barraza, J. Luz Rivera-Salas and Jose R. Gaxiola-CamachoRound 1
Reviewer 1 Report
This paper presents outcome of numerical simulations carried out to evaluate ductility response in moment resisting steel frames.
Although the topic addressed by in the paper falls within the technical area covered by this journal, this reviewer is of the opinion that this paper does not merit publication in Applied Sciences journal in its current form due to the following comments and concerns. When/if these comments/questions are addressed, this article can be considered for publication in Applied Sciences journal.
Major Questions, Comments and Concerns
1) The language of the manuscript needs to be improved. For example,
a. This sentence in line 60 is not clear, “It is particularly important for steel structures since the beneficial effect of ductility is supposed to come from different sources.”
b. Line 103, “The Relationship”, relationship needs to be in lower case.
c. Line 139, “the Finite Element Method” needs to be in lower case or followed by “FEM”
2) The literature review section is quite extensive of this manuscript. It could be condensed and merged into the introduction section.
3) It is not clear if the buildings were designed to be actual buildings? Or were they designed to be case studies?
4) The authors use two sets of units (traditional and SI). Please use a uniform presentation for units throughout the manuscript.
5) How does the definition of ductility used by the authors compares to that adopted by building codes and other researchers?
6) The discussion on the development of the FE model is poor. What was the type of elements used? What was the convergence criteria?
7) Also, was the FE model validated? How do you justify the accuracy of this model and its prediction?
8) This manuscript seems to be missing key items and would requires significant improvements.
Author Response
RESPONSE REVIEWER 1
We want to thank the reviewer for the time spent in reviewing the paper and for he/her comments. There is no doubt that by considering them we will significantly improve the quality of the paper. We particularly thank for the expression “When/if these comments/questions are addressed, this article can be considered for publication in Applied Sciences Journal”. We are giving a point-by-point response below; some comments are added in the paper to make some parts clearer; they are highlighted with red color.
Comment 1a) This sentence in line 60 is not clear, “It is particularly important for steel structures since the beneficial effect of ductility is supposed to come from different sources.
Response to Comment 1a) We thank the reviewer for the observation, what we try to say is that there are many sources of ductility in Steel buildings; we modify the text to make the point clearer (lines 59-63).
Comment 1b) Line 103, “The Relationship”, relationship needs to be in lower case
Response to Comment 1b) We made the correction (line 103).
Comment 1c) Line 139, “the Finite Element Method” needs to be in lower case or followed by “FEM”
Response to Comment 1c) Thanks again for the observation, we made the correction (line 124).
Comment 2) The literature review section is quite extensive of this manuscript. It could be condensed and merged into the introduction section.
Response to Comment 2) We significantly condensed and reduced by about 30% the literature section (lines 120-122 and 139-141). However, we think it is better to have it a separated section.
Comment 3) It is not clear if the buildings were designed to be actual buildings? Or were they designed to be case studies?
Response to Comment 3) The buildings were designed to be case studies; some comments are added in Section 4.1 of the paper (lines 198-200) to clarify the point.
Comment 4) The authors use two sets of units (traditional and SI). Please use a uniform presentation for units throughout the manuscript.
Response to Comment 4) Thanks for the observation; where units are used we change them according to the International Systems of Units lines 308-314 and Figs 1 and 2).
Comment 5) How does the definition of ductility used by the authors compares to that adopted by building codes and other researchers?
Response to Comment 5) This is an important point which justifies somehow the investigation of this paper. As stated in the paper, in 2nd paragraph of introduction (lines 60-62), this parameter is constantly used in the profession in an indirect way to estimate the building seismic design forces, but there is no engineering definition of it in our specifications or codes, even less for the different levels of ductility (local, story and global). Regarding global ductility it is shown in this paper that, although used in the profession, the definition based on absolute top lateral displacements (lines 577-578) is not appropriate. On the other hand, that definition based on interstory drifts (which is used by other researchers)(lines 328-329) is appropriate.
Comment 6) The discussion on the development of the FE model is poor. What was the type of elements used? What was the convergence criteria?
Response to Comment 6) We agree with the reviewer; additional information is added (2nd paragraph of section 4.1). It is worth to mention that the perimeter moment resisting frames of the three-dimensional buildings were used in the analysis (lines 200-202).
Comment 7) Also, was the FE model validated? How do you justify the accuracy of this model and its prediction?
Response to Comment 7) It has been shown that this type of FE formulation results in a good approximation of the structural response in parametric studies like that presented in this paper as long as it is provided a realistic modeling of the structure and of the cyclic load deformation characteristics of its structural elements. Some comments and references [62-65] were added in third paragraph of Section 4.1.
Comment 8) This manuscript seems to be missing key items and would requires significant improvements.
Response to Comment 8) We sincerely believe that by addressing the reviewer concerns given from Comments 1 to 7 the paper was significantly improved.
Reviewer 2 Report
The paper topic can contribute to enrich the literature background for researchers, and thus should be considered for publication.
Some recommendations are given before the paper would be finally accepted.
section 4.1 and figures 1-2: 3 different buildings are mentioned in the main text, as the object of investigations. But a single frame building is shown in figure 1 (and one more in figure 2), and this is partly confusing for the reader. It is recommended that the authors modify and update the original figure, by adding at least a schematic view / simple notes / labels to give evidence of the main features for the 3 case study buildings
figure 1: units should be better clarified
main text: the text chapters should be generally shortened. Prefer concise details and avoid repetitions ("it was shown earlier...", etc)
labels in figures 3 and 4 should be better related to the main text and to figures 1/2. For example, state in the previous figures the labels of storey levels "ST"
all the curves collected in figures 3 and 4 should be revised, moving from line/dot to simple dots. Actually it is clear that there is no correlation between x-axis values (the strong motion changes). As a result, the full curves have not scientific meaning. Please revise all the charts, accordingly
all the axis values in the charts of figures 3 and 4 should have the same limits (both along the x and y directions). Actually, x values span from 1 to 20 due to the reference seismic motion. Otherwise, limit values for the y axis modify for each figure. Such an assumption makes difficult a direct comparison between all the collected data, and should be revised
several numerical simulations are carried out, to collect the data discussed in this paper. however, the typical numerical model is never shown in the paper. At least an example of modelling and deformed shape should be included in the revised manuscript (section 4.1 and following chapters)
the full numerical investigation is developed on the base of simplified FE models, where the mechanical and geometrical properties of structural joints are roughly (but efficiently) described. Given such an assumption (that is realiable for extended parametric simulations, like in the current study), the manuscript should at least mention in the introduction (or in section 4.1) that the same FE method can offer - at higher levels of definition - precise feedback on the structural per formance (ductility included) of a given structural steel or steel-concrete composite joint. In doing so, the following literature documents (and others) should be cited as examples:
http://dx.doi.org/10.1016/j.engstruct.2017.02.037
https://doi.org/10.1016/j.jcsr.2017.10.003
Author Response
RESPONSE REVIEWER 2
We want to thank the reviewer for the time spent in reviewing the paper and for he/her comments. We particularly thank for the expression “The paper topic can contribute to enrich the literature background for researchers, and thus should be considered for publication”. We are giving below our point-by-point response; some comments are added in the paper to make some parts clearer; they are highlighted with blue color.
Comment 1) S
ection 4.1 and figures 1-2: 3 different buildings are mentioned in the main text, as the object of investigations. But a single frame building is shown in figure 1 (and one more in figure 2), and this is partly confusing for the reader. It is recommended that the authors modify and update the original figure, by adding at least a schematic view / simple notes / labels to give evidence of the main features for the 3 case study buildings.
Response to Comment 1) We agree with the reviewer in the sense that three different sets of buildings are mentioned, but only one of them is shown and this may create confusion. In fact only the perimeter moment resisting frames of the buildings located in Los Angeles area are use in the study; the three sets are mentioned just to show that the buildings used our study were part of a more general project (The SAC). Additional comments are added in section 4.1 (lines 200-204) to clarify the point.
Comment 2) Figure 1: units should be better clarified
Response to Comment 2) We thank the reviewer for the observation; the quality of numbers used to define the building dimensions (Figs. 1 and 2) was improved; in addition the numbers are now expressed in terms of the International Systems of Units.
Comment 3) main text: the text chapters should be generally shortened. Prefer concise details and avoid repetitions ("it was shown earlier...", etc)
Response to Comment 3) we checked all the text and reduced some expressions by following the reviewer suggestion. For example “From the earlier discussion” was deleted from first line of Section 1 (line 85); “As it is further elaborated below” was deleted from last paragraph of Introduction Section (line 100); “As stated earlier” was deleted from first line of Section 5 (line 316); “As shown” was deleted from first line of 2nd paragraph of Section 4.2 (page 240). Several irrelevant expressions were also removed in the Literature Review Section.
Comment 4) Labels in figures 3 and 4 should be better related to the main text and to figures 1/2. For example, state in the previous figures the labels of storey levels "ST"
Response to Comment 4) We thank the reviewer for the observation. The levels “ST1”, “ST2”, “ST3”… were added in Figures 1 and 2 according to the reviewer suggestion.
Comment 5) All the curves collected in figures 3 and 4 should be revised, moving from line/dot to simple dots. Actually it is clear that there is no correlation between x-axis values (the strong motion changes). As a result, the full curves have not scientific meaning. Please revise all the charts, accordingly.
Response to Comment 5) All curves in Figs. 3 and 4 were revised according to the reviewer observation.
Comment 6) All the axis values in the charts of figures 3 and 4 should have the same limits (both along the x and y directions). Actually, x values span from 1 to 20 due to the reference seismic motion. Otherwise, limit values for the y axis modify for each figure. Such an assumption makes difficult a direct comparison between all the collected data, and should be revised.
Response to Comment 6) The limits in Figs 3, 4 and 5 were revised according to the reviewer observation whenever they make sense. For example limits in Fig. 3 were made the same for beams (Fig. 3a, 3b and 3c) and for columns (Figs. 3d, 3e, 3f).
Comment 7) several numerical simulations are carried out, to collect the data discussed in this paper. However, the typical numerical model is never shown in the paper. At least an example of modelling and deformed shape should be included in the revised manuscript (section 4.1 and following chapters).
Response to Comment 7) We are sorry to say that we are not totally sure if we understand this comment. To get the results presented in Figs. 3-5 and Tables 3-10, thousands of nonlinear seismic analysis of the selected models under the action of several intensities of several strong motion were required. Obviously thousands of output files containing the information of the seismic response in terms of several parameters were also developed. In any of these nonlinear seismic analysis the deformed shape and the response parameters are continuously changing because of dynamic character of the problem. We had to extract the maximum ones. It is worth to mention that in the revised version of the problem additional information regarding the finite element model is given paragraphs 1 and 2 of Section 4.1.
Comment 8)The full numerical investigation is developed on the base of simplified FE models, where the mechanical and geometrical properties of structural joints are roughly (but efficiently) described. Given such an assumption (that is reliable for extended parametric simulations, like in the current study), the manuscript should at least mention in the introduction (or in section 4.1) that the same FE method can offer - at higher levels of definition - precise feedback on the structural performance (ductility included) of a given structural steel or steel-concrete composite joint. In doing so, the following literature documents (and others) should be cited as examples:
http://dx.doi.org/10.1016/j.engstruct.2017.02.037
https://doi.org/10.1016/j.jcsr.2017.10.003
Response to Comment 8) Some comments and references were added in third paragraph of Section 4.1, as suggested by the reviewer.
Round 2
Reviewer 1 Report
Thanks for improving your work.
Reviewer 2 Report
The authors largely improved the original paper, based on the previous recommendations. Most of theme have been properly addressed.
