Sustainability of Using Steel Fibers in Reinforced Concrete Deep Beams without Stirrups
Round 1
Reviewer 1 Report
General comment: This is a very interesting paper about the development of a nonlinear regression-based model using Steel Fibers to estimate the shear strength of deam RC beams. Significant work for the solution of this nonlinear problem is the estimation with numerical values of the influenced papameters using data from the literature. At the end of the paper the conclusions are very useful. My personal opinion is that the use of steel fibers should lead to its significant reduction of the shear reinforcement of Deep Beam and not to its complete absence, because as it is known also contributes to the tightening of the cross-section.
Detailed comments:
1. Rearrange the captures of the Table 1,4 in order to explain what exaclty is included there.
Author Response
Response to reviewer 1
The authors would like to thank the reviewer for his/her valuable comments and valuable feedback. The entire paper was updated to address your comment represented in the revised paper. For more details, please see below our detailed response to your comment.
General comment: This is a very interesting paper about the development of a nonlinear regression-based model using Steel Fibers to estimate the shear strength of deep RC beams. Significant work for the solution of this nonlinear problem is the estimation with numerical values of the influenced parameters using data from the literature. At the end of the paper the conclusions are very useful. My personal opinion is that the use of steel fibers should lead to its significant reduction of the shear reinforcement of Deep Beam and not to its complete absence, because as it is known also contributes to the tightening of the cross-section.
Response:
This is a very good comment. The goal of the current study is to determine whether it is possible to use SFRC deep beams without stirrups in place of the minimum shear reinforcement in RC deep beams. The study does not advise, however, that deep beams with stirrups be replaced with SFRC deep beams if the shear loads are greater than the minimum shear stresses. The sections “Introduction” and “Summary and Conclusions” are revised and updated to consider this point.
Detailed comments:
- Rearrange the captures of Table 1,4 in order to explain what exactly is included there.
Response:
Thank you for this comment. However, if we rearrange the captures of Tables 1 and 4, the manuscript will lack coherence in content since Table 4 depends on the contents of Table 3. Please let us know if further work should be addressed.
Note: the review report that we received only includes the previous comments, please let us know if further comments are needed. Thank you!
Reviewer 2 Report
The sustainability of steel fibers in deep reinforced concrete beams without stirrups is an important topic. Adding steel to concrete makes it difficult to evaluate shear strength and eventual failure. This creative works fills this important gap using non-linear regression base model. Their model provided better results than the literature models. The authors should be commanded for this outstanding work.
Author Response
Response to reviewer 2
The authors would like to thank the reviewer for his/her valuable comments and valuable feedback. The entire paper was updated to address your comment represented in the revised paper. For more details, please see below our detailed response to your comment.
Comment:
The sustainability of steel fibers in deep reinforced concrete beams without stirrups is an important topic. Adding steel to concrete makes it difficult to evaluate shear strength and eventual failure. This creative works fills this important gap using non-linear regression base model. Their model provided better results than the literature models. The authors should be commanded for this outstanding work.
Response:
Thank you for your valuable comment! No actions are needed.
Reviewer 3 Report
The manuscript deals with proposing a new model to predict the possibility of using steel fibers in reinforced concrete deep beams. The article contains everything needed to be published and only a couple of observations are mentioned from my behalf:
Title: ok
Abstract: ok and:
- line 25: please define “RMSE” abbreviation before using it.
Keywords: ok
Introduction: ok and:
- I am not sure that the references are well mentioned in the text (usually the mentioning is done by numbers in brackets: e.g.: [1]).
Shear strength models of SFRC deep beams: ok
Methodology: ok
Results and Discussions: ok
Summary and Conclusions: ok
Author Response
Response to reviewer 3
The authors would like to thank the reviewer for his/her valuable comments and valuable feedback. The entire paper was updated to address all comments represented in the revised paper. For more details, please see below our detailed response to comments.
The manuscript deals with proposing a new model to predict the possibility of using steel fibers in reinforced concrete deep beams. The article contains everything needed to be published and only a couple of observations are mentioned from my behalf:
Title: ok
Abstract: ok and:
- line 25: please define “RMSE” abbreviation before using it.
The definition of “RMSE” is added in line 25.
Keywords: ok
Introduction: ok and:
- I am not sure that the references are well mentioned in the text (usually the mentioning is done by numbers in brackets: e.g.: [1]).
Thank you for this valuable point. All in-text references are revised to comply with the guidelines of the journal of Sustainability.
Shear strength models of SFRC deep beams: ok
Methodology: ok
Results and Discussions: ok
Summary and Conclusions: ok
Reviewer 4 Report
Please further describe the main steps that you followed and the main outstanding outcomes in the abstract.
Please further elaborate on the novelty of your work in the abstract.
The present form of introduction is pretty modest. Please revise the latest related studies to your work. Accordingly, please include the research works in the last five years.
It is recommended to add a section “research significance” and highlight the main contribution of your findings.
Please explain the advantages of improving the mechanical properties of concrete in RC structures by including a short summary of the work titled Application of Machine Learning to Predict the Mechanical Characteristics of Concrete Containing Recycled Plastic-Based Materials.
Please further explain the failure criteria for the performed experiments.
Please elaborate on determining the steel fiber reinforced concrete using the article titled Application of Ultrasonic Measurements for the Evaluation of Steel Fiber Reinforced Concrete.
Please add a compelling discussion on the effect of key parameters that can affect the outcome of your study.
Please revise the conclusion and present a more condensed version including the major results of this research, limitations, and recommendations for future work.
Author Response
Response to reviewer 4
The authors would like to thank the reviewer for his/her valuable comments and valuable feedback. The entire paper was updated to address all comments represented in the revised paper. For more details, please see below our detailed response to comments.
Comment #1:
Please further describe the main steps that you followed and the main outstanding outcomes in the abstract.
Response:
The abstract is modified where the main steps we followed and the main outstanding outcomes in the abstract are described in lines 13 to 27.
Comment #2:
Please further elaborate on the novelty of your work in the abstract.
Response:
The abstract is revised and the novelty of this work in the abstract is described in lines 11 to 13; 19 to 21 and 25 to 27.
Comment #3:
The present form of introduction is pretty modest. Please revise the latest related studies to your work. Accordingly, please include the research works in the last five years.
Response:
The introduction section is modified, and additional up-to-date references are added. Please see lines from 31 to 94.
Comment #4:
It is recommended to add a section “research significance” and highlight the main contribution of your findings.
Response:
A new section of “research significance” is added in lines from 134 to 142:
“3. Research Significance
This study assembled databases of tested RC and SFRC specimens from the literature to assess the shear strength of SFRC deep beams without stirrups. A nonlinear regression-based model was created to evaluate the shear strength of SFRC deep beams for assisting structural engineers in using these beams. As compared to other models in the literature, the proposed SFRC shear strength model performed better and had a lower root-mean-square error. The findings of this research provide practitioners with a solid foundation for developing accurate and practical estimations of shear strength in SFRC deep beams without stirrups”.
Comment #5:
Please explain the advantages of improving the mechanical properties of concrete in RC structures by including a short summary of the work titled Application of Machine Learning to Predict the Mechanical Characteristics of Concrete Containing Recycled Plastic-Based Materials.
Response:
The advantages of improving the mechanical properties of concrete in RC structures are explained in lines from 31 to 38, references [1] and [2] are consulted for this purpose and are added to the list of references:
“Concrete, being a common construction material in the building business, has various limitations, such as a low resistance capability against tensile stresses. Concrete reinforcement fixes this vulnerability. One of these strengthening techniques involves using fibers with various steel or synthetic materials. Fiber reinforced concrete (FRC), a type of concrete reinforced with fibers, can provide better qualities than regular concrete. The fibers improve the energy absorbed during the fracture process by reducing the likelihood of cracking [1,2]. Moreover, the addition of fiber to precast concrete elements benefits the precast construction elements”.
[1] Dabiri, H.; Daneshvar, K.; Karakouzian, M.; Farhangi, V. Application of Machine Learning to Predict the Mechanical Characteristics of Concrete Containing Recycled Plastic-Based Materials. Appl. Sci. 2023, 13, 2033. https://doi.org/ 10.3390/app13042033
[2] Chao, S. H. 2020. “Size effect on ultimate shear strength of steel fiberreinforced concrete slender beams.” ACI Struct. J. 117 (1): 145–158. https://doi.org/10.14359/51718018.
Comment #6:
Please further explain the failure criteria for the performed experiments.
Response:
This is a very good comment. The compiled databases were carefully collected to make sure all specimens in the database failed in shear mode. This point is very important to build an accurate model to predict the shear strength of SFRC deep beams without stirrups.
Comment #7:
Please elaborate on determining the steel fiber reinforced concrete using the article titled Application of Ultrasonic Measurements for the Evaluation of Steel Fiber Reinforced Concrete.
Response:
A summary of the suggested article to evaluate SFRC is added in lines from 80 to 86. The reference [9] is added to the list of references.
“On cylinder and beam samples reinforced with varied steel fiber content percentages, an Ultrasonic-Pulse Velocity (UPV) was performed [9]. The findings indicate that 2% is the ideal steel fiber content for beam sections. When assessing how the fibers affect the strength of the FRC, the fiber orientation must be considered. With the inclusion of steel fibers, the amplitude of UPV reduces for cylindrical samples. Wave speed is inexorably influenced by the cure time. The maximum UPV is seen for cylindrical samples 90 days after cure”.
[9] Gebretsadik, B.; Jadidi, K.; Farhangi, V.; Karakouzian, M. Application of ultrasonic measurements for the evaluation of steel fiber reinforced concrete. Eng. Technol. Appl. Sci. Res. 2021, 11, 6662–6667. [CrossRef]
Comment #8:
Please add a compelling discussion on the effect of key parameters that can affect the outcome of your study.
A compelling discussion on the effect of key parameters on the SFRC deep beams without stirrups are added in lines from 279 to 299. Figure 8 is added to the discussion for illustration.
“5.2. Importance of key parameters
Figure 8 displays the outcomes of the feature importance research. The parameters of d, bw, a/d, ρw, lf/df, fcm, and Vf. are indicated as crucial variables. The shear strength of SFRC deep beams without stirrups is most significantly affected by the parameters d and bw, with significance values of 90% and 78%, respectively. This is because the shear strength is greatly influenced by the size of the beam. Additionally, the compression strength of the concrete and the ratio of steel reinforcement have approximately an important factor of 75%. This is because these two factors are extremely important in resisting the applied shear forces through the dowel action and compression zone contribution on the beam. The shear span-to-depth ratio, steel fiber volume ratio, and steel fiber length-to-diameter ratio all have lower significance values than the shear span-to-depth ratio (64%, 48%, and 43%, respectively), but the designer should still consider their contributions because doing so could make it more difficult to predict the shear strength. As a result, when developing the suggested regression-based model for this study, the contribution of these seven factors was considered.”
Figure 8. Features importance percentage of the key influencing parameters.
Comment #9:
Please revise the conclusion and present a more condensed version including the major results of this research, limitations, and recommendations for future work.
Response:
The conclusion section is modified to present the major results of this research, limitations, and recommendations for future work. Please see section “Summary and Conclusions” in lines from 330 to 374:
“Most modern codes still rely on regression-based models to forecast the shear strength of RC beams because of how intricate concrete's response to shear pressures is. However, since steel fibers enhance the SFRC beams' shear response, adding steel to concrete makes it more difficult to determine the shear strength and anticipate the mode of failure. To fill this gap, the experimental databases of RC and SFRC deep beams without stirrups that is currently available in the literature is used in this study to create a nonlinear regression-based model. The choice of features, data preprocessing, and model derivation were all explained. The model's performance was assessed and compared with other models that were found in the literature. The inferences that can be made are as follows:
- The longitudinal steel reinforcement significantly boosts shear strength of SFRC deep beams without stirrups. This can be justified as the steel fibers improve deep beams' capacity to carry loads by helping them bridge cracks.
- Even though the shear stresses are inversely related to the span-to-depth ratio, SFRC deep beams experience higher shear loads than RC deep beams because when the span-to-depth ratio of beams rises, the failure mode shifts from crushing of struts to diagonal shear failure.
- The results also showed that the concrete compressive strength and depth of beams have only a small impact on the performance of SFRC and RC beams, which is understandable given that the strut-and-tie model, which primarily relies on the concrete compressive strength, provides the most accurate simulation of the shear strength of deep beams.
- A survey was conducted to explore the input parameters of the available shear strength models in literatures, the investigation revealed the three variables , and are significant to quantify the shear strength contribution of steel reinforcement, concrete, and steel fibers ratio. Therefore, these three variables were utilized to build the proposed shear strength model for SFRC deep beams without stirrups.
- The proposed model outperformed the other equations in the literature since it was able to anticipate the shear strength of SFRC deep beams with the lowest RMSE (= 1.58) and lowest scatteredness, demonstrating the model's high accuracy.
- The shear stresses predictions using the proposed model revealed that the trendlines of a/d, , and versus the predicted shear stresses match the test results in terms of the average fitting line and the scatteredness of data. This demonstrates the suggested model's superior performance when considering various crucial factors that affect the shear strength of SFRC deep beams without stirrups.
The goal of the current study is to determine whether it is possible to use SFRC deep beams without stirrups in place of the minimum shear reinforcement in RC deep beams. The study does not advise, however, that deep beams with stirrups be replaced with SFRC deep beams if the shear loads are greater than the minimum shear stresses. This work is restricted to SFRC deep beams without stirrups; however, additional research is required for SFRC deep beams with stirrups because they have complex shear force transfer that must be quantified. Also, research into deep beams without stirrups reinforced with synthetic fibers is advised because these fibers play a crucial role in preventing corrosion on RC structures. Furthermore, advanced machine learning algorithms are advised to improve the prediction accuracy of shear strength.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 4 Report
N/A
