Analysis of the Seismic Performance of Rectangular Recycled Aggregate Concrete Columns with Different Parameters
, Chengxiang Xu 1,5, Yide Zhu 1, Jie Sun 1,5, Siyu Luo 1, Nianchun Deng 3,4,*, Li He 7, Yunfei Han 8 and Cai Wu 9Round 1
Reviewer 1 Report
The authors present a collection of results from previous experimental campaigns reported in literature on the seismic behavior of recycled aggregate concrete columns. Aim of the paper should be to analyze the influence of relevant parameters on the seismic performance. However, no sensitivity analysis has been carried out, and statistical methods as declared in the introduction were instead not applied. Results are just reported and illustrated in Section 3. Therefore, the novelty and the significance of the study should be highlighted, which cannot be only a collection of previous results.
A discussion section should be also added, considering for example theoretical models, and comparing the experimental results with the expected/predicted behavior of the columns.
The conclusions should be revised, how can you provide such precise concluding remarks with only few available data. For example, how can you conclude that “the optimal longitudinal reinforcement rate for seismic design of rectangular recycled aggregate concrete columns is recommended to be 1.59%”? Only data for three reinforcement ratios are provided and illustrated in Figure 2 and 3, is thus impossible to fit any model and draw general conclusions.
Some further comments:
- - Eq. (3) is not correct for the slenderness ratio;
- - Table 1 collects the result of the previous experimental campaign, however it would be helpful to add in the text a description of the performed tests.
The text of the manuscript should be also revised in deep, a lot of grammatical and semantic errors are present.
Authors list in the paper is also different from that in the MDPI portal (where only three authors are present).
The text of the manuscript should be also revised in deep, a lot of grammatical and semantic errors are present.
Author Response
Response to Reviewer 1:
Q1: No sensitivity analysis has been carried out.
Response: We are sorry for our mistake. We have added the content part of the sensitivity analysis in Section 3.2 of the paper to study the sensitivity of the seismic performance of different parameters to highlight the novelty and importance of the study. All the newly added sentences are shown as follows in blue font.
The study above makes it clear that when various parameters are changed, the sensitivity to structural bearing capacity and seismic performance differs. The average growth rate of structural bearing capacity is 21.85%, which has the highest sensitivity when the longitudinal reinforcement rate increases. Additionally, when longitudinal reinforcement rates rise, the average growth rate of structural carrying capacity falls from 24.2% to 19.5%, indicating a gradual loss of sensitivity. The average reduction rate of structural carrying capacity is 19.9%, and the sensitivity is rather high when the slenderness ratio and shear span ratio rise. Additionally, the average loss in structural carrying capacity with an increase in the slenderness ratio and shear span ratio first rises from 10.1% to 25.3% and then falls to 24.2%, demonstrating that the sensitivity initially improves and then drops. When the concrete strength grade increases, the average growth rate of structural bearing capacity is 16.3%, and the sensitivity is relatively high. And with the increasing concrete strength grade, the average growth rate of structural bearing capacity decreases from 19.1% to 13.5%, which indicates that the sensitivity gradually declines. When the axial compression ratio improves, the average enhancement rate of structural bearing capacity is 15.5%, which is less sensitive. And with the increase in axial compression ratio, the average growth rate of structural bearing capacity decreases from 18% to 12.5% and then increases to 16.1%, meaning that the sensitivity diminishes first and then increases. The average change rate of structural bearing capacity is 12.9% when the hoop reinforcement rate rises, and sensitivity decreases. Furthermore, as the hoop rate rises, the structural bearing capacity's average growth rate shifts from 17.4% to an average reduction rate of 8.4%, suggesting that the sensitivity steadily declines. When the recycled coarse aggregate replacement rate increases, the average improvement rate of structural bearing capacity is 7.35%, and the sensitivity is the lowest. In addition, as the replacement rate rises, the average growth rate of structural bearing capacity first falls from 18.5% to 2.5% before gradually rising to 2.9% and 5.5%, indicating a first decrease and then an increase in sensitivity.
Q2: Statistical methods as declared in the introduction were not applied and it would be helpful to add in the text a description of the performed tests.
Response: Thanks for the reviewer’s constructive suggestion. As suggested by the reviewer, we have added Section 2.4 Test Description to the paper to elaborate on the seven sets of tests included in this study, each of which uses the single-variable method to control for consistent values of parameters other than one of the variables under study to investigate the effect of different parameters on the seismic performance of rectangular recycled aggregate concrete columns. All the newly added sentences are shown as follows in blue font.
In this study, the single variable method is used to separately examine the effects of the recycled coarse aggregate replacement ratio, axial compression ratio, slenderness ratio, shear span ratio, hoop reinforcement rate, longitudinal reinforcement rate, and recycled aggregate concrete strength grade on the seismic performance of rectangular recycled aggregate concrete columns. The CTFM7.5C[8], C2, C3, C4 and C5[16] test samples are used to evaluate the recycled coarse aggregate replacement ratio, all other test variables are the same for each specimen other than the various recycled coarse aggregate replacement ratios. C3-4-C30-0, C3-4-C30-0.2, C3-4-C30-0.4 and C3-4-C30-0.6[9] test samples are used to evaluate the influence of axial compression ratio, and all test factors are the same for each specimen aside from the varying axial compression ratios. When studying the effect of shear span ratio, the test specimens are SRRC1, SRRC2, SRRC3[17], SRRC4, SRRC8, SRRC10 and SRRC13[11], and all test variables are the same except for the shear span ratio. To examine the impact of hoop reinforcement rate, the test samples are SRRC9, SRRC10[17], SRRC13, SRRC16 and SRRC17[11], and all the test variables are identical outside the various hoop reinforcement rates. For the study of the slenderness ratio, the test samples are SRRC1, SRRC2, SRRC3[17], SRRC4, SRRC8, SRRC10 and SRRC13[11], and all the test variables are the same except for the different slenderness ratios. The test samples used to evaluate the longitudinal reinforcement rate are RC1, RC6 and RC7[20], and all test variables are identical for each specimen with the exception of the longitudinal reinforcement rate. To study the effect of recycled aggregate concrete strength grade, the test samples are C5-4-C30-0.4, C5-4-C40-0.4 and C5-4-C50-0.4[9], and all test variables are the same for each specimen except for the recycled aggregate concrete strength grade.
Q3: A discussion section should be also added, considering for example theoretical models, and comparing the experimental results with the expected/predicted behavior of the columns.
Response: It was modified.
Q4: The conclusions should be revised, how can you conclude that “the optimal longitudinal reinforcement rate for seismic design of rectangular recycled aggregate concrete columns is recommended to be 1.59%”?
Response: We are sorry for our mistake. We have revised the conclusions related to the hoop rate and longitudinal reinforcement rate in the article to make them more rigorous. The related sentences are shown as follows in blue font.
(2) As the longitudinal reinforcement rate increases, the bearing capacity of the specimen also increases, while the ductility performance exhibits an initial improvement followed by a subsequent reduction. The optimal longitudinal reinforcement rate for seismic design of rectangular recycled aggregate concrete columns is recommended to be around 1.59%.
(3) As the hoop reinforcement rate enhances, the ductility performance of the specimen also improves, while the bearing capacity exhibits an initial increase followed by a subsequent decrease. The best hoop reinforcement rate for seismic design of rectangular recycled aggregate concrete columns is recommended to be 1.36% or so.
Q5: Eq. (3) is not correct for the slenderness ratio.
Response: It was modified.
Q6: The text of the manuscript should be also revised in deep, a lot of grammatical and semantic errors are present.
Response: We are sorry for our mistake. We have made corrections and proofread the revised manuscript with the help of a native English speaker. We have done our best to make sure that there are no similar mistakes.
Q7: Authors list in the paper is also different from that in the MDPI portal (where only three authors are present).
Response: It was modified.
Reviewer 2 Report
Please provide more details about Table 1.
Please provide more concluding results.
Author Response
Response to Reviewer 2:
Q1: Please provide more details about Table 1.
Response: It was modified.
Q2: Please provide more concluding results.
Response: Thanks for the reviewer’s constructive suggestion. As suggested by the reviewer, we have added the corresponding concluding results in Chapter 3.1 and Chapter 4. of the article, respectively. The related sentences are shown as follows in blue font.
From the aforementioned analysis, it is initially concluded that as the recycled coarse aggregate replacement ratio rises, the structure's seismic and ductility performance are negatively correlated and both decline, with the replacement rate of 0–30% providing the structure's best overall seismic performance. Likewise, the total seismic resistance of the structure is at its highest when the concrete strength grade is between C40 and C50 since the seismic and ductility performance of the structure are positively associated and both of them continue to improve as the concrete strength grade improves. As the hoop reinforcement rate rises, the structure's seismic performance is first strengthened and then decreased, so the structure's seismic resistance is greatest when the hoop reinforcement rate is close to 1.36%. Similarly, when the longitudinal reinforcement rate keeps increasing, the ductility performance of the structure first increases and then decreases, so when the longitudinal reinforcement rate is around 1.59%, it has the strongest seismic capacity.
(3) As the hoop reinforcement rate enhances, the ductility performance of the specimen also improves, while the bearing capacity exhibits an initial increase followed by a subsequent decrease. The best hoop reinforcement rate for seismic design of rectangular recycled aggregate concrete columns is recommended to be 1.36% or so.
(4) The sensitivity of different parameters to the seismic performance of the structure varies. The sensitivity of longitudinal reinforcement rate, slenderness ratio, shear span ratio, concrete strength grade, and axial compression ratio is stronger, while the sensitivity of hoop reinforcement rate and recycled coarse aggregate replacement rate is poor. To attain the best performance of the structure, engineers must take economic rationality into account and alter the fewest factors. Therefore, it is recommended to change the longitudinal reinforcement rate, slenderness ratio, shear span ratio, concrete strength grade, and axial compression ratio of the specimen to improve the seismic performance of the structure.
Reviewer 3 Report
This work is important for the domain since it deals with manipulating a large quantity of data related to the performance of rectangular concrete columns containing recycled aggregate. All chapters are well addressed and I suggest publication as is, except for minor spelling checks and punctuation and the suggestion made for the Conclusion chapter.
Title: ok
Abstract: ok
Keywords: ok
Introduction: ok
Experimental data collection: ok
Parameters analysis: ok
Conclusion: ok and:
- some future research plans could be included here.
This work is important for the domain since it deals with manipulating a large quantity of data related to the performance of rectangular concrete columns containing recycled aggregate. All chapters are well addressed and I suggest publication as is, except for minor spelling checks and punctuation and the suggestion made for the Conclusion chapter.
Title: ok
Abstract: ok
Keywords: ok
Introduction: ok
Experimental data collection: ok
Parameters analysis: ok
Conclusion: ok and:
- some future research plans could be included here.
Author Response
Response to Reviewer 3:
Q1: Minor spelling checks and punctuation and the suggestion made for the Conclusion chapter - some future research plans could be included here.
Response: Thanks for the reviewer’s constructive suggestion. As suggested by the reviewer, we have made corrections and proofread the revised manuscript with the help of a native English speaker. We have done our best to make sure that there are no similar mistakes. In addition, we have added future research plans in the Conclusion chapter. The related sentences are shown as follows in blue font.
(6) This study has reviewed and collected a large amount of data from the literature, and the conclusions are more effective, but there are still certain aspects to be improved. For instance, when the hoop reinforcement rate is around 1.36% and the longitudinal reinforcement rate is about 1.59%, the data and the seismic performance of the structure need to be supplemented and further studied. In addition, the scope of the parameters needs to be widened to make the conclusions more general. The aforementioned will be added and improved in future research.
