Experimental Investigation on the Response of Elliptical CFT Columns Subjected to Lateral Impact Loading

Round 1

Reviewer 1 Report

This is an interesting paper and the authors present an experimental investigation on the impact behavior of elliptical concrete-filled steel tubular (CFT) columns subjected to lateral loading. And the finite element model is established to evaluate the elliptical CFT column under impact load. Based on the reported findings, the paper can be a suitable publication for this journal with some minor concerns and recommendations.

1. The legend of Figure 5 e is incorrect.

2. The paper mentions the deformation of specimens. And the buckling of steel tube was not found. This is because the impact velocity is very low. Therefore, high impact velocity may cause the buckling of steel tube.

3.The impact velocities of 1.2-3.88m/s were selected in the paper. Is there any rational reason for this arrangement?

Author Response

Dear Reviewer,

My manuscript, Experimental investigation on the response of elliptical CFT columns subjected to lateral impact loading, was revised according to the your comments, and the itemized response to each comments is attached.

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present an experimental study on the response of elliptical concrete-filled steel tubular columns subjected to lateral loading. Various circular and elliptical columns are considered, with several impacts provided by a drop weight-driven test truck. The paper provides an interesting, novel, and important investigation into impacts with real-world consequences, though the discussions and modelling require some refinement prior to publication.

Major points:

1.     While this paper is largely well written, there are several points at which the incorrect use of grammar leads to the key points in the argument becoming unclear. These have been highlighted in yellow in the attached manuscript. These points should be clarified prior to publication to ensure any ambiguity is removed.

2.     The discussion provided in Section 3.2 should more closely align with the data presented in Figure 5, and should clearly refer to the various panels/sections of the figure to clarify the points of the discussion. For example, the authors state that “It can be observed that E-180-I has a lower plateau value than E-120-I.” However, this is not clear from Fig. 5, nor is it clarified exactly that the plateau value refers to. The authors should refine this discussion by clearly signposting the sections of Fig. 5 that are relevant to each discussion point.

3.     Fig. 5 should be update to visually specify the exact time window of each of the three phases. This would also help with the clarifications outlined in Point 2.

4.     As in Point 2, the discussion in Section 3.3 should more explicitly refer to Figs. 7 and 8.

5.     In Figs. 7e and 8e, the 3.5 m/s Impact 05 data does not seem to have been plotted.

6.     In Section 4.1, the authors state they used ABAQUS Explicit, rather than Implicit. The authors should clarify why this decision was made and the steps taken to ensure the results were physically meaningful.

7.     The results in Section 4.2 (Figs. 12 and 13) require further consideration and discussion. The authors state that “It can be found that good agreement is obtained for the second phase of impact load time history and the impact displacement time history between both results,” but this is not immediately clear from the figures and should be clarified; in particular, the phases of impact load time are not labelled, nor are the meanings of the colours, so it is difficult to draw conclusions of this nature. In Fig. 12b, there is little to no agreement between the predictions and experimental results, which would suggest that there is some degree of inaccuracy in the modelling approach – this panel contradicts the authors’ statement that “the FEA model can be used to predict the elliptical CFT columns under lateral loading.”

8.     Similarly, in both panels of Fig. 13, the predicted and experimental results diverge after the initial 0.4 s period – the authors need to explain in greater detail why this might be and, if possible, what steps could be taken to improve the accuracy for the later time period.

9.     The four phases outlined in Section 4.3 are very comprehensive, but it should be more explicitly clarified whether these four steps correspond to the four panels in Figs. 14 and 15.

10.  Point 5 of the Conclusions only holds true if the points above are properly clarified. The four stages should be briefly outlined here to give the reader more information than the fact that there were four stages observed.

Minor points:

1.     In Fig. 2a, the sketch is a little misleading/confusing. To the external reader, it appears that, when the drop weight is released, the wires will drag the test truck away from the specimen, rather than towards it. The authors should clarify whether or not the case and could improve the interpretability of the figure by adding directional arrows.

2.     In Fig. 6, the key refers to specimen ‘C-18-I’, whereas this should be ‘C-180-I’.

3.     The discussion around Fig. 6 (top of page 8) could be expanded to suggest reasons for why specimen E-120-I exhibited a lower peak impact load than the other specimens.

4.     On line 243, it might help to explicitly state which figure corresponds to which point.

5.     On line 267, the authors refer to Fig. 10 b, whereas it should refer to Fig. 9b.

6.     The units on line 271 should read s^-1, rather than s-1.

7.     On line 333, the authors should correct the word ‘stain’ to ‘strain’.

Author Response

Dear Reviewer,

My manuscript, Experimental investigation on the response of elliptical CFT columns subjected to lateral impact loading, was revised according to the your comments, and the itemized response to each comments is attached.

Please see the attachment.

Author Response File: Author Response.pdf