P-Delta Effects on Nonlinear Seismic Behavior of Steel Moment-Resisting Frame Structures Subjected to Near-Fault and Far-Fault Ground Motions
Round 1
Reviewer 1 Report
Brief summary
The research presented in this paper describes a comparison of P-Delta influence on the seismic behaviour of steel moment-resisting frame structures. The Authors subdivided the seismic input into near-fault and far-fault ground motions. Three different case studies have been considered, while three near- and far-fault ground motions have been selected and scaled (for three different peak-ground acceleration values). Then, nonlinear time-history analyses have been performed, comparing peak interstorey drift ratio, interstorey shear forces and components response. The Authors concluded that the structures response, comparing the near- and far-fault ground motions, is significantly different; moreover, the P-Delta effects should not be ignored to obtain accurate outcomes.
Broad comments
The topic of the study is interesting and worthy of investigation. The paper is generally well-written and well-organised.
However, it is hardly possible to draw general conclusions due to the very limited number of frames and ground motions. The Reviewer strongly suggests increasing, at least, the ground motions.
In addition, regarding the section dedicated to the description of the case studies, it should be noted that a sufficient description of the numerical models is entirely missing. What kind of formulation has been adopted to simulate the p-delta effects? How have been discretised the elements of the models? Are Authors using a fibre-sections approach? For readers, it is impossible to replicate the models herein proposed. Moreover, for what can be understood, the numerical models are very simple (two-dimensional), while nowadays, more accurate ones can be developed.
Due to these shortcomings, the Reviewer does not suggest considering the paper for publishing in this present form.
Specific comments
Page 5. Check the word “molded”.
Page 5. Please describe what the B22 element is.
Page 7. In the paragraph that starts with “Furthermore, This involves the assumption….” Some words are missing, probably some Greek letters. Correct also the capital letter in “This”.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
A comparison of P-Delta effects on the nonlinear seismic behavior of the steel moment-resisting frame structures subjected to near-fault and far-fault ground motions are shown. The author / authors analyzed the problem numerically on the examples of multi-storey steel frames. The analysis was performed on the basis of data taken from several stations recording earthquake vibrations. The performed analysis allowed for the quantification of the P-Delta effect.
The paper shows that P-Delta effects should not be neglected for low, middle, and high-rise buildings as long as the structure will be subjected to near-fault ground motions, even if the earthquake intensity is not strong.
Detailed conclusions have some practical application, but require verification on models or structures.
Due to the high significance of content, this paper should be published.
Notes: Paper requires editorial corrections in accordance with mdpi standards.
Author Response
Please see the attachment. The response is in the Reviewer#2.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript covers an interesting topic that is nowadays largerly considered. The authors have provided thorough review of the current state of the researched topic and point out the missing research topic that is covered with thins manuscript. The manuscript influence of P-Delta effects on the behaviour of moment resisting frames that are subjected either to near- or far-fault ground motion records. Although the results are obtained only on 6 ground records they show that the P-Delta effects should be considered for any height of MRF and all earthquake intenisities when such structures are subjected to near- and far-fault ground motions. However, the P-Delta effects would mostly be more prominent for near-fault gorund motions.
The manuscript is written quite well and is more or less easy to follow, however, some sentences need to be revised to be more clear and English needs some improvement in few places.
General coments
-according to figure 9. of the manuscript it seems that P-Delta effects should be included for all three types of buildings, for all earthquake intensities and for both, near- and far-fault ground motion records. EC 1998-1 in 4.4.2.2(2) requires consideration of P-Delta effects for some conditions. How do these structures compare to these conditions for various intenisites of earthquakes and near- and far-fault ground motions? Maybe this should also be included in the manuscript. Although the reference here is made to EC I would assume that AISC has also similar condition checks.
Specific comments are given in the attachement.
Comments for author File: Comments.pdf
Author Response
Please see the attachment. The response is in the Reviewer#3.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
It is not clear to the Reviewer how only three ground motions from each group could be representative enough. However, 50 ground motions are sufficient and the paper can be accepted for publication. The Reviewer strongly suggests submitting the entire work without any omission for future studies. Although three ground motions could seem sufficient at first glance, a higher number is necessary to increase the obtained results' trustability, stability, and robustness.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Please find all the comments in the cover letter that is attached.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
Thank you for your corrections, now the work makes sense. The manuscript is, in my opinion, ready for publishing.
