Seismic Fragility Curves of RC Buildings Subjected to Aging
, Olga Markogiannaki 2 and Michalis Fragiadakis 1,*Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The submitted manuscript presents the fragility curves for a four-storey RC building subjected to ageing. The building is designed based on Eurocodes 2 and 8. The topic is very interesting and the manuscript presented a good review of corrosion and previous studies. However, the main body of the research needs further clarification as follows:
1- The design of the building and the documentation provided is very limited and rudimentary. Please indicate what location in Europe is selected for the site, have you considered the national annexes if needed? Is the building designed for a specific site condition and design spectrum based on EC8? How are the checks for the inter-storey drift ratios based on EC8? How much is the dead load and live load for the slabs? Which software is used to design the frame (2D or 3D)? The design section of the manuscript needs significant improvement.
2- The pushover curve presented in Figure 2 a is not realistic. Is this the pushover from the OpenSees model? It is too ideal and does not represent the softening behaviour which is from an FE model built by using the Fibre Model.
3- Present the pushover result from pristine, and corroded models. Also indicate clearly that 0.1 and 2 correspond to what percentage of corrosion and year
Comments on the Quality of English Languageminor editing is needed.
Author Response
please see document attached
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors GENERAL COMMENT: The paper discusses the seismic fragility and the risk assessment of RC structures, giving emphasis on the effect of corrosion due to concrete ageing and the associated deterioration mechanisms. As a case study, a four-storey RC building designed to contemporary code provisions is examined. The investigation encompasses the derivation of fragility curves considering critical parameters such as the corrosion rate, the initiation time, and the cover depth. The proposed approach allows the evaluation and the quantification of the impact of corrosion mechanisms on building seismic performance. Although the submitted paper falls within the scope of the 'GeoHazards' journal, it is recommended that a significant revision be made to enhance the clarity of certain crucial aspects that are essential for publication. See detailed comments below: In section 6.1 “Four-Storey RC Building under Corrosion”, the authors performed a modal analysis to evaluate the fundamental period of vibration of the numerical model. The authors state that: It is mentioned that for the corroded cases the fundamental period is always different, and larger since the structure becomes more flexible. From results provided in section 6.2, it is not clear the role played by the changes in the fundamental period of vibration of the considered model. Moreover, how the changes in fundamental period of vibration have been evaluated. Are consistent with variations described in the existing scientific literature? As example, Ditommaso et al. 2021 (Ditommaso R, Iacovino C, Auletta G, Parolai S, Ponzo FC. Damage Detection and Localization on Real Structures Subjected to Strong Motion Earthquakes Using the Curvature Evolution Method: The Navelli (Italy) Case Study. Applied Sciences. 2021; 11(14):6496.), evaluate the changes in dynamic characteristics of numerical models and a real structure subjected to structural damage, and Cataldo et al. 2023 (Cataldo A, Roselli I, Fioriti V, Saitta F, Colucci A, Tatì A, Ponzo FC, Ditommaso R, Mennuti C, Marzani A. Advanced Video-Based Processing for Low-Cost Damage Assessment of Buildings under Seismic Loading in Shaking Table Tests. Sensors. 2023; 23(11):5303.), evaluate the variations of the fundamental period of vibration of a scaled structured tested on a shaking table and progressively damaged. Please provide a better description of the role played by the changes of the dynamic characteristics of the numerical model on the seismic fragility curves evaluation. Please revise the paper and its conclusion based on the feedback provided by the reviewer.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsIn view of the objectives outlined in this research, the great interest in the subject matter of the paper (seismic fragility and risk assessment of deteriorated RC buildings, focusing on corrosion due to concrete aging) can be stated. Overall, the methodological strategy exposed is suitable to the objectives proposed in the paper.
The results and conclusions about the complexity of quantifying aging impact on RC structures are interesting in several aspects: (i) the most significant parameter that affects the corrosion initiation is the cover depth (structural factor); (ii) the corrosion rate affects the area of the rebar during the propagation phase of chloride-induced corrosion (environmental factor); and (iii) despite the complex task carried out, this research can be considered to be an attempt to quantify the effect of aging on a probabilistic level.
However, since the ageing in reinforced concrete structures can lead to corrosion, impacting durability and seismic fragility, some reference on the seismic vulnerability of these structures should be included in Section 1 “Introduction” to address the related problems of assessing seismic vulnerability in reinforced concrete buildings using damage data from actual earthquakes. If the suggestion is allowed, a recent reference that may be useful for this purpose is: Tomás, A.; Ródenas, J.L.; García-Ayllón, S. (2017). Proposal for new values of behavior modifiers for seismic vulnerability evaluation of reinforced concrete buildings applied to Lorca (Spain) using damage data from the 2011 earthquake. Bulletin of Earthquake Engineering, 15(9): 3943- 3962. DOI: 10.1007/s10518-017-0100-3
The formal characteristics of the paper are suitable, both in the section structure adopted as in the presentation of text, tables and figures. The list of references includes a sufficient number of up-to-date articles, including at least 7 established journal papers in the latest 10 years to reflect the current state-of-technology (not considering technical codes nor the authors’ own nor user guides). However, the reference suggested above may be useful to extend, improve and complete the state of art of the research proposed in the paper.
Author Response
please see document attached
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe paper “Seismic Fragility Curves of RC Buildings Subjected to Ageing” reports an interesting research work about the evaluation of the seismic performance of existing RC structures subjected to corrosion effects considering as case study a four-storey RC building. The topic of the manuscript is current and of interest both scientific community and designers and in general, the paper appears well-written and well-organized in its different Sections. Furthermore, the results obtained are clearly discussed in Section 6.2. For these reasons, it is opinion of this reviewer that the manuscript can be considered for publication in GeoHazards after the following minor improvements:
- Section 6.1: the case study should be described in more detail, adding the main general dimensions and Figures representing plans, etc.
- Clarify if the corrosion effects, expressed in terms of steel reinforcement area reduction, are considered equal for all the rebars present in the considered structural element.
- Has a different icor value been considered for the external and internal columns?
- Have the possible brittle collapse mechanisms (shear failure) of the columns also been considered?
- lines 43-45 consider as reported in recent research works 10.1016/j.istruc.2022.11.135 and 10.1016/j.engfailanal.2022.106546 for the influence of corrosion effects due to carbonation on the structural performance of existing RC structures.
Comments on the Quality of English LanguageThe paper appears well-written. Only minor editing of English is suggested
Author Response
please see document attached
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have adequately addressed the comments. I would recommend the manuscript be published in GeoHazards.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe revised version of the paper has been improved based on the reviewer's comments. It is recommended that the paper be published in GeoHazards journal in its current form.
