FRP Bridges in the Flanders Region: Experiences from the C-Bridge Project
Round 1
Reviewer 1 Report
Interesting article (project report) in the field of modern solutions in the use of modern composite materials for bridges. Particularly interesting is the discussion of criteria for composite bridges (parts 3 and 4), where individual criteria were identified and the main problems identified. There are no references to the source texts in these chapters. Moreover, when referring to individual stages, the authors use general phrases, omitting the most important details. I understand that the text is a summary of extensive work and the availability of detailed results, but note that the project website is not in English. Also some of the results are published in languages other than English.
As a result, this summary of the project should be (in my opinion) extended not only with the most important information, but also with important details influencing the recommendations presented. In my opinion, it would by vary valuable for the reader.
For example:
Line: 274 ”critical moments - have these areas been identified? If not, this paragraph adds nothing to the text.
Line 278: "Current guidelines for the design of composite structures" - which specifically? Those available on website or maybe other standards.
Line 297-298: During the life of the structure, various non-destructive techniques (NDT) are available to inspect the FRP structures for both superficial and internal damage. What specifically. It is worth recalling the norms related to ..
Detailed Notes: Figure 1. FRP bridges in Flanders from 2010 to the present (Mid 2020) .- better: from 2010 to 2020
Author Response
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Thank you for the kind words regarding the content of the paper and we are pleased that the project results of the C-Bridge project can contribute to the current international literature. We have read your comments with care and attention and adapted these appropriately, which helped us improve this manuscript. 1. The critical moments during the production were further described in detail, the text was modified with the following parts: Line 301-304: Before the production of the bridge deck, a detailed manufacturing plan must be drawn up including production records of, among other things, the fibres (type, directions, construction), the resins (recipe, mixing ratio, preparation) and the production method (environmental conditions, manufacturer's instructions). Line 306-309: … critical moments where an independent or external party is required to perform an audit such as a visual check of the arrangement and orientation of the fibre layers before infusion and a check of a complete infusion of the bridge deck after demoulding. 2. A reference to the document ‘Prospect for New Guidance in the Design of FRP Structures’ 2016 published by Publications Office of the European Union was added to indicate the specific guideline used in the text for the material testing. 3. The most commonly used NDTs in composite bridges have been added in the text together with two guideline documents. The text in the manuscript is as follows: Line 332-336: The following NDTs can be found in the CIRIA document C779 [24] and NCHRP report 564 [43]: visual inspection, acoustic impact testing (including hammer tap test), thermography, shearography, ultrasonic inspection, radiography, acoustic emission, modal parameter method and load testing. 4. The caption under Figure 1 was adjusted in response to the reviewer's comment. Line 76: Figure 1. FRP bridges in Flanders from 2010 to 2020. |
Reviewer 2 Report
This article is about the FRP bridge project. These topics are very relevant from an ecological and economic point of view. FRP composites exhibit a lot of durability and have a reclusively low carbon footprint.
The article is very valuable and prepared with care, which can be seen especially in the detailed and very clear description of the graphs.
The introduction provide background and include relevant references.
All methods are described adequately. The exception is the statistical methods used. Results are present clearly. However, in an English-language journal, when presenting results, it would be appropriate to use '.' rather than ',' when presenting numbers.
Apart from a minor editorial remark, and I find the article very valuable and suitable for publication.
Author Response
Thank you very much for agreeing with us to the intention of this manuscript. We have read your comment and agree that in an English-language journal it is more appropriate to use ‘.’ as decimal separator in presenting the results. This detail was overlooked when adopting the results. Thanks for pointing this out. The decimal point has now been used throughout the manuscript.
Reviewer 3 Report
The subject of the study is bridges construction with fibre reinforcement polymers. The work has an in-depth description of the subject of discussion along with physical buildings located in Europe. The description introduces the recipient to the analyzed issue and allows you to understand the presented conclusions. The subject of the research is described quite extensively, moreover, supported by relevant graphics, it forms a whole, thoroughly explaining the investigated models. The obtained conclusions are presented in a logical and coherent manner for the reader. However, some parts of the proposed manuscript need improvement:
- - The legend in Figure 2 a and b should be enlarged as it is currently unreadable
- - The font of the axes and the legend in Figure 4 should be enlarged to text level for better clarity
Author Response
We are pleased with your positive response to our manuscript and are appreciative with the way you have rated it. Thank you for your comments. As suggested by the reviewer, we have enlarged the font size of the legend and the annotation in Figure 2 a and b as well as in Figure 4 in which the visibility of the lines and markers was also improved for better clarity.
Reviewer 4 Report
This project report documents valuable information regarding the construction of composite bridges, which may help address the lack of standards at the Belgian or European level for the design of such constructions. The report is well-written and easy to follow.
Author Response
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Thank you for the positive feedback. We are glad that you enjoyed our paper and that you can clearly deduce the purpose and results of the C-Bridge project. |
Reviewer 5 Report
Dear Authors, good evening.
Congratulations by the work.
Author Response
We appreciate the time and effort that the reviewers dedicated to reading our paper carefully and precisely. We are grateful for the positive feedback by the reviewer and glad that he enjoyed reading the paper.
Reviewer 6 Report
The reviewer appreciates the work done by the authors. The technical contents of the "Project Report" are in general interesting. In the reviewer’s opinion, the goal of the work must be better explained within Abstract, Introduction and Background, and Conclusions. Moreover, the publication in the “Applied Sciences, MDPI” is not recommended unless the following suggestions are taken into account within the text:
1) Please, polish the Abstract. Please, add sentences to explain the meaning, the main points, the improvement and the promising “C-Bridge project”. The logic should also be improved.
2) It is important to describe the current progress, problems and improvements to be further studied in the Introduction and Background. Please, highlight the creative contributions. A general description on the existing problems should be noted. Please, check the structure and logic of the Introduction and Background.
3) Introduction and Background. The advantages of FRP bridges with respect to the prestressed concrete ones are that they do not show serious problems during their service life related to the rheological behavior of concrete as, e.g., carbonation phenomena, corrosion along steel rebars and tendons, significant cracking and excessive deflections due to prestress losses, shrinkage and creep of concrete. Please, refer to the aforementioned issues, and cite the following references:
- Damage detection in a post tensioned concrete beam – Experimental investigation. Engineering Structures 128 (2016) 15–25.
- Prestress loss diagnostics in pre-tensioned concrete structures with corrosive cracking. Journal of Structural Engineering 146 (3) (2020) 04020013.
- Experimental–theoretical investigation of the short-term vibration response of uncracked prestressed concrete members under long-age conditions. Structures 35 (2022) 260–273.
4) The further work, related to the “C-Bridge project”, should be mentioned at the end of the "Project Report".
5) A general check of English grammar, punctuation, spelling, verb usage, sentence structure, conciseness, readability and writing style is suggested.
Author Response
We appreciate the time and effort of the reviewers dedicated to providing feedback on our manuscript and are grateful for the insightful comments on and valuable improvements to our paper.
We have gone through your comments carefully and tried our best to address them one by one. We hope the manuscript has been improved accordingly.
- As suggested by the reviewer, we polished the abstract to explain the meaning, the main points, the improvement/results and the promising of C-Bridge project. The revised text reads as follows:
Line 18-20: This knowledge consists of a current state of the art of composites in bridge construction, selection criteria for composite bridges, recommendations for specification texts and in situ testing of composite bridges and structural and vibration analysis.
Line 24-35: The results of the project enable Flemish clients to draw up specifications for FRP bridges in a correct way. Moreover, they can correctly interpret the calculation notes made available and make a correct assessment. The Flemish engineering firms on the other hand will be able to make their own designs of FRP bridges and bridge components. They can also build up a value chain within Flanders with Flemish contractors and producers. From the producers and suppliers point of view, the results of the project will lead to a clearer profile of their products on the public and private market. Finally, the general contractors and constructors will be armed to withstand the challenges that FRP bridges entail to subcontractors in terms of execution, follow-up, delivery and maintenance. The findings are helpful for the acceptance of fibre reinforced composite bridges as an alternative to timber, steel or concrete bridges and should generate a market expansion for FRP in the traditionally conservative bridge building sector, in the first place in Flanders but also internationally.
- We agree with the reviewer and accordingly incorporated the reviewer’s suggestion in the manuscript by highlighting the general existing problems before the start of the C-Bridge project. We illustrated the lack of knowledge about composite bridges in Flanders by the following addition to the manuscript.
Line 61-68: The few bridges that were built in Flanders at the start of the project were also fully outsourced to Dutch companies that were both responsible for the design and construction of these bridges, so that no experience is built up within the Flemish market. The few cases before 2018 in Flanders have therefore not led to a dissemination of knowledge in Flanders with regard to dimensioning, deformation and vibration behaviour, etc. A guarantee of durability that is given purely by the designer/manufacturer is indeed correct and permitted [18]–[21], but at the beginning of the C-Bridge project there was still too little confidence for the (potential) owners.
- We think this is an excellent suggestion. We have included your proposition of adding prestressed concrete in the ‘Introduction and background’ of our paper including the proposed papers, as this materials is currently widely used in the bridge building world for the construction of different types of bridges. We revised this part as follows:
Line 42-46: Besides, FRP bridges show fewer maintenance problems related to the rheological behaviour during their service life than, for example, prestressed concrete, where e.g., carbonation phenomena, corrosion along steel rebar and tendons, significant cracking and excessive deflections due to prestress losses, shrinkage and creep of concrete can occur [1]–[3].
- We agree with the reviewer’s assessment. Accordingly, we have revised the conclusion part of the paper by adding and emphasizing the current challenges that still remain concerning GFRP materials for bridge construction. For this we have added the following to the conclusion.
Line 651-669: However, this C-Bridge project has not yet eliminated all uncertainties about composite bridges and extensive additional research will be necessary. At the moment, for example, little information is available regarding the vibration behaviour and the human-structure interaction of GFRP bridges. Secondly, combination with other (environmentally friendly) alternatives such as flax and jute fibres are currently unknown and seen with a certain degree of suspicion by many partners in the procedure for tendering bridge projects. However, these environmentally friendly alternatives show great added value, especially when considering the production of the fibres compared to the currently used materials. Furthermore, the connection of composite bridge segments for the assembly of larger spans by, for example, bolted and/or adhesive connections, is currently rarely applied due to the challenges that still exist. Lastly, the long-term perspectives and especially the end of life of this type of bridges are still uncertain.
Besides these current uncertainties at the time of publication, the C-bridge has nevertheless led to a broadening and dissemination of important knowledge in the Flemish construction community regarding composite bridges and has significantly lowered the bar for the use of composite materials in bridge projects, as can be seen in the increasing number of composite bridges built in Flanders in recent years.
We went through the entire manuscript to eliminate grammatical, punctuation, spelling, verb usage, sentence structure, conciseness, readability and writing style mistakes.
Round 2
Reviewer 6 Report
The authors carried out the required revisions.
