Retrofitting of a Multi-Span Simply Supported Bridge into a Semi-Integral Bridge

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

The authors have effectively addressed the previous comments from this reviewer. They have added a section to the paper containing the details of the structural analysis and the calculations that the retrofitting strategy was based on. They have enhanced the discussion and highlighted the potential wider impact of their work. In this reviewer's opinion, these additions have improved the overall quality of the paper to an extent that it can be accepted for publication.

 

Some small issues that were noticed during the review: 

On line 101 - 'determination' should be corrected to 'deterioration'

The meaning of the sentence starting in line 69 was not clear - '... and provide between truckload distribution and seismic response' this part of the sentence should be clarified 

 

 

Author Response

RESPONSES TO REVIEWERS’ COMMENTS

Manuscript number: [Applsci-3322896]

Paper title: Retrofitting of a Multispan Simply-Supported Bridge into a Semi-Integral Bridge

Authors: Zhen Xu, Xiaoye Luo, Khaled Sennah, Baochun Chen and Yizhou Zhuang

 

The authors thank all reviewers for their positive and constructive comments and suggestions on our paper.

 

Reviewer 1：

Comments and Suggestions for Authors:

The authors have effectively addressed the previous comments from this reviewer. They have added a section to the paper containing the details of the structural analysis and the calculations that the retrofitting strategy was based on. They have enhanced the discussion and highlighted the potential wider impact of their work. In this reviewer's opinion, these additions have improved the overall quality of the paper to an extent that it can be accepted for publication.

 

Some small issues that were noticed during the review:

 

On line 101 - 'determination' should be corrected to 'deterioration'

 

The meaning of the sentence starting in line 69 was not clear - '... and provide between truckload distribution and seismic response' this part of the sentence should be clarified

 

Response:

We appreciate the reviewers’ comments and revise the manuscript. The revised parts were listed as following and added to the paper.   

On line 101:

• After about 20 years of service, the Jingpu Bridge has deterioration for three main problems.

On line 69 to 73:

• Among these, the integral bridge has several advantages, including superior structural integrity, durability, and resistance to the seismic hazards [16, 17]. Consequently, integral bridges are the preferred choice for both new constructions and retrofitting projects [18, 19]. However, significant flexibility in the substructure is generally required to accommodate longitudinal movements and to optimize truckload distribution and seismic response  [20-26].

Reviewer 2 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

comments have been addressed

Author Response

RESPONSES TO REVIEWERS’ COMMENTS

Manuscript number: [Applsci-3322896]

Paper title: Retrofitting of a Multispan Simply-Supported Bridge into a Semi-Integral Bridge

Authors: Zhen Xu, Xiaoye Luo, Khaled Sennah, Baochun Chen and Yizhou Zhuang

 

The authors thank all reviewers for their positive and constructive comments and suggestions on our paper.

 

Reviewer 2：

Comments and Suggestions for Authors:

comments have been addressed.

 

Response:

Thank you for your comments.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors aim to discuss the design methodology and present details of the retrofitted structural system of the Jinpu Bridge in Zhangzhou, Fujian province, China. The paper begins with a brief introduction highlighting the benefits of two types of jointless bridges. It then delves into the bridge's configuration, rating of the initial structural condition, retrofitting approach, and details of retrofit to four superstructure components. The paper concludes with a short summary. The authors' stated novel approach involves the use of semi-fixed dowel joints to connect the retrofitted superstructure to the substructure at the piers and abutments.

 

However, in this reviewer's opinion, the paper does not fully meet the scientific standards required for publication as a research article. Several significant limitations justify this conclusion:

 

1. Absence of Structural Analysis: The paper does not discuss or present the structural analysis and design calculations conducted on the bridge. Given the significant changes introduced through retrofitting, it would be valuable to assess the substructure's ability to safely support loads, distribute forces, and account for changes in deformation behavior (particularly since as stated in line 104, apart from connecting the slabs to the pier bent, no strengthening or rehabilitation works were done for the substructure). The absence of analysis details, rationale for design decisions, and design checks is a notable deficiency.

 

2. Unsubstantiated Claim: The authors state in line 186 that the bridge remains in good condition without offering any supporting evidence or methodology used to assess its condition after retrofitting. The absence of post-retrofitting structural performance assessments weakens this claim.

 

3. Lack of Lessons Learned: The paper lacks a discussion on the lessons learned from this retrofitting exercise and the potential contributions to the research and practice communities. It fails to provide valuable insights into the wider implications of this work.

 

4. Inadequate Literature Review: The paper lacks an adequate review of existing literature concerning the use of integrated abutments and jointless bridges in practice. This absence weakens the paper's foundation. Also, the authors make a claim starting from line 29, without citing any references. 

 

5. Novelty and Comparative Analysis: If the approach of using semi-fixed dowel joints is novel, it would be valuable to provide a comparative analysis of its advantages, limitations, and when it's suitable compared to other methods. This would enhance the paper's research content.

 

6. Missing Detail from Referenced Studies: While the authors mention (from line 107) relying on other studies to arrive at the details of the retrofitting strategy, the relevant findings from these studies are not presented. An incomplete list and the use of 'etc.' when referencing other articles detracts from the paper's academic rigor. A comprehensive reference list and a description of the findings used for design choices should be included.

 

Other remarks:

Several papers in the references section contain et. al. in the list of the authors (lines 195, 210, 212, 214, 218), one referenced paper says etc. (line 206). At least one of the references (line 193) is missing the names of co-authors of the paper. For all these articles mentioned, all the authors of the referenced papers must be listed. The authors should further make sure that they format the references properly and double check to ensure that all authors are appropriately included.

Line 202 has a “[“ after the article name.  

 

In Figure 1 (a): the extent of the link slab is not shown. 

In Figure 1 (b): the dimensions of the voided slab are not shown.

 

In line 101, should it be Fig. 1(b) instead of 1(a)?

 

In line 127, the ‘Figure 4(b)’ is out of place and should be removed.

 

On line 162, the section number should be 4.4 instead of 4.3

 

Comments on the Quality of English Language

Line 54 – remove extra ‘each’

Line 77 – use ‘reinforcement corrosion’ instead of ‘reinforced corrosion’ 

Line 94 – fix the first word of this line to ‘retrofitting’

Line 123 – the word ‘continuity’ is misspelled

Author Response

Comments and Suggestions for Authors:

The authors aim to discuss the design methodology and present details of the  retrofitted structural system of the Jinpu Bridge in Zhangzhou, Fujian province, China. The paper begins with a brief introduction highlighting the benefits of two types of jointless bridges. It then delves into the bridge's configuration, rating of the initial structural condition, retrofitting approach, and details of retrofit to four superstructure components. The paper concludes with a short summary. The authors' stated novel approach involves the use of semi-fixed dowel joints to connect the retrofitted superstructure to the substructure at the piers and abutments.

 

However, in this reviewer's opinion, the paper does not fully meet the scientific standards required for publication as a research article. Several significant limitations justify this conclusion:

 

Response:

To address the reviewer’s comments, the conclusion section was written to demonstrate the measurable improvements in performance and durability when transforming the bridge from a simply supported superstructure to a semi-integral bridge. The following conclusions was added to the paper.   

The retrofitting of the Jinpu Bridge into a semi-integral bridge has successfully addressed critical structural issues and demonstrated measurable improvements in performance and durability. The following points summarize the success of this approach across key components:

Superstructure Beams:

• The transformation of simply supported beams into continuous spans reduced the maximum mid-span positive bending moment by 11.1%, improving load distribution and reducing stress concentrations. Shear forces at interior supports increased by 6.4% but remained within allowable limits.
• The elimination of mid-span expansion joints enhanced durability by removing frequent failure points prone to cracking and water leakage.

Semi-Fixed Dowel Joints:

• The use of semi-fixed dowels between the superstructure beams and the substructure, comprising steel bars encased in rubber sleeves, provided controlled flexibility by accommodating some movement while providing continuity.
• Longitudinal displacement of the main beam was reduced by 80.1% under dead load and seismic conditions, demonstrating exceptional seismic resilience.
• Stress concentrations at piers and abutments were managed efficiently, maintaining structural safety within design limits.

Piers and Abutments:

• Existing piers and abutments were successfully integrated into the retrofitted system without additional strengthening, reducing costs.
• Maximum bending moments and shear forces on the pier and abutment remained well below their ultimate capacities, ensuring structural safety under all load conditions.
• Maximum displacements at the top of the pier (7.7 mm) were well below the allowable limit (52.4 mm), showing a significant seismic safety margin.

Approach Slab System:

• The introduction of a new approach slab and transition slab system improved driving comfort and accommodated thermal movements.
• Smooth transitions at the roadway interface were ensured by including expansion joints at critical locations, reducing vehicle-induced stresses.

Overall Impact:

• This retrofitting approach significantly enhanced the bridge's durability, seismic performance, and service life, while minimizing maintenance demands.
• The project serves as a cost-effective and replicable model for similar rehabilitation projects on aging infrastructure.

 

1. Absence of Structural Analysis: The paper does not discuss or present the structural analysis and design calculations conducted on the bridge. Given the significant changes introduced through retrofitting, it would be valuable to assess the substructure's ability to safely support loads, distribute forces, and account for changes in deformation behavior (particularly since, as stated in line 104, apart from connecting the slabs to the pier bent, no strengthening or rehabilitation works were done for the substructure). The absence of analysis details, rationale for design decisions, and design checks is a notable deficiency.

 

Response:

We appreciate the reviewer’s comment and agree that including details on the structural analysis would enhance the paper's clarity and completeness. The paper does present the structural analysis conducted on the retrofitted bridge, primarily using finite element modeling to evaluate the substructure's ability to support loads and manage force redistribution post-retrofitting. Key findings include the maximum bending moments and shear forces at piers and abutments, which were shown to remain well below ultimate capacities, demonstrating the adequacy of the existing substructure without additional strengthening. Response spectrum analysis confirmed significant improvements in seismic performance, with displacements and forces meeting safety criteria.

In section 5. “Finite element analysis”, we expanded on the description of the finite element modeling, including element types for the substructure and explanations for the springs that represent the contacted soil behind the abutment. This added text is shown in red in the paper. We also edited red Tables 2, 3, and 4 to provide an explanation of the symbols used in these tables for a better understanding of the analysis and design that were explained in Section 5.

Also, the following revised sentence is added in red in line 104:

“No other strengthening or rehabilitation works were done for the substructure since the calculations that are presented later show that the capacities of existing members are more than the demand based on the finite element analysis of the continuous system.”

 

2. Unsubstantiated Claim: The authors state in line 186 that the bridge remains in good condition without offering any supporting evidence or methodology used to assess its condition after retrofitting. The absence of post-retrofitting structural performance assessments weakens this claim.

 

Response:

We appreciate the reviewer’s observation. The paper showed that the finite element analysis demonstrated that the retrofitted structure met all safety and design criteria under various load conditions. The claim that the bridge remains in good condition post-retrofitting can be supported by regular inspections by the bridge owner. The summary of post-retrofitting inspection results and performance metrics, such as crack monitoring, displacement measurements, and maintenance records, is expected to substantiate the bridge's continued good condition and validate the success of the retrofitting approach. The following sentence was added to the end of the revised conclusion:

“Regular inspections by the bridge owner will help monitor the bridge's post-retrofitting condition. The post-retrofitting inspection results and performance metrics are expected to substantiate the bridge's continued good condition and validate the success of the retrofitting approach.”

 

3. Lack of Lessons Learned: The paper lacks a discussion on the lessons learned from this retrofitting exercise and the potential contributions to the research and practice communities. It fails to provide valuable insights into the wider implications of this work.

 

Response:

We revised the conclusion section to address the reviewer’s comment. Specifically, the revised conclusions, marked in red in the paper, provided the following contributions to the bridge engineering community.

1. Effectiveness of Semi-Fixed Dowel Joints:
   • The semi-fixed dowel joints proved effective in balancing flexibility and force transmission, enhancing seismic resilience and reducing displacements significantly. This insight contributes to their potential adoption in similar retrofitting projects.
2. Preservation of Substructure:
   • The success of retaining the original substructure without additional strengthening demonstrates the feasibility of cost-effective retrofits for aging bridges with intact foundations. This highlights the importance of rigorous assessment of existing components before retrofitting.
3. Elimination of Expansion Joints:
   • Transitioning to a jointless design improved durability and reduced maintenance demands. This outcome underscores the long-term benefits of adopting jointless strategies in bridge engineering.
4. Broader Impact:
   • The methodology and results serve as a replicable framework for upgrading simply supported bridges globally, contributing to sustainable infrastructure practices while enhancing safety and performance standards.

 

4. Inadequate Literature Review: The paper lacks an adequate review of existing literature concerning the use of integrated abutments and jointless bridges in practice. This absence weakens the paper's foundation. Also, the authors make a claim starting from line 29, without citing any references. 

 

Response:

To address the reviewer’s comment, the Introduction section was revised in red, and 18 references were added to the end of the paper.

 

5. Novelty and Comparative Analysis: If the approach of using semi-fixed dowel joints is novel, it would be valuable to provide a comparative analysis of its advantages, limitations, and when it's suitable compared to other methods. This would enhance the paper's research content.

Response:

The authors thank the reviewer for this constructive comment. The approach of using semi-fixed dowel joints is indeed innovative for retrofitting simply supported bridges into semi-integral configurations. To enhance the manuscript, the following text was added in red to section 4.2:

“The wall thickness of the rubber sleeve was taken 40 mm in order to ensure that the dowel joint behaves in the linear elastic range during thermal expansion and contraction due to sessional variation of temperature all over the year [32].”

Also, the following paragraph was added after Figure 10:

“The semi-fixed dowel joints balance flexibility to accommodate thermal and seismic movements while providing structural continuity. They reduce the need for extensive substructure modifications, making them cost-effective for retrofitting existing bridges with intact foundations. These joints simplify construction by allowing controlled connections without full monolithic integration, mitigating stress concentrations. They are less suited for conditions requiring high rotational capacity compared to expansion joints. They are best applied to bridges requiring moderate flexibility and durability improvements without a complete structural overhaul.” 

6. Missing Detail from Referenced Studies: While the authors mention (from line 107) relying on other studies to arrive at the details of the retrofitting strategy, the relevant findings from these studies are not presented. An incomplete list and the use of 'etc.' when referencing other articles detracts from the paper's academic rigor. A comprehensive reference list and a description of the findings used for design choices should be included.

 

 Response:

The authors thank the reviewer for the insightful comment. We revised the paper to explicitly present key findings from the referenced studies used to guide the retrofitting strategy. These include the nonlinear stiffness characteristics of semi-fixed dowel joints, the seismic performance of jointless bridges, and soil-pile interactions under seismic loads.

 

Other remarks:

Several papers in the references section contain et. al. in the list of the authors (lines 195, 210, 212, 214, 218), one referenced paper says etc. (line 206). At least one of the references (line 193) is missing the names of co-authors of the paper. For all these articles mentioned, all the authors of the referenced papers must be listed. The authors should further make sure that they format the references properly and double check to ensure that all authors are appropriately included.

Response:

All references were edited to address the reviewer’s comment.

 

Line 202 has a “[“ after the article name.  

Response:

Done. 

 

In Figure 1 (a): the extent of the link slab is not shown. 

Response:

Done.

 

In Figure 1 (b): the dimensions of the voided slab are not shown.

 Response:

The number of voided slab beams is included in the text. On the other hand, the dimensions of the voided slab (box section) are shown in Figure 6.

 

In line 101, should it be Fig. 1(b) instead of 1(a)?

 Response:

Done.

 

In line 127, the ‘Figure 4(b)’ is out of place and should be removed.

Response:

We 

 

On line 162, the section number should be 4.4 instead of 4.3

Response:

Done.

Comments on the Quality of English Language:

Line 54 – remove extra ‘each’

Response:

Done.

 

Line 77 – use ‘reinforcement corrosion’ instead of ‘reinforced corrosion’ 

Response:

Done.

 

Line 94 – fix the first word of this line to ‘retrofitting’

Response:

Done.

 

Line 123 – the word ‘continuity’ is misspelled

Response:

Done.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I've revised the paper applsci-2676946.

In my opinion, the level of originality of the article is not sufficient for a "research article" but the case study presented could be worth to be disseminated by changing the typology of the article: a "Case Report" would better suit this manuscript.

Provided that the article type change is made, the manuscript may be accepted after addressing the following points:

1) The retrfofit strategy is described only from a global and technological point of view, more details regarding the design approach and calculations should be added to make this work more solid and useful for the reader.

2) extension of the state of the art. For example, consider the following works involving slab bridges, integral bridges, retrofits and/or analysis

https://doi.org/10.3390/infrastructures7090122

https://doi.org/10.1061/(ASCE)1084-0702(2005)10:3(3

https://doi.org/10.1002/eqe.1190

https://doi.org/10.1016/j.engstruct.2021.113134

https://doi.org/10.2749/101686609788220051

https://doi.org/10.1061/(ASCE)1084-0702(2002)7:2(85)

3) line 94 - correct typos

4) line 123- correct typos

5) Figures 10 and 11 are not very clear, I recommend using colors or different shades of gray (this comment possibly applies to all figures, but priority should be given to these two figures)

Comments on the Quality of English Language

Check English grammar throughout the paper

Author Response

Comments and Suggestions for Authors:

 

In my opinion, the level of originality of the article is not sufficient for a "research article" but the case study presented could be worth to be disseminated by changing the typology of the article: a "Case Report" would better suit this manuscript.

Provided that the article type change is made, the manuscript may be accepted after addressing the following points:

 

1) The retrfofit strategy is described only from a global and technological point of view, more details regarding the design approach and calculations should be added to make this work more solid and useful for the reader.

 

Response:

The authors thank the reviewer for the insightful comment. This comment was addressed through other comments with Reviewer # 1.

 

2) extension of the state of the art. For example, consider the following works involving slab bridges, integral bridges, retrofits and/or analysis

https://doi.org/10.3390/infrastructures7090122

https://doi.org/10.1061/(ASCE)1084-0702(2005)10:3(3

https://doi.org/10.1002/eqe.1190

https://doi.org/10.1016/j.engstruct.2021.113134

https://doi.org/10.2749/101686609788220051

https://doi.org/10.1061/(ASCE)1084-0702(2002)7:2(85)

 

Response:

The literature review was revised to include an additional 18 references, including the six references suggested by the reviewer.

 

3) line 94 - correct typos

Response:

Done.

 

4) line 123- correct typos

 

Response:

Done.

 

5) Figures 10 and 11 are not very clear, I recommend using colors or different shades of gray (this comment possibly applies to all figures, but priority should be given to these two figures)

 

Response:

The authors thank the reviewer for this comment. The figures were slightly increased in size to be more readable. Also, Figure 8 provides more details on the semi-fixed dowel joint.

 

Comments on the Quality of English Language:

Check English grammar throughout the paper.

 

Response:

The paper was edited throughout to enhance the English writing. Grammarly software was used to ensure proper grammar and sentence consistency.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Retrofitting of a Multispan Simply-Supported Bridge into a Semi-Integral Bridge

Zhen Xu 1, Baochun Chen 2*, Khaled Sennah3, Xiaoye Luo 4, Yizhou Zhuang

The paper has no scientific interest as it only describes the refurbishment of a bridge without any particular or purposely developed technique. Therefore, it is not suitable for Applied Science and it should be resubmitted as a technical note. It has however many flaws and imprecisions in the concept and in the form

 

·         The paper has a format not consistent with the journal. For example, Interline space is too large and references are not listed by order of appearance but in alphabetical order. For these reasons, it was not easy to read the paper. Also, the font is not the correct one. The paper needs to be deeply revised from a formal point of view.

·         Line 44: “concrete piles” is maybe “concrete piers”…piles are at the foundation

· The introduction should provide some details of how simply supported beam can behave like a continuous beam even though its reinforcement is designed to withstand only positive moments. Moreover, a scheme of a jointed bridge transformed into an integral bridge should be added

· The literature review in the introduction is quite poor. For example, when describing durability problems related to the presence of joints, make reference to some recent work such as https://doi.org/10.3390/infrastructures6020025

·         Line 84: the sentence “Based on the inspection results of the bridge, the structural condition of the Jingpu Bridge was rated as Level 5 according to the Chinese code for technical condition evaluation of highway bridges [JTG/T 85 H21-2011 (2011)” is not clear. The author must explain what such an evaluation means. Different condition assessment methods used in different countries have different scales. To this reviewer “rated level 5” does not mean anything.

·         Line 94 “rggggggggggg” what it means?

 

·         Line 98 the authors say that “The deck expansion joints at the abutments were eliminated in the retrofitting” but this is impossible since at a certain point the bridge must finish. In fact, afterward, they show how the expansion joint at abutments is made – fig 11a

·       moreover fig 11 is not clear and should be remade 

Author Response

Comments and Suggestions for Authors:

The paper has no scientific interest as it only describes the refurbishment of a bridge without any particular or purposely developed technique. Therefore, it is not suitable for Applied Science and it should be resubmitted as a technical note. It has however many flaws and imprecisions in the concept and in the form.

 

(1) The paper has a format not consistent with the journal. For example, Interline space is too large and references are not listed by order of appearance but in alphabetical order. For these reasons, it was not easy to read the paper. Also, the font is not the correct one. The paper needs to be deeply revised from a formal point of view.

 

Response:

The authors thank the reviewer for the great suggestions to enhance the quality of the paper. The references were edited to meet the journal format. Also, the literature review, the methodology, the presentation of results, and the conclusions were revised as marked in red to address the reviewer’s comments. Careful editing to the paper format was done to meet the journal guidelines.  

 

(2) Line 44: “concrete piles” is maybe “concrete piers”…piles are at the foundation

 

Response:

Done.

 

(3) The introduction should provide some details of how simply supported beam can behave like a continuous beam even though its reinforcement is designed to withstand only positive moments. Moreover, a scheme of a jointed bridge transformed into an integral bridge should be added.

 

Response:

Figure 7 shows details of the beam reinforcement to convert the simple span into a continuous span to carry negative moments at the pier location.

 

(4) The literature review in the introduction is quite poor. For example, when describing durability problems related to the presence of joints, make reference to some recent work such as https://doi.org/10.3390/infrastructures6020025

 

Response:

The literature review was revised to include an additional 18 references, including the reference suggested by the reviewer.

 

(5) Line 84: the sentence “Based on the inspection results of the bridge, the structural condition of the Jingpu Bridge was rated as Level 5 according to the Chinese code for technical condition evaluation of highway bridges [JTG/T 85 H21-2011 (2011)” is not clear. The author must explain what such an evaluation means. Different condition assessment methods used in different countries have different scales. To this reviewer “rated level 5” does not mean anything.

 

Response:

The paragraph under Figure 3 explains that according to the Chinese code JTG/T 85 H21-2011 for the technical condition evaluation of highway bridges, Level 5 indicates that the bridge is in a "very poor" condition. This level suggests that the bridge has significant structural issues and may require immediate attention or even replacement to ensure safety and functionality. The paragraphs also mentioned that the Chinese code classifies the bridge rating into five levels, with Level 1 being the best and Level 5 representing the worst condition.

 

 (6)  Line 94 “rggggggggggg” what it means?

 

Response:

Corrected.

 

 (7)  Line 98 the authors say that “The deck expansion joints at the abutments were eliminated in the retrofitting” but this is impossible since at a certain point the bridge must finish. In fact, afterward, they show how the expansion joint at abutments is made – fig 11a

 

Response:

The authors explained in the text that the end of the bridge beams connected to the first approach slab using steel dowels, as depicted in the right joint in Figure 11(a). Also, the expansion joint was installed at the end of the second approach slab when it meets the asphalt layer, as depicted at the joint on the left side of Figure 11(a).

 

(8)   moreover fig 11 is not clear and should be remade. 

 

Response:

Figure 11 increased in size to make it more readable.

Author Response File: Author Response.pdf