The Development of Continuous Connections for Multi-Span Precast Prestressed Girder Bridges: A Review

Reviewer # 1

Reviewer’s Comment / Authors’ Response

Location

The authors present a review of types of joints for the construction of continuous precast prestressed bridges. This reviewer has the following comments:

The authors sincerely appreciate the reviewer’s time and positive feedback. All the comments have been addressed and highlighted in the revised manuscript.

1)      The paper is full of many unresolved references in the text, i.e. it is an unfinished document. It cannot be published in its current version. Please correct all the mistakes and resubmit the paper for a second revision.

We sincerely appreciate the reviewer’s careful review and feedback. We acknowledge the issue regarding the unresolved references in the transferred PDF file; however, the main manuscript Word document does not have any such issues. The reference links were correctly formatted in the original document, but some errors occurred during the conversion to PDF.

To ensure consistency and eliminate any confusion, we have now reuploaded the corrected PDF version of the manuscript.

2)      Section 2 of partially integrated connections is a good review of partial connections.

We appreciate the reviewer’s positive feedback.

3)      However continuous connections are split every about 100 meters, so as not to transfer excessive horizontal forces to the piers.

Thank you for your insightful comment. We acknowledge the importance of limiting the length of continuous connections to prevent excessive horizontal forces on the piers. To address this, we have revised the manuscript to include a discussion on the typical practice of introducing expansion joints or movement breaks in continuous bridges approximately every 100 meters. This prevents excessive thermal and shrinkage-induced stresses while maintaining structural integrity. The revised text includes the following:

“In practical bridge design, fully continuous connections are typically segmented every 80 to 120 meters to prevent the excessive accumulation of horizontal forces at the piers. These forces primarily arise due to thermal expansion, shrinkage, and long-term creep effects. Introducing expansion joints or strategically placed movement breaks within continuous bridge systems helps mitigate stress concentrations while maintaining structural integrity and load distribution efficiency.”

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4)      Section 3 of fully integrated connections is a review in my view of messy and unpractical connections, since they cause negative bending in the main beams; which are typically only pretensioned for positive bending in factory, transport, erection and final deployment.

We appreciate the reviewer’s perspective on fully integrated connections. However, this paper is part of a broader research project investigating these types of connections, specifically in Missouri Department of Transportation (MoDOT) precast girders, which are widely used across the United States. The designs analyzed in this review align with common industry practices and have been implemented in several precast bridge projects.

This comment has been highlighted in the revised manuscript.

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5) Practical modern applications of fully integrated precast continuous bridge decks usually account for negative dowels over the piers and positive segments for the main spans. These partial portions are usually connected with posttensioned cables. 

We appreciate the reviewer’s valuable insight regarding modern applications of fully integrated precast continuous bridge decks. We acknowledge that negative dowels over the piers and positive moment segments in the main spans, connected using post-tensioned cables, are commonly utilized to optimize structural performance and load distribution.

This aspect has been highlighted in the revised manuscript.

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Reviewer # 2

Reviewer’s Comment / Authors’ Response

Location

The paper is a review of various – mostly American – methods to adapt simply supported PC girders to continuity. This is widely practised in Northern America. The authors distinguish between partial continuity of adjacent spans and full continuity. In addition some advanced connecting systems are discussed. The continuity of spans is achieved in a structural manner, as well as for the purpose of seismic resistance.

Obviously, this is a review report, describing the arrangements as implemented in the US. Some general performances are depicted and discussed. The topic is useful to a wide public of readers. The illustrations are adapted to the topic, although some additional drawings would be helpful to the reading. The language is OK and no writing flaws were found. However, this reviewer would like to submit some questions and suggestions to improve the manuscript, as listed below.

We sincerely appreciate the reviewer’s thorough evaluation and positive feedback regarding the manuscript.

1. What is missing somehow in this paper is how the prestress concept changes from the initial simply supported girders to continuous behaviour. It seems of capital importance to comment on this.

We appreciate the reviewer’s comment on the importance of explaining how the prestressing concept changes when transitioning from simply supported girders to a continuous system. To address this, we have added a discussion in the revised manuscript to clarify this transition.

“Negative moment develops due to the implementation of the continuity method. The selected moment integration approach is designed to accommodate this negative moment. Additionally, precast girders typically include harped strands to account for the negative moment in continuous applications. In many cases, post-tensioning is applied after erection to enhance continuity, ensuring effective redistribution of internal forces and long-term structural serviceability.”

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2. Throughout the whole manuscript, references are sometimes difficult to read, since some error occurred due to the transforming of the file to pdf. During reading, this reviewer had to guess to which figure or reference the authors are referring.

We apologize for the inconvenience caused due to the PDF conversion. We have ensured that the revised manuscript contains no errors in the references.

3. The authors might be interested by the fact that in Europe, mostly partial continuity is implemented, in a way that is vaguely similar to the ‘extended deck reinforcement’, albeit the reinforcement is encased by a thin slab of concrete, which is integrated in the bridge deck slab. This concrete part is ‘weakened’ by the underlying polystyrene plate as shown in the picture below.

We appreciate the reviewer’s comment into the European approach to partial continuity in precast girder bridges. The use of encased reinforcement within a thin concrete slab, along with the inclusion of an underlying polystyrene plate to control cracking and behavior, presents an interesting variation of the extended deck reinforcement method.

This design has been included in the revised manuscript.

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Figure 3

4. At the beginning of section 2, you refer to Hambly (33). In my copy of this book, the jointless bridges are discussed in the last chapter. Perhaps, the authors would like to verify this.

Thank you for your careful observation. The reference has been updated.

5. In subsection 2.1 spans are named in feet. For international readers, the use of IS-magnitudes would be preferred.

We appreciate the reviewer’s suggestion regarding unit conversion for international readers. However, this paper is part of a US-DOT research project, where U.S. customary units are the standard. To maintain consistency with DOT guidelines and industry practice in the U.S., we prefer to keep the measurements in U.S. customary units.

6. In subsection 2.3, the use of bent strands is presented. This reviewer thinks large bending radii are needed to bend 7-wire strands. In addition, bending of strands over 90° or similar, introduces unequal distribution of the strand force. The authors may want to comment on this issue.

We appreciate the reviewer’s technical insight regarding the bending of 7-wire prestressing strands and the challenges associated with large bending radii and force redistribution. This comment has been included in the revised manuscript.

“The use of bent strands in continuity connections requires careful consideration of bending radii to prevent excessive stress concentrations in the 7-wire prestressing strands. Large bending radii are typically needed to avoid premature damage or loss of prestress, ensuring the strands maintain their intended tensile capacity. Additionally, when strands are bent at angles exceeding 90°, an unequal distribution of strand forces can occur, leading to localized stress variations that may affect the structural performance of the connection.”

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7. Figure 5a exhibits bent bars as a means for connection. However, most of the tensile force to resist negative bending moments, is located at the top of the girders. How is the arrangement to resist this force? Do you provide extended deck reinforcement? This also applies to subsection 3.4, which discusses the lower connection only.

We appreciate the reviewer’s technical observations. The purpose of Figure 5a and Subsection 3.4 is to illustrate different ways to develop continuity in precast prestressed girder bridges. The development of negative moments is resisted through multiple mechanisms, for instance, harped strands in precast girders, cast-in-place diaphragms, and extended deck reinforcement.

This comment has been considered in the revised manuscript.

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8. In subsection 3.2 the girder to column joint is discussed. How do the D 57-bars overlap and connect with the other rebars in the precast girders and especially with the prestressing strands ?

The extended longitudinal bars of the column do not overlap with the precast girders prestressing strands.

9. In subsection 4.1, it does not become clear where exactly the UHPC is located. Perhaps some sketch or figure would clarify this. What do you mean exactly by the construction joints ?

Ultra-High-Performance Concrete (UHPC) is placed at the connection joint. UHPC is used in girder-to-girder connections, girder-to-deck interfaces, and girder-to-column joints to improve load transfer, reduce cracking, and enhance durability. Construction joints in this context refer to the predefined discontinuities where successive concrete pours meet, often occurring at interfaces between precast and cast-in-place concrete elements.

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10. In subsection 4.2, the option of unstressed strands is presented. The reviewer must be careful to comment, since he is continuing research on this alternative, especially in view of some catastrophic events. Therefore, he entirely agrees this alternative is promising. Yet, the method to encase these ‘dummy’ strands in grouted ducts may be inefficient. The suggestion would be to place these strands in waxed tight plastic sheeting, as it is done in some countries in Europe. However, the problem seems to be that the strands need sufficient elongation before becoming active. The authors might prefer not to comment on this issue.

The use of unstressed strands in continuous precast girder applications presents a promising alternative for enhanced structural adaptability. However, the efficiency of encasing these strands in grouted ducts remains a subject of discussion, as adequate elongation before activation may be difficult to achieve. Further research is needed to evaluate the long-term effectiveness and practical implementation of these methods in different structural applications.

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Reviewer # 3

Reviewer’s Comment / Authors’ Response

Location

The paper “The Development of Continuous Connections for Multi-Span Precast Prestressed Girder Bridges: A Review” reports a detailed review about the development of continuous connections in multi-span precast prestressed girder bridges. In particular, the authors have analyzed the different techniques used to connect the spans highlighting the advantages and the related limits. Furthermore, some considerations of the static and dynamic behaviour of the bridges subjected to these interventions have been reported in the text from critical point of view. In general, the review is well-organized, and the references used appear well analyzed. For these reasons, it is opinion of this reviewer that the paper can be considered for publication in CivilEng after the following improvements:

The authors sincerely appreciate the reviewer’s time and positive feedback. All the comments have been addressed and highlighted in the revised manuscript.

- Check the references in the text. (e.g. line 39).

The references were checked in the whole manuscript.

- Improve the quality of Figure 9. In this form of the paper the information appears incomplete.

Figure 9 quality has been improved as requested.

- Section 4.1: Add some considerations about the limits and the problems of the use of UHPC.

The limitations and considerations for the use of UHPC have been included in the revised manuscript.

“While UHPC provides exceptional strength, durability, and bond performance, its application in bridge construction comes with certain limitations. The high material cost and specialized production requirements can restrict its use in large-scale projects [65,66]. Additionally, some UHPC mixes require special curing techniques to achieve optimal performance, often necessitating heat curing and specialized equipment. Workability challenges also arise due to its low fluidity, making proper placement and compaction critical, particularly in narrow connection joints [65,66]. Furthermore, the stiffness difference between UHPC and conventional concrete can lead to compatibility issues, requiring careful interface detailing to prevent premature cracking. Despite these challenges, UHPC remains a promising solution for improving structural performance in precast girder bridge continuity.

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- Some considerations on the durability of bridges should be added in the text (see 10.1016/j.engfailanal.2022.106546 for the evolution of seismic performance of existing RC bridges).

This comment has been included in the revised manuscript.

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- Section 5: the realization of post tensioned columns is not always easy. The authors should report some case studies in which this technique has been applied.

The study focuses on the behavior of continuous joints and their performance under seismic loading in Section 5. However, there is limited available data on the response of joints when post-tensioned concrete columns are used, as this is not a common practice.

- In the conclusion, the authors should add some considerations on those aspects that still need further studies.

We appreciate the reviewer’s suggestion to highlight areas that require further research in the conclusion. To address this, we have expanded the conclusion to include a discussion on key knowledge gaps and future research directions.

Reviewer # 4

Reviewer’s Comment / Authors’ Response

Location

It is surprising that the authors did not begin the paper by establishing a clear connection between the climate emergency and Multi-Span Precast Prestressed Girder Bridges. This omission overlooks an opportunity to ground their discussion within the broader context of global sustainability challenges. For example, they could have referenced a pertinent statement by Professor Pierrehumbert of Physics at the University of Oxford, who unequivocally emphasized in a 2019 paper: “Let’s get this on the table right away, without mincing words. With regard to the climate crisis, yes, it’s time to panic” (Pierrehumbert, R., 2019, Bulletin of the Atomic Scientists, pp. 1-7).

We appreciate the reviewer’s suggestion to frame the discussion within the broader context of global sustainability challenges. While the primary focus of this paper is on the structural behavior and performance of Multi-Span Precast Prestressed Girder Bridges, we acknowledge that sustainability, material efficiency, and the reduction of environmental impact are critical considerations in modern infrastructure development.

To address this, we have updated the introduction to briefly establish the relevance of sustainable construction practices in bridge engineering.

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At the very least, the authors should have highlighted how optimizing the design of Precast Prestressed Girder Bridges—such as through the use of ultra-high-performance concrete (UHPC)—can increase the durability and lifespan of these structures, thereby reducing their lifecycle environmental impacts. Such considerations are crucial for aligning bridge engineering practices with sustainability goals.

We appreciate the reviewer’s important suggestion regarding the sustainability benefits of optimizing Precast Prestressed Girder Bridges. This comment has been addressed in the revised manuscript.

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For instance, it is peculiar that in page 2 in the statement: “The development of continuous bridges offers a multitude of advantages [7,8], including reduced midspan bending moment and deflection, which allow for the use of more economical sections”, the authors failed to mention the environmental benefits associated with such designs.

We appreciate the reviewer’s suggestion to highlight the environmental benefits associated with continuous bridge designs. While our focus was on structural advantages, we acknowledge that continuous bridges also offer significant sustainability benefits, including material efficiency, reduced maintenance needs, and lower lifecycle emissions.

To address this, we have revised the statement on page 2 to incorporate the environmental benefits of continuous bridge design.

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Furthermore, the methodology employed for identifying and reviewing relevant literature is absent. Including a systematic review approach would enhance the rigor of the study. For instance, the authors could draw inspiration from Section 2.1 of the recent paper by Cao et al. (2024), titled Extended applications of molecular dynamics methods in multiscale studies of concrete composites: a review (Case Studies in Construction Materials, e04153). This section provides a well-structured example of how to conduct and present a comprehensive review methodology.

This reference has been included in the revised manuscript as suggested.