Tension Performance of Precast Bridge Deck Longitudinal Joints with Different Configurations

Round 1

Reviewer 1 Report

Good paper. 

Author Response

The authors would like to thank the reviewer for their comments and suggestions. They helped us improve the quality of our paper. 

Reviewer 2 Report

This paper presents an experiment for precast bridge deck longitudinal joint. Six test specimens were designed and tested and tension load was applied. The several research variables were considered including the joint width, presence or absence of hooked or looped steel rebars, and presence or absence of a steel plate. The finite element model (FEM) was developed and analyzed to confirm the behavior of the simulated optimal joint configuration against the experimentally obtained observations. However, there are some problems with this study and experiment. The paper should be rejected in the mind of reviewer. My major concerns are as follows:

1           The quality of the Figure is poor. In Fig. 2, the labeling font is small and illegible, and some of the components are not labeled with their names. Difficulty in identifying the spatial location of loading devices and components in Fig. 4.

2           Specimen J100-SB-SP is not mentioned in Table 1, but many conclusions in the section 3 are relevant to it.

3           Fig.7 compares the load–relative displacement curves of J100-HB-SP and J0-LB-NP to evaluate the effects of rebar type and steel plate usage. However, the joint widths of specimens J100-HB-SP and J0-LB-NP are also different.

4           Six test specimens were designed and tested, However, only the Final crack geometry of specimen J100-HB-SP was shown in this paper.

5           The nonlinear spring element (connecting two nodes) is used for modeling in this study, however, the author do not adequately describe the nonlinear spring element.

6           The total number of mesh cells was set to 6474, the number of mesh cells does not meet the requirements of analysis accuracy.

7           Comparison of the final crack geometry for the actual test specimen with the crack development observed using the high-speed PCIe camera is not meaningful.

 

8           The final crack geometry obtained using the FEM is not very similar to the final crack geometry for the actual test specimen.

Author Response

Q1. The quality of the Figure is poor. In Fig. 2, the labeling font is small and illegible, and some of the components are not labeled with their names. Difficulty in identifying the spatial location of loading devices and components in Fig. 4.

A1. The authors would like to thank the reviewer for their comments and suggestions, which helped us improve the quality of our paper. The reviewer’s comments have been fully incorporated into the revised version of this paper. Details of the same are as presented below.

• Figure 2 and Figure 4 have been revised according to the reviewer’s suggestions. (Manuscript location: Figure 2 of page 4, Figure 4 of page 6)

Q2. Specimen J100-SB-SP is not mentioned in Table 1, but many conclusions in the section 3 are relevant to it.

A2. 

As mentioned by the reviewer, the text has been revised.

 J100-SB-SP modified to J100-HB-SP.

 

Figure 7 compares the load–relative displacement curves of J100-HB-SP and J0-LB-NP to evaluate the effects of rebar type and steel plate usage. Overall, the behavior of J0-LB-NP was similar to that of J100-HB-SP; however, as shown in Table 2, the final relative displacement of J0-LB-NP (3.67 mm) was approximately 56% larger than that of J100-HB-SP. It can be concluded that the looped rebars alone were insufficiently connected to transfer load across the joint, whereas the combination of hooked top-layer rebars and the steel plate ensured integral structural performance. Therefore, hooked rebars are more effective than looped rebars in precast bridge deck joints. (Manuscript location: First paragraph of page 8)

 

Q3. Fig.7 compares the load–relative displacement curves of J100-HB-SP and J0-LB-NP to evaluate the effects of rebar type and steel plate usage. However, the joint widths of specimens J100-HB-SP and J0-LB-NP are also different.

A3. Although the parameters of this experiment are different, the joint gap would be at least 150 mm, as space would be available when looped rebar is used. Therefore, the joint gap of the two specimens are different.

Q4. Six test specimens were designed and tested, However, only the final crack geometry of specimen J100-HB-SP was shown in this paper.

A4. Out of all the specimens, J100-HB-SP had the best results for the final crack geometry. Hence, the specimen was used as a representative specimen and compared after finite element analysis.

 

Q5. The nonlinear spring element (connecting two nodes) is used for modeling in this study, however, the author do not adequately describe the nonlinear spring element.

A5. The ABAQUS proposes the use of spring elements during nonlinear implementation of connection between points and points. In this study, the nonlinear interface between the concrete cross-sections was used as a nonlinear spring element (two node connection). As stated by the reviewer, some text has been added. Here are some of the details.

 

The concrete was modeled using C3D8R 3D solid elements. The implementations of the precast concrete bridge deck units and CIP joint section were executed separately; as the contact surface be-tween the two cannot be considered fully integral, it was modeled using a nonlinear spring element (connecting two nodes) in this study (Figure 12 (a)). (Manuscript location: First paragraph of page 11)

Q6. The total number of mesh cells was set to 6474, the number of mesh cells does not meet the requirements of analysis accuracy.

A6. The total number of mesh shells is not considered to be a problem because some accuracy has been confirmed when analyzing experimental and analysis models.

 

Q7. Comparison of the final crack geometry for the actual test specimen with the crack development observed using the high-speed PCIe camera is not meaningful.

A7. Taking the reviewer’s observation into consideration, the corresponding contents have been revised as follows.

• Notably, the evolution of fracture geometry traced on the test specimen as the applied load increased (shown in Figure 11) was found to be similar to the displacement distributions observed using the high-speed PCIe camera. The goal was to obtain a more detailed view of the cracks through this experiment. However, there was no significant difference between the destruction mode confirmed visually and the destruction mode confirmed by the camera. (Manuscript location: First paragraph of page 10)

Q8. The final crack geometry obtained using the FEM is not very similar to the final crack geometry for the actual test specimen.

A8. The shape obtained using the FEM is the distribution of displacement according to stress, not the final crack shape. In this study, the initial crack load and the overall crack behavior are similar, and the load–relative displacement curves are similar. Given below are the excerpts from the manuscript regarding the same.

- Figure 14 compares the FEM- and test-obtained load–relative displacement curves. The relative displacement at initial cracking of the FEM was 0.12 mm at a load of 482 kN, compared with a relative displacement of 0.11 mm at a load of 470 kN for the test specimen. Notably, the final load applied to the FEM (840 kN) was slightly higher than that applied to the test specimen (800 kN) because the former was stiffer than the latter, and the contact surface was more rigid in the FEM than in reality. As a result, a larger load was required to reach a similar cracking condition. However, given that the initial cracking loads and overall cracking behaviors were similar, the load–relative displacement curves were comparable, and the error between the FEM and test results was less than 2%; the FEM was considered able to accurately predict the structural behavior of the longitudinal precast bridge deck joint.(Manuscript location: First paragraph of page 14)

Reviewer 3 Report

In this study, tension load was applied to a series of precast bridge deck longitudinal joint specimens to determine the influences of the joint width, rebar type, and steel plate. These influences were then evaluated to obtain an optimal joint configuration. The use of a 100 mm joint width, hooked rebars, and a steel plate was found to provide superior precast bridge deck longitudinal joint performance. Finally, a finite element analysis was conducted and its similarity to the test-observed behavior was verified. The results of this study are expected to inform improved designs for the longitudinal joints of precast bridge deck systems, facilitating expedited bridge construction while minimizing construction impacts. And my detailed reviews are as follows:

1.       Please have a thorough check, some obvious mistakes such as:

①  Lines 155, 165, 177, 189 and 200, the “Table 1” should be modified to “Table 2”.

②  Lines 177, 178 and 192, the “J100-SB-SP” should be modified to “J100-HB-SP”.

2.       Specimen J100-HB-NP can be added and compared with specimen J100-HB-SP to study the effect of a steel plate presence or absence.

3.       How to measure the joint width when the rebar type is looped rebar.

4.       How did author determine the joint width of the six specimens or what is the basis to determine the joint width.

5.       Explain the loading scheme with more details and make some supplements to the test overview. If possible, provide photos when loading.

6.       What is the practical prospect of this study. And if it is applied to actual bridges, whether its performance under car loads or other loads can be reflected only by the results of tension experiment.

7.       What connection technology did the study use.

8.       Add performance of the materials used in the study with more details.

9.       How about the constructability of the optimal specimen.

10.   What’s the originality or significant contribution of this paper.

 

Major revision and re-review.

Author Response

Q1. Please have a thorough check, some obvious mistakes such as:

-  Lines 155, 165, 177, 189 and 200, the “Table 1” should be modified to “Table 2”.

-  Lines 177, 178 and 192, the “J100-SB-SP” should be modified to “J100-HB-SP”.

A1. The authors would like to thank the reviewer for their comments and suggestions, which helped in improving the quality of our paper. The reviewer’s comments have been fully incorporated into the revised version of this paper, as detailed below.

 - As recommended by the reviewer, some text has been modified.

• Lines 155, 165, 177, 189 and 200, the “Table 1” have been modified to “Table 2”. (Manuscripts location: First paragraph of Page 7,Second paragraph of Page 7)
• Lines 177, 178 and 192, the “J100-SB-SP” have been modified to “J100-HB-SP”.(Manuscripts location: First paragraph of Page 8,Second paragraph of Page 8)

Q2. Specimen J100-HB-NP can be added and compared with specimen J100-HB-SP to study the effect of a steel plate presence or absence.

A2. In this study, the steel plate was set as a reference and the difference according to the type of rebar was compared. Therefore, as mentioned by the reviewer, the gab is 100 mm and the comparative analysis according to the presence or absence of steel plates will be conducted later when there is an opportunity.

Q3. How to measure the joint width when the rebar type is looped rebar.

A3. The joint spacing at the looped rebar is shown in Figure 2.

The rebar used in the precast market is looped rebar, and if steel plate is added to the hook rebar, it is harder to see than looped rebar. In addition, when the looped rebar is installed as shown in Figure 2, the spacing between the connections is set to 150 mm and 220 mm. For smooth comparison, the parameters were mentioned as 0 in the paper.

• * The joint widths for the looped rebar specimens are as shown in Figure 2; these values are not applicable (NA) to the joint width comparison given the differences between the hooked and looped rebar configurations and are indicated by the specimen nomenclature. (Manuscripts location:  Table 1 of  Page 3)

Q4. How did author determine the joint width of the six specimens or what is the basis to determine the joint width.

A4. In this study, the joint gap of the precast bridge decks was set to 100 mm because although the regulations on precast connections are not common at present, concrete is damaged by heat applied to rebars when welding them. Hence, the gaps of 100 mm and 150 mm between the connections were compared.

Q5. Explain the loading scheme with more details and make some supplements to the test overview. If possible, provide photos when loading.

A5. In Figure 4, (b) Test set-up for loading was added, and (c) was changed to measurement of relative disposition. The text has been modified accordingly.

• Figure 4 shows the test set-up of this study. A longitudinal load was applied using an actuator to induce tension throughout the joint in each specimen. The capacity of the actuator was set to 200 t. The relative displacement of the joint under a tension load was measured using a displacement transducer connected to the data logger (Figure 4(a)). Bridge decks to actuators requires high-strength bolts having a minimum diameter of 24 mm, but the use of bolts to attach concrete specimens to rigid frames and actuators could not provide sufficient bearing strength. Hence, 32 mm diameter reinforcement was used for these joints. To secure the concrete specimens to the test frame and prevent deformation, five 250 mm spaced rebars were arranged in two rows, 200 mm and 700 mm from each specimen end. These bars were inserted into the ducts that were preinjected into the sample. The actuator joints were attached by arranging three rebars 180 mm apart in one row, 300 mm and 320 mm from the other end of each specimen. The bar was embedded in a 50 mm hole drilled in each test sample prior to the test (Figure 4(b)). In the displacement transducer of the experiment, two attachment points were installed over the joint in the center of the test, which were 600 mm away from the fixed end of the test. The displacement transducer measured the relative displacement (Figure 4(c)). The tension load applied to the test specimen was gradually increased over time until it reached a maximum of 800 kN.(Manuscripts location: Second paragraph of Page 5)

Q6. What is the practical prospect of this study. And if it is applied to actual bridges, whether its performance under car loads or other loads can be reflected only by the results of tension experiment.

A6. Since this study considers the load combination generated by the bridge decks, only tensile force is generated at the connection of the bridge decks As a result, the vehicle load and other loads can be considered only by loading the tensile force of the precast bridge decks.

Q7. What connection technology did the study use.

A7. Table 1 describes the connection technology in this study. Therefore, we supplemented the contents related to table 1.

• Six test specimens were fabricated with the joint width, rebar type, and steel plate as the parameters, as presented in Table 1, to evaluate the effects of each parameter on the joint behavior under tension load. Specimens J100-HB-SP and J150-HB-SP were compared to evaluate the effects of joint width, and specimen J100-NB-SP was evaluated to determine the effects of the presence of rebar. Specimens J0-LB-NP and J0-LB-SP were evaluated to determine the effects of looped rebar and were compared to determine the effects of the presence of steel plate. Finally, C-SB-NP was evaluated to provide a comparison with typical CIP construction. Figure 1 depicts a side and top view of J100-HB-SP, which represents a precast bridge deck joint having a, hooked rebar, steel plate, and width of 100 mm. All rebars had an elastic modulus of 200,000 MPa and a yield stress of 400 MPa. met the SD400 specification and had a diameter d of 32 mm, corresponding to a required anchorage development or lap splice length of 15d = 480 mm. The compressive strength of the deck slab concrete was 43 MPa with an elastic modulus of 30,000 MPa. Figure 2 shows the specific configuration of each test specimen defined in Table 1.(Manuscripts location: Fourth paragraph of Page 2)

Q8. Add performance of the materials used in the study with more details.

A8. Additions have been made to the text in accordance with the reviewer’s recommendations.

• All rebars had an elastic modulus of 200,000 MPa and a yield stress of 400 MPa. met the SD400 specification and had a diameter d of 32 mm, corresponding to a required anchorage development or lap splice length of 15d = 480 mm. The compressive strength of the deck slab concrete was 43 MPa with an elastic modulus of 30,000 MPa.(Manuscripts location: Fourth paragraph of Page 2)

Q9. How about the constructability of the optimal specimen.

A9. The constructability part was added to the conclusion (point 8) and is as follows:

• 8. The gap between the appropriate longitudinal connections on the bridge deck was 100 mm, and the joint between the installed hook reinforcement and steel plate showed the most optimal longitudinal behavior.(Manuscripts location: Number 8 of  Page 15)

Q10. What’s the originality or significant contribution of this paper.

A10. The introduction has been revised and the details are as follows.

• In summary, the precast bridge deck joint has some limitations. To solve this problem, this study conducted a tensile test to analyze and optimize the behavior of the longitudinal connection of the precast bridge. To perform this optimization, the width of the joints, the presence of hooked or looped rebars, and the presence of steel plates for the structural performance of the proposed joints were evaluated using a series of specimens including existing CIP bridges.(Manuscripts location: Third paragraph of Page 2)

Reviewer 4 Report

In this manuscript the authors investigated the behavior in tension of some types of panel-to-panel longitudinal joints applied to a precast bridge deck. 

C1) The authors are requested to add the research highlights in the manuscript. 

C2) It is difficult to understand from the bridge designer point of view what the authors actually wanted to present in the manuscript.  For a bridge precast deck, it is largely known that when the joint behavior of the precast panels is the study subject, then the shear behavior of the joint is studied. Why the joint was subjected  to the axial force N in plane of the precast panels? It is the axial force the main internal force acting in the precast bridge deck when the vehicles traffic are underway? For a bridge designer, a replicating force of dual wheels of a truck must be the external load on the model.  For clarity, the authors must check carefully the mentioned references [2], [20], [22], [24].

C3) The introduction section is short, and it has not summarized the relevant research conducted on this particular topic. Moreover, in Introduction the authors should focus on the relevant references for the topic. The authors should also reference published articles related to precast panel joints which are subjected to axial forces in plan of the precast panels. If the referenced article is published in a well ranked journal, then much better is. 
C5) The authors mentioned what it was studied, but the objective of the study has not clearly stated by the authors. 

C6) The novelty and significance of the study is unclear. 

C7) There is no optimization in this manuscript. The authors should replace this word.

C8) The description of the entire bridge structure is missing or at least of a substructure formed of the precast panels and the supporting members should be described. The authors present the precast panels, only. For example, it is not clear the supporting conditions of the panels. It is for sure that they are beared by some members, but these members are not present in the description and there is no section-view or elevation-view where they can be seen.

C9) There is no technical justification based on design, practice or literature about the type and size of the studied joints. Is it a largely used this type of joint in the author's country or somewhere else. If yes, then a discussion around this type of joints should be made and also referenced.

C10) What type of bridge structure this type of panel-to-panel connections is addressed? 

C11) Where is the panel-to-panel connection located within the bridge deck? It is mentioned in the title that is a longitudinal joint but is not enough.

C12) The presence of the reinforcement bars taking different shapes in the joint space is comprehensible, but the presence of the plate made of plain steel with poor bond with concrete is not justified. 

C13) It is not very clear how the grouting is made when the steel plate is in place covering the entire panel-to-panel connection.

C14) The detailing in Figure 1 is confusing. The dashed line may be misleading for some readers.  If the a) and b) details are scaled to the same ratio, then any particular point from one detail should vertically corresponds to the same point on the other detail.

C15) The detail b) from Figure 1 has some mistakes in illustration. The steel plate seems to be without contact to other parts of the model.

C16) In Figure 2 some information is clear but some improvements must be made in respect to the size of the text corresponding to dimensioning lines in print and a better correspondence between the rebars from section and the top view.

C17) The method of testing have not been discussed in detail.

C18) The model is poor instrumented in terms of displacements collecting devices. Only one is leads to an overall low precision and no possibility of comparison

C19) The authors are requested to compare the obtained results in this study with other results reported in some previous studies.

C20) There are no standard criteria, ASTM, EN or other, on the connection failure. What standard parameters defines the failure state of the panel-to panel connection?

C21) There are some design recommendations as an outcome of the study presented in this manuscript? 

C22) There are some conclusions about the constructability as an outcome of the study presented in this manuscript? 

C23) Overall manuscript requires rigorous preview at the authors level for a consistent flow of reading and revealing the scientific facts pertaining to the area under the consideration.

C24) There is no real discussion on the acquired experimental results.

C25) The conclusions are only applied to the performed experimental investigation. No overall recommendations for the design or practice constructability of a bridge deck. Many conclusions are just simple observations rather suitable for the "Discussion" section.

C26) There is no conclusion about the adherence (bond ) of the grout to the precast panels

The study seems having applicability, but is questionable if the study was well performed and well addressed, because the axial force N no not replace the action of a double-wheel of truck. Perhaps the authors will find out a different applicability to civil structures where the joint in practice is mainly subjected to the axial force N.

The manuscript in this shape is to be rejected because has some serious flaws, the way of conducting the research do not address to a bridge deck which is mainly subjected to vehicle wheels. The authors have to make a major revision of the manuscript.

 

Author Response

Q1. The authors are requested to add the research highlights in the manuscript. 

A1. The authors would like to thank the reviewer for their comments and suggestions, which helped in improving the quality of our paper. The reviewer’s comments have been fully incorporated into the revised version of this paper, as detailed below.

• Highlights are marked in the conclusion and summary of the text.

Q2. It is difficult to understand from the bridge designer point of view what the authors actually wanted to present in the manuscript.  For a bridge precast deck, it is largely known that when the joint behavior of the precast panels is the study subject, then the shear behavior of the joint is studied. Why the joint was subjected  to the axial force N in plane of the precast panels? It is the axial force the main internal force acting in the precast bridge deck when the vehicles traffic are underway? For a bridge designer, a replicating force of dual wheels of a truck must be the external load on the model.  For clarity, the authors must check carefully the mentioned references [2], [20], [22], [24].

A2. The purpose of this study was to examine the connection of the overall precast longitudinal joint rather than to conduct a local behavior analysis with vehicle load. Because the load combination from the bottom plate is taken into account, only tensile force is generated at the bottom plate connection. As a result, the vehicle load and other loads can be considered only by loading the tensile force of the precast bridge decks.

In the future, if there is an opportunity for further research, we plan to analyze the shear behavior according to actual vehicle boarding.

Q3. The introduction section is short, and it has not summarized the relevant research conducted on this particular topic. Moreover, in Introduction the authors should focus on the relevant references for the topic. The authors should also reference published articles related to precast panel joints which are subjected to axial forces in plan of the precast panels. If the referenced article is published in a well ranked journal, then much better is.

A3. Revisions have been made to the text in accordance with the reviewer’s recommendations The contents are as follows.

• Nasrin et al. [32] determined that the bending resistance increased when ultra-high performance concrete (UHPC) was placed on the precast bridge deck joint. Sriboonma et al. [33] established that large studs did not significantly affect shear resistance and flexibility limits in the type of shear connectors. Therefore, they concluded that the connection problem can be solved by fillet welding. Hube et al. [34] demonstrated that finite element analysis is suitable for simulating motion and strength.(Manuscripts location: Second paragraph of page 2)

Q3. The authors mentioned what it was studied, but the objective of the study has not clearly stated by the authors.

A3. Based on the reviewer’s recommendation, the introduction has been modified as follows:

• In summary, the precast bridge deck joint has some limitations. To solve this problem, this study conducted a tensile test to analyze and optimize the behavior of the longitudinal connection of the precast bridge. To perform this optimization, the width of the joints, the presence of hooked or looped rebars, and the presence of steel plates for the structural performance of the proposed joints were evaluated using a series of specimens including existing CIP bridges.(Manuscripts location: Third paragraph of page 2)

Q4. The novelty and significance of the study is unclear.

A4. Revisions have been made to the text in accordance with the reviewer’s recommendations. The purpose of this study is as follows.

• In summary, the precast bridge deck joint has some limitations. To solve this problem, this study conducted a tensile test to analyze and optimize the behavior of the longitudinal connection of the precast bridge. To perform this optimization, the width of the joints, the presence of hooked or looped rebars, and the presence of steel plates for the structural performance of the proposed joints were evaluated using a series of specimens including existing CIP bridges. Subsequently, a finite element model (FEM) was developed and analyzed to verify the behavior of the simulated optimal joint configuration against the experimentally obtained observations.(Manuscripts location: Third paragraph of page 2)

Q5. There is no optimization in this manuscript. The authors should replace this word.

A5. 

As recommended by the reviewer, conclusion has been revised.

• 5. The overall structural performance of the optimal precast bridge deck joint (J100-HB-SP) was similar to that of an equivalent monolithic CIP bridge deck (C-SB-NP), indicating that J100-HB-SP is a suitable configuration for a precast bridge deck longitudinal joint.(Manuscripts location: Number 5 of page 15)

Q6. The description of the entire bridge structure is missing or at least of a substructure formed of the precast panels and the supporting members should be described. The authors present the precast panels, only. For example, it is not clear the supporting conditions of the panels. It is for sure that they are beared by some members, but these members are not present in the description and there is no section-view or elevation-view where they can be seen.

A6. As suggested by the reviewer, Figure 4 has been modified. The contents are as follows.

• Figure 4 shows the test setup of this study. A longitudinal load was applied using an actuator to induce tension throughout the joint in each specimen. The capacity of the actuator was set to 200 t. The relative displacement of the joint under a tension load was measured using a displacement transducer connected to the data logger (Figure 4(a)). Bridge decks to actuators require high-strength bolts having a minimum diameter of 24 mm, but the use of bolts to attach concrete specimens to rigid frames and actuators could not provide sufficient bearing strength. Hence, 32 mm diameter reinforcement was used for these joints. To secure the concrete specimens to the test frame and prevent deformation, five 250 mm spaced rebars were arranged in two rows, 200 mm and 700 mm from each specimen end. These bars were inserted into the ducts that were preinjected into the sample. The actuator joints were attached by arranging three rebars 180 mm apart in one row, 300 mm and 320 mm from the other end of each specimen. The bar was embedded in a 50 mm hole drilled in each test sample prior to the test (Figure 4(b)). In the displacement transducer of the experiment, two attachment points were installed over the joint in the center of the test, which were 600 mm away from the fixed end of the test. The displacement transducer measured the relative displacement (Figure 4(c)). The tension load applied to the test specimen was gradually increased over time until it reached a maximum of 800 kN.(Manuscripts location: Figure 4 of page 6, Second paragraph of page 5)

Q7. There is no technical justification based on design, practice or literature about the type and size of the studied joints. Is it a largely used this type of joint in the author's country or somewhere else. If yes, then a discussion around this type of joints should be made and also referenced.

A7. In this study, the gap between the connections of the precast floor plates was set to 100 mm. The reason for this is that although the regulations for precast connections are not common at present, concrete is damaged by heat applied to rebars when welding them, so the gaps between the connections were compared by 100 mm and 150 mm.

Figure 2 has been modified and details have been added.(Figure 2 of page 4)

Q8. What type of bridge structure this type of panel-to-panel connections is addressed?

A8. The main purpose of this study is to improve connectivity, so it can be applied to various bridges. Therefore, the type of bridge is not specified.

Q9. Where is the panel-to-panel connection located within the bridge deck? It is mentioned in the title that is a longitudinal joint but is not enough.

A9. Since the bridge decks presented in this study is located on the upper part of the bridge, only the behavior between the bridge decks was analyzed without specifying the bridge separately.

Q10. The presence of the reinforcement bars taking different shapes in the joint space is comprehensible, but the presence of the plate made of plain steel with poor bond with concrete is not justified.

A10. Even if the adhesion of the steel plate is not very good, the steel plate itself is attached to the reinforcement, and hence, it was not considered.

Figure 2 and Figure 4 have been modified to provide a better understanding. (Figure 2 of page 4, Figure 4 of page 6)

Q11. It is not very clear how the grouting is made when the steel plate is in place covering the entire panel-to-panel connection.

A11. This information can be found by looking at the modified Figure 1. As shown in Figure 1, there is a circular hole in the steel plate.(Figure 1 of page 3)

Q12. The detailing in Figure 1 is confusing. The dashed line may be misleading for some readers.  If the a) and b) details are scaled to the same ratio, then any particular point from one detail should vertically corresponds to the same point on the other detail.

The detail b) from Figure 1 has some mistakes in illustration. The steel plate seems to be without contact to other parts of the model.

A12. As suggested by the reviewer, Figure 1 has been modified. (Figure 1 of page 3

Q13. In Figure 2 some information is clear but some improvements must be made in respect to the size of the text corresponding to dimensioning lines in print and a better correspondence between the rebars from section and the top view.

A13. As mentioned by the reviewer, Figure 2 has been modified.(Figure 2 of page 4)

Q14. The method of testing have not been discussed in detail.

A14. The recommendation of the reviewer has been taken into consideration, and the details are as follows.

• Bridge decks to actuators require high-strength bolts having a minimum diameter of 24 mm, but the use of bolts to attach concrete specimens to rigid frames and actuators could not provide sufficient bearing strength. Hence, 32 mm diameter reinforcement was used for these joints. To secure the concrete specimens to the test frame and prevent deformation, five 250 mm spaced rebars were arranged in two rows, 200 mm and 700 mm from each specimen end. These bars were inserted into the ducts that were preinjected into the sample. The actuator joints were attached by arranging three rebars 180 mm apart in one row, 300 mm and 320 mm from the other end of each specimen. The bar was embedded in a 50 mm hole drilled in each test sample prior to the test (Figure 4(b)). In the displacement transducer of the experiment, two attachment points were installed over the joint in the center of the test, which were 600 mm away from the fixed end of the test. The displacement transducer measured the relative displacement (Figure 4(c)). The tension load applied to the test specimen was gradually increased over time until it reached a maximum of 800 kN.(Manuscripts location: Second paragraph of page 5)

Q15.  The model is poor instrumented in terms of displacements collecting devices. Only one is leads to an overall low precision and no possibility of comparison.

A15. Some of the text has been modified in accordance with the reviewer’s comments. The details are as follows.

• In the displacement transducer of the experiment, two attachment points were installed over the joint in the center of the test, which were 600 mm away from the fixed end of the test.(Manuscripts location: Second paragraph of page 5)

Q16. The authors are requested to compare the obtained results in this study with other results reported in some previous studies.

A16. It is difficult to compare and verify the results of this study with other studies because as of now, to the best knowledge of the authors, studies similar to this study have not been conducted. Related content will be considered in future studies.

Q18. There are no standard criteria, ASTM, EN or other, on the connection failure. What standard parameters defines the failure state of the panel-to panel connection?

A18. Since ASTM/EN has a single material reference and no bridge reference, this study used the limiting state design method. As mentioned by the reviewer, some reference has been added.(Number 40 of page 17, Number 41 of page 18)

Q19. There are some design recommendations as an outcome of the study presented in this manuscript?

A19. According to the reviewer’s comments, the conclusion (point 5) has been modified. 

• 5. The overall structural performance of the optimal precast bridge deck joint (J100-HB-SP) was similar to that of an equivalent monolithic CIP bridge deck (C-SB-NP), indicating that J100-HB-SP is a suitable configuration for a precast bridge deck longitudinal joint.(Manuscripts location: Number 5 of page 15)

Q20. There are some conclusions about the constructability as an outcome of the study presented in this manuscript?

A20. As recommended by the reviewer, the conclusion (point 8) has been modified.  The corresponding contents are as follows

• 8. The gap between the appropriate longitudinal connections on the bridge deck was 100 mm, and the joint between the installed hook reinforcement and steel plate showed the most optimal longitudinal behavior.(Manuscripts location: Number 8 of page 15)

Q21. Overall manuscript requires rigorous preview at the authors level for a consistent flow of reading and revealing the scientific facts pertaining to the area under the consideration.

A21. As recommended by the reviewer, the manuscript has been thoroughly reviewed and checked.

Q22. There is no real discussion on the acquired experimental results.

A22. As suggested by the reviewer, the conclusion (point 7) has been modified. 

• The load–relative displacement curve and overall crack pattern obtained using the FEM were similar to those observed during the test, and the final relative displacements were within 2%. Therefore, the proposed FEM was able to accurately predict the structural behavior of the precast bridge deck longitudinal joint.(Manuscripts location: Number 7 of page 15)

Q23. The conclusions are only applied to the performed experimental investigation. No overall recommendations for the design or practice constructability of a bridge deck. Many conclusions are just simple observations rather suitable for the "Discussion" section.

A23. As suggested by the reviewer, the conclusion (point 8) has been modified.  The corresponding contents are as follows.

• 8. The gap between the appropriate longitudinal connections on the bridge deck was 100 mm, and the joint between the installed hook reinforcement and steel plate showed the most optimal longitudinal behavior.(Manuscripts location: Number 8 of page 15)

Q24. There is no conclusion about the adherence (bond ) of the grout to the precast panels.

A24. The purpose of this study was to analyze the overall behavior of the bridge decks. In the current study, grout was not considered as one of the main variables.

 

 

 

 

 

 

 

 

Reviewer 5 Report

The paper examines the performance of precast bridge deck longitudinal joints with different configurations using numerical analysis and experiments.

A few studies are available in the literature about the performance of these joints in bridges under tensile loading. This study is expanding the literature by providing the result of an experimental study accompanied by finite element analyses.  

It appears that the unique aspect of the work is studying the impacts of hook rebars and steel plates. I think the focus of this research is quite important, considering the lack of adequate guidelines for detailing such joints.

I can recommend authors discuss whether code relationships can predict the observed behavior in the experiments. For example, how close is the shear capacity of the specimens calculated by the code to the experimental results?

I wonder if the authors used smeared crack model in the finite element analysis. If so, how did they remedy mesh dependency issues? For more information, you may want to take a look at:

“Element size effects in nonlinear analysis of reinforced concrete members”

https://doi.org/10.1016/S0045-7949(96)00007-7

Also, I think it would be great if the authors could include some more practical recommendations for practicing engineers. For example, what do they recommend for detailing these joints? It would be great if a relationship could be proposed for engineers to calculate the capacity of these joints.

The conclusion seems adequate to me, addressing the central question posed by the authors.

I think the literature review can be improved by incorporating of more similar studies. For example,

“Experimental and Computational Evaluation of In-Span Hinges in Reinforced Concrete Box-Girder Bridges” DOI: 10.1061/(ASCE)ST.1943-541X.0000368.

Fig. 2 can be improved to become more legible. 

Author Response

Q1. I can recommend authors discuss whether code relationships can predict the observed behavior in the experiments. For example, how close is the shear capacity of the specimens calculated by the code to the experimental results?

A1. The authors would like to thank the reviewer for their comments and suggestions, which helped in improving the quality of our paper. The reviewer’s comments have been fully incorporated into the revised version of this paper, as detailed below.

This study aims to find the optimal joint parameter sand analyze the optimal joint through actual experimentation rather than comparing the results of the real experiment and the finite element analysis.

The matter was not considered in this study. However, if there is an opportunity later, we will surely consider it in our future works.

Q2. I wonder if the authors used smeared crack model in the finite element analysis. If so, how did they remedy mesh dependency issues? For more information, you may want to take a look at:

“Element size effects in nonlinear analysis of reinforced concrete members”

https://doi.org/10.1016/S0045-7949(96)00007-7

A2. This study did not use the smeared crack model because the model has poor convergence, and hence, the gap between the bridge decks was analyzed using a nonlinear spring. The corresponding contents are as follows.

• The concrete was modeled using C3D8R 3D solid elements. The implementations of the precast concrete bridge deck units and CIP joint section were executed separately; as the contact surface between the two cannot be considered fully integral, it was modeled using a nonlinear spring element (connecting two nodes) in this study (Figure 12 (a)).(Manuscripts location: First paragraph of page 11)

Q3. Also, I think it would be great if the authors could include some more practical recommendations for practicing engineers. For example, what do they recommend for detailing these joints? It would be great if a relationship could be proposed for engineers to calculate the capacity of these joints.

A3. As mentioned above, this study aims to find the optimal joint parameters and analyze the case through the actual experimentation rather than comparing the results of the real experiment and the finite element analysis.

Therefore, the recommendation of the reviewer was not considered in this study. However, if there is an opportunity later, we will consider it and proceed.

Q4. The conclusion seems adequate to me, addressing the central question posed by the authors.I think the literature review can be improved by incorporating of more similar studies. For example,“Experimental and Computational Evaluation of In-Span Hinges in Reinforced Concrete Box-Girder Bridges” DOI: 10.1061/(ASCE)ST.1943-541X.0000368

A4. As recommended by the reviewer, reference has been added.

• Hube et al. [34] demonstrated that the finite element analysis is suitable for simulating motion and strength.(Manuscripts location:  Second paragraph of page 2, Reference of page 17)

Q5. Fig. 2 can be improved to become more legible.

A5. As suggested by the reviewer, Figure 2 has been modified.(Figure 2 of page 4)

 

Round 2

Reviewer 2 Report

The revised paper is not greatly improved, and this paper should be rejected

Author Response

The revised paper is not greatly improved, and this paper should be rejected.

- The authors would like to thank the reviewer for the comments and suggestions that helped improve the quality of our paper. We think that the reviewer's comments were addressed in the revised edition of our paper. We would be happy to make further changes if required.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have made careful revisions based on reviewers' suggestions. Only one samll question, in the introduction part, some important references are missing for prefabricated structures. Li JB, et al. Experimental study and numerical simulation of a laminated reinforced concrete shear wall with a vertical seam, Applied Sciences-Basel. 7(6): 629; doi:10.3390/app7060629. Lu Z. et al. Studies on seismic performance of precast concrete columns with grouted splice sleeve, Applied Sciences-Basel. 2017, 7(6): 571; doi:10.3390/app7060571.

Author Response

Q1. Only one small question, in the introduction part, some important references are missing for prefabricated structures. Li JB, et al. Experimental study and numerical simulation of a laminated reinforced concrete shear wall with a vertical seam, Applied Sciences-Basel. 7(6): 629; doi:10.3390/app7060629. Lu Z. et al. Studies on seismic performance of precast concrete columns with grouted splice sleeve, Applied Sciences-Basel. 2017, 7(6): 571; doi:10.3390/app7060571.

A1. The authors would like to thank the reviewer for the comments and suggestions that helped improve the quality of our paper. We think that the reviewer's comments were addressed in the revised edition of our paper. As recommended by the reviewer, the references have been added.

• As a result, several studies have been conducted to develop the connectivity and constructability of precast bridge deck joints [18–25].(Manuscript locations: First paragraph of page 2)

Author Response File: Author Response.docx

Reviewer 4 Report

I want to thank you to the authors for their response to my comments from the first review.

As I said in the previous review the study presented by the authors seems to be limited in conclusions oriented to the design or to practice.  

Without a real argument coming from the authors, the study remains not well addressed and do not have obvious improvement in applications.

The authors were not able to describe and demonstrate with arguments, or at least exemplify through published papers in well rank journals, what are the limitations of the precast deck joints that are existent in service and why studying the presented deck joints to axial force N, i.e. tensile force applied the plane of panels, it is useful for improvements in design or the construction practice.  The authors should have been known that a study is to be addressed to research area or at least to the professional area i. e. practice area.

The author's responses do not provide a clear and well-argued response to the raised comments. Here I am talking about the made comments C2, C3, C4, C5, C6, C7, C8, C9, C10, C15, C16, C18, C19, C20, C21, C22, C24.

In the following paragraphs I will underline some examples.

For example, responding to C2, the authors agree that the shear behavior is the obvious effect to the vehicle loads mentioning that this topic remains for latter if it will be some opportunities. .................... The authors should have been thinking from the beginning that the shear behavior come first and the study where the joint between precast panels is subjected in plane remains for later if it will be some opportunities. Also, the authors have not got something useful from the mentioned references [2], [20], [22], [24] from the first shape of the manuscript. 

Analyzing the author's response to comment C3, it is obvious that the objective of the study remains unclear. The authors should have been proved which are the limitations of the precast bridge deck joint. The simple fact that the authors state "the joint has some limitations" is not enough. Very likely there, but the authors should master this issue.

Regarding the comment 4, the authors were not able to highlight what is the novelty of the study and its significance.

Regarding the comment 5, the authors continue using the word optimization or optimal. For this study, in this shape, it cannot be asserted that it was involved any optimization applied to the configurations of deck joints. The number of joint configurations is low and there is no optimization criterion involved. 

Regarding the comment 6, the authors were required something, but they responded completely unsatisfactory. They were required some information useful to the readers to understand about the position of the precast panel within the bridge structure and the corresponding supporting condition. 

Regarding the comment 7, the authors were required something, but they responded completely unsatisfactory. 

Regarding the comment 8, the authors avoided to mention some types of bridge structures where this type of deck with this type of joints is applied or could be applied. 

............................................................

The failure state was not described and also, what component has caused the failure of the joint? There is no explanation about the potential components of the relative displacement between panels. Is there any contribution of the horizontal bottom face of joint to the resistance force of the joint.

Within the study there are no explaining arguments based on bond between reinforcement and concrete or shear between concrete layers at different ages considering that the connection grout is was cast in place much later.

 

As I have mentioned before, the authors gave unsatisfactory responses at too many comments which I made in the first review.

 

 

Author Response

Q1. For example, responding to C2, the authors agree that the shear behavior is the obvious effect to the vehicle loads mentioning that this topic remains for latter if it will be some opportunities. The authors should have been thinking from the beginning that the shear behavior come first and the study where the joint between precast panels is subjected in plane remains for later if it will be some opportunities. Also, the authors have not got something useful from the mentioned references [2], [20], [22], [24] from the first shape of the manuscript.

A1. The authors would like to thank the reviewer for the comments and suggestions that helped improve the quality of our paper. We think that the reviewer's comments were addressed in the revised edition of our paper. In this study, precast concrete bridge decks were installed on bridges and girders. Therefore, the study investigates the behavior of the precast bridge deck joint, which generates more tensile loads when the vehicle loads. This is because the center of the bridge deck generates a negative moment by the junction, thereby generating a tensile load. (Manuscript location : Third paragraph of page 2)

Q2. Analyzing the author's response to comment C3, it is obvious that the objective of the study remains unclear. The authors should have been proved which are the limitations of the precast bridge deck joint. The simple fact that the authors state "the joint has some limitations" is not enough. Very likely there, but the authors should master this issue.

A2. 

As suggested by the reviewer, the Introduction has been modified. The added content is as follows:

 

In summary, research on the precast bridge deck is being actively conducted. However, most of these studies focus on the shear behavior of precast bridges, and studies on the joints of the precast bridge deck are limited. The precast bridge deck is located above the bridge's piers and girders. These joints on the precast bridge deck produce more tensile loads due to negative moments when the vehicle is under load. To solve this problem, this study conducted a tensile test to analyze and optimize the behavior of the longitudinal joints of the precast bridges. (Manuscript location : Third paragraph of page 2)

Q3. Regarding the comment 4, the authors were not able to highlight what is the novelty of the study and its significance.

A3. 

Revisions have been made to the text in accordance with the reviewer’s recommendations. The highlight of this study is as follows.

In summary, research on the precast bridge deck is being actively conducted. However, most of these studies focus on the shear behavior of precast bridges, and studies on the joints of the precast bridge deck are limited. The precast bridge deck is located above the bridge's piers and girders. These joints on the precast bridge deck produce more tensile loads due to negative moments when the vehicle is under load. To solve this problem, this study conducted a tensile test to analyze and optimize the behavior of the longitudinal joints of the precast bridges. To perform this optimization, a series of specimens considering existing CIP bridges were used to evaluate the width of the joints for the structural performance of the proposed joints, the presence of hook or loof rebar, and the presence of steel plates. We then develop and analyze a finite element model (FEM) to validate the behavior of simulated optimal junction configurations using experimentally obtained observations.(Manuscript location : Third paragraph of page 2)

Q4. Regarding the comment 5, the authors continue using the word optimization or optimal. For this study, in this shape, it cannot be asserted that it was involved any optimization applied to the configurations of deck joints. The number of joint configurations is low and there is no optimization criterion involved.

A4. In this study, optimization is not required because the optimization is performed according to the junction type without showing detailed values for joint optimization. Also, a small number of joints is not a problem.

Q5.  Regarding the comment 6, the authors were required something, but they responded completely unsatisfactory. They were required some information useful to the readers to understand about the position of the precast panel within the bridge structure and the corresponding supporting condition.

A5. The introduction has been modified to resolve this issue.

 

• In summary, research on the precast bridge deck is being actively conducted. However, most of these studies focus on the shear behavior of precast bridges, and studies on the joints of the precast bridge deck are limited. The precast bridge deck is located above the bridge's piers and girders. These joints on the precast bridge deck produce more tensile loads due to negative moments when the vehicle is under load.(Manuscript location : Third paragraph of page 2)

Q6. Regarding the comment 7, the authors were required something, but they responded completely unsatisfactory. 

A6. This point indicates that the description of the substructure of the precast bridge deck is insufficient. The design, practice, or literature on the type and size of the joints studied is insufficient. Therefore, this study attempted to help understand by modifying the introduction. (Manuscript location : Third paragraph of page 2)

Q7. Regarding the comment 8, the authors avoided to mention some types of bridge structures where this type of deck with this type of joints is applied or could be applied. 

A7. The main purpose of this study is to improve connectivity it can be applied to various bridges. Therefore, the type of bridge is not specified.

Q8. The failure state was not described and also, what component has caused the failure of the joint? There is no explanation about the potential components of the relative displacement between panels. Is there any contribution of the horizontal bottom face of joint to the resistance force of the joint.

A8. We have clarified this in the revised manuscript as follows:

• In addition, in the final destruction mode of the experiment, cracks occurred in the contact part of different concretes due to the difference in their curing date. (Manuscript location : First paragraph of page 10)

Q9. Within the study there are no explaining arguments based on bond between reinforcement and concrete or shear between concrete layers at different ages considering that the connection grout is was cast in place much later.

A9. We have clarified this in the revised manuscript as follows:

• At the final load of 800 kN, the displacement was greater than 0.19 mm, the widths and lengths of the cracks clearly expanded to trace the joint geometry, and diagonal cracks developed. Furthermore, because the concrete in the joint has a difference in curing date of 28 days from that of the existing concrete, cracks occurred, as shown in Figure 10(d).(Manuscript location : First paragraph of page 10)

 

 

 

 

Author Response File: Author Response.docx

Round 3

Reviewer 4 Report

C1) Many of explanations given by the authors in the second revision phase to the raised comments from the first review are worthless, remain unclear and are not sustained by verifiable arguments.

C2) The authors continue not giving explanations to some raised comments in the first review.

C3) The authors were not able to bring evidence through published papers about necessity studying these two jointed panels subjected to axial tensile force N in their plane as an application to the bridges deck. The references starting from [24] to [31] do not mention this type of this load applied to the decks. Besides, in these papers are provided clear elevations and sections through the bridge deck in order to clarify the reader where the joint is located in span or on support (girders), what is the position about the bridge axis, perpendicular or parallel, etc.

C4) Regarding the previous comment, the sentence “In this study, precast concrete bridge decks were installed on bridges and girders” is confusing and do not clarify something.

C5) Is it possible “bridge deck joint, which generates more tensile loads when the vehicle load” ? 

C6) I quote “This is because the center of the bridge deck generates a negative moment by the junction, thereby generating a tensile load” Is it possible to give such explanation?   Very, very peculiar explanation

C7) Many conclusions looks like sentences for a Discussion section.

C8) There is no explanation of the recorded and observed experimental result. For example, in the conclusion 1, there is no explanation provided by the authors explaining why the results for joint J100-HB-SP are better than J100-HB-SP.

C9) The conclusion 2 is trivial and obvious.

C10) Conclusion 3, unexplained. Why? The authors should have had an explanation so far.

C11) Conclusion 5. What the authors understand through “optimal precast bridge” Did the authors demonstrate something related to optimal in this study?

C12 ) Have the authors some explanation about the statement from conclusion 5. Why the J100-HB-SP performed so well almost equal to the C-SB-NP.

C13) The last conclusion is confusing, English is poor. It does not seem to be a conclusion. The authors use again the word optimal.