Mechanical Properties of New Dry-Type Beam-Column Bolt Connection Joint
Round 1
Reviewer 1 Report
The authors present an interesting work on a New Dry-type Beam- Column Bolt Connection Joint. Overall, I think the work is well organized, in my opinion only needs some revisions. Below are a few comments that may contribute to enhance the quality of the paper:
Abstract and Introduction
The introduction section presents a literature review that places the work in comparison with other published work. It would be advisable to justify the relevance of this study, given the current state of knowledge, i.e., clearly make the novelty statement.
New Dry-type Connection Joint
Tables 1 and 2 need to be reviewed. The designations presented are the same and show different results. The designations of both Concrete strength and rebar types have to be improved and explained in the text.
Tests Process
This chapter is well organized.
Analysis and Comparison of Test Results
This chapter presents the results and, in some cases, tries to comment / justify the tendencies obtained. in my opinion, there is missing a very important part in this type of work: the cross-checking of the results obtained with each other, or with results from other similar or equivalent studies, ie, it is clearly lacking benchmarking. There is no attempt in this chapter to compare the results obtained with reference values or with results from other authors. This part is essential to improve the final quality of the work.
Conclusions
The conclusions reflect the rest of the document and are suitable.
Author Response
1. The introduction section presents a literature review that places the work in comparison with other published work. It would be advisable to justify the relevance of this study, given the current state of knowledge, i.e., clearly make the novelty statement.
R:
The introduction has been substantially revised by providing additional detailed background information and by further illustrating the significance and innovation of this study.
Yan conducted a reversed cyclic loading test on two precast prestressed concrete beam–column joints that were fabricated with two different concrete strengths in the keyway area.[Yan, X., Wang, S., Huang, C., Qi, A., & Hong, C. (2018). Experimental Study of a New Precast Prestressed Concrete Joint. Applied Sciences, 8(10), 1871.]
The research result is significant for the development for prefabrication so as to contribute to sustainable construction.
2. Tables 1 and 2 need to be reviewed. The designations presented are the same and show different results. The designations of both Concrete strength and rebar types have to be improved and explained in the text.
R:
The details of tests of material properties for concrete, steel bars and bolts related to table 1 and table 2 have been additional reviewed and explainations.
3. This chapter is well organized.
R:
Thanks for your support. In consideration of other reviewers’ comments, additional details of the experiment are explained in the paper. For example, we added the introduction of the layout of strain measurement gauges (section 2.2). In addition, additional details of the test results are provided. Additional details can be seen in the revised manuscript.
Strain measurement gauges are placed at key positions including the end of the column, the node area, the core area, the beam end, the ox leg, etc. to understand the variation of strain and stress of specimen under loads. The same branch of gauges with maximum electric current of 125A are adopted in this experiment. The position of gauges are shown in Figure 5: L1-L10 is used to measure the distribution of stress of reinforced concrete beams under loads; L11-L15 is used to measure the magnitude and direction of the main strain in the core region of the joints; Z1-Z8 is used to measure the distribution of strain of column under constant axial force; N1-N6 measures the stress-strain distribution of bolts under the action of horizontal load and vertical load.
At this time, force loading was changed into displacement loading. three levels of displacement loading of 95mm, 115mm, and 135mm are carried out and each level cycles three times respectively. With the load increasing, the number and width of cracks increases, and thus gradually forming through cracks as shown in Figure 7.
4. This chapter presents the results and, in some cases, tries to comment / justify the tendencies obtained. in my opinion, there is missing a very important part in this type of work: the cross-checking of the results obtained with each other, or with results from other similar or equivalent studies, ie, it is clearly lacking benchmarking. There is no attempt in this chapter to compare the results obtained with reference values or with results from other authors. This part is essential to improve the final quality of the work.
R:
We rewrote the Result analysis section in the revised manuscript. We reviewed researches on three other kinds of connection joints to find their limits and disadvantages so as to illustrate the advantages of this new dry-type beam-column bolt connection joint.
5. The conclusions reflect the rest of the document and are suitable.
R:
Thanks for your support. According to other reviewers’ comments, we added some key points in application of this new joint.
Therefore, when designing the beam end it is necessary to pay attention to avoid the reduction of capacity due to the punching failure
Reviewer 2 Report
Dear Authors,
In this study, a range of pseudo static tests of beam-column connection joints were carried out which is considered appropriate. The results of your work are really significant.
The introduction part should be improved. I suggest to make the table for a reference list, with the comparative column of the so far results and your work objective.
It can be seen from the figure that shear failure occurred in the core area of 173 the T- shaped end
174 close to the column of the beam, and large stress was generated on the top-most high-strength bolt, 175 but it is not the expected high-strength bolt failure.
Line: 183 you have two ‘end and’ words. Please proceed to correct.
Figure 10. Assembled frame beam-column joint connected by welding. IS NOT CLEAR. Please improve the graphical statement.
All figure should be improved with better resolution as well as English orthography improvement.
Thank You
Regards
Author Response
Reviewer #2:
1. In this study, a range of pseudo static tests of beam-column connection joints were carried out which is considered appropriate. The results of your work are really significant. The introduction part should be improved. I suggest to make the table for a reference list, with the comparative column of the so far results and your work objective.
R:
Thanks for your support. The introduction has been substantially revised by providing additional specific background information as well as by further illustrating the significance and innovation of this research.
Yan conducted a reversed cyclic loading test on two precast prestressed concrete beam–column joints that were fabricated with two different concrete strengths in the keyway area.[Yan, X., Wang, S., Huang, C., Qi, A., & Hong, C. (2018). Experimental Study of a New Precast Prestressed Concrete Joint. Applied Sciences, 8(10), 1871.]
The research result is significant for the development for prefabrication so as to contribute to sustainable construction.
2. It can be seen from the figure that shear failure occurred in the core area of 173 the T-shaped end 174 close to the column of the beam, and large stress was generated on the top-most high-strength bolt, 175 but it is not the expected high-strength bolt failure.
R:
The reasons why the expected high-strength bolt failure did not occur is explained.
Due to the punching failure in the core area at the t-shaped end of the precast concrete beam, the ultimate bending moment at the beam end is much lower than the theoretical bending moment value. Therefore, although the high-strength bolt produces a large stress, it is not the expected high-strength bolt that produces a large deformation, resulting in a large angular deformation of beam-column joints.
3. Line: 183 you have two ‘end and’ words. Please proceed to correct.
R:
We have updated it accordingly in the revised manuscript.
4. Figure 10. Assembled frame beam-column joint connected by welding. IS NOT CLEAR. Please improve the graphical statement.
R:
To better illustrate the properties, figure 10 (now figure 11) has been changed and additional details of the figure were illustrated.
Welded plate connection joints are often applied to connect precast concrete members as well. U.Ersoy[25] carried out a experimental research of reversed cyclic loading on a structural framework beam-column joint connected by welding(see in figure 11). The result shows that the strength, stiffness and energy consumption of joints connected by welding are equivalent to those of cast-in-situ joints, but it is difficult to control the installation quality of the joint connected by welding during on-site construction. Since there is no obvious plastic hinge area during failure in this connection mode, brittle failure is likely to occur at the welding seam under the action of repeated earthquake loads, so its energy consumption performance is poor.
5. All figure should be improved with better resolution as well as English orthography improvement.
R:
Almost all figures were replaced to improve the resolution as well as English orthography.
Reviewer 3 Report
Paper has been prepared by some authors, which have low structural knowledge. They had a lot of technical mistakes in the paper. There was no information about numerical modeling and simulation. The quality of figures was very low as well as there was no deep discussion to correlate failure modes, strains, force-deformation. There was no drawing regarding the position of strain gauges in the paper.
Author Response
Reviewer #3:
1. There was no information about numerical modeling and simulation.
R:
Numerical simulation of hysteretic curve and skeleton curve were conducted and the results were compared with the experiments in Section 3.2 and 3.3 respectively.
2. The quality of figures was very low as well as there was no deep discussion to correlate failure modes, strains, force-deformation.
R:
Some figures were replaced to improve the quality. Additional details about the failure mode were discussed just like why the expected high-strength bolt failure did not occur.
Due to the punching failure in the core area at the t-shaped end of the precast concrete beam, the ultimate bending moment at the beam end is much lower than the theoretical bending moment value. Therefore, although the high-strength bolt produces a large stress, it is not the expected high-strength bolt that produces a large deformation, resulting in a large angular deformation of beam-column joints.
3. There was no drawing regarding the position of strain gauges in the paper.
R:
We added a part (section 2.2) to introduce the layout of strain gauges.
Strain measurement gauges are placed at key positions including the end of the column, the node area, the core area, the beam end, the ox leg, etc. to understand the variation of strain and stress of specimen under loads. The same branch of gauges with maximum electric current of 125A are adopted in this experiment. The position of gauges are shown in Figure 5: L1-L10 is used to measure the distribution of stress of reinforced concrete beams under loads; L11-L15 is used to measure the magnitude and direction of the main strain in the core region of the joints; Z1-Z8 is used to measure the distribution of strain of column under constant axial force; N1-N6 measures the stress-strain distribution of bolts under the action of horizontal load and vertical load.
Round 2
Reviewer 1 Report
Authors respond appropriately to reviewers' comments and have amended the document in accordance with those comments. In these conditions I am of the opinion that the paper can be considered for publication.
Author Response
We fully agree with the reviewer’s original comments. We really appreciate the reviewer has recognized and accepted our revised work.
Reviewer 3 Report
There are more issues unclear, which should be explained:
the presented numerical simulation in figure 8 has been done by author? if so, the authors should bring all numerical details such as constitutive blocks used form modeling, failure modes, boundary conditions, software, and.... all details.
The authors mentioned that "The hysteretic curve of finite element simulation and experiments are compared". They should validate the numerical results, in terms of force-displacement, force-strain, and failure modes. Then, authors can declare they have trustable numerical models.
Re-draw figures 11 and 7. The quality of these figures are very low.
Author Response
1. the presented numerical simulation in figure 8 has been done by author? if so, the authors should bring all numerical details such as constitutive blocks used form modeling, failure modes, boundary conditions, software, and.... all details.
The authors mentioned that "The hysteretic curve of finite element simulation and experiments are compared". They should validate the numerical results, in terms of force-displacement, force-strain, and failure modes. Then, authors can declare they have trustable numerical models.
Response:
All numerical details such as constitutive blocks used form modelling, failure modes, boundary conditions, software, and et al. have been revised according to the reviewers’ suggestions. In addition, the numerical results have been validated. Part of the revised parts is listed as follows:
Finite element simulation of the mechanical properties of new dry- type connection joint were conducted using ANSYS software. Integral modeling is adopted in this study. Reinforcement units were regarded as subunits permeated in the concrete, of which mechanical properties can be superimposed on the plain concrete. The solid 65 units with kinematic hardening in the built-in material database of ANSYS software was selected as constitutive model. Parameters are set as follows: the elastic modulus was set to be 34GPa; the poisson ratio was set to be 0.2; the transfer coefficient of crack opening and crack closure were set to be 0.35 and 1 respectively meanwhile concrete compressive strength of beams and columns were set to be 32Mpa and 54 MPpa respectively. The common 3-D 4-joint unit solid 182 was chosen for high-strength bolts. The main model property was two-linear mixed-hardening. The elastic modulus was set to be 200GPa; the poisson ratio was set to be 0.45; the yield strength was set to be 618MPa and the strain-hardening modulus was set to be 20000. In-plane constraints and normal constraints were set on the top and at the bottom of the concrete column. End face of concrete beam was set as loading end. The partition type of the model is free partition, and the mesh size of screw, concrete beam and column was 25mm and 100mm respectively. ADD action was applied to nuts and screw in order to make them work together.
2.Re-draw figures 11 and 7. The quality of these figures are very low.
Response:
Figures 11 and 7 have been re-redrawn to improve the quality in the revised manuscript.
Round 3
Reviewer 3 Report
The Reviewer thinks this work could be much better than this work and it can improve a lot and the authors in the worst way considered the comments. They did the comments in rush.
The Reviewer accept the paper at the present form, but it could be much better than this weak and incomplete work.
