Structural Behavior of Floor Systems Made by Floor Plates—Mechanical Model Based on Test Results

Round 1

Reviewer 1 Report

Dear Authors,

you presented very interesting investigation and wrote a very good paper!

Despite of this assessment, please take note of my comments:

ref. line 66: There exist guidelines to deal with a lap splice! See German annex of EN 1992-1-1, chapter 10.9.3 (NA.14). (see your ref. [8])

ref. line 110: "Class 4" is not an international cassification. Please give a reference. Same in line 114 for "BE500A" and "DE500BS"

ref. chapter 2.1.3: Please name overlap length in your tests for each test series. Maybe also in table 3. 

ref. table : add also the tested amount of reinforcement in cm²/m for each series

ref. Fig.5: In addition to fig. 5 it could be helpfull to add a table with the test results F_Test / F_cal,y and additonal parameter overlapping length, amount of bending reinforcement, roughness ..

ref. 4.4.1: Eq. (5) gives the shear resistance of the interface. If you want to use this model to describe an overlapping splice, you have to show how much shear forces a lap splice induces in the interface. This is not done in your paper. How many lattice girders or which diameter has to be choosen as interface reinforcement depending on the parameter of the lap splice?

ref. 5: There is only one test in series  C with 400 mm distance of the lattice girder from the joint. Other tests were carried out with a distance of 95 mm. Therefore your proposal for a maximum distance of 400 mm is not carefully secured. Based on your tests am maximum of about 100mm is carefully secured. 

A proposal for the required dimension (diameter) and required quantity of the lattice girder in the area of the lap spice is missing.

No maximum diameter nor a maximum amount (cm2/m) of the overlapped bending reinforcement is given. This limitation should be given by the range of your test parameter.

Best regards

Reviewer

Author Response

Dear reviewer,

We thank the reviewer for his encouraging words in the introduction and recommendations. In the next; italic text will be used to answer the comments. The text of the article is also updated in a green for these comments. Orange is used for comments of the other reviewer.

ref. line 66: There exist guidelines to deal with a lap splice! See German annex of EN 1992-1-1, chapter 10.9.3 (NA.14). (see your ref. [8])

If we are well informed the German annex limits the diameter of the overlap reinforcement till 14 mm and a maximum amount of 1000 mm²/m. For most of the tests we passed the 14 mm and for the A-series also the 1000 mm²/m. This was made clear in the text.

ref. line 110: "Class 4" is not an international classification. Please give a reference. Same in line 114 for "BE500A" and "DE500BS"

Reference is added to the Belgian prescription rules of lattice girders, the so called PTV305 which is unfortunately only available in Dutch (or French). This document is however free available. For the type of the rebars reference is made to the Belgian application document of EN 1992-1-1.

ref. chapter 2.1.3: Please name overlap length in your tests for each test series. Maybe also in table 3. 

In the text of 2.1.3 the total bar length and amount of reinforcement (next suggestion) is added as table 3 is already loaded in our point of view.

ref. table : add also the tested amount of reinforcement in cm²/m for each series

See previous and also in section 2.1.1. the amount of reinforcement in the floor plates is also added in the text to be consistent.

ref. Fig.5: In addition to fig. 5 it could be helpfull to add a table with the test results F_Test / F_cal,y and additonal parameter overlapping length, amount of bending reinforcement, roughness ..

There exists a risk of overloading the table, so guidance is added to Table 4 for the ratio F_test/F_calc,u (after the figure) and locations where other relevant parameters can be found (in the beginning of the paragraph).

ref. 4.4.1: Eq. (5) gives the shear resistance of the interface. If you want to use this model to describe an overlapping splice, you have to show how much shear forces a lap splice induces in the interface. This is not done in your paper. How many lattice girders or which diameter has to be choosen as interface reinforcement depending on the parameter of the lap splice?

It was and is not the meaning to use this formula to describe the overlapping splice, as this formula is to our opinion only valid for the transfer of shear forces at the interface due to vertical (transverse) shear forces. In addition we never observed such a failure so we cannot make such statements. It was the meaning to highlight two curiosities in the actual formulation of EN 1992-1-1. The first about the possibility that you achieve a lower capacity with a double leg lattice girder and the second about combining adhesion and reinforcement contribution. Some text is added to make this clear.

ref. 5: There is only one test in series  C with 400 mm distance of the lattice girder from the joint. Other tests were carried out with a distance of 95 mm. Therefore your proposal for a maximum distance of 400 mm is not carefully secured. Based on your tests am maximum of about 100mm is carefully secured. 

This remark is correct, we rephrased it.

A proposal for the required dimension (diameter) and required quantity of the lattice girder in the area of the lap spice is missing.

In case of severe damage (a total calculation opening of above 2.4 mm or 2 mm effective) the Vierendeel-principle is proposed. On basis if the bending resistance the diameter of the diagonals can be defined. See Eq. (6) and (7), for repair however the use of post-drilled anchor rods is the only way to follow. This is now more highlighted in the text.

No maximum diameter nor a maximum amount (cm2/m) of the overlapped bending reinforcement is given. This limitation should be given by the range of your test parameter.

This is now added in ref. 5, also a reference is made to the concrete as described.

We thank you for your valuable comments and hope that we improved the manuscript. Due to the modifications, the lay-out of the figures and tables is not anymore in an optimal correspondence with the page lay-out, to our opinion this will be solved during the editing process.

Kind regards,

The authors.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper reports experimental results about floor slab made with lattice girders, with regard of some important aspects for the correct design of this structural component, usually treated in broad manner in structural design and assessment, also by the International Codes. The paper is well written and presented, the study is very interesting and very thorough. In this reviewer’s opinion, the manuscript deserves to be considered for publication in Applied Sciences. Nevertheless, some comments could be taken into account, as following reported:

- In the introduction, comments are reported for explaining the functioning of the slab in RC buildings, but maybe some comments could be added about the general slab behaviour under extreme loads, such as earthquakes, also considering the possible in-plane deformability effects.

Following authors could find the above information (https://doi.org/10.1007/s10518-019-00774-2; https://doi.org/10.1016/j.jobe.2018.05.019)

- In the introduction authors declared, at row 66, that guidelines do not take into account the forces transfer of the slab. This is not totally correct, also considering the procedures for designing the slab joists to bending and shear actions. Maybe Information about the arch and equivalent truss effects could be mentioned.

- In section 2.1.1, how many cubes were produced for assessing compressive strength of concrete?

- Why the compressive strengths in Table 1 are strongly higher than the expected values, for the selected concrete class?

- Did authors considered the restraint degree in the test setup for the specimen design?  

-To replace the sentence at row 179, which is not clear

- Additional information could be added on the theoretical curve in Figure 5 (maybe adding the reference equation in [4]).

Author Response

Dear reviewer,

We thank the reviewer for his encouraging words in the introduction and recommendations. In the next; italic text will be used to answer the comment. The text of the article is also updated in an orange colour for these comments. Green is used for comments of the other reviewer.

- In the introduction, comments are reported for explaining the functioning of the slab in RC buildings, but maybe some comments could be added about the general slab behaviour under extreme loads, such as earthquakes, also considering the possible in-plane deformability effects.

Following authors could find the above information (https://doi.org/10.1007/s10518-019-00774-2; https://doi.org/10.1016/j.jobe.2018.05.019)

As we already included comments about dynamic and fatigue aspects, the last paragraph of section 1 includes now also some words about extreme loadings I case of an earthquake (by the most recent suggested reference) and in case of fire (by an article published in the December 2020 number out of Fire Safety Journal)

- In the introduction authors declared, at row 66, that guidelines do not take into account the forces transfer of the slab. This is not totally correct, also considering the procedures for designing the slab joists to bending and shear actions. Maybe Information about the arch and equivalent truss effects could be mentioned.

The sentence at row 66 must be read together with the one at row 64, so guidelines for the design are missing. Also, the other reviewer made a comment on this, so the sentence is rephrased. Looking to arch and equivalent truss effect is not really in the scope of this article which is mostly experimentally based. We could not observe indications that can be explained by these effects.

- In section 2.1.1, how many cubes were produced for assessing compressive strength of concrete?

Each time on 3 cubes, this is added in the text.

- Why the compressive strengths in Table 1 are strongly higher than the expected values, for the selected concrete class?

This is a typical (problem) of overstrength for the floor plates. To facilitate a speedy production process the floor plates are made by a rapid cement and heat treated to allow for demoulding in 12 hours and transport to the site in 2 days. At time of arrival on site a quality of at least C30/37 is guaranteed. But the strength of the concrete is at that moment only in the early stage of developing.

- Did authors considered the restraint degree in the test setup for the specimen design?  

There was no restraint degree at the test set-up, in Figure 3 you will see clearly at the right support the hinge which is also on the left support. Neoprene mats are also used to flatten local imperfections.

-To replace the sentence at row 179, which is not clear

In the newest version this becomes sentence row 187; the sentence is rephrased.

- Additional information could be added on the theoretical curve in Figure 5 (maybe adding the reference equation in [4]).

In the actual version we added the reference equations which it makes the text more clear for the reader.

We thank you for your valuable comments and hope that we improved the manuscript. Due to the modifications, the lay-out of the figures and tables is not anymore in an optimal correspondence with the page lay-out, to our opinion this will be solved during the editing process.

Kind regards,

The authors.

Author Response File: Author Response.docx