The Application of Ni–Ti SMA Wires in the External Prestressing of Concrete Hollow Cylinders

Round 1

Reviewer 1 Report

The manuscript "Application of Ni-Ti SMA Wires to External Prestressing of Concrete Hollow Cylinders" has been reviewed.

It deals with a novel technique, base on shape memory alloys activated by joule effect, for prestressing concrete hollow cylinders.

The idea is interesting, despite the work is based on a phenomenological approach and the basic principles about shape memory alloys are only partially managed by the authors, at least as read from the manuscript. The manuscript in my opinion is not well balanced in terms of analysis no the materials (concrete and SMA). The attention is much more focused on the concrete behavionr rather than on the SMA behavior.

Bibliography is poor; fundamental works must be added. At least the following:

1) 10.1016/j.matdes.2004.02.022 (shape memory and electric current);

2) 10.4028/www.scientific.net/KEM.605.23 During heating and cooling the phase transformations (A-M) and (M-A) are associated with a change in resistivity. In same case also a transition phase (R) appears. In the whole manuscript these aspects are not considered.

3) 10.1016/j.pmatsci.2004.10.001 Basic principles and physical metallurgy on NiTi Shape Memory Alloys.

It is not reported the composition of the shape memory alloy.

Data reported in Table 1 are taken from earlier works [19, 20]. Please add details (stress strain curves, DSC, resistivity measurements ??). They would be useful.

Regarding the transformation temperatures at zero stress, the range is about 70°C. Which is the reason of such a great hysteresis?

Lines 99-100: check white spaces

Table 1 eps. res. % not (-)

Line 85: informations not information

Fig. 2 d alternator not altenator

Line 174: it is not clear "without changing the material austenitic state".

Conclusions. Damage by overheating must be considered for the SMA.

REFERENCES (All) are not in compliance with the Journal requirements. Please follow author's instructions.

After these major revisions the manuscript can be reconsidered for publication.

Author Response

Please see the attachement.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper dealed with a study of prestressing of concrete hollow cylinders with the use of nickel-titanium (Ni-Ti) SMA wires. The paper was interesting and presented important data regarding the external prestressing provided by martensitic transformation. However, some confusing questions existed and they need to be answered accordingly.

1# In fig.3, G5 kept almost unchanged with the increasing of the time. It was amazing. Why?

2# In table 6, for the sample 17 and 18 (Pipe ø 300 mm – SMA wire ø 3 mm), huge differences were observed about the value of F_sma. It should be explained carefully or the experiments should be repeated to ensure the accuracy of the experiment.

3# In table 7, it was observed that mean circumferential compression stress increased with the increasing of the diameter of the SMA for the pipe ø 200 mm and pipe ø 250 mm. However, the stress dropped to 5MPa when the diameter increased from 2mm to 3mm in the pipe ø 300 mm. Why?

4# In fig.5(c), the legend obscured the curve of Test II(6). It should be corrected.

Author Response

Please see the attachement

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Accept in present form

Reviewer 2 Report

The revised manuscript has been carefully modified. I suggest that the revised manuscript can be published.