The Design of a Structural Hyper-Resisting Element for Life-Threatening Earthquake Risk (SHELTER) for Building Collapse Scenarios: The Safety Chairs

Round 1

Reviewer 1 Report

This paper focuses on the analytical research that was carried out to develop and evaluate the mechanical behavior of safety chairs.

The introduction is very poor, despite an excellent presentation of content and discussion. It should be improved and enhanced.

First, describe the importance of the research, followed by a review of further relevant publications and a discussion of their findings. It is required for any possible publication.

The presentation of Figs. 7 and 8 might also be improved. This reviewer suggests only having one column.

 

Author Response

Comment #1

This paper focuses on the analytical research that was carried out to develop and evaluate the mechanical behavior of safety chairs.

 

Response

The authors would like to thank all the work and time given by the reviewer to appreciate our manuscript. The paper was revised addressing all comments and suggestions.

 

We also have corrected some misspellings, all of them registered with the track-changes tool. The more relevant one was in the paragraph before Fig. 16, rewritten as:

 

“For the damper (Fig. 16), its 600mm maximum stroke proved to be enough, as in the worst situation (situation 1) it deforms about 400 mm downwards (Fig. 15.a) and less than 150 mm upwards. With a maximum value of 27 kN, the axial force installed in it was well below its 50 kN limit (Fig. 16.b). The axial and shear forces inflicted by the chair on the shelter columns were also computed (Fig. 16.c and d).”

 

Comment #2

The introduction is very poor, despite an excellent presentation of content and discussion. It should be improved and enhanced. First, describe the importance of the research, followed by a review of further relevant publications and a discussion of their findings. It is required for any possible publication.

 

Response

The authors thank the reviewer for the positive evaluation of the manuscript introduction. Its first sentence was rewritten to:

 

“Fear of earthquakes is usually associated with the risk of building collapses. When buildings are not designed to prevent those collapses, their occupants may die or suffer severe injuries when an earthquake occurs.

Seismic retrofitting of vulnerable buildings is the most appropriate solution, but its costs do not allow the intervention on most of them. Once the main concern in the seismic codes is often people’s safety, a proposal for a seismic shelter was presented in [1], which works as a kind of “cocoon” to protect the occupants of seismically vulnerable buildings in case of an earthquake occurrence.”

 

Besides, in the following paragraph, after the sentence “The shelter structure was designed to resist, without significant deformation, the effects of the impacts to which it is subjected [5]”, we added the following text:

 

“There, the life-saving capsule was designed to ensure higher chances of survival for its users, and soon it was understood that specific equipment to protect the human bodies from the shock effects was needed. In this sense, safety chairs were designed, to be connected to the main shelter structure by a system of springs and dampers and equipped with anatomical restraint devices. It was also realized that it is difficult to restrain ourselves to a safety chair in the reduced amount of time available, even if an Earthquake Early Warning System (EEWS) is installed with the life-capsule, as presented in [1]. This means that the chair and the human body interact and have differentiated behaviors to respond to the collapse shock accelerations and corresponding inertial forces on human body. The life capsule structure responds with strength and stiffness to the collapse shock loads ensuring its integrity. A specific study that assumes this scenario was developed and is now presented in this paper.”

 

We would also like to clarify the reviewer that this is the third and final paper regarding the conceptualization and design of the shelter unit (the other two were [1] and [5] references, already published and already containing the references found by us, that were mainly advertising websites). This solution out-of-the-mainstream character means that other publications that can compare to our study are scarce (to avoid stating that they are null). We had similar debacles with other reviewers and, under this scenario, we realized that is mandatory to perform experimental tests that are already being conducted to sustain the results of the design stage of our shelter solution.

 

Comment #3

The presentation of Figs. 7 and 8 might also be improved. This reviewer suggests only having one column.

 

Response

The authors followed the proposed improvement to Figs. 7 and 8. We also fixed the figures’ numbering throughout the manuscript.

 

Reviewer 2 Report

The presented research topic is relevant, but the document needs revision.

1. the presrnt study belongs to an ongoing researach project. This is fine, but please provide appropriate introduction to present study and try to minimize the correlation from past publications (see for exampke the first sentence of introduction). It is good to have references to previous publications, but the present document should in any case work efficiently as stand alone publication
2. remove bold text in some sections
3. title should be revised
4. did the Authors try to fix sensors to human body? LIke J. Sens. Actuator Netw. 2022, 11(1), 10; https://doi.org/10.3390/jsan11010010 and run both coupled and uncoupled / inverse dynamic measures? - Please comment in the revised document
5. chapter 3: is there a specific reason for 78 kg and 1.78 m considerations? Apart that this corresponds to 50%  percentile of volunteers. How these parameters affect the overall experimental findings of present study?
6. Please better clarify and describe in the revised document the number and configurations of experimental tests
7. Figure 5 has poor graphical quality, please improve it
8. please provide an improved description for the shock absorber. It is not clear for the reader how the system works in the discussion of chapter 5.3
9.  

Author Response

Comment #1

The present study belongs to an ongoing research project. This is fine, but please provide appropriate introduction to present study and try to minimize the correlation from past publications (see for example the first sentence of introduction). It is good to have references to previous publications, but the present document should in any case work efficiently as stand alone publication.

 

Response

The authors thank the reviewer for the positive evaluation of the manuscript and understood its comment. To correct the introduction, its first sentence was rewritten to:

 

“Fear of earthquakes is usually associated with the risk of building collapses. When buildings are not designed to prevent those collapses, their occupants may die or suffer severe injuries when an earthquake occurs.

Seismic retrofitting of vulnerable buildings is the most appropriate solution, but its costs do not allow the intervention on most of them. Once the main concern in the seismic codes is often people’s safety, a proposal for a seismic shelter was presented in [1], which works as a kind of “cocoon” to protect the occupants of seismically vulnerable buildings in case of an earthquake occurrence.”

 

Besides, in the following paragraph, after the sentence “The shelter structure was designed to resist, without significant deformation, the effects of the impacts to which it is subjected [5]”, we added the following text:

 

“There, the life-saving capsule was designed to ensure higher chances of survival for its users, and soon it was understood that specific equipment to protect the human bodies from the shock effects was needed. In this sense, safety chairs were designed, to be connected to the main shelter structure by a system of springs and dampers and equipped with anatomical restraint devices. It was also realized that it is difficult to restrain ourselves to a safety chair in the reduced amount of time available, even if an Earthquake Early Warning System (EEWS) is installed with the life-capsule, as presented in [1]. This means that the chair and the human body interact and have differentiated behaviors to respond to the collapse shock accelerations and corresponding inertial forces on human body. The life capsule structure responds with strength and stiffness to the collapse shock loads ensuring its integrity. A specific study that assumes this scenario was developed and is now presented in this paper.”

 

We would also like to let know that this is the third and final paper regarding the conceptualization and design of the shelter unit (the other two were [1] and [5] references, already published and already containing the references founded by us, that were mainly advertising websites). This being an innovative solution is reflected in the scarcity of other publications that can be compared to our study. We had similar debacles with other reviewers and, under this scenario, we realized that is mandatory to perform experimental tests, that are already being conducted, to sustain the results of the design stage of our shelter solution.

 

Comment #2

Remove bold text in some sections.

 

Response

The bold captions were removed.

 

We also added some misspelling corrections that the first version of the manuscript, all of them registered with the track-changes tool. The more relevant one was in the paragraph before Fig. 16, rewritten as:

 

“For the damper (Fig. 16), its 600mm maximum stroke proved to be enough, as in the worst situation (situation 1) it deforms about 400 mm downwards (Fig. 15.a) and less than 150 mm upwards. With a maximum value of 27 kN, the axial force installed in it was well below its 50 kN limit (Fig. 16.b). The axial and shear forces inflicted by the chair on the shelter columns were also computed (Fig. 16.c and d).”

 

Comment #3

Title should be revised

 

Response

The title of the paper was changed to: “The design of a Structural Hyper-resisting Element for Life Threatening Earthquake Risk (SHELTER) for building collapse scenarios: the safety-chairs”.

 

Comment #4

Did the Authors try to fix sensors to human body? Like J. Sens. Actuator Netw. 2022, 11(1), 10; https://doi.org/10.3390/jsan11010010 and run both coupled and uncoupled / inverse dynamic measures? - Please comment in the revised document

 

Response

For the downfall-and-impact tests, we are using wireless impact accelerometers on the crash-test-dummy, based on MEMS technology and with a 200 G’s range, along with HFR cameras. The following text and reference [45] were added before section 5.3:

 

“Experimental tests are currently underway, where the key parameter being measured is the instant peak accelerations of the more important body parts, namely the chest and the head. Several experimental downfall-and-impact tests are being conducted, from nine (9) different heights (one meter intervals) and in different falling slopes, like those assumed for the design stage (Figure 8). A Hybrid III crash test dummy will occupy the shelter units, settled on safety chairs. The sensors being used are optical targets captured by two (2) 300 fps HFR cameras, along with twelve (12) 200 g’s wireless accelerometers [45] to sensor the crash-test-dummy, with a sampling rate of 330 Hz.”

 

Inverse dynamics measurements are not being used, once the sensors are not being applied to the spine unit directly, where the forces were estimated with the hereby presented study (the dummy back has meaningful impacts against the back pillows of the safety chair and therefore the accelerometers cannot be placed there).

 

Comment #5

Chapter 3: is there a specific reason for 78 kg and 1.78 m considerations? Apart that this corresponds to 50%  percentile of volunteers. How these parameters affect the overall experimental findings of present study?

 

Response

There is another practical reason, concerning the high cost and availability of the crash test dummies. Most of them normally correspond to a male average individual. Female and infant crash test dummies are also available, but we opted for the male for this initial study as it is the heaviest and, apparently, the most conditioning. Future studies should also comprise the other situations, as the reviewer suggests.

To clarify this view, the following text was added in the third paragraph of section 3.:

 

“As an average male model is heavier than female and infant models, it is expected that the male will suffer higher inertial forces and more severe injuries. Further studies, however, should also comprise those other situations.”

 

Comment #6

Please better clarify and describe in the revised document the number and configurations of experimental tests.

 

Response

We kindly ask the reviewer to refer to the answer to comment #4.

 

Comment #7

Figure 5 has poor graphical quality, please improve it.

 

Response

The authors followed the proposed improvement to Fig. 5. We also fixed the figures numbering throughout the manuscript.

 

Comment #8

Please provide an improved description for the shock absorber. It is not clear for the reader how the system works in the discussion of chapter 5.3.

 

Response

We added Figure 15 and the following sentence in the beginning of section 5.3:

 

“Fig. 15 depicts the components of the shock-absorber system, namely the damper device and its endings (highlighted in pink), as well as the neoprene springs and its endings (highlighted in yellow). The rubber bumpers and the UPN100 profiles are also highlighted, in red. The system behaved as expected…”

 

Round 2

Reviewer 1 Report

All comments are addressed. The paper could be accepted for publication.