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Why does the stress strain curve in Abaqus of my concrete model look like this?A question posed (2024, Jan 11, ) by Hanif Hanif on ResearchGate

 

It is a stress-strain diagram. Let’s divide the diagram into 3 different zones: 1, 2, 3, each characterized by its own typical trend.

ZONE 1: Linear law between stress and strain (Hook’s Law). The slope of such a line is a measure of the elastic module of the material. If during this phase you stop applying the force, the preserved elasticity of the material brings it back to the original dimension from which you started (i.e. the origin of the axes). Elastic modulus, also known as Young's modulus, is a fundamental property of materials that measures their stiffness or resistance to elastic deformation under stress. This property is essential in engineering and materials science, as it determines a material's ability to support loads and maintain its shape. The area of each zone (kg x m) represent the necessary energy to deform the sample of (unknown) material under test.

ZONE 2: The law between stress and strain is no more linear.  Even stopping to apply the force, the original elasticity of the material is damaged and lost and it is impossible to bring back the material to its original dimension. Noticeable is the negative slope in this zone. The deformation continues with decreasing force up to a minimum and the slope changes sign again, due (presumably) to work hardening of the material.

ZONE 3: The minimum point reached can be considered the beginning of actual failure, characterized by large deformations with smaller forces, which again follow a law that is substantially linear here, but is not necessarily the case in all materials.

Observers rightly pointed out that there may be several reasons why the stress-strain curve of a concrete model in Abaqus may show a certain behavior. So that various elements to find an explanation should include: Material properties; Concrete model; Failure criteria; Loading conditions. 

In search of an explanation one might also think of an overlap in the proposed graph between load in action and reaction. But, as far as I can see (e.g. refer to the image below - Image source: https://caeassistant.com/blog/fiding-reaction-force-on-a-body / ) Abaqus distinguishes very well in the graphical results between action and reaction by presenting two separate graphs with different trends, especially in the case of dynamic loads.

Image source: https://caeassistant.com/blog/fiding-reaction-force-on-a-body /

In this case, however, the question was asked on a single graph without specifying whether it concerns active load (e.g. Zone 1) and reactive load (e.g. Zone 2 plus Zone 3) combined together, also excluding a part of reactive load until the start of the Zone 2 (All this trying to imagine a possible explanation). But it is not the case. So I am inclined to assume that the positive slope of Zone 3 is the result of work hardening, just as the specific literature mentions about it (search for: work hardening effect in unreinforced concrete). Anyhow, in case anyone has a different, specific explanation, I'd appreciate hearing about it.

How can instructional supervision be the catalyst for innovation and excellence in education? A question posed by C.Gonzaga on ResearchGate

It should be stated that no one among humans possesses the Truth, except perhaps small fragments of it, often to be verified and proven through concrete evidence. What can be said regarding the question posed is necessarily inserted in individual experiences and in one's own intellectual path: social, educational, etc.

  Teaching supervision implies knowledge of what is supervised and therefore pedagogical attention to implicit teaching, so that in a highly evolutionary and competitive society, innovation is fueled through a cognitive stimulus that aims for excellence, above all with a disciplined and humble critical spirit, but without presumptions, arrogance or vainglory. An educational supervision that is limited to compliance actions and simple order towards pre-established schemes could not be very fruitful. In this regard it is necessary to remember how the school of "field psychology" (in particular Kurt Lewin) teaches that the more structured the (psychological) cognitive field is, the more efficient and powerful it is in analysis, but at the price of rigidity towards elements innovative critics. Conversely, the more unstructured the field is, the more creativity and willingness there is to accept and include in the field itself (through study and research) the critical elements that have emerged useful for innovation and a path to excellence. In essence, it requires a sort of pedagogical "trade off" to be evaluated, chosen and implemented based on contingent and situational elements.

Not so much from the question, but from the expected "key words" provided for the online search, we understand that these are also topics that concern Microsoft Excel. We can say that this spreadsheet, like others that exist on the market, offers a lot of potential in practical use. Equipped with many mathematical, statistical and programming logic functions, it is suitable for numerical calculation, but can also be used as a database for activities ranging from simple administrative management (orders, invoices, payments, etc.) up to real activities planning, management and control of contracts or projects, even very important and complex ones. For example, Excel can be programmable integrated with QBasic-type software, introducing procedural programming systems, although today the potential offered by Python tends to make it considered obsolete. Perhaps this is why there is news that «Microsoft has collaborated with the data science platform Anaconda to bring this functionality to life. The company uses the Anaconda Python distribution, running in Azure, to bring the most popular Python libraries to Excel, including Matplotlib and Seaborn for data visualization.( Aug 22, 2023 ref. https://techcrunch.com/2023/ 08/22/microsoft-is-bringing-python-to-excel/)» Excel's current graphing capability is good for diagramming its results, but certainly not comparable to what Python allows.

This alone indicates how careful didactic supervision can push critically to delve deeper into topics on which the field branches out, which inevitably induce the need for in-depth study, orienting teachers and students towards greater knowledge.

A simple and modest example of circumventing the potential in the field of analysis of old versions of Excel can be provided through the following reference: 

https://roccomorelli.blogspot.com/2022/07/a-tommaso-per-commenti-e-correzioni.html 

What is the best way to find out the cost of various construction materials?

 What is the best way to find out the cost of various construction materials?

Question Asked 6 days ago by 

Ali Habeeb Askar 
Lecturer 
PhD student at the University of Miskolc, Faculty of Mechanical Engineering and Informatics,Department of Fluid and Heat
Institution and department
• University of Technology, Iraq 
• Mechanical Engineering Department

Answered by R.Morelli October 24th 2023 

A unique price for a material does not exist. What is valid in one country is not valid in another. There are obvious reasons that explain this.

In the construction sector, on a chosen site, the practice of asking for at least 3 offers for the purchase of materials, products, systems, services or works is still the most widespread (and often mandatory) in many contracting bodies or companies, not only in Western economies. Obviously such a practice implies - especially for projects of large amounts and with a long completion time - the ability to technically specify what you wish to purchase, also taking into account a whole series of constraints (commercial, currency, regulatory, adherence to standards and international codes, financial codes, etc.). It is not uncommon that where public institutions are involved, there may be price lists developed by the country's civil engineering institutions, or chambers of commerce, to which these public institutions refer. Or it may be these same institutions (or enterprises) that directly develop over time, and through the history of their construction experiences, actual price lists (to be constantly updated) to evaluate the results of their tenders for the assignment of contracts. Sometimes there exists in these same institutions a rigid and severe procedure for the preparation of requests for offers and the evaluation of the results of the tenders carried out. It goes without saying that the more numerous the requests for offers, the less the result provided by the average price is affected by errors. The average price can also be obtained on the basis of a specific algorithm made known to bidders during the tender, which also provides for the exclusion of the bid with the highest price and the one with the lowest price, to limit the risks associated with the choice of an unsuitable supplier or contractor. This risk, however, can in fact be mitigated through a preventive analysis of the potential and capabilities of the supplier or contractor, even before inviting him to submit the offer in question.

Alternatively and in a completely theoretical way, a price analysis can be developed which takes into account at least the unit costs of labour, work equipment, raw materials, energy, production plants, transport, etc. But it would only be pure exercise without any reference to the price values that are actually charged on the local, national, regional and international market.

Have a look at this. (Its just an example, even if its in Italian).

https://www.piuprezzi.it/