P16485: Biochar Concrete Roofing Sheets for Nicaragua
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

During this phase, our team has accomplished everything that we had planned. Our main focus was finding a suitable roof shape and design that would accomplish the customer and engineering requirements. We have created our functional decomposition, set our morphological table, developed alternatives, and selected concepts based on determined criteria. We have also re-evaluated our benchmarking and risks, as well as analyzed feasibilities according to our concepts. Finally, we have met with a concrete company to gather more research information which we are planning to continue during the next phase.

Functional Decomposition

Fuctional Decomposition

Engineering Requirements Mapping

Engineering Requirements Mapping

Engineering Requirements Mapping Document

Benchmarking

In order to choose the best concept, we decided to benchmark three different aspects of the roof. This would help us see what concepts matched our required functions and Engineering Requirements the best.

First we decided to look at last year's biochar concrete mixes and test results in order to see if it could give us any insights. The following picture is the table of their results. What we learned from their tests is that introducing biochar into concrete greatly reduces the strength. However, adding more strong materials could combat this effect. We will have to keep this in mind when creating our biochar concrete mix.

Concrete Mixes

Next we decided to look into different roof styles that are seen in other developing countries. It was discovered that what is being used now is not optimal. This indicates that we need to use a new method in order to create cheaper roofs. We can't just use one of the existing styles because it would not meet our engineering requirements. The following table summarizes our findings.

Other Roofs in Nicaragua

Finally, in order to determine the best roof style, we benchmarked the different options. We found that there are both pros and cons to all roofs types and that we needed to determine which roof design satisfies the most of our requirements or could be modified to satisfy even more. The following table shows our findings.

Different Roof Designs

The document containing all of this benchmarking work can be found here

Microconcrete Research

Microconcrete Document

Concept Development

Concept Generation

Concept Generation

Above is a preliminary sketch of some concepts that we thought could be potential candidates for our design. On the left are 7 roof designs and on the right are 3 shingle designs. This already gives us 21 potential combinations/options. Many of these designs made it to our Morphological and Pugh Chart analyses which are shown in detail below.

Morphological Chart and Concept Selection

Morphological Chart

Morphological Chart

Selection Criteria

After looking at our customer requirements, engineering requirements and functional decomposition, the following selection criteria were chosen.

Selection Criteria

Selection Criteria

Selection Criteria Document

Concept Selection

The Pugh chart was used to compare the different concept designs that the group created. The functions were taken from our morphological table and the selection criteria were created from our requirements. Each concept was compared to the current roof being used by 4 Walls. Since the main requirement of our customer is to create a better roof than the previous one, this was the best system to compare our alternatives to. Each system had some features that were better than the current roof and some that were worse. This was noted on the chart and helped us decide the best way to choose and combine features. We determined how well certain features would perform through our benchmarking.

Pugh Chart

Pugh Chart

From the Pugh Chart this final design was chosen:

Selected Concept Description

Selected Concept Description

The final concept was chosen after evaluating the strengths and weaknesses of many combinations of criteria.

The gable roof style was chosen because it’s the roof style that is currently on the house and has good load distribution. The other roof style that is still being considered is the shed style, because it offers many of the same benefits of a gable while being a continuous surface that saves materials.

We chose rounded shingles because we thought this would be a culturally acceptable design and these shingles have good load distribution and can route water well.

Biochar and concrete were selected as the material because this is one of our customer requirements.

A corrugated surface along with a pitch will be used to redirect water, as stated above.

A tarp was selected to block water. The tarp would be put underneath the shingles so if any water were to get through it would hit the tarp and hopefully drain outside.

Resisting animals isn’t the main purpose of the roof design, but is still very important, so limiting the size of gaps in the roof was chosen as the best deterrent method. The other methods involved active pest control such as traps or baits, but we deemed them unnecessary because they were a little excessive in the scope of a roof.

The interlocking tile idea was chosen over nails and other fasteners because it would save on cost and reduce the number of tools needed. The interlocking tile method might not be as strong as using fasteners, so testing a prototype will prove its viability.

Material color was chosen to reflect radiation because it was a cost saving over putting an additional coating on the roof and it’s fairly easy to implement.

Tile thickness was chosen to block radiation from the sun because it is already inherently in the roof design and doesn’t need additional materials. It may not be as effective as other means, but will be adequate for the climate and provide shading.

For the function of stays connected to the house we selected solid shingles and trusses as the concept. The shingles will stay connected to the house by not being porous or easily degradable. The trusses are also a vital part to any roof to keep it all connected. Our project will include re-evaluating the current truss design that they have and hopefully coming up with something more structurally sound while maintaining the same cost.

Selected Concept CAD Models

Model of Current Truss Design

Model of Current Truss Design

Model of House with Shingles

Model of House with Shingles

Model showing individual shingle

Model showing individual shingle

Model of individual shingle

Model of individual shingle

Systems Architecture

Systems Architecture

Systems Architecture

We found that all of our Functional Decomposition fell into 3 categories which were shingles, tarp and trusses. This is shown above and color coded. This will help us in our next phase when we look into sub-system design.

Feasibility: Prototyping, Analysis, Simulation

Biochar Material Feasibility

The local materials in Nicaragua were given by our customer and then researched further in order to determine potential materials for our biochar. It was then determined what materials were possible to use and what was possible for us to test here in Rochester. The following was our results.

Biochar Material Feasibility

Biochar Material Feasibility

Conclusion: It has been determined that we will test biochar made from tree debris (stand in for coffee) and from bamboo. These will be the two primary biochars that will be under consideration. We will also follow up with our customer at 4 walls to determine the feasibility of corn biochar and then determine with Kathleen if corn can be turned into biochar. If this becomes a feasible option, we will consider using this in our test as well.

Budget Feasibility

One of our constraints for this project is reducing the cost of each roof to under $400. With this analysis, we can see the cost of each material according to the volume of certain roof types from our concepts.

Budget Feasibility

Budget Feasibility

Conclusion: Depending on the cost of each material, it is obvious that some roof types may be more feasible than others. The price amounts listed currently were assumed, so they are not the final amounts. As we get closer to determining what materials we are actually using, we should have a more accurate feasibility comparison. We will follow up with Manitou Concrete, as well as Kathleen, in order to help us determine reasonable pricing for certain types of concrete and biochar as we go further along with our design.

Roof Structure Feasibility

A preliminary model was made from information gathered from photos of the current houses in El Sauce. It was then analyzed for structural stability under the 6,000 lb dead load of the proposed roof design.

Biochar Material Feasibility

Biochar Material Feasibility

Conclusion: It was concluded that the current structure could support the the weight of a 6,000 lb roof. The biggest component that will effect the structural stability of the house, is how the beams are connected. The strength in a building comes from its ability to distribute loads, and if it isn't connected correctly a lot more stress will ensue.

Risk Assessment

For this phase, we have added a few more risks that we have discovered after creating a system design. The following is a snapshot of some of the risks that were added to the previous document.

Updated Risks

Updated Risks

If you would like the see the entire risk chart. You can find it here: Updated Risk Document

Updates from last phase

Last phase we determined that there was a risk that we may not be able to use the concrete testing lab at RIT. After visiting Manitou concrete, they were kind enough to offer their testing facilities if the lab here will not let us use their facilities. We have not determined if the lab here will let us use their lab, but the severity and importance of this risk has been lowered since we now have a backup plan

Preliminary Test Plan

The team then went through the engineering requirements and determined an initial test plan.

Preliminary Test Plan

Preliminary Test Plan

The original document can be found here:

Preliminary Test Plan Document

Design Review Materials

Pre-read

Please look over our problem definition page to re-familiarize yourself with our background, customer requirements and engineering requirements. Also please refer to our Pugh chart and concept selection sections before the presentation.

Presentation

Our presentation will be conducted through our edge site.

Notes from Review

Design Review Notes

Plans for next phase

By our next review, our team would like to have chosen our subsystem designs. This includes our shingle designs, trusses, and materials. We would like to being mixing up some biochar concrete samples because it takes a few weeks before you can test the samples. We want to answer the questions: Will our concept work? How will our subsystems interact with each other?

Team Shared Vision

Team Shared Vision for Phase III

The team also looked back at our shared vision for phase II and highlighted what was not completed and explained why it was not completed. You can find this document here

Individual Plans

Cindy's Three Week Plan

Adrian's Three Week Plan

Peter's Three Week Plan

Jamiya's Three Week Plan


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