Antikythera Mechanism2nd Century B.C.

Team UAH

2015Concrete Canoe

Design Paper

 

 

Table of Contents

Executive Summary ·················································································································································· ii

Project Management ················································································································································· 1

Organization Chart ···················································································································································· 2

Hull Design and Structural Analysis ························································································································· 3

Development and Testing ·········································································································································· 5

Construction ······························································································································································· 8

Project Schedule ························································································································································· 10

Design Drawing ························································································································································ 11

List of Figures

Fig. 1. Project milestones; financial and resource allocation ····················································································· 1

Fig. 2. Organization chart ·········································································································································· 2

Fig. 3. CLOCKWORK hull shape and attributes ········································································································ 3

Fig. 4. Design for composite section ························································································································· 4

Fig. 5. Transformed section analysis for the final mix ································································································ 7

Fig. 6. Material costs ($1,482) ···································································································································· 9

Fig. 7. Project person-hours (1,133) ···························································································································· 9

List of Tables

Table 1.0 Pertinent Information ·································································································································· ii

Table 3.1 Summary of Mix Proportions ··················································································································· B1

Table 6.1 Bill of Materials and Production Cost Estimate ······················································································· C1

List of Appendices

Appendix A - References ········································································································································ A1

Appendix B - Mixture Proportions ··························································································································· B1

Appendix C - Bill of Materials ································································································································· C1

Appendix D - Example Structural Calculation ········································································································· D1

 

Executive Summary 

The University of Alabama in Huntsville (UAH) is located in Huntsville, Alabama. Our concrete canoe team is commonly known as Team UAH and this is our 30th anniversary. Although our predecessors earned five national titles while representing the Southeast Conference sixteen times at that level, our teams placed 2nd in the conference concrete canoe competitions in 2012 and 2013, and 3rd last year. These less than stellar performances drove us to revise our delivery and select a motivational theme to help our team achieve another epoch moment in Team UAH’s history.

More than 21 centuries ago, a mechanism of fabulous ingenuity was created in Greece; an ancient analog computer designed to predict astronomical positions and eclipses using the oldest known gear train. Its discovery and function made us realize that all components of this competition must be in sync to achieve victory. As a result, we christened our canoe “CLOCKWORK” and sculpted our delivery as a precise mechanism designed to earn us the highest score possible.

We wove this powerful theme throughout the body pages of our design paper and carried it into our organizational chart, project schedule, and design drawing. We capitalized on the additional page devoted to “Development and Testing” to increase white space and make our paper more readable while adding technical content, such as a spreadsheet from our transformed section analysis, to make it more informative. We took advantage of Appendix D to explain how our teams obtained a service load and how one could arrive at a specification on concrete strength.

We plan to feature CLOCKWORK on our canoe and convey information on our tabletop and cutaway in a unique fashion via mechanisms. Our oral presentation will be geared toward explaining how much we’ve learned and achieved as a result of this competition. We worked hard paddling and hope to perform consistent with our theme.

This year, we made advancements in:

Project Management: We employed integrated project management to help us understand our project’s technical aspects and establish what needed to be done to meet our strategic goals.

Hull Design: We produced a fiberglass prototype and retrofitted it with different splash guards, the best of which we incorporated into our concrete canoe.

Mix Design: We designed a remarkable concrete mix ideally suited for concrete canoeing which has a flexural strength greater than its compressive strength.

Concrete Testing: We compared trial mixes based on an efficiency equation. Structural Analysis and Design: We designed a lightweight, reinforced core to increase torsional rigidity

that allowed us to accurately position and install relatively heavy reinforcement with no weight penalty. Canoe Construction: We introduced new techniques to bring our game changing ideas to practice. Sustainability: We treated sustainability as a macro concept that applied to our entire infrastructure;

thereby expanding our efforts to incorporate this concept into this competition (Princeton Review 2010).

The concrete properties used for design purposes are listed in Table 1.0; other properties, such as tensile and compressive strengths, are discussed in the section labeled “Testing” on page 7.

Table 1.0 Pertinent information. Canoe Name: “CLOCKWORK” School: UAHuntsville (UAH) Physical Attributes

[Canoe] Engineering Properties

[Concrete Mix] Primary Reinforcement

[C-Grid] Mass (Wt): 63.4 kg (140 lb) - Estimated Unit Weight (Wet): 758 kg/m3 (47.3 lb/ft3) Composition: Carbon Fiber/Epoxy Resin

Maximum Length: 6.7 m (22 ft) Unit Weight (Dry): 684 kg/m3 (43 lb/ft3) Tensile Modulus: 234 GPa (34 Msi) Maximum Width: 85.1 cm (33.5 in.) Flexural Modulus: 4.45 GPa (645 ksi) Tensile Strength: 2.0 GPa (290 ksi) Maximum Depth: 31.8 cm (12.5 in.) 7-day Flexural Strength: 1.86 MPa (270 psi) Percentage Open Area: 68%

Average Thickness: 16.5 mm (0.65 in.) Secondary Reinforcement (4) Predominate Colors: Grey and Yellow Poly(Vinyl Alcohol) (PVA) Micro Fibers, Steel Wire Mesh, Wood Screws, Staples

 

Project Management 

 

Project Milestones Financial and Resource Allocation*

Elections Mix Design Material Costs: $1,482 Hull Design Canoe Construction Total Person Hours: 1,133 Structural Analysis Documentation * See the pie charts on page 9 for details.

We sculpted our delivery as a precise mechanism designed to earn us the highest score possible. Our strategic goals were to: 1) maximize our team’s performance, 2) seek optimal solutions, 3) minimize our mistakes, 4) win the Conference competition in Chattanooga, and 5) do justice to the Southeast by finishing in the top five at the national level in Clemson.

Due to the small size of our group, we used a systems approach to look at the project holistically to see where the overlaps and interactions lay. As a result, we decided to create four different teams shown on the organizational chart on page 2: project management (PM), project engineering (PE), documentation (D), and crew (C). We created this chart to help visualize organizational relationships and assign responsibilities.

Our membership considered the election of Chapter officers and team leads to be our first milestone. Capable members were initially nominated by their peers and then elected in response to speeches outlining abilities, experience, and credentials. After selecting CLOCKWORK as our theme, we organized the teams. The text boxes on the organization chart include the names of the registered participants, their year (Fr., So., Jr., Sr., Grad), the role that they played in the effort, the team(s) that they joined, and the number of years involved in the concrete canoe competition. All of the registered participants contributed to the design and construction of our concrete canoe.

We developed a hierarchy in which our team leaders provided oversight and gave status reports at weekly officer meetings. We used our websites, Facebook, cell phones, and email accounts to maintain a global communication network to manage risks, maintain safety, sustain our effort, and complete all tasks. Each team relied on integrated program management (Ruiz et al 2012) to define, analyze, and evaluate a precise mechanism to establish their baselines, objectives, and strategies. We used critical thinking to address the lifecycle phases of the project and combined the four team mechanisms to help us understand our project’s technical aspects. This enabled us to identify significant transitional events, i.e., milestones, listed in Fig. 1. As a result, we formulated the project schedule shown on page 10, which included a critical path defined by tasks that had no float.

Our treasurer handled the financial and resource allocation summarized in Fig. 1. The majority of the materials required for mold and concrete canoe construction (see page 11, Appendix C, and Fig. 6 on page 9) were salvaged or donated. We spent an additional $409 on tools, materials and supplies. Figure 7 on page 9 details the person-hours compiled for each major activity including design, testing, and construction.

Fig. 1. Project milestones; financial and resource allocation.

We placed safety first and developed a plan which required at least two team members to be present while working. Project managers reviewed the MSDS for all the materials that we used. They also required team members to wear protective equipment (gloves, masks, goggles, etc.) and follow OSHA guidelines (OSHA 2015).

We adopted a policy of continuous risk management (Dorofee et al. 1996) and used the global communication network described earlier to identify, analyze, plan, track, and control risk.

Our quality control program relied on constant supervision by team leaders who reported progress and set measures at every stage of production. They rigorously tested construction methods and offered training sessions to support safety, minimize risk and assure that our product would be shipshape. Tasks such as

proportioning materials were completed in advance to ensure efficiency.

[Type text]   

 

James Muriki (Fr.) PE, C 

Participant – 1 yr. Registered – 1 yr. 

Hunter Fresmire (Fr.) PE, C 

Participant – 1 yr. Registered – 1 yr. 

Nic Chiandra (Jr.) PM, PE 

Participant – 2 yr. Registered – 1 yr. 

David Pemerton (Sr.) PE 

Participant – 3 yr. Registered – 0 yr. 

Matthew Pinkston (Grad.) PE, D 

Participant – 8 yr. Registered – 3 yr. 

Jonathan Carmen (Sr.) PE, D, C 

Participant – 1 yr. Registered – 1 yr. 

Stephen Phillips (Grad.) PE, D 

Participant – 5 yr. Registered – 3 yr. 

Morgan Bramlett (Fr.) PE, C 

Participant – 1 yr. Registered – 1 yr. 

Shaun Greising (So.) PE, C 

Participant – 2 yr. Registered – 2 yr. 

Jonathan Shales (So.) PE, C 

Participant – 1 yr. Registered – 1 yr. 

Will Bates (Jr.) PE 

Participant – 1 yr. Registered – 0 yr. 

Victoria Forrester (Sr.) Management Chair 

PM, D Participant – 2 yr. Registered – 1 yr. 

Ensured project milestones were met on time Kept project within budget 

Quality Assurance / Quality Control 

Tiffany Walden (Jr.) Documentation Chair Paddling Captain 

PE, D, C Participant – 2 yr. Registered – 2 yr. 

Produced Design Paper & Engineer’s Notebook 

Adam Brooks (Sr.) Canoe Chair D, PM, PE 

Participant – 2 yr. Registered – 2 yr. 

Testing and development of concrete mixes 

Construction of canoe, cross‐section, & tabletop display 

Michelle Rule (Jr.) Paddling Captain 

PE, D, C Participant – 2 yr. Registered – 2 yr. 

Scheduled practicesTrained for competition

Fig. 2. Organization chart.

Organization Chart 

 

 

Hull Design & Structural Analysis 

 

In 2013, Team UAH used parametric analysis techniques and commercially available software to produce a new hull shape. Last year’s team refined that shape to produce a canoe that had the correct weight and balance of speed, tracking and maneuverability to achieve maximum performance in two- and four-person races.

This year, we used a fiberglass prototype to train our crew and retrofitted it with different splashguards, the best of which we incorporated into our design. To improve our racing skills, we recorded videos of our teams and scrutinized others taken of our major competitors. These studies helped us learn how to vary our stroke and return rates so that we drive quickly toward hull speed, make better turns, and switch more efficiently thereby reducing deceleration. We also adjusted paddler positions to minimize detrimental effects such as rolling and pitching.

The streamlined shape of CLOCKWORK and its attributes are shown in Fig. 3. Applicable dimensions are listed in Table 1.0 on page ii, and form dimensions are given on page 11.

Fig. 3. CLOCKWORK hull shape and attributes.

The asymmetrical shape was designed to satisfy conflicting objectives (Ibrahim and Grace 2010). We determined that a combined mass (weight) [boat and crew] equal to 159 kg (350 lb) would be required to have sufficient draft [8.9 cm (3.5 in.)] for the hull to perform properly. Together with proper trim, and hydrodynamic stability, this minimum weight allows the hull to displace water efficiently and gives the largest possible waterline length, the square root of which is directly proportional to the hull speed.

Different teams’ choices of critical parameters such as combined weight, paddler positions, paddling style, choice of materials, composite lay-up, and means of transport make their boats’ hydrodynamic and structural performances very different. As explained in Appendix D, past Team UAH members have mounted strain gages on fiberglass prototypes and concrete canoes at critical locations reported by our competitors (University of Wisconsin 2015). After testing their boats under transport and racing conditions, our teams proved that the peak strain occurs directly beneath the bow paddler in the 2-man races. As noted on page D2, the critical service load

was equivalent to a 0.283 N-m (2.5 in-lb) moment applied to a 2.54 cm (1.0 in.) wide plate.

 

 

Fig. 4. Design for composite section.

Transport conditions included when the canoe was supported: 1) by foam pads placed underneath it in our trailer, 2) at mid span while on our transport vehicle, and 3) at the ends while right side up during launch and float testing.

We adopted a strategy developed for doubly-reinforced beams (Biszick et al. 2013) and designed a composite section to resist the reverse loadings which occur while concrete canoeing. We envisioned reinforcing our canoe with a graphite C-grid that consisted of 1.27 mm (0.05 in.) thick, 7.62 mm wide (0.3 in.) fiber toes on 4.57 cm (1.8 in.) x 4.06 cm (1.6 in.) centers (see Table 1.0 on page ii for material properties). Fibers would be aligned along the principal stress directions and a flotation frame employed to space two layers of the grid at a vertical distance of 6.35 mm (0.25 in.) apart. We selected a hull thickness of 15.24 mm (0.6 in.) based on our construction scenario and requirements imposed on the minimum reinforcement to wall thicknesses ratio (see Section 4.3.1; NCCC Rules 2015). Figure 4 depicts a section, shown without the flotation frame, taken along the longitudinal axis of the canoe where the distance between the graphite filaments in the C-grid is 4.57 cm (1.8 in.).

We assumed that bending was the primary mode of loading and used the transformed section method to compute the flexural stress based on a service load of 0.51 N-m (4.5 in-lb). We obtained the latter by multiplying the equivalent moment mentioned at the bottom of page 3 by the width [4.57 cm (1.8 in.)] of the composite section.

We obtained the transformed section by selecting one of the materials (our concrete) as a standard, and then formulated a non-dimensional stiffness ratio, n, in sections made from the graphite by dividing its elastic modulus by that of the concrete. Each element was stretched in a direction parallel to the neutral axis of the section by multiplying that dimension by n, and stresses were computed using:

Z

Zx I

yMn

where Mz is the bending moment, y is the distance from the neutral surface, and IZ is the moment of inertia of the transformed section with respect to its centroidal axis. The value of n for our concrete is 1.0.

Since the section was symmetrical, the centroid was located at the geometrical center of the section; and, the highest concrete stress occurred at the free surface. We checked our spreadsheet by setting the elastic modulus of the reinforcement equal to that of the concrete. This is equivalent to an unreinforced section and the result that we obtained for the flexural stress [287 kPa (41.6 psi)] matched that calculated in Appendix D. In the case of the unreinforced section, the stress in the concrete depended only upon geometry and was independent of the elastic modulus.

We performed a parametrical analysis by inputting different values for the elastic modulus of our concrete into the spreadsheet and realized that so long as the reinforcement had a higher modulus than our concrete, the stress in the latter would be lower than that in an unreinforced concrete section. As a result, we concluded that it is possible to eliminate the need to analyze a transformed section by adopting a conservative approach in which the required concrete flexural strength is based on an unreinforced section (see Appendix D). Following this simple but eloquent approach, the minimum flexural stress (strength) must be 287 kPa (41.6 psi).

Since our plan called for building a reinforced core that was lighter than one made from plain concrete, we also based our concrete density calculations on an unreinforced section. We determined that our unfinished canoe should weigh approximately 54.4 kg (120 lb) to place our lightest team at the proper depth to achieve good hull speed, stability, and wind resistance. Then, we calculated the minimum density [641 kg/m3 (40 lb/ft3)] required to achieve this condition based on the thickness [15.24 mm (0.6 in.)] and surface area [1.7 m3 (59.9 ft3)] of our boat.

When we studied the elastic curve developed for a plate in third point bending, we noticed that the deflection was inversely proportional to the flexural stiffness (EI). Our parametric analysis showed that a plate placed with a more flexible concrete (lower E) would deflect more. By comparing the results with the mix used last year (our baseline), we determined that a concrete having a modulus of 3.45 GPa (500 ksi) would work well for our application.

 

Development and Testing 

 

The development of a multilevel material design approach and use of an efficiency parameter coupled with a 7-day accelerated test program allowed us to design a final mix and a composite section which exceeded our design specifications.

We decided to use a commercially available C-grid to reinforce our canoe. As mentioned previously, the C-grid consisted of 1.27 mm (0.05 in.) thick, 7.62 mm wide (0.3 in.) fiber toes on 4.57 cm (1.8 in.) x 4.06 cm (1.6 in.) centers. According to the manufacturer, the tensile strength and modulus are 2.0 GPa (290 ksi) and 234 GPa (34 Msi), respectively (Chomarat 2010).

In prior competitions, we discovered that internal flaws in concrete mixes create weaknesses which lead to variations in performance; and, the size and shape of mix constituents matter. This year, our main goal was to design a homogeneous, lightweight and flexible mix by incorporating uniformly sized and shaped binders and aggregates. The mix had to be initially workable but then set up quickly with good early strength. Most importantly, it had to have a flexural strength and the density required to meet our design specifications.

We used last year’s mix as a baseline and developed a multi-level material design approach to arrive at our final selection. During this process, we strove to make our mix lighter, more resilient, and stiffer than the baseline, thereby decreasing weight, increasing the impact resistance, and reducing deflection of the hull, respectively. We employed an efficiency parameter to arrive at our final selection (see Table 3.1, Appendix B) based on the results obtained from a 7-day test program.

Our multilevel material design approach involved selecting cementitious materials first, then the aggregate, and finally fibers, admixtures, and additives to enhance the concrete. Without this approach, a nearly infinite combination of materials exists and finding the optimal concrete mix in a timely manner would have been impossible.

The first step involved selecting the desired cementitious materials for the concrete based on maximizing workability and paste volume. We used Portland cement (ASTM C150), Class C fly ash (ASTM C618), and Silica Fume (ASTM C1240) as binders in the final mix and made sure all requirements on mass were satisfied (Section 3.2.1; NCCC Rules 2015).

Our original plan was to formulate a concrete mix containing no hydraulic cement; however, the desired strength was not obtained without adding some cement to the mix. We ended up decreasing the cement content from 35% of the cementitious materials by weight (last year) to 25% of the cementitious materials by weight (this year).

When mixed with lime and water, fly ash forms a cementitious compound (Joshi and Lohtia 1997). Since fly ash particles have a lower density than cement, their addition lowers weight. They increase workability, as well as the amount of time available to place the concrete. This makes it easier to smooth the surface. Their addition also favorably impacts environmental sustainability (Yang et al. 2007). Since fly ash particles are typically a few micrometers in diameter and nearly spherical in shape (Majko 2007), they increase bond strength and fill in microscopic voids. This helps to maintain homogeneity in the cementitious matrix, and structural integrity in the composite section. We ended up decreasing the fly ash content from 65% of the cementitious materials by weight (last year) to 31% of the cementitious materials by weight (this year).

This year, we added silica fume, or microsilica, to the mix; it comprised 44% of the cementitious materials by weight. This constituent is an ultrafine powder collected as a by-product of silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm. We added it to reduce weight, and improve bond strength and abrasion resistance. The improvements result from the addition of the very fine powder to the cement paste mix, as well as from the pozzolanic reactions between the silica fume and free calcium

hydroxide in the paste (Detwiler and Mehta 1989).

 

 

Last year, we realized that an aggregate with a higher packing density would require less cementitious material than one having more space in between the individual aggregate particles. Since less cementitious material means a lighter weight concrete, we selected our aggregate based on its particle packing density, specific gravity, and particle shape and size. We chose K1 microspheres (3M 2015a) to decrease density and reduce particle size. This variety of microspheres has the lowest density of any of the 3M glass bubbles; K1 are also low in cost. Since these microspheres are relatively small, it made it easier for us to smooth the concrete surface. This year, we added K25 microspheres to increase the strength of our mix. They comprised 33% of the aggregates by weight.

The final step involved fine tuning the cementitious matrix by adding fibers and admixtures that conformed to ASTM standards (ASTM C1116; ASTM C494). We selected poly(vinyl alcohol) (PVA) fibers to minimize debonding and bridge micro-cracks (Xu et al. 2011). Their hydrophilic nature causes them to bond well with the cementitious matrix (Wang and Li 2006) due to the presence of polymer around the fibers (Feldman and Barbalata 1996). A disadvantage of using the fibers is that they decrease the homogeneity of the mix (Pinkston 2011); however, this detriment was outweighed by the high flexural strength that we obtained by adding them. We reduced the fiber content by nearly 50% over last year by finding a better distribution method for adding them.

We selected the admixtures and additives listed in Table 3.1 on page B1. We added SBR Latex to enhance the bonding and flexibility of the mix (Euclid Chemical 2015).

Calcium hydroxide was dissolved in water and then added to the cementitious materials. This constituent contains OH- ions which react with pozzolanic materials (i.e. fly ash and silica fume) to form a cementitious paste which hardens.

We added ViscoCrete 2100, a high range water reducer, at a dosage of 414 ml (14 oz) per 45.4 kg (100 lb) of cementitious materials to reduce the amount of water needed to maintain the desired workability and improve surface finish (Sika 2013).

Our plan for the color scheme is a grey background with yellow as the primary color for any graphics placed on top of the concrete. A grey pigment was added to the concrete mix to ensure that a uniform color would be achieved and to avoid using a coat of stain to create a base color.

We selected our final mix based on an efficiency parameter, E, that we obtained by modifying an efficiency equation developed for ultra-high performance concrete (Graybeal 2013) as follows:

∑

ɸ

. 

The sum is taken over the number of factors to be considered; Ci is a constant established depending upon their importance, xNi is the normalized value of the factor under consideration for the mix in question, xNavg is the average normalized value for that factor over all mixes considered, costM is the cost per cubic yard for the mix under consideration, and costMavg is the average cost per cubic yard for all mixes considered.

We took four factors into consideration: 1) density, ρ; 2) sustainable content, s, based on the percentage volume of sustainable material and whether that material could be obtained locally; 3) flexural strength, σ; and, 4) workability, w. Since we only considered concrete mixes having a flexural strength higher than that specified in Appendix D, we associated factors 1-4 with constants 4,3,2,1, respectively. Specifically, we obtained our efficiency parameter using:

4 3 2ɸ

1

ɸ

 

and selected the mix having the largest value.

  

 

 

We evaluated 25 trial mixes by testing unreinforced plates [5.08 cm (2.0 in.) wide by 15.24 cm (6.0 in.) long by 7.62 mm (0.3 in.) thick]. After allowing the concrete to cure for seven days, we tested the plates in pure bending (following ASTM C78) to get the concrete flexural strength and modulus.

After selecting our final mix, we studied its micro-mechanical behavior and failure by pulling tension specimens (based on ASTM E8 and ASTM D638) from which we obtained a 7-day tensile strength of 414 kPa (60 psi). As can be seen in the second column of Table 1.0 on page ii, we obtained a 7-day flexural strength and modulus, and measured the wet and dry unit weights (ASTM C138). Although we tested cylinders at 7 days (ASTM C39) and obtained a compressive strength of 1.17 GPa (170 psi), the result may be low, since the centers of the cylinders may not have been fully cured; therefore, we plan to test additional cylinders at 28 days. As seen in Appendix B, we computed the air content (10.6%), and measured the slump at 2.54 cm (1.0 in.) (ASTM C143).

As noted in Table 1.0 on page ii, our final mix has a flexural strength of 1.86 MPa (270 psi). Following the specification developed on page 4 for an unreinforced section, the factor of safety for our design is 6.5. Although it would have been possible for us to produce an unreinforced canoe, the larger deflection would have made it difficult to maintain hydrodynamic stability and dimensional tolerances.

The dry weight of our mix is 684 kg/m3 (43 lb/ft3). The latter exceeds the specifications established on page 4 making it possible to build a hydro-dynamically efficient canoe.

The final mix has a flexural modulus of 4447 MPa (645 ksi) and we inputted the latter, along with the flexural strength, into the spreadsheet developed for the transformed section method. The results are shown in Fig. 5.

Fig. 5. Transformed section analysis for the final mix.

Referring to the upper table in Fig. 5, the centroid and moment of inertia are computed by first subtracting the areas corresponding to the graphite from a solid concrete slab, then adding back these areas by considering the n value of the graphite. Since the section is symmetrical, the centroid lies at the geometrical center of the section. As noted in the lower table in Fig. 5, the highest concrete stress is 138 kPa (20 psi). This occurs at the free surface at the furthest distance from the centroid. The maximum stress in the reinforcement, 4.23 MPa (614 psi), occurs in the outermost strands of the graphite fibers. The factor of safety for the design depends on the concrete and is 13.5.

We constructed composite samples by placing our final mix over two layers of C-Grid spaced apart at the distance illustrated in Fig. 4 on page 4. When we tested 15.24 mm (0.6 in.) thick, 4.06 cm (1.6 in.) wide plates in pure bending, they resisted an average moment of 5.1 N-m (45.2 in-lb), giving us a factor of safety of 11.3. The latter is lower than that predicted by the transformed theory, most likely due to internal flaws which lead to failure. This demonstrates that the conservative approach taken by us while specifying the minimum flexural strength (see page 4) has merit when it comes to the sport of concrete canoeing.

  ConstructionThe design for our canoe was rendered using Solid Edge. The program runs on Microsoft

Windows and provides solid modeling, assembly modeling, and drafting functionality (Siemens 2015). After determining the final shape, our 2013 team generated full-scale computer cross sections at 30.48 cm (12 in.) intervals along the length. Then they used the drawings to produce plywood templates and mounted and aligned them on a wooden strongback.

They constructed a male mold by first nailing 6.35 mm (0.25 in.) thick luan strips to the cross sections over the majority of the length and then fitting foam blocks at the bow and stern. After placing a fiberglass layer over the strips and blocks, the team progressively refined the shape. They worked under subdued lighting so that spotlighting could be used to identify problem areas. These were marked, filled with drywall, and sanded until all discontinuities were removed (Team UAH 2013). Last year’s team refined the bow and stern sections to improve the hydrodynamics of their entry (Team UAH 2014).

Both teams had difficulty removing their canoes from the form and spent considerable time retrofitting the bow and stern sections with flotation. They also found it difficult to contour reinforcement in these areas. We removed these sections from last year’s form and duplicated the shapes using flotation materials so that they could be cast directly into our canoe. We used the remainder of the form to save time and as part of our sustainability effort.

The bill of materials included on the design drawing (see page 11) lists the materials used to produce the form. We added the photographs around the border to illustrate and clarify our teams’ construction techniques.

Our plan was to design and build a reinforced core to accurately position our primary reinforcement, reduce the overall weight of our canoe, and help us maintain structural integrity. We began core construction by producing a 6.35 mm (0.25 in.) thick flotation frame. This was done by placing 3.8 cm (1.5 in.) wide Cellular PVC stringers in the transverse direction at 38.1 cm (17 in.) intervals along the length of the mold. We fabricated several longitudinal stringers by first soaking 3.8 cm (1.5 in.) wide pine strips in water and then contouring them to the mold. After notching and gluing the transverse and longitudinal stringers together, we added diagonal members consisting of 2.54 cm (1.0 in.) wide balsa strips.

We began concrete canoe construction by draping a sheet of plastic over the mold to which we applied turtle wax and a mold release compound. We initially attempted to construct our boat by placing a layer of C-grid directly on the mold followed by the flotation frame. We used a steel mesh in the bow and stern sections because the mesh could be more easily contoured to the shapes.

During concrete canoe construction, we prepared several premixed batches of our concrete mix. During this process, we used a mechanical mixer to achieve better homogeneity and reduce the water content, thereby strengthening our concrete. We also timed the delivery of constituents, selected the proper mixing tools, and adjusted the mixing speed so that materials were dispersed evenly. We used a wire whip and high speed mixing to prevent our cementitious materials from clumping, thereby preventing dry particles from forming within the cement paste. For safety, we prevented microspheres from becoming airborne by mixing them with SBR latex, and used a low shear attachment to prevent breakage based on recommendations from the manufacturer (3M 2015b).

Once the concrete was ready, some of our team members used drywall knives to level it to the upper surface of the flotation frame. After stapling the outer layer of C-grid to the frame, we secured 2.36 mm (0.093 in.) diameter wires across the grid at 15.2 cm (6.0 in.) intervals down the length. Then, we used drywall knives to level the outermost layer of concrete to the upper surface of the wires. After an hour or so, we removed the wires and filled the grooves.

Our plan called for removing the boat from the mold within 24 hours so that we could place the inner layer of concrete and add concrete reliefs. But when we did so, the inner layer of C-grid and the flotation frame flexed, causing the outermost layer of concrete to delaminate from the reinforced core.

This failed attempt created a one week delay during which we spent a great deal of time and effort removing concrete from the flotation frame and bow and stern sections. We also strengthened the frame to prevent flexure during form removal and revised our construction scenario.

  

To produce the new reinforced core, our team placed a layer of C-grid on the mold and cut and contoured it to shape. We used tape and string to hold the splices in place as we positioned the modified flotation frame over this layer. We used tie wires to hold the inner layer of C-grid in place while we removed it and the frame from the mold. Then, we stapled the inner layer of C-grid to the flotation frame and removed the tape, string, and tie wires.

We began our second placement by draping a sheet of plastic over the mold to which we applied turtle wax and a mold release compound. This time, we secured 2.36 mm (0.093 in.) diameter wires across the mold at 15.2 cm (6.0 in.) intervals down the length. Then, our team members used drywall knives to level it to the upper surface of the wires. We left the wires in place to insure that the inner concrete layer would be of uniform thickness as we worked the innermost layer of C-grid and the flotation frame into position. Once this was done, we filled this configuration with concrete that team members leveled to the top of the frame.

After that, we added the outermost layer of C-grid and stapled it to the frame. During this process, we made certain that there were no opposing staples in the same location so that we could accurately compute the reinforcement thickness. After adding the outer layer with the help of the removable spacers, we draped plastic over the configuration. For the purposes of this competition, we placed concrete cylinders (ASTM C31).

Since the latex in our mix coalesced to form a film that coated the aggregate particles and the hydrating cement grains (Biszick and Gilbert 1999), we simply left the canoe and cylinders to dry. From sustainability and cost standpoints, this step saves water, time, and labor.

Our failed attempt forced us to extend the period scheduled for core construction and delayed curing by one week. We made up this time by hand sanding the outer layer of concrete after three days. During this process, we filled voids with the same mix used during the main construction and sanded after dark in soft lighting so that the shadows cast from oblique illumination could help us identify high and low areas. On the bright side, we found that sanding the boat earlier saved materials and the costs associated with them.

We cured the canoe for seven days so that the concrete would have the same flexural strength as that measured in our 7-day testing program. After removing it from the mold, we removed the spacer wires from the inner surface and filled the grooves.

We sanded the interior and applied vinyl lettering and stain to improve the boat’s aesthetics. Then, we placed the splash guard and sealed the surface. Appendix C describes all the materials and products used to produce our canoe. The pie charts shown in Figs. 6 and 7 depict the material costs and person-hours, respectively. We estimated person-hours through project completion; paddling is not included. Overall our costs and man hours stayed approximately the same as compared to last year.

Fig. 6. Material costs ($1,482). Fig. 7. Project person-hours (1,133).

During the project, we salvaged materials, and cut waste to a minimum. Our concrete sets up quickly and can be simply left to dry thereby saving cost and labor. Overall, the process can be easily done in the field making it suitable for applications ranging from sidewalks and roadways, to bridges and columns. More importantly, we were

able to successfully reduce the weight of an unreinforced canoe by 2.4 kg (5.3 lb) while adding a core containing the relatively heavy reinforcement required to sufficiently stiffen and strengthen it.

Project Schedule

Design Drawing with Bill of Materials

 

 

ASTM C31. (2012). “Standard practice for making and curing concrete test specimens in the field.” C31/C31M-12. West Conshohocken, PA. < http://www.astm.org > (23 February 2015).

ASTM C39. (2014). “Standard test method for compressive strength of cylindrical concrete specimens.” C39/C39M-14a. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C78. (2010). “Standard test method for flexural strength of concrete (using simple beam with third-point loading).” C78/C78M-10e1. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C138. (2014). “Standard test method for density (unit weight), yield, and air content (gravimetric) of concrete.” C138/C138M-14. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C143. (2012). “Standard test method for slump of hydraulic-cement concrete.” C143/C143M-12. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C150. (2012). “Standard specification for Portland cement.” C150M-12. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C494. (2013). “Standard specification for chemical admixtures for concrete.” C494/C494M-13. West Conshohocken, PA, < http://www.astm.org > (23 February 2015). ASTM C618. (2012). “Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete.” C618-12a. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C1116. (2010). “Standard specification for fiber-reinforced concrete.” ASTM C1116/C1116M-10a. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM C1240. (2014). “Standard specification for silica fume used in cementitious mixtures.” ASTM C12040-14. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM D638. (2010). “Standard test method for tensile properties of plastics.” D638-10. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). ASTM E8. (2013). “Standard test method for tensile properties of metallic materials.” E8/E8M-13a. West Conshohocken, PA. < http://www.astm.org > (23 February 2015). Biszick, K.R., Gilbert, J.A. (1999). “Designing thin-walled, reinforced concrete panels for reverse bending." Proc. of the 1999 SEM Spring Conference on Theoretical, Experimental and Computational Mechanics, Cincinnati, Ohio, June 7-9, 431-434. Biszick, K.R., Gilbert, J.A., Toutanji, H., Britz, M.T. (2013). “Doubly reinforcing cementitious beams with instrumented hollow carbon fiber tendons.” Experimental Mechanics, 53(4), ISSN 0014-4851, doi: 10.1007/s11340-012-9665-6. Chomarat (2010). “C50 – 1.8 x 1.6 carbon fiber reinforcing grids for concrete structures.” Technical data sheet. <http://www.chomarat.com/wp-content/uploads/2011/06/C50-1.8x1.6.pdf> (23 February 2015).

Appendix A – References

 

 

Detwiler, R.J., Mehta, P.K. (1989). “Chemical and physical effects of silica fume on the mechanical behavior of concrete,” Materials Journal, Nov.

Dorofee, A.J., Walker, J.A., Alberts, C.J., Higuera, R.P., Murphy, R.L., Williams, R.C. (1996). “Continuous risk management guidebook.” Carnegie Mellon Software Engineering Institute. <http://www.acqnotes.com/Attachments/Continuous%20Risk%20Management%20Guidebook.pdf> (23 February 2015). Euclid Chemical. (2015). “SBR Latex bonding adhesive.” < http://www.euclidchemical.com/fileshare/ProductFiles/techdata/sbr_latex.pdf > (23 February 2015). Feldman, D., Barbalata, A. (1996). “Synthetic polymers: Technology, properties, applications.” Chapman and Hall, London, 101. Graybeal, B. (2013). “Development of non-proprietary ultra-performance concrete for use in the highway bridge sector.” US Department of Transportation, FHWA-HRT-13-060. < http://www.fhwa.dot.gov/research/resources/uhpc/publications.cfm > (23 February 2015). Ibrahim, R.A., Grace, I.M. (2010). “Modeling of ship roll dynamics and its coupling with heave and pitch.” Mathematical Problems in Engineering, Vol. 2010, Article ID 934714, 32 pages, doi:10.1155/2010/934714. Joshi, R.C., Lohtia, R.P. (1997). “Fly ash in concrete, production, properties and uses.” Taylor & Francis Ltd. Majko, R.M. (2007). “Fly ash resource center,” information on coal combustion byproducts (CCBs).” < https://sites.google.com/site/flyashresourcecenter/home/flyash-html> (23 February 2015). NCCC Rules. (2015). “2015 American Society of Civil Engineers national concrete canoe competition rules and regulations.” < http://www.asce.org/concrete_canoe/ /> (23 February 2015). OSHA. (2015). “Laboratories”; “Hazard communication”; “Construction, concrete masonry”; “Personal protective equipment”; “Ventilation.” < http://www.osha.gov > (23 February 2015). Pinkston, M.E. (2011). “Quantitative evaluation of polymer-enhanced cementitious materials. M.S. Thesis, University of Alabama in Huntsville. Princeton Review. (2010). “Guide to 286 green colleges.” Rob Franek Publisher, Framingham, MA, 127. Ruiz, G., Koster, K., White, D. (2012). “Integrated program management for dummies,” John Wiley and Sons, Inc. < http://tech.sfsu.edu/sites/sites7.sfsu.edu.it/files/Integrated%20Program%20Management.pdf > (23 February 2015). Siemens. (2015). “Solid Edge.” < http://www.plm.automation.siemens.com/en_us/products/velocity/solidedge/ > (23 February 2015).

Appendix A – References (cont.)

 

 

Sika. (2013). “ViscoCrete 2100.” Product data sheet. <http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CCYQFjAA&url=http%3A%2F%2Fusa.sika.com%2Fdms%2Fgetdocument.get%2F89b7c847-c480-3324-989c-f7e29de95099%2Fpds-cpd-Sika%2520ViscoCrete%25202100-us.pdf&ei=BuH6UrjnLfC10AHvwIEw&usg=AFQjCNHKP5upVMtLuTqDsBh9931gvr2bQg&bvm=bv.61190604,d.dmQ> (23 February 2015). Team UAH. (2013). “APOLLO.” University of Alabama in Huntsville ASCE concrete canoe competition design paper.” Team UAH. (2014). “PHOENIX.” University of Alabama in Huntsville ASCE concrete canoe competition design paper. 3M. (2015a). “3M™ glass bubbles K1 for cryogenic insulation applications.” Product information. < http://multimedia.3m.com/mws/mediawebserver?6666660Zjcf6lVs6EVs66ssr1COrrrrQ-> (23 February 2015). 3M. (2015b). “3M™ glass bubbles – Metering and mixing guide.” <http://multimedia.3m.com/mws/mediawebserver?mwsId=66666UF6EVsSyXTtlXM6LxfVEVtQEVs6EVs6EVs6E666666--&fn=metermixguideGB.pdf&cshift_ck=null&client_id=752rfn6820 > (23 February 2015). University of Wisconsin. (2014). “NCCC design papers 2000-present.” < http://canoe.slc.engr.wisc.edu/designpapers.html> (23 February 2015). Wang, SX., Li, V.C. (2006). “Polyvinyl alcohol fiber reinforced engineered cementitious composites: material design and performances.” Proc. International RILEM Workshop on High Performance Fiber Reinforced Cementitious Composites in Structural Applications RILEM Publications SARL, In: Fischer, G., and Li, V.C. editors, RILEM Publications SARL, 65-73. Xu, B., Toutanji, H.A., Lavin, T., Gilbert, J.A. (2011). “Characterization of poly(vinyl alcohol) fiber reinforced organic aggregate cementitious materials.” Polymers in Concrete, 666, 73-83. Yang, E., Yang, Y., Li, V.C. (2007). “Use of high volumes of fly ash to improve ECC mechanical properties and material greenness.” ACI Materials Journal, Vol. 4, No. 6, pp. 303-311.

Appendix A – References (cont.)

Table 3.1 Summary of Mixture Proportions

Team UAH 2015

Appendix B – Mixture Proportions

Table 6.1 Bill of Materials and Production Cost Estimates

Team UAH 2015

Appendix C – Bill of Materials

 

 

(1)

(2)

In the past, our teams placed strain gages at critical locations on fiberglass prototypes and concrete canoes. In every case, the highest strain was measured directly under the bow paddler during 2-man races in a direction perpendicular to the longitudinal axis of the canoe (see Fig. 1). To determine the service load, Pcr, we assume that this critical section is in pure bending and load a flat test plate, having a cross section identical to that used in the prototype, until the critical strain is reached. The strain in the test plate is determined by placing a strain gage on the surface, in the x-direction, at point C (see Fig. 2). Knowing the load allows us to compute the maximum stress when we test an unreinforced concrete plate in a similar manner. A detailed step-by-step example calculation follows.

Figure 2 shows a schematic diagram for the third point bending (TPB) test which includes a prismatic beam of length, L, having a rectangular cross section with a base, b, and height, h. The beam is supported by a pin at point B and a roller at point D. Concentrated loads of equal magnitude are applied at points A and E by placing a load, P, at the center of a loading platen FG. The lengths of sections AB, BD, and DE are equal to L/3 so that the test complies with ASTM C78/C78M-10e1 (ASTM 2010); the standard established for a configuration typically referred to as “third point” or “four point” (pure) bending.

Fig. 2. Third point bending (TPB) test

Figure 3 shows the free body diagram for the configuration illustrated in Fig. 2. The reactions at the inner supports, labeled as RBx, RBy, and RD, can be determined by satisfying equilibrium.

Fig. 3. Free body diagram for third point bending (TPB) test Summing forces along the x axis,

Σ 0 0. Taking moments about point B, where positive is counter clockwise,

Σ 0 .

Appendix D – Structural Calculation

Fig. 1 Critical location.

 

 

(3)

(4)

(5)

(6)

(7)

Summing forces along the y axis,

Σ 0 2

2

2.

The shear and moment diagrams for the entire beam are shown in Fig. 4. In the region of interest (section BD), the shear is zero while the bending moment, Mz, is constant. The normal stress along the longitudinal direction, σx, is given by

,

where y is measured upward from the neutral axis which is located at the centroid of the cross section (point O in Fig. 2); Iz is the centriodal moment of inertia around the z axis about which bending occurs.

Fig. 4. Shear and moment diagrams for third point bending (TPB) test Referring to Eqn. 4, the internal stress in section BD is distributed linearly through the thickness; compression below the neutral axis, tension above it, and zero there. The maximum tensile stress occurs at points on the top surface of the beam which lie at the furthest distance, c, measured from the centroid. Referring to the cross section in Fig. 2 and recognizing that M = - PL/6, Iz = bh3/12, and c = h/2, Eqn. 4 becomes,

6 2112

.

The maximum stress under the bow paddler, σb, is found when the critical load, Pcr, is substituted into Eqn. 5. The result is,

.

Despite significant differences in hull composition and shape, our teams all found that the critical service load was equivalent to a 0.283 N-m (2.5 in-lb) moment applied to a 2.54 cm (1.0 in.) wide plate. Assuming that the plate is 5.08 cm (2.0 in) wide (“b” in Eqn. 6), the critical moment is 0.565 N-m (5.0 in-lb). We typically evaluate 15.24 cm (6.0 in.) long (“L” in Eqn. 6) plates, making Pcr = 6Mz/L = 22.24 N (5.0 lb). If the plate is 15.24 mm (0.6 in.) thick (“h” in Eqn. 6), then

σb = 287 kPa (41.6 psi) .