Historic Bridge Restoration
Sponsoring organization: Para la Naturaleza
Team members: Harry Chartoff (Biomedical Engineering ’18), Steven D’Agostino (Mechanical Engineering ’18), Margaret LaRoche (Chemical Engineering ’18)
Travis Rossen (Mechanical Engineering ’18)
Download the final presentation.
Executive Summary:
In 1968, Puerto Rico began to undergo an industrialization period that would modernize the economy. This movement posed a threat of urbanization, which meant that many of Puerto Rico’s ecosystems would be destroyed (Conservation Trust of Puerto Rico, 2016). This growing concern to protect the island’s lands led to the formation of numerous conservation groups throughout Puerto Rico. These groups include the Departamento de Recursos Naturales y Ambientales (DRNA), Fideicomiso de Conservacion de Puerto Rico (Conservation Trust of Puerto Rico), and Para La Naturaleza. In addition to the imposing threat of deforestation, the environment was already lacking preservation. As of 2015, only 16% of Puerto Rico’s lands were conserved (Para La Naturaleza, n.d.). Para La Naturaleza acts as a subsidiary of the Conservation Trust of Puerto Rico and puts an emphasis on preserving the island’s natural environment. Their objective from the Conservation Trust is to protect 33% of the island’s land by 2033 (Who are we?, 2016).
Hacienda La Esperanza is an area located in Manatí, Puerto Rico and is protected by Para La Naturaleza. This land was bought in 1975 by the Conservation Trust of Puerto Rico to protect the land (Gwenn, 2016). Through their numerous conservation efforts throughout the years, Para La Naturaleza has successfully restored the steam sugar mill, the drying house, and the Marquez manor house. Their next move is to conserve two of the historic bridges that are located on-site. In order to create designs for the bridges we created a restoration plan.
In 1968, Puerto Rico began to undergo an industrialization period that would modernize the economy. This movement posed a threat of urbanization, which meant that many of Puerto Rico’s ecosystems would be destroyed (Conservation Trust of Puerto Rico, 2016). This growing concern to protect the island’s lands led to the formation of numerous conservation groups throughout Puerto Rico. These groups include the Departamento de Recursos Naturales y Ambientales (DRNA), Fideicomiso de Conservacion de Puerto Rico (Conservation Trust of Puerto Rico), and Para La Naturaleza. In addition to the imposing threat of deforestation, the environment was already lacking preservation. As of 2015, only 16% of Puerto Rico’s lands were conserved (Para La Naturaleza, n.d.). Para La Naturaleza acts as a subsidiary of the Conservation Trust of Puerto Rico and puts an emphasis on preserving the island’s natural environment. Their objective from the Conservation Trust is to protect 33% of the island’s land by 2033 (Who are we?, 2016).
Hacienda La Esperanza is an area located in Manatí, Puerto Rico and is protected by Para La Naturaleza. This land was bought in 1975 by the Conservation Trust of Puerto Rico to protect the land (Gwenn, 2016). Through their numerous conservation efforts throughout the years, Para La Naturaleza has successfully restored the steam sugar mill, the drying house, and the Marquez manor house. Their next move is to conserve two of the historic bridges that are located on-site. In order to create designs for the bridges we created a restoration plan.
Methodology
In order to successfully create a full restoration plan for Para La Naturaleza our team carried out the following objectives:
- Gained an understanding of the current state of the bridges
- Determined potential designs for the bridges
- Determined the cost of the bridge designs and the different possible materials
- Developed informational signs for the community and tourists
To achieve these objectives our methods consisted of conducting an initial assessment of the structural integrity of the bridges through observation and field measurements. We then utilized a computer-aided design (CAD) program to create and run simulations on potential designs. We also created Excel spreadsheets to conduct a cost-benefit analysis of potential materials for construction. Finally, we designed informational signs to go on site to educate the community.
We needed to gain a clear understanding of the current state of the bridges, which was done by conducting visual assessments. Our assessments included measurements of all parts of the pre-existing structures; for example, the height of the abutments off of the water and the span of each individual part.
Once the assessments were finished, we were able to research different bridge design options. Based on our research, we were able to develop two different bridge concepts for the María Hernández Bridge and four for La Boquilla Bridge. Utilizing CAD software, we designed bridges that included the proper materials and dimensions. To ensure that our designs were realistic, we conducted interviews with Para La Naturaleza employees, force simulations, and a material cost analysis. These methods allowed us to create the best restoration plan for Para La Naturaleza to utilize our proposal recommendations.
Finally, we conducted research on how to present information in order to educate the community and tourists on the history of the bridges. We analyzed educational signs throughout popular historic sites in Puerto Rico to determine the most effective way to convey information. We coupled our research with interviews with Para La Naturaleza to ensure that our sign designs fit well within the company’s desired aesthetics.
Solutions and Recommendations
María Hernández Final Bridge Design: The Final Bridge Design consists of a flat slab connected by two ramps that go directly over the pre-existing bridge. Four flagpoles were strategically placed at each corner of the concrete slab. These flagpoles were placed where the slabs connected to each ramp to assist tractor operators with their line of sight. The materials used for the construction of the new bridge include steel rebar and concrete.
María Hernández Final Restoration Plan: The Restoration Plan was split between going through a company named Cintec or another local restoration professional. Cintec’s method of restoring bridges fit the needs of Para La Naturaleza by keeping the original bridge structurally sound. Our investigation showed that the cost of this type of restoration would most likely outweigh the cost of having a local company come in to assess the bridge.
María Hernández Recommendation: Our final recommendation for the María Hernández Bridge is to build over the pre- existing structure using the Final Bridge Design proposed. This eliminates all forces from acting upon the older bridge and still allows restoration of the historic bridge if need be. This option is also less expensive than the restoration method.
La Boquilla Bridge Design 1: This design involved constructing the bridge with steel plates on top of resurfaced abutments. These plates serve as protection between the bridge and the abutments in order to improve the bridge’s longevity. Furthermore, 4”x4” pylons would be connected to the bridge and extend to the bottom of La Boquilla River. These serve as points to connect handrails and provide increased strength for the bridge.
La Boquilla Bridge Design 2: This bridge design also utilized steel plates to create separation between the bridge and the abutments, but it does not utilize pylons that go into the ground. Instead, the pylons on this design solely extend upwards to allow the handrails to connect to them.
La Boquilla Bridge Design 3: Unlike the first two designs, this design would utilize steel H-beams instead of steel plates which would raise the bridge up higher and further from the water. This would decrease any potential water damage done to the bridge. This design also included the 4”x4” pylons that extend into the ground for added support.
La Boquilla Bridge Design 4: This design did not include the 4”x4” pylons that go into the ground, but did include the steel H-beams on the resurfaced abutments. This design is the cheapest of the four, but was not as structurally stable as Design 3.
La Boquilla Bridge Recommendation: We suggest using Design 3. This design has the best balance of both price and structural stability. It also satisfies all of Para La Naturaleza’s requirements and will be able to withstand numerous uses and large loads.
Material Recommendation
While designing our bridges we conducted research on different types of materials and how they would perform in the locations of each bridge. During this research, we looked for a balance of durability, cost, and feasibility.
María Hernández: For the María Hernández Bridge, our design utilized construction grade concrete and ½ inch steel rebar. The concrete was chosen because of its large supply on the island and cheap production cost. The steel rebar was chosen due to its low cost and ability to improve the strength of concrete.
La Boquilla: Our recommendation of building materials for La Boquilla Bridge is to use Pine or Cedar. Pine was recommended because it is inexpensive and can be strengthened with pressure treatment. Cedar was included because it is durable in wet environments and is long lasting.
Another material we presented as an option was a combination of conventional wood for the structural parts of the bridge and composite wood (Trex Decking) for the decking. This composite wood is extremely long lasting and needs little maintenance. Another building material we had to pick for La Boquilla Bridge was the specific type of spacer to be used. We recommend the use of steel H-beams since it is the most cost effective option and did not compromise structural integrity.