In Loving Memory of Marissa Jimenez You will not be forgotten.
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Senior Design Project Submittal 2012
Acknowledgements:
Dr. N. J. Delatte, P.E., Ph.D., Professor, Department of Civil and Environmental Engineering, Cleveland State University, Concrete Bridge Analysis Dr. L. Kahn P.E., Ph.D., Professor, Department of Civil and Environmental Engineering, Cleveland State University, Geotechnical Testing and Analysis Dr. P. Degroot P.E., Ph.D., Professor, Department of Civil and Environmental Engineering, Cleveland State University, Hydrologic Analysis Dr. P. Bosela, P.E., Ph. D., Professor, Department of Civil and Environmental Engineering, Cleveland State University, Structural Analysis Dr. S. Duffy, P.E., Ph.D., Professor, Department of Civil and Environmental Engineering, Cleveland State University, Structural Analysis
Joseph R. Reitz, CPESC, Avon Lake Engineering Manager, Stormwater Program Manager Don Meyer, Project Engineer, Great Lakes Construction Company, Hydraulic and Hydrological Analysis Gary Gerrone, City of Avon Lake Recreation Director
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Senior Design Project Submittal 2012
1.0.0 Introduction
1.1.0 Objective The objective of the senior design project is to familiarize graduating students with the importance of working as a team to overcome the obstacles faced during a design, build project and successfully design an existing Civil Engineering project. The first objective, before the preliminary research, was to develop a cohesive team. This was accomplished by identifying the strengths and weaknesses amongst the group. After identifying the group strengths and weaknesses we established goals, milestones and objectives. The end product or final submittal was comprised of numerous goals. Each goal had milestones specific to that goal, and was divided into objectives. The objectives were then assigned to group members according to their strengths and or interests in each particular category. Each assignment had stumbling block that required not only additional team member assistance but also professional assistance from the Civil Engineering Department. Completion of objectives achieved additional steps toward milestones while accomplished milestones produced particular goals. Goals such as Geotechnical, Hydrological, Structural, and Foundation Analysis were achieved and together provided the overall objective. As you will see from the following report, the overall project was a success as each of the group members exhibited leadership qualities and persistence. 1.2.0 Group Members Group six of the 2012 Senior Design Project consists of, in alphabetical order, Jeffrey A. Curry, Philip Dee, Daniel Moir, and Stefanos Papagianidis and the project assignment was the Bleser Park Pedestrian Bridge in the City of Avon Lake.
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Senior Design Project Submittal 2012
2.0.0 Project Description 2.1.0 Assignment The Group 6 Senior Design Project assignment was to design a pedestrian bridge and rehabilitate an existing pedestrian bridge for the City of Avon Lake located in Bleser Park. Bleser Park is located on the west side of Avon Beldon Road between Lake Road and Electric Boulevard, on Cleveland’s west side, approximately Figure 1: Bridge locations marked with blue arrows.
N o r t h Proposed Bridge
Existing Bridge
45 minutes west of downtown and just a few hundred feet south of Lake Erie in Avon Lake Ohio. The existing pedestrian bridge was visually inspected. Significant corrosion and rust and present on the underside of the super structure. The concrete at the underside of the bridge’s span is deteriorating to the point that entire sections of the bridge deck have broken away from the structure. Exposed steel reinforcement is visible and corroded. The City of Avon Lake performed recent repairs to the bridge to try and slow the degradation of the structure. A wooden deck was recently installed to cover the corrosion and pitting of the concrete as well as exposed steel reinforcement running across the top of the bridge. The hand rail, located on either side of the existing bridge span, is also showing signs of corrosion however it seems to be in stabile, functioning condition. Mr. Reitz stated that the major contributing factor of the deterioration was
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Senior Design Project Submittal 2012 from placing salt on the surface of the bridge during the winter months due to ice buildup. The topographic maps are currently a work in progress and will be attached to the Survey section of the final report.
2.2.0 Existing Bridge The existing bridge crosses Heider Ditch at Avon Lake City Hall which is located just north of Electric Avenue on west of Avon Beldon Road (State Route 83) and connects city hall to Bleser Park’s south parking lot. It is primarily used by the employees of Avon Lake’s city hall. The bridge has exceeded its anticipated useful life expectancy of 50 years and is in the beginning stages of disrepair. The general rehabilitation process would include the deconstruction of the super structure. Once the super structure is removed, the existing foundations will be re-spanned with a comparable prestressed concrete T-Shape beam. Figure 2 Beginning Stages of Disrepair Figure 3 Existing Bridge Crossing Heider Creek
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Senior Design Project Submittal 2012
According to Dr. Lustful Khan (P.E.) (2011) of the Geotechnical Engineering Department at Cleveland State University, it can be assumed that the foundations of the existing bridge will be capable of supporting an equivalent weight or less that the existing super structure. If the new span involves a load greater that the existing load, then a foundation analysis will have to occur in order to determine the capacity of the existing foundations. The foundation analysis would include either a static or dynamic test. There are Cleveland based foundations testing firms which have pioneered this area of expertise and available for any testing procedures necessary. Both the tests are extremely expensive and also very time consuming. In the best interest of Avon Lake and for economic sustainability the existing foundations will be left in place and respanned with an equivalent load or less. 2.3.0 Proposed Bridge The proposed location of the new pedestrian bridge will also cross Heider Ditch at the Avon Lake Community Center, which used to be the old Avon lake Firehouse. The Community Center is located just south of Lake Road on the west side of Avon Beldon Road and the east side of Heider Ditch. The purpose Figure 4 East Foundation Location of the proposed bridge is to link the Community Center with the newly developed
Heider Ditch Proposed East Foundation Point Community Center
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Senior Design Project Submittal 2012 parking lot located south of Lake Road, just west of Heider Ditch. Heider Ditch flows, from south to north, through Bleser Park separating the City Hall and the Community Center from Bleser Park. The overflow parking is located west of Heider ditch and the community center is located on the east side of Heider ditch at the corner of Lake Rd. and Route 83. Currently the residents have to walk a few hundred feet east on Lake Road to Avon Beldon and then south on Avon Beldon to get to the community center. Please refer to the attached site plan for the general locations described above. 2.4.0 Owner Requirements A meeting with the Parks and Recreation Director Gary Gerrone and Engineering Manager Joe Reitz was scheduled for Friday January 6th, 2012. The purpose of the meeting is to obtain a clear, concise understanding of what exactly the Owner would like to see in the preliminary design. Another objective was to obtain any additional parameters which may not be determined from technical analysis. Parameters that were discussed during the meeting include but are not limited to: Safety Budget requirements Contractor and labor requirements Material requirements Surrounding Architecture and Culture Environmental restraints
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Senior Design Project Submittal 2012
2.4.1 Safety
The City Officials have an apparent safety hazard due to the size of the existing parking lot as seen in Figure 5. While pedestrians exit their vehicles and walk to the Community Center, they are within a very close proximity of vehicles that have entered the parking lot and are attempting to park. Pedestrian traffic and vehicular traffic share the sidewalk. Less than 10 Feet Comm. Center
Figure 5: Safety Concerns with City Officials 2.4.2 Budget parameters Although there are many factors with which effect the completion of a project, budget is typically the underlying factor for the eventual demise of most construction projects. The Owners first priority is to replace the existing bridge span. As stated above, their clear intentions are to replace the super structure and reuse the existing foundations. This is the most cost effective and efficient use of the Cities budget. As for the proposed bridge the Owner requested to see alternatives. Example of design alternative can be found in section 3 along with the design selections. Alternatives are to include a cost efficient design, along with at least one landmark design. A landmark design is a design alternative that will stand out and be recognized as “The Bridge in Avon Lake”. In other words, the cost of completion for each bridge design will be compared to the overall design features, understanding that most landmark design alternatives are accompanied by a significantly larger budget.
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Senior Design Project Submittal 2012
Design criteria affecting the overall selection of the alternative include but are not limited to sustainability, aesthetics, lead time, and cost. The design criteria are typically weighted, and since the underlying factor in the choice of bridge design is cost, it is usually weighted a little higher than the other design criteria. Criteria are then ranked for each bridge typical to a “good, better, best” scenario. design selection can be seen in the following table. As seen in Table 1, the design alternatives can be chosen based on the highest ranking weighted average. This proposal will focus on these two alternatives. The Owner reserves authority of the final selection or rejection of the proposed bridge designs.
Criteria Sustainability sthetics Lead Time A Design Alternative Concrete 4 3 5 Recycled 5 1 1 Fiber Reinforced Plastic 2 4 2 Steel 2 3 3 Wood 4 4 3 Land Mark 4 5 3 Weight 25% 25% 15% Where: Weighted Average 5 = Excellent Concrete 4 = Good Recycled 3 = Average Fiber Reinforced Plastic 2 = Fair Steel 1 = Poor Wood Land Mark Cost 4 5 2 3 3 3 35%
An example of a typical
3.9 3.4 2.5 2.75 3.5 3.75
2.4.3 Contractor or labor Table 1: Design Alternative Selection Analysis requirements All contractor and labor agreements will be performed in accordance with the Collective Bargaining Agreement between the City of Avon Lake and the AFL-CIO & CLC Local 1836 (City of Avon Lake, International AFL - CIO & CLC, 2011). The entire contract is available upon request or can be viewed at the URL found in the Reference Section. 2.4.4 Material requirements As stated above, the Owner would like to see alternatives. Alternative materials include but are not limited to Concrete, Steel, Wood, and Fiber Reinforced Plastic or FRP. Each material has distinct characteristics, advantages and disadvantages. These
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Senior Design Project Submittal 2012 characteristics, advantages and disadvantages will be discussed further in the Alternatives section of the Project Submittal. With regard to material requirements, City Officials were primarily concerned with the Avon Lake, Bleser Park culture and surrounding architecture. Preliminary site investigation pictures of the surrounding architecture and culture can be found in Appendix Section 2. 2.4.5 Environmental restraints or requirements When designing a bridge it is important to identify the environmental problems linked with bridges. It is also important to consider the environment in which the bridge will be constructed. In this particular design the bridge is located in Bleser Park and will span Heider Creek. Bridges can be designed in such a way that they narrow or confine the stream impeding the lateral movement or natural flow of Heider Creek. By narrowing the arterial of the stream, increased erosion of the unstable stream banks will be flushed downstream which will also create an increase the depth. Alterations of the stream characteristics can change the natural orders of the stream causing the previous environment to change. Changing the environment would in turn alter the native fish population and would influence other native wildlife that depends on Heider Creek as their home. This proposal offers a non-obstructive design in which the foundations are constructed outside of the 100 year flood plain. Bridge placement or foundation location is not the only environmental concern that needs to be addressed. In fact it is not the bridge that will create an environmental
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Senior Design Project Submittal 2012 disturbance, it is the construction processes and maintenance of the bridge will cause environmental issues. Tree removal will destroy the homes of birds, squirrels, rodents, and insects causing the wildlife to relocate. Fortunately, the tree removal required will be minimal and may possibly be eliminated altogether. A proposition for tree removal can include a replacement tree for every tree removed. Unlike this year, the typical winter season in the Cleveland can be very harsh. Mother Nature tends to provide plenty of snow and ice for City and her surrounding suburbs. Accompanying all the snow and ice is salt and calcium. The minimum practical application range for sodium chloride, NaCl, is a pavement temperature of 15-20 degrees F and above. Rock salt can melt over five times as much ice at 30 degrees F as at 20 degrees F. NaCl will melt snow and ice down to a pavement temperature of -6 degrees F. In lower temperatures NaCl is often accompanied by calcium chloride, CaCl2, which has a greater melting power by lowering the freezing point of water more than NaCl. (Anne Marie Helmenstine, Copyright 2012) The environmental impact of the additional NaCl and CaCl2 is very broad. EPA has set the Secondary Maximum Contaminant Level (SMCL) for chloride at 250 mg/L in drinking water supplies. Salt also damages to vegetation destroy food sources, shelters, and breeding or nesting sites. Environment Canada (EC) 2000 mentions 12 reports of bird kills associated with road salt. Two reports include kills in excess of 1,000 birds. Seed eating birds may not be able to differentiate between road salt and natural food their bodies require. To address this issue, the alternative proposal design will encompass a covered bridge which will mitigate the collection of snow and ice thus reducing the amount of NaCl an CaCl2.
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Senior Design Project Submittal 2012
3.0.0 Alternatives The following section is summary of different material alternatives. The most common types of materials in which bridges are constructed will be taken into consideration while designing the Bleser Park Pedestrian Bridge. The alternatives include, but are not limited to, wood construction, steel, fiber reinforced plastics, concrete, and a recycled bridge located in Kentucky. The advantages and disadvantages associated with each design alternative have been listed below followed by the design alternatives selected for this proposal. 3.1.0 Wooden Bridges There are many advantages and disadvantages with using wood bridges are very aesthetically pleasing. The disadvantages include their susceptiblity to damage caused by extreme weather conditions, decomposition, misuse, vandals, and mechanical problems. These types of bridges require regular maintenance to preserve the material from decay. Wood needs to be treated periodically with anti-weather and preservative coatings such as creosote, pentachlorophenol and copper naphthenate. This material would rapidly decay without proper maintenance and compromise the structural integrity of the wooden bridge. This type of bridge is also susceptible to biotic deterioration. Certain plants and animals digest the cellulose and other fibrous elements that make up wood and ultimately compromise the structural integrity of the bridge. To prevent biotic Figure 6: Timber Bridge Construction
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Senior Design Project Submittal 2012 deterioration, the surface of the wooden bridge will need to be treated with oil-based wood preservatives. Another disadvantage of wood is it’s susceptibility to combust. The possibility of a fire has been considered, however due to the bridges location and lack of surrounding ignition sources, this possibility is unlikely (Gilani). Wooden pedestrian bridges have many advantages over other bridge types: High level of prefabrication Fast assembly time Low cost for transport and laying the foundation Documented quality and service life Competitive prices (Martinsons, 2010) Installation will not be delayed due to the availability of this resource as it is readily obtainable. Due to modern advances in wood preservatives, wood can now be effectively protected against decay and deterioration for periods of 50 years or more (WoodBuilders). Wood is also environmentally safe. It is an organic material and unlike steel, it will not harm the environment when it decays. With sustainability in mind, wood is the only naturally renewable building material. And financially, wood is cheaper than other materials such as steel and concrete. The wood design has been chosen as the alternative analysis. Reasons for this selection include price, aesthetics and sustainability. The wood bridge will be designed and submitted in accordance with all necessary engineering codes and regulations.
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Senior Design Project Submittal 2012
3.2.0 Steel Bridges An obvious design consideration is the steel bridge alternative. Steel is sustainable because it is one of the world’s most consistently recycled materials. It can withstand extensive deformation without failure under high tensile stress so it will give warning before it fails. Also, steel is Figure 7: Steel Bridge Alternative lighter than concrete and will require
smaller foundations. Fewer materials needed for the bridge span and foundations results in cost savings. Contrary, steel may be a bad choice. Since the bridge will be above moving water, it is vulnerable to corrosion. Connections may corrode and lose structural integrity. It will need to be painted periodically to prevent corrosion. This method of corrosion prevention is environmentally safe as non-toxic paints are available. Paint is a good solution to corrosion but continued maintenance costs can be expensive. Aluminum might be an alternative material that is less susceptible to corrosion. Aluminum does not need protective paint and required less maintenance.
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Senior Design Project Submittal 2012
3.3.0 Fiber Reinforced Plastic Fiber Reinforced Plastics (FRP) are composite materials that consist of high strength fibers immersed in a structural matrix such as epoxy or other durable resin. The most common fibers used are glass, carbon, and aramid (trade name Kevlar) (Plastic Highway Bridges, 2000). Fiber reinforced polymer super structural profiles are available in I sections and wide flange sections up to 8” x 8” x ½” with 52,500 psi compressive strength and 46,000 psi tensile strength. Other standard components have strengths ranging between 30,000 and 60,000 psi. This material can always be melted down and recycled if Avon Lake ever decides to remove it. Though it is well out of the team’s expertise, plastic reinforced with fibers might be a good material for the pedestrian bridge. Unlike steel reinforcement, plastic composite bars will not rust. Pultex fiber reinforced polymer rods and bars have 100,000 psi tensile strength and 60,000 psi compressive strength which compares well with steel (Design Manual: Fiberglass Grading and Structural Products). Aside from the high strength, FRP components have many other features and benefits. FRP is a light weight material which is easily carried and can be erected in most locations. Bridges spans are designed for quick and easy installation and assembly Figure 8: Fiber Reinforced Plastic (FRP)
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Senior Design Project Submittal 2012 utilizing modular construction. Bridge spans can be shipped fully assembled, partially assembled or completely disassembled depending on site requirements. Composite materials also require very low maintenance. Wet locations, termites, salt, and most chemicals have no effect on FRP material. Composite material can also come in any color, and painting is not necessary. Lastly FRP composites are electrically nonconductive and easy to clean. (ACMA Americam Composites Manufacturers Association, 2004) 3.4.0 Recycled Bridge Another option of recycling an existing bridge was considered as a design alternative. The bridge, located in Kentucky, is 82 years old and the state has scheduled it to be replaced. The bridge is eligible for National Register of Historical Places and the state would like for it not to be destroyed. The state is offering to disassemble the bridge and transport it to the Figure 9: Recycled Design Alternative site at their expense. The state has only agreed to do so if the bridge is reassembled to its original structure. After further review, this is not an option because the span of the recycled bridge is too long. The bridge span is approximately 120 feet in length; the bridge located in Kentucky is a three span bridge with a length of 456 feet.
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Senior Design Project Submittal 2012
3.5.0 Concrete Bridges The final option that is being considered as a design alternative is concrete. According to The World Business Council for Sustainable Development (2009), concrete is the most used construction material in the world with over 25 billion tons placed each year. Concrete offers long-lasting service with minimal maintenance, along with recycled content and end – of – service recyclability (Andrea J. Schokker, 2010). Two of the group members are currently in a pre-stressed concrete class and have used the PCI concrete manual. All of the group members will be taking a class in reinforced concrete design and be using the PCI concrete manual. Concrete is a good choice as a building material because it has a longer lifetime and much lower maintenance costs than steel. Concrete is sustainable environmentally as it consists of very little chemical admixtures. Less energy is consumed in creating concrete than steel. A study was done making two identical beams with the same moment capacities. It was determined that it took 0.89 KJ/kg to create the concrete beam and 23.70 GJ/kg to create the steel beam. Figure 10: Concrete Design Alternative
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Senior Design Project Submittal 2012
4.0.0 Sustainability Sustainability is improving the quality of human life while living within the carrying capacity of supporting ecosystems. It is the capacity to endure; to meet today’s needs without compromising the future. Sustainability encompasses the environment, resources, community, and financial obligations. The actual application of these concepts can be Figure 11: Managing Sustainability
challenging. As eco-friendly engineers, the team has considered all possible options before coming to a conclusive decision regarding this project. When considering the surrounding eco-systems, the community center pedestrian bridge will be built over a stream. This stream has important significance considering the local natural eco system. The team would like to select a building material that has the least effect on the surrounding environment. The members of the city hall engineering office have stressed that they do not want to disrupt the fish that occupy and travel through this stream. This consideration limits the location of the foundations, but protects the local natural habitat and surrounding wildlife. Reducing the amount of trees that need to be removed during construction can be solved by locating the bridge path through the area of least resistance.
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Senior Design Project Submittal 2012
According to sustainable building practices, the use of resources can be cut down maximizing production. While including the thoughts of sustainability in design with regards to resources, all possible building materials for the pedestrian bridges must be reviewed. Wood, plastics, concrete, and steel have been explored. Selecting a material that is renewable or recyclable will give the bridges high sustainability. The reduction of the overall gasoline consumption can be reduced during the transportation of the bridge material by selecting materials from local manufacturers. This will reduce the carbon footprint. Selecting a material that produces less carbon dioxide during its manufacture will also reduce the carbon footprint. Generally, a carbon footprint is a measure of the impact our activities have on the environment. Alternate solutions if any available will need to be considered. As in every construction project or work atmosphere, safety is always at the forefront. The pedestrian bridges, surrounding parking lots, and Bleser Park need to be safe as well. The main parking lot is shared by the community center and city hall. The section of parking lot by the community center gets very narrow as it approaches city hall. Potential for an accident increases as the parking lot gets narrower and nears the parallel sidewalk. When the parking lot is at maximum capacity, vehicles come very close to the sidewalk while traveling through this narrow section. Vehicles come even closer to the side walk as they back out of a parking spot in this narrow section. There is risk of traveling vehicles coming into contact with a pedestrian who is walking on the side walk. The possibility of an accident increases in the winter months if the parking lot is not properly plowed or salted.
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Senior Design Project Submittal 2012
The walking distance from the overflow parking lot to the community center is shorter than the distance from the end of the main parking lot. It is anticipated that the senior citizens will want to park in the overflow lot once the new bridge is operational. Therefore, fewer cars will park in the main parking lot and the risk of an accident will be reduced. The design team has recognized that risk may increase in the future as well. The team understands that the amount of people visiting the community center may grow. The main parking lot and overflow parking lot may reach maximum capacity and the risk of an accident may rise again in the future. Adding a small barrier between the main parking lot and the parallel sidewalk may be necessary. Another safety concern is lighting. The walkway of the community center bridge will need to be visible at night since the community center operates after dark during the winter months. Utilization of solar power with solar panels and rechargeable batteries can be used as a possible renewable energy source for bridge lighting. If however, the city does not approve, bridge lighting power can be acquired from the local power grid.
5.0.0 Preliminary Research The team met with Owners Representatives Joe Reitz and Gary Gerrone of Avon Lake’s Engineering Department to discuss the needs of the city and its residents as it pertains to the pedestrian bridges. Proposed bridge locations were determined along with a general site overview. The existing bridge conditions were examined and pictures were taken. Oxidation and decay was found on the bottom chord of the existing pedestrian bridge. Temporary repairs have been made to prolong the decay and as an added safety precaution. The city has decided to demolish the existing bridge
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Senior Design Project Submittal 2012 superstructure and re-span the existing foundations. Mr. Reitz has also provided a site plan of the Avon Lake City Hall Building, Boring Logs City Hall, Flood Plane Maps, along with Sections Views and Pier Dimension of the existing bridge. Site photographs along with photographs of the existing bridge and existing bridge conditions can be found in Appendix #5.
6.0.0 Site Survey A survey team met on location to survey the site. Pictures were taken of the area and the property was surveyed to determine elevations, location of the pedestrian bridge, and also to determine the length of the spans of the bridges. A data collector was used to collect data points to design a map that shows the proposed area of the pedestrian bridge, existing buildings, and existing utilities. The survey was completed in November and the points were placed into AutoCAD where the plan view, along with a topographic map was created. From the topographic map, the centerline profile was constructed by selecting the most probable direction for the bridge to cross Heider Ditch, and then interpolating all the elevations across that line. The survey was done such that the profile of the ridge and the creek would be very accurate. It was performed such that the density of the points shot in proximity to the crossing was far greater than elsewhere. Of course it was also important that all the necessary structures, utilities, obstructions, and boundaries were identified, and these will be shown on a plan view of the site.
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Senior Design Project Submittal 2012
The preliminary design requires an accurate site analysis. The site survey was completed and included determining the length of the region to in which the bridge may cross to a relatively similar elevation. This was done by means of a field survey, utilizing an electronic distance measuring instrument known as a total station. The elevations of the opposite sides of the ridges defining the entrance and/or exit of the bridge, along with detailed elevations of the sloping region, and definitive bottom were measured and determined as seen in Figure 12. From this information, the dimensional requirements of the superstructure, and preliminary considerations were assessed and proceed. The most valuable piece of information taken from the survey is the centerline profile and can be seen in Figure 13. It consists of a profile view of the bridge, essentially cut down the middle along with accurate detailing Figure 12: Centerline Profile Figure 13: Proposed Site Topography
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Senior Design Project Submittal 2012 of the land from side to side. Information for the span length, deck height, pier spacing, excavation and or filling was estimated from this layout. The profile revealed that the least span length dimension from side to side was approximately 84 feet with an elevation difference of about 2 feet. The lower side is the east side (community center), and this difference will likely be accommodated by a slight modification of either side. With this, information, and the concern about slope stability of foundations, it was decided that the bridge would span 6 feet past the minimum gap length, and increasing the span to 96 ft.
7.0.0 Geotechnical Analysis After meeting with Dr. Khan, we were instructed to obtain soil borings for the Senior Design Pedestrian Bridge Project. The intended purpose of procurement is to determine the classifications of the soil strata in Bleser Park, Avon Lake Ohio. Further instructions were to perform the appropriate laboratory testing to determine the soil classification. Table 2 is a list of laboratory test used to determine the soil classifications along with their respective ASTM standards code. All laboratory experiments were performed in accordance with ASTM standards.
Table 2: Required Geotechnical Analysis
Test # i. ii. iii. iv. v. vi. vii.
Laboratory Test Water Content Determination Atterburg Limits #200 Clay Content Wash Specific Gravity Consolidation Direct Shear Compaction
ASTM Standard D 2216-90 D 4318 C 117-04 D 854 D 2435-90 D 3080-90 D 698-79
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The completion of the site survey analysis determined the foundation locations and the soil sample was taken accordingly. November 11th, 2011 at a depth of approximately 10 feet 8 inches the hand held auger encountered shale. During the first eight feet of excavation, a brown and gray, firm, moist, shaley clay was observed. Just beyond the 8 foot depth, gray shale was observed (See Appendix Section 7). Upon collection of the specimen, the sample was immediately placed in plastic containers and sealed to avoid moisture evaporation. The specimen was then transported to the geotechnical laboratory located in Stilwell Hall at Cleveland State University. The individual geotechnical laboratory data sheets and calculations can be found in Section 7 of the appendix. The first test performed on the specimen was the Water content Determination Test. After all the data was recorded, it was entered into an excel spreadsheet and the moisture content calculations were performed. The results of water content determination averaged 22.5 % moisture content. The next laboratory experiment performed was the specific gravity test. Specific gravity is used to help determine unit weights of the soil. The procedure involved the soil which passed through the number 4 sieve. The results of the experiment were used to calculate the unit weight of the soil in the approximate area of the foundation. Two specific gravity reports were performed and the average specific gravity was calculated to be 2.76. The average specific gravity was then used to determine the unit weight of that soil. It was determined that the unit weight of soil was approximately 123 pcf.
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For the clay determination test, an air dried soil sample passing the number 4 sieve was washed through a number 200 sieve. After washing the soil sample, the particles remaining in the number 200 sieve were dried. Afterword’s, the dry weight of the remaining sample was compared to the dry weight of clay as a ratio of sand to clay. It was determined that the soil was made up of approximately 65% clay or silt and 35% sand particles. Since the amount of clay exceeded 50%, a grain size distribution or sieve analysis was no longer necessary. A compaction test will be performed to determine the optimum moisture content (OMC) of the soil plotting the water content versus the dry unit weight (kN/m3). OMC is the water content at which a specified compaction force can compact a soil mass to its maximum dry unit weight. The OMC was calculated at 17%. A consolidation test will be performed to determine the coefficient of consolidation, void ratio, and the compression index of the soil. These values will be used in the calculations to determine the specifications of the foundations of the pedestrian bridge. Four consolidation tests were performed at incremental point loads and the respective coefficient of consolidation was determined. Table 3 outlines the test loadings used and their respective coefficients of consolidation. Table 3: Average Coefficient of Consolidation Average Coefficient of Consolidation psi 5 10 20 40 Cv 0.032779697 0.027714402 0.023062125 0.021537896
Average Cv = 27
0.02627353
Senior Design Project Submittal 2012
The void ratio is determined by dividing the differential height by the height of the soil solids. Table 4 is a summary table of the void ratios at their respective point loads. Table 4: Void Ratio at Respective Pressure
Void Ratio for each pressure Hf,I = Psi 0 5 10 20 40 ΔHI or ΔD
Hv,I
- Hs
= Hf,I
Sum ΔHI 0 0.0203 0.03440 0.06570 0.08870
Ho - Sum ΔHI
eI
0.6273398 0.5832931 0.5526991 0.4847848 0.4348797
After determining the void ration the Compression Index was calculated. Table 5 is a summary table of the Compression Indices and the average Compression Index. The calculations were performed and the Compression Index was determined to be 0.16. Table 5: Average Compression Index
Compression Iindex, Cc Cc = (e1 - e2) / log(σ'2 / σ'1) Therefore, Cc =(e10-e40) / (log(40/10)) From 5 to 10 psi = 0.101631027 From 10 to 20 psi = 0.225606463 From 20 to 40 psi = 0.165781107 Average Cc = 0.164339532
A direct shear test was performed to determine the strength parameters of the soil (angle of friction and cohesion). The shear strength is needed to determine the stability of slopes and to find the bearing capacity for foundations.
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The Y intercept of the internal angle of friction graph is used to obtain cohesion in psi. The
Max Shear Stress, s (PSI) 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0 5 10 15 Normal Stres, σn (PSI) 20
Table 6: Cohesion C = Y intercept. B = 2.12 psi
Angle of Internal Friction y = 0.239x + 2.1166
Cohesion of the soil was then determined in psf as seen in Table 6.
Table 7 summarizes the friction angles produced under the corresponding horizontal loads. The average friction angle was determined to be 13.5 degrees. Table 7: Angle of Internal Friction Vertical Smax (PSI) Pressure 0 5 3.36 10 4.41 15 5.75 Average Friction angle, Φ⁰ = Φ = tan^-1((Smax - C) / Vertical Load,σ) 13.97963366 12.89739596 13.61979635 13.5
Detailed laboratory calculations were performed in Microsoft Excel and were attached in Appendix Section 7.
8.0.0 Hydrological Analysis The hydraulic model limits for Heider Ditch were established by the USGS, and the approximate length of the channel is 2.0 miles. The downstream limit is at the mouth of the channel while the upstream limit was established at Walker Road (Appendix Section
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8 Table 1). According to the USGS, the 100 year flood peak discharge estimates at the mouth of Heider Ditch is 1,310 ft^3/s (Appendix Section 8 Table 3). Additionally, there are two hydrological areas that need to be addressed during the design phase of the pedestrian bridge. Degradation due to drainage 100 year Flood Plane Analysis Drainage is the primary factor to the deterioration of the existing pedestrian bridge is ice and water buildup. In addition, excessive amounts of salt used to de-ice the bridge during the winter months cause the surface of the concrete to spall off. Joseph Reitz, Engineering Manager for the City of Avon Lake, stated that during heavy rains or snow melts, surface water runoff from the nearby impervious surfaces drain towards the existing pedestrian bridge. We have three designs that we would like to consider to help reduce water and ice buildup on the bridges. The first option would be to pitch or grade the bridge to drain surface water. Some form of drainage would need to be considered such as scupper drains. These drains would discharge the surface water into the creek below. The second option would be to install drainage in the impervious surfaces leading up to the bridge such as a trench drain. This drain could also discharge directly into the creek. The third option being considered is a roof over the bridge. In this case, a simple truss system or rafter system could be designed with a roof that has a pitch such as a 7-12 or a similar pitch. After discussing the options with the City of Avon Lake, our group has decided to construct a covered roof over the new pedestrian bridge and to
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Senior Design Project Submittal 2012 install a trench drain in the impervious surfaces leading up to the existing pedestrian bridge. The other area that needs to be analyzed is if the area the pedestrian bridge is to be built lies in a flood plain. If the bridge is located in a 100 year flood plain, we must consult with the Federal Emergency Management Agency (FEMA) as it pertains to the National Flood Insurance Program (NFIP). A local government must apply for a permit Table 8: USGS Output for Heider Ditch prior to any development in a 100 year flood plain. Referencing the USGS Hydrological and Hydraulic Analysis of Selected Streams in Lorain County (appendix section 8), it was determined that the water surface elevation in the area of the community center and city hall ranges between 581.35 feet and 581.83 feet as seen in the Table 8. Reviewing the Heider Ditch Floodplain Profile Elevation (appendix section 8), it is determined that the water surface elevation during a 100 year floodplain is approximately 584 feet, which is an increase of about 3 feet in depth. The water surface elevation during a 500 year floodplain is approximately 585.5 feet, a rise of 4 feet in water surface elevation. Since FEMA is concerned with the 100
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Senior Design Project Submittal 2012 year flood plain, any aspect of the bridge should be constructed at an elevation of 585 feet or above. After further review of hydrological characteristics of Heider Ditch, the City of Avon Lake expressed concerns that the flood peak discharge may be over estimated. Avon Lake decided to have an outside agency perform a hydrological analysis of Heider Ditch. The City officials provided USGS with a study, and insight into the hydrological characteristics in the upstream region of Heider Ditch (Jones and Henry, 1982). After review of the report, USGS found the analysis presented by Jones and Henry was of sound engineering judgment. As seen in section 8 of the appendix, in Figure 3: Heider Ditch Subbasin, Jones and Henry divided Heider Ditch into 7 subbasins labeled A-G. The peak flow estimates for these subbasins can be seen in Table 9. Table 9: Peak Flow Estimates for Heider Ditch
9.0.0 Structural Analysis Before any major steps can be taken into the selection of materials and members for the bridge, there are numerous issues that need to be considered with respect to the
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Senior Design Project Submittal 2012 functions of the bridge. Some of these aspects may have been mentioned previously, but they will now be elaborated on in a design related perspective. In the observation of the previous structure that connects the south parking lot of Bleser Park to City hall’s rear entrance, it can be speculated that years of liquid water, snow and ice have taken a considerable toll on the pre-stressed concrete span. Although it was an arguably economic design, it unfortunately hasn’t weathered as well as some other bridges existing in the Cleveland area. With years of near record rainfalls upon us, the reminder that infrastructure demands protection from the elements to prolong its useful life. Concrete of course, is not immune to erosion, and the walkway of a bridge span serves as an impervious surface where rainwater collects and flows off. As the water trickles off of the structure, it adheres easily to the rounded edges of a concrete T-span (rounded edges) and follows common paths along the structure every time it rains significantly. One can see this in the degradation of the concrete and the direction of the rust stains coming from the exposed rebar. Aside from aqueous forms of water, ice can cause significant damage due to eccentric loading of the bridge for sustained periods, as well as expansion and contraction internally. Solid water is unique in that is less dense than it saturated form, and thus its volume is somewhat larger. Thus when water works its way into a structure through cracks or other openings, the water occupies spaces that accommodate its liquid volume. When it freezes, it expands placing internal pressures on the structure, and depending on the severity of the infiltration, it can eventually cause serious damage. An
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Senior Design Project Submittal 2012 example of this can be seen locally on Route 90 west of Cleveland, where ice buildup inside of channels designated for electric components (wiring for lights) were subject to infiltration and thus when cold enough, pockets of ice would form. And when in significant amounts, over long periods of time, it can surpass limit states of concrete and cause failure. The replacement bridge, as well as the new bridge, must take these conditions into account, and proper design alterations will be considered. The walkway itself must be able to withstand shoveling and de-icing, as it is assumed that the bridge will be used during the winter months as well. With respect to the previous comments on weather, consideration to an option of covering the bridge with a roof that spans the length of the bridge, and thus snow removal could be insignificant. Lighting systems are also a requirement for the design, and the necessary accommodations will be made to the structure for lamp posts or spot lights. One easy way to do this on an uncovered bridge is to equip the entrance and exit with spotlights that are directed both away from the span towards the path leading to the bridge, and directed toward the middle of the span; thus covering all ground in proximity to the crossing. In the case of the covered span, lights can be imbedded along the inside of the roof such that they adequately light the walkway. If the tree line is modified or naturally non-intrusive, considerations into solar panels that charge the lighting system during the day, as well as motion activated lights that prevent unnecessary energy usage. As suggested by others, perhaps an observation area could be placed on the bridge or near the creek, and traditional viewings of creek life such as steelhead trout could be more appreciable through the structure.
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Materials that may suffice the design requirements must then be analyzed according to but not limited to, proximity of available suppliers, methods of construction, financial investment, and life expectancy. We are aware that concrete and steel are more within the range of technical experience of the group members, as well as their availability in the region, and thus they are the most likely to be used. That being said, the process of assembling superstructures of these materials is quite different, and proper planning of how the current space will be changed, occupied, and utilized will be on agenda. For example, a steel bridge consisting of truss members may be trucked in to the site previously assembled in the largest sections possible, and then a crane must navigate the members to their proper places through the trees, or around buildings if necessary. So in this small example, we would need to consider the space for a crane, truss members, and other equipment, and in some cases that could be difficult, if not improbable without instilling unwanted changes to the surrounding area. The financial investment is to be estimated to the furthest degree possible, such that any further reductions in the total cost will arise in the optimization process. When all preliminary considerations for the bridge are complete, and all the appropriate data are collected, the structural analysis can begin. The data will be sorted and the different types of design option will be analyzed accordingly. Some consideration may be applicable to the site itself which would also be a limiting parameter to the structural analysis. For the new bridge, it has been estimated that the crossing from side to side is at least 120 feet. This information reveals that a simple span may be applicable to the bridge, if the supports are extended into the slopes that grade down to the creek just before the wetted perimeter. Girders or concrete spans could connect the two sides
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Senior Design Project Submittal 2012 without obstructing the creek in its usual state, and thus allow for a practical and economical design. The replacement bridge has a span length of 74’ from the center of each caisson. Under the circumstances that the caissons are in sound condition, an opportunity to salvage part of the previous bridge arises. It has essentially decided that it is likely a new replacement bridge will utilize the existing caissons and minimize overall cost and man hours. Interestingly, it would then be tempting to replace the old bridge with a replica, and thus keeping the loads relatively similar. And in the light that newer and more efficient methods are used (i.e. polymer based rebar), a possibly lighter and or cheaper replacement could be feasible. Using a replica requires design ingenuity that would add protection from the weathering of the structure. Some Ideas have been considered such as slight grades sloping down from the centerline of the walkway, that push the runoff into gutters, or perhaps pervious walkways that collect the water and drain it properly (while adhering to expansion and contraction constraints of freezing and melting respectively). Once the conceptual design is accepted, the application of structural analysis will be applied and the structural design will take place. During the structural design process the materials being used will dictate the design specifications which must be followed. In other words each material will be designed according to the respective institute and standards manuals. For overall bridge specifications, the AASHTO-LRFD Design Specifications for Pedestrian Bridges will suffice for general checks and required loads. The AISC and ACI manuals will be used for the steel and concrete members respectively. From AASHTO, the design loads can be estimated for the structure, and they consist of the Primary loads (Dead, Live, Snow, creep etc) and Secondary Loads
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(Wind, temperature, Earthquake, temporary loads during construction etc.) (Chen, 1997). The Floor systems are essentially the most vulnerable part of the superstructure, as they support the live load and are subject to a considerable amount of weathering. Fortunately, in pedestrian bridges, the decks can be considerably light, and the live loads consist of pedestrians, bikes, and small machinery, thus leaving the decks to last longer than say a highway bridge. Considerations into moderately sized girders and a thin concrete slab walkway could be a simple alternative for the design. A 2-3 cm layer of asphalt as a top layer would serve as a means of waterproofing the deck, and it’s fairly economical (Chen, 1997). Expansion joints, bearings and railings also compose the structure with smaller but essential functions to the bridge. In the case of the simple span, we can simply pin (connect) one side of the span, and allow the other to embrace rollers. This allows for the expansion and contraction of the structure to occur without (or at least minimized) added strain to connections of the structure (Chen, 1997). Trusses, Arches, Suspension, and cable stayed bridge types are not excluded from the design considerations, and once further discussions with the park director, and park users proceed, we can obtain more feedback as to what might be preferred. The technical design process will require a prioritization of requirements for specs and limit states of members. The steps will be carried out with the assistance of organizational, and mathematically capable computer programs such as excel, lingo and MathCAD. The steps will be organized such that equations used will be followed by actual calculations, and the process will be easily interpreted and checkable.
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In the case of a prestressed concrete bridge, W.F. Chen proposes that the following steps would be taken: Table 10: Chen Technical Design Prioritization 1. 2. 3. 4. 5. 6. 7. 8. 9. Determination of cross-section geometry Determination of longitudinal section and cable path Load calculations Live Load distribution factor calculations Calculation of unfactored moments and shear demands for interior girder Load Factors for strength limit state I and service limit state I Calculation of section properties for interior girder Calculation of prestress losses Determination of prestressing force for interior girder
10. Check of concrete strength for interior girder, service limit state I 11. Flexural strength design for interior girder, strength limit state I 12. Shear strength design for interior girder, strength limit state I And these steps would be detailed within AASHTO-LRFD specifications. MathCAD provides a simple way to construct design programs that exhibits the defined variables, formula used, and the final calculations all in the same general format. The issue is that MathCAD is not necessarily as appealing in terms of format then say Microsoft Excel, which can be manipulated to organize seemingly unlimited amounts of data and perform the same tasks. The only exception is that to show sample calculations, the equations must be typed again in the math type feature and then
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Senior Design Project Submittal 2012 displayed in some fashion, which is easily navigated and interpreted. This is only mentioned because of course there are generally many equations to be used for each member, and this would require more hours of work to be allotted to group members. Nonetheless, it has been partially decided that the neatness of the Excel plus math type will be the program used in the design process, and all members have a considerable amount of experience with the program. After a detailed preliminary design is created, it will be presented to the faculty such as our advisor Dr. Delatte and other structurally focused members such as Dr. Bosela. With methods approved, we can move on to the optimization process. Accounting for the minimum sizes and quality of members, we can attempt to might gradual improvements. 9.1.0 Reinforced Concrete Design The existing pedestrian bridge that links Bleser Park to Avon Lake's City Hall is comprised of reinforced concrete. The existing bridge is in disrepair and the City of Avon is interested in replacing it. One of the options they would like is to replace it with another reinforced concrete span. A uniform load of 1.79 kips/foot was calculated using the load combinations from ASCE 7. Using this value, a positive moment of 1430 kip-ft or 17200 kip-in was calculated. Based off of this moment an area of steel reinforcement of 11.88 in^2 was calculated. It was decided that 4 #11 bars would be used over the web of the structure and 3 #14 bars would be used at the web. This would provide an area of steel of 12.99 in^ which is greater than the value of 11.88 in^2. The minimum amount of steel allowed was calculated to be 2.09 in^2. The dimensions of the vertical portion of the tee-beam were
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Senior Design Project Submittal 2012 also calculated using the positive moment. The base of the section was determined to be 21 inches wide and the effective depth was calculated to be 31.5 inches and the height of the section to be 34 inches. The strain in the extreme layer was determined to be 0.0068 which is greater than or equal to the acceptable value of 0.005. The final check to determine if the design is adequate is to compare the nominal moment to the moment calculated from the uniform loading. The nominal moment was calculated to be equal to the calculated moment. The next step in the reinforced concrete design is the shear design and stirrups. The shear calculated at the end of the bridge span is 71.6 kips and the shear at the midspan of the bridge is 17.9 kips. To determine if stirrups are required, the shear force must be compared to the shear capacity of the concrete divided by the reduction factor of 0.75. The shear force was calculated to be 83.67 kips and the shear capacity divided by the reduction factor is 95.47 kips, so stirrups are required in the design. The stirrup design consists of 2 #6 bars with a maximum spacing of 15.5 inches. The area of the stirrups is 0.88 in^2. 9.2.0 Bleser Park Covered Timber Bridge It was decided in the beginning of 2012 that the group would design a timber covered pedestrian bridge that connects the northeast portion of Bleser Park to the Avon Lake Community Center across Heider ditch to the east. Despite initial concerns with the group’s ability to design a wood structure, design procedures have been undertaken, and structural analysis is almost complete. The design of a covered bridge was decided initially regardless of the particular material types to be used, and it was assumed that both aesthetics and functionality constraints would be satisfied. The objective of this
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Senior Design Project Submittal 2012 bridge is to provide Avon Lake with an iconic structure that stimulates the value of the area, as well as provide a safe and convenient travel path for people who use the parking lot in Bleser Park to visit the community center. 9.2.1 Burr Truss Design The design to in which we have used as a template is described as a Burr arch truss, and it was established and patented in the early 1800s. The design basically combines a multiple kingpost truss and an arch, connecting them at the vertical posts along the truss (Bruce S. Cridlebaugh, 2008). The design is commonly used in covered bridges, and it is said that the design has a reputation of being very successful, thus its common use in traditional American covered bridges. The arch in addition to the truss provides for interesting combination of parallel load capabilities. Arches are typically classified by a radius of curvature that segregates it from a curved beam. For wood arches in particular, an arch can be assumed for a Radius of curvature of the bottommost face of lamination to be less than where is the thickness of the individual laminations , the member is classified as a
(Chen, 1997). When the Radius is greater than
curved beam, and the analysis is similar to that of straight beams, except with modifications via the curvature factors which affect moment resistance and radial stresses (Chen, 1997) . The Arch is known to have considerable axial forces along the arc, and it may be the most significant load path for arches in “arch action” (Chen, 1997). This arch member will be composed of laminated wood members to the degree in which the service requirements are met; in other words, the amount of timber that is glued together in constructing the beam will be dictated by the amount of load that the arch will inherit.
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The Truss as stated previously will be that designated as a multiple kingpost truss, and it can be seen in the Figure 14 below.
Figure 14: Multi Kingpost Truss (pacoveredbridges.com) The multiple kingpost trusses are an upgrade from its predecessor, the kingpost truss, which has only two large diagonal members that extend from the bottom corners of the truss, and meet at the top center kingpost. It is claimed that the multiple kingpost design allows for span lengths that are approximately twice as long as the single kingpost truss (Sherlinski, 2012). In a structural analysis done by Johns Hopkins professor Benjamin Schafer PhD and engineering technician Dylan Lamar, many aspects of the combined Burr Arch truss as well as each structure separately (i.e. Arch and Multiple Kingpost Truss) were examined in a journal article in 2008. The truss was found to have a unique relationship in adding structural rigidity under live loading, whereas the arch was found to be dominant, and inherited more of the dead loads (Schafer Ph.D & Lamar, November/December 2008). They concluded that the arch and truss combined had a synergistic relationship that gave it an overall stiffness that was 47% greater than the addition of the two stiffness coefficients for each individual structure (Schafer Ph.D & Lamar, November/December 2008). For this reason, one can appreciate the beauty of this design, and how its efficiency was only found by demonstration, since at the time of its invention, structural analysis of this type of
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Senior Design Project Submittal 2012 structure was not performed. In the two figures below, it can be seen by the shaded regions on the members (shading above member is tension; shading below indicates compression) that the stresses under dead loading (Fig. 15) are mainly compensated by the arch, whereas the stresses in the truss increase significantly under live loading (Fig. 16).
Figure 15: Axial Forces in Arch-Truss Due to Dead Load
Figure 16: Axial Forces in Arch - Truss Due to Mid-Span Live Load
During the live loading, a maximum moment is developed in the top chord of the truss, and this in particular is a perfect example of the mutual interaction between the two structures. Alone, the arch is weakest under live loading and in the case of some existing covered bridges; this loading would actually deform the arch to unallowable limits or even failure (Schafer Ph.D & Lamar, November/December 2008).
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9.2.2 Wood Types Considered The types of structural timber that may be used in the design will likely be one of three different pine species found in America. They are the Eastern pine, Southern pine, and Douglas fir trees, and they have been used regularly in wooden bridges for centuries. The strain characteristics differ somewhat among different species, and some information is shown below in a table from ASTM D25 from the timber piling council.
Table 11: Allowable Stress Values for Threaded Round Timber Piles (ASTM D25) Although some of the values fluctuate with the function of the member (i.e. piles, light framing, decking etc.) the modulus of Elasticity is consistent with the values seen in the rightmost column of the table. It is likely that the final decision will be based on a cost and availability analysis after all cross sections are selected for the structure. It is essential that the LRFD design factors be used as well as some information from the NDS on wood design. The nature of wood for purposes of structural integration is often emphasized in terms of properties such as anisotropic load resistance, moisture content, temperature control, and load duration. As an anisotropic cellular material, it is necessary to identify that
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Senior Design Project Submittal 2012 stresses are handled differently along the grain as opposed any other direction (Chen, 1997). Most wood beams have applied moments across the strong axis of a member cross section, and orientation of available members on the structure is rather important (Breyer, 1993). The moisture content drastically affects the behavior of wood under stresses, and it is in our interest to specify that all members be treated and maintained periodically. In addition, the load duration on the structure also pertains to design factors. Wood loses a significant amount of strength when subject to moisture cycling and long load durations (Chen, 1997). 9.2.3 Arch to Truss Alignment Some ambiguity lies in the specific orientation of the arch on the truss, and it can be seen in various chords to radius ratios. It can be seen by the geometry that if one selects two points on each end of the truss (i.e. ends of bottom chord) where the arch will coincide, that the highest point of the arch will vary on the kingpost with the radius. With the assumption that the arch will in fact coincide with the ends of the bottom chord, a program was written in Excel, to determine all of the dimensional characteristics of the arch on the truss. By modifying the span length and or the radius, the position of the arch at each vertical post can be calculated. With a final span length of 96 feet, the arch that also crosses the top joint on the kingpost will have a radius of 102 feet exactly for a truss (and post) height of 12 feet. Each of the heights on the other posts on either side of the radius can be found on the Arch Characteristics tables in Appendix Section 9. In addition, this sheet also contains the force resolution of the arch at each point where the arch coincides with a vertical member.
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9.2.4 Arch Lamination The member itself will be constructed out of glued laminated timber (Glulam) whereby all the members are bonded together with adhesive, while laid parallel along the grain. The thickness of this member is going to be approximately .75’ to 1.5’ depending on the final analysis. Each Connection will be bolted with a yet to be determined number and size of bolts, but it’s likely to be greater than 1 and likely 2-3. Split ring connectors will also be considered in that they apply to many of our connections throughout the structure, and they assist in transferring the shear load of wood to wood connections.
Figure 17: McGraw-Hill Dictionary of Architecture & Design
9.2.5 Truss Analysis To analyze the behavior of the truss, a program was constructed using MathCAD 15 that utilizes the stiffness method for trusses. The objective here is to resolve all of the external forces and displacements on the structure into matrices, and essentially relate them by stiffness matrices. The theory is based on the assumption of linear elastic behavior in deformation, whereby the force constant applied to a member is proportional to a
multiplied by the displacement . Each member displaces in proportion to its , its cross sectional
deformation due to stress to strain ratio,
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Senior Design Project Submittal 2012 area and its length. All of this information in addition to numbering the degrees of freedom on the structure allows for a tedious construction of a global stiffness matrix which accounts for the interaction of the entire structure. This analysis was done such that the truss could be analyzed by itself, and the most conservative values for member sizes could be determined. This of course is done in correlation with the arch analysis as to check the possible reactions from the arch on the truss and vice versa. The end result was a 36X36 matrix that could be inverted to determine displacements of each node (joints), and Appendix 9 contains a sample calculation using the 33x33 matrix partitioned from the previously mentioned matrix. After the basic analysis, internal forces in each member will be checked, and design specifications from LRFD will dictate the final characteristics of each member. It should also be noted that the truss will be placed into a more advanced structural analysis program, and the results for the combined Burr Arch truss will be checked to confirm analysis assumptions. 9.2.6 Decking and Roofing The roof of the bridge will consist of light frame wood trusses, which are placed periodically perpendicular to the top chord of the truss. It is assumed that about 18 trusses will hold up the entire roofing panels, and they will be composed of local timber that is selected on a sustainability and cost basis. The panels themselves may range from plywood to a higher quality grade sheet, and will likely be the direct base for the roofing interface. Shingles are an appealing option for the roof interface, and they will be compared to a few other perhaps “sleeker” materials. Shingles also match the preexisting pavilion in Bleser Park, which is rather traditional.
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The deck will be supported by larger timber members that span the 8’-9’ from bottom chord to bottom chord. It is still undecided whether they will be glulam beams, or large timber cuts, and a further tributary analysis is to be done for those members. The beams will have intermediate smaller X-shaped members that provide additional support to the walking surface, and these members will coincide at the joints.
10.0.0 Foundation Analysis There are three types of foundations that have been considered for this bridge design; Strip footings, drilled caissons, and pile foundations. Strip footings are designed for each pier, or abutment. When choosing a foundation, one must take into consideration that the City of Avon Lake does not want to disturb the creek. A drilled caisson (or pier) is constructed by drilling a cylindrical hole of the required depth and subsequently filling it with concrete. The shaft may be straight or the base may be enlarged by under reaming (Bowles, Foundation Analysis And Design, 1996) There are a few different choices if pile foundations are chosen. The first alternative is driven piles. These piles typically consist of preformed concrete or steel and are driven into the ground with the use of tools such as a power hammer. The second alternative is preformed driven cast in-situ piles. This foundation is basically a hollow tube with a closed end driven into the ground then filled with concrete. The third choice is driven cast in-situ pile. This is very similar to the cast in-situ piles, but as the concrete is being poured, the hollow tube is removed. The fourth choice is bored and cast in-situ piles. This foundation is created by boring a hole into the earth and filling it with concrete.
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When designing the foundation, one must take into consideration the structure load. After that has been determined, the foundation can be designed, making sure that allowable settlement occurs and the bearing capacity does not exceed an acceptable safety factor. Allowable footing settlement was determined to be 1 inch with a factor of safety of 3.0 (ODOT Bridge Engineering Section, 2005). Design analysis began with the most economical foundation. The most economical foundation was determined with the help of Dr. Khan. The order of foundation cost from least expensive to most expensive is: spread footer, drilled caisson, and pile. Therefore, spread footers were designed first. All settlement and bearing calculations were conducted with the soil parameters found in section 7.0.0. 10.1.0 Spread Footers As previously stated above, Avon Lake City Officials require the foundations to be located outside the influence of the water flow. This requirement limits the placement of the foundations to the adjacent ground level, relative to the elevation of the Community Center. Refer to Figure 18 below for proposed spread footer foundation locations with respect to the creek bank. In designing the spread footer, bearing capacity must be checked first. Bearing capacity was determined via Hansen’s equation for footings on slopes (Bowles, 1996). Bearing capacity increase as the foundation is placed further away from the creek slope. The load of the proposed community center timber bridge has yet to be determined. A conservative load was taken from the replacement reinforced concrete bridge. A uniform load of 1.79 kips/foot was calculated using the load combinations from ASCE 7.
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A conservative moment, due to horizontal wind forces of 8.6 psf acting on the roof and supporting timber members, was estimated to be 77 kip-ft. Using this load and moment, the footer size was found to be 9 feet long and 5 feet wide at a depth of 6 feet and a distance of 3 feet away from the slope. Refer to appendix 10 for foundation calculations.
Figure 18: Bridge Span and Footing Analysis Settlement was then checked with the footer dimensions previously found with the bearing capacity. These dimensions produced a settlement of 2.8 inches, which exceeds the allowable settlement of 1 inch. The spread footer base and length were increased to reduce the settlement to 1 inch or less. New footer dimensions due to settlement were found to be 32 feet long and 5 feet wide. All possible footer sizes and depths were checked via spreadsheet. Such large footer sizes suggest placing the foundation directly on the shale at a depth of 10.67 feet to reduce the footer size.
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The design of the 32 feet long and 5 feet wide footer at a depth of 6 feet would require the excavation of about 36 cubic yards for each of the two footer foundations. A small portion of the neighboring community center parking lot would need to be removed for the construction of this design. Furthermore, the east footer is in close proximity with the community center which could complicate construction. In examination of these disadvantages, overall cost and construction time was determined to be greater for spread footer than that of a drilled caisson foundation. As a result due to its easier construction, drilled caissons were then considered for the foundation design. Subsequently, the ODOT Bridge Foundation Design Practices and Procedures document advises as a minimum, that the bottom of all spread footings should be at least 6 feet below the lowest streambed elevation unless they are keyed into bedrock that is judged not to erode over the life of the structure. 10.2.0 Drilled Caissons Four drilled caissons have been deemed necessary to support the timber bridge, one at each corner. Each caisson will rest on shale at a minimum depth of 10.67 feet. As per Dr. Khan, differential settlement between each caisson must not exceed ½ inch. It has been suspected that the shale will act as bedrock. Caisson design is currently underway.
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11.0.0 Cost Estimates and Scheduling A cost estimate and schedule was derived for all three bridge projects. A total of five separate estimates are required for Bleser Park. The concrete bridges require an estimate for precast bridges and cast in place bridges. The concrete t-beam design analysis was performed and the design parameters were submitted to Sidley Precast Group. Sidley provided an estimate to cast, deliver and install the precast t-beams from Thompson Ohio. The cast – in – place estimate required additional estimates for form work, reinforcing steel, concrete and labor. The difference in the estimates is a direct correlation of the additional risk in which the construction manager would shoulder. The cost estimate and schedule are typically done simultaneously since time is a direct function of financial responsibility. The purpose of the cost estimate and schedule is to manage things like material cost, labor hours, machine hours, overhead, interest on outstanding loans, and profit margin. There are many software packages on the market to help manage a construction project. Software packages that are commonly used are Prima Vera Project Planner, and Timberline Software. These packages incorporate real time costs estimations by maintaining an updated database with current pricing on items such as steel, lumber, labor rate, and interest rates. Due to the extremely high price of these software packages, they are not available. Therefor the estimate and schedule will be managed using Microsoft Excel. The precast estimates for the 4 foot wide and the 8 foot wide bridges were estimated at $45,000 and $110,000 respectively. The cast–in–place estimates for the 4 and 8 foot wide bridges were $25,500 and $84,000 respectively. The percent difference which would be shoulder by the Construction Manager can be seen in table 12 below.
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Cost including profit and overhead Type 8 ft wide T-Beam 4 ft wide t-beam Cast-in place $ 83,924 $ 25,480 Pre-Cast $ 110,278 $ 44,559 Construction Manager will Shoulder Risk of Cast - in - Place Sidley will assume risk of Pre -Cast
Table 12 % Difference in Precast and Cast-in-Place
% savings 43% 24%
The Timber Design Alternative was originally designed to carry the lateral load in oversized foundations. The oversized foundation design raised the total price by 25%. After further analysis, a tension cable was designed to carry the lateral load. The Timber Bridge Design was estimated to $107,000 Financially, Avon Lake has approximately $100,000 in their budget for park expenses. As seen in appendix 11, the estimates for both new bridge designs are over budget by 10%. After reviewing the explored options, based on the Cities budget, neither the timber bridge nor concrete bridge is a viable solution. Future analysis involving value engineering on behalf of the City may determine that both bridge designs are financially and economically practical.
12.0.0 Bibliography
AASHTO T89 and T90. American Association of State Highway and Transportation Officials. ACI Committee 318. (2011). Building Code Requirements for Structural Concrete (2nd Printing ed.). Farmington Hills: American Concrete Institute. ACMA Americam Composites Manufacturers Association. (2004). Pedestrian Bridges. Retrieved February 20, 2012, from The Composites Growth Initiative of ACMA: http://www.mdacomposites.org/mda/PSGbridge_pedestrian_intro.html
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Andrea J. Schokker. (2010). The Sustainable Concrete Guide Applications (First ed.). (A. J. Schokker, Ed.) Farmington Hill, MI: U.S. Green Concrete Council. Andrea J. Schokker. (2010). The Sustainable Concrete Guide Strategies and Examples (First ed.). (K. S. Emily Bush, Ed.) Farmington Hills, MI: U.S. Green Concrete Council. Anne Marie Helmenstine, P. (Copyright 2012). Chemistry. Retrieved February 09, 2012, from About.com: http://chemistry.about.com/cs/howthingswork/a/aa120703a.htm ASTM D 4318 . American Standards of Testing Materials. Bowles, J. E. (1992). Engineering Properties of Soils and their Measurement (Fourth ed.). (K. K. B. J. Clark, Ed.) Boston, Massachusets: McGraw-Hill. Bowles, J. E. (1996). Foundation Analysis And Design (5th ed.). Singapore: McGraw-Hill Internation Edition. Breyer, D. E. (1993). Design of Wood Structures 3rd Ed. New York: McGraw-Hill, Inc. Bridge Builders. (n.d.). Retrieved December 7, 2011, from http://www.bridgebuilders.com/why_timber.php Bruce S. Cridlebaugh. (2008, June). Bridge Basics-A Spotter's Guide to Bridge Design. Retrieved March 2, 2012, from pghbridges.com: http://pghbridges.com/basics.htm Chen, W. (1997). Bridge Structures. In W. Chen, Handbook of Structural Engineering (pp. 10-1,to10-79). Boca Raton: CRC press. City of Avon Lake, International AFL - CIO & CLC. (2011, January 10th). Bargaining Agreement. Agreement Between City of Avon Lake, International AFL - CIO & CLC . Avon Lake, Ohio, United States: State Employment Relations Board. Das, B. M. (2007). Principles of Foundation Engineering (6th ed.). Stamford, CT: Cengage Learning. Das, B. M. (2010). Principles of Geotechnical Engineering (Seventh ed.). (H. Gowans, Ed.) Stamford: Cengage Learning. Design Manual: Fiberglass Grading and Structural Products . (n.d.). Retrieved December 7, 2011, from http://www.deltacomposites.com/lit_library/DelDesMan.pdf Dr. Yung-Tse Hung, P. P.-A. (2011). CVE 474 Environmental Engineering Laboratory Lecture Notes. Cleveland State University, Civil Engineering, Environmental Engineering. Cleveland: Ross Printing. Frank R. Walker Company. (2002). Walker's Building Estimator's Reference Book (27th ed.). (J. Ratner, Ed.) Lisle: Frank R. Walker Company.
Senior Design Project Submittal 2012
Wikipedia. (2012, February 20). Atterberg Limits. Retrieved February 26, 2012, from Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/Atterberg_limits Willis H. Wagner, H. S. (2003). Madern Carpentry. Tinley Park: The Goodheart-Willcox Company, Inc. Yaggi, W. W. (2001, May/June). The Jouranl for Surface Water Quality Professionals. Retrieved February 09, 2012, from New York Water: http://www.newyorkwater.org/downloadedArticles/ENVIRONMENTANIMPACT.cfm
