INTRODUCTION The Steel Bridge-Building Competition is sponsored by the American Institute of Steel Construction. This inter-collegiate challenge requires Civil Engineering students to design, fabricate and construct a steel bridge.
Safety is of primary importance. The AISC requests that competitors, hosts and judges take all necessary precautions to prevent injury.
The competition rules have been changed for 1995 in order to improve the contest and to assure that competitors design and build new bridges.
Ideally, students should fabricate the entire bridge themselves. However, appropriate shop facilities and supervision may not be available at every college and university. Therefore, the services of a commercial fabricator may be used provided that students observe the operations.
This booklet describes the contest and states the official rules for this year. It is distributed to universities throughout the country. A companion booklet is distributed to hosts and provides directions for conducting a competition.
Civil Engineering students are challenged to an inter-collegiate competition that includes design, fabrication and construction. Participating students gain practical experience in structural design, fabrication processes, construction planning, organization and teamwork.
The Problem Statement describes challenges encountered in a representative structural engineering project. The competition is a scaled simulation of that project.
Standards for durability, constructability, usability, strength and serviceability reflect the volumes of regulations that govern the design and construction of full-scale bridges. Criteria for excellence are represented by the award categories of stiffness, lightness, construction speed, aesthetics, efficiency and economy. As with a real construction project, safety is the primary concern
The rules of the competition accommodate a large variety of designs and allow innovation. Designers must carefully consider the comparative advantages of various alternatives. For example, a truss bridge may be stiffer than a girder bridge but slower to construct.
The Steel Bridge-Building Competition provides design and construction planning experience, an opportunity to learn fabrication procedures, and the excitement of competing against students from other colleges and universities.
A century-old bridge that crosses a river valley in a mountainous region must be replaced. The bridge carries heavy truck traffic to and from mines which are the basis for the economy of this rural region, as well as providing access and emergency services to residences. A quick replacement is necessary because no other river crossing of adequate capacity is available for miles.
The State Departrnent of Transportation has requested design/build proposals for replacing the existing bridge. Any appropriate type of bridge will be considered, but the State has specified steel as the material because of its durability and fast erection. The bridge must accommodate two lanes of traffic and be able to carry specified patterns of traffic and wind loads without exceeding deflection limits. In order to expedite environmental approvals, no piers may be erected in the river, nor may temporary scaffolding or causeways be used in the river. However, temporary shoring may be erected on the banks. Construction barges and marine cranes are not feasible due to fast currents and flash floods.
The stone abutments of the existing bridge are in good condition and will serve for the new bridge, provided that no lateral thrust nor uplift is applied to the abutments. The State DOT will not permit modification of the existing abutments. The new bridge, when complete, must be supported only by the existing abutments; for example, stays and anchorages to the river banks are prohibited.
The new bridge must accommodate modular decking, which the State DOT salvaged from another bridge. Decking units may not be modified.
Access to the construction site is limited by narrow, winding roads. This imposes restrictions on the size of components, and on the movements of construction equipment. Soil conditions restrict the weight that may be lifted by cranes.
Your company's design/build proposal is among those that the State DOT has deemed responsive. The DOT has asked each competing firm to submit a 1:10 scale model to demonstrate its concept. Models will be erected under simulated field conditions and then load tested. The DOT will evaluate the models by multiple criteria including durability, constructability, usability, stiffness, construction speed, efficiency, economy and aesthetics. The contract will be awarded to the company that submits the best model. This is an opportunity to become leaders in the bridge replacement market.
In order to compete for awards, a bridge must qualify by satisfying the following minimum standards for durability, constructability, usability, strength and serviceability.
The bridge must be constructed entirely of steel.
The bridge may be constructed only of components conforming to the restrictions on size and weight specified in "Components". The bridge must be constructable according to regulations given in "Construction" and without violating requirements listed in "Safety Regulations".
The bridge must conform to the specifications described in 'Dimensionsand Support.'
Strength and Serviceability
The bridge must pass load tests 1 and 2 described in 'Load Tests.'
Only qualified bridges are eligible to compete for awards. Categories of competition are stiffness, lightness, construction speed, efficiency, economy and aesthetics. In addition, overall performance is rated.
The bridge with the lowest incremental vertical deflection will win in the stiffness category. Incremental vertical deflection is determined from load test 3. A bridge that fails load test 3 will be eliminated from the stiffness and efficiency categories of competition.
The bridge with the least total weight will win in the lightness category. Decking and temporary shoring are not included in total weight.
The bridge with the lowest construction time will win in this category. Construction time is the product of the size of the construction team and the duration of construction. The construction team includes everyone who handles the bridge or any of its components during timed construction. A bridge that accumulates $150,000 or more in penalties will be eliminated from competition in the construction speed and economy categories (see 'Accidents.1)
The bridge with the smallest sum of normalized weight and deflection ratios (SNWD) will win in the efficiency category. The sum of normalized weight and deflection ratios is computed as
The bridge with the lowest cost (C) will win in the economy category. Cost is computed as
C = Total weight (Ib) x 1000 ($/lb) + Construction time (person-min) x 5000 ($/person-minute) + $10,000 if temporary shoring is used + Penalty costs (listed in "Accidents")
Factors that may be considered include genera! appearance, balance and proportion of the design, elegance of connections, finish, construction organization and teamwork. Quality of fabrication should not be considered because some bridges may be fabricated professionally while other are student work.
The overall performance rating of a bridge is determined by adding the rank ot the bridge in the efficiency category to the rank in the cost category. The bridge with the lowest sum will win the overall competition. A bridge that was eliminated from the efficiency and/or economy categories is not eligible for the overall performance competition. In the case of a tie, judges will use aesthetics as the tie breaker.
A bridge may be constructed only of components made entirely of steel and conforming to the following descriptions of members, cables with fittings, assemblies, and fasteners.
A member may not weigh more than 40 pounds nor exceed overall dimensions of 5'6' x 7.5,, x 7.5." A member may consist of parts connected together before timed construction begins but those parts must remain connected throughout the construction process. A member may be hinged, jointed, articulated or telescoping.
A cable together with its fittings may weigh no more than 40 pounds and must be capable of being coiled to a diameter not exceeding two feet. Fittings are eyes, hooks, plates, clamps, devises1 turnbuckles and similar parts connected to cables, and not exceeding 7.5' in any dimension. A cable with fittings may consist of parts connected together before timed construction begins but those parts must remain connected throughout the construction process. A cable with fittings may have any number of ends.
An assembly is no more than 3 members and/or cables with fittings that are connected together in the staging yards during timed construction.
Fasteners are bolts and nuts, pins, plates, shims and similar parts used for connecting members, cables and assemblies, and not exceeding 7.5" in any dimension.
Competitors provide their own tools. Only hand tools are permitted. Field welding and power tools are prohibited. Ropes are permitted but gin poles, jacks, winches, come-alongs, counterweights and other hoisting devices are prohibited. Stools, ladders and similar objects for elevating builders are prohibited.
Click here to see a site plan.
Shoring is temporary support on the river banks, and is provided by the competitors. There are no restrictions on the materials and design for temporary shoring other than it must provide sufficient strength and stability to support the bridge and builders. There is a cost assigned to temporary shoring; its advantage is that builders may be supported by the bridge only if temporary shoring is in place. If temporary shoring is used, it must be used on both banks.
During construction the top of the safety support must be in place at the midspan of the bridge with its top surface no more than 8 inches from the bottom of the bridge.
Before construction begins, all members, cables with fittings, fasteners, tools and builders are in the staging yards. Temporary shoring, if used, has been constructed and is in place on both river banks. The safety support is in place. Timing and construction begin when the builders signify that they are ready and the judge declares the start.
Time is kept from the start to finish of construction. The clock will be stopped:
Construction ceases while the clock is stopped. The clock is restarted after the situation has been corrected.
In order to expedite the competition the host may limit the clock time for constructing a bridge to 30 minutes. A higher limit may be imposed. A bridge that exceeds the limit will be eliminated from all categories of competition. If the host opts to impose a time limit, all competitors must be notified at least a month before the competition.
Construction ends when the bridge is complete, and all tools and builders are in the staging yards, and the builders signify that they are finished. Temporary shoring may remain on the banks. Installation of decking is not included in timed construction.
If any of the following safety regulations are violated the judge will stop the clock and explain the violation. Before restarting the clock, builders, tools and bridge components will be returned to the positions they occupied before the violation. Construction that necessitates violation of safety regulations is not permitted.
In general, the clock is not stopped when an 'accident' occurs. Builders involved in accidents may continue to build, and components involved in accidents may be recovered and used. Types of accidents and the corresponding cost penalties are:
DIMENSIONS AND SUPPORT
The figures titied 'Side Elevation' and 'Clearance and Deck Support"illustrate some of the following specifications.
CAUTION: A bridge could collapse or sway suddenly during load tests. Therefore, minimize the number of people near the bridge while it is being tested. During testing the bridge must be supported so that its lowest point is no more than 8 inches above ground or above the top of the safety support.
The figure titled 'Load Tests' illustrates some of the following procedures.
Load tests are conducted without temporary shoring. Load test 1 is conducted without decking; load tests 2 and 3 are conducted with two decking units installed to accommodate the load.
The judge designates two target points on the bridge, both located at midspan, one on each side. The target points should be dose to the level of the deck, and may be on the decking itself. Lateral deflection measurements are made to the target point on one side of the bridge, designated by the judge. Vertical deflection measurements am made to both target points; vertical deflection is the maximum absolute value of the two measurements.
Total lateral deflection is the absolute value of the horizontal distance of the target point from its position at the beginning of load test 2. Incremental vertical deflection is the maximum absolute value of the vertical distances of the target points from their positions at the beginning of load test
Load tests are conducted in numerical order.
Load Test 1 - Qualifying. Lateral
Load test 1 is conducted with lateral restraint installed on the abutments to prevent the ends of the bridge from sliding. As dose as practical to midspan apply a 100 pound force in the lateral direction. To pass load test 1, the lateral deflection of the bridge must not exceed 1.0'. If the bridge does not pass load Itest 1, do not conduct any other load test. Remove the lateral load; it is not part of the remaining load tests.
Load Test 2 - Qualifying. Vertical
Uniformly distribute load over an area symmetric about the middle of the deck and extending 3 feet in the span direction. Terminate load test 2 when lateral deflection reaches 1.0' or vertical deflection reaches 2.0' or 500 pounds of load has been placed. A bridge passes load test 2 if 500 pounds of load was placed without a deflection limit being exceeded. If the bridge does not pass load test 2, do not conduct any other load test.
Load Test 3 - Competition. Vertical
With the load from test 2 remaining in place, uniformly distribute additional load over an area symmetric about the middle of the deck and extending 6 feet in the span direction. Terminate load test 3 when total lateral deflection reaches 2.0' or incremental vertical deflection reaches 2.0' or 2000 pounds of additional load has been placed. A bridge passes load test 3 if 2000 pounds of additional load was placed without a deflection limit being exceeded. If the bridge passes load test 3, record the incremental vertical deflection.
EQUIPMENT PROVIDED BY HOST CHAPTER
The following equipment will be provided at the contest site by the host. Competitors may wish to acquire similar equipment for use in practice and testing before the competition.
Lateral Load Device
Capable of applying 100 lb force in the horizontal direction.
Measuring Scales and/or Instruments
2500 pounds total. The load should be supplied in uniform increments of size and weight that may be handled safely. When in place, the load should not provide significant stiffness in the longitudinal direction of the bridge. Sections of steel angle of uniform size and length are recommended for load. Sacks of material, containers of liquid, concrete blocks or jacking systems could be used.
The decking is steel bar grating identified as W-19-4 (1 x 1/8). The dimensions of a piece of grating are 3'6' x 211-3/4' x 1'. Grating has bending strength only in the direction of the main bars, which are 3'6' long. The grabng will be installed with the main bars perpendicular to the length of the bridge, creating a roadway that is 3'6' wide. Therefore, support for th~ grating must be provided along the edges that are parallel to the length of the bridge. No support is needed for the edges of the grating that are perpendicular to the length of the bridge.
When loading, do not exceed 400 psf uniform load nor 500 pounds concentrated load. Do not load on a cantilevered portion of the grating.
The top surface of each abutment should be at least 5 feet long, 3 inches wide, level, smooth, and approximately 3 feet above the ground. Temporary lateral restraints are needed during load test 1.
The safety support is intended to limit the consequences of a bridge collapsing during construction or load tests, but should not come in contact with the bridge unless there is a collapse or excessive deflection. The safety support is placed at the middle of the span and adjusted so that the top of the support is no more than 8 inches from the bottom of the bridge.
The safety support should be placed and adjusted to the proper height before the start of timed construction. At all times during construction the top of the safety support should be within 8 inches of the bottom of the bridge. If the safety support must be adjusted when the bridge is partially constructed, the clock will be stopped while the safety support is positioned. Builders areIt prohibited from being on the bridge unless the safety support is in place, as well as temporary shoring on both banks.
The safety support must be at least 6 feet wide in the lateral direction of the bridge.
The host will recruit judges. Judges have full authority over conduct of the competition and interpretation of ambiguities in the rules. Judges are empowered to halt any activity that they deem to be hazardous. Decisions1 scoring and rating are the sole responsibility of the judges and will be final.
TIPS FOR COMPETITORS
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