Balsa Bridge Cmpetitin Overview The Balsa Bridge Cmpetitin ffers participating teams the pprtunity t demnstrate knwledge f structural design principles in the cnstructin f a three-dimensinal balsa bridge structure. Students will design and build a bridge structure using specified balsa wd. The structure will be weighed and judged and then laded until failure. Objective The bjective f this cmpetitin is t design and build a 3-D bridge structure cnfrming t specific criteria. The mdel will be tested via a lading platfrm placed n the deck f the structure. The lad will be increased with respect t time until failure ccurs by the fracture f a member r a jint. Pints will be awarded fr the strength t weight rati f the bridge and fr the quality f the technical paper. Eligibility Each team may cnsist f up t fur (4) students, ne (1) f whm may be a graduate student. Each team will have ne (1) captain, wh will submit the bridge and a hard cpy f the technical reprt during registratin. One (1) structure per university will be allwed. All cmpeting bridges must meet all design specificatins. Failure t meet any requirement will result in a deductin f pints r disqualificatin. Submittals All technical papers and bridge structures must be submitted with the registratin f the team captain upn arrival at the cnference. Each bridge must have the name f the university printed in permanent black ink alng the length f ne (1) r mre f the bridge members. Materials Wd Only balsa members f A, B, r C grain types may be used. Dry density f balsa members may nt exceed 15lbs/ft3. N specialized r treated balsa wd, basswd, r ther types f wd are allwed. The nminal crss sectin f all members must be.25 in x.25 in ±.025 in. Structural members may nt extend belw the plane created by the lading deck.
Glue Only ne (1) type f glue per structure is allwed. The wd glue used must be frm the fllwing list: Elmer s Wd Glue Titebnd Original I, II, r III Wd Glues Weldbnd Glue Grilla Wd Glue Design Parameters N paint, stain, r cating f balsa members is allwed. Laminating f members is nt allwed. Gusset plates are allwed t supprt jints. Excessive glue assisting strength f bridge will result in pint deductin. All jints shuld be clean f excess glue. Length f bridge shall be strictly between 26 and 30. Height f bridge shall nt exceed 8. Width f bridge shall nt exceed 6. A 2x4 blck f wd, (actual dimensins 1.5 x 3.5 ) simulating a vehicle must be able t pass thrugh the bridge acrss the bridge span. N decking surface is required, simply an pening that can accmmdate the blck, apprximately level with span supprts. The deck f the bridge is understd t be a planar surface spanning the entire length. Number f structural members intersecting at a single jint may nt exceed six. All bridge structures must accmmdate a 1 x 1 x 9 bar placed perpendicularly n the center f the deck space frm which the lad will be applied. (See Figures 1 & 2). Testing The rder f testing will be determined by the judges, and teams will be ntified in advance f testing rder. The team captain must be present at the time f testing; ther team members are nt required but may attend. The team captain will place the bridge acrss the 24 supprt span. After the bridge is placed n the span, n adjustments may be made t the structure.
Lading will be suspended belw the bridge. The supprt mechanism cnsists f an irn bar with dimensins 1 x 1 x 9 that will be placed perpendicularly t the deck surface. Chains will be hung frm the ends f this bar. A bucket will be suspended frm the chains. Bridges will be laded until failure by filling the bucket with sand. The rate f lading will be reduced at visible defrmatin r cracking t ensure the weight at catastrphic failure is exactly recrded. Judging There will be a minimum f three (3) judges fr the cmpetitin. It will be the judges duty and respnsibility t evaluate the teams fairly and cnsistently. The teams will be evaluated based n the criteria utlined in the Scring sectin included belw. The judges ruling will be final fr all cmpetitrs. Technical Paper The technical paper shall be 750-1000 wrds in length and cnsist f: 1. Intrductin a. Name f University b. Names f team members c. Captain name and cntact infrmatin 2. Dcumentatin a. All materials used fr cnstructin f bridge, including: i. Balsa wd, including a cunt f all vertical, hrizntal, and incline members ii. The name f adhesive prduct used b. Purchase lcatin f all materials, including phtcpies f receipts f purchase.
3. Methdlgy a. Explanatin f design prcess including: i. Any and all assumptins made ii. Alternate designs cnsidered iii. Cnstructin prcess b. Estimated lad capacity with all calculatins c. Hypthesis and theries supprting chsen design. 4. Figures a. Full plan view CAD figure with all angles and dimensins t scale. All angles and dimensins shuld be within a reasnable tlerance f the actual structure. Failure t meet tlerance shall result in pint deductin frm the Technical Paper Scre. b. Additinal scaled and dimensin views may be submitted at the discretin f the team. Pints will be awarded fr clarity and detail. c. All CAD figures shall be submitted with the technical reprt n 8.5 x 11 sheets. Scring Scres fr the technical paper will be based upn rganizatin, cmpleteness, accuracy, and adherence t all requirements. A scring summary is prvided n the fllwing page. A lading capacity scre will be determined by the ultimate lad capacity (lbs) divided by the weight (grams) t tw decimal places. This value will be multiplied by ten (10) t determine the ttal pints awarded. The team with the highest ttal scre will win the cmpetitin, receiving the full seven (7) pints in the verall scre breakdwn fr the cnference. In the event f a tie, the judges shall chse the winner based n quality f cnstructin and aesthetics, which shall be judged befre lading begins.
Scring Summary Sheet ASCE Student Organizatin: Technical Paper Scring Rubric 1. Intrductin Scre /15 2. Dcumentatin /20 3. Methdlgy /40 4. Figures /25 Technical Paper Sub-Ttal /100 Infractins Deductin 1. Glue Vilatin 2. Member Vilatin 3. Jint Vilatin -10/instance -30/instance -20/instance 4. Bridge Vilates Length r Height Dimensin Disqualificatin 5. Lading Deck Fails t Meet Specificatin Disqualificatin Structural Design Scre Sub-Ttal [Lad Capacity/Ttal Mass] x 10 - Deductins Technical Paper Sub-Ttal Structural Design Sub-Ttal Overall Scre /100