Wednesday, March 17, 2010

Popsicle Stick Bridges by DLSU students

Thirteen entries from DLSU competed in the Popsicle Stick Bridge Building Contest hosted by The Civil Engineering Society (CES). Unfortunately, no entry made it in the winning bridges. The DLSU bridges were also good and well-made. Bridge no. 18 actually garnered the largest load of 111 kg with a displacement of about 25.5 mm, but it was too heavy at 1138 g making a score of only 3.82. DLSU ranked 8th in the design category (Bridge No. 23) and ranked 10th in the strength category (Bridge No. 19).

Congratulations to all DLSU participants!

Tuesday, March 2, 2010

The winning popsicle stick bridges!

In the recent DLSU-CES Popsicle Stick Bridge Building Contest held last Feb. 13, 2010, 31 bridges were tested for the Strength Category. A Universal Testing Machine (UTM) was used to test the bridge. Two 14 mm rebars spaced at a specified distance, were placed on the bridge deck. Then a hollow “cage” was placed on the rebars, on which the load from the UTM was transferred. A displacement transducer was attached to the UTM to measure the bridge displacement (D) in mm. The load P (kg) when the load dial of the UTM stops was noted indicating bridge strength. The Strength Rating is computed as (1000x P)/(D x W), where P in kg, D in mm and W = actual weight of the bridge in kg. The strength rating S is the bridge stiffness (kg/m) per unit weight (kg).

Bridge entry no. 13 from the Technological Institute of the Philippines (TIP) of Manila has the highest score. The bridge has only a weight of about 390.4 g. With P = 43 kg and d = 11.8 mm, its score S = 9.33. Observe the connections at the joints - knowing that failure will occur at the connections, the connections were glued together properly with additional cover.
The 2nd place bridge was from Pamantasan ng Lungsod ng Maynila (PLM) which had a score S=9.15 with P=36 kg, D=8.87 mm and W=443.7 g. The 3rd place goes to another entry from TIP-Manila with S=9.01, P=45kg, D=10.78 and W=463.11 g.

Congratulations to the winners and all participants. You were all winners!