Analyzation Of Bridge Failures:
The 1st bridge:
After viewing the video several times and taking notes on what had exactly occurred at the instance of failure, we finally come to a conclusion. On viewing the video, you can clearly see that one of the support members experiencing compression on the left side of the bridge snaps after a certain load, and then the gusset plate fails that is connected to that member and then the whole bridge collapses. One small error equaled catastrophe. Although the center of our bridge stayed in contact as it fell, it was only the outside supporting beams that were weak and the gusset plates around them that failed and caused catastrophe. We could have improved our design process by laminating the outside members of the bridge that experienced compression, and used more glue to secure the gusset plates to a greater extent. We just needed stronger members and more secured gusset plates and our bridge surely could have indubitably supported more weight. Deformation of compression member. Exceeded the structural integrity of the member.
The 2nd bridge:
After watching the video over and over again, we finally came to a conclusion about the bridge and how it ultimately failed in the end. It was simply a build error. When ripping the structure off of the piece of notebook paper where it sat to dry after being glued, we ripped to hard and fast at one section of the bridge, and the bottom 200 mm piece of wood slightly snapped on the left side of the bridge more towards the node. We taped this area once or twice, but nothing more could be done in order to save the member from snapping any more. We believe this is what ultimately caused the failure. We saw no other members snap under the shear force. Our bridge bent completely after the integrity of the bottom 200 mm piece failed under the shear force. The only improvements we could have made would be to have used a much thicker bottom piece of balsa wood, which was not available to us at the time. The shear force of 10.21 lbs of sand including the steel hook and block of wood ultimately compromised the structure and caused a catastrophe.
After viewing the video several times and taking notes on what had exactly occurred at the instance of failure, we finally come to a conclusion. On viewing the video, you can clearly see that one of the support members experiencing compression on the left side of the bridge snaps after a certain load, and then the gusset plate fails that is connected to that member and then the whole bridge collapses. One small error equaled catastrophe. Although the center of our bridge stayed in contact as it fell, it was only the outside supporting beams that were weak and the gusset plates around them that failed and caused catastrophe. We could have improved our design process by laminating the outside members of the bridge that experienced compression, and used more glue to secure the gusset plates to a greater extent. We just needed stronger members and more secured gusset plates and our bridge surely could have indubitably supported more weight. Deformation of compression member. Exceeded the structural integrity of the member.
The 2nd bridge:
After watching the video over and over again, we finally came to a conclusion about the bridge and how it ultimately failed in the end. It was simply a build error. When ripping the structure off of the piece of notebook paper where it sat to dry after being glued, we ripped to hard and fast at one section of the bridge, and the bottom 200 mm piece of wood slightly snapped on the left side of the bridge more towards the node. We taped this area once or twice, but nothing more could be done in order to save the member from snapping any more. We believe this is what ultimately caused the failure. We saw no other members snap under the shear force. Our bridge bent completely after the integrity of the bottom 200 mm piece failed under the shear force. The only improvements we could have made would be to have used a much thicker bottom piece of balsa wood, which was not available to us at the time. The shear force of 10.21 lbs of sand including the steel hook and block of wood ultimately compromised the structure and caused a catastrophe.