1 Pertemuan 13 Evaluasi Kasus Matakuliah: S0182/Studi Kasus Dalam Teknik Sipil Tahun: Juli 2005 Versi: 01/01

2 Learning Outcomes Mahasiswa mampu mengevaluasi dan membandingkan kasus-kasus yang mungkin terjadi di lapangan berdasarkan berbagai contoh kasus dan penyelesaian yang dipelajari, yang akan digunakan sebagai bahan pertimbangan bagi pengambilan keputusan di lapangan nantinya  C6

3 Outline Materi Tijauan terhadap kasus kegagalan konstruksi Resiko dan dampak yang ditimbulkan Meminimalkan resiko Pertimbangan teknis dalam masalah/desain konstruksi Pengambilan keputusan

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8 Activity A: New Bridge Temporary Works Superstructure crews will continue to construct temporary works in support of cable spinning. Scheduled work begins at 6 a.m. and ends at 10 p.m. An occasional graveyard shift may occur from 10 p.m. to 6 a.m. Equipment used may include tower cranes and winches. August 1-31 Activity B: Tacoma Mainline Crews will shift concrete barrier and modify striping for both eastbound and westbound lanes in order to accommodate both directions of traffic on the westbound alignment. This will allow construction activities to occur on the current eastbound lanes. The work will take place between 7 p.m. and 7 a.m. Equipment to be used will include excavators, rollers and dump trucks. August 8-10 This work is weather dependent and could be delayed due to bad weather.

9 TACOMA NARROW BRIDGE Connecting Land to Sea: Spinning the Cables Building a suspension bridge across the Narrows is the human equivalent of a spider weaving a web across the space between two trees. It looks fairly impossible. Cable spinning - laying strand after strand of steel wire - from the Tacoma anchorage to the Gig Harbor anchorage will become a simple mechanical process once an aerial is built. In late July, the bridge builders reached a new milestone when workers stretched a steel cable from the west shore of the Narrows to the top of the Gig Harbor tower. Pulling the 5/8-inch 'pilot line' is the first phase of installing the suspension system. In the months ahead, suspension crews will spin mile after mile of steel wire until a pair of 20½-inch main cables have been spun.

10 TACOMA NARROW BRIDGE Crews pulled the pilot line on a brilliant July morning as eager engineers and curious reporters waited patiently on the beach. Directly overhead, two workers pulled the first cable from a winch at the Gig Harbor anchorage, down a steep bluff and onto the beach. Once on the shores of the Narrows, the workers handed the cable off to a crew in a small boat. At the same time that two men dragged the cable from anchorage to beach, another team standing atop the Gig Harbor tower, 510 feet above water level, used a winch to lower one end of a second cable to deckhands on a Foss tugboat. Each cable was then pulled toward the other by the work boat and tugboat. The two boats met under the west span of the Narrows where deckhands connected the cable ends to a steel plate. The two winches then raised the connected cables into place. The whole process - dragging the cable to the beach, lowering the other cable from the tower and connecting the two - took slightly more than an hour.

11 TACOMA NARROW BRIDGE Now that the first wire has been placed, progressively stronger wires are being pulled across. Once the suspended walkway is complete, steel wires will be pulled across the Narrows in groups of four until all 8,816 individual cables have been placed. But before the actual 'spinning' process begins in mid-September, crews will spend the remainder of the summer building the aerial walkways.

12 TACOMA NARROW BRIDGE Concrete is poured into the towers with a bucket that can handle four cubic yards of concrete at one time. From a pumping station on land, concrete is delivered through a pipeline to the pier top, and then placed inside the tapered bucket. A tower crane, then, hoists the bucket to the top of the structure and empties the load inside the form.

13 TACOMA NARROW BRIDGE See the animation of TACOMA BRIGDE