This is Here, That's Over There
October 30, 2018 | Vaughn J. Mantor
It’s not easy to build a bridge more than 2,000 feet long and 160 feet above the water, which is full of ocean-going ships. And it’s especially difficult to build it in earthquake country amid feuding politicians. The engineers and constructors had to bring their best game to this problem. So a part of the plan included manufacturing the massive trusses elsewhere (more than 850 miles away) and shipping them and lifting them into place instead of trying to construct each truss piece by piece on the bridge.
You see the obvious problem: if a truss is not built precisely according to specification, it won’t fit, and a big problem results when the constructors try to put it in place. In addition, engineering specifications require that the cross members of the truss meet the longitudinal pieces at precise angles. The solution: laser scanning the truss at the point of manufacture and verify all the dimensions and angles before shipment.
The technicians at Verify 3D have repeatedly solved this common problem: one part (This)of a massive construction is built at one location and must be combined with another part (That) built at another location. And the This and the That are complicated and really big. Solving the problem, i.e. verifying the constructions with laser scanning, inevitably results in big savings for the project.
Some examples from our experience:
1. A new ship was being built in the North East part of the country, and the deckhouse had been built far away. The older method of fitting the two together called for multiple test fits using a $100,000-per-day crane to hold the deckhouse a couple of feet above the deck so that workers could crawl between the two and take manual measurements, looking for discrepancies. Instead, laser scanning of the deck and deck house revealed a number of mismatches. Corrections were made before the lift and the deckhouse was attached in one day without a hiccup.
2. Three steel superstructures (30’x30’x40’ each) were built in South Florida. Installation was at a 1500 foot pier along the lower Mississippi River. The special footings of the superstructures had to match the pier’s connectors to within 1/8”, and, once installed, the tops of the structures must be dead level. By using laser scanning to identify discrepancies before the superstructures left South Florida, and by using sophisticated laser scanning techniques to level the structures, the savings to the owners were more than $300,000.
3. Sometimes laser scanning can reveal solutions that do not require re-working components. Two concrete digester tanks and their lids were built on the site of a waste treatment plant. The lids must rest on corbels projecting from the walls of the tanks. As we all know, concrete is notorious for warping as it cures. Before using a very expensive crane to lift the lids in place, the builders decided to laser scan the tanks and the lids. Discrepancies in the walls of the tanks showed up clearly; they were asymmetric. Laser scanning showed the builders how to make slight changes in the steel lids, and, most important, scanning showed the builders how to align the lids to the tanks so they would fit in the first try.
A senior project manager for one of the nation’s largest engineering firms called this technology one of the best insurance policies he had ever seen.
Even if scanning shows the widely separated components match, scanning will show additional valuable information that is otherwise not available. Invariably, scanning such components at the right time benefits the project’s schedule and cost.
If you’d like a personal explanation or demonstration of the ways laser scanning can help you or if you'd like to speak to one of our clients, our contact information is directly below.
Because our experience in this technology dates back to 2002, Verify 3D knows the most appropriate equipment to use on each project and how to use it for the best benefit to our clients.
For this article, because of confidentiality and copyright restrictions, the images included are not of the sites on which we worked, but the images are very similar to the actual circumstances.