Tower Cranes In Jerusalem - Israeli Commercial Construction

Copyright 2006 by Morris Rosenthal - - contact info

The Serial Tourist's Guide to Living in Jerusalem

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Based on the neighborhood, I'm guessing that the luxury apartment building under construction here will be limited to four stories. So how do they end up with four tower cranes on the job? I've long suspected that tower cranes are overused in Israeli construction because I've seen more here, both in absolute terms and the number per construction site, than I've seen in the US in my life. For what it's worth, I lived in Boston a few years. The basic approach on Israeli construction sites is that every square foot of the site and much of the surrounding neighborhood should be reachable by crane. The main function of the cranes appears to be lifting concrete hoppers that are then dumped into the forms for walls or columns, which are often built by hand out of what appears to be scrap wood! It just boggles my mind, the mix of the latest technology and the crudest form work you could imagine. Beyond that, construction in Jerusalem proceeds very slowly, they can't work around the clock in the residential areas because the lighting required would be even more disruptive than the noise.
The sole building technique I've seen used in commercial construction in Israel is rebar and concrete, in large quantities. Rather than framing with steel, welds, bolts and rivets as is commonly seen in America, in Israel it's all reinforced concrete. The structural members just use increasing amounts of rebar for strength. The columns under construction at the right is a relatively lightweight affairs, I've seen columns where the rebar seems to take up most of the space. The concrete is sometimes brought in by mixer truck, and sometimes mixed on site. The workers are always brought in by tender and sometimes sleep on site. It's not uncommon, if you walk around construction sites on Shabbat, to see the workers hanging their clothes, which are probably hand washed. Some of the worker housing looks like shipping containers, in other cases, they may be allowed to camp out in the partially constructed buildings. The forms in the picture at the right are obviously the manufactured type, but you'd be surprised the number of hand-made wood forms you'll see on some construction sites here.
The main job of the tower cranes on a site like this is lifting the concrete hoppers to pour sections of form work. The use pumper trucks for concrete in Israel as well, but for some reason, I usually only see them on residential jobs. I suppose the reason is that commercial jobs have so many tower cranes on site they have to justify their use. To be fair, since the construction is more horizontal than vertical, the sites take up quite a bit of space, and the only access to the areas away from the edges are by crane. By the same token, the edges of the site are more likely to be lined with existing buildings than streets, so overall access is always a problem. On a site like this one with manufactured forms, the tower cranes also spend a reasonable amount of time swinging pieces of form around. I never made a serious effort at a count, but I'd guess the proportion of ground construction workers to tower crane operators on a large site like this is about 6:1.
Here's an example of a tower crane lit up at night, even though they weren't doing any work. The lights are directed down, towards the work, and there are special spotlights on the tower of the crane, right under the operator booth, that get focused right on the landing site. While it's not so easy to discern details in a small night photograph, this site, another luxury housing complex near the Yafo gate, is a pretty good example of the construction technique. The buildings are scaffolded as the crews work up with stone facing on the finished pours, and large exterior wall spaces framed with reinforced concrete posts and beams are left to be filled with block and windows. It all looks pretty slap dash until the facing stones are cemented on, and I wouldn't want to bet on how long they stay in place.
I used to assume that tower crane pedestals were anchored with reinforced footings and heavy bolts, but I've seen several examples where it looks like they are just sitting on a short rail system and weighted down with concrete blocks. While the counterweight on the arm can be moved in and out to keep the center of gravity over the tower, it's hard to imagine the a few tons of concrete stacked on the base are enough to keep it from going over due to wind loading. I guess the rails must be anchored to the stack they are sitting on as well, but I'd hate to be the operator of one of these things, and not just because I'm developing a fear of heights:-) You might think this image below of a tower crane on a residential street surrounded by trees is a trick of camera angles, but it isn't. This particular crane is on a job that I would call a three story house. Maybe it will end up being a hugely expensive single family. maybe it will carve into five or six luxury apartments, but it's the kind of job that a few years ago would have been built with pulleys and buckets of concrete. Nearly the whole length of the boom in this case is hanging out over a neighbors property.

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