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Concrete Movement Joints[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint'" <seaint(--nospam--at)seaint.org>
- Subject: Concrete Movement Joints
- From: "La Count, Curt" <Curt.LaCount(--nospam--at)Jacobs.com>
- Date: Thu, 2 Sep 1999 08:57:00 -0700
On our projects, we've been more concerned about drying shrinkage than temperature movements. Typical drying shrinkage movements are .06 %, while temperature movements are typically .1% per 100 degrees C. It takes about 60 degrees C to equal drying shrinkage. Control of the design mix, distributed steel reinforcing, fiber reinforcing and pour sequencing are methods we've used to pour plates as large as 80m, with only minor cracking. I have found it common practice, in non-seismic regions, to provide expansion joints in buildings with very small joints. The effects of pounding were apparently never investigated or the probability of occurrence thought to be remote enough to ignore. On the West coast of the US, engineers would typically think 100mm joints as minimum separations to prevent pounding. Curt La Count Jacobs Engineering Portland, OR ---------- From: Rex Donahey To: seaint(--nospam--at)seaint.org Subject: RE: SEISMIC DESIGN to UBC'97 Date: Thursday, September 02, 1999 6:28AM A major factor in cracking of large structures is shrinkage of the concrete during the construction phase. Although it can require a great deal of coordination, it is possible to detail closure strips in the building. If the strips are left open for at least 30 days, they will allow most of the shrinkage to occur with less constraint. -----Original Message----- From: Hasan Hindawi [mailto:hasanh(--nospam--at)go.com.jo] Sent: Thursday, September 02, 1999 6:01 AM To: seaint(--nospam--at)seaint.org Subject: Re: SEISMIC DESIGN to UBC'97 Greetings, 1- In Kuwait the temperature may reach 55 degrees celcius during the summer days and may drop to 20 during summer nights. And may even drop below 10 during the winter. So the actual temperature change is actually greater than 30-35 degrees celcius. But nevertheless the drop occurs. And special measures should be adopted when casting during the summer. 2- It is true that heating and air-conditioning systems reduce the effect of temperature variations, however most cracking problems occur during construction stage. The duration between pouring a slab and operating heating or a.c. is a minimum of 1 year in these parts of the world. 3- Yes I agree that critical stresses occur in the bottom floors due to the fixity of the columns to the footings. Therefore, regardless of the number of floors of a building, it is sufficient to analyze up to 6-7 floors for temperature variations Regards Hasan Hindawi
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