Checking calculations 19

[P205]

I'm writing this thread in regards to what was said in this old thread here:

http://www.eng-tips.com/viewthread.cfm?qid=321928

It leaves me feeling uneasy to say the least. I also feel compelled to ask the following question:

- In the interest of meeting the deadlines AND feeling comfortable, why not be generously conservative in most of your designs?

- Many admit to finding errors often in their own work and in others. It stands to reason that not all errors get discovered. This would lead me to want to be conservative in my design.

- Another thought, given the old triangle (cost-quality-time), if deadlines are very rushed (low time) and the structure simply needs to be satisfactory (low quality/less refined), then being conservative (higher cost) appears to be the way to solve this puzzle.

Thoughts?

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Personally, I have 8 years of design experience, and spend a lot of time reading books and teaching myself as much as I can. I usually buy a few books a year to refine my skills and knowledge. Honestly, I don't see too many peers doing that. I'm just looking to stimulate some discussion.

 

[Tomfh]

Ideem,

I agree. If you design to 100% then you’re up against the limit from the get go.

If economy is the number 1 concern then by all means go for full efficiency, however it’s not always as simple as that.

Contractor pour the concrete 10% too thick? FAILS a fresh analysis

Client wants to put slightly more load on their building? DOESNT WORK

Steel tensile area corrodes by 10%? DOESNT WORK, structure non compliant.

So leaving a bit of headroom isn’t necessarily bad practice in my opinion.

 

[Settingsun]

Regarding the two previous posts, I like to have the client involved in/making over-design decisions. Eg be honest with them about the limitations of paint/galvanising in preventing corrosion and have them agree to a documented corrosion allowance. Ask them if they're sure they'll never use a structure for any other purpose. A lot of the time they say lowest initial cost is their prime directive and I can live with a lean design in that case.

Regarding concrete poured a bit thick: a decent code will allow a reduced dead load factor for loads based on survey of an existing structure. If only they were all so decent...