Last blog we left off with testing the steel and came up with a range of results for the strength of the steel we sent out to the lab. I asked you guys which strength value you would of chosen, the lowest or the average and a few people replied and said that they would use the lowest strength and that is exactly what we did!

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CONSERVATIVE ASSUMPTIONS

With the lab results that I shared with you guys in my last blog (see here: Steel Strength) , we decided to stay on the conservative side and elected to use the lowest strength value. This was not an easy decision for the client to accept because it meant the client was now facing a $100,000+ reinforcement bill since more beams would need reinforcement due to the lower strength values.

The upside is that we are currently working in an open space (i.e. there are no tenants on the floors we are working on). So once the reinforcement is installed, the building will be able to handle modifications to its use in the future without issue. The downside is that it adds unnecessary cost to the areas where the strength was on the higher side of our results. We can justify this because the engineering needed to surgically reinforce where needed would result in higher engineer cost.

This is a case of better safe than sorry. And that's how I want to start this blog off which I call decisions.

ENGINEERING DECISIONS

Engineers often have many decisions to make that can have a great impact on cost and life safety. Much that responsibility falls on our shoulders because we are technical experts in our field and the only other person who can truly question our decision are other technical experts. The general public tends to not understand why we take certain actions, which is something that happens in many fields.

As an engineer, our decision making is performed by more than one engineer. As the complexity of the project grows, the number of people involved in decision making also increases. This quality control is done to make sure that fresh eyes are able to capture potential pitfalls that get missed due to fatigue of working on multiple projects at once.

From most important to least, our decision making process is:

1. Life safety, will our decision result in immediate safety of an otherwise dangerous situation?

2. Is our decision code compliant?

3. Does our design have an unecessarily high cost associate with it?

4. Does it meet the needs of the client?

Strangely the clients needs are last because what they want might not be safe or code compliant. However, if does meet safety and code, its just a matter of how much they are willing to spend.

EXAMPLE

We have one particular project where our client requested us design a ladder that reaches the top of a water tower AND over a wall, down onto a terrace 10ft below. While it seems that the task is trivial, the reality is that theres a few logistical issues.

• The wall is a sound barrier that is approximately 5' tall (shown below in green highlight)

• The user would need to climb ontop of the wall then turn around on top and then climb down.

It's going to cost a lot of money to do the proper research and designing a scheme that meets code requirements, if that's even possible. The next challenge is that it needs to be safe for maintenance staff to use.

The alternative is to simply access the terrace from the space below, but the tenant is refusing to provide access.

How would you approach the design? Comment below!
Hint: Decide which is most important to you, safety or code compliance! Granted you may not know what the code states, but make something up. The exercise is about logic more than knowledge!