Calculation Efficiency 3

[Johns20188]

I find that I often spend too much of my engineering fee on design calculations rather than developing drawings and end up not having enough fees to complete the drawings. How much time do you spend on calculations vs drawings? For example, do you spend 50% on calculations, 50% on drawings?

Also, does anyone have tips to decrease the amount of time it takes to calculate a design?

-John

 

[dik]

I spend more than 4x the time on drawing... a 50 hour sheet will have about 10 hrs of calcs and about 40 hours of drafting... I also put a lot on a drawing... have a lot of standard details, also, have a lot of standard calculation sheets...

Dik

 

[CBEngi]

Excel sheets will save you lots of time once they are developed. I would also recommend developing them yourself so you truly know how they work. Generally, I develop excel sheets for simple time consuming tasks, it might take a while the first time, but will save you greatly in the long run. Some excel sheets I have on hand would be as follows:

Concrete:
-Beam bending, shear
-Anchor bolt design
-Dowel shear transfer
-Simple pad and strip footing design
-Retailing wall design
-Wall bending and shear

Steel:
-Lifting pad eyes
-Anchor bolts
-base Plates
-Bolt Prying
-Tension/compression member design
-Beam columns
-Pipe pile design

I also have several timber sheets, generally if I do something more then twice and its simple I try and make an excel sheet to complete the task.

 

[IRstuff]

Mathcad or SMath Studio (which is free) can simplify life by taking into account units. any sort of unit can be directly incorporated into your worksheets, and either program can do calculations like 5 m * 5 ft = 82.2 ft^2 easily.

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[BridgeSmith]

I'll second CBEngi's promotion of Excel sheets. I don't limit their use to only simple tasks, though. I have full designs for bridge superstructures, multicolumn piers (bents, we call them. I have no idea why), precast post-tensioned retaining walls, etc. Several include macros to automate the highly repetitive tasks. Combining loads from 3 trucks in 35,000 possible combinations of positions across the bridge is one of those tasks. Excel will run all those combinations and find the critical combinations in about 5 minutes.

 

[WARose]

I don't do my own drafting.....so it depends on who is doing the drafting. Some place I've worked at, it was a nightmare that ate up too much of the job. With the guy who does my drafting currently.....it's not even a quarter of the job.

 

[BridgeSmith]

Here at the DOT where I work, we don't do any of the drafting, either. We provide some sketches to the detailers, but they do all of the actual details. It lets us focus on the analysis and structural design (although they catch many the configuration problems in the detailing process). There are some difficulties, and it takes good communication to make it work. However, I can't imagine trying to take on what these guys and gals do. Not having the skills to do my own detailing probably limits my options for working other places, but don't see myself leaving here for a job at an engineering firm, anyway.

 

[MrHershey]

I don't do my own drafting.....so it depends on who is doing the drafting. Some place I've worked at, it was a nightmare that ate up too much of the job. With the guy who does my drafting currently.....it's not even a quarter of the job.

This, can vary widely depending on who's doing the drafting for me. Some people I have trouble keeping them busy because I can't generate designs fast enough. Some take so long it makes you wonder if they're still drawing by hand and when you get it back it's riddled with mistakes.

Varies quite a bit by job type too. I've had some jobs (usually renovations) that are hundreds of hours of engineering for 1-2 sheets because most of the work is in checking something that's already there. Have also had jobs that are just a few hours of engineering for dozens of sheets just because there's so much repetition in the drafting. Really varies quite a bit.

 

[kmart30]

For me its about a 70/30 to 80/20 split with drafting taking up a majority of the time. The smaller jobs might be more like 50/50 or 60/40 but it still takes a good amount of time to produce detailed CD's. What ticks me off is when we take a fair amount of time to produce "quality" plans and the framers/contractors dont even read them and ask for a letter. Yes we charge accordingly for the changes but when you spend all this time on a good set of plans and hear this often it makes you think twice about spending so much time on them. I have tried to get away from doing drafting work but its hard to find a winner and keep them around. Good Luck!

 

[NorthCivil]

Everything I do, I do it in Mathcad/Smath. once you get the hang of it, you can perform new calculations just as fast as doing a hand calc. It drastically reduces mistakes, and sheets are easily modified to handle similar tasks.

Not a fan of excel just because the functions are buried, whereas mathcad everything is presentable and easily checked.

I thought it was standard practice until i started doing more peer reviews, blows me away that even 15 story buildings are being done fully by hand still today.

 

[12345abc6ttyui67]

We have separate engineers and drafters here. Typically 1 engineer to 2 drafters. But it can vary between about 1:1 and 1:5 depending on the job.

 

[dik]

CBENGi: Is your beam-colummn spreadsheet to CSA S16? and, if so, do you have the formulas for 13.8.2 or the referenced variables? Along with the input variables.

If you do, can you print out a solution for an HSS column, say 18' high with a load at the top of say 15K, and, with an eccentric point load of 5K with an eccentricity of 8" at say 8'? I'm in the process of writing an SMath Beam_Column and have a couple of glitches. I'll input your numbers and see how mine compares. If your spreadsheet accommodates a moment at the top and bottom, if you could put a 10'K moment top and bottom.

Thanks, if you can

Dik

 

[P205]

@dik Do you mean cl.13.8.5? The omega1 value? because 13.8.2 deals with class 1&2 of I-shaped members. (S16-09)

If so, I know the struggle.

 

[KootK]

I agree with others that a) spreadsheets are a must and b) calculation time should be a good deal less than drawing development time on most new build projects. I'll add the following to what others have said:

1) From what I've seen, a profitable job usually goes out the door with many things going either unchecked or very roughly checked with the EOR hopefully making the calls as to what is truly important based on sound engineering judgment. This is something that SE's rarely admit to for obvious reasons but I believe it to be the truth. And an important truth at that. A senior engineer's fat cat billable rate is often more justified by what they skillfully don't engineer rather than what they skillfully do engineer. That, plus leverage-able industry relationships etc. For those purists here that may be in search of a witch to hunt, move along. I've passed no moral judgment on this practice here; I'm simply reporting on my experiences to date, considerable as they are.

2) When I wax philosophical about the various ways that my designs are completed and which are the most efficient, it's not actually spreadsheets that come out as the winner. Rather, it tabulated designs. Stuff like the CRSI manual for footings etc. To that end, I've taken to using spreadsheets to generate my own project specific nomographs and tabulated designs. In this way, I generate canned designs for a handful of desirable member sizes and then instruct everyone working on the project to limit themselves to those canned designs unless there's a compelling reason to do otherwise. On certain kinds of projects, I've found that this speeds things up nicely. It also contributes to design uniformity across various project participants.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dik]

P205: 13.8.3 makes reference to 13.8.2 and the HSS falls into 13.8.3. Sorry for the confusion. Fortunately most rolled symmetric sections fall into Class 2 or 1. It's easy to determine what class... a couple of 'if' constructs.

Dik

 

[dik]

KootK: I take it a step further... I use Doropdf writer. This installs as a printer driver and I can do a bunch of things using various spreadsheets, etc. and print them to a single file... Doro asks if I want to overwrite or to append. I append things and I can have several dwgs, SMath, excel, etc. in a single 'long' project design note *.pdf file. I find Doro great for this.

 

[XR250]

I do my own drafting and perform the calculations on the fly.
I usually have about 25% time spent on calcs.