Karl Hoitsma, P.E.
Structural Engineer
Tyler, TX

I am available and ready to do consulting work for other engineers.

  • Industrial,
  • Institutional,
  • Commercial, or
  • Research

For instance, happy to assist with review, checking, calculations, or programming.

Typically available on short notice, tight deadlines, willing to work off-shift – nights, weekends.

Email: khoitsma at mathpax.com

Search the blog by subject matter:Β Tabular List β€” Blog Entry Search

Extensive experience in programming suited to engineering work — examples follow:

ASCE Exact Wind Integration (closed form equations) Developed single function to calculate all aspects of ASCE wind design:

  • force
  • moment
  • diagonal tributary elements allowed
  • horizontal offset basis
  • elevation basis
Multi-Page Apps using Dash/PythonAnywhere Apr2020 Developed working online apps for structural design:

  • Beams – strong axis bending, any Cb
  • WT eccentric braces – with plots
  • Bolt groups
  • Structural shape properties – ALL
  • Structural shape properties – filtered, sorted
WT Braces Mar 2020 Developed design basis for eccentrically loaded WT brace members, allows comparison with concentric braces
Single angle braces vs WT braces Feb 2020 I compare the simplicity and efficiency of single angles to WT braces
Calculate Beta w for Single Angles Dec 2019 The beta value for single angles is an elusive parameter.Β  I developed a closed form solution for the beta value.
AISC Bolt Shear β€” C Coefficient Jul 2019 Here is my iPhone app for determining bolt group coefficients – with plots.

See video.

ASCE 7-16 Kzt Calculation β€” with Chart Jul 2019 Here is my iPhone app for determining the ASCE Kzt parameter.

See video.

AISC Bolt Shear (with video) Jun 2019

AISC Bolt Shear Capacity β€” Improved UI Jun 2019

Here is my iPhone app for determining the allowable bolt shear in accordance with AISC.

Beautiful, very quick to use.

Brom’s Method Sep 2017 Rigid shaft foundation design
ASCE 7-16 Ice Loading Apr 2018 Developed function,Β get_iceweight()

  • for any structural shape
  • pipe, HSS, bar
  • L, 2L, 2L spaced
  • C, MC
  • W, S, M, HP
  • WT, ST, MT

Wind and Fire-proofing Dec 2017 Explicit wind calculation for steel members including fireproofed beams and columns.

Multi-Dimension Data Table using PyXLL (with video) Dec 2020
I coded a PyXLL macro that builds a multi-dimension data table.

The native Data Table provided by Excel is useful but limited to two variables.

My version is set up for 5 dependent variables and an unlimited (theoretically) number of dependent variables.

Excel Dropdown with NO worksheet data list (with video) Nov 2020
I built an Excel dropdown function β€” that requires no worksheet reference!


The dropdown built into Excel requires a range of data to populate the dropdown list. This might be an appropriate situation if the spreadsheet is a one-off. In my work, the dropdown list would more appropriately be generated in my PyXLL program.

Having the dropdown and its data provided by a PyXLL function allows:

  • central control of the list
  • easy updating
  • unrestricted placement of the dropdown β€” any spreadsheet, any tab, any cell
Feet Inches Sixteenths (FIS) Calculator
I built an Excel FIS Calculator


  • easy fraction entry
  • general triangle solutions
  • similar triangle solutions
Email: khoitsma at mathpax.com


Reference on this website to any specific commercial products, process, service, manufacturer, company, or trademark does not constitute its endorsement or recommendation by Karl Hoitsma.

. . .

This last section on this page is a toy app that I built using Observable. The user can select from 3 AISC shapes — C, S, and W. The two charts illustrate the AISC sections that have an integer depth (in inches). The first chart lists the smallest weight sections with integer depth; the second chart lists the largest weight sections with integer depth. The abscissa (domain) is limited to 200 pounds per foot.