Development Blog

User DW shared the following story. It is not meant to bash young engineers, but rather just illustrating how we tend to over-complicate things when a simple approach could do.

Get the Centroid Structural Calculator app on the Calculator product page.

New in the Centroid Structural Calculator today, is material mode that allows you to quickly lookup densities and elastic modulus for materials often encountered in building construction.

• Concrete of various grades: All grades assume a density of 23.5 kN/m³ or 150 pcf. The Calculator estimates the elastic modulus using CSA A23.3 - 2019 equation 8.1 orACI 318-19 equation 19.2.2.1a (depending on the unit system), using that assumed density.
• Typical building materials: Structural steel, aluminum, common brick, clay tile and glass using values from the CISC Handbook of Steel Construction.
• Woods of various types: Density and elastic modulus values provided by the CWC Wood Design Handbook.
• Liquid and earth: Density values from the CISC Handbook of Steel Construction.

Example use cases:

• Load estimates: Quickly find a material density to calculate dead loads.
• Beam analysis: Quickly find a value for the elastic modulus when calculating a beam deflection.

Very simple, but a nice time-saver for busy structural engineers!

Get the Centroid Structural Calculator app on the Calculator product page.

The Centroid Structural Calculator now synchronizes your calculations between your mobile phone, tablet, laptop and desktop computer. The same calculations display on your Android, iOs, Mac, Windows, Chromebook device!

• Enable device synchronization: Open the Menu and Sign In on your devices. Whatever you do next — add or delete calculations, add or delete annotations — is synchronized across all your devices in real-time.
• Work offline: Use the Calculator without an internet connection. Next time you use it while online, your calculation history with automatically synchronize again.

Example use case

You are out on a construction site and are using the Calculator on your mobile phone to check some urgent design changes. Back in the office, you open the Calculator on your PC and the calculations you did earlier are there instantly. You swipe over to the Report screen to add a couple of comments to the design calculations, and then print them to PDF for your records.

Work offline

But what if there is no internet connection available when you were on the construction site? No worries! The Calculator will work just fine while your phone is offline. And the next time you use it when online again, the Calculator will sync your calculations.

We are shifting our development focus back to the structural engineering functionality of the Calculator. Have a look at our development roadmap and let us know what functionality you would like to see.

Quick design calcs

We are developing Centroid Structural Calculator for structural engineers as tool to supplement their design software. Use Centroid Structural Calculator whenever you cannot or do not want to (because its to cumbersome) to open your finite element or spreadsheet software. It's great for quick design checks, conceptual design and when you are away from your desk.

Get the Centroid Structural Calculator app on the Calculator product page.

We have been eating your own dog food — using the Centroid Calculator in own daily work. In the process we have discovered many missing features, and fixed some bugs. We are excited to report the following list of new features…

• Landscape support: On devices with natural landscape orientation (e.g. larger tablet or Mac/PC laptop/desktop), the app will display the calculation history on the side.
• History reference: Use the result of any previous calculation by tapping it. The history provides you with an "unlimited" stack of values — remember the days of RPN (Reverse Polish Notation) calculators?
• Copy and paste: Use the new copy and paste keys (or CTRL+C and CTRL+V on desktop) to copy values to and from the device clipboard.
• Calculation groups: Use the new key to start a group of calculations. Groups demarcates calculations in the history for document view.
• Documentation view: Swipe right (or click the "annotate and print" label) to display the group of calculations with nicely formatted equations. Add annotations in the form of headings and paragraphs.
• PDF design reports: When in documentation view, use the print button to create a hard-copy or PDF. Keep a document trail of your designs.

We hope that you find these new features useful too! There is even more functionality on our development roadmap.

Get the app on the Calculator product page.

We are pleased to announce that the Calculator is now available on Google Play. Just one more option to make access more convenient for you — you can still use open in your web browser or as an installed progressive web app (PWA).

We are looking into extending this option to the Apple App Store in due course.

See all the installation options on the Calculator product page..

We thought that most structural engineers would be interested in knowing what design software their peers use, how much they invest in software, and what benefits and shortcoming they experience with their software. And with that, we ran a survey on structural design software late last year. SEABC generously allowed us to advertise the survey in the November Newsletter.

Our assumption that most structural engineers would be sufficiently interested in the information to participate in the survey was overly optimistic – only 15 people completed the survey. However, the responses were quite uniform, to the point that we think the responses may well be representative for our local industry. We are pleased to provide a summary of the survey results below. Thank you to everyone that participated in the survey. I hope that readers of the SEABC Newsletter find the information of value. It will certainly help us (and hopefully other software vendors) identify opportunities to better serve the users of our software.

Survey Results and Comments

1) Specialist structural design software

In order of number of mentions, responders listed the following oft-used software:

1. Hilti PROFIS (90%).
2. ETABS (47%).
3. WoodWorks (47%).
4. SAFE (33%).
5. SAP-2000 (33%).
6. S-FRAME (33%).
7. Simpson Strong-Tie (33%).
8. 14 other products mentioned with lesser use.

A notable number of the above products are from the Computers & Structures stable. But maybe more important than any specific products identified, is the fact that most respondents use three or more products – there is no "one size fits all" solution

2) Worksheet software

All responders use Microsoft Excel. One third use Mathcad, and some use SMath Studio (a free alternative to Mathcad) and Jabacus (online structural design tools). Weighing their peace of mind with peer reviews, independent reviews, and audits by EGBC, responders rated their confidence in their worksheets as follows:

• Nobody expressed major concerns.
• 33% neutral.
• 33% positive.
• 33% very positive; worksheets are well tested and detailed.

Structural engineers seem to feel confident using worksheets for design calculations.

3) Handheld calculators and mobile apps

Almost everyone uses handheld calculators for simple design calculations, with 74% of respondents doing so on a daily or weekly basis. 20% of respondents use custom design routines on programmable calculators. None of the respondents used mobile apps for design calculations.

4) Software expenditure

Two third of responders provided approximate dollar values for annual expenditure on structural design software:

• 60% of the responses indicated $5,000 per year or higher per user.
• The average value was between $2,500 and $3,000 per year per user.

Structural engineers seem willing to pay good money for good products.

5) Benefits and shortcomings

Respondents indicated that they were pleased with the following aspects of their software:

• Can solve complex problems (73%).
• Is user friendly and intuitive (67%).
• Provides comprehensive design reports (47%).
• Makes it easy to collaborate on designs (33%).
• Received timely updates from the vendor (33%).

Respondents reported the following annoyances:

• It is a pain to exchange data between software packages (62%).
• Design reports lack detail on assumptions and calculation steps (46%).
• It's not user friendly or intuitive (31%).
• Design features have not improved much over time (31%).

In the comments, multiple respondents expressed a wish for better help/documentation. Several also expanded on their desire for more detailed and customizable design reports.

Several items listed as benefits by some responders were listed as shortcoming by others. This contradiction could indicate that firms have different software requirements, or perhaps that there is a reluctance to replace existing (limited) software with new products.

Some unsolicited advice to software... Work on improving your user experience:

• Users want easier data exchange between software. Granted, this is a problem that no single software vendor can solve on their own.
• Users want detailed design reports. Show the assumptions, code references and calculation steps.
• Users want to see your product improve. Even if your product is great now, don't stop trying to improve the workflow and features.

6) Cloud-based design software and data

To the question whether responders would like their design software and data to be cloud-based, available on all their devices, and easily shared with team members, they indicated:

• This would be very welcome (36%).
• Would use such features only occasionally (47%).
• Not useful at all or prefer existing systems such as VPN (13%).

We have made progress with the Centroid Calculator, most notably with its support for units of measurement. You are now able to do quick conversion between metric and US customary units and use either system in design calculations.

Below are a couple of recipes below to illustrate the app's capabilities. You will help me immensely if you would do the following:

• Try some of the recipes. Please let me know what you find helpful and, more important, what is missing.
• Next time you use your regular calculator, please make a note of what structural calculations you performed. Let me know so that I can see how we can make this simpler for you in the Centroid Calculator.

A big thank you for your encouragement with my endeavours and best wishes to you for the Christmas season!

Device Support

You can use the Calculator as a website at https://centroid.app/calculator, but for the best experience install it as an app on your phone.

The current version of the Calculator works best on a smartphone. Better tablet and desktop support is on our development roadmap.

General Concepts

• Math and structural: The bottom half of the Calculator does basic math, and the top half does structural calculations.
• Calculation modes: Use the top row of keys to switch between the calculation modes, each with a set of keys related to units of measurement, beam analysis, steel design, and concrete design.
• Variables: Structural calculations use variables such as "L" for span length and "d" for section depth.
• Units: Every variable has a unit, e.g., span length in meters or feet and section depth in millimeters or inches. You can mix unit systems while performing a design, e.g., enter a beam span length in feet and loads in kilonewtons.
• Variable references: You can reference variables in math expressions and assign them to other variables. You can do so across calculation modes, e.g., use the second moment of inertia of a steel section in a beam analysis.

Calculator Recipes

1) Select a calculation mode

• Use the top row of keys to switch between calculation modes: "units", "beam", "steel" and "concrete" design.
• To clear the calculations for the current selected mode, press the blue "shift" and "clear" keys.

2) Use the answer of the previous calculation

• Press "ans" to use the previous answer in the current calculation.
• When you start a new calculation with "+", "−", "x" or "÷", the calculation will continue on from the previous calculation.

3) View previous calculations

Touch and drag the history area to scroll up and down the history of calculations.

4) Use variables

• Using a beam analysis as example, assign a value to the span length by pressing "L" and then entering a value or a math expression to calculate the value.
• Variable reference in the same calculation mode: To calculate the beam loading width as a multiple of the span length, press "Bw" and then enter the expression, e.g., "L x 0.75".
• Variable reference across calculation modes: When entering the second moment of inertia of a beam "I", you can switch to the "steel" mode and then reference the "Ix" value of a steel shape.

5) Switch unit system

• Use the "metric" and "USC" keys to switch between metric and US customary units at any time.
• All design input and output are in the current selected measurement system. In metric span length will be in meter and force in kN, and when using in US customary units, the same value will be in ft and kip.
• Switch between metric and US customary units at any time. For example, while performing a beam analysis, you can enter the span length in ft and the loads in kN.

6) Quick unit conversion

• Select the "units" calculation mode. Enter the value or a math expression you want to convert, the current unit, and then the new unit. To convert 12 feet to meter, for example, enter "12" followed by "ft" and then "m".
• You can convert between any units of the same type, i.e. one length unit to another length unit, and one force unit to another force unit. Example: convert a length value between "ft" to "in", "m" and "mm".

7) Using fraction inches

When using US customary units, it is sometimes convenient to work with decimal lengths, e.g. 27.3125 in. And sometimes you may prefer using fractions, e.g. 2 ft 35/16 in.

• Use the "dec" or "frac" key to select your preference.
• To enter a fraction, use the "a/b" key. Press "a/b" to start the fraction, go from the numerator to the denominator, and to complete the fraction. To enter 3 5/16 in, you would press the key sequence "3 a/b 5 a/b 16 a/b in". (You may substitute with the "÷" key for the second and third "a/b" keys.)
• Working with values in different units currently requires multiple calculation steps and using the "ans" key to join them. To add 1.5 m to 12 ft, your key sequences will be "12 ft m" (converts from foot to meter), and then "ans + 1.5 m" (use the answer and adds the valuer in meter). Support for different units in the same calculation is on the roadmap.

8) Use mixed units in a design

Say you want to analyze a beam and want to enter its dimensions using US customary units, and loads using metric units:

• Select "USC" units.
• Enter the span length "L" and load width "Bw" in feet.
• Select "metric" units.
• Enter the loads warea", "Wline" and/or "P" in kPa, kN/m and kN.
• For bending moment "M+" and "M-" in kNm, stay in "metric" units. For the same in ft∙kip units, select "USC" units.

9) Analyze steel shapes

• The steel design mode is currently limited to calculating section properties of I-sections, hollow rectangular and circular sections, and solid rectangular and circular sections. The Calculator determines what shape you are working with from the values you have entered:
  • I section: d, b, t and w.
  • Rectangular hollow section: d, b and t.
  • Circular hollow section: d and t.
  • Solid rectangle: d and b.
  • Solid circle: d.
• You can look up a W shape with the "W" key. Enter any one ore more digits in the section designation for a list of matching shapes, and "enter" to select the current shape.
• You can use the calculated section property values for other design calculations, e.g. assign the Ix value to the beam stiffness when calculating deflections. See the next recipe for an exampl

10) Design a steel beam

• Select "beam" mode.
• Set the support conditions for the left and right ends: simply supported (default), cantilever, continuous, or fixed.
• Press "L" and enter the span length.
• Enter an area load, line load and/or point load with the "warea", "Wline" and "P" keys. When using an area load, also enter a load width "Bw".
• Calculate the span moment with "M+" and maximum support moment with "M-".
• Calculate the maximum shear force and reaction with "V" and "R" respectively. For single-span beams the two value will be the same, but for multi-span beams (continuous supports) the reaction will be greater.
• To calculate the maximum deflection, you also have to enter the stiffness values "I" and "E". For a W section, switch to "steel" mode and use the "W" key to look up a shape. Switch back to "beam" mode, press "I" to enter the second moment of inertia, switch to "steel" and press "Ix" to reference that variable. In "beam" mode, assign the "steel" value of Young's Modulus and then calculate the deflection "d".

The beam calculations are based on tables in the CISC Handbook of Steel Construction. Area and line loads extend for the full span length, and the point load acts at midspan (end of span in case of cantilever). Continuous beams consider pattern loading of the entered loads.

The Calculator does not yest distinguish between ULS loads (for bending moment, shear and reaction) and SLS loads (for deflection). That's on development roadmap.

11) Design a concrete beam

To design the required reinforcement in a concrete beam:

• Select "beam" mode.
• Enter the span length "L" and loads "warea", "Wline" and/or "P".
• In "concrete" mode, enter the section dimension "b" and "h" and material grades "f'c" and "fy".
• Press "Mf" to enter the bending moment, switch to the "beam" mode and press "M+" to reference the span moment variable. You can do the same with the shear force "V", keeping in mind that maximum bending moment and shear may not occur at the same section.
• Press "As,bot" to calculate the required longitudinal bottom reinforcement and "Av" for the lateral shear reinforcement.

To calculate the capacity of a section:

• Enter the section dimensions and material grades.
• Enter the supplied reinforcement "As,bot", "As,top" and "Av". Use the rebar shortcuts in math expressions, e.g, "2 x 25M + 2 x 20M" for longitudinal reinforcement or "2 x 15M / 400" for lateral reinforcement.
• Press "Mr" and "Vr" to calculate the bending moment and shear force capacities.

All of the above will soon find its way into an in-app help system. For now, it lives in a blog post :)

Get the app on the Calculator product page.

We are pleased to introduce you to a new project we are working on: a scientific calculator (mobile app) with a structural engineering focus. We received very nice comments and suggestions from friends and colleagues. Today, We want to show you a prototype and ask for your feedback:

1. Please open centroid.app/calculator on your mobile phone. You should be able to do basic math and a few quick structural calculations.
2. Please let us know what you think of this concept. What kind of calculations would you like to see in the app for it to be useful and time-saving in your day-to-day work?

More information on the structural handheld calculator:

• You can use the calculator in one of two ways:
  • In your web browser like a regular website.
  • As a mobile app on your phone. When prompted, install it as an app. To remove it, uninstall like any other mobile app.
• It can calculate properties of a rectangular section (because it's the first thing that came to mind and it's easy). Calculate the properties, or reverse-calculate the dimensions from the primary section properties. Analysing a rectangular section is not particularly useful, but this feature will become relevant later when sizing sections for stress or deflection and when considering more complex shapes.
• It can design a reinforced concrete beam section (because we have the logic available in the Concrete Section Design prototype). Calculate the required reinforcement for a rectangular section under bending moment or shear. Or specify the supplied reinforcement and calculate the bending and shear capacity.
• Everything is dimensioned and metric. The plan is to make this adjustable and flexible.
• Concrete design is currently fixed to CSA A23.3:19.
• The plan is to add a calculation report (swipe right) that shows relevant design assumptions, calculation steps and code references that you can print or save to PDF. (Sometimes even a quick hand calculation requires a document trail.)
• This is just the start – the list of what the calculator cannot do (or does not do well) is much longer the list of things it can do. We are hoping you will tell us what should be on the "can do" list.

Get it on the Calculator product page.

If you've been following Centroid Structural for a while, you will know that we have a vision to develop design software that structural engineers will fall in love with.

We set out at the end of 2020 with the idea that developing structural design software that runs in a web browser will be an automatic success. Well, we were wrong. But not completely!

We developed a prototype application – Concrete Section Design. And then we interviewed about 20 local (Vancouver and Victoria, BC) structural engineers to hear what they think. A sample size of 20 is not big, but the number becomes significant when they all say the same thing.

Here is what we heard...

• Structural engineers have a love-hate relationship with their software. Their software can solve complex problems but tends to be overly complicated and it's difficult to experiment with design scenarios. They don't really like their software, but it gets the job done.
• Simple design tasks are often the most cumbersome to perform because software is set up for complex design cases.
• Commercial structural design software runs on Windows. Most don't mind this, but about a quarter of interviewees want to use other platforms as well. Some want to use the Mac computers at home, and some want to access their designs on their smartphone or tablet outside the office.
• Engineers mix and match modules from multiple design software packages. The main reason for this is cost – it's too expensive for firms to purchase all the modules of their preferred software package.
• Everyone uses Excel spreadsheets that perform magical design calculations. But in magic lies a problem – nobody really knows how their spreadsheets work. Some expressed concern about liability or difficulty conducting design reviews.
• Structural design software is not embracing the cloud in any meaningful way. It is possible to exchange data with other applications, but collaboration in teams is painful.
• Engineers think that their software looks like it was developed in the previous century. Maybe that is actually the case!
• Software vendors are slow to act (or don't act at all) on suggestions for improving their products. This is likely an inability to change, e.g. committed to a specific business model.

Listening to this group, we think we now have a much clearer idea of the expectations that structural engineers have of their software. Most important of all, we think it is essential that a software vendor actively engage with their customers to understand their needs. And that is exactly what we will be doing in coming months as we work on a new application. We will rely heavily on user feedback to validate our ideas for new structural design software.

You can read more about us or use our prototype:

• Concrete Section Design application: centroid.app/concrete-section

Please reach out to us with your comments and ideas. We'd love to hear from you!