How civil, mechanical and electrical engineers think, what to study, and the degree, FE and PE route into the field.

Foundations for Engineering & Energy Careers

## Why it matters

Engineers calculate constantly: loads, flows, currents, temperatures, costs. For decades those calculations lived on paper pads and in spreadsheets. Today many engineers also use short Python scripts, because a script is easy to check, easy to rerun when an input changes, and easy to hand to a colleague. You do not need to be a software developer; you need a few habits that make calculations trustworthy.

## The core idea: a calculation is a mini design document

A good engineering calculation, on paper or in code, always shows:

1. **Inputs** with units and where they came from.
2. **Assumptions** stated plainly ("water at 20 C, density 1,000 kg/m^3").
3. **Formulas** with a reference (textbook, code section, datasheet).
4. **Results** with units.
5. **A sanity check**: an independent estimate that shows the result is reasonable.

Code makes points 1, 3 and 4 explicit by its structure. Points 2 and 5 are up to you.

## Habit 1: put the unit in the name

Python numbers carry no units, so `length = 3` could be metres, feet or millimetres. Put the unit in the variable or function name instead:

```python
span_m = 6.0           # beam span in metres
load_kn_per_m = 4.5    # distributed load in kN per metre
total_load_kn = span_m * load_kn_per_m
print(total_load_kn)   # 27.0 kN
```

When you read `span_m * load_kn_per_m`, the units visibly multiply to kN. If you ever wrote `span_ft * load_kn_per_m`, the mismatch would jump out. (There are libraries, such as `pint`, that attach real units to numbers. They are worth learning later; naming is the habit that works everywhere.)

## Habit 2: one formula per function

Small functions with clear names are easy to check against the textbook:

```python
G = 9.81  # m/s^2

def weight_kn(mass_kg):
    # Weight in kN from mass in kg: W = m * g, newtons to kN
    return mass_kg * G / 1000.0
```

A reviewer can confirm `W = m x g` and the newton-to-kilonewton conversion in five seconds.

## Habit 3: build in a sanity check

Before trusting a result, compare it with something you know. One cubic metre of water has a mass of about 1,000 kg, so it weighs about 9.81 kN (roughly one tonne-force). If your tank function says a 1 m cube of water weighs 9,810 kN or 0.0098 kN, you have a unit error. You can make the check automatic with `assert`:

```python
assert abs(weight_kn(1000) - 9.81) < 0.01, "1,000 kg should weigh about 9.81 kN"
```

If the assertion fails, Python stops with your message, so a broken calculation cannot quietly produce a wrong number.

## A worked example: will the floor hold the tank?

A 1.2 m x 0.8 m x 1.0 m deep water tank will sit on a floor. Is the average pressure within 4.8 kPa? (That is 100 psf, a typical code design live load for corridors and assembly areas; a real check uses the governing code and a structural engineer.)

```text
Volume  = 1.2 x 0.8 x 1.0      = 0.96 m^3
Mass    = 0.96 x 1,000         = 960 kg
Weight  = 960 x 9.81 / 1,000   = 9.42 kN
Pressure= 9.42 kN / 0.96 m^2   = 9.81 kPa
```

9.81 kPa is about double 4.8 kPa, so the answer is **no**: the tank needs a stronger floor, a spreader platform designed by an engineer, or a different location. Notice that the pressure under a full-depth tank equals the water pressure at the bottom (rho x g x h = 9.81 kPa for 1 m), which is a second, independent sanity check.

This example is a teaching simplification. Real floor checks include the tank's own weight, concentrated loads at its feet, the floor's structure and the governing building code, and they are done or reviewed by a qualified engineer.

## Common mistakes

- **Mixing kN and N, or mm and m.** Factors of 1,000 are the classic engineering error.
- **Hard-coding numbers in many places.** Define constants like `G` once.
- **No sanity check.** A program that runs without errors can still be wrong.
- **Hidden assumptions.** If the density or code value is assumed, write it in a comment.

## Quick recap

- Treat a calculation as a document: inputs, assumptions, formulas, results and a check.
- Put units in names, keep one formula per function, and define constants once.
- Use an independent estimate (and `assert`) to catch unit errors.

## Try it

Open the **Do** tab. The script already runs; you will write the one formula that turns the tank's volume into a load in kN, and the checks will confirm it against the sanity check.


Write a small engineering calculation with units in every name and a built-in sanity check.

Engineering calculations with Python

Engineering Math Pre-Req: Quick and Dirty Introduction to Python

## Why it matters

Engineers do not invent safety rules from scratch for every project. Decades of experience, research and, sadly, failures are written down in **codes** and **standards**. Knowing which ones apply, which edition is in force, and how to read them is a core professional skill. On the FE and PE exams you will be expected to use them; on the job, failing to follow them can cost lives and licences.

## Codes versus standards

The words are often used loosely, but there is a useful distinction:

- A **standard** describes how to do something well: how to test the strength of concrete, the dimensions of a bolt, the method for calculating wind loads, the safety requirements for a machine guard. On its own, a standard is **voluntary**.
- A **code** is a set of requirements intended to be adopted into law, usually by a government. Once adopted, it is **mandatory** in that jurisdiction. Codes often reference standards, which makes those standards mandatory too.

Example: a city adopts the International Building Code (a model code). The building code references ASCE 7 for structural loads and ACI 318 for structural concrete. Through that chain, the load and concrete standards become legally required for buildings in that city.

## Who writes them?

Most US codes and standards are written by private, non-profit **standards developing organisations (SDOs)** using committees of volunteers: engineers, manufacturers, regulators, insurers and users. Many SDOs follow a consensus process accredited by **ANSI** (the American National Standards Institute), with public review and the right to appeal. A few you will meet:

| Organisation | Known for | Discipline |
|---|---|---|
| ICC (International Code Council) | International Building Code (IBC), Residential Code (IRC) | Civil, mechanical, electrical (buildings) |
| ASCE | ASCE 7: minimum design loads (wind, snow, earthquake) | Civil |
| ACI, AISC | Concrete (ACI 318) and structural steel (AISC 360) | Civil |
| ASME | Boiler and Pressure Vessel Code, piping, dimensioning | Mechanical |
| ASHRAE | Ventilation, energy efficiency | Mechanical |
| NFPA | NFPA 70, the National Electrical Code (NEC); fire codes | Electrical, fire |
| IEEE | Power system and electronics standards (for example, the National Electrical Safety Code for utilities) | Electrical |
| ASTM International | Test methods and material specifications | All |
| ISO / IEC | International standards | All |

Government agencies also write mandatory rules directly, such as OSHA workplace safety regulations and state transportation department specifications.

## How a model code becomes law

1. An SDO publishes a new edition of a model code, typically on a three-year cycle.
2. A state or local government **adopts** it, often with local **amendments** (for example, stricter snow loads in mountain areas).
3. Adoption takes time, so jurisdictions are often one or two editions behind the latest one.
4. The local **authority having jurisdiction (AHJ)**, such as the building department, reviews plans and inspects work for compliance.

That is why the first question on any project is: **which code, which edition, with which local amendments?** The answer is on the AHJ's website or from the building department, not on the cover of the newest book. Editions and adoption status change; check the publisher and your AHJ. For example, see the ICC at [iccsafe.org](https://www.iccsafe.org) and NFPA at [nfpa.org](https://www.nfpa.org). Checked on 2026-10-23.

## A worked example

A mechanical engineer is designing a pressure vessel for a factory in Ohio. Questions to answer before calculating anything:

- Does the state require vessels to be built to the ASME Boiler and Pressure Vessel Code? (Most states regulate boilers and pressure vessels through a state inspector.)
- Which section and edition applies?
- Which ASTM material specifications are acceptable for the steel?
- Does the owner (the factory) have its own engineering standards on top of the code?

The design is then documented with references to the exact code clauses used, so a reviewer can check every step.

## Common mistakes

- **Using the newest edition when the jurisdiction adopted an older one** (or the reverse).
- **Treating codes as the goal.** Codes are **minimums**. A design can meet code and still be a poor design.
- **Ignoring local amendments.**
- **Quoting a standard from memory.** Always cite the clause and edition you actually used.

## Quick recap

- Standards are voluntary best practice; codes are written to be adopted into law and then become mandatory, often pulling standards in by reference.
- Most are written by consensus committees at SDOs such as ICC, ASCE, ASME, NFPA, IEEE and ASTM.
- Jurisdictions adopt specific editions with amendments, and the AHJ enforces them.
- Always confirm the code, edition and amendments before designing.


Explain who writes engineering codes and standards, and how a model code becomes law.

Codes and standards

How Codes and Standards Work Together | TCA 12

Code vs Standard: What’s the Difference? (ASME/API Explained for Engineers)

## Why it matters

Engineers make decisions that other people trust with their lives without ever knowing the engineer's name: the people crossing a bridge, working next to a machine, or flipping on a light switch. That trust is why engineering has a formal ethics code, why licensed engineers can lose their licence for misconduct, and why ethics appears on the FE exam. Ethical problems rarely look dramatic at first. They usually start as a small shortcut under schedule pressure.

## The NSPE Code of Ethics

The **National Society of Professional Engineers (NSPE)** publishes a widely used Code of Ethics for Engineers. Its six **Fundamental Canons** say engineers, in the fulfilment of their professional duties, shall:

1. Hold paramount the safety, health, and welfare of the public.
2. Perform services only in areas of their competence.
3. Issue public statements only in an objective and truthful manner.
4. Act for each employer or client as faithful agents or trustees.
5. Avoid deceptive acts.
6. Conduct themselves honourably, responsibly, ethically, and lawfully so as to enhance the honour, reputation, and usefulness of the profession.

The order matters. Canon 1 comes before Canon 4: when loyalty to your employer or client conflicts with public safety, **public safety wins**. The full code, with its detailed rules of practice, is on [nspe.org](https://www.nspe.org); state licensing boards also have their own rules of professional conduct, which are legally binding for licensees. Checked on 2026-10-23.

## A real case: the Hyatt Regency walkway collapse

In 1981, two suspended walkways in the atrium of the Hyatt Regency hotel in Kansas City, Missouri, collapsed during a crowded event, killing 114 people. The original design hung both walkways from continuous steel rods running from the ceiling. During construction, a change was proposed so that the upper walkway hung from the ceiling and the lower walkway hung from the upper walkway, using two shorter rods. That change roughly doubled the load on the connection at the upper walkway, which was already marginal. The change was approved without the calculations that would have revealed the problem.

Investigations found the engineers of record responsible, and they lost their engineering licences in Missouri. The lessons are still taught everywhere:

- **Design changes need the same rigour as the original design.** A "small" detail change can transform the load path.
- **The engineer who seals the drawings is responsible** for what they approve, including shop drawings prepared by others.
- **Communication failures kill.** Responsibility for checking the change fell between the fabricator and the engineers.

## Applying the code: a scenario

You are an EIT at a firm designing a pedestrian bridge. Your supervisor asks you to finish the connection calculations by Friday so the drawings can be issued. On Thursday you find that one connection, as drawn, does not meet the required capacity. Fixing it means a redesign and a one-week delay. Your supervisor says, "Issue it; we'll fix it in the field."

Work through it with the canons:

- **Canon 1:** a connection that does not meet capacity is a public safety issue. It takes priority over the schedule.
- **Canon 2:** as an EIT, you are not the engineer of record; you need your supervising PE to review the problem.
- **Canons 3 and 5:** you cannot misstate or hide the result.
- **Canon 4:** being a faithful agent means protecting the client from a defective design, not helping them issue one.

A good response: document the calculation clearly, raise it in writing with your supervisor, propose a fix and an honest schedule, and, if it is ignored, escalate within the firm (a senior principal or quality manager). NSPE's code also says that if an engineer's judgement is overruled in circumstances that endanger life or property, they shall notify their employer or client and other authority as may be appropriate. Most problems are solved at the first step, when someone states the facts clearly and early.

## Safety is an engineering responsibility

Engineers design for safety with **factors of safety** (designing for loads larger than expected), **redundancy** (more than one load path or backup system), **fail-safe** behaviour (a system that fails into a safe state) and **hazard analysis** (asking "what could go wrong?" before it does). On site and in the lab, engineers also follow workplace safety rules. Visiting a construction site, plant or substation requires the employer's safety training, the right PPE and an escort or supervisor; this course gives awareness only, not that training.

## Common mistakes

- **Thinking ethics is only about bribery.** Most cases involve competence, honesty and safety under pressure.
- **Staying silent because you are junior.** Raising a concern early and in writing is part of the job.
- **Approving what you did not check.** A seal or signature means "I am responsible for this."

## Quick recap

- The NSPE code's first canon is to hold public safety, health and welfare paramount.
- Practise only within your competence, be truthful, be a faithful agent, avoid deception.
- The Hyatt Regency collapse shows how an unchecked design change and unclear responsibility can be fatal.
- When safety is at stake: document, raise it in writing, propose a fix, and escalate if needed.


Apply the NSPE Code of Ethics to a real-world scenario where public safety is at stake.