physics

Unreinforced masonry building

Unreinforced masonry building is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Unreinforced masonry building rather than just read about it. In short: An unreinforced masonry building (or UMB, URM building) is a type of building where load bearing walls, non-load bearing walls or other structures, such as chimneys, are made of brick, cinderblock, tiles, adobe or other masonry material that is not braced by reinforcing material, such as rebar in a concrete or cinderblock. The term is used in earthquake engineering as a classification of certain structures for earth…

Key takeaways

Unreinforced masonry building belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Unreinforced masonry building to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Unreinforced masonry building from memory before moving on to harder problems.

Reference excerpt

An unreinforced masonry building (or UMB, URM building) is a type of building where load bearing walls, non-load bearing walls or other structures, such as chimneys, are made of brick, cinderblock, tiles, adobe or other masonry material that is not braced by reinforcing material, such as rebar in a concrete or cinderblock. The term is used in earthquake engineering as a classification of certain structures for earthquake safety purposes, and is subject to minor variation from place to place.

Problems

URM structures are vulnerable to collapse in an earthquake. One problem is that most mortar used to hold bricks together is not strong enough to survive the vibrations without cracking. Additionally, masonry elements may "peel" from the building, and fall onto occupants or passersby outside. In California, the 1933 Long Beach earthquake resulted in a near-immediate statewide ban on construction of new unreinforced masonry school buildings and the Field Act. A State law enacted in 1986 required seismic retrofitting of existing structures. Retrofits are relatively expensive, and may include the building being tied to its foundation, tying building elements (such as roof and walls) to each other so that the building moves as a single unit rather than creating internal shears during an earthquake, attaching walls more securely to underlying supports so that they do not buckle and collapse, and bracing or removing parapets and other unsecured decorative elements. Retrofits are generally intended to prevent injury and death to people, but not to protect the building itself. According to the 2006-04 California seismic safety commission report, there are still 7800 URM buildings with no retrofitting in the state, including 1100 in the city of Los Angeles. The California law left implementation and standards up to local jurisdictions. Compliance took many years, and as of 2008, most (but not all) of the unreinforced masonry buildings in San Francisco have undergone retrofitting. There is particular cause for concern in regions which can generate strong earthquakes, but only rarely. Such regions may not have regulations limiting the construction of UMBs, or have only implemented them recently. Public awareness of earthquake safety may be low. For example, the Wasatch Fault in the U.S. state of Utah closely parallels the state's most populous metropolitan area, the Wasatch Front (which includes the state capital Salt Lake City). The Wasatch Front has a population of 2 million, and contains 200,000 UMBs compared with the entire state of California's 25,000. Utah has recently retrofitted many public UMBs to better withstand earthquakes, but most UMBs in the state are private homes.

The lack of earthquake codes preventing the construction of UMBs was a major factor in the high death toll in the 2010 Haiti earthquake.

Illustrations

Worked examples

Example 1 — a first encounter with Unreinforced masonry building

Start with the simplest possible case. Write down what Unreinforced masonry building claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Unreinforced masonry building before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Unreinforced masonry building ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Unreinforced masonry building

In research: Unreinforced masonry building appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Unreinforced masonry building in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Unreinforced masonry building is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earthquake and seismic risk mitigation, Earthquake engineering, Masonry buildings and structures, so understanding it makes those chapters shorter.
In everyday life: Look for Unreinforced masonry building outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Unreinforced masonry building in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Unreinforced masonry building means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Unreinforced masonry building out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Unreinforced masonry building in simple terms?

Why does Unreinforced masonry building matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Unreinforced masonry building?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Unreinforced masonry building.