What are Bridge Bearings?

The Coefficients of Steel and Concrete

A concrete column
Concrete column supporting the highway above. Photo by SS

In our previous articles, we discussed the mineral components of steel and concrete. In this article, we will dwell further into the element’s composition and how they are affected when there are changes in temperature. 

All elements on our planet change in size when the temperature increases or decreases; although very minimally, but when dealing with the engineering of buildings and bridges, this change, however slight, could become catastrophic if not properly addressed and compensated for.

Such is the case for iron, steel, and concrete. They expand and compress as the temperatures increase and decrease, respectively. A good way to remember which direction they are moving is: increase = expansion and decrease = compression.

Each element has a specific temperature coefficient. Even if it is just a tiny amount, if there is not enough room for the material to ‘stretch’ (expand) or decrease (compress), it will show signs of wear, and after a time, it could break and everything above it will collapse. In this table, we can see how much materials expand or contract per degree.

For the mathematically inclined:

If 1 mile = 5280 feet, then 1 mile equates to (12 5280’) = 63360”.
1 inch of steel expands 0.00000645” for every 1 degree Fahrenheit increase in temperature; therefore, 63360” 0.00000645” = 0.408672 inches per degree.

Thus, as the weather gets warmer, steel will expand 0.408672 inches for every one degree in temperature.

Material Expansion and Compression MUST be Compensated for in Construction!

In this Pipes and Tubes Temperature Expansion table, you can see the minimal effect of stresses that are placed on certain metals; however, if not compensated for, the integrity of the elements will be compromised.

The question then is, what happens to bridges that have steel columns? If they expand and compress without freedom of movement from temperature differentials, the steel will eventually crack and can lead to a defective bridge.

Enter Bridge Bearings

The answer is bridge bearings (previously called rollers) that allow for the stresses of the steel to move in either direction.

In the photo below, a cylindrical bearing is placed between the vertical supports, called piers, that would otherwise be permanently fastened to each other. The bearings in between them allows for the bridge to expand and compress freely.

A bridge bearing
Photo by SS

In summary, the function of a bridge bearing is to transmit and distribute superstructure loads to the substructure (bridge) and permit the superstructure to undergo the necessary movements of stress, which can consist of compression, shear, and rotation, consequently preventing overstress, which would otherwise compromise the structural integrity of the bridge. 

Bridge Bearing Types

There are several types of bridge bearings utilized and are dependent upon a number of different factors, including the length of the bridge span. The oldest bridge bearing involves just two plates resting on top of each other. 

Here is a good illustration of bridge-bearing plates. It depicts quite well how the plates are stacked on top of each other, as well as the limitations placed on it, such as the guide block, which prevents the plates from sliding off. This plate scheme can be seen on many bridges, especially those that span highways and parkways.

A common form of a modern bridge bearing is the elastomeric bridge bearing, which is more common today. Besides freedom of material stress, they also extend the life of the bridges by reducing continuous wear and tear on the bridge materials. 

The Bay Bridge collapse after the 1989 7.1 magnitude Loma Prieta earthquake is a perfect example when using inadequate bearings for a structure, especially within an earthquake zone. The use of elastomeric bridge bearing should help to alleviate the engineering errors that caused this part of the road to collapse.

As you travel, you might want to locate the bearings on the bridges you drive on, and now, have a better idea of what those things are that are attached to your bridge.


Everything You Need to Know About Amber

Amber Crystal If you’re looking for a gemstone that truly showcases the uniqueness of nature, an amber gem is a perfect choice for you. With a history of tens of thousands of years, amber is one of the oldest minerals that have been used for jewelry. Popular for its golden hues and simplicity, this gemstone is a must-have for collectors.

That said, let us walk you through a complete guide to amber.

What is Amber?

Amber is actually tree resin that has been fossilized. Resin is a fluid that flows from certain trees, primarily conifers like pine trees. This resin often contains insects that have been fossilized in it with time. The reality is that most of the inclusions in amber are actually ants, mosquitoes, and other living organisms, some of which are long gone. As a result, scientists use amber to learn more about ancient living organisms.

Amber may be burned since it is such a soft stone, and it also emits a pine-scented perfume. Additionally, when heated under the right conditions, this gemstone can potentially produce oil.

Amber, unlike most other gemstones, has a wide range of applications. It’s been used to create tobacco pipes and remove lint from clothes (owing to its abrasive properties). It’s also used to produce perfume and in traditional medicine. Even today, in the Western world, amber necklaces and bracelets are popular among mothers who feel it is a natural pain reliever for their children (there is no scientific evidence to prove this, though).

How to Evaluate Amber Gemstone

Like all other gemstones, amber is also evaluated on the basis of the 4Cs: color, cut, clarity, and carats.


Amber is available in many colors. The most popular and widely recognized shades are yellow and cognac. However, you can also find this gem in black, green, white, and butterscotch.

Yellow amber is, of course, the most popular variety due to the rarity of the other colors. The yellow hues of amber can range from orange to brown, depending on the bubbles in it.

Green amber is one of the rarest varieties that are extremely rare and valuable. Also known as cherry ambers, red ambers are a slightly rusty color and can be found in golden red to dark brown shades. Black amber is a very dark brown or red color that is formed due to the mixture of tree resin with soil or other dark inclusions.


Unlike most other gemstones, the beauty of the amber gem lies in its imperfections, especially the inclusions it features within. This gemstone is almost always found with inclusions. However, interestingly, although eye-clean amber is valuable, amber featuring interesting inclusion patterns is typically more expensive.


Amber is most cut into cabochons, with oval and round shapes being the top choice. However, this gem is also available in many other cuts, including hexagon, pentagon, hearts, triangles, and stars. Amber is pretty easy to cut due to its softness, but many jewelers choose to heat the stone to shape it instead of cutting the gem. It’s important to remember that this doesn’t change the gem’s natural properties.

Carat Weight

Amber is an extremely lightweight stone that can even float on saltwater. Even the larger size ambers are very light to hold. So, even if you buy a big amber, it will weigh less than a diamond or emerald of the same size.

Amber Jewelry

Amber is used in many jewelry pieces, including rings, necklaces, brooches, bracelets, earrings, pendants, and cufflinks. Amber’s inclusions can be eye-catching, and it’s generally beautiful from a scientific and historical standpoint.

There are two main perceptions when it comes to metals to mount amber in. Some people prefer silver-colored metals, such as white gold, as settings for their amber gemstone. The main reason behind this is the wonderful contrast of the warmness of amber and the cool tones of silver metal. Either way, silver-colored metals are believed to accentuate the charm of an amber gemstone.

On the other hand, some people choose to utilize yellow gold or rose gold settings for their amber jewelry. While these metals don’t provide as much contrast as silver, they tend to soften the color of the amber and blend well into the stone. The bottom line is that there isn’t any right or wrong choice; it’s all a matter of what you prefer.

Enhanced Amber

One very important factor you need to know about amber is that jewelers often enhance it. Almost every gemstone undergoes various treatments to help enhance its color, clarity or to improve its durability.

Here are a few ways in which an amber gemstone may be enhanced:

To Improve Clarity

Amber gemstones that seem cloudy due to the prominent appearance of tiny bubbles aren’t quite as valuable as other varieties. Therefore, jewelry makes efforts to improve the stone’s clarity by boiling it in rapeseed or linseed oil. An amber stone is slowly heated up in this oil to a boiling point, filling up the tiny bubbles with oil, which removes traces of any bubbly inclusions.

To Improve Color

Since red and green ambers are extremely rare and expensive varieties, some jewelers attempt to change the more commonly found yellow-amber color. For this purpose, they apply a black paste to the gemstone’s surface, then heat the gem to improve its clarity while allowing it to bond with the paste. Some jewelry makers also modify an amber gemstone through dyeing and other heat treatments to change or enhance their color to imitate the color of the more expensive varieties.

Where Can You Buy Amber?

Amber is a pretty popular gemstone with relatively high demand, so it should be very easy to find amber jewelry at your local jewelry store. However, if you’re looking for more options, you can always explore the web to find amber jewelry that suits your taste.

The bottom line is that although soft, amber is a beautiful-looking gem with a stunning color that requires considerable care and attention. We hope that this guide to amber helps you make the right choice when it comes to buying amber jewelry.