How bridges are built over water? | By Interesting Engineering

 🎧 Listen (for comprehension): Source 👉 How bridges are built over water?

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Bridges are marvels of engineering that stand inconspicuously amongst us. We don't think of them much even when we are passing over them. Nowhere are these structures more impressive then when they are built over water which brings us to the question; how are bridges built over water? 

When the water is shallow, construction is easy. A temporary foundation is made on which piers are built to support the upper structure and the bridge is then built! It's when the water is deep that other techniques are needed. There are many methods to complete such a task in deep water but here we will explore the main three. These three methods of bridge-building are called battered piles, cofferdams, and caissons. 

Let's begin with battered piles. These are poles that are driven into the soil underneath the water. Piles are hammered into the water until they turn outward or inward at an angle. This makes the piles firm and increases their ability to carry lateral loads. Piles are inserted in the ground using pile drivers. These are mechanical devices that may be transported to a location on a floating pile driving plant. Pile drivers may also be cantilevered out over the water from piles that have been installed in advance. With the use of pile frames, pile hammers, and winches, pile drivers hammer the piles into the soil until they turn outward or inward at an angle. The piles are now ready to carry lateral loads and can provide the foundation of support for the bridge. The next step is to construct the pile caps above the piles. Once this is done the bridge is ready to be built. 

Next up are cofferdams. These are temporary enclosures made by driving sheet piling into the bed of a body of water to form a watertight fence. This is called the cofferdam. There's more to this bridge-building technique. Once the sheet piles have been inserted in the water to create a cofferdam. The water is pumped out of the enclosure. Now, the construction workers can build the bridge as if they are working on dry land. The process then becomes relatively easy. 

Finally, caissons may be used. There are two types of caissons: open and pneumatic. An open caisson is a structure that is usually shaped like a box. It is open at the top and bottom. The caisson is usually constructed on land then floated into position and sunk so that the upper edge is above water level. The caisson has a cutting bottom edge so that it sinks through the soft silt on the bed. Inside is a series of large pipes or dredging wells. These are used to dredge up the bed material. As more material is dredged up the caisson sinks and more sections are added to the shaft to keep it above water. 

Once the caisson reaches the correct depth, concrete is laid to seal the bottom and then more concrete is poured into the caisson to form a solid post. A pneumatic caisson is similar to an open caisson but it has an airtight bulkhead above the bottom edge. This is fitted with airlocks. The space between the cutting edge and the bulkhead is called the working chamber. In this space, the water is removed using air pressure. Construction workers can then enter the chamber and excavate the soil. It is important that the air pressure in the chamber be carefully monitored so the workers do not get the bends. 

But how do engineers pick which technique to use? This all depends on the condition of the site and the technology available. These are important decisions to make that only experts can fully handle. Now that you know a bit more about how bridges are built you can admire them even more. After all, all bridge-building techniques are impressive feats of Engineering.

🗪 Discussion (create fun & interesting role-play): 

1. Warm-Up Questions:
2. Comprehension Questions:
3. More Discussion Questions:

✍ Vocabulary Review (find the word in the text that is suitable to each below description): 

1. in a way that is not easily or quickly noticed or seen
2. having only a short distance from the top to the bottom
3. a low structure built at the edge of water, used especially for getting into and out of boats
4. A pile driven at an inclination to the vertical to provide resistance to horizontal forces
5. to hit or kick something with a lot of force
6. relating to the sides of an object or plant or to sideways movement
7. Support by a long projecting beam or girder fixed at only one end (used in bridge construction)
8. a machine that lifts heavy objects by turning a chain or rope around a tube-shaped device
9. an area surrounded by fences or walls
10. having no openings to allow water to get in
11. operated by air pressure
12. Go down below the surface of something, especially of a liquid; become submerged.
13. sand or soil that is carried along by flowing water and then dropped, especially at a bend in a river or at a river's opening
14. to remove unwanted things from the bottom of a river, lake, etc. using a boat or special device
15. a deep hole in the ground from which you can get water, oil, or gas
16. to cover a surface with a special liquid in order to protect it
17. completely closed so that no air can get in or out
18. a wall that divides the inside of a ship or aircraft
19. something difficult needing a lot of skill, strength, courage, etc. to achieve it

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Building with Concrete vs. Wood - Which is Safer? | By Civil Mentors

 🎧 Listen (for comprehension): Source 👉 Building with Concrete vs. Wood - Which is Safer?

👄Read aloud (repeat after audio):

Wood and concrete have been used in construction for thousands of years and for a good reason. Both materials have properties that make them appealing building materials. In this video, we will tackle the age-old debate between wood and concrete. But before we dive headfirst into this heated debate, there are a few considerations you need to keep in mind. As professionals in construction, we know that you can look at this question from various perspectives, which ultimately affects your interpretation of the advantages and disadvantages listed below. We also recognize the distinction between immediate advantages and long-term benefits. In other words, the benefits that material provides in the long term may outweigh the drawbacks you experience today. Therefore, you should keep your own priorities in mind as you watch this video. 

According to a study, concrete is the second most used material after water, and there are lots of reasons why it is so popular. Still, there are advantages and disadvantages to using concrete as a building material: 

On the other hand, when we think of wood we often imagine a natural, sustainable, and environmentally friendly building material. And in many ways, it is. Wood stores carbon dioxide, which results in a reduction of carbon dioxide emissions by 2432 metric tons (equal to taking 500 cars off the road for a year). It is inexpensive, light, and easy to work with. A natural resource (readily available, presenting promising opportunities). 

On the other hand, concrete is often criticized for being unsustainable as it takes a lot of resources to produce. Cement, a main component of concrete is one of the world's biggest contributors to greenhouse gas emissions. Many people assume that because cement production is bad for the environment, so is concrete production. But the truth is far more complicated than that. Let's take a closer look. Concrete is durable - its lifespan is actually two or three times longer than other common building materials. Concrete is great at absorbing and retaining heat, which means it will increase the energy efficiency of a building and reduce HVAC expenses. Its reflective properties will decrease air conditioning costs in the hot summer months. Concrete produces little waste as it can be produced in batches specific to project needs. 

So now the question is which is safer concrete or wood? 

Last but not least, there's safety. In general wooden structures are not as safe as concrete buildings. Wood is vulnerable to external threats like fire, wind, insects, and moisture. All of which can result in structural damage and safety risk. While concrete is a durable, strong material, it too poses some safety risks. For example, if a concrete structure collapsed, either at a jobsite or once the building is occupied, falling concrete could seriously injure anyone who is nearby. Also, if you are a builder working with dry or wet concrete, you may experience irritation of the eyes, nose, throat, or skin. Furthermore, exposure to silica, a made ingredient in dry concrete, can even cause far more serious health issues, including lung cancer. Now that you know everything about building with concrete and wood, which one would you choose?

🗪 Discussion (create fun & interesting role-play): 

1. Warm-Up Questions:
2. Comprehension Questions:
3. More Discussion Questions:

✍ Vocabulary Review (find the word in the text that is suitable to each below description): 

1. attractive or interesting
2. to try to deal with something or someone
3. (a) serious discussion of a subject in which many people take part
4. the act of thinking about something carefully
5. a particular way of considering something
6. finally, after a series of things have happened
7. an explanation or opinion of what something means
8. a difference between two similar things
9. to be greater or more important than something else
10. a disadvantage or the negative part of a situation
11. something that is very important and must be dealt with before other things
12. able to continue over a period of time
13. the act of making something, or of something becoming, smaller in size, amount, degree, importance, etc.:
14. the act of sending out gas, heat, light, etc.
15. to express disapproval of someone or something
16. to accept something to be true without question or proof
17. involving a lot of different parts, in a way that is difficult to understand
18. the length of time for which a person, animal, or thing exists
19. to keep or continue to have something
20. the good use of time and energy in a way that does not waste any
21. able to send back light, hear, energy, or sound from a surface
22. a group of things that are dealt with or produced at the same time
23. able to be easily physically or mentally hurt, influenced, or attacked
24. to cause something, especially a problem or difficulty
25. (of a structure) fall down or in; give way.
26. (of a building, seat, etc.) being used by someone.
27. a painful or sore feeling in a part of the body
28. The state of being exposed to contact with something.

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Building of underwater structures | By Interesting Engineering

 🎧 Listening comprehension: Source 👉 Building of underwater structures

👄Read aloud:

Bridges, tunnels, dams, these monoliths of infrastructure are all around us. However, if you take a moment to really think about these structures, you might start to wonder how they were even built in the first place; how do engineers construct the foundation of bridges; when they're fully underwater; does it require a skilled team of divers working with concrete; or can the foundation simply be dropped into place; The main ways engineers build structures underwater are through cofferdams, caissons, or newer methods like drilled shaft foundations. All three of these construction techniques involve some manner of construction underwater or in the water. And they also require a bit more information to fully understand.

Let's start with cofferdams. Cofferdams are temporary structures, usually made out of welded steel sheet piles or other rigid interlocking materials which can be arranged in the riverbed or seabed around a construction site. Once a fully enclosed space has been created, the water inside is pumped out, leaving a dry workspace. Early cofferdams were made out of simple dirt mounds in the water, but these were dangerous and prone to failure. Later cofferdams then shifted to wooden piles and structures. With today's custom steel framework or piles being the safest type ever made, cofferdams are commonly used for bridge foundation construction or for pier construction closer to shore. Cofferdams are also used to put ships into dry dock to allow crews to do maintenance. For dam construction, engineers will often construct cofferdams first to keep the dam dry while they finish construction. The temporary cofferdams will then be removed and the dam structure itself allowed to serve its intended purpose. In this way, one builds a dam by first building several temporary dams, close in function to cofferdams but slightly different is a caisson. 

Caissons are essentially large concrete or steel boxes that are pushed into the seafloor, and then similar to cofferdams, the water is pumped out of the inside; however, unlike cofferdams, caissons are one solid structure. These structures will usually have crew access ports to allow workers to access the inside. Caissons and cofferdams are some of the main methods for underwater construction. They both create a dry workspace allowing work to proceed; However, they are also very expensive and are still relatively dangerous. Anytime workers are inside one of these structures, they are at risk of catastrophic failure and collapse of the dams. It's for this reason that engineers are constantly trying to find new safer underwater construction methods. 

One of the newest methods is that of drilled shafts. Drilled shafts are exactly what they sound like. Massive shafts that are drilled into the river or seabed. These shafts can be drilled with equipment mounted on barges or other structures, meaning that caissons or cofferdams are not needed for these constructions. Once the shaft is drilled, they can be backfilled with concrete or other reinforcing structures. This entire process allows engineers to avoid the dewatering process altogether. When it comes to how engineers build structures underwater, the real answer is that they try to avoid it when they can. Even for structures like bridges and tunnels, engineers will work to build as much of the structure on the surface as possible. Dewatering and underwater construction are highly expensive and dangerous endeavors but clever engineers have developed innovative engineering methods over the years to make the process as efficient as possible or even eliminate the need for it altogether.

🗪 Discussion: 

1. Warm-Up Questions:
2. Comprehension Questions:
3. More Discussion Questions:

⏺ Record

How to make concrete green | Bill Gates

 💚 Cre: Bill Gates | How to make concrete green

1. Reading comprehension:

The world is expected to add more than two trillion square feet of new building space by 2060. That's the equivalent of adding another New York City every month for the next 40 years. Many of these buildings will be made using cement, a massive emitter of greenhouse gases. But a company in Canada discovered an innovative way to reduce cement's carbon footprint. (Bill Gates)

The effects of climate change are going to happen. We're seeing it every day. But this is a solvable problem. Our industry can decarbonize. Cement is the glue. It's the active ingredient in making concrete and is the product that we build a modern society with. (Rob Niven - CEO & Founder, Carbon Cure Technologies) 

People often ask, "What is the difference between cement and concrete?" Cement is really the chemistry behind concrete. The simple analogy would be if you're baking a cake, the flour would be the cement and the cake would be the concrete, the finished product. (Bob Haldrup - Senior Vice President, Irving Materials, Inc)

To make concrete, you dig up limestone from the ground and then you run that through a kiln. Each pound of limestone that you put into this kiln, one-half goes up into the atmosphere as CO2. Carbon Cure is a technology company helping concrete producers transition into the new low-carbon economy. We developed a technology that bolts onto an existing concrete plant. We're starting with a greenhouse gas, a harmful waste product and we're turning that into value.  We add a small amount of CO2 to react with the chemistry from cement that allows you to create a higher-strength concrete. Carbon utilization is not just some abstract idea. It's not just happening in the lab. It's happening in the real world. (Rob Niven) 

The concrete industry has worked for years on sustainability and so now we're looking for new technology and Carbon Cure sequesters that CO2 into the concrete, locks it in forever. (Bob Haldrup)

Then you can actually lower the amount of cement in that concrete, it's really taken hold, and it's building real things that we can live in and drive on every single day with overpasses and roads, airports, aquariums, or it could even be tech campuses. Carbon Cure is on a mission to reduce 500 megatons of CO2 emissions per year. That is the equivalent of taking 100 million cars off the road or the equivalent of the CO2 reductions from 500 million acres of trees annually. (Rob Niven) 

We're finding in the marketplace, both with our customers and internally, people are proud to work for someplace that is taking care of the environment. (Bob Haldrup)

I'm doing it for my family. I'm doing it for my daughter. There's a real human toll to climate change, but absolutely the solutions are there. (Rob Niven) 

2. Listening & Speaking

3. Role-playing

4. Make your own talk with the below words:

Environmental Impacts of Concrete and its Solution | Civil Mentors

 💚 Cre: Civil Mentors | Environmental Impacts of Concrete and its Solution

1. Reading comprehension:

Growing concerns about the environment and climate change, in particular, have highlighted another major problem with concrete: After transportation and energy, cement production is the third biggest source of carbon dioxide emissions. That's partly because the process of making cement releases a lot of carbon dioxide, but also very importantly because of the enormous amount of cement and concrete used worldwide. 

Carbon dioxide is released in two quite different ways: 

First, because of the fossil fuel energy used during the manufacture of cement; 

Second, because cement is produced when calcium carbonate turns to calcium oxide, releasing carbon dioxide in the process. 

Concrete relies on cement, so it's anything but a sustainable material, which worries engineers, in particular because they tend to be very environmentally conscious. Since carbon dioxide is released in two ways during cement production, it follows that there are two ways of making more environmentally-friendly concrete. 

Historically, since the Industrial Revolution, much of humankind's energy has come from burning coal, which releases more greenhouse gases than other fuels, and traditionally cement kilns were coal-fired too. 

Switching them from coal to natural gas is one solution since gas releases less carbon dioxide for a given amount of energy. Making cement kilns more efficient reduces the total energy they need, which also reduces their carbon dioxide emissions. 

The other solution is to reduce the amount of cement in the concrete mixture by using recycled materials, such as fly ash from incinerators. 

Another exciting prospect is the development of concrete that doesn't use calcium carbonate at all. Instead, the carbonate is made by bubbling carbon dioxide from a power plant through seawater. This has an overall environmental benefit since it takes the harmful waste CO2 emissions from power plants and turns them into very useful concrete instead. It's a kind of carbon capture and storage. 

Another environmental drawback of concrete comes from its use of aggregates, which have to be quarried often from environmentally sensitive areas such as river valleys. Using recycled aggregates (including recycled concrete from old demolished buildings) is a possible solution here.

2. Listening & Speaking

3. Role-playing

1. What aspect of the construction industry affects the environment?
2. The cement manufacturing industry ranks in terms of carbon emissions?
3. Why have such a great amount? 
4. How is Carbon dioxide released?
5. Why do people know about the impact of cement production but still use it?
6. What fuel is used in the cement kiln?
7. Is there any way to minimize the CO2 during cement production?
8. Can we reduce the amount of cement in the concrete mixture by using recycled materials?
9. Another exciting prospect is the development of concrete that doesn't use calcium carbonate at all, how does it work?
10. What is the environmental drawback of concrete coming from its use of aggregates?

4. Make your own speech with the below words:

concerns, carbon dioxide, emission, enormous, fossil fuel, calcium carbonate, calcium oxide, sustainable, conscious, cement kiln, coal-fired, fly ash, incinerators, bubbling, power plant, drawback, river valleys

Personal Protective Equipment in Construction | Thestructuralworld

💚 Cre: Thestructuralworld | Personal Protective Equipment (PPE) in Construction

1. Reading comprehension:
In construction, different site personnel has their own responsibilities. These employees are working together to achieve a common goal which is to complete the construction project that they are involved in.  From blue-collar to white-collar job responsibilities, each had their own contribution to get the project done. Site construction involves vigorous activity. These activities are often prone to accidents, risks, and maybe hazard to the lives of the workers involved in a construction project. Nevertheless, the safety of each individual working in a construction environment is the primary priority to be achieved.
Just like safety in structural design is a must, work environmental protection should also be taken seriously. In doing so, each worker’s PPE or Personal Protective Equipment should be strictly implemented at the site at any cost at any given time. To satisfy PPE standards, each worker should wear proper construction attire to reduce or at least prevent and protect them against the safety risks to be able to achieve Health and Safety Environment throughout the course of the construction.
Here are the lists of Personal Protective Equipment (PPE) in Construction that every construction personnel should observe:
1. Head Protection/Safety Helmets/Hard HatIn the construction worksites, there is a higher chance of possible head injury due to falling debris and other related accidents.  Site Engineers and all construction personnel involved in site activities should wear a safety helmet or hard hat before entering the worksite and it should be worn at all times. The safety helmets/hard hat shall meet the specifications contained in the technical guidelines issued by the Specialize Department in accordance with international standards- OSHA or ANSI z89.1 Safety helmets/hard hats should be inspected by the safety officer to ensure that it is safe and reliable to use. It should be free from cracks and the proper shock-absorbing lining of the helmet should be in good condition. 
2. Foot Protection/Safety Shoes
Safety shoes should be worn by all of the construction personnel at the worksite to protect their feet from possible injuries. The safety shoes to be used shall be determined according to potential hazards and according to the nature of work. It shall comply with the safety standard and specifications.  For worksite safety shoes with steel toe cap covering and steel sole should be considered, although an equivalent material is also acceptable as long as it follows the safety standards. If the personnel is working in electrical installation, non-contractive footwear shall be used. 
3. Protective Clothing/Reflected Vests
Every construction personnel should wear adequate and suitable protective clothing to protect them from possible hazards due to weather changes, electricity, impacts, and other risks. For Site Engineers a reflected vest is recommended to maintain visibility when doing site inspections and other site activities. 
4. Eyes and Face Protections
Construction employees shall be provided with eye and face protection equipment when their job had a potential risk of exposing the eyes and face from hazard. They are the machines operators, welder, bar bender, and the like. Those workers whose vision requires the use of medical spectacles shall be protected by eyeglasses with protected lenses, goggles that can be worn without disturbing their work activity. Eyes and face protection equipment shall be free from structural and optical defects. Just like other PPE, it should also pass the required safety standards. Check out the following eyes and face protections available from the market. 
5. Hand Protection
All personnel handling rough, sharp, and excessive coarse material such as reinforcement bars, rods, pre-cast concrete, toxic, electric, and hot materials shall be protected by safety gloves. The material of these hand protections shall be suitable against the hazard of doing such activities. Site employees shall be protected by the different types of gloves according to their job description. For example, chrome leather gloves should be used when handling sandblasting and other materials. Gloves that are made of fabrics are used for handling rough materials. Insulated rubber gloves should be used by electricians. The different types of safety gloves are available in the market. Refer to the images below for more.        
6. Hearing Protection
In the event that noise levels in the worksite are too much to handle, ear-protected gears are also needed by the site personnel. Ear protected hazard inserted into the ear in the form of a headset, foam earplug and earmuffs shall be in accordance with international safety standards. Plain cotton to be placed in the ear just to block construction noise is prohibited to use.
The following are the hearing protection equipment that is recommended by international standards available to the market. Select each for product details. 
7. Safety Belts/ Safety Harness
Site employees working at an elevated level to about 2m or more shall be provided by a safety harness or belts to protect them from accidental falls. Anchorage point of the safety harness shall be placed above the head of the worker and not less than 5 meters from the ground level. This point should be strong enough to carry a force of not less than 5000 pounds (2275kg). The material should be made of nylon or equivalent to at least 1cm thick. The hooks attached should be fitted with a double locking device that can be open only by pressing the two parts at the same time for safety purposes.
The approved material for safety belts/safety harnesses is available below. Select the photo for the full description. 
PPE is a very important aspect to look at in site construction. Observing the above lists of personal protected equipment is a must in the construction site and it should be strictly observed at all times. This is to avoid hazards caused by physical, mechanical, and chemical aspects to ensure for the construction team to create a safe and sound construction environment.

2. Listening & Speaking:

3. Make your own speech with the below words:

blue-collar, white-collar, vigorous activity, prone, be implemented, attire, comply, potential hazard, comply, steel toe cap covering, steel sole, non-contractive footwear, adequate, reflected vest, visibility, machine operator, welder, bar bender, medical spectacles, protected lenses, goggles, disturbing, optical defect, rough and excessive coarse material, toxic, chrome leather gloves, sandblasting, insulated rubber gloves, earplugs, earmuffs, anchorage point, an important aspect