As an engineer, it's my job to design and build structures that are not only useful but also safe and last a long time.
Understanding bearing strength is an important part of structural engineering.
When you divide the effective bearing area by the maximum load that a column, wall, footing, or joint can handle until it breaks, you get the bearing strength.
It's what keeps my buildings from falling down.
As a student of engineering or as an engineer, you will have to design structures that can stand up to both natural and human forces.
That's why I need to know a lot about bearing strength to make sure my buildings are safe and last a long time.
In this article, I will dive deeper into the world of bearing strength, exploring the different factors that affect it and how engineers can calculate and ensure structural stability.
So, put on your hard hat and your thinking cap and let's explore the fascinating world of bearing strength together!
Understanding Bearing Strength
Formal definition:
The maximum load that a column, wall, footing, or joint will sustain until failure, divided by the effective bearing area.
Bearing strength is a very important idea in engineering, especially in fields like building and designing airplanes.
It refers to the maximum amount of weight or pressure that a structure can hold before collapsing.
We'll talk about bearing strength, yield strength, and ultimate bearing strength in this article.
Bearing Strength
The maximum bearing load that can be placed on a structure before it fails, divided by the area that is supporting the load, is known as bearing strength.
As was already said, a structure's bearing strength is not the maximum amount of weight or pressure it can hold before it falls apart.
Instead, it is the effective bearing area divided by the maximum load that a column, wall, footing, or joint can handle until it breaks.
Bearing strength can be measured by tensile, compression, flexural, and bending strength, as well as bearing hardness.
However, it is crucial to understand that tensile, compression, and flexural strength are not directly related to bearing strength.
In building, it's important to know the bearing strength of structures like walls and columns to make sure they can hold the loads they're meant to support.
In the same way, when designing an aircraft, the bearing strength of the airframe must be able to withstand different pressures and forces that are put on it during takeoff, flying, climbing, landing, and other operational maneuvers.
Yield Strength
Another important way to measure how strong something is is by its yield strength.
It is defined as the maximum stress that a solid material can withstand when it is deformed within its elastic limit.
Yield strength is the maximum stress or load that a solid material can handle when it is deformed up to its elastic limit, which means that it can go back to its original shape when the load is removed.
The stress or load that is needed to permanently change the shape of a material is called its yield stress.
After this point, the material won't go back to the way it was.
In ductile materials, yield strength is much lower than ultimate strength, while in brittle materials, there is no yield point, and hence no yield strength.
Ultimate Bearing Strength
Ultimate bearing strength is the most pressure that a solid material can take before it breaks.
It is often used the same way as "ultimate tensile strength." Ultimate bearing strength and ultimate tensile strength are both ways of talking about how much stress a solid material can take before it breaks.
From bearing tests, you can find out the bearing's yield stress and its ultimate stress.
Bearing Yield Strength (BYS) is found by drawing a line parallel to the initial slope of the bearing stress deformation curve at an offset strain of 0.002.
In the end, bearing strength, yield strength, and ultimate bearing strength are all important ideas in engineering.
Bearing strength is the most weight that a structure can hold before it breaks, and yield strength is the most stress that a material can take before it starts to change shape permanently.
Ultimate bearing strength and ultimate tensile strength are both ways of talking about how much stress a material can take before it breaks.
By understanding these ideas, engineers can make structures and materials that are safe and reliable.
Pushing the Limits: The Importance of Bearing Strength in Building Design
Still hard to understand? Let me change the point of view a bit:
If you want to design a building that won't fall apart like a house of cards, the key is to make sure it can hold the weight of all your unreasonable expectations, unreasonable demands, and inevitable mistakes.
Because let's face it, if you're not pushing the limits of your building's bearing strength, are you really living life to the fullest?
Okay, that was just a joke made to look like a TV ad.
Now let's go back to the explanation.
Factors Affecting Bearing Strength
Soil Factors
One of the most important things that affects the strength of a structure is how much weight it can hold.
The following soil factors affect soil-bearing capacity:
- Shear strength: Soil shear strength is a way to measure how well a soil can resist forces that try to pull it apart.
- Width and depth of the foundation: The width and depth of a foundation can have a big effect on how much weight it can hold.
In general, a foundation can hold more weight if it is wider and deeper.
- Weight of the soil and any extra weight on top of it: The weight of the soil and any extra weight on top of it can affect how much weight the soil can hold.
Compressive Strength of Concrete
Another thing that affects bearing strength is how strong concrete is when it is compressed.
The compressive strength of concrete after 28 days is used to design wall footings, and it is important to use a concrete mix with the right strength for the structure's purpose.
Shape and Dimensions of the Structure
The strength of a structure can also be affected by its shape and size, such as its width, length, and thickness.
A structure with a larger surface area will generally have a higher bearing capacity.
Load Distribution and Type of Load
The strength of a structure can be affected by the type of load that will be put on it.
The strength of a structure can be affected by live loads, dead loads, and wind loads.
Location and Orientation of the Structure
The structure's strength can also be affected by where it is and how it is set up.
The soil's ability to hold weight can be affected by things like the type of soil and the level of groundwater.
The bearing strength of a structure can also be affected by the weather, such as wind, rain, and changes in temperature.
International Building Code
The International Building Code has suggestions for what kind of foundation to use and how it should be built.
Among these suggestions, but not all of them, are the following:
- Capacity of natural or compacted soil to hold weight.
- Provisions to lessen the effects of soils that move around a lot.
- Frost line depth.
- Minimum reinforcing for footings made of concrete.
- Minimum depths for wood posts to be set in concrete footings.
Bearing Safety Factor
The bearing safety factor is used to ensure structural stability.
The factor of safety is the ratio of the maximum load that can be put on a bearing to the maximum load that can be put on it.
It is thought that failure will happen when the factor of safety is less than 1.
You can figure out the allowable bearing capacity with an equation that takes soil parameters and the shape of the foundation into account.
Evaluation Standards
The quality of field reconnaissance, soil sampling, and shear tests can affect the accuracy of stability calculations.
To make sure the safety factor is correct and reliable, evaluation standards for the factor of safety in foundation stability analysis have been made.
In the end, there are many things that affect how strong a column, wall, footing, or joint is.
Engineers have to think about the soil, the compressive strength of the concrete, the shape and size of the structure, how the load is distributed and what kind of load it is, where and how the structure is placed, and what the International Building Code says.
Additionally, the bearing safety factor is used to ensure structural stability, and evaluation standards are in place to ensure accurate and reliable calculations.
Determining Bearing Strength of Materials
Factors Affecting Bearing Strength
The strength of a column, wall, footing, or joint depends on a number of things, such as the soil, the design of the foundation, the shape and size of the structure, how the load is distributed, and the environment.
Soil factors: The bearing capacity of soil is determined by three soil factors: shear strength, foundation width and depth, and soil weight and surcharge.
When a footing is put on top of soil that doesn't stick together, its ability to hold weight depends on how wide it is.
Stability calculations can be wrong if the field reconnaissance, soil sampling, and shear tests aren't done well.
Foundation design: The International Building Code provides recommendations for foundation type and design criteria, including but not limited to bearing capacity of natural or compacted soil, provisions to mitigate the effects of expansive soils, frost line depth, minimum reinforcement for concrete footings, and minimum embedment depths for wood posts in concrete footings.
Dimensions and shape of the building: Walls and columns should be supported as close to the center of the footings as possible to prevent one-way (beam) shear failure, which happens when the beam breaks at an angle of about 45 degrees to the wall.
Load distribution is the way that the structure's loads, such as live loads, dead loads, and wind loads, are spread out.
Environmental factors include the location and orientation of the building, as well as the ground conditions and how exposed it is to things like wind, rain, and changes in temperature.
Determining Bearing Strength of Materials
Wood, steel, and copper, for example, have different bearing strengths that depend on their tensile strength, compressive strength, hardness, ductility, elasticity, and other properties that are unique to each material.
For example, the bearing strength of wood depends on its grain, density, and amount of moisture, while the bearing strength of steel depends on things like its alloy composition, heat treatment, and physical dimensions, such as its outer diameter, wall thickness, and length.
Tensile strength: A material's tensile strength is the amount of force it takes to pull it apart until it breaks.
Compressive strength: To figure out a material's compressive strength, you measure how much force it takes to crush it until it breaks.
Steel Tubing Bearing Strength
The outer diameter, wall thickness, and length of a steel tube, as well as the material properties of the steel, such as its yield strength and ultimate tensile strength, determine how much weight it can carry.
A calculator can be used by anyone who knows the loading requirements of their application and whether the tube will be used as a beam or column to figure out what size tube is needed.
Steel tubing's load-bearing strength can be calculated with the help of mathematical equations or computer programs that take all of these things into account.
For example, the load-bearing capacity of a steel tube can be calculated using the Euler formula, which takes into account the tube's length, length without support, and moment of inertia.
Other equations, like the AISC formula from the American Institute of Steel Construction, can be used to figure out how strong a steel tube is under different loads.
Soil Testing for Bearing Capacity
Soil testing is an important way to figure out how strong a building's foundation is and how much weight it can hold.
It involves putting samples of soil through tests in the lab to find out what their properties are and using other methods to find out how stable the soil is.
Lab tests for the properties of soil:
Soil samples can be put through a number of tests in the lab to find out about their properties.
These tests include the Consolidated Undrained (CU) Test, the Unconfined Compression Test, the Triaxial Compression Test, the Shear Box Test, the Vane Test, the Consolidation Test, the Swelling and Suction Test, the Permeability Test, and the Chemical Analyses.
These tests are needed to describe and classify the soil and to take note of the color, texture, and consistency of both disturbed and undisturbed samples from the site.
Ways to figure out how strong the soil is:
Different ways can be used to figure out the soil's bearing capacity, like the Terzaghi Ultimate Bearing Capacity Theory, which figures out the ultimate bearing capacity for shallow continuous foundations.
It uses an equation that takes into account soil parameters like cohesion, effective unit weight, footing depth, and footing width.
Another way to figure out how much weight an unsaturated fine-grained soil can hold is to use the shear strength from unconfined compression tests.
The bearing capacity equation (drained) only works for shallow footings that support vertical loads that are not eccentric.
Using the unconfined compressive strength to estimate the bearing capacity:
Unconfined compressive strength only works for soils that stick together.
It can't be used to figure out how much weight a non-cohesive soil can hold because it needs a different set of parameters.
Soil testing is an important way to find out how strong a building's foundation is and how much weight it can hold.
Soil properties are found through lab tests, and there are different ways to figure out how much weight a soil can hold based on its properties.
For cohesive and non-cohesive soils, it is important to use the right methods and take into account different soil parameters for each method.
Bearing Strength of Masonry
Maximum Usable Strain for Concrete Masonry
At the extreme compression fiber of concrete masonry, the most strain that can be used is 0.0025.
Reinforced Masonry
For reinforced masonry, compression and tension stresses in the reinforcement below the specified yield strength are equal to the reinforcement's modulus of elasticity times the steel strain.
Shear Capacity of Masonry
You can also figure out the nominal bearing strength of masonry by looking at how much it can hold up under stress.
In a simple span beam, the shear capacity goes from 0 at the support to infinity in the middle.
In relevant design codes and guidelines, you can find the formula for figuring out shear capacity as a function of M/Vd.
Important Considerations for Masonry Design
It's important to remember that these calculations are based on certain assumptions and design codes.
When designing masonry, you have to think carefully about things like the types of loads, the properties of the materials, and how the structure is set up.
Before doing any calculations or making any design decisions about masonry structures, it's best to check the relevant design codes and guidelines.
Effects of High Temperature on Steel
Steel is often used in building and engineering, but when it gets too hot, it loses its ability to hold weight.
About 425°C is the highest temperature above which steel starts to lose its ability to hold weight.
Between 600°C and 650°C, the steel will lose half of its strength and, depending on how much weight it is carrying, could break.
Around 500°C, the strength of hot-rolled structural steel loses a lot of its load capacity at room temperature.
At 1100°F (593.33°C), the steel still has about 50% of its strength.
When the steel melts at about 2700°F (1482.22°C), it gives up all of its strength.
Most of the time, when designing, it is assumed that all capacity is lost at about 2200°F (1204.44°C).
Effect of Fire on Structural Steel
In BS EN 10025 grade S275 steel, a grade S275 hot-rolled structural steel section that has been in a fire and gotten hotter than 600°C may lose some of its properties after it has cooled down.
No matter how hot the fire is, though, the room temperature yield stress or replacement won't be needed if the member meets all the other engineering requirements, like being straight.
When structural steel of grade S355 is heated to over 600°C in a fire, its residual yield strength and tensile strength also go down.
Bolt Shear Strength - Bearing, Tearout, and Shear Load Capacity Calculations
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Bearing strength uses
Construction of Buildings:
Buildings and structures of all kinds need to be strong enough to hold their weight.
It tells how much weight a column, wall, footing, or joint can hold before it breaks.
Engineers use calculations called "bearing strength" to make sure that the building can hold its own weight as well as the extra weight that comes from people, equipment, and the environment.
Bridge Design:
Bridges have to be built so that they can handle heavy loads like cars, wind, and earthquakes.
The bearing strength of the foundation and support structures, like piers and abutments, is a key factor in figuring out how much weight they can hold.
Engineers also use bearing strength to figure out how much weight a beam, girder, or cable can hold.
Mathematical Engineering:
In mechanical engineering, bearing strength is very important because it is used to figure out how much weight gears, bearings, and shafts can hold.
Engineers use calculations of bearing strength to make sure that the parts can handle the forces and stresses of the application, such as in heavy machinery, vehicles, and airplanes.
Aerospace Business:
Bearing strength is also important in the aerospace industry, where it is used to figure out how much weight parts like wings, fuselages, and landing gears can hold.
Engineers use calculations called "bearing strength" to make sure that the plane can handle the forces and stresses that come with flying, like turbulence, takeoff, and landing.
Offshore Buildings:
When designing and building structures like oil rigs, wind turbines, and platforms that are out at sea, bearing strength is an important factor.
These buildings must be able to stand up to rough weather, like strong winds, waves, and currents.
Bearing strength is used to figure out how much weight the foundation and support structures can hold, as well as how much weight the equipment and machinery can hold at most.
The Mining Business:
In the mining industry, bearing strength is very important because it is used to figure out how much weight can be put on underground support structures like pillars and beams.
Engineers use calculations called "bearing strength" to make sure that the structures can handle the weight of the rock above as well as the forces and stresses caused by the mining process, like blasting and drilling.
Conclusion
As we finish talking about bearing strength, it's important to remember that this idea is important not just in engineering, but in life in general.
Just like a building needs a strong base to stand tall, we need a strong base to face the challenges of life.
We need to be rooted in our beliefs, values, and principles to stand up to the things that try to knock us down.
Buildings aren't the only thing that need to be strong. Our lives also need to be strong.
We need to figure out how much weight we can carry, find the right help, and make sure we have a strong base to stand on.
So, before you leave this article, take a minute to think about how strong you are.
What do you build your house on? How much can you carry? And how can you make sure you have the help you need to face the challenges of life? Remember that a well-designed life can last just as long as a well-designed building.
So go out and build a life that can support your dreams.
Links and references
ACI 318-14 Building Code Requirements for Structural Concrete and Commentary
Chapter 3: Design Loads for Residential Buildings
Recommended Minimum Requirements for Masonry Wall Construction
