Deep Foundations and Piling Types

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Questions and Answers

What are the two main types of bolts mentioned in the fabrication process?

Ordinary bolts and high strength friction grip bolts.

Why is shop welding preferred over site welding?

Shop welding is preferred for better quality control.

What are the key tasks to be performed during the erection phase?

Secure crane information, check transport of member lengths, and decide laydown area.

What factors should be considered when selecting a crane for construction?

Avoiding marginal situations, understanding crane characteristics, and considering the operating surface. Signup and view all the answers

What is the importance of inspecting welds visually during fabrication?

Visual inspections ensure that all welds meet quality standards and are structurally sound. Signup and view all the answers

What is the primary purpose of using deep-piled foundations?

To transfer loads to a firm soil stratum with sufficient load carrying capacity. Signup and view all the answers

List two types of displacement-driven piles mentioned.

Timber and precast concrete piles. Signup and view all the answers

What are the advantages of using timber for driven piles?

It is low cost, has a renewable supply, and can be easily handled and driven. Signup and view all the answers

What is a key feature of precast concrete piles when they are prestressed?

They exhibit higher strength. Signup and view all the answers

Why is splicing not desirable for precast concrete piles?

Because it complicates the structural integrity and performance of the piles. Signup and view all the answers

Identify one type of cast-in-place pile.

Bored piles. Signup and view all the answers

What type of section is used in closed-ended steel tube piles?

Steel tube sections. Signup and view all the answers

What characteristic of bulb piles distinguishes them from other pile types?

Their bulb shape enhances load distribution. Signup and view all the answers

What is a key requirement for the temporary wire rope guys during steel erection?

They must remain until sufficient steelwork is erected to allow for the installation of permanent bracing members. Signup and view all the answers

In Option 2, what is the significance of crane positioning?

Crane positioning is critical for successfully assembling and standing the portal on the slab. Signup and view all the answers

What are the advantages of Option 1, assembling in place, despite being time-consuming?

It allows for careful progress and does not critically affect crane location. Signup and view all the answers

Why is the crane location not critical in Option 1 for steel erection?

Because the assembly is done in place, allowing for flexibility in the crane's position. Signup and view all the answers

Describe what the existing steelwork's role is during the erection of new steel structures.

Existing steelwork must be checked for clashes to ensure compatibility with the new structures. Signup and view all the answers

What does the term 'plumbing radius' refer to in the context of steel erection?

It involves aligning the radius accurately to ensure proper fit and structural integrity during erection. Signup and view all the answers

What is the purpose of the temporary support towers in the construction process?

They provide required support until the steel structure is sufficiently erected. Signup and view all the answers

What phase comes after erecting enough steelwork in Option 1?

Permanent bracing members are installed after sufficient steelwork is in place. Signup and view all the answers

What is the purpose of cutting wires once concrete has cured?

To transfer force to the concrete. Signup and view all the answers

Describe the role of tendons in post-tensioning concrete.

Tendons are tensioned by jacking against the concrete and can be either bonded or unbonded. Signup and view all the answers

What are the two main types of construction regarding the filling of ducts after stressing tendons?

Bonded and unbonded construction. Signup and view all the answers

What equipment is typically used to apply tension to the rods in post-tensioning?

A hydraulic jack. Signup and view all the answers

Why are duct tubes installed in concrete blocks before curing?

To allow for the passage of tendons later on. Signup and view all the answers

What is the function of anchorage blocks in post-tensioning?

To mechanically anchor the tendons at each end of the member. Signup and view all the answers

What is one advantage of using unbonded post-tensioning?

It allows for movement between the tendon and concrete, reducing cracking. Signup and view all the answers

Identify one potential component used in the reinforcement of concrete blocks during post-tensioning.

High-strength steel rods. Signup and view all the answers

What is the main difference in the placement of cables between pre-tensioning and post-tensioning methods?

In pre-tensioning, cables are placed in formwork and stressed before concrete is poured, while in post-tensioning, cables are placed in ducts and are unstressed until after the concrete hardens. Signup and view all the answers

How does the bonding of concrete to cables differ in pre-tensioning compared to post-tensioning?

In pre-tensioning, concrete bonds directly to the cables as it hardens, whereas in post-tensioning, concrete does not bond to the cables due to their protection by ducts. Signup and view all the answers

What action is taken after the concrete hardens in the post-tensioning process?

After the concrete hardens, the cables in post-tensioning are stressed by tensioning them against the ends of the concrete member. Signup and view all the answers

What measures are taken to maintain the stress in post-tensioning?

In post-tensioning, the cables are locked-off or anchored against the ends of the concrete member to maintain the stress. Signup and view all the answers

What is done to the ducts after the post-tensioning cables are stressed?

The ducts in post-tensioning are grouted to bond the cables, enhancing their effectiveness and stability. Signup and view all the answers

Study Notes

Deep-Piled Foundations

Deep-piled foundations are used to transfer load to a firm soil stratum with sufficient carrying capacity.

Piling Types

There are two main types of piling: displacement and cast-in-place.
Displacement piles are driven into the ground.
- Timber piles are low cost, renewable, and have a long history of successful applications.
- Precast concrete piles are higher strength because they are often prestressed.
  - They can be manufactured to required lengths and splicing is not desirable.
- Closed-ended steel tube piles are used for various projects.
- Steel "H" section piles are another popular type depending on the project.
Cast-in-place piles are formed in situ.
- Bulb piles form a large bulb at the bottom of the pile, which acts to spread the load.
- Bored piles are formed by drilling a hole in the ground and filling it with concrete.

Steel Fabrication Process

Bolting is used to join steel components, either with ordinary bolts or high-strength friction grip bolts.
Welding is another method used to join steel components:
- Shop welding is preferred over site welding due to better quality control.
- Welds require high-skill welders and must be inspected visually.
Shop assembly is used for components that are brought together to be fitted up and inspected for dimensional accuracy, squareness, and conformance with shop drawings.

Steel Erection Tasks

Secure Crane Information: Before crane lifts, obtain capacity and lifting limitations.
Check Transport of Member Lengths: Ensure that pre-fabricated lengths and dimensions are suitable for transport routes.
Decide Laydown Area: Choose a suitable area for temporary storage and staging of steel components.
Determine Size of Yard Crane: Select an appropriate crane for lifting and positioning steel components.
Determine Temporary Restraint Systems: Plan for temporary restraint systems to control the stability of steel elements during lifting and erection.
Determine Painting Area (if needed): If painting is required, define an appropriate location for coating steel elements.

Crane Selection

Avoid Marginal Situations: Ensure sufficient margin with crane capacities and operating conditions.
Consider Three Dimensional Movements: Evaluate crane movements in three dimensions when choosing the right crane.
Understand Characteristics of Different Types Select a crane based on its type, for example, rubber tyred or traced, lattice or telescopic, etc.
Consider Operating Surface: Be mindful of the operating conditions and capabilities of the crane based on the surface.
Beware of Multiple Crane Lifts: Exercise caution when using multiple cranes concurrently.

Steel Erection

Option 1 - Assemble In Place: Steel elements are assembled in place using temporary support towers and wire rope guys.
- Crane location is not critical.
- Guys must remain in place until sufficient steelwork is erected.
- This method is time-consuming but allows for controlled progress.
Option 2 - Assembled On Slab And Stood As Unit: Steel elements are assembled on a slab and lifted as a unit. This requires precise crane positioning and coordination.

Post-Tensioning

Post-tensioning involves stressing against tendons that are not bonded to the concrete. Tendons pass through flexible ducting, which is cast into the concrete. The tendons are tensioned by jacking against concrete, anchored mechanically by anchorage blocks.
Unbonded Construction: The remaining space in the ducts after stressing can be left empty.
Bonded Construction: Ducts are filled with grout under high pressure.

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Description

This quiz explores the concepts of deep-piled foundations and their various types, including displacement and cast-in-place piles. It delves into the materials used, such as timber, precast concrete, and steel, and their applications in construction. Test your knowledge on how these foundations transfer loads to a firmer soil stratum.