Construction Technology - Level 2

Question 1

Can you name some of the different foundation systems and when they might be used?

Answer 1

Strip - this is a shallow form of foundation typically used for residential housing with good ground conditions.

Pad - poor ground conditions and handling concentrated loads.

Raft - poor ground conditons, the raft spreads the load across a large area.

Piled - deep form of foundation used when ground conditions are poor and load needs transfering to depth.

Question 2

What are the different types of piling?

Answer 2

Contiguous - non connectd piles set in a series.

Secant - interlocking piles where some of the piles are cut and the secondary pile is formed within.

Driven - the pile is hammered into the ground. Need to consider noise impact.

Bored - soil is excuvated prior to forming the pile.

Load Bearing - end of the pile is in contact with load bearing strata and transfers the load.

Fricition - load the pile is transporting is supported by the friction on the surfaces of the pile.

Question 3

What type of piling was being used on the M621?

Answer 3

Cast in-situ bored concrete piles.

Question 4

Are you aware of any guidance on piling and general building standards?

Answer 4

The apporved documents set out guidance on how to comply with the building regulations.

Approved Document A: Strucutre

Question 5

What is cost assurance/benchmarking and why is it important?

Answer 5

Reviewing/Sense checking the pricing documentation submitted by the supplier.

Benchmarking - process of collecting and comparing data to identify best in class.

Benchmarking Process:

1. Define the process
2. Data collection
3. Data comparison
4. Analysis
5. Action
6. Repeat

Purpose:

Ensure value is being delivered for the Client and pricing is inline with industry price range.

How the Supplier is performing against the expected standards.

Identification of any errors or oversights in the pricing documents.

Question 6

What are the key components of a cast insitu concrete pile?

Answer 6

A bore hole is first drilled, option to have supporting steel casing around the outside of the pile.

Placement of the steel reinforcement cage.

Pouring of the concerete to form the pile.

Question 7

How does third rail electrification work?

Answer 7

The third rail is a conductor rail that runs alongside the track, with trains having contact blocks called collector shoes that make contact with the third rail, electrifying the train.

The third rail is supplied with 750V of DC from lineside conductor stations.

Question 8

How does overhead line eletrification work?

Answer 8

The overhead lines are supplied with 25,000KV of AC.

The electrified contact wire comes into contact with the trains pantograph electrifying the train.

Question 9

What are some of the advantages and disadvantages of third rail electrification?

Answer 9

Advantages:
- Not visually intrusive.
- Bridges don’t need to be adapted.

Disadvantages:
- Speeds are limited to roughly 110mph.
- 20% more electricity compared to OLE.
- Substations every 8km.
- Third rail exposed to ice and leaves.
- Risk of electrification to trespassers.

Question 10

What are some of the advantages and disadvantages of overhead line electrification?

Answer 10

Advantages:
- Reduced number of substations, only required every 40-60Km.
- Reduced risk of electrification.
- Faster train speeds.
- Lower maintenance cost compared to third rail.

Disadvantages:
- Visually intrusive.
- Exisiting infrastrucutre such as bridges and stations will require modification to facilitate.

Question 11

What are the key benefits of electrified trains compared to diesel?

Answer 11

Electric Rolling Stock 20% Cheaper than Diesel.

Maintenance is typically 33% lower.

Fuel cost 45% less.

The trains are lighter reducing wear to the tracks by on average 13% and therefore reducing maintenance requirements.

Emmissions are reduced by 20-30% per passenger mile.

Quieter.

Question 12

What was the cost and programme impact of the proposed soloution on the PSU Drainage project?

Answer 12

For each shelter:

• Programme extended by half a day.
• Cost increased by £2,000

This was based on the information provided by the contractor.

Question 13

Could you explain what the issue was on the PSU Drainage project?

Answer 13

There was a high risk of the anchors required to secure the shelter to the concrete base clashing with the steel reinforcement within the base, damaging the rebar and reducing the strength of the base.

Question 14

What is the purpose of the rebar in the concrete base?

Answer 14

It increase the bases tensile strength, making it more resistant to stretching, bending and cracking. Enabling the base to bear a heavier load.

Question 15

What sources of cost data did you use for the M621 cost assurance?

Answer 15

In house cost data from other similar schemes.

Question 16

What other potential sources of cost data are available to you?

Answer 16

SPONS

BCIS

In house cost data

Supplier Quotes

Question 17

Did the cost data require any adjustments and if so what?

Answer 17

Adjustments for inflation and location was required.

The BCIS location indicies were used.

Question 18

What inflation index did you use and why?

Answer 18

The BCIS General Building Cost Index.

Inflation in construction differs to general inflation measured in other indices like the consumer price index, meaning use of a construction specific index gives a more accurate reflection of costs.

Question 19

What was the tolerance on rates, at what point did you class them as outliers?

Answer 19

A range for the rate was calculated based on internal data held from three other schemes, any rates outside of this range was classed as an outlier.

Question 20

Are you aware of any guidance for undertaking cost assurance and benchmarking?

Answer 20

There is a newly published RICS Practice Information titled Cost analysis and benchmarking.