Reference no: EM133123900

Assignment:

The 30-year-old bridge structure in coastal NSW has 6 numbers of reinforced concrete piers (supported by driven piles).

Preliminary inspection of the marine piers shows that they are suffering badly from concrete spalling and reinforcement corrosion, mainly in the lower 1 to 2 m of the piers above the pile cap. The base of the pier (top of the pile cap) is 0.7 m above the high-water level (HWL). The piers are 7 m high.

Appropriate remediation of these areas or a system of preventative maintenance repair is required to avoid expensive future repair or replacement. A long-term design and repair solution is required to ensure the future integrity of the piers for approximately another 30 years of life.

One typical pier has been investigated in a limited fashion. Chloride ion analysis has been conducted in the preliminary investigation and the results are displayed below (Table 1). Results are in Cl by weight cement. The concrete was found to have an average of 360kg/m3 of cement and a measured strength of 35 MPa.

Half-cell potentials results are also provided which have been taken with a copper/copper sulphate reference cell in one typical 0.5 m wide strip up the West face of a pier. Results are in millivolt (mV).

In addition to the pier assessment, the concrete crash barrier on the bridge (500 m away from the pier) has been inspected and the cracks and the corrosion of the reinforcement bar have been detected in the barrier (Fig.3). The Chloride ion analysis has been conducted in the preliminary investigation at three different locations and the results are also included in the same Table 1. Also, the CO2 levels near the crash barrier were determined as 480 ppm due to the high level of traffic. The CO2 levels around the pier were determined as 400 ppm.

Question 1: Describe the investigation you would propose to confirm the cause and extent of the problem to the bridge piers to form the basis of the repairs to be undertaken.

Question 2: Discuss the different repair options available and propose your preferred solution with the reasons to repair the piers.

Question 3: Carry out preliminary design work in order to propose your preferred solution to the problem to achieve the lowest cost repair and maintenance of the full height of the piers for a 30-year life.

Question 4: Propose your solution supported by appropriate sketches and calculations as required.

Question 5: Describe the investigation you would propose to confirm the cause and extent of the problem to the crash barrier to form the basis of the repairs to be undertaken

Question 6: Propose your solution to prevent the corrosion in crash barrier in the same situation in future?

Attachment:- Chloride ion analysis.rar