Repair and Maintenance of major bridge

To

The Concessionaire,

Subject: Precarious condition of the existing major bridge at km chainage 10+100-Reg.

Dear Sir,

During the monthly inspection of the team leader, an independent engineer, of the project highway on xx/xx/2024, the condition of the existing major bridge at km chainage 10+100 has been critically examined. That is, in a manner involving a skilled analysis of merit, and the following are the observations:

1. Both the first and last spans are highly damaged. But the condition of the last span towards the project end is in extreme danger.

2. One main girder has failed in the last span.

3. The bearings are damaged.

4. The bottom reinforcements of the deck slab are being exposed. And it is undergoing severe corrosion.

Under the above circumstances, you are being instructed to take care of the repair and strengthening of the damaged spans immediately. And employ specialised farms for proper rehabilitation, as per ground reality.

This is for immediate compliance.

Thanking you,

To

The Concessionaire,

Subject: Major Concern for the Existing Major Bridge at Km. 10+100-Reg

Referred to: Independent Engineer TL’s Inspection Note, as above.

Dear Sir,

Consequent to the Team Leader’s site visit on xx/xx/2024, it has been found that, in connection with the immediate repair and the protection work that needed to be taken for the end span of Major Bridge at Km. 10+100,.

Which is in extremely dangerous condition due to the total failure of one of the simply supported girders; nothing has been done so far.

Though an investigation agency has been appointed by the EPC, the following actions are to be taken immediately, in consultation with the appropriate authority.

Divert the traffic with immediate effect after constructing diversion works (if with the consent of the highway authority required) until the existing bridge is strengthened.

Deploy extensive manning to guide the traffic while crossing the existing bridge until the diversification work is completed, and monitor the bridge closely.

Caution boards, limiting the vehicle speed to 10 kmph and written both in local and English, are to be displayed at both ends of the bridge, with larger sizes, until the diversion work is completed.

These are for immediate implementation to avoid accidents and loss of life.

Thanking you,

To

The Independent Engineer,

Subject: Restoration plan of Major Bridge Km: 10+100-Reg.

Dear Sir,

We propose the following immediate measures to be taken on a war footing basis on the span towards the project end for ensuring safe traffic movement on the weak bridge.

1. Fill the gap between the girder soffit and abutment cap top with M30-grade concrete.

2. Fill M30 concrete between the soffit of the end diaphragm and the abutment cap top.

3. Provide fillet concrete from the diaphragm 300 mm beyond the cracked portion of the central RCC girder by cleaning and hacking the surface of the diaphragm and the girder.

4. Further fill the gap on the A2 cap top till the soffit of the deck slab.

5. Similarly, fill M30 concrete at P3 between the pier cap top and the P3-A2 span diaphragm soffit. But this should be done only on the side of the end span and should keep the other span free and independent.

6. Prepare the supporting system below the end span towards A2. The crib supporting system must rest on a raft foundation. The raft must be cast at the non-scour level to sustain the flash floods. The crib support must be at the abutment face and pier faces, 1/3 spans, and mid-span under the RCC girders so as to just touch and not lift the girders.

7. Complete the proposed new bridge, and traffic shall be diverted on it before taking up rehabilitation or reconstruction of the other spans of the existing bridge as per the advice of the IC. Care shall be taken while excavating for abutments to ensure the existing bridge approaches stability.

This is for your review and approval, please.

Assuring our best services at all times

Thanking you

To

The Concessionaire

Subject: Restoration of Major Bridge at Km Chainage 10+100-reg.

Dear Sir,

After a preliminary study of the proposal submitted by you in your above-mentioned letter related to the temporary strengthening of the existing major bridge at Km Ch 10+100, we would like to inform you of our observations:

• The Investigation Condition Survey Report, submitted by you for our review, categorically reveals the following facts:

• The existing superstructure of the bridge is in distressed condition, as cracks, crushing honeycombs, and segregation of concrete in varying degrees are available in all spans.

• Cracks are also being observed in the deck slab of the end span (Medaranetla side).

• Corrosion cracks were observed in the bottom regions of the main girders.

• The Ultrasonic Pulse Velocity Test results show inconsistencies and low values at cracked locations, which corroborate the fact that the cracks are live and through.

• The results of the carbonation test explicitly support the fact that the embedded reinforcement is prone to corrosion activity.

• All the above features lead to the fact that the superstructure of the bridge at Km Ch. 10+000 is grossly weak and susceptible to any major hazards at any moment.

• Your proposal for putting new M-30 grade concrete in selective portions of the superstructure of the existing major bridge at Km Ch. 10+100 will enhance the dead load of the superstructure.

• The existing unrepaired severe vertical and diagonal cracks on the vertical faces of the soffit of all the girders in general and the end girder in particular will make the portions of the superstructure more susceptible to immediate danger only.

• Because the strength and quality of the existing concrete have already deteriorated to an alarming level.

Above all, your proposal will make the entire superstructure a rigid frame only.

So, your proposal requires further modifications and discussions.

However, the poor and disastrous condition of the major bridge at Km Ch. 10+100 is a subject of grave concern, and it’s a pity that, despite our instruction to divert the traffic in an appropriate manner until the existing bridge is rehabilitated, it is not being complied with.

So, time and again, you are being instructed to take the safety of the traffic into consideration.

This is for your information and necessary action only.

Thanking you,