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RHD Operational Procedure – Bridge Management Wing
 
Bridge Design
 
OP/BD/1.1 - Technical Approval
 
Purpose and Scope :

Bridges and other major structures are expensive investments in the infrastructure of the nation. Inadequate design can lead to expensive changes during construction and a potential major loss of investment during the life of the structure. To minimise the risk of poor design this Technical Approval operational procedure has been adopted. The procedure covers all bridges, culverts and other structures including gantries and large signboards.
 
Definitions :

Final Engineering Report – The report includes:

1. The design brief,

2. Reference documents including surveys, topographical, soils and hydrological and hydrographical.

3. Any necessary assumptions during the design.

4. The design calculations,

5. Proposed maintenance requirements.

Designs – are Final Engineering Report, detail drawings, and additional clause to the Technical Specification (Volume 3 of NCP) to be included in the Special Technical Specification in the Contract Documents. All designs drawings and specification to be completed to a standard that they can be constructed without modification.

Design Engineer – any engineer with structural engineering experience who in the opinion of the EE-BD in consultation with SE-Bridge Design Circle is sufficiently competent to carry out the particular design required.

Bridge Design Team – In the case of RHD the Division carrying out the design. In the case of a Consultant the team headed by a Senior Structural Engineer carrying out the design

Complex Bridge or structure – a bridge or structure, whose design, in the opinion of the Superintending Engineer-Bridge Design merits specialist attention. Examples of this might be construction over fast flowing rivers, railways, designs in dense urban areas or structures of specialist designs. This list of examples is not exhaustive.

TA Category A: Structure Less than 150m total span with individual spans not more than 43m and not a Complex Bridge or structure

TA Category B: Structure of 150m or more total span with individual spans not more than 43m or a Complex Bridge or structure

TA Category C: Structure containing at least one individual span greater than 43m but less than 50m

TA Category D: Structure containing at least one individual span of 50m or more.
 
Responsibility :

Additional Chief Engineer – Bridge Management Wing – Approval of in-house Design and acceptance of Consultants Design.

Superintending Engineer – Bridge Design Circle

1. Decides on whether the design is of a Complex Bridge or Structure,

2. Ensures that Technical Approval procedures are adhered to for all bridge and other structures design including structural maintenance,

3. Ensure that provision is made for designs requiring Technical Approval checks through outsourcing,

4. Reviews designs and when satisfied recommends for approval to ACE-Bridge Management Wing.

Executive Engineer – Bridge Design Divisions

1. Ensure the quality of work undertaken by his staff and that Designs are properly prepared and collated for the checker.

2. Carry out checks on Designs prepared by his staff on structures after any necessary amendment sign the Design as Checked.

3. Carry out checks as instructed by the Superintending Engineer-Bridge Design Circle and after any necessary amendment sign the Design as Checked,

4. Assist the Superintending Engineer as necessary in his duties.
 
Method :

The flowchart sets out procedure to be adopted. The tasks set out in the flowchart are more fully explained below.

4.1 COLLATE DOCUMENTS

The Designer must collate all relevant documents used or prepared in the design of the bridge or structure. These must include the following (most of which would be included in the Final Engineering Report):

· Design Brief,

· Reason for choice of structure, if no specific type of structure stated in brief,

· Soils investigation report

· Accepted soil interpretation data with design parameters clearly set out and accepted,

· Design calculations – to ASAHTO supplemented by reference to the RHD’s Bridge Designer’s handbook and its supplement.

· Design drawings – sufficient detail for construction

· Any special specifications clauses necessary to achieve the parameters used in the design,

· Requirement of Utility companies

· Basis of Earthquake design parameters

· Bridge loading

· Proximity of adjacent structures

· Notes for the Engineers Representative where special attention is necessary in the supervision of the Works,

· Definitive list of the final design parameters that may be used by the Contractor in preparing his method statement.

Additional items might include:

· Construction method

· Details of the bridge to be replaced and reason for failure

· Special requirements of the Bangladesh Inland Water Transport Authority,

· Special Requirements of Bangladesh Rail Authority,

· Special environmental issues and reports

· Landscaping reports as they affect

· Hydrological, and Hydrographical reports

Neither of the above lists is exhaustive – the designer and checker must be satisfied that all relevant documentation is included with the Design.

4.2 INDEPENDENT CHECKING

Checking means to carry out all of the following:

1. Check the design meets the requirements of the brief.

2. A full study of all relevant documents, ensuring there is sufficient information to undertake the design.

3. A check on the overall concept of the design and whether all information has been taken into consideration.

4. Check that structures are consistent with the Bridge Design Standard. The Bridge Design Hand book and its supplement should be used appropriately,

5. Check Validation and verification of any computer programme or Spreadsheet template, used in the design, has been carried out to the checkers satisfaction,

6. A full check of all calculations – in some cases this may be achieved by independent calculations,

7. A full check of the drawings.

8. A full check as to whether all requirements of the design are included either in the Technical Specification (Volume 3 of NCP) or in the additional Specification clauses identified in the design.

9. Review design parameters that may be made available to the Contractor and any advisory notes given to the Engineer’s Representative.

10. Once all the above has been checked amended and re-checked to the satisfaction of the checker, the checker will sign the designs including the drawings and calculations.

11. The checked documents should be submitted to the Superintending Engineer who shall accept them with a recommendation for approval to the Additional Chief Engineer for approval or require changes to be carried out. If changes are carried out they must follow the checking procedure described above.

4.3 APPROVAL/ACCEPTANCE

In the case of designs carried out by RHD staff the ACE BMW approves the design; in the case of designs carried out by consultants he accepts the designs as conforming to RHD standards.
 
References :

RHD Bridge Design Standards

AASHTO version as specified in RHD Bridge Design Standards

Indian Road Conference – IRC Bridge Design Standards

RHD’s Bridge Designer’s Handbook and its supplement.
 
Procedure Flowchart :

The procedure flowchart for this procedure is detailed below -
 


 


 

 

For duties associated with each grade of personnel see

 

Updated on : 1/12/2003

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