A bridge tender specification is not a description of the structure you want. It is a record of the decisions you have already taken, written down so that every bidder prices the same thing. Every decision left out of it is one that will be made for you, by whichever supplier can satisfy the document most cheaply.
That framing explains why so many specifications fail. They describe an aspiration in prose, leave the technical parameters to the designer, and then produce three offers that cannot be compared because each bidder resolved the gaps differently and entirely legitimately.
Start with the scope boundary
The first section should state which work packages are included and which are not: the span, the substructure, the approach ramps and stairs, delivery, lifting, the ground investigation, the design, the approvals. Anything not explicitly included will be excluded by at least one bidder, and the resulting price spread will be read as competitiveness rather than as different scope.
Where a package is uncertain, price it as a stated option rather than leaving it out. That keeps the comparison intact and gives the client a decision to take later with a number attached to it.
Site data the client has to supply
A specification that asks bidders to establish the site conditions is asking them to price risk. The client should supply the topographical survey, the ground investigation, the levels, the required clearance and who set it, the water levels where relevant, and the available access for delivery and lifting.
Commissioning this data before the tender is almost always cheaper than the contingency that every bidder would otherwise carry, and it removes the most common source of post-award variations.
Function before structure
Describe what the crossing has to do before describing what it is. Who uses it and in what numbers. The clear width required between parapets, stated as a maintained dimension. Whether cyclists are carried. Whether a service or emergency vehicle must reach the deck. The accessibility requirement and the gradient that applies to the approaches.
These determine the structure more completely than any amount of description, and they are the parameters a client is actually qualified to set. The way clear width, clearance and headroom interact is worth working through before this section is written, because the three are not independent.
Loads and standards
Name the design standards and the country whose national annex applies, since the Eurocodes leave the actual values to each member state and a design produced against the wrong annex is wrong by an amount nobody can estimate. State the imposed load or traffic load model, and state the occupancy category for any platform or landing.
Require the dynamic assessment and give the acceleration limits and the crowd density it is to be assessed against, because the crowd scenario changes the answer more than anything else in that check. State the deflection criterion. The full set of documents that belongs here is listed in our note on which standards a footbridge tender has to cite.
Execution, material and finish
Name the execution class expected and the part of EN 1090 that applies to the material, and require the tenderer to confirm its certification covers both. Name the alloy and temper or the steel grade if there is a reason to constrain it, and otherwise require it to be stated in the offer.
Specify the finish by system and by the quality label required rather than by appearance, and say whether different parts of the structure carry different finishes. State the design life, because it is the assumption everything else in the durability section follows from.
Deliverables
List what has to arrive with the structure: structural calculations in a form the client’s engineer can check, the declaration of performance, as-built drawings, the operation and maintenance manual with a maintenance schedule stating intervals and access methods, and the certificates covering the fabrication.
This section costs nothing and it is the one that determines whether the client can look after the asset in year twenty. It is also the one most often reduced to a single line about a handover file.
Installation constraints
State what the site allows: access routes and their restrictions, available lay-down area, permitted working hours, closure or possession windows, and any environmental constraints on the season or the method. These drive the installation method and therefore a significant share of the price, and a bidder who does not know them will either price defensively or price optimistically, and both are problems.
Evaluation criteria
Say how the offers will be assessed before they arrive. If whole-life cost forms part of the assessment, publish the period of analysis, the discount rate and the residual value method, so that the models submitted are built on the same assumptions and differ only in the maintenance schedules, which is the part that should vary.
If quality criteria carry weight, state what evidence will be scored. Vague quality criteria are scored on presentation, which favours the bidder with the better proposal writer rather than the better structure.
The test to run before issuing
Read the draft as though you were a bidder trying to price it as cheaply as possible while remaining compliant. Every place where a cheap interpretation is available is a gap, and each one should either be closed or accepted deliberately.
That exercise takes an hour and it catches more than a technical review does, because it looks for silence rather than for error.
Before the document goes out
A specification that records decisions produces comparable offers, and a specification that describes intentions produces a negotiation. The difference is almost entirely in how many parameters are stated as numbers.
Our engineers will review a draft specification against the full standards set and mark where a bidder could legitimately price something cheaper than intended, so those gaps can be closed before the document is issued rather than argued about after award.