WRONG-LENGTH BLIND BOLTS LEAD TO UNSAFE BRIDGE STRUCTURES - CROSS REPORT 1185
BRIDGE STRENGTHENING USING BLIND BOLTS GONE WRONG
WHO/WHERE/WHAT
A shear capacity metal bridge strengthening has been proposed by the introduction of cover web plates. Existing rivets have been replaced with blind bolts due to no access from the other side to facilitate the fastening of a nut.
A contractor could not find the right length of bolts so decided to use shorter ones, these, however, were too short and did not deploy on the other side of the web leaving the structure unsafe.
WHY?
Lack of control, understanding and communication.
HOW TO AVOID
Assure people doing the job understand what they are doing, why and what is the required outcome and then inspect. Retain the engineer for the duration of the project to address any supply or construction issues. Contractors, if the engineer is not retained by the client, put the clause in your contract that will account for this.
LESSONS LEARNED
Even a simple task of putting a bolt through a hole and tightening it can be done incorrectly.
The specified elements, if the variation in quality or length exists, may be changed during construction without due consideration, that be length, grade or type.
For anyone using any type of fastening, make sure to read the technical information and use them adequately. In the case of blind bolts where there is no possibility of inspection from the other side use only the sizes, you can check with the installation gauge from the fastening side.
One more thing to bear in mind is dissimilar material corrosion which may well be introduced during such operations.
We need to understand that construction is a team effort. This team effort does not only include people on site but also, project managers and designers. If there are issues coming up for whatever reasons these should be discussed among the team and the designer consulted prior to any decisions being made on-site. If such is the case that the designer needs to be employed by the contractor to advise on the issues due to the client’s appointment of the designer up to Stage 4, only, in accordance with the Structural Plan of Work, then that should be factored into the contract documentation prior to starting on site.
An attitude that disregards proper consideration and the value of communication and checking is simply wrong and may lead to disaster. In my experience, such circumstances are ever so often forced by monetary considerations associated with the consulting hours rather than the lack of will or time to find a common solution.
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