We keep hearing about the collapse of old and dilapidated buildings, especially during the monsoon season. Failure of bridges and other structures is equally common, but they do not attract as much media attention unless their failures lead to the loss of lives. With growing age of the structures, sub-optimal quality of construction and improper maintenance, etc, the risk of failure of structures is gradually on the rise and it is expected that this trend will only accelerate.
Many owners of the ageing assets are acutely aware of the risk that they carry in this regard. As a result, there is an increasing requirement of conducting structural audit of the old buildings, bridges, and other structures. Many municipal corporations mandate that all buildings older than 30 years should be audited and have structural stability certified by a licensed structural engineer.
We at GEM Engserv have had many opportunities to bid for assignments of structural audits and also fair experience of conducting such audits. Based on our experience, we have identified some actions of the asset owners that prevent them from getting the most effective structural audit services. These are discussed below, and alternate / better practice is also suggested. To appreciate our point of view, it is essential that we look at the right method and sequence of conducting the structural audit.
Structural audit comprises of the following steps:
We often find that the owners invite bids from structural auditing firms with the expectation that the auditor will inspect and issue stability certificate in one go. It is apparent from the process detailed above that no auditor can assess the efforts required to reach this end objective.
If forced, the auditor will have no option but to assume some amount of NDT and either overprice the bid or take the commercial risk! On top of that, it is also incorrect to presume that the structure is sound enough to receive a stability certificate ‘as it is’.
In order to assess the efforts, drawings, photographs, and previous audit reports are required. We have come across cases where the client responded with a comment that these documents will not be shared at the bidding stage but will be provided to the auditor after the issue of the work order. This position may stem from fear of negative publicity or loss of confidential information, but the adverse repercussion of this behavior is not adequately realized. For very old structures, drawings are often not available for obvious reasons.
However, for comparatively newer structures (constructed in the 21st century!), absence of drawings is a serious lacuna in asset management practices.
It is clear that structural audits are highly technical works and there are often queries from the auditors that can only be answered by a technical person from the owner’s side. The procurement team often lacks the technical experience to handle such queries and the communication becomes circuitous in nature with a greater risk of miscommunication.
The first visual inspection requires the expert to reach the structure at a touching distance. We have tried using binoculars, high-resolution cameras, and drones, etc., but the confidence that we get from a ‘touching distance’ inspection is unmatched. This requires aids like scaffolding, ladders, or scissor cranes, etc. Obviously, the owner is better placed to organize these resources.
Most auditors are from consulting organizations, and they do not have the capability to arrange these at the premises of the owner. We have often found owners extremely reluctant to take responsibility for providing these resources or even facilitating us in getting these through established local service providers. Auditors add value by their technical expertise and not through the provision of such resources and by transferring the responsibility to the auditor firm, owners’ risk not getting the most suitable auditor on board.
In some cases, we have come across the owners mandating certain NDT to be conducted regardless of the condition of the structure. NDT is considered an infallible tool with the expectation that the NDT results are superior and more reliable than technical judgment. Sometimes, it is also thought that more the NDT, better will be the assessment.
The nature and extent of NDT is best judged by the expert auditor who not only understands the structural behavior, but also can judge the signs and symptoms visible and connect these with deterioration in the material. Mandating NDT in the bid document may provide a false sense of comparing all bids on apple-to-apple comparison but may lead to either over-specification (and cost) or variation after the auditors feels the need for more or different tests.
Structural stability can be certified if the structural design is available, and all critical components are accessible and inspected during the audit. Often, some parts of the structure are not accessible and inspected, such as foundations and elements covered by false-ceiling and cladding etc.
Obviously, the structural engineer can not provide an unconditional stability certificate. We find that some owners do not accept any disclaimer to the structural stability certificate arising out of such genuine reasons. Forcing the auditor to furnish an unconditional stability certificate that is to apportion the risk in an unfair manner and doesn’t really protect the owner.
To get the most effective structural audits performed, it should be planned as a three-step process. Steps 1, 3, 4 ,6 & 7 should be performed by a specialist structural audit agency and steps 2 and 5 should be performed by specialist lab and contractor respectively, with coordination by the structural auditor. The owners should also understand and accept the limitation of the stability certificate and agree to carry the risk.