When facility operators and managers observe cracks and spalling in their concrete structure, or hear of other facilities experiencing cracking or a failure, they often begin to question the sturdiness of their own structures and call in a qualified engineer to examine the plant. But if the facility doesn’t have a document called a baseline, the engineer is forced to act as a detective investigating as far back as the original construction to determine whether the cracks are related to design, construction or operator error or a combination of these factors. Cracks, fissures and spalling can happen for a variety of reasons, and without the full history of the bin, it may be more difficult to determine how the problem arose, whether it is serious and how to fix it.
Dick Kobetz, president of Sunfield Engineering, Inc., says a good baseline, a collection of records and data that show the evolution of the bin since construction, is one of the key aspects in maintaining slip-formed concrete structures. In the event that you need to have an engineer inspect the facility, the more background or baseline data an investigating engineer has — versus assumptions — the more accurate the analyses and conclusions.
Concrete bins, when designed properly, are practically a zero-maintenance asset; however, there are steps that should be taken before construction and annually to ensure that the bin will function for years to come.
The first step in ensuring the longevity of a concrete structure is properly assessing the ground on which you want to lay the structure’s foundation.
Before beginning construction on any project, it’s important to hire a geotechnical engineer to survey the area. They will use soil borings to determine what type of soil is present, the substrata, what the geological layout is and how much weight can be put on the potential construction site.
“People with small projects or plans to build lighter structures may be tempted to skip this step,” says Kobetz. “The $8,000 to $12,000 required to hire a geotechnical engineer might sound like a lot, but the truth is that’s the cheapest insurance you’ll ever buy for a structure.”
Starting a project on inadequate soil can cause foundation damage later on, a problem that may be difficult and expensive to fix once the structure is fully built and in use.
Once the geotechnical report deems the area fit to build on and the structure is erected, keep the report with your baseline.
Creating a baseline
A good baseline should consist of several key pieces of data, including a survey of the property, geotechnical reports, facility drawings, construction specs, existing structural analyses, dated photos and a history log. Rarely will all of this data be available, but managers should be committed to acquiring as much information as possible.
A properly designed, constructed and operated concrete structure may last over 100 years, but it will probably endure many changes before its useful life is over. Changes in the bin over time are not cause for concern alone, but not monitoring the changes or understanding why these changes occurred can cause problems.
A history log can be crucial because it will tell you if or how much an aspect of the bin has changed since construction. Kobetz suggests using an electronic spreadsheet to document the history of the plant including new information and events such as unusual weather, structural failures or accidents. Electronic files make it easy to back up and store the data in several places, making it accessible on the corporate network as well as on the plant level computers.
Managers should document weather events, such as excessive rain, flooding, earthquakes and tornados, which occur relative to observed changes in the structure. Structural changes, such as settlement of the foundation walls, tunnels, pits and bin bottoms should also be noted as well as the cause of the change in condition and the subsequent remediation.