The subject of structural integrity and structural assessment has gained popularity. Tenants also want the reassurance that the structure they are renting is safe for those who use it, as do building owners and operators. Many readers, however, might not fully comprehend what a structural assessment involves or why they are so crucial. Let’s investigate those topics in more detail and look at the information that can be useful if you want to perform a structural assessment soon.
What is structural assessment?
Engineers can verify the accuracy, structural soundness, and strength of structures and their components using a structural assessment technique. A structural assessment is performed to determine the future usage and compliance with the current building codes as well as to examine the current condition of the structures.
In what circumstances structural assessment is needed?
- When a building has been purchased or sold.
- When new machinery is installed.
- When assessing the structural capacity and viability of any building additions or renovations.
- When a building’s usage or occupancy changes.
- When changes are found that could be a sign of a structural problem.
- When there is change in structural loading.
What are the steps for structural assessment?
- Site Background
When evaluating the current condition of the existing building, it is crucial to understand the site history. This is the first step in the process. From this point, we may start to learn more about the structure that is being evaluated. Before we begin the evaluation, there are a few things we need to know, including the building’s age or construction date, its change in occupancy, and any renovation work that has been done. These variables will already provide us a sense as to what our strategy will be and how we will be able to use this data in our evaluation.
- Actual Site Inspection and Visit
To do a preliminary evaluation of the building and ascertain the potential severity of the damages and faults, a visual site inspection is required. The Engineers should actually visit the site to conduct a visual evaluation and obtain information about the building’s condition. Physical defects including cracks, corrosion on the reinforcement, obvious beam deflections, and other visible defects should be photographed and documented.In order to detect any potential structural defects, such as cracks, excessive movements, bowing, deflections, or differential settlements, structural evaluation process involves visual observations of structural members like columns, beams, joists, load-bearing walls, slabs, roof decking, foundations, and connections. The following are typical inspection findings that can be found in concrete during site inspections and observations: –
- Cold joints
- Honeycombed concrete
- Hairline cracks in slabs and slab soffits
- Exposed steel reinforcement due to insufficient concrete cover
- Column misalignment due to bad formworks during casting
- Collecting Structural Samples for Lab Testing
Concrete samples or specimens should be gathered on the spot and transported to the lab for additional analysis. This is done to determine the density and compressive strength of the current structural members and to further validate the necessary information and data. Non-destructive testing ought to be carried out in most cases. It is advisable to do site testing, which may involve: –
- Covermeter Survey – It was carried out using a Protovale Covermeter and in accordance with the recommendation as specified in BS 1881:Part 204. The test uses the idea of the magnetic field signal produced by the equipment probe to identify embedded ferromagnetic steel reinforcing bar (herein referred to as rebar). When the device records the strongest pitched signal, the rebar is identified, and the concrete cover is then immediately read from the metre (after pre-setting the rebar size). The spacing of the main and secondary/link rebars was also calculated by finding the nearby rebars. In this exercise, covermeter test was performed at the RC member covering area not less than 500mm x 500mm at each test location. Concrete cover measurement was then obtained from the rebar nearest to the concrete surface.
- Carbonation Test – The depth of carbonation of the concrete was determined using a phenolphthalein indicator solution (colourless) in accordance with the BRE IP/6. The indicator solution was either sprayed onto the freshly cut surface of the extracted cores or the coring/hacking holes in the element. The depth of concrete, onto which the surface remains colourless after the solution was sprayed, is measured as the depth of carbonation Carbonation is a process whereby carbon dioxide and moisture from the ambient environment react with the alkaline constituent of cement paste to form calcium carbonate, thus could reduce the alkalinity of the cement paste. This reaction destroys the concrete passivation effect that protects the reinforcement. In this exercise the carbonation test was performed on the freshly cut core.
- Rebound Hammer – Rebound Hammer test was carried out using a Schmidt Rebound Hammer in accordance with the recommendation as specified in BS 1881:Part 202. In normal exercise, 12 nos rebound number readings were obtained at an interval of 25mm square grids over an area of 100mm x 75mm area at each test location.
- Resistivity Measurement – Concrete resistivity test was performed using a Wenner-Proceq Model resistivity meter. This test measure the electrical resistivity of reinforced concrete which influences the corrosion rate of the rebar. Corrosion of steel is an eletrochemical process which generates movement of ionic current and can dissolve metals. The lower the electrical resistance, the more readily the corrosion current flows through the concrete and the greater is the corrosion rate for the rebar. The classification of the rebar corrosion rate at each test location can be assessed by comparing the measured potentials with the guideline given in John P. Broomfield “Corrosion of Steel In Concrete” 1997 publication and shown in table below.
- Extraction of Concrete Strength Test – Concrete core samples of either 75mm or 100mm diameters were extracted from selected RC members using a coring machine with water cooled diamond tip core cutter. Before coring, a covermeter survey was first carried out to locate the reinforcement. The concrete cores were sent to the laboratory for compressive strength.
- Core Compressive Strength Test – The concrete core samples were tested in compression in accordance with BS 1881 : Pt 120 : 1983 to determine the estimated in-situ cube strength (EICS) of the concrete. In addition, visual examination and density measurements were also performed on these samples.
- Ultrasonic Pulse Velocity Test – The test was conducted using a “PUNDIT” tester in accordance with BS 1881 : Part 203 : 1986 employing the direct method.
Table 1: Classification of Corrosion Rate by Resistivity Test
Low corrosion rate
10 to 20
Low to moderate corrosion rate
5 to 10
High corrosion rate
Very high corrosion rate
- Damages and Defect Markups
A summary of the defects detected during the site inspection should be prepared by the engineer. It is important to accurately record on the plans any faults and defects discovered during the visual assessment. Each plan should provide a detailed description of the types of faults and their locations. This makes it simple to find and inspect the defects for future use. The engineer will create a thorough plan that takes into account all architectural and structural factors.
- Analyzing and Evaluating Test Results
The next duty for the engineer participating in the evaluation of the structural integrity of the existing building is to synthesise all the results and findings based on the physical and mechanical properties of concrete and as a result of the data and laboratory tests mentioned above. He or she should list and clearly delineate these facts before drawing a judgement on the general safety of the building. At this point, the concrete’s quality is known, the area’s actual concrete coverage has been determined, and perhaps most significantly, the concrete’s actual compressive strength f’c has been determined.
After the interpretation and conclusion are provided, a recommendation is also necessary. If structural strengthening is necessary for the affected structural members, the structural engineer will either suggest it or make the final decision. The defects that are physically visible should be repaired if necessary. Therefore, in the event of low concrete compressive strength results, a structural redesign and design of the building utilising the real design data results acquired from the laboratory testing should be taken into consideration. In order to increase the strength of the existing structures, structural retrofitting and strengthening are a necessity.
- Remedial Action
As recommended by the engineer, structural strengthening may be necessary. Planning remedial work is necessary to ensure the building is structurally sound and safe. It is important to think about the type of repair that is necessary as well as the process for carrying it out. According to the engineer’s findings and recommendations, structural improvement, jacketing, and retrofitting may be suggested. For some concrete/structural strengthening ideas, read this article at https://structuralrepairs.com.my/carbon-fibre-strengthening-the-advantages-of-carbon-fibre-for-existing-structures/For some structural strengthening projects which Structural Repairs (M) Sdn Bhd had completed previously, read the project references at https://structuralrepairs.com.my/projects/structural-repair-strengthening/
We, Structural Repairs (M) Sdn Bhd have more than 30 years of experience in this industry. We provide the structural assessment services as follows: –
Structural Assessment Services
- Condition Assessment/ Forensic Evaluation of Existing Structure
- Preliminary assessment
- Non-destructive testing
- Preparation of as-built drawings
- Budgetary cost estimation
- Setting up quality norms and procedures
- Project monitoring
- On-site real-life load tests
Kindly visit to our website at https://structuralrepairs.com.my/ or contact us at Tel: +603-91731728/29 Whatsapp: +60 12-334 9113