Strength Prediction of Iron and Steel Structures Using In-Situ Hardness Measurements

Iron and steel have been two of the main construction materials for engineering structures ever since it was introduced. The ease of construction, high strength to weight ratio are major driving forces of iron and steel construction. Researchers have found that strength of these structures reduces with ageing due to various environmental factors. In the modern world, civil infrastructure of the most of countries is getting older and needing urgent attention, repair and retrofitting to avert any catastrophic failures and thus ensure the safety of occupants. In this context, the prediction of existing strength properties of these structures is significant. However, such strength prediction has been a challengeable issue for design engineers. Considering the nature of structures, extracting iron or steel test specimens for coupon testing is not advisable as it would generate unexpected stress concentrations leading to structural failures. Therefore, there is a need to have methodology that would determine the strength properties of iron and steel members without harming to structures. This paper presents a novel method to find strength properties of iron and steel structures using in-situ Brinell hardness measurements which can be carried out through the portable hammer hitting type Brinell hardness tester. Initially, the obtained in-situ Brinell hardness values are converted to the ultimate tensile strength values which are then used for the determination of the Vicker’s hardness. The Vicker’s hardness is then used to determine the yield strength of the iron or steel material. The proposed methodology is verified with experimental material testing of a 130 years old railway bridge. It was found that the proposed methodology gives a reasonably accurate prediction for strength properties of iron and steel structures. Further, the proposed methodology was validated with a Wrought Iron bridge and a high strength steel bridge in Sri Lanka. Since in-situ test can be performed with low cost and have reasonable accuracy, it can effectively be used in the strength prediction of iron and steel structures.