Advanced structural materials


In the past few decades, the modern design philosophy of structural engineering has gradually shifted from preventing building collapse and loss of lives to high-performance objectives. However, traditional construction materials (e.g., concrete, wood, and steel) may not meet some of the high-performance structural design objectives under extreme disasters. The increasing demand for high-performance objectives has motivated the exploration of advanced structural materials. Research is currently conducted in the Institute for Steel Construction on different structural materials such as:

High-strength memory® steel: As a special type of advanced metallic materials, shape memory alloys (SMAs) have been developed toward structural engineering in recent years. SMAs can withstand large strains and still recover the initial shape via heating (i.e., shape memory effect) or unloading (i.e., superelasticity). Iron-based SMAs, which is also called memory® steel, has gained attention in construction given its low price and high recovery stress behavior. Memory® steel, which is a type of ductile high-strength steel, is currently used as prestressed elements and coupling devices in construction.

Wire and arc additive manufactured (WAAM) steel: due to unsmooth surface morphology of the steel produced by WAAM technology, there is a need to characterize the behavior of WAAM steel with regard to structural standards. The performance of the material under low and high-cycle fatigue as well as corrosion shall be still understood before it can be used in construction.

Carbon fibre reinforced polymer (CFRP): CFRPs are composite material that consist of two parts: a matrix and a reinforcement. In CFRP the reinforcement is carbon fiber, which provides its strength. The matrix is usually a polymer resin, such as epoxy, to bind the reinforcements together. CFRP material is a lightweight, strong and noncorrosive, which could be used in applications where corrosion could be an issue such as offshore structures. CFRP could be used for repair of steel structures as prestressed tendon or non-prestressed bonded systems.

Structural epoxy adhesives: structural components are often bolted or welded in construction. Structural epoxy adhesives provide another fastening solution with minimum stress concentration on the substrate steel. Given their polymeric material base, they are noncorrosive, which justify their applications in offshore structures. There are ongoing studies on different types of linear and nonlinear structural adhesives under static and cyclic loading regime. Different bond-slip models are developed to describe the material behavior of the bonded joints.

Corroded steel: in addition to the above advanced new materials, our research also considers new models for conventional old-standing issues such as corrosion in steel. Support structures for offshore wind turbines are exposed to harsh environmental conditions and simultaneously subjected to high dynamic loads due to wind, waves and operation. Despite corrosion protection, the support structure cannot be always fully protected against corrosion. This may lead to pitting corrosion of the steel surface, which causes local stress concentrations and thus affects the fatigue life of the structure. In order to evaluate the remaining service life of existing support structures after pitting, it is necessary to quantify the influence of pitting and to take it into consideration when analysing the remaining fatigue life. There is need for research to provide understanding on the notch effect due to pitting on the crack location and crack path.