Recent advances in materials science have led to the development of smart materials that can continuously adapt to different loading conditions and changing environment to meet the growing demand for smart structural systems. The unique characteristics of superelastic NiTi shape memory alloys (SMAs) have attracted the attention of structural engineers worldwide. SMAs are metallic materials that can retrieve their original shape upon exposure to various temperatures or loading/unloading conditions with minimal residual deformation. SMAs have found increasing applications in the building industry because of their high strength, high actuation and damping capacities, good durability, and superior fatigue resistance. Despite the research conducted on the structural applications of SMAs during the previous decades, the existing literature lacks reviews on their recent uses in building industry such as prestressing concrete beams, seismic strengthening of footing–column connections, and fiber-reinforced concrete. Furthermore, scarce research exists on their performance under corrosive environments, elevated temperatures, and intensive fires. Moreover, the high manufacturing cost of SMA and the lack of knowledge transfer from research to practice are the main obstacles behind their limited use in concrete structures. This paper sheds light on the latest progress made in the applications of SMA in reinforced concrete structures during the last two decades. In addition, the paper concludes with the recommendations and future opportunities associated with expanding the use of SMA in civil infrastructures.

The deterioration or ageing of the existing infrastructures coupled with increased safety requirements necessitate immediate strengthening. Developing long lasting and cost effective repair techniques and materials continue to capture the attention of concrete professionals worldwide. The main purpose of this investigation was to extend the life span of a multi-storey precast reinforced concrete structure built in Riyadh 40 years ago. The condition assessments relied on analytical tools, visual, field and laboratory experiments for core samples collected from the building. The analytical checks of the building revealed considerable deflections of some slabs because of design error. The field and chemical analysis tests performed, confirmed the occurrence of durability defects as a result of poor workmanship during the construction stage. Several state-of-the-art repair techniques and materials were used for enhancing the service life of the structure at a minimum cost. The Repair strategy implemented included, removal of the deteriorated concrete, pouring a bonding agent on the surface of the damage, followed by injecting high strength cementitious grouts, supporting the deflected slabs using I-section steel beams, using cathodic protection to prevent corrosion, strengthening the columns and beams using carbon fiber reinforced polymer (CFRP) sheets, and steel jackets. Doi: 10.28991/cej-2020-03091630 Full Text: PDF

Upgraded design standards coupled with the damage caused by natural disasters have led to the development of smart materials with the potential to modernize current construction practices. This investigation proposes a nonlinear finite element (FE) model for evaluating the performance of beam–column joints (RC-BCJ) reinforced with shape memory alloys (SMA) and steel rebars. The model was validated based on accredited experimental data, followed by parametric analysis in ABAQUS to optimize the use of SMA bars for enhancing the seismic resistance of RC-BCJ without compromising their energy dissipation capacity. Parameters investigated include the (a) SMA–steel reinforcement ratio, (b) lengths of SMA bars, (c) elastic modulus of SMA, (d) compressive strength of concrete, and (e) axial load applied on the column. The finite element simulation results indicated that the model was capable of predicting the optimum length of SMA bars sufficient for relocating the plastic hinge away from the face of the column along the beam. Further, simulation results proved that the use of SMA bars in conjunction with steel reinforcement could be considered as an effective tool for enhancing the seismic performance of RC-BCJ joints. Among the parameters investigated, high-strength concrete was the most effective in improving joint resistance.

Residual drifts are an important measure of post-earthquake functionality in bridges and buildings, and can determine whether the structure remains fit for its intended purpose or not. This study aims at investigating numerically, through finite element (FE) analysis in ABAQUS, the cyclic response of exterior steel I beam-hollow column connection using welded shape memory alloys (SMA) bolts and seat angles. This is followed by validating the numerical model using an accredited experimental data available in the literature through different techniques, (1) SMA bolts, (2) SMA angles, (3) SMA bolts and angles. The parameters investigated included: SMA type, SMA angle thickness, SMA bolt diameter, SMA angle stiffener and SMA angle direction. The cyclic performance of the steel connection was enhanced further by varying the bolt diameter, plate thickness, angle type and direction. The results revealed that the connections equipped with a combination of SMA plates and SMA angles reduced the residual drift by up to 94%, and doubled the self-centering capability compared to conventional steel connections. Moreover, the parametric analysis showed that Fe-based SMA members could be a good alternative to NiTi based SMA members for improving the self-centering capability and reducing the residual drifts of conventional steel connections.