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Concrete 3D Printing (3DP) is a potential technology for increasing automation and introducing digital fabrication in the construction industry. Concrete 3D Printing provides a significant advantage over conventional or precast methods, such as the prospects of topologically optimized designs and integrating functional components within the structural volume of the building components. Many previous studies have compiled state-of-art studies in design parameters, mix properties, robotic technologies, and reinforcement strategies in 3D printed elements. However, there is no literature review on using concrete 3D Printing technology to fabricate structural load-carrying elements and systems. As concrete 3DP is shifting towards a large-scale construction technology paradigm, it is essential to understand the current studies on structural members and focus on future studies to improve further. A systematic literature review process is adopted in this study, where relevant publications are searched and analyzed to answer a set of well-defined research questions. The review is structured by categorizing the publications based on issues/problems associated with structural members and the recent technology solutions developed. It gives an overall view of the studies, which is still in its nascent stage, and the areas which require future focus on 3D printing technology in large-scale construction projects.

To study the seismic performance of self-centering circular-section rocking steel bridge piers whose functions can be restored after an earthquake, a high-precision finite element (FE) analysis model of such a bridge piers was established. The hysteresis behavior of concrete-infilled and hollow rocking steel bridge piers was compared. In response to the characteristics of the local deformation of the wall plates and elliptical deformation of the bottom surface, two reinforcement methods for the pier bottom, namely thickening the wall plate and adding longitudinal stiffeners in the plastic zone of the pier bottom, were proposed. The pseudo static analysis of bridge piers was carried out considering the effects of overall design parameters and reinforcement parameters of the pier bottom. The results indicate that the FE model used in this paper can obtain accurate horizontal load-displacement curves of rocking steel bridge piers. The hysteresis curves of the rocking steel bridge piers and infilled concrete rocking steel bridge piers is close, and directly using hollow steel bridge piers can improve the economic efficiency of the design. Compared to adding longitudinal stiffeners, the reinforcement form of thickened wall plates at the pier bottom has a better effect in improving the seismic performance of bridge piers. The reinforcement of the pier bottom has little effect on the energy dissipation capacity of the bridge pier, but it helps to reduce residual displacement and improve lateral stiffness.