The research papers published in Proceedings of the Institution of Civil Engineers – Structures and Buildings present the development of structural knowledge in a wide variety of applications. This March issue reflects this variety ranging from research on innovative load carrying systems, which help fulfil challenging architectural aspirations, to infrastructure where structural performance can often be critical to ensuring functionality and safety.
Glass curtain walling is an extremely prevalent envelope type for offices and public buildings. The use of a pre-stressed cable net to support glazing, which is addressed in the first paper (Shi et al., 2015), is a particularly attractive structural solution for designers owing to, the low visual impact of the cables on such a transparent envelope and the system's structural efficiency. The New Beijing Poly Plaza (the headquarters of the Poly Corporation), designed by Skidmore, Owings and Merrill and completed in 2007, is currently one of the largest glass curtain walls supported in this manner at 60 m wide and 90 m tall (Steel Construction Institute, 2011). The resulting elegantly thin structure maximises the natural daylight in the building's atrium.
Shi et al. (2015) evaluate the effect of the loss of pre-stress in a single cable, the loss of pre-stress in multiple cables and the failure of the cable anchors, through a finite-element study validated by an experimental programme. Changes in cable forces and the curtain wall's deflection are determined for these different scenarios. Through the study the contribution of the glazing to the stiffness of the combined curtain wall and support structure is able to be determined.
The second paper (Zhou et al., 2015) focuses on another architecturally dramatic structural system, a diagrid (or diagonal grid) structure where, rather than having separate structural elements to deal with the vertical and horizontal loads, both loads are channelled into diagonally orientated structural elements. This structural system has been claimed to have originated from a Russian polymath Vladmir Shukhov in the late 19th century. An example of his designs using this structural system is the Shukhov Radio Tower in Moscow, built in the early 1920s (Boake, 2014). A more recent and perhaps more famous example is 30 St. Mary Axe or ‘The Gherkin' by Arup and Foster and Partners whose steel diagrid has complex nodal connections that join straight diagonal elements together to achieve the double-curved surface of the building (Munro, 2004). The design of the nodes is key to the constructability and cost of this type of structural system.
Zhou et al. (2015) document in detail the experimental study and finite-element analysis conducted to design Y-shaped nodal connections for a specific skyscraper built in Dalian, China. The Y-shaped connections are employed to transfer the forces from the diagrid structure into vertical columns, a design choice that can often be made where the diagrid meets the ground to allow easily detailing of access points into the building. The nodes considered in this study are fabricated in reinforced concrete. Based on the study practical recommendations are made for the design of such connections.
In contrast to the preceding papers the third paper (Rezaiee-Pajand and Tavakoli, 2015) addresses a type of structure generally considered a pure feat of engineering, dams. The monitoring and maintenance of such structures is paramount to ensuring their structural integrity, the failure of which can cause catastrophic effects as exemplified by the 1975 Banqiao Reservoir Dam failure in China. This disaster is thought to have caused both directly and in its aftermath the death of over a hundred thousand people (Qing, 1998). Rezaiee-Pajand and Tavakoli (2015) introduce a new method for crack detection in concrete gravity dams. Bringing together finite-element modelling and a genetic algorithm a rapid rate of convergence is achieved to obtain both the location and magnitude of cracks. The method can model existing cracks and with minimal physical data predict new ones.
In the last quarter of 2014 an earthquake in the Yunnan province of China reminded us of another type of event that can be equally devastating. The final paper (Halabian and Zafarani, 2015) offers an approach to considering the inelastic seismic response of reinforced concrete frames, their foundations and their interaction with the underlying soil. Modelling this interaction as a system with multiple degrees of freedom, rather than the more often investigated single degree of freedom, demonstrates the importance of accurately considering the flexibility of foundations in different earthquake scenarios.
