Structural performance of slab-column connenctions under impact and blast loading

This project is primarily concerned with the structural performance (strength & deformation capacity) of flat slab-column connections in reinforced concrete (RC) structures subjected to impact and blast loading. Flat slabs have been widely used in construction in the UK and worldwide due to their low cost and quick construction. Over the last 30 years, the interest on RC structures with high resilience to impulsive loads due to impact and blast has increased significantly to improve protection against the threat of terrorist acts targeting infrastructure or industrial accidents such as gas explosions or vehicle collisions. These extreme events can have catastrophic consequences in terms of human losses, economic losses and environmental impact. Structures that are required to resist high dynamic loads are for example office buildings and parking garages with high levels of threat (e.g. diplomatic buildings or important centres for business and transportation), industrial and storage facilities, nuclear power plants, protective barriers and some bridge piers. Previous research suggests that design against blast loading should be risk-based in which the type, probability and consequences of the event need to be examined against the costs of the protection and the assumed potential loss. The reliability of this type of analysis depends greatly on the accuracy in the estimation of the behaviour of the structure against impact or blast loading. The prediction of the residual strength of RC structures subjected to impulsive loading can be extremely challenging due to strong material nonlinearities and the influence of high strain rates on the behaviour. Shear mechanisms generally govern the response of RC structures subjected to impulsive loads and joint regions are generally critical. Shear failures have been observed experimentally even in members that were designed for static loading to fail in a ductile flexural manner. This is concerning since shear failures are brittle and can lead to progressive collapse of the structure. The dynamic effects on punching shear and progressive collapse are not well understood in RC structures and up to date there is no known physical model to predict the strength and deformation capacity of punching shear under impulsive loading. The principal aim of this project will be to provide a theoretical model for the design and analysis of slab-column connections under impulsive loading which can be used in practice by researchers and designers. Existing experimental data will be used to validate the model and non-linear dynamic FE analysis will be carried out to support the theoretical model.

The proposed project will contribute towards quantifying the structural performance of existing and new reinforced concrete infrastructure against impact and blast loading. This is particularly relevant for critical infrastructure in buildings, transportation and energy sectors in which structural failures can have severe consequences in terms of human and economical losses as well as environmental impact. The advancements in this area from the proposed work could help improving governmental policy making on infrastructure planning which directly affects the three pillars of sustainability: society, environment and economy. The two main types of economic and societal impacts generated from this research are (i) shaping and enhancing the effectiveness of our infrastructure and transforming evidence based policy in practice and (ii) influencing/informing practitioners and professional practice. The methodologies developed will also contribute to reduce uncertainty in appraisals and strengthening of critical structures and thus improving quality of life and national security against threats such as terrorist attacks or industrial accidents.

A direct beneficiary of the proposed project is Arup which has a well recognized experience of research & development around projects dealing with impact and blast loading through the Advanced Technology & Research Group and the Resilience, Security and Risk Group. Tony Jones and David Cormie who represent these two groups in Arup have shown their interest in the proposed topic and will be collaborating in the project by providing useful feedback and in-kind technical support. Work carried out in Arup included research on non-structural and structural elements. The model to be developed in the proposed research project will allow validating numerical tools for impact and blast design currently used in Arup and will also contribute in the area of progressive collapse and robustness. This area is a strong point of interest to Arup as shown in their latest report on robustness in 2011 for the Department for Communities and Local Government (DCLG) and the Centre for the Protection of National Infrastructure (CPNI). Both DCLG and CPNI could be indirect beneficiaries from the proposed research. Moreover, robustness is a topic that has also been raised at the Standing Committee On Structural Safety (SCOSS) which in turn has significant social impact through their studies and publications. The topic is also of relevance to documents on robustness and progressive collapse, which Arup is a key contributor (e.g. IStructE guideline documents).

The applications and suggestions for future work from the proposed project could also benefit the Future Infrastructure Forum (FIF) network supported by EPSRC, in which University of Surrey is involved in. Another potential beneficiary of this project in the UK could be the Concrete Industry Eurocode 2 Group (CIEG); the PI has been recently nominated to join this group. Both FIF and CIEG groups bring together UK academics, industry and governmental bodies. Some examples of industrial collaborators in these two groups include BRE, The Concrete Society, The Concrete Centre, Arup, Atkins, Buro Happold and Ramboll amongst others; some examples of governmental bodies involved include Network Rail, Highways agency, TFL and Infrastructure UK.

At an international level, the project could benefit the Fédération International du Béton (fib) which seeks advances in structural concrete technologies and design. Both fib and CIEG groups have recently expressed the need to carry out further research on punching shear which needs to be addressed in future codes of practise (refer to UK fib group forum in Birmingham 2011 and CIEGmkII meeting in January 2012). Hence, the project can have a relevant impact on UK design practice with social and economic benefits.