Progressive collapse is not a new phenomenon in structural engineering community. Earliest example of progressive collapse goes back to partial collapse of Ronan Point apartment building in 1968. After the bombing of the Murrah Federal Building in 1995 and collapse of Khobar Tower in 1996, considerable changes have been made in the design philosophy of the building structure to enhance progressive collapse resilience. But after the collapse of World Trade Center Towers due to terrorist attack in September 2001, many government authorities and local agencies have worked on developing guidelines for designing progressive collapse resistant structures. Among these guidelines, the U.S. General Service Administration (GSA 2003) and Unified Facilities Criteria UFC 4-023-03 published by Department of Defense (DoD 2013) provide detailed step-wise procedure and methodologies to resist the progressive collapse of building structures.
Marjanishvili (2004) discussed advantages, disadvantages, and limitations of various analysis procedure to investigate progressive collapse. Potential of nine-storey steel moment resisting building against progressive collapse was evaluated by performing linear static analysis, linear dynamic analysis, nonlinear static analysis, and nonlinear dynamic analysis (Marjanishvili and Agnew 2006). Effectiveness of different structural systems on progressive collapse resistance was also examined by researchers (Tsai and Lin 2008; Chen et al. 2012). Alashker et al. (2011) discussed various approximations considered during modeling for progressive collapse analysis and design.
Experimental investigations are equally important as they are helpful to validate the analytical findings. Kai and Li (2012) carried out experimental and analytical studies of progressive collapse resistance on four full scale beam column assemblies, which were part of eight-storey building. Behavior of steel and RC beam column assemblies with different seismic design and detailing under a progressive collapse scenario was studied (Sadek et al. 2011; Lew et al. 2013) through experimental and analytical investigations. Progressive collapse resistance of RC structure under column removal scenario was examined by many researchers (Yu and Tan 2013a, b; Su et al. 2009). Experimental studies were carried out on reduced scaled specimen such as beams and beam-column assemblies prepared with different design and detailing to observe the behavior under progressive collapse scenario. Progressive collapse resistance of precast concrete buildings was examined by Main et al. (2014) through experimental and analytical investigations on full scale test specimen. In their study, precast components were connected using steel link plates that were welded to steel angles embedded in precast beams and steel plates embedded in precast columns.
Many researchers have studied behavior of various types of precast beam column connections. Parastesh et al. (2014) developed new ductile moment resisting precast beam column connections. They have tested six full scale interior and exterior precast beam column connections under cyclic loading and compared their performance with monolithic connections. Seismic response of four full scale precast beam column connections subjected to cyclic loading was studied by Xue and Yang (2010) through experiments. Beam column connection include of exterior connection, interior connection, T connection and knee connections. Performance was evaluated in terms of stiffness degradation, energy dissipation capacity, displacement ductility, and failure mode.
Shariatmadar and Beydokhti (2014) tested three full scale precast beam to column connections by considering different detailing i.e., straight spliced, U-shaped spliced and U-shape spliced with steel plates within connection zone which was part of five-storey frame under reverse cyclic loading and compared its performance with monolithic connections. Choi et al. (2013) proposed design of precast beam column connections using steel connectors constructed by bolting steel tubes and steel plates fixed within precast components. This type of connection was suggested based on the results of cyclic load tests performed on five half scale interior precast beam column assemblies. Maya et al. (2013) recommended new beam column connection for precast construction using ultra high performance fiber reinforced concrete (UHPFRC) to achieve shorter splice length. They have tested four interior precast beam column assemblies subjected to cyclic loading.
Performance of reduced scaled and full scaled dry and wet precast exterior beam column connections were evaluated by conducting experiments under reversed cyclic loading (Vidjeapriya and Jaya 2012, 2013, 2014; Ertas et al. 2006; Joshi et al. 2005). Different means for precast beam column connections were adopted such as connection using dowel bar, dowel bar with cleat angles, cleat angles with single stiffener and double stiffener, tie rod and steel plates, use of cast in place concrete in beam and column, composite connection with welding, bolted connections, etc. Performance of precast connections was measured on the basis of strength, hysteretic behavior, energy dissipation capacity, ductility, and stiffness degradation and the same were compared with monolithic beam column connection.
Design handbooks are also available in which examples of different beam column connections are described (Elliot 2002; PCI 2010). These handbooks give design dimensions, capacity of different type of precast elements.