The increasing prevalence of mixed-material buildings that combine concrete walls and steel frames in New Zealand, coupled with a lack of specific design and detailing guidelines for concrete wall-steel beam connections, underscores the need for comprehensive research to ensure that these structures behave as intended during earthquakes. Bolted web plate connections, commonly found in steel framing systems, are typically used to connect steel beams to concrete walls. These connections are idealised as pinned during design. However, research on steel framing systems has shown that these connections can develop significant stiffness and moment resistance when subjected to large rotations during seismic loading, potentially leading to brittle failure when used in concrete wall to steel beam applications. This thesis was written to understand the seismic performance of concrete wall-steel beam bolted web plate connections, providing experimental evidence, numerical modelling insights, and design recommendations to address critical gaps in current design practices. The study is divided into three phases. First, a review of 50 concrete wall-steel frame buildings in Auckland and Christchurch was conducted to understand current design practices and typical connection details. The findings revealed significant variation in design and detailing practices and a lack of specific guidelines for concrete wall-steel beam connections. Second, an experimental programme was conducted on four full-scale concrete wall-steel beam sub-assemblages, each incorporating variations in connection detailing. The tests were designed to quantify the rotation capacity of concrete wall-steel beam connections, identify failure modes and investigate the effectiveness of potential connection improvements. Results demonstrated that concrete wall-steel beam bolted web plate connections designed using current design standards and following existing practices are vulnerable to non-ductile failure characterised by concrete breakout. However, using slotted holes in the web plate and bent reinforcing bar anchors instead of headed stud anchors improved connection rotation capacity. Third, a numerical model of a case study building was developed on OpenSeesPy, with different connection conditions assumed based on the experimental results. Pushover and time history analyses were conducted to evaluate the implications of different connection conditions (pinned vs non-pinned) on global building response and local member demands. The findings revealed that using non-pinned connection conditions does not significantly affect the global building response and shear and bending moment demands on lateral load-resisting elements. However, doing so generates overstrength moments on the connections that induce different actions on out-of-plane concrete walls connected to steel beams. Synthesising findings from all three phases, this thesis concludes with a proposed design procedure for concrete wall-steel beam connections based on a capacity design approach to ensure ductile failure modes and suppress brittle ones. Key recommendations include selecting appropriate bolt hole geometry and anchorage, providing sufficient rotation capacity, and accounting for connection overstrength in global analyses
Following the 2010/2011 Canterbury (New Zealand) earthquakes the seismic design of buildings with precast concrete panels has received significant attention. Although this form of construction generally performed adequately in Christchurch, there were a considerable number of precast concrete panel connection failures. This observation prompted a review of more than 4700 panel details to establish representative details used in both existing and new multi-storey and low rise industrial precast concrete buildings. The detailing and quantity of each reviewed connection type in the sampled data is reported, and advantages and potential deficiencies of each connection type are discussed. Following the Canterbury earthquakes, it was observed that brittle failure had occurred in some grouted metal duct connections used for precast concrete wall panels, resulting in recommendations for more robust detailing of this connection type. A set of experimental tests was subsequently performed to investigate the in-plane seismic behaviour of precast concrete wall panel connections. This testing comprised of seven reversed cyclic in-plane tests of fullscale precast concrete wall panels having wall-to-foundation grouted metal duct connections. Walls with existing connection detailing were found to perform adequately when carrying low axial loads, but performance was found to be less satisfactory as the axial load and wall panel length increased. The use of new recommended detailing was observed to prevent brittle connection response and to improve the robustness of the reinforcement splice. A parametric investigation was conducted using the finite element method to predict the failure mode of metal duct connections. From the results of the parametric study on metal duct connections it was identified that there were three possible failure modes, being reinforcement fracture, concrete spalling without metal duct pull out, and concrete spalling with metal duct pull-out. An alternative simple analytical method was proposed in order to determine the type of connection failure without using a time-consuming finite element method. Grouted sleeves inserts are an alternative connector that is widely used to connect wall panels to the foundations. The two full-scale wall panels were subjected to reversed cyclic in-plane demands until failure of either the connection or the wall panel. Wall panel failure was due to a combination of connection reinforcement pulling-out from the coupler and reinforcement fracture. In addition, non-embedded grouted sleeve tests filled with different quality of grout were conducted by subjecting these coupler assemblages to cyclic and monotonic forces
The susceptibility of precast hollow-core floors to sustain critical damage during an earthquake is now well-recognized throughout the structural engineering community in New Zealand. The lack of shear reinforcement in these floor units is one of the primary reasons causing issues with the seismic performance of these floors. Recent research has revealed that the unreinforced webs of these floor units can crack at drift demands as low as 0.6%. Such observation indicates that potentially many of the existing building stock incorporating hollow-core flooring systems in cities of relatively high seismic activity (e.g. Wellington and Christchurch) that probably have already experienced a level of shaking higher than 0.6% drift in previous earthquakes might already have their floor units cracked. However, there is little information available to reliably quantify the residual gravity load-carrying capacity of cracked hollow-core floor units, highlighting the need to understand the post-cracking behavior of hollow-core floor units to better quantify the extent of the risk that cracked hollow-core floor units pose
