Passive energy dissipation technique has been used for decades to dissipate seismic energy as the proposed devices are efficient, relatively inexpensive, easy to install and do not rely on external power supply as required by their active counterparts. Metal yielding devices are widely used for passive energy dissipation due to their simple design and stable hysteretic energy dissipation characteristics. Yielding shear panel device (YSPD) is a newly proposed metal yielding passive energy dissipation device, which exploits the inelastic shear deformation capability of a steel plate welded inside a square hollow section (SHS) to absorb seismic energy. Preliminary experiments performed in the laboratories justify the suitability of the concept by showing stable hysteresis response for YSPDs.
The current research primarily investigates the performance and the energy dissipation characteristics of YSPDs using numerical techniques. Nonlinear finite element (FE) models have been developed using the general purpose FE package ANSYS and have been verified using available test results. Material coupon tests have been analysed to obtain an appropriate material model, whilst the geometric nonlinearity has been incorporated to include large deformations observed during the experiments. Nonlinear spring elements have been used to model the appropriate support conditions, which deemed to be the most sensitive issue to affect the performance of YSPDs. Results obtained from the developed FE analysis showed reasonable agreement against the test results for both monotonic and cyclic loadings. Once verified, the FE models are used to generate reliable results for a thorough parametric study to investigate the effects of individual design parameters i.e. thickness of the diaphragm plate, size of the YSPD etc. on the overall performance of a YSPD. The potential of using stainless steel in YSPD has also been investigated as it offers significantly higher ductility than the ordinary carbon steel.
An appropriate mathematical model for YSPDs will allow to incorporate the energy dissipation characteristics of the device when installed within a structure. FE simulation results have been used to devise a mathematical model representing the force-deformation characteristics of YSPDs so that the hysteretic response of the device could be predicted using easily available parameters i.e. the geometry of the YSPD and the relevant material properties. Neural network based hybrid informational model is also developed for simulating the response of YSPDs. The proposed models showed good accuracy when compared against the available test results and the finite element simulation results. This approach will allow to model the effects of YSPD using a simple connection element i.e. nonlinear spring element with the load-deformation response obtained using the proposed mathematical model; this should save a significant amount of computational effort.
YSPD is relatively new device, which is currently going through the preliminary research phase and appropriate evaluation of its performance will pave the way for its future commercialisation. Probabilistic performance evaluation using seismic fragility and limit state probability analyses are conducted to identify the suitability of YSPDs as a passive control device. These evaluation techniques consider uncertainties associated with both the seismic demand and the performance of a structure. The proposed mathematical model is used to represent YSPDs as spring elements for analysing within a benchmark structure. The fragility analysis identified the probability of exceeding a structural damage level depending on ground motion intensity, whilst the limit state probability analysis identified the annual exceedance probability of a specified damage level. YSPDs showed good seismic performance based on fragility and limit state probability analyses. The effect of seismic hazard on the performance of YSPDs is also identified by considering seismic hazard curves from both high and moderate seismic zones.