Damage avoidance design steel beam-column moment connection using high-force-to-volume dissipators

Existing welded steel moment frames are designed to tolerate substantial yielding and plastic rotation under earthquake loads. This sacrificial design approach can lead to permanent, and often irreparable damage when interstory drifts exceed 2%. The experimental seismic performance of a 50% full-scale damage avoidance designed structural steel beam-column connection is presented. The beam-column joint region consists of a top flange-hung beam connected to the column by an angle bracket. High-force-to-volume (HF2V) devices are attached from the column to the beam to provide joint rigidity and energy dissipation as the joint opens and closes. The HF2V devices are connected either below the beam flange or concealed above the beam's lower flange. Reversed cyclic lateral load tests are conducted with drift amplitudes up to 4%. No damage is observed in the principal beam and column structural elements. The need for stiff device connections to achieve optimal device performance is demonstrated, and potential design solutions presented. Stable hysteresis and repeatable energy dissipation for a large number of cycles up to the 4% drift level is observed. It is concluded that superior and repeatable energy dissipation without damage can be achieved for every dynamic motion cycle, in contrast to conventional sacrificially designed welded moment frame connections

Repeatability and High-Speed Validation of Supplemental Lead-Extrusion Energy Dissipation Devices

Recent research on supplemental damping enabling low to no damage structures has led to new devices, such as lead-extrusion-based high force-to-volume (HF2V) devices. They provide significant energy dissipation and force capacity in a small volume, enabling a range of novel low to no damage connections and systems. However, despite several research study tests and a limited range of velocity testing, they have never been tested across a realistic velocity range or for robustness to manufacture and design across several devices. These issues are hurdles that limit professional design uptake and add uncertainty and risk to their use in design. To address them, a serious damage-free dissipation device characterise its force capacity and variability due to manufacture (repeatable quasistatic force) and velocity input (peak force to connections). These outcomes are critical to size all the connections and foundations for the resultant demands and ensure robust, effective design. This manuscript presents the quasistatic testing of 96 devices designed for the same quasistatic force capacity, as well as high-speed prototype testing at velocities up to 200 mm/sec. Quasistatic tests show device forces vary with standard deviation, σ < 6.2% of design and average force. Peak input velocities of ∼200 mm/s produced peak resistive forces of ∼350 kN and increasingly weak velocity dependence as device input velocity increased, which is an advantage as it limits large demand forces to connecting elements and surrounding structure if larger than expected response velocities occur. Overall, the devices show stable hysteretic performance, with slight force reduction during high-speed testing due to heat build-up and softening of the lead working material. This testing quantified important HF2V device dynamics and robustness for designers and is an important step towards design uptake

Experimental test and validation of a direction- and displacement-dependent viscous damper

Semiactive devices offer the opportunity to customize the device response, and thus to customize the overall structural hysteretic response. However, they are actively controlled and thus entail a significant addition of complexity and potentially cost for the added performance. This study introduces the concept, design, and experimental validation of a direction- and displacement-dependent (D3) device using viscous damping. D3 devices provide viscous damping in any individual or multiple quadrants of the force-displacement response. Previously only achievable using semiactive devices, this research presents an entirely passive and thus more robust and lower cost device. The D3 device design concept is presented and experimental tests are undertaken on a prototype device. Sinusoidal displacement inputs provide a range of velocity inputs and device forces used to characterize the damping behavior of the prototype and illustrate the ability to provide controllable viscous damping in any single or multiple quadrant(s) of the force-displacement response. Performance is characterized by device design parameters. The overall results provide a proof of concept for a new class of relatively low-cost passive devices that enable customized hysteretic behavior for any given structural application

Passive direction displacement dependent damping (D3) device

Viscous fluid damping has been used worldwide to provide energy dissipation to structures during earthquakes. Semi-active dissipation devices have also shown significant potential to re-shape structural hysteresis behaviour and thus provide significant response and damage reduction. However, semi-active devices are far more complex and costly than passive devices, and thus potentially less robust over time. Ideally, a passive device design would provide the unique response behaviour of a semi-active device, but in a far more robust and low-cost device. This study presents the design, development and characterization of a passive Direction and Displacement Dependent viscous damping (D3) device. It can provide viscous damping in any single quadrant of the force-displacement hysteresis loop and any two in combination. Previously, this behaviour could only be obtained with a semi-active device. The D3 device is developed from a typical viscous damper, which is tested to evaluate the baseline of orifice sizing, force levels and velocity dependence. This prototype viscous damper is then modified in clear steps to produce a device with the desired single quadrant hysteresis loop. The overall results provide the design approach, device characterization and validation for this novel device design

Seismic behavior of a self-centering system with 2–4 viscous damper

This research demonstrates the efficacy of 2–4 viscous dampers in self-centering rocking structures with bi‑linear elastic response, which is distinctly different to conventional fixed‑base structures. This study assesses the relative impact of 2–4 devices versus typical viscous dampers and 1–3 viscous devices. Performance is assessed by maximum displacement, total base shear, and maximum acceleration, which are indicative of structural, foundation and contents demand. Simultaneous reductions of displacement, base-shear and acceleration are only available with the 2–4 damper. Finally, a simple method is proposed to incorporate 2–4 viscous dampers into self‑centering systems using standard design approaches

A simple hybrid testing approach for dynamic analysis of civil structural control devices

Effective real-time testing of structural control devices relies on a hybrid test system that couples virtual structures under dynamic loading with physical sub-structures or devices in a dynamic test rig. The use of sensors and actuators in a closed-loop feedback system maintains the dynamic equilibrium of the overall system comprising the physical test article and virtual modelled structure. The virtual-real hybrid testing method thus alleviates much of the time and cost associated with full-scale testing and enables tests that would be infeasible without full-scale complete structural tests. Thus, it can reduce the uncertainty in designing such a full scale test by testing, in hybrid hardware in the loop fashion, the devices and sub-systems required to ensure the best overall full-scale experimental design. Hence, a major outcome is the savings in the cost, time and complexity of the resulting full scale experiment. To accomplish this goal, this research presents simple, cost-effective and robust hybrid test system, and outlines solutions to the major issues faced in developing any hybrid system. The overall approach is centred on the dSpaceTM real-time control system development tool. The major issues in developing a hybrid system are: minimal signal processing lag, optimised sensing resolution and bandwidth, and efficient model computation. All three affect the ability of the system to maintain dynamic equilibrium of the overall virtual-physical system, and thus provide an accurate test. The final system readily accommodates non-linearsingle and multi-degree-of-freedom models and an operating bandwidth of 1 kHz. Test results and experimental outcomes are based on studies of a linear single degree of freedom structure and a non-linear rocking wall system that includes impact loads and timing subject to random ground motions. The results clearly illustrate system simplicity, efficacy and how they can be used to illustrate the potential outcomes of full scale experiments but at simple, fast low cost level. Keywords