Hysteresis analysis of pre-pressed spring self-centering energy dissipation braces using different models

The ability of an idealized piecewise-linear restoring force model and a nonlinear mechanical model to describe the hysteretic performances of the pre-pressed spring self-centering energy dissipation braces was evaluated based on experimental data. The hysteretic behaviors predicted by these two proposed models were compared with the experimental results of a typical prototype brace, and the results demonstrated that the two models can explain the brace force-time responses, and that the nonlinear mechanical model is more effective in describing the stiffness transition and energy dissipation of the brace. The two proposed models can be used for the design of the pre-pressed spring self-centering energy dissipation brace specimens, and the nonlinear mechanical model may be more useful for designing the structures with the pre-pressed spring self-centering energy dissipation braces. An orthogonal experiment was applied to analyze the influences of the key parameters on the performances of pre-pressed spring self-centering energy dissipation braces based on the nonlinear mechanical model. The results indicate that the friction slip force of energy dissipation mechanism, the pre-pressed force of self-centering mechanism, and the post-activation stiffness significantly affect the hysteretic performances and equivalent viscous damping ratios of the bracing system, while the changes in other parameters only produce slight effects. The determination of the pre-pressed force of the self-centering mechanism should be coordinated with the friction slip force of the energy dissipation mechanism to achieve a better hysteretic performance of the pre-pressed spring self-centering energy dissipation brace.

Optimal Damper Slip Force for Vibration Control Structures Incorporating Friction Device with Sway-Rocking Motion Obtained Using Shaking Table Tests

In this study, a series of shaking table tests were conducted using a specimen that consisted of a superstructure, incorporating a friction device and a sway-rocking mechanism under the superstructure to determine the optimal damper slip force of a passive vibration control system considering the effects of sway-rocking motion. The adopted simple friction device, composed of rubber bands and stainless steel plates, allowed the magnitude of the slip force to be easily set. The optimal slip force of the friction device, which minimizes the peak and root-mean-square response of the superstructure subjected to earthquakes, was determined from the shaking table tests. Based on the results, the optimal slip force of the friction device was found to vary according to the input level of the ground motions and the sway-rocking conditions. The obtained results suggest that the effect of sway-rocking motion should be considered in the design of passive control structures and the determination of their optimal damper slip force.

ULTIMATE SLIP BEHAVIOR OF PERFOBOND STRIP UNDER THE LATERAL CONFINEMENT PARALLEL TO THE PBL PLATES

Perfobond strip (called PBL, hereafter) proposed by Leonhardt in Germany is widely used as the validated shear connector in steel-concrete composite structures. Fujii et al. proposed a fracture mechanism of PBL as follows: Slip force (shear force) acting on a PBL causes the expanding force which splits the concrete around the PBL. If restraint force, which is caused by cover concrete, rebar etc., resisting the expanding force exist, the slip strength is enhanced. Consequently, the fracture of PBL will happen when the expanding force exceeds the restraint force. Also, based on the above concept, they have given the evaluation formula of PBL slip strength and verified it by comparing previous experimental results. However, bonding force and frictional force are not taken into account in the formula. Through the loading tests of the composite girder, we found that the bonding and the frictional force, which appear along the boundary surface between concrete deck and steel flange, work as resistance force to not only the slip strength but also the expanding force. In this paper, the effects of the bonding force and the frictional force on the ultimate slip behavior of PBL are investigated experimentally, and an evaluation formula of PBL slip strength is improved by taking their effects into account.

Investigation on Friction Features of Dissipative Lap Shear Connections by Means of Experimental and Numerical Tests

Background:Beam-to-column joints equipped with friction dampers are a viable solution to improve the dissipative capacity of moment Resisting Frames without any damage after severe seismic events. Recently, novel systems have been developed within the RFCS FREEDAM research project.Objective:The objective of the work is to provide a rational selection based on engineering judgment, of possible materials to be used in friction dampers.Methods:Both experimental analysis and Finite Element (FE) simulations have been carried out to assess the friction coefficients of several interfaces evaluating also their ability to withstand cyclic loading histories.Results:The experimental campaign showed that both hard and soft metals can be used in combination with stainless steel obtaining satisfactory performance under cyclic loads. In addition, at high slip velocities, large temperatures are developed within the specimen. Modelling this effect is crucial as it causes a reduction in the slip force capacity. This is due to the transverse dilatation that initially increases the pressure, while bolt tightening reduces due to elongation of the shank.Conclusion:The experimental results, together with other similar data selected from technical literature, have been employed to validate FE models able to simulate the behaviour of lap shear friction connections, showing the influence of different modelling approaches over the simulated data. Subsequently, the validated model has been used to perform a set of simulations devoted to highlight the key parameters affecting the response of the lap shears and the possible strategies to improve the performance of the friction dampers.

Effect of Fabric Weave on Stick-Slip Properties of Woven Fabrics

The aim of this study was to understand the stick-slip properties of dry polyester plain, ribs and satin woven fabric weaves. It was found that the amount of stick-slip force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response. Stick-slip force and accumulative retraction force depend on fabric weave, fabric density, the number of pulled ends in the fabric and fabric sample dimensions. The weft directional single and multiple yarn stick-slip and accumulative retraction forces of dry plain fabrics in fabric edge and centre regions were higher than those in the satin fabric due to fabric weave. In addition, the warp directional single and multiple yarn stick-slip and accumulative retraction forces in the meso-cell-1 to the meso-cell-6 of dry wide and long satin fabric in fabric edge were higher than those in the weft direction due to fabric density. Stick-slip and accumulative retraction forces of polyester fabric in the multiple yarn pull-out test were higher than those of the single yarn pull-out test.

Stick-slip properties of single and multiple yarn pull-out in dry and softening treated polyester satin woven fabrics in boundary region

Purpose – The aim of this study was to understand the stick-slip properties of single and multiple yarn pull-out in dry and treated polyester satin woven fabric in boundary regions. Design/methodology/approach – Polyester satin pattern woven fabric was used to conduct the pull-out tests in order to examining the kinetic region of the force-displacement curve. Data generated from this research help the authors to obtain stick-slip force and accumulative retraction force. Findings – It was found that stick-slip force and accumulative retraction force depend on the number of pulled ends in the fabric, fabric sample dimensions and softening treatments. Stick-slip forces of polyester satin fabric in the multiple yarn pull-out test were higher than those of the single yarn pull-out test. Stick-slip force in single and multiple yarn pull-out tests in the dry polyester satin fabric was generally higher than those of the softening treated polyester satin fabric. In addition, the warp directional single and multiple yarn stick-slip and accumulative retraction forces in the dry and softening treated polyester fabrics were generally higher than those in the weft direction in the fabric edges due to fabric density. On the other hand, the amount of stick-slip force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response. Originality/value – The mechanism of stick-slip and accumulative retraction force of dry-treated polyester satin pattern woven fabrics were explained. This research could be valuable for development of multifunctional fabrics in technical textiles and ballistic.