Search

The existing constitutive models of shape memory alloy (SMA) cannot accurately describe the mechanical behavior in martensitic strengthening segment since their loading and unloading paths in strengthening segment completely overlap. This study proposes a multi-segment linear mathematical model for SMA, which realizes the separation of loading path and unloading path in strengthening segment. A four-story steel frame structure and corresponding braced structures with various SMA constitutive models are designed, and seismic control effects of SMA braces with these models are analyzed and compared through time history analysis. The results show that the sub-cycle unloading mode of SMA constitutive model affects the seismic mitigation capacity of SMA brace in a certain extent. The position of the inflection point of unloading path has very little influence on the structural control ability of SMA braces. The SMA brace using the SMA constitutive model with a single linear sub-cyclic unloading path has the minimal seismic response and the highest seismic reduction ratio. For most evaluation indexes, the seismic mitigation ability calculated by the proposed path separation constitutive model is in the middle of the results calculated by the existing models. SMA models without considering the mechanical behavior of strengthening segment may lead to an erroneous estimation of the energy consumption of SMA brace and the structural damage. The difference of simulation results among various SMA constitutive models is almost independent with ground motion. [ABSTRACT FROM AUTHOR]

This study demonstrates two types of semi-active vibration control with harmonically varying damping. The first one is performance upgrade of semi-active base isolation method for single-degree-of-freedom system and the other one is a semi-active vibration control method for parallel coupled single-degree-of-freedom system. Recent researches have demonstrated a new method for the utilization of variable damping. In those studies, the damping coefficient was harmonically controlled. Previous studies have confirmed vibration mitigation of a base-isolated structure by interference cancellation with the harmonically varying damping. However the results of previous studies had still room for improvement. Consequently, this study suggests a method for the performance augmentation. However, no such study considering the multi-degree-of-freedom system has been conducted. This paper presents the effect of the harmonically varying damping on the multi-degree-of-freedom system, especially; the influence on two structures in parallel with a variable damper between the structures is discussed. [ABSTRACT FROM AUTHOR]

In order to study the seismic performance of precast short-leg shear wall connected by grouting sleeves (PSSW), the three-dimensional numerical model was established by using the experiment of PSSW subjected to low cyclic loading. Based on good agreement between numerical results and experimental results, the numerical analysis models with different structural parameters of axial compression ratio and splicing position were designed in detail, and the effects of various parameters on the seismic performance of PSSW were analyzed. The results show that the PSSW exhibits wide and stable hysteresis loops, indicating a satisfactory hysteretic performance and an excellent energy consumption capacity. With the increase of the axial compression ratio, the shear capacity of horizontal splice seam is improved, but the ductility coefficient and total energy consumption decrease obviously. The most disadvantageous position of PSSW can be effectively avoided by changing the position of the post pouring seam. The bearing capacity of the specimens is basically stable, and the energy consumption increases significantly, so the post pouring seam of precast wall is recommended to be far away from the bottom section of the wall. In addition, the failure mechanism of different splicing positions was analyzed in detail. [ABSTRACT FROM AUTHOR]

The double rectangular tube assembled buckling-restrained brace is a new type of buckling energy consumption buckling-restrained brace. Because of its external restraining members, which are bound by high-strength bolts, its mechanical mechanism is more complicated and its failure modes are more varied. In this study, the double rectangular tube assembled buckling-restrained brace composition and three types of end constructions are introduced in detail. The influences of different design parameters on the performance of double rectangular tube assembled buckling-restrained brace are studied by numerical analysis methods; the possible failure modes and the influence of the end strengthening construction of double rectangular tube assembled buckling-restrained brace are also investigated, and a number of suggestions are proposed to improve this design. This study shows that the pinned double rectangular tube assembled buckling-restrained brace has four types of typical failure modes, namely, overall buckling failure, external end local pressure-bearing failure, bending failure of the extended strengthened core region and bolt threading failure. Rational design can prevent a buckling-restrained brace from losing its load-bearing capacity. In addition, compared with the end strengthening scheme with an external hoop, the end strengthening scheme with a strengthened bench can improve the load-bearing capacity of the double rectangular tube assembled buckling-restrained brace more effectively, and a reasonable design can also save materials. [ABSTRACT FROM AUTHOR]