Research Design Theory And The Finite Element Analysis Of Assembled All-steel Buckling-Restrained Brace

The main character of BRB is that it wont buckle but yield no matter under Compression or tension. due to the effect of constraints of the steel-encased, When facing strong earthquake,in order to reduce the earthquake’s damage, BRB’ll consume most of the earthquake energy in advance of other members.Buckling-restrained braces in this paper, based on the margin yield criterion and the analysis of the assembled all-steel BRB core under the multiple-waves buckling morphology,the influence of the assembled all-steel BRB’s gap as well as the margin yield stress are studied to provide theoretical reference for the design of BRB. In this paper, the specific research contents are as follows:First of all, without lateral pressure, the working principle of assembled all-steel BRB and the model of the brace’s operating state is introduced. Based on the margin yield criterion that specify the deflection to the gap of BRB when the brace proceed multiple buckling and the core’s margin yield, the calculation formula of the gap of linear section and crisscross section, as well as the margin yield stress. According to various initial bending, core’s thickness and length, half-wave number, the effect numerical analysis towards gap and margin yield stress has been made.Moreover, Under the action of lateral pressure, the calculation formula of the brace’s gap and margin yield stress is derived. With the formula of the margin yield stress and the limitation of confinement ratio, the formula of the encased steel’s minimum stiffness and the steel-encased bolt’s requirement can be got. By using the limitation of the margin yield stress increment ratio, the data range of buckling half-wave number can be calculated. By respectively analyzing local stability of the core’s strong axis and weak axis, the reasonable value of core’s width-to-thickness ratio is equal to the half-wave number. As for the connection of the core and encased steel, rubber spacing board is used to limit the relative displacement. According to the theory above, the weak part of the linear and crisscross Brace was proceed with reinforcement design. Also, by introducing sliding bearing, the friction between the core and the steel-encased bolt is reduced and the stability as well as the bearing capacity of the brace’s end is improved.Last but not least, by establishing the simplified model of the linear assembled all-steel BRB with ANSYS, the values of margin yield stress under various constraints can be compared with the ones in this paper. ANSYS is also applied to simulate the impact of different core’s initial bending and half-wave member on the margin yield stress. Selecting a linear BRB model, by assuming the value of gap in chapter 3 as the gap parameter, along with the margin yield stress’ s finite element analysis towards various core thicknesses(30mm,26 mm, 22mm) and various half-wave numbers(5-12), the margin yield stress of core can be calculated and then compared with the result in chapter 3. It turns out that deviation is less than 5%. Finally, by analyzing various core’s thickness towards margin yield stress,it turns out that core’s thickness has nothing to do with the margin yield stress, the same conclusion as this paper’s. I also use ANSYS to study the multiple buckling’s forming process with odd or even initial bending number. By comparing difference between the hysteresis curves, it shows that hysteresis curve will be fuller with smaller core’s gap.