新规范框架结构强柱弱梁措施效果评估

Effect evaluation on strong column and weak beam measures of frame structure in the new code

为了了解我国新颁布的规范对框架结构强柱弱梁措施提高柱端弯矩增大系数的效果,分别按照新旧规范设计设防烈度7度(0.1 g)3级框架结构和设防烈度8度(0.2 g)2级框架结构,采用时程动力分析程序,输入不同频谱的地震波,计算不同设防烈度框架结构在罕遇地震作用下的结构反应,对比分析框架结构的位移、层间位移角和塑性铰。结果表明,设防烈度为7度(0.1 g)3级框架结构,不同频谱地震波作用下新旧规范楼层顶点最大位移差值不超过1 mm,层间位移角最大差值不超过0.12%,新规范提高柱端弯矩增大系数效果不大。旧规范规定的柱端弯矩增大系数足以保证框架结构大震不倒。设防烈度为8度(0.2 g)2级框架结构,不同频谱地震波作用下新旧规范楼层顶点最大位移差值较明显,层间位移角最大差值不超过0.21%,新规范柱端弯矩增大系数效果明显,但其安全性与设防烈度为7度(0.1 g)3级框架结构相比,仍有较大差距。建议进一步提高其柱端弯矩增大系数,以充分保证其大震不倒的安全性。

In order to evaluating effect on the moment magnifying coefficients of strong column-weak beam measures at column ends of frame in the new code, seismic grade 3 frame of seismic precautionary intensity 7 （0.1 g） and seismic grade 2 frame of seismic precautionary intensity 8 （0.2 g）are designed in accordance with the old and new design codes, respectively. A time history dynamic analysis are proceeded to calculate the response of various pre- cautionary intensity frames under rare seismic wave through putting in different frequency spectrum seismic waves. The displacements, the story drift angles and the plastic hinges of the frame structures are compared and analyzed. The results show that, for seismic grade 3 frame of seismic precautionary intensity 7 （0.1 g）, the maximum dis- placement margins of the top story between the old and new codes are not more than 1 mm under different frequency spectrum seismic waves, and the story drift angle margins are not more than 0.12%. The improving effects of mo- ment magnifying coefficients at column ends in the new code is very little, at column ends in the old code is sufficient to ensure the security of frame grade 2 frame of seismic precautionary intensity 8 （0.2 g）, the maximum tween the old and new codes are obvious under different frequency spectrum and the moment magnifying coefficients under rare seismic wave . For seismic displacement margins of top story be- seismic waves, and the story drift angle margins are not more than 0.21% ,in which the effect is obvious. Compared with seismic grade 3 frame of seismic precautionary intensity 7 （0.1 g）, its security has still a large gap. It is suggested that the moment magnifying coef- ficients at column ends is further improved to ensure the security of frame under rare seismic wave.