郑玉龙, 孙玉涛, 陆春华, 刘翔, 幸左贤二. 弯折钢筋初期损伤形成的规律及机制研究[J]. 工程力学. DOI: 10.6052/j.issn.1000-4750.2022.09.0826
引用本文: 郑玉龙, 孙玉涛, 陆春华, 刘翔, 幸左贤二. 弯折钢筋初期损伤形成的规律及机制研究[J]. 工程力学. DOI: 10.6052/j.issn.1000-4750.2022.09.0826
ZHENG Yu-long, SUN Yu-tao, LU Chun-hua, LIU Xiang, KOSA Kenji. RESEARCH ON THE LAW AND MECHANISM FOR INITIAL DAMAGE FORMATION OF BENT STEEL BARS[J]. Engineering Mechanics. DOI: 10.6052/j.issn.1000-4750.2022.09.0826
Citation: ZHENG Yu-long, SUN Yu-tao, LU Chun-hua, LIU Xiang, KOSA Kenji. RESEARCH ON THE LAW AND MECHANISM FOR INITIAL DAMAGE FORMATION OF BENT STEEL BARS[J]. Engineering Mechanics. DOI: 10.6052/j.issn.1000-4750.2022.09.0826

弯折钢筋初期损伤形成的规律及机制研究

RESEARCH ON THE LAW AND MECHANISM FOR INITIAL DAMAGE FORMATION OF BENT STEEL BARS

  • 摘要: 为明晰混凝土膨胀作用下弯折钢筋脆性断裂的机理,从导致脆断的推测起源-钢筋初期损伤入手,开展月牙纹钢筋在弯折参量及梯度递增弯折角度下的加工试验与数值模拟。探究钢筋直径与弯心直径对初期损伤形成的影响规律,探索各细分阶段下受挤压钢筋横肋的形变规律、初期裂纹尺度的演变特征,以及弯弧内部残余应力响应等,从而分析带肋钢筋因弯折加工形成初期损伤的规律与机制,并进一步探索抑制初期损伤的横肋形貌与加工参量。结果表明:较大的钢筋直径和弯折角度,较小的弯心直径会大幅增加初期损伤程度;严峻条件下(钢筋直径及弯心直径分别为16 mm及32 mm,弯折90°),月牙纹钢筋的初期损伤可达400 μm(钢筋直径的2.5%),超过了日本常发生脆性断裂竹节纹钢筋的水平,这增加了弯折钢筋受应力作用下初期损伤扩展的可能性;随弯折角度递增,钢筋横肋的挤压变形与根部应力集中程度愈发显著,且弯折90°卸载后弯弧内部由受压转为受拉应力状态,加剧了初期损伤的形成以及弯折钢筋如箍筋产生脆性断裂的敏感性;通过在月牙纹横肋与基圆之间设置适当的过渡圆角可较大程度缓解初期损伤。

     

    Abstract: In order to clarify the mechanism for the brittle fracture of bent steel bars under the action of concrete expansion, starting from the presumed origin of brittle fracture - the initial damage of bent steel bars, bending processing tests and numerical simulations were carried out for crescent-shaped steel bars under bending parameters and gradient increasing bending angles. The following topics were explored, including the influence of bar diameter and bending core diameter on the formation of initial damage, the deformation behavior of the transverse rib in the bent steel bar at each subdivision stage, the evolution of the initial crack scale, and the residual stress response inside the bending arc, in order to analyze the law and mechanism of initial damage formation of ribbed steel bars due to bending processing, and further to obtain the better transverse rib morphology and processing parameters to inhibit initial damage. The results show that: a larger bar diameter and bending angle, a smaller bending core diameter will significantly increase the degree of initial damage; the initial crack of crescent-shaped rebar under severe conditions (the diameter of the steel bar and the bending core is 16 mm and 32 mm respectively, and 90° bending) can reach 400 μm (2.5% of the bar diameter), which exceeds the level of the frequently fractured bamboo-shaped steel bars in Japan, and this increases the possibility of propagation for initial damage of the bent steel bar under the action of stress; with increasing bending angle, the degree of extrusion deformation and root stress concentration of the transverse rib in the steel bar becomes more significant, and after unloading at the 90° bending, the internal bending arc part changes from compressive to tensile stress state, which aggravates the formation of initial damage and the susceptibility of bent steel bars such as stirrup to brittle fracture; and the initial damage can be substantially mitigated by setting an appropriate transition circle between the crescent transverse ribs and the base circle.

     

/

返回文章
返回