冲击载荷下智能复合式桥墩支座-阻尼系统的研究

Conventional bridge pier bearing is lack of capabilities in preventing bridge from large shock impacts such as vehicle hammerblow, blast, earthquake, etc. It is the weakest link in the bridge security system.In this project, a new smart assembled pier bearing-damping system is proposed to improve the performance and enhance the capability of bridge pier-deck structure for buffering reduction in a certain lever. This system consists of a magneto-rheological (MR) elastomer bearing and an MR grease damper. The former with variable stiffness as the main body of bearing can adjust structure intensity and resonance frequency during impact loadings, and the latter with variable damping is used to suppress pier-deck displacement.A micromechanical model considering transient magnetic forces in a unit volume of MR material will be proposed and studied in the project. And a macroscopic model considering shock and vibration dynamics of the bridge pier-MR bearing-deck system will be studied as well. The mechanism of this assembled bearing system for shock and vibration isolation will be addressed based on coupling uncertain force and magnetic field. A fail safe and optimization design principle for mechanical and magnetic structure with small energy consume are also discussed. A new MR materials including MR elastomer and MR grease which are suitable for this assembled bearing -damping device will be developed. A design methodology for this new small scale bridge bearing-damping system is proposed based on a dimensionless analysis theory.At last, simulations and lab experiments are combined to validate and evaluate its performance.The results of this proposal could afford theory preparation and technology support for developing advanced shock and vibration isolation equipment of bridge pier-deck to defense uncertain large destroying loads.

传统桥墩支座缺乏抗大载荷（车辆撞击、爆炸、地震等）冲击的能力，是桥梁结构安全体系中最薄弱环节。本课题提出一种新型智能复合式桥墩支座-阻尼系统，该系统用可变刚度的磁流变弹性材料做支座主体调节结构强度和共振频率，以可调阻尼的磁流变脂器件抑制墩梁移位，可在有限范围内缓减墩梁结构的冲击载荷并达到减灾防护的效果。通过对磁流变智能材料单元瞬态磁力微尺度建模和梁-支座-墩冲击振动传递的宏观尺度建模的研究，在不定力和磁场的耦合下揭示支座系统刚度阻尼可调的缓冲隔振机理，探索失效安全与能耗降低的机械与磁路结构优化设计原理，研制适合于该系统的新型磁流变弹性体和磁流变脂智能材料,基于无量纲理论提出小尺度复合式桥墩支座-阻尼系统的设计方法。利用仿真与小尺度台架实验结合，验证与评估该新型支座-阻尼系统抗冲与隔振的效果。该课题的成功完成，可望为我国发展抗冲击载荷破坏的先进桥梁缓冲隔振装置提供理论探索和技术储备。

针对冲击载荷下被动桥墩支座易损伤（破坏）而危及墩梁结构安全的问题，提出了基于磁流变材料刚度阻尼耦合的智能复合式桥墩支座-阻尼系统，完成了桥墩缓冲隔振系统动力学模型的建立、仿真，并集成磁流变支座与阻尼器搭建了桥梁缓冲隔振小尺度系统，开展了缓冲隔振实验研究和效果分析评价。①构建基于磁流变支座-阻尼器的桥梁缓冲隔振计算仿真系统，分析出在冲击/振动大载荷下智能桥墩支座-阻尼系统的支座回复力能够减小约40%，振动位移减小约40-50%、墩顶加速度减小约30%，从理论上验证了方案的可行性。②采用材料微观-结构宏观相结合的方式，解释了新型桥墩支座所用的磁流变智能材料的缓冲吸能机理以及阻尼器耦合的桥墩支座-阻尼系统在冲击载荷下的缓冲隔振机理,通过对支座-阻尼器系统在缓冲隔振时的能耗进行计算与结构仿真，获取兼具较佳的热功耗比和失效安全的磁流变支座-阻尼器机械与磁路结构，实现系统的集成优化。③研制出适合于智能桥墩支座-阻尼系统的新型磁流变智能材料，并制作磁流变桥墩支座-阻尼器样机，性能测试表明在磁流变支座可承受的最大热损功耗限制38.7瓦时,支座水平刚度变化最大（42.8%）。④根据无量纲及相似理论，取梁-支座-墩-地基系统中的刚度、阻尼、频率、时间等10余个关键参数，推导出了基于小尺度磁流变隔振器件的实验室桥梁隔振台架设计参数，并基于MATLAB有限元仿真系统，对小尺度三跨模拟桥梁的缓冲隔振进行了计算与优化。⑤通过设计和集成冲击激励源、智能支座-阻尼器、结构缓冲测控硬件和控制算法，搭建了小尺度三跨桥梁的实验室缓冲测控系统，实验结果与理论计算具有一致性，桥面振动加速度峰值最大减小42%，位移峰值最大减小36%，支座回复力减小约40%，有效降低了破坏性冲击对桥梁结构的伤害。本项目研究表明，磁流变支座-阻尼器复合系统在降低桥梁冲击振动和提升耗能能力上具有较明显效果，为我国发展抗冲击载荷破坏的先进桥梁缓冲隔振装置提供了理论探索和技术储备。