【作者】 李世光；

【导师】 钱宏亮；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2025， 博士

【摘要】 木网壳作为现代木结构体系的典型代表,因其优异的力学性能和独特的美学表现,在大跨度建筑中的应用日益广泛。节点是木网壳结构的关键组成部分,一类典型木网壳节点——端面抵承型螺栓连接节点(以下简称端面抵承型节点),利用木构件端面与钢毂的大面积接触(端面抵承)传力,具备较高承载能力和转动刚度,在中、大跨度重型木网壳结构的应用中展现出显著优势。然而,由于利用该接触作用,使该类型节点绕一轴的转动性能既显著受轴力影响(称其为节点弯曲-轴力耦合特性),也受其绕另一轴转动的影响(称其为节点双轴弯曲耦合特性),这给节点设计与分析带来了复杂性。目前对于端面抵承型节点力学性能及其分析方法的研究尚不系统、充分;对于含该类节点木网壳结构的承载性能研究仍不完善。这极大程度地限制了端面抵承型节点木网壳在建筑工程领域中的应用。为此本文以理论、试验及数值模拟等手段,对端面抵承型节点抗压弯性能开展了系统研究,阐明节点的受力机理,并提供了节点抗压弯的有效计算方法。基于含节点压弯构件力学性能试验,探讨了节点对结构体系稳定性的影响规律。开发了在杆件结构体系中能充分反映节点力学特性的数值模拟工具。在此基础上,对含端面抵承型节点木网壳结构的承载性能开展了研究,揭示了其破坏机理和关键影响因素,可为该类木网壳工程实践提供参考。本文主要研究工作如下:(1)构建了端面抵承型节点在压弯作用下的力学模型。将单轴受压弯的节点分隔成拉、压两组件,受拉组件为抗侧钢夹板螺栓连接,以非线性弹簧模拟;受压组件为受抵承作用的木构件端部,以修正的地基模型模拟。在充分考虑节点转动非线性的前提下,建立节点在压弯荷载作用下的变形协调方程、平衡方程及物理方程,进而计算得到节点弯矩-转角关系,并揭示节点转动的受力机理及受轴力影响机制。提出了木构件端部受抵承的拉剪破坏准则以及抗侧螺栓的极限破坏准则。此外,将该力学模型的应用范围拓展至了节点双轴受弯的情况。(2)对端面抵承型节点力学性能进行了试验及数值模拟分析。利用已有节点试验研究,建立与其对应的实体有限元参数化分析模型,对节点抗压弯性能进行了系统分析,讨论了关键参数(如几何尺寸、材料属性、螺栓连接属性等)对节点力学性能的影响规律,验证了(1)中力学模型的准确性和适用性。(3)开展了含端面抵承型节点压弯构件稳定性试验。对中部含有一节点的压弯构件进行了轴心及偏心加载试验,以考察节点对压弯构件稳定性能的影响规律。设置了2米、3.5米两种长度试件,考虑了轴心、下偏心、大偏心三种加载条件。研究结果表明:端面抵承型节点对于小偏心加载的2米长试件,刚度削弱较小,但会因节点内抵承区木材塑性变形及开裂破坏而削弱结构承载力;对于大偏心加载的2米长试件,节点会因螺栓连接及抵承区木材变形同时削弱结构刚度及承载力;对于不论大、小偏心加载的3.5米长试件,节点对弹性刚度的削弱会使其提前发生弹性失稳。节点对压弯构件稳定性能的影响规律可推演至节点对木网壳子结构稳定性的影响规律。(4)开发了考虑端面抵承型节点受力特性的有限连接单元。基于ABAQUS用户单元子程序接口,开发了用于杆系结构模拟的端面抵承型节点专用有限连接单元——UCEL,以在分析中充分考虑节点弯矩-轴力耦合及双轴弯曲耦合特性。UCEL单元具有双节点,内含一刚性杆件及若干端部弹簧,其中转动弹簧内弯矩为节点轴力及转角的函数,从而以此方式引入了轴力对节点转动性能的影响。基于Fortran语言,并利用(1)中节点力学模型,编写了有限连接单元UCEL程序脚本,并利用(3)中含节点压弯构件稳定性能试验数据验证了所开发连接单元的准确性与适用性。(5)对端面抵承型节点木网壳承载性能进行了数值模拟研究。依据相关设计规范(规程),对端面抵承型螺栓连接节点木网壳进行了合理设计,并建立了结构整体有限元分析模型。模型充分考虑了大网格、木材拉压不同性、节点耦合特性、屋面板约束效应等木网壳结构特征。通过非线性全过程分析,明确了网壳失稳前后结构各部分的受力状态及结构失效机理。同时,考察了初始几何缺陷、加载形式、结构跨度、矢跨比、屋面约束效应等对木网壳承载性能的影响规律。更多还原

【Abstract】 As one of the representative forms of modern timber structures,wood reticulated domes combine excellent structural performance with unique aesthetic appeal,leading to their increasing application in long-span buildings.The joints are the key components that determine the load-bearing performance of wood reticulated dome structures.A typical wood reticulated dome joint—the end-bearing bolted connection joint(hereinafter referred to as the end-bearing joint)—transfers forces through large-area contact(end bearing)between the timber member end face and the steel hub.With high load-bearing capacity and rotational stiffness,it offers significant advantages for medium-and large-span heavy wood reticulated dome structures.However,due to the end-bearing mechanism,the rotational performance of this joint type is significantly influenced by axial force(referred to as the bending-axial force coupling effect)and also exhibits notable interdependence between rotations about two orthogonal axes(referred to as the biaxial bending coupling effect).Currently,research on the load-bearing behavior and analytical methods of end-bearing joints remains unsystematic and insufficient,while studies on the overall failure mechanisms and parameter influence laws of wood reticulated domes with such joints are still incomplete.These limitations greatly restrict the widespread application of end-bearing joint wood reticulated domes in construction engineering.To address these issues,this study focuses on the structural characteristics of end-bearing joints,conducting theoretical,experimental,and numerical analyses of their compressive-bending performance.The force-transfer mechanism of end-bearing joints is clarified,and an effective method for calculating their compressive-bending behavior is proposed.Based on mechanical performance tests of compressive-bending members with joints,the influence of joint mechanical behavior on the stability of structural systems is investigated,and a numerical simulation tool that fully reflects joint mechanical properties in frame structures is developed.Furthermore,a systematic study on the load-bearing performance of wood reticulated domes with end-bearing joints is conducted,revealing their failure mechanisms and key influencing factors,which can serve as a reference for engineering practice.The main research work of this paper is as follows:(1)Development of a mechanical model for end-bearing joints under combined compression and bending.The joint under uniaxial compression and bending is divided into tensile and compressive components.The tensile component,consisting of bolted connections with steel side plates,is simulated using nonlinear springs,while the compressive component,involving the wood member end under bearing,is modelled using a modified foundation model.By fully considering the nonlinearity of joint rotation,deformation compatibility equations,equilibrium equations,and constitutive equations under combined compression and bending are established,enabling the calculation of the moment-rotation relationship and revealing the joint’s force-transfer mechanism.A failure criterion for timber end-bearing under combined tension and shear,as well as an ultimate failure criterion for lateral bolts,is proposed.Additionally,the application scope of this mechanical model is extended to biaxial bending scenarios.(2)The mechanical performance of the end-bearing joint was analyzed through experiments and numerical simulations.Existing joint test data and a parametric finite element model are used to conduct a comprehensive and in-depth analysis of the joint’s compressive-bending performance.The influence of the key parameters(such as geometric dimensions,material properties,connection attributes,etc.)was investigated and the applicability and accuracy of the mechanical model from(1)was validated.(3)Stability performance tests of compressive-bending members with end-bearing joints.Axial and eccentric loading tests were conducted on compression-bending members with an intermediate joint to investigate the influence of the joint on the stability performance of the member.Specimens with two lengths of 2 meters and 3.5meters were set up,considering three loading conditions:axial,lower eccentricity,and large eccentricity.The results indicate that for 2 meters members under small eccentric loading,joints cause minor stiffness reduction but significantly reduce load-bearing capacity due to plastic deformation and cracking failure in the wood end-bearing zone.For 2 meters members under large eccentric loading,the joints simultaneously reduce both structural stiffness and load-bearing capacity due to the slip of the bolted connections and the deformation of wood end-bearing zone.For 3.5 meters members under either large or small eccentric loading,the reduction in elastic stiffness induced by the joints leads to premature elastic buckling.The findings were then extended to analyze the effect of joints on the stability of the wood reticulated dome substructures.(4)Development of a finite connection element accounting for end-bearing joint behavior.Based on the ABAQUS user element subroutine interface,a specialised finite connection element(UCEL)for end-bearing joints in frame structures is developed to fully consider bending-axial force coupling and biaxial bending coupling effects.The UCEL element features two nodes,incorporating a rigid link and several end springs.The rotational spring’s internal moment is a function of joint axial force and rotation,thereby introducing the axial force’s influence on rotational behavior.A Fortran-based UCEL program script is written using the joint mechanical model from(1),and its accuracy and applicability are validated against experimental data from the compressive-bending member stability test of(3).(5)Numerical simulation of the load-bearing performance of wood reticulated domes with end-bearing joints.Following relevant design codes,a reasonable design for reticulated domes is proposed,and a global finite element model is established.The model incorporates key structural features,including large grid spacing,timber anisotropy,joint coupling effects,and roof panel constraints.Through nonlinear full-range analysis,the stress state and failure mechanism of the reticulated dome before and after buckling are clarified.Additionally,the influence of initial geometric imperfections,loading patterns,span,rise-to-span ratio,and roof constraints on load-bearing performance is investigated.更多还原