Measurement and assessment of geometric imperfections in thin-walled panels

Thin-walled members may be subject to performance limitations arising through local or distortional buckling of slender elements comprising the cross-section of the member, or overall buckling of the member. The effects of structural instability may be aggravated by the presence of geometric imperfections in these elements. An investigation is presented into methods of measuring and assessing geometric imperfections in cold-rolled thin-walled steel panels. These methods can be used to characterise the geometry of prismatic thin-walled members that exhibit performance sensitivity due to geometric imperfections. The measurement procedures investigated include close-range photogrammetry, precise optical levelling, and the use of a co-ordinate measurement machine. The assessment procedure comprises a least-squares spectral decomposition of the measurements to characterise the imperfections existent in the panels under investigation, and estimates of the precision of the derived Fourier coefficients are used to inter-compare the three measurement procedures. The investigation has demonstrated that statistically significant imperfections may exist in thin-walled members at short and medium wavelengths, leading to a reduction in the load carrying capacity. Both optical levelling and the co-ordinate measurement machine technique can yield desirable results, but for high precision work, use of the co-ordinate measurement machine is recommended.     

Material and geometric nonlinear isoparametric spline finite strip analysis of perforated thin-walled steel structures—Analytical developments

This paper presents the analytical developments of the application of the Isoparametric Spline Finite Strip Method (ISFSM) to the material inelastic and geometric nonlinear analysis of perforated thin-walled steel structures. The general theory of the ISFSM is briefly introduced. The formulations of the kinematics, strain–displacement and constitutive assumptions are presented, and the tangential stiffness matrix is derived by applying the incremental equilibrium condition. The requirements for strip continuity and boundary conditions are also discussed. In particular, the plasticity theory and the methods to integrate the ‘rate equations’ are emphasized, and the related ‘backward Euler return method’ and use of a ‘consistent material modulus’ are highlighted. The present isoparametric spline finite strip analysis is verified against a number of analyses of perforated and non-perforated plates and plate assemblages, as described in the companion paper (Yao and Rasmussen, submitted for publication) [1], demonstrating its accuracy and efficiency for the predictions of the inelastic post-buckling behavior of perforated thin-walled steel structures.     

Material and geometric nonlinear isoparametric spline finite strip analysis of perforated thin-walled steel structures—Numerical investigations

The theoretical developments of a material inelastic and geometric nonlinear analysis by use of the isoparametric spline finite strip method (ISFSM) are presented in a companion paper (Yao and Rasmussen (submitted) [1]). In the present paper, the numerical implementation of the analysis is reported, including nonlinear solution techniques, inelastic material models, selective reduced integration strategies, convergence criteria, and solution procedures. The reliability and efficiency of the method are demonstrated by a number of numerical examples, including analyses of flat plates with different material plasticity models, a classical nonlinear shell problem, perforated flat and stiffened plates, and perforated stiffened channel section storage rack uprights.     

A simplified method for collapse capacity assessment of moment-resisting frame and shear wall structural systems

A simplified methodology for predicting the median and dispersion of collapse capacity of moment-resisting frame and shear wall structural systems subjected to seismic excitations is proposed. The method is based on nonlinear static (pushover) analysis. Simple mathematical models denoted as “generic structures” are utilized to model moment-resisting frames and shear walls. After examining a wide range of structural parameters of the generic structures, a comprehensive database of collapse fragilities and pushover curves (using ASCE 7-05 lateral load pattern) are generated. Based on the obtained pushover curves, closed-form equations for estimation of median and dispersion of building collapse fragility curves are developed using multivariate regression analysis. Comparing the estimates of the median collapse capacity calculated from the closed-form equations with the actual collapse capacities determined from nonlinear response-history analysis indicates that the simplified methodology is reliable. The effectiveness of this methodology for predicting the median collapse capacity of frame and wall structures is further demonstrated with two case studies of structural systems designed based on current seismic provisions.     

单层单向索结构玻璃幕墙的受力性能研究

利用大型有限元分析软件SAP2000介绍了单层单向索结构玻璃幕墙的组成,并对江苏省南通市中国近代第一城展览馆幕墙工程进行了风荷载研究,得出了一些有益的结论,为玻璃幕墙在今后的设计研究积累了丰富的资料。     

Effect of geometric and process variables on the performance of inclined plate settlers in treating aquacultural waste

Inclined plate settlers are used in treating wastewater due to their low space requirement and high removal rates. The prediction of sedimentation efficiency of these settlers is essential for their performance evaluation. In the present study, the technique of dimensional analysis was applied to predict the sedimentation efficiency of these inclined plate settlers. The effect of various geometric parameters namely, distance between plates (w(p)), plate angle (alpha), length of plate (l(p)), plate roughness (epsilon(p)), number of plates (n(p)) and particle diameter (d(s)) on the dynamic conditions, influencing the sedimentation process was studied. From the study it was established that neither the Reynolds criterion nor the Froude criterion was singularly valid to simulate the sedimentation efficiency (E) for different values of w(p) and flow velocity (v(f)). Considering the prevalent scale effect, simulation equations were developed to predict E at different dynamic conditions. The optimum dynamic condition producing the maximum E is also discussed.     

双孔箱形框架式地道桥的结构分析及施工方法

以某下穿铁路钢筋混凝土箱形框架式地道桥为例,对其结构特点、内力计算、设计及施工方法等方面进行了研究,得出了具体的结论,以完善双孔箱形框架式地道桥的设计和施工,并推广其应用。     

内嵌秸秆板复合墙体热工性能测试及性能优化

将秸秆板装配在由肋梁和肋柱构成框格形式的墙体中,可作为一种新型装配式节能生态复合墙体应用于村镇住宅中。通过标定热箱实验方法直接进行墙体传热系数的测试,再基于有限元软件ABAQUS对该墙体进行一维稳态传热数值模拟。对比发现,数值模拟求得的传热系数与实测值相对误差仅为8.8%。最后再针对传热系数对复合墙体的保温隔热性能进行优化分析。     

南京金奥大厦巨型斜支撑异形铸钢节点试验研究

南京金奥大厦超高层建筑采用巨型支撑-筒中筒三重抗侧力结构体系,其中提供抗侧力刚度及支承外挂墙体的巨型钢斜支撑为此结构的一大特点。巨型钢斜支撑的节点采用异形铸钢连接节点,对其进行了在平衡和不平衡荷载工况下的3个足尺模型试验研究,利用ANSYS软件进行了有限元分析。有限元分析结果与试验实测值吻合良好。结果表明,节点应力分布不均匀,销栓孔壁承压区局部应力集中但无明显塑性变形,该节点基本处于弹性阶段工作,可以满足结构多道设防的性能化设计要求。     

T形截面钢骨混凝土柱延性性能分析

利用大型有限元分析软件ABAQUS分析了T形截面钢骨混凝土柱在低周反复荷载作用下的受力性能,综合钢骨混凝土柱现有的试验研究成果,研究了T形截面钢骨混凝土柱在不同轴压比系数、配钢率、混凝土强度等级和长细比等参数对其延性的影响,得出了T形截面钢骨混凝土柱具有很好的延性性能,并提出了不同参数影响下T形截面钢骨混凝土柱满足一定延性要求的轴压比限值。     

Stability of thin-walled high-pressure cylindrical pipes with non-circular cross-section and variable wall thickness subjected to non-homogeneous corrosion

This paper proposes a method for determining the critical time of stability loss of thin-walled cylindrical pipes with non-circular cross-section and variable wall thickness along the directrix subjected to non-homogeneous corrosion from the inside. The method is based upon the model of a thin elastic cylindrical shell with a non-circular cross-section and variable wall thickness along the directrix. It is shown that the critical time can be established if the solution of the respective problem of the static stability loss for the non-circular cylindrical shell with variable wall thickness along the directrix, not subjected to corrosion, and the law of corrosion rate change are known. Numerical results are connected with the pipe of the elliptical cross-section.     

轻质隔墙体隔声性能改善途径的分析

目前使用较多的轻质隔墙体的隔声量普遍偏低,难以满足人居声环境的相关要求.分析表明,影响轻质隔墙体隔声能力的因素是面密度低、共振现象、吻合相应以及声桥等.改善轻质隔墙体隔声性能的途径有采用板面-空腔-板面结构,以及采用不同材质和面密度的墙板组合,中间空气层添加吸声材料,两侧板之间设置减震装置等措施.     

密肋复合墙体填充砌块的性能分析

为了进一步深化对密肋复合墙体的认识，通过分析研究了密肋复合墙体填充砌块-加气混凝土的保温性能、隔声性能、抗渗性能、吸能能力、节能效果和环境的相容性能以及加气混凝土的力学性能随含水率变化的规律，并建立不同含水率的加气混凝土拉压强度、弹性模量的计算公式，研究结果表明只要不在长期湿度较大的地方使用，加气混凝土是目前所有外墙材料中节能效果好、绿色环保的墙体材料。     

Modeling of structural coupling for assessment of modal properties of twin tall buildings with a skybridge

This paper describes analytical modeling of structural coupling for generic twin buildings with a skybridge. The structural coupling of the interconnected buildings is modeled by introducing a six-degree-of-freedom model lumped at the skybridge level. The equations of motion of the reduced system are derived. In free vibration analysis, the natural frequencies and modal shapes are obtained for various levels of the relative stiffness of the inter-building beam representing the skybridge. Dependence of the calculated natural frequencies and modes of vibration on the skybridge stiffness is investigated. The empirical formulas to describe these quantities are proposed for preliminary design of twin buildings with structural coupling.     

钢构件与混凝土墙端板连接的有限元分析

采用通用有限元分析软件对混凝土后锚固受拉节点进行了模拟计算分析,通过比较不同螺栓直径、螺栓间距的条件下锚板的受力性能,探讨了锚板厚度与螺栓间距、直径的关系以及为保证锚板的出平面刚度应采用的厚度。     

砖混房屋墙体裂缝的原因分析与结构措施

对砖混房屋墙体裂缝产生的原因、机理以及裂缝形式进行了详细论述，并针对各种裂缝提出相应的结构布置措施，指出在砖混房屋设计中抗裂的一般注意事项。     

预制混凝土夹心保温墙板热工性能优化设计建议

预制混凝土夹心保温墙板具有较好的承载、保温与隔声等性能,是目前装配式建筑中主流的外围护构件,但在目前的设计与实际应用中,墙板实际的热工性能未能充分的得到发挥。结合前期学者的理论研究与实际的工程应用,针对如何提升墙板热工性能给出了优化设计的建议,为夹心保温墙板的设计与应用提供参考。     

曲折线形型钢梁折点部位应力状态研究

结合实际工程中的应用情况,通过有限元分析,对型钢梁折点部位进行详细的应力分析,推导出曲折线变化与应力变化的相关规律,为曲折线形型钢梁体系力学分析提出理论依据。     

点式连接预制混凝土夹心保温外挂墙板抗弯性能研究

开展与主体结构点式连接、同时配制GFRP连接件及钢筋桁架连接件预制混凝土夹心保温外挂墙板静力压弯试验,并利用ABQUS有限元软件建立外挂墙板抗弯计算模型,将其与试验结果进行对比。在验证了有限元分析模型准确性的基础上,对连接件的种类,连接件的布置方式、间距等影响墙板抗弯性能的主要因素进行参数化分析。分析结果表明GFRP连接件、钢筋桁架连接件的布置间距和钢筋桁架连接件的直径对墙板抗弯性能影响较大,钢筋桁架连接件的强度等级影响相对较小。     

反转式稳定土拌和机转子参数和罩壳形状对性能的影响

本通过反转式拌和机转子的工作过程运动分析，提出了降低功率消耗，合理设计转子参数及罩壳形状的方法。