火灾后桥梁拉索性能评估方法研究

以桥梁火灾后拉索受损实例为研究主体,通过对桥梁拉索受损状况现场检测、失火模拟试验及理论计算分析,完成对受损拉索性能的检测评估分析,研究一套系统的桥梁安全性评估方法。     

钢结构火灾温度推定方法研究

钢结构火灾后受损评估鉴定中,为了快速、准确地确定钢结构火灾温度,对评估加固工作提供可靠依据,本文在总结工程经验的基础上,结合试验研究,提出了六种简单易行的钢结构火灾温度推定方法,并以工程实例对比介绍了方法的使用过程。研究成果可供火灾后钢结构受损评估鉴定时参考。     

两种住宅建筑节能评估方法的比较

住宅的节能评估对推动建筑节能工作至关重要。本文分别探讨了建筑节能评估中常用的两种方法——节能综合指标限值法和对比评定法，并使用建筑能耗动态模拟软件DeST，计算了3种不同类型住宅建筑的全年采暖空调能耗，采用这两种节能评估方法分别分析了节能效果。结果表明．对比评定法比现有标准中的限值法更符合实际情况，更有利于住宅节能技术的推广应用。     

城市建筑火灾损失与防火安全水平的评价

城市建筑火灾损失的评价旨在对建筑物的各种存在状态和潜在的火灾危害进行一种理论分析和实际评价。对不同类型的建筑物和实际存在的防火安全度，提出了消防安全资金投入比例的一种理论计算方法。通过对几种火灾安全评估模型的分析，确定用表格数值的方法去评价我国现有的建筑防火安全水平，并以此为基础，讨论了城市防火安全评定的有关问题。     

长大高风险隧道施工风险评估及管控措施

对长大高风险隧道施工建立一种科学的风险评估方法 ,并根据评估结果提出隧道施工风险控制措施是社会安全发展的需要。本文结合实例从模糊综合评估的角度出发,综合使用了风险矩阵法、专家调查法、风险层次法对施工风险出现的概率以及造成损失的严重性进行了评估,并提出了风险管控措施,提升了隧道施工安全性。     

对施工招标中两种评标方法的分析研究

介绍了经评审的最低投标价法和综合评估法两种、平标方法的概念、评标过程，分析了两种方法的特点，同时指出使用中存在的主要问题，并提出相应的对策。     

恒压钻入法检测火后混凝土损伤程度的可行性研究北大核心

采用改进的恒压钻芯机对不同温度下的混凝土试块进行钻入试验,发现钻入速度随混凝土受火温度的升高而升高。又通过混凝土材性损伤的三个力学指标,弹性模量、抗压强度和劈拉强度来评估恒压钻入法的可行性。结果表明,恒压钻入法可以作为检测混凝土高温受损程度的一种辅助方法,基本可以反映出损伤随深度的变化。     

底框砌体剪力墙震损房屋损伤评估及抗震加固

在完成3层足尺底框配筋砌块短肢砌体剪力墙房屋系统的拟动力子结构抗震性能试验后,模型的梁、板、柱、墙等结构构件均出现了不同程度的损坏。本文详细介绍拟动力抗震性能试验对结构构件造成的损伤,并根据对损伤程度的评估,分别选用粘钢、粘贴玻璃纤维布和裂缝修补技术3种最常用的加固方法对受损部位进行加固,以期获得上述3种方法在地震区对震后受损建筑进行加固或对建筑进行抗震加固时的适用性特征。文中详细介绍上述3种常用加固方法的施工步骤,并按照要求实施加固施工,为研究震后受损结构构件加固后的抗震性能试验研究做准备。     

基于专家评价和BP网络的组合赋权法

针对软件可信性评估问题中出现的属性权重的确定方法问题,提出了一种基于专家评价和BP网络的组合赋权法,并给出了用户的预期的概念,具有一定的理论和实际意义。     

恒压钻入法检测火后混凝土损伤程度的可行性研究

采用改进的恒压钻芯机对不同温度下的混凝土试块进行钻入试验,发现钻入速度随混凝土受火温度的升高而升高。又通过混凝土材性损伤的三个力学指标,弹性模量、抗压强度和劈拉强度来评估恒压钻入法的可行性。结果表明,恒压钻入法可以作为检测混凝土高温受损程度的一种辅助方法,基本可以反映出损伤随深度的变化。     

Shear capacity of steel plate girders with large web openings, Part II: Design guidelines

The present design procedure for the shear capacity of steel girders with large web openings is based on the shear buckling capacity of webs, as given by Eurocode 3, modified to account for the effect of the openings by means of reduction factors determined on the basis of numerical simulations. Guidelines are given for the use of the design procedure in practical design. Equations for determination of the secondary effects are presented, as well as some cut-off factors which limit the shear capacity for certain opening configurations. Requirements for design of welds are also given. Further, the paper presents equations for shear and primary moment interaction. Finally, two design examples illustrate the features of the guidelines in practical design of girders with openings.     

An approximate expression for room view factors

Calculation of the exchange of heat by radiation between the surfaces of a room involves the use of view factors. The algebraic forms for the view factors are somewhat cumbersome, as is also the network of conductances with which they are associated. The network can be simplified with some loss of accuracy to a star form, which in turn leads to the simplified expression for view factors given in this paper. View factors lie between 0 and 1. The standard deviation of the difference between their exact and approximate values is less than 0.03.     

Bioavailability of heavy metals from polluted soils to plants

The aim of this work was to estimate, on the basis of soil extraction procedures, whether a given soil is suitable for cultivation of plants used as food or feed. The paper discusses the transfer of metal ions (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) from contaminated soils to plants in terms of transfer factors (TF). The knowledge of transfer factors for a given element should enable prediction, before plants are sowed, whether a given soil is suitable for the cultivation of plants for consumption purposes. TF can only be evaluated when a linear relationship is observed between soil and plant composition for a given element. Such a relationship is rarely observed between the total soil content of a given metal and that of the plant. For this reason, it was necessary to develop an extraction procedure that would represent the content of metal available to plants during growing season. Several extracting agents were tested. The extracting agent that fulfilled these criteria was 2% (w/v) ammonium citrate. Statistically significant correlation coefficients were determined between the citrate-soluble fraction of soil and content in plant in the case of all the elements studied, except Ni. If a statistically significant correlation exists, it is then possible to evaluate the soil-plant transfer factor for a given metal in plants.     

Partial safety factors for homogeneous reliability of nonlinear reinforced concrete columns

The design of reinforced concrete structures is based on the verification of the rules defined by standard specifications, where partial safety factors are introduced to ensure safety. However, the use of constant factors for different kinds of columns leads to inhomogeneous safety levels. In this paper, a new format for concrete and steel safety factors is proposed, in order to ensure uniform target reliability. These factors are given in terms of the column design parameters, such as material strengths, steel ratio, slenderness and loading eccentricity. The adopted mechanical model takes into account material and geometrical nonlinearities. The response surface technique is used to evaluate the structural reliability. Numerical applications show how the calibrated safety factors lead to a better design than those proposed by the Eurocode2.     

北京大屯里某住宅综合楼结构设计

北京大屯里四区板式住宅综合楼,是集居住、休闲、健身、购物、家庭办公于一体的多功能公寓式高级住宅,整体建筑风格追求欧式古典主义,平面布置讲究高度灵活,房间开间、进深均为大尺度。该工程结构特点为各种不利因素过于集中,针对这些不利因素采取相应的技术措施,对结构工程中一些难点问题提出解决思路,仅为类似工程结构设计提供思考。     

Values as determinants of preferences for housing attributes

Preferences for housing attributes have beenstudied from different theoretical perspectivesand with a great variety of methodologicalapproaches. In explaining housing preferencesthe influence of both macro-level andmicro-level factors has been shownextensively. Relatively little attention hasbeen given, though, to motivational micro-levelfactors such as goals and values. In thisarticle micro-level motivational factors arestudied as determinants of stated preferencesfor housing attributes. The relationshipsbetween such motivational factors as values andgoals on the one hand and preferences forhousing attributes on the other are consideredfrom the perspective of means-end theory. Asemi-structured interviewing technique calledladdering is used for the measurement ofmeans-end chains. Some of the results of apilot project in which means-end theory wasapplied to preferences for housing attributeswill be discussed in the sequel.     

一种基于Morgenstern-Price法假定的三维边坡稳定性分析法

 通过侧向剪力系数和侧向剪力分布函数对条间力进行假定,提出所有条柱满足3个力的平衡、滑坡体满足3个力矩平衡的三维边坡极限平衡分析法,可看作是二维Morgenstern-Price法的三维扩展。利用滑体力的平衡条件和边界条件分别得到条柱各行和各列的安全系数,再利用滑体整体力矩平衡条件确定侧向剪力系数?1,?2,?3,?4。该法考虑了所有条间剪力对安全系数的影响,采用直接迭代法求解,提高计算效率。算例分析表明,对于对称边坡,侧向剪力系数?1,?3,?4对安全系数影响不大;对于非对称边坡,?4对安全系数影响也不大,且获得的安全系数均与已有文献结果接近。非对称复合滑动面算例还表明,简化方法给出的安全系数不一定偏于安全。     

CFRP拉索试验桥锚具的有限元分析

以国内首座CFRP索斜拉桥上使用并获得国家专利的直筒加内锥式锚具为研究对象,选取CFRP筋所受径向挤压应力作为主要研究参数,对其进行影响因素的分析,并提出相应的优化方案。研究表明:采用优化方案后,锚具的挤压应力在锚固长度范围内有所减少且分布更趋于均匀,锚固能力较原锚具也有所提高,说明优化方案是可行的。     

高等级公路沥青路面典型结构的识别方法

建立路面典型结构设计方法的关键在于从众多可供选择的路面结构中优选出具有良好使用性能的路面结构作为典型结构的标准模式,本文利用模糊数学和系统科学的方法对这一问题进行了研究.首先,通过模糊统计和最小二乘回归建立了决定路面使用性能好坏的车辙、平整度等五种因素的隶属函数集;而后,在专家打分的基础上,用层次分析法的权重模型和基于非线性规划的Ekclid权重模型两种方法求得了上述五种因素的权重,并以模糊综合评价为手段,获得了不同路面的综合评价;最后,发展并依靠最大隶属度原则、相对最大隶属度原则以及字典排序原则,选择出具有忧良使用品质的路面结构作为典型路面结构.     

Multiobjective Design of Laminated Cylindrical Shells for Maximum Pressure and Buckling Load

Abstract: Multiobjective design of a laminated cylindrical shell is obtained with the objectives defined as the maximization of axial load and external and internal pressures subject to a strength constraint. The failure under axial load and external pressure may occur by buckling. The ply angle is taken as the design variable. The weighted global criterion method is employed to solve the vector-optimization problem, which involves minimization of the distance to ideal solution vector in L₂ metric. A symmetrically laminated and balanced shell is considered as an example. Pareto optimal solutions are given for two- and three-objective design problems, and numerical results are presented in the form of tradeoff curves and surfaces. The effects of problem parameters are investigated, and the results are given for various weighting factors and shape parameters.