不同弹塑性分析软件在超限高层建筑抗震性能分析中的联合应用研究

基于性能的设计方法很难将结构整体与局部关键构件的性能用一种结构分析软件全面把握，联合使用目前成熟的动力弹塑性分析软件PERFORM-3D和ABAQUS，可以利用各自特点对结构的抗震性能进行全面评价。以某超限高层结构为例，首先建立该结构在大震作用下所需达到的抗震性能目标，在PERFORM-3D软件中对整体结构在不同水准下的性能目标直接进行定义，使用ABAQUS软件对关键构件的钢骨、钢筋等局部应力状态进行分析。通过对结构构件性能水准的整体判定和关键构件的局部分析，全面评价了该超限高层结构的抗震性能，从而确定其是否达到预期的抗震性能目标。结果表明，两种软件的联合应用既可以反映结构的整体抗震承载力及抗侧刚度，又能够很好地把握结构关键构件的局部应力状态，可以更为全面且可靠地反映结构的抗震性能。     

非均质灰岩储层可变模型测井评价

灰岩储层一般呈现较强的非均质性,主要表现在毫无规律的孔渗关系、模糊的物性与含油性关系。碎屑岩储层中常用的单一模型处理方法只适合具有统一孔喉结构类型的灰岩储层,无法保证整个非均质灰岩层段处理结果准确。为揭示灰岩孔隙结构与灰岩测井处理模型的对应关系,采用5M孔隙结构分类技术(以Micro-,Micro+,Meso-,Meso+,Macro为代号的5种孔喉结构类型),结合灰岩储层类型测井自动识别,实现了非均质灰岩储层类型与测井处理模型自动匹配的多模型测井处理技术。这种多模型的测井处理技术,相比常规方法更适合非均质灰岩储层测井解释。该方法已经在南海东部很多非均质灰岩油藏中得到应用,取得了较好的效果。     

Predicting construction firm performance: an empirical assessment of the differential impact between industry‐ and firm‐specific factors

It is obvious that the performance of firms hinges upon the dynamics of both industry‐ and firm‐specific factors. A less obvious, and perhaps a more important, line of inquiry is that to the extent that they have a bearing on firm performance, how much do these two groups of factors respectively predict firm performance? To date, performance differences among construction firms that stem from industry‐ and firm‐specific differential effect has remained largely unexplored. Using a dataset comprising 526 firms across various construction‐related sectors, the sector‐by‐sector firm performance variation that is attributable to the heterogeneity of both industry‐ and firm‐specific characteristics was empirically examined. That statistically significant results of different effect sizes are found indicates that although these factors are often assumed to be intertwined it is possible to study their respective impact on firm performance. Future studies could usefully replicate and extend this study to construction firms in other countries to further investigate what drives firm performance under different national, industry and firm contexts.     

深圳证券交易所营运中心抬升裙楼施工阶段应力监测与分析

深圳证券交易所营运中心的抬升裙楼采用超长巨型悬挑钢桁架结构体系,具有悬挑跨度大、受力复杂、临时支撑卸载难度大的特点。采用自主研发的基于有线应变数据采集与无线信号传输的应变监测系统,在施工阶段,尤其是在卸载过程中,对抬升裙楼关键构件进行实时应力监测。通过长期应变监测数据统计分析、双轴对称测点应力对比分析以及焊接对结构局部应力增量影响试验研究,对施工中的抬升裙楼进行实时安全评估。结果表明：卸载过程中裙楼结构受力稳步转换;龙骨焊接施工产生的焊接残余应力对焊接区域附近的结构局部应力增量有显著影响。     

结构可靠度分析中作用的随机过程组合方法

结构可靠度分析应以直接描述作用随机变化的概率模型和随机过程组合方法为基础,但在目前的作用概率组合中,对由频遇值、准永久值参与组合的可变作用实际采用的是以最大值表达的随机变量组合方法,这将导致不合理的分析结果。依据可变作用的等时段平稳二项矩形波过程概率模型,确定与频遇值、准永久值超越比率对应的时段样本,提出可变作用频遇序位值和准永久序位值的概念,据此建立以作用序位值表达的随机过程组合方法和可靠度分析模型。该方法以随机过程理论为基础,具有明确、合理的工程概念,可准确反映作用组合的基本思想,得到合理的可靠度分析结果,从根本上克服了目前随机变量组合方法的缺陷。     

大跨度装配整体式钢-混凝土组合空腹楼板受力性能试验研究

长沙市某多层大跨度工业厂房采用装配整体式钢-混凝土组合空腹楼盖结构,为评价该结构体系的安全状况,采用缩尺模型试验和有限元分析相结合的方法对30m×30m楼盖结构进行了动力特性和力学性能研究。结果表明：组合空腹楼盖下层钢肋处于拉-弯、上层混凝土肋板处于压-弯的受力状态,从支座到跨中,其轴力逐渐增大而弯矩逐渐减小,应力分布比较均匀;剪力键主要承受弯矩和剪力,从支座到跨中,其弯矩和剪力逐渐减小。在竖向荷载作用下,楼板以弯曲变形为主,试验最大挠度为16.63 mm,为跨度的1/361。结构前8阶振型均为竖向振动,振动规律类似于实体平板,基本频率的理论计算值与实测值分别为3.3 Hz和3.0 Hz。对比试验数据与有限元分析结果二者吻合较好,验证了理论分析与原型结构设计的正确性。     

考虑累积损伤退化的钢材等效本构模型研究

在结构抗震分析中,钢材在循环荷载作用下的一维本构关系是利用杆系模型进行结构弹塑性地震响应分析的基础。为了更准确地模拟结构在强震作用下的反应,提出能够考虑累积损伤、刚度和强度退化的钢材等效本构模型,包括骨架曲线、滞回准则以及退化特征,利用损伤控制因子数学模型对钢构件、节点及结构的损伤退化全程进行描述。根据提出的等效本构模型并利用有限元软件ABAQUS提供的用户材料子程序UMAT,采用Fortran语言开发能够进行钢框架强震作用分析的损伤退化过程计算程序。采用等效本构模型对典型试验进行模拟分析,其结果与试验结果吻合良好,充分证明钢材等效本构模型用于钢构件在强震作用下弹塑性分析的准确性及可行性。     

使用损伤与高温耦合作用下钢筋混凝土梁火灾试验研究与数值分析

为研究不同裂缝宽度对钢筋混凝土梁抗火性能的影响,以混凝土裂缝最大宽度wmax为损伤指标,制作7个钢筋混凝土梁试件,加静载使其产生最大宽度为0.05 mm、0.10 mm、0.15 mm、0.20 mm、0.25 mm、0.30 mm的裂缝,模拟其正常使用时受力状态,并对其进行火灾试验。试验结果表明:不同试件相同位置测点升温大致相同,但截面历经最高温度相差较大,最大温差达到150℃;裂缝宽度越大,试件最终破坏时历经最高温度越小,挠度增长越快。采用ANSYS有限元软件分析梁截面的温度场分布,结果表明:由于初始损伤的存在,相同截面高度处,不同截面沿跨度方向的温度曲线出现波动,裂缝处尤为明显;同一截面,沿截面高度方向的温度曲线出现平台,且裂缝越宽,平台越长,使得截面高温承载力显著退化。提出了考虑裂缝影响的高温作用下混凝土梁承载力简化计算模型,较未考虑裂缝影响的高温作用下混凝土梁承载力的计算精度提高显著。     

Approximations for heterogeneous finite source queues

The exact solution for heterogeneous finite source queues involves a definition of state which is unmanageable for large customer numbers. Accordingly various approximations are considered in an attempt to obtain a simple but reasonably accurate solution. The approximations examine simplified definitions of state with a consequent reduction in the number of states and associated balance equations; one such approximation converts the heterogeneous problem to an equivalent homogeneous problem through either time or rate averaging the problem components. Applications include earthmoving, quarrying and open-cut mining operations where the plant frequently have different characteristics. The exponential solution in such cases is anticipated to provide a hower bound estimate on operation productivity, by analogy with the homogeneous case.     

Heterogeneous households and firms in an urban model with open space and agglomeration economies*

This paper develops a model with heterogeneous households and firms that can locate anywhere in the city. The main features of the model are household preferences for open space which depend on distance to the greenbelts at the city periphery, and agglomeration economies for firms. Numerical results show equilibrium location patterns, rents, and wages under different model specifications. Under most conditions, monocentric location patterns (where there is a higher concentration of firms in the centre zones compared to surrounding zones) are observed, but duocentric location patterns for firms can emerge if both open space values and travel costs are high.