国家标准《建筑结构荷载规范》修订概要

国家标准《建筑结构荷载规范》此次修订是在全球气候变化、反恐以及经济全球化的背景下进行的。修订要点主要包括增加温度作用和偶然荷载内容,规范涵盖范围由直接作用扩充到间接作用。收集补充了我国最新的风、雪和气温气象数据,更新各城市基本雪压和风压值,填补建筑结构设计全国基本气温数据空白,以应对灾害性天气对工程结构安全构成的威胁。调整部分楼面及构件的活荷载,增加可变荷载考虑设计使用年限调整系数,完善并适当提升建筑结构的可靠水准。补充各类屋面的不均匀积雪分布情况,以提高大跨轻型屋面抗雪灾能力。规范修订全方位综合调整了风荷载水准,修订后的风荷载计算公式与参数更加通用透明,另外还增加了高层建筑横风向及扭转风振响应计算。     

可行性研究中基础数据的收集与处理

当前,在我国基础数据收集与处理中存在着很多问题。在可行性研究中,基础数据的收集与处理是第一步骤,是其后所有步骤的基础。而且可行性研究的可靠性、科学性在很大程度上依赖于基础数据收集、处理的程度。基础数据的收集与处理是真实的、可靠的,可行性研究才有意义,才能使项目     

昌吉体育馆结构屋面荷载设计

本工程屋面建筑造型复杂,屋面风荷载和雪荷载无法直接参考常规屋面形式确定,在设计中为了准确确定屋面风荷载和雪荷载,对屋面分别进行了风洞测压试验和雪荷载数值模拟试验。将试验结果和试验数据进行统计分析,形成了用于结构整体屋面设计的计算参数;并对屋面钢结构布置尤其是支座形式的选择进行了优化,有效地减小了温度应力的影响。     

折叠网架结构变形-荷载随机过程概率预测模型北大核心CSCD

节点位移的控制是折叠网架结构正常使用的关键。根据概率理论和数理统计原理建立二维连续型随机变量位移和荷载的概率预测模型,基于有限的试验数据,进行不同雪荷载工况下节点位移的预测。计算结果表明:100,120,140mm厚雪荷载作用时,节点竖向位移和水平位移预测值与试验测试值吻合较好,所有节点平均预测精度大于或等于97.0%;分析了边跨节点和120mm厚雪荷载作用下的节点位移预测值与实测值偏差较大的原因;120mm厚雪荷载作用时的节点位移应格外关注;相邻两级荷载的比值大于0.8是模型适用的条件。     

严寒地区雪景观视觉舒适度研究

严寒地区积雪期长,雪景观对户外环境的视觉舒适度形成了不同的影响。实验以雪景观图片为素材,利用打分法和图片分析法获取数据,通过数据统计分析发现,雪景观对视觉舒适度有不利影响。其中,高亮度雪占整个图像面积的比例与视觉舒适度呈负相关;丰富的景观层次、色彩有助于提升雪环境中的视觉舒适度。基于以上分析,提出了通过植物种植、地形处理、园林建筑小品设计、视野控制等措施来减少视域中高亮雪面积比例、增加景观层次、丰富景观色彩,从而提升风景园林中雪景视觉舒适度的对策,以期对提高严寒地区雪景观舒适度提供借鉴和参考。     

大数据时代下的刑事电子数据收集研究

以数据为核心的电子数据证据具有海量性、普遍性和易变性,需要对一般性的取证原则即全面收集原则、依法收集原则和及时收集原则作出新的阐释,同时建立起专属于电子数据收集程序的无损取证原则。电子数据收集的基本原则指导相关性识别、电子数据的调取、搜查、扣押、冻结和实时搜集等具体的收集环节。大数据推动数据驱动型侦查模式变革,进而引发以电子数据为核心的证据制度变革。     

折叠网架结构变形-荷载随机过程概率预测模型

节点位移的控制是折叠网架结构正常使用的关键。根据概率理论和数理统计原理建立二维连续型随机变量位移和荷载的概率预测模型,基于有限的试验数据,进行不同雪荷载工况下节点位移的预测。计算结果表明:100,120,140mm厚雪荷载作用时,节点竖向位移和水平位移预测值与试验测试值吻合较好,所有节点平均预测精度大于或等于97.0%;分析了边跨节点和120mm厚雪荷载作用下的节点位移预测值与实测值偏差较大的原因;120mm厚雪荷载作用时的节点位移应格外关注;相邻两级荷载的比值大于0.8是模型适用的条件。     

浅析电子数据收集提取的规范化

刑事诉讼中电子数据的收集和提取的规范化,是证据审查的重要内容。从审查判断电子数据的原则出发,针对电子数据的"三性":真实性、合法性、关联性,提出收集和提取过程中的完整性、客观性及其规则是真实性的最重要因素,通过案例介绍了手机短消息和即时通信聊天记录、撤回的微信视频以及网站数据的网络在线收集和提取的规范化。     

论刑事案件初查阶段电子数据的收集与使用

侦查机关在初查阶段收集提取电子数据的权利,本文以初查阶段电子数据收集与使用的相关规定为切入点,分析收集提取电子数据与立案前禁止采取强制性侦查措施原则的冲突,提出初查阶段电子数据收集使用的适用准则及必要限制。     

基于BIM的设施管理运维数据收集

本文阐述了BIM应用于FM所需要的运维数据支持,具体包含了全建筑生命周期的各个阶段收集运维所需数据的过程以及运维团队不同层面的数据需求。收集到的数据根据运维需求进行筛选,而在数据收集过程中需要根据运维需求收集相应的数据。     

Reliability of Steel Truss Roof Systems Under Variable Snow Load Profiles

The probabilistic safety analysis of steel truss roof systems under variable snow load profiles is investigated. The roofs of structures such as industrial buildings or sports halls, which require wide areas, are frequently subjected to unexpectedly high loads. Therefore, compared to the residential buildings, that type of buildings often comes across failure or prohibition of usage. Probabilistic techniques are utilized for the analysis of the problem. Thirty-six steel roof structures with different structural dimensions and load variations are modelled and their failure probabilities are calculated. In this paper, a complicated stochastic analysis is reduced to the solution of a load–resistance (S–R) problem by utilizing sensitivity analyses. Firstly, the structures were designed through structural analyses, and then the sensitivity analyses were conducted to understand the response of the structure to the load and to the span-length parameters. In this paper, a reliability study which gradually monitors the effect of geometrical parameters on the failure trend is presented. Three different snow load distribution functions were used. The relation between failure, and load or structural dimension variations was investigated. The results obtained in this study are discussed and compared with the results from the literature for similar structures subjected to snow loads. It is observed that for the snow load distributions with high standard deviations the structural reliability indices may give results below the target safety levels of the design codes. Finally, the assessment of the results shows that the effect of the standard deviation of the snow load on failure probability is much more than the effect of intensity of the nominal snow load.     

雪灾下轻钢结构大面积破坏的概率成因

现行可靠度设计统一标准在分析轻钢结构构件可靠度时,对荷载效应比值的取值范围考虑不够充分。针对此不足,提出了1种基于应力的荷载效应比值计算方法,解决了在构件失效是由多种形式内力引发的情形下选择何种荷载效应来计算荷载效应比值的问题。以多个轻钢结构构件为例,采用该方法分析了轻钢结构中荷载效应比值的取值范围。揭示了雪荷载不利布置下,轻钢结构的荷载效应比值将会非常高的现象。接着对按现行分项系数设计的轻钢结构进行了可靠度校核,表明轻钢结构的可靠性处于较低的水平。最后分析了雪荷载超过设计标准时轻钢结构可靠度随不同荷载效应比值的变化规律。结果表明当雪荷载超载较大时,荷载效应比值越大的结构可靠性越低。这从可靠性的角度为近年雪灾中轻钢结构大面积破坏的现象提供了补充解释。     

温泉融化路面冰雪试验及其对路面强度影响研究

川西高海拔地区冬季寒冷,路面冰雪问题严重威胁行车安全。而川西丰富的地热资源给解决路面冰雪问题提供了清洁高效的新方法。以海拔高度4 200 m的雀儿山隧道为例,通过数年监测明确了区域气象与温泉温度变化规律,进而研究了PVC与不锈钢管两种管道引入温泉融化路面冰雪效果及其对路面强度影响。结果表明:与间距24 cm布置的PVC管相比,间距40 cm的不锈钢管试验段路面冰雪融化时间降低了47%,保障了路面在30 h降下12 cm雪的环境中无积雪。与原路面相比,加入不锈钢管后抗压与抗折强度分别提高了 12.7%和11.3%,提高了路面的承载能力。研究成果对于高原和高纬度地区利用温泉消除道路冰雪具有借鉴意义。     

踏雪迎春赏梅怡情--浅谈天津市首届迎春梅花展设计

天津市水上公园迎春梅花展设计,利用春节严寒的有利气候条件,采用先进人工造雪机,在盆景园营造白雪皑皑的雪景;采用先进技术手段,使不同花期的梅花集中在春节期间竞放,真正实现了佳节赏佳花,观佳景,入佳境.     

薄壁型钢檩条抗积雪荷载作用的设计方法研究

近年来我国多次发生在积雪荷载作用下门式刚架轻钢房屋发生破坏事故。本文分析了积雪荷载在房屋屋面形成的特点和屋面积雪荷载作用下薄壁型钢檩条的破坏特征。探讨了现行设计规范和技术规程中檩条抗积雪荷载设计方法的合理性,指出了计算模型存在的不足。压型钢板屋面在积雪荷载作用下,不宜作为檩条可靠的侧向支撑,檩条计算应按屋面不能阻止檩条侧移和扭转进行强度和稳定计算。通过大量算例计算和分析比较,研究了屋面坡度与扭转翘曲正应力对檩条截面正应力的影响规律和程度,指出了现行设计规范和技术规程中薄壁型钢檩条抗积雪荷载的设计方法的适用性和缺陷。对于目前大量采用的屋面坡度较小的轻钢建筑檩条进行强度和稳定计算时,不宜忽略扭转翘曲正应力的影响。探讨了在屋面积雪荷载作用下门式刚架轻钢房屋发生破坏的原因。提出了薄壁型钢檩条抗积雪荷载作用的设计方法建议。     

Fragility analysis of woodframe buildings considering combined snow and earthquake loading

This paper describes a study to evaluate appropriate percentages of design snow load (factors for use with nominal values provided by the current design load standard for structural design in the United States, ASCE 7-02) when snow load is being taken into account in a seismic fragility analysis. The procedure is illustrated through the development of seismic fragility curves for one and two-story woodframe structures in three locations (Memphis, TN; Carbondale, IL; and Boston, MA) having both moderate snow and seismic hazards. The fragilities are cast in terms of displacement criteria (maximum shearwall drift) with the snow load serving to add seismic weight to the structure. The structures are analyzed using a nonlinear dynamic time-history analysis procedure. The seismic hazard is defined using USGS seismic hazard maps and uncertainty in the seismic hazard at each location is characterized by a suite of ordinary ground motion records. The ground snow hazard is defined through an analysis of data from first-order weather stations at the sites considered. Through a series of multi-hazard convolutions, parametric studies, and the construction of fragility curves, percentages of design snow load are determined for use in constructing displacement-based seismic fragilities and calculating failure probabilities (by convolving with appropriate seismic hazard functions). Practical implications for fragility analysis considering multiple hazards and performance-based design of woodframe structures also are discussed.     

Effects of wind exposure on roof snow loads

This paper presents results from an investigation of the suitability of the exposure coefficient as defined in ISO 4355 “Bases for design of structures—Determination of snow loads on roofs”, based on thorough analyses of weather data from 389 weather stations in Norway for the reference 30-year period 1961–1990. First, the background of the exposure coefficient is examined. Historical field investigations of snow loads on roofs are also evaluated. Next, values for the exposure coefficients in Norway are calculated according to ISO 4355. Finally, possible approaches aiming at improving calculations of wind exposure on roof snow loads are suggested. It is shown that the exposure coefficient as defined in ISO 4355 does not reflect the actual effects of wind exposure on roof snow loads in Norway, the main reasons being oversimplifications in the definition of the coefficient and the extreme variations of the climate in Norway. The definition is based on coarse simplifications of snow transport theories, and must be revised and improved to serve as an applicable tool for calculations of design snow loads on roofs in Norway.     

The Installation and Use of a Snow Pillow to Monitor Snow Water Equivalent

In February 1993, a snow pillow was installed at Widdibank Fell near Cow Green reservoir (in Upper Teesdale) to monitor snow water equivalent.
This paper describes existing snow-measurement techniques in the UK and the site-selection process and installation details for the snow pillow. Following a winter of more than 100 days with snow cover at the site, the success of the pillow in representing site and catchment snow conditions and in providing operationally useful snowmelt information for flood warning has been assessed.     

拱形钢棚在冰雪荷载作用下倒塌事故分析

介绍了一拱形钢棚在冰雪荷载作用下坍塌的情况,对其主要构件进行了强度和稳定性验算,分析了钢棚坍塌的原因,最后对存在的一些问题进行了总结.     

低层双齿大棚屋面风致积雪分布研究

为研究低层双齿大棚屋面的风致积雪分布规律,基于FLUENT软件中的Mixture多相流模型,建立了风雪两相流场模型。为验证风雪两相流场的准确性并选择合适的湍流模型,采用k-w,SST k-w和k-kl-w湍流模型分别对立方体周围积雪分布进行数值分析,并将数值分析结果与试验结果进行对比以验证数值方法的正确性,进而详细研究了风速、风向角、屋面坡度比和结构双齿长宽比对低层双齿大棚屋面风致积雪分布的影响。结果表明:风雪两相流模型和k-kl-w湍流模型建立的风雪两相流流场可以较好地反映低层双齿大棚屋面的积雪分布情况; 大棚屋面积雪厚度随着风速和屋面坡度比增大而减小,且屋面坡度比的影响程度较风速与风向角的影响小; 大棚屋面积雪受侵蚀和堆积区域位置随风向角变化而变化; 大棚结构长宽比对屋面积雪分布的影响较小; 低层三齿大棚屋面和低层四齿大棚屋面的屋面积雪分布系数可参考低层双齿大棚屋面; 提出的低层双齿大棚屋面积雪不均匀分布系数可为低层双齿大棚屋面的冬季防雪灾设计提供参考。