柳州地区建筑材料放射性水平及其致居民剂量

本文采用全国统一方法,检测了广西柳州地区常用建材中~(226)Ra、~(232)Th、~(40)K的比活度.以煤灰砖最高,石灰石最低。比活度依次为煤灰砖>粘土砖≈土壤>水泥>灰砂砖>混凝土制品>石灰石.经估算,煤灰砖致居民的有效剂量当量较大,为3.98mSv·a~(-1);其它各种建材致居民的有效剂量当量在0.23—1.01mSv·a~(-1)之间,低于、等于或略高于本底.     

风场类型对高层建筑风致响应的影响研究

风荷载是影响高层建筑安全性的重要因素之一,而不同的风环境会对高层建筑的风致响应存在不同程度的影响,基于此背景,本文通过高层建筑多自由度气动弹性模型风洞试验,获得了结构原始加速度时程曲线,采用随机减量法对其气动阻尼进行识别,分析了风场类型对高层建筑气动阻尼比和风致加速度响应的影响。结果表明:横风向气动阻尼比随折减风速的变化起伏较大,顺风向气动阻尼比随折减风速的增大而增大;折减风速小于特定值时,地貌类型对气动阻尼影响较小;随着风场类型从A类变化为D类,结构横、顺风向的气动阻尼比的变化趋势趋于平缓,气动阻尼比的正峰值减小,正峰值风速增大。高层建筑横风向的加速度响应大于顺风向;风场类型从A类变化为D类的过程中,横、顺风向的加速度响应均减小。风向角对气动阻尼比和加速度响应均存在较明显的影响。     

对现行民用建筑防火技术体系的分析与探讨

以"处方式"为主要特征的《建筑设计防火规范》、《高层民用建筑设计防火规范》等技术规范构成了我国现行民用建筑防火技术体系,其分类标准和技术体系尚需细化,诸多防火设计与建筑功能设计的矛盾仍无法得到有效解决.由于专家论证、性能化防火设计等途径尚未完善,因此细化建筑分类标准,完善防火技术手段,加快规范体系更新,仍是促进民用建筑防火技术体系不断完善成熟的有效途径.     

Photocatalytic activity of titanium dioxide modified concrete materials – Influence of utilizing recycled glass cullets as aggregates

Combining the use of photocatalysts with cementitious materials is an important development in the field of photocatalytic air pollution mitigation. This paper presents the results of a systematic study on assessing the effectiveness of pollutant degradation by concrete surface layers that incorporate a photocatalytic material – Titanium Dioxide. The photocatalytic activity of the concrete samples was determined by photocatalytic oxidation of nitric oxide (NO) in the laboratory. Recycled glass cullets, derived from crushed waste beverage bottles, were used to replace sand in preparing the concrete surface layers. Factors, which may affect the pollutant removal performance of the concrete layers including glass color, aggregate size and curing age, were investigated. The results show a significant enhancement of the photocatalytic activity due to the use of glass cullets as aggregates in the concrete layers. The samples fabricated with clear glass cullets exhibited threefold NO removal efficiency compared to the samples fabricated with river sand. The light transmittance property of glass was postulated to account for the efficiency improvement, which was confirmed by a separate simulation study. But the influence of the size of glass cullets was not evident. In addition, the photocatalytic activity of concrete surface layers decreased with curing age, showing a loss of 20% photocatalytic activity after 56-day curing.     

汶川地震中房屋建筑震害特征及抗震设计思考

汶川5·12特大地震造成了为数众多的建筑物不同程度的损坏。地震发生后,四川大学随即组织了现场勘查队奔赴受灾最为严重的地区了解建筑物的受损情况。本文基于大量的现场勘查资料介绍了砌体结构、框架结构、底框或局部底框砌体结构及楼梯间的震害特点。在定性分析的基础上提出以下观点:合理设计和施工的砌体结构有可能获得良好的抗震性能;按现行规范设计的钢筋混凝土框架结构难以实现"强柱弱梁"的要求;填充墙对框架抗震性能有显著的影响;在地震区应慎用底框砌体结构;合理的结构布置和施工质量是结构获得良好抗震性能的前提;仅用延性系数来衡量结构抗震性能具有一定的片面性;楼梯间结构设计宜考虑地震作用的影响。     

Advanced rescue techniques: lessons learned from the collapse of a building in Nairobi, Kenya

This paper examines the collapse of a five-storey building in Nairobi, Kenya, on 23 January 2006. It draws on reports from local authorities and on debriefings by Israel's Home Front Command (HFC), including information on injury distribution, rescue techniques, and the mode of operation. Most of the 117 people found under the structure were evacuated on the first day to a public hospital, which was overwhelmed by the incident. HFC forces arrived 23 hours after the disaster. At that stage, two people were still buried under the building and special techniques (tunnelling and scalping) were required to secure their evacuation. The two people quickly recovered after a short stay in hospital. Local technology is the preferred option during such events because time is crucial. International cooperation is required when this technology is not available. All of the hospitals in the disaster area, including private facilities, should participate in treating casualties.     

高层建筑电梯活塞效应及烟气控制分析

在电梯运行活塞效应及其对火灾烟气影响理论分析基础上,分析电梯井和前室加压及压力波动情况;结合高层建筑烟控系统的原理,通过合理的压差设计,可保证电梯系统在最大容许压差和最小容许压差之间正常工作。通过对活塞效应及其对电梯与建筑空间之间压差影响的分析发现,极限状态下烟气可能卷入电梯井和前室,对人员的疏散造成威胁,提出了控制活塞效应影响的上限临界压差。研究表明,合理的排气泄压系统、气压式挡烟系统、可变送风系统及火灾层带通风排烟设施的系统等均能对火灾烟气进行有效控制,提高电梯疏散的安全性。研究所得的结论为火灾中利用电梯进行疏散提供了理论指导及一种烟气控制的方法。     

排烟口布置方式对高层建筑火灾排烟效果的影响

高层建筑发生火灾时,烟气对人员的生命安全有着非常大的威胁,因此有效地控制烟气在建筑物内的扩散对于人员的逃生是非常重要的。通过高层建筑内烟气流动的数学模型,采用k-ε两方程三维紊流模型对高层建筑火灾时排烟口布置于走廊顶棚和走廊侧壁时的机械排烟进行模拟。结果表明,排烟口的布置方式不同对排烟效果的影响很大。排烟口置于顶棚时比排烟口置于侧壁时排烟效率高近10％,走廊内危险性低。在进行排烟设计时应优先考虑将排烟口设置在走廊顶部。     

南京典型古建筑的消防现状调查和消防对策

通过对江苏南京代表性古建筑朝天宫、甘熙故居、鸡鸣寺和净觉寺的实地深入调查,从结构、材料、内容、布局和环境等方面分析了古建筑普遍存在的火灾危险性,考察了古建筑中现代消防设施建设、消防资金投入、消防管理措施和现代消防材料和技术应用的现状,发现多数古建筑在消防防护方面仍处于保守、常规、落后和消极的状态。为实现对古建筑价值的最大限度保护,应从消防安全布局、消防站建设、消防通道设计、消防给水供应、消防通讯保障、消防装备配置等方面进行性能化设计和规划;在遵循“修旧如旧”的修缮和维护原则下,需要勇于尝试和接纳纳米材料等新型化学保护材料和技术。     

建筑火灾增长阶段室内温度的时间特性研究

为研究建筑火灾增长阶段室内温度的时间变化规律,提出了高温烟气的主要几种热损失的计算方法,发展了受火室与未受火室及环境的热平衡方程,并采用牛顿-拉菲尔森法迭代得到受火室的温度变化.计算了慢速、中速、快速、超快速四种火灾增长速率下,受火室气相温度及烟气热损失随时间的变化.本文的研究方法及有关结果可以为建筑防火及安全疏散提供有力依据.