加筋复合砂石垫层在软弱地基土中的运用

通过工程实践与设计体会,论述了加筋复合砂石垫层加固软弱地基土的原理、设计方法及施工技术要求,实践表明,土工筋带复合砂石垫层处理软弱地基是一种安全合理、经济可行的处理方法,值得推广应用。     

加筋复合砂石垫层在软弱地基土中的应用

结合工程实例,介绍了加筋复合砂石垫层在软弱地基土中的应用。     

谈砂石垫层法在地基处理中的应用及质量控制

砂石垫层法是地基浅层处理的种常用方法（即“换填法”）。当软弱土地基的承载力和变形不能满足建筑物的要求，厚度又不很大时，常采用强度较高的砂石垫层置换基础底面下处理范围内的部分或全部软弱土层以提高地基承载力，使其满足建筑物上部荷载的要求。河南科技大学新校区一期首批工程的施工实践证明，砂石垫层法设计在洛阳新区是种行之有效的地基基础处理方法。下面就砂石垫层法在地基处理中的应用及质量控制谈一些看法。     

在软弱地基中加筋砂石地基施工技术

以华松电力节能移变项目办公楼软弱地基处理为例,对土工筋带砂石地基处理的加固机理、施工工艺和施工措施等方面进行全面介绍,简述了土工筋带加筋砂石垫层地基处理的施工技术,以使加筋垫层技术更加完善。     

砂石垫层在浅层地基处理中的问题

实践证明，对于中小型建筑物，采用砂石垫层作为浅层地基处理的方法，效果显著。这种方法可就地取材，施工机具简单、快捷而经济。因此在浅层软弱地基处理中得到广泛应用。当建筑物基础下持力层较软弱又不太厚时，不能满足上部结构对地基承载力及变形的要求，采用砂石垫层置换部分软弱土层，以提高基础下地基承载力，减少地基沉降量和不均匀变形。此外，砂石垫层还可以加速软弱土层的排水固结，提高其强度，避免地基土塑性破坏；在膨胀土中，砂石垫层可以调整甚至消除膨胀土的胀缩作用，以控制建筑物的变形，从而控制墙体裂缝的出现。     

砂石垫层在软弱地基及膨胀土地基处理中的应用

砂石垫层的应用颇为广泛,主要是用它来置换部分软弱土层,以提高基础下的地基承载力,减小地基沉降量。一、应用概况1.建筑物基础下的持力层比较软弱,其承载力和变形满足不了上部结构荷载对地基的要求,且软弱土层的厚度又不很大时,采用砂石垫层置换部分软弱土层,以提高基础下地基承载     

软弱地基处理的简捷方法──砂石垫层

１．前言 在多层建筑设计施工中，常遇到地基土为软弱土，即：淤泥、淤泥质土、冲填土、杂填土或其它高压缩性土组成。这些地基土不宜做天然地基，须经人工处理方可成为承载地基。本文中，笔者将就处理此种地基土的简捷方法──砂石垫层（换填法之一）的使用，谈谈自己的体会。     

高填土路堤荷载下混凝土芯砂石桩复合地基变形与承载力试验研究

混凝土芯砂石桩复合地基由竖向增强体混凝土芯砂石桩、水平加筋砂石垫层和地基土共同组成,是一项将砂石桩良好的排水固结特性、预制混凝土桩高强度竖向承载和加筋垫层应力扩散调整功能进行有机结合而成的新技术,适合于处理高含水率深厚淤泥质软土地基。结合实际工程应用围绕混凝土芯砂石桩复合地基的变形和承载力两大特性开展了大量的现场观测和原位测试,研究分析了高填土路堤荷载作用下混凝土芯砂石桩复合地基的表面沉降、分层沉降、深层水平位移、桩土应力分布、桩身荷载传递规律、强度和承载力特性等,进一步揭示了混凝土芯砂石桩复合地基的加固机理,对工程设计与施工具有重要指导意义。     

砂石垫层施工技术在软弱地基基础加固处理中的应用

本文结合笔多年建筑工程施工管理实践,分析介绍了砂石垫层加固处理软弱地笨的适用范围和作用：对砂石垫层加固设计与施工要点及质量检测进行了详细阐述;并结合工程应用实例,对其处理软弱地基效果进行了论证说明。     

级配砂石垫层处理软弱地基技术及工程应用

本文介绍了用级配砂石垫层处理软弱地基的设计方法及施工质量控制要点 ,并结合工程实例 ,证明这一地基处理方法的有效性。     

Magnetoelastische Spannkraftmessung in Bauwerken

Magnetoelastic Measurement of Prestressing Force in Civil Structures The knowledge of the tensile force of prestressing steel elements and its reliable and non‐destructive determination are of essential importance for the assessment of the structural health condition of prestressed concrete structures and tie‐back systems in terms of structural safety, serviceability and durability. For the evaluation of the prestressing force in steel tension members, the measurement technique presented in this contribution is using the magneto‐elastic effect (ME‐effect) of ferromagnetic materials. This effect describes the reverse‐proportional correlation between the mechanical stress and the magnetic properties of ferromagnetic materials. The cylindrical coiled sensors pushed over the tendon and the measuring device developed and practically optimized at the iBMB/MPA of the TU Braunschweig enable a fast and reliable measurement of the prestressing steel force after an initial calibration. In this contribution first the state of the art of prestress measurement techniques for steel tension members is presented. Afterwards, the ME‐measuring method with the basics and merits of magneto‐elastic prestressing force identification is shown. Further recent research results as well as several building applications will be discussed.     

土体干缩裂隙的形成发育过程及机理

土体干缩开裂(龟裂)是一种常见的自然现象,龟裂的产生会破坏土体的完整性,极大地弱化土体的工程性质。基于室内试验结果,发现龟裂发育过程可分为3个典型阶段,具有很强的时序特征,且新生裂隙一般垂直已有裂隙生长。根据水土相互作用原理和基本土力学理论,建立了土体龟裂概念模型,对实验室和自然界中观测到的相关龟裂现象及其机理进行了分析,得到如下主要结论:(1)土体中存在收缩变形空间是龟裂发育的前提,主要与土质条件有关;(2)龟裂是土体发生张拉破坏的表现形式,孔隙水的表面张力及干燥过程中引起的基质吸力(毛细水作用力)会在土体中形成张拉应力场,这是导致龟裂的主要力学诱因;(3)当张拉应力场的大小超过土体的抗拉强度或土颗粒间的联接强度时,裂隙便会产生,导致局部区域积聚的应变能释放,应力场重新调整。从宏观上看,基质吸力和抗拉强度是控制龟裂发育的两个关键力学指标,但从微观上看,土体材料尤其是结构的非均质性对裂隙发育过程和裂隙网络的几何形态特征均有重要影响。通常情况下,大部分裂隙都是在饱和阶段产生,且裂隙产生时对应的临界含水率有可能高于液限;土体表面上的"杂点"易导致应力集中,裂隙往往率先在"杂点"处产生;(4)受表面和裂隙面张拉应力场的共同作用,表层土体边缘会发生向上卷曲变形,产生"煎饼效应"。此外,土体在收缩过程中还存在收缩核现象。     

Zustandsuntersuchung und Instandsetzung am Hauptdach des Hauses der Kulturen der Welt in Berlin

The main roof of the ”Haus der Kulturen der Welt“ in Berlin Which is very well‐known on account of its history and striking structural design – was to be inspected by the author to determine its condition and analysed with regard to the durability of the existing liquid synthetic sealant. The roof structure consists of a biaxial, curved area‐covering structural element with circumferential edge beams of pre‐stressed lightweight concrete. This is the result of the reconstruction between 1984 and 1987 following a partial collapse of the then Berlin Congress Hall in 1980. The very thin roof shell is also made of lightweight concrete and, like the edge beams, has a polyurethane‐based spray‐on seal that was specially developed for this purpose as protection against the ingress of moisture. The reason why this, at the time, novel type of seal was chosen was that it should take into account the fact that the roof design urgently needed some kind of protection against moisture that had to compensate the expected changes shape and crack movements of the roof with no damage. The following article reports on the nature, scope and main results of the analysis of the condition of the roof seal, edge beams and abutments. It will also describe the repair recommendations resulting from the investigations, which form the basis of the execution of work at the present point in time. Apart from presenting the technical principles and special features of the building that have to be taken into account during any repairs, the special features of the execution will also be addressed.     

Alternative Methods of Procurement for Works of Water and Environmental Management

The paper considers methods of procurement for the construction of water- and sewage-treatment works other than the traditional use of the ICE 5th Edition Conditions of Contract and Bills of Quantities. This is as a consequence of the speed at which schemes are currently required within the water industry.
The paper particularly focuses on the use of target contracts, using the Institution of Chemical Engineers'Green Book form, and considers various types of target. It also discusses the form which tender documents may take, and how targets may be calculated.
Tendering procedures, including the use of two-stage tenders and negotiated targets, are considered, as are the procedures for cost monitoring and the financial management of the contract. Finally, the role of the engineer and quantity surveyor is considered.     

Innovative technique for identification of prestressing tendons layout in post-tensioned bridges using a probe with MEMS accelerometer

Post-tensioned concrete bridges are currently often constructed engineering structures. In this type of bridges it is crucial that geometrical layout of prestressing system complies with the design requirements. Unfortunately, major errors still occur during assembly of tendon routes. This has often negative effects. In a local aspect, it may cause a local damage, such as spalling of concrete cover. In a global aspect, prestressing may produce distribution of forces in the bridge structure different from the expected. That is why numerous methods have been developed to control the accuracy of executed tendon routs. Some of them, e.g. geodetic measurements with levelers, require direct access to tendon sheaths. Other methods, which can be used after casting of concrete (mainly NDT methods) have a series of resolution, efficiency and accessibility limitations. Hence, the paper presents a proposal of an alternative method for control of tendons routing using a special probe with Micro Electro-Mechanical Systems capacitive accelerometer. The paper presents a concept of tests performed with the probe, evaluation of the probe application in the view of a random process and finally assessment of the results obtained with the use of the constructed measurement system in trial laboratory conditions.     

A Survey of Ferruginous Minewater Impacts in the Welsh Coalfields

The aim of this study was to locate all ferruginous discharges within the Welsh coalfield areas and to assess their impact upon receiving watercourses. The project was undertaken in two stages. In the first stage, visual assessments were carried out on an area of river bed affected by iron hydroxide deposition. Chemical samples of the discharges and the receiving watercourse were analysed for a suite of physico-chemical determinands. Ninety discharges were located impacting upon 59.4 km of river, and an area of 22 ha was affected by iron hydroxide deposits.
A ranking method, incorporating the physical/chemical determinands, was developed to assess the comparative impact which discharges were having on receiving watercourses. A total of 33 of the top ranked discharges- (20 to classified watercourses and 13 to unclassified watercourses) having the highest environmental impact were selected; chemical, biological and fisheries impact assessments were then carried out on these discharges in the second stage of the project. The sites were then ranked on the basis of biological and fisheries impact. A list of the highest impacted sites was produced, and some of these were further investigated for remediation options and associated costs.     

约束受热伸长中空柱填充混凝土的耐火性能

在圆形中空柱中填充混凝土是一种很好的柱子加固方案,因为它能够增加柱子在室内和高温环境下的承载能力。然而,发生火灾时,对受热伸长的约束可能会改变其力学性能。通过对约束受热伸长中空柱进行一系列耐火试验后,得出试验结果。试验对柱子长细比﹑承载等级﹑周围结构刚度以及所占钢筋的百分比和混凝土强度等参数进行了测定。结果显示,这些柱子的极限抗火时间都小于46min。在柱子内层墙面使用混凝土环,从其性能上来讲在火灾时并没有太大优势,因为混凝土环会受到钢管过热而带来的大面积碎裂。柱子最主要的破坏方式即是整体屈曲。然而,在一些试验样本上也出现了局部屈曲。     

Reliability of composite steel bridge beams designed following AASHTO''s LFD and LRFD specifications

Composite steel beam bridges designed following AASHTO's Load Factor Design (LFD) method and the newly developed Load and Resistance Factor Design method (LRFD) are proportioned for different loading conditions. They need to satisfy these conditions at maximum design load, an overloading condition, and fatigue load. The ultimate strength of compact composite steel beams is based on the fully plastic stress distribution. The capacity of non-compact beams is based on the yield or partially-plastic moment, depending on whether the beam violates all or few of the compactness or ductility requirements. In this paper, the reliability for the ultimate flexural capacity limit state of composite steel beams is investigated. The structural reliability is measured in terms of the reliability index. The statistical data on strength are generated starting from statistics on material properties and using the Monte Carlo simulation method. Statistical data on load components are compiled from the available literature. The scope of the study covers a wide range of rolled beams, span lengths, beam spacings, and two yield strengths. The deterministic study showed that the design of composite steel beams is usually not governed by the maximum design load combination, but rather by the overloading condition. The results of the reliability study indicate non-uniformity in the safety of steel bridges that are designed by the AASHTO LFD code. This is also true for AASHTO's LRFD code since it is not calibrated for the overloading condition. The value of the reliability index is a function of the compactness classification, method of design, beam spacing, span length, and section size.     

Application of sonic and radar tests on the piers and walls of the Cathedral of Noto

The authors applied systematically sonic tests, radar tests and other diagnostic techniques on the remaining walls and piers of the Cathedral of Noto. The experimental survey was carried out by the Laboratory of the DIS, Politecnico of Milan (Person in Charge: Prof. Binda, Prof. Baronio) in collaboration with the designers (Ing. R. De Benedictis, Arch. S. Tringali) and the experts working on the reconstruction. The Prefettura of Siracusa founded the research. The right aisle and most of the dome of the Cathedral collapsed in 1996. The aim of the research was to verify the state of damage and the possibility of conservation of the walls and piers in view of the reconstruction of the damaged part of the Cathedral. Furthermore, the sonic tests were used to control the effect of grout injection used as a possible technique for repair of the damaged masonry (Proceedings of the Conference on Nondestructive Evaluation of Civil Structures and Materials, Boulder, Colorado; (1992) 329; Proceedings of the Sixth Conference on Structural Faults and Repair, 3 (1995) 195). In the following the results will be reported and the reliability of the tests will be discussed as it was confirmed by the use of other complementary diagnosis techniques (Proceedings of the Sixth International Conference on Structural Studies, Repairs and Maintenance of Historical Buildings, STREMAH 99, Dresden, Germany, (1999) 323).     

Umfangreicher Validierungsdatensatz eines großen Verwaltungsgebäudes für Software zur DIN V 18599

Detailed Data Set of a Large Administration Building as a Validation Model for DIN V18599‐Software. The calculation method of DIN V 18599 represents a very complex model for the estimation of the energy efficiency of buildings. The method is used for certificates too, thus, the number of users is quite high. This fact and the complexity of the method causes high demands on the related software products. Most of the end user software tools work with the calculation engine ibp18599kernel developed by Fraunhofer‐Institut for Building Physics. There is a continuous quality control for both, the kernel and the user interfaces, i.e. the end user software. This paper gives an overview of the process of quality control as well as a documentation of a validation model used within this process, i.e. a complex administration building as a sample.