Controlled blasting of concrete

In an old concrete building made available by the Stockholm Real Estate Office, several experiments at full-scale were made on different methods of localised cutting, including controlled blasting with charges inserted into drilled holes and with lay-on, metal-enclosed explosives. Some punching shear to the rear of the wall was noted with the latter, which sometimes produced violent shock waves. The inserted charges performed well, however, and were found to be more economical and environmentally better than conventional cutting methods. The author works at the Swedish National Testing Institute.     

VFT‐WIB‐Brücke bei Vigaun – Verbundbrücke mit externer Bewehrung

VFT‐WIB viaduct in Vigaun – a composite bridge with external reinforcement. With the introduction of the composite dowel the possibility is given to develop new construction methods for bridges. The VFT‐WIB construction method is used for the first time for the road bridge in Vigaun/Austria, which is in service since autumn 2008. The cross‐section is composed out of two prefabricated elements with halved rolled girders, working as bottom flange. The composite dowels are manufactured by cutting the rolled girder into two halves with a special cutting‐line. These halved girders work as external reinforcement, which leads to very slender and economical composite structures. Below details about the planning process, the design and the construction process of 78m long three span framing bridge over the railway line from Salzburg to Wörgl are shown.     

延长盾构机刀具使用寿命的措施

对盾构刀盘和刀具进行了针对性的论述,在盾构刀盘、刀具的设计开发过程中,通过分析刀盘和刀具的受力状况,统计刀盘和刀具的损坏形式,对刀具进行了有针对性的研究改进,从而使产品质量、性能更加可靠完善。     

Ventilation rates in recently constructed U.S. school classrooms

Low ventilation rates (VRs) in schools have been associated with absenteeism, poorer academic performance, and teacher dissatisfaction. We measured VRs in 37 recently constructed or renovated and mechanically ventilated U.S. schools, including LEED and EnergyStar‐certified buildings, using CO₂ and the steady‐state, build‐up, decay, and transient mass balance methods. The transient mass balance method better matched conditions (specifically, changes in occupancy) and minimized biases seen in the other methods. During the school day, air change rates (ACRs) averaged 2.0±1.3 hour^?1, and only 22% of classrooms met recommended minimum ventilation rates. HVAC systems were shut off at the school day close, and ACRs dropped to 0.21±0.19 hour^?1. VRs did not differ by building type, although cost‐cutting and comfort measures resulted in low VRs and potentially impaired IAQ. VRs were lower in schools that used unit ventilators or radiant heating, in smaller schools and in larger classrooms. The steady‐state, build‐up, and decay methods had significant limitations and biases, showing the need to confirm that these methods are appropriate. Findings highlight the need to increase VRs and to ensure that energy saving and comfort measures do not compromise ventilation and IAQ.     

Water and Sewerage Charges in Scotland

The paper outlines the statutory arrangements governing water and sewerage charges in Scotland, and comments on the factors affecting the levels of charges. Trends in revenue expenditure over the period 1989–90 to 1992–93 are considered in relation to increases in personal community water charge levels, metered water rates, and costs per household. Non-domestic sewerage rates and industrial effluent charges are also discussed. Some comparisons are made with England and Wales and with other countries. The funding arrangements for capital expenditure and their effect on the levels of charges are described, with particular reference to debt levels and rising expenditure to meet UK and EC standards. Factors affecting future charge levels are also identified.     

Neue Untersuchungen zum Ermüdungsverhalten von Verbundträgern aus hochfesten Werkstoffen mit Kopfbolzendübeln und Puzzleleiste

New investigations on the fatigue behavior of composite beams made of high strength materials with two different kinds of shear connection. Scope of the research project [1] was the investigation of the fatigue behaviour of different shear connectors (headed studs ∅︁ 22 mm and puzzle‐strip) together with high strength materials (steel S 460 and concrete C 80/95). For both types of shear connectors cyclic push‐out‐tests as well as large scale experiments with composite beams under cyclic loading have been carried out. The headed studs failed after a mean lifetime of 2,3 million cycles, the residual strength after 1 million cycles was reduced by about 25% compared to the static push‐out strength. In the puzzle‐strip cracks were visible, however, the residual strength was not reduced at all. Further, the push‐out tests with headed studs show a slight improvement of the fatigue behaviour using high strongth concrete (HSC). The cyclic beam tests show that the prediction of the fatigue according to EC 4 – as for specimens with normal strength materials – is not satisfactory. A good prediction of the crack propagation (and fatigue) can rather be achieved by using a crack‐slip‐relationship [6]. Also for shear joints with continuous puzzle‐strips a threshold value can be determined by fracture mechanics to which no further crack propagation (theoretically) occurs. However, this depends on the state of the cutting‐induced heat treatment of the surface material and on the surface roughness.     

考虑黄河冲刷要求的盾构法隧道最小覆土厚度分析

 针对兰州地铁1号线下穿黄河段盾构法隧道的最小覆土厚度问题,基于高压富水弱胶结砂卵石地层特性,分别提出由盾构掘削面稳定性与盾尾后方隧道抗浮稳定性决定的最小覆土厚度的修正算法,明确盾尾后方隧道受到的总浮力可以归纳为因浆液包裹产生的静态上浮力,以及地层应力引起的竖向不平衡力对应的动态上浮力,计算发现隧道抗浮稳定性要求的最小覆土厚度明显大于1.0 D(D为隧道直径),《地铁设计规范》(GB50517-2003)提出一般不宜小于1.0 D的最小覆土厚度有待进一步完善。在考虑隧址附近既有桥墩影响条件下,得出考虑冲刷要求的隧道最小覆土厚度方案是安全可行的,同时明确既有构筑物局部冲刷对新建构筑物的影响。研究结论可为盾构法隧道浅覆土穿越江河的稳定性控制奠定理论基础。     

Dünnschichtiger Oberflächenabtrag von Beton in kerntechnischen Anlagen

Automated thin‐layer surface cutting of concrete in nuclear facilities. Thin‐layer surface cutting of concrete layers or coatings as well as small‐area cutting of so‐called hot spots are central tasks in the demolition of nuclear facilities. The aim of the present work is to develop a basic carrier that independently climbs and works on ceilings and walls. This carrier system can be equipped with different tools. The great advantage of this innovative system is the compact construction (surface area about 1.4 m²) and the free moveability without an expensive supporting structure. The usual set‐up time can be saved completely, the system fits through doorways and can be used immediately.     

典型钢梁与箱型柱采用梁翼切削或梁翼加盖板抗弯接头的破坏模式

本文主要介绍二十二组钢梁与箱型柱抗弯接头试体的耐震行为与破坏模式,其中十七组试体采用梁翼切削(reduced beam section,RBS)式接头,另五组以梁翼加盖板的补强(enlarged beam section,EBS)式接头,所有试体均为梁腹栓接、梁翼焊接(BWWF)的现场施作接头。试验结果显示,七组梁翼切削试体及三组梁翼加盖板试体具有4%弧度层间位移角或3%塑性转角以上的变形能力,此十组试体的平均梁塑铰应变硬化系数为1.22。由试体破坏形式归纳,造成梁柱接头变形能力不足的破坏模式包括:梁翼板全渗透焊道断裂、梁翼板于梁腹扇形开孔尖端附近断裂、梁翼切削段内断裂、柱内横隔板与柱板间焊道破坏、及柱板冷(氢)裂五类。探讨此试体破坏原因发现,在六组钢梁与柱内横隔板电溶渣焊焊道侧接合的试体中,三组试体破坏发生于电溶渣焊与柱板接合界面附近,破坏机率高达50%,此现象应值得钢构业重视。本研究成果也发现,高达55%试体未满足台湾钢结构设计规范3%塑性转角或美国AISC耐震特别规定4%层间位移角的变形需求,此显示钢梁与箱型柱采用梁翼切削或加盖板抗弯接头的设计、施工与检测技术有相当大的改善空间。     

城市隧道爆破对附近地表的振动监测与影响分析

对某现场爆破振动地表振动速度峰值监测结果进行了研究,拟合得到了地下工程岩石开挖爆破地面振动速度的变化规律,并对同断面、同药量、同测点掏槽爆破地表质点振速和非掏槽地表质点爆破振速进行比较,结果表明掏槽爆破产生振速较大,合理设计掏槽为关键点。     

Connection bridge effect on a DNA‐like two‐spiral‐up‐tower building

In the recent years, more and more great ideas about architectural design were inspired from bionics, that is, the China National Stadium, Taipei 101, and India Lotus Temple were first inspired from bird's nest, bamboo, and blooming lotus, respectively. However, being a feast to the eyes, those innovative architectures with complex structural behavior and unknown seismic performance are always being a challenge to structural engineers. Hereinafter, a DNA‐like high‐rise building with two separate spiral‐up towers was first outlined, in which each of the tower consist of an interior reinforced concrete core with inserted steel columns and an exterior composite frame made of steel beams and steel pipe–concrete columns. To study the influence of the connection bridges on the seismic performance under different level of earthquake excitation and torsional effect under gravity load, the load transfer mechanism of vertical force and lateral force was conducted, and a finite element model was built with parametrical studies. It can be concluded from the results from the parametrical studies that the drift angle was sharply decreased at the locations where the connection bridges combines two single towers, indicating that the lateral confinement effect of the connection bridges not only strengthen the whole structure but also leads to a discontinuity of the structural stiffness.     

Modellversuche und numerische Simulationen mit der Diskrete‐Elemente‐Methode zum räumlichen passiven Erddruck

Model tests and numerical simulations with the Distinct‐Element‐Method to spatial passive earth pressure. The growing urban development in connection with a closer approach of excavations to existing buildings requires a more careful dimensioning of the excavation walls which specially refers to the movement of retaining walls. For more realistic investigations own model experiments were planned, made and analysed. New testing and measuring methods were developed which for the first time made it possible to record stress distributions along girders. The Distinct‐Element‐Method (DEM) was extended and improved to enable the numerical simulation of load tests. This method allows to describe the experiments with an adequate accuracy. Based on this knowledge, conditions not covered by experiments could be simulated by means of the DEM. Accordingly, the test matrix could be extended.     

截柱扩跨技术在工程改造中的应用

某三层框架结构,底层需截柱扩跨。工程改造前进行了检测鉴定并对比了设计计算值和现场实测值。正确评估建筑物的结构承载能力,不但可以挖掘潜力,减少投入,也可弥补不足,消除隐患。     

管幕内顶进箱涵前端网格横截面尺寸确定

上海市中环线虹许路北虹路下立交工程是目前世界上在饱和含水软土地层中施工的横截面最大的管幕法工程。为保证在管幕内顶进大断面箱涵(前端嵌固钢板制网格框架)的施工过程中开挖面的稳定性,设计合理的网格横截面尺寸十分重要。根据对网格后端开挖面处的土拱效应分析,采用静力平衡条件与土体的剪切强度条件作为基本控制条件,并结合土体的自稳条件,给出了网格横截面尺寸的合理计算方法,以使网格横截面尺寸设计更加合理,最后以实例说明了具体计算过程。     

A new method to evaluate roadheader operational stability

Roadheader, one of the mechanized excavation equipments, has an exceptional place among the other excavation methods. Determination of the stability states of the roadheader is an important matter for the efficiency of excavation. For this reason, a new method has been developed to obtain numerical values that indicate stability states of such machines. The method has been developed for both longitudinal and transverse cutting head type machines by establishing stability equations for states of turning around the vertical axis, turning to the side direction, turning to the back direction and sliding in all cutting modes. A computer program based on these equations has been written in C++ programming language. The stability analysis can be made either for one point on the excavation face or whole face. Obtained values can be used to compare the stability states of various roadheaders in the same cutting condition as well as using to compare the stability states of a roadheader. A stability index that has also been established can only be used to compare a stability state of a roadheader in different cutting conditions. The developed methodology was tested in a transverse cutting head type roadheader for arcing, lowering and lifting modes. It has been obtained that the stability state of turning around the vertical axis of the roadheader is the most critical state especially in arcing mode. The effects of the machine design parameters, cutting head and tunnel parameters on the stability of the roadheaders can also be investigated by this method.     

Leichte Dachschalen aus Carbonbeton

Light‐weight precast shell elements made of textile reinforced concrete: production, experimental investigations and application potential For single curved barrel‐vault shells made of textile reinforced concrete (TRC) a manufacturing process has been developed that comprises the production of the precast parts as well as tailored solutions for transport and mounting of the filigree shells at the construction site. Furthermore, the load‐bearing capacity of the shells could be verified experimentally using large‐scale tests of prototypes. Saw cuts document the high production quality of the precast parts.The developed methods were successfully applied within the research project by constructing a large‐scale roof structure consisting of five barrel‐vault shells. The cross‐sectional thickness of the 10 m2 large elements amounts to only 2 cm emphasizing the high strength and application potential of TRC.     

基于Flac3D软件的某路堑开挖稳定性分析

铁路路堑稳定性是铁路安全的一个重要保障。本文利用Flac3D软件．基于Mohr—Coulomb屈服准则，对某铁路路堑进行了数值模拟计算，以确定其应力、位移状态及塑性区分布情况．进而分析和评价路堑安全性，最后得出Flac3D软件在铁路路堑稳定性分析中应用的合理性和适用性。     

Zur Berechnung von Holzstabtragwerken mit mehrlagigen nachgiebigen Verbundquerschnitten

Calculation of timber structures made of multilayered beam elements with flexible composite sections. The board rib construction technology offers owners, engineers, and architects the opportunity to realise efficient, economic and aesthetical shell‐like buildings. Board rib shells are relatively under‐utilized in spite of their advantages. The reason for this is the lack of a suitable computation method for these complex structural systems made of flexible composite cross‐sections. The solution methods used so far are restricted to just special cases or they represent only approximations. With an efficient, user‐friendly and reliable computation method, such structures will be realised more frequently than at present. Applicability and limitations of the derived method are given in order to avoid inexact solutions. This work presents a finite beam element with a quadratic formulation for the longitudinal displacements for almost any multilayered flexible composite cross‐sections with spatial structural behaviour at geometrical nonlinear theory of 2^nd order. The composite elements are verified with the help of analytical solutions depending on the ratio of the element length and of the joint stiffness. The element is also capable, for example, to calculate wood‐concrete‐composite floors including the effects of creep and shrinkage in sub‐sections.     

磨料射流切割混凝土的机理及试验研究

笔者通过对后混合磨料水射流切割机理的分析，从理论上探讨了磨料水射流形成的液固两相射流具有一定的冲蚀动能，阐述了高能束液固两相射流产生的冲蚀动能，在大干物料的体积能时，可将其物料切割，并提出了磨料仓中的磨料所处的高度产生的重力因素，高速水射流产生的真空卷吸作用因素，水射流对磨料的冲刷作用使其紊流流动而进入射流中的作用因素。是磨料能够混入射流的动力，并且利用高压水射流切割设备，对三种混凝土试件(C30、C40、C50)进行切割试验研究，分析了改变压力，改变喷嘴横移速度，改变喷嘴靶距等切割参数对其切割深度的影响，得出的结论。可作为设计磨料水射流切割装置的参考依据。     

Kraftflussoptimierte Verbindungen im Ingenieurbau

Force flow optimized joints in timber engineering The manufacturing of geometric complex joints can be done by means of CAD‐systems linked to CAM for production. Hereby, different methods for direct geometry generation are used and discussed in this paper. The most elaborate method is the fabrication of a connection prototype to mold the specific joint, followed by casting in high‐performance grout material (polymer concrete, UHPC, etc.). Other methods to obtain the complex geometry are based on laser cutting technology of planar surfaces to generate the shape of the specific joints. Here, parametric design tools generate the joint surface followed by cutting and folding to produce a formwork for the joint geometry. A third method describes the production of a hollow body by 3‐D printing which is used also as formwork. After hardening of the finalized joint, enclosed structural members can be mounted and connected depending on the loading situation. The structural design of the joints can be done by commercially available packages (FE‐software, e.g. ANSYS and ABAQUS) involving the material characteristics of the grouting material. The Universities of Applied Science in Trier and Mainz are jointly developing methods for form generation, numerical modeling and fabrication, which are presented in this paper.