厂房预应力屋架的施工及抗裂分析

汉江集团丹江铝业 3万 t铝冶炼工程 (以下简称三期技改 )的铝电解车间、氧化铝仓库为 2 4 m跨 ,铸造车间为 30 m跨的排架结构 ,折线形预应力钢筋混凝土屋架近 1 50榀。30 m跨屋架采用 C50混凝土 ,2 4 m跨采用 C40混凝土 ,屋架上、下弦及各腹杆非预应力筋为 级钢筋 ,下弦预应力筋为 s5mm高强碳素钢丝 ,采用后张法施加预应力。1　预应力屋架的预制预应力屋架在施工现场预制 ,工艺流程如下 :平整预制场地→支模→绑扎钢筋→浇捣混凝土→抽管→拆侧模→养护→张拉预应力筋→孔道灌浆。1 .1　支模、布筋场地夯实地面松土后 ,做砖胎底模 ,在胎…     

大跨度预应力拱板屋架施工质量控制措施

某国家粮库预应力屋盖体系为预应力拱板结构，构件体积大、板壁薄、自重大。为保证施工质量，预制时在两榀屋架预制场地中间留设伸缩缝。上下弦连接板预制成半成品，在屋架整体成型时与上下弦混凝土浇筑连接。分两组由拱板下弦跨中同时向拱板支座浇筑混凝土，然后从拱板支座连续沿拱板上弦向中间合龙，使浇筑荷载相对均衡。     

24m跨屋架桅杆吊装法

咸丰清城绿色食品公司魔芋干片车间建筑面积为84.4m×24.4m≈2059m~2。屋盖采用24m跨预应力混凝土折线形屋架及1.5m×6.0m预应力混凝土屋面板装配式结构。屋架总共为15榀,每榀屋架重11t,支承屋架的柱顶标高为6.000m。一、吊装方案选择该工程由于地处山区,没有大吨位吊车,决定选用桅杆安装屋架,用12t汽车     

后张预应力钢筋混凝土空腹屋架施工技术

预应力钢筋混凝土空腹屋架，具有跨度大、造价低、施工方法简单、不需维修等特点，被广泛用于工业与民用建筑较大跨度厂房中。裕国编组站机车检修库、沈阳新北站601客车整备库、苏家屯客车厂整修车间均采用了24m、27m跨后张预应力钢筋混凝土屋架梁。预应力钢筋混凝土空腹屋架采用预制法施工。由上弦杆、腹杆及下弦杆组成。其中腹杆预制后再与上弦杆、下弦杆浇注成整体。预应力筋大多采用冷拉Ⅳ级粗钢筋或钢绞线，布置在下弦杆件内(见图一)。     

大跨度预应力混凝土屋架吊装施工方法

本文结合咸阳4390工厂115号厂房的施工,介绍48m跨,38吨重的预应力混凝土屋架选用双机台吊的施工方法,2台主吊车位于屋架一侧同时抬吊,2台辅助吊车在屋架另一侧安装檩条、支撑等,操作简单,便于施工。屋架为半榀预制,扶直时选用80吨汽车吊,吊索合理布置,通过手拉葫芦调整吊索长度,使屋架下弦保持水平并就位于拼装架内。     

混凝土集料膨胀引起的质量事故

一、概况自1986年3月10日至5月26日,上海混凝土制品五厂接连发生部分构件(预应力屋架、预应力花栏梁、预制桩)出现局部混凝土爆裂现象。其中3月6日生产已运往工地安装的一榀屋架,在4月26日发现有二处爆裂点,同时在另一工程也发现     

大跨度预应力钢筋混凝土折线形屋架吊装要点

内蒙古普拉特交通能源有限公司(包头)垃圾焚烧发电厂由八冶建设集团有限公司承建,其中原生态垃圾库、成品垃圾库屋架结构为预应力折线型钢筋混凝土屋架,车间屋架跨度为27m,屋脊距下弦高度为3.12m,屋架为现场预制,每榀屋架重14.57t,预制时为四榀叠打,共54榀。预应力钢筋混凝土折线形屋架现阶段施工中较为少见,施工工艺较为复杂,屋架几何尺寸大,纵向抗弯曲变形性能差,易断裂,现主要就屋架吊装做一简述。     

单层工业厂房屋盖拆除施工安全技术措施

我公司1983年以来,陆续拆除过杭州重型机械厂铸工车间24m跨及杭州制氧机厂加工车间24m跨、18m跨等屋盖系统,并均有装配式天窗。这些厂房就是在五十年代后期、六十年代初建造的,是预制全装配式钢筋砼结构,屋架是套用苏联三铰拱式和拱型预应力钢砼屋架,屋面采用1.5m×6.0m或3.0m×6.0m的大型屋面板,由于这些构件砼制作质量较差,经过二、三十年的使用,使砼早期碳化,钢筋锈蚀,屋面板砼整块整块的脱落,对车间的安全生产危害很大,所以在技术改造中首先对这些工程的屋盖系统要全部拆除,重新安装钢砼结构或钢屋架砼屋面板等。拆除屋盖系统要比安装屋盖系统困难得     

24m预应力屋架楼层预制土法吊装技术

四川长虹集团公司科技开发中心５０１号工程 ,占地面积４２０２．４ｍ２,建筑面积３０５４８ｍ２,总投资８３００万元 ,为１０层框架、预应力槽形板楼盖结构 ,建筑造型呈Ｅ字形。我公司分Ａ、Ｂ两个区进行施工 ,采用楼层预制土法吊装ＹＷＪＡ -２４折线形屋架 ,取得了较好的技术经济效果。１ＹＷＪＡ -２４楼层预制法Ｂ２ 区多功能大厅３层屋盖设有４榀ＹＷＪＡ -２４预应力混凝土折线形屋架 ,因结构特点及施工场地所限 ,不便在地面上布置生产 ,故改在Ｂ２ 区３层楼面上预制（图１） ,以便吊装 ,避免运输等困难。屋架在３层楼面上平卧预制 ,…     

大跨度预应力砼折线形屋架吊装安全技术

1.工程概况三明国家粮食储备库扩建工程是国家投资的第二期1000万吨中央直属储备粮库的项目,总建筑面积为21093m2,其中平房仓面积为19355m2。平房仓屋盖采用预制装配式结构吊装,结构主要组成为:预应力钢筋混凝土折线形屋架,屋加钢支撑,预应力钢筋混凝土屋面板。主要吊装构件如下表1预应力钢筋砼折线形屋架在仓内就地预制,屋面板及支撑在工厂预制。本工程屋架与排架柱以及屋面板与屋架采用焊接连接;屋架的支撑系统,包括竖向垂直支撑,钢系杆,上下弦水平支撑采用螺拴焊接。2.吊装方案2.1吊装方法采用节间综合安装法,单机起吊。即屋架扶直就位后…     

Critical Factors in Financing and Management of Light Rail Transit Systems： Delphi Methodology Approach

In recent years, a large number of LRT （light rail transit） networks and tramways have been built in Spain using the tender system. The rhythm of construction has been such that very few analyses have been carried out and those that have were only partially done because the main participants involved had ulterior motives which impeded their having a critical and independent opinion of the projects carried out. Within this framework, the Delphi methodology presents itself as a very useful instrument, as the intrinsic advantages that it has added to the characteristic that the experts who participate in the project can remain anonymous without detracting value from the conclusions obtained as these are grouped together according to their worth.     

Flexible Pavement Design Simulation Using Mechanistic-Empirical Pavement Design Guide

The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.     

Unanticipated Bond Failure over Supporting Band Beams in Grouted Post-Tensioned Slab Tendons with Little or No Initial Prestress

After grouting the ducts in a large band beam and one-way slab post-tensioned floor system in a large shopping mall （in excess of 1.5 km2 in plan）, doubts arose concerning the level of initial prestress and the strength and serviceability of the slabs was questioned. To assess the strength of the slabs, it was assumed, as a worst case scenario, that some spans may have been constructed with zero initial prestress. Load tests on prototype specimens, with similar dimensions and reinforcement quantities as the floor slabs, were performed to assess the stress development in initially unstressed, but fully grouted, tendons. Unexpected bond failures occurred at the junctions of slab and band beam where the abrupt change in section depth caused a sudden change in tendon stress. The maximum stress that was developed in the initially unstressed tendons at these locations was about 60% of the strength of the tendons.     

地下室外墙型钢三角架单侧支模施工技术

北京金融街E10项目地下4层(地下四层~地下二层层高均为3.7 m,地下一层层高为5.1 m),地上10层,结构形式为框架-剪力墙结构;建筑面积25992 m2,基坑深17.760m,建筑檐高45.000m。本工程场地狭小,地下室东侧外墙距红线1.15~1.7m,南侧外墙距红线0.6~0.7 m,西侧外墙距红线0.56~6.7 m,北侧围墙距红线     

Infilled Reinforced Concrete Beams for Sustainable Construction

This paper presents a study carried out on infilled reinforced concrete beams for sustainable construction. In reinforced concrete beams, less stressed concrete below neutral axis can be replaced by some light weight material to reduce the weight of the structure and also achieve the economy. The used infilled material is brick. Sustainability can be achieved by replacing the partially used concrete. By saving concrete, the authors save cement, which reduces the green house gases emissions. So it is considered as environment friendly. Since infilled beam acts like a layered member, there needs a theory to analyze it. Method of initial functions is used for the analysis of the infilled RC （reinforced concrete） beams. This method is successfully applied on infilled beam. Results show that physical conditions are verified for infilled beam.     

Economy of RHA （Rice Husk Ash） in Concrete for Low-Cost Housing Delivery in Nigeria

Delivery of housing units in adequate quantity and quality has been the pursuits of individuals and successive governments in Nigeria. Still, the gap between demand and supply is becoming wider on daily basis due to exorbitant cost of building materials that is beyond the reach of average Nigerians. Concrete being the most acceptable construction material is expensive due to high cost of cement. Efforts made to reduce the cost of cement were to no avail, thus there is need to look elsewhere. Past researches showed that substituting cement with 15% of RHA （rice husk ash） in concrete improves the performance of concrete and reduces global warming as a result of emissions from cement production. This paper looks into the effect of using RHA as partial substitute of cement on the cost of a low-cost housing unit. Results showed that cement based construction materials are responsible for 82.58% of the total cost in which cement is responsible for 42%. When 15% RHA was used to substitute cement over N90,000 was saved, amounting to about 7% of the total cost of the building. In addition, depletion of natural resources was reduced.     

局部等电位联结常见问题及处理

在建筑电气工程施工中,等电位联结是十分重要的环节,但目前一些不规范做法,难以保证人身安全。建筑物等电位联结分为总等电位联结、局部等电位联结及辅助等电位联结。在建筑物内做等电位联结的目的,是在一定程度上降低建筑内或局部空间内间     

Bending Stresses of Steel Web Tapered Tee Section Cantilevers

Although commonly used, no design method is available for steel web tapered tee section cantilevers. This paper investigates the bending stresses of such beams. Relationships between the maximum compressive stress and the degree of taper were investigated. An analytical model is presented to determine the location of the maximum stress when subjected to a uniformly distributed load or a point load at the free end and was validated using finite element analysis and physical tests. It was found that the maximum stress always occurs at the support when subjected to a uniformly distributed load. When subjected to a point load at the free end and the degree of taper is up to seven, it was found that Miller＇s equation could be used to determine the location of the maximum stress. However, it is shown that when the degree of taper is greater than seven, Miller＇s equation does not accurately predict the location and the analytical model should be used. It was also found that the location of the maximum stress was solely dependent on the degree of taper, while a geometric ratio, fl was required to determine the magnitude of the maximum stress. A simple method that predicts the magnitude of the maximum stress is proposed. The average error in the prediction of the magnitude of the maximum stress is found to be less than 1.0%.     

Probabilistic Seismic Hazard Assessment for Bridgetown-Barbados,Employing Subduction Interface Characteristic Earthquakes

A new probabilistic seismic hazard analysis was performed for the city of Bridgetown, Barbados, West Indies. Hazard computations have been performed using the standard Cornell-McGuire approach based on the definition of appropriate seismogenic sources and expected maximum magnitudes, the authors take into consideration the possibility of large subduction interface earthquakes of magnitude 8.0-9.0 beneath the Barbados accretionary prism via application of a characteristic model and slip rates. The analysis has been conducted using a standard logic-tree approach. Uniform hazard spectra have been calculated for the 5% of critical damping and the horizontal component of ground motion for rock site conditions setting 5 return periods （95, 475, 975, 2,475 and 4,975 years） and spectral accelerations for 34 structural periods ranging from 0 to 3 s. The disaggregation results suggest that the magnitude-distance pair that dominates the hazard yields M 7.4 and 8.6 and a distance of 42.5 km in the Interface Subduction Zone beneath Barbados for the 475 and 975 years RP （return period）, respectively. An event with an M 8.0 at a distance of 107.5 km in the Intraplate Subduction Zone is the second scenario that dominates the hazard for both 475 and 975 years RP.     

Use of Geophysical Techniques for the Localization of the Restricting Zones of Permeability in the Bottom of Basin： Forecasting the Zones of Clogging

Measurements of dielectric parameters followed by permeability tests are performed on soil samples of infiltration basin. The dielectric parameters are obtained by TDR （time domain reflectrometry） measurements from which it is found that the measurement of the permittivity, the electrical conductivity and the relaxation time of compacted soil allows the mapping of the values of the coefficient of permeability at the surface of an infiltration basin. With the distribution of the coefficient of permeability, the areas of water stagnation can be detected before the basin filling. The study proves that the TDR measurements for the detection of these zones can be used for the management of infiltration basins for sustainable working and their remediation can be undertaken before the rainy seasons.