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1、Large span continuous beam bridge construction control content and method ofKeywords: large span continuous beam bridge; construction control;Abstract: in our country, the suspension bridge, arch bridge, continuous rigid frame bridge and other aspects of research and practice has achieved good resul

2、ts, but for large span prestressed concrete continuous beam bridge construction control technology of the relatively few studies. So the research and application of large span prestressed concrete continuous beam bridge construction control technology has very practical significance in engineering.

3、This paper first analyzes the influence of long-span bridges construction control factors, followed by the construction of the contents and methods of construction control, the control principle are elaborated.1 PrefaceThe construction of long span bridge to go through a complicated process, in this

4、 process will be a lot of certain and uncertain factors, leading to the bridge structure s actual status deviates from the theoretical calculation state. Therefore, the bridge construction control is the focus of the construction process by analyzing deviations which occur in the identification, ide

5、ntify problems and timely rectification, and the structure of the follow-up phase undertakes forecasting, make construction system is always in control.Effects of 2 factors in the construction control of 1Large span continuous beam bridge construction control the main purpose is to make the actual c

6、onstruction condition and maximize the ideal design ( alignment and stress ) coincide. To achieve these goals, we must fully understand the construction state may deviate from the theoretical design status of all the factors, so as to implement effective control of the construction of have a definit

7、e object in view.2.1 structure parameters 2 Regardless of the bridge construction control, the structure parameters are very important factors to consider, structural parameters control in the construction simulation analysis of basic information, whose accuracy directly affects the accuracy of anal

8、ytical results. In fact, the actual bridge structure parameters are generally very difficult to design for structural parameters of identical, there is always some errors, control of construction how to properly credited for these errors, so that the structural parameters of the actual structure par

9、ameters as close as possible to the bridge, is the first problem to be solved. Structure parameter mainly includes structure cross section dimension, structure the elastic modulus of the material, material density, coefficient of thermal expansion of materials, construction loads, prestressing or ca

10、ble force etc.2.2 construction technologyConstruction control for construction services, in turn, construction quality has a direct impact on the implementation of target of control. In addition to the requirements of construction technology must comply with the control requirements, the constructio

11、n control must be included in the construction conditions of non ideal brings the fabrication, installation and other aspects of the error, and make the construction state is maintained in the control of.2.3 construction monitoringConstruction control of bridge monitoring is one of the most basic me

12、thods. Monitoring includes stress monitoring, deformation monitoring. Because the measurement apparatus, instrumentation installation, measurement method, data acquisition, environment, errors exist, therefore, structure always exist error monitoring. In the control process, in addition to the measu

13、ring device, method to try to reduce the measurement error, in the control analysis must be included in the.2.4 changes of temperatureTemperature change on the stress and deformation of the bridge structure has great influence, this effect varies with the temperature change in different time on the

14、structure, state ( stress, deformation ) were measured, the results are not the same, if the construction control of neglected the factors, it is difficult to obtain the true state of the data structure thus, it is difficult to ensure the effectiveness of control, therefore, must consider the influe

15、nce of temperature change. Is generally a day the temperature variation in smaller morning as required to control data acquisition time. But for seasonal temperature difference and the bridge body temperature residual effects to attention.The 2.5 material shrinkage, creepOn the concrete bridge struc

16、ture, material shrinkage, creep of structural internal force, deformation has a greater influence, mainly due to the large span continuous beam bridge construction concrete common loading age short, each stage of age difference between the major cause, control should be carefully studied, in order t

17、o adopt reasonable, practical creep parameters and calculate model. Shrinkage, creep will also influence the bridge after the operational phase of the structure deformation, which is also the setting pre-arch factors need to be considered.Construction of the 3 control tasks and work contentThe bridg

18、e construction control task is to bridge construction process control 3 , to ensure that the construction process of bridge internal force and deformation of structure is always in the allowable safety limits, ensure that a bridge state (including the bridge linear and bridge structure internal forc

19、e ) meets the design requirements. The bridge construction control the control missions, the construction control work mainly includes the following aspects:3.1 geometric ( deformation ) controlThe method of construction, the bridge structure in the construction process to produce deformation ( defl

20、ection ), and the deformation of the structure will be affected by many factors, is very easy to make the bridge structure in the construction process of the actual position ( elevation elevation, position ) state to deviate from the expected state, so that the bridge could not smooth closure, or in

21、to a bridge linear shape and design do not meet the requirements, so we have to carry out control of bridge structure in construction, make its actual location in the state and the desired state between the error in the permissible range and into the bridge linear state meet the design requirements.

22、The 3.2 stress controlBridge structure in the construction process and the stress condition of bridge state and design accord with the construction control is the important issue to clear. Usually by structural stress monitoring to understand the actual stress state, if it is found that the actual s

23、tress state and stress state theory (Computational ) differential overrun must carry checks and regulation, which is within the allowable range change. Structure stress control is not so easy to find if the deformation, stress control not do ones best to structural damage, serious will happen struct

24、ural damage ( China Ningbo Zhaobaoshan Bridge Girder fracture is one example), therefore, must be the implementation of strict control on structural stress. Stress control of the project and the precision is not well defined, according to the actual situation, usually including:The structure caused

25、by stress ( the actual stress and design phase should be controlled within + 5% ). The structure under construction load stress ( the actual stress and design phase should be controlled within + 5% ). The structure of prestressing force in addition to the tensioning implement double control ( oil ga

26、uge control and elongation control, elongation error allowed within plus or minus 6% ), must also consider the pipe friction influence ( for post tensioned structure ). The temperature stress, especially large volume foundation, pier column. The other stresses, such as foundation displacement, wind

27、load, snow load caused by structural stress. The construction used in the bridge construction safety has a direct influence on the rack, basket, cable hoisting system in a safe range of stress.3.3 stability controlThe stability of bridge structure is related to the safety of bridges, it is with brid

28、ge strength has equal or even more important. The world has had many bridges in the construction process due to instability and cause the whole bridge failure examples, the most typical is Quebec Canada ( Quebec ) bridge. The bridge on the south side of the anchor frame truss is finished, because th

29、e cantilever end of the buckling of web plate and the bottom chord bar suddenly collapses fall. China Sichuan River Bridge by cantilever girder hoisting system in main span of bear large axial force and failure. Therefore, the construction process of the bridge construction should not only strictly

30、control the stress and deformation, and to strictly control in each stage of construction structure of local and overall stability. Mainly through the stability analysis ( stability safety coefficient ), and with the structural stress, deformation to comprehensive assessment, control of its stabilit

31、y.3.4 safety controlBridge construction safety control during the bridge construction control is the important content in the construction process, only to ensure the safety, just talk to go up the other control and bridge construction, in fact, bridge construction safety control is the control of d

32、eformation, stress control, stability control integrated embodiment, each of the above gets out of control, safety get control ( because the bridge construction quality problems caused by security issues except). Due to the structure of different forms, directly affects the construction safety facto

33、rs are not the same, in construction control of the basis of the actual situation, determine its safety control key.4 construction control methodContinuous beam bridge construction monitoring and recognition is to adjust to the trailer, construction cycle, its essence is to make construction accordi

34、ng to a predetermined desired state (mainly the construction elevation ) smoothly. But whether the theoretical ideal state, or the actual construction error, therefore, construction control of the core mission is to all sorts of error analysis, recognition, adjustment of structure, making prediction

35、s.4.1 predictive control methodPredictive control law refers to fully consider the impact of various factors and structural state of bridge construction to achieve the goal, the structure of each construction stage ( segment ) before and after the formation of forecast, make construction along a pre

36、determined state. As a result of predictive state and the actual state of unavoidable errors exist, some kind of error on the construction goals influence in subsequent construction state prediction for consideration, this cycle until the completion of construction, and obtained with design accord w

37、ith the structure state. This method is applicable to all bridges, and for those who have a structure with adjustable bridge construction control must use this method. Predictive control based on modern control theory, the prediction methods are common Calman filter method, grey system theory contro

38、l method.4.2 adaptive control methodIn view of the continuous beam bridge completed segment is not controllable and construction of linear error corrective control limited, the error is very important, so, the adaptive control method in the control is very effective.4.3 linear regression analysis me

39、thodLinear regression analysis method is based on the cantilever box girder with cantilever length of cantilever deflection, the weight of a Yuan linear regression treatment or two element linear regression, linear regression mathematical model establishment of deflection summary. It can be used for

40、 the analysis of box beam deflection regularity, can also be used to predict the pending construction of beam deflection. But it is not possible to temperature and construction caused by error correction, and requires a more regular data lines, in the relatively small number of beam section obtained

41、 by the regression curve precision is hard to guarantee.5 SummaryMainly discusses the effect of large span continuous beam bridge construction control factors, construction control task and work content and construction control method. Our country in bridge construction control theory and practice i

42、s not to establish a set of perfect construction control technology system and management system. Therefore, in-depth study of the bridge construction control theory, development is more reasonable, practical control software and more convenient, accurate monitoring equipment, establish and improve

43、the control technology of bridge construction system and management system is the future development of bridge construction the urgent need for work.ReferenceLiu Laijun 1. Large span bridge construction control analysis of uncertain factors D. Master Dissertation of Changan University, 20022 Xiang Z

44、hong-fu. Control technology of bridge construction M. Beijing: China Communications Press, 20013 Gu Anbang, Chang Ying, Le Yun. Long span prestressed concrete continuous rigid frame bridge construction control theory and method J. Journal of Chongqing Jiaotong College大跨径连续梁桥施工控制的内容与方法探析论文关键字：大跨径；连续梁

45、桥；施工控制 论文摘要：我国在悬索桥、拱桥、连续刚构桥等方面的研究与实践取得了较好的成果，但对大跨预应力混凝土连续梁桥的施工控制技术研究相对较少。因此研究和应用大跨预应力混凝上连续梁桥施工控制技术具有极现实的工程意义。本文首先分析了大跨桥梁影响施工控制的因素，其次对施工控制的内容及方法、施工控制的基本原理等进行了的阐述。 1 序言 大跨度桥梁的施工要经过一个复杂的过程，在此过程中将受到许多确定和不确定因素的影响，导致桥梁结构的实际状态偏离理论计算分析状态。因此，桥梁施工控制的重点就是通过对施工过程中出现的偏差进行分析识别，发现问题并及时进行纠偏，同时对结构的后续阶段进行预测，使施工系统始终处于

46、控制之中。 2 影响施工控制中的因素1 大跨径连续梁桥施工控制的主要目的是使施工实际状态最大限度地与理想设计状态（线形与受力）相吻合。要实现上述目标，就必须全面了解可能使施工状态偏离理论设计状态的所有因素，以便对施工实施有的放矢的有效控制。 2.1 结构参数2 不论何种桥梁的施工控制，结构参数都是必须考虑的重要因素，结构参数是控制中的结构施工模拟分析的基本资料，其准确性直接影响分析结果的准确性。事实上，实际桥梁结构参数一般很难与设计所用的结构参数完全吻合，总是存在一定的误差，施工控制中如何恰当地记入这些误差，使结构参数尽量接近桥梁的真实结构参数，是首先需要解决的问题。结构参数主要包括结构构件截

47、面尺寸、结构材料弹性模量、材料容重、材料热膨胀系数、施工荷载、预加应力或索力等内容。 2.2 施工工艺 施工控制是为施工服务的，反过来，施工的好坏又直接影响控制目标的实现。除要求施工工艺必须符合控制要求外，在施工控制中必须计入施工条件非理想化带来的构件制作、安装等方面的误差，使施工状态保持在控制中。 2.3 施工监测 监测是桥梁施工控制的最基本手段之一。监测包括应力监测、变形监测等。因测量仪器、仪器安装、测量方法、数据采集、环境情况等存在误差，所以，结构监测总是存在误差的。在控制过程中，除要从测量设备、方法上尽量设法减小测量误差外，在进行控制分析时必须将其计入。 2.4 温度变化 温度变化对桥

48、梁结构的受力与变形影响很大，这种影响随温度的改变而改变，在不同时刻对结构状态（应力、变形）进行量测，其结果是不一样的，如果施工控制中忽略了该项因素，就必然难以得到结构的真实状态数据，从而也难以保证控制的有效性，所以，必须考虑温度变化的影响。一般是将一天中的温度变化较小的早晨作为控制所需实测数据的采集时间。但对季节温差和桥梁体内的温度残余影响要予以重视。 2.5 材料收缩、徐变 对混凝土桥梁结构而言，材料收缩、徐变对结构内力、变形有较大的影响，这主要是由于大跨径连续梁桥施工中混凝土普遍加载龄期短、各阶段龄期相差大等引起的，控制中要予以认真研究，以期采用合理的、符合实际的徐变参数和计一算模型。收缩

49、、徐变还将影响成桥后运营阶段的结构变形，这也是设定预拱度需要考虑的因素。 3 施工控制的任务与工作内容 桥梁施工控制的任务就是对桥梁施工过程实施控制3，确保在施工过程中桥梁结构的内力和变形始终处于容许的安全范围内，确保成桥状态（包括成桥线形与成桥结构内力）符合设计要求。桥梁施工控制围绕上述控制任务而展开，其施工控制的工作内容主要包括以下几个方面： 3.1 几何（变形）控制 不论采用什么施工方法，桥梁结构在施工过程中总要产生变形（挠曲），并且结构的变形将受诸多因素的影响，极易使桥梁结构在施工过程中的实际位置（立面标高，平面位置）状态偏离预期状态，使桥梁难以顺利合拢，或成桥线形形状与设计要求不符，

50、所以必须对桥梁实施控制，使其结构在施工中的实际位置状态与预期状态之间的误差在容许范围之内和成桥线形状态符合设计要求。 3.2 应力控制 桥梁结构在施工过程中以及成桥状态的受力情况是否与设计相符合是施工控制要明确的重要问题。通常通过结构应力的监测来了解实际应力状态，若发现实际应力状态与理论（计算）应力状态的差别超限就要进行原因查找和调控，使之在允许范围内变化。结构应力控制的好坏不像变形控制那样易于发现，若应力控制不力将会给结构造成危害，严重者将发生结构破坏（我国宁波的招宝山大桥主梁断裂就是一个例子），所以，必须对结构应力实施严格控。对应力控制的项目和精度还没有明确的规定，需根据实际情况确定，通常

51、包括： 结构在自重下的应力（实际应力与设计相差宜控制在+5%）。结构在施工荷载作用下的应力（实际应力与设计相差宜控制在+5%）。结构预加力除对张拉实施双控（油表控制和伸长量控制，伸长量误差允许在6%以内）外，还必须考虑管道摩阻影响（对于后张结构）。温度应力，特别是大体积基础、墩柱等。其他应力，如基础变位、风荷载、雪荷载等引起的结构应力。施工中用到的对桥梁施工安全有直接影响的支架、挂篮、缆索吊装系统等的应力在安全范围内。 3.3 稳定控制 桥梁结构的稳定性关系到桥梁结构的安全，它与桥梁的强度有着同等的甚至更重要的意义。世界上曾经有过不少的桥梁在施工过程由于失稳而导致全桥破坏的例子，最典型的是加拿

52、大的魁北克（Quebec）桥。该桥在南侧锚锭析架快要架完时，由于悬臂端下弦杆的腹板屈曲而发生突然崩塌坠落。我国四川州河大桥也因悬臂体系的主梁在吊装主跨中段承受过大的轴力而失稳破坏。因此桥梁施工过程中不仅要严格控制应力和变形，而且要严格地控制施工各阶段结构构件的局部和整体稳定。目前主要通过稳定分析计算（稳定安全系数），并结合结构应力、变形情况来综合评定、控制其稳定性。 3.4 安全控制 桥梁施工过程中安全控制是桥梁施工控制的重要内容，只有保证了施工过程中的安全，才谈得上其他控制与桥梁的建设，其实，桥梁施工的安全控制是上述变形控制、应力控制、稳定控制的综合体现，上述各项得到了控制，安全也就得到了控

53、制（由于桥梁施工质量问题引起的安全问题除外）。由于结构形式不同，直接影响施工安全的因素也不一样，在施工控制中需根据实际情况，确定其安全控制重点。 4 施工控制的方法 连续梁桥是施工监测识别调整预告施工的循环过程，其实质就是使施工按照预定的理想状态（主要是施工标高）顺利推进。而实际上不论是理论分析得到的理想状态，还是实际施工都存在误差，所以，施工控制的核心任务就是对各种误差进行分析、识别、调整，对结构未来做出预测。 4.1 预测控制法 预测控制法是指在全面考虑影响桥梁结构状态的各种因素和施工所要达到的目标后，对结构的每一施工阶段（节段）形成前后进行预测，使施工沿着预定状态进行。由于预测状态与实际

54、状态免不了有误差存在，某种误差对施工目标的影响则在后续施工状态的预测予以考虑，以此循环，直到施工完成和获得与设计相符合的结构状态。这种方法适用于所有桥梁，而对于那些已成结构状态具有不可调整性的桥梁施工控制必须采用此法。预测控制以现代控制论为理论基础，其预测方法常见的有卡尔曼滤波法、灰色系统理论控制法等。 4.2 自适应控制法 鉴于连续梁桥已完成节段的不可控性以及施工中对线形误差的纠正措施有限，控制误差的发生就显得极为重要，所以，采用自适应控制法对其进行控制也是很有效的。 4.3 线形回归分析法 线形回归分析法是通过对悬臂箱梁挠度与悬臂长度、悬臂重量的一元线形回归处理或二元线形回归处理，总结建立

55、挠度线形回归数学模型。它可以用于分析箱梁挠度变形的规律，也可以用于预测待施工梁段的挠度。但它无法对温度和施工引起的误差进行修正，并且要求有较多有规律的数据才行，在梁段数比较少时所得到的回归曲线的精度难以保证。 5 小结主要讨论了影响大跨度连续梁桥施工控制的因素、施工控制的任务与工作内容以及施工控制的方法。我国在桥梁施工控制的理论与实践还未建立起一套完善的施工控制技术系统和组织管理系统。因此，深入研究桥梁施工控制理论，研制更加合理、实用的控制软件以及更加方便、精确的监测设备，建立完善的桥梁施工控制技术系统和组织管理系统是今后桥梁建设事业发展迫切需要进行的工作。参考文献1刘来君.大跨径桥梁施工控制不确定因素分析D.长安大学硕士学位论文，2002.2向中富.桥梁施工控制技术M.北京:人民交通出版社，2001.3顾安邦，常英，乐云样.大跨径预应力连续刚构桥施工控制的理论与方法J.重庆交通学院学报