基于层次分析法的钢-混凝土桥梁安全评价

钢-混凝土组合桥梁在一般生活及生产实践中十分常见,然而在其施工和运维过程中,由于缺乏成熟的评价管理体系,使得桥梁生命周期内的安全运行存在一定隐患。构建了钢-混凝土组合桥梁安全综合评价指标体系,通过1~9标度法确定各级指标判断矩阵,并结合层次分析法对钢-混凝土组合桥梁安全综合评价体系中各级指标进行权重计算。通过某桥梁实际工程验证,该桥梁在四级评估体系中判断等级为二级,计算逻辑清晰,评价等级与实际情况相符,为钢-混凝土组合桥安全综合评价的工程实践提供了一种可靠思路。

钢-混凝土组合桥梁中无抗剪配筋的桥面板在轴向拉力作用下的抗剪极限承载力试验研究

完成31根钢筋混凝土梁的剪切破坏试验,对钢-混凝土组合桥梁中无抗剪配筋的桥面板在轴向拉力作用下的抗剪极限承载力进行了研究。试验中主要考虑了轴向拉力对抗剪极限承载力的影响,同时对配筋率、最小抗剪配筋、混凝土强度等级等其他因素也进行了研究。试验结果表明,欧洲规范2第1部分中用来计算无抗剪配筋的钢筋混凝土构件的抗剪极限承载力的公式过于保守,建议进行修正。

钢-混凝土组合桥梁在云南山区常规大跨梁桥中的应用

云南山区地形多变、地质复杂、抗震要求高、生态环境脆弱;区域内钢-混凝土组合结构的使用和推广需要考虑的因素很多。该文从山区桥梁特点入手,并以此为基础,分别就钢-混凝土组合结构在云南山区的适用跨径、桥面板选型、截面设计选型意图、施工方法等方面进行说明,并对近几年钢-混凝土组合梁在云南山区的应用推广情况进行了简要介绍。

钢-混凝土组合简支梁桥温度影响因素及分布模式

以一座钢-混凝土组合简支箱梁桥为例研究钢-混凝土组合简支梁桥温度影响因素及分布模式。首先,建立桥梁截面热传递理论模型,通过有限元热分析得到温度时变曲线与截面温度分布,并与实测结果对比验证热传递模型的有效性;其次,通过验证的有限元模型进行参数分析,研究桥梁曲率、季节、桥面厚度、板悬臂长度以及梁高对截面有效温度、竖向与横向温度梯度的影响;最终,提出本桥钢-混凝土组合箱型截面升温、降温情况下,竖向正、负温差分布模式,并与AASHTO,EC等规范规定的温度分布模式进行比较。

关于钢-混凝土组合梁桥设计与质量安全探讨

本文对钢-混凝土组合梁桥的设计确保施工质量安全进行了分析和探讨,由分析可知,对于跨径较大的钢-混凝土组合梁桥,为使设计更经济、施工过程保证质量安全,可以采取在跨中附近设置临时墩的施工方法。此外,研究还发现,在对组合梁的钢梁进行施工时宜选择箱形截面替代槽形截面,以降低施工难度。下面就钢-混凝土组合梁桥结构设计、施工要求等问题进行详细探讨。

不同的预应力工法对钢-混凝土组合梁强度的影响研究

以某钢-混凝土组合梁桥工程为例,应用有限元分析软件Midas Civil,在考虑不同的预应力施工工序的情况下,对结构强度进行分析研究。得出不同的预应力加载方法对结构的受力状态影响较大,提出了较合理的预应力施加方法,从而可以此为参考,为今后的钢-混凝土组合桥梁设计提供帮助。

浅论钢筋混凝土联合梁桥在北京市的应用

在市局的有关领导直接支持下,我市的钢与混凝土联合梁桥(以下简称联合梁桥)近十年来有很大发展,我个人是这一桥梁结构在专业设计院的积极倡导者与参加者之一。现将有关这一桥梁结构的浅见做如下介绍。 一、情况回顾 本市第一座人行联合梁桥1985年建于新街口,第一座车行联合梁桥1992年建于北二环积水潭立交桥的主桥处(25m+36.5m+25m)。近十年来。

Static cyclic-loading test on new type of rigid connection of steel girder and reinforced concrete pier

A new type of rigid connection of steel girder and reinforced concrete pier of a bridge is proposed. The components in rigid connection are installed by high strength bolts on the spot, which are very convenient in construction. The moment from superstructure can be effectively transferred to substructure, and the plates provided for shear transferring can withstand the majority of total horizontal force. With static cyclic loading test, useful experimental data is obtained on the new type of connection of steel superstructure and concrete substructure. As a result, the stress transfer mechanism of the rigid connection can be made clearly and the seismic performance of this structure can also be clarified. Compared computed strength and ductility with actual results, it can be found that this type of connection has good energy absorption capacity in spite of large displacement and no local buckling arises at the locations where stress concentration occurs. Because of doing away with the expensive bearing, this new type of composite structure can be expected to construct a bridge with high seismic resistant capacity thus saving in total construction cost.

Strengthening of Concrete Box Girder Bridges under Close-in Detonations

The response of a bridge superstructure under blast loading might depend largely on the extent of the local damage experienced due to close-in explosion threats. This paper investigates the local and structural response of box girder bridge decks strengthened using CFRP （carbon fiber reinforced polymers） under close-in detonations. Due to the lack of experimental research on this topic, the study is conducted using the explicit finite element computer program LS-DY-NA. The numerical study will be verified using the results of strengthened reinforced concrete slabs under field detonations. The blast load was assumed to be detonated above the bridge deck. The key parameters investigated are the charge size, and the strengthening location on the deck. This paper will present the results of this investigation and provides recommendations for predicting the local damage level based on the CFRP strengthening design under blast threat.

Linear monitoring for cast-in-place reinforced concrete arch bridge construction

Linear monitoring is an important link of bridge construction control,which is conducted in key processes of construction to ensure the security of bridge in construction procedure. Combining with main arch construction monitoring program of No. 2 bridge in north district of Changbai international tourism resort,main content and key technologies are recommended. Considering the various influential factors during the construction process,linear adjustment is handled to ensure that the stress and linear of main arch meet design requirements.

钢混组合梁桥的新技术

钢板具有高的抗拉强度,但是相对于由压应力引起的屈曲来说相对脆弱。然而,当钢板与混凝土结合,屈曲增加的抵抗力和重型加劲肋的阻力是没有必要的,这样使钢桥对混凝土桥更具有经济效益和竞争力。钢混组合的新型结构形式已经在日本几个实际的桥梁中积极提出和发展了。利用钢管混凝土梁桥的新思路设计的钢-混凝土复合材料,也被分析和证明是经济可行的。

Seismic response analysis of a reinforced concrete continuous bridge considering coupling pounding-friction effect

To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete （RC） continuous bridge is selected as the research object. Three bridge finite element （FE） models were built using OpenSees, in which the longitudinal and transverse pounding elements, as well as the transverse failure element of bearings were introduced. Based on this, tire seismic response analysis considering the coupling pounding-friction effect was conducted for the continuous bridge subjected to bi-directional ground motions. Furthermore, the influential parameters were analyzed. The analysis results indicate that the coupling pounding-friction effect can alter the internal force distribution of the bridge structure and generate additional torsional force to bridge columns. The friction coefficient and longitudinal pounding gap size are two important factors. The appropriate friction coefficient and longitudinal pounding gap size can significantly reduce seismic response of girders, and effectively transfer part of the girder inertia force from the fixed columns to the sliding columns, which can reduce the seismic demands of the fixed columns and improve the seismic performance of continuous bridge structures.

Distribution of Reinforcement in Tensile Flanges of Concrete T-shape Continuous Beam

In this paper the analysis of tensile stress distribution in flexural continuous T- beam has been presented. The observed damages in carrying deck of RC bridge over the Wieprz River in Baranow indicate that over pillar zones are not protected enough. The results of numerical analysis have shown that tensile stress in T- section beam appears not only in a web but in flanges as well. Thus reinforcing bars should be distributed within the whole effective width. This fact is mentioned in building codes, for example, in Eurocode 2： ＂Design of concrete structures＂, both in part 1.1 ＂General rules and rules for building＂ and in part 2 ＂Reinforced and prestressed concrete bridges＂, but there are not detailed rules how to place the bars in flanges of T-section.

Properties of Fresh and Hardened Self-compacting Concrete Produced by Using Locally Available Materials

Self-compacting concrete （SCC） is defined so that no vibration is necessary for the compaction. The main criteria of producing SCC have to satisfy the following characteristics [1, 2, 3]： （1） Ability to flow into and completely fill complex forms under its own weight; （2） Ability to pass through and bond to congested reinforcements; （3） High resistance to aggregate segregation. Self-compacting concrete presents a significant sign in improving the product quality and efficiency of the building industry. It also enhances the working conditions and the quality and appearance of concrete. Japan has been used self-compacting concrete in bridge, building and tunnel construction since the early 1990s. In the last decade, SCC has been produced a high potential for greater acceptance and wider applications in highway bridge construction in the Europe and U.S.. However, till now, there is no application of SCC in the construction industry in Egypt. Therefore, the main objective of this research is to produce SCC by using the locally available materials in our region such as basalt, gravel, sand, limestone powder and silica fume. Experimental programme was designed to characterize the properties of fresh and hardened SCC. It comprises different concrete mixes thbricated with different types and percentages of constituent materials. Three full-scale reinforced concrete beams were fabricated from the SCC mixes and tested under flexure. For the purpose of comparison, an extra RC beam was made of conventional normal concrete to serve as a reference beam. This study, in general, demonstrated that the applications of SCC in construction industry oiler products with enhanced characteristics as well as could be economical.

横向预应力下多梁式组合小箱梁长期性能

以一典型简支多梁式组合小箱梁桥为研究对象,将横梁近似视作支承在多片主梁上的多跨弹性支承连续梁,在混凝土板和钢梁间无相对滑移的平截面假定下,推导综合考虑混凝土收缩徐变作用的组合小箱梁在横向施加预应力下的横梁内力、横向长期应力和变形的计算公式,并将理论计算值和有限元软件MIDAS计算值对比分析。结果表明,两者吻合良好;在长期荷载作用下,结构挠度不断增加,预应力的施加能降低长期附加变形量以及横梁长期应力变化幅度;同时发现MIDAS会低估混凝土收缩徐变以及预应力筋松弛对这类组合梁桥横向长期附加应力的影响.

Crack detection of reinforced concrete bridge using video image

With the digital image technology,a crack detection method of reinforced concrete bridge was studied for the performance assessment.The effects including the image gray level,pixel rate,noise filter,and edge detection were analyzed considering cracks qualities.A computer program was developed by visual C++6.0 programming language to detect the cracks,which was tested by 15cases of bridge video images.The results indicate that the relative error is within 6%for cracks larger than 0.3 mm cracks and it is less than 10%for crack width between 0.2 mm and 0.3 mm.In addition,for the crack below 0.1 mm,the relative error is more than30%because the bridge is in safe stage and it is very difficult to detect the actual width of crack.

Proposition of a New Type of Jointless System For Existing Concrete Bridges

Since 1990s, the use of deicing salts （i.e., chlorides） has dramatically increased in areas with heavy snowfall in Japan. As a result, the water mixed with salts has accelerated the damage of the reinforced concrete （hereafter, RC） structures. Recently conducted inspection results of RC bridges have reported that many of the damages or deteriorations are observed at the girder ends and abutments This is caused from the water leakage due to the aged expansion joints. In general, the cost for repairing the damaged RC structures is much higher than that for renewing the expansion joints. Therefore, to prevent these damages, we developed a new highly durable jointless system, named RC plug joint, for existing RC bridges with a bridge length less than 40 meters. The RC plug joint connects the abutment＇s backwall to the superstructure＇s deck using reinforcing steel bars and fiber reinforced concrete. The newly developed RC plug joint system can prevent water leakage and allow for a smooth ride of vehicles at the joint. This paper will explore and discuss the development of the RC plug joint, analysis of conducted investigations, and future installation methods.

Unified expression for failure of reinforced concrete members in bridge

Reinforced concrete structural elements with box section are commonly used in the horizontal and vertical structure of bridges. The reinforced concrete structure in bridge often failed under the combined forces of bending, axial load, shear and torsion caused by wind and earthquake. It is very important to study the mechanism of RC box section structures subjected to a combi-nation of forces. A theoretical study and deduction of the unified expression for failure of reinforced concrete members with box section under combined bending, shear, axial force and torsion were carried out with stress equilibrium assumption. Comparison of theoretical analysis results with experimental results showed that the unified expression for failure of reinforced concrete members with box section can be used for static calculation of such structure members.

Dynamic Detection of Reinforced Concrete Bridge Damage by Finite Element Model Updating

The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM （mathematical model updating method） from incomplete test data. A well suited finite element model of a repaired bridge is carried out. The diagnosis enables us to locate and detect the damage in a reinforced concrete bridge. Thus, developments of analytical predictions have been checked by modal testing techniques. Besides, the FTCS （finite time centered space） scheme is developed to solve the set of equations which can easily handle finite element matrices of a bridge model. It is shown in this study that the method is applied to detect damages as well as existing cracks in real time of a repaired bridge. To check the efficiency of the method, the repaired bridge of OuedOumazer in Algeria has been selected. It is proven that identification methods have been able to detect the exact location of damage areas to be corrected avoiding the inaccuracy from the finite element model for the mass, stiffness and loading.

G1501公路大泖港桥主桥工程建设中一些关键技术问题的探讨

G1501公路大泖港桥主桥工程建设包括大跨度预应力混凝土连续梁旧桥的拆除和大跨度钢-混凝土混合梁新桥的重建,在整个建设过程中存在一些关键技术问题需要关注与解决。在工程实施前期对旧桥拆除方案进行了比选,并针对实施方案作了详细的施工风险分析,制定了可操作性强的旧桥拆除施工方案。在新桥建设施工中,重点关注了整个主桥的施工方法以及施工步骤的可行性,并对施工过程中的关键节点进行了详细的受力分析,以确保主桥施工过程的结构安全性。