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2019 - 11 - 09
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Distinguished users:Hello! First of all, thank you for your long-term concern and support for Empoda Industrial Systems Co., Ltd.  This revision includes computer website (www.szenpuda.com) and mobile website (m.szenpuda.com), aiming to further play the role of external publicity and communication of the website, and to provide customers with better service. At the same time, it also shows customers the new look of Enpda's continuous development.Compared with the old version of the website, the new page style is adopted and the whole structure is clearer. But we can't be perfect eith...
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2019 - 05 - 21
On May 18, Enpuda delivered another batch of hydraulic silent servo oil source system equipment to Taiwan's agents to help Empoda successfully gain access to the Taiwan market and lay a solid foundation.The key technology of hydraulic servo cylinder controls the minimum displacement loading of 1 micron/s, and the maximum noise of silent servo oil source is less than 62 decibels. Users come to our company for acceptance on the spot and use calibration instruments to measure all the indicators meet the requirements.This is the second cooperation after the success of the last project. It is a hig...
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In October 2018, a teacher from Shijiazhuang Railway University came to our company to make a technical discussion on the 'Rail Rolling Contact Fatigue Test Bench'. After more than one year's exchange of theoretical and practical experience between the two sides, and consultation with relevant experts from Southwest Jiaotong University and China Academy of Railway Sciences, the project has been deeply understood and discussed; for dynamic fatigue test-bed, multi-channel coordinated loading test-bed, rail rolling contact fatigue test-bed. The technology of wheel-rail fatigue test-bed is deeply ...
2018 - 06 - 14
On June 20, our company, together with Southwest Jiaotong University Railway Development Co., Ltd. and Hong Kong Polytechnic University, completed the most critical test in the project of 'High-speed Railway Turnout Safety Monitoring System'. Rail fracture signal acquisition and validation under natural frequency and load applied by dynamic fatigue test bench. In the course of two years'research in more than a dozen relevant experimental centers in China, they finally reached a cooperative relationship with our company.Dr. Wang of Hong Kong Polytechnic and Zhang Gong of Southwest Jiaotong Univ...
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In March of spring blossom, after a month of basic information collation, various department managers organization and coordination, ushered in the Enpda ERP project officially successful online operation. It also marks a big step forward in the internal management of the company in the new year.Enpuda ERP system operation project is an important measure to improve company management and control, optimize resource allocation, enhance core competitiveness of enterprises, and promote enterprise management and development. The project has received the attention and support of company leaders and ...

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets

Date: 2019-07-26
Views: 9

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets

Huang Peiyan, Han Qiang, Tang Liqun and Yan Quansheng

(College of Traffic & Communications, South China Univ. of Tech.,Guangzhou 510640)

Liu Heping, Wang Xiaotian and Luo Lifeng

(Guangdong Highway Bureau, Guangzhou 510075)

AbstractIt is an advanced strengthening method to reinforce or repair the concrete

structures by affixing high-strength fiber sheets or fiber plates. Based on the previousbasic researches,authors have plaited some carbon fiber sheets ( plates) and Aramidfiber sheets or high strengthened glass fiber sheets. Using these fiber sheets, thestrengtheningof a RC frame arch bridge which on the load 321 was completed. Theanalysis results obtained by static and dynamic load tests and the traffic circumstancesshow that the strengthening method is effective, and the technique is economical.

Keywords :fiber sheet; RC frame arch bridge; strengthening

Due to the factors of low design grade, aging structure, bad environment, improper construction and overload, the damage of concrete bridges is becoming more and more serious, and there are many dangerous bridges in China. Among them, there are more than 2000 large and medium-sized old dangerous bridges in urgent need of reinforcement and maintenance in Guangdong Province alone. In order to reinforce and maintain these old dangerous bridges economically and efficiently, high-strength fiber cloth or fiber sheet sticking reinforcement technology has attracted much attention at home and abroad because of its advantages of high strength, corrosion resistance, light weight, convenient construction and short construction period (1-6).

In recent years, experts and scholars from abroad, especially from Japan and Europe and America, have done a lot of research on the mechanism of strengthening concrete bridge joints with fiber sheet or fiber sheet, and have been widely used in engineering. In China, the national industrial building diagnosis and Reconstruction Engineering Technology Research Center, Tsinghua University, Tianjin University, Southeast University, Tongji University and South China University of technology and other units have also done a lot of work in strengthening concrete components with carbon fiber cloth or carbon fiber sheet, some of which have been used in engineering practice [7].

On the other hand, the tension members of the old dangerous concrete bridge are easy to produce cracks. After strengthening the cracked concrete members with fiber sheet or fiber sheet, the failure mode and strength of the members are different from those without cracks. Therefore, with the support of National Natural Science Foundation of China (19972020), Guangdong Natural Science Foundation of China (990567) and key research project of Guangdong Provincial Science and Technology Commission (99m02104g), the research group has carried out a series of researches on the bearing capacity and failure mechanism of these components, and obtained some staged results [8-12]. In order to apply the above research results to engineering practice rapidly, Guangdong Provincial Department of Transportation approved the project of 'Research on the detection, evaluation method and reinforcement technology of the bearing capacity of old dangerous highway bridges in Guangdong Province' last year, and entrusted Guangdong Provincial Highway Administration Bureau and Transportation College of South China University of technology to undertake the project. A concrete rigid frame arch bridge on national highway 321 is listed as the experimental bridge of our research group because of its damage, heavy production and intensive maintenance. From this year to this month, in order to ensure the Spring Festival games, the research group adopted self-made carbon fiber, aramid fiber and high-strength glass fiber thin board to reinforce the rigid frame arch bridge (half of the arch bridge). After the reinforcement, the dynamic and static load test confirmed the reinforcement effect, and then it was put into operation. So far, it is in good condition. This paper introduces the strengthening technology and method of the bridge.

1 project overview

A rigid frame arch bridge on national highway 321 is divided into two parts: the old bridge was built in 1987, the new bridge was built in 1996, with design load; it is steam 20, hang-100; the new and old bridges are two lane reinforced concrete rigid frame arch structures, with bridge deck width of 9.5m and span of 70m. The bridge has been in good operation since its completion and opening to traffic. However, due to the continuous growth of traffic volume in recent years, especially the emergence of a large number of overloaded vehicles, the bridge appears a serious disease. After inspection by the Municipal Highway Bureau in July 2001, it was found that there were many cracks on the top chord and nodes of the new bridge, and some cracks had penetrated through the top chord (Figure 1). Although the deck pavement was basically intact, most of the rib gusset plates were seriously damaged. In order to ensure traffic safety, the Municipal Highway Bureau implemented traffic control on the new part (half width) of the bridge in early November of the same year.

In December 2001, the new part of the bridge was inspected by the school of transportation, South China University of technology. It was found that the new bridge was seriously damaged and its bearing capacity was significantly reduced. In order to ensure traffic safety, it must be reinforced. In addition, since the new bridge was under traffic control, all vehicles have been driven from the old bridge. After more than a month of traffic, cracks also appeared in the top chord of the old bridge. In order to restore the design capacity of the bridge as soon as possible and ensure the Spring Festival transportation in 2002, the bridge must be strengthened as soon as possible.

2 reinforcement plan

The strengthening scheme of rigid frame arch bridge is determined on the basis of the previous research of this research group, through theoretical and finite element analysis, simulation experiment, and comparison with domestic and foreign reference materials. Among them, the flexural tensile and shear simulation experiments of the top chord and other components are summarized as follows.

2.1 simulation experiment

The size of the simulated test piece is 0.1mx0.2mx1.8m, and the calculated size is 0.1mx0.2mx1.6m; the concrete and concrete material used in the test piece is C40 medium sand macadam concrete, its elastic modulus E. = 30gpa, shear modulus G, = 0.43x E. (MPA), Poisson's ratio 0.20, and concrete tensile strength R, = 5.15mpa; the carbon fiber material is made of carbon fiber t300-3k produced by Toray company of Japan, which is 0.1M wide x 0.5mm thick (any length) The elastic modulus E, = 240gpa, tensile strength R, = 2100mpa, Poisson's ratio 0.29 of carbon fiber sheet (prepreg) of Italy, the same below; the aramid fiber sheet adopts aramid fiber K49 produced by Toray Corporation of Japan, and the high-strength glass fiber strip adopts glass fiber filament produced by Toray Corporation of Japan, which is compiled by our research group and cooperative research unit. The proposed aramid fiber sheet specification is: 0.1M wide x 0.4mm thick; the specification of high-strength glass fiber tape is: 0.1M wide x 0.4mm thick.

In order to make the simulation experiment close to the actual situation, the test pieces are divided into three groups: (1) unreinforced reinforced concrete beam; (2) reinforced beam with carbon fiber sheet pasted at the bottom; (3) first apply static load to unreinforced reinforced concrete beam to make it appear enough long cracks, and then paste carbon fiber sheet and aramid fiber sheet respectively according to the reinforcement method shown in Figure 2. The static load test is carried out on MTS-810 testing machine, and the test results are listed in

Table 1. It can be seen from table 1 that the ultimate bearing capacity of the strengthened specimen shown in Figure 2 is 1.52 times of that of the unreinforced specimen.

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets

2.2 reinforcement plan

In order to restore or even improve the bearing capacity of the bridge, the scheme is proposed to strengthen the upper chord, node, diagonal brace, top of arch rib and other components of the new bridge (downstream side) as follows:

(1) epoxy chemical pressure grouting is used to reinforce the existing cracks;

(2) paste a layer of carbon fiber sheet on the bottom and side of the top chord, the side of the joint, the side of the diagonal brace and the top and bottom of the arch rib (all are bending and pulling areas), and paste a aramid fiber hoop or a high-strength glass fiber hoop on the bottom and side of the top chord (see Figure 3). Specification of carbon fiber sheet: 0.1M wide x 0.5mm thick (any length, the same below); specification of aramid fiber sheet: 0.1M wide x 0, 4mm thick; specification of high-strength glass fiber strip: 0.1M wide x 0.4mm thick;

(3) in the shear part of the diagonal brace, high-strength fiberglass tape is used for winding reinforcement (Fig. 3);

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets

4) spray (or apply) glass fiber epoxy resin to the reinforcement part;

(5) color treatment shall be carried out for construction parts requiring aesthetic treatment.

On the other hand, because the bridge deck pavement is basically intact, but most of the rib gusset plates are seriously damaged, it is decided that this reinforcement project will not replace the bridge deck pavement, only reinforce some of the rib gusset plates which are seriously damaged. After using ANSYS large-scale finite element analysis program to analyze the stress of each part of the gusset plate, the reinforcement scheme is proposed as follows:

(1) carbon fiber sheet, aramid fiber sheet or high-strength glass fiber sheet are used to reinforce the rib Ye plate near the arch crown according to the scheme shown in Figure 4 (a);

(2) carbon fiber sheet and aramid fiber sheet or high-strength glass fiber sheet are used to reinforce the rib Ye plate of the top chord according to the scheme shown in Figure 4 (b).

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets

3 construction process

The construction technology of fiber sheet has a great influence on the reinforcement effect. In order to ensure the reinforcement effect as much as possible, the following construction technology is adopted in this study according to the site conditions.

(1) the construction steps of epoxy chemical pressure grouting are as follows:

① position and seal the grouting nozzle; ② grouting (determine the corresponding type of AB grouting resin according to different parts and width of the crack); ③ confirm that the grouting is completed and remove the machine after the initial setting of the resin.

(2) the construction steps of pasting fiber sheet are as follows:

① base grinding treatment; ② bottom resin coating: ③ repair and fill the defects and uneven parts on the concrete bonding surface; ④ brush and paste epoxy glue (domestic Shenli bell brand epoxy adhesive), and paste fiber sheet; ⑤ use special inflation pressure band or vacuum absorption method to pressurize the fiber sheet.

(3) after reinforcement, apply or spray glass fiber epoxy resin on and near the outer surface of the fiber sheet;

(4) color treatment shall be carried out for the construction site and its adjacent areas.

4 Analysis of reinforcement effect

According to the requirements of 'test method for long-span concrete bridge', the static and dynamic load tests of the strengthened rigid frame arch bridge are carried out (details will be reported in another paper). The test results show that the original design bearing capacity of the bridge is restored through the reinforcement of the above methods. The bridge has been in good operation since it was opened to traffic on February 3.

The results show that compared with the same technology at home and abroad, the reinforcement technology shown in this paper has the following characteristics besides the common advantages of fiber material, i.e. high strength, corrosion resistance and light weight

(1) according to the actual needs of the engineering structure, the fiber materials can be imported or domestic carbon fiber and aramid fiber with different properties;

(2) the fiber sheet is made by our research group and cooperation unit, and the matrix material is domestic epoxy resin;

(3) all binders are made of domestic materials;

(4) the strengthening layer of fiber sheet is composed of stress layer, protective layer (anti-aging, anti-collision) and decorative layer, which has the advantages of reasonable structure, durable and beautiful appearance;

(5) the performance price ratio of the reinforcement technology is better than the existing reinforcement technology, such as steel plate reinforcement, external reinforcement reinforcement, etc;

(6) the unit price of this reinforcement technology is the same as that of steel plate reinforcement technology, and the total unit price is about 960 yuan / m2;

(7) convenient on-site construction;

(8) less supporting equipment is required.

Therefore, the method in this paper will play an important role in the reinforcement of old dangerous bridges in the future.

A Project on Strengthening re Frame Arch Bridge With Fiber Sheets   Reprint

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