Application of ACM Brace Retrofitting Countermeasure to Steel Structure

1、 Application of ACM Brace Retrofitting Countermeasure to Steel StructureAbstractAn advanced seismic retrofitting work for steel building structure with a doubtful seismic performance using ACM (Advanced Composite Material) bracing method, which consists of CFRP (Carbon Fiber Reinforced Plastic) rod

2、and steel sleeve, was proposed in this paper. In order to save a lot of residents lives against a large-damaged earthquake, the retrofitting work using ACM bracing method to steel story building structure built by an old earthquake resistant design code was conducted. ACM bracing method was more eco

3、nomically and quickly applied to steel two-story building structures in comparison with the steel K -shaped bracing method used as before. This kind of retrofitting countermeasure will lead to an extreme decrease in earthquake damages for the existing old steel building structures built by some old

4、earthquake resistant design codes.1. Introduction It is well known in Japan that a lot of reinforced concrete story buildings built by some old earthquake resistant design codes before 1981 were destroyed in the 1995 Hyogoken Nanbu Earthquake. Therefore, Japanese Government has adopted several signi

5、ficant politics concerning this issue since 1995 in order to reduce a lot of earthquake damages for RC and steel story building structures (referred to as S building) built before 1981 as quickly as possible. As some seismic retrofitting policies adopted by Japanese Government had been not carried o

6、ut smoothly, Japanese Government has been demanding a numerical target to quickly improve a seismic retrofitting ratio for all buildings by many local self-governments in Japan. This numerical target of seismic retrofitting ratio including RC and S buildings as well as wooden houses is 90% until 201

7、7. In general, a seismic retrofitting work for RC and S building structure using a typical steel brace requires not only a large amount of cost but also the residents' removal or temporary evacuation. It is more desirable and convenient for a lot of RC and S building owners that the seismic retr

8、ofitting work is conducted as quickly and economically as possible. It is therefore very important for structural engineer to propose a new retrofitting technique instead of X and K shape steel braces. At the present time, a seismic resistant performance of RC or S building structure is judged from

9、a seismic index of structure, Is, evaluated by some criteria established by the Japan building disaster prevention association (Housing Bureau in the Ministry of Land, Transport and Tourism in Japan 2001; Japanese Structural Engineer Association 2006). The number of steel brace required for the seis

10、mic retrofitting work of RC and S building structures can be decided to satisfy a given seismic judgment index value, Iso.The author has already proposed a seismic retrofitting countermeasure for RC building structure using an advanced composite material (referred to as ACM) bracing method (Takatani

11、 2008 and Takatani 2011), which consists of a carbon fiber reinforced plastic (referred to as CFRP) material, steel sleeves and anchors, in order to save a lot of residents lives against a large-damaged earthquake. It is well known that CFRP material has several advantages of strong and light-weight

12、 feature, good durability, and wide applicability in comparison with the steel material. In this paper, ACM bracing method is applied for the seismic retrofitting work of S two-story building structure instead of steel bracing method.2.Seismic Retrofitting Work using ACM Bracing Heretofore, the stee

13、l bracing method has been used for the seismic retrofitting work of RC and S building structures in Japan. The steel brace as shown in Figure 1 (a) is used on the outside of RC building, and is usually done in the inside of structure. While, Figure 1(b) shows ACM brace installed on the outside of st

14、ructure. It is more desirable and very important for a lot of RC building structure owners that an earthquake resistant reinforcement work for RC building structure can be conducted as quickly and economically as possible ,and also can be done without residents removal or temporary evacuation. The s

15、eismic retrofitting work conducted on the outside of RC building structure shown in Figure 1 may be more convenient for both the residents in RC buildings and their owners. It is, therefore, very important for structural engineer to propose a new seismic retrofitting technique instead of the steel b

16、race technique under conditions with low cost and short construction period. (a)Steel brace (b) ACM brace Figure 1. Sketch for seismic retrofitting works using steel brace and ACM brace ACM bracing method was proposed in order to aim at both low cost and short construction period in comparison with

17、the steel bracing method. ACM bracing method consists of CFRP rod and CFRP sheet, steel sleeve, and steel anchor. Figure 2 shows ACM brace rod including CFRP rod and steel sleeve for ACM bracing method. The length 600mm of steel sleeve was decided from CFRP rod pull-out experiments from steel circul

18、ar cylinder sleeve, and also can bear about 500 kN pull-out force. While, CFRP rods with various diameters are shown in Figure 3, and the material properties for CFRP rod is indicated in Table 1. The diameter of CFRP rod used for ACM bracing method is 10mm, and its tensile strength is 169.5 kN. Acco

19、rdingly, three CFRP rods with 10mm diameter can bear about 500kN pull-out force. An advanced Epoxy resin developed by Konishi Co. Ltd. was employed for bonding between CFRP rods and steel cylinder sleeve (Horii 2007). Figure 4 indicates steel anchors embedded in RC column, and the anchor diameter an

20、d length were decided from pull-out experiment under 500 kN shear force. Figure 5 shows steel cylinder sleeve and nuts for the ACM bracing, whose pull-out bearing capacity is about 500 kN Hisabe (2007). Also, the CFRP rod of the ACM bracing is shown in Figure 6, and the length of the CFRP rod is 500

21、m required for ACM bracing method applied to RC 3 -story building structure. Figure 7 indicates a CFRP sheet used to make a reinforcement of RC column against tensile force due to earthquake motions.Figure 2. ACM brace using CFRP rodFigure 3. CFRP rod (Intended Type, Mitsubishi Plastics Co. Ltd.) Fi

22、gure 4. Anchors for ACM brace Figure 5. Steel sleeves for ACM braceFigure 6.CFRP rod (V10mm,5100m) Figure 7. CFRP sheet for ACM brace RC column surface around an anchor was pasted and covered with four CFRP sheet layers with different directions taking into consideration a tensile force direction.Fi

23、gure 8. Elevation view of RC building with the ACM brace Figure 8 illustrates two typical elevations for the seismic retrofitting work using ACM bracing method. As the anchor embedment point in Plan A shown in Figure 8 (a) is located at the intersection area of RC column and beam where many reinforc

24、ing steel bars in RC column and beam gather around, it may be not so easy for a boring workman to make an anchor hole for ACM bracing method without cutting the reinforcing steel bars in this intersection area. Therefore, Plan B shown in Figure 8 (b) was proposed instead of Plan A, and the anchor em

25、bedment point avoids the intersection area of RC column and beam. In addition, it is found that the static deformation of RC building structure in Plan B is smaller than that in Plan A through the structural analyses for both Plan A and B. This is because that the rigid part around the intersection

26、area of RC column and beam is usually assumed on the structural analysis. Conforming to custom on structural analysis, this rigid part around the intersection area is defined by the width of RC column or beam (Aoyama 1988).Figure 9 indicates RC 3-story structure retrofitted by ACM braces (Takatani 2

27、008 and Takatani 2011). After the installation of ACM brace, the steel anchor and sleeve were treated with a tarnish preventive. After this work, the steel cover was fixed on RC column surface as shown in Figure 9. After covering work of ACM brace, the final painting work was conducted and the cover

28、ing box was made waterproof.Figure 9. Completion of ACM braces3.Application of ACM Brace to Steel Structure The seismic retrofitting work using ACM bracing method was conducted for S two-story structure shown in Figure 5. Figure 5 shows the floor plan and the elevation view of this S structure. The

29、number of ACM brace is decided by the seismic index of structure, Is, evaluated by some criteria established by the Japan building disaster prevention association in 2001 (Housing Bureau in the Ministry of Land, Transport and Tourism in Japan 2001). The seismic index of structure, Is, must satisfy a

30、 given seismic judgment index value, Iso, of the seismic index of structure. In this case, the seismic judgment index value, Iso, is 0.7.Figure 10. Floor plan and elevation viewTable 2 shows the seismic index of structure, Is, of the S building structure. It can be seen from Table 2 that the seismic

31、 index value of structure, Is, of the first floor in X direction is less than the seismic judgment index value, Iso =0.7, and the seismic index values of structure, Is, in Y direction are more than Iso =0.7. According to the seismic index values of structure, Is es are located on the east side and t

32、he west one of this S structure.Next, the construction process of this ACM bracing method is described. Figure 11 shows steel anchor fixed on steel column, and the anchor size was decided from pull-out experiment under 500kN shear force. Figure 12 indicates steel cylinder sleeves for ACM brace, whos

33、e pull-out bearing capacity is about 500kN and length is 600mm.Figure 11. Anchors for ACM braceFigure 12. Steel sleeves for ACM braceFigure 12 shows a bracket fixed on steel column, and the steel column before ACM brace installation work is indicated in Figure 14. Figure 15 illustrates polishing wor

34、k on the surface of steel column by a grinder before welding work of bracket. The welding work of bracket by a welder is shown in Figure 16. Figure 17 and 18 show a bracket fixed on steel column by the welding work. Figure 19 indicates steel anchor fixed on a bracket by the welding work.Figure 13. S

35、teel bracket for ACM braceFigure 15. Polishing work on steel column before welding work of steel bracketFigure 16. Welding work of steel bracket and a welder Figure 17. Completion of welding work of steel bracketFigure 18. Bracket after welding work Figure 19. Steel anchor after welding workFigure 2

36、0. CFRP rod cutting work Figure 21. Steel sleeve with three CFRP rodsFigure 22. Steel sleeves before Epoxy resinFigure 23. Epoxy resin injection work into steelInjectionsleeves Figure 20 indicates a cutting work of CRFP rod by a saw, and three CFRP rods are installed into each steel sleeve as shown

37、in Figure 21. Figure 22 indicates steel sleeves before Epoxy resin injection work, and Epoxy resin injection work into steel sleeve is shown in Figure 23. Figure 24shows steel sleeves after Epoxy resin injection work.Figure 25 indicates tightening work of sleeve-nut with a large screwdriver at the s

38、teel anchor. Both ends of ACM brace rod were fixed by four sleeve-nuts as shown in Figure 26 so that the tensile force of 10kN acts in the ACM brace. The shock absorbing rubber shown in Figure 27, which was newly developed by SRI Hybrid Co. Ltd., was used between the fixed anchor and the sleeve-nut.

39、Figure 24. Steel sleeves after Epoxy Figure 25.Tighten work of steel-nut resin injection work with a screwdriver Figure 26. Completion of tightening 27. Rubber ring for shock absorbing double Figure steel sleeve nuts Figure 28. Steel sleeve and bracket Figure29. Steel sleeve and bracket after after

40、anti-rust painting finishing painting work Figure 30. Completion of ACM brace installationAfter the installation of ACM brace, the steel anchor and sleeve are treated with a tarnish preventive as shown in Figure 28 and 29. Photo 30 indicates the installation completion view of ACM brace fixed on S s

41、tructure. It is found from this photo that ACM bracing method has a scenic view from the outside of the retrofitted structure because there is not much things to obstruct the view from the inside of the structure.4.Concluding Remarks In this paper, an advanced seismic retrofitting work for RC and S

42、story building structures built by some old earthquake resistant design codes before 1981 was reported st a large-damaged earthquake. ACM bracing method consists of CFRP rod, steel sleeve, and steel anchor. This ACM bracing method was applied to S two- story building structure in 2010. Materials in

43、the seismic retrofitting work using ACM bracing method and the construction process of ACM brace were described in this paper.The summary obtained in this paper is as follows.(1) ACM brace retrofitting work has several construction advantages such as short construction period and low cost in compari

44、son with the steel bracing method. Namely, ACM bracing method has a high cost performance.(2)Although the installation work of steel braces requires a large construction machine of a crane-currying truck, the installation of ACM brace is not needed any large construction machine and also is effectiv

45、ely conducted under a safe operation.(3) The construction work of ACM brace retrofitting countermeasure does not require a professional engineer or an expert.This ACM bracing method may support a seismic retrofitting politics in the region where has a slightly delay in the seismic countermeasures, a

46、nd can be a driving force to increase the safety of structures against a large earthquake and changes to a strong region against natural disasters. This kind of seismic retrofitting work for RC and S story building structures will lead to a decrease of earthquake damages in many countries.Tomiya Tak

47、atania*aMaizuru National College of Technology, Maizuru, Kyoto, JapanThe 2nd International Conference on Rehabilitation and Maintenance in Civil Engineering<文献翻译二：译文>ACM支撑加固措施在钢结构中的应用摘 要 一种先进的钢结构抗震改造方法在一片质疑种被提出，该方案采用了AMC（一种先进复合材料）支撑方法。该方案采用CFRP(碳纤维增强塑料)杆和钢套管,在本文中有介绍。AMC支撑法运用在旧规范下设计的钢结构，可以让居民在大

48、地震中的存活率大大提高。AMC支撑法相比过去使用的K型支撑法更加经济、方便。这种改造方案将大大减少那些在旧规范下设计、建造的钢结构建筑在地震中的受损程度。1. 介 绍在日本人们都知道，大量在1981年之前的旧规范下建造的钢筋混凝土建筑于1995年的阪神地震中被摧毁了。因此，自1995年以来日本政府对此采取了一些重要的决议，以尽可能快地减少对建造在1981年之前的钢筋混凝土和钢结构建筑结构（简称为建筑）在地震中可能造成的地震损失。日本政府采取的一些抗震防范措施没有顺利推行，日本政府要求地方政府能够尽快达到目标数值以提高建筑物的抗震能力。这个数值要求到2017年抗震改造的房屋包括混凝土建筑和木制建

49、筑经过加固措施的比例为90%。一般情况下，使用一个典型的钢支撑的钢筋混凝土和建筑结构的抗震加固工程，不仅需要大量的成本，还需要居民的搬迁或临时疏散。对许多钢筋混凝土和建筑业主来说，能够接受的抗震加固方案是尽可能快地以及具有性价比的方案。因此，它是非常重要的结构工程师提出了一种新的改造技术，而不是和形状的钢支柱。因此结构工程师提出一个非常重要的一种新的改造技术而不仅仅是简单的X和K型钢支撑。目前，钢筋混凝土结构关于抗震性能的抗震性能指标的评定是通过由日本建筑灾害建立评价预防协会规定的一些标准评定的（国土、交通、旅游、住房局2001；日本结构工程师协会2006）。钢筋混凝土结构抗震加固工程所需的钢

50、支撑的数量，可以由一个给定的地震判断指标值判定。作者已经提出了采用先进的复合材料，钢筋混凝土建筑结构抗震加固措施（简称ACM）支撑法（Takatani 2008 and Takatani 2011）,由碳纤维增强塑料（简称碳纤维复合材料）材料、钢制套筒和锚固件，以保障大量的居民在大地震中的生命安全。众所周知，碳纤维复合材料具有强、重量轻、耐久性好、适用性广等优点，与钢结构相比具有良好的耐久性和适用性。在本文中，ACM的支撑方法D适用于抗震加固的两层建筑结构以用来代替钢支撑法。2. AMC支撑法在地震加固改造中的实际运用 迄今为止，在日本钢支撑的方法已被广泛运用于钢筋混凝土建筑结构抗震加固工作。

51、如图1（a）所示的钢支撑露钢筋混凝土结构的外部，通常是做在结构内部的。同时，图1（b）显示ACM支架安装在结构之外。对许多钢筋混凝土结构的业主来说，抗震加固工程能够是一种快速、经济地进行，在进行抗震加固施工的施工尽可能避免居民搬迁或零时疏散。图1所示的钢筋混凝土建筑结构的抗震加固工程，是对钢筋混凝土房屋的居民和业主都方便的工程。因此，在低成本、短期施工的要求下，结构工程师在施工过程中，提出了一种新的抗震加固技术。 （a）钢支撑 (b）ACM支撑ACM支撑法针对低成本和施工工期短的要求提出的。ACM支撑法采用碳纤维杆和碳纤维布、钢套筒和钢锚。图2显示了ACM支撑杆包括碳纤维杆与钢套筒。钢套筒长度

52、600mm，从碳化纤维强化塑料的拉拔试验看其能承受500千牛的力。同时，在图3中显示了不同直径的碳纤维复合材料杆。用于ACM支撑法碳纤维杆的直径为10mm，其拉伸强度为169.5 千牛。因此直径10mm碳纤维杆可承受约500千牛的力。一种先进的环氧树脂由小西有限公司开发用于黏结CFRP筋钢缸套（堀井株式会社2007）。图4显示钢锚嵌入钢筋混凝土柱，进行不同锚杆直径和长度下的500千牛拉拔试验。图5显示钢制气缸套和螺母对于ACM的支撑，其抗拔承载力约为500千牛。同时，对ACM支撑碳纤维杆如图6所示，和碳纤维杆的长度所需的ACM 500m支撑法适用于3层钢筋混凝土建筑结构。图7显示了一张碳纤维布

53、加固钢筋混凝土柱对地震运动的拉力。图2.ACM支撑使用碳纤维杆图3.碳纤维杆（预应力型，三菱塑料有限公司） 图4.ACM撑锚 图5.ACM支撑钢套 图6.CFRP杆（V10mm，5 100m） 图7.碳纤维布的ACM支撑锚粘贴在钢筋混凝土柱表面，并覆盖有四个不同方向的碳纤维复合材料层且考虑到拉伸力方向。图8。ACM支撑钢筋混凝土建筑立面图图8显示了两种典型使用ACM支撑法的抗震加固工作高度。随着埋深点计划如图8（a）所示位于钢筋混凝土柱和梁的交叉区域的钢筋混凝土柱和梁的交叉，它可不是无聊的工人在AMC支撑法的交汇区域只打锚孔而不切割钢筋。因此，B计划显示在图8（b）提出了替代方案，和埋深点避免钢筋混凝土柱的截面积钕梁。此外，还发现在平面图