4. Criterion of Rebar arrangement

Size: px

Start display at page:

Download "4. Criterion of Rebar arrangement"

Bruno Floyd
5 years ago
Views:

1 4. Criterion of arrangement 1) coating It means the shortest distance to the surface of concrete to cover rebar surface. coating thickness of each part must be considered in the period of plan after considering durability, refractory, safety in structure endurance & errors in construction carry-out. There are examples of coating case as ground criterion for all construction without segmenting the case of ground and also the case of foundation regularly. By the effect of CO 2, humidity, acid gas, there will be going on of neutralization step by step from the surface of concrete. If the coating is small, its speed to arrive rebar will be faster. If so, the rust will expand, the adhesion of concrete coating will drop, white phenomenon will exist, senility of structure body will facilitate. Concrete pouring under water Classification Concrete burying under ground forever after land pouring concrete adjoined Foundation Foundation Size All rebar All rebar Minimum coating/thickness (Unit:mm) Remark Concrete part to expose to outdoor air and to adjoin land directly Wall, pillar Beam (outside exposure beam) Slab(foundation slab) over HD29 below HD25 below HD Slab, Wall, Under Flooring over HD35 below HD Concrete part not to adjoin land and outdoor air Beam, Pillar Tiehoop Stirrup Spiral rebar 40 Shell, Member All rebar 20 Note : direct exposure to the air of outdoor means the case of direct exposure of climate change and humidity change.

2 < Independent foundation > < Pile foundation > Coating thickness 80 < Pillar > Coating thickness 80 Cushion Coating thickness 50 Hoop Lean Concrete Lean Concrete Coating thickness 40 < Beam > < Wall & Slab > Coating thickness 20 Stirrup Slab Wall Coating thickness Coating thickness In Shear wall, the arrangement of rebar should be to the inside of vertical rebar. Regarding wall, horizontal rebar should be arranged to the outside of vertical rebar. Regarding outside wall in underground which compressed by the land, more arranged rebar should be arranged to the outside after comparing the arrangement quantity between vertical rebar and horizontal rebar.

3 2) distance Deformed rebar Classification Distance Net distance Net Distance Over 1.5 times of nominal diameter Over 1.25 times of max. size of thick aggregate. Over high value in 25mm 3) Type of tying Regarding the working of tying, there are folded tying(lap splice), compressed tying(welded splice), mechanical spiral tying(mechanical splice). But compressed tying(welded splice), mechanical spiral tying(mechanical splice) have to be effected over 125% of resistance strength(fy) in plan criterion. Folded tying (lap splice) It is tying method to fold the fixed length from end part to new tying part by using regular rope currently.

4 Folded tying(lap splice) The value in ( ) is the case of upper part rebar. Type Concrete (kgf/cm 2 ) Size Tying length of deformed rebar to be extended A Class Tying A Class Tying Tying length of deformed rebar to be compressed Under D19 Over D d (41.0d) 39.3d (51.1d) 41.0d (53.3d) 51.1d (66.4d) SD30 (fy=3,000 ) 240 Under D19 Over D d (38.2d) 36.8d (47.8d) 38.2d (49.7d) 47.8d (62.2d) 21.6d 270 Under D19 Over D d (36.1d) 34.7d (45.1d) 36.1d (47.0d) 45.1d (58.6d) Under HD19 Over HD d (54.6d) 52.4d (68.1d) 54.6d (71.0d) 68.1d (88.5d) SD40 (fy=4,000 ) 240 Under HD19 Over HD d (51.0d) 49.1d (63.8d) 51.0d (66.2d) 63.8d (83.0d) 28.8d 270 Under HD19 Over HD d (48.1d) 46.3d (60.2d) 48.1d (62.5d) 60.2d (78.2d) 1. The length of folded tying of rebars which have different diameter must over high value between the fixed length of high diameter rebar and the folded tying length of low diameter rebar. 2. The tying position must be placed to low stress / to compressed stress of concrete. 3. By the criterion of concrete structure plan, it is mentioned that it is available for folded tying in case of D29~D35 rebar. However, you have to check in advance the problem such as the net distance of rebar is not secured and also the tying length will be exaggerated if you apply folded tying of thick rebar. Generally, there are more advantageous case by using mechanical tying instead of folded tying in case of over D29 rebar. A class tying : must be zigzag(rotation) tying arrangement and arranged rebar quantity is over 2 times of required rebar quantity which defined in total block of tying part and also under 50% of rebar tying quantity within required folded length. B class tying : it is available for the tying of anti-earthquake plan and generally it is applicable to all construction site. Regarding SD500, you must apply 1.25times of B class tying. Regarding beam main bar tying, you must apply B class tying if you don't mention tying position specially. But, you can apply A class tying if you want to tying the compressed part of concrete. (the compressed part of concrete : upper part main bar places near center part of span, lower part main bar places near pillar)

5 The tying length of wall vertical length is available around 40db of under HD19 especially. Example of folded tying(lab splice) Folded tying of vertical rebar in case the distance of rebar arrangement is different Tension bar(ls) Slab upper part Tension bar(ls) Tying Length of Slab upper part Tying Length of Vertical rebar Fixed length of Tension bar Wall S : Distance of Ls : Tying length of Tension bar Folded tying of horizontal rebar Example) Length of folded tying to be extended of vertical & horizontal rebar Tying Length of Tension bar(ls) Diameter Length

Compressed tying(welded splice) It is the tying method to compress

As shown in figure(a), place 2 bars 3mm away, heat up both of the ends by

figure(b), usually available for all bars.

As the mechanical splice method, it is rebar tying method to connect the

6 Compressed tying(welded splice) It is the tying method to compress through heat-treatment end to end by using machinery. As shown in figure(a), place 2 bars 3mm away, heat up both of the ends by using mechanical equipment and add pressure to weld splice them figure(b), usually available for all bars. Mechanical spiral tying(mechanical splice). As the mechanical splice method, it is rebar tying method to connect the spiral part with nut & coupling by cutting screw by expanding the end of rebar over the regular size. (A) Connect Nut (C) Move Coupler (B) Connect Coupler (D) Move Nut

7 4) Fixing and tying In order to effect the adequate resistance strength of rebar, it is essential to obtain the enough adhesion strength with concrete. The more you increase the net distance & coating thickness of rebar, the larger of adhesion strength. Fixing length is the buried length in concrete to effect the adequate resistance strength of rebar and fix the length with the criterion of max. stress point of appropriate rebar. The fixing and tying length of rebar is changing by the strength of material and type of rebar arrangement, etc. i. It will be lengthen by using HD(high density) rebar.(sd40 is 1.33times of SD30A) ii. It will be shorten by using HD concrete.(inverse proportion from square root of concrete strength) iii. It will be shorten if net distance and coating thickness of rebar increase. iv. It will be shorten by the restriction effect if it is surrounded by stirrup and tie hoop. Caution : If the fixing and tying length of rebar will be shorten, the resistance strength of rebar will be reduced as long as the shortened length. Also, in case the heavy binding of splice part of rebar needlessly sometimes, binding has only the role to prevent the movement of rebar when pouring concrete and also no relation to adhesion strength of rebar. (the tensile of a D25 rebar is =20.16tonf) If the position of extended rebar for the tying of poured concrete is wrong, it is available for bending of splice with the angle of under if error is trivial but you need to take additional action to increase the section of additional material if error is over that angle. In case slab or wall rebar will be cutted by temporary exit such as material pick-up exit, etc, you must extend the rebar which is over the length of splice to both ends of exit. If width of exit is narrow or the length of rebar extended is shorten, the length of splice will be shorten when pouring exit concrete later.

8 Calculation of bar length What should be added to original length : splice length, fixed length Splice length Splice length : extra length to lap the bars Fixed length Fixed length : developed length when the bar is fixed Method to calculate fixed length fixed length of tension bar 90 Standard hook Fixed length of rebar which has standard hook fixed length of tension bar - In case of fixing to neighbor beam - - In case of fixing to end pillar - Tension bar and compression bar tension bar : The main usage is tension bar because rebar is reinforced material to reinforce the tension of weak point of concrete. compression bar : the rebar to be arranged in addition to increase the resistance strength in concrete material and it is mainly applicable to the pillar of high building to cover the compression. Refer to the diagram (#22 page) for tying & fixing per rebar diameter Compression Tension

9 5) Form of fixed beam When arranging beam, the marked on drawing as bending bar is mainly Japanese method of rebar arrangement. Our standard will be cut-bar instead of bending bar(japanese method). The length to extend to reverse side from max. Stress point of fixed length. Hook should place over the center of pillar. Fixed length is fixed length of tension upper bar. In case of fixing with standard hook, fixed length of rebar which has standard hook will be applied. If not, fixed length of tension bar will be applied. is generally fixed length of lower compression bar and it is available of fixation if it is extended to pillar over 15cm without hook.

10 6) Example of fixed length per rebar diameter Fixed length of tensile rebar Fixed length of tensile rebar in slab(sd ) 240kgf/ kgf/ kgf/ kgf/ kgf/ (unit:mm) Remark When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times Fixed length of tensile rebar in foundation, pillar, beam, wall(sd) HD10 HD13 HD16 HD19 HD22 HD25 HD29 HD32 240kgf/ General bar Upper bar kgf/ General bar kgf/ Upper bar General bar Upper bar kgf/ General bar Upper bar (unit:mm) kgf/ General bar Upper bar When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times

11 Fixed length of compression bar Fixed length of compression bar(sd) (unit:mm) 240kgf/ 270kgf/ kgf/ 350kgf/ kgf/ 50N/ 500kgf/ HD10 HD HD HD HD HD HD HD When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times 7) Example of splice length per rebar diameter 1) Classification of tension splice A class tying : must be zigzag(rotation) tying arrangement and arranged rebar quantity is over 2 times of required rebar quantity which defined in total block of tying part and also under 50% of rebar tying quantity within required folded length. B class tying : it is available for the tying of anti-earthquake plan and generally it is applicable to all construction site. Actual arranged rebar requirement Required rebar Q ty Max. splice % within folded splice length 50% 50% 2 2 2) Upper bar : horizontal rebar without concrete harded over mm under splice part and fixed length 3) The rebar with folded splice without contacting directly each other in bending material must not depart over little value between 150mm or 1/5 of folded splice length.

12 A class splice length of tension rebar Splice length of slab(sd) HD10 HD13 HD16 HD19 240kgf/ kgf/ kgf/ kgf/ kgf/ When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times (unit:mm) Remark A class splice length of foundation, pillar, beam, wall(sd) 240kgf/ 270kgf/ kgf/ 350kgf/ General bar Upper bar General bar Upper bar General bar Upper bar General bar Upper bar HD HD HD HD HD HD HD HD When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times (unit:mm) kgf/ General bar Upper bar B class splice length of tension rebar It is available for the tying of anti-earthquake plan and generally it is applicable to all construction sites. B class splice length of slab(sd) HD10 HD13 HD16 HD19 240kgf/ kgf/ kgf/ kgf/ kgf/ When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times (unit:mm) Remark

13 B class splice length of foundation, pillar, beam, wall(sd) HD10 HD13 HD16 HD19 HD22 HD25 HD29 240kgf/ General bar Upper bar kgf/ General bar Upper bar kgf/ General bar Upper bar kgf/ General bar Upper bar When HD32 using 2050 SD rebar(fy=500n/ =5,000kgf/ ), apply times1590 (unit:mm) kgf/ General bar Upper bar Splice length of compression rebar HD10 HD13 HD16 HD19 HD22 HD25 HD29 HD32 fck = 21N/ = 70N/ (kgf/ - 700kgf/ ) SD (fy=n/ =4,000kgf/ ) SD500 (fy=500n/ =5,000kgf/ )

14 Fixed length of tension bar which has standard hook fy=n/ (4,000kgf/ ) fixed length of tension bar tension destroyed section of concrete (diameter) (diameter) min tension or 3db HD10 ~ HD25 4db HD29 ~ HD35 5db over HD38 HD10 HD13 HD16 HD19 HD22 HD25 HD29 HD32 240kgf/ kgf/ kgf/ kgf/ kgf/ When using SD500 rebar(fy=500n/ =5,000kgf/ ), apply 1.25 times. 50N/ 500kgf/ Fixed length and splice length of binded rebars. Increase the fixed length and splice length of binded rebars as follows. a) 3pcs binded rebars : increase 20% b) 4pcs binded rebars : increase 33% The splice of each rebar must not duplicated

18. Wall rebar arrangement

18. Wall rebar arrangement 1) Sequence of rebar arrangement The worker is not allowed to change the rules and instructions of reinforcement without permission. All the reinforcement should be in accordance