Description: Omitted
Articli 12. Caulking
Riveted joints required for caulking shall be well caulked so as to completely prevent leakage.
Description: Omitted
Section 3 High Strength Bolt Joints
Article 13. Application
When high strength bolt connections are used for joints of members, these joints shall as a rule not be used for structural joints directly related to watertightness.
Description:
In recent years, high strength bolt connections have been widely used for joints of general steel sructures because of their favorable aspects such as easy and rapid construction, low noise, simple and secure retightening after inspection, safety against vibrations, etc. High strength bolt connections can be divided into two groups; friction type or bearing type (the direction of load applied to the bolt axis) and tension type (the direction of load to the joint is the same as the bolt axis direction). In many cases, loads in both directions are present together.
A friction connection is one of the connecting methods which has become prevalent in Japan, and this joint is to transmit the stresses with friction force generated between joint members by tightening them with bolts. The friction joint stipulated in this section is, as those used in building or bridges, equipped with the bolts having enough strength so that the failure of the joint results from the fracture of the parent metals under static or repeated loads.
A bearing connection has the advantage of a friction joint under normal working loads and is designed based on ultimate proof stress of a joint under an extraordinary load by using shearing of bolts.and bearing of bolts and holes.
A tension connection is used not only to supplement the weak points of a conventional tension joint by the high strength of the bolts but also to utilize the effect of a bolt tightening force, and the tension joint does not mean simple tension bolts which do not give an initial axial force to the bolts as shown in Section 4 or wfyich do not expect, such a force.
In this Section, high strength bolt friction connections and bearing connections are specified as substitutes for riveted joints. In this specification, however, only reference material is attached for bearing connections and tension joints are not referred to.
High strength bolt joints are used mainly for hydraulic gates and steel structures related to hydraulic gates.
Loading conditions for a gate leaf are in most cases more severe than those for bridges or buildings, and thus care should be given to the employment of the high strength bolt connections. It is also specified not to use this type of joint for structural joints directly related to watertightness, taking account of changes in slip coefficients due to water infiltration and corrosion of high strength bolts. When it is necessary to use them, consideration should be given to secure watertightness dependent upon the location and working conditions and to maintain the strength of high strength bolt connections. Accordingly, it is preferable not to use this type of joint for high pressure gate leaves or portions difficult for repair and inspection for the present. Attention should be paid not to generate rust, even if it is used for a portion not related to a watertightness connection.
Article 14. Bolts, Nuts and Washers for High Strength Bolt Friction Connections
*
T. Bolts, nuts and washers to be used for friction connections shall be'of Class 1 and 2 types of sets specified in JIS B 1186 (1976) “Sets of High Strength Hexagonal Bolt, Hexagonal Nut and Plain Washers for Friction”.
The bolt length shall be obtained by adding those listed in Table 5.14-1 to the tightening length, and the effective thread length shall be obtained by subtracting the tightening length frorfHhe bolt length.
Table 5.14-1 Lengths to be Added to Tightening Lengths (mm)
Nominal diameter
Length to be added
M 16
30 and over
M 20
35 and over
M 22
40 and over
M 24
45 and over
Description:
JIS B 1186 specifies classes 1 to 3 of high strength bolts for a friction . joint (F8T, F10T, Fl IT), but class 3 (Fl IT) is excluded from this standard.
As sufficient tightening cannot be obtained if there is a shortage in the bolt thread length, effective thread lengths to be added to tightening lengths are standardized. (See Fig. 5.14-1)
Fig. 5.14-1 High Strength Friction Joint
Article 15. High Strength Bolt Friction Joints
In the design of joints, the following points shall be taken into consideration in addition to those specified in Section 1:
The number of bolts in one row parallel to the direction of the stress of the joint shall not be excessive, otherwise the allowable strength per bolt shall be decreased.
If the faces of a bolt head or a nut are inclined more than 1/20 to a member material, a taper filler or a taper washer shall be used.
3'. For joints with many bolt lines or rows, the bolts shall be arranged as close together as possible.
The diameter of a bolt hole shall be the sum of the nominal diameter and 1.5mm for bolts having a nominal diameter of less than 16mm, and 2.5mm for bolts having a nominal diameter of more than 20mm.
Description:
Friction joints are those used to transmit the stresses by friction between member plates. The general requirements specified in Section 1 apply to these joints.
Several considerations required especially for designing the joints are mentioned in this Article.
By increasing the number of bolts in one row along the stress direction of a joint, the slip load per bolt is not very much influenced as long as the number does not exceed, but the force shared by each bolt under the bearing condition is not uniform and the load is concentrated on the end bolt similarly to the case of a riveted joint.
Like a riveted joint, as the number of bolts increases, the fatigue strength of the joint decreases. (The degree of decrease is extreme in a riveted joint.) But failure occurs in the parent metals and not in the bolts in general. Thus, according to experience, it is permissible to use about eight bolts, but the arrangement should be noted sufficiently. If the number needs to be increased, it is necessary to reduce the allowable stress per bolt.
When joints are eccentric or bolt faces or nut underfaces slope to member faces, the bolts themselves are subjected to bending stresses, and there may be a reduction in bolt strengths and friction forces. That is why this paragraph is specified.
For joints having many bolt lines and rows,.it is said that slip coefficients increase with a closer arrangement of the bolts and that slip coefficients decrease 10 to 20% as the number of interlocated bolts decreases. Therefore, bolts must be arranged closely.
The diameters of holes for friction joint bolts are generally to be the nominal diameter of the bolts plus 1.5mm. With the tendency of enlargement of structures in recent years, the clearances of bolt holes have beep reviewed from various practical viewpoints, and thus it is stipulated that a nominal diameter plus 2.5mm may be permissible for M20 bolts or larger, after making reference to related data.
It is permissible that the tolerance of a bolt hole as a limit in processing work be + 0.5mm, and + lmm for 20% of one bolt group. Therefore-, the tolerance of diameter of holes for M20 bolts becomes 23 mm.
Note: In calculating effective cross-sectional areas of joints with friction joint bolts, the clearances specified in this paragraph must be added as diameters of holes.
Article 16. Performance of High Strength Bolt Friction Joints
Necessary processes shall be applied to friction faces of the member plates to be connected prior to connection.
Connection shall be made closely between: mutual member materials and between a member material and a splice plate.