1. What is high-strength bolt

高強螺栓，施工中所說的高強螺栓是高強度摩擦預緊螺栓的簡稱。在日常溝通中，僅僅是簡略了“摩擦(Friction)”“預緊(Grip)”兩個詞，卻造成了許多工程技術人員對高強螺栓基本定義的理解，產(chǎn)生了誤區(qū)。

High strength bolts, referred to in construction as high-strength bolts, are short for high-strength friction pre tensioned bolts. In daily communication, simply abbreviating the words "friction" and "Grip" has caused many engineering and technical personnel to misunderstand the basic definition of high-strength bolts.

高強螺栓.jpg

High strength bolts.jpg

顛覆一：

Disruption 1:

誤區(qū)：材料等級超過8.8級的螺栓，就是”高強螺栓“。

Misunderstanding: Bolts with a material grade exceeding 8.8 are considered "high-strength bolts".

高強螺栓和普通螺栓的核心區(qū)別并不在于使用材料的強度，而是受力的形式。本質(zhì)是是否施加預緊力，并利用靜摩擦力抗剪。(1)*實際上在英標規(guī)范，美標規(guī)范中提到的高強螺栓(HSFG BOLT)只有8.8級和10.9級兩種(BS EN 14399 / ASTM-A325&ASTM-490)，而普通螺栓卻有包含有4.6，5.6，8.8，10.9，12.9等(BS 3692 11款表2);由此可見，材料強度高低并不是區(qū)別高強螺栓與普通螺栓的關鍵。

The core difference between high-strength bolts and ordinary bolts is not the strength of the materials used, but the form of force applied. The essence is whether to apply preload and use static friction to resist shear. (1) In fact, in the British standard specifications, the American standard specifications only mention two types of high-strength bolts (HSFG BOLT): grade 8.8 and grade 10.9 (BS EN 14399/ASTM-A325&ASTM-490), while ordinary bolts include 4.6, 5.6, 8.8, 10.9, 12.9, etc. (Table 2 of BS 3692 Clause 11); It can be seen that the strength of the material is not the key to distinguishing high-strength bolts from ordinary bolts.

2.正確理解“高強”，強在何處

2. Correctly understand "high strength" and where it lies

按照GB50017，計算單個普通螺栓(B類)8.8級和高強螺栓8.8級抗拉及抗剪強度。

According to GB50017, calculate the tensile and shear strength of individual ordinary bolts (Class B) with grade 8.8 and high-strength bolts with grade 8.8.

通過計算我們可以看到，相同等級的情況下，普通螺栓的抗拉強度和抗剪強度的設計值都要高于高強螺栓。那么高強螺栓，“強”在哪里?

Through calculation, we can see that under the same grade, the design values of tensile strength and shear strength of ordinary bolts are higher than those of high-strength bolts. So where is the strength of high-strength bolts?

為回答這一個問題，必須從兩種螺栓的設計工作狀態(tài)入手，研究其彈塑性變形的規(guī)律，并理解到設計破壞時的極限狀態(tài)。

To answer this question, it is necessary to start with the design working states of the two types of bolts, study their elastic-plastic deformation laws, and understand the limit state at the time of design failure.

普通螺栓和高強螺栓工作狀態(tài)下應力應變曲線

Stress-strain curves of ordinary bolts and high-strength bolts under working conditions

設計破壞時的極限狀態(tài)

Ultimate state at design failure

普通螺栓：螺桿本身發(fā)生超過設計允許的塑性變形，螺桿被剪壞。

Ordinary bolt: The screw itself undergoes plastic deformation that exceeds the design tolerance, resulting in the screw being sheared out.

普通螺栓連接，開始承受剪力前連接板間就會發(fā)生相對滑移，繼而螺栓桿和連接板接觸，發(fā)生彈塑性形變，承受剪力。

For ordinary bolted connections, relative slip occurs between the connecting plates before they begin to bear shear force, and then the bolt rod contacts the connecting plate, causing elastic-plastic deformation and bearing shear force.

高強螺栓：有效摩擦面間的靜摩擦力被攻克，兩塊鋼板發(fā)生相對位移，設計考量上即為破壞。

High strength bolt: The static friction force between the effective friction surfaces is overcome, and the two steel plates undergo relative displacement, which is considered as failure in design considerations.

高強螺栓連接，摩擦力承受剪力，當荷載增大到摩擦力不足以抵抗剪力，靜摩擦力被攻克，連接板發(fā)生相對滑移(極限狀態(tài))。但此時雖然破壞，但螺栓桿與連接板發(fā)生接觸，依然可以利用其本身的彈塑性形變，承受剪力。

In high-strength bolt connections, the frictional force first bears the shear force. When the load increases to a point where the frictional force is insufficient to resist the shear force, the static frictional force is overcome, and the connecting plate undergoes relative slip (ultimate state). But although it is damaged at this time, the bolt rod can still use its own elastic-plastic deformation to withstand shear force when in contact with the connecting plate.

(3)顛覆二：

(3) Subversion 2:

誤區(qū)：高強螺栓的承載能力高于普通螺栓，是為”高強“。

Myth: High strength bolts have a higher load-bearing capacity than ordinary bolts and are considered "high strength".

由單個螺栓的計算可知，高強螺栓抗拉和抗剪的設計強度均低于普通螺栓。其高強實質(zhì)是：正常工作時，節(jié)點不允許發(fā)生任何相對滑移，即：彈塑性變形小，節(jié)點剛度大。

According to the calculation of a single bolt, the design strength of high-strength bolts in terms of tensile and shear strength is lower than that of ordinary bolts. The essence of its high strength is that during normal operation, nodes are not allowed to experience any relative slip, that is, small elastic-plastic deformation and high node stiffness.

可見：在給定設計節(jié)點荷載的情況下，用高強螺栓設計的節(jié)點并不一定能節(jié)省螺栓使用數(shù)量，但是其變形小，剛度大，儲備高。適合用主梁，等要求節(jié)點剛度較大的位置，符合“強節(jié)點，弱桿件”的基本抗震設計原理。

It can be seen that under a given design node load, nodes designed with high-strength bolts may not necessarily save on the number of bolts used, but they have small deformation, high stiffness, and high safety reserves. Suitable for using main beams and other locations that require high node stiffness, in accordance with the basic seismic design principle of "strong nodes, weak members".

高強螺栓之強，并非在于其本身的承載能力設計值，而是表現(xiàn)于其設計節(jié)點的剛度大，性能高，抗破壞的能力強。

The strength of high-strength bolts is not determined by their designed load-bearing capacity, but by the high stiffness, high safety performance, and strong resistance to failure of the designed nodes.

3.高強螺栓的對比

3. Comparison of high-strength bolts

普通螺栓和高強螺栓由于其設計的受力原理不同，其在施工檢驗方法上有極大的區(qū)別。

Ordinary bolts and high-strength bolts have significant differences in construction inspection methods due to their different design stress principles.

同等級普通螺栓各項機械性能要求均比高強螺栓略高，但高強螺栓較普通螺栓多一項沖擊功的驗收要求。

The mechanical performance requirements of ordinary bolts of the same grade are slightly higher than those of high-strength bolts, but high-strength bolts have an additional acceptance requirement for impact energy compared to ordinary bolts.

標識樣式對比

Comparison of logo styles

普通螺栓和高強螺栓的標示是對同等級螺栓現(xiàn)場識別的基本方法。由于英美標準中對于高強螺栓扭矩值計算的取值并不相同，所以識別兩種標準的螺栓也有必要。

The identification of ordinary bolts and high-strength bolts is the basic method for on-site identification of bolts of the same grade. Due to the different values for calculating the torque value of high-strength bolts in British and American standards, it is also necessary to identify bolts from both standards.

對比

Price comparison

高強螺栓：(M24，L60，8.8級)

High strength bolts: (M24, L60, Grade 8.8)

普通螺栓：(M24，L60，8.8級)

Ordinary bolt: (M24, L60, Grade 8.8)

可見普通螺栓大約為高強螺栓的70%，結合其驗收要求的對比，可以得出，其溢價部分就應該是為了保證材料的沖擊功(韌性)性能。

It can be seen that ordinary bolts are about 70% of the price of high-strength bolts. Based on the comparison of their acceptance requirements, it can be concluded that the premium part should be to ensure the impact energy (toughness) performance of the material.

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