Элементы из конструкционной стали соединяются друг с другом с помощью накладных элементов или соединителей, которые могут быть угловыми профилями., plates or even parallel flange channels (ПФК). Это некоторые из распространенных конфигураций, принятых на рабочих местах., особенно когда в основном используются болты или болтовые соединения. For welded connections, элементы иногда напрямую соединяются друг с другом без каких-либо наполнителей или промежуточных соединителей.. In this article we focus on bolts, шестигранная головка и потайная, и некоторые из распространенных болтовых соединений, используемых.
Болты с шестигранной головкой и потайной головкой
The hexagonal head bolt on the left is the normal structural fastener. The countersunk bolt on the right has a tapered head that sits flush with the surface of the ply, which matters where a protruding head would foul a bearing surface or a moving part. That taper is also what reduces its bearing capacity, as covered below.
Американский институт стальных конструкций (Aisc)
AISC в основном использует английские единицы измерения. (дюйм, фунты) although the SI counterpart is also supported and available. One thing to take note of is that the dimensions in the English system are usually in increments of one eighth of an inch (⅛”), которые могут не совсем совпадать с теми, что в SI.
Сравнение диаметров болтов
| ½” | – |
| ⅝” | M16 |
| ¾” | M20 |
| ⅞” | М22 |
| 1» | M24 |
| 1 ⅛” | М27 |
| 1 ¼” | M30 |
| 1 ⅜” | – |
| 1 ½” | M36 |
These are nearest practical equivalents, not interchangeable sizes. A ¾” bolt is 19.05 mm against 20 mm for an M20, so the hole sizes and edge distances differ and the two cannot be substituted for one another on a drawing.
Высокопрочные болты
Specifications for bolt materials are covered by the American Society for Testing and Materials (ASTM), and AISC sorts them into two groups by strength:
Группа А — ASTM F3125 Grades A325, A325M and F1852; ASTM A354 Grade BC; ASTM A449
Группа Б — ASTM F3125 Grades A490, A490M and F2280; ASTM A354 Grade BD
ASTM F3125 is a consolidated specification that absorbed the older standalone A325, А490, F1852 and F2280 documents, which is why those now appear as grades within it rather than as specifications in their own right. Older drawings and calculations still call them out the old way.
Besides differences in strength and other properties, these groups have different requirements for minimum pretension depending on bolt diameter.
Еврокод 3 (Национальное приложение Великобритании)
The Eurocode is entirely in SI units, so bolts are designated in millimetres with the size prefixed by “M”, for example M16 meaning a 16 mm diameter bolt.
| М12 |
| M16 |
| M20 |
| M24 |
| M30 |
Bolt Classes and Strengths
Eurocode bolts are classified by a two-part designation that encodes both strengths. For a class written as a.b, the ultimate tensile strength is а × 100 МПа, and the yield strength is б/10 of that value. So Class 4.6 has an ultimate tensile strength of 400 MPa and a yield of 240 МПа, while Class 8.8 has 800 MPa ultimate and 640 Выход МПа.
Getting these two the right way round matters, because the bolt resistance formulas take the ultimate value. In calculating actual bolt resistances, the capacity is also affected by the preload, called pretension in AISC terms, which in certain cases increases the bolt carrying capacity if the right amount of tension is applied.
| Класс | Растяжимый, fub (МПа) | Урожай, fyb (МПа) | Diameter range |
| 4.6 | 400 | 240 | М5 – M36 |
| 4.8 | 400 | 320 | М1.6 – M16 |
| 5.8 | 500 | 400 | М5 – M24 |
| 8.8 | 800 | 640 | М1.6 – M36 |
| 9.8 | 900 | 720 | М1.6 – M16 |
| 10.9 | 1000 | 900 | М5 – M36 |
| 12.9 | 1200 | 1080 | М1.6 – M36 |
Примечания к шестигранным болтам и болтам с потайной головкой
The differences in geometry between hexagonal and countersunk bolts affect the bearing capacity, because the tapered head removes material from the ply it sits in. The effective thickness in bearing is the ply thickness less the depth of the countersink, which is what the figure below shows. (See AISC Manual 14th edn, инжир. 7-10.)
фигура 1. Эффективная толщина опоры болта с потайной головкой
Спецификации соединений и отверстия под болты
Болтовые соединения могут быть указаны как плотно затянутые., с предварительным натяжением или критическим скольжением. These conditions play a large role in the choice of bolt hole used. Hole types are standard (нормальный, in EN terms), oversized, or slotted short or long, and they are adopted according to the connection specification. The RCSC specification sets out the requirements for the snug-tight condition. If the connection is designed for anything other than snug-tight, that condition must be clearly identified on the drawings, whether it is an AISC pretension or an EN preloading requirement.
The distinction is not paperwork. A snug-tight bolt resists load by bearing once it has slipped into contact, while a slip-critical connection is designed so that the clamping force stops the plies moving at all.
Slip-critical connections matter wherever slip has to be prevented, and different factors are applied in the calculation of slip resistance depending on the hole type, since an oversized or slotted hole gives the ply more room to move before it bears. В большинстве случаев, standard or normal bolt holes are adopted together with a specified level of pretension or preload. These variables can be modelled and analysed using tools like Анализ и проектирование стальных конструкций SkyCiv, which helps engineers account for connection behaviour in the wider structural system.
фигура 2. Болтовой угол, тип соединения на срез
Болтовые соединения
Bolted connections can be used both in shear plate connectors such as web plates, тройники, and web and seat angles, and in moment connections (жесткий, полностью сдержанный) которые обычно используют наполнитель, пластины непрерывности и сращивания. Using bolts means adding an intermediate connector or connecting element of the kind just mentioned.
фигура 3. Болтовое соединение с фланцевой пластиной
In theory there are many ways to combine connection configurations. На практике, buildability and fabrication cost mean certain connection types are favoured over others and are therefore more widely adopted. Here are some of the common connection types that use bolts, with brief descriptions.
ножницы (просто) Различные типы структурных опор
- Одинарная/двойная пластина (tab or fin) uses a plate or plates to connect a beam web to the supporting member, a girder or a column. One side usually needs a weld at the edge of the plate, while bolts connect it in lap to the beam web.
- Одинокий/Двойной угол is similar to plates, except that angles can be bolted on both sides of the connection.
- Угол сиденья, как следует из названия, uses an angle section to bear the flange of the supported member (or the flat wall for a closed section) so the beam can sit on it. Bolts can be used throughout this connection type.
момент (Сдержанный) Различные типы структурных опор
- Фланцевые пластины, used alongside a shear connection, provide continuity to flanges framing into the columns of a moment-resisting frame, or more generally in member splices.
- Collar and Through Plates are found on HSS columns (RHS или CHS) forming part of a moment-resisting frame. A through plate cuts through the column, while a collar plate is fitted around it, worn much like a collar on a shirt. Both are expensive to fabricate because of the cutting and fitting involved.
Посетите нашу статью о Типы стальных соединений Узнать больше, compare fasteners in bolts vs welds vs rivets, or try our калькулятор прочности болта на сдвиг. В bolts documentation covers how bolt grades, hole types and pretension are entered in the connection design module.
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Выбирайте болтовое соединение, set the bolt grade, diameter and hole type, and every bolt check comes back with its utilization ratio and the clause behind it. Он запускается в браузере, нечего устанавливать.
Ссылки
[1] Американский институт стальных конструкций (Aisc). (2016). Спецификация для зданий из конструкционной стали. Чикаго, НАШИ 60601-6204
[2] Американский институт стальных конструкций (Aisc). (2011). Руководство по стальным конструкциям. 14й Эд. Чикаго, НАШИ 60601-6204
[3] Институт стальных конструкций и Британская ассоциация производителей металлоконструкций. (2014). Соединения в стальных конструкциях Простые соединения по Еврокоду 3. Аскот SL5 7QN; Лондон SW1A 2ES, Великобритания
[4] Институт стальных конструкций и Британская ассоциация производителей металлоконструкций. (2014). Соединения в стальных конструкциях, устойчивые к моменту соединения по Еврокоду 3. Аскот SL5 7QN; Лондон SW1A 2ES, Великобритания
