In steel structure, the connection of beam and column is usually in three forms, flexible connection (also known as articulated), semi-rigid connection and rigid connection.In engineering practice, how to distinguish a rigid and semi-rigid nodes belong to or hinged connection basically is to see its rotational stiffness, rigid connection should not produce obvious connection Angle deformation, a fallin the connection Angle deformation of structure resistance should be less than 5%.
Semi-rigid connections are somewhere in between.
The semi - rigid connections of the beam can be used to connect the upper end of the beam with high strength bolting, or with the upper, lower Angle steel and high strength bolts connected to the flange.The design requirements are as follows:
(1) the transmission of the force in the connection of the end plate to the end plate can simplify the bending moment of the beam to a pair of force pair, and the tension is transmitted by the pull flange.The tensile bolts are arranged in symmetrical arrangement of the flange flange.Pressure can be delivered through the end plate or the flange of the column, the pressure zone bolt can be set in a small amount, and with the pull bolt to transmit the shear force.
(2) in the joint of the upper and lower Angle steel connecting with the upper and lower Angle steel, the connected Angle steel on the tension side is not only the deformation of the legs, but also the horizontal limb.Therefore, the stiffness of the Angle steel is slightly lower than that of the end plate.
The classification of connective properties shall be characterized by the following three indicators: flexural rigidity, rotational stiffness, ductility (rotational capacity).
Flexural capacity is the main project of connection strength, and also has the shear strength.In theory, the ability to withstand the bending moment and shear force should not be lower than that of the beam, which is not lower than the plastic hinge moment of the beam and the full plastic shear of the web.The framework of the earthquake zone should be more demanding, reflecting the principle of "strong connection-weak components".For flexible connections, only shear resistance is required.Semi-rigid connection between rigid and flexible connection must have a certain resistance to bending.
The rotational stiffness of the connection is reflected by the slope of the bending moment - Angle curve. It is not constant, and the rotational stiffness has an influence on the deformation and bearing capacity of the frame.The influence of deformation needs to be analyzed with the normal use limit state.For this reason, the stiffness of the secant line under the initial stiffness or standard load of the connection should be investigated.The rigidity of the rigid connection, which theoretically needs to be infinite, can be regarded as a rigid connection only if it reaches a certain threshold value. The problem is how to define the quantity.
The rotational capacity is the ductility index, and the plastic design framework requires that the plastic hinge parts have a certain rotational capacity so that the subsequent internal force redistribution can occur.
1. The rigid connection of this structure assumes that the beam connections are sufficiently rigid and that no relative rotation between the beam columns can withstand the bending moment.When the hinge branch is connected with the structure to assume the gravity load, the vertical shear force is transmitted between the main beam and the column, and the bending moment is not transmitted.This connection can be rotated without constraint.
2. In the traditional analysis and design of steel structure frame, to simplify the analysis and design process of beam-column connection is admitted as the ideal hinged connection or completely rigid connection, and thought: connect the rotational restraint to achieve ideal just answer of more than 90%, can be seen as just answer;Under the action of external force, the change of Angle of Angle between column beam and beam is regarded as the hinged joint of more than 80% of the ideal hinge.The assumption of the ideal hinge will mean that there is no moment between the beam and the column, and in turn, the beams and columns that are joined together will rotate independently.
Resistance to bending moments of column foot called just answer column foot, instead can not resist bending moments of column foot is called a hinged column foot, just answer with hinged difference is whether can pass bending moment, look from actually, if the anchor on the outer edge of the flange, is just meet, and is generally not less than four, if the inside of the flange, is articulated, usually for two or four.
Foot is obvious difference between these two column for lateral control, if the structure of lateral control is strict, just pick up the column is adopted at the foot, such as crane load, crane load is dynamic loading, is sensitive to lateral comparison, and lateral assembly crane rail card phenomenon, at this time should be take pedestal design fresh-from-stats-class column foot.
"If need adding shear key is hinged column foot, anchor bolt cannot bear the" shear himself this other words a bit is not rigorous, it should be said that "if it is hinged column foot generally need adding shear key".Because the axial force of the column foot of the steel structure hinge pin is relatively small, the friction of the base and the basic concrete performance can hardly meet the requirements, so the shear key needs to be set in most column feet
The difference between fresh and articulated:
1. Just connect the bending moment and shear force, and the hinge can only transmit the shear force.
2. There is also a difference in structure: the connections between the upper and lower flaps and the abdominal plates are required to be connected.Hinged as H steel, only the web has a connection structure.
The force of the pin is divided into:
(a) hinge pin (b) just after the pin
The structure of the concrete structure is just connected, namely, the axial force N, horizontal shear V and bending moment M are also present, so the basic size is larger.
There are two kinds of cylindrical legs that are common in light steel structure. The force is different.
1. For hinge pin, only axial force N and horizontal force exist
2. In addition to the axial force N and horizontal force V, there is a certain bending moment M,
3. The base of the pin is larger than the hinge pin.
For the node design of the first leg:
1. When used for industrial plant and bridge crane, the pin should be designed as
2. The rigid column foot should pay attention to the following problems:
The basic construction unit should have certain technical level
Shears should be set
* the question of just picking up and reconnecting is, in theory, the point that the hinge is whether the node can turn, and the whole point is that the point is not rotating at all, and the hinge is free to turn.This node can not only bear the bending moment of shear force, but also have sufficient stiffness.The diplomatic envoy's point is very small under the bending moment.In theory, not just pick up, as long as the function is the deformation, in actual engineering, after reaching a certain stiffness, we can think in engineering is just answered, if can bear the bending moment and deformation is bigger, but we think is half just answer, is elastic fixation.
Articulated well understanding, but free to rotate, just can not bear the moment, then can only resist shear force and axial force.Specific to a component, such as the working type member, the flange is mainly bent, the abdominal plate is mainly shear.Because the discussion of some comrades had not learned mechanics, I'll explain plain, for the moment, the farther from centroid axis, the greater contribution to the bending moment, so flange bending moment farthest from the centroid.The shear stress is the largest in the shape of the heart, so the abdominal plate is mainly cut.Generally speaking, specific to the node, such as the end plate connection, the thickness of the end plate of any bolt in the outside of the flange will meet the requirements.Hinged node bolts are arranged near the center of the spindle.