CN112711784B - Support connection method of bolted steel beam - Google Patents
Support connection method of bolted steel beam Download PDFInfo
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- CN112711784B CN112711784B CN201911019008.1A CN201911019008A CN112711784B CN 112711784 B CN112711784 B CN 112711784B CN 201911019008 A CN201911019008 A CN 201911019008A CN 112711784 B CN112711784 B CN 112711784B
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Abstract
The invention discloses a support connecting method of a bolted steel beam, which comprises the steps of obtaining the total load of the steel beam; adjusting the connection between the web plate of the steel beam and the flange of the steel beam and the support respectively to enable the steel beam and the support to be in a first connection state, and applying a first load and preload to be borne by the steel beam in the first connection state; bolting a web at least one end of the steel beam and at least one flange at least one end to the brace, removing the preload from the steel beam, and applying a second load to the steel beam. The implementation of the method for connecting the supports of the bolted steel beams can effectively homogenize the positive and negative bending moments at the two ends of the steel beams and the span, thereby improving the stress performance and the economical efficiency of the steel beams in the structure and providing a direction for the feasibility of the scheme of the structure.
Description
Technical Field
The invention relates to the technical field of engineering, in particular to a support connecting method of a bolted steel beam.
Background
In the current specification and engineering structure theory, the bolt-type support connection generally refers to a hinged support of a web support bolt connection of a steel beam, or a fixed support of a web and a flange of the steel beam which are simultaneously connected with the support bolt connection. When calculating the bending moment borne by the web and the flange of the steel beam and the support in the two manners, it is generally assumed that the rigidity of the steel beam node is generated at one time and bears all loads.
However, in actual design and construction (manufacturing), it is found that, taking a single-span beam as an example, when two ends of the single-span beam are hinged, a bending moment diagram (fig. 1) of the single-span beam under the action of a full-span uniformly distributed vertical load q is distributed in a parabolic shape, at this time, bending moments at two ends of the single-span beam are zero, and a maximum bending moment M is generated in the span CS ＝ql 2 (8) maximum difference between bending moment amplitudes at both ends and midspan 1 ＝ql 2 /8. When the two ends of the single-span beam are supposed to be fixedly supported, a bending moment diagram (shown in figure 2) of the single-span beam under the action of the full-span uniformly-distributed vertical load q is still distributed in a parabolic shape, but at the moment, extreme negative bending moment M is generated at the two ends of the single-span beam Aa ＝M Ba ＝-ql 2 12, generating a small positive bending moment M in the midspan Ca ＝ql 2 /24, amplitude difference delta between negative bending moment at two ends and positive bending moment across 2 ＝ql 2 /24. Therefore, the calculated amplitude difference of the positive bending moment in the span relative to the bending moment amplitude difference delta of the hinged support at the two ends is realized by adopting a mode of assuming that the two ends of the single-span beam are fixedly supported 1 ＝ql 2 The/8, although reduced, however,the hogging moment at the two ends of the single span beam is doubled compared with the midspan positive bending moment.
It is known that the existence of such a condition easily causes poor stress performance and economic efficiency of the steel beam in the structure in actual design and construction (manufacturing), and even a condition that misjudgment of the structure is not feasible may occur in severe cases.
Disclosure of Invention
The embodiment of the invention discloses a support connecting method of a bolted steel beam, which can effectively homogenize positive and negative bending moments at two ends and a span of the steel beam, thereby improving the stress performance and the economical efficiency of the steel beam in a structure.
The invention provides a support connecting method of a bolt-jointed steel beam, which comprises the following steps
Calculating the total load borne by the steel beam;
adjusting the connection states of a web plate and a flange of at least one end of the steel beam and a web plate and a flange of a support respectively so as to enable the steel beam and the support to be in a first connection state, and applying a first load and preload to be borne by the steel beam in the first connection state;
bolting a web and at least one flange of at least one end of the steel beam to a web and flange of the brace, removing the preload on the steel beam, and applying a second load on the steel beam;
and the sum of the magnitude of the first load and the magnitude of the second load is equal to the magnitude of the total load.
As an alternative embodiment, in the embodiment of the present invention, the first connection state is any one of an unconnected state, a hinged state or a semi-fixed state.
As an alternative, in an embodiment of the present invention, when the steel beam and the support are in the first connection state, at least one of the flanges at least one end of the steel beam may be displaced relative to the support along an axial direction of the steel beam.
As an alternative implementation manner, in an embodiment of the present invention, the support is provided with a screw hole for connecting with the web and the flange of the steel beam, and the screw hole is a strip-shaped hole extending along the axis of the steel beam in the length direction.
As an alternative, in an embodiment of the invention, when the first connection state is a semi-solid support, the flange for directly supporting the roof panel is bolted to the flange of the support.
As an alternative embodiment, in an embodiment of the invention, for flanges for directly supporting floor panels, the flange is arranged with the nut end of the connecting bolt facing away from the floor panel before being bolted to the flange of the carrier, and the non-nut end of the connecting bolt facing towards the cavity protection element in the floor panel.
As an alternative, in the embodiment of the present invention, for the flange for directly supporting the roof panel, before bolting with the flange of the support, the flange is provided with the protective sleeve and the connecting bolt penetrating through the roof panel, and the connecting bolt on the flange is partially exposed from the protective sleeve.
Wherein, the flange for directly supporting the floor and roof panels is the flange of the steel beam.
As an alternative implementation, in the embodiment of the present invention, the total load is a uniform load and/or a concentrated load, the first load and the second load are a uniform load and/or a concentrated load, and the preload includes a load consistent with the total load distribution and/or a pre-stress different from the total load distribution.
As an alternative embodiment, in the embodiment of the present invention, the total load is q, the preload is p, and the first load is q 1 The second load is q 2 Wherein q is 1 +q 2 = q, and q 1 +p<μ q, wherein μ is a coefficient, and μ is less than or equal to 1.
As an alternative, in the embodiment of the present invention, before the calculating the total load borne by the steel beam, the method further includes
And respectively bolting the web plate and the flange of the steel beam with the web plate and the flange of the support.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
(1) Effectively reducing the bending moment of the bolted steel beam. The embodiment of the invention provides a method for applying preload to a bolted steel beam, which comprises the steps of adjusting the connection between the steel beam and a support into two different states, applying the load born by the steel beam in a segmented mode correspondingly, applying the preload when the flange of the steel beam is not or not completely connected with the flange of the support, and removing the preload after the flanges of the steel beam and the flange of the support are adjusted to be bolted, so that the positive and negative bending moments at two ends and across of the bolted steel beam can be effectively homogenized by utilizing the applied preload and the unloaded preload, the bending moment is effectively reduced, the stress performance and the economy of the steel beam in the structure are further improved, and a direction is provided for the feasibility of a structural scheme.
(2) The structure performance is excellent and the economic performance is good. By adopting the support connection method of the bolted steel beam, the section of the steel beam is reduced compared with the section of the steel beam which is hinged in the whole process or fixed in the whole process, so that the section height of the steel beam which cannot meet the use requirement and is limited by space can be well met, the material cost is effectively reduced, and the economic performance is better.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a bending moment diagram of a traditional steel beam with two hinged ends under the action of a full span uniform vertical load;
FIG. 2 is a bending moment diagram of a conventional steel beam with both ends fixedly supported under the action of a full span uniformly distributed vertical load;
FIG. 3 is a flow chart of a method of connecting a brace of a bolted steel beam according to an embodiment of the present invention;
FIG. 4 is a schematic view of a bolted steel beam hinge according to an embodiment of the present invention;
FIG. 5 is a schematic view of a bolted steel beam provided in an embodiment of the present invention;
FIG. 6 is a moment diagram of a steel beam hinged at both ends under a first load and preload in accordance with a first embodiment of the present invention;
FIG. 7 is a moment diagram of the first embodiment of the present invention with the steel beam clamped at both ends unloaded for preload and under a second load;
FIG. 8 is a graph of the bending moments of FIGS. 6 and 7 superimposed;
FIG. 9 is a bending moment diagram of the steel beam hinged at both ends under the action of a pre-tension load in case two of the present invention;
FIG. 10 is a bending moment diagram of the steel beam at two ends for bracing and relieving the pre-tension load and under the second load in case two of the present invention;
FIG. 11 is a view showing the action of the bending moment in the stack of FIGS. 9 and 10.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the present invention, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "center", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are used primarily to better describe the invention and its embodiments and are not intended to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.
Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meanings of these terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.
Furthermore, the terms "mounted," "disposed," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art according to specific situations.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish one device, element, or component from another (the specific nature and configuration may be the same or different), and are not used to indicate or imply the relative importance or number of the indicated devices, elements, or components. "plurality" means two or more unless otherwise specified.
The following detailed description is made with reference to the accompanying drawings.
Example one
Referring to fig. 3, fig. 3 is a schematic flow chart illustrating a method for connecting a support of a bolted steel beam according to an embodiment of the present invention; as shown in fig. 3, the steel beam includes a web and flanges, wherein the flanges may include an upper flange and a lower flange. The method for connecting the supports of the bolted steel beams can comprise the following steps:
101. and calculating the total load borne by the steel beam.
In the structural theory, the total load of the steel beam can be calculated according to a formula specified in relevant specifications. Specifically, the total load of the steel beam may be a uniform load and/or a concentrated load. That is, the total load of the steel beam can be uniform load or concentrated load, and can also include uniform load and concentrated load. It will be appreciated that in other embodiments the total load of the steel beam may also be a vertical load and/or a horizontal load.
102. And adjusting the connection states of the web plate and the flange at least one end of the steel beam and the web plate and the flange of the support respectively so as to enable the steel beam and the support to be in a first connection state, and applying a first load and preload to be borne by the steel beam in the first connection state.
It will be appreciated that in this embodiment, the support may be a column, beam, floor or other structural member or support to which the beam is connected. The brace may also include a web and a flange.
As an alternative, when the support is a steel column, the steel column may be a rectangular steel column, the steel beam may be a rectangular steel beam, a web of the steel beam is bolted to the steel column by a bolt pair, and a flange of the steel beam is not connected to the steel column.
As another alternative, when the support is a steel beam (the steel beam may be used as a steel main beam), the steel beam may be used as a steel secondary beam, in which case the web of the steel beam is bolted to the web of the support through a bolt pair, and the flange of the steel beam is not connected to the flange of the support.
Specifically, as shown in fig. 4, taking a main steel beam and a secondary steel beam as an example, the web 11 of the main steel beam 10 is bolted (in a movable state) to the web 21 of the secondary steel beam 20 by the bolt pair 12, and the flange of the main steel beam 10 is not connected to the flange of the secondary steel beam.
In this embodiment, the first connection state includes, but is not limited to, one of an unconnected state, a hinged state, or a semi-fixed state. Specifically, when the first connection state is a hinged connection, the web of the steel beam is connected with the web of the support, and the flange of the steel beam is not connected with the flange of the support; when the first connection state is the unconnected state, the web and the flange of the steel beam are not connected with the web and the flange of the support at the moment; when the first connection state is semi-solid support, the web plate of the steel beam is connected with the web plate of the support, and the upper flange or the lower flange of the steel beam is connected with the upper flange or the lower flange of the support; and when the first connection state is a fixed support, the web plate and the flange of the steel beam are bolted with the web plate and the flange of the support.
In the case of the bolted steel beam according to the invention, when the first connection state is semi-solid, then at least one flange of the steel beam should be bolted to a flange of the support, and the flange may preferably be a flange for directly supporting a roof panel.
Further, in the actual construction (manufacturing) and the application and calculation of the load, the first connection state is preferably unconnected, hinged or semi-fixed, and when the steel beam and the support are in the first connection state, the flange of the steel beam can be displaced relative to the support along the axis direction of the steel beam. For example, it can be seen from the above that if the first connection state is the disconnected state, in which the flange is not connected to the flange of the support, the flange can be displaced relative to the support, and if the first connection state is the hinged state, the web is connected to the counter-bar of the support, in which case the flange can likewise be displaced relative to the support.
Furthermore, for the bolting of the steel beam and the support, the web and the flange of the support may be respectively provided with a screw hole for connecting with the web and the flange of the steel beam, and the screw hole is a strip-shaped hole extending along the axis of the steel beam in the length direction. Specifically, the screw hole may be an elongated elliptical hole, and in the first connection state (the fixed support state), the web of the steel beam may be connected to the screw hole on the web of the support through the bolt pair, and the flange of the steel beam may also be connected to the screw hole on the flange of the support through the bolt pair.
In addition, when the flange of the steel beam is connected with the screw hole through the bolt pair in the first connection state (non-fixed support state), the nut of the bolt pair of the flange of the steel beam is not screwed with the screw rod, so that the flange can be displaced relative to the support along the axial direction of the steel beam.
The first load and the preload are applied when the steel beam is in the first connection state, so that the first load and the preload can be utilized to enable the steel beam and the support to bear the first load and the preload to generate bending moment when the steel beam and the support are in the first connection state, and the subsequent bending moment homogenization on the steel beam is facilitated.
In this embodiment, the first load is a partial load of the total load, and the first load may be a uniform load and/or a concentrated load.
The preload in this embodiment refers to a load and various actions whose effect direction is consistent with the load effect direction of the steel beam, and specifically includes any load and action consistent with and/or inconsistent with the load distribution of the steel beam, for example, it may include distributed load, concentrated load, stacked load, mounted load, pressure, tension, compression, tension, support displacement, temperature action, and so on.
Optionally, the preload may be applied in the following manner: after the steel beam is in the first connection state, a load, such as pre-stacking or pre-mounting, is applied to the steel beam, which is consistent with the load distribution that the steel beam should bear in the current first connection state. The magnitude of the preload is different from or the same as the first load.
103. Bolting the web and at least one flange of at least one end of the steel beam to the web and flanges of the brace, removing the preload from the steel beam, and applying a second load to the steel beam.
In this embodiment, when the web of the at least one end of the steel beam and the at least one flange of the at least one end are bolted to the web and the flange of the support, the at least one end of the steel beam and the support may be in a fixed support state, i.e., a second connection state.
Specifically, as shown in fig. 5, in actual construction (manufacturing), when the flange bolted to the flange of the support in the second connection state is a flange for directly supporting a floor panel, as an alternative, a nut (i.e., a nut end) of the flange 13 bolted to the flange 23 of the support in the first connection state, which is not screwed and needs to be screwed in the second connection state, may be arranged away from the floor panel, and the other end (i.e., a non-nut end) of the connecting bolt extends toward the floor panel, and a cavity protecting member is arranged around the connecting bolt in the floor panel to ensure that the connecting bolt can slip in the first connection state. Specifically, the cavity protection member may be a protection cover covering the non-nut end or a soft material that is easily compressed and deformed and covers the non-nut end.
The nut end of the connecting bolt is arranged at one end deviating from the building roof panel, so that the nut end can be conveniently screwed down in the subsequent construction of the building roof panel, and the flange is bolted with the support.
As another alternative, a connecting bolt and a protective sleeve are provided on the flange for directly supporting the roof panel, and penetrate through the roof panel, so as to ensure that the connecting bolt can axially slide along the beam in the first connecting state. The nut end of the connecting bolt is exposed out of the protective sleeve. It can be seen that in this manner, the height of the portion of the bolt exposed from the protective sleeve should not only satisfy the reliability of the connecting bolt itself and the requirements for subsequent tightening operations, but also satisfy the requirements for casting construction (or manufacturing) of the face layer of the roof panel, so as not to affect the construction (or manufacturing) installation of the face layer of the roof panel.
The design of exposing the protective sleeve at the nut end of the connecting bolt is adopted, so that the nut end of the bolt can be screwed down when the flange and the support are required to be bolted, and construction operation is facilitated.
Specifically, as shown in fig. 5, the web 11 of the main steel beam 10 and the web 21 of the support (the secondary steel beam 20) are bolted by the bolt pair 12, and the flange 13 of the main steel beam 10 is similarly bolted by the bolt 12 and the flange 23 of the secondary steel beam 20, in this state, the secondary steel beam, whether it is a web or a flange, cannot move relative to the main steel beam 10, that is, the secondary steel beam 20 and the main steel beam 10 are fixed.
In this embodiment, the sum of the magnitude of the second load and the magnitude of the first load is equal to the magnitude of the total load. That is, the second load is a residual load of the total load of the steel beam excluding the first load. The second load may likewise be a vertical load and/or a horizontal load. This corresponds to equal and opposite loads being applied to the steel beam, since the preload applied to the steel beam is removed in the case where the web at least one end of the steel beam and at least one of the flanges are bolted to the bracket (i.e., in the second connection state). Specifically, the total load is q, and the first load is q 1 Preload is p and the second load is q 2 And removing the preload corresponds to applying a load p' having the same magnitude and the opposite direction to the preload p to the steel beam, so that the total load, the first load, the second load and the preload satisfy the following relations:
q 1 +p+p’+q 2 ＝q； (1)
p＝-p’； (2)
wherein q > q 1 ≥0，q＞p≥0，q≥q 2 > 0, and q 1 +p<μ q, wherein μ is a coefficient, and μ is less than or equal to 1. In particular, μ is the load factor, q is the load factor when μ is equal to 1 1 +p<q。
Further, since the preload is applied to the steel girder when the steel girder is in the first connection state, the step of removing the preload of the steel girder in the second connection state may be performed before or after the second load is applied to the steel girder. That is, after the two ends of the steel beam are adjusted from the first connection state to the second connection state, the preload of the steel beam can be removed, or the preload of the steel beam can be removed after the second load is applied to the steel beam.
Specifically, when the preload is removed, for example, the preload and the pre-tension are taken as an example, the removal of the preload and the removal of the pre-tension is equivalent to the relaxation, and the removal of the preload is equivalent to the pressure relief, which is equivalent to the upward loading, for example, the preload is taken as an example. As a result, a midspan negative bending moment is generated, a support positive bending moment is generated at both ends, and a large negative bending moment is generated in the support due to the rest of the load applied after the reduction.
In addition, since the preload is applied to the girder when the girder is in the first connection state, and the preload is removed after the girder is adjusted from the first connection state to the second connection state, it is equivalent to a force having the same magnitude as the preload but opposite in direction to the preload applied to the girder in the second connection state. Taking the preload as the pretension, in this way, the process of applying the pretension and the process of removing the pretension correspond to pretension and tension release, and the pretension load is completely zero from pretension to tension release, but because the two stages are different in state (the first connection state is different from the second connection state), a certain amount of pretension bending moment is stored in the steel beam in a superposed manner, and the part of bending moment is called pretension bending moment (if the preload is preload, called preload pretension bending moment).
104. And respectively calculating the internal force of the steel beam based on the first load and the preload, respectively calculating the internal force of the steel beam based on the second load which is unloaded from the preload and is applied to the steel beam, and superposing the internal forces of the steel beam to obtain the target internal force.
Specifically, the target internal force may be calculated by:
the internal force under the action of the first load and the second load is superposed to obtain the internal force of the load, then the internal forces for applying preload and removing preload are superposed to obtain the pre-internal force, and the pre-internal force and the internal force of the load are superposed to obtain the target internal force.
The basic theory of the structure shows that the distribution of the internal force of the structure is related to the distribution of the rigidity of the structure. The node and the member with high rigidity have large internal force distribution. The node and the member with low rigidity have small internal force distribution. The invention adopts the method that a certain node (support) with larger internal force in a bent member is connected in stages, so that the rigidity of the first stage is weakened relative to the second stage, namely relative to the traditional rigidity, or the certain constraint of the certain node or the certain support of the traditional structure is relieved in the first stage, and the certain constraint or the various constraints are included, or the part of the certain constraint or the parts of the various constraints, such as the bending angle constraint of one end of the bent member. The state of the structure in the first stage (i.e., the first connection state) is referred to as state 1, and in state 1, the preload is applied, so that the conventionally generated large node internal force is necessarily transferred to the small node internal force (rod end internal force) in the conventional structure, and the internal forces of the structure and its components, such as the bending moment of the bent component, are accordingly transferred and redistributed. That is, the preload applied in State 1 produces a preload internal force, such as a bending moment, that is small or even zero at large magnitudes of conventional internal force bending moments and large at small magnitudes. In the second stage, the adjustment configuration is bolted, referred to as state 2. In state 2, removing the preload, which corresponds to applying a load equal to the preload but opposite in direction, may be referred to as a reverse preload, and the reverse preload, of course, produces an internal bending moment that is substantially opposite in direction to the conventional internal bending moment, thereby allowing the entire conventional internal bending moment to be cancelled. The state 1 preload is superimposed with the state 2 unload, and the preload unload is zeroed, i.e., the reverse preload cancels out the preload to zero. Based on different states, although the preload and the unload generate the internal force bending moment in opposite directions, the magnitude distribution is completely different, so that the magnitude distribution cannot be completely counteracted. The residual internal force bending moment after partial offset in the superposition is pre-established before the loading of the traditional structure, so the residual internal force bending moment is called as the pre-internal force bending moment.
That is, the present invention is to apply a load in stages and a measure of internal force by connecting the bolted steel beam to the bracket in stages. The measure of the internal preload refers to the measure of applying preload and removing preload. The method adopts the measures of internal force in advance, mainly utilizes the characteristic that the connection states of two stages are different, applies preload in the first stage and then removes the applied preload in the second stage, so that the steel beam generates a bending moment of internal force in advance which is beneficial to reducing the load bending moment, and the aim of homogenizing the internal force (bending moment) borne by the steel beam is fulfilled.
The basic definition of preload in the measure of the internal force is that the preload is applied in advance and is consistent with the direction and distribution of the loaded load, such as pre-stacking and pre-mounting. Preload is broadly defined as any load and/or effect that is pre-applied in a direction consistent with, distributed in the same direction as, or different from the direction of the load being applied. From the distribution characteristics, a distribution load and/or a concentration load is included. From the application method, the application method can be pretension force (pretension for short), or pre-pressure (pre-pressure for short), pre-counter-tension, pre-counter-pressure, or other loads or actions, or the combination of several or various of the above.
Furthermore, the method for connecting the supports of the bolted steel beams is mainly applied to the condition that the total load borne by the steel beams can be divided into two parts to be applied respectively in the first connection state and the second connection state, but the influence on the structural bending moment amplitude difference of the steel beams after the application is not large.
It will be appreciated that the method of the present invention may be employed so long as the boundary abutment stiffness is generated in stages. In addition, by adopting the scheme of the invention, the preloading and the unloading preloading are respectively applied when the steel beam is in two different connection states, so that the bending moment homogenization of the steel beam can be facilitated, and the bending moment peak value and the amplitude difference of the steel beam are reduced.
It can be known that, in order to calculate the internal force better according to the actual engineering requirements, before calculating the total load borne by the steel beam, the web and flanges of the steel beam may be bolted to the support, and the web and flanges of at least one end of the steel beam may be used as a basis, and then the connection state of the web and flanges of at least one end of the steel beam to the support may be adjusted to the first connection state, and in the first connection state, the connection stiffness of the web and flanges of at least one end of the steel beam to the support is smaller than the connection stiffness of the web and flanges of at least one end of the steel beam to the support during bolting, so that the purpose of generating and loading different loads at different stages to homogenize the internal force of the steel beam in the connection state of the steel beam and the support of the present invention may be achieved.
The derivation and demonstration of the target internal force will be described in detail with reference to the drawings.
Case one
Referring to fig. 6 to 8, the steel beam is taken as a single span beam, the span of the beam is l, the first connection state is hinge support, the second connection state is fixed support (i.e. the steel beam is bolted to the support), the applied preload is the preload consistent with the total load distribution, and the total load is the full span uniform load.
As shown in fig. 6, (a) of fig. 6 shows a bending moment diagram of the steel girder subjected to the first load in a hinge-supported state, and (b) of fig. 6 shows a bending moment diagram of the steel girder subjected to the preload in a hinge-supported state. Firstly, adjusting the connection state of a web plate of a steel beam and a support to enable the steel beam to be in a hinged state, and applying a first load q on the steel beam 1 First load q 1 For a constant load to be distributed vertically, the bending moment at both ends of the steel beam is zero, i.e. M A1 ＝M B1 =0, maximum bending moment Mc is generated during midspan 1 ＝q 1 l 2 /8。
And applying a preload p on the steel girder in a vertically downward direction, at which both ends of the steel girder do not generate a hogging moment, i.e., M Ap ＝M Bp =0, a maximum positive bending moment is generated in the span, that is, the maximum bending moment generated in the span of the steel beam is M Cp ＝pl 2 /8。
As shown in FIG. 7, (a) of FIG. 7 shows the bending of the steel beam in the clamped state to remove the preloadMoment diagram, fig. 7 (b) shows the bending moment diagram of the steel beam under the second load in the clamped state. Secondly, the two ends of the steel beam are adjusted to be fixed by hinging, and the preloading p applied previously is removed, namely the unloading operation is carried out. Compared with the first connection state, the operation is equivalent to that preload p 'with the same magnitude and opposite directions is applied in the second connection state, namely p' = -p, the positive and negative distribution of the generated bending moment is just opposite to that in the first connection state, namely, the positive bending moment M with relatively large amplitude is generated at the two ends of the steel beam at the moment Ap’ ＝M Bp’ ＝p’l 2 /12＝pl 2 12, generating a negative bending moment M with a relatively small amplitude in the span Cp’ ＝p’l 2 /24＝-pl 2 /24。
Since the preload p is applied in the first connection state and then adjusted to the second connection state to be removed, the preload is completely zero in the process, but since the states of the two stages are different, a certain amount of bending moment, which is called pre-internal force bending moment, is stored in the steel beam in a superimposed manner. The pre-internal force bending moment is distributed linearly in a constant amount, which happens to be mutually reduced with the negative bending moment at two ends of the traditional steel beam, so that the bending moment distribution of the steel beam can be further homogenized.
Further, after removing the preload p, the second load q is applied to the steel beam 2 At the moment, the two ends of the steel beam generate extreme negative bending moment M A2 ＝M B2 ＝-q 2 l 2 12, generating a small positive bending moment M in the midspan C2 ＝q 2 l 2 /24。
As shown in fig. 8, (a) in fig. 8 is a superposition of action diagrams of the preload and the unload moment in the two connection states, fig. 8 (b) is a superposition of action diagrams of the moment in the two connection states under the first load and the second load, and fig. 8 (c) is a superposition of action diagrams of the moment in fig. 8 (a) and fig. 8 (b).
Respectively superposing the bending moments at the two ends in the two connection states to obtain a first bending moment amplitude value at the two ends of the steel beam as follows:
in a similar way, the bending moments in the midspan of the two connecting states are respectively superposed to obtain a second target bending moment amplitude of the midspan of the steel beam:
subtracting the absolute value of the formula (3) and the formula (4) to obtain the absolute value to obtain the bending moment amplitude difference delta of the steel beam, namely the bending moment amplitude difference between the two ends of the steel beam and the span (namely the target bending moment)
Due to q 1 +q 2 Q, and q 1 +p<μ q, wherein μ is less than or equal to 1, so
Difference of bending moment (target bending moment)
This shows that, under the action of the vertical load uniformly distributed over the full span of the steel beam, the bending moment amplitude difference obtained by adopting the scheme of the embodiment of the invention is as follows
Bending moment amplitude difference delta compared with two-end hinge analysis of assumed steel beam in traditional technology 1 ＝ql 2 The/8 is reduced, and the amplitude difference delta between the two-end negative bending moment and the mid-span positive bending moment of the steel beam is compared with the two-end fixed support analysis of the traditional assumed steel beam 2 ＝ql 2 The/24 is also reduced and tends to homogenize. Therefore, the method for realizing the pre-internal force connection of the steel beam in a segmented manner can effectively reduce the bending moment amplitude difference between the two ends of the steel beam and the span, so that the method can effectively reduce the bending moment amplitude difference between the two ends of the steel beam and the spanThe stress performance of the steel beam in the structure can be improved, and the safety of the steel beam in the structure can be improved.
Further, as can be seen from the above, the difference in the magnitude of the bending moment is
And q is 1 + p < μ q; thus, there is q 1 +p≤q/4。
When q is 1 If =0, then p ≦ q/4, if p =0, then q 1 ≤q/4。
Namely, through the proportion of adjusting first load, second load and preloading, can effectively improve the moment of flexure width difference of girder steel to make the moment of flexure distribution of girder steel more homogenization.
Case two
Referring to fig. 9 to 11, the first connection state is a hinged state, the second connection state is a fixed state (i.e. the steel beam is bolted to the support), the applied preload is a concentrated pre-tension load consistent with the total load direction, and the total load is a full span uniform load.
As shown in fig. 6 (a), the two ends of the steel beam are adjusted to be in a hinged state, and a part of uniformly distributed vertical load q is applied 1 Zero support bending moment and maximum bending moment M generated in midspan C1 ＝q 1 l 2 /8。
As shown in FIG. 9, in the hinged state, a proper amount of downward pretension P is applied first, and the two-end support bending moment M is AP ＝M AP =0, generating a large positive bending moment M across CP ＝Pl/4。
The web and flanges of the beam are bolted to the brace and the pretension P applied in the previous state, called "let-down", is removed. Compared with the prior state, the method is equivalent to applying pre-tension P' with equal magnitude and opposite directions, and the positive distribution and the negative distribution of the generated bending moment are opposite. The beam end of the steel beam generates positive bending moment M with relatively large amplitude AP’ ＝M BP’ = Pl/8, and a negative bending moment M with relatively small amplitude is generated in the midspan CP’ And (4) = -Pl/8. From pre-tensioning to releasing, the pre-tensioning load is completely zero in the process, but because the states of the two stages are different,a certain amount of bending moment M is stored in an overlapping way APP’ ＝M BPP’ ＝M CPP’ And (5) Pl/8, namely pre-tensioning pre-internal force bending moment. The pretensioning type pretensioning internal force bending moment is distributed in a full span positive bending moment, and the positive bending moment is distributed in a constant straight line with Pl/8. This happens to be mutually subducted with the traditional great support hogging moment, superposes with the traditional less mid-span positive bending moment, makes traditional bending moment distribution can further homogenize.
As shown in fig. 10, (a) of fig. 10 is a bending moment diagram of the steel beam in a fixed state for releasing the pre-tension, and (b) of fig. 10 is a bending moment diagram of the steel beam in a fixed state for bearing the second load. In the second stage of the firm supporting state, the uniformly distributed vertical load q of the rest part is applied 2 And other loads of the rest part, the second stage is actually the traditional two-end fixed support, namely the bending moment distribution generated by the load of the part is the same as that of the traditional stage and is unchanged, M A2 ＝M B2 ＝-q 2 l 2 /12；M C2 ＝q 2 l 2 /24. I.e. the second bending moment is q 2 l 2 /24。
As shown in fig. 11, (a) in fig. 11 is a bending moment diagram in which the first load and the second load are superimposed, fig. 11 (b) is a bending moment superimposed diagram in which the pretension is applied and the pretension is removed, and fig. 11 (c) is a bending moment applied diagram in which the first load, the second load, the pretension and the pretension are superimposed.
By utilizing the superposition principle of the structural theory, the first bending moment and the second bending moment which cause the disappearance of the bending moment of the support and the increase of the midspan bending moment are superposed, and the obtained full-load bending moment loaded by stages is necessarily homogenized. And then superposed with a pre-tensioning type pre-internal force bending moment capable of improving the bending moment distribution, namely, the bending moment obtained by applying a pre-tensioning measure, to obtain a final bending moment, wherein,
It is understood that when the first connection state and the second connection state are other states, for example, the first connection state is a semi-solid, and the preload applied in the second connection state is a pre-tension, etc., the analysis process is similar to that of the first and second cases, and the detailed description thereof is omitted.
It should be noted that the first load q is described above 1 The value can be 0, in which case the steel beam is only under the action of the preload in the first connection state, and similarly under the action of the total load in the second connection state. Therefore, the method of the invention is not only suitable for the condition that the total load of the steel beam can be applied in two stages, but also suitable for the condition that the total load of the steel beam can not be applied in two stages.
Furthermore, the bending moment homogenizing mode of the embodiment of the invention is not only suitable for single-span beams, but also suitable for multi-span beams, wall beams, structural beams, plates, retaining walls and other steel beams.
Furthermore, it should be understood that the definition of bending moment homogenization in the present invention refers to: the bending moment distribution of the steel beam tends to be homogenized, that is, the target bending moment is the bending moment tending to be homogenized, or homogenized bending moment, or bending moment with smaller bending moment amplitude difference or even zero.
Similarly, when the preload is the pre-tension load or the pre-tension load, the force analysis process is the same as the preload and pre-tension analysis process, and the details are not repeated here.
It should be appreciated that the method of the present invention is applicable not only to new projects, but also to existing renovation projects. Specifically, when the method is applied to a new construction, the total load and the preload of the steel beam can be obtained through simulation, analysis and calculation, and then the preload and the total load are applied in stages according to the actual installation condition of the steel beam.
The support connecting method of the bolted steel beam provided by the embodiment of the invention mainly generates the connecting state of the steel beam and the support in stages by human initiative, applies the total load born by the steel beam in stages correspondingly, applies the preload in stages and removes the preload in stages, thereby effectively reducing the amplitude difference of positive and negative bending moments between two ends of the steel beam and a span, being further beneficial to improving the stress performance and the economical efficiency of the steel beam in the structure and providing a direction for the feasibility of the structural scheme of the steel beam.
The support connection method of the bolted steel beam disclosed by the embodiment of the invention is described in detail, a specific example is applied in the method to explain the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (6)
1. A method of connecting supports of bolted steel beams, the method comprising:
calculating the total load borne by the steel beam;
adjusting the connection states of a web plate and a flange at least one end of the steel beam and a web plate and a flange of a support respectively so as to enable the steel beam and the support to be in a first connection state, wherein the first connection state is any one of an unconnected state, a hinged state or a semi-fixed state, and a first load and a preload which are born by the steel beam in the first connection state are applied;
bolting a web and at least one flange of at least one end of the steel beam to a web and flange of the brace, removing the preload on the steel beam, and applying a second load on the steel beam;
wherein the sum of the magnitude of the first load and the magnitude of the second load is equal to the magnitude of the total load;
the first load is uniformly distributed load and/or concentrated load, the second load is vertical load, or the second load comprises vertical load and horizontal load.
2. The method of claim 1, wherein the at least one flange at the at least one end of the steel beam is displaceable relative to the bracket in a direction along the axis of the steel beam when the steel beam is in the first connection with the bracket.
3. The method of claim 2, wherein the brackets are provided with threaded holes for connection to the web and flanges of the steel beam, the threaded holes being elongated holes extending lengthwise along the axis of the steel beam.
4. A method according to any one of claims 1 to 3, wherein when said first connection is semi-braced, said flanges are bolted to flanges of said support for directly supporting a floor panel.
5. A method according to claim 4, wherein for a flange for directly supporting a floor panel, the flange is bolted to a flange of the carrier with the nut end of the connecting bolt of the flange disposed away from the floor panel and the non-nut end of the connecting bolt of the flange facing the cavity protection component in the floor panel.
6. A method according to claim 4, wherein for flanges used to directly support roof panels, protective sleeves and connecting bolts are placed through the roof panels on the flanges prior to bolting to the flanges of the support, and wherein the connecting bolts on the flanges are placed partially exposed to the protective sleeves.
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| CN1099086A (en) * | 1993-04-01 | 1995-02-22 | 大能产业株式会社 | Prestressing force composite beam works job practices and be used for the prestressing force composite beam of this method |
| CN106638961A (en) * | 2017-01-10 | 2017-05-10 | 北京交通大学 | Assembly type steel frame connection node with post-seismic recoverable function |
| CN106968348A (en) * | 2017-04-17 | 2017-07-21 | 苏州科技大学 | A kind of Self-resetting steel-frame beam column connected node |
| CN109930699A (en) * | 2019-03-07 | 2019-06-25 | 深圳市建筑设计研究总院有限公司 | The connection structure of girder steel and beams of concrete |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1099086A (en) * | 1993-04-01 | 1995-02-22 | 大能产业株式会社 | Prestressing force composite beam works job practices and be used for the prestressing force composite beam of this method |
| CN106638961A (en) * | 2017-01-10 | 2017-05-10 | 北京交通大学 | Assembly type steel frame connection node with post-seismic recoverable function |
| CN106968348A (en) * | 2017-04-17 | 2017-07-21 | 苏州科技大学 | A kind of Self-resetting steel-frame beam column connected node |
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