METHOD OF CONTROLLING THE DISTRIBUTION OF INTERNAL FORCES AND DEFORMATIONS ALONG THE FRAME STRUCTURE AND THE FRAME STRUCTURE
A frame structure is configured to be connected to a frame rafter with a roof plane braced with horizontal bracing and walls braced with vertical bracing. The frame structure includes a column having a profile selected from a profile group consisting of two back-to-back oriented profiles, two face-to-face oriented profiles, one open profile, and one closed profile, said column comprising a web connected to a flange. A base of the web is provided with a simple connection with anchors for attachment to a concrete base. A bracket is attached to the flange by connecting elements through holes. The brackets have vertical sides with vertical guides for anchor rods for embedding in the concrete base. At least one of the anchor rods is provided with at least one rectification nut below the vertical guide and at least one securing nut above the vertical guide.
This application is a continuation of International Application No. PCT/CZ2024/000025, filed Sep. 12, 2024, which published in the English language as WO 2025/067574 A1 on Apr. 3, 2025, and which claims priority under 35 U.S.C. § 119(b) to Czech Patent Application No. PV 2023-372, filed on Sep. 29, 2023, the disclosures of which are incorporated herein by reference in their entireties.
BACKGROUND OF THE DISCLOSUREThe invention relates to frame structures and a method of controlling the distribution of internal forces and deformations along a frame structure.
The design of steel structures is a highly specific field. The reliability and durability of structures are mainly determined by the connections.
The current level of knowledge of the analysis of steel structures and the approach to the design of connections is based on traditional knowledge, which is further developed and integrated in the component method in the Eurocode EN 1993-1-8 (2005): Eurocode 3: Design of steel structures Part 1-8: Design of joints [Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC, Directive 2004/18/EC], which has become part of the current standards. While this approach may not be part of all standards in the world to the extent that it is currently in the European Standards, the principles are not different and are taught in engineering courses around the world. Decomposing a connection and describing its individual components not only in terms of strength but also it's stiffness and then composing them into a comprehensive structural model is a concept that has been used for decades around the world.
Typical components according to the Eurocode are column web in shear, column flange in compression, column flange in tension, column flange in bending, end plate in bending, angle cleat in bending, bolts in tension, bolts in shear, bolts in compression, concrete in compression, end plate in bending under compression, base plate in bending and tension, anchor bolts in tension. Any analysis of the connection must be based on these principles or at least take them into account.
Analytical methods have been developed for each of the above components. These methods are publicly available and describe the ultimate strength and stiffness or flexibility of each component. However, these methods have their limitations. Each of these components has a different level of analytical complexity, which in turn affects the reliability of the final results. From a technical point of view, this is a type of analysis where very large and very small numbers are combined and any uncertainty significantly affects the final solution. A typical example is the concept of effective lengths in T-stub analysis in Eurocode EN 1993-1-1 (2005): Eurocode 3: Design of steel structures Part 1-1: General rules and rules for buildings [Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC, Directive 2004/18/EC]. The effective length determined by the shape of the plastic lines and the energy associated with achieving plastic response along these lines can be a source of computational uncertainty in determining the tensile capacity of a T-section. There is no doubt that determining its stiffness is an order of magnitude more complicated.
While the resulting ultimate capacity of a component can be determined with sufficient accuracy even with respect to the above, the situation is quite different in the case of stiffness analysis, since the range of results is very sensitive to any kind of imperfection, either material or geometric, or even inaccuracies due to the mathematical approximation inherent in the analytical formulae. This affects the final result of the initial rotational stiffness of the connection when the components are compound back into the model. This is the reason why the method is suitable for determining the ultimate capacity of a connection but unsuitable for determining the rotational stiffness of a connection. This is a well-known phenomenon in current practice.
Romeo et al. describe in Riccardo Romeo, Eric Puntel, Simone Pierobon, Nadia Baldassino, Component method applied to base plate connections of steel racks, Journal of Constructional Steel Research, 2023 the difficulties in applying the above component method to column bases in case of racking systems. It shows that the prediction of moment capacity has sufficient reliability when compared with experimental data, while the prediction of rotational stiffness is difficult and cannot be relied upon. It requires testing in the laboratory even for the very simple connection that his racking system uses. Šabatka, Lubomír Šabatka, DrahošKolaja, Martin Vild, František Wald, Jaromír Kabeláč, Marta Kuříkovś, Joint stiffness and its influence on design of steel structural elements, Czech Technical University, Prague, pointed out the difficulties of the component method in estimating the rotational stiffness of very standard connections. The discrepancies he encountered were in the tens of percentages. The discrepancies described affect the frame analysis so significantly that they may not reflect the real behavior of the structure, especially not on frames with a higher degree of statical indeterminacy. This could lead to underestimation of the design and cause building failures. Pan describes in Jianrong Pan, Shizhe Chen, Zhan Wang and Hui Lu, Initial rotational stiffness of minor-axis flush end-plate connections, Advances in Mechanical Engineering 2018, Vol. 10(1) 1-9 uncertainties in the analytical determination of T-stub stiffness relative to the minor axis. Components such as end plate in bending, angle in bending, concrete in compression, end plate in bending and compression, column end plate in bending and tension, column flange in bending show higher sensitivity to any kind of imperfections.
The construction of single-story and multi-story buildings is normally carried out as a framed structure with moment resisting connections. Typically, frame structures are made of rolled or welded sections. Developments in technology and new construction details allow for more frequent use of cold-formed sections for smaller buildings.
The great advantage of cold-formed profiles is their low weight, which allows easy handling without the use of heavy machinery. However, the cold-formed profiles are more susceptible to local loss of stability and thus lead to a different type of detailing than traditional steel structures.
The stability of the portal frame is strongly influenced by two cross-section parameters, namely the torsional constant and the warping constant of the profile. These two parameters are usually one of the weakest points of modern open thin-walled frame structures. The deplanation of an open section is related to the bimoment acting on the flanges of the section. This form of deformation occurs when the profile is loaded by transverse shear, if the load is eccentric with respect to the shear center (in this case the so-called Wagner term).
The frame structure consists of vertical elements, columns, horizontal elements: frame rafters or floor beams and bracings in the vertical and horizontal planes, connected by either rigid or flexible connections to form a spatial structure. The frame structure includes moment connections and hinge connections. The hinge connections are simple and allow rotation in the joint. Moment connections are rotationally rigid or semi-rigid and are more complex in design.
Moment connections do apply typically to frame structures made of hot rolled profiles. It is not easy to achieve moment-bearing connections in cold-formed frame structures. Often only so-called semi-rigid connections can be achieved. Due to these complications, the connections of columns to the concrete foundation are most often made as hinged connections.
The most common connection to the foundation structure that achieves moment capacity uses a welded plate attached trough the web of the column. This type of connection is commonly used nowadays, and its moment capacity depends on the number and arrangement of bolts passing through the column, the thickness of the column flange and web and its material, the tensile capacity of the anchors used, and the flexibility of the column base end plate including the anchors. Experience with this type of connection shows that the achievable moment capacity and rotational stiffness tend to be too low and the tensile forces in the anchors tend to get higher when the anchors are placed too close together. The documents below describe the specific solutions known to date.
Document US 2023110886 A1 describes the increase of the moment capacity of a joint by welding an end plate in order to increase the ductility of the joint. The solution is oriented to structures subjected to seismic loads.
The documents US 20230110886 A1 and US 20210095491 describe the increase in ductility of a connection in the load spectra typical for earthquake loading, i.e. accidental loading of a cyclic character that results in a damage to a connection that is designed for the effects of permanent and variable loading only. It is therefore an add-on device that improves a connection designed for a different loading spectra. This design solution is suitable for conventional hot rolled sections and takes advantage of the toughness of the thick column flange, which is stressed by a combination of local compressive loading and local flange bending, and relies on contact with the concrete through the face plate. The solution is not suitable for use with cold-formed sections which are sensitive to local concentrated loads. Also, a welded end plate connection is not feasible in case of cold formed profiles. It also, does not prevent warping of the cross-section, it also does not allow the rectification of column by its rotation with respect to the concrete foundation.
The document US 20210095491, which represents a connection with a DAA mechanism, does not act as a moment connection in the load spectra that corresponds to the ultimate limit state. The joint cannot be considered as a rotationally rigid because the web is not welded to the end plate at all. In a structural analysis, such a connection would have to be considered as a connection with zero rotational stiffness.
The document US 2018313053 A1 describes a solution using brackets cast in concrete. This causes limitations during the construction phase, as the horizontal and vertical positioning of the brackets may be inaccurate before concreting, or they may be displaced during concreting or omitted altogether. The erection of the structure may then be adversely affected.
EP 0864702 A1 describes a solution that uses an end plate welded to the column base. The moment capacity of the connection and, in particular, its rotational stiffness is then dependent on the flexibility of the end plate. The disadvantage of this connection is that it is intended only for columns made of two profiles oriented back-to-back and the asymmetry of the connection, where the bolts in the opposite flanges always pass through the opposite profile and the mobilization of connection then occurs only by engaging the fasteners, i.e. the bolts passing through the web of column profile. The asymmetry of the connection can also result in stresses in the connection causing torsional stresses and deformation of the connection.
The document US 200200952275 describes the pinned connection between the column and the concrete foundation, which is considered as in the design of a structure for a combination of permanent and variable loads. The method proposes to widen the concrete foundation by concreting the column and filling the gap between the column and the new concrete with an elastic material. This modification ensures that in the event of earthquake loading, the steel column contacts the new concrete through the layer of elastic material. This will transfer stresses from the earthquake to the foundation by bending moment. This solution does not allow the column to rotate, it does not prevent deplaning of the cross-section. The connection behaves like a hinge under the loading typical for ultimate and serviceability limit states and therefore does not allow the transfer of bending moment under constant and variable loads. Another pinned connection is also described in the CN document 203452266.
The documents CN 110318479, CN 110835974 and CN 113374079 is supposed to describe the earthquake resistant connection between the column and the concrete foundation. The connection does not provide moment capacity or rotational stiffness with respect to either the major or minor axis, and does not prevent warping deplanation of the cross-section. At the same time, they do not meet the standard anchorage requirements for portal frame connections. According to the CN document 110318479, the connection does not transmit any horizontal loads, due to the length of the anchors above the concrete foundation, they will bend at very low forces, the same applies to vertical loads, where the spring stiffness cannot reach sufficient level, and does not prevent the whole building from being lifted up by wind suction and the subsequent destruction of the concrete foundation when dropped down. The connection acts as a mechanism and cannot be used in the building structure.
The disadvantage of the above solutions is that they are not structurally adapted to the connection of a thin-walled cold-formed column with a concrete foundation and do not always allow the control of the rotational stiffness of the connection and its moment capacity. Another disadvantage is that they require the anchors to be fitted before the foundation structure is concreted.
BRIEF SUMMARY OF THE DISCLOSUREA method of controlling the distribution of internal forces and deformations along a frame structure comprising columns connected to rafters or beams and roof and side planes braced in their planes with bracing members, according to the invention, resides in the ability of continuous varying of the distribution of internal forces and deformations along the frame structure by adjusting the magnitude of the rotational stiffness and adjusting the magnitude of the moment capacity of the connection between the column and the concrete foundation, and by adjusting the magnitude of the rotation of the column relative to the concrete foundation.
The adjustment of the magnitude of the column's rotation relative to the concrete foundation is preferably carried out by adjusting the height of both the rectification nuts located on the threaded anchoring rod of the upper part of the anchoring rods below the vertical guides of the anchoring rods, connected to the lower end of the column, and at the same time the securing nuts located on the threaded rods of the upper part of the anchoring rods above the vertical guides of the anchoring rods, with the upper part passing through the vertical guides and the lower part embedded in the concrete foundation.
In a further preferred embodiment, the adjustment of the amount of rotation of the column relative to the concrete foundation is performed by height adjustment of the rectification and securing nuts to continuously control the amount of rotation of the column relative to the concrete foundation until the required value is reached at the completion of the assembly. Preferably, the controlling of the amount of rotation of the column relative to the concrete foundation is repeatedly carried out by a scanning device placed between the bracket and the concrete foundation at least until the required value is reached at the end of the installation.
By the column rotation it is meant the angular change between the medium axis of the column and the horizontal plane of the concrete foundation caused by the adjustment of the rectification and securing nuts. This rotation may or may not be associated with the generation of forces and stresses at the connection, depending on whether the rotation is induced on the frame structure or on a separate member.
Angular or rotational deformation in the connection is associated with the transfer of forces from the load. Its magnitude is determined by the dimensions, shape and material of the parts of the connection and their deformability under load. The rotation of the connection is then the resultant of the increments of deformations of all parts of the connection.
The required rotational stiffness of the connection yields from the global analysis. It is the value of rotational stiffness at which the optimum distribution of internal forces over the frame structure occurs. The required bending moment is the magnitude of the bending moment from the load generated in the connection, which corresponds to the required rotational stiffness. The moment capacity of the connection must be greater than the required bending moment and at the same time the moment capacity of the concrete foundation must be greater than the required bending moment.
Preferably, the setting of the magnitude of the rotational stiffness and the setting of the magnitude of the moment capacity of the column-concrete base connection is carried out in a decision cycles in incremental steps, where in the first step is tested the possibility of installing the brackets on the standalone column only at a time when the other elements of the frame structure have not yet been installed, then the connection between the column and the concrete foundation transmits the internal forces and, in particular, the moments from all loads and, if the moments from all loads are greater than the moment capacity of the concrete foundation or the connection between the column and the concrete foundation, then either the moment capacity of the concrete foundation can be increased by changing its dimensions or the dimensions of the bracket connection, consisting of a brackets with vertical guides on its vertical sides for anchor rods, or the second step is proceeded to, where it is proposed to install the brackets on the standalone frame, when the frame consisting of columns and frame rafters is assembled, then the connection between the column and concrete foundation transfers the internal forces and especially the moments from the permanent loads from the dead weight of the purlins and the cladding and any variable loads from wind and snow and the service loads and if the internal forces and especially the bending moments from these loads are greater than the moment capacity of the concrete foundation or the column-concrete base connection, either the moment capacity of the concrete foundation may be increased by changing its dimensions or the dimensions of the brackets or the third step may be followed, where it is proposed to install the brackets on the finished frame with purlins and bracing system already installed, then the column-concrete base connection shall transmit the internal forces and especially the moments from the permanent loads from the dead weight and any variable loads from wind and snow and the loads due to services, and if the internal forces and especially the bending moments from these loads are greater than the moment capacity of the concrete base or the column-concrete base connection, either the moment capacity of the foundation may be increased by changing its dimensions or the dimensions of the brackets, or the fourth step may be followed, where it is proposed to mount the brackets on the finished frame with purlins, bracing systems and cladding already installed together with the other permanent loads, then the column-concrete base connection will transmit the internal forces and especially the bending moments from the variable wind and snow loads and the loads due to additional services only, and if the internal forces and especially the bending moments from these loads are greater than the moment capacity of the concrete foundation or column connection with the concrete foundation, the moment capacity of the concrete foundation can be increased by changing its dimensions and the moment capacity of the column-concrete base connection can be increased by changing its dimensions, or the first step is proceeded to, and the decision cycle with incremental steps is proceeded in this decision cycle with a change in the selection of the connection parameters until the strength condition is fulfilled, where the applied bending moment is less than the lesser of the moment capacity of the column-concrete base connection.
In a further preferred embodiment, the setting of the magnitude of the rotational stiffness and the setting of the magnitude of the moment capacity of the column-concrete base connection is performed in a decision iteration cycle where the analytical model successively selects the quantity, dimensions and materials of the top elastic washers, top steel washers, bottom steel washers and bottom elastic washers and the material and dimensions of all parts of the column-concrete base connection up to the required magnitude of the rotational stiffness and the required magnitude of the moment capacity of the column-concrete base connection.
A frame structure for controlling the distribution of internal forces and deformations along a frame structure comprising columns connected to rafters having a roof plane stiffened with horizontal bracing members and walls stiffened with vertical bracing members, according to the invention, further comprising a column comprising at least one web connecting two flanges, wherein the base of the column is provided with a simple connection with anchors for attachment to the concrete foundation and at least one bracket is connected to the column flange by fasteners through holes, the bracket having vertical guides on its vertical sides for anchor rods for anchors in the concrete base, the anchor rods being provided with at least one rectifying nut below the vertical guides and at least one securing nut above the vertical guides.
In a preferred embodiment, the anchor rod is further provided with at least one bottom steel washer placed between the bracket vertical guide and the rectification nut and at least one top steel washer placed between the bracket vertical guide and the securing nut.
Preferably, a top flexible washer is placed between the top steel washers and a bottom flexible washer is placed between the bottom steel washers.
The simple connection between the base of the column and the concrete foundation is preferably formed by elements selected from the group: at least one bolted angle, welded end plate, metal plate in concrete.
The bracket is preferably selected from the group: flat plate, end-bent plate.
The frame structure is preferably a steel structure.
In various preferred embodiments, the diameter of the fasteners is equal to or larger than the diameter of the holes, or the diameter of the fasteners is smaller than the diameter of the holes to allow for initial slippage and redistribution of bending moments.
The fasteners are conveniently selected from the group of bolts with nuts, self-tapping screws and self-drilling screws.
The column is preferably selected from the group of two back-to-back oriented uni-axial symmetrical profiles, two face-to-face oriented uni-axial symmetrical profiles, one open profile, one closed profile.
Preferably, the space between the column flanges is filled with concrete.
The bracket is preferably in a shape selected from the group an n-angle polygon, where n is 3 to 8, a circle, an oval and an irregular surface.
The vertical guide is conveniently connected to the plate of the bracket in an asymmetrical design. In preferred embodiments, it is formed by elements selected from the group: circular tube, square tube, rectangular tube, oval tube.
The anchor in the connection between the base of the column and the concrete foundation is preferably made up of elements selected from the following groups: chemical anchor, mechanical anchor, screw anchor.
The frame structure for controlling the distribution of internal forces and deformations according to the technical design allows easy implementation of the moment connection of the steel column to the concrete foundation using standardized bolted brackets. The mechanical properties of the connection, rotational stiffness and moment capacity can be controlled by selecting the correct geometry and materials. The connection's deformation characteristics, when properly designed, ensure that the slender profile of the column connected to the concrete foundation does not get damaged. The connection can be made on a newly constructed structure or on an existing structure where an increase in load capacity is required.
These properties can be used to optimize frame structures and thus save material or to increase the load capacity of existing structures when snow loads increase due to climate change, in line with the latest adjustment of European standards for loads, or for buildings where solar panels will be retrofitted and the existing load capacity of the frame is insufficient. Another possible use of the connection is when designing a strategy against column damage from building traffic. The connection allows the installation of a barrier against impact by, for example, a forklift truck.
Another advantage of the certain embodiments of the proposed connection is that in a fire scenario, when the highest temperature is reached under the ceiling or the roof structure, the connection between the column and the concrete foundation is still relatively cold, thus showing moment capacity in a situation where the roof structure loses stability due to increased temperature. This can control the roof collapse which happens inward the building which tends to prevent the fire from spreading to surrounding buildings.
Another advantage of certain embodiments of the proposed connection is that the column is rigidly connected to the foundation during the installation and there is no need for temporary stabilization. This contributes to the reduction of accidents in terms of health and safety protection on site. In addition, the column's verticality can be rectified during installation using rectification nuts.
Embodiments of the invention include any combination of embodiments according to the following clauses.
Clause 1. A frame structure connected to a frame rafter with a roof plane braced with horizontal bracing and walls braced with vertical bracing, the frame structure comprising: a column (6) having a profile selected from a profile group consisting of two back-to-back oriented profiles, two face-to-face oriented profiles, one open profile, and one closed profile, said column comprising a web (18) connected to a flange (19), wherein a base of the web (18) is provided with a simple connection (7) with anchors (11) for attachment to a concrete base (9), and a bracket (1) is attached to the flange (19) by connecting elements (16) through holes (12), the bracket having vertical sides with vertical guides (2) for anchor rods (15) for embedding in the concrete base (9), at least one of the anchor rods being provided with at least one rectification nut (8) below the vertical guide (2) and at least one securing nut (5) above the vertical guide (2).
Clause 2. The frame structure of clause 1, further comprising a second flange (19), wherein the base of the web (18) is provided with a simple connection (7) with anchors (11) for attachment to a concrete base (9), and the bracket (1) or a second bracket (1) is attached to the flange (19) by connecting elements (16) through holes (12), the bracket or the second bracket having vertical sides with vertical guides (2) for anchor rods (15) for embedding in the concrete base (9), at least one of the anchor rods being provided with at least one rectification nut (8) below the vertical guide (2) and at least one securing nut (5) above the vertical guide (2).
Clause 3. The frame structure of clause 1, wherein the anchor rod (15) further comprises at least one bottom steel washer (13) positioned between the vertical guide (2) of the bracket (1) and the rectification nut (8), and at least one top steel washer (4) positioned between the vertical guide (2) of the bracket (1) and the securing nut (5).
Clause 4. The frame structure of clause 3, wherein a top elastic washer (3) is placed between the top steel washers (4) and a bottom elastic washer (14) is placed between the bottom steel washers (13).
Clause 5. The frame structure of clause 1, wherein the simple connection (7) between the base of the column (6) and the concrete base (9) is formed by elements selected from the group consisting of at least one bolted angle, a welded base plate (17), and an anchoring plate (24) encased in concrete (20).
Clause 6. The frame structure of clause 1, wherein the bracket (1) is selected from the group consisting of a flat plate and a plate having ends and being folded at the ends.
Clause 7. The frame structure of clause 1, wherein the frame structure is a steel structure.
Clause 8. The frame structure of clause 1, wherein a diameter of the connecting elements (16) is equal to or greater than a diameter of the openings (12).
Clause 9. The frame structure of clause 1, wherein a diameter of the connecting elements (16) is smaller than a diameter of the openings (12).
Clause 10. The frame structure of clause 1, wherein the connecting elements (16) are selected from the group consisting of bolts with nuts, self-tapping bolts, and self-drilling bolts.
Clause 11. The frame structure of clause 1, wherein a space between the flanges (19) of the column (6) is filled with concrete (20).
Clause 12. The frame structure of clause 1, wherein the bracket (1) has a shape selected from the group consisting of an n-angle polygon where n is 3 to 8, a circle, an oval, and an irregular surface.
Clause 13. The frame structure of clause 1, wherein the vertical guide (2) is asymmetrically connected to the bracket (1).
Clause 14. The frame structure of clause 1, wherein the vertical guide (2) comprises elements selected from the group consisting of a circular tube, a square tube, a rectangular tube, and an oval tube.
Clause 15. The frame structure of clause 1, wherein the anchors (11) at the connection between the column base and the concrete base (9) comprise elements selected from the group consisting of a chemical anchor (21), a mechanical anchor (22), and a screw anchor (23).
Clause 16. A method comprising: selecting a stage of construction of a frame structure according to clause 22, the stage of construction being selected from the group consisting of installation of the bracket (1) on a standalone column (6) before other frame elements are mounted, installation of the bracket (1) on a standalone frame after columns (6) and frame rafters are assembled, installation of the bracket (1) on a frame after purlins and bracing system are installed, and installation of the bracket (1) on a frame after purlins, bracing systems, cladding, and other permanent loads are installed; determining the loads to be transmitted by the connection between the column (6) and the concrete base (9) corresponding to the selected stage of construction; selecting dimensions and materials of the bracket (1), the vertical guides (2), and the anchor rods (15) such that a rotational stiffness and moment capacity of the connection between the column (6) and the concrete base (9) are each set to values at which an applied bending moment in the connection does not exceed the moment capacity of the connection between the column (6) and the concrete base (9); and physically installing the bracket (1) on the column (6) and embedding the anchor rods (15) in the concrete base (9) at the selected stage of construction.
Clause 17. The method of clause 16, wherein the selecting dimensions and materials further comprises adjusting a height of the rectification nuts (8) located on a threaded upper part of the anchor rods (15) below the vertical guides (2) of the bracket (1); and at or near a same time adjusting the securing nuts (5) located on the threaded upper part of the anchor rods (15) above the vertical guides (2) of the bracket (1), with the upper part of the anchor rods (15) passing through the vertical guides (2) and a lower part of the anchor rods embedded in the concrete base (9), to set a magnitude of a rotation of the column (6) relative to the concrete base (9).
Clause 18. The method of clause 16, wherein a magnitude of the rotation of the column (6) relative to the concrete base (9) is continuously controlled by adjusting a height of the rectification nuts (8) and the securing nuts (5) until a required value of the magnitude of the rotation of the column (6) relative to the concrete base (9) is reached at an end of a process of assembly.
Clause 19. The method of clause 16, wherein continuous controlling the magnitude of the rotation of the column (6) relative to the concrete base (9) is repeatedly carried out by a sensor device positioned between the bracket (1) and the concrete base (9) at least until the required value is reached at the end of assembly.
Clause 20. The method of clause 16, wherein the selecting dimensions and materials of the bracket (1), the vertical guides (2), and the anchor rods (15) is performed by sequentially selecting in an analytical model a quantity, dimensions, and materials of top elastic washers (3), top steel washers (4), bottom steel washers (13), and bottom elastic washers (14) and the material and dimensions of all parts of the connection between the column (6) and the concrete base (9) up to a desired rotational stiffness and a desired magnitude of the moment capacity of the connection between the column (6) and the concrete base (9).
The following detailed description will be better understood when read in conjunction with the appended drawings. For illustrative purposes, there are shown in the drawings various embodiments, including embodiments which may be presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings, which are at least partially schematic:
Certain terminology is used in the following description for convenience only and is not limiting.
The words “right,” “left,” “lower,” and “upper” designate directions in the drawings to which reference is made. The words “inner” and “outer” refer to directions toward and away from, respectively, the geometric center of an object and designated parts thereof. Unless specifically set forth otherwise herein, the terms “a,” “an,” and “the” are not limited to one element but instead should be read as meaning “at least one.” “At least one” may occasionally be used for clarity or readability, but such use does not change the interpretation of “a,” “an,” and “the.” Moreover, the singular includes the plural, and vice versa, unless the context clearly indicates otherwise. “Including” as used herein means “including but not limited to.” The word “or” is inclusive, so that “A or B” encompasses A and B, A only, and B only. The terms “about,” “approximately,” “generally,” “substantially,” and like terms used herein, when referring to a dimension or characteristic of a component, indicate that the described dimension/characteristic is not a strict boundary or parameter and does not exclude minor variations therefrom that are functionally similar. At a minimum, such references that include a numerical parameter would include variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit thereof.
Example 1A single-story portal frame type of building was designed for difficult climatic conditions with snow and wind loads and with the requirement for increased traffic inside and outside of the building. The most suitable solution from all possible options appears to be the solution where the space between the flanges 19 of the column 6 is filled with concrete 20, since the steel-concrete column together with the brackets 1, see
In the second step, the connection is activated during the assembly of a portal frame without purlins, and bracing systems. This achieves a different load level for the design of the column base connection, which corresponds to the variable load from snow and wind and all permanent loads except for the self weight of the frame members themselves.
In the third step, the column base connection is activated during the assembly of the frame structure, including bracing system and purlins. A structural analysis of the frame is performed again, this time for permanent loads from the cladding and any other permanent loads and variable loads from wind and snow.
In the fourth step, the column base connection is activated on the frame structure that includes bracing system, purlins, rafters, cladding, and any other permanent loads. Therefore, forces due to variable loads from wind and snow only are transferred by the column base connection. This will be reflected in the structural analysis in this step.
Furthermore, the dimensions of the bracket 1, material and a number of top steel washers 4, top elastic washers 3, bottom steel washers 13 and bottom elastic washers 14, and the diameter, material and the length of the anchor 15 were gradually selected in the analytical model, see
Based on the above design from the simulation performed on the analytical model, the brackets 1 were mounted on a standalone frame, as shown in
Due to the change of use of an existing building, new solar panels need to be installed on the roof. The load on the roof has been increased due to the additional weight. The analysis showed that the frame structure of the existing building cannot support the increased load, but there is a reserve in the concrete foundation 9.
The brackets 1 were connected to the column 6 base on a portal frame with already erected purlins, roof bracing systems and other structural parts contributing to the permanent loading and anchored to the concrete foundation 9 with anchoring rod 15. Rectification nuts 8 on the inner side of column are tightened strongly against bracket 1. A top elastic washer 3 has been used under the securing nut 5 on the anchor rod 15.
Once all brackets were installed on all the columns, the solar panels can be installed on the roof. After the solar panels are installed, the bracket base connection transfers the internal forces and especially the bending moments from the variable loads due to the wind and snow and the increased live load from the solar panels. In order to avoid exceeding the bearing moment of the concrete foundation 9 in the soil, the top elastic washers 3 were used under the securing nut 5 on the anchor rods 15 to offset the magnitude of the rotational stiffness of the column base connection in order to match the magnitude of the required bending moment.
The bracket connection changes the distribution of internal forces along the frame structure so that the roof can withstand the increased load, while still ensuring that when the limit load is reached, the elastic deformation of the top elastic washers 3 causes the bracket connection to rotate and therefore the limiting moment capacity of the connection does not get exceeded.
Example 3According to the invention, a single-story portal frame type of building was designed with the requirement of a moment capacity of the connection of the column 6 to the concrete foundation 9 to achieve the stabilization of the column 6 during the fire situation where a building is expected to collapse inwards, so the fire does not get spread on neighboring buildings. The highest temperature is reached at the level of the frame rafters or floor beams, while the column footings 6 still remain in a relatively cold region, so that they are able to maintain some moment capacity required just for a fire situation. This mechanism can be used to control the roof collapse during the fire scenario, where the roof collapses inwards and the fire does not spread to surrounding buildings. The bracket connection was designed in a decision iterative cycle, where the analytical model iteratively selected the quantity, dimensions and materials of the top elastic washers 3, top steel washers 4, bottom steel washers 13 and bottom elastic washers 14 and the material and dimensions of all parts of the bracket connection up to the required magnitude of the rotational stiffness and the required magnitude of the moment capacity of the connection of column 6 to the concrete foundation 9, so that its moment capacity is higher than the moment in the column footing corresponding to the fire collapse of the rafters.
Example 4The building where the local damage to the cladding or its connection to the frame structure occurred due to the parasitic stresses in the envelope that were not taken into account by the building design was reinforced by the application of brackets 1 at the joint of column 6 and concrete foundation 9.
The hinged or semi-rigid footing of the existing building with welded base plate 17, see
Another embodiment of the invention addresses the increase in moment capacity by utilizing the composite interaction of the columns with concrete infilling the space between the column 6 flanges, as shown in
Another embodiment of the invention addresses the case of structures that are not symmetrical, for example, with differently spaced vertical bracing in side or gable walls thereof, where torsional stresses typically on the gable column may occur. In these cases, the bracket connection transfers the torsional moment to the foundation.
In these cases it is advantageous to use both closed and open profiles. Example of closed profiles, square rolled tubes, are shown in
When an open profile is used, see
With respect to the methods and processes described herein, those skilled in the art will recognize that boundaries between the above-described operations are merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Further, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure.
LIST OF REFERENCE SIGNS
-
- (1) Bracket
- (2) Vertical guide
- (3) Top elastic washer
- (4) Top steel washer
- (5) Securing nut
- (6) Column
- (7) Simple connection
- (8) Rectification nut
- (9) Concrete foundation
- (10) Bolt of a simple angle cleat connection
- (11) Anchoring bolt
- (12) Openings
- (13) Bottom steel washer
- (14) Bottom elastic washer
- (15) Anchoring rod
- (16) Connecting element
- (17) Base plate
- (18) Web
- (19) Flange
- (20) Concrete
- (21) Chemical anchor
- (22) Mechanical anchor
- (23) Screw anchor
- (24) Anchoring plate
Claims
1. A frame structure connected to a frame rafter with a roof plane braced with horizontal bracing and walls braced with vertical bracing, the frame structure comprising:
- a column (6) having a profile selected from a profile group consisting of two back-to-back oriented profiles, two face-to-face oriented profiles, one open profile, and one closed profile, said column comprising a web (18) connected to a flange (19),
- wherein a base of the web (18) is provided with a simple connection (7) with anchors (11) for attachment to a concrete base (9), and a bracket (1) is attached to the flange (19) by connecting elements (16) through holes (12), the bracket having vertical sides with vertical guides (2) for anchor rods (15) for embedding in the concrete base (9), at least one of the anchor rods being provided with at least one rectification nut (8) below the vertical guide (2) and at least one securing nut (5) above the vertical guide (2).
2. The frame structure of claim 1, further comprising a second flange (19), wherein the base of the web (18) is provided with a simple connection (7) with anchors (11) for attachment to a concrete base (9), and the bracket (1) or a second bracket (1) is attached to the flange (19) by connecting elements (16) through holes (12), the bracket or the second bracket having vertical sides with vertical guides (2) for anchor rods (15) for embedding in the concrete base (9), at least one of the anchor rods being provided with at least one rectification nut (8) below the vertical guide (2) and at least one securing nut (5) above the vertical guide (2).
3. The frame structure of claim 1, wherein the anchor rod (15) further comprises at least one bottom steel washer (13) positioned between the vertical guide (2) of the bracket (1) and the rectification nut (8), and at least one top steel washer (4) positioned between the vertical guide (2) of the bracket (1) and the securing nut (5).
4. The frame structure of claim 3, wherein a top elastic washer (3) is placed between the top steel washers (4) and a bottom elastic washer (14) is placed between the bottom steel washers (13).
5. The frame structure of claim 1, wherein the simple connection (7) between the base of the column (6) and the concrete base (9) is formed by elements selected from the group consisting of at least one bolted angle, a welded base plate (17), and an anchoring plate (24) encased in concrete
(20).
6. The frame structure of claim 1, wherein the bracket (1) is selected from the group consisting of a flat plate and a plate having ends and being folded at the ends.
7. The frame structure of claim 1, wherein the frame structure is a steel structure.
8. The frame structure of claim 1, wherein a diameter of the connecting elements (16) is equal to or greater than a diameter of the openings (12).
9. The frame structure of claim 1, wherein a diameter of the connecting elements (16) is smaller than a diameter of the openings (12).
10. The frame structure of claim 1, wherein the connecting elements (16) are selected from the group consisting of bolts with nuts, self-tapping bolts, and self-drilling bolts.
11. The frame structure of claim 1, wherein a space between the flanges (19) of the column (6) is filled with concrete (20).
12. The frame structure of claim 1, wherein the bracket (1) has a shape selected from the group consisting of an n-angle polygon where n is 3 to 8, a circle, an oval, and an irregular surface.
13. The frame structure of claim 1, wherein the vertical guide (2) is asymmetrically connected to the bracket (1).
14. The frame structure of claim 1, wherein the vertical guide (2) comprises elements selected from the group consisting of a circular tube, a square tube, a rectangular tube, and an oval tube.
15. The frame structure of claim 1, wherein the anchors (11) at the connection between the column base and the concrete base (9) comprise elements selected from the group consisting of a chemical anchor (21), a mechanical anchor (22), and a screw anchor (23).
16. A method comprising:
- selecting a stage of construction of a frame structure according to claim 1, the stage of construction being selected from the group consisting of: installation of the bracket (1) on a standalone column (6) before other frame elements are mounted, installation of the bracket (1) on a standalone frame after columns (6) and frame rafters are assembled, installation of the bracket (1) on a frame after purlins and bracing system are installed, and installation of the bracket (1) on a frame after purlins, bracing systems, cladding, and other permanent loads are installed;
- determining the loads to be transmitted by the connection between the column (6) and the concrete base (9) corresponding to the selected stage of construction;
- selecting dimensions and materials of the bracket (1), the vertical guides (2), and the anchor rods (15) such that a rotational stiffness and moment capacity of the connection between the column
(6) and the concrete base (9) are each set to values at which an applied bending moment in the connection does not exceed the moment capacity of the connection between the column (6) and the concrete base (9); and
- physically installing the bracket (1) on the column (6) and embedding the anchor rods (15) in the concrete base (9) at the selected stage of construction.
17. The method of claim 16, wherein the selecting dimensions and materials further comprises adjusting a height of the rectification nuts (8) located on a threaded upper part of the anchor rods (15) below the vertical guides (2) of the bracket (1); and at or near a same time adjusting the securing nuts (5) located on the threaded upper part of the anchor rods (15) above the vertical guides (2) of the bracket (1), with the upper part of the anchor rods (15) passing through the vertical guides (2) and a lower part of the anchor rods embedded in the concrete base (9), to set a magnitude of a rotation of the column (6) relative to the concrete base (9).
18. The method of claim 17, wherein a magnitude of the rotation of the column (6) relative to the concrete base (9) is continuously controlled by adjusting a height of the rectification nuts (8) and the securing nuts (5) until a required value of the magnitude of the rotation of the column (6) relative to the concrete base (9) is reached at an end of a process of assembly.
19. The method of claim 18, wherein continuous controlling the magnitude of the rotation of the column (6) relative to the concrete base (9) is repeatedly carried out by a sensor device positioned between the bracket (1) and the concrete base (9) at least until the required value is reached at the end of assembly.
20. The method of claim 16, wherein the selecting dimensions and materials of the bracket (1), the vertical guides (2), and the anchor rods (15) is performed by sequentially selecting in an analytical model a quantity, dimensions, and materials of top elastic washers (3), top steel washers (4), bottom steel washers (13), and bottom elastic washers (14) and the material and dimensions of all parts of the connection between the column (6) and the concrete base (9) up to a desired rotational stiffness and a desired magnitude of the moment capacity of the connection between the column (6) and the concrete base (9).
Type: Application
Filed: Mar 27, 2026
Publication Date: Aug 6, 2026
Inventor: Jiri MARES (Roztoky)
Application Number: 19/631,409
