Parallelogram supporting structure for large-size cantilever floor slab of frame structure

Abstract

The invention discloses a parallelogram supporting structure for a large-size cantilever floor slab of a frame structure, and belongs to the technical field of building structure engineering. The frame structure comprises three stand columns distributed in a right triangle mode, a connecting beam is connected between the two stand columns located on the right-angle sides, and the stand columns located on the two acute-angle points are each provided with a cantilever beam. The parallelogram supporting structure comprises a main transverse rib, a secondary transverse rib and two longitudinal ribs. The two ends of the main transverse rib are connected with the midpoint areas of the two cantilever beams correspondingly. The secondary transverse rib is parallel to the main transverse rib, and two ends of the secondary transverse rib are respectively connected with midpoint areas of the two connecting beams; the two ends of each longitudinal rib are connected to the middle area between the corresponding cantilever beam on the side where the longitudinal rib is located and the connecting beam. According to the invention, the natural vibration frequency of the floor slab can be obviously improved, the vibration acceleration of the floor slab under dynamic loads such as walking can be reduced, and the use comfort of a frame structure building can be improved.

Description

Technical Field

[0001] This invention relates to the field of building structure engineering technology, specifically to a parallelogram support structure for large-size cantilevered floor slabs in frame structures. Background Technology

[0002] Currently, research on optimizing the comfort of cantilevered floor structures mainly focuses on improving material properties or adjusting beam cross-sectional dimensions and floor slab thickness to enhance stiffness and comfort. However, as building structures develop towards lightweight and high-efficiency designs, how to effectively improve floor slab stiffness and enhance user comfort while controlling structural self-weight is a pressing issue. Traditional methods often rely on increasing floor slab thickness or using high-strength materials, but this leads to a significant increase in structural mass, reduced economic efficiency, and limited applicability to the renovation of existing buildings. Therefore, there is an urgent need for a structurally sound, lightweight auxiliary structure that significantly contributes to stiffness, effectively improving overall stiffness and comfort without significantly increasing the floor slab's self-weight. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems in the prior art and provide a parallelogram support structure for large-size cantilevered floor slabs in frame structures.

[0004] This invention provides a parallelogram support structure for large-sized cantilevered floor slabs in a frame structure. The cantilevered floor slab is supported by three columns, lacking a fourth corner column. The three columns are connected sequentially by two connecting beams, and the two columns adjacent to the fourth corner column are also connected to cantilever beams. One end of each cantilever beam is connected to one of the columns, and the other end converges at the location of the missing fourth corner column. The parallelogram support structure is connected to the connecting beams and the cantilever beams and includes a main transverse rib, a secondary transverse rib, and two longitudinal ribs. The two ends of the main transverse rib are connected to the midpoint regions of the two cantilever beams, respectively. The secondary transverse ribs are parallel to the main transverse ribs, and their two ends are connected to the midpoint regions of the two connecting beams, respectively. The two ends of each longitudinal rib are connected to the middle region of the corresponding cantilever beam and the connecting beam on their respective sides. The main transverse rib, longitudinal rib, and secondary transverse rib together form a parallelogram support frame.

[0005] Preferably, the main transverse ribs, longitudinal ribs, and secondary transverse ribs are all I-shaped steel ribs.

[0006] Preferably, the web of the I-shaped steel rib is provided with transverse stiffening ribs.

[0007] Preferably, when the connecting beam and the cantilever beam are reinforced concrete beams, a sleeve is pre-embedded at the connection point of the connecting beam and the cantilever beam, the sleeve is provided with an end plate, and the upper and lower flanges of the main transverse rib, longitudinal rib and secondary transverse rib are all connected to the end plate by bolts.

[0008] Preferably, when the connecting beam and the cantilever beam are I-beams, longitudinal stiffening ribs and / or transverse stiffening ribs are provided at their connection points, and the upper and lower flanges of the steel ribs are respectively connected to the upper flange of the I-beam and the longitudinal stiffening ribs by bolts.

[0009] Preferably, the main transverse ribs and / or longitudinal ribs and / or secondary transverse ribs are components made of H-beams with cross-sectional specifications of HN500×200×10×16 or HM500×300×11×15.

[0010] Preferably, the main transverse ribs, longitudinal ribs, and secondary transverse ribs are all connected to the cantilever beam and the connecting beam by single-sided high-strength bolts.

[0011] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention, through a parallelogram support structure composed of main transverse ribs, longitudinal ribs, and secondary transverse ribs, forms an efficient spatial force-bearing system in the weak area caused by missing columns. This parallelogram support structure not only significantly improves the vertical stiffness and torsional stiffness of the floor slab, but also effectively reduces deformation under static loads. By significantly increasing the natural frequency of the floor slab and reducing its vibration acceleration under dynamic loads such as pedestrian traffic, it improves the user comfort of frame structure buildings.

[0012] The parallelogram support structure of this invention fully leverages the high material utilization rate of I-shaped steel ribs, achieving maximum stiffness contribution with minimal increase in self-weight. This avoids the problems of significantly increased structural self-weight, higher material costs, and increased foundation load associated with traditional methods that rely on increasing floor slab thickness or using high-strength materials.

[0013] The parallelogram support structure of the present invention has a clear and reasonable force transmission path. The main transverse ribs, longitudinal ribs and secondary transverse ribs can work together to efficiently transfer the load at the cantilever end to the stable support structure.

[0014] The parallelogram support structure of the present invention uses single-sided high-strength bolts for connection nodes and can be equipped with transverse stiffening ribs in the web to ensure the reliability of the connection and the local stability of the node. Attached Figure Description

[0015] Figure 1 This is a top view of the structure according to an embodiment of the present invention.

[0016] Figure 2 This is a top view of the connection node between the steel rib and the I-beam of the present invention.

[0017] Figure 3 This is a cross-sectional view of the connection node AA between the steel rib and the I-beam of the present invention.

[0018] Figure 4 This is a schematic diagram of the cross-section of the steel rib BB of the present invention.

[0019] Figure 5 This is a cross-sectional view (CC) of the connection node between the steel rib and the I-beam of the present invention.

[0020] Figure 6 This is a side view of the connection node between the steel rib and the I-beam of the present invention.

[0021] Figure 7 This is a top view of the connection node between the steel rib and the concrete beam of the present invention.

[0022] Figure 8 This is a cross-sectional view of the connection node between the steel rib and the concrete beam in this invention.

[0023] Figure 9 This is a side view of the connection node between the steel rib and the concrete beam of the present invention. Figure 10 These are diagrams illustrating three support schemes in embodiments of the present invention.

[0024] Figure 11 This invention relates to the overall modeling and mesh generation of the sixth floor slab in an embodiment of the invention.

[0025] Figure 12 This is a three-dimensional model of the sixth floor slab in an embodiment of the present invention.

[0026] Figure 13 This is an example of grid division for cantilevered floor slabs in an embodiment of the present invention.

[0027] Figure 14 The first-order vertical vibration mode diagram and frequency calculation results are shown in the embodiment of the present invention.

[0028] Figure 15 The following are acceleration time history curves for three support schemes in embodiments of the present invention.

[0029] Figure 16 The results show the first-order vertical vibration mode and acceleration response of Scheme 4 of the present invention.

[0030] Explanation of reference numerals in the attached figures: 1. Column; 2. Connecting beam; 3. Cantilever beam; 4. Main transverse rib; 5. Longitudinal rib; 6. Secondary transverse rib; 7. Sleeve; 8. Bolt; 9. End plate; 10. Longitudinal stiffening rib; 11. Transverse stiffening rib. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” indicate that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0033] The embodiments of the present invention are applicable to cantilever structures formed by the lack of a single column in a frame structure or to working conditions where the beam height is limited.

[0034] Combination Figures 1 to 4 As shown in the figure, this embodiment provides a parallelogram support structure for large-size cantilevered floor slabs in frame structures, such as... Figure 1 As shown, three columns are arranged in a triangle on the connecting beam and the cantilever beam. The columns on both sides are connected to the middle column by connecting beams. A cantilever beam is also provided on each of the two columns near the missing corner column. This parallelogram support structure includes: a main horizontal rib, a secondary horizontal rib, and two longitudinal ribs; the two ends of the main horizontal rib are connected to the midpoint areas of the two cantilever beams respectively; the secondary horizontal rib is parallel to the main horizontal rib and its two ends are connected to the midpoint areas of the two connecting beams respectively; the two ends of each longitudinal rib are connected to the middle area of ​​the corresponding cantilever beam and the connecting beam on its side; the main horizontal rib, longitudinal rib, and secondary horizontal rib together form a parallelogram support frame; in this embodiment, the main horizontal rib is both a reinforcement of the cantilever section and a reference side of the entire parallelogram; the longitudinal rib is both a force transmission rod and a connecting rod that pulls the cantilever area and the non-cantilever area together; the secondary horizontal rib strengthens the safety zone and completes the closed loop of force flow. The parallelogram-shaped support structure in this embodiment is a hollow truss, with its main components bearing axial tensile and compressive forces. Compared to simply increasing the cross-section of beams and slabs, this invention provides a significant contribution to stiffness with minimal increase in self-weight. It not only reduces material costs, but more importantly, the lightweight support structure is more advantageous for seismic design. Simultaneously, this invention directly increases the natural frequency of the floor slab through the aforementioned support structure, moving it away from the frequency range sensitive to pedestrian loads. Furthermore, the formed closed force loop effectively suppresses and disperses vibration energy, reducing vibration acceleration. Compared to traditional methods that often rely on increasing floor slab thickness or using high-strength materials, which may increase mass and lower frequency, the lightweight and high-stiffness characteristics of this embodiment optimize both frequency and acceleration parameters, increasing the natural frequency of the floor slab, reducing its vibration acceleration, and improving the comfort performance of the building structure.

[0035] In a preferred embodiment of the present invention, the main transverse ribs, longitudinal ribs, and secondary transverse ribs are all I-shaped steel ribs. More specifically, the cross section of the I-shaped steel rib consists of two parallel flanges and a web connecting the flanges. The web mainly bears the tensile and compressive forces caused by bending moment, is far from the neutral axis, and can provide a large moment of inertia of the cross section. The web mainly bears the shear force. For the main transverse ribs and secondary transverse ribs of the present invention, which are mainly subjected to bending, the I-beam concentrates its material as much as possible in the upper and lower flanges, providing the maximum bending stiffness with the minimum amount of steel used. In a more preferred embodiment, the strong axis direction of each steel rib is aligned with the main direction of the bending moment to be resisted, realizing the directional reinforcement of stiffness. More specifically, for the main transverse ribs and secondary transverse ribs, their strong axis is perpendicular to the floor slab plane, resisting the vertical bending of the floor slab in the most effective way. At the same time, the parallel upper and lower flanges of the I-beam provide a connecting plane for connection.

[0036] In a preferred embodiment of the present invention, the web of the I-shaped steel rib is provided with transverse stiffening ribs to enhance the stability of the web.

[0037] In a preferred embodiment of the present invention, when the connecting beam and the cantilever beam are reinforced concrete beams, a sleeve is pre-embedded at the connection point of the connecting beam and the cantilever beam to facilitate the dispersion of concentrated forces. The sleeve is provided with an end plate, and the upper and lower flanges of the main transverse rib, longitudinal rib and secondary transverse rib are all connected to the end plate by bolts.

[0038] In a preferred embodiment of the present invention, when the connecting beam and the cantilever beam are I-beams, longitudinal stiffening ribs and / or transverse stiffening ribs are provided at their connection points, and the upper and lower flanges of the steel ribs are respectively connected to the upper flange and the longitudinal stiffening rib of the I-beam by bolts.

[0039] In a preferred embodiment of the present invention, the main transverse ribs and / or longitudinal ribs and / or secondary transverse ribs are components made of H-beams with cross-sectional specifications of HN500×200×10×16 or HM500×300×11×15.

[0040] As a preferred embodiment of the present invention, the connections between the main transverse ribs, longitudinal ribs and secondary transverse ribs and the cantilever beam and the connecting beam are all realized by single-sided high-strength bolts. The single-sided high-strength bolt consists of a main screw, a sleeve body, a split gasket, large and small washers and large and small nuts. The single-sided high-strength bolt has the advantages of single-sided installation, no need for hole opening, small cross-section weakening, and being detachable at the same time.

[0041] In order to reflect the advantages of the parallelogram support structure of the large-size cantilever floor slab for the frame structure in this embodiment, we also carried out finite element analysis and verification. In this embodiment, the span of the cantilever floor slab is 8.7m * 9.0m.

[0042] We used SAP2000 software to model the sixth floor slab of a certain building, analyzed the comfort of the new combined cantilever structure and the floor slab under pedestrian excitation, and at the same time carried out relevant research on the design method of the cantilever floor slab support structure. First, we designed three different floor slab support structures. The connection form between the support and the beam is the rigid connection default in the SAP2000 software. The three different floor slab support structures are respectively abbreviated as Scheme One, Scheme Two and Scheme Three; the specific designs of the three schemes are as follows: Scheme One is a parallel support, as Figure 10 shown in (a), that is, the support structure adopted by the floor slab of this building. Steel pipes with specifications of 350×500×10 and 250×500×10 are used to replace the concrete support. The steel pipe with a specification of 350×500×10 is used as the support connecting the diagonals, and the remaining two steel pipes have a specification of 250×500×10; Scheme Two is a rectangular frame support, as Figure 10 shown in (b). To strengthen the connection performance between the cantilever beam and the column, the parallel support is optimized into a rectangular frame support. Among them, the steel pipe with a specification of 250×500×10 is parallel to the connection diagonal connecting the two columns, and the steel pipe with a specification of 300×500×10 is perpendicular to this diagonal; Scheme Three is a "day" - shaped support, as Figure 10 shown in (c). To improve the stiffness of the central area of the floor slab, a cross beam is added in the center of the rectangular frame support to form a "day" - shaped support. The newly added cross beam uses a rectangular steel pipe with a specification of 300×500×10, and the remaining design parameters are the same as those of Scheme Two.

[0043] The overall floor slab structure modeling and mesh division in this embodiment are as Figure 11 shown, and the three - dimensional modeling is as Figure 12As shown, quadrilateral and triangular grids are adopted at the cantilever floor slab, while only quadrilateral grids are used for the remaining floor slabs. All nodes adopt rigid connection forms, and the bottom of the columns is set as a fixed connection constraint. Given that the core analysis object of this embodiment is the floor slab cantilever structure, only the grid convergence analysis is carried out for the cantilever floor slab. Five different sizes of grids are set, from large to small, which are 1m, 0.75m, 0.5m, 0.35m, and 0.25m respectively. The specific division method is as Figure 13 shown. It can be seen from the data in Table 1 that the influence on the results is very small when the grid size is less than 0.5m. Therefore, the floor slab area is finally divided with a grid with a maximum size of 0.5m.

[0044] Table 1 All of the above three schemes adopt reinforced concrete floor slabs with a thickness of 100mm. According to the requirements of the "Technical Standard for Vibration Comfort of Building Floor Slabs" (JGJT 441-2019), when calculating the comfort level, when the floor slab adopts a reinforced concrete floor slab and a steel-concrete composite floor slab, the elastic modulus of concrete can be increased by 1.20 times and 1.35 times respectively according to the specified values in the current national standard "Code for Design of Concrete Structures" (GB50010).

[0045] Modal analysis Modal analysis is carried out in the SAP2000 software. The first-order vertical vibration modes and corresponding natural vibration frequencies of the three support schemes are calculated by the eigenvalue modal analysis method. The analysis results are as Figure 14 . The results show that the support members arranged diagonally have a significant impact on the first-order vertical vibration mode of the structure: from the comparison of the natural vibration frequencies, since the diagonal support members are not configured in Scheme 2, its natural vibration frequency is significantly lower than that of Scheme 1 and Scheme 3; further analyzing from the morphological characteristics of the vibration mode, the vertical displacement response of Scheme 2 shows a distribution law with the maximum at the cantilever end and relatively large at the mid-span, while the maximum vertical displacement responses of Scheme 1 and Scheme 3 are only concentrated in the cantilever end area; Scheme 3 configures a "day" - shaped support system to strengthen the connection stiffness between the cantilever beam and the column, and its vertical displacement response at the mid-span is significantly smaller than that of Scheme 2. From Figure 14 the results, all three schemes meet the requirement of 3Hz in the "Technical Standard for Vibration Comfort of Building Floor Slabs" (JGJT 441-2019), but it is still necessary to conduct a time-history analysis on the floor slab and analyze its acceleration response by applying pedestrian loads.

[0046] Time-history analysis According to the structural vertical natural vibration frequencies corresponding to the three schemes obtained from the modal analysis f 1 = 6.03Hz, f 2 = 5.60Hz and f 3 = 6.06Hz, the corresponding pedestrian frequencies are selected =3.02Hz =2.80Hz and =3.03Hz. The time history function is represented by a Fourier series, and the formula obtained by taking the first three orders is:

[0047] The time history functions corresponding to each scheme were imported into the analysis model, and time history analysis was carried out using the Ritz modal analysis method. The aforementioned modal analysis results show that all three schemes exhibit the characteristic of having the largest first-order vertical natural displacement response at the far end of the cantilever beam. Therefore, the pedestrian load loading point was set at this location as the most unfavorable loading condition. Furthermore, considering that the vertical displacement response at mid-span in Scheme 2 is also relatively significant, an additional mid-span loading condition was added. The acceleration time history curves of Scheme 1 (cantilever end loading), Scheme 2 (mid-span loading and cantilever end loading), and Scheme 3 (cantilever end loading) are shown below. Figure 15 As shown, the corresponding peak accelerations are 0.0408 m / s², 0.0375 m / s² (0.0269 m / s² when loaded at the cantilever end) and 0.0478 m / s², respectively.

[0048] It can be seen that the peak acceleration of all three schemes is less than 0.05 m / s². 2 It meets the requirements of the "Technical Standard for Vibration Comfort of Building Floors" (JGJT 441-2019), with the peak acceleration of Scheme 2 being 0.0375 m / s². 2 The lowest value was achieved, reducing acceleration by 8.1% and 21.5% compared to Scheme 1 and Scheme 3, respectively. Scheme 2, applying a pedestrian vibration load at mid-span, had a peak acceleration of 0.0269 m / s². 2 Since it also meets the specifications, it can be concluded that the optimal form of support should be a rectangular frame support.

[0049] After determining the support form, we further studied the impact of the support cross-sectional shape on structural comfort and designed Scheme 4, replacing the original rectangular support steel tube cross-section with H-shaped steel cross-sections. The original rectangular steel tubes with cross-sections of 250×500×10 and 300×500×10 were replaced with HN500×200×10×16 and HM500×300×11×15 sections respectively, while ensuring their load-bearing capacity. Modal and time history analyses were performed, and the results are as follows. Figure 16 As shown.

[0050] Firstly by Figure 16 (a) It can be seen that after changing the support cross-section, the first mode shape of the floor slab also changed. SAP2000 calculated the natural frequency of the floor slab to be 5.36Hz, and the location of the maximum displacement changed from the cantilever point to the mid-span. Therefore, in the time history analysis, the most unfavorable load case should be arranged at the mid-span position, while also considering the load case at the cantilever point. The resulting time history curve is as follows: Figure 16(b) and Figure 16 As shown in (c), it can be seen that under the most unfavorable working condition, the peak acceleration at mid-span of the floor slab supported by the H-beam is 0.036 m / s². 2 Compared to the rectangular support, the peak acceleration decreased by 4%, reaching 0.026 m / s² at the cantilever. 2 Meanwhile, Scheme 4 uses 485 kg less steel than Scheme 2, which shows that Scheme 4 not only uses less steel but also provides better comfort. Therefore, H-beams were ultimately chosen as the support section.

[0051] Since the form of the supporting cross-section also affects the comfort of the structure, the embodiments of the present invention adopt Scheme 2 plus Scheme 4, that is, the steel ribs are made of H-beams of HM500×300×11×15 and HN500×200×10×16, which not only reduces the amount of steel used by 485kg, but also reduces the peak acceleration by 4%. Moreover, the load-bearing capacity of this cross-section is close to that of the original building floor slab concrete support, ensuring static performance while also meeting the comfort specifications.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A parallelogram support structure for a large-span cantilevered floor slab in a frame structure, wherein the cantilevered floor slab is supported by three columns and lacks a fourth corner column, the three columns are connected sequentially by two connecting beams, and the two columns adjacent to the fourth corner column are each connected to a cantilever beam, one end of the two cantilever beams being connected to one of the columns, and the other end converging at the location of the missing fourth corner column; characterized in that, The parallelogram support structure is connected to the connecting beam and the cantilever beam, and includes a main transverse rib, a secondary transverse rib, and two longitudinal ribs: the two ends of the main transverse rib are connected to the midpoint area of ​​the two cantilever beams respectively; the secondary transverse rib is parallel to the main transverse rib, and its two ends are connected to the midpoint area of ​​the two connecting beams respectively; the two ends of each longitudinal rib are connected to the middle area of ​​the cantilever beam and the connecting beam on the corresponding side respectively; the main transverse rib, longitudinal rib, and secondary transverse rib together form a parallelogram support frame.

2. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 1, characterized in that, The main transverse ribs, longitudinal ribs, and secondary transverse ribs are all I-shaped steel ribs.

3. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 1, characterized in that, The web of the I-shaped steel rib is provided with transverse stiffening ribs.

4. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 2, characterized in that, When the connecting beam and the cantilever beam are reinforced concrete beams, a sleeve is pre-installed at the connection point of the connecting beam and the cantilever beam. The sleeve is provided with an end plate, and the upper and lower flanges of the main transverse ribs, longitudinal ribs and secondary transverse ribs are all connected to the end plate by bolts.

5. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 2, characterized in that, When the connecting beam and the cantilever beam are I-beams, longitudinal stiffening ribs and / or transverse stiffening ribs are provided at their connection points. The upper and lower flanges of the steel ribs are respectively connected to the upper flange and the longitudinal stiffening rib of the I-beam through bolts.

6. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 1, characterized in that, The main transverse ribs and / or longitudinal ribs and / or secondary transverse ribs are components made of H-beams with cross-sectional specifications of HN500×200×10×16 or HM500×300×11×15.

7. The parallelogram support structure for large-size cantilevered floor slabs in frame structures as described in claim 1, characterized in that, The main transverse ribs, longitudinal ribs, and secondary transverse ribs are all connected to the cantilever beams and connecting beams by single-sided high-strength bolts.

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