Prefabricated ultra-high performance concrete components and construction methods with improved shear resistance

Abstract

The present invention belongs to the technical field of building structures, and specifically relates to a prefabricated ultra-high performance concrete (UHPC) component with improved anti-punching bearing capacity, including a concrete column and a concrete slab, wherein both ends of the concrete column penetrate the concrete slab, the concrete column is provided with bundled steel bars inside, and a prefabricated UHPC component is provided inside the concrete slab, and the side wall of the prefabricated UHPC component is provided with upper steel bar holes and lower steel bar holes of the component, and the upper steel bars and lower steel bars penetrate the upper steel bar holes and lower steel bar holes of the component respectively. The present invention can be optimized and adjusted according to the type and size of the reinforced concrete column and the thickness of the reinforced concrete slab, and can fully improve the anti-punching bearing capacity at the slab-column node, reduce the brittle shear damage of the structure, and thus improve the stability and safety of the structure.

Description

Technical Field

[0001] The invention belongs to the technical field of building structures, and in particular relates to a prefabricated ultra-high performance concrete component with improved shear resistance and a construction method. Background Art

[0002] Reinforced concrete slab-column structure, also known as beamless floor structure, is a structural form in which there is no beam between columns and the floor slab is directly supported on the columns. Although this structural form seems simple, its stress performance is very complex. With the extensive theoretical and experimental research of domestic and foreign scholars, this structural form has gradually gained a clearer understanding.

[0003] With the development of social economy, people have put forward higher requirements for indoor space, especially in the fields of public buildings such as office buildings and commercial buildings. Some traditional structural forms can no longer meet people's requirements for building space. The plate-column structure has the advantages of simple structure, simplified formwork, lower floor height and thus larger net space, which just meets people's demand for building space.

[0004] In this type of structure, since the floor slab is directly supported by the column, the column and floor slab bear large bending moments and shear forces at the node connection, which makes it easy for brittle punching failure to occur at the slab-column node. Although the brittle punching failure of the slab-column node itself is only a local phenomenon, this brittle failure is likely to cause a chain reaction in the structure, leading to the continuous collapse of the structure.

[0005] Punching failure of reinforced concrete slab-column joints is caused by the failure of the slab along the oblique section due to bidirectional shear, forming a spatial failure cone, which is a local brittle punching failure near the slab-column connection. In order to improve the punching performance of slab-column joints, traditional reinforcement methods include adding column caps and configuring shear steel bars. However, these methods have problems such as complex construction, increased concrete consumption, and reduced net height between layers.

[0006] According to previous studies on ultra-high performance concrete (UHPC) slab-column joints, the use of UHPC at the slab-column joint can significantly improve the shear bearing capacity of the slab-column joint (reference: Fang Zhi, Chen Jiaxing, Cao Qing. Experimental study on the punching shear performance of UHPC two-way slabs [J]. China Journal of Highway and Transport, 2021; Fan Jiansheng, Wang Zhe, Yang Song, et al. Study on the punching and bending performance of ultra-high performance concrete slabs [J]. Engineering Mechanics, 2021). However, the cost of UHPC is currently high, so the use of UHPC in the entire structure may lead to a significant increase in the cost of the overall structure, so it is not suitable for large-scale use. Summary of the invention

[0007] The purpose of the present invention is to provide a prefabricated ultra-high performance concrete component and a construction method with improved shear bearing capacity, which can be optimized and adjusted according to the type and size of the reinforced concrete column and the thickness of the reinforced concrete slab, so as to fully improve the shear bearing capacity at the slab-column node, reduce the brittle shear damage of the structure, and thus improve the stability and safety of the structure.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A prefabricated ultra-high performance concrete component with improved shear resistance comprises a concrete column and a concrete slab, wherein both ends of the concrete column penetrate the concrete slab, the concrete column is provided with bundled steel bars inside, a prefabricated UHPC component is provided inside the concrete slab, an upper steel bar and a lower steel bar are provided in the concrete slab respectively, upper steel bar holes and lower steel bar holes are provided on the side wall of the prefabricated UHPC component, the upper steel bar and the lower steel bar penetrate the upper steel bar holes and the lower steel bar holes of the component respectively, and expansion components are provided on the upper and lower sides of the prefabricated UHPC component respectively.

[0010] The prefabricated UHPC component is arranged in a conical shape.

[0011] The inclination angle of the prefabricated UHPC component is 21°-45°.

[0012] The prefabricated UHPC component is a conical table.

[0013] The prefabricated UHPC component is a circular table.

[0014] The prefabricated UHPC component is a special-shaped platform.

[0015] A construction method for a prefabricated ultra-high performance concrete component with improved punching shear bearing capacity, the construction method comprising the following steps:

[0016] S1: Determine the upper cross-sectional dimensions and thickness of the prefabricated UHPC components according to the geometric shape and size of the concrete column, and determine the inclination angle of the prefabricated components according to the actual engineering requirements;

[0017] S2: Then determine the location of the reserved steel bar holes according to the reinforcement conditions of the concrete slab;

[0018] S3: Before pouring, the surface of the prefabricated UHPC component is roughened;

[0019] S4: Apply lubricant on the surface of the steel bar, then insert it into the upper steel bar hole and the lower steel bar hole of the precast UHPC component, and then pour ordinary concrete inside the precast UHPC component;

[0020] S5: After the internal pouring of the prefabricated UHPC component is completed, grouting is performed at the reserved upper and lower steel bar holes of the component to ensure that the steel bars are in full contact with the concrete. Then, the external concrete of the prefabricated UHPC component is poured to complete the construction of the component.

[0021] The technical effects achieved by the present invention are:

[0022] The prefabricated ultra-high performance concrete component and construction method for improving the shear resistance of the present invention are simple to construct and convenient and quick to install; the prefabricated component has the advantage of improving construction efficiency, and during the installation process, fewer personnel and equipment are required, thereby reducing costs; the shape of the prefabricated UHPC component is similar to a hollow trapezoid, which, compared with a general rectangular parallelepiped, not only saves the use of UHPC, but also intersects with the spatial conical oblique cracks formed at the slab-column node, preventing the development of the shear oblique cracks, thereby improving the shear resistance of the slab-column node, and preventing the brittle shear failure of the slab-column structure under the action of vertical loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a front view of the overall structure of the conical platform prefabricated UHPC component of an embodiment of the present invention;

[0024] Figure 2 This is a front view of the overall structure of the conical platform prefabricated UHPC component combined with the extended component in an embodiment of the present invention;

[0025] Figure 3 It is a front view of the structure of a conical platform prefabricated UHPC component combined with an extended component according to an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of a conical platform prefabricated UHPC component according to an embodiment of the present invention;

[0027] Figure 5 This is a front view of the overall structure of the circular table prefabricated UHPC component of an embodiment of the present invention;

[0028] Figure 6 2 is a schematic diagram of the structure of a circular table prefabricated UHPC component according to an embodiment of the present invention;

[0029] Figure 7 This is a front view of the overall structure of the special-shaped platform prefabricated UHPC component of an embodiment of the present invention;

[0030] Figure 8 2 is a schematic diagram of the structure of a prefabricated UHPC component of a special-shaped platform according to an embodiment of the present invention;

[0031] Fig. 9 is a schematic diagram of mesh division in finite element analysis in an embodiment of the present invention;

[0032] Fig.10is a schematic diagram of a tensile stress cloud diagram in a finite element analysis of an embodiment of the present invention;

[0033] Fig.11 It is a force-displacement curve diagram of a slab-column structure of ordinary concrete and a slab-column structure with prefabricated UHPC components according to an embodiment of the present invention.

[0034] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0035] 1. Concrete column; 2. Concrete slab; 3. Prefabricated UHPC component; 4. Bundled steel bars; 5. Holes for lower steel bars in the component; 6. Upper steel bars; 7. Lower steel bars; 8. Extended component; 9. Holes for upper steel bars in the component; 10. Inclination angle. DETAILED DESCRIPTION

[0036] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0037] Embodiment 1:

[0038] like Figure 1-Figure 11 As shown, a prefabricated ultra-high performance concrete component with improved shear resistance is described below by taking a conical platform prefabricated UHPC component 3 as an example. Its construction method is similarly applicable to a circular platform prefabricated UHPC component 3 and a special-shaped platform prefabricated UHPC component 3; it includes a concrete column 1 and a concrete slab 2, both ends of the concrete column 1 pass through the concrete slab 2, a bundled steel bar 4 is arranged inside the concrete column 1, a prefabricated UHPC component 3 is arranged on the inner side of the concrete slab 2, an upper steel bar 6 and a lower steel bar 7 are respectively arranged in the concrete slab 2, an upper steel bar hole 9 and a lower steel bar hole 5 are opened on the side wall of the prefabricated UHPC component 3, the upper steel bar 6 and the lower steel bar 7 pass through the upper steel bar hole 9 and the lower steel bar hole 5 of the component respectively, and an expansion component 8 is respectively arranged on the upper and lower sides of the prefabricated UHPC component 3.

[0039] Among them, the conical platform prefabricated UHPC component 3 determines the cross-sectional shape of the conical platform prefabricated UHPC component 3 according to the size and geometric shape of the concrete column 1, and then determines the thickness of the conical platform prefabricated UHPC component 3 according to actual engineering requirements; the positions of the upper steel bar holes 9 and the lower steel bar holes 5 of the component are determined according to the reinforcement conditions of the concrete slab 2.

[0040] like Figure 1-Figure 4 As shown, the prefabricated UHPC component 3 is arranged in a cone shape.

[0041] The inclination angle 10 of the prefabricated UHPC component 3 is 21°-45°.

[0042] The smaller the inclination angle 10 of the prefabricated UHPC component 3 with the horizontal line, the larger the UHPC area is, and the cost of the structure may be relatively high, which does not achieve the purpose of being more economical. The larger the inclination angle 10 of the prefabricated UHPC component 3 is, the smaller the UHPC area is, and the purpose of improving the shear bearing capacity of the structure may not be achieved. The inclination angle 10 of the four sides of the prefabricated UHPC component 3 According to the research of previous scholars, the inclination angle 10 of the spatial conical crack formed at the slab-column node under the vertical load of the slab-column structure and the horizontal line is about 21° to 45°. In order to make the prefabricated UHPC component 3 intersect with the spatial conical crack, so as to achieve the purpose of restraining the development of the spatial conical crack, it is recommended that the inclination angle 10 of the prefabricated UHPC component 3 be selected between 21° and 45°.

[0043] For the plate-column structure with general punching load, Figure 1 , 5 As shown in Figure 7, the shape of the precast components is reinforced, and for the slab-column joints with large punching loads, Figure 2 and 3 The prefabricated components shown in the figure are reinforced. The prefabricated components are extended outwards in the upper section and extended inwards in the lower section, which can further limit the development of cracks on the plate surface and further improve the shear resistance of the structure. For the plate-column nodes with large shear loads, the manufacturing method of the prefabricated components of the circular platform and the special-shaped platform is the same as that of the square column, so the figures of the circular platform and the special-shaped platform are not included in the content.

[0044] like Fig.11 As shown in the figure, the peak load value of the slab-column structure with prefabricated UHPC components is 514518N, while the peak load value of the slab-column structure with ordinary concrete is 292265N. By comparing the two sets of data, it can be seen that the load performance of the slab-column structure with prefabricated UHPC components is far better than that of the slab-column structure with ordinary concrete.

[0045] The prefabricated UHPC component 3 is a conical table.

[0046] Embodiment 2:

[0047] like Figure 4 and Figure 5 As shown, the prefabricated UHPC component 3 is a circular table.

[0048] Embodiment 3:

[0049] like Figure 6 and Figure 7 As shown, the prefabricated UHPC component 3 is a special-shaped platform.

[0050] Specifically, in the embodiment 1 of this scheme, the conical platform prefabricated UHPC component 3 is mainly explained in detail, and its construction method and function are the same as those of the above-mentioned embodiments 2 and 3. By setting prefabricated UHPC components 3 of different shapes, prefabricated components of different shapes can be used according to actual needs.

[0051] Embodiment 4:

[0052] A construction method for a prefabricated ultra-high performance concrete component with improved anti-punching bearing capacity, the construction method comprising the following steps:

[0053] S1: According to the geometric shape and size of the concrete column 1, determine the cross-sectional size and thickness of the prefabricated UHPC component 3, and determine the inclination angle 10 of the prefabricated component according to actual engineering requirements;

[0054] S2: Then determine the position of the reserved steel bar holes according to the reinforcement condition of the concrete slab 2;

[0055] S3: Before pouring, the surface of the prefabricated UHPC component 3 is roughened;

[0056] S4: Apply lubricant on the surface of the steel bar, then insert it into the upper steel bar hole 9 and the lower steel bar hole 5 of the prefabricated UHPC component 3, and then pour ordinary concrete inside the prefabricated UHPC component 3;

[0057] S5: After the internal pouring of the prefabricated UHPC component 3 is completed, grouting is performed at the reserved upper steel bar holes 9 and lower steel bar holes 5 of the component to ensure that the steel bars are in full contact with the concrete, and then the external concrete of the prefabricated UHPC component 3 is poured to complete the construction of the component.

[0058] Embodiment 5:

[0059] like Figure 9-11 As shown, in order to verify the rationality of the structural form of the present invention, a finite element modeling analysis was conducted, and the slab-column structure using the prefabricated UHPC component 3 was analyzed in ABAQUS software. According to the finite element results, the slab-column structure using the prefabricated UHPC component 3 has a peak load increased by 76.05% compared with the ordinary reinforced concrete slab-column structure. It can be seen that the prefabricated UHPC component 3 can significantly improve the shear resistance of the slab-column node.

[0060] The concrete plastic damage model is used for both ordinary concrete and UHPC;

[0061] The expansion angle is 30 and the viscosity coefficient is 0.05;

[0062] Constraint method: Binding constraints are used between precast components and ordinary concrete, and the constraint method of the bottom support is U3=0;

[0063] Loading method: Establish a reference point on the upper surface of the column and couple it with the upper surface of the column to apply displacement on the reference point.

[0064] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A construction method for a prefabricated ultra-high performance concrete component with improved anti-punching bearing capacity, characterized in that: The invention comprises a concrete column (1) and a concrete slab (2), wherein both ends of the concrete column (1) penetrate the concrete slab (2), a bundled steel bar (4) is arranged inside the concrete column (1), a prefabricated UHPC component (3) is arranged inside the concrete slab (2), an upper steel bar (6) and a lower steel bar (7) are arranged inside the concrete slab (2), an upper steel bar hole (9) and a lower steel bar hole (5) are opened on the side wall of the prefabricated UHPC component (3), the upper steel bar (6) and the lower steel bar (7) penetrate the upper steel bar hole (9) and the lower steel bar hole (5) respectively, and an expansion component (8) is arranged on the upper and lower sides of the prefabricated UHPC component (3); The inclination angle (10) of the prefabricated UHPC component (3) is 21°-45°, so as to make the prefabricated UHPC component (3) intersect with the spatial conical crack, thereby achieving the purpose of restraining the development of the spatial conical crack; The prefabricated UHPC component (3) is a conical platform, and the shape of the conical platform is small at the top and large at the bottom; The construction method further comprises the following steps: S1: According to the geometric shape and size of the concrete column (1), determine the upper cross-sectional size and thickness of the prefabricated UHPC component (3), and determine the inclination angle (10) of the prefabricated component according to actual engineering requirements; S2: Then, the positions of the reserved steel bar holes are determined according to the reinforcement conditions of the concrete slab (2); S3: Before pouring, roughening the surface of the prefabricated UHPC component (3); S4: applying lubricant on the surface of the steel bar, then inserting the steel bar into the upper steel bar hole (9) and the lower steel bar hole (5) of the precast UHPC component (3), and then pouring ordinary concrete inside the precast UHPC component (3); S5: After the internal pouring of the prefabricated UHPC component (3) is completed, grouting is performed at the reserved locations of the upper steel bar holes (9) and the lower steel bar holes (5) of the component to ensure that the steel bars are in full contact with the concrete. Then, the external concrete of the prefabricated UHPC component (3) is poured to complete the construction of the component.

Images