A method for converting the impact load on the top surface of a construction protection shed into a static load

Abstract

The present invention belongs to the field of civil engineering and relates to a calculation method for converting the impact load on the top surface of a construction protection shed into a static load. It is characterized in that the protective plate on the top surface of the protection shed has two layers, which are fully paved with materials such as wooden boards or steel plates, and jointly form the complete structure of the protection shed with the steel frame of the protection shed. By analyzing the energy conservation during the impact process and the elastic deformation relationship of the top surface of the protection shed, the calculation formula for the impact load on the top surface of the protection shed is derived, and a method for converting the impact load into a static load is further proposed. By converting the impact load into a static load, the present invention can provide theoretical support for the load combination design of the protection shed, thereby improving the protection ability of the protection shed in the face of critical situations such as high-altitude falling objects, and better ensuring the life safety of workers at the construction site.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering and relates to a method for converting the impact load on the top surface of a construction protection shed into a static load. Background Art

[0002] At a construction site, a protection shed is a relatively common safety protection facility, aiming to ensure the safety of construction workers and important mechanical equipment and avoid safety accidents caused by falling objects from a height, etc. With the development of society, each province has successively introduced corresponding technical standards and specifications, stipulating that protection sheds must be set within the falling radius of buildings, specific personnel activity areas, and important equipment areas. In addition, the specifications clearly define the protection ability and load combination of the protection shed, and the safety protection facilities are becoming more and more standardized.

[0003] However, in the design of the protection shed, how to ensure that its top surface can still meet the corresponding strength and stiffness requirements under the action of the corresponding impact load has always been the key and difficult problem in the design of the protection shed. The protection facility standards and specifications introduced by some provinces and cities only include the relevant regulations on self-weight load, static load, and live load, and there are no relevant regulations on impact load. In addition, since most of the current construction protection sheds are two-layer protection structures, when the impact energy is too large, the situation of piercing the first-layer protection board on the top surface of the protection shed may occur. How to calculate the impact load at this time and convert it into a static load still lacks a relatively reliable calculation method at present. Therefore, there are relatively large potential safety hazards in the design method of the protection shed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for converting the impact load on the top surface of a construction protection shed into a static load for the calculation problem of the top surface of the construction protection shed under the action of the impact load.

[0005] The present invention is achieved through the following technical solutions:

[0006] Step 1: Calculate the static displacement of the impact point along the impact direction caused by the self-weight of the impact object in the form of a static load according to formula (4) :

[0007] The uniform load generated by the self-weight of the impact object on the contact surface in the form of a static load is:

[0008] (1)

[0009] In the formula: is the uniform load generated by the self-weight of the impact object on the contact surface in the form of a static load, is the mass of the impact object, is the acceleration due to gravity, is the contact area between the impact object and the top surface of the protection shed;

[0010] The bending moment formula of the system caused by the dead weight of the impact object in the form of a static load is:

[0011] (2)

[0012] Where: is the bending moment of the system caused by the dead weight of the impact object in the form of a static load, is the distance between the calculation point of a single piece of material on the top surface of the protective shed and the left hinge point, is the span of a single piece of material on the top surface of the protective shed, is the length of the contact surface between the impact object and the top surface of the protective shed along the span direction of a single piece of material;

[0013] Then the deflection formula of the system caused by the dead weight of the impact object in the form of a static load is:

[0014] (3)

[0015] Where: is the deflection of the system caused by the dead weight of the impact object in the form of a static load, is the elastic modulus of the material on the top surface of the protective shed, is the moment of inertia of the cross-section of the top surface of the protective shed;

[0016] The static displacement of the impact point along the impact direction caused by the dead weight of the impact object in the form of a static load is:

[0017] (4)

[0018] Step 2: Calculate the impact loads caused by the impact object on different cross-sections according to formulas (9) and (10):

[0019] Energy conservation formula:

[0020] (5)

[0021] Where: is the height of the impact object from the top surface of the protective shed, is the layer spacing between the two layers of protective plates on the top surface of the protective shed, is the displacement of the impact point along the impact direction at the second layer of the protective plate on the top surface of the protective shed caused by the impact load, is the uniformly distributed impact load caused by the impact object at the first layer of the protective plate on the top surface of the protective shed, is the maximum deflection value of the paving material under normal use conditions. For wood, it is 1 / 250 of the span, and for steel, it is 1 / 150 of the span, is the area amplification factor. When the paving material is wood, it is taken as 1.4, and when the paving material is steel, it is taken as 2, is the deflection amplification factor, It is the uniformly distributed impact load caused by the impact object at the second layer of the protective plate on the top surface of the protective shed;

[0022] Introduce the elastic deformation relationship of the materials on the top surface of the protective shed:

[0023] (6)

[0024] By combining the above two equations, we can obtain:

[0025] (7)

[0026] Solve for the dynamic load factor as:

[0027] (8)

[0028] Then the impact load is:

[0029] (9)

[0030] (10)

[0031] Step 3: Convert the impact load into a static load according to formula (11):

[0032] (11)

[0033] In the formula: is the converted static load, is the impact load.

[0034] The beneficial effects of the present invention: Aiming at the problem of how to calculate the impact load and convert the impact load into a static load after the first layer of the protective plate on the top surface of the construction protective shed is penetrated by the impact object, a calculation method for converting the impact load on the top surface of the construction protective shed into a static load is reasonably proposed, providing theoretical guidance for making up for the problem that the impact load is not included in the load action and load combination during the design process of the protective shed, and providing a scientific and effective calculation method for ensuring the protection ability of the protective shed under the action of the impact load and improving the overall safety of the protective shed. Brief Description of the Drawings

[0035] Figure 1 It is the top surface layout diagram of the construction protective shed in the embodiment of the present invention;

[0036] Figure 2 It is the model simplification diagram in the embodiment of the present invention;

[0037] Figure 3 It is the single-layer cross-sectional view of the top surface of the construction protective shed in the embodiment of the present invention.

[0038] In the figure: 1 frame, 2 keel, 3 paving material, 4 falling object. Specific implementation manner

[0039] The present invention will be further described below with reference to the accompanying drawings and through embodiments.

[0040] Embodiment

[0041] A method for converting the impact load on the top surface of a construction protection shed into a static load, characterized in that the protection board on the top surface of the protection shed has two layers, which are composed of materials such as wooden boards or steel plates and are fully paved, and together with the steel frame of the protection shed, they form a complete structure of the protection shed. In a certain construction site, 10mm×1000mm ordinary steel plates are used as the paving material on the top surface of the composite slab, and are fully paved on the top keel of the protection shed. The moment of inertia of the material cross-section is 83333mm 4 , and the elastic modulus is 206000N / mm 2 . The protection shed has 3 spans, the spacing is 1500mm, the deflection amplification factor β is taken as 9, and the layer spacing between the protection boards on the top surface of the protection shed is 600mm; a falling object has a mass of 10kg, a transverse cross-section of 300mm×300mm, and falls from a height of 10m above the top surface of the protection shed without an initial velocity. The gravitational acceleration is 9.80m / s 2 . After free fall, it falls onto the construction protection shed, and the impact point is at the midpoint position of the top surface of the protection shed.

[0042] A method for converting the impact load on the top surface of a construction protection shed into a static load includes the following steps:

[0043] Step 1: Calculate the static displacement of the impact point along the impact direction caused by the self-weight of the impact object in the form of a static load :

[0044] The uniform load generated by the self-weight of the impact object on the contact surface in the form of a static load is:

[0045]

[0046]

[0047] Step 2: Calculate the impact load caused by the impact object on different protection boards:

[0048] Solve for the dynamic load factor as:

[0049]

[0050] Then the impact load is:

[0051]

[0052]

[0053] Step 3: Convert the impact load into a static load:

[0054]

[0055]

[0056] Although the specific calculation method of the present invention is described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or deformations that can be made without creative efforts on the basis of the design scheme of the present invention are still within the protection scope of the present invention.

Claims

1. A method for converting the impact load on the top surface of a construction protection shed into a static load, characterized in that, The top protection board of the protective shed has two layers, which are fully covered with materials such as wooden boards or steel plates, and jointly form the complete structure of the protective shed with the steel frame of the protective shed. The specific steps are as follows: Step 1: Calculate the static displacement Δ of the impact point along the impact direction caused by the dead weight of the impact object in the form of a static load according to formula (4). st : The uniform load q generated by the self-weight of the impact object on the contact surface in the form of a static load is: In the formula: m is the mass of the impact object, g is the acceleration due to gravity, and A is the contact area between the impact object and the top surface of the protective shed; The bending moment formula of the system caused by the self-weight of the impact object in the form of a static load is: In the formula: M is the bending moment of the system caused by the self-weight of the impact object in the form of a static load, x is the distance between the calculation point of a single material on the top surface of the protective shed and the left hinge point, l is the span of a single material on the top surface of the protective shed, and a is the length of the contact surface between the impact object and the top surface of the protective shed along the span direction of a single material; Then the deflection formula of the system caused by the self-weight of the impact object in the form of a static load is: In the formula: f is the deflection of the system caused by the self-weight of the impact object in the form of a static load, E is the elastic modulus of the material on the top surface of the protective shed, and I is the moment of inertia of the cross-section of the top surface of the protective shed; The static displacement Δ of the impact point along the impact direction caused by the dead weight of the impact object in the form of a static load st is as follows: Step 2: Calculate the impact load caused by the impact object at different cross-sections according to formulas (9) and (10): Energy conservation formula: mg(h + s)+mgΔ d2 = 0.5q d1 Aωαβ + 0.5q d2 AΔ d2 α(5) Where: h is the height of the impact object from the top surface of the protective shed, s is the layer spacing between the two layers of protective plates on the top surface of the protective shed, Δ d2 is the displacement of the impact point at the second layer of the protective plate on the top surface of the protective shed caused by the impact load along the impact direction, q d1 is the uniformly distributed impact load caused by the impact object at the first layer of the protective plate on the top surface of the protective shed, ω is the maximum deflection value of the material laid on the top surface under normal use conditions, taking 1 / 250 of the span for wood and 1 / 150 of the span for steel, α is the area amplification factor, β is the deflection amplification factor, q d2 is the uniformly distributed impact load caused by the impact object at the second layer of the protective plate on the top surface of the protective shed; Introduce the elastic deformation relationship of the material on the top surface of the protective shed: Combining the above two formulas, we can get: The dynamic load factor K is obtained as follows d2 as Then the impact load is: Step 3: Convert the impact load into a static load according to formula (11): Where: q h is the converted static load, and q d is the impact load.

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