Method for calculating supporting pressure of automobile crane

Abstract

The invention provides an automobile crane supporting pressure calculation method which mainly comprises the following steps: equivalently transferring all loads of a crane to a point O based on a static load test to obtain a test condition self-weight load standard value Nz and a test condition vertical load standard value Ne which act on the point O, a torque standard value Me generated by the test loads and a test condition total torque standard value Ms; the stabilizing moment Mw is caused by the dead load, and when the total moment standard value Ms is calculated, the landing leg on the light load side keeps the gravity of the crane, namely 15% of the dead load standard value Nz. According to the method, the traditional calculation method is improved, and the factor that the light load side supporting leg is influenced by the gravity of the crane during the static load test is considered, so that the pressure calculation result is more accurate.

Description

Technical Field

[0001] The invention mainly relates to the technical field related to crane force analysis, and specifically is a method for calculating the supporting pressure of a truck crane. Background Art

[0002] A truck crane is a boom-type crane installed on an ordinary car chassis or a special car chassis. When in operation, the load of the entire machine is transferred to the foundation through four outriggers. In order to prevent the truck crane from overturning due to insufficient bearing capacity of the foundation, it is necessary to use the outrigger pressure to calculate the foundation bearing capacity.

[0003] In the prior art, a method for calculating the outrigger pressure of an automobile crane is proposed in the related art with publication number CN 116383555 A and titled A method for calculating the outrigger pressure of an automobile crane. However, in its technical solution, the calculation of the allowable total moment is obtained by the proportional coefficient of the overturning moment and the stabilizing moment. When conducting a static load test, the light-load side outrigger does not consider the influence of the crane's gravity, so the calculated allowable total moment is not accurate, which leads to a large error in the subsequent calculation of the outrigger pressure, and the accuracy needs to be further improved. Summary of the invention

[0004] In order to solve the shortcomings of the current technology, the present invention combines the existing technology and provides a method for calculating the support pressure of a truck crane from the perspective of practical application. The method improves the traditional calculation method and takes into account the factor that the light-load side support leg is affected by the gravity of the crane during the static load test, so that the pressure calculation result is more accurate.

[0005] The technical solution of the present invention is as follows:

[0006] A method for calculating the support pressure of a truck crane comprises the following steps:

[0007] S1. Based on the static load test, all the loads of the crane are equivalently transferred to point O, and the standard value of the test condition deadweight load Nz and the standard value of the test condition vertical load Ne acting on point O, the standard value of the moment generated by the test load Me, the standard value of the total moment of the test condition Ms, and the stability moment M caused by the deadweight load are obtained. w ; Point O is the geometric center point of the four legs of the truck crane, Nz, Ne, Me, Ms, M w Calculate according to the following formula:

[0008] N z =(Q1+Q2+Q3)g (1)

[0009] N e =1.25Q e g (2)

[0010] Me =1.25Q e g(R-max{a / 2,b / 2}) (3)

[0011] M s =(0.35N z +0.5N e )×min{a,b} (4)

[0012] M w =M s -M e (5)

[0013] Among them, Q1 represents the weight of the whole crane in driving state, Q2 represents the weight of the detachable counterweight of the crane, Q3 represents the weight of the crane's jib and other accessories, and Q e It indicates the rated lifting capacity of the crane matched with R, R indicates the working radius, g is the acceleration of gravity, a indicates the longitudinal span of the outrigger, and b indicates the lateral span of the outrigger;

[0014] S2. Based on the change of the lifting load during the operation of the truck crane, the standard value of the total vertical load N at point O and the standard value of the forward tilting moment M generated by the deadweight load of the hoisted object are obtained. q , standard value of total moment M;

[0015] S3. Based on the standard value N of the total vertical load and the standard value M of the total moment, the pressure value of each leg when the leg is under pressure is calculated to obtain the pressure curve of each leg.

[0016] Further, in step S2, the standard value of the total vertical load N at point O and the standard value of the forward tilting moment M generated by the deadweight load of the hanging object are calculated. q , the total torque standard value M is calculated according to the following formula:

[0017] N=(Q1+Q2+Q3)g+φ(Q g +Q S +Q)g (6)

[0018] M q =φ(Q g +Q s +Q)g(R-max{a / 2,b / 2} (7)

[0019] M=M w +M q (8)

[0020] Where φ is the dynamic load coefficient, Q s Indicates the mass of the sling, Q g It represents the mass of the hook, Q represents the mass of the load, M>0 represents the forward moment, and M<0 represents the backward moment.

[0021] Further, in step S3, when the truck crane is working, as the boom rotates, the direction of the total moment standard value M also rotates. A coordinate system is established with the lateral span direction of the outrigger as the x-axis, the longitudinal span direction as the y-axis, and point O as the origin. The angle between M and the x-axis is θ. When M and the x-axis are in the same direction, θ=0°, and counterclockwise is positive. The pressures N1, N2, N3, and N4 corresponding to the outriggers T1, T2, T3, and T4 are calculated according to the following formulas:

[0022]

[0023] Furthermore, when M is in the first quadrant, N1 is the largest and N3 is the smallest, if N3≤0, it means that the outrigger T3 has left the ground. At this time, all the loads are borne by N1, N2, and N4 and should be redistributed. At this time, the pressures N1, N2, and N4 of the outriggers T1, T2, and T4 are calculated according to the following formula:

[0024]

[0025] Beneficial effects of the present invention:

[0026] In the present invention, when calculating the standard value of the total moment of the static load test, the force on the light-load side outrigger is retained at 15% of the crane's gravity, thereby obtaining a more accurate standard value of the total moment under the static load test. This value plays a key role in the subsequent pressure calculation when the outrigger is subjected to force, and can improve the accuracy of the calculation results of the outrigger force, making the calculation results more accurate, and effectively preventing the overturning of the truck crane caused by insufficient bearing capacity of the foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the plan layout of the truck crane.

[0028] Figure 2 Schematic diagram of equivalent transfer of load at point O by crane.

[0029] Figure 3 This is a schematic diagram of how load changes when a crane is operating.

[0030] Figure 4 This is the force analysis diagram of the outrigger under the combined action of N and M;

[0031] Figure 5 Schematic diagram of the redistribution of outrigger forces.

[0032] Figure 6 It is a schematic diagram of the relationship curve between the outrigger pressure and angle. DETAILED DESCRIPTION

[0033] The present invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the application.

[0034] This embodiment provides a method for calculating the support pressure of a crane, which is mainly used to calculate the stress conditions of the four legs of the crane when the crane is working, so as to avoid the overturning problem of the truck crane caused by insufficient bearing capacity of the foundation.

[0035] The method of this embodiment is specifically as follows.

[0036] The plane layout of the truck crane is as follows: Figure 1 As shown. Figure 1 In the figure, T1, T2, T3, and T4 are the numbers of the four legs, and point O is the geometric center of the four legs. In the coordinate system, the x-axis is the horizontal span direction of the legs, the y-axis is the longitudinal span direction of the legs, and the y-axis points to the front of the vehicle, and point O is the origin of the coordinate system.

[0037] The load of the crane on point O:

[0038] Based on the provisions of the overall anti-overturning stability of the truck crane, during the static load test, the entire load of the crane is equivalently transferred to point O, see Figure 2 , the standard value of the self-weight load acting on point O in the test condition can be obtained as N z And the standard value of vertical load under test conditions N e , the standard value of the moment generated by the test load is M e , and the standard value of the total moment of the test condition M s In a specific implementation manner provided in this embodiment, main parameters of the truck crane are shown in Table 1.

[0039] Table 1 Truck crane parameters

[0040]

[0041] Test condition Deadweight load standard value N z The calculation formula is as follows:

[0042] N z =(Q1+Q2+Q3)g (1)

[0043] Standard value of vertical load under test conditions N e The calculation formula is as follows:

[0044] N e =1.25Q e g (2)

[0045] Standard value of moment generated by test load M e The calculation formula is as follows:

[0046] M e =1.25Q e g(R-max{a / 2,b / 2}) (3).

[0047] For the test condition, the standard value of the total moment M s When calculating, the outrigger on the light-load side retains the standard value of the crane gravity, i.e., the deadweight load N. z 15%, then there is

[0048]

[0049] Therefore, the standard value of the total moment under test is M s It can be expressed as:

[0050] M s =(0.35N z +0.5N e )×min{a,b} (4)

[0051] In the above formula, Q1, Q2, Q3, Q e , a, b are shown in Table 1; g is the acceleration due to gravity, which is 9.8 m / s 2 .

[0052] During the static load test, the stabilizing moment M caused by the deadweight load is w It can be calculated as follows:

[0053] M w =M s -M e (5).

[0054] When the truck crane is in operation, the lifting load changes. The standard value of the total vertical load at point O is N, and the standard value of the forward tilt moment generated by the deadweight load of the hoisted object is M. q , the standard value of the total moment M, see Figure 3 , can be calculated according to the following formula:

[0055] N=(Q1+Q2+Q3)g+φ(Q g +Q S +Q)g (6)

[0056] M q =φ(Q g +Q s +Q)g(R-max{a / 2,b / 2} (7)

[0057] M=M w +M q (8)

[0058] Where: Q1, Q2, Q3, Q e , Q s , Q see Table 1; φ is the dynamic load coefficient, which is taken as 1.15. When M>0, it is the forward tilting moment, and when M<0, it is the backward tilting moment.

[0059] As described in Table 2 below, these are the calculated values ​​of the equivalent load on point O when the truck crane is in operation.

[0060] Table 2 Equivalent load on point O during operation of truck crane

[0061] Standard value of total vertical load N(kN) Total torque standard value M (kN·m) 775.67 2174.62

[0062] Truck crane outrigger pressure calculation:

[0063] 1) When the four legs are under pressure

[0064] When the truck crane is working, the direction of the total moment M rotates with the rotation of the boom. Assuming that the angle between M and the x-axis is θ, when M and the x-axis are in the same direction, θ = 0°, and counterclockwise is positive. The force analysis of the outrigger under the combined action of N and M can be seen in Figure 4 .

[0065] The pressures N1, N2, N3, and N4 of the outriggers T1, T2, T3, and T4 are calculated using the following formula:

[0066]

[0067]

[0068] 2) When the three legs are under pressure

[0069] According to the above formulas, when M is in the first quadrant, N1 is the largest and N3 is the smallest, N3≤0 may occur, which means that the outrigger T3 has left the ground. At this time, N3=0, and the pressure is borne by N1, N2, and N4, and should be redistributed. Figure 5 .

[0070] For each angle where N3≤0, the pressures N1, N2, and N4 of the legs T1, T2, and T4 are calculated using the following formula:

[0071]

[0072] The same applies when M is located in other quadrants.

[0073] The relationship curve between the pressure N of each leg and θ calculated by the above method of this embodiment is as follows: Figure 6 As shown. Figure 6 The horizontal axis is the θ value, and the vertical axis is the outrigger pressure value.

[0074] Furthermore, the most unfavorable rotation angle of M and the standard value of the maximum pressure of the outrigger can be obtained, as shown in Table 3.

[0075] Table 3M's most unfavorable rotation angle and standard values ​​of the maximum pressure of the outriggers

[0076]

[0077] Based on the above calculation results, the bearing capacity of the support surface can be verified. Table 4 shows the relevant parameters of the support surface.

[0078] Table 4 Support surface parameters

[0079] project symbol unit Numeric Eigenvalue of foundation bearing capacity <![CDATA[f ak ]]> kPa 100 Quality of outrigger pads <![CDATA[Q d ]]> t 0.4 Leg pad length c m 2 Width of leg pads d m 2

[0080] Assuming that the cushion is sufficiently stiff, the outrigger is located at the center of the cushion, which is axially compressed, and the maximum foundation pressure p max Calculate as follows:

[0081]

[0082] Where: N Figure 4 ;Q d , c, d are shown in Table 4. Finally, the foundation bearing capacity is judged whether it meets the requirements according to the calculation results, as shown in Table 5.

[0083] Table 5 Bearing capacity of supporting surface

[0084] <![CDATA[The maximum foundation pressure p max (kPa)]]> <![CDATA[Characteristic value of subgrade bearing capacity f a (kPa)]]> in conclusion 93 100 Meeting the requirements

[0085] Note: a is the corrected characteristic value of foundation bearing capacity. Since the cushion is located on the surface and has a small width, f a =f ak .

[0086] In this embodiment, in order to verify the accuracy of the method proposed in the present invention, actual test verification is also carried out based on the provided outrigger pressure calculation method. The actual test parameters of the truck crane are shown in Table 6.

[0087] Table 6 Crane test parameters

[0088] Empty rear Rear 8.6t Rear 4.4t Empty side Side 6.3t Driving weight m1(t) 73.1 67.8 65.2 74.1 67.8 Rated load Qn(t) 18.3 17.3 14.7 15.3 15 Working radius R(m) 29.9 31.8 37.4 36 36.7 Boom length L(m) 68.9 68.9 68.9 68.9 68.9 Active weight m2(t) 80 80 80 80 80 Other accessories m3(t) 0 0 0 0 0 Longitudinal distance a(m) 9.4 9.4 9.4 9.4 9.4 Horizontal distance b(m) 9.6 9.6 9.6 9.6 9.6 Hook sling Q1(t) 0.3 0.3 0.3 0.3 0.3 Heavy objects Q2(t) 0 8.3 4.1 0 6 φ 1.15 1.15 1.15 1.15 1.15

[0089] The calculated data and measured data are shown in Table 7.

[0090] Table 7 Comparison of calculated data and measured data

[0091]

[0092] Tests have shown that the maximum deviation of the outrigger pressure data calculated by this method can be controlled within 5%, which has a higher calculation accuracy than traditional methods.

Claims

1. A method for calculating the support pressure of a truck crane, characterized in that: The steps include: S1. Based on the static load test, all the loads of the crane are equivalently transferred to point O, and the standard value of the test condition deadweight load Nz and the standard value of the test condition vertical load Ne acting on point O, the standard value of the moment generated by the test load Me, the standard value of the total moment of the test condition Ms, and the stability moment M caused by the deadweight load are obtained. w ; Point O is the geometric center point of the four legs of the truck crane, Nz, Ne, Me, Ms, M w Calculate according to the following formula: <h2 style=";text-align:left;direction:ltr">N<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> (Q1+Q2+Q3)g (1) N e =1.25Q e g (2) M e =1.25Q e g(R-max{a / 2,b / 2}) (3) M s =(0.35N z +0.5N e )×min{a,b} (4) M w =M s -M e (5) Among them, Q1 represents the weight of the whole crane in driving state, Q2 represents the weight of the detachable counterweight of the crane, Q3 represents the weight of the crane jib and accessories, and Q e It indicates the rated lifting capacity of the crane matched with R, R indicates the working radius, g is the acceleration of gravity, a indicates the longitudinal span of the outrigger, and b indicates the lateral span of the outrigger; S2. Based on the change of the lifting load during the operation of the truck crane, the standard value of the total vertical load N at point O and the standard value of the forward tilting moment M generated by the deadweight load of the hoisted object are obtained. q , standard value of total moment M; S3. Based on the standard value N of the total vertical load and the standard value M of the total moment, the pressure value of each leg when the leg is under pressure is calculated to obtain the pressure curve of each leg.

2. The method for calculating the support pressure of a truck crane according to claim 1, characterized in that: In step S2, the standard value of the total vertical load N at point O and the standard value of the forward tilting moment M generated by the deadweight load of the hanging object are calculated. q , the total torque standard value M is calculated according to the following formula: N=(Q1+Q2+Q3)g+φ(Q g +Q S +Q)g (6) M q =φ(Q g +Q s +Q)g(R-max{a / 2,b / 2} (7) M=M w +M q (8) Where φ is the dynamic load coefficient, Q s Indicates the mass of the sling, Q g It represents the mass of the hook, Q represents the mass of the load, M>0 represents the forward moment, and M<0 represents the backward moment.

3. The method for calculating the support pressure of a truck crane according to claim 2, characterized in that: In step S3, when the truck crane is working, as the boom rotates, the direction of the total moment standard value M also rotates. A coordinate system is established with the lateral span direction of the outrigger as the x-axis, the longitudinal span direction as the y-axis, and point O as the origin. The angle between M and the x-axis is θ. When M and the x-axis are in the same direction, θ=0°, and counterclockwise is positive. The pressures N1, N2, N3, and N4 corresponding to the outriggers T1, T2, T3, and T4 are calculated according to the following formulas:

4. The method for calculating the support pressure of a truck crane according to claim 3, characterized in that: When M is in the first quadrant, N1 is the largest and N3 is the smallest. If N3≤0, it means that the outrigger T3 has left the ground. At this time, all the loads are borne by N1, N2, and N4 and should be redistributed. At this time, the pressures N1, N2, and N4 of the outriggers T1, T2, and T4 are calculated according to the following formula:

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