A foundation platform for vibration reduction and isolation of mechanical equipment and its design method

Abstract

The present invention discloses a basic platform for vibration reduction and isolation of mechanical equipment and a design method thereof, belonging to the field of mechanical vibration reduction. The basic platform includes a cast iron platform, a reinforced concrete platform, a vibration isolator, a pedestal and a ground anchor; the cast iron platform is fixed to the upper surface of the reinforced concrete platform by a plurality of ground anchors, a plurality of pedestals are evenly arranged below the reinforced concrete platform, and a vibration isolator can be detachably installed between the lower surface of the cast iron platform and each of the pedestals, and the vibration isolator is composed of at least one spring. The present invention improves the component structure of the basic platform, utilizes the vibration isolator to reduce the vibration of the platform itself and attenuate the transmission of vibration of external power equipment and pipelines to the equipment installed on the platform, and guides the design of the structural parameters and construction plan of the basic platform through innovative design methods, thereby solving the technical problems of inaccurate vibration control, lack of special design pertinence, and difficult maintenance in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical vibration reduction, and relates to a vibration isolation platform and a design method. More specifically, it relates to a basic platform and a design method for vibration reduction of mechanical equipment. The platform can be used for self-vibration isolation of mechanical equipment and production equipment, and can also be used to isolate the interference of external vibration of the platform. Background Art

[0002] Many mechanical equipment and production equipment will generate large vibrations during operation, which will cause damage to the equipment itself and generate noise pollution. Some equipment needs to be isolated from the influence of external environmental vibration during operation or testing to maintain the accuracy and effect of production and testing. These all require vibration reduction and isolation measures to be taken on the equipment to reduce these influences. At present, the measures used in my country to reduce vibration of mechanical equipment and testing equipment are mainly to fill the lower part of the platform with buffer materials such as sand and rubber pads to achieve the purpose of vibration reduction and isolation. However, this method is relatively simple and has limited vibration reduction effect. It cannot accurately control the vibration of mechanical equipment and isolate the interference of external vibration, and there is no accurate theoretical design method. Therefore, a design method and scheme for a vibration test basic platform is proposed.

[0003] The technical solution most similar to the present invention is a building vibration isolation platform (CN201220312355) of Jiangsu Construction Vocational and Technical College, which has the following disadvantages:

[0004] 1. The platform of this design is to lay vibration isolation pads and fill glass wool under the foundation, which is similar to the traditional method of filling sand and other buffers. The vibration reduction effect is limited and the mechanical vibration cannot be accurately controlled;

[0005] 2. This design is suitable for mechanical equipment with low requirements for vibration isolation, but it is not very suitable for mechanical equipment with strict requirements for vibration isolation, such as vibration and noise detection of ships, warships, vehicles, large precision processing machines, etc.

[0006] 3. The platform does not have a precise design process and cannot be specially designed for specific objects.

[0007] 4. The platform is a disposable device and cannot be maintained. When it reaches its service life or the buffer ages and fails, it can only be dismantled and rebuilt. Summary of the invention

[0008] In response to the above defects or improvement needs of the prior art, the present invention provides a basic platform for vibration reduction and isolation of mechanical equipment and a design method thereof, the purpose of which is to improve the component structure of the basic platform, use vibration isolators to reduce the vibration of the platform itself and attenuate the transmission of vibration of external power equipment and pipelines to the equipment installed on the platform, and guide the design of structural parameters and construction plans of the basic platform through innovative design methods, thereby solving the technical problems of inaccurate vibration control, lack of special design targeting, and difficult maintenance in the prior art.

[0009] To achieve the above object, according to one aspect of the present invention, a basic platform for vibration reduction and isolation of mechanical equipment is provided, comprising: a cast iron platform, a reinforced concrete platform, a vibration isolator, a base and a ground anchor;

[0010] The cast iron platform is fixed to the upper surface of the reinforced concrete platform by a plurality of ground anchors, a plurality of bases are evenly arranged below the reinforced concrete platform, and a vibration isolator is detachably installed between the lower surface of the cast iron platform and each of the bases, and the vibration isolator is composed of at least one spring;

[0011] Each of the vibration isolators is provided with a connecting steel plate at both ends, and anchor sleeves are buried in the lower surface of the reinforced concrete platform and the upper surface of the base; the connecting steel plates are fixed in the corresponding anchor sleeves by bolts according to preset positions; the center elevation deviation of the bottom of a single vibration isolator is not greater than 5mm, the deviation of the plane position is not greater than 3mm, and the inclination of a single vibration isolator is not greater than 1 / 300.

[0012] Furthermore, a plurality of ground anchor installation holes formed by secondary cement casting are provided on the upper surface of the reinforced concrete platform for correspondingly installing each of the ground anchors; the ground anchor installation holes are square holes, and the inner diameters gradually increase from top to bottom.

[0013] Furthermore, each of the vibration isolators is connected in parallel with a damper.

[0014] Furthermore, each vibration isolator is provided with vibration-damping rubber inside.

[0015] Furthermore, it comprises a platform foundation and a foundation pit; the platform foundation is located at the bottom of the foundation pit, and the base is fixed on the platform foundation; vibration isolation joints are arranged around the platform foundation, and vibration-damping materials are filled in the vibration isolation joints.

[0016] Furthermore, the vibration-damping material is vibration-damping sand, vibration-damping carbon flowers, vibration-damping rubber or polystyrene vibration-damping plate.

[0017] Furthermore, stairs are arranged around the platform foundation inside the foundation pit, a maintenance space is provided between the platform foundation and the reinforced concrete platform, and a drainage system is arranged on the platform foundation.

[0018] According to another aspect of the present invention, there is provided a method for designing a basic platform as described in any one of the above items, comprising the following steps:

[0019] (1) Determine the platform design mass m:

[0020] The platform design mass m is greater than 10 times the mass of the equipment to be installed, wherein the platform design mass m is the mass of the assembly consisting of the cast iron platform and the reinforced concrete platform above the vibration isolator;

[0021] (2) Determine the natural frequency f n :

[0022] The natural frequency f of the base platform is designed according to the frequency of the equipment to be installed. n , f>(3~5)f n , f is the minimum excitation frequency of the equipment to be installed;

[0023] (3) According to m and f n , calculate the total stiffness K required for the vibration isolator, then select the vibration isolator arrangement method according to the design size of the basic platform, determine the number of vibration isolators arranged n, and calculate the stiffness k required for each vibration isolator, K=nk;

[0024] (4) Determining the height of each component structure of the basic platform according to the design size and design quality of the basic platform;

[0025] (5) Checking the natural frequency and overall flatness of the foundation platform;

[0026] (6) Based on the parameter design results of steps (1) to (5), determine the reinforcement structure of the reinforced concrete platform and the construction plan of each component structure of the foundation platform.

[0027] Furthermore, the step (3) includes the following sub-steps:

[0028] (3.1) Establishing system vibration model

[0029] According to the structure of the basic platform, the vibration system formed by the basic platform is simplified into a single-degree-of-freedom vibration model, which consists of a mass block m, a massless ideal spring K and a massless damper C, located on the completely rigid foundation. The mass block can only move in the vertical direction. The motion differential equation of the vibration system is:

[0030]

[0031] Where y is the vibration displacement, is the first-order differential of y, is the second-order differential of y, and the ideal spring K is the total stiffness K required by the isolator;

[0032] (3.2) Natural frequency

[0033] The natural frequency of the vibration system is related to the platform design mass m and the total spring stiffness K. The natural frequency of the system is:

[0034]

[0035] If the static sinkage of the spring of the vibration system is known, that is, the compression of the spring after the rigid body presses on the spring, the natural frequency of the system is:

[0036]

[0037] δ is the static sinking of the spring;

[0038] (3.3) Determination of the system frequency ratio of the vibration system

[0039] For single-degree-of-freedom vibration, when the vibration driving force is a simple harmonic force, the vibration isolation transmissibility T of the isolator can be obtained:

[0040]

[0041] T T is the force transmitted to the foundation through the isolator, T0 is the driving force on the mass block, ξ is the system damping ratio, is the system frequency ratio, that is, the ratio of the driving force frequency to the natural frequency of the vibration system;

[0042] when When T < 1, the vibration isolator plays a role of vibration isolation, and the transmission rate decreases with the increase of frequency ratio;

[0043] when When T>1, the isolator is in the resonance region, and the isolator will increase the amplitude of the isolated body;

[0044] when When , the transmissibility increases with the increase of damping; when The transmissibility decreases as the damping increases.

[0045] Further, the steps include the connection construction scheme design of the vibration isolator and the construction scheme design of the vibration isolation joint;

[0046] The construction scheme of the vibration isolator is designed as follows: first, pour the concrete of the lower column of the vibration isolator to form the foundation, and during the pouring process, the position of the anchor sleeve must be fixed; after the strength of the foundation reaches the design requirements, the vibration isolator is installed, and then the steel bars of the reinforced concrete platform are tied above the vibration isolator, and the formwork is supported and concrete is poured to obtain the reinforced concrete platform; when supporting the formwork and pouring concrete above each vibration isolator, temporary lateral supports are set for the other vibration isolators around the vibration isolator to prevent horizontal displacement of the other vibration isolators around the vibration isolator;

[0047] The construction scheme of the vibration isolation joint is designed as follows: the raft foundation under the foundation is cast separately from the foundation soil around the foundation pit, thereby forming a vibration isolation joint around the raft foundation to separate the foundation platform from the surrounding foundation soil; and then filling the vibration isolation joint with vibration-damping material.

[0048] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0049] 1. The basic platform of the present invention is mainly used as an installation platform for system equipment. Its main function is to install and fix most equipment and pipeline accessories and bear their mass load. It is mainly based on the vibration isolator to reduce the system's own vibration and attenuate the transmission of vibration of external power equipment and pipelines to the system equipment. Since each vibration isolator adopts an assembled installation design, it is easy to carry out adaptive design and accurate calculation of various performances and sizes, and easy to maintain later. The basic platform is widely applicable to large-scale mechanical equipment (marine machinery, ships, and production equipment). It can be used to avoid the introduction of external vibrations during equipment self-detection, and can also be used to reduce the vibration of production equipment itself.

[0050] 2. The design of the ground anchor installation hole with a small top and a large bottom in the secondary pouring makes the cast iron platform and the reinforced concrete platform firmly connected, and the overall flatness is easy to adjust. The design, installation and maintenance are very convenient, and the performance is reliable.

[0051] 3. The vibration isolators of the platform are of various forms. A single spring can be used, or several springs can be combined to form a vibration isolator. The vibration isolator can reduce the natural frequency of the equipment support system, thereby isolating the high-frequency vibration generated by the equipment. At the same time, it absorbs the vibration energy through parallel damping and / or filling vibration-damping rubber, and ensures the stability of the equipment. It can also significantly reduce the environmental vibration around the equipment and eliminate structural secondary noise.

[0052] 4. By placing the foundation platform in the foundation pit and coordinating the design of the vibration isolation joint, the platform foundation can be separated from the surrounding of the foundation pit to reduce the introduction of external vibrations, and vibration-damping materials can be filled in the vibration isolation joints to further reduce the introduction of external vibrations.

[0053] 5. Since the present invention is of assembled design and has maintenance space, it can be maintained manually. The platform is located in the foundation pit, and stairs are provided to facilitate workers to enter and exit the maintenance space for replacement and maintenance of parts such as vibration isolators and bolts. A drainage system is provided to prevent water accumulation in the foundation pit from corroding the equipment, thereby extending the life of the equipment.

[0054] 6. The design calculation process of the foundation platform of the present invention is relatively rigorous, and can be accurately designed according to the needs of actual vibration reduction equipment, and can be applied to the design of platforms of various sizes.

[0055] 7. The connection method between the cast iron platform and the reinforced concrete platform, and the connection method between the vibration isolator and the base are safe and reliable, and the construction is convenient. The construction plan of the vibration isolation joint is simple and the practical effect is obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a schematic cross-sectional view of a basic platform structure of a preferred embodiment of the present invention;

[0057] Figure 2 It is a simplified vibration system model of the base platform;

[0058] Figure 3 It is a simplified forced vibration system after the vibration equipment passes through the vibration isolator and the rigid foundation;

[0059] Figure 4 It is the relationship diagram of transmissibility T, frequency ratio and damping;

[0060] Figure 5 is a schematic diagram of the spring and foundation plan layout of a specific example of the present invention;

[0061] Figure 6 It is a schematic diagram of the structural parameters of a single spring of a spring isolator;

[0062] Figure 7 It is a schematic diagram of the layout of the ground anchor installation holes of a specific example of the present invention;

[0063] Figure 8 It is the installation diagram of the vibration isolator;

[0064] Fig. 9 It is a schematic diagram of the general assembly of the foundation platform in the foundation pit according to the preferred embodiment of the present invention;

[0065] Fig.10 yes Fig. 9 A partial enlarged view showing the height and width dimensions of a part of the structure in a specific example of the present invention;

[0066] Fig.11 It is a design flow chart of the present invention.

[0067] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0068] 1-cast iron platform, 2-reinforced concrete platform, 3-vibration isolator, 4-base, 5-ground anchor, 6-connecting steel plate, 7-anchor sleeve, 8-bolt, 9-platform foundation, 10-foundation pit, 11-vibration isolation joint, 12-water pump installation hole. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0070] The present invention provides a set of foundation platforms for large equipment seismic isolation, as well as a method flow for designing the foundation platform, and introduces the platform structure and design method of the present invention in detail through a specific case of a 6m×9m foundation platform. The foundation platform has made innovations in the selection of vibration isolators, the connection method of each component, the surrounding foundation and space settings (vibration isolation joints, maintenance channels, underground maintenance space), etc.

[0071] like Figure 1 As shown, the foundation platform of the present invention is mainly composed of the following parts: an upper cast iron platform 1, a reinforced concrete platform 2, a vibration isolator 3, a foundation 4 and a drainage system, etc. The specific design process of the present invention and the main composition, function, selection criteria and interconnection relationship of each component will be introduced one by one below.

[0072] The process of platform design method:

[0073] 1. Determine the platform design mass m. The platform design mass m is the mass of the installation assembly of the reinforced concrete platform above the vibration isolator and the cast iron platform, which should be greater than 10 times the mass of the system equipment to be installed.

[0074] 2. Determine the natural frequency of the system. Usually, the larger the frequency ratio, the better. In order to ensure the effectiveness of the vibration isolation system in actual engineering, the present invention takes f>(3~5)f n , f is the lowest excitation frequency of the device, f n is the natural frequency of the platform itself.

[0075] 3. Calculate the stiffness of the vibration isolator based on the design mass and the natural frequency of the system. Substitute the design mass and the natural frequency of the system into formula (2) to calculate the total stiffness required for the vibration isolator. Determine the arrangement and quantity of the vibration isolators based on the platform size, and then obtain the stiffness required for each vibration isolator.

[0076] 4. Further design the platform height according to the platform design quality. According to the determined platform quality, match the platform height. Calculate the height of each part of the platform based on the bulk density of the materials of each component of the platform and the required height of the design.

[0077] 5. Check the system frequency and overall flatness. Calibrate the platform parameters based on the parameters in steps 1 to 4 to verify whether they meet the design requirements.

[0078] 6. Combine the design parameters of steps 1 to 5 and use PKPM design software to design the construction drawing. Use PKPM structural design software to model, calculate and analyze the platform to obtain the reinforcement diagram of the reinforced concrete structure. PKPM structural design software is a commonly used concrete structure design software in this field, so it will not be described in detail.

[0079] 7. Construction scheme design: According to the designed parameters and concrete reinforcement structure, design the construction scheme for the key parts of the foundation platform.

[0080] The following is a more specific introduction using a 6m×9m foundation platform design as an example. Its performance requirements are as follows:

[0081] This platform is mainly used as an installation platform for system equipment. Its main function is to install and fix most equipment and pipeline accessories and bear their mass load. Through the design of vibration isolators and vibration reduction components, it reduces its own vibration and attenuates the transmission of vibration of external power equipment and pipelines to system equipment. Its requirements include load-bearing, processing and installation accuracy, overall dimensions, platform form, etc.

[0082] (1) Load-bearing capacity: The main user object - a pump unit has a deadweight of about 5 tons. When in use, a maximum of 4 units can be used. Together with auxiliary structures such as the equipment base, the total mass of the equipment running on the platform is about 20 tons;

[0083] (2) Equipment frequency: The main user object - the speed is about 1200 to 3000 rpm, that is, the main excitation frequency is designed to be 20Hz to 50Hz. The platform natural frequency is required to be no greater than 6Hz.

[0084] (3) Installation accuracy: The requirements for the processing and manufacturing of cast iron platforms shall be in accordance with the national standard GB / T22095-2008, and the 3rd level accuracy shall be implemented. The specific requirements for the platform are as follows:

[0085] a. The overall flatness needs to be no greater than the flatness tolerance of the corresponding size. The flatness tolerance of a 6m×9m cast iron platform is 280μm;

[0086] b. The proportion of platform support area should not be less than 10%;

[0087] c. The roughness of the upper panel is processed according to the machining finishing process.

[0088] (4) Dimensions: The platform size is 6m×9m, and the cast iron platform size is 6m×9m×0.35m. The total height from the upper surface of the platform to the lower edge of the vibration isolator should not exceed 1.5m.

[0089] (5) Select an independent vibration isolation platform according to the vibration isolation requirements. The lower part of the platform is the vibration isolator and the base, and the upper part is the reinforced concrete structure and cast iron platform, such as Figure 1 , Fig. 9 shown.

[0090] The core design points and design ideas are as follows:

[0091] Cast Iron Platform:

[0092] The cast iron platform is a heavy-duty platform structure. The ground anchor locking components firmly fix the platform and the foundation as a whole. It is an internationally common platform installation method that can effectively reduce the vibration generated by operation and allow the equipment to operate on a stable basis. The platform is equipped with a large number of standard T-blocks and locking screws to meet the clamping requirements of any equipment, and each platform module is equipped with a universal connecting bolt to ensure that each piece of cast iron is tightly connected. After the construction is completed, the overall cast iron platform is tested for flatness, and the flatness of the working panel is required to meet the corresponding requirements, otherwise it needs to be adjusted horizontally.

[0093] Reinforced concrete platform:

[0094] There is a reinforced concrete platform under the cast iron platform with ground anchor installation holes. The square holes are small at the top and large at the bottom, and secondary cement pouring is used to ensure that the foundation will not be disconnected from the platform when the structure is subjected to large vibration waves.

[0095] Vibration isolator design:

[0096] The design of vibration isolators needs to consider the system vibration model, the system natural frequency, and the system frequency ratio:

[0097] 1. System vibration model

[0098] According to the platform structure, the system can be simplified into a single-degree-of-freedom vibration model. For the convenience of research, the vibration system is integrated and simplified into three parameters for research: the vibration system consists of a mass block m, a massless ideal spring K and a massless damper C, which is located on a completely rigid foundation. The mass block can only move in the vertical direction. Its model is as follows: Figure 2 shown.

[0099] The differential equation of motion for this system is:

[0100]

[0101] 2. Natural frequency

[0102] The natural frequency of the vibration system is related to the total mass m of the vibrating rigid body (cast iron platform + reinforced concrete structure) and the total spring stiffness K (the sum of all spring stiffnesses). The natural frequency of the system is:

[0103]

[0104] If the static sinkage of the vibrating system is known, that is, the compression of the spring after the rigid body presses on it, the natural frequency of the system is:

[0105]

[0106] δ is the static sinking of the spring.

[0107] 3. Determination of system frequency ratio

[0108] The vibration isolator in the present invention can achieve the vibration isolation effect because the rigid connection between the vibration source and the foundation is replaced by an elastic support, thereby reducing the exciting force transmitted from the vibration source to the foundation within a certain frequency range.

[0109] The vibration equipment is connected to the rigid platform foundation through vibration isolators, which can be simplified as follows: Figure 3 The forced vibration system shown in Figure 1 is a forced vibration system. The periodic rotation of the equipment generates periodic external force to excite the system vibration, and its motion differential equation is:

[0110]

[0111] The effect of the vibration isolator is quantified by the vibration isolation transmissibility T. When the mass block is forced to vibrate, the ratio of the force transmitted to the foundation through the spring to the driving force that forces the mass block to vibrate is called the transmissibility T. The transmissibility is a physical quantity that characterizes the vibration isolation effect of the vibration isolator. The smaller the transmissibility, the better the vibration reduction effect. For single-degree-of-freedom vibration, and when the vibration driving force is a simple harmonic force, it can be obtained:

[0112]

[0113] T T is the force transmitted to the foundation through the vibration isolator; T0 is the driving force on the mass block. ξ is the system damping ratio, is the frequency ratio, that is, the ratio of the driving force frequency to the natural frequency of the system.

[0114] Depend on Figure 4 It can be seen that:

[0115] when When T is less than 1, the isolator plays a role of vibration isolation, and the transmission rate decreases with the increase of frequency ratio.

[0116] when When T>1, the isolator is in the resonance region, and the isolator will increase the amplitude of the isolated body.

[0117] when When , the transmissibility increases with the increase of damping; when The transmissibility decreases as the damping increases.

[0118] Generally, the larger the frequency ratio, the better. In this example, based on the minimum excitation frequency of the equipment being about 20Hz and the standard requiring the natural frequency of the vibration isolation system to be no greater than 6Hz, the frequency ratio can be considered to be 5, that is, the system frequency can be taken as 4Hz. When the maximum excitation frequency of the equipment is 50Hz, the frequency ratio is 50 / 4=12.5, which still meets the requirements. Therefore, the system frequency is determined to be 4Hz.

[0119] 4. Selection of vibration isolators

[0120] Generally speaking, in order to achieve the purpose of vibration isolation, the vibration isolation material or vibration isolator should meet the following requirements:

[0121] (1) Excellent elastic properties and low stiffness;

[0122] (2) Large bearing capacity, high strength and appropriate damping;

[0123] (3) Good durability and stable performance, and no significant changes in performance due to changes in external temperature, humidity and other conditions;

[0124] (4) Strong resistance to acid, alkali and oil corrosion;

[0125] (5) It is easy to obtain materials;

[0126] (6) Easy to process, manufacture, repair and replace.

[0127] In vibration isolation projects, steel spring isolators have the advantages of stable performance, strong bearing capacity, long life, strong resistance to environmental pollution, reliable calculation, low natural frequency, etc. They are widely used in vibration isolation and have standardized products. Commonly used are steel cylindrical helical spring isolators. Steel spring isolators are widely used, from vibration isolation of various precision instruments to vibration isolation of tens of tons of forging hammers, vibration isolation of hundreds of tons of railway tracks, and even vibration isolation of entire buildings. Steel spring isolators can achieve satisfactory results.

[0128] The biggest advantage of steel spring isolators is their low natural frequency, which usually ranges from 2Hz to 6Hz. Therefore, their vibration isolation effect is very good, and damping components such as rubber pads and dampers can be added as needed to dissipate vibration energy.

[0129] 5. Calculation of vibration isolator parameters

[0130] In this case, the main user of the foundation platform is a pump unit with a deadweight of about 5t. When in operation, there are up to 4 units. Together with auxiliary structures such as the equipment base, the total mass of the equipment running on the platform is about 20t. According to the standard that the design mass of the platform should be greater than 10 times the mass of the equipment, the design platform mass in this case is 200t (total mass of cast iron platform + reinforcement + reinforced concrete structure + foundation column), including the structural assembly formed by the cast iron platform and the reinforced concrete platform.

[0131] At this time, the natural frequency of the base platform f n =4.0Hz, mass m=200t=2.0×10 5 kg, the total stiffness required for the vibration isolator can be calculated by formula (2):

[0132] K = 1.263 × 10 8 N / m=1.289×10 4 kg / mm

[0133] According to formula (3), the static sinking degree of the vibration isolator can be calculated as δ=15.63 mm, that is, the static sinking amount of the platform should not be less than 15.63 mm, so the stroke of the spring can be designed and limited accordingly.

[0134] Drainage system design:

[0135] An underground water storage system is set up in the platform foundation and a vacuum water pump is installed at the bottom. If there is too much water, the water can be directly discharged into the ditch to avoid long-term water accumulation on the platform.

[0136] Vibration isolator layout design:

[0137] The entire reinforced concrete structure and cast iron platform are located on the vibration isolator. In this case, the vibration isolator is a vibration damping spring, and the spring is designed according to the national standard GB / T23934-2015 according to the national standard second-level accuracy standard. Figure 6 shown.

[0138] Design requirements and interfaces:

[0139] (1) Total load capacity: 200 tons, 20 positions in total, cross section of each position: 1000 mm × 1000 mm, spring travel: 20 mm.

[0140] (2) Natural frequency: The first-order frequency of the system consisting of the cast iron platform, foundation and isolator (spring) is designed to be 4 Hz.

[0141] (3) Design life: Under the premise of ensuring regular maintenance, the service life of the spring is 30 years.

[0142] Layout plan:

[0143] Twenty square anvil blocks are set up as the base at the bottom of the reinforced concrete platform. The cross section of each base is 1000mm×1000mm. Four springs are arranged at each position, for a total of 80 springs. The required total stiffness is K=1.289×10 4 kg / mm, the stiffness of each spring is k = 161.14kg / mm. The single load capacity must be at least 200t / 80*1.2 = 3.0t. Taking 1.2 times is used as a safety reserve to improve reliability. The distribution position of each vibration isolation spring is as follows Figure 5 shown.

[0144] Four springs form a vibration isolator, which is welded to the steel plate at the top and bottom. The steel plate and the vibration isolator are connected by countersunk bolts. During construction, the anchor sleeve is first embedded in the lower column concrete, connected to the vibration isolator by connecting bolts, and then the upper anchor sleeve of the vibration isolator is installed, and finally the upper column concrete is poured. Before pouring, the slag and debris on the spring support surface should be cleaned or rinsed, and the steel mesh should be tied and laid as required, the formwork should be supported, the concrete should be poured, and the height of the vibration isolator should be measured after compaction.

[0145] like Fig.11 As shown in the figure, the specific design and calculation process of the 6m×9m platform structure is as follows:

[0146] 1. Determine the design mass of the platform. As mentioned above, the design mass of the platform is taken as m = 200t.

[0147] 2. Determine the natural frequency of the system. As mentioned above, in this case, the frequency ratio is 5, that is, the system frequency f n It can be taken as 4Hz.

[0148] 3. Calculate the stiffness of the vibration isolator based on the design mass and system frequency. Substitute the mass and frequency into formula (2) to calculate the total stiffness required for the vibration isolator. Determine the arrangement and quantity of the vibration isolators based on the platform size, and then obtain the required stiffness of each vibration isolator and the corresponding vibration isolator stroke.

[0149] Platform natural frequency f n =4.0Hz, mass m=200t=2.0×10 5 kg, according to formula (2) The total stiffness required for the isolator can be calculated:

[0150] K = 1.263 × 10 8 N / m=1.289×10 4 kg / mm

[0151] According to formula (3) The calculated static sinking degree of the isolator is δ=15.63mm, that is, the static sinking amount of the platform should not be less than 15.63mm, which limits the travel of the spring.

[0152] Since there are 80 springs in this case, the required total stiffness is K = 1.289 × 10 4 kg / mm, the stiffness of each spring is k=K / 80=161.14kg / mm. The load capacity of a single spring must be at least 200t / 80*1.2=3.0t, with 1.2 times as a safety reserve.

[0153] 4. Further design the platform height according to the platform design quality. According to the determined platform design quality, match the platform height. Specifically, calculate the height of each part of the platform based on the bulk density of the materials of each component of the platform and the design required height. Specifically, in this case:

[0154] (1) The total height of the cast iron platform is set at 350mm (the cast iron platform includes the cast iron table top and reinforcement ribs. The solid thickness of the cast iron table top is required to be no less than 170mm-200mm, and 200mm is taken; the thickness of the reinforcement ribs is required to be no less than 50mm, and 150mm is taken). The height of the solid cast iron plate of the cast iron table top is 200mm, that is, 6*9*0.2*7.6=82.08t; the reinforcement ribs (including the hollow iron table + ribbed ribs) are 150mm, and the mass is 0.1 times the mass of the solid cast iron plate, that is, 82.08*0.1=8.208t; the total mass of the cast iron platform is 82.08+8.208=90.288t.

[0155] (2) For reinforced concrete structure, assuming the height of the thick plate is h, the total mass of the reinforced concrete platform can be calculated as 6*9*h*2.6=140.4*h. Assuming the height of the thick plate is h=800mm, the mass of the reinforced concrete platform is 112.32t and the total height is 800mm.

[0156] (3) The height of the isolator is 300 mm and its mass is small and can be ignored.

[0157] Therefore, the platform design mass of the basic platform is 90.288t+112.32t=202.608t, and the total height from the bottom of the vibration isolator to the platform surface is 350+800+300=1450mm. The summary data is shown in the following table.

[0158] illustrate: 1. Vibration isolator height 300mm 2. Cast iron bulk density 7.6t / m3 3. The total mass of the hollow iron table + reinforcement ribs is 0.1 times that of the cast iron table top. <![CDATA[4. The unit weight of reinforced concrete (concrete) is taken as 2.6 t / m 3 , increasing the reinforcement ratio will increase the unit weight]]> 5. The cross section of the foundation column is 1000mm×1000mm, and there are 20 6m*9m platforms. 6. The total height is the height from the bottom of the vibration isolator to the upper surface of the cast iron platform. 7. The total mass is the total mass of the structure above the vibration isolator

[0159] The installation holes of the ground anchor and the layout of the cast iron platform plate are as follows: Figure 7 As shown, the spring installation diagram is as follows Figure 8 , the platform infrastructure diagram is as follows Fig. 9 , Fig.10 .

[0160] 5. Check the system frequency and overall flatness. Calibrate the platform parameters based on the parameters in steps 1 to 4 to verify whether they meet the design requirements. Specifically:

[0161] (1) Check the system frequency. From the stiffness K = 1.289 × 10 4 kg / mm, the total mass of the platform is 202.608t, and the actual frequency of the system is calculated to be 3.97Hz by substituting it into formula (2), while the design frequency is 4Hz, which meets the design requirements.

[0162] (2) Overall flatness. According to the national standard GB / T 22095-2008 "Cast Iron Plate", Article D.1.1, the flatness tolerance calculation formula is t = c1 × l + c2, t is the flatness tolerance of the entire working plane, in micrometers (μm); l is the nominal length of the diagonal of the plate in millimeters, which is a coefficient related to the accuracy level of the plate. When the accuracy is level 3, c1 = 0.024, c2 = 20, the diagonal length of the 6m × 9m platform is l = 10.817m, and the calculated flatness tolerance is t = 280μm, that is, the overall flatness of the platform shall not be greater than 280μm.

[0163] Since the design mass of the platform is 200t, the total mass of the equipment should not be greater than 20t when the platform is in use.

[0164] 6. Use PKPM design software for construction drawing design. Use PKPM structural design software to model, calculate and analyze the platform to obtain the reinforcement diagram of the reinforced concrete structure.

[0165] 7. Construction plan design: Design the construction plan for key parts of the platform.

[0166] (1) Vibration isolator connection structure

[0167] There is a steel plate on the upper and lower sides of the vibration isolator, namely the upper and lower connecting steel plates. The connecting steel plate is connected to the vibration isolator by countersunk bolts. During construction, the anchor sleeve is first embedded in the lower column concrete, connected to the vibration isolator by connecting bolts, and then the upper anchor sleeve of the vibration isolator is installed, and finally the upper column concrete is poured. For specific relationships, see Figure 8 , Fig. 9 .

[0168] Vibration isolator installation instructions:

[0169] 1) The center elevation deviation of the bottom of the vibration isolator shall not exceed 5mm, and the plane position deviation shall not exceed 3mm.

[0170] 2) The inclination of a single vibration isolator shall not exceed 1 / 300.

[0171] 3) Installation order:

[0172] ① Process bolts, sleeves and upper and lower connecting steel plates of vibration isolators;

[0173] ②Install the bolt sleeve;

[0174] ③ Pour the concrete of the lower column of the vibration isolator, and make sure that the bolt sleeve is fixed during the pouring process;

[0175] ④After the concrete reaches the strength requirement, start installing the vibration isolator. First, connect the vibration isolator to the upper and lower connecting steel plates with countersunk bolts, then align the lower connecting steel plate with the lower bolt sleeve and fix it with bolts. Next, align the upper connecting steel plate with the upper bolt sleeve and fix it with bolts, then tie the steel bars of the upper beam, support the formwork, and pour concrete.

[0176] 4) When supporting the upper formwork of the vibration isolator and pouring concrete, temporary lateral supports must be set up for the vibration isolators on all sides to avoid horizontal displacement of the vibration isolators.

[0177] 5) The isolator connecting plate, exposed parts of the bolts and nuts should be treated with rust prevention.

[0178] 6) During the installation phase of the vibration isolator, the horizontality of the top surface of the pier (or column), the top surface of the vibration isolator, and the plane position and elevation of the center of the vibration isolator should be observed and recorded.

[0179] (2) Construction and vibration isolator maintenance channel design

[0180] A manned space is reserved at the bottom of the design to maintain the vibration isolator. The width of the space is not less than 600mm and the height is not less than 800mm, which is convenient for manual maintenance.

[0181] In order to facilitate access to the bottom of the pit for construction and maintenance, a staircase is designed at the edge of the foundation pit. Therefore, the distance between the edge of the platform and the edge of the foundation pit is set to 1000mm, and the distance should not be less than 600mm.

[0182] For normal use, a 990mm wide cantilever cover is set up. During normal use, this area will be covered and opened for repair during maintenance.

[0183] (3) Vibration isolation joint design

[0184] In order to isolate the platform foundation from the surrounding soil and make it an independent foundation, the raft foundation is cast separately from the surrounding foundation pit and a 100mm wide vibration isolation joint is set. Figure 8 The platform foundation structure is shown in the schematic diagram. The vibration isolation gap can be filled with materials such as vibration isolation sand, vibration isolation carbon flowers, vibration reduction rubber, or polystyrene vibration isolation plates to further reduce the interference of external vibration.

[0185] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a basic platform for vibration reduction and isolation of mechanical equipment, the basic platform comprising: A cast iron platform (1), a reinforced concrete platform (2), a vibration isolator (3), a base (4) and a ground anchor (5); The cast iron platform (1) is fixed to the upper surface of the reinforced concrete platform (2) by means of a plurality of ground anchors (5); a plurality of bases (4) are evenly arranged below the reinforced concrete platform (2); a vibration isolator (3) is detachably installed between the lower surface of the reinforced concrete platform (2) and each of the bases (4); the vibration isolator (3) is composed of at least one spring; Each of the vibration isolators (3) is provided with a connecting steel plate (6) at both ends, and anchor sleeves (7) are embedded in the lower surface of the reinforced concrete platform (2) and the upper surface of the base (4); the connecting steel plates (6) are connected and fixed to the corresponding anchor sleeves (7) by bolts (8) according to preset positions; the center elevation deviation of the bottom of a single vibration isolator (3) is not greater than 5 mm, the deviation of the plane position is not greater than 3 mm, and the inclination of a single vibration isolator (3) is not greater than 1 / 300; Characterized in that the design method comprises the following steps: (1) Determine the platform design mass m: The platform design mass m is greater than 10 times the mass of the equipment to be installed, wherein the platform design mass m is the mass of the assembly consisting of the cast iron platform (1) and the reinforced concrete platform (2) above the vibration isolator (3); (2) Determine the natural frequency f n : The natural frequency f of the base platform is designed according to the frequency of the equipment to be installed. n , f>(3~5)f n , f is the minimum excitation frequency of the equipment to be installed; (3) According to m and f n , calculate the total stiffness K required for the vibration isolator, then select the vibration isolator arrangement method according to the design size of the basic platform, determine the number of vibration isolators arranged n, and calculate the stiffness k required for each vibration isolator, K=nk; (4) Determining the height of each component structure of the basic platform according to the design size and design quality of the basic platform; (5) Checking the natural frequency and overall flatness of the foundation platform; (6) Determine the reinforcement structure of the reinforced concrete platform and the construction plan of each component structure of the foundation platform according to the parameter design results of steps (1) to (5); The step (3) comprises the following sub-steps: (3.1) Establishing system vibration model According to the structure of the base platform, the vibration system formed by the base platform is simplified into a single-degree-of-freedom vibration model, which consists of a mass block m, a massless ideal spring K and a massless damper C, and is located on the completely rigid foundation (4). The mass block can only move in the vertical direction. The motion differential equation of the vibration system is: Where y is the vibration displacement, is the first-order differential of y, is the second-order differential of y, and the ideal spring K is the total stiffness K required by the isolator; (3.2) Natural frequency The natural frequency of the vibration system is related to the platform design mass m and the total spring stiffness K. The natural frequency of the system is: If the static sinkage of the spring of the vibration system is known, that is, the compression of the spring after the rigid body presses on the spring, the natural frequency of the system is: δ is the static sinking of the spring; (3.3) Determination of the system frequency ratio of the vibration system For single-degree-of-freedom vibration, when the vibration driving force is a simple harmonic force, the vibration isolation transmissibility T of the isolator can be obtained: T T is the force transmitted to the foundation through the isolator, T0 is the driving force on the mass block, ξ is the system damping ratio, is the system frequency ratio, that is, the ratio of the driving force frequency to the natural frequency of the vibration system; when When T < 1, the vibration isolator plays a role of vibration isolation, and the transmission rate decreases with the increase of frequency ratio; when When T>1, the isolator is in the resonance region, and the isolator will increase the amplitude of the isolated body; when When , the transmissibility increases with the increase of damping; when The transmissibility decreases as the damping increases.

2. The design method according to claim 1, characterized in that: The step (6) includes the connection construction scheme design of the vibration isolator and the construction scheme design of the vibration isolation joint; The construction scheme of the vibration isolator is designed as follows: first, the concrete of the lower column of the vibration isolator (3) is poured to form the foundation (4), and the position of the anchor sleeve (7) must be fixed during the pouring process; after the strength of the foundation (4) reaches the design requirements, the vibration isolator (3) is installed, and then the steel bars of the reinforced concrete platform (2) are tied above the vibration isolator (3), and the formwork is supported and concrete is poured to obtain the reinforced concrete platform (2); when the formwork is supported and concrete is poured above each vibration isolator (3), temporary lateral supports are provided for the other vibration isolators (3) around the vibration isolator (3) to prevent horizontal displacement of the other vibration isolators (3) around the vibration isolator (3); The construction scheme of the vibration isolation joint is designed as follows: the raft foundation below the foundation (4) is cast separately from the foundation soil around the foundation pit, thereby forming a vibration isolation joint around the raft foundation to separate the foundation platform from the surrounding foundation soil; and then filling the vibration isolation joint with vibration-damping material.

3. A basic platform for vibration reduction and isolation of mechanical equipment, characterized in that: It is obtained according to the design method described in claim 1 or 2.

4. A basic platform for vibration reduction and isolation of mechanical equipment as claimed in claim 3, characterized in that: The upper surface of the reinforced concrete platform (2) is provided with a plurality of ground anchor installation holes formed by secondary cement pouring, which are used to correspondingly install each of the ground anchors (5); the ground anchor installation holes are square holes, and the inner diameters gradually increase from top to bottom.

5. The basic platform for vibration reduction and isolation of mechanical equipment according to claim 3, characterized in that: Each vibration isolator (3) is connected in parallel with a damper.

6. A basic platform for vibration reduction and isolation of mechanical equipment as claimed in claim 3, characterized in that: Each vibration isolator (3) is provided with vibration-damping rubber inside.

7. A basic platform for vibration reduction and isolation of mechanical equipment according to any one of claims 3 to 6, characterized in that: It comprises a platform foundation (9) and a foundation pit (10); the platform foundation (9) is located at the bottom of the foundation pit (10), and the base (4) is fixed on the platform foundation (9); a vibration isolation joint (11) is arranged around the platform foundation (9), and the interior of the vibration isolation joint (11) is filled with vibration-damping material.

8. A basic platform for vibration reduction and isolation of mechanical equipment according to claim 7, characterized in that: The vibration-damping material is vibration-damping sand, vibration-damping carbon flowers, vibration-damping rubber or a polystyrene vibration-damping plate.

9. The basic platform for vibration reduction and isolation of mechanical equipment according to claim 7, characterized in that: Stairs are arranged around the platform foundation (9) inside the foundation pit, a maintenance space is arranged between the platform foundation (9) and the reinforced concrete platform (2), and a drainage system is arranged on the platform foundation (9).

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