Calculation method for representing performance indexes of pier attached anti-collision facility

Abstract

The invention relates to a calculation method for characterizing performance indexes of a pier-attached anti-collision facility, and belongs to the technical field of anti-collision performance evaluation, and the method comprises the steps: carrying out the integration of an impact force time history in a time domain, and obtaining an impact impulse time history relation; calculating a reduction rate based on the impact impulse time history relationship; according to the calculated reduction rate, the whole fluctuation process of the impact force time travel curve is described, and the larger the reduction rate is, the better the performance of the anti-collision facility is. The obtained reduction rate is more accurate, and the protection performance of the anti-collision facility can be better reflected.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-collision performance evaluation, and relates to a calculation method for characterizing the performance indexes of pier-mounted anti-collision facilities. Background Art

[0002] Currently, the protection performance evaluation of pier-mounted anti-ship / car collision facilities is mainly based on the comparison of the peak impact forces before and after the installation of anti-collision facilities, and the peak impact force reduction rate is used as the performance index, as shown in the following formula:

[0003]

[0004] Where φ is the reduction rate, F max无防护 represents the peak impact force before the installation of anti-collision facilities, and F max有防护 represents the peak impact force after the installation of anti-collision facilities.

[0005] Existing relevant specification documents only make simple regulations on the effective protection performance requirements of pier-mounted anti-collision facilities, that is, the structural anti-ship collision facilities should reduce the ship collision effect borne by the main bridge structure to an acceptable level for itself. There are also relevant specification documents using the ship collision force reduction rate as an index to evaluate the protection performance. For example, for composite fixed protection structures, it should be not less than 20%. By analyzing these specification documents, it can be found that the reduction rate index regulations for composite anti-collision facilities of railway bridges are lower than those of highway bridges, while the regulations for steel + composite anti-collision facilities are higher than those of highway bridges.

[0006] For the overall fixed composite anti-ship collision device, existing relevant specifications give two impact force time history curves with a peak reduction rate of 23%, as shown in Figure 1 (a). Combining with the existing performance index calculation method, it can be known that the protection performance meets the requirements. The purpose of installing anti-collision facilities is to effectively reduce bridge damage. By inputting the two impact force curves into the bridge structure respectively, the comparison of the dynamic responses of the bridge itself with and without protection is obtained, as shown in Figure 1 (b) - (d). It can be found that under the existing performance indexes, the protection of this anti-collision device for the pier is basically zero, indicating that this evaluation index may overestimate the performance of the protection structure. To sum up, the current specifications for the performance of anti-collision facilities are not mature, and the accuracy of evaluating their performance indexes is insufficient.

[0007] Obviously, the impact force time history is a curve with serrated and continuous fluctuations. Only extracting the peak points as performance indexes in the entire time domain will lead to insufficient data. This is because the peak points usually only exist for a very short time, so the impact load characteristics in the entire time domain cannot be considered. The peak reduction rate index essentially simplifies the dynamic problem with a static idea, and it is obviously unreliable to measure the entire impact process by comparing a single peak in the time domain. As shown in Figure 1As shown in (e), to describe the fluctuation process over the entire time history \(t\), the usual approach is to solve the reduction rate \(d\varphi\) for each time step \(dt\). However, since the impact force time history is a continuously fluctuating curve, the reduction rate \(\varphi(t)\) obtained by this method is still a fluctuating curve, making it impossible to quantitatively determine the reduction rate of the anti-collision facility. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a calculation method for characterizing the performance indicators of a pier-attached anti-collision facility, solving the problem that the existing reduction rate calculation method cannot accurately measure the performance of the anti-collision facility.

[0009] To achieve the above purpose, the present invention provides the following technical solutions:

[0010] A calculation method for characterizing the performance indicators of a pier-attached anti-collision facility, comprising:

[0011] Integrate the impact force time history in the time domain to obtain the impact impulse time history relationship;

[0012] Calculate the reduction rate based on the impact impulse time history relationship;

[0013] According to the calculated reduction rate, describe the entire fluctuation process of the impact force time history curve. The larger the reduction rate, the better the performance of the anti-collision facility.

[0014] Furthermore, the impact force time history is an impact force time history curve obtained by numerical simulation methods, used to reflect the relationship between the impact force and time during the impact process.

[0015] Furthermore, the integration of the impact force time history in the time domain to obtain the impact impulse time history relationship is expressed as follows:

[0016]

[0017] Where \(I\) 有防护 and \(I\) 无防护 represent the impulses with and without protection respectively, and \(F\) 有防护 (t) and \(F\) 无防护 (t) represent the impact forces at time \(t\) with and without protection respectively.

[0018] Furthermore, the calculation of the reduction rate based on the impact impulse time history relationship includes:

[0019] Calculate the reduction rate based on the cumulative impulse calculation method; or

[0020] Calculate the reduction rate based on the impulse curve slope calculation method.

[0021] Furthermore, the formula for calculating the reduction rate based on the cumulative impulse calculation method is as follows:

[0022]

[0023] Among them, φ1 represents the reduction rate calculated based on the cumulative impulse.

[0024] Furthermore, when different anti-collision facilities are in protection, it is possible that the cumulative maximum impulse is greater than that without protection. At this time, the reduction rate calculated according to the calculation method based on the cumulative maximum impulse is negative, and this negative reduction rate has no actual physical meaning. Therefore, only when the calculated reduction rate is positive is it used as the performance index of the anti-collision facility.

[0025] Furthermore, the reduction rate is calculated by the calculation method based on the slope of the impulse curve, and the calculation formula is as follows:

[0026]

[0027] Among them, φ2 represents the reduction rate calculated based on the slope of the impulse curve; tan I 有防护 and tan I 无防护 respectively represent the slopes of the impulse curves with and without protection.

[0028] The beneficial effects of the present invention are as follows: After the impact force time history is integrated and transformed in the time domain in the present invention, the impulse curve becomes a straight line in form; at this time, the contributions of both to the pier are still the same, and at the same time, the sawtooth fluctuations of the original impact force curve are eliminated. The present invention proposes two methods for calculating the reduction rate. Compared with the original method, the method based on the cumulative impulse calculation eliminates a large number of high-frequency values of the impact force curve and considers the entire impact process. In the method based on the slope of the impulse curve, the slope of the impulse curve hardly fluctuates significantly during the entire impact process, and the reduction rate dφ at each time step dt is approximately equal to the reduction rate φ over the entire time history. Therefore, the static calculation formula can be used to describe the entire fluctuation process of the impact force time history curve, and the obtained reduction rate will be more accurate. Although the method based on the slope of the impulse curve still uses the static method, the presented results are the time domain results considering the dynamics at each time, having better theoretical advantages and being able to better reflect the protection performance of the anti-collision facility.

[0029] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification.

[0030] Other advantages, objects and features of the present invention will be set forth in part in the following description, and in part will be obvious to those skilled in the art upon examination of the following, or may be learned from the practice of the present invention. The objects and other advantages of the present invention may be realized and obtained by the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0032] Figure 1 For the comparison of existing performance indicators, (a) is the impact force time history curve, (b) is the pier top displacement time history curve, (c) is the pile top moment time history curve, (d) is the pile top shear force time history curve, and (e) is the reduction rate curve φ(t) for each time step dt;

[0033] Figure 2 (a) Impact force time history and (b) impact impulse time history of the improved method of the present invention;

[0034] Figure 3 Flow chart of the calculation method for characterizing the performance indicators of the pier attached anti-collision facility described in Embodiment 1 of the present invention;

[0035] Figure 4 Flow chart of the calculation method for characterizing the performance indicators of the pier attached anti-collision facility described in Embodiment 2 of the present invention;

[0036] Figure 5 Example curve comparison of the steel structure protection device adopted by a certain bridge, where (a) is the impact force time history and (b) is the converted impulse time history;

[0037] Figure 6 In (a)-(l) are 12 groups of impact force time history curves and impulse time history curves selected in Embodiment 2;

[0038] Figure 7 In (a)-(b) are Figure 6 Comparison of pier damage reduction under 12 working conditions given. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0040] It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0041] In the following description, a large number of details are explored to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0042] Embodiment 1:

[0043] The present invention provides a calculation method for characterizing the performance indicators of the pier-attached anti-collision facility. First, through data collection or by numerical simulation methods, the impact force time history curves under unprotected and protected conditions are obtained, as shown in (a) below. Then, the impact force time history is integrated in the time domain to obtain the impact impulse time history relationship, as shown in (b) below. The integration formula is as follows: Figure 2 as shown in (b) below. The integration formula is as follows: Figure 2 as shown in (b) below. The integration formula is as follows:

[0044]

[0045] where I 有防护 and I 无防护 respectively represent the impulses under protected and unprotected conditions, and F 有防护 (t) and F 无防护 (t) respectively represent the impact forces at time t under protected and unprotected conditions.

[0046] It can be found that after the integral transformation, the impulse curve becomes a straight line in form. At this time, the contributions of both to the pier are still the same, and at the same time, the sawtooth fluctuations of the original impact force curve are eliminated.

[0047] such as Figure 3As shown, in this embodiment, a new method for calculating the reduction rate is proposed, that is, calculating the reduction rate based on the cumulative impulse calculation method. As shown in Equation (3), that is, extracting the cumulative impulse of the entire collision process for comparison. Compared with the existing reduction rate calculation methods, a large number of high-frequency values of the impact force curve are eliminated, and the entire impact process is considered.

[0048]

[0049] Among them, φ1 represents the reduction rate calculated based on the cumulative impulse. It can be found that after improvement, Figure 2 the impact impulse reduction rate in (b) is 0. Combining with Figure 1 the reduction rate of the pier dynamic response with and without protection in is also 0, indicating that it is feasible to use the impact impulse as a performance index. Accordingly, an improved performance index calculation method is proposed, and the reduction rate is defined as the comparison of the cumulative maximum impulse with and without protection.

[0050] Embodiment 2:

[0051] In this embodiment, another method for calculating the reduction rate is proposed. As Figure 4 shown, that is, a calculation method based on the slope of the impulse curve. It can be found from (b) in Figure 2 that the slope of the impulse curve hardly fluctuates significantly during the entire impact process, and the slope dφ obtained in each time domain is approximately equal to the average slope φ2 of the impact process. In this way, the original static force calculation formula can describe the entire impact process, and the obtained reduction rate will be more accurate, as shown in Equation (4).

[0052]

[0053] It can be found that after improvement, Figure 2 the impact impulse reduction rate in (b) is 0. Combining with Figure 1 the reduction rate of the pier dynamic response with and without protection in is also 0, indicating that it is feasible to use the impact impulse as a performance index. Accordingly, an improved performance index calculation method is proposed, and the reduction rate is defined as the comparison of the slopes of the impact impulse time history curves with and without protection.

[0054] The two reduction rate calculation methods proposed in Embodiment 1 and Embodiment 2 can both describe the entire fluctuation process of the impact force time history curve, but there are differences in describing the impulse curve. To illustrate the differences, taking the impact force time history curve of a steel structure protection device adopted by a certain bridge as an example, as Figure 5 shown in (a)-(b) in. First, integrate the impact force time history into the impulse time history. The method based on the slope of the impulse curve also considers the entire loading process of the impulse, as Figure 5As shown in (b) thereof, while the cumulative impulse method only considers the peak value of the impulse curve. At the same time, as mentioned above, the slope dφ≈φ obtained in each time domain of the loading section of the impulse curve, such as Figure 5 The dotted line in (b) thereof coincides well with the actual loading section curve. Therefore, although this calculation method still uses the static method, the presented results are the results of each time domain considering the dynamic force. In summary, the calculation method based on the slope of the impulse curve has better theoretical advantages.

[0055] Example 3:

[0056] In this example, all domestic and foreign literatures related to pier anti-collision facilities in the past five years were collected, and 84 impact force time history curves with / without protection were obtained, involving 42 types of pier-mounted anti-collision facilities. Since each literature corresponds to piers of different sizes, for the convenience of analysis and comparison, the piers of a certain channel bridge were uniformly used as the reference, and the above ship collision force curves were respectively applied to the same water level of the pier for analysis. Twelve groups of results were randomly selected to evaluate the improved performance index calculation method proposed above. The selected impact force time history and impulse time history are shown in Figure 6 (a)-(l) thereof.

[0057] Calculations using the two improvement methods proposed in Examples 1-2 found that when different anti-collision facilities are used for protection, their cumulative maximum impulse may be greater than the cumulative maximum impulse without protection. At this time, according to the calculation method based on the cumulative maximum impulse, the reduction rate will be negative, which has no physical meaning at this time. Figure 7 (a)-(b) thereof show the result comparison of calculating the performance index of the anti-collision facility by three methods. Among them, the peak value method is the method adopted by the prior art mentioned in the background technology, the cumulative impulse method is the cumulative impulse calculation method provided in Example 1, and the impulse slope method is the impulse curve slope calculation method provided in Example 2. The comparison of pier damage reduction respectively uses three indicators that can intuitively reflect pier damage, namely pier displacement, bending moment, and shear force. These indicators are all data known from existing materials. At the same time, the comparison of the pier damage situation needs to give the comparison of the entire impact process. Combining Figure 7 the results, through comparative analysis, it can be found that calculating the reduction rate based on the calculation method of the slope of the impulse curve is closer to the actual reduction situation, indicating that the improved method proposed by the present invention can replace the original method and can better reflect the protection performance of the anti-collision facility.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A calculation method for characterizing the performance indicators of pier-mounted anti-collision facilities, characterized in that: Including: Integrating the impact force time history in the time domain to obtain the relationship between the impact impulse time history; Calculating the reduction rate based on the relationship between the impact impulse time history; According to the calculated reduction rate, describe the entire fluctuation process of the impact force time history curve. The larger the reduction rate, the better the performance of the anti-collision facility.

2. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facility according to claim 1, wherein: The impact force time history is the impact force time history curve obtained by the numerical simulation method, which is used to reflect the change relationship of the impact force with time during the impact process.

3. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facility according to claim 2, wherein: The integration of the impact force time history in the time domain to obtain the relationship between the impact impulse time history is expressed as follows: Where I 有防护 and I 无防护 represent the impulse with and without protection respectively, and F 有防护 (t) and F 无防护 (t) represent the impact force at time t with and without protection respectively.

4. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facilities according to claim 3, wherein: The calculation of the reduction rate based on the relationship between the impact impulse time history includes: Calculating the reduction rate based on the cumulative impulse calculation method; or Calculating the reduction rate based on the impulse curve slope calculation method.

5. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facility according to claim 4, wherein: The calculation formula for calculating the reduction rate based on the cumulative impulse calculation method is as follows: Where φ1 represents the reduction rate calculated based on the cumulative impulse.

6. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facilities according to claim 5, characterized in that: When different anti-collision facilities are in protection, it is possible that the cumulative maximum impulse is greater than that without protection. In this case, the reduction rate calculated according to the cumulative maximum impulse calculation method is negative, and this negative reduction rate has no actual physical meaning. Therefore, only when the calculated reduction rate is positive, it is used as the performance index of the anti-collision facility.

7. The calculation method for characterizing the performance indicators of the pier-mounted anti-collision facilities according to claim 4, characterized in that: The calculation formula for calculating the reduction rate based on the impulse curve slope calculation method is as follows: where φ2 represents the reduction rate calculated based on the slope of the impulse curve; tan I 有防护 and tan I 无防护 represent the slopes of the impulse curves with and without protection, respectively.

Images