Bridge pier water blocking ratio calculation method based on flow velocity weight

Abstract

The invention relates to the technical field of river power, and discloses a bridge pier water resistance ratio calculation method based on flow velocity weight, which comprises the following steps: S1, obtaining a water body flow velocity vij before a bridge is built at each group of bridge piers under a certain frequency flood Pj; s2, selecting a water blocking ratio calculation section, orthogonal to the main flood flow direction of the river channel, at the bridge site, and calculating the average flow velocity Vj of the river channel water body under the condition of Pj; s3, calculating the water blocking area Sij of each pier under the condition of Pj; s4, calculating the flow velocity weight wij of the water blocking ratio of each pier under the condition of Pj; s5, calculating a pier water blocking ratio fvj based on the flow velocity weight under the condition of Pj; and S6, determining the water blocking ratio based on the flow velocity weight by taking fv = max {fvj}. Compared with the prior art, the method has the advantages that the influence condition that the water body flow velocities at different positions of the river channel are different and the water blocking degrees are different is considered, the pier water blocking ratio calculation method based on the flow velocity weight is provided, the flow velocity weight is introduced into the water blocking ratio calculation formula, and therefore the actual water blocking condition of engineering can be better reflected.

Description

Technical Field

[0001] The invention relates to the field of river dynamics technology, and in particular to a method for calculating a bridge pier water resistance ratio based on flow velocity weight. Background Art

[0002] In the flood control evaluation of river-related bridges, the water resistance ratio is a very important parameter, which can reflect the degree of water resistance of the bridge piers. According to the "Technical Specifications for Construction Projects within the Scope of River Management" (DB44 / T 1661-2021), the definition of the water resistance ratio refers to the ratio of the project area of ​​the water-blocking structure of the construction project perpendicular to the flood flow direction in the engineering section under the design flood level to the flow area of ​​the same water-passing section before the construction of the project, expressed as a percentage. For bridge projects, the water resistance ratio of the bridge f = s / A, where s is the water resistance area of ​​the bridge; A is the flow area of ​​the river before the bridge is built at the bridge site. When judging the impact of bridges on river water resistance, relevant technicians often use the water resistance ratio f as a controlling parameter for analysis. The larger the water resistance ratio of the bridge, the greater the water resistance effect of the bridge on the river; the smaller the water resistance ratio of the bridge, the smaller the water resistance effect of the bridge on the river.

[0003] For wide and shallow rivers, when there is no obvious distinction between the main channel and the beach, the water velocity of the river is roughly the same, and the above water resistance ratio calculation formula can reflect the water resistance of the bridge. However, for rivers with a main channel and a beach, since the water velocity of the main channel is much higher than that of the beach, the water resistance per unit area of ​​the bridge piers arranged in the main channel is much higher than that of the bridge piers arranged in the beach, and the applicability of the water resistance ratio calculation formula begins to decline.

[0004] The above water resistance ratio formula does not take into account the influence of different water flow velocities at different locations in the river channel and different water resistance degrees. For rivers with developed main channel beaches, it is difficult to objectively reflect the degree of waterlogging of bridge piers. Therefore, a calculation method for bridge pier water resistance ratio based on flow velocity weight is proposed, and the flow velocity weight is introduced into the above water resistance ratio calculation formula, so as to better reflect the actual water resistance of the project. Summary of the invention

[0005] To solve the above technical problems, the purpose of the present invention is to provide a method for calculating the water resistance ratio of bridge piers based on flow velocity weight, and introduce the flow velocity weight into the above water resistance ratio calculation formula, so as to better reflect the actual water resistance situation of the project.

[0006] Based on this, the present invention provides a method for calculating the water resistance ratio of a bridge pier based on flow velocity weight, which comprises the following steps:

[0007] S1, according to the river hydrology, geology, topography, meteorology and other conditions, obtain the flood frequency Pj, (j = 1, 2, ..., m, m is the number of frequency floods), generate the flow velocity distribution map at the bridge site under the condition of Pj, and use the software numerical simulation results to read the water flow velocity vij before the bridge is built at each group of piers (i = 1, 2, ..., n, n is the number of pier groups in the river);

[0008] S2, select the water resistance ratio calculation section orthogonal to the main flood direction of the river at the bridge site, and obtain the area Aj of the river flow section and the flow rate Qj of the river flow section under the condition of Pj on the water resistance ratio calculation section;

[0009] S3, according to Vj = Qj / Aj, calculate the average flow velocity Vj of the river water under Pj condition;

[0010] S4, measure the plane angle rij (i=1, 2, ..., n) between the axial direction of the bridge pier along the water flow direction and the main flood direction of the river;

[0011] S5, according to Sij = (bij*cos(rij)+aij*tan(rij))*hij, calculate the water blocking area Sij (i=1, 2, ..., n) of each pier under the Pj condition, where bij is the width of the pier along the bridge axis under the Pj condition, aij is the length of the pier along the water flow direction under the Pj condition, and hij is the river water depth at the i-th group of piers under the Pj condition;

[0012] S6, calculate the velocity weight wij of the water resistance ratio of the i-th group of bridge piers under the condition Pj, wij=vij / vj, (i=1, 2, ..., n);

[0013] S7, calculate the pier water resistance ratio fvj based on the velocity weight under the condition Pj, fvj=Σwi j*s ij / Aj, (i=1, 2, ..., n);

[0014] S7, repeating steps S1 to S6, calculating the pier water resistance ratio fvj based on the flow velocity weight under each Pj condition (j=1, 2, ..., m);

[0015] S8, take fv=max{fvj}, j=1, 2, ..., m, which is the water resistance ratio of the bridge.

[0016] The embodiment of the present invention provides a method for calculating the water resistance ratio of a bridge pier based on flow velocity weight. Compared with the prior art, the method has the following beneficial effects:

[0017] This application takes into account the influence of different water velocities and different water resistance degrees at different locations in the river channel, and proposes a calculation method for the water resistance ratio of bridge piers based on flow velocity weight. The flow velocity weight is introduced into the above-mentioned water resistance ratio calculation formula, so as to better reflect the actual water resistance situation of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic cross-sectional view of the arrangement of bridge piers according to some embodiments of the present application;

[0019] Figure 2 A schematic plan view of the arrangement of bridge piers according to some embodiments of the present application;

[0020] Figure 3 This is a flow chart of a method for calculating the water resistance ratio of a bridge pier based on flow velocity weight in this application;

[0021] In the picture, 1, 1# pier; 2, 2# pier; 3, 3# pier. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0023] It should be understood that the present invention uses the terms "front", "back", etc. to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, "front" information may also be referred to as "back" information, and "back" information may also be referred to as "front" information without departing from the scope of the present invention.

[0024] like Figures 1 to 3 As shown, an embodiment of the present invention provides a bridge across a river, the river width at the bridge site is 160m, the angle between the bridge axis and the river channel is 180°, there are 3 groups of piers 1#, 2# and 3# arranged on the riverbed, and the abutments are all buried below the riverbed surface. Among them, 1# pier 1 is located on the left bank river beach, with a pier width of 2m and a length of 25m in the downstream direction; 2# pier 2 is located in the main channel, with a pier width of 3.5m and a length of 26m in the downstream direction; 3# pier 3 is located on the right bank river beach, with a pier width of 1.5m and a length of 25m in the downstream direction. At the bridge site, the main channel and the side beach of the river channel are well developed, the left bank beach is 40m wide, the main channel is 60m wide, and the right bank beach is 60m wide. According to hydrological data, at the proposed bridge site, under the flood frequency P=5%, the water level is 2.00m and the cross-sectional flow is 582.00m 3 / s; Under flood frequency P = 2%, the water level is 2.30m and the cross-sectional flow is 677.82m 3 / s; Under flood frequency P = 1%, the water level is 2.50m and the cross-sectional flow is 734.85m 3 / s. Now calculate the water resistance ratio of the bridge based on the flow velocity weight.

[0025] The calculation process of the bridge pier water resistance ratio based on flow velocity weight is as follows:

[0026] S1. According to the river hydrology, geology, topography, meteorology and flood control standards, the numerical simulation results of MIKE software were used to obtain the water flow velocity vij (i=1, 2, ..., n, n is the number of pier groups in the river, here n=3; j=1, 2, 3) before the bridge was built at each group of piers under the conditions of three frequency floods Pj (j=1, 2, ..., m, m is the number of frequency floods, here j=3, corresponding to different frequency floods of 20, 50 and 100 years, respectively), see Table 1.

[0027] Table 1 Calculation table of water velocity vij before bridge construction at each group of piers

[0028] Pier Number 1# 2# 3# Flood frequency Pj Flow rate vi1(m / s) 0.30 1.50 0.20 P1＝5％ Flow rate vi2 (m / s) 0.33 1.65 0.22 P2＝2％ Flow rate vi3 (m / s) 0.36 1.80 0.24 P3＝1％

[0029] S2, select the water resistance ratio calculation section at the bridge site that is orthogonal to the main flood direction of the river, obtain the river flow area Aj and river flow Qj under the Pj condition, and calculate the average flow velocity Vj of the river water body under the Pj condition according to Vj=Qj / Aj, as shown in Table 2.

[0030] Table 2 Calculation table of average flow velocity Vj of river water

[0031]

[0032] S3, calculate the water blocking area S ij (i = 1, 2, 3; j = 1, 2, 3) of each pier under the condition of Pj, as follows:

[0033] S31, the plane angle ri j (i = 1, 2, 3; j = 1, 2, 3) between the axial direction of the bridge pier along the water flow direction and the main flood direction of the river channel is measured, which is determined according to the numerical simulation results of MIKE software and is summarized in Table 3.

[0034] Table 3r ij summary table

[0035] Pier Number 1# 2# 3# Flood frequency Pj Angle (°) r11＝3 r21＝3 r31＝4.5 P1＝5％ Angle (°) r12＝3 r22＝3 r32＝4.5 P2＝2％ Angle (°) r13＝3 r23＝3 r33＝4.5 P3＝1％

[0036] S32, according to Sij = (bij*cos rij+aij*tan rij)*hij, (i=1, 2, 3). Where bij is the width of the bridge pier along the bridge axis under the Pj condition, aij is the length of the bridge pier along the water flow direction under the Pj condition, and hij is the river water depth at the i-th group of bridge piers under the Pj condition. The calculation results are listed in Table 4.

[0037] Table 4 Sij calculation table

[0038]

[0039] S4, calculate the velocity weight wij of the water resistance ratio of the i-th group of bridge piers under the condition of Pj, wij=vij / vj, (i=1ˉn). See Table 5.

[0040] Table 5 Calculation table of flow rate weight wij

[0041]

[0042]

[0043] S5, calculate the pier water resistance ratio fvj based on the flow velocity weight under the condition of Pj, fvj=Σwij*sij / Aj, (i=1, 2, 3).

[0044] Fv1=Σwi1*si1 / A1

[0045] =(0.273*6.61+1.366*29.14+0.182*5.19) / 530=8.03%.

[0046] S6, repeat the above steps S1 to S5, and we can get:

[0047] Fv2=Σwi2*s i2 / A2==8.02%,

[0048] Fv3=Σwi3*si 3 / A3==8.34%,

[0049] S7, take fv = max{fvj}, j = 1, 2, 3. This is the bridge water resistance ratio.

[0050] fv=max{8.03%, 8.02%, 8.34%}=8.34%.

[0051] The water resistance ratio of the proposed bridge based on the flow velocity weight is 8.34%, corresponding to the P3=1% frequency flood condition, and the water resistance ratio of the proposed bridge based on the flow velocity weight has been calculated.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for calculating the water resistance ratio of a bridge pier based on flow velocity weight, characterized in that: The steps include: S1, according to the river hydrology, geology, topography, meteorology and other conditions, obtain the flood frequency Pj, (j = 1, 2, ..., m, m is the number of frequency floods), generate the flow velocity distribution map at the bridge site under the condition of Pj, and use the software numerical simulation results to read the water flow velocity vij before the bridge is built at each group of piers (i = 1, 2, ..., n, n is the number of pier groups in the river); S2, select the water resistance ratio calculation section at the bridge site that is orthogonal to the main flood direction of the river channel, and calculate the river channel flow section area Aj and the flow rate Qj of the river channel flow section under the condition of Pj on the water resistance ratio calculation section; S3, according to Vj = Qj / Aj, calculate the average flow velocity Vj of the river water under Pj condition; S4, measure the plane angle rij (i=1, 2, ..., n) between the axial direction of the bridge pier along the water flow direction and the main flood direction of the river; S5, according to Sij = (bij*cos(rij)+aij*tan(rij))*hij, calculate the water blocking area Sij (i=1, 2, ..., n) of each pier under the Pj condition, where bij is the width of the pier along the bridge axis under the Pj condition, aij is the length of the pier along the water flow direction under the Pj condition, and hij is the river water depth at the i-th group of piers under the Pj condition; S6, calculate the velocity weight wij of the water resistance ratio of the i-th group of bridge piers under the condition Pj, wij=vij / vj, (i=1, 2, ..., n); S7, calculate the pier water resistance ratio fvj based on the flow velocity weight under the condition Pj, fvj = Σwij*sij / Aj, (i = 1, 2, ..., n); S7, repeating steps S1 to S6, calculating the pier water resistance ratio fvj based on the flow velocity weight under each Pj condition (j=1, 2, ..., m); S8, take fv=max{fvj}, j=1, 2, ..., m, which is the water resistance ratio of the bridge.

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