CN-116186849-B - Rigidity design method of self-supporting stiffening steel chimney

CN116186849BCN 116186849 BCN116186849 BCN 116186849BCN-116186849-B

Abstract

The invention discloses a rigidity design method of a self-supporting stiffening steel chimney, and belongs to the technical field of structural engineering. Firstly, according to the initially designed chimney size and the designed basic wind pressure value, respectively calculating a forward wind load standard value and a horizontal wind vortex-induced resonance equivalent static load, and solving to obtain a cylinder top horizontal displacement theoretical solution based on a structural mechanics virtual work principle. And secondly, taking the influence of deformation characteristics of the chimney shell and the like into consideration, multiplying the theoretical solution by a horizontal displacement maximum value correction coefficient to obtain a horizontal displacement true value with the maximum absolute value of the top of the chimney barrel. Finally, it is checked whether the true value of the horizontal displacement exceeds the specification limit to determine whether the chimney wall thickness needs to be increased to increase its stiffness. The method is accurate and reliable, is simple and convenient to calculate, can save construction consumables as much as possible on the premise of ensuring the structural rigidity of the chimney barrel, and is beneficial to obtaining a reasonable and reliable rigidity design scheme of the self-supporting stiffening steel chimney under the combined action of downwind and crosswind loads.

Inventors

WANG DENGFENG
LIU SIYANG
YANG SHIQING
LU ZHENGHONG
ZHANG YUAN
Bao dongyang
CHENG JIAJUN
CHENG JI

Assignees

江南大学
华仁建设集团有限公司

Dates

Publication Date: 20260508
Application Date: 20230207

Claims (8)

1. The method for designing the rigidity of the self-standing stiffening steel chimney is characterized by comprising the following steps of: Firstly, preliminarily setting the total height H of a cylinder body of the self-supporting stiffening steel chimney, the middle surface diameter D of a circular section of the cylinder body and the wall thickness t of the cylinder body, and determining the design basic wind speed v 10 of an engineering construction region at the standard height of the cylinder body 10m away from the ground; Determining wind load annular body form coefficients mu s , wind vibration coefficients beta z and wind pressure height change coefficients mu z of different positions of the preliminary set steel chimney structure when the downwind load acts, so as to calculate downwind wind load standard values w k of different positions of the surface of the steel chimney; Judging whether a steel chimney generates a horizontal wind direction vortex-induced resonance response or not through a Reynolds number Re, and obtaining a vortex-induced resonance horizontal wind load calculation formula and a horizontal wind load static amplitude p L,j,max born by a chimney barrel in a resonance area based on a Lu Man sinusoidal force model when the Reynolds number Re is more than 3.5 multiplied by 10 6 ; the Reynolds number Re is calculated as follows: (1) Wherein v is the actual wind speed of the calculated altitude; the method of multiplying the static amplitude p L,j,max of the crosswind resonance load by the equivalent coefficient gamma eq of the crosswind resonance power in static analysis is adopted to obtain an equivalent crosswind direction vortex-induced resonance static wind load p L,j,eq ; Based on the structural mechanics virtual work principle, according to the principle that the cantilever flexural member ignores the influence of axial deformation and shear deformation on the displacement of the cylinder top under the action of wind load, solving to obtain a horizontal displacement theoretical solution taking the cylinder top displacement delta c caused by bending deformation as a rigidity control point under the action of the equivalent transverse wind direction vortex-induced resonance static wind load p L,j,eq ; Providing a correction coefficient beta of the maximum horizontal displacement of the top of the chimney barrel; Correcting the theoretical solution of the horizontal displacement of the top of the chimney barrel under the action of the designed wind load to obtain the true horizontal displacement value delta max with the maximum absolute value of the barrel top section: (3) Step four, checking rigidity; If the maximum value of the horizontal displacement of the modified cylinder top section does not exceed the horizontal displacement limit value H/100 at the design wind speed, judging that the steel chimney structure meets the rigidity requirement at the design wind speed, wherein the rigidity checking formula is as follows: (4) And fifthly, when the initially designed steel chimney structure cannot meet the formula (4) and the rigidity design cannot meet the requirement, reinforcing the horizontal wind load resistance rigidity of the chimney by adopting a method of thickening the wall thickness t of the chimney, encrypting the circumferential stiffening ribs or increasing the sections of the circumferential stiffening ribs, and repeatedly performing rigidity checking calculation according to the steps one to four until the rigidity checking calculation requirement of the formula (4) is met.
2. The method for designing the rigidity of the self-supporting stiffened steel chimney according to claim 1, wherein the standard value w k of the downwind load is calculated as follows: (5) (6) Wherein w k is a standard value of forward wind load at any position in the circumferential direction at the z-height, beta z is a wind vibration coefficient at the z-height, mu s is a circumferential body type coefficient of the wind load, mu z is a change coefficient of wind pressure height at the z-height, w 0 is basic wind pressure of a chimney construction site, namely a wind pressure value corresponding to the design basic wind speed v 10 , and rho=1.25 kg/m 3 is standard air density.
3. The method for designing the rigidity of the self-supporting stiffening steel chimney according to claim 2, wherein the wind load annular body form factor mu s is a function of the calculated position and the wind passing annular included angle theta at the determined height position of the cylinder structure, and the body form factor specification values of different high-diameter ratio structures are subjected to numerical fitting by using Fourier series to obtain the following calculation formula: (7) Wherein mu s (theta) is the body type coefficient of the surface of the steel chimney, theta is the circumferential included angle between the calculated point and the wind passing direction, and c i is the Fourier series fitting coefficient.
4. The method for designing the rigidity of a self-supporting stiffened steel chimney according to claim 3, wherein a calculation formula of a cross wind load and a calculation formula of a wind load amplitude of the section of the chimney barrel subjected to cross wind vortex-induced resonance are as follows: (8) (9) (10) Wherein p L,j (z, T) is the horizontal wind load of vortex-induced resonance in the unit height range at the z height when the j-th order vortex-induced resonance occurs at the T moment, p L,j,max (z) is the horizontal wind load amplitude of the vortex-induced resonance in the unit height range at the z height when the j-th order vortex-induced resonance occurs, v cr,j is the critical wind speed when the j-th order resonance occurs, mu L is the lift coefficient, mu L =0.25;ω j is the self-vibration circle frequency of the chimney corresponding to the j-th order vibration mode of the cylinder, T is time, f j is the self-vibration frequency of the j-th vibration mode of the chimney, and S t is Stokes number; The calculation formula of the horizontal wind direction vortex-induced resonance equivalent static wind load p L,j,eq is as follows: (11) Wherein p L,j,eq is equivalent static wind load in the unit height range of the j-th order crosswind direction vortex-induced resonance under the action of the designed basic wind speed v 10 when the j-th order vortex-induced resonance occurs in the structure, and gamma eq is equivalent dynamic coefficient of the designed crosswind direction vortex-induced resonance under the action of the basic wind speed.
5. The method for designing the rigidity of a self-supporting stiffened steel chimney according to claim 4, wherein the value range of the transverse wind direction vortex-induced resonance dynamic equivalent coefficient gamma eq under the action of the basic wind speed is [52,56].
6. The method of designing the stiffness of a free-standing stiffened steel chimney of claim 5, wherein the bending moment M p (z 0 ) caused by the effect of the crosswind equivalent static load at any height position z 0 is calculated as follows: (12) (13) (14) z 0 ＞H 2 M p,3 (z 0 ) = 0 (15) Wherein H 1 is the height of the starting point of the horizontal wind vortex-induced resonance region, H 2 is the height of the vertex of the horizontal wind vortex-induced resonance region, and when H 2 is more than or equal to H, H 2 =H is taken; The calculation formula for obtaining the starting point height H 1 of the resonance area and the peak height H 2 of the resonance area according to the change rule of the wind profile index is as follows: (16) (17) (18) where v H is the wind speed at the total height H of the cylinder and α is the surface roughness coefficient.
7. The method for designing the rigidity of the self-supporting stiffened steel chimney according to claim 6, wherein the calculation formula of the theoretical solution delta c of the horizontal displacement of the chimney top caused by the equivalent static load action of the crosswind in the third step is as follows: (19) Wherein E is the elastic modulus of steel, and I is the moment of inertia of the circular section of the chimney.
8. The method for designing the rigidity of the self-supporting stiffening steel chimney according to claim 7, wherein the maximum horizontal displacement correction coefficient beta of the top of the chimney barrel is directly calculated according to the following formula, which is obtained by adopting a least square method to carry out numerical fitting on the maximum horizontal displacement correction coefficient beta of the top of the chimney barrel: (20) And lambda 1 、λ 2 、λ 3 、λ 4 、μ 1 、μ 2 、μ 3 、μ 4 is a fitting formula coefficient corresponding to the stiffening steel chimney structures with different heights and different height-diameter ratios respectively.

Description

Rigidity design method of self-supporting stiffening steel chimney Technical Field The invention relates to a rigidity design method of a self-supporting stiffening steel chimney under the combined action of downwind and crosswind loads, and belongs to the technical field of structural engineering. Background The self-supporting steel chimney is widely applied in the fields of steel, thermal power, metallurgy and the like. The wall of the self-supporting steel chimney is thinner, the height diameter is larger, the self-supporting steel chimney has the characteristics of high flexibility, large body weight, light weight, small damping and the like, is a typical wind sensitive structure, and wind load becomes a control factor in the design process of the self-supporting steel chimney. The high-rise circular section steel chimney can be subjected to the combined action of downwind and crosswind in the use process, so that the displacement of the steel chimney structure under the combined action of downwind and crosswind loads is controlled, the rigidity of the steel chimney for resisting wind loads is ensured not to be too weak, and a practical and reliable rigidity design method is provided. At present, most of domestic steel chimney manufacturers carry out structural design according to the chimney design specification (GB 50051-2013) in China and work according to the prior experience, but the calculation method specified in the specification mainly aims at concrete and brick chimneys, and the quantitative terms related to the self-standing pure steel chimneys with larger height diameters are less and cannot completely meet the requirements of the structural design of the existing projects. Regarding wind-induced response calculation regulation, the chimney structure is simplified into a thin-walled circular tube component by the specification, and the given wind-induced response calculation formula does not consider the influences of factors such as the non-uniform rigidity distribution of the cylinder caused by the characteristics of the steel chimney shell, the initial defects of the structure and the existence of stiffening ribs. In addition, the standard adopts an equivalent load calculation formula to consider the loads of the downwind direction and the crosswind direction, the given bidirectional wind load effect combination calculation method is relatively simple and general, and the reliability of the bidirectional wind load effect combination calculation method still needs to be subjected to in-depth verification and research. On the one hand, the safety of the chimney structure cannot be guaranteed under certain special conditions, and on the other hand, the utilization rate of materials for designing the chimney structure is low, so that the chimney structure is not economical. Therefore, the displacement response of the self-supporting steel chimney under the combined action of downwind and crosswind loads is necessary to be researched, and the structural rigidity design method is provided, so that the manufacturing cost of the self-supporting steel chimney is reduced as much as possible on the premise of ensuring the structural rigidity of the chimney barrel body, and the economic benefit of the product is improved. Disclosure of Invention In order to optimize the rigidity design to improve the safety of a chimney structure and improve the utilization rate of materials, the invention provides a rigidity design method of a self-standing stiffening steel chimney, which comprises the following steps: Firstly, preliminarily setting the total height H of a cylinder body of the self-supporting stiffening steel chimney, the middle surface diameter D of a circular section of the cylinder body and the wall thickness t of the cylinder body, and determining the design basic wind speed v 10 of an engineering construction region at the standard height of the cylinder body 10m away from the ground; According to the building structure load standard (GB 50009) of China, determining wind load circumferential body type coefficients mu s, wind vibration coefficients beta z and wind pressure height change coefficients mu z at different positions of a preliminarily set steel chimney structure, so as to calculate forward wind load standard values w k at different positions of the surface of the steel chimney; and secondly, the high-rise structure is easy to generate a wind vibration response in the transverse wind direction, wherein the wind vibration resonance in the transverse wind direction is a main factor of the steel chimney to generate the wind damage in the transverse wind direction. And judging whether the steel chimney generates a horizontal wind direction vortex-induced resonance response or not by comprehensively considering the characteristics of the circumferential flow characteristic, the cylinder surface boundary layer morphology, vortex shedding and the like of the cylindrical structure through the