A temperature control method for assembling incremental launching construction process

Abstract

The application relates to the field of incremental launching construction technology, and discloses a method for temperature control in the process of assembling and incremental launching construction, which comprises determining a longitudinal friction coefficient and a longitudinal friction force of an incremental launching device, analyzing the temperature of a steel box girder, modeling and analyzing the steel box girder, determining a pier with a temperature force greater than the maximum value of the longitudinal friction force of the incremental launching device and defining the pier as a problem pier, and taking temperature control measures for the problem pier. According to the application, the determination of the longitudinal friction coefficient in the process of assembling and incremental launching construction is optimized, the longitudinal friction force of the incremental launching device in the process of incremental launching construction is obtained based on the optimized longitudinal friction coefficient, the most unfavorable temperature gradient is obtained through temperature analysis, the temperature effect of the steel box girder under the most unfavorable temperature gradient is obtained through finite element modeling, the problem pier is determined by comparing the maximum value of the temperature force and the longitudinal friction force of the incremental launching device, and a structure layer with a smaller friction coefficient than the longitudinal friction coefficient is additionally arranged on the problem pier. Finally, the purpose of ensuring the safety of the assembling and incremental launching process is achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the field of incremental launching construction technology, and particularly relates to a temperature control method for incremental launching construction. BACKGROUND

[0002] Under the action of sunshine, sudden temperature drop and environmental temperature of the natural environment, a large temperature gradient is formed between the surface and the interior of the lower steel beam structure of a steel box girder. The gradient distribution is not only shown in the vertical direction, but also increases with the bridge width and the bridge length, and is shown in the horizontal direction and the bridge direction, so that temperature stress is generated, and diseases such as uneven stress distribution of the cross section, local buckling and support displacement are caused, and the bridge structure will be collapsed in a serious case. Therefore, attention must be paid to the temperature field distribution and temperature effect of the steel box girder under the natural environment.

[0003] The bridge is constructed by using the incremental launching method. Due to the irradiation of sunlight, the temperature of the south side web plate of the closed steel box girder without the installed concrete bridge deck is higher than that of the north side web plate. The transverse temperature difference will generate a large transverse bending deformation, and the safety in the incremental launching process is affected.

[0004] Therefore, in addition to the temperature action modes of the vertical temperature difference and the transverse temperature difference, it is necessary to calculate the temperature stress and deformation of the steel box girder structure in combination with the stress characteristics in the incremental launching process of the steel box girder without pavement, so as to provide technical support for the bridge construction. SUMMARY

[0005] The application aims to provide a temperature control method for the incremental launching construction process, so as to solve the technical problems in the background technology.

[0006] In order to achieve the above-mentioned purpose, the application discloses a temperature control method for the incremental launching construction process, the steel box girder is pushed to the pier in the incremental launching construction process, and the method comprises the following steps.

[0007] Determine parameters, the parameters comprising a longitudinal friction coefficient and a longitudinal friction force of the launcher;

[0008] Perform temperature analysis on the steel box girder based on the measured temperature field, and obtain a measured temperature field analysis result;

[0009] Model analysis is performed on the steel box girder by using a finite element software and based on the measured temperature field analysis result, and a model analysis result is obtained;

[0010] Based on the model analysis result, a pier where the temperature force is greater than the maximum value of the longitudinal friction force of the launcher is predicted and determined, and is defined as a problem pier;

[0011] Temperature control measures are taken for the problem pier.

[0012] By the above, by determining the parameter optimization assembly longitudinal friction coefficient determination in the process of incremental launching construction, based on the optimized longitudinal friction coefficient gets the longitudinal friction force of the incremental launching construction, the maximum value of the longitudinal friction force of the incremental launching is the maximum temperature force that can be borne; the most unfavorable temperature gradient is obtained by analyzing the measured temperature field; the temperature effect of the steel box girder under the most unfavorable temperature gradient is obtained by modeling; the problem pier is determined by comparing the temperature force and the maximum value of the longitudinal friction force of the incremental launching; temperature control measures are taken for the problem pier.

[0013] As preferred, the longitudinal friction coefficient specifically includes:

[0014] In the process of assembly incremental launching construction, the steel box girder support is sequentially provided from top to bottom with: rubber pad, super pad steel plate, steel pad and pier;

[0015] The longitudinal friction coefficient includes the following steps:

[0016] The friction coefficient between the steel surface of the steel box girder and the rubber surface of the rubber pad is obtained, the friction coefficient between the rubber surface of the rubber pad and the steel surface of the super pad steel plate is obtained, the friction coefficient between the steel surface of the super pad steel plate and the steel surface of the steel pad is obtained, the friction coefficient between the steel surface of the steel pad and the concrete surface of the pier is obtained, and the friction coefficient is determined by the material properties;

[0017] The longitudinal friction coefficient μ = min [μ1, μ2, μ3, μ4], wherein min [] represents the minimum value.

[0018] By the above, by comparing the friction coefficients between the contact surfaces and selecting the minimum value as the longitudinal friction coefficient, the accuracy of the longitudinal friction coefficient is improved.

[0019] As preferred, the longitudinal friction force of the incremental launching in the determination parameter specifically includes:

[0020] The longitudinal friction force f of the incremental launching is calculated tt , Wherein, G s is the gravity of the total bridge steel amount, Q pier is the number of piers of the whole bridge, Q tt is the number of incremental launchers distributed transversely to the pier.

[0021] By the above, by calculating the friction force of the incremental launching, the maximum value of the friction force of the incremental launching is obtained, which is the maximum temperature force that can be borne between the steel box girder and the pier.

[0022] As preferred, the temperature analysis of the steel box girder based on the measured temperature field specifically includes:

[0023] Select a section of steel box girder as the monitoring object, continuously monitor, take one end of the section of steel box girder as the test section, and arrange a plurality of temperature measuring points on the test section to collect temperature data, at least one of the temperature measuring points is located on the top plate of the test section, at least one of the temperature measuring points is located on the bottom plate of the test section, at least one of the temperature measuring points is located on one side of the test section. The web plate, at least one of the temperature measuring points is located on the other side of the test section, and the web plate obtains the measured data set;

[0024] Select the measured data of any date in the measured data set, and perform temperature analysis on the top plate, bottom plate and two side web plates of the steel box girder based on the measured data of the arbitrary date, and compare the temperature difference between the top plate and the bottom plate and between the two side web plates.

[0025] Through the above, by arranging temperature measuring points on the top plate, bottom plate and two side web plates and continuously monitoring, data basis is provided for temperature analysis of the steel box girder in the measured temperature field.

[0026] As preferred, the measured temperature field analysis result specifically includes:

[0027] Based on the temperature difference comparison, temperature gradient analysis is performed on the steel box girder, and the maximum temperature gradient is selected, and the maximum temperature gradient is defined as the most unfavorable temperature gradient.

[0028] Through the above, by performing temperature gradient analysis on the steel box girder, the heating condition of the steel box girder is determined, and the most unfavorable temperature gradient obtained provides data basis for temperature force calculation.

[0029] As preferred, the modeling analysis of the steel box girder based on the measured temperature field analysis result by using finite element software specifically includes:

[0030] Local modeling of the steel box girder segment is performed by using finite element software, and local analysis is performed.

[0031] Based on the assembly jacking construction sequence and the stress condition of the steel box girder in the jacking construction, a jacking model of the steel box girder is established by using finite element software, and overall analysis is performed.

[0032] Through the above, local modeling and overall modeling provide data basis for local analysis and overall analysis.

[0033] As preferred, the model analysis result specifically includes:

[0034] When the local analysis is performed, any date is selected, and the displacement and stress distribution on the steel box girder section at the any date is calculated by using the finite element software to obtain the time when the maximum deformation and the maximum stress appear on the steel box girder section at the any date, and the position where the maximum stress appears;

[0035] When the overall analysis is performed, the temperature effect of the steel box girder jacking model under the most unfavorable temperature gradient and different overall temperature changes is calculated by using the finite element software, the temperature effect includes displacement and stress, the displacement includes longitudinal displacement, transverse displacement and vertical displacement, and the longitudinal displacement is positive in the jacking direction; the maximum value among the longitudinal displacement, the transverse displacement and the vertical displacement under the action of the most unfavorable temperature gradient is compared to obtain the maximum stress and the position where the maximum stress appears; under the action of different overall temperatures, the temperature effect under the comparison of overall temperature and annual average temperature is obtained.

[0036] Through the above, the temperature effect of the steel box girder is determined through local analysis and overall analysis, which provides a basis for determining the problem pier.

[0037] As preferred, based on the analysis results of the model, the pier where the temperature force is greater than the maximum value of the longitudinal friction force of the jacking device is predicted and determined as the problem pier, which specifically includes:

[0038] The temperature force F of the steel box girder jacking to each pier is pre-calculated ti , F ti =k*Δt, wherein k is the temperature force parameter of the steel box girder, Δt is the temperature change amount, and i is the pier number;

[0039] Each temperature force F ti is compared with the friction force f ttmax of the jacking device, when F ti >f ttmax , the pier with the number i corresponding to the F ti is defined as the problem pier.

[0040] Through the above, the problem pier is determined through the comparison of each temperature force and the maximum value of the friction force of the jacking device, and the pier that needs to take temperature control measures is determined.

[0041] As preferred, the temperature control measures are taken on the problem pier, which specifically includes:

[0042] During the assembly jacking construction process, a structure layer with a friction coefficient less than the longitudinal friction coefficient is arranged on the temporary fulcrum of the problem pier, and the structure layer is used to limit the relative displacement of the temporary fulcrum due to temperature change on the structure layer.

[0043] Therefore, the temporary fulcrum structure is not damaged by adding the structural layer with the friction coefficient less than the longitudinal friction coefficient.

[0044] Beneficial effects: the method for temperature control in the assembling and pushing construction process of the application optimizes the determination of the longitudinal friction coefficient in the assembling and pushing construction process by determining parameters, obtains the longitudinal friction force of the pusher in the pushing construction based on the optimized longitudinal friction coefficient, and the maximum value of the longitudinal friction force of the pusher is the maximum temperature force that can be borne; the most unfavorable temperature gradient is obtained by analyzing the measured temperature field; the temperature effect of the steel box girder under the most unfavorable temperature gradient is obtained by finite element modeling; the problem pier is determined by comparing the temperature force and the maximum value of the longitudinal friction force of the pusher, a structural layer with a friction coefficient less than the longitudinal friction coefficient is added to the problem pier, and the purpose of ensuring the safety of the assembling and pushing process is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 The schematic block diagram of the method for temperature control in the assembling and pushing construction process provided by the embodiments of the application is shown in the figure.

[0047] Figure 2 The temperature sensor arrangement provided by the embodiments of the application is shown in the figure.

[0048] Figure 3 The figure of the environmental temperature change at the bridge site provided by the embodiments of the application is shown in the figure.

[0049] Figure 4 The comparison figure of the temperature of the top plate measuring point provided by the embodiments of the application is shown in the figure.

[0050] Figure 5 The temperature change curve figure of the bottom plate measuring point provided by the embodiments of the application is shown in the figure.

[0051] Figure 6 The temperature change curve figure of the web measuring point provided by the embodiments of the application is shown in the figure.

[0052] Figure 7 The comparison figure of the temperature difference of the main measuring points of the top plate and the bottom plate provided by the embodiments of the application is shown in the figure.

[0053] Figure 8 The comparison figure of the temperature difference of each measuring point of the south side web and the north side web provided by the embodiments of the application is shown in the figure.

[0054] Figure 9A top plate temperature change graph provided for the embodiment of the present application;

[0055] Figure 10 A bottom plate temperature change graph provided for the embodiment of the present application;

[0056] Figure 11 A web temperature change graph provided for the embodiment of the present application;

[0057] Figure 12 A steel box girder temperature change graph provided for the embodiment of the present application;

[0058] Figure 13 A steel box girder temperature gradient measured value graph provided for the embodiment of the present application;

[0059] Figure 14 A local finite element model provided for the embodiment of the present application;

[0060] Figure 15 A steel box girder section boundary constraint graph provided for the embodiment of the present application;

[0061] Figure 16 A global finite element model provided for the embodiment of the present application;

[0062] Figure 17 A steel box girder temperature field at 13:00 on December 26 provided for the embodiment of the present application;

[0063] Figure 18 A steel box girder temperature effect at 13:00 on December 26 provided for the embodiment of the present application;

[0064] Figure 19 A steel box girder temperature field at 13:00 on July 7 provided for the embodiment of the present application;

[0065] Figure 20 A steel box girder temperature effect at 13:00 on July 7 provided for the embodiment of the present application;

[0066] Figure 21 A steel box girder longitudinal displacement graph provided for the embodiment of the present application;

[0067] Figure 22 A steel box girder transverse displacement graph provided for the embodiment of the present application;

[0068] Figure 23 A steel box girder vertical displacement graph provided for the embodiment of the present application;

[0069] Figure 24 A steel box girder upper flange stress (MPa) graph provided for the embodiment of the present application;

[0070] Figure 25 A steel box girder lower flange stress (MPa) graph provided for the embodiment of the present application;

[0071] Figure 26 Different temperature longitudinal deformation schematic diagram of steel box girder is provided for the embodiments of the application. DETAILED DESCRIPTION

[0072] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0073] In this document, the term "comprising" is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device. Without more limitations, the elements defined by the statement "comprising" do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0074] The embodiments disclose a method for temperature control in a splicing and pushing construction process, as shown in the method for temperature control in a splicing and pushing construction process. Figure 1 The method comprises the following steps of:

[0075] Determining parameters, the parameters comprising a longitudinal friction coefficient and a longitudinal friction force of a pusher;

[0076] Performing temperature analysis on the steel box girder based on a measured temperature field to obtain a measured temperature field analysis result;

[0077] Performing modeling analysis on the steel box girder by using finite element software and based on the measured temperature field analysis result to obtain a model analysis result;

[0078] Based on the model analysis result, predicting and determining a pier at which a temperature force is greater than a maximum value of the longitudinal friction force of the pusher, and defining the pier as a problem pier;

[0079] Taking temperature control measures on the problem pier.

[0080] The longitudinal friction coefficient in the splicing and pushing construction process is determined by optimizing the parameters, the longitudinal friction force of the pusher in the pushing construction is obtained based on the optimized longitudinal friction coefficient, the maximum value of the longitudinal friction force of the pusher is the maximum temperature force that can be borne, the most unfavorable temperature gradient is obtained by analyzing the measured temperature field, the temperature effect of the steel box girder under the most unfavorable temperature gradient is obtained by modeling, the problem pier is determined by comparing the temperature force and the maximum value of the longitudinal friction force of the pusher, and the temperature control measures are taken on the problem pier.

[0081] Specifically, the longitudinal friction coefficient specifically includes:

[0082] In the process of assembling and pushing construction, the steel box girder support is sequentially provided from top to bottom with rubber pads, super pad steel plates, steel pads and piers.

[0083] The longitudinal friction coefficient includes the following steps:

[0084] The friction coefficient μ1 between the steel surface of the steel box girder and the rubber surface of the rubber pad, the friction coefficient μ2 between the rubber surface of the rubber pad and the steel surface of the super pad steel plate, the friction coefficient μ3 between the steel surface of the super pad steel plate and the steel surface of the steel pad, and the friction coefficient μ4 between the steel surface of the steel pad and the concrete surface of the pier are obtained, and the friction coefficient is determined by the material properties.

[0085] The longitudinal friction coefficient μ = min [μ1, μ2, μ3, μ4], wherein min [] represents the minimum value.

[0086] In an embodiment 1, the friction coefficient values are respectively: the friction coefficient between steel and rubber pad is 0.25; the friction coefficient between steel and steel is 0.15 (without lubrication); the friction coefficient between steel and concrete is 0.2-0.25; and the longitudinal friction coefficient of the steel box girder during pushing is the minimum value of 0.15.

[0087] By comparing the friction coefficients between the contact surfaces and selecting the minimum value as the longitudinal friction coefficient, the accuracy of the longitudinal friction coefficient is improved.

[0088] Specifically, the longitudinal friction force of the pusher in the parameter determination specifically includes:

[0089] The longitudinal friction force f of the pusher is calculated tt , Wherein, G s is the gravity of the steel amount of the whole bridge, Q pier is the number of piers of the whole bridge, and Q tt is the number of piers transversely distributed with the pusher.

[0090] In an embodiment 1, the steel amount of the whole bridge is 570,000 tons, the average vertical support reaction force of each pier is about 20,000 KN, and 2 pushers are transversely distributed, so the longitudinal friction force of each pusher is: 10,000 KN x 0.15 = 1,500 KN. When the longitudinal temperature force of each support is greater than 1,500 KN, the main girder is considered to slide longitudinally.

[0091] The maximum value of the friction force of the pusher is obtained by calculating the friction force of the pusher, and the maximum value is the maximum temperature force that can be borne between the steel box girder and the bridge section.

[0092] Specifically, the temperature analysis of the steel box girder is based on the measured temperature field, specifically including:

[0093] A section of the steel box girder is selected as the monitoring object for continuous monitoring. One end of the section of the steel box girder is taken as the test section, and multiple temperature measuring points are arranged on the test section for temperature data collection. At least one temperature measuring point is located on the top plate of the test section, at least one temperature measuring point is located on the bottom plate of the test section, at least one temperature measuring point is located on one side of the test section, and at least one temperature measuring point is located on the other side of the test section. The measured data set is obtained.

[0094] In the measured data set, the measured data of any date is selected, and the temperature analysis of the top plate, the bottom plate and the two side plates of the steel box girder is based on the measured data of any date. The temperature difference between the top plate and the bottom plate and the temperature difference between the two side plates are compared.

[0095] In one embodiment 1, in the observation of the actual temperature field, a surface-mounted temperature sensor is used to observe the inner and outer surfaces of the steel box girder. When collecting the measured data, the sensor temperature data is collected every half hour by the collection instrument. The instrument model is JM165-B temperature sensor of Sichuan Jinma Technology Co., Ltd. The temperature sensor has a temperature measurement range of -45-125℃, a sensitivity of 0.1℃, and an accuracy of ±1.0℃ when the temperature is 0-+50℃.

[0096] In order to grasp the temperature change on the cross section, during the incremental launching construction, the temperature effect test section on the main girder is selected as the 46.4m behind the guide beam, i.e. the maximum cantilever end of the incremental launching construction in this embodiment. 20 temperature measuring points are arranged on the test section, and the measuring point positions are as shown in Figure 2

[0097] In the measured data set, the lowest temperature in winter and the highest temperature in summer are selected as typical dates for temperature analysis.

[0098] By arranging temperature measuring points on the top plate, the bottom plate and the two side plates and continuously monitoring, a data basis is provided for the temperature analysis of the steel box girder in the measured temperature field.

[0099] Specifically, the measured temperature field analysis result is obtained, specifically including:

[0100] Based on the temperature difference comparison, the temperature gradient analysis of the steel box girder is carried out, and the maximum temperature gradient is selected. The maximum temperature gradient is defined as the most unfavorable temperature gradient.

[0101] In embodiment 1, from December 2021 to November 2022, the change of environmental temperature during the observation period at the bridge site is as shown in Figure 3 ​As shown, according to the observation results, the lowest temperature weather in winter on December 26, 2021 and the highest temperature weather in summer on July 7, 2022 are selected as typical dates for temperature analysis.

[0102] The temperature changes of the measuring points on the steel box girder section have typical seasonality, and the temperature changes of the main measuring points on December 26, 2021 with the lowest winter temperature and July 7, 2022 with the highest summer temperature are selected for comparison, as shown in Figures 4 to 8 .

[0103] As can be seen from the comparison of a and b in Figure 4 , Figure 5 and Figure 6 , the temperature changes of the top plate and the bottom plate have obvious seasonality. The highest temperature of the top plate on a typical winter day can reach 12.4℃, and the temperature difference between the transverse measuring points is about 5℃. The highest temperature in summer can reach 63.3℃, and the temperature difference between the transverse measuring points can reach 8.6℃. The highest temperature of the bottom plate on a typical winter day is 2.6℃, and the temperature change range is small, with a temperature difference of about 1℃ between the transverse measuring points. The highest temperature of the bottom plate on a typical summer day can reach 45.6℃, and the temperature change range is large, with a temperature difference of up to 8.8℃ between the transverse measuring points.

[0104] On a typical winter day, the south side web plate receives strong solar radiation and warms up quickly, with a maximum temperature of 15℃. On the contrary, the north side web plate warms up slowly and the maximum temperature is only 2.5℃. On a typical summer day, the south side web plate and the north side web plate have the same temperature change trend, with a maximum temperature of about 44℃.

[0105] As can be seen from the comparison of a and b in Figure 7 and Figure 8 , the seasonal temperature change has little effect on the temperature difference between the top plate and the bottom plate of the steel box girder, but has a significant effect on the temperature difference between the south and north side web plates. The maximum temperature difference between the top plate and the bottom plate on a typical winter day is 11℃, and on a typical summer day it is 25.23℃. The temperature difference between the south and north side web plates on a typical winter day exceeds 16℃, and the temperature of the south side web plate is always higher than that of the north side web plate. On a typical summer day, the temperature difference between the south and north side web plates does not exceed 4℃, and the temperature of the north side web plate is higher than that of the south side web plate in the first 3 hours, and the opposite is true in the last 3 hours.

[0106] Therefore, it can be concluded that the atmospheric temperature has a significant effect on the temperature field of the steel box girder, and the temperature difference between the top plate and the bottom plate in summer is more obvious than in winter, and the temperature difference between the south and north side web plates in winter is larger.

[0107] The domestic and foreign bridge and culvert design general specifications consider the temperature gradient caused by solar radiation, and the selected gradient mode is the vertical temperature difference of the steel box girder, which often occurs in the summer high temperature period. According to the observation results, the top plate, the bottom plate transverse temperature difference and the south and north side web plate vertical temperature difference on July 3, 2022 and July 7, 2022 with the largest temperature difference are selected for temperature analysis.

[0108] Under sunlight conditions, the temperature changes of various components of the steel box girder on July 3, 2022 and July 7, 2022 are as follows: Figures 9 to 10 As shown.

[0109] Figures 9 to 10 The figures show the temperature variation curves of the main measuring points of the steel box girder under solar radiation on July 3, 2022, and July 7, 2022. The temperature change of the top slab follows the same trend as the atmospheric temperature change, but the temperature fluctuation of the top slab is larger and the temperature rises rapidly. After 2 PM, the temperature in the middle of the top slab is significantly higher than that of the bottom slab. The temperature change of the bottom slab is basically consistent with the atmospheric temperature change, but slightly lags behind. After 4 PM, the temperature in the middle of the bottom slab is higher than that on both sides. The temperature change of the web slab is gradual. The temperature on the south side of the web slab is lower than that on the north side before 12 PM, but higher than that on the north side after 12 PM. The temperature change trends of the north and south sides of the web slab are the same, with a small temperature difference. Under solar radiation, the top slab temperature rises rapidly and reaches its peak first, generally coinciding with the time of the highest ambient temperature of the day. The peak temperatures of the bottom slab and web slab lag behind the top slab, occurring at 5 PM and 6 PM respectively, with the bottom slab temperature peak being higher than that of the web slab.

[0110] Compare the average temperatures at each measuring point over the two days, such as Figure 12 As shown, a large lateral temperature difference was observed in the top plate around 2 PM, while the largest lateral temperature difference in the bottom plate occurred around 5 PM. Both showed a characteristic that the temperature in the middle was greater than that on the sides. The temperature of the south side web plate was lower than that of the north side web plate before 12 PM, and then the temperature rose to exceed that of the north side web plate.

[0111] Analyze the vertical temperature difference between the two sides of the web and the lateral temperature difference between the top and bottom plates under solar radiation, such as... Figure 13 As shown. By Figure 13 It can be seen that the maximum transverse temperature difference between the top and bottom plates of the steel box girder section is 8.8℃, and the maximum vertical temperature difference between the south and north webs is 18.2℃. This is taken as the maximum temperature gradient, i.e. the most unfavorable temperature gradient.

[0112] By conducting temperature gradient analysis on the steel box girder, the heating condition of the steel box girder was determined, and the obtained most unfavorable temperature gradient provided a data basis for the calculation of temperature force.

[0113] Specifically, the steel box girder was modeled and analyzed using finite element software and based on the measured temperature field analysis results. This included:

[0114] Local modeling and analysis of steel box girder segments were performed using finite element software.

[0115] Based on the assembly and launching construction sequence and the stress conditions of the steel box girder during launching, a launching model of the steel box girder was established using finite element software for overall analysis.

[0116] In the embodiment 1, the modeling of the local model comprises:

[0117] The finite element analysis software ABAQUS is used to establish a steel box girder segment for local analysis. Since the temperature field of the steel box girder is uniformly distributed in the longitudinal bridge direction and the thickness of the structural steel plate is thin, the temperature difference in the longitudinal bridge direction and the temperature difference in the thickness direction of the steel plate can be ignored. When the finite element model is used for thermal analysis, the three-dimensional thermal shell element DS4 (four-node quadrilateral shell element with 4 nodes and no heat transfer capacity in the thickness direction of the steel plate) is used, which can well simulate the heat transfer of the thin steel plate. When the temperature effect analysis is performed, the S4RT temperature-displacement coupled element is used.

[0118] A steel box girder standard segment with a length of 174 m is selected in the longitudinal bridge direction for finite element analysis. The actual size of the beam segment is modeled in detail and the element mesh is divided. The finite element analysis model is composed of 68034 nodes and 58172 elements. The steel box girder model includes 368 components, which are assembled according to the drawings. Since the components of the steel box girder are connected by welding, the model is considered as a whole during modeling, and the tie constraint in ABAQUS can be used to simulate the welding connection. As shown in Figure 14 The analysis model of the transient temperature field and temperature effect of the steel box girder is shown.

[0119] The temperature field of the steel box girder is calculated using ABAQUS. Since the temperature field of the steel box girder will be different due to changes in solar radiation intensity, wind speed and air temperature, the analysis type of the temperature field is transient analysis.

[0120] When using finite element software to solve the transient temperature field, the initial condition of the calculation is the initial temperature field of the steel box girder. The measured data shows that the temperature in the steel box girder is close to the atmospheric temperature at about 6 o'clock, so the atmospheric temperature at 6 o'clock is set as the initial uniform temperature of the steel box girder in the Load module of ABAQUS. The thermal radiation effect is equivalent to a convective load, which is then converted into a comprehensive temperature and loaded to the boundaries of the steel box girder.

[0121] One end of the steel box girder model segment is fixedly constrained, and the other end is not subjected to any constraint, to simulate the state that the end of the steel box girder can deform freely, as shown in Figure 15 .

[0122] The modeling of the overall model comprises:

[0123] According to the construction sequence of one side of the bridge and the stress condition of the steel box girder during the pushing process, the Midas / Civil finite element software is used to establish a steel box girder pushing model, as shown in Figure 16The steel box girder is simulated by beam elements, and the connections between the piers and the main girder are simulated by elastic connections. According to the construction progress, a finite element model with a length of 691.7 m is established, at this time the steel box girder is in the maximum cantilever state before being jacked to the 46# pier. The model has 229 nodes and 222 beam elements. The temperature load is applied by temperature gradient and system temperature.

[0124] Through local modeling and overall modeling, data basis is provided for local analysis and overall analysis.

[0125] Specifically, the model analysis results are obtained, specifically including:

[0126] When performing local analysis, any date is selected, and the displacement and stress distribution on the cross section of the steel box girder at any date are calculated by using the finite element software, to obtain the time when the maximum deformation and the maximum stress appear on the cross section of the steel box girder at any date, and the position where the maximum stress appears;

[0127] When performing overall analysis, the temperature effect of the steel box girder jacking model under the most unfavorable temperature gradient and different overall temperature changes is calculated by using the finite element software, the temperature effect includes displacement and stress, the displacement includes longitudinal displacement, transverse displacement and vertical displacement, and the longitudinal displacement is positive in the jacking direction; the maximum values among the longitudinal displacement, the transverse displacement and the vertical displacement are obtained by comparison under the most unfavorable temperature gradient, and the maximum stress and the position where the maximum stress appears are also obtained; under different overall temperatures, the temperature effect under the comparison of overall temperature and annual average temperature is obtained.

[0128] In the embodiment 1, the local analysis results include:

[0129] When performing local analysis, December 26, the lowest temperature in the monitoring period, and July 7, the highest temperature, are selected as typical dates. When calculating the displacement and stress distribution on the cross section of the steel box girder on the two days by using the finite element software, it is found that the maximum values of stress and deformation appear at about 13 o'clock on the two days, and the temperature distribution and temperature effect of the cross section of the steel box girder at this time are as shown in Figures 17 to 20 .

[0130] The displacement and stress (Mises equivalent stress) of the cross section of the steel box girder are calculated, and the results are as shown in Figure 18 and Figure 20 , and the conclusions are as follows:

[0131] On December 26, the maximum deformation on the cross section of the steel box girder caused by solar radiation appears at 13 o'clock, the maximum deflection of the top plate is 5.1 mm, the deflection of the top plate flange is 2.0 mm, the upward deflection of the middle part of the bottom plate is 2.1 mm, the downward deflection of the bottom plate flange is 3.2 mm, and the maximum deformation of the web is 0.9 mm; the maximum stress appears at 13 o'clock in the afternoon, and the stress near the connection between the south web and the top plate is the maximum, which can reach 16.7 MPa.

[0132] The maximum deformation of the steel box girder section caused by solar radiation occurred at 13:00 on July 7, with a 10.3 mm downward deflection in the middle of the top plate, a 5.2 mm downward deflection in the flange of the top plate, a 3.6 mm downward deflection in the middle of the bottom plate, a 5.1 mm downward deflection in the flange of the bottom plate, and a maximum deformation of 3.8 mm in the web. The maximum stress occurred at 13:00, when the maximum stress in the middle of the top plate of the steel box girder reached 20.8 MPa.

[0133] The overall analysis results include:

[0134] According to the finite element model, the temperature effects of the steel box girder under the most unfavorable temperature gradient (vertical temperature difference of 18.2°C and horizontal temperature difference of 8.8°C) and overall temperature change were calculated, including displacement (longitudinal displacement is positive in the direction of jacking) and stress.

[0135] Under the action of temperature gradient, the displacement calculation result is the displacement of the steel box girder caused by temperature gradient, and the longitudinal displacement is positive in the direction of jacking. From Figures 21 to 23 it can be seen that the longitudinal and horizontal displacements of the cantilever end of the steel box girder under the action of temperature gradient are small, and the vertical displacement is the largest, reaching 11.8 cm. The stress calculation result is the stress of the steel box girder caused by temperature gradient, and the positive stress is positive in tension and negative in compression. From Figures 24 to 25 it can be seen that the maximum positive stress of the upper flange of the steel box girder caused by the most unfavorable temperature gradient is 38.7 MPa, and the maximum positive stress of the lower flange can reach 34.9 MPa, and the maximum values all occur near the 44# pier.

[0136] Under the action of overall temperature, although the change of overall temperature is simple in form and has a long period, the temperature effect on the structure is not negligible. According to the meteorological data, the annual average temperature at the bridge site of the present embodiment is 20.4°C, and the relative deformation (the elongation of the main girder to both ends is positive) of the steel box girder under different overall temperatures (10.4°C, 15.4°C, 25.4°C and 30.4°C) is shown in Figure 25 , the overall temperature affects the longitudinal deformation of the steel box girder, and when the overall temperature is greater than the annual average temperature, the main girder is stretched outward at both ends, and when the overall temperature is less than the annual average temperature, the opposite is true.

[0137] Through local analysis and overall analysis, the temperature effect of the steel box girder is determined, which provides a basis for the determination of problem piers.

[0138] Specifically, based on the model analysis results, the piers where the temperature force is greater than the maximum value of the longitudinal friction force of the jacking device are predicted and determined, and are defined as problem piers, which specifically include:

[0139] Pre-calculate the temperature force of the steel box girder when jacked to each pier where k is the temperature force parameter of the steel box girder, Δt is the temperature change, and i is the pier number.

[0140] The temperature force The friction force of the pusher When The corresponding bridge pier with the number i is defined as the problem bridge pier.

[0141] The problem bridge is determined by comparing the temperature force with the maximum value of the friction force of the pusher, and the bridge pier that needs to take temperature control measures is determined.

[0142] Specifically, the temperature control measures for the problem bridge pier include:

[0143] In the process of assembling and pushing construction, a structural layer with a friction coefficient less than the longitudinal friction coefficient is arranged on the temporary fulcrum of the problem bridge pier, and the structural layer is used to limit the relative displacement of the temporary fulcrum due to temperature changes on the structural layer.

[0144] In the first embodiment, according to the temperature analysis, when the temperature of the steel beam increases by more than 20℃, the longitudinal length change of the steel beam will cause the friction force generated by the steel beam on the temporary support. When the friction force exceeds 1500KN, the temporary cushion block will slide longitudinally. Because the temporary fulcrum is composed of multiple cushion blocks, the sliding layer is uncertain. Because the assembly time is old, the temperature changes day and night every day, and after multiple sliding, the structure of the cushion block changes greatly, and the stress is not clear, which may cause damage to the structure of the temporary fulcrum.

[0145] In order to solve the relative displacement of the temporary fulcrum caused by the temperature change of the steel beam, and thus the structural damage, a structural layer with a friction coefficient less than the longitudinal friction coefficient is arranged on the temporary fulcrum, and the friction coefficient is 0.1. Thus, the relative displacement of the temporary fulcrum due to temperature changes can only move in this structural layer, thereby solving this phenomenon.

[0146] By adding a structural layer with a friction coefficient less than the longitudinal friction coefficient, it is ensured that the structure of the temporary fulcrum will not be damaged.

[0147] In summary, the method for temperature control in the process of assembling and pushing construction in the embodiment determines the longitudinal friction coefficient in the process of assembling and pushing construction by optimizing the parameters, obtains the longitudinal friction force of the pusher in the process of pushing construction based on the optimized longitudinal friction coefficient, and the maximum value of the longitudinal friction force of the pusher is the maximum temperature force that can be borne. The most unfavorable temperature gradient is obtained by analyzing the measured temperature field, the temperature effect of the steel box girder under the most unfavorable temperature gradient is obtained by finite element modeling, the problem bridge pier is determined by comparing the temperature force with the maximum value of the longitudinal friction force of the pusher, and a structural layer with a friction coefficient less than the longitudinal friction coefficient is added to the problem bridge pier, so as to achieve the purpose of ensuring the safety of the assembling and pushing process.

[0148] ​Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, modifications or equivalent replacements of the technical solutions described in the foregoing embodiments can still be made by those skilled in the art, or some technical features can be replaced by equivalent features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for temperature control of a segmental push construction process in which a steel box girder is pushed onto a pier, characterized in that, The method comprises: determining parameters, the parameters comprising a longitudinal friction coefficient and a longitudinal friction force of the pusher; performing temperature analysis on the steel box girder based on a measured temperature field to obtain a measured temperature field analysis result; performing modeling analysis on the steel box girder based on the measured temperature field analysis result by using a finite element software to obtain a model analysis result; based on the model analysis result, predicting and determining a pier where a temperature force is greater than a maximum value of the longitudinal friction force of the pusher, and defining the pier as a problem pier; taking temperature control measures for the problem pier; the longitudinal friction coefficient specifically comprises: in the process of assembling and pushing construction, the steel box girder support is sequentially provided from top to bottom with rubber pads, super pad steel plates, steel pads and a pier; the acquisition of the longitudinal friction coefficient comprises the following steps: obtaining a friction coefficient between a steel surface of the steel box girder and a rubber surface of the rubber pad a friction coefficient between the rubber surface of the rubber pad and a steel surface of the super pad steel plate a friction coefficient between the steel surface of the super pad steel plate and a steel surface of the steel pad a friction coefficient between the steel surface of the steel pad and a concrete surface of the pier the friction coefficient is determined by material properties the longitudinal friction coefficient wherein, denotes taking the minimum value; the longitudinal friction force of the pusher in the determination of parameters specifically comprises: Calculating longitudinal friction of a pusher , , wherein, is the weight of the steel of the whole bridge, is the number of piers of the whole bridge, is the number of pushers allocated transversely to the piers of the bridge; the temperature analysis on the steel box girder based on the measured temperature field specifically comprises: selecting a section of steel box girder as a monitoring object for continuous monitoring, taking one end of the section of steel box girder as a test section, arranging multiple temperature measuring points on the test section for temperature data collection, at least one of the temperature measuring points being located on the top plate of the test section, at least one of the temperature measuring points being located on the bottom plate of the test section, at least one of the temperature measuring points being located on one side web of the test section, and at least one of the temperature measuring points being located on the other side web of the test section to obtain a measured data set; selecting measured data of an arbitrary date in the measured data set, and performing temperature analysis on the top plate, the bottom plate and the two side webs of the steel box girder based on the measured data of the arbitrary date, and comparing the temperature difference between the top plate and the bottom plate and between the two side webs; the measured temperature field analysis result specifically comprises: based on the temperature difference comparison, performing temperature gradient analysis on the steel box girder, and selecting a maximum temperature gradient, and defining the maximum temperature gradient as an adverse temperature gradient; the modeling analysis on the steel box girder based on the measured temperature field analysis result by using the finite element software specifically comprises: performing local modeling on the steel box girder section by using the finite element software, and performing local analysis; based on the assembling and pushing construction sequence and the stress condition of the steel box girder in the pushing construction, establishing a steel box girder pushing model by using the finite element software, and performing overall analysis.

2. The method for temperature control of the incremental launching construction process according to claim 1, characterized in that, the model analysis result specifically comprises: when performing the local analysis, selecting an arbitrary date, calculating the displacement and stress distribution on the steel box girder section at the arbitrary date by using the finite element software to obtain the time when the maximum deformation and the maximum stress appear on the steel box girder section at the arbitrary date, and the position where the maximum stress appears; In the integral analysis, finite element software is used to calculate the temperature effect of the steel box girder jacking model under the most unfavorable temperature gradient and different integral temperature changes, the temperature effect including displacement and stress, the displacement including longitudinal displacement, transverse displacement and vertical displacement, and the longitudinal displacement being positive in the jacking direction; the maximum value among the longitudinal displacement, the transverse displacement and the vertical displacement under the most unfavorable temperature gradient is compared, and the value of the maximum stress and the position where the maximum stress occurs are obtained; under different integral temperatures, the temperature effect under the comparison between integral temperature and annual average temperature is obtained.

3. The method for temperature control of the incremental launching construction process according to claim 2, characterized in that, The model analysis result is used to predict and determine the bridge pier where the temperature force is greater than the maximum value of the longitudinal friction force of the jacking device, and the bridge pier is defined as a problem bridge pier, and specifically includes the following steps: Pre-calculate the temperature force of the steel box girder when jacking to each pier , wherein is a temperature force parameter of the steel box girder, is a temperature change amount, is a pier number; The temperature forces corresponding to the maximum longitudinal friction force of the pusher are compared, and when the temperature force corresponding to the maximum longitudinal friction force of the pusher is greater than the temperature force corresponding to the maximum longitudinal friction force of the bridge piers, the bridge pier with the number is defined as the problem bridge pier.

4. The method for temperature control of the incremental launching construction process according to claim 3, characterized in that, The temperature control measure is taken for the problem bridge pier, and specifically includes the following steps: In the process of the assembly jacking construction, a structure layer with a smaller friction coefficient is arranged on the temporary fulcrum of the problem bridge pier, and the structure layer is used to limit the relative displacement of the temporary fulcrum due to temperature change on the structure layer.

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