Method for calculating longitudinal internal force and deformation of cable trench structure under action of vehicle bias

Abstract

The invention relates to a method for calculating longitudinal internal force and deformation of a cable trench structure under a vehicle bias action, which is applied to single-side driving, and is used for calculating a horizontal load delta sigma k transmitted to a trench side wall by a wheel through foundation soil, and calculating soil mass resistance of the trench side wall and the bottom by adopting a Werkel assumption; calculating the inertia moment I of the channel section of the channel structure: calculating the internal force and the deformation value of the cable channel by adopting an elastic foundation beam method according to the horizontal load delta sigma k, the soil mass resistance of the side wall and the bottom of the channel and the inertia moment I of the channel section; according to the pure bending structure, longitudinal reinforcing bars of the channel are calculated according to the C-shaped section beam; according to the method, the influence of single-side extrusion of the channel on longitudinal stress of the cable channel is considered, and a responsive load action model, a load calculation method, a longitudinal internal force calculation method and a deformation calculation method based on the elastic foundation beam and longitudinal reinforcement design of the channel are provided, so that long-term stability and safety of the cable channel structure of which the single side is influenced by driving are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of cable trench structures, and in particular to a method for calculating longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure. Background Art

[0002] The existing cable trench structure design methods mainly focus on the simplification of trench structure and the calculation of loads. Currently, there are two types of simplification of trench structure, namely, the cover plate sunken trench and the cover plate flat trench. The geometric model and mechanical model are as follows: Figure 1 , Figure 2 shown.

[0003] According to the different stress modes, the channel can be analyzed as a plane strain model. According to the different docking modes between the cover plate and the channel, the stress models of the channel are also different, which are:

[0004] (1) The side wall and bottom plate of the cover-sunk trench form a groove-shaped frame structure. The cover plate of the cable trench has a function of limiting the displacement of the top of the trench side wall toward the inside of the trench, which can be simplified into a horizontal simply supported support, such as Figure 1 As shown, it is an over-static structure; the sunken cover plate, in addition to bearing its own weight and the vertical earth pressure of the overlying soil layer and the ground overload, is also subject to the horizontal load transmitted after being squeezed by the two side walls of the channel, and is a compression-bending member;

[0005] (2) The stress model of the channel with a flat cover can be simplified into two parts: a statically determinate structure of a groove type formed by the two side walls and the bottom plate, and the cover plate is simplified into a statically determinate beam simply supported at the center of the two side walls.

[0006] The types of loads in the trench include: dead load, live load and accidental load. Dead loads mainly include the dead weight of the structure, the weight of the soil covering the cover plate, the water and soil pressure on the side walls, the reaction force of the foundation soil under the bottom plate, etc. Live loads mainly include equipment loads in the trench, construction loads, ground live loads (vehicle loads), etc. Accidental loads include earthquake loads, impact loads, etc.

[0007] Under the non-driving lane and the channel uniformly distributed load, the load model is as follows Figure 3 As shown in the figure, the load model does not include accidental loads such as earthquake loads and impact loads. The load composition is as follows:

[0008] (1) The soil load at the top of the trench acts on the trench top plate;

[0009] (2) The soil load in the trench, the trench deadweight, and the equipment load in the trench react together on the trench bottom plate through the reaction force of the foundation soil;

[0010] (3) The water and soil pressure on the side walls of the channel acts symmetrically on the channel;

[0011] (4) The surface is mainly green or pedestrian walkways, and the uniform live load is 10kN / m 2 .

[0012] The schematic diagram of the load effect on the channel under the carriageway is as follows Figure 4 As shown in the figure, compared with the non-driving carriageway, its load action mode is similar. The difference is that the uniformly distributed load on the surface is changed from general live load to vehicle load, which affects the foundation soil reaction at the bottom of the ditch and also affects the water and soil pressure on the side walls of the ditch.

[0013] There is a significant difference from the above two working conditions. Under the condition of single-side driving, due to the shallow soil cover, the single-side overload caused by driving exceeds 10kN / m 2 The uniform distribution value of the non-driving lanes results in different live loads on both sides of the channel, which in turn causes eccentric loading in the channel and causes uneven stress on the foundation soil.

[0014] like Figure 5 As shown in the paper "Channel Load Model and Structural Optimization Design for Unilateral Driving" published in Engineering Technology Research in October 2021, a load calculation model considering unilateral driving is proposed, and the channel load under the extrusion of unilateral driving is calculated. And for the case of single-vehicle driving, a calculation method for channel internal force is proposed, that is, the internal force of the channel under different loads is calculated using the method of structural mechanics. The calculation diagram of channel internal force and the magnitude of internal force value are shown as follows Figure 6 shown.

[0015] The existing cable trench structure design takes into account the influence of unilateral eccentric load on the internal force of the trench, and can arrange reinforcement according to the calculation results. However, for cable trench projects laid in urban environments, there is a situation where vehicles on one side continuously squeeze the trench side wall, such as Figure 7 As shown in the figure, the other side of the lane will be deformed as a whole when it is squeezed by the side of the car due to the planting of greenery. The soil of the side wall and the bottom plate will produce elastic force due to the squeezing of the channel structure. Assume that their resistance coefficients are k s , k b In addition, existing design methods cannot take into account the overall deformation of the channel. Summary of the invention

[0016] In view of the deficiencies in the prior art, the present invention provides a method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure to solve the above problems.

[0017] The present invention provides the following technical solutions:

[0018] A method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure, which is applied to single-side driving and establishes a force model based on the cable trench structure;

[0019] Calculate the horizontal load Δσ transmitted by the wheel to the channel side wall through the foundation soil k , and the Winkel assumption is used to calculate the soil resistance of the channel sidewalls and bottom;

[0020] Calculate the moment of inertia I of the channel cross section of the channel structure:

[0021] According to the horizontal load Δσ k , soil resistance of the trench sidewalls and bottom and the moment of inertia I of the trench section, and the elastic foundation beam method are used to calculate the internal force and deformation value of the cable trench;

[0022] According to the pure bending structure, the longitudinal reinforcement of the channel is calculated according to the C-section beam.

[0023] Preferably, the moment of inertia I of the channel cross section is determined by calculating the C-shaped cross section of the channel:

[0024]

[0025] Where I is the moment of inertia of the channel cross section of the channel structure, m 4 ;

[0026] b e is the outer width of the channel structure, m;

[0027] h e is the external height of the channel structure, m;

[0028] b i is the inner width of the channel structure, m;

[0029] h i is the inner height of the channel structure, m.

[0030] Preferably, the diffusion angle θ of the vehicle load is 45°, and the horizontal load Δσ added to one side of the channel is calculated as k , kPa;

[0031]

[0032] Among them, p is the concentrated load value of the wheel, kN; b is the width of the wheel, m; l is the longitudinal ground width of the wheel, m; a is the distance between the wheel and the channel close to the wheel side, m.

[0033] Preferably, the horizontal load Δσ k The p·b·l in the formula can be directly taken as the wheel pressure value on one side of each axle.

[0034] Preferably, the horizontal load Δσ kConsidering the worst case without diffusion, b+2a takes the value of 1.

[0035] Preferably, the base coefficient of the foundation soil for the soil resistance of the channel sidewalls and bottom is determined according to the recommended value of the geotechnical engineering investigation report; or it can be determined according to the highway industry standard JTG D63-2019 "Specifications for Design of Highway Bridge and Culvert Foundations".

[0036] Preferably, the horizontal load Δσ transmitted from the wheels of each axle of the vehicle to the side wall of the channel through the foundation soil is calculated separately. k , within the length range of the elastic foundation beam equivalent to the channel, select the group with the largest combined load applied to the channel at the same time.

[0037] Preferably, the length of the channel equivalent elastic foundation beam is 15 m.

[0038] The present invention has the following beneficial technical effects:

[0039] Compared with the existing design method based on the load structure method for calculating the internal force generated by the unilateral extrusion of the cable trench and calculating the annular reinforcement, the present invention takes into account the influence of the unilateral extrusion of the trench on the longitudinal force of the cable trench, and proposes a corresponding load action model, a load calculation method, a longitudinal internal force calculation method and a deformation calculation method based on elastic foundation beams, and a reinforcement design for the longitudinal direction of the trench, filling the gap in the existing design regarding the calculation of the longitudinal internal force and deformation of the trench, and ensuring the long-term stability and safety of the cable trench structure that is affected by traffic on one side.

[0040] The invention can meet the needs of cable trenches constructed in road green belts or sidewalks, where one side is squeezed by road traffic loads, while the other side is dominated by greenery or pedestrians. The trench structure and its design method can take into account the influence of eccentric load squeezing, and also have the function of meeting the structural safety and durability of the trench under the influence of force and deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a typical cable trench structure;

[0042] Figure 2 It is the structural form of a typical cable trench and its calculation diagram;

[0043] Figure 3 It is the channel load model when there is no vehicle driving on the non-driving lane.

[0044] Figure 4 It is a channel load model under the carriageway affected by traffic.

[0045] Figure 5 It is the channel load model when driving on one side.

[0046] Figure 6This is a simplified diagram for calculating the internal forces of a single-sided vehicle.

[0047] Figure 7 It is the bias load acting on the channel when the vehicle is driving on one side.

[0048] Figure 8 It is the deformation of the channel caused by the bias load acting on the channel during unilateral driving of the present invention.

[0049] Fig. 9 This is the channel stress model of the present invention considering the uniformly distributed load on both sides of the channel.

[0050] Fig.10 The present invention takes into account the stress and deformation of the channel caused by unilateral extrusion on both sides of the channel.

[0051] Fig.11 It is a reference for the base bed coefficient value of the channel sidewall and bottom of the present invention.

[0052] Fig.12 It is the elevation, plane and lateral arrangement drawing of the city-A class vehicle load of the present invention.

[0053] Fig.13 The present invention discloses the distribution of the channel side wall load under the action of the single-sided vehicle wheel pressure.

[0054] Fig.14 It is a simplified diagram of elastic foundation beam calculation of the longitudinal internal force of the cable trench structure considering the eccentric load effect of the present invention.

[0055] Fig.15 It is a schematic diagram of the cross-sectional dimensions of the cable trench of the present invention.

[0056] Fig.16 It is the calculation model and calculation result of the channel elastic foundation beam of the present invention.

[0057] Fig.17 It is the calculation result of internal force and deformation of the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] Figure 5 The instructions are as follows:

[0060] p0 is the soil load and surface live load at the top of the channel, which are evenly distributed on the cover plate. When calculating the internal force of the cover plate, the self-weight load of the cover plate must also be considered;

[0061] p is the reaction force at the bottom of the trench, which is balanced with the trench top p0 and the self-weight of the trench structure, the equipment load in the trench, the cable laying construction and maintenance load, etc., and acts on the bottom plate as a uniformly distributed reaction force;

[0062] e1 is the water and soil pressure on the ditch sidewall facing the lane, and its value is calculated according to the static soil pressure or active soil pressure;

[0063] e1' is the water and soil pressure on the ditch side away from the roadway. Its value is also calculated according to the static soil pressure or active soil pressure. When the surface height on both sides of the ditch is the same, it is equal to e1;

[0064] e2 is the additional horizontal load caused by the live load on the ground surface. Its value matches the use of the ground surface. Usually, the uniformly distributed live load on the ground surface is taken as q L =10kN / m 2 The calculation shows that the two sides of the channel are arranged symmetrically;

[0065] e3 is the horizontal load added to one side of the channel caused by the vehicle load on the road. Its value is calculated according to formula (1) and converted to the equivalent soil layer thickness. Since the converted distribution range is wide, it can be considered that it is equally distributed along the upper and lower sides of the channel sidewall, but it does not appear at the same time as e2.

[0066] r e It is the unevenly distributed load on the base caused by the unevenly distributed horizontal load on both sides of the channel bottom, which is obtained by the static equilibrium method.

[0067] It should be noted that when the channel side wall is multi-layer soil, the soil side pressure should be a broken line. The paper mainly focuses on the analysis method. For the convenience of comparison, the assumption of a straight trapezoid is adopted.

[0068] A method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure, such as Figure 7-17 As shown:

[0069] When driving on one side, the bias pressure generated by the vehicle load acts on the side wall of the trench (cable trench), causing the trench structure to be squeezed laterally, resulting in lateral foundation resistance and trench bottom foundation resistance. Since the overall stiffness of the trench structure is large, it is assumed that the resistance of the trench side wall and bottom is linearly distributed, and the Winkel assumption can be used to calculate the resistance of the soil. The geometric model is as follows: Fig. 9 As shown:

[0070] The main parameters in the formula are described as follows:

[0071] p0 is the soil load and surface live load at the top of the channel, which are evenly distributed on the cover plate. When calculating the internal force of the cover plate, the self-weight load of the cover plate must also be considered;

[0072] p is the reaction force at the bottom of the trench, which is balanced with the trench top p0 and the self-weight of the trench structure, the equipment load in the trench, the cable laying construction and maintenance load, etc., and acts on the bottom plate as a uniformly distributed reaction force;

[0073] e1 is the water and soil pressure on the ditch sidewall facing the lane, and its value is calculated according to the static soil pressure or active soil pressure;

[0074] e2 is the additional horizontal load caused by the live load on the ground surface. Its value matches the use of the ground surface. Usually, the uniformly distributed live load on the ground surface is taken as q L =10kN / m 2 The calculation shows that the two sides of the channel are arranged symmetrically;

[0075] e3 is the horizontal load added to one side of the channel caused by the vehicle load on the road. Its value is calculated according to formula (1) and converted to the equivalent soil layer thickness. Since the converted distribution range is wide, it can be considered that it is equally distributed along the upper and lower sides of the channel sidewall, but it does not appear at the same time as e2.

[0076] Due to the load generated by the channel due to the squeezing of vehicles passing through, the load model and main parameters are as follows Fig.10 As shown:

[0077] where Δσ k is the active load; k s ·Δx is the horizontal soil resistance; k b ·Δy is the vertical soil resistance; the two change linearly; θ is the diffusion angle of the vehicle load, which can be taken as 45° according to the experience of foundation pit engineering. According to the balance of forces, it can be calculated as follows:

[0078]

[0079] Where: p is the concentrated load value of the wheel, kN;

[0080] b is the width of the wheel, m;

[0081] l is the longitudinal contact width of the wheel, m;

[0082] a is the distance between the wheel and the channel close to the wheel side, m;

[0083] Δσ k is the uniformly distributed load value acting on the channel side wall due to surface overload, kPa; or, the horizontal load transmitted to the channel side wall by the wheels through the foundation soil.

[0084] At this time, the lateral force and vertical force generated by the unilateral extrusion of the channel structure can be calculated using the elastic foundation model assumed by Winkel. Due to the large stiffness of the channel structure, it can be assumed that the distribution of the elastic resistance of the channel sidewall and bottom is linear. The values ​​of the elastic foundation model parameters can be determined through experiments. When there is no experience, the empirical values ​​of the existing foundation can be referred to. The values ​​are taken from the highway industry standard JTG D63-2019 "Highway Bridge and Culvert Foundation and Foundation Design Specifications" as follows Fig.11 As shown, Fig.11 The values ​​in are applicable to the case where the maximum displacement at the foundation ground does not exceed 6 mm. When the displacement is larger, it should be appropriately reduced.

[0085] The concentrated load of vehicles can be calculated by referring to the provisions of "Urban Bridge Design Code" CJJ11-2011. Its distribution is as follows: Fig.12 As shown; combined with the wheel pressure effect on one side of the vehicle Fig.13 As shown, Fig.13 The main parameters and their values ​​are as follows:

[0086] (1) a1 is the distance between the outer side of the wheel of vehicle axle 1 and the side wall of the channel, and its value is determined by the distance between the road boundary line and the side wall of the channel;

[0087] (2) a2 is the distance between the outer side of the wheels of axles 2 to 5 of the vehicle and the side wall of the channel. Its value is determined by the distance between the road boundary line and the side wall of the channel. For example, when driving parallel to the road boundary line, its value is a1 + 0.175 m;

[0088] (3) q1~q4 are the loads transmitted from the wheels to the sidewalls of the channel through the foundation soil. The downward and surrounding diffusion angles are set at 45°. Formula (1) can be used for calculation. The p·b·l in formula (1) can be directly taken as the wheel pressure value (kN) on one side of each axle.

[0089] (4) The deformation of the channel deformation joint reaches 30 mm. Under normal circumstances, the lateral deformation of the channel does not exceed 10 mm. Therefore, the length of the equivalent elastic foundation beam of the channel can be considered to be 15 m. The moment of inertia I of the channel structure is determined by calculating the C-section of the channel. The C-section of the channel is as follows: Fig.15 As shown, the calculation can be done using formula (2);

[0090]

[0091] Where: I is the moment of inertia of the channel cross section, m 4 ;

[0092] b e is the outer width of the channel, m;

[0093] h e is the channel outer height, m;

[0094] b i is the inner width of the channel, m;

[0095] h i is the height in the channel, m;

[0096] t1, t2 are the bottom plate thickness and side wall thickness of the channel, m;

[0097] (5) The base coefficient of the lateral foundation soil of the trench can be determined based on the recommended value in the geotechnical engineering investigation report. If there is no experience, it can be determined based on Fig.11 Determined according to different foundation soil types;

[0098] (6) According to the different minimum distances a1 and a2 between the vehicle and the channel side wall, the values ​​of q1 to q4 are directly calculated according to Fig.14 The fixed combined spacing acts on the side walls of the channel; Fig.14 The wheels of vehicle axles 1 to 4 are located in the elastic foundation beam equivalent to the channel with a length of 15m, and the wheels of vehicle axle 5 are located outside the elastic foundation beam equivalent to the channel with a length of 15m; at this time, the load q4 of the wheels of vehicle axle 5 on the channel side wall is not calculated.

[0099] (7) Using the elastic foundation beam method, calculate the internal forces and deformation values ​​of the channel;

[0100] (8) According to the pure bending structure, the longitudinal reinforcement of the channel is calculated according to the C-section beam.

[0101] Example:

[0102] According to conventional trench structure engineering, the worst case horizontal load Δσ is considered k No diffusion, (b+2a) takes the value of 1, the distance between the channel sidewall and the channel top is equal, that is, the load diffused by the vehicle directly acts on the top of the channel; at the same time, the common wheel distributed load value refers to the existing traffic engineering value, that is, p·b·l directly takes the wheel value, such as Fig.12 The values ​​shown are 30kN, 70kN, 70kN, 100kN, and 80kN respectively; a1 = 0.7750m, a2 = 0.60m, and the distributed loads are:

[0103]

[0104] The widths acting on the channel sidewalls are 1.80m, 2.9m, and 1.45m respectively. Assuming that the outer height of the channel sidewall is 2.0m, the outer width is 2.0m, and the wall thickness is 0.25m, the cross-sectional area is 1.375m 2 , Sectional moment of inertia I = 10.09375m 4 , other main calculation parameters are as follows:

[0105] (1) The elastic modulus of concrete is taken as 3.0×10 7 kN / m 2 ,

[0106] (2) The base coefficient of the channel sidewall is k = 5000 kN / m 3 ;

[0107] The calculation model of elastic foundation beam is as follows Fig.16 As shown; the calculation results of internal force and deformation are shown in Fig.17 As shown;

[0108] According to the calculation results, the lateral deformation of the channel did not exceed 10 mm, but the bending moment reached 215.10 kN·m. For the channel structure, this is an internal force that cannot be ignored and requires reinforcement according to the geometric dimensions of the cross-section.

[0109] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure, characterized in that: Applied to one-side driving, the force model is established according to the cable trench structure; Calculate the horizontal load Δσ transmitted by the wheel to the channel side wall through the foundation soil k , and the Winkel assumption is used to calculate the soil resistance of the channel sidewalls and bottom; Calculate the moment of inertia I of the channel cross section of the channel structure: According to the horizontal load Δσ k , soil resistance of the trench sidewalls and bottom and the moment of inertia I of the trench section, and the elastic foundation beam method are used to calculate the internal force and deformation value of the cable trench; According to the pure bending structure, the longitudinal reinforcement of the channel is calculated according to the C-section beam.

2. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 1 is characterized in that: The moment of inertia I of the channel section is determined by calculating the C-section of the channel: Where I is the moment of inertia of the channel cross section of the channel structure, m 4 ; b e is the outer width of the channel structure, m; h e is the external height of the channel structure, m; b i is the inner width of the channel structure, m; h i is the inner height of the channel structure, m.

3. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 1, characterized in that: The diffusion angle θ of the vehicle load is 45°, and the horizontal load Δσ added to one side of the channel is calculated. k , kPa; Among them, p is the concentrated load value of the wheel, kN; b is the width of the wheel, m; l is the longitudinal ground width of the wheel, m; a is the distance between the wheel and the channel close to the wheel side, m.

4. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 3 is characterized in that: Horizontal load Δσ k In p·b·l, the wheel pressure value on one side of each axle can be directly taken.

5. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 3 is characterized in that: Horizontal load Δσ k Considering the worst case without diffusion, b+2a takes the value of 1.

6. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 1, characterized in that: The base bed coefficient of the foundation soil for the soil resistance of the channel side walls and bottom is determined according to the recommended value in the geotechnical engineering investigation report; or it can be determined according to the highway industry standard JTG D63-2019 "Specifications for Design of Highway Bridge and Culvert Foundations".

7. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 1, characterized in that: Calculate the horizontal load Δσ transmitted from the wheels of each axle of the vehicle to the side wall of the channel through the foundation soil k , within the length range of the elastic foundation beam equivalent to the channel, select the group with the largest combined load applied to the channel at the same time.

8. The method for calculating the longitudinal internal force and deformation of a cable trench structure under vehicle bias pressure according to claim 7, characterized in that: The length of the channel equivalent elastic foundation beam is 15m.

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