Bearing capacity design method of UHPC-RC (Ultra High Performance Concrete-Reinforced Concrete) laminated wall

Abstract

The invention belongs to the technical field of constructional engineering, and particularly relates to a bearing capacity design method of a UHPC-RC composite wall, which comprises the following steps: acquiring structural parameters of the UHPC-RC composite wall based on preset boundary conditions, and simulating mechanical properties of the UHPC-RC composite wall by adopting finite element software; based on the structure parameters of the UHPC-RC composite wall, the stress-strain relation between the UHPC outer acanthus and the UHPC core plate is calculated, and a calculation expression based on the flexural capacity of the UHPC-RC composite wall is established. According to the method, the flexural capacity of the UHPC-RC composite wall can be accurately and conveniently calculated by analyzing and calculating the flexural capacity of the UHPC-RC composite wall, and then the method is applied to safety evaluation of UHPC-RC composite wall components in an assembly type shear wall structure, so that the safety and stability of a UHPC-RC composite wall system are ensured, and the construction period is shortened. And whether parameter configuration such as UHPC strength and reinforcing bars is reasonable or not can be judged according to the bearing capacity design value in the design stage, so that the effect of optimal design is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of construction engineering, and particularly to a bearing capacity design method for UHPC-RC composite walls. Background Art

[0002] The UHPC-RC composite wall is a new type of composite plate shear wall. Its uniqueness lies in the use of UHPC inner and outer precast plates, and secondly, the connection method of UHPC post-casting and straight anchoring and short lap of steel bars. This new type of composite shear wall has the characteristics of good seismic performance and strong self-centering ability. However, at present, there is little research on this type of shear wall structure at home and abroad, and there is no theoretical basis and analysis and design method that can guide engineering applications, let alone corresponding codes and specifications to follow. Summary of the Invention

[0003] The present invention aims to provide a bearing capacity design method for UHPC-RC composite walls. Through the analysis and calculation of the flexural bearing capacity of the UHPC-RC composite wall system, the flexural bearing capacity of the system can be accurately and conveniently calculated, and then applied to the shear wall structure to ensure the safety and stability of the shear wall structure. Moreover, at the design stage, it can be judged whether the parameters such as UHPC strength and steel bar reinforcement are reasonable according to the design value of the bearing capacity, so as to achieve the effect of optimized design.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A bearing capacity design method for UHPC-RC composite walls includes the following specific steps:

[0006] Step 1: Obtain the structural parameters of the UHPC-RC composite wall and establish a calculation expression for the flexural bearing capacity based on the UHPC-RC composite wall.

[0007] Step 2: Judge the concrete structure. If the concrete structure is determined to be a UHPC-RC composite wall structure, then based on the calculation expression for the flexural bearing capacity of the UHPC-RC composite wall, execute the methods of Steps 3 to 6.

[0008] Step 3: Calculate N respectively according to the following formula c is the pressure borne by the core slab in the compression zone; N U is the pressure borne by the UHPC precast slab in the compression zone; N t is the resultant force of the tension longitudinal bars; N′ t is the resultant force of the compression longitudinal bars;

[0009]

[0010] N U =(b - b0)E U ε cu x / 2

[0011] N t = f y A s

[0012] N’ t = σ y A’ s

[0013] Where: N c is the pressure borne by the core slab in the compression zone;

[0014] N U is the pressure borne by the UHPC precast slab in the compression zone;

[0015] N t is the resultant force of the tension longitudinal reinforcement;

[0016] N′ t is the resultant force of the compression longitudinal reinforcement;

[0017] N sw is the force borne by the vertical distributed reinforcement in the tension zone;

[0018] N’ sw is the force borne by the vertical distributed reinforcement in the compression zone;

[0019] N is the axial compression load;

[0020] h and b are the height and width of the shear wall section respectively;

[0021] b0 is the thickness of the core slab;

[0022] a s is the distance from the resultant force point of the compression zone end longitudinal reinforcement to the edge of the compression zone h w0 = h - a s ;

[0023] L c is the length of the boundary element;

[0024] f y is the yield strength of the reinforcement;

[0025] ρ sw is the reinforcement ratio of the vertical distributed reinforcement;

[0026] x is the height of the compression zone;

[0027] f c is the axial compressive strength of the in-situ concrete of the core slab;

[0028] f U is the axial compressive strength of the UHPC of the precast slab;

[0029] ε c0is the peak compressive strain of the in-situ concrete of the core slab;

[0030] ε cu is the ultimate compressive strain of the in-situ concrete of the core slab;

[0031] ε U0 is the peak compressive strain of UHPC, taking ε U0 = f U / E U ;

[0032] E U is the secant stiffness at the peak point of the stress-strain curve of the UHPC of the precast slab;

[0033] Step 4: Calculate the height of the compression zone of the normal section according to the following formula:

[0034]

[0035] Step 5: Calculate the bending moment provided by the core slab in the compression zone respectively according to the following formula; M U is the bending moment provided by the UHPC precast slab in the compression zone; M sw is the bending moment provided by the tension distributed longitudinal reinforcement; M' sw is the bending moment provided by the compression distributed longitudinal reinforcement:

[0036]

[0037] M U = N U (h w0 - x / 3)

[0038] M sw = f y ρ sw b(h w0 - 2x) 2

[0039]

[0040] Step 6: Calculate the sum of the bending moment values of the control section according to the following formula:

[0041]

[0042] As a further improvement of this technical solution: Step 1: Obtain the structural parameters of the UHPC-RC composite wall and establish a calculation expression for the flexural bearing capacity of the UHPC-RC composite wall, specifically:

[0043] Obtain the structural parameters of the UHPC-RC composite wall, simulate the mechanical properties of the UHPC-RC composite wall using finite element software, determine the normal section stress distribution curves of the UHPC outer leaf and the NC core at the peak point, summarize the normal section stress distribution curve of the UHPC-RC composite wall at the peak point, and establish a calculation expression for the flexural bearing capacity of the UHPC-RC composite wall.

[0044] As a further improvement of this technical solution: The obtaining of the structural parameters of the UHPC-RC composite wall and the simulation of the mechanical properties of the UHPC-RC composite wall using finite element software to determine the normal section stress distribution curves of the UHPC outer leaf and the NC core at the peak point includes:

[0045] Obtain the structural parameters of the UHPC-RC composite wall;

[0046] Based on the preset boundary conditions, simulate the mechanical properties of the UHPC-RC composite wall using finite element software;

[0047] Output the stress distribution diagram of the normal section of the UHPC-RC composite wall at the peak point after calculation by the finite element software, and summarize the stress distribution diagram of the normal section of the UHPC-RC composite peak point based on the normal section state of the UHPC-RC composite wall at the peak point of the pseudo-static test.

[0048] As a further improvement of this technical solution: The summarization of the normal section stress distribution curve of the UHPC-RC composite wall at the peak point is specifically:

[0049] Based on the normal section state of the UHPC-RC composite wall at the peak point, make basic assumptions about the peak point state of the UHPC-RC composite wall;

[0050] Based on the basic assumption conditions and the stress distribution diagram of the normal section of the UHPC-RC composite wall at the peak point, establish a simplified curve of the normal section stress distribution of the UHPC precast slab, a simplified curve of the normal section stress distribution of the core slab, and a simplified curve of the normal section stress distribution of the longitudinal reinforcement at the peak point of the UHPC-RC composite wall.

[0051] As a further improvement of this technical solution: The basic assumptions include:

[0052] (1) Assume that all specimens satisfy the plane section assumption;

[0053] (2) Assume that the section tension is only borne by the distributed reinforcement, and the tensile strengths of the normal concrete and ultra-high performance concrete in the tension zone are ignored;

[0054] (3) Assume that the vertical distributed reinforcement has yielded and participated in the tensile load-bearing outside the 2x range extending from the edge of the compression zone to the tension zone;

[0055] (4) It is assumed that the contribution of the truss reinforcement to the flexural bearing capacity is not considered.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] Through the analysis and calculation of the flexural bearing capacity of the UHPC-RC composite wall, the flexural bearing capacity of the UHPC-RC composite wall can be accurately and conveniently calculated, and then applied to the safety assessment of the UHPC-RC composite wall components in the precast shear wall structure, ensuring the safety and stability of the UHPC-RC composite wall system. Moreover, it can also judge whether the parameters such as the UHPC strength and the reinforcement configuration are reasonable according to the design value of the bearing capacity during the design stage, so as to achieve the effect of optimized design.

[0058] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it in accordance with the content of the specification, the following takes the preferred embodiments of the present invention and describes them in detail with the accompanying drawings. The specific implementation manners of the present invention are given in detail by the following embodiments and their accompanying drawings. Brief Description of the Drawings

[0059] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and the schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0060] Figure 1 is the flowchart of the present invention;

[0061] Figure 2 is the structural schematic diagram of the UHPC-RC composite wall in the present invention;

[0062] Figure 3 is the schematic diagram of the mesh element division during the finite element process;

[0063] Figure 4 is the schematic diagram of the stresses of the UHPC-RC composite walls with different height-width ratios and their internal steel bars during the finite element process;

[0064] Figure 5 is the normal section stress distribution curve of the precast slab UHPC, the core slab concrete and the internal longitudinal steel bars at the peak point;

[0065] Figure 6 is the calculation sketch of the normal section bearing capacity of the UHPC-RC composite wall involved in the present invention;

[0066] Figure 7 is the normal section strain distribution diagram;

[0067] Figure 8 is the simplified diagram of the normal section stress distribution of ordinary concrete;

[0068] Figure 9 It is a simplified diagram of the normal section stress distribution of UHPC;

[0069] Figure 10 It is a simplified diagram of the normal section stress distribution of steel bars.

[0070] Reference numerals: 1, steel reinforcement cage; 2, precast UHPC inner and outer leaf plates; 3, UHPC post-cast strip; 4, NC core plate; 5, horizontal connection joint seam. Specific implementation manner

[0071] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. In the following paragraphs, the present invention will be described more specifically by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0072] The bearing capacity design method of the UHPC-RC composite wall includes the following specific steps:

[0073] Step 1: Obtain the structural parameters of the UHPC-RC composite wall and establish a calculation expression for the flexural bearing capacity based on the UHPC-RC composite wall, specifically:

[0074] Obtain the structural parameters of the UHPC-RC composite wall and simulate the mechanical properties of the UHPC-RC composite wall using finite element software;

[0075] Based on the structural parameters of the UHPC-RC composite wall, simulate the mechanical properties of the UHPC-RC composite wall using finite element software, determine the normal section stress distribution curves of the UHPC outer leaf plate and the NC core plate at the peak point, summarize the normal section stress distribution curve of the UHPC-RC composite wall at the peak point, and establish a calculation expression for the flexural bearing capacity based on the UHPC-RC composite wall;

[0076] Among them, obtaining the structural parameters of the UHPC-RC composite wall and simulating the mechanical properties of the UHPC-RC composite wall using finite element software includes:

[0077] Obtain the structural parameters of the UHPC-RC composite wall;

[0078] Based on the preset boundary conditions, simulate the mechanical properties of the UHPC-RC composite wall using finite element software;

[0079] Output the stress distribution diagram of the normal section of the UHPC-RC composite wall calculated by the finite element software, and summarize the normal section state of the UHPC-RC composite wall at the peak point based on the normal section state of the UHPC-RC composite wall at the peak point of the pseudo-static test.

[0080] Among them,Figure 5 For the stress distribution curves at the peak points of the precast slab UHPC, the core slab concrete, and the internal longitudinal reinforcement under different axial compression ratios and different height-width ratios, it can be summarized from the normal section stress distribution that the vertical distribution reinforcement outside twice the compression zone range has yielded and participated in tension. The core slab concrete in the compression zone reaches the peak strain.

[0081] The peak point state is: when the edge strain of the core slab concrete reaches its limit value, it can be determined that the UHPC-RC composite wall reaches the peak point;

[0082] Based on the normal section state of the UHPC-RC composite wall at the peak point, basic assumptions are made for the peak point state of the UHPC-RC composite wall;

[0083] The basic assumptions include:

[0084] (1) Assume that all specimens satisfy the plane section assumption;

[0085] (2) Assume that the section tension is only borne by the distribution reinforcement, and the tensile strengths of the normal concrete (NC) and ultra-high performance concrete (UHPC) in the tension zone are ignored;

[0086] (3) Assume that the vertical distribution reinforcement has yielded and participated in the tensile load-bearing outside the 2x range extending from the edge of the compression zone to the tension zone;

[0087] (4) Assume that the contribution of the truss reinforcement to the flexural bearing capacity is not considered.

[0088] Based on the basic assumptions and the normal section stress distribution curve, simplified curves of the normal section stress distribution of the UHPC precast slab, the core slab, and the longitudinal reinforcement of the UHPC-RC composite wall at the peak point are established;

[0089] Based on the simplified curves of the normal section stress distribution of the UHPC precast slab, the core slab, and the longitudinal reinforcement, the force equilibrium equation of the UHPC-RC composite wall is established:

[0090] N = N t -N t -N sw +N sw +N c +N U

[0091]

[0092] N U =(b - b0)E U ε cu x / 2

[0093] N t= f y A s

[0094] N’ t = σ y A’ s

[0095] N sw = f y ρ sw b(h w0 - 2x)

[0096] N sw = f y ρ sw b(x - a s ) / 2

[0097] In the formula: N c is the pressure borne by the core slab in the compression zone;

[0098] N U is the pressure borne by the UHPC precast slab in the compression zone;

[0099] N t is the resultant force of the tension longitudinal reinforcement;

[0100] N′ t is the resultant force of the compression longitudinal reinforcement;

[0101] N sw is the force borne by the vertical distributed reinforcement in the tension zone;

[0102] N’ sw is the force borne by the vertical distributed reinforcement in the compression zone;

[0103] N is the axial compression load;

[0104] h and b are the height and width of the shear wall section respectively;

[0105] b0 is the thickness of the core slab;

[0106] a s is the distance from the resultant force point of the compression zone end longitudinal reinforcement to the compression zone edge, h w0 = h - a s ;

[0107] L c is the length of the boundary element;

[0108] f y is the yield strength of the reinforcement;

[0109] ρ sw is the reinforcement ratio of the vertical distributed reinforcement;

[0110] x is the compression zone height;

[0111] f c is the axial compressive strength of the in-situ concrete of the core slab;

[0112] f U is the axial compressive strength of the UHPC of the precast slab;

[0113] ε c0 is the peak compressive strain of the in-situ concrete of the core slab;

[0114] ε cu is the ultimate compressive strain of the in-situ concrete of the core slab;

[0115] ε U0 is the peak compressive strain of UHPC, taking ε U0 = f U / E U ;

[0116] E U is the secant stiffness at the peak point of the stress-strain curve of the UHPC of the precast slab.

[0117] Based on the force equilibrium equation of the UHPC-RC composite wall, construct an expression for the height of the compression zone;

[0118]

[0119] Based on the expression for the height of the compression zone of the UHPC-RC composite wall, construct a calculation expression for the flexural bearing capacity.

[0120]

[0121] M U = N U (h w0 - x / 3)

[0122] M sw = f v ρ sw b(h w0 - 2x) 2

[0123]

[0124] Step 2: Judge the concrete structure. If the concrete structure is determined to be a UHPC-RC composite wall structure, then based on the above calculation expression for the flexural bearing capacity of the UHPC-RC composite wall, implement the methods in Steps 3 to 6;

[0125] Step 3: Calculate N respectively according to the following formula c is the pressure borne by the core slab in the compression zone; N U is the pressure borne by the UHPC precast slab in the compression zone; N tThe resultant force of the tension longitudinal reinforcement; N′ t The resultant force of the compression longitudinal reinforcement;

[0126]

[0127] N U =(b - b0)E U ε cu x / 2

[0128] N t =f y A s

[0129] N t =σ y A s

[0130] In the formula: N c Is the pressure borne by the core slab in the compression zone;

[0131] N U Is the pressure borne by the UHPC precast slab in the compression zone;

[0132] N t Is the resultant force of the tension longitudinal reinforcement;

[0133] N’ t Is the resultant force of the compression longitudinal reinforcement;

[0134] N sw Is the force borne by the vertical distributed reinforcement in the tension zone;

[0135] N’ sw Is the force borne by the vertical distributed reinforcement in the compression zone;

[0136] N is the axial compression load;

[0137] h and b are the height and width of the shear wall section respectively;

[0138] b0 is the thickness of the core slab;

[0139] a s Is the distance from the resultant force point of the compression zone end longitudinal reinforcement to the edge of the compression zone h w0 =h - a s ;

[0140] L c Is the length of the boundary member;

[0141] f y Is the yield strength of the reinforcement;

[0142] ρ sw Is the reinforcement ratio of the vertical distributed reinforcement;

[0143] x is the height of the compression zone;

[0144] f c is the axial compressive strength of the in-situ concrete of the core slab;

[0145] f U is the axial compressive strength of the UHPC of the precast slab;

[0146] ε c0 is the peak compressive strain of the in-situ concrete of the core slab;

[0147] ε cu is the ultimate compressive strain of the in-situ concrete of the core slab;

[0148] ε U0 is the peak compressive strain of the UHPC, taking ε U0 = f U / E U ;

[0149] E U is the secant stiffness at the peak point of the stress-strain curve of the UHPC of the precast slab;

[0150] Step Four: Calculate the height of the compression zone of the normal section according to the following formula:

[0151]

[0152] Step Five: Calculate the bending moment provided by the core slab in the compression zone respectively according to the following formula; M U is the bending moment provided by the UHPC precast slab in the compression zone; M sw is the bending moment provided by the tension distributed longitudinal reinforcement; M' sw is the bending moment provided by the compression distributed longitudinal reinforcement:

[0153]

[0154] M U = N U (h w0 - x / 3)

[0155] M sw = f y ρ sw b(h w0 - 2x) 2

[0156]

[0157] Step Six: Calculate the sum of the bending moment values of the control section according to the following formula:

[0158]

[0159] Using the modified formula proposed in this paper, the normal section bearing capacity of RC-UHPC composite walls under different axial compression ratios and height-width ratios was calculated, and the results are shown in the following table. The data shows that the deviation between the calculation results of the modified formula and the finite element simulation results is controlled within 12%, and the average relative error is 5%. The two are in good agreement, verifying the accuracy of the modified formula in predicting the normal section bearing capacity of RC-UHPC composite walls.

[0160]

[0161]

[0162] As mentioned above, only the preferred embodiments of the present invention are described, and there is no limitation to the present invention in any form; any ordinary technician in the industry can smoothly implement the present invention according to the description shown in the accompanying drawings of the specification and the above description; however, any equivalent changes made by those familiar with the technology in the technical field of the present invention within the scope of the technical solution of the present invention by using the technical content disclosed above, such as slight modifications, decorations, and evolutions, are equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. Design method for the bearing capacity of UHPC-RC composite wall, characterized in that, It includes the following specific steps: Step 1: Obtain the structural parameters of the UHPC-RC composite wall and establish a calculation expression for the flexural bearing capacity of the UHPC-RC composite wall; Step 2: Judge the concrete structure. If the concrete structure is determined to be a UHPC-RC composite wall structure, then based on the calculation expression for the flexural bearing capacity of the UHPC-RC composite wall, execute the methods in Steps 3 to 6; Step 3: Calculate N respectively according to the following formula c is the pressure borne by the core slab in the compression zone; N U is the pressure borne by the UHPC precast slab in the compression zone; N t is the resultant force of the tension longitudinal bars; N′ t is the resultant force of the compression longitudinal bars; N U =(b - b0)E U ε cu x / 2 N t = f y A s N t = σ y A s Where: N c is the pressure borne by the core plate in the compression zone; N U is the pressure borne by the UHPC precast slab in the compression zone; N t is the resultant force of the tension longitudinal reinforcement; N′ t is the resultant force of the longitudinal reinforcement under compression; N sw is the force borne by the vertical distributed steel bars in the tension zone; N’ sw is the force borne by the vertical distributed steel bars in the compression zone; N is the axial compressive load; h and b are the height and width of the shear wall section respectively; b0 is the thickness of the core slab; a s The distance from the resultant force point of the longitudinal bars at the end of the compression zone to the edge of the compression zone is h w0 = h - a s ; L c is the length of the edge member; f y is the yield strength of the steel bar; ρ sw is the vertical distribution steel bar reinforcement ratio; x is the height of the compression zone; f c is the axial compressive strength of the in-situ concrete of the core slab; f U is the axial compressive strength of precast slab UHPC; ε c0 is the peak compressive strain of the in-situ concrete of the core board; ε cu is the ultimate compressive strain of the in-situ concrete of the core plate; ε U0 is the peak compressive strain of UHPC, taking ε U0 = f U / E U ; E U is the secant stiffness at the peak point of the stress-strain curve of the precast slab UHPC; Step 4: Calculate the height of the compression zone of the normal section according to the following formula: Step 5: Calculate the bending moments provided by the core slab in the compression zone according to the following formula; M U is the bending moment provided by the UHPC precast slab in the compression zone; M sw is the bending moment provided by the tension distributed longitudinal reinforcement; M’ sw is the bending moment provided by the compression distributed longitudinal reinforcement: M U = N U (h w0 - x / 3) M sw = f y ρ sw b(h w0 - 2x) 2 Step 6: Calculate the sum of the bending moment values of the control section according to the following formula:

2. The bearing capacity design method of the UHPC-RC composite wall according to claim 1, characterized in that, Step 1: Obtain the structural parameters of the UHPC-RC composite wall and establish a calculation expression for the flexural bearing capacity of the UHPC-RC composite wall. Specifically: Obtain the structural parameters of the UHPC-RC composite wall, simulate the mechanical properties of the UHPC-RC composite wall using finite element software, determine the normal section stress distribution curves of the UHPC outer leaf slab and the NC core slab at the peak point, summarize the normal section stress distribution curve of the UHPC-RC composite wall at the peak point, and establish a calculation expression for the flexural bearing capacity of the UHPC-RC composite wall.

3. The bearing capacity design method of the UHPC-RC composite wall according to claim 2, wherein, The obtaining of the structural parameters of the UHPC-RC composite wall and the simulation of the mechanical properties of the UHPC-RC composite wall using finite element software to determine the normal section stress distribution curves of the UHPC outer leaf slab and the NC core slab at the peak point includes: Obtain the structural parameters of the UHPC-RC composite wall; Based on the preset boundary conditions, simulate the mechanical properties of the UHPC-RC composite wall using finite element software; Output the stress distribution diagram of the normal section of the UHPC-RC composite wall at the peak point calculated by the finite element software, and summarize the stress distribution diagram of the normal section of the UHPC-RC composite peak point based on the normal section state of the UHPC-RC composite wall under the pseudo-static test at the peak point.

4. The bearing capacity design method of the UHPC-RC composite wall according to claim 3, characterized in that, Summarize the normal section stress distribution curve of the UHPC-RC composite wall at the peak point. Specifically: Based on the normal section state of the UHPC-RC composite wall at the peak point, make basic assumptions about the peak point state of the UHPC-RC composite wall; Based on the basic assumption conditions and the stress distribution diagram of the normal section of the UHPC-RC composite wall at the peak point, establish a simplified curve of the normal section stress distribution of the UHPC precast slab, a simplified curve of the normal section stress distribution of the core slab, and a simplified curve of the normal section stress distribution of the longitudinal reinforcement at the peak point of the UHPC-RC composite wall.

5. The bearing capacity design method of the UHPC-RC composite wall according to claim 4, characterized in that, The basic assumptions include: (1) Assume that all specimens satisfy the plane section assumption; (2) Assume that the section tension is only borne by the distributed reinforcement, and ignore the tensile strength of the ordinary concrete and ultra-high performance concrete in the tension zone; (3) Assume that the vertical distributed reinforcement has yielded and participated in the tensile bearing outside the range of 2x extending from the edge of the compression zone to the tension zone; (4) Assume that the contribution of the truss reinforcement to the flexural bearing capacity is not considered.

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