CN107862165B - Multi-level numerical simulation method for safety assessment of reinforced concrete plant - Google Patents
Multi-level numerical simulation method for safety assessment of reinforced concrete plant Download PDFInfo
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Abstract
The invention discloses a multi-level numerical simulation method for safety assessment of a reinforced concrete plant, which comprises a numerical simulation process of two levels of key components in the whole plant and the plant, wherein firstly, a whole beam unit model of the plant is established according to the actual structural information of the reinforced concrete plant, the stress time course of each component is arranged, and the key components in the plant are determined; then, a local detail model is established for the key component, the existing defect damage is introduced, the damage constitutive relation of the key component is determined, and a corrected local detail model is obtained; and based on the corrected local detail model, the damage evolution process of the key component is simulated by considering the dynamic effect of the crane in the moving process, and the structural degradation process information is obtained and can be used for plant safety evaluation. The method establishes the model of the steel-concrete plant through the multi-scale simulation method, considers the influence of damage evolution caused by defects in the existing steel-concrete plant on structural performance degradation, and is particularly suitable for the safety assessment and the transformation and reinforcement process of the steel-concrete plant.
Description
Technical Field
The invention discloses a method for evaluating the safety of a reinforced concrete structure, in particular to a multi-level numerical simulation method for evaluating the safety of a reinforced concrete plant, and belongs to the field of the safety evaluation of the reinforced concrete structure and the simulation of a performance degradation process.
Background
Most of the existing methods for evaluating the safety of reinforced concrete structures are elastic analysis, which rarely involves damage analysis of materials, and even fails to consider the structural damage evolution caused by existing defects and evaluate the influence of the structural damage evolution on structural performance degradation, so that a new method needs to be developed to meet the requirement. Moreover, the reinforced concrete plant has a large spatial dimension, and the actual structural performance deterioration process has a multilayer property, so that a multilayer simulation method for the reinforced concrete plant also needs to be developed.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects that the existing safety assessment method does not consider material damage and the influence of the existing structural defects on the structural performance, the invention provides a multi-level numerical simulation method for the safety assessment of a reinforced concrete plant.
The technical scheme is as follows: the invention relates to a multi-level numerical simulation method for safety assessment of a reinforced concrete plant, which comprises a numerical simulation process of two levels of key components in the whole plant and the plant, and specifically comprises the following steps:
step 1, establishing an integral beam unit model of a reinforced concrete plant according to actual structural information of the reinforced concrete plant, arranging stress time courses of concrete members in the plant, and analyzing and determining key members in the plant;
and 3, based on the corrected local detail model, considering the dynamic effect of the crane moving process to simulate the damage evolution process of the key component, and obtaining the structural degradation process information, wherein the information can be used for plant safety assessment.
In the step 1, the method for determining the key component comprises the following steps: the method comprises the steps of applying actual crane load to an integral beam unit model of a factory building, obtaining stress time courses of dangerous sections of concrete members in the factory building by using an influence line method, analyzing stress results, wherein the parts with the maximum stress levels and stress amplitudes in the concrete members are dangerous parts of the integral structure of the factory building, and the members where the dangerous parts are located are key members.
In the step 2, the local detail model is established in an equivalent simplification mode, and due to the fact that stress levels and stress amplitude conditions of different parts in the key component are different, the local detail model is equivalently simplified and divided into three parts:
(1) ignoring secondary components in the integral beam unit model except the key components;
(2) adopting beam unit simulation for the non-dangerous part of the key component;
(3) and simulating dangerous positions in the key components by using a solid unit, and simulating the reinforcing steel bars by using a truss unit.
After the local detail model is established, the existing defects in the actual structure are introduced into the model by utilizing a continuous damage mechanics theory, the material rigidity reduction and evolution process caused by the defects are described, and the corrected local detail model, namely the local detail model considering the defects, is obtained.
The methods for introducing the defects are as follows:
(1) defect introduction position: simulating defective damage by reducing the stiffness of corresponding cells in the local detail model based on the real damage condition in the image;
(2) determination of material properties: if the damage of the existing defect reaches the critical value of damage, simulating by using the elastic constitutive relation after the rigidity is reduced; the entity units of the rest non-defective parts adopt the determined damage constitutive simulation damage evolution process; neglecting the damage of the steel bar embedded in the concrete, and simulating by using a nondestructive steel bar elastic constitutive model; calculating the non-dangerous part of the key component by using the concrete elastic constitutive structure;
(3) the unit attribute at the defect position: for macroscopic surface defects with the scale of decimeter level mainly appearing in the reinforced concrete plant, the unit type of the defect position is consistent with that of the integral beam unit model.
In the step 3, an equivalent crane load is applied to the modified local detail model, and the damage evolution process of the key component and the stress time course of the dangerous part caused by the defects in the moving process of the crane are simulated through finite element analysis, so that the structural degradation process information of the key component is obtained.
Has the advantages that: compared with the prior art, the method has the obvious advantages that the model of the reinforced concrete plant is established by a multi-scale simulation method, key components in the plant are simulated in a key mode on the basis of simulating the whole structure of the plant, the existing defects are introduced, and the influence of damage evolution caused by the defects in the existing reinforced concrete plant on structural performance degradation is considered; in addition, the dynamic effect of the crane in the moving process is considered in the damage evolution process, the simulation structure is more accurate, and the method is particularly suitable for the safety assessment and the transformation and reinforcement process of a reinforced concrete plant.
Drawings
FIG. 1 is a frame diagram of a reinforced concrete plant for structural performance degradation evaluation using the multi-level numerical simulation method of the present invention;
FIG. 2 is a schematic diagram of an integral beam unit model of a steel-concrete plant built in an embodiment, wherein FIG. 2(a) is a finite element model diagram of the integral plant, FIG. 2(b) is a schematic diagram of a finite element model of a longitudinal direction of the plant, and FIG. 2(c) is a schematic diagram of a finite element model of a transverse bent of the plant;
FIG. 3 is a stress time chart of each component in the factory building arranged in the embodiment;
FIG. 4 is a partial detail model diagram of key components built in the example;
FIG. 5 is a partial detail model diagram after the existing defect damage is introduced in the embodiment;
FIG. 6 is a diagram of the response time course of the crane displacement for studying the dynamic effect of the crane load in the embodiment;
fig. 7 is a cloud chart of a damage evolution process of a crane beam as a key component simulated in the embodiment, wherein fig. 7(a) -7 (d) respectively show damage conditions of the crane beam at different moments when a crane load acts on the crane beam;
fig. 8 is a time course chart of the stress of the bottom steel bar across the middle calculated in the embodiment.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
The invention relates to a multi-level numerical simulation method for safety assessment of a reinforced concrete plant, which comprises a numerical simulation process of two levels of a whole plant and key components in the plant, wherein the method is used for establishing a whole model of the reinforced concrete plant and a local detail model of the key components by a multi-scale simulation method on the basis of theories and technologies such as continuous damage mechanics, finite element simulation and the like, meanwhile, the method considers the influence of damage evolution caused by existing defects in the reinforced concrete plant on structural performance degradation, and finally obtained structural degradation process information can be used for safety assessment and reconstruction reinforcement of the reinforced concrete plant, and the model can be updated according to information fed back by a reconstruction reinforcement method and a new detection result, as shown in figure 1.
Examples
Taking a reinforced concrete factory building as an example, the multilevel numerical simulation method for safety assessment of the reinforced concrete factory building is explained.
Step 1, establishing an integral beam unit model according to actual structural information of the steel-concrete plant, and determining key components by arranging stress time courses of all concrete components.
As shown in fig. 1, the actual structural information of the steel-concrete plant includes structural dimensions, material parameters, component arrangement, loading form, existing defect information, and the like; the key points for establishing the integral beam unit model are as follows: neglecting secondary structural components such as wind-resistant columns and external walls, and mainly considering main structural components such as beams, columns and inter-column supports; the finally established integral beam unit model is shown in figure 2.
Then, an actual crane load is applied to the integral beam unit model of the factory building, the stress time course of the dangerous section of each concrete member is obtained by using an influence line method, as shown in fig. 3, the dangerous part of the key member can be judged by comparing the stress, and the stress result is analyzed to obtain: in the concrete member, the stress level and the stress amplitude of the end section of the crane beam and the middle section of the beam span are maximum, and then the sections are the bottom sections of the upper column and the bottom sections of the lower column; the cross section of the end part of the crane beam, the cross section of the beam span and the cross section of the upper column bottom are dangerous parts of an integral structure, namely, the crane beam and the bracket form a key component of a steel-concrete workshop.
the method can establish a local detail model for the identified key components in an equivalent simplification mode, and because the stress levels and the stress amplitude conditions of different parts in the key components are different, the method is divided into three parts in an equivalent simplification mode:
neglecting secondary components such as an inclined strut, a roof truss system, a bracket upper column and the like;
secondly, simulating the lower part of the bracket at the non-dangerous part by adopting a beam unit;
and thirdly, simulating two dangerous positions of a bracket joint and a crane beam by using a solid unit, and simulating the reinforcing steel bar by using a truss unit. And assuming that the connection among different units is good and the displacement is coordinated and consistent, the beam unit and the solid unit are connected and transited by adopting a multipoint constraint method, and the reinforcing steel bar unit and the concrete solid unit are constrained by adopting an embedded method. The obtained local detail model is shown in fig. 4.
The method for introducing the defective real damage information has the following points:
the defect introduction position: and correspondingly reducing the rigidity of the unit at the middle edge of the upper flange span of the local detail model based on the real damage condition of the field detection result so as to simulate the existing defect, as shown in fig. 5.
Determining material properties: assuming that the damage of the existing defect reaches the damage critical value, namely the damage does not develop any more, the elastic constitutive relation after the rigidity is reduced can be used for simulation approximately; the entity units of the rest non-defective parts adopt a plastic damage constitutive simulation damage evolution process; the damage of the steel bars embedded in the concrete can be ignored, so that the damage-free steel bar elastic constitutive simulation is used; in addition, the non-dangerous part of the key component is calculated by utilizing the concrete elastic constitutive.
③ unit property at the defect: the existing defects in the field detection result belong to macroscopic surface defects, and the scale is in the decimeter level, so that grid refinement is not needed. The unit types at the defect positions are consistent with the whole unit types and are hexahedron eight-node units.
And 3, considering the dynamic effect of the crane in the moving process, applying equivalent crane load to the modified local detail model, simulating the damage evolution process of the key component and the stress time course of the dangerous part through finite element analysis, obtaining the structural degradation process information of the key component, and using the obtained degradation process information for safety evaluation.
Fig. 6 provides a comparison of sets of maximum vertical displacement of the crane. It can be seen that the dynamic effect of the crane load has a large effect on the structural response, and the dynamic effect increases the displacement peak by about 6%, so the invention takes the effect of the dynamic effect into account in the simulation process.
Fig. 7(a) -7 (d) provide the evolution process of the damage of the critical component caused by the existing defect, which is as follows:
firstly, when the crane runs for 1.57s, the damage and the damage of the concrete begin to appear at the bottom of the crane beam, and an initial first crack is formed. The damage range is very small at this time, and the crack does not extend into the web.
② continue to run for 0.14s, the initial crack rapidly propagates to the web, no longer propagates at 2/3 point on the web, and maintains this length until the end of loading. The second crack at the bottom started to initiate, in a direction substantially parallel to the first crack.
③ when the crane is running for 3s, the running time of the crane is over half, besides a plurality of long cracks, there are also obvious oblique cracks (such as the cracks numbered VII in figure 7 (d)), but the length is relatively short.
After the end of the loading, a total of 8 relatively long cracks were observed, which were interspersed with a number of closely spaced short cracks whose crack directions were essentially parallel.
Fig. 8 provides a stress time course across the bottom rebar. It can be seen from the figure that when the position of the steel bar 2-2 is on the same side as the existing defect, the stress level peak value of the steel bar is increased by 19.4%, that is, the structural performance degradation speed affected by the existing defect is 1.2 times that of the original structure, which shows that the method of the present invention can effectively simulate the acceleration effect of the existing damage on the structural performance degradation process of the steel-concrete factory building.
Claims (1)
1. A multi-level numerical simulation method for safety assessment of a reinforced concrete plant is characterized by comprising a numerical simulation process of two levels of key components in the whole plant and the plant, and specifically comprises the following steps:
step 1, establishing an integral beam unit model of a reinforced concrete plant according to actual structural information of the reinforced concrete plant, arranging stress time courses of concrete members in the plant, and analyzing and determining key members in the plant; the determination method of the key component comprises the following steps: the method comprises the steps of applying actual crane load to an integral beam unit model of a factory building, obtaining stress time courses of dangerous sections of concrete members in the factory building by using an influence line method, analyzing stress results, wherein the parts with the maximum stress levels and stress amplitudes in the concrete members are dangerous parts of the integral structure of the factory building, and the members where the dangerous parts are located are key members;
step 2, establishing a local detail model for the identified key component, introducing existing defect damage, determining the damage constitutive relation of the key component, and obtaining a modified local detail model;
the local detail model is established in an equivalent simplification mode, and the equivalent simplification of the local detail model is divided into three parts:
(1) ignoring secondary components in the integral beam unit model except the key components;
(2) adopting beam unit simulation for the non-dangerous part of the key component;
(3) simulating dangerous positions in the key components by adopting a solid unit, and simulating the reinforcing steel bars by using a truss unit;
introducing existing defects in an actual structure into the local detail model by utilizing a continuous damage mechanics theory, describing a material rigidity reduction and evolution process caused by the defects, and obtaining a modified local detail model; introducing existing defects in the local detail model specifically according to the following method:
(1) defect introduction position: simulating defective damage by reducing the stiffness of corresponding cells in the local detail model based on the real damage condition in the image;
(2) determination of material properties: assuming that the damage of the existing defect reaches a damaged critical value, simulating by using an elastic constitutive relation after the rigidity is reduced; the entity units of the rest non-defective parts adopt the determined damage constitutive simulation damage evolution process; neglecting the damage of the steel bar embedded in the concrete, and simulating by using a nondestructive steel bar elastic constitutive model; calculating the non-dangerous part of the key component by using the concrete elastic constitutive structure;
(3) the unit attribute at the defect position: for macroscopic surface defects with the scale of decimeter level appearing in the reinforced concrete plant, the unit type of the defect is consistent with that of the integral beam unit model;
step 3, based on the corrected local detail model, considering the dynamic effect of the crane moving process to simulate the damage evolution process of the key component, and obtaining the structural degradation process information for plant safety evaluation; specifically, an equivalent crane load is applied to the modified local detail model, and the damage evolution process of the key component and the stress time course of the dangerous part caused by the defects in the moving process of the crane are simulated through finite element analysis, so that the structural degradation process information of the key component is obtained.
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