CN109885974B - Bearing capacity damage calculation method taking loading initial point as damage starting point - Google Patents
Bearing capacity damage calculation method taking loading initial point as damage starting point Download PDFInfo
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- CN109885974B CN109885974B CN201910221700.6A CN201910221700A CN109885974B CN 109885974 B CN109885974 B CN 109885974B CN 201910221700 A CN201910221700 A CN 201910221700A CN 109885974 B CN109885974 B CN 109885974B
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Abstract
The invention discloses a bearing capacity damage calculation method taking a loading initial point as a damage starting point, which comprises the following steps: establishing a skeleton curve according to the load displacement curve; determining an initial slope K of a skeleton curve 1 Peak load of the skeleton curve P m Failure point (Δ) of test piece u ，0.85P m ) And determining the slope K of the damage line according to the damage point 2 (ii) a Determining the displacement as Δ i Characteristic value P of time ss 、P re (ii) a Determining a damage value D according to a damage calculation formula P . The invention provides a new method and a new thought for structural earthquake damage research by using a load displacement curve obtained by test loading, taking the bearing capacity as a basic factor for evaluating the damage condition and taking the initial loading point as a damage starting point.
Description
Technical Field
The invention belongs to the field of structural damage calculation, and particularly relates to a bearing capacity damage calculation technology taking a loading initial point as a damage starting point.
Background
Since the earthquake will cause damage to the building structure, the bearing capacity and remaining life of the building structure in the subsequent service period will be greatly influenced after the building structure is subjected to earthquake damage. And the damage calculation method of the structure under the earthquake action is the theoretical basis of the earthquake-resistant design of the structure, and the internal damage condition of the structure is the important basis for reinforcing the structure after earthquake. Therefore, the method has great significance for the earthquake-resistant design and earthquake damage assessment of the structure by correctly mastering the damage level of the structure under the earthquake action and finding a reasonable calculation method to quantitatively describe the damage degree of the structural member under the earthquake action.
At present, the damage calculation method has the following defects: 1) the existing calculation method is complex; 2) the existing damage starting point definition is not in accordance with the actual situation.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects of the prior art, the invention provides the bearing capacity damage calculation method taking the initial loading point as the damage starting point by carrying out statistical analysis on the damage calculation method of the building structure and summarizing the advantages and the disadvantages of the existing damage calculation method.
The technical scheme is as follows: in order to solve the technical problem, the invention adopts the following technical scheme: a bearing capacity damage calculation method taking a loading initial point as a damage starting point comprises the following steps:
step 1), establishing a skeleton curve; loading the test piece to obtain a load displacement curve; defining an outer envelope of the load displacement curve as a skeleton curve of the test piece;
the method specifically comprises the following steps: loading the test piece according to a loading system of first load control and second displacement control to obtain a load displacement curve; defining the outer envelope of the load displacement curve as the skeleton curve of the test piece, and assuming that the function expression is P-f (delta) i ) P is the load, Δ i Is a displacement.
Step 2) determining the initial slope of the skeleton curve, and obtaining the slope of the damage-free straight line; determining peak load P of skeleton curve m Determining the damage point of the test piece, and determining the slope K of the damage line according to the damage point 2 ；
The method specifically comprises the following steps: the point B is a peak point of positive loading, and the corresponding load is a positive peak load P m (ii) a Load from peak load P m Down to 0.85P m Corresponding point C (Delta) u ，0.85P m ) Is the failure point of the forward loading; if the test piece is not damaged, the load displacement curve develops along the tangent of the point O of the initial loading point, and the straight line is called a non-damaged straight line; assuming that the slope of the tangent line at the initial point of the forward loading, i.e. the initial slope of the skeleton curve, is k 1 The function expression of the intact line is P ═ k 1 △ i (ii) a Taking the point O as a damage starting point, if a completely damaged test piece is loaded, developing a load displacement curve of the test piece along a straight line OC, and calling the straight line as a damage straight line; assuming that the slope of the damage line is k 2 ，k 2 ＝0.85P m /△ u So the function expression of the damage line is P ═ k 2 △ i (ii) a Of negative skeleton curvesThe initial slope, peak load, failure point and slope of the damage line are the same as the forward calculation method.
Step 3) determining the displacement as delta i Time, bearing capacity reduction value P caused by damage of test piece ss And the residual bearing capacity value P of the point of the test piece relative to the damage end point re ；
The method specifically comprises the following steps: taking the abscissa as delta on the skeleton curve i Point E, perpendicular to point E, intersects with intact line OA at point D, intersects with line OC at point F, and has x-axis coordinate Δ of D, E and point F i (ii) a The length of the score line segment DE is P ss ＝k 1 △ i －f(△ i ) The length of the segment EF is P re ＝f(△ i )－k 2 △ i (ii) a Then for point E, P ss The value of the reduction of the bearing capacity of the test piece due to damage, P re The residual value of the bearing capacity of the point of the test piece relative to the damage terminal point; the values of the negative loading and the positive loading are the same;
step 4) determining a damage value D according to a damage calculation formula P : point O is the starting point of damage and point C (. DELTA.) u ，0.85P m ) Is a damage point of the test piece and is defined as a damage terminal point; line OA is a non-destructive line; the straight line OC is a damage straight line; the formula for calculating the bearing capacity damage is as follows:
has the advantages that:
1. the method is based on a skeleton curve, takes the loading initial point as the damage starting point, and the damage value of the damage point is 1, so that the method is more in line with the actual situation, and the problem that the damage value is not converged at the damage point is solved;
2. the invention provides a new method for the structural damage test research based on the attenuation of the bearing capacity, is suitable for the condition that the cyclic damage does not need to be considered in the structural damage performance research, and is more suitable for the monotonous loading working condition of the component.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a loading regime of the present invention;
FIG. 3 is a schematic view of a load displacement curve according to the present invention;
FIG. 4 is a schematic view of a skeleton curve according to the present invention;
FIG. 5 is a schematic diagram of a feature point and a feature slope according to the present invention;
FIG. 6 is a schematic diagram of a method for calculating damage according to the present invention.
Detailed Description
As shown in fig. 1, a method for calculating a load bearing capacity damage using a loading initiation point as a damage initiation point mainly includes the following steps:
step 1) establishing a skeleton curve; as shown in fig. 2 to 4, the skeleton curve is determined by a load displacement curve; in the anti-seismic test research, a loading system of first load control and second displacement control is generally adopted, and the loading system is shown in fig. 2. The test piece was loaded according to this loading schedule, and a load-displacement curve as shown in fig. 3 was obtained. In the figure, P is load and Delta is displacement; as shown in fig. 4, the outer envelope of the load-displacement curve is defined as the skeleton curve of the test piece, and the functional expression thereof is assumed to be P ═ f (Δ) i )。
Step 2) As shown in FIG. 5, determine the initial slope K of the skeleton curve 1 Peak load of the skeleton curve P m Load from peak load P m Down to 0.85P m Point of failure (Delta) of time-corresponding test piece u ，0.85P m ) And determining the slope K of the damage line according to the damage point 2 (ii) a As shown in fig. 5, point B is the peak point of the positive loading, and the corresponding load is the peak load P of the positive loading m (ii) a Point C (. DELTA.) u ，0.85P m ) Is a failure point of the positive loading; if the test piece is not damaged, the load displacement curve develops along the tangent of the initial loading point (O point), and the straight line is called a non-damaged straight line (or a linear elastic straight line); assuming that the slope of the tangent line at the initial point of the forward loading, i.e. the initial slope of the skeleton curve, is k 1 ，k 1 Can be calculated by METLAB software, so that the function expression of the straight line is P ═ k 1 △ i (ii) a Taking the point O as the starting point of damage, if the pair is completely destroyed (damage)The test piece with the value 1) is loaded, the load displacement curve of the test piece will develop along a straight line OC, which is called a damage straight line. Assuming that the slope of the damage line is k 2 ，k 2 ＝0.85P m /△ u So the functional expression of the damage line is P ═ k 2 △ i (ii) a The initial slope, peak load, failure point and slope of the damage line of the negative skeleton curve are the same as those of the positive calculation method.
Step 3) As shown in FIG. 6, determine the displacement as Δ i Characteristic load P of time ss 、P re (ii) a A simplification of the framework curve from fig. 5 with positive loading is shown in fig. 6. Arbitrarily taking the abscissa as Delta on the skeleton curve i Point E, perpendicular to point E, intersecting line OA at point D and intersecting line OC at point F, and D, E and point F having x-axis coordinates Δ i As shown in fig. 6. The length of the score line segment DE is P ss ＝k 1 △ i －f(△ i ) The length of the segment EF is P re ＝f(△ i )－k 2 △ i . Then for point E, P ss Is the bearing capacity reduction value, P, of the test piece caused by damage re The remaining value of the bearing capacity of the point of the test piece relative to the damage end point is shown. The values of the negative loading and the positive loading are the same.
Step 4) determining a damage value D according to a damage calculation formula P . Point O is the starting point of damage and point C (. DELTA.) u ，0.85P m ) The point of failure of the test piece is defined as the damage endpoint. The line OA is a non-damaged line (or a linear elastic line); the straight line OC is a damage straight line; curve OBC is called skeleton curve; the formula for calculating the bearing capacity damage is as follows:
Claims (2)
1. a bearing capacity damage calculation method taking a loading initial point as a damage starting point is characterized in that: the method comprises the following steps:
step 1) establishing a skeleton curve; loading with load control first and displacement control lastA system, loading the test piece according to the loading system to obtain a load displacement curve; defining the outer envelope of the load displacement curve as the skeleton curve of the test piece, and the function expression of the skeleton curve is P ═ f ([ delta ]) i ) P is the load, Δ i Is a displacement;
step 2) determining the initial slope of the skeleton curve, and obtaining the slope of the damage-free straight line; determining the peak load P of the skeleton curve m Determining the damage point of the test piece, and determining the slope K of the damage line according to the damage point 2 (ii) a If the test piece is not damaged, the load displacement curve develops along the tangent of the point O of the initial loading point, and the straight line is called a non-damaged straight line; the slope of the tangent line of the initial point of the positive loading, namely the initial slope of the skeleton curve is k 1 The function expression of the intact line is P ═ k 1 △ i (ii) a The point B is a peak point of positive loading, and the corresponding load is a positive peak load P m (ii) a Load from peak load P m Down to 0.85P m Corresponding C point (Delta) u ，0.85P m ) Is a failure point of the positive loading; taking the point O as a damage starting point, if a completely damaged test piece is loaded, developing a load displacement curve of the test piece along a straight line OC, and calling the straight line as a damage straight line; the slope of the damage line is k 2 ，k 2＝ 0.85P m /△ u So the function expression of the damage line is P ═ k 2 △ i (ii) a The initial slope, peak load, damage point and slope of the damage straight line of the negative skeleton curve are the same as those of the positive skeleton curve;
step 3) determining the displacement as delta i Time, bearing capacity reduction value P caused by damage of test piece ss And the residual bearing capacity value P of the point of the test piece relative to the damage end point re ；
Step 4) determining a damage value D according to a damage calculation formula P : the formula for calculating the bearing capacity damage is as follows:
2. the method of claim 1, wherein the load bearing capacity damage calculation method using the initial loading point as the damage starting point comprises: said step 3) P ss 、P re The specific determination method comprises the following steps: taking the abscissa as delta on the skeleton curve i Point E, perpendicular to point E, intersects with intact line OA at point D, intersects with line OC at point F, and has x-axis coordinate Δ of D, E and point F i (ii) a The length of the score line DE is P ss ＝k 1 △ i －f(△ i ) The length of the segment EF is P re ＝f(△ i )－k 2 △ i (ii) a Then for point E, P ss Is the bearing capacity reduction value, P, of the test piece caused by damage re The residual value of the bearing capacity of the point of the test piece relative to the damage terminal point; the values of the negative loading and the positive loading are the same.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107831069A (en) * | 2017-11-27 | 2018-03-23 | 中南大学 | A kind of method that elastic deformation energy at rock material peak load point is determined in Point Load Tests |
| CN107844622A (en) * | 2017-09-04 | 2018-03-27 | 湘潭大学 | A kind of simply supported beam damage recognition methods based on faulted condition uniform load face curvature |
| CN108920739A (en) * | 2018-04-27 | 2018-11-30 | 天津大学 | A kind of material constitutive model numerical analysis method considering damage cumulating effect |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107844622A (en) * | 2017-09-04 | 2018-03-27 | 湘潭大学 | A kind of simply supported beam damage recognition methods based on faulted condition uniform load face curvature |
| CN107831069A (en) * | 2017-11-27 | 2018-03-23 | 中南大学 | A kind of method that elastic deformation energy at rock material peak load point is determined in Point Load Tests |
| CN108920739A (en) * | 2018-04-27 | 2018-11-30 | 天津大学 | A kind of material constitutive model numerical analysis method considering damage cumulating effect |
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