A method for assessing and predicting the collapse of steel structure buildings under explosion scenarios

Abstract

The present invention provides a method for assessing and predicting the collapse of steel structures under explosion scenarios, comprising the following steps: S1. Determining the range of damaged beams and plate components to be considered when analyzing the collapse of steel structures under explosions; S2. Based on a theoretical calculation formula for the reduction coefficient of the anti-collapse capacity of beam and plate structures under explosions, combined with the principle of resistance equivalence, deriving a method for simulating damage to steel beams and plates under explosion scenarios; S3. Establishing a continuous collapse analysis model for steel structures to assess the continuous collapse resistance of the structure. The method for assessing and predicting the collapse of steel structures under explosion scenarios described in the present invention can relatively accurately and efficiently assess and predict the continuous collapse resistance of steel structures under explosion loads, providing technical support for the assessment, modification, and improvement of building collapse resistance in actual engineering projects.

Description

Technical Field

[0001] The present invention belongs to the technical field of building collapse assessment and prediction, and in particular relates to a method for assessing and predicting the collapse of a steel structure building under an explosion scenario. Background Art

[0002] High-rise and super-high-rise buildings often utilize steel structures as their primary structures. However, these steel structures often integrate multiple functions and have high mobility. If they experience progressive collapse, they can cause significant casualties and economic losses. Explosions are a major cause of progressive collapse in buildings. Progressive collapse of buildings under blast loads is a complex, nonlinear process. Current research primarily uses the alternative force path method to analyze and assess the collapse resistance of building structures. This method has the advantage of analyzing only the behavior of the remaining structure after the removal of load-bearing components, making it widely applicable. However, because it fails to account for the interaction between blast loads and the structure, or the impact on components surrounding the removed columns, the results may differ from the actual situation, making them potentially dangerous. While direct simulation methods can account for the interaction between blast loads and the structure, they require detailed models of explosives, air, and structure, resulting in low computational efficiency and high computer requirements, making them unsuitable for practical engineering applications. Therefore, it is necessary to develop a method for predicting the progressive collapse of steel structures that considers the interaction between blast and structure, allowing for accurate and relatively efficient assessment of the collapse resistance of steel structures. Summary of the Invention

[0003] In view of this, in order to overcome the shortcomings of the existing alternative force transmission path method and direct simulation method in evaluating the progressive collapse resistance of steel structure buildings, the present invention aims to propose a collapse assessment and prediction method for steel structure buildings under explosion scenarios, so as to solve the problems that the alternative force transmission path method commonly used in collapse analysis cannot reflect the interaction process between the explosion load and the building structure, resulting in a certain difference between its collapse assessment results and the actual situation, and the accuracy needs to be improved; the direct simulation method requires the establishment of a complex calculation model, consumes a lot of computing resources, is inefficient, and is not suitable for actual engineering.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A method for assessing and predicting the collapse of a steel structure building under an explosion scenario comprises the following steps:

[0006] S1. Determine the scope of damaged beams and plates when analyzing the collapse of steel structures under explosions;

[0007] S2. Based on the theoretical calculation formula of the reduction coefficient of the anti-collapse capacity of beam and slab structures under explosion, combined with the principle of resistance equivalence, a method for simulating the damage of steel structure beams and slabs under explosion scenarios is derived;

[0008] S3. Establish a progressive collapse analysis model for steel structures to evaluate the progressive collapse resistance of the structure.

[0009] Furthermore, the specific method of step S1 is as follows:

[0010] Determine the failed columns in the steel structure under explosion scenarios, and the beams and plate components connected to the failed columns are all within the scope of components that need to be considered for damage.

[0011] Furthermore, the specific method of step S2 is as follows:

[0012] A local analysis model of the frame is created, and the resistance reduction coefficient of the beam-slab structure under explosion is calculated using a theoretical formula. The calculated resistance reduction coefficient is used to reduce the strength and elastic modulus parameters of the material in the local analysis model. Then, a nonlinear static analysis is performed on the local analysis model to obtain the resistance curve of the local analysis model structure. The resistance reduction coefficient is compared with the nonlinear static analysis results of the local analysis model without parameter reduction to obtain the resistance reduction coefficient of the macro model. By comparing with the reduction coefficient calculated using the theoretical formula, the plates or plate and beam components that need to be corrected for the material reduction coefficient and the correction range are determined. The specific correction method and calculation formula of the reduction coefficient are obtained through simulation calculation, and a simplified simulation method for frame beam-slab damage under explosion scenarios based on material parameter reduction and reduction coefficient correction is established.

[0013] Furthermore, the LS-DYNA explicit dynamic finite element analysis software was used to create a local analysis model of the frame, in which the steel beams and steel columns were simulated using beam elements, and the reinforced concrete slabs were simulated using shell elements.

[0014] Furthermore, in step S3, a steel structure progressive collapse analysis model is established using LS-DYNA explicit dynamic finite element analysis software in combination with a multi-scale modeling method;

[0015] Among them, steel beams and steel columns are simulated by Beam units, reinforced concrete slabs are simulated by layered shell units, and nodes are simulated by macro units.

[0016] Furthermore, the specific method of step S3 is as follows:

[0017] After the steel structure progressive collapse analysis model is created, according to step S1 and the set working conditions, the beams and plate components that are damaged under the explosion scenario are determined. The performance of the beams and plate components is reduced using the steel structure beam and plate damage simulation method under the explosion scenario in step S2. Subsequently, the failed columns set in the working condition are removed, and a nonlinear dynamic analysis is performed on the remaining structure to evaluate and predict the progressive collapse resistance of the steel structure.

[0018] Compared with the existing technology, the method for assessing and predicting the collapse of steel structure buildings under explosion scenarios described in the present invention has the following advantages:

[0019] (1) The method for assessing and predicting the collapse of steel structure buildings under explosion scenarios described in the present invention can relatively accurately and efficiently assess and predict the progressive collapse resistance of steel structure buildings under explosion loads, providing technical support for the assessment, modification and improvement of the anti-collapse performance of buildings in actual engineering projects.

[0020] (2) Compared with the traditional alternative force transmission path method, the method for assessing and predicting the collapse of steel structure buildings under explosion scenarios described in the present invention, on the one hand, takes into account the interaction between the explosion load and the structure, and introduces the damage caused by the explosion to the beams and plate components into the continuous collapse analysis, thereby improving the accuracy of the collapse assessment. On the other hand, compared with the direct simulation method, it improves the calculation efficiency, thereby achieving a relatively accurate and efficient assessment and prediction of the anti-collapse performance of steel structure buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 This is a schematic diagram of the range of beam and slab components that are damaged by explosions when analyzing structural collapse according to an embodiment of the present invention;

[0023] Figure 2 This is a diagram of a local analysis model of the framework according to an embodiment of the present invention;

[0024] Figure 3 A diagram of a steel frame collapse analysis model according to an embodiment of the present invention;

[0025] Figure 4 A comparison diagram of vertical displacement time history curves of failed column top nodes according to an embodiment of the present invention;

[0026] Figure 5 This is a diagram of the frame collapse mode obtained by simulation using the present invention in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0028] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0029] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0031] A method for assessing and predicting the collapse of steel structures under explosion scenarios is proposed. The method first determines the range of beam and slab components whose damage is considered during explosion damage analysis. A simplified simulation method for steel frame beam and slab damage under explosion is proposed based on the theoretical calculation formula for the reduction factor of the anti-collapse capacity of beam and slab substructures under explosion, combined with the principle of resistance equivalence. Finally, an efficient steel structure collapse analysis model is established. Based on the above method, explosion-induced beam and slab damage is introduced, and structural dynamic analysis is performed in conjunction with the alternative force transmission path method to evaluate the structure's progressive collapse resistance. The method specifically includes the following steps:

[0032] (1) First, determine the scope of beams and slabs that are considered damaged by explosions during structural collapse analysis. That is, the beams and slabs connected to the failed columns under explosions are considered damaged by explosions. For example, when the bottom side columns of the frame fail, the components considered damaged by explosions are the longitudinal beams on the left and right sides connected to the columns, a horizontal beam, and the floor slabs on both sides of the columns. Figure 1 As shown in (a); when the bottom corner column of the frame fails, the components considered for explosion damage are the longitudinal and transverse beams connected to the column and the corner floor slab, as shown in Figure 1As shown in (b); when the middle column at the bottom of the frame fails, the components considered for explosion damage are the two longitudinal and transverse beams connected to the column and the four adjacent floor slabs, as shown in Figure 1 (c) If multiple columns fail, the method for determining the scope of damaged components is the same as above. For example, if two adjacent side columns fail, the components considered to be damaged by the explosion are the three longitudinal beams, two transverse beams and three floor slabs connected to the two columns. Figure 1 (d) shown.

[0033] (2) According to the theoretical calculation formula of the collapse resistance reduction coefficient of the beam-slab substructure under explosion and the principle of resistance equivalence, a simplified simulation method for the damage of steel frame beams and slabs under explosion is established. Specifically, a local analysis model of the frame structure is adopted, and the resistance reduction coefficient calculated by the theoretical formula is used to reduce the parameters such as the strength and elastic modulus of the material in the model. A nonlinear static analysis is performed on the local analysis model. By comparing the collapse resistance reduction coefficient value obtained from the macro model with the above theoretical value, the plate or plate and beam components that need to be corrected by the material reduction coefficient are judged. Then, a correction method for the reduction coefficient is proposed through simulation calculation. A simplified simulation method for the damage of frame beams and slabs under explosion based on material parameter reduction and reduction coefficient correction is established, thereby introducing the damage of beams and slabs under explosion into the continuous collapse analysis of steel structures.

[0034] (3) A multi-scale modeling approach was used to establish an efficient analysis model for the steel structure. For the beam and slab components that were subject to explosion damage based on the working conditions, the aforementioned simplified damage simulation method was used to reduce their performance. The failed columns in the working conditions were then removed, and a nonlinear dynamic analysis was performed on the remaining structure to evaluate and predict the progressive collapse resistance of the steel structure. When the vertical displacement of the failed column top could not reach final stability, the steel structure was considered to have undergone progressive collapse.

[0035] The present invention is further described below with reference to specific examples:

[0036] The method proposed in this invention and the alternative force transmission path method were used to perform a progressive collapse analysis on an 8-story steel frame. The steel frame has a 5×5 span, a longitudinal span of 9.0m, a transverse span of 6.0m, and a typical bay size of 9.0×6.0m. The frame has 8 floors, and each floor is 4.0m high. The steel beams of the steel frame are 356×171×51UB, the outer steel columns are 305×305×137UC, and the inner steel columns are 305×305×198UC. The thickness of the reinforced concrete slab is 120mm, and the diameter of the steel bars in the slab is 12mm with a spacing of 200mm. The compressive strength of the concrete is 35MPa, and the yield strength of the steel used in the steel beams and columns is 355MPa.

[0037] Step 1: First, determine the range of beam and slab components to be considered for explosion damage during structural collapse analysis. This example simulates the impact of a car-type explosion on a steel frame. It assumes that the three adjacent side columns are damaged by the explosion. Based on the criteria for defining the range of beam and slab damage, the components damaged by the explosion are determined to be the four longitudinal beams connected to the three failed columns, the three transverse beams, and the four reinforced concrete slabs.

[0038] Step 2: Use but not limited to LS-DYNA explicit dynamic finite element analysis software to establish a local analysis model of the frame, such as Figure 2 As shown, steel beams and columns are simulated using, but not limited to, beam elements, and reinforced concrete slabs are simulated using, but not limited to, shell elements. The resistance reduction coefficients of the beam-slab substructure calculated from theoretical formulas are used to reduce parameters such as the strength and elastic modulus of the materials used in the material models for the steel beam and reinforced concrete elements. Nonlinear static analysis is then performed on the local analysis model to obtain a resistance curve for the model structure. This resistance reduction coefficient is then compared with the nonlinear static analysis results of the local model without parameter reduction, resulting in the calculated resistance reduction coefficient. By comparing this with the theoretically calculated reduction coefficient, the slabs or slab-beam components requiring material reduction coefficient correction, as well as the correction range, are identified. Simulations are then performed to determine the specific correction method and calculation formula for the reduction coefficient, and a simplified simulation method for frame beam-slab damage under explosions based on material parameter reduction and reduction coefficient correction is established.

[0039] Step 3: Using but not limited to LS-DYNA explicit dynamic finite element analysis software, and using a multi-scale modeling approach, i.e., using but not limited to Beam units to simulate steel beams and steel columns, using but not limited to layered shell units to simulate reinforced concrete slabs, and using but not limited to macro units to simulate nodes, an efficient analysis model for progressive collapse of steel frames was established, such as Figure 3 As shown in Figure 2, the performance of the beams and slabs considered for blast damage, identified in Step 1, was reduced using the damage simplification simulation method established in Step 2. The damage to the beams and slabs caused by the interaction between the blast load and the structure was incorporated into the progressive collapse analysis. The three side columns adjacent to the corner columns were then removed from the model, and a nonlinear dynamic analysis was performed on the remaining structure. The structural anti-collapse performance was evaluated by analyzing whether the vertical displacement of the failed column top nodes ultimately stabilized.

[0040] Step 4: For the alternative force transfer path method, directly establish a progressive collapse analysis model for the entire frame structure according to the modeling method in Step 3. Then, remove the three side columns adjacent to the corner columns and perform a nonlinear dynamic analysis on the remaining structure. By analyzing whether the vertical displacement of the failed column top node eventually stabilizes, the anti-collapse performance of the structure is evaluated.

[0041] The vertical time history curve of the control node obtained by the method proposed in this invention and the alternative force transmission path method is as follows: Figure 4 As shown in the figure, by comparing the calculation results of the two methods, it is found that the deformation of the failed column top node obtained by the alternative force transmission path method eventually tends to be stable, indicating that the frame structure did not undergo continuous collapse. However, the deformation of the failed column top node obtained by the method proposed in this invention did not eventually tend to be stable, indicating that under the conditions of considering the interaction between the explosion and the structure and the damage to the beam and slab components, the frame structure will undergo continuous collapse, as shown in the figure. Figure 5 As shown, it is verified that the currently commonly used alternative force transmission path method is unsafe when performing structural collapse assessment, while the method proposed in the present invention can improve the accuracy of the assessment.

[0042] In addition, compared with the direct simulation method, which requires the establishment of detailed explosive, air and structural models, complex modeling work, a huge number of model units, and model calculation time of several days or even longer, the method proposed in the present invention has a small modeling workload, a small number of units, and a model calculation time of only about 4 hours, which greatly improves the calculation efficiency and is suitable for engineering practice.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for assessing and predicting the collapse of a steel structure building under an explosion scenario, characterized in that: The steps include: S1. When analyzing the collapse of steel structures under explosion, determine the failed columns in the steel structure under the explosion scenario. The beams and plates connected to the failed columns are all included in the range of components that need to be considered for damage. S2. Based on the theoretical calculation formula for the reduction coefficient of the anti-collapse capacity of beam and slab structures under explosion, combined with the principle of resistance equivalence, a method for simulating damage to steel structure beams and slabs under explosion scenarios is derived. The specific method of step S2 is as follows: A local analysis model of the frame is created, and the resistance reduction coefficient of the beam-slab structure under explosion is calculated using a theoretical formula. The calculated resistance reduction coefficient is used to reduce the strength and elastic modulus parameters of the materials in the local analysis model. A nonlinear static analysis is then performed on the local analysis model to obtain a resistance curve of the local analysis model structure. This is compared with the nonlinear static analysis results of the local analysis model without parameter reduction to obtain the resistance reduction coefficient of the macro model. By comparing this with the reduction coefficient calculated using a theoretical formula, the plates or plate-beam components that require material reduction coefficient correction and the correction range are determined. The specific correction method and calculation formula for the reduction coefficient are obtained through simulation calculations, and a simplified simulation method for frame beam-slab damage under explosion scenarios is established based on material parameter reduction and reduction coefficient correction. S3. Establish a progressive collapse analysis model for steel structures to evaluate the progressive collapse resistance of the structure. The specific method of step S3 is as follows: After the steel structure progressive collapse analysis model is created, according to step S1 and the set working conditions, the beams and plate components that are damaged under the explosion scenario are determined. The performance of the beams and plate components is reduced using the steel structure beam and plate damage simulation method under the explosion scenario in step S2. Subsequently, the failed columns set in the working condition are removed, and a nonlinear dynamic analysis is performed on the remaining structure to evaluate and predict the progressive collapse resistance of the steel structure.

2. The method for assessing and predicting the collapse of a steel structure building under an explosion scenario according to claim 1 is characterized by: The local analysis model of the frame is created using LS-DYNA explicit dynamic finite element analysis software, in which the steel beams and steel columns are simulated using beam elements, and the reinforced concrete slabs are simulated using shell elements.

3. The method for assessing and predicting the collapse of a steel structure building under an explosion scenario according to claim 1, characterized in that: In step S3, a steel structure progressive collapse analysis model is established using LS-DYNA explicit dynamic finite element analysis software in combination with a multi-scale modeling method; Among them, the steel beams and steel columns are simulated by Beam elements, the reinforced concrete slabs are simulated by layered shell elements, and the nodes are simulated by macro elements.

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