KR20150114613A - Evaluation method for reliable seismic performance factor of Diagrid structural system using test data - Google Patents

Abstract

The present invention provides a method for evaluating a seismic coefficient of a diagrid structure system. The method includes: an experiment step for evaluating performance of a structure of a diagrid module used in the diagrid structure system; a modeling step for modeling finite elements with respect to the diagrid module; a comparison and evaluation step for comparing and evaluating a result of a structure performance evaluation experiment on the diagrid module and a result of finite element modeling interpretation; a variable interpretation step based on an angle of a brace member and the shape of a node applying the finite element modeling; a non-linear dynamic interpretation step using a variable obtained by the finite element modeling; and a step for obtaining the seismic coefficient of the diagrid structure system by the non-linear dynamic interpretation.

Description

Technical Field [0001] The present invention relates to a seismic performance evaluation method for a diagrid structural system,

The present invention relates to a method for evaluating the seismic coefficient of a diagrid structure system, and more particularly, to a method for evaluating a seismic coefficient required for a seismic design of a structure utilizing a diagrid system composed only of a tensile material and a compression material.

Typically, the design seismic load in the seismic design of a building reduces the elastic design spectrum by using the response correction factor to reflect the inelastic behavior of the structure at the time of the earthquake to the design so that the design value is reduced from the elastic behavior to the design load I am using it.

 The response correction factor is a coefficient that lowers the seismic load that can be applied to the building, assuming that the structure does not collapse due to the inelastic deformation even if the seismic load exceeds the design strength in the seismic resistance system of the building.

In various domestic and international architectural standards, these response correction factors are suggested to use a constant value for each structural system.

However, since the response correction coefficient values of the structural types proposed in the architectural standard are presented only for the generalized structural form, they are difficult to apply to various and complex structural forms.

Especially in the case of the new system such as the Diagrid system which is used in the skyscraper recently, there is no response correction coefficient value that can be clearly presented yet. The diagrid system refers to a structural system in which large diagonal birds connected to each other resist both vertical load and horizontal load, unlike the conventional structure in which the vertical load and the horizontal load are respectively resisted using pillars and braces . This is advantageous in that it can design more efficient and economical high-rise buildings by resisting one member of large diagonal line against all loads unlike the conventional method in which inefficient members are designed by a separate load resistance mechanism Respectively. In other words, for a lateral load such as seismic load, a large diagonal new member is resisting with tensile force and compressive force, and this type of structure shows distinctly different structural performance from the moment rigidity resistance method according to the joining of the column-to- Has been proved through various researches both at home and abroad.

However, since it is difficult to clearly evaluate the seismic performance of the diagrid structure as the current structural analysis method, only the response correction coefficient value in the generalized structural form, which has been presented previously, is used, This causes the seismic performance of the diagrid system, which exhibits high structural performance, to be excessively low, which causes excessive cost and time to be consumed in the diagrid structure.

Therefore, it is a reality that analytical study of high - rise model for various models and variable elements of actual diagrid structure is required.

The object of the present invention is to provide a method of calculating a response correction coefficient value that can be utilized in a seismic design reflecting a load resistance mechanism of a diagrid system.

According to an aspect of the present invention, there is provided a method for controlling a diagrid node, Constructing modeling according to the shape of the grid; Comparing structural performance test results with modeling analysis results; A step of analyzing variables according to the angle and shape of the brace member constituting the diagrid structure; Replacing the structural performance of the modeled diagrid node with a nonlinear dynamic analysis model; Performing a nonlinear dynamic analysis using the substituted diagrid node, and calculating an earthquake resistance value of the diagrid structure through the nonlinear dynamic analysis.

An experimental step for evaluating the structural performance of the diagrid module used in the diagrid structure system; A finite element modeling step for the diagrid module; A step of comparing the structural performance evaluation test result with the finite element modeling analysis result for the diagrid module; A variable analysis step according to a brace member angle and a node type using the finite element modeling; A nonlinear dynamic analysis step through the variables detected in the finite element modeling; And detecting the seismic coefficient of the diagrid system through the nonlinear dynamic analysis. The present invention also provides a method of evaluating an earthquake resistance of a diagrid structural system.

In the method for evaluating the seismic coefficient of the diagrid structure system, the experimental steps for evaluating the structural performance of the diagrid module used in the structural system are as follows. Six basic modules having a triangular shape are hexagonal and one diagrid node And the diagrid node may have a configuration in which a compressive force and a tensile force can act in six directions.

In the method for evaluating an earthquake-resistance of the diagrid structure system, the finite element modeling step uses modeling of a structure in which a diagrid node is located at the center of a hexagonal shape composed of six basic modules executed in the experimental step, The analysis step according to the member angle and the node type may reflect the change of the angle of the brace member and the change of the shape of the diagrid node which can be changed according to the construction requirement.

In the method for evaluating the seismic coefficient of the diagrid structure system, the variable detected in the finite element modeling step may be data necessary for implementing the constraint condition between the node and the member in the nonlinear dynamic analysis.

The present invention involves the following effects.

First, the method of evaluating the seismic performance of the dihedral structure system of the present invention can provide an earthquake resistance value for a more accurate seismic design for a dihedral structure system in which the application range is extended.

Second, the method of evaluating the seismic performance of the dihedral structure system of the present invention enables the provision of the earthquake resistance coefficient table that can be used in the design of the diagrid system during the construction process, thereby guiding the structural details and structural design in the structural design office smoothly And thus, productivity can be improved in the domestic steel industry.

Third, the method of evaluating the seismic performance of the dihedral structure system of the present invention can provide more accurate seismic design data, thereby reducing the dependence on foreign countries in the design of the diagrid structure system and the seismic design of the domestic diagrid structural system It may be possible to secure a unique and excellent location in the area.

1 is a schematic diagram showing an experimental system of a method for evaluating a seismic performance of a dihedral structure system according to an embodiment of the present invention.
2 is a schematic block diagram of a seismic performance evaluation method for a diagrid structural system according to an embodiment of the present invention.
3 is a graph showing the response correction coefficients used in the seismic design.
4 is a schematic diagram showing an experimental system of a method for evaluating seismic performance of a diagrid structural system according to an embodiment of the present invention.
5 and 6 are schematic diagrams of a finite element modeling method of a seismic performance evaluation method of a diagrid structure system according to an embodiment of the present invention.
7 is a diagram showing an example of a comparative evaluation of a seismic performance evaluation method of a diagrid structure system according to an embodiment of the present invention.
FIG. 8 is a diagram showing an example of a tilt angle, which is one of the design variables obtained in the comparative evaluation of the seismic performance evaluation method of the diagrid structural system according to the embodiment of the present invention.
9 is a schematic block diagram of a seismic performance evaluation method for a diagrid structural system according to an embodiment of the present invention.

The method of evaluating the seismic performance of the dihedral structure system of the present invention can provide a design factor that enables more accurate seismic design for the grid structure system. In other words, accurate response correction coefficient values are presented through various experiments on typical structural systems such as conventional bearing wall system, building frame system, moment frame system, and double frame system. In the case of the structural system, the structural performance against the lateral force of the column and the beam is presented as the building regulation. However, in the case of the diagrid system, the structure used in the skyscraper The system does not yet define the structural performance of displacement values for lateral forces between braces and nodes. Therefore, in order to solve the problem, the present invention is different from the conventional evaluation process, which is limited to the conventional structure information analysis and analysis model setting and design. (2) Diagrid node finite element modeling step, (3) Structural performance evaluation (comparison) step according to experimental result and analysis result, (4) Brace member angle and node type , Which is specialized in the diagrid system and is divided into four specific stages of the variable analysis step.

The specific configurations of these steps are (1) the absence of structural performance specifications for diagrid nodes and braces, and (2) the 1: 1 correspondence of various brace angles and node shapes used in a building.

(1) Diagrid frame test

An experimental body implementing the seismic performance evaluation method of the dihedral structure system of the present invention occupies a size of 6m x 6m with a 1/4 scale 1/4 scale scale model. Fig. 1 and / or Fig. 4 shows an experimental apparatus for evaluating seismic performance. The upper front node was moved using an actuator having a maximum load of 3,000 kN. In order to prevent the out-of-plane deformation of the specimen, which may be caused by the repetitive force, a frame with rollers was installed on both sides of the specimen. The displacement gauge was installed in the lateral direction at two locations at the rear upper and lower nodes and the braces where buckling is expected. Strain gauges were installed at predicted stress concentrations in joints and braces, and gauges for measuring strain rates of BRB seams were installed before stiffeners were joined. The strength of the test specimens was determined using the BRB force protocol by AISC Seismic Provisions (2005) and considering the diagrid specimens that are expected to be buckled early, the steps (0.001 rad, 0.002 rad, 0.0045 rad, 0.009 rad, 0.015 rad) Additional planning.

That is, the six diagrid modules (triangular base modules) of the diagrid system seismic performance evaluation experimental apparatus as shown in FIG. 4 are constructed as a basic framework of a hexagonal frame, and the diagrid nodes and six The goal is to measure the behavior of the braces. At this time, the load was applied repeatedly to the upper left node with 3000 ton Actuator. In this case, the cyclic load is a method that takes into consideration the case where the wind load and the seismic load are repeatedly applied to the building during the lateral force acting on the skyscraper. The cyclic load by the actuator is based on AISC Seismic Provisions (2005) , And the yielding of the framing member at this time was defined as the point at which member deformation occurred due to the buckling caused by the applied load. In the experiment, the displacement of the frame according to the load at the upper left node was measured and used for comparison with the finite element analysis results.

(2) Diagrid finite element analysis

In the method for evaluating seismic performance of the dihedral structure system of the present invention, the analysis step is executed after the experiment evaluation step for the diagrid node is executed. That is, the same structure as the diagrid node in the experimental stage is finite element modeled, and the finite element method is applied to the behavior of six modeled bracing Is modeled. As mentioned above, the analysis was carried out under the same conditions as the experiment, where the same conditions were defined as six diagrid modules (triangular base modules) connected to the center of the diagrid node As shown in Fig. 5 and Fig. 6, the loading condition is also measured by applying the cyclic load based on the AISC Seismic Provisions (2005) to the upper left node. Lt; / RTI > The data of the analysis result also confirmed the load value applied to the upper left node and the displacement value of the node accordingly.

(3) Comparison of experimental and analytical results for diagrid modules

After the finite element analysis step of the seismic performance evaluation method of the dihedral structure system of the present invention is executed, the present invention executes a comparative evaluation step of comparing and evaluating the actual value and the analytical result for the same diagrid module (frame module). In the comparative evaluation step, it is performed by confirming whether or not the displacement value according to the repeated load of the upper left node of the module is converted into a graph. At this time, as shown in FIG. 7, the analytical value is about 5% The material properties of the analysis and the joining conditions of the node and the brace members are adjusted so that the analysis can realize the structural behavior of the actual frame. That is, the control unit executing the comparison and evaluation step compares the analysis value with the experimental value to determine whether the current modeling structure is appropriate or not by using a predetermined preset error range stored in the storage unit If it is determined that the analysis value does not exist within the preset error range with respect to the experimental value, the predetermined modeling and finite element analysis step and the comparison determination step are repeatedly executed. On the other hand, if it is determined that the analysis value is within the preset error range with respect to the experimental value, the controller determines that the model in which the finite element analysis has been performed is appropriate and analyzes the model used in the finite element analysis, .

(4) Variable analysis according to brace member angle and node type

After the comparative evaluation step of the experimental results and the analysis results is executed, the method of evaluating the seismic performance of the diagrid structure system of the present invention is characterized in that the diagrid nodes are connected to the brace members, Step. That is, in the diagrid system, not only the shape is changed according to the angle of the brace member constituting the triangular basic module but also the magnitude of the load applied to the members of each layer is changed. A grid base module can be created.

However, since it is not practicable to conduct experiments on all the nodes, the experiment is conducted only in the basic form as a whole, and the diagrid node for the other types evaluates the structural performance only by the analysis and reflects the result in the nonlinear analysis model .

Through the above-described series of steps, the control unit finally calculates the response correction coefficient for the diagrid system. Here, the basic meaning of Response Modification Factor (Factor) is defined as a value that corrects and secures the response or reaction of a structure. In other words, the value of the response or response of the structure is not an accurate value, And it means that a correction is necessary to set an accurate value, and a coefficient used for such correction is a reaction correction coefficient. In general, elastic design is the basic principle in structural design, but exceptionally, inelastic design is allowed for seismic loads, in order to simultaneously achieve economical efficiency and stability. That is, the design seismic load specified in the seismic design is the load for the earthquake with a probability of 10% during the life of the building in the area where the building is located and the return period of the seismic load (return period) The earthquake load which occurs once in 475 years is 0.21% at the annual rate. It is uneconomical to design the building to behave elastically in response to such an earthquake, so the current standard allowing the inelastic behavior of the structure is valid can do.

 The seismic design of a building is generally performed by using a pre-calculated lateral force, and the seismic resistance element is designed for the member force obtained here. These lateral forces are applied differently according to the allowable stress design method or the strength design method. The US Uniform Building Code (ICBO, 1991) specifies the lateral forces that can be applied with acceptable stress design, while the NEHRP specification (BSSC, 1991) defines the lateral force by the strength design method. The design seismic load used for the seismic design of a building is to calculate the horizontal strength required for the structure to behave elastically, where the seismic load is applied as the value of the base shear when using the equivalent static analysis method have. The bottom shear force can be estimated by dividing the horizontal strength required for the structure to behave in the elastic region against the seismic load by the response correction factor.

 For this purpose, the response correction factor is introduced in the calculation of the design seismic load to reduce the intensity requirement of the elastic state as shown in FIG. 3. In the domestic building load standard, the response correction coefficient is applied in the following arithmetic expression , And the response correction factor is located in the denominator as shown in the bottom shear force equation and serves to reduce seismic force.

Where V is the floor shear force, Cs is the seismic response coefficient, W is the effective weight of the entire building, SD1 is the response spectrum acceleration, IE is the importance coefficient, and T is the natural frequency of the structure.

In summary, the response correction factor serves to lower the required strength of a structure to have a linear elastic behavior with respect to seismic loads, ultimately allowing the structure to perform inelastic behavior, Can be defined as the ratio of the elastic demand strength to the elastic demand strength.

Since 1988, earthquake regulations have been applied to high-rise buildings in relation to conventional seismic design. However, due to lack of experience of earthquakes, most of the foreign standards are used in accordance with the design procedure. Design parameters have also been lacking in clarity. Since 1988, domestic seismic design standards have been applied for over 12 years without any change. However, due to frequent earthquakes in Korea at that time, And the earthquake in Yeongwol province of Gangwon province on December 13, 1996, the Ministry of Construction and Transportation decided to strengthen the earthquake regulations and domestic seismic engineering continued to develop.

The EESK 97 was proposed by the Earthquake Engineering Society of Korea (EESK) in 1997, which is based on the seismic design criteria study on the upper concept of seismic design. The first revision work was started in 1997, and in 2000, a small amendment was made through AIK 2000, including the "Rules on Structural Standards of Buildings" and "Building Load Standards" In AIK 2000, some seismic design standards were revised along with other Korean load criteria, and seismic loads with allowable stress levels were used. The ground conditions of AIK 2000 and UBC 94 were used. In comparison of the elastic spectrum, the seismic load is large at UBC 94, but in the long period, AIK 2000 is larger appear. As mentioned above, AIK 1988 was basically based on ATC 3-06 and UBC 85. The basic structure of AIK 2000 is the same as AIK 1988, will be. However, it has not been able to properly accommodate the contents of developed earthquake engineering, and it is not enough to reflect the newly applied structural system in Korea. Therefore, new seismic reference standards were proposed through the study of improvement of seismic design criteria, which was resumed in 2002, in order to introduce the newly changed technical level and design concept of seismic engineering and to meet the development of various structural systems. It was reflected in "Section 3.6 earthquake load" of the "Architectural Structural Design Standard (2005, Ministry of Construction and Transportation Notice)" (KBC 2005) enacted. In case of KBC 2005, the earthquake load proposed in EESK 1997 is used and the design method is to follow IBC 2000 method. The concept of seismic design of IBC 2000 is accepted widely, but it is accepted considering the real situation of Korea. In KBC 2005, the structural design method is based on the permissible stress design method, the strength design method or the limit state design method, or the structural design method, which the Minister of Construction and Transportation recognizes that the performance is equivalent to or better than the allowable stress design method, The IBC 2000, which is the root of the KBC 2005 seismic design criteria, does not completely accept the performance based seismic design, which is a global trend in the seismic engineering field. However, Because it considers Maximum Considered Earthquake and Design Earthquake, it approaches the performance based design method (PBSD) compared to existing standards.

Table 1 below shows the change in the method of obtaining the design base shear force in the seismic design criteria of Korea.

Design basis
/ Design method Bottom shear force Coefficient AIK 1988
Allowable stress level

또는,

or,

A area coefficient (0.12, 0.08)
S ground coefficient (3 groups) EESK 97
Strength design level

Ca Cv earthquake group
Soil classification: 6 groups AIK 2000
Allowable stress level

A area coefficient (0.11, 0.07)
S: Ground coefficient (4 groups) KBC2005
Strength design level

SD1, SDS: Response spectrum acceleration
Soil classification: 5 groups

In Table 3.1, I, IE are the importance coefficients, R is the response correction factor, W is the effective building mass, and T is the natural vibration period of the structure. The EESK 97 research report only defined the upper concept of the seismic design, so it could not be implemented under the actual lower seismic criteria. Recently, KBC 2008 revision plan is underway in Korea. In this KBC 2008 (plan), we tried to reflect the internationalization tendency of earthquake load notation and the characteristics of domestic soil in the standard. In addition, IBC and other standards have been unreasonably high or incorrectly revised. From KBC 2005, the design load was 2/3 times the 2400 earthquake load, and the load factor was not multiplied. However, at the time of the enactment of KBC 2005, local factors were defined according to the seismic zones in the upper standard (the rules on the structure standards of buildings, etc.), so the area coefficient appropriate for the repetition period (see Table 0306.3.1) could not be used on the surface. Reflecting the international trend of seismic design, KBC 2008 tried to express that the standard earthquake load was set to the 2400 repetition period. Since the concept of the 2400 repetition cycle has already been reflected in KBC 2005, it was only necessary to change the expression in KBC 2008. In summary, the magnitude of the seismic design seismic load increased from 500 to 2400 in KBC 2008, so the load seems to increase externally, but the actual size was revised so as not to change with KBC 2005 It can be said that.

In the seismic evaluation method of the diagrid system structure according to the present invention, the method of calculating the shear force of the system under the KBC 2005 method is reduced as shown in the following equation.

More specifically, the response correction coefficient for the diagrid system derived from the seismic performance evaluation method for the diagrid system of the present invention can be evaluated through the following process. First, the relationship between the base shear force and the roof layer displacement and the reaction correction factor for the structural system are set by using the experimental results of the steel braced frame structure for the normal response correction factor. The diaper was divided into Reserve Strength, Ductility and Viscous Damping, which were evaluated as follows.

: 강도계수(Strength Factor)

: Strength Factor

: 연성계수(Ductility Factor)

: Ductility Factor

: 감쇠계수(Damping Factor)

: Damping Factor

However, the Japanese Building Standard Law (BSL) does not address irregularities in the two-stage design process. In addition, the proposed design formula eliminates the non-uniformity of the frame structure and the vertical stiffness distribution. And the design seismic force is increased, so that the effect of using the substantially reduced response correction coefficient is shown. In designing a framing system with uneven planes or stiffness, the use of a larger value of the design base shear force can be expected to have the effect of restraining the use of a non-uniform framing system. In addition, It may reduce uncertainty.

First, the intensity factor (Rs) can be estimated from the results of a nonlinear static analysis or pushover analysis. Nonlinear static analysis is an analytical method that can evaluate the holding strength of a building or frame system. The shear force (Vo) of the building is calculated by using the nonlinear static analysis to establish the relationship between the floor shear force and roof layer displacement of the building. The overstrength of the building is obtained as the difference between the design base shear force (Vd) and the maximum floor shear force (Vo) of the building.

The Ductility Factor (Rμ) is a factor for the ductility ratio () taking into account the inelastic behavior of the structure and is the most consistent factor with the concept of seismic design. Since the structure can absorb energy through inelastic deformation, A load that is larger than the lateral load that can be sustained in the elastic region can be supported. The coefficient reflecting this effect is the ductility coefficient.

Where Cy is the inelastic limit bottom shear force ratio of the structure to the total weight of the structure (W) and Ceu is the ratio of the bottom limit shear force of the structure to the total weight of the structure.

The method for evaluating the seismic coefficient of the diagrid structure system of the present invention is as shown in FIG. 9, briefly summarizing the main procedures for estimating and evaluating the seismic performance coefficients and the collapse margin ratio described above. The structural characteristics of the structural system to be evaluated are grasped, and related information such as the behavior characteristics of the members and the influence of the material properties are synthesized. Based on the information, we design an optimized analytical model that can adequately explain the characteristics of the structural system. Then, the seismic record data for nonlinear analysis are normalized and the MCE ground behavior is connected to the analysis model cycle. Building collapse evaluation is performed using nonlinear static analysis (Pushover Analysis) and nonlinear dynamic analysis (Response History Analysis). The nonlinear static analysis is used to demonstrate the behavior of the nonlinear model and the strength factor (Ω) and ductility capacity (μc) are estimated. Nonlinear dynamic analysis is used to select median collapse capability and collapse margin ratio (CMR).

In order to evaluate these estimated values, the uncertainties due to various factors in the analysis process are taken into consideration and corrected. The calibrated value is compared with the allowable reference value. The allowable limit value of the collapse margin is defined in the low probability interval which is acceptable for the MCE soil behavior given uncertainly on collapse fragility. The more robust design requirements, the wider the experimental data and the more structured systems with more detailed nonlinear analysis models, the lower collapse uncertainties can reach the same level of safety in the smaller collapse margin. The above procedure is repeated according to the evaluated results, and the seismic shape coefficients suitable for the structural system are selected. The estimated seismic performance coefficient is summarized by the characteristics of the analytical model of the structural system and applied to the structural system through objective evaluation.

 The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (4)

An experimental step for evaluating the structural performance of the diagrid module used in the diagrid structure system;
A finite element modeling step for the diagrid module;
A step of comparing the structural performance evaluation test result with the finite element modeling analysis result for the diagrid module;
A variable analysis step according to a brace member angle and a node type using the finite element modeling;
A nonlinear dynamic analysis step through the variables detected in the finite element modeling;
And detecting the seismic coefficient of the diagrid system through the nonlinear dynamic analysis. The method according to claim 1,
[6] The method of claim 1, wherein, in the experimental step for evaluating the structural performance of the diagrid module used in the structural system, six triangular basic modules are hexagonal, one diagrid node is located at the center, Wherein the diaphragm structure system has an arrangement structure capable of applying compressive force and tensile force in six directions. The method according to claim 1,
Wherein the finite element modeling step uses modeling of a structure in which a diagrid node is located at a center of a hexagonal shape composed of six basic modules executed in the experiment step, Wherein the angle of the brace member and the change of the diagrid node shape that can be changed as needed are reflected in the analysis. The method according to claim 1,
Wherein the variables detected in the finite element modeling step are data necessary for implementing a constraint condition between a node and a member in a nonlinear dynamic analysis.

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