For the "design seismic force - ductility" joint law, we can understand from the seismic force and structural interrelationships: on the one hand, the design of the structure of low seismic force, through the greater inelastic deformation to dissipate more seismic energy; on the other hand, the greater the structural inelastic deformation, the more severe the reduction in stiffness, the damping of the structure, and the more the structure is inelastic deformation. On the other hand, the greater the inelastic deformation of the structure, the more serious the reduction of stiffness, the greater the damping, the more the period grows compared to the structure with high design seismic force, and the more the total seismic force on the structure is reduced. This makes us in the design process, without reducing the vertical bearing capacity of the components to ensure the structural ductility of the premise, can take a less than the intensity of the defense seismic response level as the design of the seismic action taken. On the other hand, if the design seismic force is lower, the yielding part of the structure in the yielding of the horizontal and vertical bearing capacity does not reduce the premise of inelastic deformation needs to be achieved the greater the structural need for better ductility performance.
In this way, we need to solve the following two problems:
A. How to establish a proper link between the seismic action at the intensity of the defense and the design seismic force values;
B. How to establish a correspondence between the design seismic force and the required structural ductility.
For problem A, many scholars, represented by N.M. Newmark, believe that reducing the seismic acceleration at the intensity of the defense to the design acceleration of the structure through the seismic force reduction factor R (China, the United States, etc.) or the structural performance coefficient q (European **** body, New Zealand, etc.) is equivalent to giving the structure a smaller yield capacity, and the structure will be designed through the vertical capacity without any reduction in the vertical bearing. Under the condition that the vertical load bearing capacity is not reduced, the structure can withstand larger earthquakes through the inelastic deformation after yielding to realize the goal of "not falling down after big earthquakes". Therefore, the key to adopt a low design seismic force is to ensure that the structure and members can achieve the required ductility under large earthquakes. The seismic force reduction factor, R, or the structural performance factor, q, is handled slightly differently in national design codes, but in general, R or q is the ratio of the seismic action at the intensity of protection to the seismic action used in the design of the structural cross-section. The larger the R or q, the greater the ductility required of the structure, and the smaller the R or q, the smaller the ductility required of the structure. In this way, all can realize the "big earthquake does not fall".
For problem B, there are generally three design options: (1) higher seismic force - lower ductility program; (2) medium seismic force - medium ductility program; (3) lower seismic force - higher ductility program. -higher ductility scheme. The high seismic force scheme mainly ensures the load carrying capacity of the structure, and the low seismic force scheme mainly ensures the ductility of the structure. The actual earthquake damage shows that these three programs, from the point of view of seismic effect and economy, can achieve the setup goal. China's seismic design adopts the program (3) that is, lower seismic force - higher ductility program, that is, the use of significantly less than the intensity of the fortification of the ground motion acceleration of small earthquakes to determine the design of the structure's seismic action, and it is combined with the other load internal forces, cross-section design, through the reinforced concrete structure in the seismic response after yielding Through the reinforced concrete structure after the yielding of the seismic response process to form a more favorable energy-consuming institutions, so that the main energy-consuming parts of the structure has a good post-yield deformation capacity to achieve the goal of "big earthquake does not fall". Of course, we also have to see that, although all three schemes can guarantee "no collapse in large earthquakes", in terms of improving the structural behavior under small and medium-sized earthquakes, Scheme (3) is obviously inferior to Schemes (1) and (2) in that it only improves the level of structural ductility but does not improve the level of structural yielding significantly. In other words, in terms of guaranteeing "no damage in small earthquakes and repairable in medium earthquakes", schemes (1) and (2) are superior to scheme (3).
Ground shaking propagates in the form of waves in the ground and on the surface, which is very random due to the uncertainties in the characteristics of the earthquake source, the fault mechanism, the propagation path and other factors. To derive how ground shaking reacts differently to different structures, it is necessary to build a bridge between ground shaking characteristics and structural responses. Because the shape characteristics of the ground vibration response spectrum respond to the characteristics of different types of structural dynamic maximum response, so the seismic influence coefficient spectrum curve is generally used as the basis for calculating the seismic effect in various projects.
China's spectral curve comprehensively considers the effects of intensity, epicenter distance, site category, structural self-vibration period and damping ratio. According to the newly revised zoning map of China's ground shaking parameters, the design basic seismic acceleration under the seismic protection intensity (moderate earthquake) is given. Through the influence of magnitude, epicenter distance, site category and other factors on the structural response spectrum, the seismic code takes the dynamic amplification factor as 2.25. According to the statistical data, the intensity of multiple earthquakes is reduced by about 1.55 degrees compared with the basic intensity, which is equivalent to the reduction of seismic action by 0.35 times, i.e., the coefficient of reduction of seismic force is 1/0.352.8 Thus, we can get the design acceleration of the structure at the time of small earthquakes, and the ratio of the value and the gravitational acceleration is the design acceleration at the time of small earthquakes. The ratio of this value to the gravity acceleration is the maximum value of the horizontal seismic effect coefficient at the time of the small earthquake.
Compared with other countries, China's seismic force reduction coefficient R2.7~2.8, the value of which is comparable to that of New Zealand's "finite ductility framework" (R=3); it is in between that of the European *** homogeneous low ductility DC "L" (R=2.5) and the medium ductility DC "L" (R=2.5) and the medium ductility DC "L" (R=2.5), and it is also in between the European "L" and the European "L". M" (R=3.75); and slightly smaller than the US "general framework" (R=3.5). From the point of view of R alone, it seems that the ductility requirements of the Chinese code for large earthquakes are at the level of "moderately ductile structures" compared with other countries. However, the values of peak acceleration coefficients for horizontal ground motions for the Chinese code are lower than those of other countries (see table below). Structural dynamic amplification factor difference is not mostly in the vicinity of 2.25, and China's spectral curve platform section is very small compared with other countries, the falling section is steeper, resulting in the response spectrum of the value of the other countries is lower, in essence, China's R = 2.8 is equivalent to the European **** body of the R = 5.0 or so, so in essence, our country adopts a "lower seismic force --Therefore, in essence, China adopts the "lower seismic force - higher ductility" program. The ductility demand required under a major earthquake should be high compared to other countries. National norms UBC 1997 New Zealand NZS3101 Europe EC8 China GB50011-2001 Acceleration factor 0.075~0.400.21~0.420.12~0.360.05~0.401.2 Calculation of seismic action With the continuous maturity of the reaction spectrum theory, each country accepts bottom shear method and vibration mode decomposition reaction spectrum method for the effect of seismic force on the structure. Method and vibration mode decomposition reaction spectrum method and other methods. China's specification:
The bottom shear method is applicable to the height of not more than 40m, shear deformation-based and mass stiffness along the height of the structure is uniformly distributed, as well as the structure of the approximate single-mass point. The total seismic force of the structure is determined by, and then distributed along the height by inverted triangle distribution, and the additional concentrated force at the apex which may be increased by the top seismic force in an earthquake is considered.
The mode decomposition reaction spectrum method is applicable to most of the currently existing building structure systems. The participation of different vibration modes of each cycle in the seismic response is considered through the combination of vibration modes. For the structure without torsion calculation, first determine the standard value of horizontal seismic action of each vibration mode at each mass point, and then determine the horizontal seismic effect according to the formula; for the structure with torsion coupling calculation, take two orthogonal horizontal displacements and corner displacements of its floor with three degrees of freedom, and determine the standard value of the seismic action of each vibration mode in the two horizontal directions and corner direction of each floor, and then determine the horizontal seismic effect according to the formula.
Specification also stipulates that, for particularly irregular buildings, Category A buildings, specification of the height range of high-rise buildings listed in Table 5.1.2-1, the application of elastic time-course analysis method of multiple earthquakes under the supplementary calculations, can be taken as the average of the results of multiple time-course curves and vibration decomposition of the results of the reaction spectrum method of calculation of the larger value. In addition, the results of general elastic time-course analysis is conducive to the determination of the weak layer site.
For 9 degrees of high-rise buildings in the region to consider the vertical seismic force, take and bottom shear method similar method, only the value of the vertical seismic force for the value of the horizontal seismic force of about 0.57 times.
For the long period structure, the ground motion acceleration and displacement in the earthquake may have a greater impact on the structure, and the vibration mode decomposition reaction spectrum method can not be estimated, the new specification at the same time also increased the minimum value of the horizontal seismic shear force of the floor, see seismic specification 5.2.5.2 structural deformation calculation Seismic defense of the three levels of the requirements are guaranteed by the two-stage design: Under the bearing capacity check of multiple earthquakes, the main structure of the building is not damaged, and the non-structural components are not overly damaged to ensure the normal use of the building; the main structure of the building suffers damage under rare earthquakes, but does not collapse. Structural seismic deformation calculation is a very important content of the two-stage design.
The first stage of design, deformation calculation to elastic interstorey displacement angle. To ensure that the structure and non-structural components do not crack or cracking is not obvious, to ensure the overall seismic performance of the structure. The new specification increases the scope of deformation calculation, to the bending deformation of the main high-rise buildings can be deducted from the overall bending deformation of the structure, because this part of the displacement of the structure is harmless displacement, just the human comfort feel different,
The second stage of the deformation calculation for the rare earthquake under the weak layer of the elastic-plastic deformation calculation to elastic-plastic interlayer displacement expressed. According to the seismic experience, experimental research and analysis of the calculation results, the interlayer ultimate displacement angle is proposed when members and nodes reach the ultimate deformation, to prevent the structural weak layer elastic-plastic deformation is too large to cause structural collapse. The code has clear provisions on the scope of the check calculation, but considering the complexity of the elastic-plastic deformation calculation and the lack of practical software, there are different requirements for different buildings. In the future development, the scope of calculation can be extended to a larger range, and even based on the displacement control method to design the structure, to meet the special requirements of certain types of buildings on the structural displacement, to ensure that the displacement of the structure in the acceptable range.
It should be noted that displacement control and seismic design at this stage is still limited to the response of the structure under a single earthquake. How to effectively consider the impact of cumulative damage on structural deformation and seismic performance in high seismicity areas and under multiple earthquakes to ensure the safety of the structure throughout its life span requires further research. 3 Talking about seismic conceptual design with frame structure as an example Due to the complexity of seismic design of buildings, seismic conceptual design becomes particularly important in actual projects. It mainly includes the following contents: building design should pay attention to the regularity of the structure; choose a reasonable building structure system; and design the ductility of lateral force-resistant structures and members. This paper focuses on the capacity design method in the conceptual seismic design by taking the frame as an example.
Capacity design method is the main content of structural ductility design, including the internal force adjustment and construction of our code two aspects. It is the late 1970s, New Zealand well-known scholars T. Paulay and Park proposed the reinforced concrete structure in the design of the seismic force to take the low value of the case of sufficient ductility. The core idea is: through the "strong columns and weak beams" to guide the structure to form a "beam-hinge mechanism" or "beam-column-hinge mechanism"; through the "strong shear and weak bending" to avoid the structure from reaching the expected seismic force. Through "strong shear and weak bending", the structure can avoid shear damage before reaching the expected ductility; through the necessary structural measures, the parts that may form plastic hinges have the necessary plastic rotation capacity and energy consumption capacity. From the above three aspects to ensure that the structure has the necessary ductility. As a common structural form, the ductility design of frame structure is mainly reflected from these three aspects.3.1 Strong Columns and Weak Beams Structural dynamic response analysis shows that the deformation capacity of the structure is related to the damage mechanism. There are three typical energy-consuming mechanisms, "beam hinge mechanism", "column hinge mechanism" and "beam-column hinge mechanism". The beams of "beam-hinge mechanism" and "beam-column-hinge mechanism" yield first, which enables the whole frame to have larger internal force redistribution and energy consumption capacity, large ultimate interstory displacement, large number of plastic hinges, and no overall structural failure due to individual plastic hinge failure. As a result, it has good seismic performance and is an ideal energy-consuming mechanism for reinforced concrete. Our specification is to allow columns, shear walls out of the hinge beam-column hinge program, to take relative "strong columns and weak beams" measures to delay the columns out of the hinge time. However, we can not completely exclude the possibility of weak layer of the column hinge mechanism, and thus need to limit the axial pressure ratio of the column, if necessary, through the time course analysis method to determine the weak layer of the structure, to prevent the emergence of the column hinge mechanism.
Our common "strong columns and weak beams" adjustment measure is to artificially increase the bending capacity of the columns, inducing plastic hinges to appear at the end of the beams first. This is to take into account the actual bending moment in the column may increase in the earthquake. Before the plastic hinge appears in the structure, the structural members are degraded due to the cracking of the concrete in the tension zone and the inelastic nature of the concrete in the compression zone, and the bond between the reinforcement and the concrete is degraded, resulting in a reduction in the stiffness of each member. The beam stiffness reduction is relatively serious compared to the compressed column, the structure transitions from the initial shear-type deformation to the shear-bending deformation, and the bending moment in the column increases proportionally compared to the bending moment at the end of the beam; at the same time, the period of the structure is lengthened, which affects the magnitude of participation coefficients of the structure's vibration modes; the coefficient of seismic force is changed, which results in the bending moment of some of the columns, and the actual yield strength of the beams is improved by the structural reasons and the artificial increase of the reinforcement bars in the design The actual yield strength of the beam is increased due to constructional reasons and the artificial increase of the reinforcement in the design, which leads to the increase of bending moments in the columns when the beam develops plastic hinge. After the structure appears plastic hinge, there is also the existence of the above reasons, and the inelastic process after the structure yielding is the process of further increase of seismic force, the column bending moment increases with the increase of seismic force. The overturning moment caused by the seismic force changes the actual axial force in the column. The axial-to-pressure ratio limits in our code generally ensure that the columns are within the range of the large bias, and the reduction in axial force can also lead to a reduction in the yield capacity of the columns.
Seismic code provisions: in addition to the top of the frame and column axial compression ratio of less than 0.15 and frame support beams and frame columns, the design value of the column end moment should be consistent with the first level of 1.4, the second level of 1.2, the third level of 1.1. 9 degrees and the first level of frame structure should be consistent with the area of the actual allocation of reinforcement and the strength of the material to determine the standard value. The bottom column axial force is large, the ability of plastic rotation is poor, in order to avoid the column foot out of the hinge after the pressure collapse, one, two, three frame structure bottom, the design value of the column end section combined bending moment were multiplied by the increase factor of 1.5, 1.25 and 1.15. the adjusted combined bending moment of the corner column should be multiplied by the coefficient of not less than 1.10. The design value of the combined moment of the limb section of the shear wall of the first seismic grade shall be adjusted, forcing the plastic hinge to appear at the bottom of the wall limb to strengthen the part, and the design value of the moment at the bottom of the strengthened part and above the first floor shall be the design value of the combined moment of the limb section at the bottom of the wall limb, and the other parts of the wall shall be multiplied by the increase factor of 1.2. For part of the frame-supported earthquake-resistant wall structure, the upper end of the columns of the first and second frame columns and the lower end of the bottom columns, the design value of the combined bending moment should be multiplied by an increase factor of 1.5 and 1.25, respectively.
The above "strong columns and weak beams" adjustment measures, after the analysis of the nonlinear dynamic response, basically to meet the requirements of the big quake does not fall down. In 7 degree zone, the reinforcement of beam is controlled by gravity load, and the reinforcement of column is basically controlled by minimum reinforcement ratio. The relative bending capacity of columns and beams is increased comprehensively. At the same time, it is difficult to appear positive moment plastic hinge in 7 degree zone, which plays a favorable role in resisting large earthquakes. In 9-degree zone, the real allocated reinforcement area and standard value of material strength are used to calculate the internal bending moment of the column, and the increase of beam reinforcement in the structure also leads to the increase of the design value of the internal bending moment of the column, and under the input of multi-wave, the rotation of beam-end plastic hinge is large and develops more sufficiently, and the plastic hinge of column-end is insufficiently developed and rotates less. The plastic deformation is more concentrated with the beam end, which meets the design requirement of seismic capacity. For 8 degree zone, the seismic displacement response is almost the same as 9 degree, but the column end plastic hinge is more than 9 degree, the rotation is big, and the beam end plastic hinge appears sufficiently, but the rotation is small, so the effect of "strong column and weak beam" is not obvious, and the relevant experts suggest that when the 8 degree secondary seismic grade, the bending moment increase coefficient should be taken as 1.35, which is to be further improved.3.2 Strong Shear and Weak Bending Strong shear and weak bending "strong shear and weak bending" is to ensure that the plastic hinge section in the expected inelastic deformation does not occur before the shear damage. In the case of common structures, it is mainly manifested at beam ends, column ends, reinforced areas at the bottom of shear walls, shear wall openings connecting beam ends, and core areas of beam-column nodes. Compared with non-seismic, the enhancement measures are mainly manifested in improving the role of shear; adjust the shear bearing capacity of two aspects.3.2.1 Role of shear One, two, three frame beams and seismic walls in the span-height ratio greater than 2.5 connecting beams, shear design value Which, a take 1.3, take 1.2 for the second level, take 1.1 for the third level, the first level of the frame structure and the 9 degrees should still be in line with. One, two, three frame columns and frame columns, shear design value of which, take 1.4 for primary, 1.2 for secondary, 1.1 for tertiary, primary frame structure and 9 degrees should also comply. One, two, three seismic wall bottom reinforcement parts, shear design value of which, a take 1.6, two take 1.4, three take 1.2, 9 degrees should also comply. Beam-column node, one or two seismic grade for node core area seismic shear bearing capacity check, three or four should be consistent with seismic structural measures, 9 degrees of protection and a level of seismic grade of the frame structure, taking into account the beam end has appeared plastic hinge, the node of the shear force is completely by the beam end of the actual yield bending moment decided by the beam end of the actual allocation of the area of the reinforcement bars and the material strength of the standard value of the calculation, at the same time multiplied by the increase in the coefficient of 1.15. The other level is calculated according to the design value of the beam end moment, with a shear force increase factor of 1.35, and the second level is 1.2. 3.2.2 Shear Resistance Equation Experiments on the shear capacity of reinforced concrete continuous beams and cantilever beams under low weekly repeated loads in China and abroad show that the reduction of shear strength in the shear compression zone of the concrete, the reduction of the aggregate occlusion force between diagonal cracks, and the reduction of the longitudinal reinforcement dark pinning force are the main reasons for the reduction of the beam's shear load capacity. The code reduces the shear capacity of concrete to 60% of the non-seismic capacity, with no reduction in the reinforcement term. Similarly, experiments on the shear capacity of biased columns show that repeated loading reduces the shear capacity of columns by 10% to 30%, which is mainly caused by the concrete term, adopting the same practice as that of beams. Experiments on shear walls show that repeated loading reduces the shear capacity by 15% to 20% compared with monotonic loading, and the non-seismic shear capacity is multiplied by a reduction factor of 0.8. Seismic shear bearing capacity of beam-column nodes consists of two parts of shear bearing capacity of concrete diagonal compression bars and horizontal hoops, and the relevant experts have given the relevant formulas.
In order to prevent diagonal compression damage of beams, columns, connecting beams, shear walls, and nodes, we stipulate the upper limit of shear bearing capacity for shear sections, i.e., we stipulate the upper limit of hoop ratio.
Through inelastic dynamic response analysis shows that the above measures basically meet the requirements of strong shear and weak bending. Due to the second level of seismic grade beams and columns in the large earthquake plastic rotation is still very large, the experts suggest that the shear force increase factor should not be too large than the difference between the first level, for the beams to take 1.25 better, for the columns appropriate to take 1.3 ~ 1.35. The reasonableness of the value needs to be further improved.
It should be noted that the beam-column node is very complex, to ensure that the beam-column reinforcement in the node of the reliable anchorage, at the same time in the beam-column end of the bending damage occurs before the node does not occur in the shear damage, the essence of which should belong to the "strong shear and weak bending" category. Moreover, the node is only one or two seismic grade shear adjustment, the coefficient of increase is smaller than the column, structural measures are also weaker than the column end. Therefore, the statement of "stronger nodes" is not worth advocating.3.3 Structural measures Structural measures are the guarantee that the plastic hinge zone of beams, columns and shear walls can achieve the actual required plastic rotation capacity and energy dissipation capacity. It is interrelated with "strong shear and weak bending" and "strong columns and weak beams" to ensure the structural ductility. "Strong shear weak bending" is to ensure that the plastic hinge rotation capacity and energy consumption capacity of the premise; "strong columns and weak beams" of the degree of strictness, affecting the corresponding structural measures, if the implementation of strict "strong columns and weak beams If the implementation of strict "strong columns and weak beams", to ensure that the columns in addition to the bottom does not appear outside the plastic hinge, the corresponding axial pressure ratio and other structural measures should be looser. In our country, we adopt relative "strong column and weak beam" to delay the time of column hinge, so we need to take more strict structural measures. 3.3.1 Constructional measures of beam The ductility of beam plastic hinge section is related to many factors, the section ductility is lowered with the increase of tensile reinforcement reinforcement rate and yield strength; it is increased with the increase of compressive reinforcement reinforcement rate and concrete strength, and it is increased with the increase of section width. With the increase of compression reinforcement ratio and concrete strength, the section ductility decreases with the increase of tensile reinforcement ratio and yield strength; with the increase of compression reinforcement ratio and concrete strength, the section ductility increases with the increase of section width; the hoop reinforcement in plastic hinge area can prevent the longitudinal reinforcement from compression flexure, improve the ultimate compressive strain of concrete, prevent the development of diagonal cracks, resist shear, and give full play to the deformation of plastic hinges and the ability to dissipate energy; the smaller the beam height to span ratio is, the greater the shear deformation ratio is, and the more likely to occur in the damage of diagonal cracks, which reduces ductility. If the hoop ratio of beam longitudinal reinforcement is too low, the reinforcement may yield or even pull off after beam cracking. Therefore, the specification for the beam longitudinal bar maximum reinforcement rate and minimum reinforcement rate, hoop encryption zone length, maximum spacing, minimum diameter, maximum limb spacing, volume hoop ratio have strict provisions. In order to resist the possible positive bending moment at the end of the beam and ensure the section ductility, the area ratio of tension and compression reinforcement at the end of the beam is restricted. At the same time, the minimum width, span-to-height ratio and height-to-width ratio of the beam are also stipulated.3.3.2 Constructional Measures for Columns Columns are compression and bending force members, and the axial compression ratio has a large influence on the ductility and energy consumption. When the axial pressure ratio is small, the column occurs large partial pressure damage, large deformation, good ductility, but energy consumption is reduced; with the increase of axial pressure ratio, energy consumption increases, but the ductility decreases sharply, and the hoop reinforcement on the ductility of the help is reduced. For columns designed with low seismic forces, we mainly ensure their ductility, and energy consumption is put into the second place. The code limits the axial compression ratio, which is generally within the range of large partial pressures. Hoop reinforcement likewise plays a large role in ductility, restraining the longitudinal bars, increasing the compressive strain in the concrete, and stopping the development of diagonal cracks. Columns are generally symmetrically reinforced, and the greater the longitudinal reinforcement ratio, the greater the deformation of the column at yield, and the better the ductility. Therefore, the minimum reinforcement rate of longitudinal reinforcement, the length of hoop encryption area, the maximum spacing, the minimum diameter, the maximum limb spacing, and the volume of hoop rate of the column have been strictly specified. Meanwhile, the height-to-width ratio, shear-to-span ratio, minimum height and width of the section of the columns are stipulated to improve the seismic performance.3.3 Nodal construction measures Nodal points, as the anchorage area of beam and column reinforcement, have a great influence on the structural performance. In order to ensure that under the action of seismic and vertical loads, the core area of the node when the shear-pressure ratio of the node core area is low to provide the necessary constraints for the core area of the node, to maintain the node in the unfavorable situation of the basic shear capacity, so that the beam-column longitudinal reinforcement of the reliable anchorage, the core area of the node of the maximum spacing of the tendons, the minimum diameter, the volume of the hoop rate has made the provisions. Reliable anchorage of beam and column longitudinal bars in the node is the main content of the node construction measures. The specification of the diameter of the beam reinforcement in the node; the anchorage length of the longitudinal reinforcement of the beam and column; and the anchorage method have detailed provisions.3.3.4 Shear wall construction measures In order to ensure the ductility and energy-consuming capacity of the shear wall, provide constraints on the wall limbs, and prevent the emergence of large cracks, the specification of the edge elements of the shear wall has made detailed provisions; and the axial compression ratio of the shear wall has been restricted; in order to ensure the bearing capacity and lateral stiffness of the shear wall, a minimum diameter and volume ratio are proposed for the shear wall. In order to ensure the bearing capacity and lateral stiffness of the shear wall, the minimum wall thickness is required; in order to prevent diagonal tensile shear damage, limit the development of diagonal cracks, and reduce temperature shrinkage cracks, the minimum reinforcement ratio, maximum spacing, and minimum diameter of horizontal and vertical distribution tendons of shear walls are stipulated.
Summary; frame structure is mainly through the calculation and structural measures to achieve the "pursuit of the ability of the beam-hinge mechanism of the design scheme" so as to realize the "small earthquake is not bad, the earthquake can be repaired, the earthquake does not fall" of the three levels of fortification goals. References
1. Bai Shaoliang et al. Comparison of design codes from various countries to see the effectiveness of China's reinforced concrete building structure seismic capacity design measures (I, II) Chongqing University, School of Civil Engineering, 2001
2, Concrete Structure Design Code GB 50010-2002 China Building Industry Press, 2002
3, Seismic Design Code for Buildings GB50011-2001 China Building Industry Press, 2001
3, Seismic Design Code for Buildings GB50011-2001 China Building Industry Press, 2001
4, high-rise building concrete structure technical regulations JGJ3-2002 China Building Industry Press, 2002