Confusion in the application of existing building seismic identification software
Wang Suojun
above
The seismic verification of existing buildings can be roughly divided into two methods: the comprehensive seismic capacity index method and the seismic component bearing capacity verification algorithm.
The comprehensive seismic capacity index method is mainly used for Class A buildings. The seismic resistance of Class A buildings with brick-concrete structures is calculated by the wall ratio of the structure, and the yield strength of the floors is calculated by the concrete structure. Because of the convenience of the software in the calculation of seismic components, even for Class A buildings, the software not only provides the accounting structure of the comprehensive seismic capacity index method, but also gives the calculation results of the bearing capacity of the components.
We know that Class A is equivalent to the 78th version of the anti-gauge, but the 78th version of the anti-gauge seismic load adopts the calculation method of the seismic parameters and the elastoplastic reduction coefficient C, and the safety degree is "Da Lao K", which is not the same as the limit state based on probability theory that we are using now. The seismic influence coefficient of the 78th edition of the code is basically the same as that of the 89th code (in fact, the maximum value of the seismic influence coefficient of the continental anti-gauge is the same), so the software adopts the calculation method of the 89th edition of the anti-gauge for Class B buildings, but the relevant parameters are still combined with the 78-version anti-gauge. As shown in the figure below (many screenshots in this article are from pkpm and YJK software training materials and manuals):
The above figure can be understood as follows: the seismic component bearing capacity test algorithm of Class A building adopts the current software bearing capacity component test algorithm, but the calculation parameters and seismic action measures are adjusted (not adjusted) according to the 78 version of the anti-compliance regulations.
5.2.16 of the "Building Seismic Appraisal Standard GB50023-2009" stipulates:
This sentence can be understood as: when the brick-concrete structure of Class A building is irregular or ultra-high, it is likely to be unsafe to use the comprehensive index method of Class A building, and the seismic bearing capacity test algorithm of Class B building, which is equivalent to the 89th edition of the code, should be used.
But that's not what the YJK software training course says, look at the following figure:
The software says: When a Class A building complies with 5.2.16, the program follows the calculation method in section 5.3.18 of the specification. Let's take a closer look at verse 5.3.18:
5.3.18 means: when the class B buildings of brick-concrete structures are more regular, we can also use the comprehensive seismic capacity index method of class A buildings (5.2.13), but we need to use the intensity influence coefficient.
5.2.16 and 5.3.18 are commonly said that when the class A brick-concrete structure is irregular and over-high, the bearing capacity method of the base shear method of the class B building should be used to check the calculation, and the simplified comprehensive seismic capacity index method can be used if the class B brick-concrete brick-concrete is very regular.
However, according to the software training materials, it becomes that irregular Class A buildings can still use the comprehensive capacity index method, but it is necessary to mention the impact coefficient of D seismic intensity to Class B buildings.
I checked the two software, YJK and PKPM, and the statement is consistent. But I think my understanding is correct, the logic of the two software seems to be wrong, but the software can be used in engineering in this way. When we encounter this situation in practical work, one is the method of directly checking 5.2.16 according to the software, and the other is the method of directly adopting the 89 version of the specification of Class B buildings. The two methods should not envelop the design, but should be cross-referenced to each other for more comprehensive consideration.
under
According to the "Technical Regulations for Seismic Reinforcement of Buildings JGJ116-2009", the comprehensive seismic capacity index of the floors and wall sections of the brick-concrete structure and the seismic bearing capacity of the wall sections can be used by the wall reinforcement coefficient ŋ method:
For the reinforcement factor, it is further divided into the strength enhancement factor
and stiffness enhancement coefficients
。
When we calculate the floor seismic capacity index and the comprehensive seismic capacity index of the wall rate, we use the double-check wall rate method, which is the same as the stiffness enhancement coefficient
Independent. However, when the seismic component bearing capacity test algorithm is adopted, the stiffness increase coefficient must be used, and the total seismic shear force calculated by the base shear force needs to be assigned to each wall segment, and the stiffness of the wall segment needs to be calculated.
However, what is puzzling is that the "Technical Regulations for Building Seismic Reinforcement JGJ116-2009" only gives the stiffness enhancement coefficient of the mortar surface layer, the reinforced mortar surface layer and the polymer mortar surface layer reinforcement method, but does not give the reinforcement coefficient of the reinforced concrete slab wall (the seismic reinforcement specifications in various regions are consistent with the national standard, and there is no stiffness increase coefficient of the concrete slab wall, and only the group standard of the high-ductility concrete masonry reinforcement specification considers the stiffness increase coefficient of the concrete slab wall), so the software compilation believes that The spirit of the software is not to consider the change of wall stiffness after reinforced concrete slab wall reinforcement, so the seismic force distribution before reinforcement is adopted. Is the spirit of the specification really not considering the increase in stiffness after the reinforcement of the board wall? PKPM and YJK still have the same point of view, which makes people puzzled.
Knowing these problems, how can we use operations in our actual work?
If the comprehensive capacity index method is used, because the wall ratio is reviewed, it has nothing to do with the stiffness enhancement coefficient. If the seismic component bearing capacity method can be divided into the "building seismic reinforcement technical specification JGJ116-2009" method and the "masonry structure reinforcement design code method", if the former is adopted, pay attention to the concrete slab wall reinforcement, seismic shear distribution and reinforcement before the change, there may be problems, it is recommended to adopt the latter method, the program is completely in accordance with the method of the "masonry code" to calculate the strength and stiffness of the reinforced composite masonry, theoretically more reasonable.
Personally, it is recommended to use both methods to calculate and make a comprehensive judgment with mutual reference, but not to use the envelope design method commonly used in new buildings, but to use cross-reference comprehensive judgment and bottom-line thinking, of course, this bottom line is based on a clear and correct concept.
July 1, 2024