The nearest seismic monitoring station is “51ybt” monitoring station, which is about 11km away from project I ~ III and about 4km away from project IV ~ VI.

Since the 617 earthquake, as of 9 a.m.

6.17 the seismic intensity distribution map (extracted from China Seismological Network) is as follows: Figure 1 the intensity map of Sichuan Changning M6.0 earthquake.

Overview of precast buildings in the local survey.

The structural form is assembled integral shear wall structure, the seismic fortification intensity is 7 degrees, the design basic seismic acceleration is 0.10g, the design earthquake is divided into group II, the construction site is class II, the characteristic period is 0.40s, and the maximum value of horizontal seismic influence coefficient in case of frequent earthquakes is 0.08.

Figure 5 ， distribution of precast buildings and 51ybt monitoring stations Figure 6 ， distribution of precast buildings, epicenter and “51ybt” monitoring stations see Table 1 for the basic information of precast projects in this survey.

The types of precast components of the project include: load-bearing PC wall panel (considering its bearing vertical and horizontal loads), precast composite beam (only connecting beam), precast composite plate, precast staircase, precast parapet, precast air conditioning board, non load-bearing PC wall panel (not considering its bearing vertical or horizontal loads).

5 and Fig.

Flat End Socket Cross Pin

The investigation results are detailed in FIG.

Figure 2 distribution of epicenter and monitoring stations Figure 3 ＾ 6.17 record of measured ground motion acceleration of “51ybt” monitoring station Figure 4 ＾ the response spectrum recorded by 51ybt monitoring station can be obtained from Figure 4.

Fig.

The distribution details of the survey project, epicenter and seismic monitoring station “51ybt” are shown in Fig.

Article 5.1.2 of the code for seismic design of buildings (hereinafter referred to as the code) shows that the maximum value of seismic acceleration time history used for 0.1g time history analysis in degree 7 area: 35 cm / S2 for frequent earthquakes (small earthquakes) and 100 cm / S2 for fortification earthquakes (medium earthquakes), that is, the peak acceleration of this earthquake is between the design acceleration of 7 degree (0.1g) small earthquakes and the design acceleration of medium earthquakes, which is 1.68 times that of small earthquakes.

11 typical nodes of PC wallboard connection Fig.

After the 6.0-magnitude earthquake in Yibin on June 17, 2019, in order to timely understand the current situation of precast buildings in Yibin area, conduct post earthquake assessment to ensure the safety of people’s lives and property, summarize experiences and lessons, and provide support for further promoting the development of precast buildings, Sichuan Provincial Department of housing and Urban Rural Construction organized an expert group to conduct a comprehensive investigation on the post earthquake situation of precast buildings under construction and completed in Yibin area from June 20 to June 22, 2019.

3.

It is a single storey office building.

Investigation with the strong support of Yibin housing and Urban Rural Development Bureau and Sichuan Renming Housing Industry Technology Co., Ltd., on June 21, 2019, the investigation team conducted a detailed investigation on the current situation of the six precast concrete buildings listed in Table 1 (several buildings of the same type in the same project are regarded as one), as follows.

Fig.

on June 24, 45 aftershocks of magnitude 3 or above, 8 times of magnitude 4 or above and 2 times of magnitude 5 or above have occurred in the area near the junction of Changning and Gong county in Yibin (28.40 degrees north latitude and 104.80 degrees east longitude).

Figure 7 actual view of project I figure 8 standard floor building plan Figure 9 standard floor structure plan Figure 10 wall panel split figure 3.1.2 precast building implementation of the project.

Table 1 basic information of cast project note: the data of “*” is provided by each construction party.

The insulation method is internal insulation mortar.

2.

The influence coefficient of short-term building earthquake in this earthquake is large.

1.617 basic information of Yibin M6.0 earthquake according to the official measurement of China Seismological Network: at 22:55 on June 17, a M6.0 earthquake occurred in Changning County, Yibin City, Sichuan Province (28.34 degrees north latitude and 104.90 degrees east longitude), with a focal depth of 16 km.

12 ~ 15.

6.

3.1 project I 3.1.1 project overview the project is about 51 kilometers away from the epicenter.

The seismic fortification intensity of cast buildings in this survey is 7 degrees (0.1g).

3.1.3 investigation and analysis the investigation team inspected the facade of the office building, all rooms on floors 1 ~ 4, and comprehensively investigated the floor slab, wall and wall end nodes, stairwell and partition surface.

Some internal partitions are made of foam concrete light-weight strips, some walls under windows are masonry infilled walls, and other partitions are non load-bearing PC wallboards (some wallboards are partially embedded with polystyrene boards).

According to the seismic wave records provided by Sichuan Seismological Bureau, the location of “51ybt” seismic monitoring station is 28.71 degrees north latitude and 104.57 degrees east longitude (Figure 2, in which the Red Pentagram is the location of the earthquake), and the peak ground motion acceleration recorded by the monitoring station is 59.0cm/s2.

15 cracks in light partition wall according to the site conditions and the visit to residents and the construction party, after the 617 earthquake, no cracks were found in the main structural components and their connecting parts of the cast project, and the main structure was intact..

Assembly rate: 68.2%.

12 exterior walls, beams and stairs ； Fig.

Detail 11 of connection node drawing of non load bearing PC wallboard and load bearing PC wallboard.

There are 4 floors in total, with a building height of 14.7m and a building area of about 1350 m2.

At present, it has been completed and put into use.

The seismic fortification category of buildings is standard fortification category.

13 main and secondary beams and laminated plates ﹐ Fig.

The actual view is shown in detail 7, the standard floor layout is shown in detail 8 and 9, and the wall panel split is shown in detail 10.

14 exterior wall cracks ﹐ FIG.

The precast buildings in this survey are located in Xuzhou District, Yibin City, north of Jinsha River, about 50km away from the epicenter, and the seismic intensity in this area is close to 6 degrees.