Influence of Precast Member Corbels on Seismic Performance of Precast Beam-Slab-Column Joints

To improve the construction efficiency of precast structures, reinforced concrete corbels acted as support members are the most common connection method. This work presents the performance of a specific beam-to-column connection using corbels with different anchorage arrangements in precast beam-slab-column interior joint taken out from precast underground subway station. This paper investigates the performance of a specific full-scale precast concrete beam-slab-column interior joint with corbels and various connected methods subjected to low-cycle repeated loading. Meanwhile, the influences of concrete corbels (including column- and beam-end corbels) on the shear strength and deformation are investigated. The analyses results indicated that (1) corbels of the laminated beam (composite beam) can obviously improve the shear stress of the core region, which was beneficial for specimen design followed the strong-joint-weak-member concept; (2) a simplified approach to deal with the uneven thickness of corbels in the core region was proposed, which was utilized to study the effect of thickness on the shear performance of the core region; (3) the shear stress increased with respect to the compression stress, and the shear strain had a trend of decreasing according to calculating results using modified compression field theory; and (4) the deterministic expressions were proposed to predict the designed load of column corbels based on three different connection methods between laminated beams and core region of joint.

Incremental dynamic analysis of underground subway station structure

Incremental dynamic analysis constitutes the basis of seismic performance evaluation and seismic vulnerability assessment. In this paper, a typical two-story three-span subway station structure is selected as an example structure and its incremental dynamic analysis procedure are presented, including selection of ground motion, intensity measure and limit state determination. The incremental dynamic analysis procedure provided in this study can be a basis for further study on seismic design for underground structural systems.

Safety Problem of Gaseous Extinguishing System in Underground Subway Station

The gaseous fire extinguishing agents CO₂, Halon 1301, and HCFC-BLEND A and a clean fire extinguishing agent are installed and operated in 85.5%, 6.19%, 4.14%, and 4.62% of the city railroad subway stations of Korea, respectively. The fire extinguishing halon gases Halon1301 and HCFC-BLEND A currently used in city railroad subway stations are already regulated globally because of global warming and ozone layer destruction.Moreover, the use of Halon 1301 is prohibited because of the development of alternative clean fire extinguishing gas. However, newly installing and operating CO₂, unlike the use of halon gas, has not been sanctioned. In particular, even though a fire extinguishing CO₂ facility has the serious safety problem of choking accidents occurring as a result of operation in a closed space because of the characteristics of a subway station, the situation has not been improved. The Organisation for Economic Co-operation and Development designates CO₂ as the major substance causing global warming and forcibly allocates the reduction of carbon emissions to member countries through a reduction policy. Therefore, overall annual replacement of CO₂ fire extinguishing facilities installed and operated in subway stations is necessary, and the problems of fire extinguishing operation characteristics and maintenance of fire extinguishing gas facilities should be reviewed. The purpose of this work is to presentthe maintenance status of fire extinguishing gas facilities installed and operated in the city railroad subway stations of Korea. Furthermore, the preparation of measures and laws for preventing fatalities resulting from choking caused by fire extinguishing CO₂ facilities and for improving cooperation with the international environmental response is proposed.

Risk Analysis and Control Factors Based on Excavation of a Large Underground Subway Station under Construction

Considering the convenience of pedestrian transfer, reasonable structural stress and beautiful shape design, most subway stations adopt symmetrical design. At present, the new subway station is developing in the direction of a multidimensional space, as well as a large scale, and complex structure. Tunnel construction also presents unpredictability, coupling amplification and high risks. For example, a subway extension project involves construction, which would affect the normal use of the subway or damage its structure. Based on excavation of the largest underground subway station under construction in China, the Erligou station extension project (line 16 of Beijing Metro), and using theoretical analysis, numerical simulation, monitoring data, and other research methods, this paper quantitatively analyzes the risk of a large space station’s construction process on the adjacent existing station structure and track, as well as highlights key, high-risk sub-projects, or construction steps, combined with specific engineering measures to ensure safety during construction of a new station. The general rules concerning large space subway station construction are further summarized to provide reference for similar projects.