Numerical Simulation of the Daikai Station Subway Structure Collapse due to Sudden Uplift during Earthquake

The Daikai Station subway structure in Japan completely collapsed during the Hyogoken-Nanbu earthquake that occurred on January 17, 1995. Based on the numerical results obtained by two-dimensional finite-element analysis, the structure is believed to have collapsed as a result of strong lateral vibration. However, because it deformed in an approximately symmetrical manner with respect to the shortened central columns, it might have experienced catastrophic collapse due to vertical impulse motion. To investigate the dynamic response behavior of the structure due to sudden upward loading, a three-dimensional elastoplastic transient response analysis was conducted considering an isolated upward pulselike displacement wave from the bedrock. The results of this study suggest that the central column of the structure reached axial compression failure due to the amplitude of the displacement wave increasing significantly at the lower end of the column. This method can numerically reproduce the collapsed state of the structure and the considerable settlement of the ground surface due to the occurrence of the high-intensity earthquake

Cross-ancestry genome-wide analysis of atrial fibrillation unveils disease biology and enables cardioembolic risk prediction

心房細動の遺伝的基盤を解明 --大規模ゲノムデータによる病態解明と遺伝的リスクスコア構築--. 京都大学プレスリリース. 2023-01-20.Atrial fibrillation (AF) is a common cardiac arrhythmia resulting in increased risk of stroke. Despite highly heritable etiology, our understanding of the genetic architecture of AF remains incomplete. Here we performed a genome-wide association study in the Japanese population comprising 9, 826 cases among 150, 272 individuals and identified East Asian-specific rare variants associated with AF. A cross-ancestry meta-analysis of >1 million individuals, including 77, 690 cases, identified 35 new susceptibility loci. Transcriptome-wide association analysis identified IL6R as a putative causal gene, suggesting the involvement of immune responses. Integrative analysis with ChIP-seq data and functional assessment using human induced pluripotent stem cell-derived cardiomyocytes demonstrated ERRg as having a key role in the transcriptional regulation of AF-associated genes. A polygenic risk score derived from the cross-ancestry meta-analysis predicted increased risks of cardiovascular and stroke mortalities and segregated individuals with cardioembolic stroke in undiagnosed AF patients. Our results provide new biological and clinical insights into AF genetics and suggest their potential for clinical applications

Impact-Resistant Behavior of Steel-Fiber-Reinforced Porosity-Free Concrete Beam

Porosity-free concrete (PFC) is a newly developed ultra-high-strength concrete with a compressive strength of 400 MPa. PFC reduces the weight of bridge superstructures, protects against collisions with flying objects, increases seismic-resistant capacity, and improves long-term durability. At present, basic material properties of PFC, such as compressive strength, tensile strength, and tensile toughness have been revealed. However, impact resistance has not been examined. In this study, in order to investigate the impact-resistant behavior of steel-fiber-reinforced PFC, falling-weight impact-loading tests were conducted on a PFC beam, considering the mixing ratio of steel fiber and the height of falling-weight as variables. To investigate the effects of compressive strength on the impact-resistant behavior of the concrete beam, tests using high-strength concrete (HC) with a compressive strength of 100 MPa were also conducted as general high-strength concrete. From this experimental study, the following results were obtained: 1) impact resistance capacity of the PFC beam can be more drastically improved by mixing 2 vol.% of steel fiber compared to the HC beam; 2) bonding resistance between PFC and steel fiber could play an important role in upgrading the impact resistance. PFC mixed with 2 vol.% steel fiber could be used as an effective reinforcement material for impact protection structures

Top-amd seat angle接合のてこ作用に関する非線形解析

Nonlinear finite element (FE) analyses are performed to simulate the behavior of top- and seat-angle connections. Contact model with small sliding option is applied between contact pair surfaces of all connecting elements. Bolt pretension force is introduced in the initial steps of analysis. Numerical analysis results together with the prediction by Kishi-Chen power model are compared with experimental ones to examine the applicability of proposed analysis method and power model. The study is farther extended by analyzing the models varying connection parameters, material properties of connection assemblages, and magnitude of bolt pretension. The following results are obtained: 1) bolt sustains additional tensile force due to prying action; 2) prying force develops more quickly due to increment of bolt diameter, gage distance from angle heel to the centerline of bolt hole, and reduction of angle thickness; and 3) bolt pretension increases the initial connection stiffness