To accurately assess the seismic damage of high-rise structures under long-period ground motions (LPGMs), a 36-story SRC frame-RC core tube high-rise structure was designed. Twelve groups of LPGMs and twelve groups of ordinary ground motions (OGMs) were selected and bidirectionally input into the structure. The spectral acceleration S_90c considering the effect of higher-order modes was adopted as the intensity measure (IM) of ground motions, and the maximum inter-story drift angle θ_max under bidirectional ground motions was taken as the engineering demand parameter (EDP). Structural Incremental Dynamic Analysis (IDA) was conducted, the structural vulnerability was investigated, and seismic vulnerability curves, damage state probability curves, vulnerability index curves, as well as the probabilities of exceeding performance levels and vulnerability index of the structure during 8-degree frequent, design, and rare earthquakes were obtained, respectively. The results indicate that structural damage is significantly aggravated under LPGMs, and the exceeding probabilities for all performance levels are greater than those under OGMs, failing to meet the seismic fortification target specified in the code. When encountering an 8-degree frequent earthquake, the structure is in a moderate or severe damage state under LPGMs and is basically intact or in a slight damage state under OGMs. When encountering an 8-degree design earthquake, the structure is in a severe damage or near-collapse state under LPGMs and is in a moderate damage state under OGMs. When encountering an 8-degree rare earthquake, the structure is in a near-collapse state under LPGMs and in a severe damage state under OGMs.

The permeability coefficient of saturated clay plays a crucial role in practical engineering applications. In this paper, based on the fractal geometry theory and combined with the relationship between the flowing water volume and non-flowing water volume in saturated clay, the theoretical formulas for the effective pore specific surface area and the effective void ratio of saturated clay are established. Based on the capillary seepage channel model of saturated clay, combined with Poiseuille’s law and the concept of equivalent hydraulic radius, the theoretical formula for the permeability coefficient of saturated clay is established. Finally, the physical parameters of the remolded clay samples are measured and substituted into the modified Kozeny–Carman equation and the equivalent capillary seepage equation of saturated clay before and after the modification. Through the comparative analysis of the above theoretical values and the measured values of indoor seepage tests, it is found that the saturated clay seepage equation established in this paper is more suitable for dense saturated clay with relatively small pores. It has the characteristics of higher calculation accuracy and easier acquisition of basic parameters. The research results provide important references for practical engineering and the study of saturated clay seepage theory, and have broad prospects for practical engineering applications.

Traditional pseudo-static loading tests fail to capture the unique characteristics of special ground motions, limiting their ability to accurately evaluate the seismic performance of steel-reinforced concrete (SRC) columns. In this study, eight SRC columns were subjected to pseudo-static tests using far-field, near-field, and traditional loading protocols to investigate their structural response under different seismic scenarios. The results show that far-field loading, characterized by repeated large displacement cycles, leads to increased damage accumulation, reduced hysteresis curve fullness, greater bearing capacity loss, significant stiffness degradation, and diminished ductility and energy dissipation. In contrast, near-field loading—dominated by an initial extreme displacement—results in fewer but less developed cracks and a larger concrete crushed zone at failure. The severe initial damage under near-field loading causes a noticeable decline in stiffness and strength during subsequent cycles. During the second loading stage, both the peak load and post-peak deformation capacity are further reduced, significantly impairing the columns’ ability to resist additional seismic demands. These findings highlight the critical role of loading history in shaping the seismic behavior of SRC composite columns.

Based on the characteristics and distribution patterns of collapsed holes in cast-in-place bored pile foundations in the typical coastal area of Guangdong Petrochemical Company, the deformation and collapse behavior of pile walls in the project zone were systematically monitored and measured using a specialized pore diameter detection system for cast-in-place bored pile quality assessment. A collapse rate parameter is proposed and established as an evaluation index for pile wall stability and collapse. Using the basic principles of Quantification Theory I and considering the collapse characteristics of pile walls in a cast-in-place bored pile project in Guangdong, the influencing factors and mechanisms of pile wall collapse are comprehensively analyzed and evaluated. A quantitative theoretical evaluation model for the influencing factors of pile wall collapse is then established. Focusing on the construction technology of cast-in-place bored piles, the proposed quantitative theoretical evaluation model is applied to quantitatively analyze and assess the factors contributing to pile wall collapse in the project area. The relationships between pile wall collapse rate in the Guangdong Petrochemical Company cast-in-place bored pile project and influencing factors such as stratum structure, soil properties, sand layer thickness, drilling depth, and drilling methods are systematically determined. The primary collapse factors and secondary influencing factors in the pile wall collapse of the cast-in-place bored pile engineering zone are identified, providing a theoretical basis for determining optimal prevention and control measures against pile wall collapse during the drilling process of cast-in-place bored piles.

Seven groups of near-field pulse-like ground motions and three groups of ordinary ground motions were bidirectionally inputted into a symmetrical high-rise structure to comparatively study the deformation and energy dissipation characteristics of the structure. The results reveal that compared to ordinary ground motions, under near-field pulse-like ground motions, the inter-story drift angles of the structure significantly exceed the code limit, accompanied by a downward shift of the floors with the maximum drift angles. Moreover, the input energy is substantially higher and the hysteresis energy dissipation supersedes damping energy dissipation as the dominant mode. During an 8-degree frequent earthquake, coupling beams are the main energy-dissipating members, the floors below 2/3 of structural height mainly dissipate hysteresis energy by coupling beams, while the floors above 2/3 of structural height mainly dissipate hysteresis energy by frame beams. During 8-degree design earthquakes and rare earthquakes, frame beams are the main energy-dissipating members, the hysteresis energy ratio of coupling beams is significantly reduced, and the hysteresis energy ratio of shear walls gradually increases. During 8-degree design earthquakes, the 1st floor mainly dissipates hysteresis energy by shear walls, the 2nd to 6th floors mainly dissipate hysteresis energy by coupling beams, and the 7th to 36th floors mainly dissipate hysteresis energy by frame beams. During 8-degree rare earthquakes, the hysteresis energy on the 1st to 2nd floors is mainly dissipated by shear walls, while it is mainly borne by frame beams on other floors.