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A sand compaction pile (SCP) with a high area replacement ratio (>50%) has been recently employed to improve the soft clay ground in offshore projects, but its performance is still not completely known. Therefore, to provide a comprehensive understanding of the SCP method, a series of laboratory model tests were performed on the SCP-improved clay ground using high (70% and 100%) and the low-to-medium (0%, 14%, and 38%) area replacement ratios. The internal stress and strain responses of SCP-improved ground with a high area replacement ratio were different from those with a low-to-medium ratio. Typically, under high ratios, the loaded SCPs bulged, resulting in the bending of the adjacent SCPs, while under low-to-medium ratios, the SCPs deformed individually. Essentially, the additional lateral confinement is provided by the adjacent SCPs under the high replacement ratio. An improved model to predict the bearing capacity of the SCP-improved ground was proposed by incorporating a coefficient of lateral pile interaction that reflects the failure mechanism. The prediction using the proposed model showed good agreement with the observations in the west artificial island of the Hong Kong–Zhuhai–Macao Bridge project. This study provides a universal mathematical model to predict the bearing capacity of the clay ground improved by SCP varying from low to high area replacement ratios, leading to a comprehensive understanding of the performance of this modern technique. [ABSTRACT FROM AUTHOR]

Modular construction has been widely employed to build low-to-medium-rise buildings but limited for high-rises partly due to the knowledge gap about the lateral force resistance of modular high-rises. Most modular high-rises adopt in situ cores which still require substantial onsite works to resist lateral loads. Previous research developed a module wall system for modular high-rises to replace in situ cores. This study aims to propose coupling beams concealed in corridor slabs for modular high-rises without in situ cores. A 40-story public housing building in Hong Kong (HK) was adopted for the case study. A finite element (FE) model of precast concrete coupled shear walls was formulated using the OpenSees software and validated by reported test results. For the case building in the scenarios with and without coupling beams, the seismic and wind performances were respectively compared according to the results of the nonlinear dynamic analysis using the FE model and those of the nonlinear static analysis using an ETABS model of the building. The study not only proves that precast concrete coupled shear wall system is technically feasible to resist the seismic and wind loads for modular high-rises in HK but also facilitates the application of precast concrete modules in high-rise buildings. [ABSTRACT FROM AUTHOR]

Presents information on a study which analyzed the performance of laterally loaded sleeved piles in sloping ground in Hong Kong, China. Details on the construction of sleeved piles that support high-rise buildings on hilly terrain; Methodology; Results and discussion.

• Parametric study is conducted on module wall-core system of concrete modular high-rises. • Generalized modulus reduction method is developed to consider the influence of vertical connections on module walls. • Thicker module wall improves precast ratio by thinning core wall without negative effects on structural responses. • Reduced stiffness of module walls magnifies deflection, vibration, and core wall failure. • Defective connections put local core walls at risk with limited impact on global responses. High-rise modular buildings are attractive for metropolises, but few applications exist. One reason is the lack of relevant knowledge about their lateral force resistance. Existing high-rise modular buildings generally adopt cast-in-situ concrete cores, which can work with precast module walls in concrete modular buildings to resist lateral loads together. This study aims to parametrically examine the module wall-core system. A typical 40-story public residential building in Hong Kong was selected as the case building and re-designed to be a concrete modular building. A method called generalized modulus reduction method was adopted to consider the influence of vertical grouted connections on lateral behavior of slender precast concrete walls. A three-dimensional finite element model using this method was established to study the influence of three parameters on the structural responses of the case building under the Hong Kong code-specified wind loads, which were the module wall thickness, the reduced lateral stiffness of module walls, and the defect distribution scenarios of vertical inter-module connections. Results show that the developed method can well consider the influence of vertical grouted connections. The module wall-core system can provide sufficient stiffness and strength for the case building, and module walls play a leading or even a major role. It is beneficial to increase the thickness of module walls due to reduced site work for core walls without adverse effects on the structural responses of buildings. With the reduced lateral stiffness of module walls, the case building's deflection increases speedily, with more serious wind-induced vibration and more vulnerable core walls. When more defective vertical inter-module connections are concentrated on the bottom stories, there are relatively small impacts on overall structural responses of the case building, while strong adverse impacts on core walls at the corresponding bottom stories. For ensuring safer structural design, the influence of vertical inter-module connections on the global lateral force resistance of concrete modular high-rises cannot be ignored. [ABSTRACT FROM AUTHOR]