Wei Xuan

To mitigate the environmental impact induced by CO₂ emissions and nonrenewable resource consumption, which are typically associated with Portland cement production, ground granulated blast furnace slags (GGBSs) are usually added to the cement. In this study, the stabilisation effect of alkali‐activated GGBS on saline soil and the hydration products of alkali‐activated GGBS were investigated by unconfined compressive strength tests and scanning electron microscopy, respectively. The results show that Ca(OH)₂ and NaOH as alkaline activators for GGBS significantly improve the unconfined compressive strength of saline soils. This strength is also enhanced by Na₂SO₄; however, the increase is considerably less than that provided by Ca(OH)₂ and NaOH. In contrast, Na₂CO₃ is not a suitable alkaline activator for GGBS and has no significant effect on the unconfined compressive strength of saline soils. The study results further show that the morphology of hydration products varies because of the different alkaline activators involved in the hydration reaction with GGBS in saline soils.

A series of unconfined compression tests were performed to investigate the influence of wheat straws on the unconfined compression strength for saline‐alkaline soils and saline‐alkaline soils mixed with cement. In unconfined compression tests, 20 groups of soil specimens were prepared at five different percentages of wheat straws content (i.e., 0.0%, 0.1%, 0.15%, 0.2%, and 0.25% by weight of saline‐alkaline soils) and four different percentages of cement content (i.e., 0%, 3%, 6%, and 9% by weight of saline‐alkaline soils), and unconfined compression tests were carried out after 3‐, 7‐, 14‐, 28‐, and 56‐day curing periods. Test results indicated that the inclusion of wheat straws within saline‐alkaline soils and saline‐alkaline soils mixed with cement leads to an increase in the unconfined compressive strength of specimens and also changed the brittle behavior to a more ductile one for specimens. In addition, based on the results from unconfined compression tests, a formula for predicting the unconfined compression strength of specimens related to cement content, wheat straw content, curing periods, etc., was determined, and comparing with the results from unconfined compression tests, it had higher precision in predicting the unconfined compression strength of specimens.

In this paper, monotonic horizontal loading tests were carried out to study the bearing capacity of the cone-shaped foundation in marine fine sand. With load-controlled methods, the horizontal load was applied to the rod of cone-shaped foundation at loading eccentricity ratios of 5.0, 6.0, and 7.0. In addition, theoretical analysis was used to investigate the horizontal ultimate bearing capacity, and finite element analysis was also used in this paper to investigate the influence factors of the bearing capacity of cone-shaped foundation. Based on the theoretical analysis, the formula for horizontal ultimate bearing capacity was deduced. Test results show that, at the same loading eccentricity, cone-shaped foundation can provide higher H-M bearing capacity as well as lower lateral deflection compared to regular circular foundation for wind turbines. In addition, the deflection-hardening behavior of load-deflection curve for cone-shaped foundation is also observed. Numerical analysis results show that the H-M bearing capacity of the cone-shaped foundation increases with increasing aspect ratio and buried depth, however, and decreases with increasing loading eccentricity. Based on the results from finite element analyses, several equations to calculate the maximum moment bearing capacities are put forward, which take the aspect ratio, loading eccentricity, and embedded depth into account.

A static loading test was carried out on a 1/3‐scale concrete‐filled square steel tubular column‐steel beam frame (CFSTSBF) specimen with 2 spans to study its progressive collapse behaviors under the middle column failure scenario using the alternate load path method and to examine the failure mode and load transfer and main resistance mechanisms of the residual structure. Then, theoretical models of the specimen, involving the whole collapse process, were developed, and the resistance and deformation relationships of each model were calculated and validated with test results. The results indicated that the specimen collapse process includes the elastoplastic stage, plastic stage, transfer stage, and catenary stage, the beam mechanism and catenary mechanism were the principal mechanisms for the structure against progressive collapse, and catenary action can significantly strengthen structural resistance. The modified theoretical models with higher practical accuracy could be used to assess structural performances against progressive collapse.

For a new type of postearthquake temporary prefabricated lightweight steel structure proposed in this paper, mainly composed of steel frame, prefabricated hanger slabs, prefabricated hanger columns, reinforced concrete superposed slabs, etc., parameters of dynamic property for the structure, including natural frequency, vibration mode, damping ratio, etc., are determined by the test method. For prefabricated hanger columns and prefabricated hanger slabs, they are all produced with construction waste in factory and assembled on‐site, which can form exterior walls. The united method, based on forced vibration method and ambient random vibration method, can quickly obtain accurate natural frequencies of the full‐scale two‐story experimental model. In this paper, damping oscillatory method is used to obtain damping ratio which can be determined only by the test method. In order to analyse the modal of the experimental model, a finite element model for the full‐scale two‐story experimental model is established, where the weight of prefabricated hanger slabs is assumed to be supported by prefabricated hanger columns, and the stiffness of prefabricated hanger columns is also increased. In addition, the connections between lightweight steel frame and prefabricated hanger columns are regarded as flexible connection. Comparing natural frequencies obtained from the finite element method with that obtained from the test method, magnification factor of stiffness for prefabricated hanger column is determined. In the analysis of modal for the full‐scale two‐story experimental model, the results show that the experimental model satisfies the requirement of design for seismic performance.