Xiaomin Huang

This paper introduces an innovative inner core for buckling-restrained braces, referred to as the Aluminum-Engineered Cementitious Composite-Circular Frustum Composite (ALECCYT) inner core, which incorporates multi-stage energy dissipation mechanisms and self-centering capabilities. The initial stiffness calculation formula for the self-centering circular frustum (YT) device is derived theoretically, and a sizing design methodology for its critical components is proposed, specifically tailored to achieve a preset failure mode. Based on this, seven YT device specimens with varying tonnages, both conforming and non-conforming to the design methodology, were designed and analyzed through finite element simulations. The results demonstrate that the hysteretic curve of the appropriately designed YT device exhibits a flag-like shape, with minimal residual displacement after unloading, effective hysteretic energy dissipation, and robust self-centering capabilities, while adhering to the intended failure mode. Conversely, specimens that fail to meet the buckling constraints may encounter failures such as Shape Memory Alloy (SMA) buckling, steel ring buckling, and Carbon Fiber Reinforced Polymer (CFRP) ring buckling during loading, leading to the inefficient utilization of material strengths. The findings from the finite element analyses provide preliminary validation of the effectiveness of the proposed design methodology.

Cement concrete is widely used in various levels of highways, and it is prone to diseases such as cracking, potholes, and local collapse during operation. The maintenance and repair of existing cement concrete has become an important task in the daily operation and maintenance of roads and bridges. However, traditional cement-based repair materials have problems such as long maintenance periods and low bonding strength with existing concrete. In view of this, this article proposes an early strength and high ductility cement composite material, aiming to achieve good curing age, compressive performance, and relatively low price. The compressive performance tests of a new type of composite material were conducted to study the effects of PVA fiber content, fly ash (FA) content, and sand cement ratio on the axial compression performance. The results show that the FA content is 50wt.% When the PVA fiber content is around 2% and the sand cement ratio is 0.36, the compressive performance of early strength and high ductility cement composite materials at different ages is better. Under optimal mix ratio conditions, the axial compressive strength of early strength and high ductility cement-based composite materials at 2 h, 1 day, 3 days, and 28 days reaches 18.1, 27.5, 34.4, and 37.6 MPa; The peak strain at each age is greater than 0.5%.

Cement concrete is widely used in pavement, bridge decks and expansion joint anchorage zones. It is prone to cracking, potholes, spalling and other diseases during use. Cement-based repair materials generally have problems such as a long curing period, low bonding strength with existing concrete, and insufficient mechanical properties. Given this, this paper proposes an early-strength high-ductility cement composite material with the goal of short curing age, excellent tensile mechanical properties and relatively low price. The tensile mechanical properties of the composite material at different ages were tested, and the tensile constitutive model of the composite material was proposed. The results show that when the fly ash content is about 50 wt.%, the PVA fiber content is about 2%, and the sand-binder ratio is 0.36–0.50, the tensile properties of the early strength high ductility cement composite material at each age are better. Under the condition of optimum mix ratio, the tensile strength of 1, 3 and 28 d of early strength high ductility cement-based composites reached 4.58 MPa, 4.67 MPa and 4.64 MPa respectively, and the strain corresponding to 0.8 times of peak stress in softening section could reach 2%.

In this paper, OpenSees is used to analyze the moment-curvature (M-φ) curves of the bottom cross section of 4×40m continuous girder piers under the same reinforcing conditions, which are completely made of C40 concrete, partially made of Engineered Cementitious Composite material concrete(ECC) outsourced concrete, and completely made of ECC concrete, and then evaluate its seismic performance. Meanwhile, the yield curvature and ultimate curvature changes of the abutment section under different axial compression ratios are investigated. The results show that the yield curvature and ultimate curvature of ECC are larger than those of ordinary concrete, and the deformation capacity of ECC is stronger under the same axial force. The results also show that the yield moment and yield curvature of the section gradually increase with the increase of axial compression ratio, and the curvature ductility of the section deteriorates.

The dynamic characteristics of a continuous rigid-frame bridge with fabricated super-high piers (CRFB-FSP) connected by grouting sleeves and adjacent continuous beam bridges (AB) are significantly different, and they are prone to pounding under earthquake excitation. At present, the pounding response between the CRFB-FSP and AB is still unclear, and the impact of the pounding on the seismic performance of a CRFB-FSP is still in the exploratory stage. In this study, two 1/20 scaled models of a CRFB-FSP (MB) and a cast-in-place AB were designed and manufactured. Then, according to the research purpose and the output performance of the shaking table, three each of non-long-period (NLP) ground motions and near-fault pulse-type (NFPT) ground motions were selected as the inputs of the excitation shaking table test. The peak ground acceleration (PGA) changes from 0.5 g to 1.5 g. According to the similarity ratio (1/20), the initial gap between the MB and AB was taken as 7 mm (prototype design: 140 mm). Furthermore, the longitudinal pounding response between the CFRB-FSP and AB, as well as its influence on the seismic performance of the CFRB-FSP, was systematically investigated through a shaking table test and finite element analysis (FEA). The results showed that the pounding with the CRFB-FSP easily caused a persistent pounding, which may increase the damage risk of the pier. The peak pounding force under the NFPT ground motion was more significant than under the NLP ground motion, whereas the pounding number under the NFPT ground motion was smaller. The peak pounding force increased with the increase in the initial gap, pounding stiffness, span, and pier height. With and without pounding, the CRFB-FSP reflected higher-order mode participation (HMP) characteristics. After pounding, under the NFPT excitation, the HMP contribution increased significantly compared with that of the without pounding condition, while this effect under the NLP excitation was smaller. The peak displacement of the main beam of the CRFB-FSP increased with the increase in the main beam span, pier height and initial gap. The peak bending moment of the pier bottom increased with the increase in the main beam span and initial gap, however, decreased with the increase in the pier height. Moreover, the peak displacement of the main beam and the peak moment of the pier bottom of the CRFB-FSP both reduced. In contrast, the corresponding seismic response of the AB increased under the same conditions.

For the long-span concrete-filled steel tube arch bridge, its dynamic characteristics and performance is closely related with the mass and stiffness distribution of the structure. The reason for this is that the relative height of deck has led to change in the mass and stiffness distribution system change, and structure seismic response changed consequently. In this paper, a systematic study on the effect of the relative deck height on the structure dynamic characteristics and further study of structure seismic response are carried out. Some useful conclusions can be drawn and used as a reference for similar projects.