317 publications from this institution
No abstract is provided for this article.
FRP-confined concrete/UHPC (ultra-high-performance concrete) core-encased rebar (FCCC-R) is a recently developed novel structural component for FRP-concrete composite structures. FCCC-R utilization can improve both the strength and ductility of composite structural members under both axial compression and combined bending-compression loading. When implemented in vertical structural members such as columns and shear walls with a low shear-span ratio, FCCC-Rs are subjected to combined axial compression and shear. In this study, the shear behaviour of FCCC-Rs is experimentally investigated. A total of 28 FCCC-R specimens are tested. The failure mechanism and modes, the load–deflection curves and the ultimate strength were obtained from the experiments. The FCCC-Rs exhibited higher load capacity and deformability. It could be concluded that the combination of the FRP tube, concrete and rebar can achieve the effect of “1+1+1>3”. Furthermore, the influence of the shear-span ratio, concrete strength, tube thickness and fibre orientation are examined. Finally, design equations for the shear strength of FCCC-Rs are proposed, which attain a good agreement with the test data.
The three dimensional (3D) printing technology has undergone rapid development in the last few years and it is now possible to print engineering structures. This paper presents a study of the mechanical behavior of 3D printed structures using cementitious powder. Microscopic observation reveals that the 3D printed products have a layered orthotropic microstructure, in which each layer consists of parallel strips. Compression and flexural tests were conducted to determine the mechanical properties and failure characteristics of such materials. The test results confirmed that the 3D printed structures are laminated with apparent orthotropy. Based on the experimental results, a stress–strain relationship and a failure criterion based on the maximum stress criterion for orthotropic materials are proposed for the structures of 3D printed material. Finally, a finite element analysis was conducted for a 3D printed shell structure, which shows that the printing direction has a significant influence on the load bearing capacity of the structure.
Cellular materials, widely found in engineered and natural systems, are highly dependent on their geometric arrangement. A nonuniform arrangement could lead to a significant variation of mechanical properties while bringing challenges to material design. Here, this proof-of-concept study demonstrates a machine-learning-based framework with the capability of accelerated characterization and pattern generation, which also opens new avenues for the programmability of function at the system level.
FRP strips, which are light-weight, high-strength and anticorrosion, are crossed and woven to form a flexible plane FRP web. The web can acquire the adequate stiffness and bearing capacity in the results of the tension applied by tendons in out-plane direction. Then the tensed FRP web can act as roof structures. It is an innovative structure for the FRP application for large-span buildings. In this paper, the basic configuration of FRP woven web structure is introduced, and its structural characteristic is investigated. Three key states of a simple FRP woven web structure from the construction to the service, including the initial prestressed state, the out-of-plane tensioned state and the service loading state, are analyzed. The response of strips within a simple FRP woven web structure is finally examined, which confirms the feasibility of the structure form.
9月28日 晴 现代社会总是以国民幸福感来评价一个国家是否真正的发达，尽管这个衡量标准比以GDP金钱作为衡量标准要“高尚”得多，但我始终觉得，一个人乃至一个国家的幸福感都不是别人给得了的，自始至终，是否幸福只有自己给的了自己，
This paper presents an innovative large-span roof system, namely the fiber-reinforced polymer (FRP) woven web structure (WWS). A FRP WWS is composed of light-weight, high-strength, and corrosion-resistant FRP strips that are “woven” into a web in a desirable pattern. The two ends of each FRP strip are anchored on an inner ring beam and an outer ring beam, respectively. During the construction process, the inner ring beam is forced to move out-of-plane by a set of prestressed tendons or by a heavy mass suspended from the inner ring beam, which induces tension in the FRP web and imparts geometric stiffness to the web to resist a variety of external loads. In this paper, the basic layout, the strip anchorage system, and the construction scheme of a simple FRP WWS are first presented, followed by a description of some more complex forms of the FRP WWS. A matrix approach for the mathematical description of the three-dimensional geometric configuration of the FRP WWS is next proposed, which provides a tool to ensure the most compact assembly of strips into a roof structure. The response of strips within a WWS and that of the whole structure are finally examined, which confirms the feasibility of the FRP WWS.
Self-centering structures have been demonstrated to be an effective method by which to improve seismic resilience. Most related research is focused on the seismic performance of self-centering structures without initial damage, whereas the post-earthquake performance of structures, which is significant for their repair and operation, is less investigated. Based on this, this study aims to evaluate the post-earthquake behavior and explore the damage evolution of a novel self-centering shear wall with replaceable devices, including disc springs to apply restoring force and friction pads to dissipate energy. Cyclic loading tests were conducted on two intact self-centering shear walls to investigate their seismic performance in our previous studies, and limited damage was observed after the tests. Thus, in this study, cyclic loading was directly applied to the two damaged self-centering shear walls to obtain their post-earthquake performance. The results indicate that the damaged self-centering shear walls exhibited satisfactory seismic behavior; their bearing capacity was reduced at small drift ratios as compared to that of the intact specimens, whereas no decrease of their bearing capacity occurred even at a 3% drift ratio. Moreover, the damaged self-centering shear wall exhibited appreciable energy dissipation and self-centering capabilities, and the residual drift ratio was less than 0.5% at a 2.1% drift ratio. However, the damage at the bottom of the RC wall after the post-earthquake test was obvious, revealing that the novel self-centering RC shear wall would need to be repaired after several earthquakes. Therefore, two effective methods were further developed to improve the post-earthquake performance of the novel self-centering shear wall.
In the ultimate failure mode of columns in RC structures under seismic load, the longitudinal reinforcement generally suffers from severe buckling due to the axial compressive load, spalling of concrete cover and dilation of concrete core. Proper configuration of RC columns to postpone or prevent the buckling phenomenon can enhance the seismic performance and make full use of the strength of steel reinforcement. In this paper, a new concept and configuration of FRP-confined concrete core-encased rebar (FCCC-R) for RC columns is proposed. The concrete surrounded the longitudinal rebar is confined by an FRP tube, which can prevent the rebar from premature buckling. The axial compressive behavior of the hybrid bar considering different parameters, including the slenderness ratio, FRP tube diameter, mortar strength, and bar position was studied experimentally. Furthermore, finite element (FE) simulation was carried out and calibrated by test results. Based on the FE model, additional discussion and a parametric study was performed. Finally, the minimum FRP tube diameter required for the FCCC-R considering the compressive behavior enhancement effect was calculated, and design curves for 3 types of steel bars with nominal yield strengths of 400 MPa, 800 MPa, and 1100 MPa were proposed.
The low stiffness of pultruded glass fiber reinforced polymer (pGFRP) flexural members has been one of the main issues limiting their possible applications ever since this type of material was invented. In this regard, curved-pultrusion technique is adopted in this work to produce GFRP arch beams, and a new GFRP beam-string structure is proposed. Specifically, experimental, numerical, and analytical programs were conducted to investigate the flexural performance of curved-pultruded GFRP arch beams subjected to varying boundary conditions. The flexural strength and stiffness were successfully enhanced by up to 27% and 109%, respectively, which was attributed to the arch mechanism enabled by proposed GFRP beam-string structure. In addition, the progressive failure of GFRP material and the imperfect load-transfer between GFRP arch beam and tension string were investigated through finite element modeling. Then, web crippling strength of GFRP arch beams was predicted with modifications to an existing model, and internal forces of beam-string were analyzed. The GFRP beam-string structure proposed in this work effectively sheds light on possible approach to improve the flexural stiffness of pGFRP members, and with successful demonstration of this work, it is rationally believed that possible applications of curved-pultruded GFRP members can be greatly broadened.
A method to improve the mechanical behavior of 3D-printed elements is presented. 3D-printed elements are orthotropic and weak in their interlayers; thus, FRPs, which are easy-formed, light-weighted and high-strength, are ideal materials to enhance 3D-printed elements. To investigate the reinforcement effect, uniaxial compression tests were conducted on circular column specimens, and four-point flexural tests were conducted on beam specimens. The results indicated that wrapping 3D-printed columns with FRPs changed their failure modes from brittle to ductile, increased the peak loads that they could endure by 1427.2–1792.0% and increased the largest deformations they could achieve by 833.9–1171.3% using different numbers of layers and types of reinforcement. For the 3D-printed beams reinforced with FRPs, the bearing capacities were increased by 179.6–604.5%, and their flexure deflections at their mid-spans were increased by 40.8–225.8%. The failure modes of the 3D-printed beams were affected by numbers of layers and types of reinforcement. Additionally, finite element analyses were conducted to simulate the failure modes of the 3D-printed elements based on the maximum stress criterion. The results showed that the predicted failure locations corresponded with the experimental failure locations observed. According to this study, 3D-printed elements reinforced with FRP sheets showed potential for future development and applications in construction.
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