Key Engineering Materials Vols. 400-402

Abstract: In this paper, eight reinforced concrete (RC) beam to concrete-filled steel tubular (CFST) column joints enclosed by rebars were tested under reversal horizontal displacement with constant axial load in order to study their seismic behavior. The test parameters are axial load level and the section type of CFST column. In this study, the failure model, hysteretic characteristic, ductility and energy dissipation were investigated. The results indicated that the anti-earthquake abilities of all joints satisfied with the demand on the code.

Abstract: This paper discussed the results of experiments on bolted moment connection joints of square or circular concrete filled steel tubular (CFST) columns and H-shaped steel beam using high-strength blind bolts under cyclic loading. The objective of this work was to study the seismic performance of the blind bolted flush endplate connections to CFST columns. The test parameters varied were the column section type and the thickness of the endplate. The feasibility of the proposed beam-column connection is successfully verified by the experiments. The test results showed that under cyclic loading the tested specimens displayed large rotation ductility capacities and could satisfy the request of the structural seismic design. When subjected to cyclic loading, most of failure modes of the tested joints are similar to those under monotonic loading. Moreover, the energy dissipation of the type joints is influenced by the column section type and the thickness of the endplate.

Abstract: This paper introduces a new connection－inner and through-type diaphragm, which is recommended by Technical Specification for Structures with Concrete-filled Rectangular Steel Tube Members. It studies some factors including the additional plates installed on both sides of the flanges, the width-to-thickness ratio of the column and the length of the through diaphragm which have an influence to the seismic resistance behaviors of connection through cyclic test. The results show the hysteresis curves attained in the experiment are full and the rigidity deterioration is not obvious. The connection models have a good energy dissipation capacity. Meanwhile the stress distributing can be ameliorated and the ductility of the connections can also be improved through welding the additional plates to both sides of the flanges.

Abstract: Application of carbon fiber material to reinforced concrete structure is a systems engineering involving materials, design and application, which is also an applied science involving numerous subjects. Carbon cloth is used to reinforce structures in many projects, but the study on strengthening frame joints is still little. Especially the study on aseismatic performance of frame structure side joints is much less. In this paper, the author established constitutive relation of RC frame side joints strengthened with carbon cloth and made a numerical simulation analysis of four side joints of beam column plate under low-cycle repeated load with ANSYS, a software based on finite element analysis. The author analyzed the failure mode and the mechanism under stress, found out the characteristics of hysteretic curve of such kind of joints, acquired ductility coefficient and equivalent viscous damping ratio coefficient and studied the structure ductility and seismic-energy-dissipating capacity. It was shown that failure mode transited from shear brittle failure of core space to ductile failure of plastic hinge of beam end, joints’ seismic-energy-dissipating capacity and ductility were improved observably, joints’ displacement between layers was reduced, and rigidity and aseismatic capacity of component were improved after the joints’ being reinforced with carbon cloth. And aseismatic performance of structure was superior obviously.

Abstract: The anti-seismic behavior of RC frame with buckling restrained braces (BRBs) subjected to severe earthquake action in seismic region was investigated in this paper. A design process of the buckling restrained braces used for stiffness-deficiency concrete frame structures was given, the design of the buckling restrained braces was conducted for a common frame structure, the layout of these braces in it was given by taking an actual engineering for illustrations, and the static analysis and time-history dynamic analysis were also performed. The results of computation showed that the use of buckling restrained braces has led to several functional improvements, such as the increase in structure stiffness, reduction of story displacement, and improved energy dissipation ability when compared with the frame without such braces. Analysis results showed further that RC frame with BRBs could absorb and dissipate seismic energy more effectively, improving anti-seismic performance of the framed structure.

Abstract: In this paper, a damaged R.C. frame with special-shaped columns has been strengthened for earthquake resistance. The strengthening method combines wrapping steel outside and stick steel. The experimental research on seismic behavior of the strengthened frame was performed. Through the quasi-static test, the load-displacement hysteretic curves under horizontal low-cycle loading are given, and the failure modes of the strengthened frame structure are summarized. This paper gives the analysis of its bearing capacity, stiffness deterioration, energy dissipation capability and ductility property. After comparing the strengthened frame with that before damaged, we draw a conclusion that the method of seismic strengthening in this paper can effectually improve the carrying capacity of damaged R.C. frame with special-shaped columns, and make the strengthened frame have better ductility.

Abstract: The study of this paper focuses on the seismic performance of a new complex tall building-FSRMW (frame-supported-reinforced-masonry-shear-wall).The new structure combines the advantages of RMW (reinforced-masonry-shear-wall) and FSRCW (frame-supported- reinforced- concrete-shear-wall) and have good economic value and extensive use value.Big space can be gained by using the structure, which provide a new appropriate selection for the design of hotel, multifunctional office building and dwelling house with shop at bottom. Substructure pseudodynamic testing were adopted to carrying out the seismic testing of 1:4 Reduced-scale models of FSRMW.Seismic evaluation of this structure has been carried out by substructure pseudodynamic testing of 1/4-scale specimen.The dynamic response of the tested structure under the influence of earthquake excitation is analyzed.The horizontal bearing capacity and the damage degree of the test model are investigated. The testing are cited to illustrate that the seismic performance of the structure(frame-shear-wall-supported reinforced masonry shear wall) is better than that structure(frame- supported reinforced masonry shear wall) and can be satisfied with the design request of 6-8 degree seismic zone.

Abstract: The performance-based seismic design of structure is in a research and development situation. A method is proposed in this paper to adapt the present demand. This method is based on the current Chinese code for seismic design of buildings. In design process, the earthquake action and lateral displacement are considered, and thus the design spectrum curve for equivalent single degree of freedom system is established. Thus the performances of structure at different earthquake levels are obtained and checked to satisfy the design requirements. After accomplishment of design, an elasto-plastic static analysis of structure may be conducted to fully examine its performance.

Abstract: Based on the dynamic characteristics analysis results of a precise three-dimensional finite element model, the earthquake responses of the bridge are analyzed in this paper. The influences of cable local modes and stabilizing cables on the seismic response are investigated by using different mode combinations and different models. It is found that the influence of cable local modes is negligible on the side towers while significant and not negligible on the main tower; the influence of the stabilizing cables is significant and not negligible on side towers, while minor and negligible on the main tower. As for the deck displacements, the influence of cable local modes is minor and negligible, while that of longitudinal stabilizing cables is significant and not negligible.

Abstract: Seismic response of a multi-span bridge is investigated in this study using an Internet based testing platform. The platform, NetSLab, was developed based on client/server concept along with a proposed data model and communication protocols. The platform is capable of transferring control and feedback data and signals among remotely located structural testing laboratories or computers connected by Internet. In these tests, a three-pier bridge system was simulated in which a Glass Fiber Reinforced Plastic (GFRP) retrofitted reinforced concrete pier was tested physically in Hunan University and a Carbon Fiber Reinforced Plastic (CFRP) reinforced concrete retrofitted pier was tested physically in Harbin Institute of Technology and the third one was simulated numerically in Tsinghua University. The bridge was loaded to simulate the responses under ground motions corresponding to earthquake hazards for a highly seismic location with 63%, 10%, 2% chance of exceedance in 50 years. The experiments demonstrate that the bridge structure with retrofitted piers has adequate behavior under earthquake loading even in areas of high earthquake intensity.