Advanced Materials Research Vols. 639-640

Abstract: This paper aims to put forward a new method of strengthening the existing bridges with narrow decks and low bearing capacity to overcome the high cost and pollution problems in dismantling them. The method, strengthening bridges by built stringers and cross beams, is by widening some parts of a bridge. Based on the basic theory of finite element, we have set up an analysis model of strengthening the bridges by widening, which helps to demonstrate the rationality of this method. Meaningful conclusions have been drawn from the parameter analysis of the rigidity of the new widening stringers, the rigidity of the new cross beams and the relative settlement of the new and the old foundations. This method can be referenced by the reinforcement and maintenance of medium and small bridges.

Abstract: Corrosion is one of the major problems for the existing structures and may cause significant decrease in drift capacity and strength of RC (reinforced concrete) columns due to reduction of effective cross-section of reinforcing bars, alteration of bond characteristics between reinforcing bars and concrete, and cover cracking along the reinforcing bars. Therefore, rehabilitation of corrosion-damaged columns is extremely important, particularly in seismic regions and if a substandard construction methodology is used. In this paper, an experimental work is presented on the seismic performance of rehabilitated/retrofitted substandard RC columns, which were damaged due to corrosion of reinforcing bars. For this purpose, four substandard columns were tested under high axial load and reversed cyclic lateral loads. The columns were constructed with extremely low quality concrete and plain round bars. The spacing and details of transverse reinforcing bars did not comply with the code regulations as well. Then, the specimens, except the reference one, were subjected to accelerated corrosion process. One of the corrosion-damaged specimens was tested before rehabilitation/retrofitting procedure, while the other two specimens were tested after rehabilitation/retrofitting procedure. The test results clearly demonstrated the efficiency of the applied rehabilitation/retrofitting procedure, both in terms of strength and ductility. Furthermore, analytical predictions about strength and failure modes of the specimens are compared with experimental findings.

Abstract: At present, the round steel pipe section is used more often in the transmission tower. This paper introduces the strengthening measures to the steel pipe node, which shows that ring-stiffener is a kind of very good strengthening measure. Then it is focus on the research of ultimate bearing capacity of the space type KK-intersecting nodes by the ANSYS finite element analysis software. Try to find the differences between the node with ring-stiffener and without ring-stiffener. Get the conclusions through the analysis and comparison, and provide a reference for practical engineering.

Abstract: The test process and analysis of 3 walls and the expand calculation about walls are introduced in this paper. Through a series of low-cycle repeated load experiments, the paper do comparative studies on the seismic behavior of concrete shear wall and brick wall strengthened with reinforced concrete splint firstly. Because of the limitations of experiment, the study focuses on the unreinforced brick wall, the 120mm shear wall, the brick wall strengthened with double 60mm reinforced concrete splint and the brick wall strengthened with single 60mm reinforced concrete splint. On the basis of the experiment, we use the finite element software to establish a rational numerical model. Through the finite element analysis, the paper expands the calculation about walls and makes up for the lack of experimental research. Based on the analysis results, we get the conclusion that the reinforced concrete splint can enhance the seismic behavior of the unreinforced brick wall. Taking no consideration of structures’ integral stability, the seismic behavior of brick wall strengthened with double 60mm reinforced concrete splint is equivalent to the 120mm shear wall.

Abstract: Strengthening the brick walls with reinforced concrete splint is a conventional and effective method of strengthening masonry structures. To the method, the text process and analysis of 6 brick walls strengthened with reinforced concrete splint and the existing calculation analysis method about bearing capacity are introduced in this paper. Through the series of low-cycle repeated load experiments, we study the different performance between unreinforced brick wall and brick wall strengthened with reinforced concrete splint. Based on the analysis, we find the seismic capacity of the brick wall strengthened with reinforced concrete splint such as the bearing capacity and ductility is enhanced clearly. Meanwhile, the calculation parameter in technical specification for seismic strengthening of buildings has good accordance with the experiment results.

Abstract: The mechanical properties of fire-damage reinforced concrete columns strengthened with bonded steel angles were studied. Nine specimens were tested, including three normal temperature controlled columns, six heated under ISO834 standard fire. After exposure to fire, three of the six were rehabilitated with the bonded steel angles. It was shown by test results that the destructive properties of reinforced concrete columns with bonded steel angles may change and the small eccentric compression specimens may become large eccentric compression due to the steel angles increased the amount of steel in the tension zone of the specimen. In this research, compared with these under normal temperature, the bearing capacity of specimens which were exposure to fire was only ranged from 0.25 to 0.37 times. But the bearing capacity of specimens rehabilitated by the bonded steel angles can increase to 2.86 to 4.04 times of the originals and it can reach to the level of that in normal temperature.

Abstract: According to the characteristics of the aluminum conductors, coated-steel reinforced (ACSR), combined the feature that isotropic and continuity of the folded yarns, establish the calculated equation of the Poisson ratio of the discrete and anisotropic wires. After given the calculated equation of stiffness of large cross-section wires, we obtained the calculated equation of elastic modulus, shear modulus and Poisson ratio. These wires stiffness not only reflect the characteristics of the composite material, but also provide guidance and reference for the mechanical calculation of the wires and installation of overhead conductor and ground wires and the following equation also has certain value in mechanics calculation and lines of construction.

Abstract: Pseudo-dynamic testing using force- mixed control strategy is presented for structures with large stiffness. In this proposed method, the displacement response of the specimen measured by a linear variable displacement transducer with higher resolution than that in the actuator is fed back. A proportional-integral controller is adopted in the outer displacement control loop, and a coefficient CF is employed to convert the displacement to force command. Numerical and experimental validations show that this method exhibits excellent performance in terms of stability and accuracy if proper controller parameters are adopted and is superior to the conventional displacement control method for large-stiffness structures.

Abstract: A remotely collaborative pseudo-dynamic testing platform for bridge structures has been developed based on NetSLab system. It can be used for seismic performance investigation of large-scale bridge structures by combining the Internet and sub-structure technology. The testing platform consists of three modules: control center, physical tester and virtual tester. Through a network communication platform, the operation of receiving and feedback of test data between various modules can be realized. Based on the previous research work, a further improvement of the dynamic structural model, the finite element numerical analysis and the rational division of sub-structure has been achieved. A series of remotely virtual collaborative pseudo-dynamic test of bridge structures has been conducted to verify the feasibility of the test platform.

Abstract: A networked structural laboratory system NetSLab has been developed for shared use of laboratory facilities and computing resources. The NetSLab consists of a network based communication platform and a series of hybrid testing programs. In this paper, a hybrid testing program for simulating seismic responses of composite frame structures with buckling restrained braces has been developed. The entire frame structure is simplified as a multi-degree-of-freedom model and only the relationship between story shear force and story drift is considered. The hybrid testing program consists of three types of modules, namely control center, physical tester, virtual tester. Control center organizes testing procedure and handles numerical integration. Physical tester and virtual tester generate restoring forces of substructures using actual testing equipment or numerical simulation. The substructure tested can be any continuous multi-story or a single brace taken from the entire frame structure. A serial port communication method is utilized to transfer request and feedback data between physical tester and the control computer of Popwil electro-hydraulic servo system. A series of virtual and physical hybrid tests of composite frame structures with buckling restrained braces under earthquake excitations were carried out. The results validated the reliability of the testing program.