Advanced Materials Research Vols. 250-253

Abstract: Based on mechanical characteristics of high rise structures with strengthened stories, the author performed direct displacement based seismic design on a high rise structure with 2 strengthened stories according to the direct displacement based seismic design principle. The performance levels are set to be “serviceability” under medium earthquake and “life safety” under major earthquake, respectively. The design procedures are with the following features: (1) Definition and selection of “key” stories are based on mechanical characteristics of high rise structures with strengthened stories; (2) Determination of mode number and calculation of horizontal earthquake action verified the availability of the design procedure; (3) some new ideas are proposed to improve the earthquake action calculation and structural performance control. The design procedure verified the effectiveness, feasibility and availability of the proposed direct displacement based seismic design method.

Abstract: A smart piezoelectric friction damper (SPFD) is presented based on improved Pall friction dampers and its damping force model is analyzed. The wind-induced vibration control of Benchmark model using semi-active control strategies based on the classical LQR is studied. The results of simulation analysis show that the semi-active control effects of the standard wind-control model with SPFD is evident. Compared to uncontrolled structures, the wind-induced vibration responses of the controlled structures are effectively reduced. In addition, parameter optimization of the semi-active control system based on the limit Hrovat optimal control algorithm is carried out. The analysis shows that the robustness of the semi-active control system to the stiffness uncertainty of Benchmark Model is very good, but the robustness to the damping uncertainty is not so good.

Abstract: Fatigue damage becomes an emerging problem in lots of concrete structures which will subject to cyclic loadings during their working life. This paper presents a study on interfacial shear fatigue performance of a high-strength concrete structure strengthened by carbon fiber-reinforced plastic (CFRP) plate, which has been established as an effective method for rehabilitation and strengthening of concrete structures. Based on the static test, a new experimental investigation of the shear fatigue performance along the concrete-plate interface under the low cycle fatigue load in the condition of R=0.1 is presented. The main variable is the concrete strength. Compared with the static ultimate strength, fatigue strength decreases. Therefore, a safety factor of the fatigue strength at the interface of CFRP and concrete should be applied in design.

Abstract: According to the ancient wooden architectural features, the different destructions of wood structures are discussed. On the basis of the importance and principle of Chinese historic building reinforcement and maintenance, ancient architectural wood structure reinforcement is introduced. Finally several proposes about the Chinese historic building reinforcement maintenance is given.

Abstract: In order to discuss the effect of earthquake and dynamic ice loads to a bridge pier, this paper considered the effect of added mass of dynamic water, and it deduced the dynamic equilibrium equations for a bridge pier subject to earthquake and dynamic ice loads on the basis of nonlinear Morision equation. Using numerical analysis method, it discussed the dynamic response of a bridge pier subject to different types of earthquake loads, forced ice loads, and both earthquake and forced ice loads. Through comparing the pier responses in different work conditions, it discovered that the dynamic responses of the bridge pier subject to forced dynamic ice loads rise and fall severely at the time of ice buckling broken periodic change. The coupling effects of forced dynamic ice loads and earthquake especially near-fault earthquake enhance the dynamic response of bridge pier significantly.

Abstract: A numerical calculation model of the dynamic response of a tall building -base- foundation system was built. In the modeling, the beams, columns and stakes was described by the BEAM188, and the floor slab described by the SHELL63. The natural frequency and mode of the vibration of the system were calculated by using ANSYS and the response of the system under both horizontal and vertical seismic action were calculated by using the module, Time-History Seismic Analysis, with the elastic modulus of foundation being set as 20MPa, 20GPa, and 30GPa respectively. The result shows that, the horizontal displacement amplitudes of the system were 0.198m, 0.095m and 0.095m respectively under horizontal seismic action, and were 1.13×10^-5m, 1.4×10^-11m and 1.4×10^-11m respectively under vertical seismic action. So the structures on soft foundation take on stronger capacity of resisting vertical earthquake than that on rigid foundation, and the opposite is the case of resisting horizontal earthquake. The story drifts are respectively 6.2×10^-12m, 2.34×10^-6m and 3.46×10^-6m under horizontal seismic action, and respectively 4.3×10^-12m, 4.85×10^-6m and 4.78×10^-6m under vertical seismic action. The story drifts on soft foundation under both horizontal and vertical earthquake action are much less than that on rigid foundation.

Abstract: Some damages of piles can be unavoidably caused by natural disasters and extreme constructions. Usually, piles can be cut into two parts by shocks such as earthquakes, that is fracture piles. Obviously, the dynamic behavior of a single fracture pile is different from that of normal piles. But the problems of inspection, appraisal, repairs and maintenance of piles will face us. By studying dynamic behavior of a single fracture pile of vertical oscillation, the paper introduces a dynamic model of the fracture pile. The model is not perhaps perfect, but it is a method to begin to study the vibration of the fracture pile. The individual example does not detail the dynamic characteristics of the fracture pile, but the tendency of the curve of the dynamic impedance versus frequency can give a mainly rule.

Abstract: In the past many researchers studied dynamic stiffness and damping coefficients of surface and embedded rigid foundations of arbitrary shapes in the elastic homogenous half space. Dynamic stiffness and damping coefficients were obtained by using regularly shaped foundations instead of arbitrarily shaped ones. Obviously, the calculating methods were not perfect. In addition, the two parameters mentioned above were calculated only in the case of a single foundation. But the cases of two or more foundations were not presented because the interactions between foundations were not considered in all present papers. This paper eliminates two faults named above by using the assumption of the plane strain and of dynamic foundation-soil interaction factors. The calculating method of dynamic impedances presented by the paper proved to be accurate and practical.

Abstract: A large under-construction chimney at BALCO Power Plant in central India collapsed on Sep. 23, 2009 under severe stormy weather, causing serious casualties and massive economic losses, while another, similarly built, survived. So far, there has been no strict and scientific analysis on the cause of the accident. In this paper, finite element method is used to simulate the effect of wind loads and the whole collapse procedure based on the investigation of information about the design, the construction, the site related records, etc. The results show that the initial part of the chimney destroyed is the top of the structure (specifically the construction platform and the partial top cylinder wall of the chimney); then the debris from the top fells and crashes the lower part of the structure, eventually leading to the whole structure collapsing. The analysis results are basically consistent with the observation of the debris and the toppling scene and what the witnesses described, and scientifically clarify the actual cause of the chimney collapse. In addition, by comparing the chimney design codes between the USA and China, along with the analysis results, some suggestions are proposed to prevent similar accidents in chimney projects.

Abstract: The debonding behavior at the interface between fiber-reinforced plastic (FRP) sheet and concrete is a key problem for the application of FRP plate, which has been widely applied in the civil engineering for rehabilitation and retrofitting of conventional structures. This paper presents the experimental and nonlinear finite element analysis results of the CFRP-strengthened high-strength concrete member. On the basis of the test, considering of the adhesive layer, explicit finite element is used for simulating the shear failure of CFRP-strengthened concrete, obtain the whole process of structure deformation development, describe the conformation and development of crack and the failure mode. The FE result coincides with the experimental result.