Advanced Materials Research Vols. 374-377

Abstract: The inner and outer surfaces of concrete lining in deep alluvium freezing shaft are exposed to different temperatures, taking the hydration heat of cement for pyrogen. Additional stresses are therefore observed in concrete lining, owing to its marked temperature drop at early ages. This paper makes a numerical calculation of the temperature and the thermal stress on freezing shaft lining by finite element methods and engineering monitoring. The results reveal that the concrete of shaft lining has a high heat-release rate in the early age. And the time when shaft lining reaches its maximum temperature is 4 days earlier than it reaches its maximum thermal tension stresses. At the time of one day after the shaft lining pouring, the inner and outer surface of shaft lining will crack owing to its hoop tension strain is greater than ultimate tension strain. The crack of concrete will increase with the modifications of temperature.

Abstract: The shear-type friction damper using aluminum alloy as the friction material were designed and tested under cyclical loading to investigate the effect of the lap gap to the frictional performance. The test results indicated that the dampers with a lap gap could also absorb energy stably with the same hysteretic behavior as a general friction damper; the frictional force of the shear-type friction damper depended not only upon the bolts tension by the high-strength bolts that clamped the sliding steel plate but also strongly upon the scale of lap gap. The lap gap changed in a scale of 0.12mm only, the average sliding force has four times increase at a lower level of bolt tension, and a double effect to increasing sliding force at the higher level of bolt tension.

Abstract: In this paper, the experimental study on the self-tapping screw’s pullout resistance in the wood structure was conducted. Domestic ordinary screws were used together with imported or domestic wood to fabricate 6 screw connection specimens in wooden walls. Then monotonic loading tests were conducted and it can be concluded that, the common round screw connection strength mainly depends on the failure mode, the lack of cooperation effect significantly influences the strength of screw connections, and the dispersion of screw connection stiffness is high. So, to obtain formulae for the self-tapping screw connection strength and stiffness by further experimental study will be very necessary.

Abstract: The evaluation of the extreme hydrodynamic forces-induced dynamic response in bed is particularly important for coastal geotechnical engineers involved in the design of the foundations of marine structures at estuarine area. As the two main sorts of extreme hydrodynamic forces in Qiantang estuary, tidal bore and storm surge are considered in this work. This paper presents an analytical solution of the tidal bore induced estuary bed response. State-space method together with Laplace-Fourier transform techniques are used to solve the governing equations. The tidal bore-induced response of estuary bed can be calculated by using the matrix theory, boundary conditions and inverting integral transform. Compared with the special solution in preceding literatures, it’s shown that the proposed method has the advantage of high calculation efficiency and accuracy.

Abstract: Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. The solitary wave theory can be considered good representations of tsunami, storm surge and nonlinear shallow water waves. Based on the same theoretical formulation mentioned in the Part I, we derive the analytical solutions for dynamic responses of an estuary bed to solitary wave excitation are studied by state-space method. State-space method together with Laplace-Fourier transform techniques are used to solve the governing equations. The solitary wave-induced response of estuary bed can be calculated by using the matrix theory, boundary conditions and inverting integral transform. Compared with the special solution in preceding literatures, it’s shown that the proposed method has the advantage of high calculation efficiency and accuracy.

Abstract: Wavelet transform can characterize the local features of the signal in the time domain and frequency domain, enlarges and identifies the mutation signal of the structural response at different scales as a new signal analysis tools. In this paper, based on the structural deflection curve, propose a wavelet-based method to identify the beam structural damage. Use wavelet function to decompose the deflection curve of the structure after injury. Determine the existence of damage by the change and distribution of wavelet transform coefficients, determine the damage location, and simulate a cantilever bridge to verify this method.

Abstract: The deformation tendency and order of magnitude for surrounding rock, expressing the state of rock mass, always change the construction schemes and treatment measures. The monitoring is the most important guarantee for safety construction and operation in civil engineering. However, due to the unsuitable monitoring sections and equipments selected, the budget remains stubbornly high. Most of business owners just carry out some of them or even give up the monitoring. This brings enormous hidden trouble to construct. Based on the Doupengshan highway tunnel, the optimal design method for safety monitoring was studied by comprehensive analysis of the geological conditions, the results of numerical modeling and monitoring data. The main aim of monitoring is to obtain the most poor condition information rather than all of them. It’s best to employ different type of monitoring instruments in order to verify results each other. That is to say, the monitoring of internal force or displacement can take the place of the convergence monitoring every two sections. The new monitoring design saves the budget 20% than origin one. The research result will guide the monitoring design for similar engineering.

Abstract: The hybrid seismic isolation system , consisting of the SMA strands-laminate rubber bearing combined with magneto rheological damper ,was explored, for the sake of improving seismic isolation efect of the SMA strands-laminate rubber bearing under great earthquake ，especially when level shear deformation of SMA rubber bearing is bigger(D>0.55d) ．So does its mechanical model. In this paper，we compare the SMA strands-laminate rubber bearing with the hybrid seismic isolation system. Simulation analysis results indicate that the hybrid seismic isolation system is able to achieve both low interstory drift and acceleration and,at the same lime，limit the base displacement．The security of isolated structure was improved largely.

Abstract: Theoretical study on earthquake damage under seismic load about of concreate structure，in order to better study the damage evolution mechanism of reinforced concrete frame structure in earthquake. The two-parameter seismic damage factor model,which is based on deformation and dissipation,was improved using the theoretical analysis method in this study .Using the three-level earthquake-resistant design damaging index based on the importance of structure as the collapse criteria for evaluation. Using the nonlinear dynamic finite element method and do a collapse numerical simulation analysis of a three layers concrete frame. Calculate the dynamic response and damaging factor of each time step, and study the damage evolution.The results show that the improved damage index calculating model can calculate both on the maximum damage index and structure damage index quantificationally and continuously and describe the process of collapse damage of the integral structure.

Abstract: A typical failure of the light framed arch bridge under frequently super loads is studied, by means of establishing the EFM solid models for the whole bridge and the bracing strut to analyze the failure mechanism of the bracing strut in the Pingzhai framed arch bridge from the mechanical behavior and some defect of the structure itself, simulating the deterioration of reinforced concrete in wet joint of the bracing strut. Based on the mechanics, a new practical method for restoring and reinforcing the above bracing strut is presented also, which has been proved to be successful in the engineering practice.