Advanced Materials Research Vols. 243-249

Abstract: The increasing world population and the shortage of adequate housing create an enormous demand for future housing with an expectable demand for sustainable solutions. The low-emission construction model of steel building system could be introduced and promoted in the civil building. There are four main ways including the standardized design, industrialized production, assembly of construction and social services to develop this model which can meet the demands of the function goal, the low-emission goal and the cost-benefit ratio evaluation criteria. Which way should be applied as the uppermost one is the key problem to realize the environment protection strategy scientifically in housing industry. The evaluation model was proposed and the AHP method was applied in calculation to draw the conclusion that the standardized is most important countermeasure.

Abstract: A triangular transfer hall is planned be built to distribute passenger flow rationally and improve multi-line transfer capability in the city of Shanghai, China. A large-scale reinforced-concrete bracing system, which is established to ensure the stability of the foundation pit, will be demolished with the completion of foundation pit. The influences of construction vibration on the surrounding environment are concerned. An evaluation method, which is generally applied to the ground vibrations caused by operation of machines, road and railway traffic, and construction activities such as piling and blasting, is then extended to assess the ground vibrations generated by structure demolition. It is found that the ground vibrations generated by demolition construction will affect the environment and human activities if without any vibration control measures.

Abstract: The main purpose of this paper is to evaluate the influences of construction vibration, which is generated by structure demolition, on the structural safety and stability. As presented in the companion paper, the influences of construction vibration on the surrounding environment were assessed. In this paper, another issue is concerned. For this purpose, field measurements are conducted on site. Then the obtained data, mainly the structural strain are analyzed by the presented evaluation method and compared to the allowable strength values suggested by the existing code. It is found that the ground vibrations generated by demolition construction will not cause harmful effects on the structures.

Abstract: The attenuation of ultrasonic pulse velocity in various sized concrete specimens under uniaxial compression loading is tested. Tests were conducted on prisms of 25×25×50 cm fabricated with dam concrete(maximum aggregate of 80mm),and standard 15×15×30 cm prisms,10×10×20 cm prisms which were made with the wet-screened components of dam concrete. Ultrasonic attenuation has been shown to increase significantly as distributed damage in concrete increases. Large changes in attenuation with increasing damage levels were found for all specimens at all power levels. Results also show that the rule of ultrasonic propagation in concrete is apparently affected by the scale effect and the effect of wet screen sieve of aggregate. These conclusions proposed can be applied to determining the extent of damage of mass concrete due to the complex load and other environmental effects.

Abstract: Through tensile tests of shape memory alloy(SMA) wires, bars and plates, this paper analyzes hysteretic energy-dissipating capacities of these smart SMA materials in cyclic loading conditions. According to the test results, this article demonstrates the influence on energy dissipating capacity of SMA wires, bars and plates by different strain amplitudes, loading frequencies, cyclic numbers and pre-strains, then obtains change rules of hysteretic energy-dissipation. The test results show that the SMA wires is better than the other two SMA bars and plates, the SMA wires, bars and plates had better to be training before civil engineering application.

Abstract: In this study, carbon fiber reinforced polymer (CFRP) laminates that were under three-point bending load within and without initial impact damage, were detected and monitored by ultrasonic C-scan method. The defect morphology at various load levels was recorded. The dynamic monitoring for the growth of delaminations in CFRP laminates was acquired, and it provided an experimental evidence for the health monitoring on CFRP in service.

Abstract: This paper presents some selected results obtained from the field measurements of wind effects on Guangzhou International Sports Arena (GISA) during the passage of Typhoon Fanapi in September, 2010. The field data such as wind speed, wind direction and acceleration responses, etc., were simultaneously and continuously recorded during the typhoon. The measured acceleration data are analyzed to obtain the information on dynamic characteristics and wind-induced response of the large-span roof structure. The first four natural frequencies and vibration mode shapes of the roof are identified on the basis of the field measurements using the stochastic subspace identification (SSI) method and comparisons with those calculated from the computational model of the roof are made. The damping ratios of the roof are also identified by the SSI method and compared with those estimated by the random decrement method, and the amplitude-dependent damping characteristics are presented and discussed. Furthermore, the field measurement results are compared with the wind tunnel test results to examine the accuracy of the model test results and the adequacy of the techniques used in wind tunnel tests.

Abstract: The Guangzhou New TV Tower (GNTVT), completed its construction in May 2009 in Guangzhou China, is a super tall tube-in-tube structure with a total height of 600m. A complicated structural health monitoring (SHM) system consisting of over 700 sensors has been implemented to the GNTVT for both in-construction and in-service real-time monitoring. This implemented SHM system has monitored the structural responses of the GNTVT after having completed its construction under different loading events (the typhoon, the earthquake and normal wind loading conditions). Firstly, the time history and PSD of the acceleration response under different loading events have been compared. Secondly, the modal properties (modal frequencies, mode shapes, and damping ratios) of the structure under different loading events have been identified. The results of this paper supply some references for better understanding the dynamic characteristics of supertall under different loadings.

Abstract: The electrical responses of carbon black filled silicone rubber to cyclic loading were investigated by electrical resistance measurements. Results indicated that the resistance of specimen appeared irreversible decrease in the earlier cycles of the first group test. The relation of the resistance and uniaxial cyclic loading are repeatable after 5 cycles while the irreversible micro-cracks are almost no longer generated. The resistance of each effective conductive path, the number of effective conductive path and average effective cross-sectional area of the insulating film between the adjacent conductive particles are key factors of the piezoresistivity.

Abstract: The fiber grating sensor with its unique advantages in the structural health monitoring used and more extensive. Based on Fiber Bragg Grating as an example, this paper expounds the FBG sensor system integration method, the principle of fiber grating sensors, aiming at temperature drift characteristics of FBG, proposes a new method of temperature drift compensation by using metal platinum resistance. On the other hand, the existing fiber grating monitoring system is used mostly in the series of topological way, which impacts of the sensor's survival rate, this paper proposes a new method of combining the series-parallel topological way, using relatively cheap couplers, increasing the survival rate of the sensor, thus improving the efficiency of structural health monitoring.