Advanced Materials Research Vols. 919-921

Abstract: Acoustic thermometry method is used to measure two-dimensional temperature distribution of a circular boundary temperature field experimentally. The measured temperature field is compared with a point-by-point temperature measurement, the results shows that the acoustic method is consistent with the point-by-point measurement which proves that it is reliable to use this method to measure the two-dimensional temperature distribution.

Abstract: This paper presents a first program of non-destructive tests carried out on two medieval façades and inside the main rooms of Palazzo Ducale in Venice, i.e. the room of Maggior Consiglio and the room of Scrutinio. A probably multiple leaf load-bearing brick masonry and an external cladding of polychrome stones compose these façades under investigation. The aim of the tests concern the improvement of knowledge about the construction technique and the mechanical features of these important historical facades. The program was set up after a preliminary historic investigation. Non-destructive and minor-destructive investigations (i.e. pattern surveys, endoscopic tests and georadar test) on the inner sides of the two walls of the area under examination were carried out for the analytical determination of the construction technique and structural characteristics, not clearly inferable from the literature.Due to the complexity of the structure and the transformations undergone in seven hundred years of life, and to the very limited investigable areas of the internal surface, the results of investigations cannot be extended to the entire structure. Nevertheless, these tests provide valuable clues to give a correct interpretation of the construction technique and to contribute to identify the possible mechanical properties, which provide knowledge about the health state of the building.

Abstract: Based on stochastic subspace method, the natural frequency of the bridge arch rib, damping ratios and vibration mold parameter was obtained by modal parameter identification of a concrete filled steel tubular arch bridge under ambient excitation, and the Midas Civil finite element software was used to establish a computational model of the bridge. Measured results and calculated results were compared, and the reliability of the identification results have been verified, the identified dynamic properties can be served as the basis in the finite element model updating, damage detection, condition assessment and health monitoring of the bridge.

Abstract: Based on firefly algorithm (FA), a novel method is proposed for moving force identification (MFI) in this paper. The basic principle of FA is introduced, some key parameters, such as light intensity, attractiveness, and the rules of movement are defined. The inverse problem on MFI is transformed into a constrained optimization problem and then can be hopefully solved by FA. In order to assess the accuracy and the feasibility of the proposed method, a beam-like truss bridge subjected to moving forces is taken an example for numerical simulation. The robustness of the method is also evaluated by adding noise into the structural responses. The illustrated results show that the proposed method can accurately identify two moving forces from incomplete structural response at only one strain sensor with stronger robustness.

Abstract: The City Hall of Mirandola was stricken and damaged by Emilia-Romagna earthquake sequence of May 2012. This paper presents the procedure for the structural monitoring control of a masonry historic building that presents a serious damage pattern. Structural monitoring was carried out with transducers installed to control the serious cracks that regards the main volumes of the building. The global structural health monitoring was useful to define the actual condition of the dynamic behavior of the damaged construction that are subjected to different mechanism. Ground penetrating radar allows to detect the depth of the cracks and the condition of the masonry. These researches are useful also for the structural future rehabilitation and to define the possible changes in the structural behavior.

Abstract: In order to solve the inverse problem on structural damage detection (SDD) in the field of structural health monitoring (SHM), a FGAPSO algorithm is proposed by a fusion of the genetic algorithm (GA) and the particle swarm optimization (PSO) in this study. For improving the simple GA with drawbacks of easy precocious and of lower computation efficiency, the real-coded GA is implemented, the chaotic logistic mapping is chosen for initializing population, the self-adaptive crossover-mutation operators and elitist strategy are employed. The GA is then mixed with the PSO algorithm for the population diversity and convergence by exchanging genes between two new populations internally and the goal of improving GA is attained at last. Further, some numerical simulations on a 13-bar planar truss structure with several damage cases have been carried out for assessing the performance of the FGAPAO. The illustrated results show that the proposed FGAPSO algorithm is better than any of conventional GA and PSO. Even for the slight damage case, it is still more feasible and effective for SDD.

Abstract: The paper presents a critical analysis of the structural response and the level of damage of a historic tower of Santo Stefano of Sessanio that was hit by the main L Aquila earthquake of April 2009. A FE model was constructed to simulate the structural behaviour during the seismic event. The presence of a reinforced concrete slab in the upper part of the tower probably cause a different dynamic behavior compared with the lower masonry circular walls. Have also been investigated boundary conditions at the base, the different mechanical property of masonry and the contribution of the stiffness of the wooden floors.

Abstract: Vibration is an important comfort issue for the metro surrounding buildings. Among the many methods of subway vibration control, building isolation is the necessary supplement to the track isolation for metro surrounding buildings with sensitive constructive forms or specific comfort needs. Laminated rubber bearings are widely used for the building isolation. In order to further improve the isolation effectiveness, researchers intend to use laminated rubber bearings with relatively thick rubber layers. However, the frequency dependency and temperature dependency are not well explored for the thick rubber bearings. And since constrains from the steel plates to rubber layers are relatively small for thick rubber bearings, its not clear if it is accurate to simply apply the equations for common laminated rubber bearings to the thick ones. In this paper, a compressive properties test is carried out for both thick and thin rubber bearings. Both thick and thin rubber bearings are manufactured by a kind of High Damping Rubber (HDR) and a kind of Nature Rubber (NR). The frequency dependency and temperature dependency are tested. The accuracy of applying the current design equations to thick rubber bearings is discussed based on the test results.

Abstract: Engineering structure often produces the crack in the use of a certain year, the crack will decline the stiffness of structure which affects the safety of the structure and the vibration characteristics of structure. A method of identifying the crack damage from beam by using the vibration modal displacement component to strutting the damage identification was put forward, the finite element models of beam which no crack, different position and different depth were established, the damage displacement modal parameters of beams pre and post were calculated, the change rule that the displacement modals variation of transverse component and displacement modals rate of change of axial displacement difference along with the different of the cracks depth and position was analyzed., The calculations showed that the sensitive to the crack position and depth along the crack direction displacement modal transverse component variation and change rate of the axial displacement difference can be used as the basis for crack damage identification of beam.

Abstract: Development of on-site fast detector using for waterproof membrane joint peeling strength has improved the waterproof membrane on-site construction quality evaluation level and construction quality decision capability. Detectors capabilities in two-dimensional movement and multi-angle detection fill the domestic gap. Verification test result of the detector shows that, the peeling force will fluctuate within certain scope with peeling of joints; the longer the membrane is stretched, the greater the error is; the error caused by angle deviation is about 7% and error caused by joint deviation is about 4%, and the test result satisfies the evaluation requirement on waterproof membrane joint peeling strength at construction site. The development of detector improves the construction quality, construction management and acceptance of waterproof membrane.