Papers by Keyword: Masonry Structure

Abstract: IIn the present study, Acoustic Emission (AE) monitoring technique is applied in order to characterize the brick masonry of two important military buildings located in Northern Italy: the barracks of Alessandria and Boves. The internal brick masonry walls of the two barracks object of the study are tested by two double flat-jack systems, in order to analyze the compressive strength of the structural material. Flat-jack testing is a versatile and powerful technique that provides significant information on the mechanical properties of historical constructions. The first applications of this technique on some historical monuments clearly showed its great potential. The flat-jack test method is only slightly destructive, and when double jacks are used, this test works according to the same principle as a standard compressive test. The difference is that it is performed in situ and the load is applied by means of two flat-jacks instead of the loading platens. During the tests, the stress-strain relationship of the masonry is determined by gradually increasing the pressure applied by the flat-jacks in the course of three loading-unloading cycles. Moreover, AE technique is coupled to the flat-jack testing, in order to assess the extent of damage in the masonry texture. Thus, AE technique makes it possible to highlight critical phenomena and fracture mechanics scale effects in the masonry by identifying the critical conditions, not entrusted to an analysis of the loading process (compression or shear), rather depending primarily on the distribution and evolution of crack patterns.

Abstract: The safety work of historical and monumental building heritage requires the use of innovative materials compatible with the high architectural value. The Fiber Reinforced Polymers (FRP) represent a valid alternative to traditional ones, and the carbon fiber sheets are very light and easy to glue to the masonry structures. However, the durability of the application of FRP sheets is still uncertain in the long time behavior, especially with regard to cyclic fatigue loads such as seismic ones. In this work an experimental analysis on a set of strengthened masonry walls under fatigue tests (loading and freezing-thawing test) has been carried out in order to evaluate creep effects. During cyclic tests in the laboratory it was possible to monitor the damage pattern through the acoustic emission (AE) technique. The AE monitoring is useful to estimate the amount of energy released from fracture propagation in the adherence surface between masonry and FRP sheet. The different phases of damage evolution are recognized through the analysis of AE data over time. In particular, the time dependence of AE counting number is useful to indicate the beginning of the unstable damage growth and predicts the possible failure of the specimens at the 80% of the test duration. Furthermore, a sudden decay in the AE frequency is detected during the last phase of the fatigue tests. These results illustrate the applicability and the advantages of AE technique for the monitoring of long-term damage growth in strengthened masonry.

Abstract: The paper is focused on damage detection of brick columns using the non-destructive method - modal analysis. The four brick columns, each made from four bricks and mortar, were tested. The two of them were made using one type of mortar and the second two using another type. The differences in the dynamic behavior were investigated using multi reference modal analysis. Conclusion summarizes the comparison of dynamic behavior of columns and damage detection in some of them.

Abstract: In order to know seismic damage characteristics of multi-story brick masonry structure and improve its seismic capability, five kinds of earthquake damage or collapse forms of multi-story masonry brick structure are summed up based on earthquake disaster survey, each of which is analyzed with mechanics. And the failure mechanism of each seismic damage form of multi-story brick masonry structure are proposed, which provides effective engineering experience for the seismic or anti-collapse design of multi-story masonry brick structure. The research has the important significance in improving the seismic capacity of multi-story brick masonry structure and reducing the earthquake casualties.

Abstract: A full scale masonry model of two-floor and single bay was built in this paper and was strengthened by ring-beam and constructional column. And then pseudo-dynamic testing was conducted to study the time-history curves of displacement, velocity, acceleration response and restoring force in 7 degree rarely earthquake. Results show that the earthquake performance is steady and there are no visible cracks on the model after the testing. Windows and doors perform well because of the constraint of ring-beam and column, whereas failures often occurred when the structures were not strengthened. Seismic performance is largely improved by ring-beam and constructional column and the structure can resist 7 degree rarely earthquake.

Abstract: This study simulated the condition of below-wall raft foundation supported masonry structure perpendicularly penetrated by shallow-buried and mining tunnelling using 3D MIDAS/GTS software with consideration of the coaction of structure, ground and tunnel. The load and deformation patterns of structure before and after the penetration of tunnelling excavation face were evaluated. Results from the study showed that: when the horizontal distance between the central axis of the structure and the axis of the tunnel L=0 m, the settlement of the structure increased before and after the penetration of tunnel through the masonry structure, and the settlement became stable after the tunnel passed through a certain distance (approximately 2.4 times of the thickness of ground cover); the structure settled overall and the difference of settlement was relatively small; the maximum first principal stress P₁ and the maximum deformation rate E₁ showed an overall increasing trend. With the increase of L from 0, inclination of the structure towards the tunnel was witnessed, the settlement of foundation appeared to be linearly distributed and the inclination rate of foundation first increased then reduced; P₁ showed a decreasing trend and E₁ first reduced, then increased and decreased again.

Abstract: The results of this paper are being summarized in a series of articles categorized into the principal properties of the mortars, for example compression strength, admixtures, air-content and water cement ratio, and the impact of those properties on bond strength were analyzed. The second purpose of this article deals with the relationship between brick’s properties with bond strength. The results shown that those effecting factors mainly through make an influence on the amount of hydration products and the bonded area to determine bond strength.

Abstract: In the program, dynamic experiments were carried out on two scale models of the recycled tires-asphalt sands (RT-AS) base isolation device. The device consists of recycled tires and the mixture of asphalt and sand at the ratio of 3:1 in weight. Since the tires consists of rubber, the elastic deformation can consume energy, and for asphalt-sands , the friction between sands and the elastic deformation of the mixture of asphalt-sands can also consume energy, RT-AS base isolation device can help the superstructure consume part of energy from seismic wave. In this way, the device can not only can protect environment through recycling worn tires, but isolate the structure from the shaking ground and decrease the damage to the superstructure. To investigate the effectiveness of a new seismic isolation device (RT-AS),two scale models of one-storied masonry structure were built up according to the ratio of 1:12. During the experiment, The WE-Z30 Precise Mini-seismic Shaking Table System was employed with the seismic wave of the earthquake in Wen Chuan in 2008 according to the record of NS direction of Shifang seismographic observatory, The experiment was conducted under three level of vibrating load using vibration exciter, and the positive effect of RT-AS device on reducing the acceleration response of the building was discussed.

Abstract: In this paper, I use the finite element software abaqus to simulate the damage form of masonry walls in the case of force. Advantages and disadvantages of various simulation methods are fully considered. Masonry walls are considered homogeneous isotropic continuum,was built by using integrated model. And I adopt concrete damage model to define material properties. The results showed that the model in this paper well simulated the failure characteristics of the wall.

Abstract: This paper presents the 3D dynamic crack growth simulation of unreinforced baked brick shear wall by using particle discretization scheme finite element method (PDS-FEM), which is efficient and capable of computing bifurcation/branching in cracking. The technology of fast modelling of bricks and cements by applying VB script in AUTOCAD is illustrated briefly. The shear wall including mortar joints is modelled in detail. The model parameters are calibrated by using standard static tests. Since the computation cost is high in structural level fracture analysis, parallel computation technology is employed. Finally, with two-phase failure criterion of mortar under multi-dimension stress state, the performance of low and high loading speed is compared. The numerical results verify the availability of dynamic fracture analysis of masonry structure by using PDS-FEM.