Out-of-Plane Flexure of Masonry Panels with External Thermal Insulation

The combined seismic and energy retrofit of existing aged buildings represents a topic of importance for the building stock. The current study investigates the out-of-plane performance of a specific type of thermo-insulation scheme with panels attached on the external facades of multistory buildings. The investigation was carried out through flexure tests of prototype masonry specimens. From the comparison of their flexural performance, with or without thermo-insulating attachments, the influence of thermal insulation on the out-of-plane behavior of clay brick masonry is demonstrated. It was found that when the thermo-insulating attachment is in tension from such out-of-plane flexure of the masonry facade it performs in a satisfactory way and gives an increased flexural capacity for the assembly. The thermal insulating panels, although partially debonded from the masonry substrate at a limit-state, do not collapse, even when the masonry panel develops large flexural cracks. This is due to the presence of the used plastic anchors. When the thermo-insulating panel is subjected to compression during such an out-of-plane flexure the resulting increase in the out-of-plane load bearing capacity is relatively small. Based on these observations it can be concluded that such thermo-insulating panels may also lead to a less vulnerable seismic performance than that of the same masonry panel without this type of thermo-insulating attachment. This was also confirmed when the in-plane behavior was considered from a separate investigation already published. The employed numerical modeling was successful in simulating the most important aspects of the out-of-plane response of the tested masonry wallets with or without thermo-insulating attachments. The good agreement with observed performance as well as the general nature of this numerical simulation confirms its validity for further use.

Out-of-plane flexural testing and stiffness response of concrete masonry walls with NSM steel reinforcement

Near-surface mounted (NSM) reinforcement is used to retrofit masonry structures for increased strength and resiliency; however, its application to new masonry construction remains largely unexplored. Four masonry walls measuring 3.2m tall were constructed from hollow concrete blocks to assess the potential of NSM reinforcement to increase flexural stiffness. Two of the walls were reinforced conventionally, and two were reinforced with NSM bars. Each wall had a total area of steel reinforcement of 600mm2 and was loaded under conditions of third-point out-of-plane flexure. All four walls had similar flexural strength, ranging from 24kNm to 26kNm; however, the stiffness (determined using direct measurement of curvature, curvature calculated using conditions of equilibrium and compatibility, and the load displacement response) of the NSM reinforced walls was twice that of the walls with conventional reinforcement. The flexural stiffness of the masonry walls was underestimated by current Canadian design standards provisions under low out-of-plane loads.

Modelling of Auxetic Foam Embedded Brittle Materials and Structures

Building structures use brittle materials extensively. Under impact or blast loads these structures perform poorly due to tensile strains caused by Poisson’s effect normal to the direction of such loadings. Auxetic materials exhibit negative Poisson’s ratio – a property which can be exploited to eliminate those tensile strains. In this study, Auxetic layers embedded masonry is modelled using a representative volume element (RVE) with periodic boundary conditions and an explicit finite element (EFE) modelling method for a boundary value problem of a masonry wall with an Auxetic foam rendered face is subject to out-of-plane load. The RVE is limited to in-plane loads only and hence subjected to in-plane shear and compression and the EFE was used to assess the performance under out-of-plane loading. The results show significant post-yield strain hardening under axial compression and in-plane shear and high increase in capacity for walls under out of plane flexure.

Determination of the Eccentricity of a Rotor by Impulse Excitation Technique of Vibration

The aim of this paper is the development and validation of an impulse excitation technique to determine static imbalance of a rotor. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone. In determining the center of mass three measurements are needed: one in plane flexure, and other out of the plane flexure, to which is added a measurement for a balanced rotor. By the means of Finite Element Method (FEM), the natural frequencies and shape modes of two rotor specimens are determined. The analysis is carried out in balanced condition as well as unbalanced one, after artificially induced imbalance. The vibration responses of the specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform (FFT). To validate the results of the modal parameters estimated using Finite Element Analysis (FEA) these are compared with experimental ones.

Research on the Floating Motion Platform for Detecting Surface Defects in KDP Crystal

The ultra-precision floating motion platform is the key device for equipment detectingand processing optical elements, and this paper mainly studies the floating motion platform used fordetecting the surface detects in KDP crystal. The load capacity of air cushion supporting the floatingmotion platform is studied theoretically and experimentally, and finally the supply pressure of thefour air cushions were optimized under the guidance of its load characteristic curve. The structureparameter of plane flexure hinge, a key part of floating motion platform, is optimized and thesimulation results show that the optimized plane flexure hinge can eliminate the disturbance inZ-direction obviously, which is produced by the two motors. Finally the support position of crystalholder is optimized by means of static and modal analysis; and the set of optimized support way canmake the maximum deformation of the platform reducing by 2μm and make the 1st order naturalfrequency increase from 49.078Hz to 51.787Hz.