BRJ – Volume 59, Number 3–4, 2011

Peter Stanak, Jan Sladek, Vladimir Sladek and Slavomir Krahulec:
Composite circular plate analyzed as a 3-D axisymmetric piezoelectric solid . . . . . . . . . . . . 125 – 140
Robin Davis P.:
Performance of open ground storey building designed as per Indian seismic code . . . . . . . . . 141
Alaa M. Rashad, Osama A. Hodhod and Ahmed M. Ragab:
Effect of size and concrete cover thickness on the residual capacity of loaded
rectangular rc columns after heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 – 174
Alexander Tesar and Jan Bencat:
Dynamic testing in monitoring of thin-walled bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  175 – 196
Ladislav Sator, Vladimir Sladek and Jan Sladek:
Meshless analysis of circular plate with variable bending stiffness . . . . . . . . . . . . . . . . . . . . 197 – 216
Peter Matiasovsky and Peter Mihalka:
Moisture induced deformations of calcium silicate boards . . . . . . . . . . . . . . . . . . . . . . . . . . 217 – 227

Abstracts

Composite circular plate analyzed as a 3-D axisymmetric piezoelectric solid
Peter Stanak, Jan Sladek, Vladimir Sladek and Slavomir Krahulec
A numerical analysis based on the meshless local Petrov-Galerkin (ML PG) method is proposed for a composite circular plate. A two-layer plate is considered with one layer made of piezoelectric material. Axial symmetry of geometry and boundary conditions reduces the original 3-D problem into a 2-D problem in the angular cross section. Nodal points are uniformly distributed in the analyzed domain,
but without loss of generality. Each node is the centre of a small circular sub-domain. The local integral equation (LIE) formulation is constructed from the equations of motion for the mechanical fields and quasi-static Maxwell’s equations on the chosen sub-domains. The unit step function is used as a test function in derivation of the LIE s. The Moving least-squares (MLS) method is applied for approximation of spatial variations of all physical quantities. Special coupling equations are introduced to ensure interface coupling of both layers. Varying electric loads applied to piezoelectric layer are considered in addition to mechanical load in order to suppress the plate deflection.
Keywords: meshless analysis, piezoelectric materials, moving least-squares approximation, axial symmetry

Performance of open ground storey building designed as per Indian seismic code
Robin Davis P.
Open ground storey buildings are very common in the urban Indian environment, as this kind of building provides parking space in the ground storey. It was learned from the recent past earthquakes that this type of buildings is one of the most highly vulnerable type. Under earthquake loads large lateral displacements are induced at the first floor level of OGS buildings. This results in large curvature in the ground storey columns. Bending moments and shear forces are also increased so that when compared to a bare framed building, ground storey columns show magnification in the forces. Design codes recommend a factor to account for such magnification of bending moments and shear forces. In the present study, comparative performances of four storeyed OGS framed buildings, designed as per Indian code, is evaluated by considering three cases of designed buildings. First case considered only gravity loads, to represent buildings type designed as per earlier codes. In the second case, the building is designed as per the existing code but without considering magnification factor 2.5. In the third case the building is designed as per the existing code (considering magnification factor 2.5) as it is. Nonlinear static pushover analyses of designed buildings were carried out including effects of infill walls. The relative performance of three cases is evaluated as per the Capacity spectrum method prescribed by ATC-40. The building designed with the magnification factor 2.5 is found to achieve the performance criteria specified for both rare and frequent earthquakes, compared to other two buildings. The factor suggested by the IS code is hence found to be appropriate to satisfy the building performance criteria as per ATC-40.
Keywords: open ground storey building, soft-storey, nonlinear static analysis, magnification factor

Effect of size and concrete cover thickness on the residual capacity of loaded rectangular rc columns after heating
Alaa M. Rashad, Osama A. Hodhod and Ahmed M. Ragab
The present research work has been planned to investigate the effect of column cross section size and aspect ratio on the resistance of elevated temperature. The investigation has taken into account different types of coarse aggregate and thicknesses of concrete cover. A total of thirty-six column samples have been tested. There were two main groups, gravel concrete group and dolomite concrete group. Each group containing three sets of column dimensions namely 100 × 150 × 700 mm, 150 × 150 × 700 mm and 150 × 200 × 700 mm. Each set included three different concrete cover thicknesses of 10, 15 and 20 mm. Among the thirty-six samples, there were eighteen samples tested directly at room temperature, so called control samples. The others were exposed to elevated temperature up to 650°C, for 30 min. Every sample was equipped with thermocouples to monitor the temperature distributions inside it at its mid-height. The experimental results showed that the residual load capacity of any sample was influenced by aggregate type, concrete cover and the cross sectional size. It has been found that there was a reasonably linear relation between the residual load capacity of the column and the ratio of exposed area to cross sectional area. Also the results showed that for the same thickness of concrete cover, the elevated temperature below the cover thickness was affected by the column size.
Keywords: RC columns, elevated temperature, concrete cover, axial load, aggregate Type

Dynamic testing in monitoring of thin-walled bridges
Alexander Tesar and Jan Bencat
Multi-functioning and interactive mechanics in dynamic testing and monitoring of thin-walled bridges are treated in the present paper. The approach enables multiple functions in dynamic testing and virtual monitoring of bridges made of integrated thin-walled members with their hierarchical configuration. Theoretical, numerical and experimental in situ assessment of the problem is presented. Some results of structural application are submitted.
Keywords: dynamic testing, interactive mechanics, multi-functioning, optimization, thin-walled bridge, ultimate behavior, virtual monitoring, wave propagation

Meshless analysis of circular plate with variable bending stiffness
Ladislav Sator, Vladimir Sladek and Jan Sladek
The paper presents the meshless strong formulation of the solution of thin plate bending problems of circular plates with variable bending stiffness. The 4th order governing partial differential equation (PDE ) is decomposed into two 2nd order PDE. For the approximation of field variables in the developed strong mesh-free formulation we use the Moving Least Square approximation scheme. The modified differentiation is proposed to increase the accuracy of higher order derivatives of field variables. The accuracy, convergence of accuracy and computational efficiency are studied in boundary value problems for the circular plate with central hole and variable bending stiffness. The presented method gives reasonable numerical results for a decomposed formulation of the discussed problem.
Keywords: plate bending problem, variable bending stiffness, meshless formulation, decomposition, Moving Least Square method, numerical tests

Moisture induced deformations of calcium silicate boards
Peter Matiasovsky and Peter Mihalka
Building capillary porous composite materials are very hydrophilic ones, which results in strong fluid-skeleton interactions. For determination of the fluid-skeleton coupling coefficients of porous material the experimental procedure based on measurement of moisture deformations under isothermal sorption, and simultaneously the measurement of the water sorption isotherms is necessary. The equipment for measurements of temperature and moisture expansion, together with water vapour sorption enabled the application of complex methodology of poromechanical properties determination for thermal insulation calcium silicate boards. The moisture induced deformations and elasticity moduli during wetting and drying process in the whole saturation interval were analysed.
Keywords: moisture induced deformation, poromechanical coupling, lightweight calcium silicate, elasticity modulus, damage