The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage ...index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.
The composite lighting poles are filament wound GRP tapered tubes with a variable wall thickness across the length. In this study, the effective flexural properties of GRP poles have been determined, ...experimentally and theoretically. Cantilever bending tests were performed on full-scale GRP tubes and the effective flexural modulus was calculated from the initial slope of the flexural stress-strain curve based on the classical beam theory. The results show that the strain range corresponding to the linear behaviour is the same as under three-point and four-point tests with smaller specimens. Unlike other methods, the proposed method considers the variation of the crosssectional properties across the pole length. The effective properties of GRP tubes were further determined considering the orthotropic and unsymmetrical layup of the wall segment. A sensitivity analysis was performed at the lamina as well as the laminate level in order to evaluate the influence of material properties of the matrix and the fibres, the amount and orientation of the fibres as well as the layer thickness. Finally, the effective (replacement) flexural modulus of a filament wound tube was determined based on the classical lamination theory and compared to experimentally determined values. It was concluded that the replacement flexural modulus is a matrix dominated property highly influenced by the fibre volume fraction.
The main aim of this study is to analyze fiber-reinforced polymer (FRP) bridge decks according to their material, cross-section, and shape geometry. Infill cell configurations of the decks ...(rectangular, triangular, trapezoidal, and honeycomb) were tested based on the FRP cell units available in the market. A comparison was made for each cell configuration in flat and curved bridge shapes. Another comparison was made between the material properties. Each model was computed for a composite layup material and a quasi-isotropic material. The quasi-isotropic material represents chopped fibers within a matrix. FE (finite element) analysis was performed on a total of 24 models using Abaqus software. The results show that the bridge shape geometry and infill configuration play an important role in increasing the stiffness, more so than improving the material properties. The arch shape of the bridge deck with quasi-isotropic material and chopped fibers was compared to the cross-ply laminate material in a flat bridge deck. The results show that the arch shape of the bridge deck contributed to the overall stiffness by reducing the deformation by an average of 30–40%. The results of this preliminary study will provide a basis for future research into form finding and laboratory testing.
This study presents a complex experimental research of a damaged steel railway bridge. Before the reconstruction, the elastic behavior of the material was evaluated using the hole-drilling strain ...gauge method of determining residual stresses at the relevant cross-sections. During the reconstruction project (lifting of the structure), a short-term monitoring system was installed at the critical cross-sections for continuous recording of strain. The aim was to evaluate the quality of the reconstruction intervention and prevent further damages. Following a successful reconstruction, a diagnostic load testing was performed according to Croatian standards. The purpose of the load testing (static and dynamic) was to evaluate the ability of the bridge to carry the design loads and calibrate the finite element models. During static load testing vertical displacement was measured as well as strain. Dynamic load testing of the bridge was performed in order to determine the main dynamic parameters of the structure and to calculate the dynamic factor. In order to select the appropriate measurement parameters and methods used during this experimental research it was necessary to consider the bridge type, materials and reconstruction or strengthening interventions. Especially, since this bridge was an example of insufficient inspection and maintenance during service. A well-designed monitoring and diagnostic load testing needed to be performed in order to obtain useful results for the decision makers involved.
In finite element analysis of steel‐reinforced elastomeric bearings (SREB) under compression, modeling of rubber as a nearly or fully incompressible material requires special attention. In this ...study, finite element simulations of circular elastomeric pads and rectangular SREB under compression were performed to analyze the effects of rubber compressibility with respect to different pad geometries and shape factor values. The ratio of the compressive modulus for a compressible rubber to that of an incompressible rubber was also introduced based on the previously derived exact solutions as well as the ad hoc approximations. This ratio accurately represents the influence of compressibility on compressive stiffness in terms of relative compressibility (K/G) and shape factor values. Numerical results were also compared with the experimental results on rectangular SREB with moderate shape factors. Recommended values for relative compressibility of carbon black‐filled rubbers in the range of 50–200 result in underestimated compressive stiffness, especially for bearings with shape factor values greater than five. It is recommended to adjust the relative compressibility, considering the shape factor, so that the compressive stiffness does not decrease by more than 50% compared to the incompressible case.
Climate change is expected to have a severe impact on cultural heritage in the future. This study presents the methodology developed during the FP7 project Climate for Culture, of assessing the ...climate change impact on collection objects in cultural heritage buildings. The main innovation lies in coupling new high resolution future climate projections with building simulation tools in order to predict future indoor climate and identify future risks in historic buildings. The case study is an intermittently heated wooden chapel in Croatia. The whole building simulation model of the chapel was validated using a newly developed method of accuracy assessment in the context of preventive conservation. Even though modeling intermittent heating induces limitations in the model, it can be used for computing of future indoor data. Future indoor climate data was assessed for possible risks of biological, mechanical, and chemical damage to painted wooden panels using the newly developed specific climate risk assessment. When using this method of damage assessment on buildings with active climate control, especially with intermittent heating, it is recommended to determine the relevant season for the damage process in order to objectively analyze results.
Pomoću puzanja i relaksacije polimernih materijala koji se rabe u potresnoj izolaciji opisana su viskoelastična svojstva. Posebno poglavlje posvećeno je dinamičkim viskoelastičnim svojstvima. Kao ...primjer primjene viskoelastičnih svojstava kod protupotresnih naprava prikazani su viskoelastični prigušivači. Dinamičkim ispitivanjem elastomernih ležajeva koji se koriste u potresnoj izolaciji određena je količina prigušenja te prikazan dijagram sile i pomaka u ovisnosti o vremenu.
In the period 1993-1997 investigations were conducted on natural low marshy grassland of facies Arrhenatheretum elatioris alopecurosum located 60 km west of Osijek and 7 km south of the river Drava. ...Variants of nitrogen fertilization, NPK fertilizers and non-fertilized were comprised in the investigation. Presence of 121 plant species of which 22 grass and grass-like species, 12 legumes and 87 other plant species was determined. On the average of five years grassland fertilization affected changes in density value of all plant groups. The highest grass density was found out with the variant fertilized with N120P12K120 and the highest legumes density appeared to be on non-fertilized variant. In 1997 Centaurea jacea, Cerastium holosteoides and Myosotis arvensis dissapeared from plant density of other species due to fertilization and mowing effect. Grasses Alopercurus pratensis and Poa pratensis var. angustifolia as well as leguminoses Trfolim pratense and Lathyrus pratensis are especially characterized by good fodder and density value.
U članku se objašnjava koje se radnje moraju provesti u postupku ocjenjivanja sukladnosti građevnog proizvoda. To su: ispitivanja i nadzor. Dan je tabelarni pregled radnji koje treba provesti s ...podacima o subjektima koji ih provode. Posebno je opisana prva radnja u sustavu – početno ispitivanje. Prikazani su primjeri istraživanja tipova građevnih proizvoda koji su provedeni u Laboratoriju za ispitivanje konstrukcije Zavoda za tehničku mehaniku Građevinskog fakulteta u Zagrebu.
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