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Present work focused on the flexural and thermo-mechanical characteristics of epoxy based composites filled with 3 different calcium carbonate (CaCO3) concentrations: 1.5, 3 and 5 wt.%. Composite specimens were fabricated through conventional casting method and subjected to flexural test via 3 point bending fixture. Additionally, dynamic-mechanical analyzer (DMA) with single cantilever mode was used to reval the thermo-mechanical responses of samples. The findings showed that the filler concentration increase led to the increase of storage modulus (E') for all specimens while the glass transition temperature (Tg) slightly decreased for 1.5 wt. % CaCO3 filled epoxy composite. The 5 wt.% CaCO3 loaded composite showed maximum E' and Tg values with 10% and 1.5% improvement, respectively. Based on flexural test results it was surprisingly found that, 1.5% wt. CaCO3 addition attained the highest strength with ~30% improvement among all samples. However, 5 wt.% CaCO3 introduced composites displayed the lowest mechanical performance due to the presence of agglomerates/tactoids, which was verified from SEM images as well. [ABSTRACT FROM AUTHOR]

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Because the coal seam is particularly thick and the mining intensity is large, the mining of extremely thick coal seams often causes a wide range of disturbed fractures, which in turn induces the phenomenon of strong underground pressure such as induced support crushing and water inrush. Through theoretical analysis, laboratory similarity simulation test, and other methods, this paper studies the effect of mining thickness on overburden movement and underground pressure characteristics for extremely thick coal seams by sublevel caving with high bottom cutting height. Some conclusions can be drawn as follows: (i) under the “beam-hinged cantilever beam rocks” structure theory, the rock pillar thickness which needs to be controlled increases linearly as a function of mining thickness is achieved, and the reason of increased of support resistance in full-mechanized caving mining in extremely thick seams is explained in the theory; (ii) based on the results of the theoretical analysis and the lab simulation tests, the law of the abutment pressure peak is inverse to the full-seam mining thickness, and the distance between abutment peak and working face is proportional to the full-seam mining thickness, that is to say that the damage range of overlying strata increased; (iii) there are three working states of loading support in extrathick coal seams, such as normal circumstance, lower main roof pressure, and higher main roof pressure, meanwhile these states keep changing; (iv) under the guarantee of stope safety conditions, due to lower support strength, it will benefit the special thick seam top-coal caving under normal circumstance; (v) increasing the supporting strength can balance the impact loading under the lower main roof pressure, guaranteeing valid support for roof strata; (vi) by releasing high pressure, due to lower production, lower recovery rate of coal and other measures guarantee the stability of the stope support in the case of the higher main roof pressure. [ABSTRACT FROM AUTHOR]

An analytical model of impact energy harvester consisting of a cantilever beam with integrated piezoelectric patches and a ball is developed in this paper. The material chosen to extract the energy is porous PZT, a composite material made of two phases: air and PZT. This material offers good control of the capacitance and the stiffness of the resultant composite material and expands the design space for the harvester. The cantilever beam is modelled using a single degree-of-freedom approximation, and a load resistor is used to represent the external circuit. The response of the energy harvester and the power output is obtained for harmonic base excitation, and the effect of excitation frequency, boundary distance, load resistance and porosity of the PZT material. The results highlight the potential for the impact harvester and motivate further studies to optimize the harvester. [ABSTRACT FROM AUTHOR]

This paper aims to present an investigation about the effect of construction errors on the snow-induced failure of tribune columns and roof. The structure, located in the town of Kalkandere in the province of Rize, Turkey, collapsed on January 3, 2016 and is considered as a case study. This low-sloped built variable-truss steel roof structure supported on reinforced concrete columns of 3.2 m covers a total of 626.46 m2 closed areas in plan. The roof of the tribune collapsed partially without any indication during first snowfall after construction, at midnight on a winter day, fortunately before the opening hours. The meteorological records and observations of local people are combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. The snow load value is derived as 3.14 kN=m2, which is 4.19 times greater than the design value. A three-dimensional finite-element model of the existing steel tribune roof with reinforced concrete columns is generated for four cases considering project drawings and site investigations. The compressive strength of concrete is calculated as 13.50 MPa, the type of steel longitudinal and confinement bars is defined as S420. At the end of the study, it is shown that the reinforced concrete tribune structure with steel truss cantilever systems has enough stability, rigidity, and is located within the safety limits for Cases 1 and 3. The failures occurred during Cases 2 and 4. From the analyses, inadequate concrete strength was determined as a secondary parameter causing this failure. Also, it is indicated that the possible reasons for the collapse are some mistakes made in the design of connection details, incorrect arrangement of the structure, existence of short column, overlap regions between the rigid tribune blocks, and individual columns and construction workmanship errors. [ABSTRACT FROM AUTHOR]

This paper presents lateral buckling failures of laterally unrestrained steel cantilever roof of a tribune with slender cross section under snow load. A structure located in eastern part of Turkey, and collapsed on October 25, 2015 is considered as a case study. This mild sloped roof structure was built from a variable I beam, and supported on steel columns of 5.5 m height covering totally 240 m 2 closed area in plan. The roof of the tribune collapsed completely during first snowfall after construction without any indication. The meteorological records and observations of local people are combined together to estimate the intensity of snow load in the region, and it is compared with the values specified by the code. Also, the wide/thickness and height/thickness ratios for flange and body are evaluated according to the design codes. Three dimensional finite element model of the existing steel tribune roof is generated by ANSYS commercially available software, considering the project drawings and site investigations to determine the buckling modes and related buckling loads. The analytical solutions of the cantilever beam are carried out and buckling load are obtained as q = 22.236 kN / m 2 . To validate the analytical solution using finite element analyses, one cantilever beam is modelled separately with roof slope. At the end of the analyses, the buckling loads are obtained as q = 22.440 kN / m 2 . It is seen that there is a good agreement between the results and maximum difference is attained as 0.91%. After the finite element analyses considering full system, the buckling load is obtained as q = 31.00 kN / m 2 . The failure mechanism using buckling mode shapes is very similar to site investigation. The obtained results are lower than the derived snow load considering field investigation. These results can be evaluated as the evidence to explain the reason of failures. The experimental, numerical and analytical works conducted in this study indicate that the snow could be trigger of the collapse, but not alone the main reason for this situation, with the combination of inadequate section properties, faulty design and workmanship errors during construction. [ABSTRACT FROM AUTHOR]

The structure of Joaquin Sorolla railway station in Valencia is based on a modular construction concept. Like a Meccano or a "construction set", it is composed of identical elements prepared to be bolt-connected together. In structural terms, the "mushroom" or "umbrella" type is considered. Simply formed by a central column with a cantilever roof, it is a classical typology in structural engineering. The main innovative features of the project are the successive sequence of the different modules - with and without column - and the height transition from the platforms to the hall, considering a similar "umbrella" type structure but inclined. This structural concept is supported by its refined details: first, the bolted connections between modules and secondly identifying the shape of the central connection between the diagonal beams of the modules, which identify the butt joint itself. Viewed from the underneath, the modules offer a strong structural composition of an expressive, modular coffered ceiling, intended to become the representative image of the station. In the formalization of the structure, the paintings of Joaquin Soralla have been a source of inspiration, particularly the painting of "Boy playing with a boat". The light treatment, mirrored and reflected in the moving water surface, is of particular importance in this picture. The brush strokes in the picture draw the luminous atmosphere of Mediterranean beaches and the white steel structure of the station, with its refined elements and details, representing the boat the child is playing with, define a welcoming iconic symbol for Valencia. [ABSTRACT FROM AUTHOR]

Wind pressure and wind field around long cantilever annular roofs were simulated numerically by using commercial software FLUENT and k-ε turbulence model. The effects of key parameters such as the coming wind direction, roof angle, ventilation rate, openings on the roof, and cornice on wind pressure distribution around the roof were analyzed, and the effects of vertical aerodynamic control plates fixed to and openings along the roof's out-edge on wind pressure distribution of annular roof were investigated. The results show that the negative wind pressure occurs on the upper surface of horizontal roof under any coming wind angle, and higher negative pressure always appears at the out-edge of the roof. The optimal inclination angle of roof should be among the range of 0° - 15°. The increase of ventilation rate on windward surface of structural system can reduce mean wind pressure on the horizontal roof, while roof cornice has little influence on wind pressure. Both vertical aerodynamic control plates fixed to the roof and openings along the perimeter of the roof can obviously reduce wind pressure of horizontal roof effectively. [ABSTRACT FROM AUTHOR]

The article examines an algorithm used for processing the results of laboratory tests when experimental data was obtained in the aerodynamic tunnel. The paper deals with information when data about pressure distribution on the surfaces of a designed building are recalculated into wind loads required for calculating a virtual model for the finite element method. Due to differences in methodology between experimental airflow testing in the aerodynamic tunnel and the simulation of wind loads for a complex facility referring to the finite element method, the proposed investigations are actual while taking into account the current design codes and climatology conditions for an individual site. A review of similar problems, design conditions, the principles of the conducted experiment, a concept of the algorithm, basic assumptions and some results are briefly described in the paper. The final conclusions and recommendations can help with choosing the right solution during such calculations. [ABSTRACT FROM AUTHOR]

Abstract: This is a study of nonlinear traveling wave response of a cantilever circular cylindrical shell subjected to a concentrated harmonic force moving in a concentric circular path at a constant velocity. Donnell''s shallow-shell theory is used, so that moderately large vibrations are analyzed. The problem is reduced to a system of ordinary differential equations by means of the Galerkin method. Frequency–responses for six different mode expansions are studied and compared with that for single mode to find the more contracted and accurate mode expansion investigating traveling wave vibration. The method of harmonic balance is applied to study the nonlinear dynamic response in forced oscillations of this system. Results obtained with analytical method are compared with numerical simulation, and the agreement between them bespeaks the validity of the method developed in this paper. The stability of the period solutions is also examined in detail. [Copyright &y& Elsevier]

Abstract: We analyzed the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure was fitted with two fibre Bragg gratings (FBG) sensors. One of them measured vibration and the other measured the temperature inside of the cantilever beam, while the beam was exposed to fire. A high-temperature probe based on a simple packaging system, which isolates the sensing FBG from any mechanical action, was developed. A low-cost fibre Bragg grating interrogation system, including easy assembly and maintenance, was used for the measurements. The temperature in the cantilever beam increased until 150°C and a reduction in the strength of concrete was observed through modal analysis. Results reveal a considerable reduction in strength occurs even with exposures to moderate temperatures (less than 90°C). [Copyright &y& Elsevier]

Semi-passive damping techniques have been developed recently to address the problem of structural damping. Contrary to the standard passive piezoelectric damping, these new techniques adapt to environmental variations. Moreover, they present interesting multimodal damping performances. However, their efficiency is strongly correlated with their electromechanical coupling. The enhanced semi-passive damping technique presented herein compensates for this drawback. It reinforces the electromechanical coupling by artificially increasing the voltage amplitude delivered by the piezoelectric patches. Theoretical predictions and experimental results show a - 24 dB attenuation on the vibration of a resonant cantilever steel beam, while reducing the piezoelectric material volume by 83%. [ABSTRACT FROM AUTHOR]

In this paper, we present a scalable microchannel-embedded cantilever flowsensor with electronic readout. The scalable nature of the sensor addresses the need to realize arrays of flowsensors to characterize localized flow patterns. The electronic readout addresses the need to integrate flowsensors in microfluidic channels for closed-loop flow control. The in-channel nature of the flowsensor provides a wide choice for the cap material (e.g., PDMS, glass, silicon, etc.) enabling division of labor between integrated circuit (IC) and microfluidic foundries. This also holds promise for large-scale integrated microfluidic systems. The cantilever beam is placed inside a microfluidic channel in such a way that it utilizes drag forces to cause a flow-induced stress underneath the beam anchor. A Wheatstone bridge of piezoresistors placed directly under the anchor converts the flow-induced stress into a differential output voltage. We present an analytical model and 3-D simulations for the proposed flowsensor. Flowsensors fabricated by standard photolithography were tested to experimentally verify the validity of the model and simulation results. A flow sensitivity (unamplified) of 0.5 ppm/(μL/s) was measured with first generation devices with water flow from 10 μL/min to 100 μL/min. Through experimental results, it is also shown that scaling down the size of the flowsensor results in higher sensitivity. We present a prediction on the noise-floor of flow measurement based on the results obtained using these prototype flowsensors. [ABSTRACT FROM AUTHOR]

Abstract: Modeling and vibration control of a smart beam is investigated using piezoelectric damping-modal actuators/sensors. Theoretical formulations based on damping-modal actuator/sensors and numerical solutions are presented for the analysis of laminated composite beam with integrated sensors and actuators. Emphasis in this study is also given to the fiber orientation and the effect of actuator location on the control system. An instantaneous optimal close loop control algorithm coupling the direct and inverse piezoelectric effect is presented and used as an adaptive shape control of the dynamic response of the integrated laminated structure. An illustrative example, vibration control of large flexible structures is performed. A good correspondence has been obtained in all the examined results. [Copyright &y& Elsevier]

The paper presents an extension of vortex particle methods (VPM) in the context of pseudo-three-dimensional (pseudo-3D) multi-slice coupled numerical model for complex aeroelastic interactions of thin-walled structures. The flow around immersed bodies is analysed using pseudo-3D VPM with boundary element discretisation. The existing coupled model performs the aeroelastic interactions of line-like flexible structures using rigid cross-sections; the deformation of the system is analysed using the natural vibration modes of beam elements. The novelty of the presented coupled model is the inclusion of 3D shell vibration modes for structural analysis within the existing framework. The structural equations are formulated at the mid-surface of the thin shell elements and solved in the modal coordinate system. The slice-wise pressures on surface panels are projected to the corresponding structural nodes. New positions and velocity of surface panels are calculated to satisfy the velocity boundary conditions for solving new surface vortex streets. The coupled method has been validated by identifying the critical flutter wind speed of a T-shaped cantilever system. Benchmarks aeroelastic flapping of different flexible plates are studied further. The vortex-induced vibration of a circular pipe and the ovalling oscillations in circular shells are simulated to show the applicability of the method. Finally, the aeroelastic response of a cantilever roof system is analysed under different incoming wind speeds. • An extension of pseudo-3D vortex particle methods for FSI of thin-walled structures. • The boundary element method is used for the discretisation of deforming geometry. • Structural equations are solved at mid-surface of shell elements in modal coordinate. • Validation of the method is performed on aeroelastic flapping of thin flexible plates. • The method is proposed for aeroelastic interactions of towers, chimneys, and roofs. [ABSTRACT FROM AUTHOR]

Selective detection of short-range interaction forces was carried out with the second flexural mode of a commercially available dynamic mode cantilever. A higher mode has a higher spring constant and a lower mechanical quality factor, which are suitable for the small amplitude operation in dynamic force microscopy. With 0.70 Å amplitude of the second flexural mode, atomically resolved constant frequency shift images of the Si(111)-7×7 reconstructed surface were obtained. The ultrasmall amplitude operation enabled imaging with high stability, due to the detection of the interaction force gradients at relatively long distances from the sample surface, and is an effective way to observe reactive surfaces while avoiding modifications and damaging of the tip and the sample. [ABSTRACT FROM AUTHOR]