Search results for "CANTILEVER"
showing 10 items of 60 documents
Serviceability and Ultimate Safety Checks of SegmentalConcrete Bridges through N-M and M-V Interaction Domains
2015
In current engineering practice, safety checks on serviceability and determinations of ultimate limit states of segmental bridges built by cantilevering are generally performed, either considering separately the contributions of axial force N, bending moment M, and shear force V, or considering the interaction effects through approximate expressions supplied by building codes. During construction stages and service life, the interaction between internal forces can be of fundamental importance in establishing the actual degree of structural safety and, for this reason, a different philosophy for performing checks in segmental bridges is proposed in this paper, plotting N-M and M-V interactio…
Simplified model for compressive response of RC column footing with square cross-section
2017
Abstract In this paper, a simplified calculus model for the prediction of the compressive response of RC column footing with a square cross-section is presented. As it is well-known RC concrete footing are designed adopting uniform contact pressures on the substrate and assuming a strut and tie model in deep members and a cantilever beam or slab model in flexible members. Deep and flexible members are distinguished in literature only based on the tangent of the angle expressed as the ratio between the depth and the shear span of the footing. In this paper, several subgrade contact pressures distribution for column footings (rigid or soft soils) were considered in developing a mechanical mod…
Partial Elastic Scheme Method in Cantilever Construction of Concrete Arch Bridges
2013
AbstractIn this paper, a study about stay stressing procedures of concrete arch bridges built by cantilevering with temporary stays is presented. Particularly, the partial elastic scheme method is proposed to find the initial cable forces, and a forward procedure is implemented to follow the actual sequence of construction by extending a procedure already applied to concrete cable–stayed bridges. The theoretical treatment is followed by a numerical application on a case study of a concrete arch bridge, and a comparison between initial cable forces found by the partial elastic scheme method and classical backward analysis is presented here. Results show the effectiveness of the proposed proc…
The influence of time-dependent phenomena in segmental construction of concrete cable-stayed bridges
2011
Construction stages of a cable-stayed bridge are characterized by a sequence in which geometric configuration, restraints and consequently stress and strain patterns vary many times till the final arrangement is achieved. When construction of concrete bridges is made by cantilever method the influence of time-dependent phenomena becomes significant. In this study an evaluation of stay stressing procedures is given by taking into account creep and shrinkage in cantilever construction of concrete cable-stayed bridges. A methodology of stay stressing is proposed with the final target of reaching the desired geometric configuration. Comparison with classical analyses performed by backward metho…
A parametric study of curved incrementally launched bridges
2013
Abstract The structural behaviour of incrementally launched bridges in the construction stages depends on different parameters involving deck, nose, supports and guide devices, because static schemes vary continuously with the advance of the deck above the piers. For this reason temporary stresses in the deck, during launching, are rather different from those occurring in service life. Horizontally curved launched bridges also present the effects of torsion induced by geometric curvature. A parametric study is presented in order to analyse the influence of design parameters on the construction of these bridges. Analyses were carried out by extending to curved beams a procedure based on the …
Serviceability of segmental concrete arch-frame bridges built by cantilevering
2013
The evaluation of the safety degree in service life for a segmental prestressed concrete bridge built by the cantilever method presents different aspects related to strength, deformability, durability and to effects of time-dependent phenomena as creep and shrinkage. The case-study of a prestressed concrete frame bridge with inclined piers is presented, built by cantilevering, with precast segments. By considering the fundamental items of design and construction stages, the implications due to the arch effect in this static scheme are investigated, with respect to an equivalent bridge with a final scheme of continuous girder on vertical piers. The birth of a significant value of axial force…
Effect of FRP strengthening on the flexural behaviour of calcarenite masonry walls
2017
The use of fiber-reinforced polymers (FRP) for structural strengthening has become increasingly popular in recent years. Several applications of FRP have been proposed and applied, depending on the target of the technique, kind and/or material of the structural member. In particular, because of their great tensile strength, FRP materials are commonly used to enhance the out-of-plane behaviour of masonry walls, allowing to increase their strength, ductility and improving safety against overturning. For these reasons, FRP laminates are often applied in vulnerable ancient buildings in seismic areas to reinforce façades and walls with poor structural features. However, some issues arise when a…
Rainfall energy harvester
2015
This chapter provides a detailed study on the harvest of the energy contained in raindrops by means of piezoelectric transducers. The energy harvester has the role of an electric source, able to recharge storage devices of small electronic components, such wireless sensors, by using the vibrational energy released by the drops hitting the transducer, reducing in such a way the chemical waste of conventional batteries. In technical literature, diverse studies agree on the level of suitable generated voltage on the electrodes of a piezoelectric transducer subjected to rainfall, but a complete characterization on the supplied power is still missing. This work, also to limit optimistic forecast…
Elasticity and yield strength of pentagonal silver nanowires: In situ bending tests
2014
This paper reports in situ mechanical characterization of silver nanowires (Ag NWs) inside a scanning electron microscope using a cantilevered beam bending technique. Measurements consisted in controlled bending of a cantilevered NW by the tip of an atomic force microscope glued to the force sensor. Relatively high degree of elasticity followed by either plastic deformation or fracture was observed in bending experiments. Experimental data were numerically fitted into the model based on the elastic beam theory and values of Young modulus and yield strength were extracted. Measurements were performed on twenty Ag NWs with diameters from 76 nm to 211 nm. Average Young modulus and yield streng…
Visible photothermal deflection spectroscopy using microcantilevers
2012
International audience; Photothermal deflection spectroscopy based on bi-material cantilevers combines the sensitivity of miniature sensors and the selectivity of optical spectroscopy. In this paper, we report on the photothermal response of the microcantilevers functionalized with nanometer thin organic films in the visible region. Unlike responses in the infrared regime, in the optical region, light absorption by all the cantilever constituents must be considered for extraction of the physical parameters of the organic layer. A model of photothermal deflection for the optical region has been developed for two absorbing layers consisting of a thick metal (>200 nm) and a thin organic film. …