Search results for "Bending moment"
showing 10 items of 45 documents
Bending-Shear interaction domains for externally prestressed concrete girders
2013
In prestressed concrete structures, the evaluation of the safety level is generally carried out by separating the bending moment strength and the shear force capacity. Actually interaction between bending moment (M) and shear force (V) can have significant consequences on evaluations in service life, especially when the ultimate limit state (ULS) is considered. In this paper, the M-V interaction is addressed for prestressed concrete girders, in the cases of both bonded and unbonded prestressing tendons. It can be demonstrated, by drawing the interaction domains (M-V), that a significant reduction of the safety level has to be considered when shear force is evaluated together with bending mo…
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…
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…
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 …
A practical approach for the strength evaluation of RC columns reinforced with RC jackets
2015
Abstract Reinforced concrete (RC) jacketing is nowadays one of the most common techniques adopted for seismic retrofitting of existing RC columns. It is used to increase load-carrying capacity and ductility of weak existing members by means of a simple and cheap method. The structural efficiency is related to two main effects: – the enlargement of the transverse cross section; – the confinement action provided by the external jacket to the inner core. Several theoretical and experimental studies were addressed in the past to investigate on how it is possible to calculate the strength enhancement due to these effects and to highlight the main key parameters influencing the structural behavio…
Load carrying capacity of RC compressed columns strengthened with steel angles and strips
2012
Abstract In this paper a comparison between the analytical expressions for the prediction of the load carrying capacity of strengthened reinforced concrete (RC) columns with steel angles and strips is made. Expressions examined consider: the strength contribution due to the confinement effects induced by transverse strips; the composite action due to steel angles and unconfined concrete core; the strength contribution due to the composite actions of angles and concrete core taking into account that steel angles are subjected to axial force and bending moment and concrete core is confined by transverse strips. Design rules given by recent codes for the design of the strengthened columns are …
Adjustable prestressing for construction stages of incrementally launched bridges
2014
Incrementally launched bridges, which are generally built with the static scheme of a continuous beam on supports, change their scheme several times during launching. In these different configurations, internal forces vary and bending moments of opposite signs occur in the same sections for different positions of deck during advancement. In these bridges, two different kinds of prestressing are necessary: a temporary one during launching and a definitive one in service life. In this study, the possibility of implementing automatic adjustable prestressing for the launching stages is investigated; the launch prestressing is partially supplied by a system which can change the tension value in …
Interaction between Longitudinal Shear and Transverse Bending in Prestressed Concrete Box Girders
2017
In box girder bridges, the quantity and distribution of reinforcement to be put in concrete elements of sections can be evaluated only by considering the deformation of the cross section in addition to the longitudinal analysis of the static scheme, establishing the entire state of stress of box sections. This leads to a need to evaluate the interaction between internal forces obtained by the global analysis and the ones obtained by the local analysis of the cross sections. The frame effect implies the elastic deformation of slabs and webs, whereas eccentrically applied loads lead to cross-section distortion with the loss of the box shape. Hence, the reinforcement is strongly influenced by …
Simplified Procedure for Evaluating the Effects of Creep and Shrinkage on Prestressed Concrete Girder Bridges and the Application of European and Nor…
2013
The effects of time-dependent phenomena on concrete prestressed girder bridges are investigated. The study concerns the case of bridges built directly in their final configuration and that of bridges built by a sequence of stages in which geometry, restraints, and loads vary until the final configuration is achieved. An analytical approach based on the principles of aging linear viscoelasticity and the age-adjusted effective modulus method is followed. The paper has two aims: the first is to provide an efficient and simplified tool for the evaluation of the structural response in the early stages of design; the second is to compare the results of the analyses on actual cases of bridges when…
RC column externally strengthened with RC jackets
2013
In this paper the behaviour in compression of RC columns externally strengthened with concrete jacketing is analysed and a cross-section analysis of the jacketed member under axial load and bending moment is developed. The focus was to study the effect of confinement of concrete jacket on concrete core and the behaviour of compressed bars with buckling effects. Some other important aspects such as shrinkage, creep, old to new concrete surfaces and bond split effects were not included in the model because: the use of thick non-shrink grout jacket and a well-roughened surface of old-to-new concrete was supposed; long term effects were included though corrective coefficients for monolithic beh…