11 research outputs found
Modeling for assessment of long-term behavior of prestressed concrete box-girder bridges
Large-span prestressed concrete (PC) box-girder bridges suffer excessive vertical deflections and cracking. Recent serviceability failures in China show that the current Chinese standard modeling approach fails to accurately predict long-term deformations of large box-girder bridges. This hinders the efforts of inspectors to conduct satisfactory structural assessments and make decisions on potential repair and strengthening. This study presents a model-updating approach that aims to assess the models used in the current Chinese standard and improve the accuracy of numerical modeling of the long-term behavior of box-girder bridges, calibrated against data obtained from a bridge in service. A three-dimensional finite-element model representing the long-term behavior of box-girder sections is initially established. Parametric studies are then conducted to determine the relevant influencing parameters and to quantify the relationships between those and the behavior of box-girder bridges. Genetic algorithm optimization, based on the response-surface method (RSM), is used to determine realistic creep and shrinkage levels and prestress losses. The modeling results correspond well with the measured historic deflections and the observed cracks. This approach can lead to more accurate bridge assessments, which result in safer strengthening and more economic maintenance plans
Analytical model for residual bond strength of corroded reinforcement in concrete structures
Bond strength deterioration in corrosion-damaged reinforced concrete structures significantly affects serviceability and load-carrying capacity in their remaining service life. This paper presents a new analytical model for predicting the cracking development in the surrounding concrete and the residual bond strength of rebar in concrete structures due to reinforcement corrosion. The proposed analytical method adopts the thick-walled cylinder model for the cover concrete and considers the realistic properties of the corrosion-induced cracked concrete such as anisotropic behavior, residual tensile strength, and reduced tensile stiffness. As corrosion progresses, three phases for bond strength evolution associated with concrete cracking development are defined and the corresponding corrosion levels in each phase are determined. By using the constructed new governing equation, the crack width growth in the concrete cover and the radial bursting pressure at the bond interface are evaluated. The ultimate bond strength is then estimated from the contributions of adhesion, confinement, and corrosion pressure as a function of corrosion level. Finally, the effectiveness of the proposed analytical model is demonstrated by comparing the predicted results with experimental data available, and the results show that the proposed model is useful for predicting the bond strength evolution of the corroded rebar in concrete structures
Inclined reinforcement around web opening in concrete beams
YesTwelve reinforced-concrete continuous deep beams
having web openings within interior shear spans were
tested to failure. The main variables investigated were
the opening size and the amount of inclined
reinforcement around openings. An effective inclined
reinforcement factor combining the influence of the
amount of inclined web reinforcement and opening size
is proposed and used to analyse the structural behaviour
of continuous deep beams tested. It was observed that
the end support reaction, diagonal crack width and load
capacity of beams tested were significantly dependent on
the proposed effective inclined reinforcement factor. As
this factor increased, the end support reaction and
increasing rate of diagonal crack width were closer to
those of companion solid deep beams. In addition, a
higher load capacity was exhibited by beams having an
effective inclined reinforcement factor above 0.077 than
the companion solid deep beam. A numerical procedure
based on the upper-bound analysis of the plasticity
theory was proposed to estimate the load capacity of
beams tested. Comparisons between the measured and
predicted load capacities showed good agreement