Rapid repair techniques for severely earthquake-damaged circular bridge piers with flexural failure mode

In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1：2.5 scaled circular pier specimens are conducted to evaluate the efficiency of the proposed repair techniques. For the purpose of rapid repair, the repair procedure for all the specimens is conducted within four days, and the behavior of the repaired specimens is evaluated and compared with the original ones. A finite element model is developed to predict the cyclic behavior of the repaired specimens and the numerical results are compared with the test data. It is found that all the repaired specimens exhibit similar or larger lateral strength and deformation capacity than the original ones. The initial lateral stiffness of all the repaired specimens is lower than that of the original ones, while they show a higher lateral stiffness at the later stage of the test. No noticeable difference is observed for the energy dissipation capacity between the original and repaired pier specimens. It is suggested that the repair technique using the early-strength concrete jacket confined by carbon fiber reinforced polymer （CFRP） sheets can be an optimal method for the rapid repair of severely earthquake-damaged circular bridge piers with flexural failure mode.

Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

This paper numerically studied the effect of uncertainty and random distribution of concrete strength in beams failing in shear and flexure using lattice modeling,which is suitable for statistical analysis.The independent variables of this study included the level of strength reduction and the number of members with reduced strength.Three levels of material deficiency(i.e.,10%,20%,30%)were randomly introduced to 5%,10%,15%,and 20%of members.To provide a database and reliable results,1000 analyses were carried out(a total of 24000 analyses)using the MATLAB software for each combination.Comparative studies were conducted for both shear-and flexure-deficit beams under four-point loading and results were compared using finite element software where relevant.Capability of lattice modeling was highlighted as an efficient tool to account for uncertainty in statistical studies.Results showed that the number of deficient members had a more significant effect on beam capacity compared to the level of strength deficiency.The scatter of random load-capacities was higher in flexure(range:0.680-0.990)than that of shear(range:0.795-0.996).Finally,nonlinear regression relationships were established with coefficient of correlation values(R^(2))above 0.90,which captured the overall load-deflection response and level of load reduction.