Rapid repair of severely earthquake-damaged bridge piers with flexural-shear failure mode

An experimental study was conducted to investigate the feasibility of a proposed rapid repair technique for severely earthquake-damaged bridge piers with flexural-shear failure mode. Six circular pier specimens were first tested to severe damage in flexural-shear mode and repaired using early-strength concrete with high-fluidity and carbon fiber reinforced polymers （CFRP）. After about four days, the repaired specimens were tested to failure again. The seismic behavior of the repaired specimens was evaluated and compared to the original specimens. Test results indicate that the proposed repair technique is highly effective. Both shear strength and lateral displacement of the repaired piers increased when compared to the original specimens, and the failure mechanism of the piers shifted from flexural-shear failure to ductile flexural failure. Finally, a simple design model based on the Seible formulation for post-earthquake repair design was compared to the experimental results. It is concluded that the design equation for bridge pier strengthening before an earthquake could be applicable to seismic repairs after an earthquake if the shear strength contribution of the spiral bars in the repaired piers is disregarded and 1.5 times more FRP sheets is provided.

Serviceability evaluation of water supply networks under seismic loads utilizing their operational physical mechanism

The serviceability of water supply networks(WSNs)under seismic loads has significant importance for estimating the probable losses and the impact of diminished functionality on affected communities.The innovation presented in this paper is suggesting a new strategy to evaluate the seismic serviceability of WSNs,utilizing their operational physical mechanism.On one hand,this method can obtain the seismic serviceability of each node as well as entire WSNs.On the other hand,this method can dynamically reflect the propagation of randomness from ground motions to WSNs.First,a finite element model is established to capture the seismic response of buried pipe networks,and a leakage model is suggested to obtain the leakage area of WSNs.Second,the transient flow analysis of WSNs with or without leakage is derived to obtain dynamic water flow and pressure.Third,the seismic serviceability of WSNs is analyzed based on the probability density evolution method(PDEM).Finally,the seismic serviceability of a real WSN in Mianzhu city is assessed to illustrate the method.The case study shows that randomness from the ground motions can obviously affect the leakage state and the probability density of the nodal head during earthquakes.

Impact of Spatial Scale and Building Exposure Distribution on Earthquake Insurance Rates:A Case Study in Tangshan,China

In order to examine the effect of spatial scale and building exposure distribution on the pure rate of earthquake catastrophe insurance,this study described three modules for rate determination,put forward the general assumptions and principles for calculating the pure insurance rate,and introduced three types of building distribution and their calculation.Taking Tangshan City of Hebei Province in China as an example,we analyzed the pure rate of regional earthquake insurance in terms of spatial scale and building exposure distribution by using the method of control variables.The results show that for districts(or counties)with large differences in seismic risk,the risk areas can be further divided to apply differential rates.In areas with a diverse distribution of potential earthquake source areas and large differences in building density,there is a risk of overestimating or underestimating the pure rate of earthquake insurance when buildings are distributed evenly or partially evenly.This violates the break-even principle of rate setting.This study also provides a reference for earthquake catastrophe insurance companies to choose the spatial scale and the detailed level of exposure distribution in rate determination.

Seismic performance of fabricated continuous girder bridge with grouting sleeve-prestressed tendon composite connections

The seismic performance of a fully fabricated bridge is a key factor limiting its application.In this study,a fiber element model of a fabricated concrete pier with grouting sleeve-prestressed tendon composite connections was built and verified.A numerical analysis of three types of continuous girder bridges was conducted with different piers:a cast-in-place reinforced concrete pier,a grouting sleeve-fabricated pier,and a grouting sleeve-prestressed tendon composite fabricated pier.Furthermore,the seismic performance of the composite fabricated pier was investigated.The results show that the OpenSees fiber element model can successfully simulate the hysteresis behavior and failure mode of the grouted sleeve-fabricated pier.Under traditional non-near-fault ground motions,the pier top displacements of the grouting sleeve-fabricated pier and the composite fabricated pier were less than those of the cast-in-place reinforced concrete pier.The composite fabricated pier had a good self-centering capability.In addition,the plastic hinge zones of the grouting sleeve-fabricated pier and the composite fabricated pier shifted to the joint seam and upper edge of the grouting sleeve,respectively.The composite fabricated pier with optimal design parameters has good seismic performance and can be applied in high-intensity seismic areas;however,the influence of pile-soil interaction on its seismic performance should not be ignored.

Complete solutions for elastic fields induced by point load vector in functionally graded material model with transverse isotropy

The paper develops and examines the complete solutions for the elastic field induced by the point load vector in a general functionally graded material(FGM)model with transverse isotropy.The FGMs are approximated with n-layered materials.Each of the n-layered materials is homogeneous and transversely isotropic.The complete solutions of the displacement and stress fields are explicitly expressed in the forms of fifteen classical Hankel transform integrals with ten kernel functions.The ten kernel functions are explicitly expressed in the forms of backward transfer matrices and have clear mathematical properties.The singular terms of the complete solutions are analytically isolated and expressed in exact closed forms in terms of elementary harmonic functions.Numerical results show that the computation of the complete solutions can be achieved with high accuracy and efficiency.