Alper Ucak

Constitutive Model for Cyclic Response of Structural Steels with Yield Plateau

A rate-independent cyclic plasticity model for structural steels with a yield plateau is proposed. The model couples nonlinear kinematic hardening with a memory surface in the plastic strain space, to account for the progressive cyclic hardening/softening effects and a pseudomemory surface in the deviatoric stress space to correctly describe the plateau response. A simple identification procedure to calibrate the material dependent parameters is outlined and the accuracy of the proposed model is verified against experimental data available in the literature for proportional and nonproportional loading paths.

Load Path Effects in Circular Steel Columns under Bidirectional Lateral Cyclic Loading

AbstractRigorous numerical analyses are conducted to study the effects of bidirectional lateral cyclic loading on the hysteretic response of stocky circular thin-walled steel columns. Four unidirectional and eight bidirectional lateral displacement controlled load paths are considered; different performance indices obtained from the lateral load paths under consideration are compared. The results obtained from these comprehensive numerical analyses indicate that bidirectional lateral cyclic loading has a very limited effect on the ultimate strength of stocky circular thin-walled steel columns, but significantly decreases the ductility when compared with unidirectional lateral loading.

Simulation of Chlorine Decay in Drinking Water Distribution Systems

This work presents a model that evaluates the decay of the chlorine concentration in drinking water distribution networks. The model may use either Lagrangian based time driven or event driven methods depending on the hydraulic characteristic of the pipes. The decay of the chlorine within a pipe is evaluated by using a single equation that incorporates the bulk decay, radial diffusion and subsequent pipe-wall reaction of chlorine. The equation is embedded into a computer program called DYNAQ, which can perform dynamic water quality analysis in drinking water distribution networks. The developed model is also applied to an existing water distribution network and the comparison of the model results with a currently available model is presented.

The Response of the Seismically Isolated Bolu Viaduct Subjected to Fault Crossing

The effect of fault crossing on the response of the seismically isolated Bolu Viaduct is investigated. The seismic ground motions at the site of the Viaduct are generated following a rigorous methodology, which is based on seismological data available in the literature and finite-fault modelling techniques of the extended source. The generated motions are used to study the effect of fault crossing and fault crossing angle on the nonlinear behaviour of the seismically isolated Viaduct. It is shown that fault crossing is an important factor in the earthquake response of seismically isolated bridges, and that this effect needs to be considered in the design and detailing of the isolation system.