Tengfei Xu

Vulnerability Analysis of Metro Network Incorporating Flow Impact and Capacity Constraint after a Disaster

AbstractThis paper presents a modified topological vulnerability analysis for the metro network. The flow impacts and the capacity constraint are taken into account in this work. A node-based congestion is considered in the travel time model for the metro network. The logit-based path choice model is adopted to assign the flow in the network. Based on the present approach, the efficiencies of the metro network with either fully or partly damaged stations can be analyzed. The vulnerability of the Beijing metro network was studied based on the present method. The results show that the flow in the network plays an important role in the vulnerability analysis. Topological methods neglecting either the flow or the flow impacts would underestimate the vulnerability of the network. Both the magnitudes and patterns of origin-destination (O-D) demand influence on the assessment of vulnerabilities of the metro network and on the importance ranking of stations. Additionally, in a busy metro network the vulnerability...

Reliability analysis of circular concrete-filled steel tube with material and geometrical nonlinearity

Most of the previous research on concrete-filled steel tube is restricted to a deterministic approach. To gain clear insight into the random properties of circular concrete-filled steel tube, reliability analysis is carried out in the present study. To obtain the structural nonlinear response and ultimate resistance capacity, material and geometrical nonlinear analysis of circular concrete-filled steel tube is performed with a three-dimensional degenerated beam element. Then we investigate the reliability of concrete-filled steel tube using the first-order reliability method combined with nonlinear finite element analysis. The influences of such parameters as material strength, slenderness, initial geometrical imperfection, etc. on the reliability of circular concrete-filled steel tube column are studied. It can be concluded that inevitable random fluctuation of those parameters has significant influence on structural reliability, and that stochastic or reliability methods can provide a more rational and subjective evaluation on the safety of CFT structures than a deterministic approach.

Probabilistic Analysis about Shrinkage and Creep Effect of Continuous Steel-Concrete Composite Beams with LHS

Steel-concrete composite girder is consisted of concrete slab and steel girder connected through shear connectors. Owing to shrinkage and creep of concrete, redistribution of structural internal force and stress should be caused. It is widely accepted that shrinkage and creep models of concrete possess large randomness. The influences of stochastic variation of creep and shrinkage model, compressive strength of concrete, elastic modulus model of concrete, ambient humidity, load and shear connector stiffness on structural responses of continuous steel-concrete composite beam are investigated in the present study. Through Latin Hypercube Sampling (LHS) approach, the time variant probabilistic responses of deflection, interface slip, and stress of concrete slab and steel girder of continuous steel-concrete composite beam are studied.

Influence of steel–concrete bond damage on the dynamic stiffness of cracked reinforced concrete beams

In this article, experiments focusing at the influence of steel–concrete bond damage on the dynamic stiffness of cracked reinforced concrete beams are reported. In these experiments, the bond between concrete and reinforcing bar was damaged using appreciate flexural loads. The static stiffness of cracked reinforced concrete beam was assessed using the measured load–deflection response under cycles of loading and unloading, and the dynamic stiffness was analyzed using the measured natural frequencies with and without sustained loading. Average moment of inertia model (Castel et al. model) for cracked reinforced beams by taking into account the respective effect of bending cracks (primary cracks) and the steel–concrete bond damage (interfacial microcracks) was adopted to calculate the static load–deflection response and the natural frequencies of the tested beams. The experimental results and the comparison between measured and calculated natural frequencies show that localized steel–concrete bond damage does not influence remarkably the dynamic stiffness and the natural frequencies both with and without sustained loading applied. Castel et al. model can be used to calculate the dynamic stiffness of cracked reinforced concrete beam by neglecting the effect of interfacial microcracks.

Reliability Analysis of Circular Concrete-Filled Steel Tube with Material and Geometrical Nonlinearity

Most of the previous researches on the concrete-filled steel tube are restricted to deterministic approach. To give a clearer insight about random properties of circular concrete-filled steel tube, reliability analysis is carried in the present study. Material and geometrical nonlinear analysis of a circular concrete-filled steel tube is performed with a three-dimensional degenerated beam element, which can efficiently obtain the structural nonlinear responses. Through the combination of first order reliability method and nonlinear finite element analysis, the reliability about ultimate resistance capacity of the concrete-filled steel tube is investigated. The influences of parameters such as material strength, slenderness, initial geometrical imperfection, and etc. on reliability of circular concrete-filled steel tube column are studied. Some conclusions obtained from reliability analysis may be beneficial for rational analysis and design of the concrete-filled steel tube in practical engineer structures.