State Key Laboratory for Disaster Reduction in Civil Engineering

Shanghai, China

State Key Laboratory for Disaster Reduction in Civil Engineering

Shanghai, China

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Chen S.,State Key Laboratory for Disaster Reduction in Civil Engineering | Chen S.,Tongji University | Wu P.,Tongji University
Journal of Constructional Steel Research | Year: 2017

Steel reinforced concrete column has been widely applied in high-rise buildings and long-span structures. In this paper, an analytical study is carried out for predicting the axial compressive behavior of steel reinforced concrete (SRC) column using cross-shaped steel section with flanges. Firstly, respective material models were established for different components in the composite cross-section, including highly confined concrete, partially confined concrete, unconfined concrete, steel section as well as steel reinforcement. For highly confined concrete, the interaction mechanism between steel section and confined concrete has been investigated, based on which a uniaxial stress-strain relation is established. For partially confined concrete, as the hoop may not yield, an iterative procedure is applied to calculate the real stress in hoops and then the effective lateral confining pressure. For steel section, the biaxial stress state is considered in the material model. Based on section analysis method, a unified analytical model is then proposed and verified through comparison of analytical results with test results on SRC and partially confined SRC (PSRC) short columns. At last, a simplified method for calculating the real stress of the hoop and then the strength of partially confined concrete was proposed to avoid the iterative process and save the computing time. © 2016 Elsevier Ltd


Li G.Q.,State Key Laboratory for Disaster Reduction in Civil Engineering | Li G.Q.,Tongji University | Wang P.,State Key Laboratory for Disaster Reduction in Civil Engineering | Wang P.,Shandong University | Wang Y.,University of Manchester
Journal of Constructional Steel Research | Year: 2010

This is the first of the three companion papers dealing with the restrained steel column behaviours in fire. This paper reports the results of two new fire tests on axially and rotationally restrained steel columns that have different axial restraint stiffness. Axial and rotational restraints were applied by a restraint beam. The external applied axial load was kept constant during the fire test. The increase and decrease in axial force in the restrained steel column was borne by the restraint beam. Test results included the temperature, the axial displacement and the lateral deflection of the test column. It was found that the axial restraint reduced the buckling temperature of a restrained column. The effects of axial restraint to the failure temperature depended on the load ratio and the axial restraint stiffness ratio. A Finite Element Method (FEM) model was built to simulate the fire test. The damping factor fitting for simulating behaviours of restrained steel column in fire was selected through parametric analysis. The validated FEM model was used to perform parametric studies on the behaviour of restrained steel column in Part 2, results of which were used to develop a practical design method for restrained steel column in fire in Part 3. © 2010 Elsevier Ltd. All rights reserved.


Zhang C.,Tongji University | Li G.-Q.,State Key Laboratory for Disaster Reduction in Civil Engineering
Advanced Steel Construction | Year: 2013

A modified one-zone model has been proposed for structural fire safety design. In the model, a quantity which considers the heat sink effect of steel members in fire compartment is added to the heat balance equation for one-zone compartment fire model. In this paper, the proposed model is solved by FEM simulations. The results from FEM simulations are verified by program OZone (V2.0). Case studies have been conducted with investigating parameters including number of steel members, compartment dimension, opening area, fire load density and steel insulation thickness. The results of the studies show that for fire compartments with bare steel members, the steel heat sink effect is greater for compartments with smaller floor area, larger opening, lower fire load density, and more steel members; and for fire compartments with insulated steel members, the steel heat sink effect is greater for compartments with larger floor area, smaller opening, higher fire load density, and more steel members with thinner insulation. Correspondingly, the over-predictions of the maximum steel temperatures by the current model are comparatively more severe for those compartments. The proposed model can yield more economical fire resistance design than the current model, which is recommended for practical usage.


Hu B.,Hefei University of Technology | Li G.-Q.,State Key Laboratory for Disaster Reduction in Civil Engineering | Li G.-Q.,Tongji University | Sun J.-Y.,China State Construction Engineering Corporation
International Journal of Impact Engineering | Year: 2014

Preventing unauthorized vehicles from approaching a protected area by anti-ram bollard systems installed in the perimeter of buildings and infrastructures would consequently reduce blast and debris threats of vehicle borne improvised explosive devices. In this paper, an explicit finite-element model, which is more comprehensive than existing numerical models, was developed to simulate the performance of fixed anti-ram bollard system subjected to vehicle impact. Different materials for different locations of the foundation support, differences in weight and configuration between test vehicles and vehicle model, and more accurate contact algorithm used between truck and bollards were taken into account. The accuracy of the developed model was validated through comparing the impact results with four existing crash tests. Based on the verified numerical model, 72 numerical experiments of K4-rating shallow footing fixed anti-ram bollard systems (SFFABSs) were investigated according to orthogonal design. The minimum height of the bollard H min during the impact was proposed as a new deformation tolerance for K4-rating SFFABS. The new deformation tolerance is defined as the H min value of 564 mm or above according to SD-STD-02.01 Revision A, and a more reliable deformation tolerance is defined as the Hmin value of 587 mm or above. Orthogonal analysis for the experimental factors with respect to Hmin showed that height of the bollard, diameter of the bollard, and strength of the steel tube have greatly significant influences on Hmin. © 2013 Elsevier Ltd. All rights reserved.


Wang W.,State Key Laboratory for Disaster Reduction in Civil Engineering | Wang W.,Tongji University | Wang W.,Georgia Institute of Technology | Chen Y.,State Key Laboratory for Disaster Reduction in Civil Engineering | And 3 more authors.
Journal of Constructional Steel Research | Year: 2010

This paper deals with experimental investigations to study the seismic behavior of thick-walled circular hollow section (CHS) X-joints subjected to out-of-plane bending (OPB). Important geometric parameters were varied in designing three full-scale joint specimens in order to evaluate their effect on connection behavior. Test results indicated that the failure modes and the connection efficiency of these joints significantly depended on the brace-to-chord thickness ratio τ and the brace-to-chord diameter ratio β. The tension fracture was identified as a critical failure mode for thick-walled X-joints with large β. CHS X-joints with larger β ratio were found to demonstrate better connection ductility and more satisfactory energy dissipating capacity than those joints with smaller β ratio under cyclic OPB loading. This observation was further verified by the proposed simplified analytical model results. Finite element (FE) analyses were performed to simulate the experimental behavior and facilitate the interpretation of the important test observations. © 2010 Elsevier Ltd. All rights reserved.


Zhang J.,Tongji University | Zhang J.,State Key Laboratory for Disaster Reduction in Civil Engineering | Li J.,Tongji University | Li J.,State Key Laboratory for Disaster Reduction in Civil Engineering
Science China: Physics, Mechanics and Astronomy | Year: 2014

Over the past 2 decades, tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory. The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states. Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian, cylindrical, mixed cylindrical-Cartesian, and other forms, and the homogeneity of loading functions discussed. It is found that under certain supplementary conditions from physical meanings, an unambiguous definition of the cohesion in a strength criterion, which is demanded in an elastoplastic damage model, is usually available in an explicit or implicit form, and in each case the loading function is still homogeneous. To apply and validate the presented theory, we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete, and their performances in triaxial compression prove to have improved significantly. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.


Li J.-T.,Tongji University | Li G.-Q.,State Key Laboratory for Disaster Reduction in Civil Engineering | Li G.-Q.,Tongji University | Lou G.-B.,State Key Laboratory for Disaster Reduction in Civil Engineering | And 2 more authors.
Journal of Constructional Steel Research | Year: 2012

Three tests at elevated temperatures were carried out to invest the fire-resistant capacity of flush end-plate composite joints. The axial force was considered in two of the three tests simulating fire conditions to investigate its effect on the connection's load carrying ability (one with fire protection and the other without fire protection). Summaries have been given on the failure mechanisms, temperature distribution, loading carrying capacity of the composite joint and the mutual influence between joints and beams at elevated temperatures. Date shows that the failure mode of the flush end-plate joint without stiffener is usually dominated with the yielding of the bottom flange of steel beam near the supports, elements of the composite connection have different rate of temperature increase, and the axial force from restrained composite beam influences the rotational stiffness and moment capacity of joints. This paper also theoretically presents how the interaction of joints and beam developed in fire conditions. A practical simplified method is proposed to calculate the non-linear variable characteristics of composite connection in the analysis of catenary action of beams at elevated temperatures. The proposed method is verified by the experimental investigations. This study offers a feasibility of fire-resisting design and evaluation for the composite beam with semi-rigid connections in the complete temperature range. © 2012 Elsevier Ltd. All rights reserved.


Li G.-Q.,Tongji University | Li G.-Q.,State Key Laboratory for Disaster Reduction in Civil Engineering | Zhang C.,Tongji University
Journal of Constructional Steel Research | Year: 2012

The maximum steel temperature of key elements to natural fires should be considered in evaluating the fire resistance of steel structures by rational approach. Natural fires are complex that advanced analytical simulations are always required to obtain the temperature distribution of steel members in natural fires. Simple calculation approaches which can give acceptable predictions are needed for the daily design work. This paper proposes a simple approach for calculating the maximum steel temperature of insulated steel members subjected to natural fires. The approach adopts time equivalent to relate natural fires with the standard fire, and use a simple quadratic equation for calculating the maximum steel temperatures. By comparing with numerical results and test data, the proposed approach can give satisfactory prediction of maximum steel temperatures in the range from 300 to 600 °C. The approach only need hand calculations which is easy and convenient for practical usage. © 2011 Elsevier Ltd. All rights reserved.


Zhang J.,Tongji University | Li J.,State Key Laboratory for Disaster Reduction in Civil Engineering
Engineering Structures | Year: 2012

A class of widely used plastic-damage models for concrete employ the Lubliner yield criterion, whose properties in triaxial stress states have not received due attention. This paper intends to provide a thorough investigation into this strength theory for its application in 3D simulation of concrete structures. Its algebraic formulation and geometric representation are analyzed with a particular perspective on the similarity in form between the yield conditions in triaxial compression and other stress states, from which it is found that there is a strong dependence of triaxial tensile strength on the compressive cohesion and strength increase in triaxial compression fails to be described appropriately. Effective calibration methods are proposed for concrete under uniform and non-uniform confinement respectively to take into account both strength increase and strength ratio. © 2012 Elsevier Ltd.


Huang H.,State Key Laboratory for Disaster Reduction in Civil Engineering | Sun Y.,Tongji University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Global assessment of structural conditions is important for structural health monitoring system. In particular, online or almost online structural parametric identification, based on vibration data measured from sensors, has received considerable attention recently. However, the problem becomes more challenging when the structure is complex and the number of degree-of-freedom (DOF) is large. A newly proposed time domain analysis methodology, referred to as the sequential nonlinear LSE (SNLSE) approach, has been studied and shown to be useful for the online tracking of parameters for structures with small DOFs. In this paper, the SNLSE approach will be applied for global assessment of an experimental cable-stay bridge model with large DOFs. A dynamic equivalent model of the bridge will be established and finite element analysis will be carried out to formulate the equation of motion. Numerical analysis will be conducted with different simulated damage scenarios and limited number of response data is considered. The capability of the proposed SNLSE approach in identifying the structural parameters and assessing the structural conditions will be verified. © 2014 SPIE.

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