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Du Y.,Tianjin University | Du Y.,National University of Singapore | Chen Z.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Chen Z.,Tianjin University | Yu Y.,Tianjin University
Thin-Walled Structures | Year: 2016

High-strength steel members are susceptible to local buckling. Rectangular concrete-filled tubular (CFT) columns could make full use of high-strength steel by restraining its buckling inward. This paper reports an experimental investigation of rectangular CFT columns using high-strength steel. Three current design codes are evaluated with the experiments both from this study and the previous literature. It indicates that EC4, AISC 360 and GB50936 tend to be unsafe incorporating high-strength steel and high aspect (h/b) ratio. Design recommendations of the width-to-thickness (h/t) ratio are proposed to account for the different h/b ratio effects for rectangular CFT columns. © 2016 Elsevier Ltd


Du Y.,Tianjin University | Du Y.,National University of Singapore | Chen Z.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Chen Z.,Tianjin University | Xiong M.-X.,Guangdong University of Technology
Construction and Building Materials | Year: 2016

This paper experimentally and theoretically investigates the behavior of rectangular concrete-filled tubular (CFT) columns using Q460-grade steel. Analysis of concrete contribution ratio (CCR), ductility and strength index (SI) was performed based on the experimental results. Finite element analysis was conducted to predict the behaviors of the test columns and to choose the suitable steel material model for Q460-grade steel. A comprehensive database including this study was established to evaluate the current design approaches for rectangular CFT columns using high steel strength (HSS). Augmentation factor is proposed to evaluate the effect of both the width-to-thickness ratio and the HSS. A new design method was developed and verified to extend the steel strength limitation for designing rectangular CFT columns to 460 MPa in DB 29-57 based on this research. © 2016 Elsevier Ltd


Wang J.-H.,Tianjin University | Wang J.-H.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Liu J.-L.,Tianjin University | Liu J.-L.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Zhou Y.-R.,China Oilfield Services Ltd.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

Load-controlled model tests are conducted to study the bearing capacities of suction anchors with taut mooring systems under combined static and cyclic loads at the optimal loading point using an electric servo loading apparatus developed by the authors. Failure modes of anchors, effects of static loads on cyclic bearing capacities and variations of cyclic bearing capacities with the number of cycles to failure are analyzed based on test results. The following conclusions are drawn. Failure of anchors is the translational failure mode of pullout from the soft stratum if the vertical ultimate resistance acting on anchors is less than the lateral one acting on anchors under combined static and cyclic loads. The displacement along the mooring direction at the loading point is about 0.6 times the anchor diameter when anchors are in the ultimate states under static loads. The cyclic bearing capacity of anchors increases with the increase of static load ratios and the cyclic load withstood by anchors also depends on static load ratio for a specified number of cycles to failure. The cyclic load withstood by anchors is the maximum when the static load ratio is about 0.5. Cyclic bearing capacities of anchors decrease with the increase of the number of cycles to failure for a specified static load ratio. The effect of loading directions on the variation of the cyclic bearing capacity with the number of cycles to failure is not obvious when the loading direction varies from 30 to 40 degrees for a specified static load ratio. The cyclic bearing capacity of anchors is not less than 75% of the static bearing capacity if the static load ratio is greater than 0.5 and the number of cycles to failure is less than 1000.


Wang J.,Tianjin University | Zhao N.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Zhao N.,Tianjin University | Nash P.,Illinois Institute of Technology | And 4 more authors.
Journal of Alloys and Compounds | Year: 2013

Bulk Ti2AlC-Al2O3/TiAl composites were in situ synthesized by vacuum sintering mechanically alloyed Ti-50 at.% Al powders coated with carbon nanotubes (CNTs). The pre-alloyed Ti-50 at.% Al powder was obtained by ball milling Ti and Al powders. The multi-walled carbon nanotubes as the carbon resource were covered on the surface of the pre-alloyed powders by immersing them into a water solution containing the CNTs. A zwitterionic surfactant was used to enhance the dispersion of the CNTs on the powder surface. The samples were cold pressed and sintered in vacuum at temperatures from 950 to 1250 °C, respectively. The results show that the reaction of forming Ti2AlC can be achieved below 950 °C, which is 150 °C lower than in the Ti-Al-TiC system and 250 °C lower than for the Ti-Al-C system due to the addition of CNTs. Additionally, the reinforcement of Al2O3 particles was introduced in situ in Ti2AlC/TiAl by the drying process and subsequent sintering of the composite powders. Dense Ti 2AlC-Al2O3/TiAl composites were obtained by sintering at 1250 °C and exhibited a homogeneous distribution of Ti 2AlC, Al2O3 and precipitated Ti3Al particles and a resulting high hardness. © 2013 Elsevier B.V. All rights reserved.


Le C.-H.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Le C.-H.,Tianjin University | Ding H.-Y.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Ding H.-Y.,Tianjin University | Zhang P.-Y.,Tianjin University
Gongcheng Lixue/Engineering Mechanics | Year: 2013

For towing stability, sinking, fine leveling construction and structural strength purposes, it is necessary to set bulkheads in the concrete bucket foundation. Usually the influence of bulkheads on the bearing capacity of a foundation is not considered, however, bulkheads actually have a certain influence on the bearing mode and bearing capacity. The influence of bulkheads on the bearing mode was quantitatively analyzed by the comparison of two concrete bucket foundations with and without bulkheads. The results show that the bearing modes of two foundations with and without bulkheads are similar. No obvious effect on the bearing capacity when the load is small, so it is reasonable that not to consider the role of the bulkheads in foundation design, but as the load increases, the effect of bulkheads on the bearing capacity improvement gradually appears, when the bucket foundation reaches the ultimate bearing capacity, 6.9% of vertical bearing capacity, 18.3% of horizontal bearing capacity and 16.5% of bending bearing capacity increase, which means that in extreme conditions a concrete bucket foundation with bulkheads will have greater safety margin.


Han Q.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Han Q.,Tianjin University | Liu Y.,Tianjin University | Xu Y.,Tianjin University | Xu Y.,Key Laboratory of Coast Civil Structure and Safety of Ministry of Education
Thin-Walled Structures | Year: 2016

In this paper, the theoretical and practical formulas of initial stiffness of welded hollow spherical joints were presented, and the elastic and elastoplastic critical displacements and rotations were obtained respectively. A mechanical model considering the stiffness characteristics of joints was proposed, the criterion of eccentric states and bearing stages was established to analyse the influence on the stability of single-layer latticed domes. Results indicate that the practical initial stiffness formulas proposed fit well with the theoretical solutions. The mechanical model can accurately simulate the stiffness characteristics and bearing stages of joints in the failure process of structure. Compared with the experimental results, the average error of mechanical model for the initial slope of load-rotation curve is 8%, and the average error for the ultimate bearing capacity is 7%. The stiffness degeneration of the joints in the plastic stage may cause a significant reduction in stability capacity of the structure. The stability reduction factors of K6 and Geodesic domes are between 0.7 and 1.0, and the stability reduction factors of K8-lamella domes are between 0.65 and 1.0. © 2016 Elsevier Ltd


Wang J.,Tianjin University | Wang J.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Liu J.,Tianjin University | Liu J.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Yang Y.,Tianjin Xince Eletronics Apparatus Technology Co.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2012

Suction anchors subjected to inclined loads at the optimal load attachment point are an important taut mooring foundation of deepwater floating production and storage facilities. Sediments in the deepwater areas are generally soft clay with high water contents. It is important for designers to understand failure modes and bearing capacities of suction anchors with taut mooring system in soft clay. Geometry characteristic parameters of anchors, shear strengths of strata and loading cases may be main factors affecting failure modes and bearing capacities of suction anchors. In order to better understand variations of failure modes and bearing capacities resulting from variations of various affecting factors, model tests were conducted under 1g condition for suction anchors with taut mooring system in soft clays. Effects of the friction resistance of the outside wall, geometric characteristic parameters, the variation of soil shear strength along the depth, the loading direction and cyclic loads on the failure mode and the bearing capacity of suction anchors with taut system were studied. Following conclusions were obtained based on model test results. There are three typical failure modes for suction anchors subjected to the inclined load at the optimal load attachment point: (1) the anchor failure is the vertical pullout mode if the vertical ultimate resistance of an anchor is less than the lateral ultimate resistance; (2) the anchor failure is the mode of lateral squeezing strata if the vertical ultimate resistance of an anchor is larger than the lateral ultimate resistance; (3) the anchor failure is the mode of squeezing strata along the inclined upward direction if the lateral ultimate resistance of an anchor is close to the vertical ultimate resistance. For specified stratum, the loading direction and the load case, the failure mode can be changed to increase the bearing capacity of an anchor by optimizing geometric parameters of an anchor. If the lateral ultimate resistance of an anchor is less than the vertical ultimate resistance, the bearing capacity of the anchor does not increase with the increase of the vertical ultimate resistance. The failure of anchors is always the vertical pullout mode if the vertical ultimate resistance of an anchor is less than the lateral ultimate resistance when the loading direction angle from the horizontal decreases from 40 degree to 20 degree for suction anchors with taut mooring system. The cyclic load is an important factor affecting the failure mode and the bearing capacity. The degradation of the vertical ultimate resistance is larger than the degradation of the lateral ultimate resistance under cyclic loads. The failure of an anchor is still the vertical pullout mode under combined static and cyclic loads if the failure of an anchor is the vertical pullout mode under static loads. If the failure of an anchor is lateral failure mode strata under static loads, the failure mode of the anchor will depend on the cyclic degradation of the vertical ultimate resistance under combined static and cyclic loads. When model test results were predicted using the limiting equilibrium analysis method, predicted bearing capacities were basically in agreement with model test results and predicted failure modes were only in qualitative agreement with test results. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).


Liu R.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Wang L.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Wang L.,Tianjin Institute of Geotechnical Investigation and Surveying | Ding H.-Y.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

As a towering building, the offshore wind turbine is often subjected to significant horizontal load. The large-diameter shallow bucket foundation is a new kind of foundation to adapt to the special load conditions of offshore in China. The classical approach for the bearing capacity is not able to evaluate the bearing capacity of large-diameter bucket foundation. The failure envelopes of large-diameter bucket foundation on soft soil ground without drainage conditions in V-H, V-M, H-M and V-H-M loading spaces are investigated by means of the finite element method. Some formulas are obtained to describe the failure envelopes in V-H and V-M loading spaces. It is shown that the failure envelopes in V-H and V-M spaces are symmetric, while the failure envelope in H-M space becomes more asymmetric with the increasing depth ratio. The vertical load V affects the shape of the failure envelope in V-H-M loading space. The asymmetry of the failure envelope around M-axial recedes with the increasing vertical load. According to the relationship between the actual combined loading and the computed failure envelopes, the stability of large-diameter shallow bucket foundation can be determined.


Tan Y.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Wu Y.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Wu Y.,YELLOW AND CO
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2015

Reinforcement of bridges and culverts cross a river often produces a certain effect on its flood safety, and a demonstration of flood safety at the design stage of reinforcement becomes an indispensable part of the reinforcement project. This paper describes three alternative schemes for the reinforcement of Yusha bridge cross the Haiguan channel in Haikou city, and presents a one-dimensional hydraulic model for this project developed on the platform of HEC-RAS simulation model with an analysis on the impact of these schemes on the water level in the channel and the stability of river regime. We have obtained results of intuitive simulation for the flood safety of bridges and culverts, which provides useful information for the Yusha bridge reinforcement and other similar projects. © Copyright.


Li S.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Yang M.,State Key Laboratory of Hydraulic Engineering Simulation and Safety
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2012

When an automatic tilting water gate is operating, instability could occur such as frequent swinging, flapping and random hydraulic acting, and these instable phenomena directly impact structure security and project efficiency. To simulate the hydrodynamic loads on such a gate, in this paper a 3-D large eddy simulation (LES ) turbulence model is developed in combination with a volume-of-fluid free-surface tracking technique, and its results agree quite well with the measurements of physical model tests. It is used to analyze the the gate conditions of dynamic and static balances. The results show that if the standard deviation of fluctuating pressures on both surfaces of the gate is below 1.4 Kpa or the opening angel is large, the gate will operate in a good stability condition. The stability index proposed in this paper for evaluation of the tilting gate's stability provides a reliable criterion for similar designs. © Right.

Loading State Key Laboratory of Hydraulic Engineering Simulation and Safety collaborators
Loading State Key Laboratory of Hydraulic Engineering Simulation and Safety collaborators