Sep 2010, Volume 4 Issue 3
    

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  • Research articles
    A model reference adaptive control based method for actuator delay estimation in real-time testing
    Cheng CHEN, James M. RICLES
    2010, 4(3): 277-286. https://doi.org/10.1007/s11709-010-0072-8
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    Real-time testing provides a viable experimental technique to evaluate the performance of structural systems subjected to dynamic loading. Servo-hydraulic actuators are often utilized to apply calculated displacements from an integration algorithm to the experimental structures in a real-time manner. The compensation of actuator delay is therefore critical to achieve stable and reliable experimental results. The advances in compensation methods based on adaptive control theory enable researchers to accommodate variable actuator delay and achieve good actuator control for real-time tests. However, these adaptive methods all require time duration for actuator delay adaptation. Experiments show that a good actuator delay estimate can help optimize the performance of the adaptive compensation methods. The rate of adaptation also requires that a good actuator delay estimate be acquired especially for the tests where the peak structural response might occur at the beginning of the tests. This paper presents a model reference adaptive control based method to identify the parameter of a simplified discrete model for servo-hydraulic dynamics and the resulting compensation method. Simulations are conducted using both numerical analysis and experimental results to evaluate the effectiveness of the proposed estimation method.
  • Research articles
    Cyclic responses of three 2-story seismic concentrically braced frames
    Ching-Yi TSAI, Keh-Chyuan TSAI, Chih-Han LIN, Chih-Yu WEI, Kung-Juin WANG, Yi-Jer YU, An-Chien WU,
    2010, 4(3): 287-301. https://doi.org/10.1007/s11709-010-0087-1
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    Three full scale two-story steel concentrically braced frames (CBFs) were tested at the National Center for Research on Earthquake Engineering (NCREE) in Taipei. The specimen is a single bay with the braces arranged in a two-story X-brace configuration. The main differences among the three tests are the brace types (hollow structural or wide-flange section) and the design criteria adopted for the gusset plate connections. Results of these three tests confirm that the two-story X-shape steel CBFs all have rather good energy dissipation characteristics up to a story drift of about 0.03 radians under the cyclically increasing lateral displacements. Severe brace local buckling and out-of-plane displacements were observed during each test. Tests confirm that both the 2t-linear and 8t-elliptical designs of the gusset plate connection provide satisfactory ductility for the steel CBF. Hollow structural section (HSS) braces fractured at a story drift smaller than that found using wide flange sections. The nonlinear fine element method (FEM) program ABAQUS was used to simulate the responses of the specimen. The base shear versus the story drift relationships obtained from the tests and the FEM analytical results are quite agreeable in various levels of lateral frame displacement. The analytical results confirm that the severe out-of-plane buckling of the braces can be accurately simulated. FEM analyses also illustrate that the steel moment resisting frame takes about 40% story shear when the inter-story drift is greater than 0.02 radians.
  • Research articles
    A new type of quadratic acceleration method
    Changqing LI, Menglin LOU,
    2010, 4(3): 302-310. https://doi.org/10.1007/s11709-010-0026-1
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    The polynomial acceleration method for time history analysis is presented, in which accelerations between several equal neighboring time steps were assumed to be a polynomial function of time interval. With a higher order polynomial used, a higher accuracy can be obtained, but the stability field of the method becomes narrower. When stability field and computational accuracy are taken into account at the same time, the quadratic acceleration method is superior to linear and cubic acceleration methods in choosing the maximum acceptable time step size. It is also shown that the quadratic acceleration method has desirable arithmetic damp, amplitude decay rate and period elongation rate, though its conditional stability restricts its application in stiff structures.
  • Research articles
    A method for examining the seismic performance of steel arch deck bridges
    Cheng-Yu LIANG, Airong CHEN,
    2010, 4(3): 311-320. https://doi.org/10.1007/s11709-010-0080-8
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    To examine the seismic resistance performance of a steel arch bridge during a strong earthquake, an approach is proposed in this paper to determine the ultimate strain of an arch rib using the static elasto-plastic large deformation theory. A steel fixed-end deck arch bridge with a span length of 200 m was used as an example in this study. The ultimate strain of the arch rib was calculated using the elasto-plastic finite element model. The seismic responses of the arch bridge exposed to strong earthquakes in two and three directions were also simulated. Moreover, the effect of earthquake motion in the lateral direction on the elasto-plastic earthquake response was discussed, and the seismic resistance of the structure was analyzed. The results show that steel arch bridges have preferable seismic resistance under strong earthquake conditions. While lateral earthquake motion has some influence on the damage to an arch bridge, it has little effect on the displacement, axial force, and bending moment responses of the arch rib. It is feasible to examine the seismic performance of the arch bridge by ascertaining the out-of-plane and in-plane earthquake responses of the bridge.
  • Research articles
    Parametric oscillation of cables and aerodynamic effect
    Yong XIA, Jing ZHANG, Youlin XU, Yozo FUJINO,
    2010, 4(3): 321-325. https://doi.org/10.1007/s11709-010-0028-z
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    This paper addresses the aerodynamic effect on the nonlinear oscillation, particularly parametric vibration of cables in cable-stayed bridges. A simplified 2-DOF model, including a beam and a stayed cable, is formulated first. Response of the cable under global harmonic excitation which is associated with wind speed is obtained using the multiple scales method. Via numerical analysis, the stability condition of the cable in terms of wind speed is derived. The method is applied to a numerical example and a long-span bridge to analyze its all stay cables. It is demonstrated that very large vibration at one of the longest cables in the middle span of the bridge can be parametrically excited when the wind speed is over around 210 km/h (58.5 m/s).
  • Research articles
    Windborne debris damage prediction analysis
    Fangfang SONG, Jinping OU,
    2010, 4(3): 326-330. https://doi.org/10.1007/s11709-010-0067-5
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    Windborne debris is one of the most important causes of the envelop destruction according to the post-damage investigations. The problem of windborne debris damage could be summarized as three parts, including windborne debris risk analysis, debris flying trajectories, and impact resistance of envelope analysis. The method of debris distribution is developed. The flying trajectories of compact and plate-like debris are solved by using a numerical method according to the different aerodynamic characteristics. The impact resistance of the envelopes is also analyzed. Besides, the process of windborne debris damage analysis is described in detail. An example of industrial building is given to demonstrate the whole method by using the observed data of typhoon Chanchu (2006). The method developed in this paper could be applied to risk assessment of windborne debris for structures in wind hazard.
  • Research articles
    Resistance of large caisson in floating transport considering the influence of air
    Junjie ZHENG, Zongzhe LI, Dongan ZHAO, Qiang MA, Rongjun ZHANG,
    2010, 4(3): 331-338. https://doi.org/10.1007/s11709-010-0085-3
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    This paper deals with the floating resistance of super large caisson by numerical simulation, and the influence of air resistance on the caisson, which is often ignored by previous researchers, is considered. The floating caisson of Taizhou Highway Bridge’s middle tower pier is investigated, and the software package FLUENT is used to simulate the floating process of large-scale rounded rectangular steel caisson. This simulation adopts the volume of fluid (VOF) model with water-air two-phase flow, which can take both the hydraulic resistance and air resistance into account. Subsequently, the analyses on hydraulic resistance and air resistance under different working conditions, such as different flow velocities and different draughts of water are performed, and the results are compared with those calculated by related empirical formula. The comparison shows that the air resistance takes up notable portion in the total resistance on the floating caisson, and the effect of air resistance on the safety of caisson should be paid sufficient attention to rather than be ignored.
  • Research articles
    Concurrent fatigue crack growth simulation using extended finite element method
    Zizi LU, Yongming LIU,
    2010, 4(3): 339-347. https://doi.org/10.1007/s11709-010-0078-2
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    In this paper, a concurrent simulation framework for fatigue crack growth analysis is proposed using a novel small time scale model for fatigue mechanism analysis and the extended finite element method (X-FEM) for fatigue crack growth simulation. The proposed small time scale fatigue model does not require the cycle counting as those using the classical fatigue analysis methods and can be performed concurrently with structural/mechanical analysis. The X-FEM greatly facilitates crack growth simulation without remeshing requirements ahead of the crack tip as in the classical finite element method. The basic concept and theory of X-FEM was briefly introduced and numerical predictions of stress intensity factors are verified with reference solutions under both uniaxial and multiaxial loadings. The small time scale fatigue model is integrated into the numerical simulation algorithm for concurrent fatigue crack growth analysis. Model predictions are compared with available experimental observations for model validation.
  • Research articles
    Influence of initial curing conditions and exposure environments on chloride migration in concrete using electrochemical method
    Wen XUE, Weiliang JIN, Hiroshi YOKOTA,
    2010, 4(3): 348-353. https://doi.org/10.1007/s11709-010-0077-3
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    To investigate the influence of initial curing conditions and exposure environments on chloride ions’ migration in concrete, the specimens that were cured in different conditions and placed in several marine environments were studied. The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test. The effective chloride diffusion coefficients (De) were calculated from the steady-state on the basis of Nernst-Planck’s equation. The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly. De reflected the density and pore connectivity of concrete. The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.
  • Research articles
    Corrosion damage assessment and monitoring of large steel space structures
    Bo CHEN, You-Lin XU, Weilian QU,
    2010, 4(3): 354-369. https://doi.org/10.1007/s11709-010-0088-0
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    Large steel space structures, when exposed to a harsh corrosive environment, are inevitably subjected to atmospheric corrosion and stress corrosion cracking. This paper proposes a framework for assessing the corrosion damage of large steel space structures subjected to both stress corrosion cracking and atmospheric corrosion. The empirical model for estimating atmospheric corrosion based on measured information is briefly introduced. The proposed framework is applied to a real large steel space structure built in the southern coastal area in China to assess its corrosion damage and investigate the effects of atmospheric corrosion on stress corrosion cracking. Based on the results, the conceptual design of the corrosion monitoring system of large steel space structures is finally conducted as the first step for a real corrosion monitoring system.
  • Research articles
    Trial design of arch bridge of composite box section with steel web-concrete flange
    Jiangang WEI, Qingwei HUANG, Baochun CHEN,
    2010, 4(3): 370-375. https://doi.org/10.1007/s11709-010-0073-7
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    The concrete arch bridge is a natural and appropriate structural solution, aesthetically pleasing and easily integrated into the environment, especially in mountainous and island areas. However, construction difficulty and cost will increase with heavy self-weight when the span enlarges. A potential solution is to use a composite box arch ring with steel web-concrete flange. Taking Wanzhou Yangtze River Bridge (the longest concrete arch bridge in the world with a main span of 420 m) as a prototype, trial designs of a composite box arch with steel webs (including corrugated steel webs and plain steel webs) and concrete flanges were carried out. Comparison of quantities and structural behaviors of the prototype concrete arch with the two trial designed composite arch was presented. It is shown that the self-weight of the composite arch can reduce about 28% and the structures can meet the design requirements, therefore it is possible to use the two composite arches in long span arch bridges.
  • Research articles
    Nonlinear analysis of pre-tensioned glass wall facade by stability function with initial imperfection
    Siu-Lai CHAN, Yaopeng LIU, Andy LEE,
    2010, 4(3): 376-382. https://doi.org/10.1007/s11709-010-0086-2
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    Pre-tensioned high strength trusses using alloy steel bar are widely used as glass wall supporting systems because of the high degree of transparency. The breakage of glass panes in this type of system occurs occasionally, likely to be due to error in design and analysis in addition to other factors like glass impurity and stress concentration around opening in a spider system. Most design does not consider the flexibility of supports from finite stiffness of supporting steel or reinforced concrete beams. The resistance of lateral wind pressure of the system makes use of high tension force coupled with the large deflection effect, both of which are affected by many parameters not generally considered in conventional structures. In the design, one must therefore give a careful consideration on various effects, such as support settlement due to live loads and material creep, temperature change, pre-tension force, and wind pressure. It is not uncommon to see many similar glass wall systems fail in the wind load test chambers under a design wind speed. This paper presents a rigorous analysis and design of this type of structural systems used in a project in Hong Kong, China. The stability function with initial curvature is used in place of the cubic function, which is only accurate for linear analysis. The considerations and analysis techniques are believed to be of value to engineers involved in the design of the structural systems behaving nonlinearly.
  • Research articles
    Computational simulation methods for fiber reinforced composites
    Vladimír KOMPI, Zuzana MURINKOV, Sergey RJASANOW, Richards GRZIBOVSKIS, Qinghua QIN,
    2010, 4(3): 396-401. https://doi.org/10.1007/s11709-010-0079-1
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    Trefftz-finite element method (Trefftz-FEM), adaptive cross approximation BEM (ACA BEM) and continuous source function method (CSFM) are used for the simulation of composites reinforced by short fibers (CRSF) with the aim of showing the possibilities of reducing the problem of complicated and important interactions in such composite materials.