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CONTENTS
Volume 14, Number 3, September 2002
 

Abstract
The free vibration analysis of stiffened laminated composite plates has been performed using the layered (zigzag) finite element method based on the first order shear deformation theory. The layers of the laminated plate is modeled using nine-node isoparametric degenerated flat shell element. The stiffeners are modeled as three-node isoparametric beam elements based on Timoshenko beam theory. Bilinear in-plane displacement constraints are used to maintain the inter-layer continuity. A special lumping technique is used in deriving the lumped mass matrices. The natural frequencies are extracted using the subspace iteration method. Numerical results are presented for unstiffened laminated plates, stiffened isotropic plates, stiffened symmetric angle-ply laminates, stiffened skew-symmetric angle-ply laminates and stiffened skew-symmetric cross-ply laminates. The effects of fiber orientations (ply angles), number of layers, stiffener depths and degrees of orthotropy are examined.

Key Words
finite element method, free vibration, frequency, stiffened plates, laminated plates, composite, layered model

Address
Guo MW, Parsons Brinkckerhoff Inc, 510 1st Ave North,Suite 500, Minneapolis, MN 55403 USA
Parsons Brinkckerhoff Inc, Minneapolis, MN 55403 USA
Univ Kentucky, Dept Civil Engn, Lexington, KY 40506 USA
Fuzhou Univ, Dept Civil Engn, Fuzhou 35002, Fujian Province, Peoples R China

Abstract
This paper presents a numerical procedure for solving initial-value problems using the special functions which belong to a class of Rvachev\'s basis functions R-bf based on algebraic and trigonometric polynomials. Because of infinite derivability of these functions, derivatives of all orders, required by differential equation of the problem and initial conditions, are used directly in the numerical procedure. The accuracy and stability of the proposed numerical procedure are proved on an example of a single degree of freedom system. Critical time step was also determined. An algorithm for solving multiple degree of freedom systems by the collocation method was developed. Numerical results obtained by R-bf functions are compared with exact solutions and results obtained by the most commonly used numerical procedures for solving initial-value problems.


Key Words
vibrations, numerical solution, Rvachev\'s basis functions, collocation method

Address
Gotovac B, Univ Split, Fac Civil Engn, Matice 15, Split 21000, Croatia
Univ Split, Fac Civil Engn, Split 21000, Croatia


Abstract
The assessment of structural performance of transfer structures under potential seismic actions is presented. Various seismic assessment methodologies are used, with particular emphasis on the accurate modelling of the higher mode effects and the potential development of a soft storey effect in the mega-columns below the transfer plate (TP) level. Those methods include response spectrum analysis (RSA), manual calculation, pushover analysis (POA) and equivalent static load analysis (ESA). The capabilities and limitations of each method are highlighted. The paper aims, firstly, to determine the appropriate seismic assessment methodology for transfer structures using these different approaches, all of which can be undertaken with the resources generally available in a design office. Secondly, the paper highlights and discusses factors influencing the response behaviour of transfer structures, and finally provides a general indication of their seismic vulnerability. The representative Hong Kong building considered in this paper utilises a structural system with coupled shear walls and moment resisting portal-frames, above and below the TP, respectively. By adopting the wind load profile stipulated in the Code of Practice on Wind Effects: Hong Kong-1983, all the structural members are sized and detailed according to the British Standards BS8110 and the current local practices. The seismic displacement demand for the structure, when built on either rock or deep soil sites, was determined in a companion paper. The lateral load-displacement characteristic of the building, determined herein from manual calculation, has indicated that the poor ductility (brittle nature) of the mega-columns, due mainly to the high level of axial pre-compression as found from the analysis, cannot be effectively alleviated solely by increasing the quantity of confinement stirrups. The interstorey drift demands at lower and upper zones caused by seismic actions are found to be substantially higher than those arising from wind loads. The mega-columns supporting the TP and the coupling beams at higher zones are identified to be the most vulnerable components under seismic actions.

Key Words
earthquakes, wind, transfer, structure, displacement, seismic, assessment

Address
Su RKL, Univ Hong Kong, Dept Civil Engn, Pokfulam Rd, Hong Kong, Hong Kong, Peoples R China
Univ Hong Kong, Dept Civil Engn, Hong Kong, Hong Kong, Peoples R China
Univ Melbourne, Dept Civil & Environm Engn, Parkville, Vic 3052, Australia

Abstract
This study aims at postulating a simple methodology for predicting the failure modes of monotonically loaded reinforced concrete beam-column joints. All the factors that affect the failure modes of joints are discussed in detail using an experimental database of monotonically loaded exterior beam-column joints. The relative contributions of the strut and truss mechanisms to joint shear strength are determined based on the test results. A simple design equation for the beam longitudinal reinforcement ratio for joints with low, medium and high amount of stirrups is developed. The factors influencing the failure modes of monotonically loaded exterior beam-column joints are investigated in detail. Design charts that predict the failure modes of exterior beam-column connections both with and without stirrups are developed. Experimental data are compared with the design charts. The results show that the simple methodology gives very accurate predictions of the failure modes.

Key Words
reinforced concrete, monotonically loaded exterior beam column connection, failure mode

Address
Bakir PG, Istanbul Tech Univ, Fac Civil Engn, TR-80626 Istanbul, Turkey
Istanbul Tech Univ, Fac Civil Engn, TR-80626 Istanbul, Turkey

Abstract
Because of the increasing span of arch bridges, ultimate capacity analysis recently becomes more focused both on design and construction. This paper investigates the static and ultimate behavior of a long-span steel arch bridge up to failure and evaluates the overall safety of the bridge. The example bridge is a long-span steel arch bridge with a 550 m-long central span under construction in Shanghai, China. This will be the longest central span of any arch bridge in the world. Ultimate behavior of the example bridge is investigated using three methods. Comparisons of the accuracy and reliability of the three methods are given. The effects of material nonlinearity of individual bridge element and distribution pattern of live load and initial lateral deflection of main arch ribs as well as yield stresses of material and changes of temperature on the ultimate load-carrying capacity of the bridge have been studied. The results show that the distribution pattern of live load and yield stresses of material have important effects on bridge behavior. The critical load analyses based on the linear buckling method and geometrically nonlinear buckling method considerably overestimate the load-carrying capacity of the bridge. The ultimate load-carrying capacity analysis and overall safety evaluation of a long-span steel arch bridge should be based on the geometrically and materially nonlinear buckling method. Finally, the in-plane failure mechanism of long-span steel arch bridges is explained by tracing the spread of plastic zones.

Key Words
ultimate behavior, steel arch bridges, linear buckling, geometrically nonlinear buckling, geometrically and materially nonlinear buckling

Address
Cheng J, Tsing Hua Univ, Dept Civil Engn, Beijing 100084, Peoples R China
Tsing Hua Univ, Dept Civil Engn, Beijing 100084, Peoples R China
Tongji Univ, Dept Bridge Engn, Shanghai 200092, Peoples R China

Abstract
The scaling laws for vibration response of anti-symmetrically laminated plates are derived by applying the similitude transformation to the governing differential equations directly. With this approach, a closed-form solution of the governing equations is not required. This is a significant advantage over the method employed by other researchers where similitude transformation is applied to the closed-form solution. The scaling laws are tested by comparing the similitude fundamental frequencies to the theoretical fundamental frequencies determined from the available closed-form solutions. In case of complete similitude, similitude solutions from the scaling laws exactly agree with the theoretical solutions. Sometimes, it may not be feasible to select the model which obeys the similarity requirement completely, therefore partial similitude is theoretically investigated and approximate scaling laws are recommended. The distorted models in stacking sequences and laminated material properties demonstrate reasonable accuracy. On the contrary, a model with distortion in fiber angle is not recommended. The derived scaling laws are very useful to determine the vibration response of complex prototypes by performing the experiment on a model with required similarities.

Key Words
similitude, laminate, plates, vibration, anti-symmetric laminate, scaling law, frequency invariant

Address
Singhatanadgid P, Chulalongkorn Univ, Dept Engn Mech, Bangkok 10330, Thailand
Chulalongkorn Univ, Dept Engn Mech, Bangkok 10330, Thailand

Abstract
Following a series of experiments on isolated low-rise RC shear walls with openings, a theoretical study on the backbone curve of a perforated shear wall shows that there are some important observations from experimental results that make clear a semi-empirical formula of the backbone curve of a perforated wall. Critical shear zones can be depicted from the configuration of shear walls with openings. Different factors, including the size and location of shear wall openings, the wall\'s height/width ratio, horizontal and vertical steel bar ratios, and location and amount of diagonal steel bars are involved in the derivation of the backbone curve. Bending and shear effects are also considered in the paper. In addition, a comparison of load and displacement for solid and perforated shear walls is discussed. Generally, the comparison between experimental curves and computed backbone curves is favorable.

Key Words
backbone curve, low-rise, shear wall, RC wall, perforated shear wall, load-displacement curve

Address
Yang JS, Carson KC Mok Consulting Engineer PA, 9001 Ottawa Pl, Silver Spring, MD 20910 USA
Carson KC Mok Consulting Engineer PA, Silver Spring, MD 20910 USA
Univ Missouri, Dept Civil Engn, Rolla, MO 65409 USA


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