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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Structural Engineering and Mechanics
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Volume & Issues
Volume 12, Issue 6 - Dec 2001
Volume 12, Issue 5 - Nov 2001
Volume 12, Issue 4 - Oct 2001
Volume 12, Issue 3 - Sep 2001
Volume 12, Issue 2 - Aug 2001
Volume 12, Issue 1 - Jul 2001
Volume 11, Issue 6 - Jun 2001
Volume 11, Issue 5 - May 2001
Volume 11, Issue 4 - Apr 2001
Volume 11, Issue 3 - Mar 2001
Volume 11, Issue 2 - Feb 2001
Volume 11, Issue 1 - Jan 2001
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Structural identification of a steel frame from dynamic test-data
Morassi, A. ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 237~258
DOI : 10.12989/sem.2001.11.3.237
Structural identification via modal analysis in structural mechanics is gaining popularity in recent years, despite conceptual difficulties connected with its use. This paper is devoted to illustrate both the capabilities and the indeterminacy characterizing structural identification problems even in quite simple instances, as well as the cautions that should be accordingly adopted. In particular, we discuss an application of an identification technique of variational type, based on the measurement of eigenfrequencies and mode shapes, to a steel frame with friction joints under various assembling conditions. Experience has suggested, so as to restrict the indeterminacy frequently affecting identification issues, having resort to all the a priori acknowledged information on the system, to the symmetry and presence of structural elements with equal stiffness, to mention one example, and mindfully selecting the parameters to be identified. In addition, considering that the identification techniques have a local character and correspond to the updating of a preliminary model of the structure, it is important that the analytical model on the first attempt should be adequately accurate. Secondly, it has proved determinant to cross the results of the dynamic identification with tests of other typology, for instance, static tests, so as to fully understand the structural behavior and avoid the indeterminacy due to the nonuniqueness of the inverse problem.
Impact study for multi-girder bridge based on correlated road roughness
Liu, Chunhua ; Wang, Ton-Lo ; Huang, Dongzhou ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 259~272
DOI : 10.12989/sem.2001.11.3.259
The impact behavior of a multigirder concrete bridge under single and multiple moving vehicles is studied based on correlated road surface characteristics. The bridge structure is modeled as grillage beam system. A 3D nonlinear vehicle model with eleven degrees of freedom is utilized according to the HS20-44 truck design loading in the American Association of State Highway and Transportation Officials (AASHTO) specifications. A triangle correlation model is introduced to generate four classes of longitudinal road surface roughness as multi-correlated random processes along deck transverse direction. On the basis of a correlation length of approximately half the bridge width, the upper limits of impact factors obtained under confidence level of 95 percent and side-by-side three-truck loading provide probability-based evidence for the evaluation of AASHTO specifications. The analytical results indicate that a better transverse correlation among road surface roughness generally leads to slightly higher impact factors. Suggestions are made for the routine maintenance of this type of highway bridges.
Shaking table study of a 2/5 scale steel frame with new viscoelastic dampers
Chang, K.C. ; Tsai, M.H. ; Lai, M.L. ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 273~286
DOI : 10.12989/sem.2001.11.3.273
Viscoelastic (VE) dampers have shown to be capable of providing structures with considerable additional damping to reduce the dynamic response of structures. However, the VE material appears to be sensitive to the variations in ambient temperature and vibration frequency. To minimize these effects, a new VE material has been developed. This new material shows less sensitivity to variations in vibration frequency and temperature. However, it is highly dependent on the shear strain. Experimental studies on the seismic behavior of a 2/5 scale five-story steel frame with these new VE dampers have been carried out. Test results show that the structural response can be effectively reduced due to the added stiffness and damping provided by the new type of VE dampers under both mild and strong earthquake ground motions. In addition, analytical studies have been carried out to describe the strain-dependent behavior of the VE damper. The dynamic properties and hysteresis behavior of the dampers can be simulated by a simple bilinear model based on the equivalent dissipated energy principle proposed in this study.
Fuzzy logic based estimation of effective lengths of columns in partially braced multi-storey frames
Menon, Devdas ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 287~299
DOI : 10.12989/sem.2001.11.3.287
Columns in multi-storey frames are presently categorised as either braced or unbraced, usually by means of the stability index criterion, for estimating their effective length ratios by design aids such as 'alignment charts'. This procedure, however, ignores the transition in buckling behaviour between the braced condition and the unbraced one. Hence, this results in either an overestimation or an underestimation of effective length estimates of columns in frames that are in fact 'partially braced'. It is shown in this paper that the transitional behaviour is gradual, and can be approximately modelled by means of a 'fuzzy logic' based technique. The proposed technique is simple and intuitively agreeable. It fills the existing gap between the braced and unbraced conditions in present codal provisions.
Shear-fatigue behavior of high-strength reinforced concrete beams under repeated loading
Kwak, Kae-Hwan ; Park, Jong-Gun ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 301~314
DOI : 10.12989/sem.2001.11.3.301
The purpose of this experimental study is to investigate the damage mechanism due to shear-fatigue behavior of high-strength reinforced concrete beams under repeated loading. The relationship between the number of cycles and the deflection or strain, the crack growths and modes of failure with the increase of number of cycles, fatigue strength, and S-N curve were observed through a fatigue test. Based on the fatigue test results, high-strength reinforced concrete beams failed at 57-66 percent of static ultimate strength for 2 million cycles. The fatigue strength at 2 million cycles from S-N curves was shown as about 60 percent of static ultimate strength. Compared to normal-strength reinforced concrete beams, fatigue capacity of high-strength reinforced concrete beams was similar to or lower than fatigue capacity of normal-strength reinforced concrete beams. Fatigue capacity of normal-strength reinforced concrete beams improved by over 60 percent.
Viscoplastic collapse of titanium alloy tubes under cyclic bending
Lee, Kuo-Long ; Pan, Wen-Fung ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 315~324
DOI : 10.12989/sem.2001.11.3.315
This paper presents the experimetal result on the viscoplastic response and collapse of the titanium alloy tubes subjected to cyclic bending. Based on the capacity of the bending machine, three different curvature-rates were used to highlight the viscoplastic behavior of the titanium alloy tubes. The Curvature-controlled experiments were conducted by the curvature-ovalization measurement apparatus which was designed by Pan et al. (1998). It can be observed from experimental data that the higher the applied curvature-rate, the greater is the degree of hardening of titanium alloy tube. However, the higher the applied curvature-rate, the greater is the degree of ovalization of tube cross-section. Furthermore, due to the greater degree of the ovalization of tube cross-section for higher curvature-rates under cyclic bending, the number of cycles to produce buckling is correspondingly reduced. Finally, the theoretical formulation, proposed by Pan and Her (1998), was modified so that it can be used for simulating the relationship between the controlled curvature and the number of cycles to produce buckling for titanium alloy tubes under cyclic bending with different curvature-rates. The theoretical simulation was compared with the experimental test data. Good agreement between the experimental and theoretical results has been achieved.
A direct modification method for strains due to non-conforming modes
Choi, Chang-Koon ; Chung, Keun-Young ; Lee, Tae-Yeol ;
Structural Engineering and Mechanics, volume 11, issue 3, 2001, Pages 325~340
DOI : 10.12989/sem.2001.11.3.325
This paper addresses an efficient modification method that eliminates the undesirable effects of strains due to various non-conforming modes so that the non-conforming element can pass the patch test unconditionally. The scheme is incorporated in the element formulation to establish new types of non-conforming hexahedral elements designated as NHx and NVHx for the regular element and variable node element, respectively. Non-conforming displacement modes are selectively added to the ordinary (conforming) element displacement assumptions to improve the bending behavior of the distorted solid element. To verify the validation of proposed direct modification method and the improvement of element behavior, several numerical tests are carried out. Test results show that the proposed method is effective and its applications to non-conforming solid elements guarantee for the element to pass the patch test.