Showing papers in "Advances in Structural Engineering in 2000"
TL;DR: In this article, a review of possible damage patterns due to asynchronous motion of RC bridges is presented and a brief literature review is undertaken, followed by an assess- ment of the status of seismic design codes concerning this issue.
Abstract: The assumption that earthquake response of extended structures, of which bridges is one example, may be studied ignoring the possibility of out-of- synch motion of various supports is examined in this paper. The purpose is to assess whether the reduction of dynamic response is sufficient to offset the increase in relative displacements, due to independent motion of different supports. The paper starts with a review of possible damage patterns due to asynchronous motion. Thereafter, a brief literature review is undertaken, followed by an assess- ment of the status of seismic design codes concerning this issue. Advanced inelas- tic analysis, using sophisticated material models and analysis techniques, is then employed to explore characteristics of input motion and structural configuration, which may lead to unconservative results from conventional (synchronous) analy- sis. Natural and artificial earthquake records are applied, representing travelling wave as well as geometric incoherence effects. Two model structures of medium span RC bridges are studied, subjected to different boundary conditions that influence the mode contributions. This is undertaken under transverse, longitudinal and verti- cal earthquake motion. The large volume of results, represented as displacement and force time-histories as well as Fourier amplitude spectra of the acceleration response, are distilled and used to assess the balance between dynamic de-tuning and static relative displacements. It is concluded that the conventional synchronous case provides conservative results for vertical vibrations. However, unconservative results, of up to 30%, are obtained for transverse and longitudinal response of short periods of structural vibrations, as well as cases where the higher modes of response are likely to be excited.
44 citations
TL;DR: It is demonstrated that unidentifiable cases are not treatable by existing results valid only for identifiable cases for which the dimension of the manifold is exactly zero and the new proposed method in effectively addressing unidentifiability issues.
Abstract: The present study addresses the issues of non-uniqueness and unidentifiability arising in structural model updating. A Bayesian probabilistic framework is used for model updating which properly handles the uncertainties due to model error and measurement noise associated with model updating. Uncertainties in the model parameters are quantified by probability density functions (PDF) specifying the relative plausibilities of the possible values of the parameters. The Bayesian formulation is well-suited for updating the PDF of the uncertain model parameters taking into account engineering experience and measured dynamic data. Methods are presented for approximating this updated PDF for the general unidentifiable case for which the region of significant probabilities is concentrated in the neighborhood of a manifold of lower dimension than the original parameter space. This PDF is useful for both model updating and structural damage predictions. Asymptotic approximations are also developed for computing the u...
43 citations
TL;DR: In this paper, the influence of compaction methods on the strength of concrete-filled steel tubular members is investigated, and it was found that better compaction of concrete resulted in higher values of the ultimate strength.
Abstract: Tests on twenty-one concrete filled steel tubes to investigate the influence of compaction methods on the strength of concrete filled steel tubular members are reported. Two parameters were investigated, including slenderness ratio and load eccentricity. It was found that better compaction of concrete resulted in higher values of the ultimate strength of concrete filled steel tubular members. The tests show the importance of good concrete compaction for concrete filled steel tubes.
31 citations
TL;DR: In this article, the fiber-reinforced plastic composites are used to strengthen the critical regions of the reinforced concrete frames, so that the seismic behavior (including ductility and energy dissipation cap) is improved.
Abstract: Reinforced concrete buildings with shearwalls are very efficient to resist earthquake disturbances. In general, reinforced concrete frames are governed by flexure and low-rise shearwalls are governed by shear. If a structure includes both frames and shearwalls, it is generally governed by shearwalls. However, the ductility of ordinary reinforced concrete framed shearwalls is very limited. The experiments on framed shearwalls made of corrugated steel was recently reported. It was found that the ductility of framed shearwalls can be greatly improved if the thickness of the corrugated steel wall is appropriate to the surrounding reinforced concrete frame. If the thickness of the corrugated steel wall is too large when compared to the surrounding frame, the ductility will be reduced. It is shown in this paper that the fiber-reinforced plastic composites can be used to strengthen the critical regions of the reinforced concrete frames, so that the seismic behavior (including ductility and energy dissipation cap...
26 citations
TL;DR: An analytical procedure for the elastic buckling of a multi-step non-uniform column subjected to concentrated axial compressive forces is presented in this paper, where the governing differential equation for the buckling problem is estab- lished.
Abstract: An analytical procedure for the elastic buckling of a multi-step non- uniform column subjected to concentrated axial compressive forces is presented in this paper. The governing differential equation for the buckling problem is estab- lished. Special solutions of the governing equation for five different types of non- uniform columns are given. The procedure for determining the fundamental solu- tions that satisfy the normalization conditions is proposed. Using the fundamental solutions and a recurrence formula developed in this paper, the bending moment function that includes only one unknown parameter for each step column can be easily determined. Thus, it is convenient to establish the eigenvalue equation for buckling of a multi-step non-uniform column in terms of the normalized funda- mental solutions of the governing equation. The eigenvalue equations for three gen- eral boundary conditions are given. A numerical example shows that the proposed procedure for determining the critical buckling force of a multi-step non-uniform column with general boundary conditions is a simple, efficient and exact method.
25 citations
TL;DR: In this article, the effect of earthquake ground motion spatial variations on pounding responses of adjacent structures is evaluated by two single-degree-of-freedom (SDOF) oscillators with multiple supports.
Abstract: Pounding damage is a serious seismic hazard in highly populated areas during major earthquakes. This paper evaluates the effect of earthquake ground motion spatial variations on pounding responses of adjacent structures. Adjacent structures are modeled as two single-degree-of-freedom (SDOF) oscillators with multiple supports. Pounding effects are simulated by spring-dashpot pounding elements. Linear elastic and nonlinear inelastic responses are considered in the analysis. Spatial ground motion input is stochastically simulated. The simulated spatial ground motion time histories are compatible with Newmark and Hall design spectrum individually and with an empirical coherency function between each other. The Newmark method with constant acceleration assumption is employed in step-by-step integration to calculate structural response. Numerical results are presented and discussed in terms of various structural and ground motion parameters.
20 citations
TL;DR: In this article, an analysis of the local buckling of composite laminated plates and folded plate assemblies subjected to arbitrary loading is presented using the spline finite strip method, which utilises B 3 -spline functions for the longi- tudinal variation of buckling displacements, and an interpolation of Hermitian poly-nomials for the buckling displacement in the transverse direction.
Abstract: An analysis of the local buckling of composite laminated plates and folded plate assemblies subjected to arbitrary loading is presented. The analysis uses the spline finite strip method, which utilises B 3 -spline functions for the longi- tudinal variation of buckling displacements, and an interpolation of Hermitian poly- nomials for the buckling displacements in the transverse direction. While the spline finite strip method is fairly well-known in buckling analysis, its direct application to the local buckling of composite laminates has been more limited. The method is programmed to study the local buckling of laminated flat plates and L-sections. Examples of the accuracy of the method compared with independent studies, and the influence of increasing the number of lengthwise section knots, are presented for plates of finite length that are subjected to compression, bending and shear.
20 citations
TL;DR: In this paper, the results of a series of tests on high-strength concrete, reported in the literature, from six research studies are used to review the existing recommendations in ACI 318-95 for design of splices and anchorage of reinforcement.
Abstract: The use of high-strength concrete is becoming popular around the world. The american code, ACI 318-95 is used in many countries to calculate the development length of deformed bars in tension. However, current design provisions of ACI 318-95 are based on empirical relationships developed from tests on normal strength concrete. The results of a series of tests on high-strength concrete, reported in the literature, from six research studies are used to review the existing recommendations in ACI 318-95 for design of splices and anchorage of reinforcement. It is shown that ACI 318-95 equations may be unconservative for some cases beyond 62 MPa (9 ksi).
16 citations
TL;DR: In this article, a review of the development of steel space structures is provided, with particular attention to the new technologies and new structural forms employed in China, including composite space trusses, composite reticulated shells, triple-layer space strutses, partial double-layer (single-layer) lattice shells, prestressed grid structures, cable-stayed grid structures; new types of joints; theoretical work and application research.
Abstract: The last decades have seen major advances in the research, design and construction of steel space structures (space grid structures) in China. This paper provides a review of these developments, with particular attention to the new technologies and new structural forms employed in China. The following topics on new technologies and new structures are given emphasis: long-span and large-area grid structures; composite space trusses; composite reticulated shells; triple-layer space trusses; partial double-layer (single-layer) lattice shells; prestressed grid structures; cable-stayed grid structures; special grid structures; new types of joints; theoretical work and application research. Prospects for steel space structures in the 21st century are presented at the end of this paper.
12 citations
TL;DR: In this paper, a full-size test program was carried out on 26 simply-supported and continuous reinforced and partially prestressed concrete beams to study the cracking behaviour and damping characteristics of concrete beams.
Abstract: A full-size test program was carried out on 26 simply-supported and continuous reinforced and partially prestressed concrete beams to study the cracking behaviour and damping characteristics of concrete beams. The beams were subjected to free vibration tests and logarithmic decrement values corresponding to each load level were measured. Separate regression analyses on the reinforced and the partially prestressed beams were undertaken. These analyses resulted in two separate empirical formulae for predicting the logarithmic decrement of damping in reinforced and in partially prestressed beams. Comparison with test results from all 26 beams indicates that the predictions are accurate. It is also found that the damping formula for reinforced beams is applicable to both single and continuous spans. The proposed damping formulae predict damping from the residual crack widths of the beams. As such, formulae developed for predicting residual crack widths from given variables defining the beams and their deflection-span ratios are also reported.
11 citations
TL;DR: In this article, the aerodynamic responses of a tall steel lattice transmission tower were examined using a 1:100 full aeroelastic model in a boundary-layer flow with adequate turbulence intensities.
Abstract: The aerodynamic responses of a tall steel lattice transmission tower are examined using a 1:100 full aeroelastic model in a boundary-layer flow with adequate turbulence intensities. Since the structure modelled is composed of 583 thin wall steel tubes, it is difficult to construct a perfect aeroelastic model. In this study, an equivalent scattered stiffness method was developed to overcome the difficulties. The results presented and discussed include the aerodynamic force coefficients, acceleration responses and wind load factors at various wind velocities and wind attack angles. It is revealed that the wind load factors increase with wind mean velocity and along the model height. The wind-induced dynamic responses in two sway directions are approximately equal for any wind attack angle. In other words, across-wind vibration is evident. Spectral analysis based on the Kaimal spectrum and F.E.M., which takes into account wind-structure coupling effects, was also developed for calculating the wind-induced dy...
TL;DR: In this paper, the problem of large displacement and large rotation analysis of space frame structures by means of group theory and substructuring technique is addressed by using one element per member, so that the number of degrees of freedom could be kept to minimum.
Abstract: The reduction of the number of unknowns while capturing the essential physical features in a nonlinear analysis of large spatial structures has long been a challenging task for researchers. We approach the problem of large displacement and large rotation analysis of space frame structures by means of group theory and substructuring technique. An accurate nonlinear analysis requires an element that accurately reflects the nonlinear behavior of the structure being modeled. Therefore details of the element formulations and updating procedure for large rotation will be given. The present formulation is capable of modeling a structure (with small to moderate axial force in its members) using one element per member, so that the number of degrees of freedom could be kept to minimum. The present methodology is based on the approach in a paper by Healey and Treacy. Axial deformation only was considered and matrix-iteration was used. We extend their idea to deal with the analysis of symmetry structures under going ...
TL;DR: In this paper, the authors present an assessment of the most commonly adopted dome configurations and their effect on the dome characteristics such as the stiffness/weight value, member stress distribution, number of joints and members, degree of redundancy and cost.
Abstract: Braced domes may be fabricated in any of several common grid configurations. With different configurations, the dome performance varies considerably affecting both its competitiveness and suitability for specific applications. The study presented in this paper is an assessment of the most commonly adopted dome configurations and their effect on the dome characteristics such as the stiffness/weight value, member stress distribution, number of joints and members, degree of redundancy and cost. The study is parametric and covers wide variations of dome span/rise ratio and boundary conditions. The results of this study could be of significant value to the design of future braced dome structures.
TL;DR: In this article, a set of analytical benchmark solutions for steel frames comprising non-compact sections, which can be used to verify the accuracy of simplified concentrated plasticity methods of advanced analysis were obtained using a distributed plasticity shell finite element model.
Abstract: Application of "advanced analysis" methods suitable for non-linear analysis and design of steel frame structures permits direct and accurate determination of ultimate system strengths, without resort to simplified elastic methods of analysis and semi-empirical specification equations However, the application of advanced analysis methods has previously been restricted to steel frames comprising only compact sections that are not influenced by the effects of local buckling A research project has been conducted with the aim of developing concentrated plasticity methods suitable for practical advanced analysis of steel frame structures comprising non-compact sections This paper contains a comprehensive set of analytical benchmark solutions for steel frames comprising non-compact sections, which can be used to verify the accuracy of simplified concentrated plasticity methods of advanced analysis The analytical benchmark solutions were obtained using a distributed plasticity shell finite element model that
TL;DR: In this article, the important aspects of softening of concrete frame structures are reviewed, and an example is presented to demonstrate that a HSC frame structure with steeper softening slopes will have a lower collapse load.
Abstract: In the 21st century, computing facilities will make it possible to opt on a regular basis for more accurate rigorous methods of analysis. A rigorous collapse load analysis requires a knowledge of the behaviour of plastic hinges up to advanced curvatures. Concrete sections characteristically soften, that is the bending moment capacity decreases with increasing curvatures after the end of the plastic plateau while steel sections undergo a hardening phase. Consideration of softening is essential in a rational analysis. In this paper, the important aspects of softening of concrete frame structures are reviewed. High-strength concrete (f'c > 50 MPa) is a more brittle construction material than normal strength concrete. High-strength concrete sections show a steeper softening slope when compared with similar normal strength concrete sections. An example is presented to demonstrate that a HSC frame structure with steeper softening slopes will have a lower collapse load.
TL;DR: In this article, the behaviour of steel column base connections is reviewed, focusing on the results from programmes of laboratory testing and finding that pinned bases provide significant rotational restraint and are capable of transferring quite large moments into the foundations.
Abstract: Previous studies of the behaviour of steel column base connections are reviewed; attention is concentrated on the results from programmes of laboratory testing. Nominally pinned bases are shown to provide significant rotational restraint and to be capable of transferring quite large moments into the foundations. Ways of representing these effects in frame analysis are investigated and, based on sample studies, a recommendation is provided.
TL;DR: In this paper, a concentrated plasticity formulation suitable for practical advanced analysis of steel frame structures comprising non-compact sections is presented, referred to as the refined plastic hinge method, implicitly accounts for the effects of gradual cross-sectional yielding, longitudinal spread of plasticity, initial geometric imperfections, residual stresses, and local buckling.
Abstract: Application of "advanced analysis" methods suitable for non-linear analysis and design of steel frame structures permits direct and accurate determination of ultimate system strengths, without resort to simplified elastic methods of analysis and semi-empirical specification equations. However, the application of advanced analysis methods has previously been restricted to steel frames comprising only compact sections that are not influenced by the effects of local buckling. A concentrated plasticity formulation suitable for practical advanced analysis of steel frame structures comprising non-compact sections is presented in this paper. This formulation, referred to as the refined plastic hinge method, implicitly accounts for the effects of gradual cross-sectional yielding, longitudinal spread of plasticity, initial geometric imperfections, residual stresses, and local buckling.
TL;DR: The polynomial optimization technique is used to determine the minimum cost of reinforced concrete members by considering several design variables such as breadth, depth, area of reinforcing steel etc and is represented in the form of “Nomograms” which will facilitate the work in the design office.
Abstract: Structural optimization seeks the selection of design variables to achieve within the limit (constraints) placed on the structural behaviour, geometry or other factors; its goal of optimality defined by the objective function for specified loading conditions. The three basic features design variables, objective function and constraints contrive to form the design problem. There are several mathematical techniques to solve such problems. The polynomial optimization technique is a recently evolved procedure which is concerned with finding the minimum of a polynomial objective function subjected to constraints. A structural design problem has been formulated in this manner which enables minimum cost design to be derived rapidly and simply. A paper deals with the application of Polynomial optimization technique to R.C.C. beam-member design problem. In the present study this technique is used to determine the minimum cost of reinforced concrete members by considering several design variables such as breadth, d...
TL;DR: In this article, an analytical study on interface failure under the joint action of constant compression and cyclic anti-plane shear is presented, where analytical solutions are presented for the evolution and distributions of shear stress and displacement along the entire length of the shear beam during unloading and reloading processes.
Abstract: Based on the so-called "shear beam model", an analytical study is presented on interface failure under the joint action of constant compression and cyclic anti-plane shear. Analytical solutions are presented for the evolution and distributions of shear stress and displacement along the entire length of the shear beam during unloading and reloading processes. Results indicate that, owing to the existing of a damage process zone ahead of the crack tip, both unloading and reloading are inelastic and are accompanied by friction and damage dissipation. Furthermore, "stress locking" will occur if an unloading process can not erase the damage zone left by its neighboring loading process. Analysis of structural response presented at the end of the paper clarifies two different kinds of structural responses: 1) contact plastic shakedown and 2) progressive failure.
TL;DR: The importance of information technology research and development for economic growth and prosperity is presented in this article, where the major missio of the research for fundamental science and engineering base is discussed.
Abstract: In this paper, importance of information technology research and development for economic growth and prosperity is presented. Major missio of the research for fundamental science and engineering base is discussed. Critical points of the mechanics and materials research in the 21 st Century are proposed.
TL;DR: In this paper, the authors discuss three methods for solving the damping coupled modal coordinate system equations of suspension bridges and demonstrate that non-classical damping may have a significant influence on the seismic response of the suspension bridges.
Abstract: Modern suspension bridges have stiffening steel decks and RC towers The well separated different materials cause damping to be unevenly distributed for the complete bridge, known as “non-classical” damping The equations of motion for such structures are damping coupled in the modal coordinate system Most commercial dynamic finite element analysis computer programs can not solve these equations This paper discusses three methods for solving the equations and their implementation in computer programs The seismic response analyses of the Tsing Ma bridge and Humen bridge indicate that non-classical damping may have a significant influence on the seismic response of suspension bridges
TL;DR: In this paper, the design of reinforcement in prestressed concrete beams with openings based on the application of regression analysis to experimental data is discussed. But the results, verified by tests and the finite element method, show that a new method described in the paper is simple, convenient and reliable, and can be used in engineering design.
Abstract: This paper is concerned with the design of reinforcement in prestressed concrete beams with openings, based on the application of regression analysis to experimental data. The results, verified by tests and the finite element method, show that a new method described in the paper is simple, convenient and reliable, and can be used in engineering design.
TL;DR: In this paper, the buckling behavior of a uniformly compressed rectangular composite panel with the two unloaded edges elastically restrained is analyzed using a semi-numerical approach, the finite strip method.
Abstract: This paper gives details of theoretical investigations into the buckling behaviour of uniformly compressed rectangular composite panel with the two unloaded edges elastically restrained. The theoretical elastic buckling analysis employs a semi-numerical approach, the finite strip method. This general method of approach is to postulate a fifth degree polynomial function which describe the buckled form of the panel. Based on the principle of minimum potential energy, the strain energies of the restraining medium along the unloaded edges are evaluated in term of matrix form. This elastic restraint stiffness matrix can be added directly onto the existing stiffness matrix. To utilize the Rayleigh-Ritz method, coefficients in the deflection series are evaluated. Hence the elastic buckling stiffness of the composite panel are obtained.
TL;DR: In this paper, the response of complete Torospherical shells under internal dynamic pressure was investigated and it was shown that the response depends not only on the frequency of dynamic pressure but also on the ratio of the radii of the toroidal segments to that of the spherical segments.
Abstract: The study reported here is concerned with the response of complete Torospherical shells under internal dynamic pressure. The Torospherical shell modelled from an Ellipsoidal shell consists of a combination of spherical segments joined with toroidal segments of circular cross-section. The nonlinear systems of dynamic equations formulated were solved using trigonometric projection procedures and Newton's iterative processes. Two types of torospherical shells were analysed and compared. Results show that the dynamic response of the Torospherical shells subjected to internal dynamic pressure depends not only on the frequency of dynamic pressure but specifically on the ratio of the radii of the toroidal segments to that of the spherical segments. We also discovered that if loss of dynamic stability of ellipsoidal shells is largely axisymmetrical, loss of dynamic stability of Torospherical shells is asymmetrical with formation of circular waves in the circumferential direction. The modes of vibration of the Tor...
TL;DR: In this article, the behavior of very slender concrete filled tubular columns and hollow tubular column with circular sections subjected to axial load was investigated experimentally, and the results indicated that the concrete infill increases the compressive load capacity of the steel tube.
Abstract: The behavior of very slender concrete filled tubular columns and hollow tubular columns with circular sections subjected to axial load was investigated experimentally. A total of fifteen specimens including eleven concrete filled steel tubular columns and four hollow tubular columns were studied. The main objectives of these tests were twofold: first, to describe a series of tests on very slender composite columns; and secondly, to compare the accuracy of the predictions by using the recommendations of LRFD, AIJ, EC4 and DL/T 5085. Experimental results indicate that the concrete infill increases the compressive load capacity of the steel tube. The loading capacity of the concrete filled steel tubular columns can be conservatively predicted by using LRFD, AIJ, EC4 and DL/T 5085 recommendations for normal length columns.