Nonlinear Analysis Program Research Articles

Seismic capacity of masonry infilled RC frame strengthening with expanded metal ferrocement

This research was to investigate the behavior of masonry infilled reinforced concrete frame strengthening with expanded metals under cyclic loading. In this study, a prototype frame was chosen from a three-story reinforced concrete building that was not designed for earthquake load. Three specimens were built to full scale of 1:1 ratio including, the reinforced concrete bare frame (BF), the brick masonry infilled frame (W) and the masonry infilled frame strengthening with an expanded metal sheet (W-SR). The specimens were tested under constant vertical load and cyclic lateral load. The infilled frame strengthening with expanded metal sheet (W-SR) provided the lateral strength, stiffness and energy dissipation capacity of 1.25, 1.26, 1.27 times those of the brick masonry infilled frame (W), respectively. An analytical model based on an equivalent strut was proposed for masonry infill panels. In this approach, the nonlinear behavior obtained from the masonry prism test results was employed to determine the lateral strength and stiffness of the masonry panel model. The hysteretic behavior of the infill panel and infilled frame was evaluated using a nonlinear structural analysis program, RUAUMOKO. The results of the hysteretic behavior were compared with the experimental results to validate the proposed model.

Simplified Step-by-Step Nonlinear Static Program Investigating Equilibrium Conditions of Electrons in Atom and Ionization Energies: Case Study on Argon

For investigation of equilibrium conditions of electrons in an atom, and Ionization Energies of Elements, a simplified deterministic static model is proposed. The electrons are initially uniformly and sparsely arranged on the outer surface of nucleus. Then, by taking into account the nucleus-electron interaction (attractive and repulsive) and the mutual electron-electron repulsions, and by a simple step-by-step nonlinear static analysis program, all the electrons are found to equilibrate on the outer surface of the same sphere, which is concentric and larger than nucleus. In a second stage, starting from an equilibrium sphere of electrons, one of the electrons is subjected to gradual forced removal, radially and outwards with respect to nucleus. Within each removal step, the produced work increment is determined and the increments are summed. When no more significant attraction is exerted by nucleus to removed electron, the total work gives the Ionization Energy. After removing of single electron, the remaining electrons fall on a lower shell, that is, they equilibrate on the outer surface of a smaller concentric sphere. For nucleus-electron interaction, an L-J (Lennard-Jones) type curve, attractive and repulsive, is adopted. When the parameter of this curve is n > 1.0, the Ionization Energy exhibits an upper bound. As parameter n increases from 1.0 up to 2.0, the attractive potential of L-J curve is gradually weakened. The proposed model is applied on Argon. It is observed that, as the number of electrons increases, the radius of equilibrium sphere increases, too, whereas the attractive nucleus-electron potential is reduced; thus the Ionization Energy is reduced, too. Particularly, as the number of electrons and the radius of equilibrium sphere exceed some critical values, the above two last quantities exhibit abrupt falls. A regular polyhedron is revealed, which can accommodate Elements up to atomic number Z = 146, that is 28 more than Z = 118 of existing last Element, as guide for initial locations of electrons in the above first program.

Experimental Validation of Numerical Model for Bi‐Tilt‐Isolator

Bi‐Tilt Isolator (BTI) is composed of bi‐tilt beveled substrate and slider. The advantages of BTI are that the maximum upload seismic force of structure can be easily controlled and displacement of isolation layer will be reduced. Sliding force, friction force, and impulse force are caused in the slanting process of BTI, nonlinear behavior. A nonlinear mathematical model is derived based on the sliding upwards, sliding downwards, and transition stages. Then, BTI element of nonlinear analysis program, GENDYN, is developed by the fourth‐order Runge‐Kutta method, the discretized ordinary differential equation for three movement stages of BTI. Then, test set‐up of superstructure installed with BTI is tested and recorded the real displacement and acceleration responses under conditions of full lubrication, mild lubrication, and without lubrication between interface of bi‐tilt beveled substrate and slider with three various initial displacements. The comparison of simulation results and test results shows the following: (1) root mean square error is below 1.35% for WD40 sprayed, 0.47% for WD40 whipped, and 0.54% for without lubrication, respectively; (2) the maximum root mean square error for simulating with cubic polynomial function of friction is much less than those of constant friction except conditions of full lubrication, which are not affected by kinetic friction force; (3) application of cubic polynomial function for simulating friction of BTI with three different lubricated conditions can perform very fine simulation results, compared with the test results. This proposed mathematical model and BTI element of GENDYN program, using cubic polynomial function of friction, perform fine simulation capability to assess nonlinear isolation effect of structure installed with BTI.

Performance assessment of novel hollow and solid RC columns using simulation of shaking table test

The purpose of this study was to investigate the seismic performance of novel hollow and solid reinforced-concrete (RC) columns with triangular reinforcement details when subjected to impulsive near-fault ground motions. The results of numerical simulations of shaking table tests on six hollow columns and six solid columns are presented. The developed reinforcement details are shown to be economically feasible and rational, and they facilitate shorter construction periods. The use of a sophisticated non-linear finite-element analysis program enhanced the accuracy and objectivity of the assessment process. The computer program RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used to analyse the RC structures. The equations of motion were solved by numerical integration using the Hilber–Hughes–Taylor algorithm. The numerical method used gave a realistic prediction of seismic performance throughout the input ground motions for several column specimens investigated. As a result, the developed triangular reinforcement details were considered to be superior to existing reinforcement details in terms of the required seismic performance. Such an analysis to study the seismic response of novel hollow and solid RC columns should lead to realistic and safe design.

Accuracy of three-dimensional seismic ground response analysis in time domain using nonlinear numerical simulations

To provide appropriate uses of nonlinear ground response analysis for engineering practice, a three-dimensional soil column with a distributed mass system and a time domain numerical analysis were implemented on the OpenSees simulation platform. The standard mesh of a three-dimensional soil column was suggested to be satisfied with the specified maximum frequency. The layered soil column was divided into multiple sub-soils with a different viscous damping matrix according to the shear velocities as the soil properties were significantly different. It was necessary to use a combination of other one-dimensional or three-dimensional nonlinear seismic ground analysis programs to confirm the applicability of nonlinear seismic ground motion response analysis procedures in soft soil or for strong earthquakes. The accuracy of the three-dimensional soil column finite element method was verified by dynamic centrifuge model testing under different peak accelerations of the earthquake. As a result, nonlinear seismic ground motion response analysis procedures were improved in this study. The accuracy and efficiency of the three-dimensional seismic ground response analysis can be adapted to the requirements of engineering practice.

Structural stability of cable-stayed bridges during construction

This paper presents an investigation of the stability characteristics of steel cable-stayed bridges during construction. In general, cable-stayed bridges are subjected to quite large compressive forces induced by stayed cables, and may become unstable during their construction stage, due to the excessive compressive forces induced by added construction loads. To solve the structural instability problems of the bridges under construction, a nonlinear analysis program was developed based on the theory of nonlinear finite element analysis. The complex stability characteristics of cable-stayed bridges during construction were investigated through a series of rigorous geometric nonlinear analyses, including various structural nonlinearities such as cable-sag effect, beam-column effect of girder and mast, large displacement effect, and girder-mast-cable interaction. To consider the construction characteristics of the cable-stayed bridges, a three-step analysis method is proposed, and used in the present study. In addition, the effects of various cable-arrangement types and girder-mast stiffness ratios on the stability characteristics were extensively investigated. Typical buckling modes can be classified into two categories, depending on the location of critical member or members.

Investigation of Plastic Hinge Length in Reinforced Concrete Columns on Column Behavior

In reinforced concrete buildings in case of a possible earthquake, the buildings slamp as they lost their horizontal stability because of hinging of column ends. The assumptions for plastic hinge lengths are present during project stage of reinforced concrete buildings. According to Turkish Earthquake Regulations, although plastic hinge length is determined to be 0.5h, it's known that plastic hinge length is determined via various formulas in some other regulations all over the world. In reinforced concrete columns, it's necessary to indicate the effect of plastic hinge length on the column behavior. For this purpose, pushover analysis of 5 column samples having different plastic hinge lengths was performed with non-linear analysis program. As a result of pushover analysis, situations of plastic hinges formed in columns and their load-displacement curves were determined. The graphs and the data were compared and the results were discussed.

Influence of the SMA Constitutive Model on the Response of Structures

Strong earthquakes may impose significant displacements in structures, which can result in excessive displacements at structural joints. Previous numerical studies have shown that the recentring capability of shape memory alloys (SMA) can be applied to limit joint openings and maximum longitudinal displacements. However, these studies do not focus on the influence of the SMA constitutive model adopted on the estimated displacements. A sensitivity analysis was performed using simplified two-degree-of-freedom models, which represent two-frame reinforced concrete bridges with various ratios of natural periods of vibration, connected by SMA bars. These models were implemented in a MATLAB based program for nonlinear dynamic analysis. The obtained results show that the relative displacements are more sensitive to the SMA model than the absolute displacements.

Inelastic Seismic Response of Building with Friction Damper

Dampers are used to control response of structure in recent years. Seismic response is reduced by adding energy dissipation capacity to the building. Dampers are provided to dissipate energy to reduce the damages on buildings. Relative displacement of two floors are opposed by damper elements. Dampers dissipate energy with no or little degradation in strength and stiffness. This work presents the response of structure with energy dissipation device i.e. friction damper built on soft soil when the structure is subjected to a ground motion. Parameters that influence strength and stiffness of structure and energy dissipating device are studied. Response of structure with energy dissipating device is analyzed and it is shown that building with damper shows better performance during earthquake. Building structures are designed using results from elastic analysis, though inelastic behavior well observed during the earthquake. Actual response of the structure can be estimated in the inelastic range by using nonlinear structural analysis programs. Inelastic Damage indices of structural component, overall building are computed by formulating Modified Park and Ang model. Nonlinear analysis program IDARC 2D is used for modeling and analysis. Modeling of friction damper is done using a Wen–Bouc model without stiffness and strength or strength degradation. These devices are modeled with an axial diagonal element. Pseudo force approach is introduced to consider the forces in damper elements, that is, forces in damper elements are subtracted from external load vector. Smooth hysteretic model is used to model response of friction dampers. Nonlinear dynamic analysis is carried out using Newmark-Beta integration method and the pseudo-force method. Damaged state of structure is obtained to observe whether elements are cracked, yielded or failed during analysis. Response parameters such as lateral floor displacement, storey drift, base shear are also computed.

STANDARD SECTION DESIGN OF ICH RC TOWER SUPPORTING 5.0MW WIND TURBINE

A new-type wind power tower, internally confined hollow reinforced concrete (ICH RC) tower was developed and its standard sections were designed. Its targeting turbine capacity was 5.0 MW and the large displacement effect by turbine weight was considered. CoWiTA which is a non-linear analysis program was used for analyzing each section. Initial bottom diameter of the tower was 5.5 m with hollow ratios; 0.9, 0.85, 0.80, and 0.75 and 10% smaller diameter case was also considered with the same hollow ratios. In addition, the ICH RC tower could be separated into some modules for convenience of construction and installation. Each cross section at top and bottom of modules was designed and analysis of the sections was performed as well. As a result, all design cases except one case showed enough performance to support a 5.0 MW turbine. Also, it was confirmed that the modularized ICH RC wind tower satisfied with required load condition at each height by analyzing modules.

Manufacturing and evaluation of Large-scale Composite Bumper System for bridge pier protection against ship collision

An innovative Large-scale Composite Bumper System (LCBS) for bridge piers against ship collision was recently proposed at Nanjing Tech University. The modular segment of LCBS is made of Glass Fiber-Reinforced Polymer (GFRP) skins, GFRP lattice webs, Polyurethane (PU) foam cores and ceramic particles in which Vacuum Assisted Resin Infusion Process (VARIP) is adopted in the manufacturing process. This novel bumper system offers several remarkable advantages, such as: self-buoyancy in water, modular fabrication of segments, efficiency for on-site installation, excellent corrosion resistance, as well as ease in replacing damaged segments. In this paper, the manufacture procedures as well as the installation process of LCBS were introduced. An in-depth analysis of performance evaluation of LCBS was then conducted for a real cable stayed bridge using a nonlinear explicit dynamic finite-element analysis program (LS-DYNA). The simulation results indicated that LCBS can effectively increase the impact time of ship-bridge collision, and reduce the peak collision forces to a non-destructive level, leading to a good effect in energy dissipation. The results suggest that LCBS is an effective bumper system for protecting bridges and ships in ship-bridge collisions.

Theoretical and revisited experimentally retrieved He-broadened line parameters of carbon monoxide in the fundamental band

We report revisited experimentally retrieved and theoretically calculated He-broadened Lorentz half-width coefficients and He- pressure-shift coefficients of 45 carbon monoxide transitions in the 1←0 band. The spectra analyzed in this study were recorded over a range of temperatures between 79 and 296K. The He-broadened line parameters and their temperature dependences were retrieved using a multispectrum nonlinear least squares analysis program. The line shape models used in this study include Voigt, speed dependent Voigt, Rautian (to take into account confinement narrowing) and Rautian with speed dependence, all with an asymmetric component added to account for weak line mixing effects. We were unable to retrieve the temperature dependence of line mixing coefficients. A classical method was used to determine the He-narrowing parameters while quantum dynamical calculations were performed to determine He-broadening and He-pressure shifts coefficients at different temperatures. The line mixing coefficients were also derived from the exponential power gap law and the energy corrected sudden approximation. The current measurements and theoretical results are compared with other published results, where appropriate.

Experimental and numerical results of dynamics behavior of a nonlinear piezoelectric beam

ABSTRACTThis article presents a numerical formulation and experimental implementation for the dynamics behavior verification of the nonlinear piezoelectric beam through harmonic excitation. The nonlinear piezoelectric beam dynamic analysis program is developed with MATLAB software. To verify the nonlinear piezoelectric beam dynamic analysis results, the experimental results are used for the vibration analysis of a piezoelectric beam to the harmonic excitation of the base of the beam. Then, the piezoelectric effect on the output voltage, velocity, acceleration values, and the time response are obtained. Afterwards, the effects of the excitation velocity and the position of concentrated mass on the output voltage are verified.

Evaluating nonlinear effective stress site response analyses using records from the Canterbury earthquake sequence

A widely used one-dimensional nonlinear effective stress site response analysis program is used to model the response of potentially liquefiable soils during strong shaking. Ground motion records from six events of the 2010–2011 Canterbury earthquake sequence and the extensive site investigation data that have been obtained for the Christchurch area provide the basis for the analyses. The results of the analyses depend significantly on the input motions and soil profile characterization, so these important aspects are examined. Deconvolved Riccarton Gravel input motions were generated, because recorded rock or firm layer motions were not available. Nonlinear effective stress seismic site response analyses are shown to capture key aspects of the observed soil response through the comparison of acceleration response spectra of calculated surface motions to those of recorded surface motions; however, equivalent-linear and total stress nonlinear analyses capture these aspects as well. Biases in the computed motions compared to recorded motions were realized for some cases but they can be attributed primarily to the uncertainty in the development of the input motions used in the analyses.

Development of a General Component-Based Connection Element for Structural Fire Engineering Analysis

This paper reports on the development of a general-purpose Eurocode-compliant component-based connection finite element for steel-to-steel joints in fire. The development begins by utilising the temperature-dependent connection component characteristics previously developed at the University of Sheffield to create a component-based connection finite element to model flush endplate connections. Subsequently the element was extended to a new connection type with high ductility, the reverse channel. The component models have been developed for the reverse channel under tension and compression. The element has been incorporated into the nonlinear global structural analysis program Vulcan, in which it has been used along with a static-dynamic formulation. The use of the element is illustrated by modelling a fire test at the University of Manchester in which reverse channel connections were used.

TIME-HISTORY ANALYSIS RESULTS OF RC FRAMES FOR DIFFERENT GROUND ACCELERATIONS

Recent earthquake in Japan has increased the interest in seismic-resistance performance of building structures in Korea. Earthquake damages not only collapsed the buildings but also caused huge loss of both human lives and property. Therefore, the school buildings, which are often used as an emergency shelter during an earthquake, should be evaluated of their seismic-resistance performance. This study used a nonlinear dynamic analysis program, OpenSees, to perform nonlinear static and dynamic analyses for the seismic-resistance evaluation of school buildings, which were not designed for an earthquake load. Actual earthquake waves were normalized to make them similar to design acceleration spectrum as specified by current seismic design code KBC 2009. Three actual ground accelerations (i.e., El Centro 1940, Kobe 1995 and Northridge 1994) were used to carry out time-history analysis in order to evaluate the overall behavior of the structure and local nonlinear deformation at the element level. The analysis result shows that the old school building not designed for an earthquake may be damaged seriously by an earthquake load of the magnitude equivalent to current design spectrum standard.

Comparison of Nonlinear Analysis Programs for Small-size Reinforced Concrete Buildings I

For small-size reinforce-concrete buildings, Midas Gen, OpenSees, and Perform-3D, which are structural analysis programs that are most popularly used at present, were applied for nonlinear static pushover analysis, and then difference between those programs was analyzed. Example buildings were limited to 2-story frames only and frames with one or more rectangular walls. Analysis results showed that there was not much difference for frames only based on capacity curves. There were some differences for frames with rectangular walls, but it was not so significant. The global behaviors represented by the capacity curve were not so different, but the feature of each analysis program appeared when the results were analyzed in more detail. Therefore, the program users should understand the feature of the program well, and then conduct performance assessment. The result of this study is limited to low-story frames only and frames with rectangular walls so that it should be noted that it is possible to get different results for frames with non-rectangular walls or mid- to high-rise buildings.

Comparison of Nonlinear Analysis Programs for Small-size Reinforced Concrete Buildings II

Comparison of Nonlinear Analysis Programs for Small-size Reinforced Concrete Buildings II

Experimental and numerical investigation on frame structure composed of steel reinforced concrete beam and angle-steel concrete column under dynamic loading

This paper describes experimental and numerical investigations on two specimens of frames composed of steel reinforced concrete beam and angle-steel concrete column under horizontal low cyclic loading. Based on the test results, the relationship curves of the horizontal load-displacement and the failure modes are acquired. Meanwhile the hysteretic behaviors, skeleton curves, stiffness degradation, energy dissipation, residential deformation of the two specimens are studied. Nonlinear structural analysis program OpenSEES is employed to predict the experimental curves. Using the verified numerical model, the influences of slenderness ratio, axial compression ratio, steel ratio of column, cross-section moment resistance of I-shaped steel in beam, ratio of longitudinal rebars of beam and prestressing level on skeleton curves are investigated. The results indicated that the two specimens exhibited the favorable ductility and energy dissipation capacity, and the beam depth could be reduced to improve service function because of the application of the prestress. The ultimate horizontal load decreases with the increase of column slenderness ratio, and firstly increases then decreases with the increase of axial compression ratio. In the meantime, the descent segment of skeleton curve is smooth with the increase of column slenderness ratio, and becomes steeper with the increase of axial compression ratio.

Ground Motion Site Amplification Factors for Sites Located within the Mississippi Embayment with Consideration of Deep Soil Deposits

In this study, site amplification factors for the deep soil deposits of the Mississippi embayment are computed using a nonlinear site response analysis program first to develop a model for nonlinear soil response for possible use by ground motion developers and second to address site amplification estimation. The effects of geology, sediment depth, and average shear wave velocity at the upper 30 m of soil ranging 180–800 m/s, as well as the effect of peak ground acceleration at the bedrock on nonlinear ground motion amplification for the upper embayment, are investigated. The site response computations cover various site conditions, sediment depth of 70–750 m, and peak acceleration of input rock motions of 0.01–0.90 g. The amplification (or de-amplification) at various frequencies implied by the sediment depth is greater than that implied just by site classification of the top 30 m of soil.