Multi-story Frame Structures Research Articles

System buckling analysis for multi-story frames subjected to nonconservative forces

The evaluation of the effective length factor (K-factor) of columns based on the system buckling approach is a convenient tool in the stability design of multi-story frames. This method is superior to other analytical approaches, such as isolated subassembly and story-based approaches, in that inter-column and inter-story interactions are inherently taken into account. In this study, in order to investigate the effect of nonconservative forces on buckling loads and K-factors for the single- and multistory framed structures, the system buckling approach is presented. For this purpose, the finite element model, based on the Hamilton’s principle, is formulated for the stability analysis of framed structures subjected to nonconservative forces. In numerical examples, buckling loads and K-factors for single- and multi-story frames subjected to conservative or nonconservative forces are evaluated and compared with those obtained by other researchers. Especially the effect of the stiffness ratio of girder to column on K-factors is investigated for nonconservative systems.

Nonlinear Modeling and Mitigation of Seismic Pounding between R/C Frame Buildings

A multi-link finite element contact model reproducing Jankowski’s nonlinear viscoelastic relationships is devised and implemented for a time-history analysis of seismic pounding. The mechanical and algorithmic parameters are calibrated with a numerical test case study, represented by two single-story R/C frames. A real case study, concerning two adjacent buildings representative of a stock of R/C multi-story frame structures with insufficient separation joints at rest, is then examined. A damped interconnection-based mitigation solution consisting in linking the two structures with fluid-viscous dissipaters is proposed. The benefits of this retrofit strategy are discussed by comparison with the response in original conditions.

An Analytical Study of Dynamic Characteristics of Multi-Story Timoshenko Planar Frame Structures

This paper concerns in-plane vibration analysis of coupled bending and longitudinal vibrations in multi-story planar frame structures based on the advanced Timoshenko bending theory. It takes into account the effects of both rotary inertia and shear distortion. A wave based vibration analysis approach is proposed. From a wave vibration standpoint, vibrations propagate along a uniform waveguide (or structural element), and are reflected and transmitted at discontinuities (such as joints and boundaries). Reflection matrices at various boundaries, as well as transmission and reflection matrices at joint discontinuities are derived. Natural frequencies of coupled bending and longitudinal in-plane vibrations are obtained by assembling these propagation, reflection, and transmission matrices. Numerical examples are presented along with comparisons to results available in literature. The examples show good agreement with the results presented in the available literature.

Influence of pinching effect of exterior joints on the seismic behavior of RC frames

Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.

Analysis and Research on Reinforcement and Reconstruction Method of Adding Shear Wall for Multi-Story Frame Structure

Recently, earthquakes occurred frequently, and our country has established a new seismic code. As the seismic intensity increases, some low frame structures cannot reach the requirements of layer displacement, layer displacement angle, stability, etc. Thus, they require reinforcement. The shear wall is good for resisting lateral force, and rational shear wall can control the shifting and shaking efficiently, thus making the distribution of internal force more reasonable. Through analysis on reinforcement and reconstruction method of adding shear walls for multi-story frame structure, the rules in terms of different layer displacement, layer displacement angle and overturning moment are found out, and the added shear wall, which can efficiently improve seismic fortification intensity, can serve as the main component for resisting lateral force. The conclusions are as follows: under earthquake action, through the method of adding shear wall, the deformation, layer displacement and layer displacement angle can be controlled effectively. Besides, the integrity and seismic behavior are inhanced, achieving the goal of improving anti-seismic grade of structure.

Wave vibration control of planar frame structures based on the advanced Timoshenko bending theory

Coupled bending and axial vibrations in a planar multi-story frame structure are controlled from a wave vibration standpoint, in which vibrations are described as waves that propagate along uniform waveguides, and are reflected and transmitted upon structural discontinuities. The bending vibrations are modeled using a Timoshenko model, which takes into account the effects of rotary inertia and shear distortion. The axial vibrations are modeled using elementary theory, as it is typically valid for frequencies up to twice the cutoff frequency of Timoshenko bending waves. Regardless of the complexity of a structure, when it is modeled from a wave point of view, it consists of only two basic types of structural components, namely, structural elements and joints. In this paper, both structural element and structural joint controllers are designed based on various control strategies such as optimal damping and optimal energy absorbing. Numerical examples are presented. Results are compared to those obtained based on the classical Euler–Bernoulli model that are available in the literature. As was expected, good agreement between the results of the models at low frequencies was obtained.

Numerical Simulation for Progressive Collapse and Protection of a Multi-Storey Building due to an Explosion in its Basement

The progressive collapse of a multi-story building and its protective effect with aluminum foam under an explosion in its basement are numerically investigated in this paper. The three-dimensional coupling model composed of a multi-story frame structure with a basement and the surround soil is modeled using ANSYS/LS-DYNA. The progressive collapse of the entire structure under explosive impact and the protective effect of the aluminum foam are simulated using the proposed three-stage simulation method (TSSM). The result shows that, the aluminum foam as a protective layer can reduce the impact effects very well, and then can prevent progressive collapse effectively. The same model is also simulated by direct simulation method (DSM) and alternative load path method (ALPM). By comparison with the two methods, the TSSM is illustrated practical, accurate and economic for the analysis of progressive collapse.

Nonlinear optimal oil damper design in seismically controlled multi-story building frame

The purpose of this paper is to propose a practical method for optimum design of non-linear oil dampers with relief mechanism installed in multi-story framed building structures. The optimum design problem is formulated so as to minimize the maximum interstory drift or maximum acceleration of top-story under design earthquakes in terms of a set of relief forces subject to an inequality constraint on the maximum ratio of the damping force to the relief force and an equality constraint on the sum of relief forces of oil dampers. The proposed method to solve the optimum design problem is a successive procedure which consists of two steps. The first step is a sensitivity analysis by using nonlinear time-history response analyses, and the second step is a modification of the set of relief forces based upon the sensitivity analysis. An advanced reduction method based on static condensation of the frame and energy equivalence transformation of oil dampers is proposed and introduced into the optimum procedure to reduce the computational load. Numerical examples are conducted to demonstrate the effectiveness and validity of the proposed design method.

Subspace system identification of support‐excited structures—part I: theory and black‐box system identification

SUMMARYThis paper reviews the theoretical principles of subspace system identification as applied to the problem of estimating black‐box state‐space models of support‐excited structures (e.g., structures exposed to earthquakes). The work distinguishes itself from past studies by providing readers with a powerful geometric interpretation of subspace operations that relates directly to theoretical structural dynamics. To validate the performance of subspace system identification, a series of experiments are conducted on a multistory steel frame structure exposed to moderate seismic ground motions; structural response data is used off‐line to estimate black‐box state‐space models. Ground motions and structural response measurements are used by the subspace system identification method to derive a complete input–output state‐space model of the steel frame system. The modal parameters of the structure are extracted from the estimated input–output state‐space model. With the use of only structural response data, output‐only state‐space models of the system are also estimated by subspace system identification. The paper concludes with a comparison study of the modal parameters extracted from the input–output and output‐only state‐space models in order to quantify the uncertainties present in modal parameters extracted from output‐only models. Copyright © 2012 John Wiley & Sons, Ltd.

Study on FEM Analysis of Multistory Steel Frame Structure and its Optimal Design

An finite element model (FEM) of multistory steel frame structure is established by applying ANSYS parametric design language(APDL) in this paper, where the objective function of optimization is defined as the minimum volume of a Pin framework. The optimal design are carried on by applying the optimized toolbox of ANSYS, based on analysis the situation of the most disadvantageous load combination. Several approaches have been proposed to avoid restraining to the local minimum. Experimental results show that the section size of the structural element improved obviously.

Wave control of vibrations in multi-story planar frame structures based on classical vibration theories

An active control approach to vibrations in multi-story planar frame structures is presented in this paper. The controller is designed from a wave vibration standpoint, in which vibrations are described as waves that propagate along uniform waveguides, and are reflected and transmitted upon structural discontinuities. Regardless of the complexity of a structure, from the wave point of view it consists of only two basic types of structural components, namely, structural elements and joints. In this paper, vibrations in a multi-story planar frame structure are controlled through controlling its structural elements and its joints.

Analysis on Progressive Collapse Resistance of Reinforced Concrete Frame Structures

In this paper the analysis is conducted to investigate the progressive collapse resistance of typical reinforced concrete(RC) multi-story frame structures, which are designed according to the China code for seismic design of buildings. The analysis results show that the progressive collapse resistance will be enhanced with the seismic fortification intensity increasing. The progressive collapse resistance of RC frame structures with low seismic fortification intensity are poor. This implies that as for RC frame structures with low seismic or non-seismic demand, close attention must be paid to continuity and ductility in order to prevent progressive collapse.

Comparison of Probabilistically Evaluated COF with the Base Shear Distribution of IBC and Japanese Code

In the earthquake resistant design concept, frame structures are usually designed with a column over design factor (COF) to ensure the preferable failure mode during earthquakes. Initially, in the present study, the failure modes of multistory ductile frame structures are investigated probabilistically by applying the first order reliability method (FORM). The base shear distribution of the International Building Code (IBC-2006), which adopted the seismic design provisions of ASCE 7-05, and the Ai distribution of the Building Standard Law of Japan are taken into account in this study. Based on the investigations, the target values of the COF that probabilistically ensure the preferable entire beam hinging failure mode prior to story collapse are evaluated and compared. The study has been conducted for different reliability levels and the corresponding COF values are presented in this paper.

PROBABILISTIC EVALUATION OF COF FOR STEEL FRAMES CONSIDERING SYSTEM RELIABILITY

Steel frames are usually designed with a column overdesign factor (COF) to ensure the preferable failure mode, which is yielding of all beams in flexure prior to the yielding of columns. In the present study, in consideration of the uncertainties of earthquake loads and the strengths of structural members, the failure modes of multistory ductile frame structures are investigated probabilistically. The first-order reliability method (FORM) and the dimension reduction integration (DRI) method with fourth-moment standardization are applied in the investigation. The Ai distribution of load along the height of the frame is taken into account. By comparing the Ai distribution and the triangular distribution results, it is observed that the target COF requirement is affected by the load distribution. To evaluate the target COF requirement that probabilistically avoids undesirable story collapse modes, the system reliability must be considered. In the present paper, the concept of system reliability is introduced in the determination of the target COF. It is observed that the target values of COF considering system reliability are higher than those of the most likely failure mode. This study was conducted for different reliability levels and the corresponding COF values are presented in this paper.

Design Principle of Crack Control of Large Multi-Story Frame Structure and its Application

Crack control design of reinforced concrete structure focuses on the cracks caused by temperature and shrinkage stress, which is traditionally controlled through “resistance” or “relieving”. Related standard of China adopts easier way of expansion joint to relieve temperature and shrinkage stress. This method, however, is difficult to apply to modern super large buildings. Principle of “resistance in conjunction with relieving” was adopted in the design of Yongjin Plaza in Zhejiang province. No running through expansion joint was made in 136m×124m cast-in-situ multi-story concrete frame, instead, expansion joint is adopted in partial roof and floor. Steel bar quantity in coumns and beams was determined by factors of both load and temperature. Later-poured-zone, low expansion concrete, limited cement ratio and good curing measure were adopted to control cracks successfully.

Influence of exterior joint effect on the inter-story pounding interaction of structures

The seismic induced interaction between multistory structures with unequal story heights (inter-story pounding) is studied taking into account the local response of the exterior beam-column joints. Although several parameters that influence the structural pounding have been studied sofar, the role of the joints local inelastic behaviour has not been yet investigated in the literature as key parameter for the pounding problem. Moreover, the influence of the infill panels as an additional parameter for the local damage effect of the joints on the inter-story pounding phenomenon is examined. Thirty six interaction cases between a multistory frame structure and an adjacent shorter and stiffer structure are studied for two different seismic excitations. The results are focused: (a) on the local response of the critical external column of the multistory structure that suffers the hit from the slab of the adjacent shorter structure, and (b) on the local response of the exterior beam-column joints of the multistory structure. Results of this investigation demonstrate that the possible local inelastic response of the exterior joints may be in some cases beneficial for the seismic behaviour of the critical column that suffers the impact. However, in all the examined cases the developing demands for deformation of the exterior joints are substantially increased and severe damages can be observed due to the pounding effect. The presence of the masonry infill panels has also been proved as an important parameter for the response of the exterior beam-column joints and thus for the safety of the building. Nevertheless, in all the examined inter-story pounding cases the presence of the infills was not enough for the total amelioration of the excessive demands for shear and ductility of the column that suffers the impact.

Seismic Design of Friction-Damped Precast Concrete Frame Structures

This paper presents the seismic design of unbonded posttensioned precast concrete frame structures that use friction dampers for supplemental energy dissipation. A procedure is described to determine the friction damper slip forces and posttensioning steel areas needed to satisfy prescribed design lateral strength and energy dissipation requirements for a trial frame with given geometry, beam and column member dimensions, and selected damper distribution. The proposed design procedure assumes that the lateral strength requirements for the frame have been obtained from a linear elastic analysis of the structure under equivalent lateral forces. Nonlinear reversed-cyclic analyses of friction-damped precast concrete beam-column subassemblies and multistory frame structures under lateral loads are conducted to critically evaluate the design procedure and to identify areas where improvement may be needed. The analytical results show that friction-damped precast frames can be designed to achieve significant energy dissipation levels while maintaining a large level of self-centering capability due to the posttensioning force.

Development of wooden portal frame structures with improved columns

In Japan, the lifetime cycle of most housing lasts around 20–30 years. A governing factor in this respect is poor durability due to old-fashioned use of the house. As a solution of this problem, houses can be built with a skeleton structure that allows free partition of spaces by future owners. To develop the skeleton structure effectively, multistory frames with spans of 6 to 10 m are required. For this reason, attention has been focused on the behavior of multistory timber frame structures. In this article, two types of wooden portal frame structures are proposed. Both structures have improved vertical columns with short horizontal members glued in. The aim of this study was to investigate structurally effective solutions with these types of columns. The first type of the new structure changed the location of the moment-transmitting ductile connection with the improved columns. The second type of structure used an extended panel zone. Nine portal frame specimens were tested. The stiffness values were improved by around 1.7 and 3.5 times when compared with the control, and the strength was improved by around 1.25 and 1.45 times.

RC構造物における曲げ降伏先行型連層方立て壁の架構に与える影響に関する解析的研究

The purpose of this study is to grasp influences of multi-story mullion-type walls on behavior of RC structure frame analytically. A fiber-model is applied to the mullion-type walls, and 1 span multi-story RC frame structures which have the multi-story mullion-type walls and which are designed without regarding ones as structual elements are analized with push-over method. The conclusions are as follows. Mullion-type walls can raise horizontal load-carrying capacity, but there is possibility of story-collapse at lower story in the case of a structure with many stories. The mullion-type walls may affect upper structural elements because of the accumulation of the axial elongations of the mullion-type walls. Axial elongations of the mullion-type walls whitch exsist in a lower story are suppressed, so that, some additional axial force ratios of ones rise to more than 0.3-0.4.

The Behaviour Of Multi-storey Composite Steel Framed Structures In Response To Compartment Fires

This paper presents a summary of the PhD research project “The behavior of multistory composite steel frame structures in response to compartment fires.” The original assumptions, conclusions and suggested further work of the thesis are revisited and newly discussed in the context of structural fire engineering design post 9-11. The aims of the original PhD research were to extend the understanding of whole frame structural response to fire beyond the research carried out on the Cardington frame fire tests by studying configurations not identical to Cardington, to allow extended application of the at the time new techniques, in real design. Serious post-flashover fires in real buildings in the 1990s had shown that whole frame response of composite steel structures was significantly better than previously thought and it seemed that the amount of passive fire protection applied to steel was conservative. In addition it was clear our understanding of real structural fire responses including alternative load bearing mechanisms in fire could result in a more robust approach to structural design. The events of 9-11 and recent tall building fires around the world have meant that fire resistance ratings of tall building structures are being scrutinized again but this time the issue is whether the ratings are adequate or should there be alternative means of engineering structural resilience in fire, especially if total evacuations and extreme events like fire spread to multiple compartment floors are to form the basis of design for tall buildings in the future. The conclusions of this work are that the beam spans (6-9 m) considered by the PhD research were short in comparison with some modern construction particularly in high rise design. The design fires considered by the sensitivity analysis were severe but could be exceeded if fire spreads via the façade to the compartments above. Conclusions resulting from the sensitivity analyses carried out with regard the effects of different fire scenarios and the effects of different edge restraint on the structural behavior of a composite floor remain valid. Runaway failure (a rapid increase in mid-span deflection) was observed in the analyses conducted as part of the PhD research but local cracking and rupture or unzipping of reinforcement could not be modeled. These kind of failure modes were not observed at Cardington and this is a shortfall of the tests in terms of ultimate limit state design. A suggested piece of further work resulting from the PhD was a test to failure of a composite slab. However, there is currently still no experimental evidence to check if reinforcement rupture or unzipping type failures in a composite floor should be a concern. In contrast recent research since 9-11 is beginning to identify potential global progressive collapse mechanisms in different long-span floor systems. Failure mechanisms are being validated against evidence from real fires such as WTC 1, 2 and 7. It is clear that key possible failure mechanisms of composite frame structures in fire are still to be quantified and understood.