Earthquake Response Analysis Research Articles

A STUDY OF EVALUATION OF EARTHQUAKE INPUT ENERGY BASED ON RESPONSE SPECTRUM CHARACTERISTIC

In this paper, the influences of the phase characteristic and the response spectrum characteristic of the earthquake wave on the earthquake input energy are examined based on the earthquake response analysis using the simulated seismic wave which is adjusted the normalized response spectrum. As a result, the characteristic of ƒ value proposed by Akiyama and Kitamura is clarified, and proposes the response spectrum effect value SM and ƒ* value considering SM value. The earthquake input energy of any earthquake wave without the case that earthquake response analysis is able to estimate using ƒ* value. Moreover in this paper, ƒ* value corresponding to the earthquake load which Japanese Building Standard Act provide is presumed by conducting seismic response analysis of real buildings. Therefore, on the comparing with ƒ* values of the existing seismic waves, the quantitative evaluation about that earthquake damage can be performed. The evaluation of the earthquake input energy based on ƒ* value as well as acceleration at the maximum is necessary for the evaluation of the earthquake wave. The ƒ* values are useful on the evaluation of the input earthquake wave.

BEHAVIOR OF REINFORCED CONCRETE BUILDINGS SUBJECTED TO MANY CYCLIC LOADINGS

In recent earthquakes, the number of cyclic loadings has exceeded that expected. Some experiments were conducted on reinforced concrete elements subjected to many cyclic loadings. The following observations are notable. 1) Slip-stiffness degradation occurs and the hysteretic shape tends to become reverse S-shaped. As a result, hysteretic energy decreases for every cyclic loading. 2) A directional point transfers to large deformation. A new hysteretic model was developed for reinforced concrete elements, which can be considered as slip-stiffness degradation and transference of directional point. Earthquake response analyses of reinforced concrete model buildings for long-period ground motion were conducted using the developed hysteretic model. The maximum response didn't increase greatly from that with the TAKEDA model.

Earthquake response analysis of two-storey steel portal frames with shear collapse of beam on 1st storey by using pseudodynamic testing procedure

Earthquake response analysis of two-storey steel portal frames with shear collapse of beam on 1st storey by using pseudodynamic testing procedure

OPTIMUM STRENGTH DISTRIBUTION OF STRUCTURAL MEMBERS IN STEEL FRAMES

The deformation concentration into a relatively weak story often causes the collapse of the structure and must be carefully prevented in design practice. In this paper, we proposed a simple method to modify the member strengths in order to make the story drift angles uniform over the building height. This method is based on the optimum story shear force coefficient proposed by us in a previous paper. The applicability of the method was confirmed by numerical results of a nonlinear earthquake response analysis for four example frames.

Site response zones and short-period earthquake ground motion projections for the Las Vegas Basin

A deterministic seismic hazard analysis was conducted to address the effect of local soil conditions on earthquake-induced strong ground motion in the Las Vegas Basin, Nevada (US). Using a large geological and geotechnical database, two response units were defined: a fine-grained unit, predominantly clay; and a coarse-grained unit, predominantly gravel. A moderate number of high-quality shallow shear wave velocity measurements were collected from which characteristic shear wave velocity profiles were developed for each response unit. An equivalent-linear one-dimensional site response model was used. The model was calibrated using a basin-wide, small-strain ground motion database. Calibration tests showed that ground motion projections become increasingly conservative with increasing ground-motion amplitude. Projections were overconservative for the coarse-grained response unit, likely due to the sparseness of the velocity database. For the earthquake response analyses, historical ground motions were used to model characteristic ‘bedrock’ motion for earthquakes on 10 faults judged to be critical. Response spectral envelopes were generated for each unit through Monte-Carlo simulations. For the fine-grained response unit, 95th percentile peak ground acceleration, peak spectral acceleration and predominant period were 310 cm/s2, 1100 cm/s2, and 0.29 s, respectively. With respect to codified design spectra, projections are lower at short periods and higher at long periods. Projections of peak spectral accelerations for the coarse-grained response unit, were more than double that of codified spectra; however, they are believed to be overconservative. Near-fault effects and basin-edge effects, though potentially important, were not considered in these analyses.

Nonlinear response analyses of a soil–structure interaction system using transformed energy transmitting boundary in the time domain

The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed.

Nonlinear Response Analysis Considering Dynamic Stiffness with Both Frequency and Strain Dependencies

The time domain evaluation of the frequency-dependent dynamic stiffness was studied and some transform methods are being proposed. In this paper, the nonlinear response analysis method of the dynamic stiffness with both frequency and strain dependency was studied. First, the frequency-dependent complex stiffness was calculated at each strain level, and then they were transformed to the impulse response in the time domain. The characteristics of the complex stiffness and the impulse response of both two-layered soil and viscoelastic dampers were investigated. Then, the nonlinear time-history response analysis method considering both dependencies using the impulse response of each strain level was proposed. The earthquake response analysis of a structure on the two-layered soil was carried out as an example. The efficiency of the method was confirmed through these investigations.

Two-Dimensional Nonlinear Earthquake Response Analysis of a Bridge-Foundation-Ground System

This paper presents a two-dimensional advanced nonlinear FE model of an actual bridge, the Humboldt Bay Middle Channel (HBMC) Bridge, and its response to seismic input motions. This computational model is developed in the new structural analysis software framework OpenSees. The foundation soil is included to incorporate soil-foundation-structure interaction effects. Realistic nonlinear constitutive models for cyclic loading are used for the structural (concrete and reinforcing steel) and soil materials. The materials in the various soil layers are modeled using multi-yield-surface plasticity models incorporating liquefaction effects. Lysmer-type absorbing/transmitting boundaries are employed to avoid spurious wave reflections along the boundaries of the computational soil domain. Both procedures and results of earthquake response analysis are presented. The simulation results indicate that the earthquake response of the bridge is significantly affected by inelastic deformations of the supporting soil medium due to lateral spreading induced by soil liquefaction.

Earthquake testing and response analysis of concentrically-braced sub-frames

The results of shake table tests on three concentrically-braced sub-frames are compared with a series of correlative inelastic analyses. Both transient time-history and nonlinear static (pushover) analyses are considered. The lateral resistance of the test frames is provided by a pair of cold-formed tubular steel members. The brace cross-section is varied between tests to investigate the influence of brace slenderness on the stiffness, resistance and ductility displayed by the frame under strong earthquake loading. Response simulations using a two-dimensional analytical model of the test frame are compared with the experimental results. Brace strengths and elastic test frame properties established in complementary static tensile tests and low-level shake table tests, respectively, are used to determine model input data. The transient acceleration and displacement response of the frames calculated in nonlinear time-history analyses are compared with corresponding experimental measurements. The base shear–frame drift relationship is calculated using pushover analyses that consider either the resistance of both frame braces or the tension brace alone. These are compared with the experimental hysteretic response of the test frame. On the whole, the analytical results are observed to agree well with the experimental results, especially with respect to brace tension forces and frame base shear. Cases where the experimental and analytical responses deviate are identified and the implications for earthquake response assessment and design are discussed.

EARTHQUAKE RESPONSE ANALYSIS OF SOIL-STRUCTURE INTERACTION SYSTEM USING TRANSFORMED ENERGY TRANSMITTING BOUNDARY IN TIME DOMAIN

The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of the soil-structure interaction systems. However, the analysis is applied only for the linear analysis or the equivalent linear analysis because it can be calculated only in the frequency domain. The author has proposed some transform methods of the frequency dependent impedance to the time domain. In this paper, an earthquake response analysis method for the soil-structure interaction system using the energy transmitting boundary in the time domain is proposed. First, the transform of the transmitting boundary matrices to the time domain using the author's methods is studied. Then, a time history earthquake response analysis is performed using the boundary. Through these analyses, the efficiency and the validity of the proposed method are confirmed.

EFFECT OF SIDE WALLS ON SEISMIC PERFORMANCE OF OLD RC COLUMNS

This study is intended to get an answer to the question that the adding of side walls to old RC columns is effective to enhance their seismic performance or not. For this purpose, ten half-scale model specimens simulating columns designed by the pre-1971 codes with/without side walls were tested until they collapsed. The tests revealed the side-wall adding increased lateral strength but decreased deformability. Then the earthquake response analyses were conducted for three-story model buildings consisting of the tested columns with/without side walls, where the observed load-deflection relations until collapse were used. The side-wall adding was judged as “advantageous” if the ratio of maximum response drift to drift at collapse became smaller than that of the case without side walls. The side-wall adding was “advantageous” in most examples.

STUDY ON ELASTO-PLASTIC WIND RESPONSE CHARACTERISTICS OF DETACHED TIMBER BUILDINGS WITH VISCO-ELASTIC DAMPERS

The purpose of this paper is to understand elasto-plastic wind response characteristics of detached timber buildings with visco-elastic dampers that began to spread recently. The following approach is employed in this study. 1) Loading experiments acting long-duration random waves such as wind forces on a timber-frame wall with the dampers are conducted to examine their dynamic behavior. 2) Accuracy of time history behavior analysis of the wall is verified by comparing their results with the experiment results. 3) Time history wind response analyses with single degree of freedom models of the buildings are carried out to examine their characteristics. Furthermore, elastic response analyses and earthquake response analyses are carried out, then the wind response characteristics are set out by comparing each other.

PREDICTION OF ENERGY ABSORPTION CAPACITY OF HYSTERESIS DAMPERS INSTALLED IN DAMAGE CONTROL STRUCTURES

In this paper, the energy absorption capacity of a hysteresis damper installed in a damage control structure was investigated. The performance of a hysteresis damper is limited by its fracture. The method predicting the metal fatigue life is extended to apply to the evaluation of the life of dampers. However, the method based on the energy absorption is necessary for the earthquake-resistant design. The conclusions obtained from this paper can be summarized as follows. (1) The energy-based method to evaluate the ultimate performance of a hysteresis damper was proposed based on the results of the cyclic loading tests. (2) The characteristic of the distribution of the energy response of the damage control structure is clarified based on the results of the earthquake response analyses. (3) By using these results, the simple method to predict the energy absorption capacity of the damper was proposed.

EVALUATION OF EARTHQUAKE RESPONSE FOR EACH FRAME OF MULTI-STORY ASYMMETRIC BUILDINGS

An evaluation method of time history earthquake responses for the shear and drift of each frame in a multi-story asymmetric building is proposed to improve the seismic evaluation method of the Calculation of Response and Limit Strength. Both the time history earthquake response analysis and the modal adaptive pushover analysis, which is a static analysis, for a four-story reinforced concrete asymmetric building are conducted to reduce the building to two kinds of the single degree of freedom systems, the dynamic reduction system and the static reduction system. Using the responses of the dynamic reduction system, the first mode components of the shear and drift responses of each frame are evaluated. The higher mode components of the responses are also evaluated by the proposed method. The validity of the proposed method is demonstrated through comparing the predicted responses with the time history responses analyzed.

ESTIMATION OF EARTHQUAKE INPUT LEVEL BASED ON DAMAGE OF STEEL GYMNASIUMS DUE TO THE 2004 MID NIIGATA PREFECTURE EARTHQUAKE

This paper presents result of estimation of earthquake input level to steel gymnasiums subjected to the 2004 Mid Niigata Prefecture Earthquake. The earthquake response analysis of 55 steel gymnasiums located in the stricken area of this earthquake was carried out to determine damage-causing earthquake input energy (Vd). In this paper, the Vd values of each gymnasium were compared with a pseudo-velocity response spectrum (Vs) prescribed in the Japanese building code. From the result of the analysis, the earthquake input level (Vd/Vs) to the gymnasiums in Kawaguchi-machi was estimated to be more than 1.5.

STUDY ON EFFECT OF ORTHOGONAL WALL OF WOODEN FRAMED HOUSE, NAGAYA, MODELS CONSIDERING FLOOR STIFFNESS

We carry out earthquake response analyses of two Nagaya models with uni-axial eccentricity considering their floor stiffness subjected to bi-directional input earthquake motions, and examine the orthogonal wall effects. The orthogonal wall effect means how walls perpendicular to the eccentric direction will control the tortional vibration. The different two Nagaya models are one- and four-unit types. We choose the floor stiffness, the shape ratio of depth to width on the plan, the eccentric ratio, the wall quantity and its ratio, and the kind of input motions and their level in the analyses as parameters. The results obtained show that the factors of the orthogonal wall effects are mainly the floor stiffness and the shape ratio. The required wall ratio of depth to width is 2.0 for motions with Vmax=10cm/s, and the required yield shear coefficient of depth is 0.5 for motions with Vmax =50cm/s. The kind of motions and their level do not become the factors of the effect.

STUDY ON EFFECT OF ORTHOGONAL WALL OF WOODEN FRAMED HOUSE, NAGAYA, MODELS CONSIDERING FLOOR STIFFNESS

We carry out earthquake response analyses of two Nagaya models with uni-axial eccentricity considering the floor stiffness and examine the orthogonal wall effects. The effect means how walls perpendicular to the eccentric direction will control the torsional vibration. The two different Nagaya models are one- and four-unit types. We choose the floor stiffness, shape ratio of the length to the width on the plan, eccentric ratio, wall quantity and the wall ratio, and kinds of input motions and their maximum value in the analyses as parameters. The results obtained show that the factors of the orthogonal wall effect are mainly the floor stiffness and shape ratio, and that the demand ratios are 2.0 and 1.5 for the two models. The kinds of input motions and their maximum values do not become to the factors of the effect.

Dynamic dam-reservoir interaction analysis including effect of reservoir boundary absorption

Based on the scaled boundary finite-element method, the governing equations for the analysis of dam-reservoir interaction including the reservoir boundary absorption are developed. Coupling with the equation of dam-unbounded foundation interaction, it can effectively carry out the earthquake response analysis of dam-reservoir-foundation system. The proposed approach has the advantages that the effect of compressibility of reservoir water as well as the energy absorption of reservoir boundary on the earthquake response of arch dams and gravity dams can be efficiently evaluated and higher accuracy can be achieved. In comparison with the methods available in the literature, the computational cost can be reduced to a great extent. It facilitates the application of earthquake response analysis of dam-reservoir-foundation system including reservoir boundary absorption to the engineering practice.

Transverse earthquake response analysis of a seismically isolated regular bridge with partial restraint

Most of the seismically isolated bridges in Taiwan share a common feature in that both ends of the superstructures are restrained from transverse movement. They are defined as partially restrained seismically isolated (PRSI) bridges. From measured acceleration responses, effectiveness of the longitudinal seismic isolation of the PRSI bridges had been confirmed. Nevertheless, the seismic isolation behavior in the partially restrained direction was not observed. The effectiveness of the partially restrained seismic isolation is evaluated in this paper. Analytical expressions are derived to assess the effect of the partial restraint on the transverse dynamic characteristics of a seismically isolated regular bridge. A non-isolated, a seismically isolated and a PRSI bridge model are constructed for a highway bridge. Nonlinear time history analyses of the bridge models under earthquake excitations are carried out to investigate their transverse seismic responses. Analytical results indicate that the composite damping ratio of a seismically isolated regular bridge may be decreased due to the partial restraint. Comparisons of the transverse earthquake responses show that the partially restrained seismic isolation is effective in column shear reduction. However, increased seismic demands on the abutment shear and the bending moments in the superstructure of the PRSI bridge are observed. It may be necessary to inspect the transverse seismic capacities of the abutments and bridge girders for practical application of the partially restrained seismic isolation. In addition, an equivalent linear analysis procedure is modified to estimate the transverse earthquake response of the PRSI bridge. It is shown that the modified procedure may be applied to practical design and analysis of the PRSI bridges.

Seismic response characteristics of bridges using double concave friction pendulum bearings with tri-linear behavior

The friction pendulum system (FPS) is one of the most effective and frequently used seismic isolation devices. In this paper, a double concave friction pendulum system (DCFP) with tri-linear behavior is studied. The DCFP consists of two sliding surfaces with different friction coefficients and radii of curvature. The effects of DCFP systems with various friction values and restoring properties on a bridge are investigated under various earthquake excitations. Earthquake response analyses are carried out in the time domain on a simple bridge model with a DCFP system having various properties. Investigations are carried out on the reduction of the base-shear force on the bridge pier due to the DCFP. The advantages of a DCFP with tri-linear behavior are explored.