scholarly journals Mode superposition in multi-degree of freedom systems using earthquake response spectrum data

1962 ◽  
Vol 52 (2) ◽  
pp. 405-416 ◽  
Author(s):  
H. C. Merchant ◽  
D. E. Hudson
Keyword(s):  
Response Spectrum ◽  
Weighted Average ◽  
Strong Motion ◽  
Design Criterion ◽  
Degree Of Freedom ◽  
Dynamic Responses ◽  
Base Shear ◽  
Earthquake Excitation ◽  
True Value ◽  
The Absolute

ABSTRACT Dynamic responses of a series of typical three-degree of freedom structures to strong-motion earthquake excitation were calculated by analog computer techniques and were compared with approximate responses obtained by a superposition of individual modes derived from response spectrum curves. The results indicate that a suitably weighted average of the sum of the absolute values of the individual modes and the square root of the sum of the squares of the modes will give a practical design criterion for the base shear forces in multi-story buildings. For critical designs, this weighted average reduces to the absolute sum of the modes, which is found to be close to the true value for a significantly high proportion of typical earthquake-structure combinations.

Estimation Accuracy of Absolute Maximum Elasto-Plastic Displacements of MDOF Oscillators Based on a Modal Combination Rule With Post-Yielding Modal Properties and Linear Response Spectrum Values

2018 ◽  
Author(s):  
Tomoyo Taniguchi ◽  
Yoshihiko Toda ◽  
Yusuke Ono ◽  
Kyosuke Mukaibo
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Degree Of Freedom ◽  
Estimation Accuracy ◽  
Absolute Maximum ◽  
Earthquake Excitation ◽  
Linearized System ◽  
The Absolute ◽  
Plastic Displacement ◽  
Mode 3

Taniguchi, et al. [1] developed an analytical method for evaluating the absolute maximum elasto-plastic displacements of multi-degree-of-freedom (MDOF) oscillators under the action of base excitation based on a modal combination. Its essence is that 1) modal frequencies, shapes and damping during yielding of any member of the MDOF oscillators are readily specified by the modal analysis with the secondary stiffness of the members being yielded, 2) assuming that a bilinear hysteresis may describe the force-displacement relationship of each mode, an equivalently linearized system consisting of a single-degree-of-freedom (SDOF) oscillator is introduced to approximate the absolute maximum elasto-plastic displacement of each mode, 3) the absolute maximum elasto-plastic displacement of the MDOF oscillator is evaluated by the Square Root of Sum of Squares rule (SRSS-rule) by combining the maximum elasto-plastic displacement of each mode approximated by the proposed equivalently linearized system. This study first provides small modification in the equivalently linearized system. Then, employing a couple of MDOF oscillators whose spring at arbitrary storey may yield and an accelerogram, the maximum elasto-plastic displacement of the MDOF oscillator is calculated by the proposed method and is compared with that computed by the time history analysis. Their comparison suggests that the proposed method can reasonably evaluate the absolute maximum elasto-plastic displacement of the MDOF oscillator subjected to earthquake excitation as the conventional SRSS-rule does that for the linear MDOF oscillators.

scholarly journals “Effect of floating columns on buildings subjected to seismic forces”

2021 ◽  
Vol 1197 (1) ◽  
pp. 012018
Author(s):  
Neha Pawar ◽  
Kuldeep Dabhekar ◽  
Prakash Patil ◽  
Isha Khedikar ◽  
Santosh Jaju
Keyword(s):  
Load Transfer ◽  
Response Spectrum ◽  
Research Work ◽  
Functional Requirements ◽  
Base Shear ◽  
Response Spectrum Analysis ◽  
Earthquake Excitation ◽  
Transfer Path ◽  
Recent Trends ◽  
Seismic Forces

Abstract In Recent Trends, buildings are planned to fulfill their architectural and functional requirements but sometimes this creates complexity in its structural strength. One such element is the floating column. It is used to boost Floor Space Index. The Earthquake forces developed at different storey need to be carried down by the shortest path. Discontinuity in the load transfer path leads to poor seismic performance of the structure. Hence as per IS: CODE-1893:2016 clause no-7.1, the Construction of Floating Column is restricted. But there is no limit to research work. The purpose of this research is to analyze the structural irregularity occurring due to floating columns and also to find out the optimized solution to decrease the risk due to earthquake excitation. For Simplicity, the focus of this study is limited to symmetrical G+8 Structure. Finite element Based ETabs software has been used for the analysis. Response spectrum analysis was done in the software. Total ten models are considered with different conditions and their results were compared in terms of Storey displacement, Storey drifts, Base Shear and Overturning moments. All results are compared with the conventional building.

Measured natural periods of concrete shear wall buildings: insights for the design of Canadian buildings

2012 ◽  
Vol 39 (8) ◽  
pp. 867-877 ◽  
Author(s):  
Damien Gilles ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Shear Wall ◽  
Mode Shapes ◽  
Design Stage ◽  
Base Shear ◽  
Period Equation ◽  
Input Load ◽  
Structural Engineers

Structural engineers routinely use rational dynamic analysis methods for the seismic analysis of buildings. In linear analysis based on modal superposition or response spectrum approaches, the overall response of a structure (for instance, base shear or inter-storey drift) is obtained by combining the responses in several vibration modes. These modal responses depend on the input load, but also on the dynamic characteristics of the building, such as its natural periods, mode shapes, and damping. At the design stage, engineers can only predict the natural periods using eigenvalue analysis of structural models or empirical equations provided in building codes. However, once a building is constructed, it is possible to measure more precisely its dynamic properties using a variety of in situ dynamic tests. In this paper, we use ambient motions recorded in 27 reinforced concrete shear wall (RCSW) buildings in Montréal to examine how various empirical models to predict the natural periods of RCSW buildings compare to the periods measured in actual buildings under ambient loading conditions. We show that a model in which the fundamental period of RCSW buildings varies linearly with building height would be a significant improvement over the period equation proposed in the 2010 National Building Code of Canada. Models to predict the natural periods of the first two torsion modes and second sway modes are also presented, along with their uncertainty.

Estimation of Track Irregularity Based on Genetic Algorithm and Unscented Kalman Filtering

2012 ◽  
Author(s):  
Hongmei Shi ◽  
Zujun Yu
Keyword(s):  
Genetic Algorithm ◽  
Kalman Filtering ◽  
High Speed ◽  
Measurement Data ◽  
Estimation Method ◽  
Coupling Model ◽  
Dynamic Responses ◽  
The Real ◽  
True Value ◽  
Track Irregularity

Track irregularity is the main excitation source of wheel-track interaction. Due to the difference of speed, axle load and suspension parameters between track inspection train and the operating trains, the data acquired from the inspection car cannot completely reflect the real status of track irregularity when the operating trains go through the rail. In this paper, an estimation method of track irregularity is proposed using genetic algorithm and Unscented Kalman Filtering. Firstly, a vehicle-track vertical coupling model is established, in which the high-speed vehicle is assumed as a rigid body with two layers of spring and damping system and the track is viewed as an elastic system with three layers. Then, the static track irregularity is estimated by genetic algorithm using the vibration data of vehicle and dynamic track irregularity which are acquired from the inspection car. And the dynamic responses of vehicle and track can be solved if the static track irregularity is known. So combining with vehicle track coupling model of different operating train, the potential dynamic track irregularity is solved by simulation, which the operating train could goes through. To get a better estimation result, Unscented Kalman Filtering (UKF) algorithm is employed to optimize the dynamic responses of rail using measurement data of vehicle vibration. The simulation results show that the estimated static track irregularity and the vibration responses of vehicle track system can go well with the true value. It can be realized to estimate the real rail status when different trains go through the rail by this method.

Soil-Structure Interaction in Buildings from Earthquake Records

1990 ◽  
Vol 6 (4) ◽  
pp. 641-655 ◽  
Author(s):  
Gregory L. Fenves ◽  
Giorgio Serino
Keyword(s):  
Soil Structure ◽  
Dynamic Properties ◽  
Strong Motion ◽  
Longitudinal Direction ◽  
Soil Structure Interaction ◽  
Base Shear ◽  
Foundation Soil ◽  
Soil System ◽  
Structure Interaction ◽  
Building Foundation

An evaluation of the response of a fourteen story reinforced concrete building to the 1 October 1987 Whittier earthquake and 4 October 1987 aftershock shows significant effects of soil-structure interaction. A mathematical model of the building-foundation-soil system provides response quantities not directly available from the records. The model is calibrated using the dynamic properties of the building as determined from the processed strong motion records. Soil-structure interaction reduces the base shear force in the longitudinal direction of the building compared with the typical assumption in which interaction is neglected. The reduction in base shear for this building and earthquake is approximately represented by proposed building code provisions for soil-structure interaction.

Seismic Response of Embankment Dams Based on Recorded Strong-Motion Data in Japan

2019 ◽  
Vol 35 (2) ◽  
pp. 955-976 ◽  
Author(s):  
DongSoon Park ◽  
Tadahiro Kishida
Keyword(s):  
Time Series ◽  
Seismic Response ◽  
Prediction Models ◽  
Strong Motion ◽  
Dynamic Responses ◽  
Design Stage ◽  
Ground Acceleration ◽  
Motion Data ◽  
Embankment Dams ◽  
Strong Motion Database

It is important to investigate strong-motion time series recorded at dams to understand their complex seismic responses. This paper develops a strong-motion database recorded at existing embankment dams and analyzes correlations between dam dynamic responses and ground-motion parameters. The Japan Commission on Large Dams database used here includes 190 recordings at the crests and foundations of 60 dams during 54 earthquakes from 1978 to 2012. Seismic amplifications and fundamental periods from recorded time series were computed and examined by correlation with shaking intensities and dam geometries. The peak ground acceleration (PGA) at the dam crest increases as the PGA at the foundation bedrock increases, but their ratio gradually decreases. The fundamental period broadly increases with the dam height and PGA at the foundation bedrock. The nonlinear dam response becomes more apparent as the PGA at the foundation bedrock becomes >0.2 g. The prediction models of these correlations are proposed for estimating the seismic response of embankment dams, which can inform the preliminary design stage.

Dynamic Analysis of Response of Cofferdam with Steel Sheet Piles Induced by Earthquake Excitation

2011 ◽  
Vol 117-119 ◽  
pp. 695-698
Author(s):  
Chun Yi Cui ◽  
Zhong Tao Wang ◽  
Jian Huang
Keyword(s):  
Geometric Nonlinearity ◽  
Steel Sheet ◽  
Natural Frequencies ◽  
Response Spectrum ◽  
Seismic Excitation ◽  
Earthquake Excitation ◽  
Positive Direction ◽  
Steel Sheets ◽  
Port Engineering ◽  
Horizontal Displacements

For its construction convenience and structure integrity, cofferdams are widely employed in port engineering. Past experience has shown that cofferdam are subjected to damage due to earthquake excitations. Numerical analyses with both response spectrum and step-by-step integration methods are conducted by using Lanczos eigenvalue extraction technique to obtain natural frequencies and modes, and solving dynamic equations with Newmark implicit method to consider geometric nonlinearity. The computational results show that the natural frequency of cofferdam system is low and the horizontal translation stiffness of cofferdam in positive direction is higher than that in negative direction. Under seismic excitation, the displacement response of inner steel sheet is much more obvious than that of outer one. And the distribution of horizontal displacements in steel sheets presents the characteristics that the corresponding values increase with their heights in the cofferdam system. On the contrary, the deviatonic stresses of cofferdam decrease with the augments of height.

scholarly journals Implementation of the structural performance factor (Sp) within a displacement-based design framework

2018 ◽  
Vol 51 (3) ◽  
pp. 159-165 ◽  
Author(s):  
Dion Marriott
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Structural Performance ◽  
Integration Time ◽  
Design Framework ◽  
Base Shear ◽  
Structural Behaviour ◽  
Performance Factor ◽  
Design Response Spectrum ◽  
Displacement Based

This paper discusses the application of the Structural Performance factor (SP) within a Direct Displacement-Based Design framework (Direct-DBD). As stated within the New Zealand loadings standard, NZS1170.5:2004 [1], the SP factor is a base shear multiplier (reduction factor) for ductile structures, i.e. as the design ductility increases, the SP factor reduces. The SP factor is intended to acknowledge the better-than-expected structural behaviour of ductile systems (both strength, and ductility capacity) by accounting for attributes of response that designers are unable to reliably estimate. The SP factor also recognizes the less dependable seismic performance of non-ductile structures, by permitting less of a reduction (a larger SP factor) for non-ductile structures. Within a traditional force-based design framework the SP factor can be applied to either the design response spectrum (a seismic hazard/demand multiplier), or as a base shear multiplier at the end of design (structural capacity multiplier) – either of these two approaches will yield an identical design in terms of the required design base shear and computed ULS displacement/drift demands. However, these two approaches yield very different outcomes within a Direct-DBD framework – in particular, if SP is applied to the seismic demand, the design base shear is effectively multiplied by (SP)2 (i.e. a two-fold reduction). This paper presents a “DBD-corrected” SP factor to be applied to the design response spectrum in Direct-DBD in order to achieve the intent of the SP factor as it applies to force-based design. The proposed DBD-corrected SP factor is attractive in that it is identical to the SP relationship applied to the elastic site hazard spectrum C(T) for numerical integration time history method of analysis within NZS 1170.5:2004 [1], SP,DDBD = (1+SP)/2.

scholarly journals Ground accelerations caused by large quarry blasts

1961 ◽  
Vol 51 (2) ◽  
pp. 191-202
Author(s):  
D. E. Hudson ◽  
J. L. Alford ◽  
W. D. Iwan
Keyword(s):  
Response Spectrum ◽  
Strong Motion ◽  
Complete Response ◽  
Charge Weight ◽  
Total Charge ◽  
Ground Acceleration ◽  
Acceleration Time

Abstract Ground acceleration-time measurements have been made within 2000 ft. of two quarry blasts of total charge weight 185 tons and 673 tons. Ground accelerations were of a character and magnitude similar to those associated with damaging earthquakes. Complete response spectrum curves calculated from the acceleration records are presented. Direct comparisons are made between these results and previous similar measuements and calculations using identical instruments, which have been made of strong-motion earthquakes, H. E. blasts, and the Rainier nuclear blast.

Sign in / Sign up

Export Citation Format

Share Document