Conceptually the method is a simplification of modal analysis, i. Lets assume the excitation angle 0 and building principle direction is u1 so i will apply response spectrum function per ibc 2006 in u1 direction by a scale factor. Since the response spectra give only maximum response, only. I do not think it would be reasonable to consider pdelta analysis with response spectrum load cases the basic reason behind this is that the results of response spectrum would loose signs as soon as the modal combination is done using methods like srss, cqc etc. Mar 04, 2014 module 9 response spectrum modal analysis 1. Modal analysis is performed to identify the modes, and the response in that mode can be picked from the response spectrum. Structural testing part 2, modal analysis and simulation br0507.
The frequency response function is very simply the ratio of the output response of a structure due to an applied force. Response spectrum method of analysis with simplified. Cascaded analysis of secondary systems using response spectrum method. As a result, when modal response spectrum analysis is used, a threedimensional model is required for all structures, including those with diaphragms that can be designated as flexible. Obtaining joint accelerations for response spectrum analysis of multidof structure. Aug 31, 2018 channel provide you knowledge about all competitive exam including computer proficiency test and current affairs too. Response spectra can also be used in assessing the response of linear systems with multiple modes of oscillation multidegree of freedom systems, although they are only accurate for low levels of damping. Nasahdbk7005 march, 2001 i foreword this handbook is approved for use by nasa headquarters and all field centers and is intended to provide a common framework for consistent practices across nasa programs.
At the point in time where iyiti is maximum, the response is defined as yi. Construction of design response spectrum the chilean way. Shock response spectrum analysis results result is a single output set containing the combined responses of the spectrum analysis. Response spectrum method of analysis mechanical engineering. Response spectrum analysis rsa is a lineardynamic statistical analysis method which measures the contribution from each natural mode of vibration to indicate the likely maximum seismic response of an essentially elastic structure. Using the acceleration response spectrum, an equivalent static load is derived which will provide the same maximum response as that obtained in each. Comparison of some code provisions prescribed by different earthquake codes.
Responsespectrum analysis technical knowledge base. Introduction the basis of engineering seismology is the need to quantify how a given structure will respond to complex ground motions. The results from the x, y, and zdirection analyses are tabulated below. We measure both the applied force and the response of the structure due to the applied force simultaneously.
When defining response spectrum load case in etabs, we have three directions. Response spectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration. Analysis of building with response spectrum method seismic analysis of highrise building having following data is analyzed for different models of lateral load resisting systems. Modifications to modal response spectrum analysis method modified to require 100% of the mass introduces rigid body mode concept for t response spectrum modal analysis 1. Johnson department of earth and environmental science, new mexico tech 1. Sep 10, 20 the response spectrum method of analysis is developed using the following steps. Topic 6 structural dynamics iii analysis of elastic mdof systems equations of motion for mdof systems uncoupling of equations through use of natural mode shapes solution of uncoupled equations recombination of computed response modal response spectrum analysis by example use of reduced number of modes. The response spectrum analysis uses the natural periods from the eigenvalue analysis.
Pdf response spectrum analysis of structures subjected to. Modal and response spectrum analyses of an iter divertor. Seismic analysis modal spectral analysis it defines the seismic behavior of the structure as the superposition of n. Dynamic design analysis method ddam response spectrum. Response spectrum method of analysis seismic analysis of. The updated documents, reevaluation of regulatory guidance on modal response combination methods for seismic response spectrum analysis issued in 1999 nuregcr6645, bnlnureg52276 and draft regulatory guide dg1127 issued in 2005 contain new recommendations. Shock response spectrum analysis is the maximum response of a series of single degree of freedom systems having the same.
Based on a paper presented at imacxxvii, the 27th international modal analysis conference, society for experimental mechanics, orlando, fl. Datta department of civil engineering, iit delhi response spectrum method of analysis response of the system in the ith mode is 5. Useful elearning website will also be shown to give idea about topic clearly. Structural testing part 2, modal analysis and simulation. The vertical response spectrum along zdirection as well as horizontal response spectrum along x and y directions in fig. It requires to define a design response spectrum,in general, a spectrum of pseudo. Apply the load at the base and assume 2 % constant modal damping. Mechanical vibrations overview of experimental modal analysis. Response spectrum analysis the seismic loads are taken into account according to the response spectrum analysis method. These peak responses are then combined to estimate a total response. Examples would include measuring the vibration of a cars body when it is attached to a shaker, or the noise pattern in a room when excited by a loudspeaker modern day experimental modal analysis systems are composed of 1 sensors such as transducers typically. What is the difference between equivalent static analysis and.
Iit delhi response spectrum method of analysis response of the system in the ith mode is. There is also a requirement that the cumulative modal weight of all modes within the cutoff frequency range must be greater than a specified value, with the navsea 3010 default being 80%. Modal analysis is the study of the dynamic properties of systems in the frequency domain. Objectives response spectrum analysis using response spectrum curve. Max versus it is standard to present the curve in terms of s. Nov 22, 2017 equivalent static method esm and response spectrum method rsm both attempt to quantitatively estimate force due to an earthquake on a structure in terms of a set of static forces applied at specific points. If the address matches an existing account you will receive an email with instructions to reset your password. Dynamic analysis of a structure subjected to earthquake excitation using the response spectrum. Introduction to structural dynamics and earthquake engineering module 9 response spectrum modal analysis prof. A replacement for the srss method in seismic analysis, e.
The shock response spectrum is a graphical representation of an arbitrary transient acceleration input, such as shock in terms of how a single degree of freedom sdof system like a mass on a spring responds to that input. Modifications to modal response spectrum analysis method modified to require 100% of the mass introduces rigid body mode concept for t response spectrum analysis and nonlinear properties. The first step in a modal response spectrum analysis is the determination of the 3d modal shapes and natural frequencies of vibration eigenmodes and eigenvalues. Pdf multi modal response spectrum analysis implemented in. Tutorial for response spectrum analysis using caepipe. The response can be measured as displacement, velocity or acceleration. It is apparent that all response spectrum curves represent the properties of the earthquake at a specific site and are not a function of the properties of the structural system. Lateral loads are far too high for mounting structure to survive. Multi modal response spectrum analysis implemented in opensees.
Channel provide you knowledge about all competitive exam including computer proficiency test and current affairs too. My question is why we dont apply u2 and u3 in the same load case. Analytical modal analysis depends on the generation of the equations of motion of a system through a finite element model. The response spectrum method of analysis is developed using the following steps. What is difference between time history analysis and. Today, this task can be performed very reliably and efficiently by many computer programs dedicated to seismic response analysis for the purposes of earthquakeresistant design. Response spectrum is a plot of the peak or steadystate response displacement, velocity or acceleration of a series of oscillatorsof varyingnatural frequency, that are forced into motion. This method requires a previously calculated number of undamped free vibration frequencies and the corresponding mode shapes. What is difference between time history analysis and response.
Aug 30, 2016 this feature is not available right now. Responsespectrum analysis rsa is a lineardynamic statistical analysis method which measures the contribution from each natural mode of vibration to indicate the likely maximum seismic response of an essentially elastic structure. Pdf response spectrum analysis of structures subjected. Response spectrum analysis massachusetts institute of. This cumulative modal weight criterion is for identifying the modes that will be. The structural analysis of high rise multistory storey reinforced concrete symmetrical and asymmetrical frame building is done with the help of sap software.
Instructional material complementing fema 451, design examples seismic load analysis 9 17 1a, 1b stiffness soft story irregularity vertical structural irregularities irregularity 1a exists if stiffness of any story is less than 70% of the stiffness of the story above or less than 80% of the average stiffness of the three stories above. From a set of frf measurements made at defined points on a structure, we can begin to build up a picture of its response. Topic 6 structural dynamics iii analysis of elastic mdof systems. Three modal combination techniques such as square root of sum of the squares srss, complete quadratic combination cqc. Approximate modal response spectrum method of analysis.
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