Modal analysis and modal testing ods, mimo, oma dewesoft. Aug 31, 2014 mod05 lec20 response spectrum method of analysis nptelhrd. Mar 30, 2014 a detailed derivation of the equations used to generate the response spectrum curves at a given joint location is presented as follows. Enter a new world of software engineering and digital signal analysis and save valuable time.
Responsespectrum analysis is a lineardynamic statistical analysis method which measures the contribution from each natural mode of vibration to indicate the likely maximum seismic response. Response spectrum analysis of asymmetrical building. 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. The three curves displacement response spectrum, pseudovelocity spectrum, and pseudoacceleration spectrum are normally plotted as one curve on special log paper. The objective of this project was to reevaluate the current regulatory guidance for combining modal responses in response spectrum analysis, evaluate recent technical developments, and recommend revisions to the regulatory guidance. Comparative study of static and dynamic seismic analysis. Modal response spectrum analysis using risa youtube. The equivalence is restricted to a single mode of vibration. The results from the mrs analysis are compared with the results obtained from an equivalent lateral force elf analysis of the same frame. Earthquake time history data is converted into a response spectrum.
Pdf response spectrum analysis of structures subjected to. Approximate modal response spectrum method of analysis. Seismic applications of nonlinear response spectra based on the. Mass participation of second vertical mode is driving. Get ansys response spectrum analysis tutorial pdf file for free from our online library pdf file. This is to certify that the project entitled seismic analysis of high rise building by response spectrum method submitted by ms. Mar 22, 2014 presentation on response spectrum analysis as per indian code. Modifications to modal response spectrum analysis method modified to require 100% of the mass introduces rigid body mode concept for t modal response analysis is a response of all modes. In a response spectrum analysis, the damping is included in the acceleration spectrum data, so the modal analysis must be undamped or you would be double counting the damping. Theory of response spectrum analysis earth and environmental. In the present study, response spectrum analysis is performed.
It is far easier to perform than timehistory analysis that requires structural dynamic analysis computer software. Introduction to structural dynamics and earthquake engineering module 9 response spectrum modal analysis prof. By any sdof system, it is meant a sdof system with any natural frequency. Effective and affordable modal analysis and modal testing solution for ods, mimo, and oma testing methods. Response spectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration, velocity, or displacement as a function of structural period for a given time history and level of damping. The first data reported from an earthquake record is generally the peak ground acceleration pga which expresses the tip of the maximum spike of the acceleration ground motion figure 1. The project is in seismic design category d and has irregularities which require use of a modal response spectrum analysis for seismic loading. The analysis shall include sufficient modes to capture participation of 100% of the structures mass. Since the response spectra give only maximum response, only. Topic 6 structural dynamics iii analysis of elastic mdof. Introduction structural analysis is mainly concerned with finding out the behaviour of a structure when subjected to some action.
Pdf response spectrum analysis of structures subjected. For each damping value the magnitude of the response spectrum must be given over the entire range of frequencies needed, in ascending value of frequency. Response spectrum analysis massachusetts institute of. Mar 04, 2014 module 9 response spectrum modal analysis 1. Dynamic design analysis method ddam response spectrum analysis with abaqus summary the dynamic design analysis method ddam is a u. Evaluation of modal combination methods for seismic response. What is difference between time history analysis and. Pdf response spectrum analysis of frame structures. Methodology the design lateral shear force at each floor in each mode is computed by staad in accordance with the is. For the love of physics walter lewin may 16, 2011 duration. Seismic analysis of a reinforced concrete building by. Then open the response spectrum and insert rs displacment. 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 analysis is a linear dynamic statistical analysis method which measures the contribution from each eigenmode to indicate the likely maximum seismic response of an elastic structure. Mar 21, 2015 modal and response spectrum is 18932002 analysis 0f r. Earthquake analysis and design of simple structures and. Response spectrum analysis can be used to estimate the peak response displacement, stress, etc. However, the pseudovalues have minimum physical significance and are not an essential part of a response spectrum analysis. For this purpose, it shall be permitted to represent all modes. Response spectrum method of analysis mechanical engineering. Sep 10, 20 equivalent lateral force for an earthquake is defined as a set of lateral force which will produce the same peak response as that obtained by dynamic analysis of structures. Nonlinear modal analysis, force analogy method, state space method, geometric nonlinearity, response spectra analysis. The results from the x, y, and zdirection analyses are tabulated below. 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. The spectrum can be used in the subsequent response spectrum analysis, or it can be written to a file for future use. When an analysis is completed, analyze the results using load cases or load combinations with various postprocessing functions from the results menu. General the response spectrum is a plot of the maximum response maximum displacement, velocity, acceleration or any other quantity of interest to a specified dynamic loading applied on all.
Tutorial for response spectrum analysis using caepipe. Navy methodology for qualifying shipboard equipment and supporting structures for survival of shock loading due to underwater explosions undex. I have previously contacted bentley about how to set up the model to use the direct analysis method with the response spectrum analysis. Perform analysis by clicking perform analysis or using the main menu, analysis perform analysis. 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. Modal response spectrum analysis earthquake resistance. The usual application of this method is in seismic earthquake analysis. Complications may occur with the response spectrum method for large systems. Earthquake engineering, reliability analysis, earthquake engineering, fragility curves, shear wall system, flat slab structures. Multi modal response spectrum analysis implemented in opensees. 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. Shock response spectrum analysis results result is a single output set containing the combined responses of the spectrum analysis. Seismic design of buildings worked examples worked examples presented at the workshop ec 8.
Can ram elements perform an eigenvalue solution to determine mode shapes without the response spectrum data. The response spectrum method rsm was introduced in 1932 in the doctoral. Response spectrum analysis of structures subjected to seismic actions chapter pdf available january 20 with 4,519 reads how we measure reads. The implementation in diana assumes that the contribution of damping is negligible and that the base acceleration spectrum has a working direction i, i. Mar 11, 2017 a response spectrum analysis calculates the maximum response of a structure to transient loads such as displacement,velocity or acceleration, that are forced into vibration by a base vibration or shock. Dynamic analysis of multistory building using response. Responsespectrum analysis technical knowledge base. Highlights from chapter 12 of asce 716 provisions for. Seismic analysis of a reinforced concrete building by response spectrum method. The sdof response spectrum method usually gives less conservative results than simplified procedures, yet easy to perform. Now, it is necessary to construct the design response spectrum. We measure both the applied force and the response of the structure due to the applied force simultaneously. Selected nodes and members of the studied frame vi.
It is practical to envelope response spectra such that a smooth curve represents the peak response for each realization of. Derivation of responsespectrum equations technical. Response spectrum method of analysis seismic analysis of. The motivation for moving linear response history lrh analysis from chapter 16 to chapter. Lateral loads are far too high for mounting structure to survive. Introduction the basis of engineering seismology is the need to quantify how a given structure will respond to. The video shows a sismic analysis for a threestory building subjected to an elastic pseudoacceleration response spectrum 84. With our solution, you are able to excite the structure with an impact hammer or modal vibration shaker and easily measure the response. The effective damping of the isolated modes of response is limited to 30 percent of critical. Modal analysis is performed to identify the modes, and the response in that mode can be picked from the response spectrum. 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. The response can be measured as displacement, velocity or acceleration.
Pdf on jul 3, 2014, jozsef simon and others published multi modal response spectrum analysis implemented in opensees find, read and cite all the. Johnson department of earth and environmental science, new mexico tech 1. With this response spectrum, it is possible to predict the maximum response for any sdof system. 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. Note that milstd1540c and milstd810e require this format for certain shock environments. The shock response spectrum is a useful tool for estimating the damage potential of a shock pulse, as well as for test level specification.
Construction of design response spectrum the chilean way. Reevaluation of regulatory guidance on modal response. Tutorial for response spectrum analysis using caepipe the following are the steps for performing the response spectrum analysis using caepipe. Seismic analysis of high rise building with is code 18932002 and is code 18932016 narayan malviya1. Response spectrum analysis requires that isolator units be modeled using amplitude dependent values of effective stiffness. The purpose of this report is to explain the shock response spectrum and to give a. Seismic analysis of highrise building by response spectrum. Response spectrum analysis which way is forward article pdf available october 2014 with 5,564 reads how we measure reads. The system of equations for base excitation may then be. Pdf in the framework of seismic design of structures, response. We will use the first two modes form the modal analysis and calculate on two points. Responsespectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration, velocity, or displacement as a function of structural. In addition, the results of a modal analysis will tell you much about the dynamic characteristics of the model, including whether or not you really have a.
Response spectrum method of analysis free download as powerpoint presentation. Using the acceleration response spectrum, an equivalent static load is derived which will provide the same maximum response as that obtained in each. 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.
We recommend that you register using the same email address you use to maintain your asce member account. Set options related to response spectrum analysis in response spectrum load cases. The closer the mass participation of the first mode gets to 100% the closer the load distribution is. The damping is included in the acceleration data when the transient acceleration time history is converted to a response spectrum using a q value in the conversion. The frequency response function is very simply the ratio of the output response of a structure due to an applied force. What is the difference between equivalent static analysis. Cascaded analysis of secondary systems using response spectrum method. The modal test is an indispensable tool to determine natural frequencies and mode shapes of any structure. Responsespectrum analysis 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. This chapter uses the modal response spectrum mrs method of analysis to examine a sixstory momentresisting frame. Earthquake response spectrum analysis of 4 story shear. In the subsequent load cases, only the spectra should be defined. Results of the analysis the analysis was performed for static and seismic loads.
If there is more than one response spectrum defined in the input file, the load data representing the dynamic weight should accompany the first set of spectrum data only. Response spectrum analysis is an inexpensive approach to estimate the peak response of a model usually a model of a structure subjected to base motion. A modal or natural frequency analysis also known as normal modes or eigenvalue analysis forms the basis of several other dynamic analyses, including the modal approach formulations and response spectrum analysis. Comparison of some code provisions prescribed by different earthquake codes.
The method is only approximate, but it is often a useful, inexpensive method for preliminary design studies. Ram elements dynamic modal analysis faq bentley communities. Response spectrum analysis, mode shapes, modal mass participation factors, natural frequency, eigenvalues, eigenvectors. The results of a response spectrum analysis are given in terms of individual and combined modal forces. Response spectrum analysis this chapter describes the response spectrum analysis rsa with module spectr. Ram elements will perform an eigen solution without the response spectrum curve data. What scale factor should i apply to the response spectrum. Confused about direct analysis method and modal response. Responsespectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration, velocity, or. Response spectrum method of analysis with simplified. This is called modal mass participation factor which shows how much a particular mode is contributing to the overall deformation of the system. Time history analysis provides both the time history of the response for example.
More accurate values of response may be obtained for buildings by the modal analysis method, using modified design response spectra for inelastic analysis. Mod05 lec20 response spectrum method of analysis youtube. Dynamic analysis using response spectrum seismic loading before the existence of inexpensive personal computers, the response spectrum method was the standard approach for linear seismic analysis 15. In nuclear piping engineering, the response spectrum method of analysis is widely used to analyze piping systems. The response spectrum method of analysis is developed using the following steps. A significant amount of increase in the lateral stiffness has been observed in all models of brace frame and shear wall frame as compared to bare frame. The matter of combining modal responses is of great interest. Earthquake response spectrum analysis of 4 story shear building shear building modal analysis earthquake response spectrum modal spectral accelerations modal displacements floor displacements story drifts inertia forces shear forces overturning moments input and output files in this example we compute the.
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