Response spectrum analysis is a method for estimating structural responses to short, nondeterministic, transient dynamic events. Seismic performance of rc building using spectrum response and. 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. How to scale base shear in etabs the structural world. If you want the program to make a spectrum for you, activate the generate response spectrum checkbox and specify values in the oscillating frequency hz and damping ratio 0. Feel free to book us or attend our training program to learn all of these. This toolbox is suitable for carrying dynamic response spectrum analysis drsa for a given structure, as well as producing linear elastic response spectra and elastoplastic response spectra, using elasticideally plastic forcedeformation relation. Response spectrum method is a linear dynamic statistical analysis method. Response spectra as a useful design and analysis tool for. In the present study, the response spectrum analysis rsa of regular rc building frames is compare with response spectrum analysis of regular building and carry out the ductility based design. Rsa is essentially taking the linear response of the different fundamental frequencies of vibration and adding them up to determine the total response. Response spectrum method in seismic analysis and design of structures.
Question is, do you really need to perform the rsa. It assumes that the building responds in its fundamental mode. New developments in the response spectrum method have led to calculations in seismic stresses that are more accurate, and usually lower, than those obtained by conventional methods. A response spectrum is a plot of the peak or steadystate response displacement, velocity or acceleration of a series of oscillators of varying natural frequency, that are forced into motion by the same base vibration or shock. This method requires a previously calculated number of undamped free vibration frequencies and the corresponding mode shapes. The response spectrum method and the simplified techniques derived from it have become popular methods of seismic analysis and design. The necessary functions included involve apart from drsa and spectra production, linear. Responsespectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration, velocity, or displacement as a function of. Nov 22, 2017 response spectrum method in seismic analysis and design of structures. Variations of the ground motion due to wave passage, loss of coherency with distance and variation of local soil conditions are included. Response spectrum method in seismic analysis and design of. A response spectrum analysis requires the specification of an excitation spectrum, also known as a frequencyacceleration spectrum. Comparison of some code provisions prescribed by different earthquake codes. An example of time history analysis with a finite element model for the ground wave movement with abaqus software is detailed in the next section.
In seismic design of structures, the smoothed response spectra are commonly used as. Time history analysis is a more accurate, more computationally intensive method than response spectrum analysis and is best suited to the transient loadings where the profile is known. Rsa for irregular structures technical knowledge base. This is very important because response spectrum analysis rsa is based on a. Results of response spectrum ram staad opentower forum. Since the exact time history of the load is not known, it is difficult to perform a timedependent analysis. This short video gives a succinct overview of the concept of a response spectrum and contains a very basic discussion about how to use it. This approach defines a series of forces acting on a building to represent the effect of earthquake ground motion, typically defined by a seismic design response spectrum. Response spectrum method in seismic analysis and design of structures new directions in civil engineering book 4 1st edition, kindle edition by ajaya kumar gupta author isbn. May 24, 2019 if you are scaling the response spectrum to match with the static analysis results, you need to input the computed scale factor and specified it under response spectrum cases in etabs. Shock response spectrum srs use the shock response spectrum srs to estimate the damage potential of mechanical impulses or stationary random vibrations. For each mode, a response is read from a design spectrum based on the modal frequency and a given damping ratio. 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.
Introduction the most direct description of an earthquake motion in time domain is provided by accelerograms that are recorded by instruments called strong motion accelerographs. Using the acceleration response spectrum, an equivalent static load is derived which will provide the same maximum response as that obtained in each. Cascaded analysis of secondary systems using response spectrum method. Several methods are available to predict bridge response to incoherent ground motions, but are typically cost prohibitive to implement in standard bridge designs. Response spectrum 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. 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. After the introduction to prt in chapter 1, chapter 2 teaches the reader how to teach motivation. Originally, when we were studying the dynamics of a simple single degree of freedom structure, we noticed that given one type of earthquake, we dont have to keep solving the equat.
Note that milstd1540c and milstd810e require this format for certain shock environments. It plots the peak acceleration responses of a bank of single degreeoffreedom sdof spring, mass damper systems all experiencing the same baseexcitation as if on a rigid massless. Sep, 2012 the pdelta kg analysis is the one i used in the staadpro analysis and im well aware of this analysis. 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. The response spectrum method of analysis is developed using the following steps. Response spectrum analysis massachusetts institute of. Sep 10, 20 the response spectrum method of analysis is developed using the following steps. The accelerograph records three orthogonal components of ground acceleration.
This new textbook examines the wealth of information on the response spectrum method generated by the latest research and presents the background theory in simplified form. 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. These new approaches are based on the method of mode acceleration and. Examples of such events are earthquakes and shocks. Variations of the ground motion due to wave passage, loss of coherency with distance. Response spectrum method in seismic analysis and design of structures new directions in civil engineering. One of the topics we deliver on the training is response spectrum analysis rsa. In a response spectrum analysis, summation of the support reactions does not match the base shear reported.
Pivotal response treatment for autism spectrum disorders 1st edition. In a response spectrum analysis, the results of a modal analysis are used in terms of a known spectrum to calculate displacements and stresses in the model. Introduction the basis of engineering seismology is the need to quantify how a given structure will respond to complex ground motions. 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. My question is why we dont apply u2 and u3 in the same load case. What is difference between time history analysis and response. 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. Harmonic analysis and cepstral analysis advanced parametric sinusoidal modeling is offered with your choice of frequency estimation methods. 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. This is useful if in comparing the seismic responses obtained with the use of both spectral analysis and time analysis. Response spectrum method in seismic analysis and design of structures new directions in civil engineering gupta, ajaya kumar on.
Responsespectrum analysis etabs computers and structures. Browse the amazon editors picks for the best books of 2019, featuring our favorite reads in more than a dozen categories. So i will apply response spectrum function per ibc 2006 in u1 direction by a scale factor. Elastic response spectrum file exchange matlab central. Response spectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration. Approximate modal response spectrum method of analysis. If you are scaling the response spectrum to match with the static analysis results, you need to input the computed scale factor and specified it under response spectrum cases in etabs. For complex or irregular structures which do not have clearly defined orthogonal directions, it may be unclear as to how the orientation of response spectrum analysis should be applied. Responsespectrum analysis provides insight into dynamic behavior by measuring pseudospectral acceleration, velocity, or displacement as a function of structural. Response spectrum analysis can be used to estimate the peak response displacement, stress, etc. We also teach how to build the site specific spectra curve that need to load to structures. Response spectrum method of analysis with simplified. Saiid saiidi, have made a study to better understand the bridge response due to site response effect. The example problem in the book is solve by the author manually and the modal analysis was done using sap 2000 and i wanted to verify the accuracy of the result by comparing them with midas gen and staadpro, midas gen result is very close with the book s output within 1 to 2 % difference however, staadpro.
The structural analysis of high rise multistory storey reinforced concrete symmetrical and asymmetrical frame building is done with the help of sap software. It is part of the process of structural design, earthquake engineering or structural assessment and retrofit see structural engineering in regions where earthquakes are prevalent. For this to be true, the building must be lowrise and must not twist significantly when the ground moves. The structures response is determined by its mass and stiffness distributions. Wilson explains that combined directional effects may be accounted for more effectively by using an alternative method in which the srss combination of two. Part of the international union of theoretical and applied mechanics book. Responsespectrum analysis technical knowledge base.
The spectrum can be used in the subsequent response spectrum analysis, or it can be written to a file for future use. Understand that the method of determining response spectrum sasat for a given diagram of accelerations ft, where t refers to period, sa refers to acceleration spectrum, t refers to time, while ft is a given time analysis function. Shock response spectrum srs analysis crystal instruments. Seismic analysis is a subset of structural analysis and is the calculation of the response of a building or nonbuilding structure to earthquakes. The response is calculated for each direction separately. Part of the sustainable civil infrastructures book series suci. Base shear does not match the summation of shears ram. What is difference between time history analysis and. This barcode number lets you verify that youre getting exactly the right version or edition of a. The shock response spectrum is a useful tool for estimating the damage potential of a shock pulse, as well as for test level specification.
Using response spectrum method with the help of analysis and design tool staad pro v8i, to evaluate analysis parameters such as nodal displacement, shear forces in column, compressive and tensile. Random vibration and response spectrum approaches in seismic. In the paper entitled orthogonal effects in rsa, dr. Buy response spectrum method in seismic analysis and design of structures new directions in civil engineering book 4. However, as response spectra and dynamic analysis are being included within the newer building codes and as performancebased design pbd techniques are. A new response spectrum method is developed for seismic analysis of linear multi. Response spectrum method in seismic analysis and design of structures book. A responsespectrum 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. Book description new developments in the response spectrum method have led to calculations in seismic stresses that are more accurate, and usually lower, than those obtained by conventional methods. This is to convert the spectrum into required units and for the base shear to scale it to an appropriate level. Modal analysis is performed to identify the modes, and the response in that mode can be picked from the response spectrum. The first version of this chapter on the response spectrum method was. Response spectrum analysis the seismic loads are taken into account according to the response spectrum analysis method.
This new textbook examines the wealth of information on the response spectrum method generated by the latest research and presents the background theory in. Oct 15, 2017 response spectrum analysis as per is1893 in staad pro. Doi link for response spectrum method in seismic analysis and design of structures. Shock response spectrum analysis a shock response spectrum srs is a graphical presentation of a transient acceleration pulses potential to damage a structure. Pdf response spectrum analysis of structures subjected to. The purpose of this report is to explain the shock response spectrum and to give a. Obtaining joint accelerations for response spectrum analysis of multidof structure. The one that the software reports as the base shear, is the correct value to use. This new textbook examines the wealth of information on the response spectrum method generated by the latest research and presents the background. Mar 25, 2010 with this book, readers will gain proficiencies in the following.
With this book, readers will gain proficiencies in the following. Response spectrum analysis in etabs software issues. It is helpful to keep in mind that a response spectrum is simply a graph of the maximum value usually displacement or. For nonlinear analysis one typically uses a pushover curve nonlinear static analysis or time history analysis nonlinear dynamic analysis. Response spectrum method in seismic analysis and design of structures ajaya kumar gupta download bok. Johnson department of earth and environmental science, new mexico tech 1. Response spectrum analysis and nonlinear properties. The resulting plot can then be used to pick off the response of any linear system, given its natural frequency of oscillation. Response spectrum method of analysis seismic analysis of.
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