On the correct application of the 1004040 rule for. According to iso 19002, when the response spectrum method is used and one design spectrum is applied equally in both horizontal directions, the complete quadratic combination cqc method may be used for combining modal responses and the square root of the sum of the squares srss may be used for combining the directional responses. Peak acceleration an overview sciencedirect topics. A replacement for the srss method in seismic analysis. Review results disp, forces, stresses velocity or accelof specify stresses if needed mass damping stiffness damping freq. For example, the original complete quadratic combination cqc rule 8, 9 for modal response combination has been extended to a new method called cqc3 6, 1015, to combine modal responses. The relatively new method of modal combination is the complete quadratic combination, cqc, method 1 that was first published in 1981. In this study the mrha is identified as the most accurate analysis method for the study of the seismic. This disambiguation page lists articles associated with the title cqc. Modal response combination methods for seismic response spectrum analysis manuscript completed. It is based on random vibration theories and has found wide acceptance by most engineers and has been incorporated as an option in most modern computer programs for seismic analysis. The list of acronyms and abbreviations related to cqc complete quadratic combination. In using this method, the complete quadratic combination cqc is adopted for classically damped linear systems and the complex complete quadratic combination ccqc formula is adopted for nonclassically damped linear systems.
Jmc, earthquake resistant regulations for building structures in japan, japan ministry of construction, tokio, 1980. It is used for structures having closely spaced frequencies. The modal response is determined by means of the following formula. This information should not be considered complete, up to date, and is not intended to be used in place of a visit. Modal response combination methods for seismic response spectrum analysis. Square root of the sum of the squares srss complete quadratic combination cqc in this study, the result of a response spectrum analysis was analyzed using the absolute and srss generic methods, and the results were compared. Simplifications of cqc method and ccqc method springerlink. Complete quadratic combination cqc or the square root of the sum of the squares srss to obtain the response at each dof. Dependent damping ratio apply psd excitation at desired nodes 5. Newmarks combinations to obtain the global response due.
Alternatively, an eswl for the total peak response can be expressed as a linear combination of the background and resonant loading components. The result of a response spectrum analysis using the response spectrum from a ground motion is typically different from that would be calculated directly from a linear dynamic analysis using that ground motion directly, since. It expresses the structural response in terms of uncoupled sdof modal responses, yet accounting fully for modal response variances and cross. Absolute peak values are added together square root of the sum of the squares srss complete quadratic combination cqc in this study, the result of a response spectrum analysis was analyzed using the absolute and srss generic methods, and the results were compared. The forces that result from this combination are typically dominated by a single mode in. A complete quadratic combination cqc method is proposed which reduces errors in modal combination in all examples studied. Complete quadratic combination method cqc and double sum methods dsm table 71. Nuregcr6645 reevaluation of regulatory guidance on. In using this method, the complete quadratic combination cqc is adopted for classically damped linear systems and the complex complete.
Comparisons with response calculations using the srss and the complete quadratic combination rules are given and discussed in detail. Utilize the complete quadratic combination cqc method instead of the squarerootofsumofsquares srss method. Complete quadratic combination cqc or the square root of the sum of the. Complete quadratic combination cqc double sum dsum grouping grp naval research laboratory sum nrlsum rosenbluethrose 6. The cqc method degenerates into the srss method for systems with wellspaced natural frequencies. If an internal link led you here, you may wish to change the link to point directly to the intended article. Subtracting the modal combination of story shears at one level from modalcombination of story shear at the level below does not represent the mrs analysis story force. Because it is wellknown for a long era that application of the squarerootofsumofsquares srss method in seismic analysis for combining modal maxima can yield significant errors. Cqc is defined as complete quadratic combination somewhat frequently. Cqc as abbreviation means complete quadratic combination. The purpose of this note is to present an improved technique to be used in place of the srss method in seismic analysis. Rigid response at high frequencies, the spectral acceleration becomes equal to the maximum ground accel eration, which is also called the zero period acceleration zpa. In the general data of the model you can activate the cqc rule and for load cases of type earthquake there are two new properties available, the angular frequency and the lehrs damping.
Dynamic wind effects on buildings with 3d coupled modes. Complete quadratic combination cqc a method that is an improvement on srss for closely spaced modes. The responsespectrum mode superposition method is widely used for seismic response analyses of linear systems. In using this method, the complete quadratic combination cqc is adopted for classically damped linear systems and the complex complete quadratic. The modal maximum response, r, does not assume an absolute value and it retains the algebraic sign asdociated with the product of all components e. About quadratic combinations robot structural analysis. An engineering approach for 3d numerical earthquake analysis. This design spectrum is commonly based on a uniform hazard spectrum, which is developed by computing the spectral amplitude at each period that has a specified probability of. A replacement for the srss method in seismic analysis wiley online. This method is described in several textbooks wilson, 2004. Thus, it is an improvement over the classical srss rule which neglects contributions from modal cross. Srss rule for structural systems with well separated and closely spaced modal frequencies, subjected to wide. The cqc complete quadratic combination rule is available in rfem and rstab since version x. There are two commonly used procedures for seismic design lateral forces.
The cqc method degenerates into the srss method for systems with well. Srss method for srss method, the correlation coefficients equal. This method which is similar to the rose method is again based on the application of random vibration theory. Apparently, the invented approximate methods produce some amount of errors in comparison with exact time history analysis but the recently proposed method namely, complete quadratic combination cqc and sum root of the sum of squares srss drastically reduces the computational time by combination of peak responses in each mode. In the framework of seismic design of structures, response spectrum analysis rsa is the most commonly used approach in practice. A comparative analysis on absolute and srss methods of.
The complete srss modal combination rule, earthquake. The comparative performance of seismic response spectrum. What is shorthand of complete quadratic combination. The complexcompletequadraticcombination ccqc method for seismic response of nonclassically damped linear mdof system article pdf available january. The complete quadratic combination 3 cqc3 method is briefly described in. Complete quadratic combination how is complete quadratic. Response spectrum method of analysis with simplified. These individual modal responses are combined using one of the square root of the sum of squares srss, the complete quadratic combination cqc, the asce498 asce, the ten percent ten, or the absolute abs methods to obtain the resultant responses. A replacement for the srss method in seismic analysis, e. Earthquake lateral force analysis the design lateral force shall first be computed for the building as a whole. One of the definitions of cqc is complete quadratic combination. Comparative study of equivalent lateral force method and. Quadratic combination rule cqc can accurately account for the modal coupling.
This design lateral force shall then be distributed to the various floor levels. The meaning of cqc abbreviation is complete quadratic combination. The most popular combination rule is the complete quadratic combination cqc which is also prescribed by the most of seismic design codes and is based on the assumptions that the seismic acceleration is a white noise process and the peak factor ratios. The cqc rule called complete quadratic combination rule takes care of this correlation. Mdof modal spectral analysis university of nebraska. Since the cqc method only involves a small increase in numerical effort, it is recommended that the new approach be used. Complete quadratic combination, see seismic analysis. Complete quadratic combination cqc rule dlubal software. Rational design spectra for structural reliability. Seismic analysis of transformer using different mode. Implementation of modal combination rules for response. Square root of the sum of the squares method srss and ten percent method tpm. A replacement for the srss method in seismic analysis nrc. Complete quadratic combination cqc results are generally conservative, but the correlation between time.
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