Dynamic Amplification Factor

Following the linear static analysis procedure recommended by the US General Service Administration (GSA), the potential of an earthquake-resistant RC building for progressive collapse is evaluated in this study. Nonlinear static and nonlinear dynamic analyses are conducted to estimate the progressive collapse resistance of the building subjected to column failure. Under an approximate deflection demand, different collapse resistances are obtained. It indicates that different criteria for estimating the collapse resistance may be adopted for these two nonlinear analysis methods. The nonlinear static approach leads to a conservative estimation for the collapse resistance if ''2.0'' is used as the dynamic amplification factor (DAF). As the column-removed building is loaded into a significantly yielding phase, different assessed results are obtained by the linear static method and the nonlinear acceptance criterion suggested by the GSA guidelines. A DAF considering the inelastic dynamic effect may be needed in the GSA linear procedure. The capacity curve constructed from the nonlinear static analysis is shown to be capable of predicting the progressive collapse resistance and the DAF of a column-removed RC building.

The performance of substation equipment during an earthquake depends on their configuration, strength of construction, ductility and dynamic properties. Substation equipment's are lightly damped structures having one or more natural modes within the frequency band of ground excitation. The satisfactory operation of substation during and after an earthquake depends on the survival, without malfunction, of many diverse type of equipment. Porcelain components are identified as most vulnerable parts against earthquake vibrations than any other components of the substation. In this present work, substation equipment i.e., circuit breaker is used for analytical procedure. Electrical equipment is mounted on support structure. Support structure and porcelain insulator amplify the ground acceleration at the base of porcelain components. Dynamic characteristics of substation equipment are considered by carrying out finite element analysis. In the present work, maximum response spectral accelerations & displacements of supporting structures, equipment and for both equipment placed on support structures are evaluated with respect to the zone factors. Furthermore, dynamic amplification factor (DAF) of substation support structures and along with its electrical equipment are obtained and effect of different parameters (e.g. support mass, height and stiffness) are discussed along with the recommendations available in International standards.

Progressive collapse occurs when there is not logical proportion between failure of a structural member and the result caused, and this will lead failure and collapse of adjacent structural members or even global collapse, namely the system is not able to bear service loads. In this paper, developing a numerical model based on different scenarios, progressive collapse of a 10-story building of seismically designed CBF steel frame was investigated. On this basis, progressive collapse-impact factor of structural members in different stories was determined in order to find the critical location of element removal. In this analysis, according to predefined scenarios, critical columns and related bracings were removed from the numerical model concurrently and the structure response was studied. Removing building members is to study specific aspects in which the member was lost due to extreme events or abnormal loads. To perform nonlinear analyses, the OpenSees software and its fiber elements were used for the modeling of linear and nonlinear behaviour of structural members. Possibility of members’ plasticity along the member length and cross section and buckling of compression members is considered in the model. Analysis results showed that elements removal in mid stories leads to higher responses and thereby increase in progressive collapse-impact factor and it was the criteria of determination of critical location of removals.

Analytical solution of transverse shear strain vibration of a tube caused by internal gaseous detonation near the second critical speed (shear group velocity) is not reported in the literature. It is performed based on a steady state model and first order shear deformation theories (model I and II) in this paper, and the results are verified through comparison with the finite element results reported in the literature. There are no known experimental ways of directly measuring dynamic transverse shear strain and only theoretical results and numerical data are available. The finite element method is very time consuming compared with the analytical solution. It is shown in this paper that the resonance phenomenon of the transverse shear strain vibration near the second critical speed can be predicted by steady state model and first order shear deformation theories. The first order shear deformation theory (model II) has a good agreement with finite element results in prediction of dynamic amplification factors and critical speeds.

Following the linear static analysis procedure recommended by the US General Service Administration (GSA), the potential of an earthquake-resistant RC building for progressive collapse is evaluated in this study. Nonlinear static and nonlinear dynamic analyses are conducted to estimate the progressive collapse resistance of the building subjected to column failure. Under an approximate deflection demand, different collapse resistances are obtained. It indicates that different criteria for estimating the collapse resistance may be adopted for these two nonlinear analysis methods. The nonlinear static approach leads to a conservative estimation for the collapse resistance if ''2.0'' is used as the dynamic amplification factor (DAF). As the column-removed building is loaded into a significantly yielding phase, different assessed results are obtained by the linear static method and the nonlinear acceptance criterion suggested by the GSA guidelines. A DAF considering the inelastic dynamic effect may be needed in the GSA linear procedure. The capacity curve constructed from the nonlinear static analysis is shown to be capable of predicting the progressive collapse resistance and the DAF of a column-removed RC building.

The dynamic amplification factor (DAF) estimated from an inelastic single-degree-of-freedom (SDOF) system is favorable for progressive collapse evaluation of building structures. In this paper, analytical expressions are obtained for the DAFs of an inelastic SDOF model subjected to step loadings. The capacity curve is used to derive the force-and displacement-based DAFs. Numerical analyses are carried out to verify the accuracy of the proposed method. An inelastic fixed-fixed beam is used to demonstrate its application to a multi-hinge structure. The study results indicate that the force-and displacement-based DAFs may be estimated by the analytical methodology.