Journal of Earthquake Engineering

Peak ground velocity (PGV) has received much less attention in the technical literature than more widely-used parameters such as peak ground acceleration (PGA) and response spectral ordinates. However, there are many examples of the use of PGV in engineering seismology and earthquake engineering, including as a parameter from which to estimate macroseismic intensity and structural damage. PGV is also employed in some methods for the assessment of liquefaction potential and, because of its relationship to ground strains, in the seismic design and assessment of buried pipelines. One of the most important uses of PGV has been in the construction of elastic response spectra. There are relatively few predictive equations for PGV, compared to those for PGA and spectral ordinates, but 25 such equations are reviewed and summarised. The issue of scaling PGV from response spectral ordinates is explored and it is shown that the common practice of scaling PGV from spectral accelerations at 1.0 second should not be continued because the ratio of the two quantities is highly variable. A more stable relationship exists between PGV and the spectral acceleration at 0.5 second response period; however, it is clearly preferable to estimate peak velocities directly and PGV equations should be derived together with equations for spectral ordinates in the same way as PGA.

In this paper, two sets of earthquake ground-motion relations to estimate peak ground and response spectral acceleration are developed for sites in southern Spain and in southern Norway using a recently published composite approach. For this purpose seven empirical ground-motion relations developed from recorded strong-motion data from different parts of the world were employed. The different relations were first adjusted based on a number of transformations to convert the differing choices of independent parameters to a single one. After these transformations, which include the scatter introduced, were performed, the equations were modified to account for differences between the host and the target regions using the stochastic method to compute the host-to-target conversion factors. Finally functions were fitted to the derived ground-motion estimates to obtain sets of seven individual equations for use in probabilistic seismic hazard assessment for southern Spain and southern Norway. The relations are compared with local ones published for the two regions. The composite methodology calls for the setting up of independent logic trees for the median values and for the sigma values, in order to properly separate epistemic and aleatory uncertainties after the corrections and the conversions.

The paper presents a computer-automated performance-based design procedure for optimally proportioning a steel building framework to resist earthquakes. Modal pushover analysis is employed to evaluate structural demands imposed by design earthquakes representing a range of hazard levels (e.g. immediate-occupancy, life-safety and collapse-prevention). First-order Taylor series and sensitivity analysis are employed to formulate corresponding performance constraints explicitly in terms of member sizing variables and target lateral displacements. A generalised optimality criteria algorithm is employed to find the least-weight structure that experiences minimal damage (as characterised by ductility demand) while simultaneously satisfying all performance constraints at all hazard levels. The design methodology is illustrated for a nine-storey planar steel building framework.

The objective of this paper is to introduce a Rational Polynomial Approximation (RPA) method for modelling the response of structures that contain discrete elements with linear frequency-dependent stiffness and damping characteristics. The RPA method consists of two steps: First, system identification is performed to obtain a rational polynomial approximation for the system's transfer functions. Then, a time-domain model for the system is realised. The main advantage of the RPA method is that the resulting model is a system of ordinary differential equations, facilitating time history analysis of both linear and nonlinear structures using standard time-step integration algorithms and procedures.

Viscoelastic (VE) dampers comprise one of the primary classes of frequency-dependent dampers with both frequency-dependent stiffness and damping. VE dampers are used for mitigation of seismic- and wind-induced structural vibration. When using VE dampers in analysis, effective modelling of the frequency-dependent characteristics of the VE damper plays a key role in accurate simulation of structural responses.

Following a description of the theory behind the RPA method, the efficacy of the method is verified through several numerical examples employing VE damped structures. The results are compared with Kasai's fractional derivative model for VE dampers. Application of the RPA method to nonlinear structures is also given. The RPA method is shown to be effective and efficient for modelling VE damped structure.

In this paper, the methodology for evaluation of conventional and adaptive pushover analysis presented in a companion paper is applied to a set of eight different reinforced concrete buildings, covering various levels of irregularity in plan and elevation, structural ductility and directional effects. An extensive series of pushover analysis results, monitored on various levels is presented and compared to inelastic dynamic analysis under various strong motion records, using a new quantitative measure. It is concluded that advanced (adaptive) pushover analysis often gives results superior to those from conventional pushover. However, the consistency of the improvement is unreliable. It is also emphasised that global response parameter comparisons often give an incomplete and sometimes even misleading impression of the performance.

Cable-stayed bridges exhibit unique responses under a strong motion. It is partly due to the complexity in their damping mechanism. Recently, the benchmark problem of a cable-stayed bridge was developed to clarify the effectiveness of various seismic control strategies. Due to the new development of magnetorheological dampers, the application of variable dampers in bridges becomes possible. In this study, the effectiveness of the nonlinear viscous damping force scheme and the two-step friction damping force scheme are investigated. It is found that the nonlinear viscous damping force scheme is effective to control the response of the cable-stayed bridge with less demand for the damping force capacity of a damper. In addition, the two-step friction damping force scheme shows the improvement over conventional friction damping because the energy dissipation of a damper can be increased.