EVALUATION OF CAPACITY SPECTRUM METHOD FOR ESTIMATING THE PEAK INELASTIC RESPONSES

The accuracy of the capacity spectrum method (CSM) depends on the precise estimation of equivalent period and damping ratio as well as the modification of the demand spectrum. In this paper, the CSM provided in ATC-40 for estimating the peak inelastic responses is evaluated. First, the effect of equivalent period and damping ratio estimation on the accuracy of the CSM is assessed. Analyses results indicate that the difference between estimation methods is large when the structural nonlinearity is large, but becomes negligible as the hardening ratio increases. Next, the reduction factors provided in ATC-40 and Eurocode are evaluated. It is found that the acceleration responses obtained using the factor of Eurocode is closer to the actual ones than those obtained using the factors of ATC-40. Finally, the demand spectrum is constructed using the peak absolute acceleration and pseudo-acceleration. The results obtained using the peak absolute acceleration is found to be generally larger than those obtained using the pseudo-ones. Since the original CSM generally underestimates the response, the use of peak absolute acceleration in the construction of demand spectrum produces the response relatively closer to the exact one. However, the use of peak absolute acceleration overestimates the response more when the original CSM overestimates the response.     

IDENTIFICATION AND VERIFICATION OF SEISMIC DEMAND FROM DIFFERENT HYSTERETIC MODELS

The goal of this paper is to develop a modified Bouc-Wen hysteretic model from cyclic loading test data for reinforced columns, including the behavior of stiffness degradation, strength deterioration, pinching and softening effects of RC members. Seismic demands on this inelastic single degree of freedom system when subjected to both near-fault ground motion and far-field ground motion excitations were examined.

The cyclic loading test of reinforced concrete columns was experimentally observed and a system identification computer program was developed to solve each control parameter of the hysteretic model. A least-squared method for identifying parameters of the model is proposed in this paper. The hysteretic constitutive law produces a smoothly varying hysteresis such as the control-parameters for strength deterioration, stiffness degradation, pinching and softening effects. Two implementations of (1) flexure damage and (2) shear damage were conducted to provide better understanding of hysteretic behavior of RC structural members. A pseudo-dynamic experiment was also developed to verify the model parameters.

Based on the developed hysteretic model, the seismic demand of this inelastic model was investigated by using both near-fault ground motion data and far-field ground motion data as input motion. An R-μT inelastic response spectrum from different hysteretic models was generated.     

Parliament and the Committee for Accommodation, 1644–6*

With the emerging conflict between the presbyterian and independent ministers in 1643–4, the independent MPs recognized a need for parliamentary action to secure religious liberty in post‐war establishment of a uniform state church. The lead in this was given by such prominent figures as Oliver St John and Oliver Cromwell, who set up a committee for accommodation in autumn 1644 to establish legal safeguards for godly separatists. This article seeks to demonstrate that the lay members from the Houses participated in the proceedings of the committee with as much fervour and awareness of the issue under consideration as the clerical members, employing procedure as a tool of policy making. Their often extended debates offer the historian a rare opportunity to explore in detail a committee at work during this period. The debates show that the scope of religious liberty as envisioned by the majority of MPs was decidedly limited. Furthermore, the article asserts that the committee became an arena for both genuine efforts at compromise and expressions of factional interest and that its proceedings were inextricably bound up with the wider Westminster politics and the vicissitudes of war. Thus, the committee proceedings shed light on the emergence of divisions in parliament and how these metamorphosed over the course of the revolutionary decade. Ultimately, the failure of the committee's enterprise contributed to polarisation within the godly community and to its disintegration.