Seismic Hazard Analysis for Kuala Lumpur,Malaysia

In the past, probabilistic seismic hazard analysis (PSHA) has been performed by researchers to assess the level of seismic hazard in Kuala Lumpur, Malaysia and its vicinity. However, the peak ground acceleration (PGA) values obtained are high due to unsuitable ground motion prediction equation (GMPE). This article is divided into two parts: development of a suitable GMPE and the PSHA for this region. Two main sources have been identified as the contributors to earthquake hazard in Peninsular Malaysia, namely the Sumatra strike-slip fault and Sumatra subduction zone. For the subduction zone, nine recorded large earthquake events are analyzed and regression analysis is performed to obtain a new GMPE for this region. In performing PSHA, the strike-slip fault is divided into 14 zones based on the individual fault segments, while the subduction is divided into 4 zones. Historical earthquakes of this region are collected, processed, and segregated according to the zones. PSHA has been conducted by modeling the source seismicity using Gutenberg-Richter and characteristic earthquake models. The developed GMPE has been used along with other attenuation models: Megawati and Pan [2010] Megawati, K. and Pan, T. C. 2010. Ground-motion attenuation relationship for the Sumatran megathrust earthquakes. Earthquake Engineering and Structural Dynamics, 39: 827–845. [Web of Science ®] , [Google Scholar] and component attenuation model (CAM) by Balendra et al. [2002] Balendra, T., Lam, N. T. K., Wilson, J. L. and Kong, K. H. 2002. Analysis of long-distance earthquake tremors and base shear demand for buildings in Singapore. Engineering Structures, 24: 99–108. [Crossref], [Web of Science ®] , [Google Scholar] for subduction; and Sadigh et al. [1997] Sadigh, K., Chang, C. Y., Egan, J. A., Makdisi, J. and Youngs, R. R. 1997. Attenuation relationships for shallow crustal earthquakes based on California strong motion data. Seismological Research Letters, 68: 180–189. [Crossref] , [Google Scholar] and CAM for strike-slip fault. The peak ground accelerations in Kuala Lumpur for 10% and 2% probability of exceedances in 50 years are found to be 16.5 gal and 23.4 gal, respectively. From deaggregation analysis, the main contributor for the 10% probability of exceedance in 50 years is found to be a 7.5 M_w earthquake at 300 km, originating from the strike slip fault. Finally, the design response spectrum for Kuala Lumpur is developed for rock sites, which would be amplified further by local soil profile.     

Completeness Verification of Complex Response Spectrum Method for Underdamped and Overdamped Multiple-Support Systems Regarding the Decoupled Damping as Mathematical Parameter without Physical Meaning

The completeness of the complex response spectrum method for both formally underdamped and overdamped modes is theoretically proved, and the physical meanings of the decoupled modes as well as involved parameters are recognized and clarified in this paper. For the system with relatively large non-classical damping, the eigenvalue pairs generated by the complex mode decomposition method are real and the so-called modal damping ratios are larger than unity. In this paper, we firstly clarified that the decoupled modes are virtual and the so-called modal frequency and damping ratio are mathematical parameters that have no physical meaning. Then, the completeness of the complex response spectrum method for both formally underdamped and overdamped modes is rigorously proved by allowing the “damping frequency” to be an imaginary number. For the virtually overdamped modes, Duhamel integral involved in the calculation for formally underdamped modes automatically convert to hyperbolic Duhamel integral. A numerical example taken from the published literature is given to verify this method. Structural responses for the system with coupled damping under multi-support seismic excitations are further analyzed and numerical results indicate the accuracy of complex response spectrum method.     

Seismic Response of Bridges Subjected to Different Earthquake Types Using IDA

Incremental Dynamic Analysis (IDA) was used to evaluate the seismic response of straight, continuous 4-span bridges with different sub-structure configurations. Three different record sets were chosen to represent three different earthquake types which can occur for a site such as Vancouver (i.e., crustal, subduction interface, and subduction inslab earthquakes). Seventy eight records were considered in each set (i.e., a total of 234 records) and the capacities of the bridges were evaluated using a fast IDA algorithm. A simplified method to account for the effects of spectral shapes was used. Different subsets of the records with specific characteristics were also used in the IDA. The bridges were designed and evaluated for two different design force modification factors and bridges with different degrees of irregularity were studied. Comparisons of the IDA results obtained indicated that in most of the cases the interface record sets resulted in lower median collapse capacities and hence were the most critical of the ground motions studied.     

Direct Displacement-Based Seismic Design of Eccentrically Braced Steel Frames

A series of eccentrically braced frames (EBF) are designed and subjected to nonlinear analyses to highlight ambiguities and differences in current seismic design provisions for EBF structures. This provides motivation to implement better guidance for the checking of local displacement demand considerations and move towards a displacement-based design approach. A recently proposed direct displacement-based design (DDBD) procedure for EBFs is then described and further developed in this article through the calibration of a spectral displacement reduction factors that relate the displacement of an inelastically responding structure to that of the equivalent linear representation used in the DDBD of EBFs. Such an expression is calibrated as part of this study using an experimentally validated numerical model also proposed here for the EBF links such that the actual hysteretic behavior of the links is well represented. The DDBD guidelines are applied to EBF systems from 1–15 stories in height and their performance is verified via nonlinear dynamic analyses using two different sets of design spectrum compatible ground motions. The results of the study indicate the robustness of the proposed DDBD method in limiting the interstory drifts to design limits for a variety of EBF systems with short links, thus demonstrating that the proposed DDBD method is an effective tool for seismic design of EBFs.     

Fore-Arc and Back-Arc Ground Motion Prediction Model for Vrancea Intermediate Depth Seismic Source

A next generation ground motion model for the prediction of spectral accelerations both in the fore-arc and back-arc regions of the Carpathians Mountains is developed in this research for the Vrancea intermediate depth seismic source in Romania. This ground motion prediction equation (GMPE) is an updated version of the model given in Vacareanu et al. [2014] and is applicable in both the fore-arc and the back-arc regions. The strong ground motion database from which the prediction model is derived consists of over 700 triaxial accelerograms from Vrancea subcrustal seismic events, as well as from other intermediate-depth earthquakes produced in other seismically active regions in the world. The applicability of this ground motion prediction model in both the fore-arc and the back-arc region is tested using the analysis of residuals. Moreover, the appropriateness of this GMPE for soil classes B and C defined in EN 1998-1, as well as for average soil conditions is investigated. All results suggest that this model is an improvement of the previous versions of ground motion prediction equations for Vrancea intermediate-depth seismic source and its use in both the fore-arc and the back-arc regions make it a reliable candidate for more accurate seismic hazard studies of Romania.     

Time-Domain Spectral Matching of Earthquake Ground Motions using Broyden Updating

Time-domain spectral matching of an earthquake ground motion consists of iteratively adding sets of wavelets to an acceleration history until the resulting response spectrum sufficiently matches a target spectrum. The spectral matching procedure is at its core a nonlinear problem because the addition of a wavelet often causes shifting in the time of peak response or creation of a larger second peak at a different time. A modification to existing time-domain spectral matching algorithms is proposed using Broyden updating for solving the set of nonlinear equations. Three wavelet bases are evaluated and the corrected tapered cosine wavelet is selected. The proposed algorithm is then tested and compared with other methods that are commonly used for spectral matching. The results show that the proposed algorithm is able to match the target spectrum while reasonably preserving the spectral nonstationarity, energy development, and the frequency content of the original time histories.     

Numerical Evaluation of Seismic Soil Pressures on Rigid Walls Fixed to the Bedrock

Seismic soil pressures developed on a 7 m rigid retaining wall fixed to the bedrock are investigated using a finite element model that engages nonlinear soil intended materials available in OpenSees. This allows incorporation of the inelastic behavior of the soil and wave propagation effects in the soil-wall system seismic response. The nonlinear response of the soil was validated using the well-stablished, frequency-domain, linear-equivalent approach. An incremental dynamic analysis was implemented to comprehensively examine the effect of soil nonlinearity and input motion on the induced seismic pressures and to evaluate current code equations/methodologies at different levels of earthquake intensity. The results show that soil nonlinearity and seismic wave amplification may play an important role in the response of the soil-wall system. Therefore, methodologies that rely only on peak ground acceleration may introduce large bias on the estimated seismic pressures in scenarios where high nonlinearity and site amplification are expected.     

Influence of Diaphragm Flexibility on Seismic Response of Unreinforced Masonry Buildings

The effects of diaphragm flexibility on the seismic response of low-rise unreinforced masonry buildings are examined using one-way stiffness- and strength-eccentric single-story systems subjected to unidirectional ground excitation. A wide range of diaphragm stiffnesses are considered. Results show that diaphragm flexibility can induce different effects depending on the configuration of the system and the level of diaphragm flexibility. When diaphragm is relatively stiff, amplified displacement demands can be imposed on the flexible side of the structure. When diaphragm is relatively flexible, peak displacements of in-plane loaded walls generally reduce. A diaphragm classification is developed to capture these salient effects.     

A Microscale Approach for the Seismic Response of MDOF Structures Including Soil-Foundation-Structure Interaction

In this article, a three-dimensional microscale computational framework utilizing the discrete element method is presented to analyze the seismic response of soil-foundation- MDOF structure systems. The proposed approach is used to explore the response of MDOF structures on a square embedded footing founded on a dry granular deposit. Computational simulations were conducted to investigate the response of the system to several base excitations. The impact of replacing a MDOF structure with its equivalent single degree of freedom (ESDOF) structure while accounting for soil-foundation-structure interaction (SFSI) is investigated. Detrimental or beneficial effect of SFSI on the response is also examined.     

Influence of Ground Motion Duration on Damping Reduction Factor

This article investigates the influences of the effective ground motion duration (GMD) on damping reduction factor. The GMD are associated with 25 Chi-chi earthquake ground motion records and harmonic sine wave. The study shows that damping reduction factor decreases with the increasing of the damping ratio, and decreases with the increasing of the effective duration of the ground motion and the number of cycles of harmonic excitation. A nonlinear multiple regression analysis based on the statistical mean values of the present study is employed, and a modified damping reduction factor considering the effects of GMD is suggested.