Seismic Testing of Critical Lifelines Rehabilitated with Cured in Place Pipeline Lining Technology

Trenchless technology is well accepted for repairing critical underground lifelines with minimal ground surface disruption. The cured in place pipeline (CIPP) lining process is an application of trenchless technology that involves the installation of fiber reinforced composites inside existing pipelines. The uncertain performance of pipelines reinforced with CIPP linings in seismic areas is a barrier to the adoption of this method for seismic retrofit. This article evaluates experimentally the transient seismic response of pressurized pipelines reinforced with fiber reinforced polymer (FRP) linings. The test results show that reinforced pipelines can accommodate very high intensity ground motions and can provide substantial seismic strengthening in addition to efficient rehabilitation of aging underground infrastructure.     

Characterization of Ductility and Inelastic Displacement Demand in Base-Isolated Structures Considering Cyclic Degradation

New designed or retrofitted structures with the use of isolation system may exhibit nonlinear deformations during strong ground motions. Inelastic displacement ratio of base-isolated structures is studied in this paper by employing two degree of freedom model taking into account inelastic behavior of isolators and superstructure. Parametric study is conducted to evaluate influence of isolator and superstructure properties on inelastic displacement ratio according to two sets of near-fault and far-fault ground motions. Accuracy of proposed equations in the literature to evaluate inelastic displacement ratio are studied, as well. Furthermore, cyclic degradation effects are investigated by considering stiffness and strength degradation and pinching in hysteresis model of superstructure. Eventually, inelastic responses of isolated structures with two types of isolators (lead rubber bearing and friction pendulum bearing) are compared.     

A Microtremor Survey in the Area Shocked by the ML 5.2 Salò Earthquake (North Italy): An Empirical Approach to Determine the Effects of Ground Motions

In this work, the results of a quick microtremor survey performed in the municipalities situated in the epicentre area of the Ml 5.2 2004 Salò earthquake (North Italy) are presented. The aim of this study is to understand if the large amount of damage caused by the event (about 215 million euros only in the areas near to the epicenter) is correlated more to the local surface geology conditions or to the vulnerability of ancient Italian historical centers.

A preliminary seismic zonation was carried out in 5 villages including about 30 measurements of microtremors analyzed by the Nakamura technique (hereinafter HVNR). The points of measurement were carefully selected considering sites located both near damaged buildings and over different local geology conditions (alluvium deposits, fluvial-glacial deposits, debris fans and rock). In order to strengthen the HVNR results and to evaluate the reliability of the Nakamura analysis, a comparison with spectral ratios calculated on earthquakes (hereinafter HVSR) recorded at the strong motion station of Vobarno was made. In general, the outcomes of the survey highlight a possible correlation between local geology conditions and ground motion amplification for different frequency bands. In order to check if this evidence is linked with the damage, a series of macroseismic intensity values were collected for different zones of the investigated area, and a nonparametric correlation approach was used to establish a possible correlation between damage and ground motion amplification for selected frequency bands. The results show, from a statistical point of view, that in the area surrounding the epicenter of the November 24, 2004 mainshock, the damage pattern is not strongly dependent upon the local surface geology but more correlated to the low quality of the civil structures present in the area, including old buildings of the last century.     

Preparation of Engineering Geological Maps of Bam City Using Geophysical and Geotechnical Approach

Engineering geological mapping was carried out at a scale of 1:25000 in the city of Bam, located in southeastern Iran, to provide engineering geological information as a base for seismic microzonation of the city. In this study, Seismic Refraction and Vertical Seismic Profiling (VSP) surveys were employed along with boreholes in order to identify the characteristics of subsurface material in Bam city. A number of different kinds of maps of the city were prepared consisting of Iso-depth, Iso-velocity, and Iso-Poisson's Ratio maps. The study also involves trial pitting and continuous core recovery, in-situ, and laboratory tests. Borehole data, index properties of soils, and standard penetration test results were used to assess subsurface conditions. Geophysical and geotechnical data were combined to simulate geotechnical boreholes and prepare engineering geological maps to provide basic data for seismic geotechnical microzonation to facilitate in the reconstruction of the city of Bam.     

Response Sensitivity of Highway Bridges to Randomly Oriented Multi-Component Earthquake Excitation

In two-dimensional and single axis three-dimensional finite element analyses, the ground motion incidence angle can play a significant role in structural response. The effect of incidence angle for three-dimensional excitation and response is investigated in this paper for response of highway bridges. Single-degree-of-freedom elastic and inelastic mean spectra were computed from various orientation techniques and found indistinguishable for combinations of orthogonal horizontal components. Probabilistic seismic demand models were generated for the nonlinear response of five different bridge models. The negligible effect of incidence angle on mean ensemble response was confirmed with a stochastic representation of the ground motions.     

Development of Damage Patterns and Fragility Curves in Brick-nogging Buildings from the Thabeikkyin Earthquake,Myanmar, 2012

The Thabeikkyin earthquake (moment magnitude scale of 6.8) occurred on November 11, 2012; its epicenter was located 25 km from Thabeikkyin Township, Mandalay Region, Myanmar. Many buildings were damaged severely during the earthquake. In this study, damage patterns of brick-nogging buildings were firstly developed, and damage grades were characterized to allow for easy classification of the damaged buildings. The damaged data of all building types in the surveyed areas were collected by classifying the four damage levels as no damage, slight damage, moderate damage, and heavy damage. To develop the damage patterns of brick-nogging buildings, damage categories were arranged into three damage grades (slight, moderate, and heavy damage). Secondly, a questionnaire survey was conducted to calculate the seismic intensities of the affected areas. Medvedev–Sponheuer–Karnik (MSK) seismic intensities for the surveyed areas were estimated by analyzing the questionnaire survey responses. Finally, fragility curves for brick-nogging buildings were constructed using the estimated seismic intensities from the survey responses combined with the damage levels. These fragility curves may be useful to assess damage to brick-nogging buildings and to predict the number of damaged buildings in future earthquakes.     

Long-Period Ground Motion Simulation and its Impact on Seismic Response of High-Rise Buildings

This paper first critically reviews a seismological model and then a three-segment curve model (in log-log space) to model the Q-f relationship is proposed to overcome the potential biased estimation in the long-period range by the “coda wave” method. The optimal curve-fitting process is performed to determine the Q-f relationship for the Hong Kong region. The calibrated seismological factors are incorporated with the stochastic simulation procedure to generate synthetic ground motions, which are validated through comparison with seismic records. The impact of long-period ground motions on the seismic response of high-rise buildings is finally manifested through a numerical study.     

Seismic Reliability of Code-Conforming Italian Buildings

ABSTRACT

This paper presents and discusses some research results related to the seismic failure risk of standard, residential and industrial, buildings designed for damage, and life-safety according to the Italian seismic code, which is somewhat similar to Eurocode 8. The five considered structural typologies are as follows: masonry, cast-in-place reinforced concrete, precast reinforced concrete, steel, and base-isolated buildings. The archetype structures have been designed according to standard practice at three sites, representative of the seismic hazard across the country. Seismic risk is defined here as the annual rate of earthquakes able to cause structural failure in terms of usability-preventing damage and global collapse. For each structure, the failure rates have been evaluated in the framework of performance-based earthquake engineering, that is, via integration of site’s probabilistic hazard and structural fragility. The former has been computed consistently with the official hazard model for Italy that is also used to define design actions in the code. The latter has been addressed via nonlinear dynamic analysis of three-dimensional numerical structural models. Results indicate that, generally, design procedures are such that seismic structural reliability tends to decrease with increasing seismic hazard of the building site, despite the homogeneous return period of exceedance of the design seismic ground-motion.     

Safety vs. Economy in Performance-Based Design of Buildings: Inevitable Compromise or False Dilemma?

The objective of the present paper is to investigate the influence of the design objective on the total cost of buildings. A series of reinforced concrete buildings are designed for various design objectives, and the construction cost is calculated. Additionally, the earthquake losses for three different earthquake scenarios are estimated. The total cost of the buildings is calculated as the sum of the construction cost plus the earthquake losses. The whole investigation demonstrates that designing for elastic response against the design earthquake is both the safest and the most economical in long-term option in the case of strong seismic excitations.     

Fragility Curves for RC Frames Subjected to Tohoku Mainshock-Aftershocks Sequences

The damaging effects of aftershocks are overlooked by current building codes and not properly accounted for in commercial seismic loss assessment software. In this paper, an evaluation of the seismic fragility relationships for reinforced concrete (RC) frame systems prone to mainshock-aftershocks sequences is conducted. Fiber-based finite element models for different types of RC frames are established and subjected to a suite of ground motions obtained from the Tohoku sequence. Fragility relationships are derived with and without consideration to multiple earthquake effects. The results from this study confirm that multiple earthquakes have significant effects on the vulnerability relationships of RC frames.