Seismic Vulnerability Assessment of Modular Steel Buildings

Contemporary seismic design is based on dissipating earthquake energy through significant inelastic deformations. This study aims at developing an understanding of the inelastic behavior of braced frames of modular steel buildings (MSBs) and assessing their seismic demands and capacities. Incremental dynamic analysis is performed on typical MSB frames. The analysis accounts for their unique detailing requirements. Maximum inter-story drift and peak global roof drift were adopted as critical response parameters. The study revealed significant global seismic capacity and a satisfactory performance at design intensity levels. High concentration of inelasticity due to limited redistribution of internal forces was observed.     

Study of Effects of Sediment-Damping,Impedance Contrast,and Size of Semi-Spherical Basin on the Focusing and Trapping of the Basin-Generated Surface Waves

This article presents the effects of sediment-damping, impedance-contrast (IC), and size of semi-spherical (SS) basin on the focusing and trapping of the basin-generated surface (BGS) waves and the spatial-variation of average-spectral-amplification (ASA), differential ground motion (DGM), and average-aggravation-factor (AAF). A frequency-dependent focusing of the BGS-wave is inferred. Increase of ASA, DGM, and AAF with increase of size of the SS-basin with a fixed-shape-ratio revealed that the BGS-wave focusing has counter-balanced the sediment-damping effects. It is concluded that the BGS-wave focusing and trapping in the SS-basin is more sensitive to change of IC as compared to the similar change of sediment-damping.     

Robust Period-Independent Ground Motion Selection and Scaling for Effective Seismic Design and Assessment

A period-independent approach for the selection and scaling of ground motion records aimed at reducing demand variability is proposed for seismic response history analysis. The same set of scaled records can be used to study various structures at the same site regardless of their dynamic characteristics. The statistical robustness of the proposed and current approaches is compared through nonlinear inelastic dynamic analyses performed on single-degree-of-freedom systems and multi-story braced frames. The proposed approach leads to consistent response predictions with a limited number of records. This is advantageous for day-to-day structural design or assessment against code hazard-based seismic demand levels.     

Experimental Investigation of Circular Reinforced Concrete Columns under Different Loading Histories

Three reinforced concrete (RC) circular column specimens without an effective concrete cover were tested under constant axial compressive as well as cyclic lateral loading. The seismic behavior of the specimens under different loading paths was examined with the objective of understanding the influence of displacement history sequence on the seismic behavior of the columns in near-fault earthquakes. The influence of displacement history sequence upon the hysteretic characteristics, stiffness degradation, lateral capacity, as well as energy dissipation analysis was conducted. The hoop strains of lateral reinforcement at varied column heights under cyclic loading were attained by means of 8–16 strain gauges attached along the hoops. Additionally, the characteristics of strain distribution were investigated in the transverse reinforcement. The results of strain distribution were evaluated with Mander’s confinement stress model and the distribution around the cross section. The length of the plastic hinge at the end of the specimen was evaluated by measurement as well as the inverse analysis. Finally, the deformation of the specimen, which includes the components of shear deformation, bending deformation and bonding-slip deformation, was evaluated and successfully separated.     

Modification of Ductility Reduction Factor for Strength Eccentric Structures Subjected to Pulse-Like Ground Motions

This article investigates the ductility reduction factors for RC eccentric frame structures subjected to pulse-like ground motions. The structural models are with the strength eccentricities which are much disadvantageous than the stiffness eccentricities during the inelastic response range. A method to determine the ductility reduction factors of the strength eccentric structures is suggested by modifying those of reference symmetric structures through an eccentricity modification factor. The four factors of strength eccentricity ratio, ductility ratio, story number and velocity pulse of ground motions, are investigated to gain insight into this modification factor. It shows that the ductility reduction factors of the eccentric structures are clearly smaller than those of the symmetric structures. The eccentricity modification factor is mainly affected by the strength eccentricity and the ductility ratio, decreasing with the increment of the eccentricity or the decrement of the ductility ratio in a medium eccentricity range. The earthquake pulse-like effect and the eccentricity have coupling influence on the modification factor, while the effect of story number is not apparent. Based on the results of a comprehensive statistical study a simplified expression is suggested, which can estimate the eccentricity modification factors for both pulse-like and nonpulse-like ground motion cases.     

Impact of Vertical Ground Excitation on a Bridge with Footing Uplift

Ground motions recorded in the epicentral region of an earthquake often have a strong vertical component with dominant high frequencies. Damage to bridges in near-source regions due to strong vertical ground motion has been reported. The beneficial effects of footing uplift on structural performance in form of reduction of seismic response of structural members have been confirmed in previous research. The uplift of bridge piers has been utilised in a very limited number of bridge structures, e.g., the South Rangitikei railway bridge in New Zealand. However, the near-fault seismic behaviour of bridges with footing uplift has been even less addressed. In this study shake table investigations were carried out on the response of a single-span bridge model with footing uplift subjected to simultaneous vertical and horizontal excitations. Near-fault ground motions recorded in the Canterbury earthquake sequences of 2010 and 2011 were used. The experimental results show that inclusion of vertical ground motions produce stronger axial force in the pier and larger bending moment in the deck. Concurrent horizontal and vertical excitations may also cause more frequent footing uplift than the solely horizontal excitations.     

MOUND BUILDING AT LAKE JACKSON (8LE1), TALLAHASSEE,FLORIDA: NEW INSIGHTS FROM GROUND PENETRATING RADAR

Abstract

The Lake Jackson Mounds site (8LE1), located near Tallahassee, Florida, has long been considered to be a frontier Mississippian center. This assertion is primarily based on elaborate burial goods recovered during salvage excavations in the 1970s. Ground penetrating radar (GPR) on the two largest intact mounds at Lake Jackson revealed new information about their morphology and construction histories. These findings demonstrate that mound-building practices at the site were distinct from earlier, local Woodland mound-building traditions, and more similar to those of other Mississippian centers, such as Etowah and Moundville. Lake Jackson revitalized mound building in the Tallahassee area under the influence of external connections with groups in the Mississippian interaction network. These findings show how mound building was an integral practice for expressing and expanding Mississippian ideologies and rituals. This work also shows the utility of GPR in exploring mounds' morphologies and construction histories.     

Pitted stone cobbles in the Mesolithic site of Font del Ros (Southeastern Pre-Pyrenees,Spain): some experimental remarks around a controversial tool type

The presence of cobbles with activity-related marks in the Mesolithic site of Font del Ros (Berga, Spain), and in particular one group of artefacts – pitted stones – raises problematic issues associated with the characterization of percussion activities. Although these artefacts have generated an extensive bibliography on ethological, ethnographic, ethnoarchaeological and archaeological levels, various questions persist in relation to their possible contextual function. In this paper we present the results of an experimental programme in which three types of activities that could create pitted stones are reproduced: bipolar knapping of vein quartz, hazelnut cracking, and hazelnut grinding. The aim of this experimental programme is to describe marks and use-wear traces related to such activities.     

Improving the interpretability of 3D GPR data using target–specific attributes: application to tomb detection

Three–dimensional (3D) ground–penetrating radar (GPR) represents an efficient high–resolution geophysical surveying method allowing to explore archaeological sites in a non–destructive manner. To effectively analyze large 3D GPR data sets, their combination with modern visualization techniques (e.g., 3D isoamplitude displays) has been acknowledged to facilitate interpretation beyond classical time–slice analysis. In this study, we focus on the application of data attributes (namely energy, coherency, and similarity), originally developed for petroleum reservoir related problems addressed by reflection seismology, to emphasize temporal and spatial variations within GPR data cubes. Based on two case studies, we illustrate the potential of such attribute based analyses towards a more comprehensive 3D GPR data interpretation.     

An approach to mapping buried prehistoric palaeosols of the Atlantic seaboard in Northwest Europe using GPR, geoarchaeology and GIS and the implications for heritage management

Widespread layers of well-preserved organically and archaeologically rich palaeosols dating to the Bronze Age and Iron Age are known from across the Atlantic seaboard of Scotland, including the Western Isles, Orkney and Shetland. The survival of these soils has been facilitated by an overburden of Aeolian sand forming dunes above them. Whilst these soils display archaeological importance, they are constantly under threat from erosion through storm damage due to their exposed coastal position. This presents certain challenges with regard to heritage management, since their extents are largely unknown, normally only being identified when exposed by wind and storm erosion. Consequently, following such damage mitigation can only be reactionary in response to archaeological deposits being uncovered, and left open to threat, Without accurately mapping the extent of these important deposits, archaeological landscape management is compromised.This paper presents a case study aimed at enabling proactive management of these deposits through rapid three-dimensional mapping undertaken using a combination of borehole-calibrated GPR survey and GIS modelling. The results demonstrate how effective baseline data can be generated to highlight areas of greater or lesser risk thereby providing the potential for quantifying and predicting the effects of damage from future storm events.