Rocking Soil-Structure Systems Subjected to Near-Fault Pulses

Seismic performance of rocking soil-structure systems subjected to near-fault pulses is investigated considering foundation uplifting and soil plasticity. An extensive parametric study is conducted including medium-to-high-rise buildings with different aspect ratios based on shallow raft foundation at stiff-to-rock sites. Mathematical directivity and fling pulses are used as input ground motion. The superstructure is assumed to have three different boundary conditions: (a) fixed-base, (b) linear soil-structure interaction (SSI), and (c) nonlinear SSI. Evidently, the prevailing pulse period T_p is a key parameter governing nonlinear SSI effects. The normalized acceleration response spectra reveal that despite beneficial effects of foundation uplifting and soil yielding in most cases, there are some minor regions in which the response accelerations are amplified. In addition, more slender buildings significantly benefit from uplifting and soil yielding when subjected to short- and medium-period directivity pulses compared to squat structures. However, response amplifications with respect to fixed-base structures are considerable in case of slender structures subjected to medium- or long-period directivity pulses. So that neglecting the SSI effects on seismic performance of rocking structures with shallow foundations, as mostly assumed in common practice, may give rise to inaccurate estimations of force demands against near-fault pulselike ground motions. Furthermore, the envelope of residual foundation tilting θ_r is limited to 0.015 rad, in case of directivity pulses.     

Effect of Nonlinearity of Frame Buildings on Peak Horizontal Floor Acceleration

Using representative numerical models of eight code-designed steel moment-resisting frame buildings and several ground motions, time-history analyses are performed and a critical evaluation of Peak Horizontal Floor Acceleration (PHFA) demands is conducted. The frames are modeled alternatively as linear and nonlinear systems to isolate the effect of building nonlinearity on PHFA. In most cases, PHFA is reduced when nonlinear behavior of a building is considered; however, in some cases, significant amplification of PHFA is observed. Results from the numerical study provide insight into the trend of modal response modification factors presented taking ground motion spectral shape into account.     

Review of Different Pushover Analysis Methods Applied to Masonry Buildings and Comparison with Nonlinear Dynamic Analysis

This article presents the comparison among different nonlinear seismic analysis methods applied to masonry buildings, i.e., pushover analyses with invariant lateral force distributions, adaptive pushover analysis and nonlinear dynamic analysis. The study focuses on the influence of lateral force distribution on the results of the pushover analysis. Two simple benchmark case studies are considered for the purpose of the research, i.e., a four-wall masonry building prototype without floor rigid diaphragms and a two-wall system with a cross-vault. The comparative study offers a useful review of pushover analysis methods for masonry structures and shows advantages and possible limitations of each approach.     

Unusual Overshooting in Steady-state Response for Structure-dependent Integration Methods

It is numerically illustrated that an unusual overshooting phenomenon might occur in the solution of a forced vibration response if a structure-dependent integration method is applied to conduct the analysis, such as Chang explicit method [2002] and CR explicit method [2008]. This overshooting may occur in the steady-state response of a high frequency mode and it becomes significant as the natural frequency of the mode increases. This unusual overshooting behavior can be successfully detected by using a local truncation error derived from a forced vibration response rather than a free vibration response. A missing loading term in the difference equation for displacement increment is responsible for this unusual overshoot. It is analytically and numerically verified that the unusual overshooting behavior will automatically disappear after introducing the missing loading term into the difference equation for displacement increment.     

Analytical Seismic Assessment of a Tall Long-Span Curved Reinforced-Concrete Bridge. Part I: Numerical Modeling and Input Excitation

The seismic response of bridges is affected by a number of modeling considerations, such as pier embedment, buried pile caps, seat-type abutments, pounding, bond slip and architecturally flared part of piers, and loading considerations, such as non-uniform ground excitations and orientation of ground motion components, which are not readily addressed by design codes. This article addresses a methodology for the nonlinear static and dynamic analysis of a tall, long-span, curved, reinforced-concrete bridge, the Mogollon Rim Viaduct. Various modeling scenarios are considered for the bridge components, soil-structure interaction system, and materials, i.e., concrete and reinforcing steel, covering all its geotechnical and structural aspects based on recent advances in bridge engineering. Various analysis methodologies (nonlinear static pushover, time history response to uniform and spatially variable seismic excitations, and incremental dynamic analyses) are performed. For the dynamic analyses, a suite of nine earthquake accelerograms are selected and their characteristics are investigated using seismic intensity parameters. A recently developed approach for the generation of non-uniform seismic excitations, i.e., spatially variable simulations conditioned on the recorded time series, is used. Methods for the evaluation of structural performance are discussed and their limitations addressed. The numerical results of the seismic assessment of the Mogollon Rim Viaduct are presented in the companion article (Part II). The sensitivity of the bridge response to the adopted modeling, loading and analyzing strategies, as well as the correlation between structural damage and seismic intensity parameters are examined in detail.     

田螺山遗址古菱角埋藏环境调查与保护对策的初步研究

本文运用多种化学分析方法分析了浙江省田螺山遗址的地层土壤和地下水环境,得出了不同地层中主要元素的分布规律：再对古菱角外壳遗存和现代菱角外壳进行扫描电镜和元素分析,总结古菱角经长期埋藏后,外壳结构和化学元素的变化规律：最后初步探索古菱角类植物遗存的科技保护时策。     

浙江越窑青瓷标本信息数据库管理系统的设计与实施

对文物标本进行系统分析归纳是传统工艺研究的必要途径,为实现越窑青瓷标本资料的资源共享,提高实验室工作效率,实现分析数据的科学管理,本研究开发设计了“浙江越窑青瓷标本信息数据库管理系统”.该系统基于B/S结构模式,以浙江省博物馆陶瓷标本中心的各类越窑瓷片标本来源、形态、化学成分、物理性能、显微结构、制作工艺等相关信息数据为基础,采用Wi ndows平台,以Visual Studi0 2010为开发环境,结合ASP.NET 4.0框架以及SQL Server数据库技术而构架.经过系统测试和实际运行证明,此管理系统具有良好的应用界面,交互性强,运行稳定,数据处理方便等优势,对实现古陶瓷研究信息资源共享,全面开展越窑青瓷的科学化研究提供了一个良好的数据平台.     

REVISITING PLATFORM MOUNDS AND TOWNHOUSES IN THE CHEROKEE HEARTLAND: A COLLABORATIVE APPROACH

Abstract

This article describes the development and initial results of the Western North Carolina Mounds and Towns Project, a collaborative endeavor initiated by the Tribal Historic Preservation Office of the Eastern Band of Cherokee and the Coweeta Long Term Ecological Research Program at the University of Georgia. The goal of this project is to generate new information about the distribution of late prehistoric mounds and historic period townhouses in western North Carolina. This ongoing research has produced updated location and chronological data for 15 Mississippian period mounds and historic Cherokee townhouses, and led to the discovery of a possible location for the Jasper Allen mound. Using these new data, I suggest that David Hally's model for the territorial size of Mississippian polities provides a useful framework for generating new research questions about social and political change in western North Carolina. I also posit that the cultural practice of rebuilding townhouses in place and on top of Mississippian period platform mounds, a process that Christopher Rodning describes as “emplacement,” was common across western North Carolina. In terms of broader impacts, this project contributes positively to the development of indigenous archaeology in the Cherokee heartland.     

Organisational Needs and Priorities of Heritage Areas in the USA

Academics and practitioners alike know relatively little about the core competencies that are transferable from one heritage-area initiative to another. Often those new to the field have had to look to consultants or peers for advice regarding the essential core competencies needed to make their emerging organisations a success.This research surveyed the executive directors of the known universe of 154 heritage areas in the USA for the purposes of identifying the essential core skills they feel are needed to create and sustain a multi-jurisdictional heritage-tourism initiative. In addition, the importance-performance methodology employed in the survey instrument made it possible to assess their critical needs and priorities for training. Results of this study contributed to the design of the Heritage Development Institute, recently created to serve the executive staff of the nation's heritage areas at the College of Charleston on behalf of the Alliance of National Heritage Areas (www.cofc.edu/~heritage).     

秦陵7号坑铜水禽彩绘保护及分析

K0007号陪葬坑出土了一批青铜水禽,在其中发现了少量残存的彩绘。本文从铜禽彩绘的保护、清理、彩绘颜料分析和彩绘施彩工艺分析等方面对铜水禽彩绘进行了分析研究。