Seismic Evaluation of Tall Buildings Using a Simplified but Accurate Analysis Procedure

A simplified analysis procedure for evaluating the nonlinear seismic responses of tall reinforced concrete (RC) buildings is examined in this study. It is called the Uncoupled Modal Response History Analysis (UMRHA) procedure. It can be viewed as an extended version of the classical modal analysis procedure, where the nonlinear response of each vibration mode is first computed, and they are later on combined into the total response of the structure. The procedure requires the knowledge of the modal hysteretic behavior, which can be obtained from a cyclic modal pushover analysis. The responses of four tall buildings in Bangkok to distant large earthquakes are computed by this procedure and compared with those obtained from the Nonlinear Response History Analysis (NLRHA) procedure. These four buildings have different heights—varying from 20 to 44 stories, different configurations of floor plan, and different arrangement of RC walls. The comparison shows that the UMRHA procedure is able to accurately compute the story shears and story overturning moments, floor accelerations, and inter-story drifts of all these tall buildings. The required computational effort is also extremely low compared to that of the NLRHA procedure. Moreover, since the UMRHA procedure computes the response of each individual vibration mode, it provides more understanding and insight into the complex nonlinear seismic responses of these tall buildings.     

Effects of Geometrical Features on the Seismic Response of Historical Masonry Towers

ABSTRACT

Historical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features.     

Scalar Structure-Specific Ground Motion Intensity Measures for Assessing the Seismic Performance of Structures: A Review

The assessment of the seismic performance depends on the choice of the earthquake Intensity Measure (IM). During the past years many IMs, which take into account not only earthquake characteristics but also structural information, have been proposed. However, no consensus on which IM is the best predictor of the seismic response exists. Along these lines, the objective of this paper is to present the various developed scalar structure-specific seismic IMs and the problems associated with their use in practice, so that the engineer may become familiar with them and their implications in the context of Performance-Based Earthquake Engineering.     

PROVENANCING AND ARCHAEOLOGY OF ROMAN MILLSTONES FROM SARDINIA (ITALY)

Summary. Sardinia was an important Roman settlement and trade centre between 238 BC–500 AD and is an ideal site for study of Roman trade. Study of Roman millstones in Sardinia shows that the commonest type is the Pompeian (hour-glass) mill (forty-eight stones studied), with smaller numbers of cylindrical hand querns (sixteen stones studied). Most of these millstones are composed of igneous rocks which include grey vesicular lavas of basic/intermediate composition and a distinctive reddish rhyolitic ignimbrite. There is historical and archaeological evidence for millstone manufacture at six localities in Sardinia. Visual and petrographic study and X-ray fluorescence analysis for major and trace elements of seventeen millstone samples, and fifty rock samples from potential source areas have been used to provenance the igneous rock millstones. The grey vesicular lava millstones have varied sources within the Tertiary-Recent volcanic rocks of Sardinia, while the millstones composed of rhyolitic ignimbrite are from a single source of Tertiary ignimbrite at Mulargia (central west Sardinia). A single hand mill from the north of Sardinia was imported probably from Agde in southern France, and is the only sample composed of non-local rock. Mulargia millstones were widely traded within the western Mediterranean and show a rapid decrease in frequency of occurrence with increasing distance from the source. Sardinia was therefore an important centre of Roman millstone production and a source of millstone trade during the period of Roman settlement.     

Poaceae phytoliths from the Niassa Rift,Mozambique

The most common grass phytoliths from “Zambezian” miombos are described here for the first time. Their potential for long term preservation in sediments makes them a useful tool in the reconstruction of ancient plant communities and plant/human interactions. We processed 60 plant samples (26 identified genera and species), with an average of 300 phytoliths counted per sample to a total of 18,586. Forty-seven morphotypes were described as per the International Code for Phytolith Nomenclature, with exceptions, including forty-five discreet shapes and two articulated forms, which can be used as comparative reference materials. We conducted three forms of statistical analyses: Discriminant Analysis, Cluster Analysis, and Principal Component Analysis. The highest biomineral content was recorded among the Bambuseae and Paniceae, while the lowest silica production is detected in the Cynodonteae tribe. Typologically, the subfamily Panicoideae yielded 50% of the types reported here, 32% are from the Chloridoideae, 12% from the Bambusoideae, and 8% from the Arundinoideae sensu lato. Overall, the idealized Zambezian Poaceae phytolith spectrum is dominated by a small subset of Poaceae short cells, which include five morphotypes conventionally associated with Panicoid grasses (Bilobate concave outer margin long shaft, Bilobate concave outer margin short shaft, Bilobate convex outer margin long shaft, Bilobate convex outer margin short shaft, Cross), one morphotype commonly seen in Chloridoid taxa (saddle), and two types that appear across subfamily boundaries (tower, tower horned). The next logical step to take in regional phytolith research is the account of phytoliths deposited in soils underneath living plants, for they represent the interface between existing vegetation communities and the inevitably distorted fossil assemblages that the paleobotanist uses for environmental reconstruction.     

Identifying the sources of Inka period ceramics from northern Chile: results of a neutron activation study

To examine regional patterns of ceramic production and distribution during the era of Inka domination in northern Chile, we determined the elemental compositions of 157 samples of archaeological ceramics and geological clays from the sites of Catarpe and Turi using instrumental neutron activation analysis. We identified two major and three minor composition groups in the ceramics. The major groups, High Cr and Low Cr, are linked to clays from two broad geological contexts within the region, while the minor Low Na group is made up of ceramics imported from northwestern Argentina. The distribution of the composition groups indicates that, in the Catarpe–Turi region, patterns of ceramic production differed for different vessel types: jars were made from clay and temper acquired near the sites where the jars were used, while bowls were made of material coming from more distant sources. The geographical distribution of the analyzed ceramics indicates that bowls were exchanged between Catarpe and Turi in a pattern more similar to tribute/extraction than to market exchange, with Catarpe being the dominant site. The compositional analysis also demonstrates that Inka-style ceramics were being locally produced at sites in this region during the era of Inka domination.     

Characterization of bricks and tiles from the 17th-century brick Chapel,St. Mary's City,Maryland

The brick Chapel at St. Mary's City, Maryland, built around 1667, would have been an impressive structure on a colonial frontier where all the other buildings were built only of wood. While the building is no longer extant, the bricks remaining in the buried foundations hold information about the technologies and materials used by brickmakers in the 17th-century Chesapeake region. Instrumental neutron activation analysis (INAA) and petrographic analysis of thin sections were used to compare the Chapel bricks and other 17th-century bricks and tiles from several Chesapeake contexts to locally available clay sources. While the composition of the Chapel bricks is generally consistent with that of clays available in southern Maryland, these historic materials could not be linked to any one deposit, and may reflect the mixing of clays from multiple sources. In contrast, building materials from other 17th-century buildings at St. Mary's City could be more precisely “matched” to specific local clay deposits. This paper reports on our initial investigations toward understanding the technology of the Chapel bricks and their relationship to other bricks from St. Mary's City.     

Testing technological practices: neutron activation analysis of neolithic ceramics from Valencia,Spain

Using instrumental neutron activation analysis (INAA) of prehistoric pottery, daub, and modern clay samples from Valencia, Spain, we tested expectations on changes in raw material use with socio-economic shifts during the Neolithic (ca. 5600–2800 BC). Elemental analysis identified three distinctive clay source groups used by Neolithic potters. Contrary to expectations, a shift in raw material use was identified between the Early and Middle Neolithic despite general similarities in technological practices. In the Late Neolithic, pottery production became more specialized, but potters used the same range of clay sources documented earlier. This study illustrates the utility of INAA for testing hypotheses of prehistoric craft production.     

Production centers of cooking pots in Iron Age Judah

This paper will present and discuss a multifaceted research project dealing with the production of cooking pots during the Iron Age II (ca. 1,000–586 BCE) Judah (modern Israel). In particular the new compositional analysis of 541 cooking vessels from 11 sites in Iron Age Judah will be presented. The study employs petrographic and chemical (NAA) analysis. The results of this ongoing research have already produced interesting information about production centers and movements of cooking pots in Iron Age II Judah. Apparently, the vast majority of the cooking pots sampled were made of a similar type of clay, related to terra rossa soil. This is true also for sites in the northern Negev and Judean Desert, where the type of soil was not available in the region of the sites. Furthermore, many of the cooking pots distributed around Judah were made in Jerusalem according to a well-located chemical profile (JleB). Other groups may represent Judean Shephelah production centers as the Lachish area as well as production centers in southern Israel or ancient Edom. The implications of the importation patterns of cooking pots by peripheral Judean sites will be discussed.     

左江流域种植业区划

左江流域六县(市)地处桂西南喀斯特地区,区内农业资源和生产水平各有差异。为了配合该地区经济的全面开发,我们收集了该地区七十一个行政乡农业生产有关的特征数据,运用数学的方法--聚类分析法和电子计算机技术,对该地区农业的空间布局进行合理调整--种植业类型区划分,并分别论述各类型区的特点及今后发展方向。为该地区今后在农业生产上做到宜地适种、扬长避短,并在此基础上向区域化、集约化的农业迈进提供科学依据。