Sustainability of Highway Bridge Networks Under Seismic Hazard

In order to evaluate the seismic risk of transportation networks, it is necessary to develop a methodology that integrates the probabilities of occurrence of seismic events in a region, the vulnerability of the civil infrastructure, and the consequences of the seismic hazard to the society, environment, and economy. In this article, a framework for the time-variant seismic sustainability and risk assessment of highway bridge networks is presented. The sustainability of the network is quantified in terms of its social, environmental, and economic metrics. These include the expected downtime, expected energy waste and carbon dioxide emissions, and the expected loss. The methodology considers the probability of occurrence of a set of seismic scenarios that reflect the seismic activity of the region. The performance of network links is quantified based on individual bridge performance evaluated through fragility analyses. The sustainability and risk depend on the damage states of both the links and the bridges within the network following an earthquake scenario. The time-variation of the sustainability metrics and risk due to structural deterioration is identified. The approach is illustrated on a transportation network located in Alameda County, California.     

Effect of Topology Irregularities and Construction Quality on Life-Cycle Cost of Reinforced Concrete Buildings

Life-cycle cost (LCC) analysis entails consideration of building performance throughout the structures’ life. The impact and interaction of topology irregularities and construction quality (CQ) on LCC, however, are often ignored and require a more detailed evaluation. In this article, different levels and interaction of soft story (SS) and CQ are analytically modeled to quantify corresponding fragility curves and LCC (by considering hazard level, limit state cost, and probability of being in different damage states). The proposed method is illustrated with a three-, six-, and nine-story reinforced concrete building located in Vancouver (located in west coast of Canada).     

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.     

Optimum Design Approaches for Improving the Seismic Performance of 3D RC Buildings

In this article, a number of design approaches for 3D reinforced concrete (RC) buildings are formulated in the framework of structural optimization problems and are assessed in terms of their performance under earthquake loading. In particular, three design approaches for RC buildings are considered in this study. In the first, the initial construction cost is considered as the objective function to be minimized. The second one is formulated as a minimization problem of the torsional response, while a combined formulation is also examined as the third design approach. The third approach is considered with two distinctive formulations. According to the first approach, the torsional behavior is minimized by minimizing the eccentricity between the mass and rigidity centers, while the second one is achieved by minimizing the eccentricity between the mass and strength centers. It is shown that the optimized designs obtained according to the minimum eccentricity of the rigidity center behave better in frequent (50/50 hazard level) and occasional (10/50 hazard level) earthquakes, while the designs obtained according to the minimum eccentricity of the strength center formulation was found better in rare (2/50 hazard level) events. Designs obtained through a combined formulation seem to behave equally well in the three hazard levels examined.     

A cost surface model of volcanic glass quarrying and exchange in Hawai‘i

The spatial distribution of artifacts from the Pu‘u Wa‘awa‘a volcanic glass source (North Kona District, Hawai‘i Island) shows a pattern of direct access by those living in the immediately vicinity of the source with subsequent down-the-line exchange. Most quarrying and exchanges likely occurred within a single day’s travel from sites where artifacts were deposited. The exception to this is the discovery of non-local direct access evident in assemblages from the extreme southern end of Hawai‘i Island; these visits may have involved voyages by canoe. While people did not often travel far for volcanic glass they nonetheless appear to have had unfettered accessed to source material and freely conducted inter-community exchanges. This implies volcanic glass was treated as a common pooled resource and the existence of informal exchange relationships.     

Robust Performance-Based Design Optimization of Steel Moment Resisting Frames

The concept of performance-based design is considered in the framework of Robust Design Optimization (RDO) for the design of steel structures. The RDO problem is treated as a two-objective optimization problem where the initial construction cost and the variance of the maximum interstorey drift for the 10% in 50 years hazard level are considered as the problem objectives to be minimized. The structural performance is evaluated by means of the reliability demand and resistance methodology of the FEMA-350 guidelines in order to take into account both uncertainty and randomness in a consistent manner. The structure is designed to respond for different levels of seismic hazard levels with a desired confidence. The limit-state damage cost is used as a measure for the assessment of selected designs that have been obtained through the proposed RDO formulation. The non deterministic finite element problem encountered, is solved using the Monte Carlo Simulation method. The NSGA-II algorithm has been combined with the Evolution Strategies optimization algorithm for solving the two-objective optimization problem at hand.     

The Influence of Masonry Infill Walls in the Framework of the Performance-Based Design

In this article, a performance-based seismic design (PBD) methodology is proposed for the design of reinforced concrete buildings, taking into account the influence of infill walls. Two variants of the PBD framework are examined: The first is based on the non-linear static analysis procedure (NSP) while the second relies on the non-linear dynamic analysis procedure (NDP). Both design approaches are compared in the context of structural optimization with reference to the best possible design achieved for each case examined. Life-cycle cost analysis is considered a reliable tool for assessing the performance of structural systems and it is employed in this study for assessing the optimum designs obtained. The optimization part of the problem is performed with an Evolutionary Algorithm while three performance objectives are implemented in all formulations of the design procedures. The two most important findings can be summarized as follows: (i) if structural realization follows the design assumptions, then total expected life-cycle cost of the three type of structures, bare, fully infilled and open ground story, is almost the same and (ii) if an open ground story building is designed as bare or as fully infilled frame, real performance will be much worse than anticipated at the design stage.     

Transportation corridors and political evolution in highland Mesoamerica: Settlement analyses incorporating GIS for northern Tlaxcala, Mexico

Investigations of the functional utility and social elaboration of natural transportation corridors contribute to generating more comprehensive understandings of complex macroregional phenomena such as political evolution. In this article, highland central Mexican transportation corridors are analyzed through GIS applications and a reconsideration of settlement data from an important corridor in northern Tlaxcala. The location of the study region, within the corridor connected to the northeastern Basin of Mexico, makes it particularly relevant for examining interregional exchanges and the transformation of a more rural landscape adjacent to core areas of urbanization and state political expansion. Conclusions drawn from the study are largely complementary to the interpretations made by the surveyors [Merino Carrión, B.L., 1989. La Cultura Tlaxco. Serie Arqueológica, Colección Científica 174, Instituto Nacional de Antropología e Historia, Mexico City], but provide an updated assessment of prehispanic political evolution ca. 900 BC–AD 1519. Specifically, the study tracks the evolution of early ceremonial centers, Teotihuacan’s territorial expansion through the region, political balkanization following the collapse of Teotihuacan, and the establishment of small, independent polities encountered by the Spanish. New contributions include quantitative measures relevant to assessing the systemic integration of the region and the social value of the corridor during different chronological phases, elucidating the differing expansionary trajectories of Teotihuacan and the Aztec Empire.     

Using multi-criteria cost surface analysis to explore past regional landscapes: a case study of ritual activity and social interaction in Michigan,AD 1200–1600

Major advances have occurred in the analytical use of GIS in archaeology, particularly in uses of this tool for furthering understandings of past social landscapes. A major focus of these efforts has been visibility studies and archaeologists have paid less attention to how GIS can facilitate the study of another important socio-spatial component, movement. This paper examines the GIS application of multi-criteria cost surface analysis as a robust technique for modeling past movement and applies this approach to the Late Prehistoric period (ca. AD 1200–1600) in Michigan as a case study. This analysis extends understandings of the role of localized connections and tribal territoriality with the spread of maize agriculture in this period and adds further support to the proposal that earthwork enclosures served as uniquely accessible ritual centers for social, economic and ideological interaction between separate tribal communities within the Late Prehistoric regional organization. By showing this technique can build on and validate models of past social developments, grant real insights into social connections and affiliations, and stimulate new directions for future research, this specific case illustrates the general heuristic value of multi-criteria cost surface analysis for exploring regional landscapes in archaeology.     

WHEN SHOULD SEISMIC RETROFITTING OF EXISTING STRUCTURES BE IMPLEMENTED IN ORDER TO MINIMIZE EXPECTED LOSSES

The usual outcomes of the seismic safety analysis for an existing civil engineering structure axe the probability of exceedance of specified limit states and the increase in safety due to retrofitting interventions. This information can be used in several ways. For a single structure, one can compare it with desired target reliability values; for structures belonging to a network, e.g. highway bridges [Donferri et al., 1998], electric networks [Vanzi 1996, 2000) or strategic buildings [Nuti and Vanzi, 1998] they can also be used to assess the priority of interventions.

In this study, an alternative use of the reliability values for existing structures is proposed, which answers the following question: when, i.e. in which year from the date of construction, should seismic retrofitting be implemented so as to minimize the expected total cost? In the expected total cost, here, both the costs of retrofitting and possible disruption, due to delayed retrofitting, are accounted for.

The method proposed computes the expected costs by analysing the branches of the event tree for the problem built after strong but reasonable and highly simplifying assumptions on the problem. Although these assumptions limit the general applicability of the solutions obtained, they allow the building up of an extremely agile and effective solution scheme.

The results obtained from the study, i.e. the year in which it is economically best to implement retrofitting and what the expected annual equivalent cost is, are presented in diagrams and in analytical form, as a function of the most important variables. Finally, an example application on a real structure is presented, which shows all the steps to undertake with the proposed method.