Smart Lead Rubber Bearings Equipped with Ferrous Shape Memory Alloy Wires for Seismically Isolating Highway Bridges

Shape memory alloys (SMA) can substantially improve the damping capacity and re-centering capability of elastomeric isolators. The objective of this study is to assess the seismic performance of smart lead rubber bearings (LRBs) equipped with double cross ferrous SMA wires. Hysteretic shear response of SMA wire-based LRB is determined using finite element method. The seismic response of a multispan continuous steel girder bridge isolated by SMA-LRB is evaluated. Hybrid SMA-LRB bearing exhibits a significantly lower shear strain demand (up to 46% reduction) and a higher energy dissipation capacity (up to 31% increase) compared to the LRB.     

The social networks of the Buckinghamshire gentry in the thirteenth century

This empirical study offers a contribution to a continuing debate about the county community and the significance of feudal ties by analysing the contacts of twenty small and middling knightly families. It explores their geographical range and the relative significance of horizontal and vertical ties. The evidence indicates a world dominated by local connections, stretching five to ten miles from a family manor. Nonetheless, the gentry were not necessarily restricted by county boundaries in their connections, as patterns of monastic patronage show. Nor were their social networks always limited to their neighbourhood. The search for good marriages mobilised wider networks, while financial pressures led families to look to towns like Oxford and London for credit. Ties with feudal superiors were rare, except for tenants of the honor of Wallingford, who had links with the earls of Cornwall. Horizontal ties with other gentry families and family members significantly outnumbered those with any other groups, and this applied both to supportive relationships and conflictual ones. Placing this study in the context of other gentry studies, I conclude by emphasising the prevalence of local ties mainly with those on the same social level or below. Although there is evidence to suggest that wealthier families with several manors had wider ranging connections, the everyday world of these men was apparently a fairly parochial one.     

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.     

The social networks of the Buckinghamshire gentry in the thirteenth century

This empirical study offers a contribution to a continuing debate about the county community and the significance of feudal ties by analysing the contacts of twenty small and middling knightly families. It explores their geographical range and the relative significance of horizontal and vertical ties. The evidence indicates a world dominated by local connections, stretching five to ten miles from a family manor. Nonetheless, the gentry were not necessarily restricted by county boundaries in their connections, as patterns of monastic patronage show. Nor were their social networks always limited to their neighbourhood. The search for good marriages mobilised wider networks, while financial pressures led families to look to towns like Oxford and London for credit. Ties with feudal superiors were rare, except for tenants of the honor of Wallingford, who had links with the earls of Cornwall. Horizontal ties with other gentry families and family members significantly outnumbered those with any other groups, and this applied both to supportive relationships and conflictual ones. Placing this study in the context of other gentry studies, I conclude by emphasising the prevalence of local ties mainly with those on the same social level or below. Although there is evidence to suggest that wealthier families with several manors had wider ranging connections, the everyday world of these men was apparently a fairly parochial one.     

博弈论视角下的卢沟桥事变

本文主要运用博弈论模型对卢沟桥事变从一个"地方性"事件演变为中日两国之间的全面战争这一过程进行分析.本文认为,卢沟桥事变发生伊始,中日两国都不同程度地想避免卷入全面战争,但是由于双方在卢沟桥事变后所采取的对策使得他们陷入了"谁是懦夫"的困境中,最终导致了全面战争的爆发.     

A Stability-Based Target Displacement for Direct Displacement-Based Design of Bridge Piers

P-Δ effects can cause instability if they are not properly accounted for during the design of bridge piers and other structures. When a bridge pier is designed with the Direct Displacement-Based Design Method, P-Δ effects are evaluated at the end of the design process and compared to the flexural strength of the pier to find a stability index. If the stability index exceeds the specified value, the design must be repeated, iteratively reducing the target design displacement. This article presents a model that when used at the beginning of design (without knowledge of strength) allows the estimation of the maximum lateral displacement that a bridge pier can sustain without exceeding the specified value of the stability index, therefore eliminating the need for iteration. The examples that are presented prove that the model is accurate and very useful for design of extended pile bents.     

Real-time Seismic Damage Detection of Concrete Shear Walls Using Artificial Neural Networks

Concrete shear walls are widely employed in buildings as a main resistance system against lateral loads. Early identification of seismic damage to concrete shear walls is vital for deciding post-earthquake occupancy in these structures. In this article, a method based on artificial neural networks for real-time identification of seismic damage to concrete shear walls was proposed. Inter-story drifts and plastic hinge rotation of concrete walls were used as the inputs and outputs of a MLP neural network. Modal Pushover Analysis was employed to prepare well-distributed data sets for training the neural network. The proposed method was applied to a five-story concrete shear wall building. The results from the network were compared with those obtained from Nonlinear Time History Analysis. It was observed that the trained neural network successfully detected damage to concrete shear walls and accurately estimated the severity of seismic-induced damage.     

Impact Stiffness of the Contact-Element Models for the Pounding Analysis of Highway Bridges: Experimental Evaluation

For the requirement of pounding analysis of highway bridges, how to properly choose the impact stiffness has become a primary issue for an achieving accurate result. This article presents an evaluation test of the impact stiffness of four types of contact-element models based on the shaking table test results of a steel highway bridge model. The analytical results indicate that the theoretical impact parameters are significantly larger than the identified values because the assumptions for deriving those models cannot match the actual impact conditions. The possible reasons causing those differences are discussed at the end of this study.     

The Impact of Flood-Induced Scour on Seismic Fragility Characteristics of Bridges

Earthquake in the presence of flood-induced scour is a critical multihazard scenario for bridges located in seismically-active, flood-prone regions. The present article evaluates seismic performance of four example reinforced concrete bridges when they are pre-exposed to regional flood hazards. Nonlinear time history analyses of the example bridges are performed for a suite of ground motion time histories in the presence and absence of scour expected from different intensity flood events. Fragility analysis is performed to develop seismic fragility curves of the example bridges for various scour depths. Results show nonlinear increase in bridge seismic fragility with increase in scour depth.     

Performance-Based Seismic Assessment of Superelastic Shape Memory Alloy-Reinforced Bridge Piers Considering Residual Deformations

The application of superelastic Shape Memory Alloy (SMA) reinforcement in plastic hinge regions of bridge piers has been proven to reduce the residual displacement after a strong shaking owing to its unique shape recovery characteristics; however, the maximum deformation of the piers could increase due to the relatively lower modulus of elasticity of SMA bars and lower hysteretic energy dissipation capacity. In this context, this article applies a recently formulated probabilistic performance-based seismic assessment methodology that considers both the maximum and the residual deformation simultaneously to evaluate the performance of SMA reinforced bridge piers.