Bridges in a road network play a significant role in supporting the flows of people, goods, and freight during an earthquake event and are expected to maintain their functionality following the event. Thus, measuring the capability of a bridge immediately following an earthquake event is critical for understanding the post-earthquake functionalities of transportation networks and supply chain systems involving highway bridges. To this end, this paper proposes a new metric for measuring the resistant capacity of a highway immediately following an earthquake event, which is here called instantaneous resilience. The proposed metric first compares the reliability indices of a bridge before and following an earthquake event to measure the immediate earthquake impact. Although this comparison (i.e., robustness measure in this paper) indicates the remaining strength of the bridge subjected to a given earthquake event, it does not reflect collapse failure modes appropriately. Therefore, the proposed instantaneous-resilience metric combines the robustness measure with the structural redundancy measure to consider various scenarios of load path distribution. The proposed metric is computationally efficient because, in the process, it utilizes a generalized reliability-intensity (R-I) surface of a bridge which can be used to calculate the pre- and post-earthquake reliabilities of any bridge designed based on the American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD). Without developing bridge-specific fragility curves and performing structural analysis of a bridge, the proposed measure enables engineers to make a preliminary assessment of the immediate impact of the earthquake on bridges on a quantitative basis. The step-by-step calculation process of the proposed instantaneous-resilience of a bridge is presented, and its potential use in highway network performance assessment is illustrated with a simple hypothetical network system.

公路网中的桥梁在地震事件中对人员，货物和货物的流动提供支持方面起着重要作用，并有望在地震发生后保持其功能。因此，在地震事件发生后立即测量桥梁的能力对于理解交通网络和涉及公路桥梁的供应链系统的地震后功能至关重要。为此，本文提出了一种新的度量标准，用于测量发生地震后立即发生的高速公路的抗力能力，在此称为瞬时回弹力。。拟议的度量标准首先比较地震发生前后的桥梁可靠性指标，以衡量地震的直接影响。尽管此比较（即本文中的稳健性度量）表明了在给定地震事件下桥梁的剩余强度，但它并未适当反映倒塌破坏模式。因此，所提出的瞬时弹性度量结合了鲁棒性度量和结构冗余性度量，以考虑各种负载路径分布情况。提议的指标在计算上是有效的，因为在此过程中，它利用桥梁的广义可靠性强度（RI）表面，该表面可用于计算根据美国国家公路和运输官员协会（AASHTO）的荷载和阻力系数设计的任何桥梁的地震前和地震后可靠性设计（LRFD）。拟议的措施无需开发特定于桥梁的脆性曲线并进行桥梁结构分析，就可以使工程师对地震对桥梁的直接影响进行定量的初步评估。提出了桥梁瞬时弹性的分步计算过程，并通过一个简单的假设网络系统说明了其在高速公路网络性能评估中的潜在用途。拟议的措施无需开发特定于桥梁的脆性曲线和进行桥梁结构分析，就可以使工程师对地震对桥梁的直接影响进行定量的初步评估。提出了桥梁瞬时弹性的分步计算过程，并通过一个简单的假设网络系统说明了其在高速公路网络性能评估中的潜在用途。拟议的措施无需开发特定于桥梁的脆性曲线和进行桥梁结构分析，就可以使工程师对地震对桥梁的直接影响进行定量的初步评估。提出了桥梁瞬时弹性的分步计算过程，并通过一个简单的假设网络系统说明了其在高速公路网络性能评估中的潜在用途。