Journal of Performance of Constructed Facilities

Elastomeric bearing pads are commonly used to support precast prestressed bridge girders. Previous studies on such pads have been conducted only at ambient temperatures. Bridges are susceptible to fire due to the potential for crashed or overturned vehicles, and the pad behavior at such elevated temperatures should be explored. A typical bridge fire in the vicinity of girder supports can have a significant effect on the performance of the bearing pads. In this study, a one-span full-scale bridge comprised of standard precast concrete I-girders and composite deck with elastomeric bearing pads was tested under a combined hydrocarbon pool fire and simulated live load. The test was conducted for 60 min, and the fire temperature at the bearing pads reached as high as 400°C. The affected bearing pads were then tested for hardness, shear modulus, compression set, and adhesion strength as per current standards. All material properties except for the compression set indicated small changes and were within the acceptable limits. Numerical simulation using a linear elastic model and thermomechanical analysis was also conducted with nonlinear finite element software. The pad shear strain, tensile stress, and bond stress increased by up to 30–50% for 50, 60, and 70 elastomer hardness levels at 200°C temperature exposure. The effect of fillers on bearing pad performance is negligible.

To investigate the dynamic responses and damage modes of the dome of a liquefied natural gas (LNG) storage tank under aircraft impact, a finite-element (FE) model of a $\mathrm{160,000}\text{-}{\mathrm{m}}^3$ LNG storage tank for an actual LNG project and two kinds of aircraft was established. Through comparison of the results of a numerical simulation and an impact perforation test, the accuracy of the numerical simulation method and the material model were confirmed. The FE model of the aircraft also was validated, based on the Riera method. The dynamic responses and failure phenomena of the dome and wall of the LNG tank under aircraft impact were studied, respectively. Based on the simulation results, the influence of the reticulated shell on the antishock capability of the dome was evaluated. The numerical results revealed that the LNG outer tank was able to resist the impact of a Bombardier Challenger 850 and a Boeing 757 flying at $100\mathrm{m}/\mathrm{s}$; the ability to withstand shock loading was improved greatly by the combined effects of the concrete and reticulated shells. However, when the Bombardier Challenger 850 aircraft hit the tank wall at $100\mathrm{m}/\mathrm{s}$, the aircraft penetrated into the LNG outer concrete structure. More seriously, when the Bombardier aircraft hit the ring beam, in addition to the penetration damage at the direct impact site, there was a wide range of collapse near the breakdown hole, and the structure was severely damaged.

Coastal bridges are vulnerable to large hydrodynamic loads during extreme events. During the 2004 and 2005 hurricane seasons, these loads exceeded the capacity of bridge spans resulting in bridge failures across the Gulf Coast region. This case study provides a forensic evaluation of a simply supported bridge span that failed during Hurricane Katrina (2005). The damaging coastal processes were simulated using sophisticated hydrodynamic models [advanced circulation (ADCIRC) + simulating waves nearshore (SWAN), XBeach] that reasonably reproduced the water levels, waves, and velocities at the bridge location. The bridge’s vulnerability to trapped-air effects, wave-induced loads, and drag forces was evaluated using the model results. All of these loads exceeded the structural capacity at the span that failed. However, a detailed evaluation of the modeling results suggests that this bridge span failed due to large drag-induced loads as a result of flow convergence near the bridge abutment. The superelevation of the bridge spans may have contributed to the damage by causing localized increases in flow velocity below the span beams but also possibly mitigated wave-induced damage. This may be the first known case in which drag-induced loads contributed to bridge failure during a hurricane. As such, high velocity flows may also pose a hazard to bridges and overpasses located in coastal floodplains.

This paper describes a model updating procedure implemented in NOSA-ITACA, a finite-element (FE) code for the structural analysis of masonry constructions of historical interest. The procedure, aimed at matching experimental frequencies and mode shapes, allows for fine-tuning the calculations of the free parameters in the model. The numerical method is briefly described, and some issues related to its robustness are addressed. The procedure is then applied to a simple case study and two historical structures in Tuscany, the Clock Tower in Lucca and the Maddalena Bridge in Borgo a Mozzano.

Rib-to-deck joints in orthotropic steel decks (OSDs) are among the most fatigue-prone details of steel bridges. To improve the fatigue performance of existing bridges with OSDs, a strengthening method using externally bonded fiber-reinforced polymer (FRP) angles was proposed and experimentally studied. This study also presents a field investigation of strengthened OSDs with FRP angles. First, on-site strengthening procedures with glass FRP (GFRP) angles were proposed and demonstrated on a long-span suspension bridge. Two-day field strain monitoring indicated that daily equivalent stress ranges (ESR) decreased significantly after strengthening. The strengthening mechanism was further studied through numerical analysis, in which the effective notch stress method and submodel technique were adopted to investigate stress fields of the welded details. The results showed that among the dimensions under investigation, thicker, wider, and longer GFRP angles generally result in better fatigue performance by providing higher additional local stiffness to rib-to-deck joints. Calculation of stress intensity factors at crack tips resulted in similar conclusions to the effective notch stress analysis, and the strengthening effect was found to be more remarkable for deeper cracks.

Earthquakes can substantially disrupt the operation of critical lifelines in a community, particularly water, gas, and other below-ground infrastructure. The damage that occurs to lifelines in a community from an earthquake can, in turn, have a substantial impact, resulting in social and economic disruption. Furthermore, the duration of the loss in functionality of lifelines is a key factor in the economic disruption that results from an earthquake. In this study, a virtual community known as Centerville was subjected to earthquakes of varying intensity, each having the same assigned point source location, using a well-known attenuation model in order to examine the restoration of communities in the aftermath of an earthquake. The virtual community model being studied has the essential physical components that describe a community, but the focus of this paper is the natural gas network, which is composed of a processing plant, compressor stations, city gate stations, district regulating stations, and buried pipelines. Based on the level of damage that occurred to the network components and their connectivity (topology) throughout the community, the functionality of supplier nodes is assessed using Monte Carlo simulation, and functionality curves are presented for the community’s natural gas network. Notably, the effect of the industrial makeup of a community on its natural gas recovery following an earthquake, as well as the influence of replacing conventional steel pipes with high-density polyethylene (HDPE) ductile pipelines, is examined. As expected, the ability of the HDPE pipe to reduce the network recovery time is substantial and is quantifiable at the community level using the approach presented herein.

Neither structural properties nor wind loads are deterministic; accordingly, a fragility analysis of overhead transmission towers can be employed to comprehensively evaluate their strength capacity. Here, a fragility analysis method for a transmission line under wind loading is developed that incorporates the uncertainties of structural parameters and wind loads into a numerical model. First, a simplified model with one tower and two span lines is presented to improve calculation efficiency; this model is validated via a comparison with a complete tower-line system under both static and dynamic conditions. Then the fragility analysis process for transmission towers subjected to wind loading is presented in three main steps: development of uncertainty models and wind loadings, nonlinear dynamic analysis, and regression analysis. Afterwards, the random variables and their corresponding probability distributions are determined. Finally, a case study of a real operational transmission tower under wind loading is carried out. The results indicate that the consideration of a greater number of uncertainty parameters leads to a greater dispersion of the fragility curve and that the wind attack angle has a significant influence on the fragility curve.

Relatively few studies have been conducted to examine the effects of static pile driving on existing tunnels, and there is a lack of guidance and case studies that can be used as references. This article presents a case study of the tunnel of the Wuxi Metro Line 2 in China that was performed to investigate the mechanism by which static pile driving affects an existing metro tunnel structure. The study provides a theoretical basis for the design of construction schemes for static-driven piles. The effects of pile driving–induced soil compaction and excess pore-water pressure (EPWP) are studied through numerical calculations and are then combined using the superposition principle. In addition, the numerical results are compared with field measured data. The following results are obtained. First, static pile driving results in horizontal compression and vertical extension of the existing tunnel. The horizontal convergence of the tunnel segment near the center of the pile group is $-3.56\mathrm{mm}$. The opening of the circumferential joints is 1.15 mm, which leads to the risk of water leaks. Second, the EPWP-induced horizontal and vertical extension of the tunnel segment are approximately 50% and 33%, respectively, of the deformation caused by soil compaction before the dissipation of the EPWP and decrease to 25% and 20%, respectively, after the dissipation of the EPWP. Third, the combined effects of static pile driving–induced soil compaction and EPWP calculated based on the superposition principle are consistent with the field observations. This study provides a new procedure for static pile-driving simulations, reveals the influence of static pile driving on the deformation of an existing tunnel, and can be used to guide the design and formulation of construction schemes for static piles.