Journal of Performance of Constructed Facilities

To protect against military invasions and terrorist attacks requires the development of probabilistic models for predicting the effect of various local hard-missile impact effects on reinforced concrete (RC) protective panels. Because of the severity and irreversible repercussions of such events, the current work enhanced previously developed finite element calculations with the addition of experimental data from the literature. The improved model predicts the probabilistic models more accurately than the previous ones, and minimizes statistical uncertainty due to the incorporation of fresh data. The parameters investigated in the study were the penetration depth of the missile, perforation limit of the target, missile ballistic limit, and residual velocity of the missile. Among the components are residential slabs, bunkers, containments, aircraft shelters, and storage tanks. These models were built using probabilistic approaches and the Bayesian method. All aleatoric and epistemic uncertainties involved in missile impact contact with the target, geometrical configurations, material qualities, and measurement mistakes are accounted for by the updated formulas. These models also take into consideration strain-rate effect, multimodal response of the structure, and numerous failure mode transitions, among other things. An assessment with experimental findings was carried out to establish the dependability and credibility of the updated equations, and the acquired results demonstrate the trustworthiness of the anticipated formulas. This study accommodates natural disasters and accidental events such as windborne missiles, and impacts due to pressure pipes debris, iron rods, etc.

This paper presents the investigation results of a base-isolated RC frame-shear wall structure located in Luding County, Sichuan Province, China, which was damaged by a Ms 6.8 earthquake on September 5, 2022. This recently constructed school office building was about 9 km away from the epicenter. The isolation layer of this building consists of 54 rubber bearings and 12 viscous dampers. These viscous dampers or their connections failed during the earthquake, and the limit state included connection breaking or global buckling of the damper. Also, the superstructure suffered some minor damage. To investigate the cause of structural damages, a nonlinear time-history analysis is conducted using the ground motions recorded by four seismic stations close to the building. The onsite investigation and numerical simulation results revealed the possible reasons for the failure.

Expansive clay soils are subject to considerable volume changes due to seasonal variations in soil–water content. Its shrink–swell characteristics can lead to differential movements, which can cause damage to lightly weighted structures and pavements. The damage can be severe with the presence of trees, as the root system would take a significant quantity of water from the soil, resulting in restricted shrinkage settlement. This paper presents a case study of tree-root-induced subsidence and cracks in the surface of a netball court located in an eastern suburb of Melbourne, Australia. A geotechnical investigation was conducted, and four boreholes were drilled close to and sufficiently away from a group of Australian native Eucalypts (Corymbia maculata). The daily water use of the selected tree was monitored using a sap flow instrument. The soil suction and water content profile were developed based on the measurement results, indicating that the severe soil drying developed at 1.5 m below the surface of the netball court, where the soil was the driest up to 1.0 m located approximately 7.6 m from the tree group. A contour map was delineated based on the level survey carried out around the cracking surface of the court, and the results revealed that the crack is most likely attributed to the soil settlement caused by the drying effect of tree roots.

The maintenance of external facades’ claddings has been neglected over the years. The maintenance actions were limited to total replacement when the claddings showed a severe degradation condition. However, in the last years, this attitude started to change, but stakeholders faced two different approaches in performing maintenance activities. The first approach corresponds to the application of time-based maintenance policies, in which the maintenance activities are carried out periodically with predetermined schedules. In the second approach, condition-based maintenance policies are adopted, in which the degradation condition is assessed through regular monitoring and, posteriorly, the more adequate maintenance activities are defined. This study intends to compare these two maintenance policies and analyze whether there are advantages in implementing condition-based maintenance strategies in an economical and very common cladding solution. Therefore, the influence of the two maintenance policies on rendered facades is analyzed in terms of service life, maintenance costs, efficiency index, and number of replacements. A multiobjective optimization is performed to understand whether there is an optimal time interval for performing the inspections in condition-based methodologies. Based on these results, an equivalent time-based maintenance policy is developed. The periodicities for the maintenance activities recommended in the literature are constant regardless of the maintenance strategy adopted. Consequently, it is impossible to define an efficient plan for all maintenance strategies assuming the same time of intervention. In fact, the periodicities of the maintenance actions must be adjusted according to the maintenance strategy adopted. The comparison between both policies revealed small differences between maintenance costs, service life, and efficiency indices. However, in time-based maintenance policies, more interventions are always performed during the time horizon, increasing users’ disturbance and the risk of unplanned maintenance because coatings are not regularly monitored between inspections.

Abstract

The damages incurred in RC walls subjected to combined loading of blast and fragment as a result of a cased-charge detonation are studied here using the finite-element (FE) analysis method. A series of FE analyses were performed to estimate the intricate effects of cased explosive charges on severe crushing of concrete leading to spalling, penetration, or even scabbing and perforation in concrete. An increase in fragment penetration and perforation was noted under combined loading of blast and fragment compared with fragment loading alone, which highlights its severity. Subsequently, the response of RC walls of different thicknesses and concrete compressive strengths under different cased loadings and fragment shapes was also studied. Results showed that the response of the RC wall is considerably affected by charge weight, casing weight, concrete compressive strength, wall thickness, and fragment shape. The spherical end fragment penetration under combined loading of blast and fragment was noted to increase by 5.4%–23.1% compared with similar fragment loading alone, considering different concrete strengths. Moreover, based on the numerical study, the empirical relation of fragment penetration is modified and proposed to include the effect of explosive charge and casing weight. The measures to prevent excessive scabbing and concrete perforation using composite sections of concrete-steel and concrete-sand-steel, respectively, are also presented. This study emphasizes the importance of considering combined blast and fragment loading of protective structures and its mitigation using composite sections.

Practical Applications

The results of the present study may provide guidance for the analysis and design of reinforced concrete walls that are subjected to combined loading of blast and fragments because these walls are primarily designed for civil and military protective infrastructures to withstand accidental or intentional blast loadings. The results highlighting the performance efficiency of the composite sections in mitigating the combined effect of blast and fragment loading may provide further guidance on their practical applicability in military protective infrastructures.

Weathering steel enhances corrosion-resistant steel features over conventional steel when a patina properly forms on the weathering steel surface. The patina is a dense protective oxide film layer that develops on the steel member surface. The patina defends the steel from corrosion by preventing moisture, oxygen, and contaminant penetration. However, long periods of moisture and deicing chemicals applied during wet wintry conditions hinder proper patina formation. Weathering steel bridges in Arkansas are uncoated and exposed to ambient conditions that may promote steel corrosion. This paper presents the approach used by the authors to relate weathering steel bridge corrosion to bridge condition in order to prioritize bridges for remediation based on their oxide film deterioration severity. The study protocol used was to review uncoated weathering steel (UWS) bridges and prioritize bridges based on their need for immediate remediation. The potential for incorporating the use of a small unmanned aircraft system (UAS) for future bridge inspections is discussed. The research work in this paper serves as a basis for establishing bridge inspection guidelines to identify and grade oxide film degradation for bridge condition and performance.

Vehicle collision is an important reason for failing urban or highway bridges. However, few works have focused on the probability of damage to a bridge under such extreme loads. In this work, an impact-fragility analysis was conducted to calculate the probability of exceeding a damaged state of bridge systems, in which the probability of damage is conditional upon vehicle impact velocity, and soil–structure interaction (SSI) is included. Available impact tests of scaled vehicle–bridge pier systems conducted by previous researchers were utilized to validate the finite-element (FE) model and material models. Then, a three-span bridge with SSI was created for the fragility analysis using the validated high-fidelity FE method, in which the uncertainties of bridge materials and vehicle impact velocity were considered. The results indicated that SSI has a great influence on the dynamic performance of bridges; also, the probability of damage for each damage state increases significantly with the effects of SSI when the vehicle impact velocity is higher than a threshold value. The results also imply that boundary conditions of the bridge pier, the tonnage of the vehicle, and the pier diameter have a great effect on the threshold value of impact velocity leading to a damaged state.

A 193.5-m high concrete tube-shaped TV tower in the city of Nantong, China, was founded on short piled–raft footing, whose safety was threatened by implementation of four 10.9–26.5-m-deep excavations for an interchange subway station within close proximity. Considering the great damage potential of the TV tower associated with excavation-induced ground movement, a row of barrier piles consisting of bored piles was initially constructed between the excavations and TV tower. Field monitoring data indicated that the TV tower developed limited settlements during excavation of the two farthermost subway zones. However, it suffered notable settlements during excavation of the second farthest subway zone; hence, large-diameter metro-jet-system (MJS) piles along with bislurry piles were constructed between the excavations and TV tower to mitigate the adverse excavation influence. As a result, the tower gradually stabilized as construction continued, but it still exhibited an accelerated rate of differential settlement. Since excessive differential settlements might incur cracking, tilting, or even an overturning failure of the tower, it was determined finally to underpin the TV tower with long end-bearing steel pipe piles before excavation of the closest subway zone. With the aid of the comprehensive underpinning plan, the tower gradually became steady during excavation of the closest subway zone, without suffering structural damages or excessive deformations. The lessons and experience learned from this project as well as the extensive protection plans and measures are practically useful for engineers worldwide to safeguard high-rise superstructures sensitive to ground movement.

A case history of surcharge-induced large deformations and noticeable leakages occurring on existing underlying twin tunnels in soft ground is presented in this paper. The field conditions are well-documented in terms of the processes of the surcharge and discharge as well as the structural mechanical responses of the tunnels. The longitudinal distribution curve and evolution of the tunnel vertical displacement are investigated in association with the surcharge and discharge activities. Structural damages and transverse deformations, including water leakages, cracks, unfilled corners, dislocations, and horizontal convergences, are also explicitly examined and analyzed. To derive insight into the relationship between the tunnel deformations and the surcharge, the ground settlements at different elevations due to the surcharge are calculated using a simplified method without considering the effect of the existing tunnel. Further, a modified two-stage method is adopted to estimate the longitudinal tunnel settlements, bending moments, and shear forces, in which the tunnel and underlying ground are modeled as a Timoshenko beam and Winkler foundation, respectively. Finally, for the upcoming preparation for the tunnel operation and planned road construction, practical suggestions for strengthening the tunnel and future construction activities are proposed.