Journal of Performance of Constructed Facilities

Uncertainties about the initial surface elevation of the slab-on-grade floor of a residential single-family home have been shown to complicate the analysis of elevation survey data for single slabs. However, because significant and consistent literature exists on the distribution of maximum elevation differences on new slabs, elevation data should be more useful for groups of homes. To test this hypothesis, a simulation study was conducted in which groups of 100 virtual slabs were distorted according to several different distributions of maximum slab distortion and the resulting elevation profiles analyzed statistically. The findings are presented in terms of cumulative distribution functions. An application using real data is presented to demonstrate how these results allow one to estimate postconstruction distortion for groups of residential slab-on-grade floors.

A major concern for projects involving deep excavations in urban areas is the response of adjacent buildings and utilities to excavation-related ground movements. Unfortunately, a purely theoretical approach to estimating building response to excavation-related deformations is not possible due to the variability of the many factors that contribute to the response. Consequently, building response must be estimated and evaluated primarily based on empirical observations and various structural approximations. The goal of estimating and evaluating building response is to provide limiting criteria that will safeguard the structure against unacceptable damage. Thus, estimating the extent of the building response and consequently the severity of excavation-related building damage is critical to establishing rational limiting criteria for excavation support system designs. The most common measure of damage severity is the onset and growth of cracks in interior walls of adjacent structures. Although several procedures have been suggested for estimating excavation-related crack growth, all of the procedures have a common aspect in that they require the input of a critical strain, or the strain at the onset of cracking, as a critical input parameter. This paper presents the results of three-dimensional finite-element analyses of a building adjacent to an excavation. The analyses were used to evaluate the magnitude of strain that developed in the interior walls in response to the excavation-related ground movements. This paper describes the procedures used to model and analyze the building. The paper also presents computed building responses at dates corresponding to observations of cracking and presents discussions of strain levels in infill panel walls where cracking was observed and in panels where cracking was not observed. The analyses showed that the initial cracking observed in selected infill wall panels could not have occurred solely in response to excavation-related deformations. Consequently, it was found that the wall panels cracked as a result of a combination of strains induced in the structure from self-weight settlement and excavation-induced displacements at the supports. These analyses allowed the writers to suggest critical strain criteria.

Aftershocks occur following an earthquake of large magnitude (referred to as the mainshock) and cause further damage to buildings that may have sustained damage in the mainshock. In this paper, an object-oriented framework is proposed to estimate seismic losses of light-frame wood buildings subjected to mainshock and aftershock sequences. Mainshocks are simulated as a homogeneous Poisson process, whereas aftershocks are simulated as a nonhomogeneous Poisson process. Back-to-back mainshock-aftershock nonlinear dynamic analysis is performed to determine the maximum interstory drift attributable to each earthquake occurrence (either mainshock or aftershock). Seismic risk is quantified in terms of economic losses in this paper. The damage loss (transition cost) and downtime cost are included in the loss estimation, considering a time-discount factor. Last, the proposed framework is demonstrated by an example that examines the seismic loss of typical light-frame wood residential buildings in the United States. The results show that aftershocks and downtime cost are important contributors to total seismic losses. Future work is identified to further investigate the effect of mainshock and aftershock sequences on seismic loss.

Terrazzo is a high-grade flooring widely specified by architects for its aesthetic and durable characteristics. However, misunderstanding of material behavior and specifications can result in early deterioration, leading to additional cost and questions of liability. Deficient terrazzo performance is usually avoidable and clearly unacceptable in a material specified for its durability. In this paper, examples are used to define common cases of inadequate performance and mitigation strategies. The underlying causes of terrazzo deterioration are addressed in regard to stress concentrations, differential movements, impact loads, and terrazzo material properties. Ultimately, expected performance relies on effective interaction among the multidisciplinary team working on the project, including the architect, engineer, contractor, and terrazzo subcontractor. It is therefore important to provide a comprehensive program of defined expectations, proper specifications, intelligent design and detailing, quality assurance of the installed product, and communication among the project team. With these in place, durable terrazzo flooring can be consistently provided.

To improve building maintainability by preventing defects, a scientific maintainability scoring system necessitates a centralized database of defects and their systematic analysis or grading. Unlike causes, impacts of defects are not well defined. This research establishes bottom-up, qualitative failure mode effect and criticality analysis (FMECA) as a suitable defect grading tool and develops criticality parameters applicable for buildings. For two major systems, nine subsystems, and 62 components of Singapore commercial buildings, 319 defects were identified. Thirty-four experienced facility managers graded 45% of them as critical in a five-point Likert scale during a face-to-face questionnaire. Most critical defects were from five mechanical-electrical subsystems, namely, sanitary plumbing, HVAC, elevator, electrical, and fire protection. They are rare but significantly affect users and system performance. Though four civil-architectural subsystems were simpler, their defects showed higher frequency and economic impact. These subsystems were basement, facade, wet area, and roof. Here, structural members are excluded as beyond the scope of regular maintenance. The proposed method aptly evaluated defects from both complex and simple subsystems whose general characteristics matched with the identified nature of associated defects. The knowledge elicited will contribute to developing a Comprehensive Maintainability Scoring System (COMASS) with guidelines weighted as per their ability to mitigate both critical and noncritical defects.

Repair actions are generally used to prevent failures and to maintain or extend the lifetime of deteriorating structures. To establish optimum inspection/repair planning for a structure, its performance under uncertainty should be assessed and predicted using probabilistic concepts and methods. This paper presents such an approach applied to deteriorating reinforced concrete (RC) structures under pitting corrosion. The inspection/repair plan is obtained from a probabilistic optimization process. Formulation of the extended lifetime for a given number of inspections is based on a decision tree analysis considering probability of damage detection. A damage detectability function is used to quantify the relation among damage intensity, quality of an inspection method, and probability of damage detection. The probability of repair representing the decision maker’s willingness to make a repair is also considered in the decision analysis. Effects of probabilities of inspection/repair and number of inspections on extended lifetime of an RC structure are investigated. To establish a cost-effective inspection/repair planning process, the formulation proposed is a biobjective optimization problem under uncertainty considering maximization of expected extended lifetime and minimization of expected total cost. The proposed approach is applied to an existing bridge.

This paper describes the structural aspects of the collapse of the Concorde overpass, crossing Autoroute 19, in Laval, north of Montréal. The original design and the reinforcing details for the thick cantilever slab that failed are discussed. Results from testing a simulated portion of the bridge with as-designed and as-built details are presented. The structural analysis results, by using various bridge design codes to determine the design forces, are compared. The results from nonlinear finite-element analysis, simulating the concrete deterioration, are used to explain the cause of failure of the thick cantilever slab under essentially its self-weight after 36 years in service.

This paper analyzes the raw database of the entire bridge inventory in the United States and derives distinctive bridge type-specific structural performances. The distributions, 15-year histories, and average ages of bridges and structurally deficient bridges of the various structural design and construction types are determined to study typical trends of structural deficiency. Based on the concept of structural deficiency and the objective of life-cycle expectancy, the multiple-criteria diagnostic approach of the analysis determines and compares the condition, durability, longevity, and equivalent performances. The comprehensive results provide a national network-level comparative basis for the operational performances of all coded bridge types. The approach characterizes the probability of bridge structural system deficiency, consequences attributable to deficiency, and time to renewal. Thus, the structural performance levels reflect structural reliability and vulnerability indexes for bridge serviceability. The concept presents an objective comparison source for the long-term overall utility and value of bridge type alternatives and helps to identify life-cycle issues and the need for improvements to increase desirability of bridge types.

A probabilistic procedure for the assessment of the time-dependent reliability of existing prestressed concrete (PSC) box-girder bridges is presented. These bridges are subject to increased traffic loads and an aggressive environment, which result in structural deterioration such as cracking and corrosion. In this paper, a multiple-peak vehicle load model is proposed based on acquired traffic load data, which cannot be properly described by previous single-peak probability distributions. With the proposed vehicle load model, the maximal vehicle loads during the remaining life of bridges are obtained for evaluating the influence of the increase in traffic loads on bridge reliability. Time-dependent corrosion models are adopted to account for pitting corrosion because of chloride attack as well as uniform corrosion because of concrete carbonation. A degenerated shell element is used for accurate and efficient modeling of the PSC box-girder. Postcracking behaviors of reinforced concrete box-girders, simulated by using different crack models and elements, are compared with laboratory test results. To increase the efficiency of probabilistic analyses, an adaptive importance sampling method in conjunction with the truncated Latin hypercube sampling is used. Application of the proposed methodologies is demonstrated by a case study, in which the time-dependent reliabilities of a deteriorating PSC box-girder bridge are obtained.

To install the continuous welded rail (CWR) on the viaduct, it is necessary to consider the accumulated axial force owing to temperature difference and the additional force of the rail exerted by the track-bridge expansion as a result of temperature difference, the so-called track–bridge interaction. This paper used $A$-thermal fiber bragg grating (FBG) sensors which do not need the temperature compensation, and electronic sensors as monitoring instruments to detect performance changes in CWR axial force. These optical fiber sensors coupled with the developed track axial force calculation software and monitoring platforms calculate the axial force distribution along the track to be monitored. To better understand the influence of the change in the bridge’s structure expansion and the change in concrete slab strain on track axial forces, sensors are set up at bridge expansion joints (EJs), rail ends, and concrete slab beds. Monitoring results show that optic fiber sensors provide sensitive, clear, and stable signals. They are also durable and appropriate for long-term monitoring, providing a complete track safety warning system.

Density criterion for base materials is the most common practice in quality control and quality assurance for pavement construction. However, cases in which the base material has met the density requirement but turned out to be the cause of a premature failure exist. It means meeting the density requirements would not prevent the premature failures from occurring. Field studies indicated that these base materials are found to be either too weak to provide sufficient base support or too brittle, which causes cracks in base layers which in turn leads to secondary damage in other pavement layers. This paper documents the pavement layer moduli obtained from eight forensic investigations spanning 10 years. Falling-weight deflectometer and dynamic cone penetration tests were conducted to determine the layer moduli on sections that were either too weak or too brittle. In some cases, laboratory tests were performed to evaluate the base materials’ reactions to the stabilizers (lime or cement) and base susceptibility to moisture. On the basis of the analysis results, the following ranges of base moduli are recommended for flexible pavements with more than 2.5 million equivalent single axle load design traffic: greater than 345 MPa (50 ksi) for unbound aggregate base; and from 1,033 MPa (150 ksi) to 3,445 MPa (500 ksi) for stabilized bases. Because currently no construction control requirements to limit the base modulus exist, threshold values for base moduli established from the forensic studies described in this paper will be beneficial to minimize potential premature failure.

A qualitative analysis based on four private finance initiative (PFI) projects during the operational monitoring stage is demonstrated in this paper. The investigation focused on how the design and contractual risks were reflected and handled at the operational stage of the PFI projects. Some unforeseen project risks that occurred during the operational stage were highlighted, and more focus on the risk control of future PFI procurement from the various parties involved is recommended. The research process includes documentation review and a semistructured interview survey. It is found that the public sector still is liable to some unforeseen risks during the operational stage, although the private sector takes most of the risks according to the contract. Recommendations are made for further research and improvements on the PFI project management.