Journal of Performance of Constructed Facilities

Stockbridge-type tuned-mass dampers are commonly used in highway sign and traffic signal support structures throughout the U.S. to reduce wind-induced and truck gust–induced vibrations. Effectiveness of these dampers in mitigating excessive structural vibrations, and thereby preventing connection failures and the development of fatigue cracks in tubular members, is highly dependent on the dynamic characteristics of both the damper and the structure. In addition, the expected amplitude of vibration should be taken into account when designing damping devices for a given structure because damping is a function of both frequency and amplitude of structural motion. The practice of optimizing the damper design for specific structures, however, is very limited, and the same number and configuration of dampers (with identical dynamic parameters) are universally used in many structures, irrespective of their span length and weight. To achieve optimal damping performance for highway sign trusses, this paper investigates the dynamic behavior of dampers through a series of laboratory experiments and a simplified analytical model. The testing and analysis results suggest significant improvement in vibration response and fatigue performance of structures over the currently installed dampers by implementing a few simple recommendations for damper selection.

This paper provides a straightforward way to evaluate tunnel settlement caused by land subsidence in the soft deposits of Shanghai. By analyzing field measurements of tunnel settlement and land subsidence, it was found that the tunnel settlement was caused by ground subsidence under the tunnel, and was unrelated to the compression of the upper soil layers. Because significant compaction of the upper layers can occur due to urban construction, the measured land subsidence, which is the ground surface subsidence, cannot represent the sublayer subsidence. To solve this problem, this paper takes metro stations as the monitoring point at the depth of the tunnel, and uses a cubic spline function to fit the line of the station points. The derived fitting curve is then used to represent the ground subsidence under the tunnels. The rationality of taking the stations as monitoring points is verified based on a load transfer analysis. The proposed method is applied to investigate the settlement of metro tunnels in Shanghai. It was found that land subsidence–induced settlement accounts for 62.5% of the maximum cumulative settlement in some sections of Metro Lines No. 1 and No. 2 up until 2010.

Bridge superstructures built with adjacent precast concrete voided members have the advantages of low profiles, faster construction times, no requirement for deck formwork, and the consequent reduction of the duration of workers’ exposure to construction vehicles and traffic. These reasons make this type of construction a preferred design. However, the mechanism that transfers load between adjacent beams often cracks, leading to leakage of salt-laden water runoff between the individual beams and to corrosion of the reinforcement. Two bridges in Virginia provide a contrast in performance: one box beam structure that was highly deteriorated after 31 years of service, and one adjacent voided slab bridge that was in relatively good condition after more than 50 years of service. Researchers conducted both destructive and nondestructive evaluations of beams from these structures, including in situ assessment of the concrete and prestressed reinforcement and sampling of the concrete core. Maintenance practices, concrete quality, and construction quality control appear to be the major factors influencing the conditions of these structures. Recommendations are provided to help prevent premature deterioration in future designs using adjacent precast concrete voided members.

Specimens of rib-to-deck welds and diaphragm-to-rib welds in steel bridge decks were tested to crack under cyclic load. The cracks were repaired by rewelding. After the rewelding, other treatments were considered, including polishing, heat treatment, and strengthening with carbon fiber–reinforced polymer (CFRP). Fatigue tests were again conducted on the repaired specimens. The microstructure of the rewelded areas was observed using a metallurgical microscope. The position and propagation of the new cracks were discussed to evaluate the efficacy of the repairs. The results indicated that new cracks occurred in the rewelded zone. After the initial cracking of roof-to-rib welds, crack propagation remained at a similar speed. Polishing, heat treatment, and CFRP strengthening can improve the fatigue life after a rewelding repair; the best rewelding timing is suggested to be the intermediate stage of crack propagation. The fatigue life after rewelding is determined by the new weld.

The Beijing Olympic Watchtower (BOW) is a landmark building with irregular shape and complex structural configuration; however, excessive human-induced vibrations of the sightseeing platform may occur during service, resulting in discomfort or panic of sightseers. Therefore, tuned mass dampers (TMDs) were designed to control the maximum acceleration under human activities. This paper presents the finite-element (FE) simulation of the vibrations under different human densities and moving frequencies. Field vibration tests on the fifth sightseeing platform of the BOW were further conducted to study the dynamic behavior of the platform and to validate the effectiveness of TMDs. The tests consisted of two free vibration modal tests (before and after the construction of the floor surface layer) and tests to measure the dynamic responses with controlled crowd moving. It is observed that prior to the use of TMDs, the accelerations significantly exceeded the threshold value, and there was lateral torsional vibration of the platform; resonance occurred as the crowd moved at 2.5 Hz, resulting in significant human discomfort. After the installation of TMDs, the human-induced responses were significantly mitigated, although due to the absence of a floor surface layer during the field measurement, there were some differences between the designed and measured modal frequencies, and the TMDs may not have fully reached their capacity.

Excavation-induced ground settlement causes adverse impact or damage on adjacent facilities. If a foundation pit is connected to the facilities, the responses of the facilities can be influenced by soil inside the pit. Through an extensive long-term monitoring program, this study investigates the responses of a newly built metro line to the excavations of foundation pits that shared structures with a metro station. The vertical displacement and the relative deflection of the rail tracks are analyzed in association with the excavation processes. The rotation of the metro station due to asymmetric soil unloading in each pit is studied. Moreover, a comparison of displacement development between the rail tracks and the supporting structures is carried out. Results indicated that (1) the rail tracks inside the metro station moved upward significantly, whereas the rail tracks in the tunnels settled slightly; (2) significant relative deflection of rail tracks was observed in the longitudinal direction and the maximum relative deflection was located at the connections between the metro station and shield tunnels; (3) the asymmetric soil unloading resulted in distortions of the metro station and the displacement of the rail track close to the pit was larger than the track located farther away from the pit; (4) the displacement developments of the rail tracks were concurrent with those of the interior steel columns and the common walls (the walls shared by the metro station and the foundation pits in this study) and the maximum displacements of the metro line were close to the vertical displacement of the common walls throughout each excavation; and (5) the superimposed effect caused by the deep excavations resulted in excessive movements of the rail tracks and noticeable dislocations were observed at the connection between the metro station and shield tunnels.

This paper describes a statistical survey on the pathology of architectural concrete surfaces, based on the inspection of 53 Portuguese buildings (110 surfaces). The most common type of anomalies in architectural concrete surfaces, their probable causes, adequate diagnosis methods, and suitable maintenance and repair techniques are studied via quantitative indicators, including correlations, in the application of the procedures and classifications from an inspection, diagnosis, and repair expert system for architectural concrete surfaces. The structural integrity of concrete elements is out of this paper’s scope. The results show the importance of a complete set of construction details, including the formwork specifications, which are essential for the surfaces’ quality. Related to two-thirds of the registered causes of anomalies, execution is a key stage, greatly benefiting from the use of specialized labor. Regular cleaning procedures and the enhancement of surface protection throughout the surface service life may also prevent a number of relevant anomalies, as the most frequent anomalies (approximately half the occurrences) are aesthetic.

This paper presents the analysis of the anomalies of external door and window frames, based on the inspection of 295 frameworks, in a total of 96 buildings in various locations in Portugal. With these inspections it was possible to validate a classification system previously proposed, determine the most common types of anomalies, their probable causes, related diagnosis tests, and respective rehabilitation techniques. This study also allowed determining some of the most common features usually found in this type of nonstructural element and correlate them with their materials, characteristics, position and location, and filling an existing knowledge gap on the short- and long-term behavior of these construction elements, which can be found in every new and old building. The analysis of these data is presented in various charts, to facilitate their interpretation and help identify the conditioning parameters in the performance and durability of this type of nonstructural system.

Due to urbanization, the number of residential buildings in coastal areas has increased significantly. Additionally, due to the increase in sea surface temperature associated with climate change, the intensity and frequency of hurricanes has also increased substantially. This paper presents a systematic framework for the optimal adaptation of residential buildings at a large scale under various scenarios of impending climate change during a long-term interval. Different adaptation strategies are investigated to ensure adequate structural performance and to mitigate the damage loss and adverse consequences to society. A genetic algorithm–based optimization process is adopted to determine the optimal adaptation types associated with buildings within an investigated region. The framework considers the probabilistic occurrence models of hurricanes, structural vulnerability of typical residential buildings, possible climate change scenarios, and optimization of various climate adaptation strategies in a lifecycle context. The proposed approach is illustrated on residential buildings located in Miami-Dade County, Florida.

This paper presents a validated support system for the inspection, diagnosis, and rehabilitation of flat roofs, with the purpose of standardizing and systemizing procedures within a proactive, diagnostic maintenance strategy for the prevention of anomalies in the flat roof system. In this study, a classification of anomalies is proposed and their most probable causes are presented, classified, and correlated. To aid the diagnosis of anomalies several in situ nondestructive methods were studied and classified, along with various rehabilitation techniques, in order to maintain and/or restore the functional properties of the flat roof system. Four correlation matrices were created and validated. These matrices relate anomalies with their most probable causes, with other anomalies, with the most adequate diagnosis methods, and with the respective rehabilitation techniques. Also, several forms were created containing essential information regarding each anomaly, diagnosis method, and rehabilitation technique. The proposed system was validated and calibrated through extensive campaign involving the examination of 105 flat roofs in various locations in Portugal. The use of the flat roof is gaining momentum in the construction sector, making it necessary to increase the effectiveness and objectivity of the actions to be taken upon the occurrence of anomalies.

This paper presents a numerical simulation on the collapse behavior and structural stability of a reinforced concrete superlarge cooling tower subjected to strong winds. Results demonstrated that the cooling tower locally collapsed inward because of a loss of material strength rather than loss of stability. The critical wind pressure corresponding to material failure was far less than that corresponding to buckling, according to elastic stability analysis. Finally, a parametric analysis was conducted to investigate the influence of design parameters on the wind-resistant performance of the tower, including the thickness of the shell structure as well as the concrete cover, reinforcement space of the shell structure, and reinforcement ratio of the shell structure. The research presented in this paper can help to clarify the collapse mechanism of superlarge cooling towers and contribute to the improved design of future towers.

This paper presents a discussion and the experimental proof-of-concept results of a novel ultrasonic testing (UT) method to identify the onset of delamination in reinforced concrete bridge decks. The novel UT method aims to provide a system that can be used to monitor and diagnose problems with the steel reinforcement, the steel reinforcement–concrete interface, and the concrete with a single approach. The method utilizes simple-to-interpret energy-based measurements and demonstrates the potential to examine large areas relative to most conventional nondestructive testing methods used for bridge decks. The proposed UT method monitors the leaked energy from a waveguide (steel reinforcing bar) to identify the type, onset, and location of deterioration in reinforced concrete. The proof-of-concept results presented in this paper illustrate the method’s ability to identify the onset of delamination (i.e., cracks) with widths less than 0.2 mm (0.008 in.) and its sensitivity to early stage corrosion. This paper also presents the summary of an in-depth review of literature on the status of commercial and research-based ultrasonic testing applications for reinforced concrete.

Excessive vibration of arch bridge hangers is a potential threat to the driving safety of high-speed trains; therefore, it is important to study the vibration characteristics and fast warning method of the hanger under environmental factors such as high-speed train load and ambient excitation. The Nanjing Dashengguan Yangtze River Bridge, the longest high-speed railway arch bridge in the world, with a design speed of $300\mathrm{km}/\mathrm{h}$, was selected as the research subject in this paper to investigate the fast warning method for rigid hangers in a high-speed railway arch bridge. This work analyzes the influence of environmental factors on the hanger’s transverse vibration characteristics using long-term monitoring data: several transverse vibration characteristics of the hanger, which are induced by train or ambient wind, were obtained through vibration data collected from the structural health monitoring system; eight train load cases were classified; and the methods of excluding train speed, temperature, and ambient wind are introduced. This paper proposes a method for establishing a reference service condition database including different subdatabases for a hanger. Finally, three reference service condition subdatabases are provided as examples to introduce the fast warning method. The conclusions show that environmental factors influence a hanger’s transverse vibration characteristics, and environmental factors must be considered in the condition evaluation of the hangers. All of these provide a systematic method for establishing a hanger’s reference service condition database, which can be used for fast warning of hanger anomalies in a high-speed railway arch bridge.

The colossal backlog of deteriorated concrete bridge decks draws attention to the importance of nondestructive testing (NDT) technologies as potential bridge condition assessment tools. The selection of NDT techniques to evaluate the current state of bridge decks is a decision variable. The foremost objective of this study was to conduct a comparative analysis of the common NDT methods for detecting subsurface defects in concrete bridge decks, particularly rebar corrosion, delamination, and cracking. Thus, impact echo (IE), ultrasonic pulse echo (UPE), ground-penetrating radar (GPR), infrared thermography (IRT), and half-cell potential (HCP) were appraised and ranked from the perspective of five performance measures: capability, speed, simplicity, accuracy, and cost. The information sought to identify the significance of the factors affecting the analysis was collected through a survey questionnaire of bridge engineers having extensive NDT experience. In order to incorporate the imprecise information and vagueness of human judgment in decision-making, the fuzzy analytical hierarchy process (FAHP) was employed. The fuzzy preference program (FPP) nonlinear method was adopted to determine the relative weights using MATLAB. The outcomes revealed that each technology can address specific bridge challenges. For instance, some technologies are associated with simplicity and lower cost, whereas others excel in accuracy or speed. Thus, a decision regarding the selection of a technology is guided by the objectives of the assessment and the most important performance parameters. The proposed methodology should assist bridge stakeholders in the rational appraising of NDT technologies for bridge decks based on a wide scope of information sources.

This paper presents the contribution of geomatics to the Seismic Risk of Monumental Buildings (RiSEM) project and illustrates the metric survey that was conducted on several towers in San Gimignano. Three-dimensional (3D) models and other graphical documentation supported the seismic vulnerability assessment, as required by Italian regulations. After the evaluation of still available databases, a laser scanning technique was chosen for acquiring 3D and high-resolution data, providing an exhaustive description, albeit limited to the external walls, of the towers under investigation. Through the accurate analysis of the structures, different graphical outputs have been defined for documentation purposes, describing the geometric characteristics of the towers, and for the assessment of a structure’s stability.

Open web steel joists (OWSJs) are prefabricated lightweight roof structure components that are designed for conventional loads in accordance with current standards and specifications. The resistance function currently used to design joists against blast loading is linearly elastic and perfectly plastic after the elastic deflection limit, which does not account for the different failure mechanisms of the joist components and system. For blast analysis and design of such roof trusses, further investigation of the behavior of these joists is needed. This paper presents numerical modeling and experimental evaluation of three different steel joist systems to failure to develop an accurate representation of the static resistance and energy absorption capabilities of OWSJ roof trusses to failure. Experimental results were used to verify robust explicit numerical models for predicting the static resistance function of OWSJ roof trusses. A deformable weld behavior was used to simulate all spot welds connecting web members to the joist top and bottom chords. Additionally, a criterion that predicts the failure of the end connection bearing seat of the joist system was included in the numerical simulation. The results of the numerical modeling and the experimental evaluation demonstrate the inadequacy of the current resistance models used for blast analysis purposes based on energy comparisons using various damage levels.

Prediction of structural response at the sudden removal of gravity load-bearing element in structures is an important issue in assessing progressive collapse potential of structures. In this paper, the effect of the postelastic stiffness ratio, as an effective parameter on the dynamic increase factor (DIF), in nonlinear static analysis of structures at the column removal is investigated, and a modified empirical DIF is presented. For this purpose, a series of low- and midrise moment frame structures with different span lengths and various numbers of stories are prepared, and the effect of the postelastic stiffness ratio on DIF is investigated, using several nonlinear static and dynamic analyses. For each postelastic stiffness ratio, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out, and modified empirical DIF formulas are derived. Finally, an empirical formula is recommended that relates to the postelastic stiffness ratio. The new modified DIF can be used with a nonlinear static analysis instead of a nonlinear dynamic analysis to assess the progressive collapse potential of steel moment frame buildings having different postelastic stiffness ratios.

Cracks observed in the secondary lining of loess highway tunnel may be caused by various sources, among which flooded surrounding loess is a possible one. This paper studies the influence of flooded surrounding loess on tunnel lining by carrying out in situ investigation, in situ permeability test, and numerical simulations. The statistical analysis of tunnel distress reveals that the length of vault cracks accounted for more than 70% of the total length of tunnel cracks, the cracks in two adjacent sidewalls between the uplink and the downlink were much longer than that of the other two, and the vault cracked more seriously than the sidewalls. Tunnel construction caused ground cracks that allow surface water to infiltrate through the cracks, which floods and deteriorates the surrounding loess, leading to cracking of the tunnel lining. An empirical equation for predicting water infiltration through in situ loess is proposed based on the in situ permeability test, which was used to determine the flooded cases in the numerical simulation. Numerical simulations based on finite-element method were performed to investigate the mechanical response of tunnel lining in different flooded cases. The simulation results show that the tensile stress in the vault and the compressive stress in the sidewalls increased significantly after the surrounding loess was flooded; the vault cracks were due to exerted tensile stress exceeding the capacity of tunnel lining, whereas the sidewall cracks were due to the high localized compression; and the vault cracks prior to the sidewall. The simulation results are generally in good agreement with the in situ observation. This case study may have value for optimal design and long-term operation of future tunnels constructed in similar geological environments.

This paper reviewed mechanistic-empirical (ME) design and analysis frameworks and identified a weak link: a cracking amount model connecting pavement damage (predicted from mechanistic-empirical analyses) and asphalt cracking distresses. The importance of cracking amount models has not received the attention it deserves. After reviewing all the available existing cracking amount models in the technical literature, a universal cracking amount model was proposed for fatigue and reflective cracking. The new model governed by two parameters ($\alpha$ and $\beta$) fits naturally into the general ME design system. Parameter $\alpha$ is related to pavement life and can be directly predicted from ME analysis because it is the time (or number of load applications) when accumulated pavement damage reaches 100%. Parameter $\beta$ is a shape parameter function of traffic, environment, subgrade, pavement structure and material properties, and existing pavement surface condition when considering asphalt overlays. Because parameter $\alpha$ can be determined by the ME design and analysis system, $t$, the key parameter in the new universal model, is to quantify parameter $\beta$. Both fatigue cracking data in the long-term pavement performance database and asphalt overlay reflective cracking data in Texas were used in this paper to demonstrate and calibrate the new model and develop the $\beta$ functions. In this paper, different $\beta$ functions were established for fatigue and reflective cracking. Further model validation and calibration with more field data, varied traffic load spectra, different environmental conditions, and different materials are still required.

Pile-wharf structures are one of the substantial facilities for marine transportation along the shorelines. Due to their logistical significance, keeping the pile-wharf structures operational under all circumstances is crucial. Seismic forces are one of the major threats that can disrupt the functionality of the pile-wharf structures. This paper focuses on the seismic evaluation and upgrade of an existing wharf structure in Turkey by using the performance-based evaluation principles of a displacement-based design approach. According to the insufficient seismic performance of the existing wharf structure, two retrofitting schemes were proposed that considered the practicality and cost-efficiency aspects. In both schemes, additional piles were used to withstand the seismic demands, eliminate the torsional irregularity, and increase the lateral stiffness of the structure. The key differences between the proposed retrofitting schemes were the numbers and layout patterns of the additional piles. The numbers of additional piles used in the first and second schemes were 18 and 15, respectively. This study indicates that the performance-based evaluation of wharf structures using a displacement-based design approach provides a thorough understanding of the nonlinear behavior of marine structures and that the addition of piles is a reliable method for improving the seismic performance of pile-wharf structures.

This study focuses on the partial seismic collapse of a building during the earthquake of L’Aquila (Italy) on April 6, 2009. Designed in the early 1960s, the seven-story building has a reinforced concrete frame structure. In elevation, above a first basement and a ground floor, three wings rise. The collapse affected the north wing, where all the columns at ground story and three columns, located at the interface with the other wings, failed on the full height. In the same area, subjected to strong distortions, a third collapse mechanism involved (at stories 1–4) a beam supporting a nonstructural wall inserted in recent renovation works. Previous investigations explained why the collapse was confined to the north wing, providing (and based on) the knowledge of the building to the date of the earthquake in terms of geometry, material properties, acting loads, and seismic input to the site. This study aims to simulate the structural response during the earthquake to investigate the sequence of the different mechanisms and their possible interdependence. Nonlinear dynamic analyses on OpenSees adopt a refined three-dimensional finite element model with beam-columns fiber elements and the components of the ground motion at site. Results up to the collapse onset (1) satisfactorily simulate the identified collapse mechanisms; (2) clarify the interaction and the likely sequence among the different mechanisms; and (3) highlight the negative role of the nonstructural wall in the collapse. Conclusions provide comprehension of the past design procedures and of the possible flaws affecting the structures of the time.

Investigating causes of water main failures can help utilities reduce their frequency and save on lifecycle costs, but procedures are not well established in most utilities. A process to track failures is recommended for asset management programs, and it requires effective management of data from failure sites for ultimate use in decisions. Practices for data collection at failure sites show a mixture of approaches, which are not always integrated with enterprise databases. Current investigative practices split into how frequent minor and largely infrequent major failures are handled. Minor failures are treated like maintenance events, with data entered on forms for transfer to databases. Major events are normally handled by separate investigations, but procedures are not standardized. Water utilities can learn from procedures for investigating natural gas pipeline failures, which follow protocols that would apply to higher-consequence events. Standardization in water main data categories could make asset management and failure investigations more effective.