Journal of Performance of Constructed Facilities

An extensive experimental study was performed to apply acoustic emission (AE) monitoring to assess the bond strength of corroded large-scale RC beam specimens. This paper demonstrates the data obtained from AE monitoring of these RC beams, while being exposed to localized, accelerated corrosion procedures at one of the end sides of each beam. Five RC beams were corroded through an electrically accelerated corrosion process to reach 5, 10, 20, and 30% of steel mass loss. The beams were constantly monitored during the accelerated corrosion tests via half-cell potential (HCP) measurements and three attached AE sensors distributed along the span of the beam. During the test, the corrosion and cover crack initiation were monitored and the crack width measurements were attained daily. The results showed that the analysis of AE signal parameters acquired throughout the corrosion period enabled the detection of both corrosion and cover crack onset earlier than HCP readings and prior to any signs of visual cracking, regardless of sensor location. Acoustic emission parameters examined in this paper {cumulative number of hits, cumulative signal strength (CSS), historic index [$H$ ($t$)], and severity ($S_r$)} were shown to be highly correlated with the level of corrosion propagation. The study also presents developed damage classification charts interrelating the results of crack growth and mass losses to the average values of $H$ ($t$) and $S_r$. These charts can be used to quantify the level of deterioration of RC structures due to reinforcement corrosion.

Integral watertight concrete structures can be an effective and durable solution for underground facilities. The paper presents an evaluation of the major causes of and responsibilities for wide through cracks in a large mat foundation. A large number of leaking cracks with a width of up to 0.8 mm were observed in the mat foundation. Considering the importance of water leaking through the cracks in terms of the serviceability and durability of watertight concrete structures, emphasis is placed on the effect of early-age temperature rise in mat foundation. Mitigation strategies to prevent the formation and propagation of early-age through cracks are discussed. The concrete technology methods are aimed at reducing the concrete temperature by using low-heat generating concrete. In general, when assessing the risk of early-age cracking, drying and autogenous shrinkage may be ignored. The role of cement type, concrete cover and reinforcement to limit the width of cracks was analyzed.

Signs of premature deterioration are customarily observed in areas adjacent to joints in concrete pavements. These areas, especially in cold regions, continue to hold water/solution (due to application of deicing salts) long after wetting events. This solution can contribute to the deterioration process by physical or chemical mechanisms. Until now, the root causes of joint deterioration are not fully understood because a multitude of reactions and mechanisms may be responsible for this deterioration. The goal of this study is to use forensic evaluation to classify the source of this damage and identify aspects contributing to joint deterioration of regional roads (chloride-based salts are directly applied) and residential streets (salts are borne by vehicle tires) in Winnipeg, Manitoba, Canada. In addition to visual inspection, this study characterizes the quality of air-void parameters and bulk properties (e.g., absorption, penetrability) of cores collected from both regional roads and residential streets. Also, the alteration of microstructure in concrete was assessed by thermal, mineralogical, and microscopy studies. The results revealed that the cores collected from regional roads had high intensity of microcracks and most air voids (both small and large) were filled with various levels of secondary depositions compared with the cores collected from residential streets. The deterioration of concrete is explained by a combination of physical and chemical aspects, due to the interaction of salts, freezing/thawing cycles, and wetting/drying with the hydrated paste.

Seismic vulnerability of a two-story stone masonry building supported on U-FREIs (unbonded fiber-reinforced elastomeric isolators) is evaluated. The prototype building is located in Tawang, India, and is the first such U-FREI-supported prototype masonry building constructed anywhere in the world. The base-isolated (BI) building is numerically simulated by three-dimensional nonlinear finite elements (FEs). Experimentally obtained mechanical characteristics of U-FREIs are used in defining the nonlinear properties of the model used for simulating U-FREIs. Reduction in seismic vulnerability of the BI building as compared to that of a fixed-base (FB) building is evaluated using analytical fragility curves. Significant reduction in probability of exceedance of all the considered damage states of BI buildings is observed as compared to that of FB buildings.

Forced-vibration tests were conducted on the Daniel-Johnson multiple-arch dam located in northeastern Quebec, Canada. This outstanding structure for its size and complexity is the largest multiple-arch dam in America. The tests aimed to determine the dynamic properties of the dam-reservoir-foundation (DRF) system to be used as a basis for the update of a finite-element model of the system required for further seismic performance assessment. The test procedure is described and the modal properties derived from the recordings are presented together with the extraction procedure, which was particularly complicated because of the coupling of the numerous global and local modes of such a complex structure. Several linear three-dimensional finite-element models were developed to be correlated with the measured dynamic properties. A parametric study on the dam-foundation elasticity was first performed, and the influence of the reservoir water modeling was then extensively studied. The selected model properties resulting from the numerical correlation study enabled reproduction with good accuracy of eight of the measured vibration modes, making the model suitable for seismic analyses.

This paper presents the assessment of a fire-damaged reinforced concrete (RC) supporting structure of an arc furnace. The arc furnace rests over a thick RC slab supported by nine RC columns. During the process of operation, the bottom steel plate of the arc furnace was damaged locally. Liquid hot metal at a temperature of approximately 1,400°C came out through a damaged thermocouple hole and spread out over the floor. Visual inspection, rebound hammer (RH) tests, ultrasonic pulse velocity (UPV) tests, and concrete core sampling, etc., are carried out for the assessment of the present condition. Low UPV and low compressive strength are observed from the in situ measurements, which indicate loss of integrity of the fire-affected concrete. A hybrid methodology is adopted wherein in situ material parameters of the fire-damaged structure from the concrete core samples and rebar samples are used in the analysis to check the structural adequacy of the fire-damaged structure. It is observed that the residual strengths of the structural components are found to be adequate for the given loading. Furthermore, necessary repair measures are suggested to improve quality, integrity, and long-term durability of the furnace-supporting structure.

The watertightness of facade windows is a key aspect for guaranteeing habitability requirements in buildings. However, given the difficulty in reproducing atmospheric stress conditions outside the laboratory, no consolidated method exists for applying the test to facades in use. This study proposes an innovative method to test on-site the watertightness of facade windows simulating the impact of rain and wind. This was achieved by means of depressurization using the blower door test in interior rooms combined with the projection of exterior water. The use of nondestructive testing techniques supported by practice yielded an effective method of control and diagnosis capable of determining critical points susceptible to water leakage for windows on site.

Frost heave of foundation materials causes severe joint deterioration in concrete pavements. Sufficient freezing depth, continuous water supply, and frost susceptible geomaterials are the three necessary factors leading to frost heave. To investigate the frost actions of deteriorated pavements with frost heaves at joint locations, the longitudinal pavement surface profiles were plotted by measuring vertical heaves crossing transverse joints. Specimens were cored to determine the moisture conditions at different layers. Ice lenses were found at layer interfaces, and frozen base layers with low permeability contributed to trapping water within joint spaces. Another objective of this study was to determine the local freeze-thaw conditions in pavements. Temperature sensors were installed during the reconstruction to estimate the frost penetration depths, lengths of freezing and thawing periods, and number of freeze-thaw cycles at different depths. Up to 1.1 m frost penetration depth was found, and it showed various lengths of freezing periods. The last objective was to evaluate the frost-heave and thaw-weakening susceptibility of the reconstructed foundation materials. Results indicated that all three geomaterials were medium frost-heave susceptible, and the soft subgrade showed high thaw-weakening susceptibility.

Tube-to-transverse plate stiffened connection details are widely used in cantilevered sign support structures in New Jersey and many other states. This stiffened fillet-welded connection showed a lower stress level than the socket connection at the fillet weld toe at the base. However, the tip of stiffener location on the tube wall becomes a more critical fatigue crack location according the AASHTO. This paper evaluates a reliability-based fatigue assessment for the potential crack initiation at the tip of stiffener. A synthetic analysis of 1-h averaged wind speed wind data from two New Jersey weather stations was performed. The wind data were transformed to the transient domain to represent the turbulent natural wind phenomena and the effective stress ranges and number of cycles were obtained using the rainflow counting technique. To evaluate fatigue resistance of these connection details, existing fatigue test data of fatigue crack initiation at the tip of stiffener were analyzed and a statistical analysis of linear stress-life ($S–N$) fatigue data provided fatigue coefficients. The probability of fatigue crack initiation versus time of sign structures with different orientations of sign panel was determined using a reliability-based fatigue assessment approach. Results showed that the probability of crack initiation during the life span is dependent on wind cycles, orientation, and fatigue coefficients obtained from experimental S–N curves. The results can be used to estimate inspection frequencies of this critical detail in sign structures.

With the rapid development of large-span space structures, it has become increasingly important to develop earthquake-resistance theory to a level that is much more safe under unexpected earthquake events. Motivation arises in part due to the expected seismic performance of large-span space structures being subverted in the 2013 Lushan earthquake. The seismic damage suffered by space double-layered lattice structures during the Lushan earthquake, and the possible causes for the structural damage, are investigated and discussed in this paper. The damage distributions in typical space double-layered lattice structure such as the Lushan Gymnasium and the Lushan Middle School Gymnasium are described in detail, and the possible causes for the observed damages are summarized. To further study the seismic performance of typical space double-layered lattice structures, numerical simulations were conducted using finite-element software, and the findings were compared with actual damage investigation results. Some recommendations are made for antiseismic designs of double-layered lattice structures.

A reticulated shell is one of the conventional long-span space structures, prone to progressive collapse under a severe earthquake because of its unique single-layer feature. However, the collapse mechanism of this type of structure has not been well studied. In this paper, a numerical modeling technique using the fiber beam elements is developed. A corresponding material model, based on the inclusion of damage accumulation, is also developed in order to determine the failure criteria of structural members. An effective way to simulate the buckling behavior of the structural members is also used in the numerical simulation. The relevant numerical method is developed and validated against experimental tests: good agreement is achieved. Based on this numerical method, a parametric study of the reticulated shell under severe earthquake loading is performed, the responses of the structure are investigated, and a three-stage collapse mechanism of this type of structure is observed.

In the current study, three one-third scaled beam-slab substructures comprising a cast-in-place reinforced concrete specimen and two precast concrete (PC) specimens were tested under a pushdown loading regime to investigate the effects of connection types on the behavior of PC structures to mitigate progressive collapse. A special link was designed to enhance the connection between PC slabs and PC beams. The test results, including load-displacement curves, ultimate load capacity, ultimate deformation capacity, and local strains, are presented. The failure mode and mechanisms of load redistribution are further discussed. It is demonstrated that the PC specimen with welded connections achieved brittle failure with the lowest ultimate load capacity and deformation capacity. Although the lowest initial stiffness and first peak load capacity were achieved in the PC specimen with pinned connections, its large rotational ability ensured that the specimen failed in a ductile manner, which allowed the development of considerable tensile membrane actions. The main source of the membrane action was from the reinforcement mesh in the topping layer. Despite severe separations occurring between the PC slabs and beams, no PC slab collapsed even though the maximum displacement was larger than double the beam span.

The purpose of this paper is to present information on the damage resulting from pounding between adjacent buildings during the 2015 Gorkha earthquake. The cases of pounding observed in the affected region of central Nepal are classified into five damage severity levels. Typical and unique cases of pounding damage are highlighted and discussed. Although poundings between adjacent buildings were rarely observed in Kathmandu Valley, it was relatively more frequent in hilly regions. Pounding events observed in Kathmandu Valley were primarily confined to multistoried RC structures. Pounding damage was also observed between masonry structures particularly at hilly urban settlements in Kabrepalanchok and Sindhupalchok district. Multiple cases of pounding between masonry structures with adjacent RC structures were also observed. Pounding damage observed in the field are presented in terms of various building configurations for the three categories of buildings involved, i.e., between RC structures, between masonry structures, and between RC and masonry structures. Pounding resulted in severe damage to masonry buildings. Based on the observations, building configurations that are vulnerable to pounding damage and distributions of pounding damage based on locality are discussed.

As indispensable electric power equipment in substations, high-voltage power transformers have experienced severe damage in past earthquakes. This paper illustrates an earthquake-damaged 500-kV power transformer: all three 550-kV bushings fractured, oil conservator supports were sheared off, and leaked transformer oil caused a fire. A detailed finite-element model of the power transformer was developed. The modal and response-history analyses using the finite-element model were conducted to investigate possible reasons for the power transformer earthquake damage. The results indicated that the local modes of the transformer components, such as bushings and turrets, and the oil conservator dominate the power transformer vibration. Spectral accelerations at the top flange plates of the turrets on the transformer tank were significantly amplified for the transformer bushings. Peak resultant bending moments at the bottoms of the air-side insulators of the 550-kV bushings subjected to the Wenchuan earthquake motions exceeded their bending capacities. Accelerations for the oil conservator were also greatly amplified, thus the oil conservator supports suffered large translational and torsional deformations to the earthquake motions. It is concluded from the earthquake damage and seismic analyses that this type of power transformer is vulnerable to strong earthquakes because the earthquake effect is not adequately considered in the power transformer structural design.

This paper presents two case studies of performance analysis of slopes reinforced using micropiles. Finite-element analyses were performed using the shear-strength reduction method for limited equilibrium analysis (i.e., factor of safety). Different mitigation designs for micropiles were compared in each case, where Case 1 included underpinning and strengthening with inverted L-shaped micropiles and Case 2 included reinforcing with gantry-style micropiles. In this study, performance measures, including reinforcement efficiency, deformation distribution, settlement of supported walls, and safety factor, were carefully examined and are here presented in detail. In summary, the proposed micropile applications were found to provide foundation stability and inhibit displacement in order to strengthen the studied slope. Wall underpinning with inverted L-shaped micropiles was found to further improve the safety factor, total displacement, and soil subsidence. In both cases, the direct benefit of installing single-row vertical micropiles to form a retaining wall in the ground was enhancement of the safety factor by approximately 6–40% and reduction of maximum displacement is significantly reduced from approximately 53–67%. In Case 2, micropiles with a gantry configuration were found to enhance the safety factor by a maximum of approximately 59% and to reduce total displacement and soil subsidence by approximately 73 and 84%, respectively.

The safety and serviceability of civil infrastructures have to be ensured either as part of a periodic inspection program or immediately following a given hazardous event. The use of digital imaging techniques to identify the deformed or deteriorated surfaces of structures is a substantial area of research and aims to investigate a number of unknown parameters, including damage quantification and condition rating. This manuscript illustrates the integration of previously developed fuzzy logic–based decision-making tools with the currently developed image processing algorithm to quantify the damage for the condition rating of civil infrastructures. The proposed integrated framework exploits visual specifics of different elements of the infrastructure to perform automated evaluation of structural anomalies such as cracks and surface degradation. Two different image segmentation tools, (1) bottom hat transform and (2) hue, saturation, color (HSV) thresholding, are applied to identify the surface defects. The developed image processing software is used with the fuzzy set framework proposed in the previous research to gauge the damage indices due to various deterioration types like corrosion, alkali aggregate reaction, freeze–thaw attack, sulfate attack, acid attack or loading, fatigue, shrinkage, and honeycombing. Case studies of a long-span bridge and a warehouse building are illustrated for concept validation. The refined comprehensive method is presented as a graphical user interface (GUI) to facilitate the real-time condition assessment of civil infrastructures.