Journal of Performance of Constructed Facilities

Projected masonry bays are a common feature on many historic buildings. Over the course of the last 100 years or so, bays have been constructed utilizing a wide variety of masonry and framing configurations to provide structural support to these eccentric architectural elements. Mechanisms to resist the natural tendency of the bay construction to “sag” and/or rotate away from the plane of the wall have historically included corbelled and/or cantilevered masonry, steel tension ties, counterweight beams, and a variety of steel, concrete, and wood framing configurations. Many of these support system mechanisms have satisfactory in-service performance, whereas others have been found to permit undesirable behavior. Unanticipated flexibility in the bay support may result from improper interaction of the various structural components. Distortion of the bay construction leads to distress, premature deterioration, and sometimes failure within the bay assemblies. This paper will present a case study pertaining to the investigation, analysis, and repair of a projected masonry bay system involving several different support mechanisms and will focus on a specific structure in which effective support assemblies were integrated into the existing building fabric.

The current North American design standards provide seismic force modification factors for the rectangular masonry structural walls category only; no similar provisions for flanged and end-confined masonry structural walls exist. This study demonstrates that seismic force reduction factor ($R$) values calculated for rectangular walls was close to 5.0, which is consistent with the value stipulated by the ASCE 7, and was 36 and 90% higher for the corresponding flanged and end-confined walls. The deflection amplification factor ($Cd$) values calculated for rectangular walls were higher than specified in the ASCE 7 for the special reinforced masonry wall category. Values of the ductility-related force modification factor ($Rd$) for flanged and end-confined walls were, respectively, at least 30 and 100% higher than those of rectangular walls specified in the National Building Code of Canada (NBCC). Quantification of the seismic response parameters within this study is expected to facilitate adoption of the flanged and end-confined wall categories in North American masonry codes as a cost-effective technique to enhance the seismic performance of masonry construction.

Long cantilevered balconies used as seating areas in auditoriums, theaters, churches, and stadiums are often susceptible to excessive vibrations because of crowd movements. Measurement and analysis of the responses of such structures when subjected to human movements can provide a reasonable estimate of their dynamic properties. However, it is generally very difficult to artificially excite such massive structures with a measured input force at the same level as that exerted by a crowd. In addition, it is not yet well understood how human occupants’ presence may change the dynamic properties of these structures. This paper presents details of a remote vibration monitoring system (RVMS) installed on a large cantilevered balcony structure to collect the vibration records generated by rhythmic crowd activities. The results of the studies conducted indicate that the presence of human occupants resulted in a consistent reduction in the natural frequencies of the structure and an increase in the damping ratios for higher modes. Conclusions were also drawn regarding the applicability of the damping ratios recommended by a number of standards and design guides for the structure used in this study.

This paper examines the seismic response of two full-scale pile-to-deck connections of marginal wharves built in the 1980s at the Port of Los Angeles. The first test represented a precast pretensioned concrete pile-deck connection at Berth 145. This berth required extending the deck for a new crane rail and a new line of piles. The proposed wharf upgrade considered leaving the existing piles if their lateral displacement capacity exceeded the expected seismic demands. A representative connection was tested to assess the rotation capacity under reversed cyclic loading. The second test represented a typical steel pile-deck connection used in Berth 226. In this structure, the piles support a crane rail. A reversed cyclic loading test was also conducted to assess the connection deformation capacity. Both connections were able to carry the imposed axial load throughout, even when the flexural strength had degraded. The precast pile-deck connection maintained the flexural strength up to a rotation of 0.04 rad, and the steel pile-deck connection maintained its flexural strength up to a rotation of 0.015 rad.

Small-format aerial photography (SFAP) is a low-cost solution for bridge-surface imaging and is proposed as a remote bridge-inspection technique to supplement current bridge visual inspection. Providing top-down views, photos taken from airplanes flying at 305 m (1,000 ft) allow for the visualization of subinch (i.e., large) cracks and joint openings on bridge decks or highway pavements. An onboard global positioning system can help geo-reference images collected and allow automated damage detection. However, the site lighting, surrounding tree shades, and highway surface reflectivity may affect the quality of the images. Several examples of bridge evaluation using SFAP are presented to demonstrate the capability of remote sensing as an effective tool for bridge-construction monitoring and condition assessment. A deck condition rating technique for large crack detection is proposed to quantify the condition of the existing bridge decks.

A forensic study was conducted to investigate the premature cracking distress on an ongoing construction project on State Highway (SH) 24. Transverse cracks occurred at approximately every 9–15 m (30–50 ft) along the 9.6 km (5.9 mi) project. The field tests involved both destructive tests, including trenching and coring, and nondestructive tests, including falling weight deflectometer (FWD) and ground-penetrating radar (GPR) tests. The laboratory tests mainly included cement-treated base material and asphalt mixture material series tests. By integrating all the test results, it was concluded that the premature cracking was originating from the cement-treated base (CTB). Although CTB is not a new concept in pavement construction, stabilization of base materials is a complex process, which, if not handled properly, may lead to premature failures. The two primary factors that contributed to the premature failure are (1) an excessive amount of cement in the CTB, and (2) a high moisture content when the CTB was compacted (almost 2% above optimum moisture). It was believed the possibility of premature failure could be reduced significantly, if the lab verification tests were conducted on the CTB before construction started. Pavement life analysis was conducted to evaluate the current structure adequacy to sustain future traffic. In addition, extensive material design was conducted for the final wearing course asphalt mixture, which was intended to mitigate the effect of existing cracks by resisting crack propagation from the underlying structure.

In-place nondestructive simulation evaluation of the remaining bending strength of wooden utility poles is vital to the continued and successful operation of the poles, viability of the electrical transmission and delivery system, and reduction of system disruption potential. A methodology for nondestructively assessing the strength of in-place wood utility poles was developed and is proposed in this paper. Because of the nonhomogeneous and anisotropic nature of wood and the variability of in-place utility poles, a deterministic approach does not seem feasible. The proposed method combines multiple variables to statistically predict the breaking strength, or modulus of rupture, of wood poles. The full-scale testing methodology was tested on real life poles. Results from in-field simulation tests were correlated to data from failure testing of the full-scale poles. The proposed static bending approach is quite accurate, utilizing a device that applies a horizontal force on an in-place utility pole and measures the resulting deflection. The slope of the force-deflection curve and the pole moment of inertia from a regression analysis correlate well to the breaking strength of the poles. Additionally, a method for measuring and adjusting for the tilt of the utility pole under test was determined. Full-scale field simulated testing and break testing data that provide significant insight into nondestructive wood pole testing are provided in this paper. Recommendations for increasing the validity of the proposed model with additional test data, together with implementation of additional relevant parameters, are made.

The residual static load (RSL) is defined in the ASCE 74 standard as the loading criteria for a broken wire condition. However, a transmission line designed on the basis of the RSL may be unsafe because the RSL takes no account of the dynamic impact effect. This study develops a general finite-element analysis procedure to resolve the conductor breakage problem and to determine the broken wire load (BWL) for the transmission-line design. The developed procedure can account for the impinging and friction effects between the broken conductor and the ground. A three-span transmission line with the line configurations previously tested at full-scale was examined, and the results showed that the developed procedure could predict a realistic time history of responses. The developed procedure was then applied to a nine-span transmission line, and the results showed that the peak BWL was significantly greater than the RSL, indicating that the peak BWL instead of the RSL should be used to check the extreme load case for the conductor’s breakage condition.

The current International Building Code (IBC) allows wood-frame (i.e., light-frame wood) construction to be three stories high or four stories high if sprinklers are included in the design. Several jurisdictions within the United States have opted to allow four and five stories if sprinklers are present. This paper presents a comprehensive numerical analysis of a six-story wood-frame building designed on the basis of the 2006 IBC methodology and a building designed by using the direct-displacement design (DDD) approach. The objectives of the design methods are different and are explained herein. Incremental dynamic analysis (IDA) was used to numerically investigate the response of the buildings on the basis of two criteria: the peak interstory drift and the building’s base shear capacity. Gypsum wall board was included in both models, but exterior finishes (e.g., stucco) were not.