Journal of Performance of Constructed Facilities

During the 17 January 1994 Northridge, California, earthquake, a moderate earthquake, alleged non structural cladding panels and connections unintentionally participated in lateral load-resisting structural systems. As a consequence, unanticipated cladding damage occurred, including life-safety problems when dozens of panels fell and others were left hanging precariously. Experimental and analytical research studies have repeatedly shown that cladding does influence the behavior of building systems, often adversely. In spite of this, the stiffness, strength, mass, and damping properties of the cladding panels and connections continue to be ignored by designers. A rational basis must be developed and implemented for engineering all cladding that could post life-safety hazards and for designing heavy cladding as an integral part of the structure of three-dimensional building systems. Codes, practice, and university education must reflect this change. Leaders are needed in code development, building design, analysis, detailing, and fabrication for a collaborative, multidisciplinary effort to ensure predictable, reliable, and safe performance of cladding during seismic events, one issue of overall cladding performance.

This report describes a series of field tests of multibeam prestressed box girder bridges. The objective of the test was to investigate the in-situ performance of the grouted shear keys, located at the longitudinal joints between adjacent girders. The longevity of these joints can be a problem with this type of bridge; failure of the joint will typically not only compromise the load-sharing mechanism between adjacent girders, but also lead to the failure of the deck waterproofing system, with attendant corrosion problems. The tests consisted of monitoring relative displacements occurring across the intergirder joints, as well as bending strains in the girders themselves during passes of a preweighted tandem-axle dump truck, with axle loads typically in the range of 84.7 kN (19 kips). Relative displacements were measured with an especially designed transducer, having a resolution on the order of .00254 mm (0.1 mil), which was bonded to the underside of the bridge across the intergirder joints. Bending strains in the girders were measured with conventional foil strain gauges, having a gauge length of 38 mm (1.5 in.). All bridges tested exhibited relative displacements across at least some of the joints, which indicated a fractured shear key.

Major dams in the world are often instrumented and monitored in order to detect anomalies, and to enable a timely response either in the form of repairs, reservoir management, or evacuation. Traditionally, the analysis of monitoring data has been done on an instrument-by-instrument basis, which is tedious to perform and difficult to interpret. The objective of this paper is to propose a statistical estimation procedure, principal component analysis, to identify the principal modes of deformation of the dam from a historical record of instruments. This approach reduces the number of analyses that need to be performed, provides a more representative model for the response of the dam, and a more robust model for the detection of the onset of anomalies in the response of the facility.

In order to resist sulfate in soil or ground water, concrete must be of high quality, be well consolidated, be as impermeable as possible, and have sulfate-resistant cement. This paper describes the damage to concrete flatwork caused by sulfate attack. Four of six laboratory tests indicated that the silty clay fill supporting the concrete flatwork had a “severe” concentration of soluble sulfate. Expansion of the silty clay fill probably uplifted and cracked the concrete flatwork. Then moisture migrated up through the flatwork cracks and upon evaporation, the salts were deposited on the concrete crack faces. This increased the soluble sulfate concentration causing the concrete paste to literally dissolve away. One method to prevent the concentration of sulfate at flatwork cracks is to provide a capillary break, such as a layer of 2 cm (3/4 in.) open-graded gravel, beneath the concrete flatwork.

A case history of pavement deterioration is described. There were three pavement concerns: an inadequate pavement section, seepage of water through the base material, and settlement of utility backfill. The main pavement deficiency was the aggregate base, which in some locations was much less than the original pavement recommendations. Water migrated into the base causing the compacted clay subgrade to become wet with a corresponding reduction in shear strength. Because of the thin aggregate base, the pavement section could not sustain the traffic loads, resulting in alligator cracks, rutting and, in some cases, complete disintegration of the pavement. It was also observed that water was flowing through the aggregate base. For inclined pavements with a permeable aggregate base constructed on top of a clay subgrade, theoretical analysis indicates that the majority of water will flow through the base material instead of into the subgrade.

The behavior of residential structures subjected to large ground movements was evaluated by observing the response of six test foundations constructed over an advancing longwall mine panel. The foundations were subjected to both horizontal and vertical movements, with the induced curvature from the vertical movements being the primary damage mechanism. A plain concrete footing experienced significant damage, with cracks up to 18 mm in width. Both posttensioning and the use of minimal standard reinforcing were effective at controlling foundation damage, with the standard reinforcing being much more economical. Reinforcing amounts only sufficient to insure the yield moment is greater than the cracking moment are necessary. Additional measures may be necessary to provide adequate stiffness for preventing superstructure damage.

High-wind events such as storms and hurricanes cause severe damage to low-rise buildings (housing, schools, and industrial, commercial, and farm buildings). Roof claddings often suffer the worst, which then leads to accelerated damage to the whole building. Australia leads the way in solving this international problem through extensive research and development work, and has adequate documents in place. This paper first illustrates briefly the nature of high-wind events and then the commonly observed damage to buildings. Australian research work and design practice are then described, based on which suitable design recommendations for wind-resistant buildings are presented.