Journal of Performance of Constructed Facilities

The writer is engaged by the Occupational Safety and Health Administration (OSHA) to study the National Bureau of Standards (NBS) report on the L'Ambiance Plaza Building collapse and develop supplemental information for its use in legal proceedings. The study includes a review of the design of the lifting collar/shearhead assemblages. The paper is a summary of that review and the, writer's interpretation of subsequent evidence. Copies of design calculations and contract drawings are studied. In the paper, the absence of consideration of the effect of the lifting conditions on stresses in the arm channels in these calculations is noted. Questionable design details for welds connecting lifting angles to arm channels and header bars to header channels are also noted. The faulty condition of some of these welds as shown by lifting collar sectioning is illustrated. Evidence presented after the negotiated settlement of November 1988 reinforces the writer's finding that any of these deficiencies, and particularly the combination of unwise welds poorly executed, could have resulted in the initiation of the collapse. Recommendations for further investigation of these deficiencies are presented.

Full‐scale static and dynamic load tests are conducted for two precast, posttensioned reinforced concrete viaduct girders 22.3 m long. The first girder deflects 19.3 mm at midspan when subjected to a 3,240 kN static load, simulating the superimposed dead load and the RL loading of $\mathrm{BS}5400$ for railway bridges. The second girder is subjected to the dynamic load generated by an empty six‐car train traveling at 30, 60, 70, and 74 km/h. Under the dynamic loads, the midspan strains and deflections are approximately equal to those under the static axle loads. The results show that the longitudinal force transmitted to the piers by an emergency braking is larger than that created by normal traction, the fundamental frequency of the girder is 4.2 Hz, and the forcing frequency of the train is between 0.6 to 1.0 Hz. The frequencies of the combined dynamic system, including the train and the girder, are therefore well detuned. Hence, the effects of dynamic amplification are insignificant, and the girders can be analyzed according to the static axle loads for trains operating below 74 km/h.

An investigation of masonry wall and window systems is performed on a central Illinois institutional building. The building suffered from water leakage and masonry cracking. Design and construction defects are identified including inadequate flashing, freeze‐thaw damage, and damaged window seals. The investigation was performed such that moisture could be found in the form of ice and melting ice.

Investigation of damaged swimming pools in Southern California reveals that severe damage often occurs when the earth materials or bearing support is provided by material having different engineering properties. This often occurs in hillside area where steep slopes and alluvial filled canyons are found. Consolidation of man-made earth fill, colluvium, and alluvium is generally much greater than the parent bedrock found on many residential lots. Consolidation and creep can occur over a period of time due to changes in moisture content as fill and other earth materials become saturated. It is important that a comprehensive geotechnical investigation be carried out, even for this simplest of engineered structures. Damage to swimming pools can be mitigated by supporting the base of the pool entirely on bedrock, using deep foundations such as piers or piles.

It is commonly assumed that open-graded gravel dumped behind gravel walls will not settle. This paper presents a case history where open-graded gravel was dumped behind garage walls; stairs were then built atop the gravel; and the gravel and the stairs settled with time. The stairs were initially constructed to slant away from the buildings, but in some cases they settled so much that they now tilt toward the buildings. The typical amount of settlement of the entryway stairs was about 1–2 in. (2.5–5.1 cm). The settlement of the gravel backfill could have been triggered by light vibration or perhaps even the flow of water down through the gravel backfill. The potential for settlement can be reduced by placing the gravel in thin layers and densifying the gravel using vibratory compaction equipment on each layer.