Search

This paper describes an investigation into the effective length of columns subjected to axial loads, for the various conditions encountered during the construction of buildings using the lift-slab method. Many designers of lift-slab construction have assumed an effective length factor, [KAPPA], for all conditions, equal to 2.0, and have believed that this assumption is reasonable or conservative. The investigation shows that for many conditions a [KAPPA] value equal to 2.0 is reasonable or conservative; however, the investigation also shows conditions where effective length factors greater than 2.0 should be used, and where effective lengths much lower than 2.0 could be used. DOI: 10.1061/(ASCE)0887-3828(2002)16:4(141) CE Database keywords: Columns; Buckling; Slabs; Soil-structure interaction; Stability; Effective length.

The failure of two reinforced concrete structures is recounted, one involving a warehouse structure and the other an offshore platform base structure. Design details and factors leading to the collapses are identified and discussed. The structures were subsequently analyzed using nonlinear finite-element analysis procedures, taking into account relevant second-order behavior models. The analyses provided an accurate assessment of the load capacities and failure modes observed, as well as meaningful insights into the underlying behavior mechanisms and factors leading to the failures. This paper supports the view that nonlinear analysis techniques have become useful everyday tools for design office applications, particularly in forensic work, and also gives evidence suggesting that errors in the design of modern structures can be potentially more catastrophic than in the past, and that advanced assessment techniques will assume increased importance as a result. CE Database keywords: Structural failure; Concrete structures; Finite element method; Shear.

Two manufactured metal building warehouses loaded with agricultural products failed in service. Inspection revealed considerable damage to the structure and the foundation. The building owner filed suit against the building supplier, the building erector, and the soils testing laboratory whose engineer had designed the foundation. The agricultural product imposed substantial outward lateral pressures on the walls of the structures. Review of the available design documents indicated that these loads had not been accounted for in design. A structural analysis revealed that elements of the structure were underdesigned for the agricultural product loads. In addition, the foundation did not have any slab reinforcement to resist the loads. To prevent similar failures, these loads must be accounted for in design. The steel structure design and foundation design were both deficient. A contributing factor was the lack of communication between the designer of the structure and the designer of the foundation, due to the lack of a single engineer of record to take responsibility for the buildings. CE Database keywords: Structural failure; Litigation; Loads; Building design.

There has been a growing interest in research in the field of the service life of structures due to a perceived lack of performance of built structures in the last several decades, To address this issue, it has been suggested that more emphasis should be given to in-service performance of a structure that could possibly be based on design-life concepts. Applying such concepts, with the numerous variables and parameters involved, is a complex issue. The present paper summarizes the findings of recent research, showing possible approaches to the consideration of design-life concepts as well as some discussion of the difficulties associated with them. The life span of a structure is broken up into the typical stages of progression, that is, conceptual design, final design, construction, and maintenance and repair, with the various influences identified and discussed at each of these stages. It followed from our research that quality-control and quality-assurance procedures at the design and construction stage have considerable influence on the design life of a structure. It was found that further developments in these areas are needed if the durability of a structure is to be predicted.

Over the last 30 yr, Eastern Canada has experienced several droughts during which extensive settlement problems developed in lightweight buildings rounded on the Champlain Sea clays. These clays are known for their open structure, which collapses when the moisture content is decreased and does not return to its initial state if water is added to the soil. This type of situation occurs during droughts in which the lack of rainfall causes the desiccation of clays. If trees are located in close proximity to buildings rounded on shallow footings the problem is exacerbated, since the roots can grow beneath the foundations and extract moisture during droughts. This will cause the clays to shrink and the structures to settle. The goal in dealing with these clays is to try to maintain a constant soil moisture. The elimination of planter areas around the perimeter of the buildings can help reduce moisture changes. This paper presents the results of a field monitoring program, on the effectiveness of different irrigation systems, in maintaining a constant soil moisture and in reducing building settlements in the clay deposits of Montreal Island.

This paper describes the reactivation of an ancient landslide during the construction of a fill buttress. Even though precautions were taken during construction of the buttress, such as excavating it in 30-m-long (100-ft-long) segments, the ancient landslide nevertheless was reactivated. The reactivated landslide moved laterally about 5-8 cm (2-3 in.), which resulted in significant damage, such as cracking to building foundations, walls, and ceilings, as well as distortion of door frames and windows. An interesting observation was that the ancient landslide, once activated, did not stop immediately after the buttress had been backfilled. The lateral movement continued for about 10 months, at a decreasing rate of movement. This movement was probably due to the slow closure of the ground cracks as well as the deformation of the landslide into the buttress. This case history illustrates the disadvantage of using a buttress to stabilize an ancient landslide, especially when the excavation is below the rupture surface.

In November of 1990, approximately 850 m (2,800 ft) of the 2020 m (6,620 ft) long Lacey V. Murrow Bridge (LVMB), a 50-year-old floating concrete bridge over Lake Washington near Seattle, sank after a major storm. The bridge had been closed for renovations for several months when it sank; there were many structural changes and interim conditions which affected the performance of the bridge. The investigation described herein identifies the most probable causes of the failure. The primary cause of the sinking of the LVMB was water that accumulated in the bridge during renovation. Hydrodemolition, rain, and wave splash water entered through construction openings and severed roadway drains. The cause of the failure was unrelated to strength reductions caused by the openings, and the age and condition of the bridge were of minor significance.