Suspension Cable Design of the New San Francisco–Oakland Bay Bridge

Various factors contribute to the difficulty in designing the main suspension cable for the new San Francisco–Oakland Bay Bridge Self-Anchored Suspension Span (or East Bay Bridge Suspension Span). The key factors are bridge design life, cable geometry, cable anchorage layout, cable construction method, and cable corrosion protection system. This paper describes the unique main suspension cable geometry layout for the East Bay Bridge Suspension Span, reviews the available technologies for each of the aforementioned design considerations, and presents the final cable design recommendations.     

Case Study of Courtyard House Damaged by Expansive Soils

This paper presents a case study of a U-shaped, courtyard house damaged by expansive soils. The field investigation revealed that the damage was caused by edge heaving as a result of water ponding in the courtyard. A back-analysis procedure using finite-element analysis is presented that is based on the measured slab surface levels. The back-analysis provides a representation of the underlying ground movement. The results of the back-analysis compared reasonably well with the actual observations in the field. It was deduced that the slab cracking could have been prevented and the distortion of the house would have been significantly reduced if a strap beam had been added in the courtyard area.     

Study of Expansive Soils and Residential Foundations on Expansive Soils in Arizona

Construction on expansive soils is challenging and thus prone to some problems and litigation. The engineering community makes extensive use of local experience and empirical procedures to address these problems. Although there has been extensive study of expansive soils and foundations on expansive soils, data related to performance of residential structures are limited in general and limited in the Phoenix area, in particular. In this study, an overview of the Phoenix Valley, Arizona, geotechnical practice and foundation performance related to residential structures on expansive clays, was developed through surveys and interviews with geotechnical engineers, structural engineers, and homebuilders. Using data obtained from files of Phoenix area geotechnical firms and government agencies, the existing Natural Resource Conservation Service map showing expansive soil locations throughout the Phoenix region was updated through the use of correlation developed in this study relating expansion index to common soil index properties such as Atterberg limits and percent passing the No. 200 sieve. Files of forensic investigations linked to expansive soil regions were made available for this study by several geotechnical engineering firms, and Phoenix Valley areas where forensic investigations have been identified, were mapped for comparison to regions identified in the updated map as having expansive soils. Comparison of the forensic investigation map to the updated map of expansive clay locations revealed that most of the forensic investigations were in regions identified with clays labeled as high to moderately high expansion potential, with a few forensic investigations in regions of medium expansion potential. Finally, unsaturated flow analyses were conducted for an Arizona expansive clay profile for two very different landscaped conditions of well-irrigated turf and desert landscape. The results of the numerical analyses were consistent with the reported observations and modes of failure identified through the surveys and interviews conducted with engineering and homebuilder professionals, including the finding that site drainage was found to be extremely important to good foundation performance, regardless of the type of landscape selected.     

Reconstructing Contaminant Deposition in a San Francisco Bay Marina, California

Two sediment cores were collected from a marina in the San Francisco Bay to characterize historical sediment contamination resulting from the direct discharge of industrial wastewater from Naval Air Station Alameda. Depth profiles of trace metals, petroleum hydrocarbons, and radionuclides were determined with a 12-cm spacing down to a depth of 120 cm. The chronology of sediment accumulation is established by depth profiles of sedimentary time markers in conjunction with information on site history. The traditional approach of determining sediment accumulation rates by measuring atmospheric 210Pb deposition was obscured by a larger source of 210Pb in the sediments from the decay of anthropogenic 226Ra, likely from luminescent paints used at this facility and released to the marina. The sedimentation rates inferred from the data indicate that the greatest amount of contamination by trace metals and petroleum hydrocarbons took place between 1940 and 1960. In addition, anthropogenic 226Ra activities are positively correlated with some of the contaminants in the sediments, allowing the wastewater discharged from the facility to be distinguished from baywide contamination. In locations such as this, where there is a complex history of contaminant deposition, a source-specific tracer may be the only feasible method of attributing historical contamination to a point source.     

Experimental Evaluation of Compressive Behavior of Orthotropic Steel Plates for the New San Francisco–Oakland Bay Bridge

Compression tests were conducted on two reduced-scale orthotropic plates to verify the design strength of steel box girders for the new San Francisco–Oakland Bay Bridge. The first specimen was composed of three longitudinal closed ribs and a top deck plate. It failed in global buckling, followed by local buckling in the deck plate and ribs. The second specimen, which was composed of four longitudinal T-shaped ribs and a bottom deck plate, experienced global buckling as well as local buckling in the ribs and the deck plate. The ultimate strength and failure mode of both specimens were evaluated by two bridge design specifications: the 1998 AASHTO load and resistance factor design specification and the 2002 Japanese JRA specification. Findings from code comparisons showed that: (1) Sufficient flexural rigidity of ribs were provided for both specimens; (2) the JRA specification slightly overestimated the ultimate strength of both specimens; and (3) neither specifications predicted the observed buckling sequence in Specimen 2. A general-purpose nonlinear finite element analysis program (ABAQUS) was used to perform correlation study. The analysis showed that the ultimate strength and postbuckling behavior of the specimens could be reliably predicted when both the effects of residual stresses and initial geometric imperfections were considered in the model.     

Design of Looping Cable Anchorage System for New San Francisco–Oakland Bay Bridge Main Suspension Span

Located at the rocky edge of the Yerba Buena Island, the west anchorage of the San Francisco–Oakland Bay Bridge suspension span serves as the anchor for this single tower self-anchored suspension bridge. With extensive comparative studies on numerous alternatives, the new looping cable anchorage system is recommended for the final design of the west anchorage of the self-anchored suspension span. The looping cable anchorage system essentially consists of a prestressed concrete portal frame, a looping anchorage cable, deviation saddles, a jacking saddle, independent tie-down systems, and gravity reinforced-concrete foundations. This anchorage system is chosen for its structural efficiency and dimensional compactness. This paper describes major design issues, design philosophy, concept development, and key structural elements and details of this innovative suspension cable anchorage system.     

Abolition of Standard of Care in Residential Design? Study of SB 800’s Impacts on Design Professionals

California Civil Code §§895 through 945.5, also known as “SB 800,” has dramatically changed the legal landscape for residential construction projects in California. The law sets forth new, legislatively defined, actionable defects; a detailed prelitigation repair process; and available damages and defenses. This paper examines the impacts of the law on design professionals and concludes that the law appears to have supplanted the standard of care for design professionals in connection with residential construction—meaning that their services may now be measured against codified standards instead of against the performance of their peers. Alternatively, rather than supplanting the standard of care, the law may have the practical effect of shifting the burden of proof from homeowner claimants to the allegedly negligent design professionals, thereby requiring the defendant design professional to show that their services comply with the standard of care in order to escape liability. In either event, the playing field has changed dramatically for design professionals. This paper suggests ways in which design professionals might tailor their practices to best position themselves for claims which are sure to arise out of SB 800.     

Drivers for Cost Estimating in Early Design: Case Study of Residential Construction

This paper proposes the use of a series of independent variables for an early estimation of the building construction cost of residential buildings. Based on 70 German residential properties, these variables serve as the cost drivers of a project, and the regression model, tested against the 70 properties, has a mean absolute percentage error of 9.6%. When applied to predict the cost of five more properties that were excluded from the 70 in the regression model, the percentage error ranges between–12 and 13%. The identified cost drivers are: compactness of the building, number of elevators, size of the project, expected duration of construction, proportion of openings in external walls, and region.     

Development and Validation of a New Field Measurement Technique for Estimating the Local and Total Air Duct Leakage in Residential Buildings

The paper proposes a new measurement technique for estimating the local and total leakage rates in typical residential buildings. It is based on the duct pressurization technique in which the duct system is pressurized by using a calibrated fan while all registers are sealed off. It also includes a zone bag that can be inserted inside the duct system to create an artificial partial restriction and consequently different levels of leak pressures and flows. An experimental facility Air Duct Leakage Laboratory (ADLL) has been established, which has two different air duct configurations and a wide range of known leakage levels controlled by holes created at several locations of ductwork. The proposed technique has been validated by experiments at the ADLL. The validation results indicated that the proposed technique could be a good method for accurately estimating the total and local leakages and provides a great opportunity to focus on right locations to repair and to provide accurate information if the duct repair is cost effective.     

Adoption of the International Residential Code in a High Natural Hazards Region—An Overview

South Carolina was among the first jurisdictions to adopt the 2000 International Residential Code (IRC). The adoption of this statewide building code met with significant opposition and resulted in moratoria being placed on all seismic design and wind-borne debris provisions in the code. A study was conducted to determine how well the IRC has been adopted by coastal South Carolina communities, with the discovery that most plan preparers and building departments are not following the IRC. This paper documents some of the activities and observations made during this process. The observations are troubling and point to a significant need for ongoing professional education. The findings also demonstrate the need for greater resources to be allocated not only to educational needs, but also to code enforcement.     

Evaluation of the Design, Planning, Construction Phases, and Structural Content of Permanent Residential Dwellings Built after the 1999 Eastern Marmara Earthquakes in Turkey

The aim of this study is to survey and evaluate permanent housing structures built after the Marmara earthquakes based on the principles of earthquake resistant design of reinforced concrete structures. The seismicity of Turkey requires immediate attention as there is a high probability of another major earthquake event in the next 30?years in Istanbul. The classification of structural systems, the damage patterns and behaviors of structural systems, and structural and nonstructural components under lateral earthquake loads, are analyzed. Based on this analysis, reliable structures can be built without overextending the Turkish economy, and loss of life and structural damage can be reduced by designing structures with greater earthquake energy dissipation capacity. The selection of project areas and the strength of the structural system are thoroughly analyzed taking postearthquake public psychology into account. Structural characteristics of permanent housing built subsequent to the Marmara earthquakes are critiqued and documented with a case study.