Fazil Najafi

USER COST MODEL FOR BRIDGE MANAGEMENT SYSTEMS

User cost models are used in bridge management systems to quantify, in economic terms, the potential safety and mobility benefits of functional improvements to bridges. One component of many such models is a formula to predict traffic accident risk on the basis of bridge characteristics such as roadway width and approach roadway alignment. A critical analysis of the user cost model used in AASHTO’s Pontis and Bridgit systems found that the model was overly sensitive to extremes of roadway width, yielding unrealistically high benefit estimates. A new model was developed using Florida data on bridge characteristics and traffic accidents. The new model has superior behavior and statistical characteristics on a full inventory of state highway bridges. Since it relies solely on National Bridge Inventory data items, the model is readily transferable to many different bridge management systems.

Radon reduction systems in the construction of new houses in Gainesville, Florida

High radon level exposures increase human risk of lung cancer. The objective of this paper is to present the results of the effectiveness of applying the Enkavent mat method and the suction pit method; as tested by a University of Florida research team; to reduce radon entry in new houses built in the city of Gainesville and the surrounding Alachua County area in Florida. Both of these passive techniques include placement of a barrier under the concrete floor slab right on top of the soil at the new building sites. Passive and active techniques applied in the construction of new houses reduced radon levels to below the minimum requirements of 148 Bq m(-3) (4 pCi L(-1)). The mitigation systems investigated in this research were adopted by the Florida Legislature to become part of the new building construction code in Florida.

REGIONAL LAND USE SCHEMES GENERATED BY TOPAZ

Dickey J. W. and Najafi F. T. (1973) Regional land use schemes generated by TOPAZ, Reg. Studies 7, 373–386. TOPAZ, which is the Technique for the Optimal Placement of Activities in Zones, was developed to provide the urban planner with a series of alternative solutions from which he could determine the land use pattern with the least amount of cost involved. In line with this objective, TOPAZ was applied to the New River Valley Planning District. The District was divided into 40 zones and five activities—residential, commercial, public/semi-public, industrial, and recreational—were investigated. Cost information for land, building units, and utilities was obtained for all activities. A constant cost of travel was assumed. Regional land use and transportation data were developed and utilized in the computer programme. The TOPAZ generated several alternative solutions with maximum and minimum costs of travel, buildings, utilities, access facilities, and so on. The resulting land use patterns were compared w...

Performance Bond Benefit–Cost Analysis

A performance bond provides the assurance that an awarded construction project will be satisfactorily completed in the event that the contractor is unable to complete the project as agreed and the contract is terminated. First passed into U.S. law in the late 1800s, performance bonds protect against financial losses. The ability of contractors to provide a performance bond has mistakenly been assumed as a guarantee that contractors will perform well on the projects they are awarded. Indications are that there is a need to evaluate the benefits and the costs of using performance bonds. This paper examines the benefit–cost ratios of performance bonds on a national basis. Analysis was performed on state construction project data collected for contract awards from September 2007 to September 2009. The results of the analysis suggest that states with a small number of defaults, or none at all, did not benefit from having performance bonds, whereas those states with numerous defaults did benefit. In conclusion, the results suggest that performance bonds are beneficial to states that experience a large number of defaults.

PROCEDURE FOR MONITORING AND IMPROVING EFFECTIVENESS OF QUALITY ASSURANCE SPECIFICATIONS

Writing quality assurance specifications is as much an art as a science. The specifications must be introduced and monitored in the field before it can be concluded that they are providing the levels of construction quality and performance that are desired. Even those specifications that have proven their adequacy must continue to be monitored in a changing construction environment. Little guidance currently exists, however, on how a highway agency can objectively assess and monitor its quality assurance specifications. A procedure that responds to this need is presented. The procedure can be used to assess how well a specification is working or to monitor the specification to ensure continuing effectiveness. A major benefit is that the procedure can identify inconsistencies that should be corrected if the specification is to be truly effective. Continuous quality improvement is thus made possible. Therefore, it is emphasized throughout that agencies need to have good pavement or asset management systems and databases. The procedure was tested on a state highway agency’s asphalt pavement specifications. It was concluded that the effectiveness of the agency’s specifications could be improved. It is likely that some of the suggested improvements also apply to other agencies. Among these is the need for all to know what quality level the agency wants and for the agency to clearly state this in its specifications. In most cases, essentially the same quality level should be specified for a quality characteristic, regardless of the number of samples obtained for evaluation of acceptance to be taken from a lot. Additionally, if specifications are to be not only effective but cost-effective as well, establishing the optimal quality level becomes paramount.

Assessment of Flowable Fill Strength in Pavement Construction

Flowable fill is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. It generally consists of sand, portland cement, fly ash or slag, and water. It does not settle or require vibration or other means of compaction, it can be excavated, and it is safer than other forms of fill. One approach to predicting its ability to be excavated is to develop a correlation using early-age strength and long-term strength. Flowable fill mixture exhibiting strength less than 0.689 MPa (100 psi) is classified excavatable; mixtures with strengths higher than 0.689 MPa are difficult to excavate and are considered nonexcavatable. Because flowable fill is generally used for backfill and is placed underneath pavement, few studies have been undertaken evaluating moisture effects on long-term strength of flowable fill while underneath pavement. This paper presents the results of a laboratory study evaluating moisture effects on long-term strengths of flowable fill and assesses an acceler...

COST-BENEFIT HIGHWAY PAVEMENT MAINTENANCE

Many methods used in highway maintenance plans are complex, and agencies often exclude components related to user costs in the work zone (such as vehicle operating costs, delay costs, and crash costs) when making project improvement decisions. Highway users are taxpayers, and considering the user costs in project rehabilitation, resurfacing, and reconstruction provides the greatest return on project tax dollars spent. A simple five-step procedure that includes user work zone costs in the selection of highway maintenance projects has been developed and applied to the city of Gainesville, Florida, roadway improvement network projects: (1) collect distress data, (2) prepare inventory forms for the roadway networks, (3) prepare a maintenance cost plan, (4) prepare priority rankings for project improvements, and (5) select and implement project rehabilitation on the basis of priority ranking. These five steps assist highway agencies (public works officials and highway engineers) in simplifying maintenance programs in light of limited funding and help agencies choose priorities for highway maintenance funding for projects.

The computer in the construction industry

Abstract Computer technology in the 1980s has changed drastically. Microcomputers perform functions that only large and expensive mainframe computers performed a decade ago. Computers are used today by a rapidly growing majority of construction firms. This paper investigates computer applications in various aspects of the construction industry, such as planning, surveying, designing, graphics, pre-bidding, budgeting, scheduling, quality and cost control and equipment management. It also includes the results of a questionnaire directed at the construction industry concerning: 1. (1) types of construction (e.g. design, construction management, etc.) 2. (2) the companys annual dollar volume of work 3. (3) types of computers used 4. (4) usage of commercial software and percentage of usage for various activities within the construction industry 5. (5) the extent computer utilization has advanced the construction industry, etc. In the construction industry, small and minicomputers predominate in types of computers used. Commercial software is more commonly used which requires constant revision and improvement. Software problems are the major cause of user dissatisfaction with the use of computers. Overall, the research findings indicate that computer use has helped the construction industry and the number of users will continue to increase. The computerization of scheduling techniques and construction material codings have helped improve speed and accuracy of computer data entry. To completely harness the computer technology and to produce tangible cost savings, it is necessary for the construction industry to enhance user capability.

PAYING EQUITABLY FOR URBAN CONGESTION THROUGH NATIONAL ROAD PRICING SYSTEM

Automated toll collection (ATC) systems have been implemented successfully in the United States to collect tolls on bridges and at tunnels and turnpikes. A conceptual national automated road pricing system (NARPS) is described. NARPS consists of a nationwide application of an integrated and coordinated ATC system. Its primary purpose is to collect variable tolls on congested urban roads to improve traffic distribution and the overall efficiency of the highway system. The components of the proposed system are transponders, detectors, and processors used to automatically identify approaching vehicles at normal speed, calculate applicable tolls, and maintain local data bases of all tolls and vehicles to be processed remotely in a control center. A nationwide application of an integrated ATC system offers numerous significant advantages: cost savings, efficiency, traffic management, and a host of secondary applications that are not feasible with localized ATC systems. The management of the system is simplifie...

Radon entry control in new house construction.

People exposed to high concentration levels of radon face an increased risk of developing lung cancer. The risk is directly proportional to the length and level of radon exposure. Because of health reasons, it is safer to build new houses with radon mitigation systems installed in slab-on-grade houses. However, the interrelationships between parameters and factors governing radon entry and control are highly complex. A study performed by the University of Florida has examined the effectiveness of different radon entry control approaches. The analysis was based on 47 houses from three research projects conducted by the University of Florida (14 houses), Florida Solar Energy Center (13 houses), and GEOMET Technologies (20 houses). The evaluation of the performance and effectiveness of improved floor slabs, space conditioning, and ventilating systems were analyzed. Statistical analyses of the interrelationship between various parameters were also performed. Study findings such as the important factors in reducing radon entry and the effectiveness of passive construction approach and active subslab depressurization systems are presented in this paper.