Constructability and Economics of FRP Reinforcement Cages for Concrete Beams

This paper presents a quantitative economic analysis and a qualitative constructability analysis of three-dimensional fiber-reinforced plastic (FRP) reinforcement cages for concrete beams. Material, labor, and life-cycle costs are provided, and construction practice aspects are discussed. The results of the analyses indicate that prefabricated FRP cages can offer benefits to the construction industry. Although the initial costs of the FRP materials are likely to be higher than those of steel rebar, there is a significant potential for cost savings due to reduced maintenance and labor costs, as a result of the corrosion resistance of the FRP and the increased construction productivity. When direct life-cycle costs are considered, FRP reinforcements already constitute, in many cases, an economically competitive alternative to conventional steel reinforcement in adverse environments. If, in addition, the indirect cost savings as well as quality and safety issues are considered, the FRP reinforcement may be even more competitive.     

Hydraulic Design of a Longitudinal Culvert for Lock Filling and Emptying Systems

The U.S. Army Corps of Engineers is planning navigation improvements for many projects to meet predicted increases in tow traffic. Some of these improvements include the addition or replacement of the navigation lock. Innovative design and construction techniques are being investigated to try and reduce construction costs as well as operation and maintenance costs. The Corps identified that a savings in lock construction could be achieved if the conventional concrete gravity lock walls with culverts inside them could be replaced with thin walls and longitudinal culverts located inside the chamber. This culvert design was designated the In-Chamber Longitudinal Culvert System (ILCS). An extensive research effort led to the development of the ILCS design. This paper provides a brief summary of the research results and the accompanying design guidance developed for low to medium lift ILCS locks. The guidance includes culvert location; port size, location, and spacing; port extensions; culvert-roof overhang; and wall baffles. Lock chamber performance characteristics, based on acceptable filling and emptying operations determined using a laboratory model, are also presented. The ILCS is a feasible design based on the hydraulic performance determined from the investigation.     

Economic Evaluation of Reinforced Concrete Structures with Columns Reinforced with Prefabricated Cage System

A new reinforcement system termed the prefabricated cage system (PCS) that can be used as an alternative to the rebar reinforcement cage is economically evaluated. PCS is a prefabricated reinforcement that enables easier, faster, and more reliable construction. Use of PCS shortens the construction schedule time and lowers total construction cost. This is important to both owners and construction contractors. The engineering economics methods presented in this paper would also be of interest to researchers. Reinforced concrete structures with PCS reinforced columns have been considered in this research, as it is one of the major applications of PCS. Various parameters affecting the economics of PCS are reviewed and a case study structure is analyzed comparing the costs of the structure with rebar reinforced columns to costs of the structure with PCS reinforced columns. The investigation shows that using PCS results in a 33.3% time savings and a 7.1% cost savings over rebar for each column. This results in an average of 3.6% savings on total project cost; an average of 22.2% savings on total column costs; 20.4% savings on total project time period, and 33.3% savings on columns construction time period. The cost savings are estimated based on production of small quantities of PCS reinforcement. Mass production of PCS reinforcement would result in even higher cost savings.     

Knowledge and Reasoning for MEP Coordination

The coordination of mechanical, electrical, and plumbing (MEP) systems is a major challenge for complex buildings and industrial plants. The process involves locating equipment and routing connecting elements for each building system. This multidiscipline effort is time-consuming and expensive and requires knowledge regarding each system over the project life cycle. Current practice requires representatives from each MEP trade to work together to identify and resolve interferences. Effective MEP coordination requires recalling and integrating knowledge regarding design, construction, operations, and maintenance of each MEP system. Currently, designers and constructors use tailored CAD systems to design and fabricate MEP systems, but no knowledge-based computer technology exists to assist in the multidiscipline MEP coordination effort. The paper describes results from a research project to capture knowledge related to design criteria, construction, operations, and maintenance of MEP systems and apply this knowledge in a computer tool that can assist designers and builders in resolving coordination problems for multiple MEP systems.     

新型电控液压锁的设计与分析

针对新型电控液压锁的关键部件阀块进行设计与分析,运用三维设计软件对阀块路由进行合理设计,并进行有限元分析其可靠性。该装置具有设备重量小、安装空间小、安装容易、维护容易、可靠性高、节约成本等优点。     

Projected cost-effectiveness of primary angioplasty for acute myocardial infarction

OBJECTIVES: This study sought to evaluate the cost-effectiveness of primary angioplasty for acute myocardial infarction under varying assumptions about effectiveness, existing facilities and staffing and volume of services. BACKGROUND: Primary angioplasty for acute myocardial infarction has reduced mortality in some studies, but its actual effectiveness may vary, and most U.S. hospitals do not have cardiac catheterization laboratories. Projections of cost-effectiveness in various settings are needed for decisions about adoption. METHODS: We created a decision analytic model to compare three policies: primary angioplasty, intravenous thrombolysis and no intervention. Probabilities of health outcomes were taken from randomized trials (base case efficacy assumptions) and community-based studies (effectiveness assumptions). The base case analysis assumed that a hospital with an existing laboratory with night/weekend staffing coverage admitted 200 patients with a myocardial infarction annually. In alternative scenarios, a new laboratory was built, and its capacity for elective procedures was either 1) needed or 2) redundant with existing laboratories. RESULTS: Under base case efficacy assumptions, primary angioplasty resulted in cost savings compared with thrombolysis and had a cost of $12,000/quality-adjusted life-year (QALY) saved compared with no intervention. In sensitivity analyses, when there was an existing cardiac catheterization laboratory at a hospital with > or = 200 patients with a myocardial infarction annually, primary angioplasty had a cost of < $30,000/QALY saved under a wide range of assumptions. However, the cost/QALY saved increased sharply under effectiveness assumptions when the hospital had < 150 patients with a myocardial infarction annually or when a redundant laboratory was built. CONCLUSIONS: At hospitals with an existing cardiac catheterization laboratory, primary angioplasty for acute myocardial infarction would be cost-effective relative to other medical interventions under a wide range of assumptions. The procedure's relative cost-ineffectiveness at low volumes or redundant laboratories supports regionalization of cardiac services in urban areas. However, approaches to overcoming competitive barriers and close monitoring of outcomes and costs will be needed.     

Building Reuse Assessment for Sustainable Urban Reconstruction

Building reuse is a linchpin to managing solid waste. Despite the various benefits beyond contributing to sustainability that can be realized through building reuse, including direct and indirect cost savings, truncated construction schedules, and reduced site disruptions, little formal consideration has been given to this topic, which places professional engineers at a disadvantage when considering this as a design option. As each building project has its own specific requirements, reuse is not always the most economical solution, but, in cases where reuse is in part motivated by other factors such as heritage protection, substantial economic and environmental savings can be realized in tandem. Based on nearly two decades of professional experience, a generalized assessment method for reuse is proposed to facilitate benefit maximization. Applying this 10-step method, the costs related to building replacement and sustainable reuse are compared using two case histories and a theoretical building. A clear correlation is shown with the potential for savings as a function of project size.     

The Contribution of Niobium Bearing Steels and Enhanced Sustainability

With the growing concern for the environmental impact of greenhouse gases and the rapid depletion of important resources,the use of Nb-bearing steels for advanced high strength steel applications can reduce raw material usage and the carbon footprint.The conservation and more efficient use of ironmaking and steelmaking raw materials is an urgent issue for steel producers globally.Recently-developed Nb-microalloyed steel applications provide a more effective product design and reduce CO 2 emissions and energy consumption per tonne of steel.A sustainability structural steelstudy presents the positive cost and reduced environmental impact of Nb-microalloyed steels.This analysis compares the CO 2 emission reduction and energy savings in the steelmaking process melted in both the Basic Oxygen Furnace (BOF) and the Electric Arc Furnace (EAF).Nb-microalloyed structural steels offer the opportunity to reduce the total weight of a given structure compared to a non-microalloyed steel construction.Generally,one considers the savings associated with less material and lower construction costs.In addition,there is an environmental benefit in the reduction in emissions (kilograms of CO 2) and less energy consumption (GJ) due to the fact that less steel is melted.Plus,there are lighter sections and less material weight in the final end user design which reduces transportation and fabrication costs.A forecasted trend is presented which introduces an increased usage of microalloyed steel grades to replace traditional commodity-type non-alloyed higher carbon-manganese grades for environmental benefits and significant cost reduction.     

Optimal Allocation of Construction Planning Resources

Efficient allocation of resources for construction planning activities requires construction planning resource requirements to be determined on a cost-effective and value-adding basis. However, although some research studies have indicated that increasing resource allocations to construction planning activities will lead to improved project performance, other research studies have indicated that investing in construction planning beyond an optimum point will lead to a deterioration in project performance. This study explored the concept of optimal planning of construction projects by examining 52 building projects undertaken in Australia. The relationships between planning input (ratio of planning costs to total project costs) and the probabilities of achieving poor performance and good performance were modeled using logistic, linear, and curvilinear regression analyses. A probable optimum planning input based on the sample studied was derived. It is suggested that any additional planning efforts beyond this optimum point would be essentially wasted because the additional planning costs would not achieve any savings in project cost but merely add to the overhead costs and therefore increase the overall project cost. A model for optimal planning is presented and discussed.     

Practical Issues for the Application of High-Performance Concrete to Highway Structures

In recent years, the advantages of high-performance concrete (HPC) have been well documented. Among others, these advantages include enhanced design flexibility and improved durability performance that results in reduced maintenance costs and an increased service life. Despite these obvious benefits, the implementation of HPC has been very slow. This can be attributed to several factors including the uncertainty related to current design codes and a lack of familiarity of designers and contractors with practices and requirements for proper design and construction of high-performance concrete structures. This paper introduces and discusses several fundamental issues that affect the implementation of HPC and impact the practitioner. These include issues related to quality control∕quality assurance, specifications, material performance, and structural behavior. Within the scope of this discussion, the fundamental differences and similarities between HPC and conventional concrete are discussed. The objective of this discussion is to provide the practicing engineer with a conceptual understanding of the practical issues that affect the design and use of HPC for highway structures with the desire to further stimulate the implementation of HPC.     

Restructuring the Undergraduate Laboratory Instructional Process

There is little doubt that a laboratory experience can be a beneficial component of the undergraduate engineering learning process. Observing physical demonstrations of textbook and lecture information can enhance a student’s perception of a concept and produce clarity of key issues. Unfortunately, limitations often exist that constrain the developing laboratories and sometimes reducing the student’s experience to little more than performing “cookbook” experiments and copying previous lab reports; an exercise that benefits neither the instructor nor the student. This paper summarizes an alternative approach for undergraduate laboratory instruction that relies on the undergraduate students working in teams to design and conduct experiments. The instructor acts as mentor to a process that ensures a quality laboratory exercise without being the sole responsible party. The students’ learning is increased and the laboratory experience is enhanced due, in part, to the experiments being designed by students and for students; matching students’ needs, education, and interests with experiments. An additional benefit comes from participants being immersed into the concepts of experimental design and analysis using a team of peers.     

Animation Tools for Extraterrestrial Construction

This paper explores the idea of developing space‐construction animation “tools” to facilitate extraterrestrial design and construction activities. These tools would integrate engineering operations in space. However, in order to develop such tools, it is necessary to determine their functional requirements. This involves an assessment of existing technological trends as well as an understanding of the future needs of this technology. The need for improved forms of communication between parties involved in space design and construction suggests the need for a dynamic or animated representation of the construction processes. Computer animation offers a unified approach to modeling the spatial dynamics so crucial in the planning and controlling of construction activities, and evaluation of automation models. For remotely monitored processes, simply providing critical information in an easily—and quickly—understood format could aid the space‐construction manager in anticipating interference and other critical conditions. The use of animation during remotely monitored or remotely controlled construction processes in space could significantly assist construction equipment operators.     

Cost-Estimating Tools for Low-Impact Development Best Management Practices: Challenges, Limitations, and Implications

Tools were developed for estimating costs of vegetative roofs, rainwater catchment systems, and bioretention facilities. These tools provide a detailed framework to facilitate cost estimation for capital costs, operation and maintenance costs, and life-cycle net present value. The tools can provide users with planning-level cost estimates and serve as a format for cost-reporting for past, current, and future projects. Very little cost data was available in the public forum, and prolific inconsistencies of supporting details were found in the available cost data. To address this, design assumptions were established for each facility type and professionally prepared cost estimates based on these design assumptions were used. Electives in design, such as plant selection and media depth, also greatly affected costs. To make the user aware of these effects, the model separates each option into line items that can be elected or excluded as appropriate. To facilitate collecting future cost data, best management practice (BMP) designers and builders should use these tools to record actual costs and report them to a clearinghouse such as the BMP Database.     

Use of GIS and Topology in the Identification and Resolution of Space Conflicts

Construction activities need space on the jobsite for their execution. Workers, equipment, materials, temporary facilities, and the developing structure share the limited jobsite space during the construction period. Multiple types of spaces for different purposes on various locations are required to execute various activities at different times. Hence, space planning helps provide a safe and productive environment. Planners mentally link two-dimensional (2D) drawings and execution schedules to generate dynamic multiple types of space requirements, which is a complex task. Therefore, researchers suggest the use of four-dimensional (4D) modeling and building information modeling (BIM) for space planning. Both simulate the construction process by linking the execution schedule with a three-dimensional (3D) model to visualize the construction sequence in space planning. However, both still lack features such as topography modeling and geospatial analysis, which affect space planning. In this work, 4D geographic information systems (GIS) were used for space planning that facilitates topographic modeling, different types of geospatial analyses, and database management. GIS was also used to generate multiple types of spaces corresponding to various activities. A feature attribute table (FAT) associated with each space describes when, where, and how long that space will be required on the jobsite. GIS-based area topology was implemented through a set of validation rules that define how working areas have to share the jobsite. A GIS-based methodology that enables space planning, time-space conflict identification, and conflict resolution prior to the construction was developed and implemented.     

Construction Congestion Cost (CO3) Traffic Impact and Construction Cost

The Construction Congestion Cost System (CO3) is an integrated set of tools to estimate impact of traffic maintenance contract provisions on congestion, road user cost, and construction cost. Engineers use CO3 to produce realistic budgets and select practical contracting methods that provide an acceptable balance between construction cost and congestion. This paper demonstrates computation of impacts associated with alternative methods of maintaining traffic during construction. The Routes Sheet computes equivalent average vehicle routes for complex diversion routes. The Input Sheet provides for documentation of vehicle and route inputs and computes user cost for individual trips through the work zone, diversions, and cancellations. The Traffic Sheet computes daily traffic impacts and user costs for each construction method. The Construction Sheet computes impact of different construction methods on construction costs. The Impact Sheet summarizes daily impacts and computes total project traffic impacts, road user costs, and construction costs for all alternatives. These tools provide practical information with which engineers select construction methods whose impacts are acceptable.     

Cost-Benefit Model for the Construction of Tornado Shelters

Tornadoes have been identified as one of the leading causes of death and injuries among natural disasters in the United States. Shelters play an important role in tornado mitigation efforts, since tornado-related mortality and injury rates are higher when tornado shelters are not available. This paper describes a methodology to address the viability of construction of tornado shelters in areas which have significant tornado hazards. A cost-benefit model that estimates the relative advantages of three tornado shelter construction strategies was developed and tested. The model accounts for factors such as probability of tornado occurrence, historical death and injury rates, economic incentives, and local construction and maintenance costs. The implications of factors such as useful life period, discount rate, and occupancy on the viability of the shelter were also studied. Relevance of this model to decision makers, as well as future needs for the model, is discussed.     

Incorporating Maintainability in Constructability Review Process

Life cycle cost or total cost analysis of a facility begins with the initial design concept and ends with the decommissioning of the facility. Decisions made during the design and construction phases routinely consider only the construction costs when analyzing the constructability of the project. Often the impacts of such decisions on the maintenance requirements for the facility are not fully appreciated and are therefore not formally addressed. The concept of “maintainability” addresses this concern and is a logical extension of the constructability concept. As such, maintainability may be incorporated as a part of the formal constructability review process (CRP). This article describes a model format for incorporating the best practices for maintainability into the CRP. The added life cycle value of incorporating maintainability into the CRP can only be assessed by analysis of accurate and complete maintenance cost data. Insights from such an analysis may facilitate more accurate estimates of the total costs of facilities.     

Prototype Tool for Mechanical, Electrical, and Plumbing Coordination

Effective mechanical, electrical, and plumbing (MEP) coordination requires recalling and integrating knowledge regarding design, construction, and operations and maintenance of each MEP system. Currently, the MEP coordination process involves a series of meetings where representatives from each MEP trade overlay drawings of their respective systems to detect and eliminate numerous types of interferences. Tailored computer tools used to design and fabricate MEP systems almost always generate these drawings, but no knowledge-based computer technology exists to assist in the multidiscipline MEP coordination effort. The purpose of this research was to develop a technology that integrates a number of knowledge bases—design criteria, construction, and operations and maintenance—into a knowledge-based system that is able to provide valuable insight to engineers and construction personnel, to assist them in resolving coordination problems for multiple MEP systems. This research provides a foundation for future researchers to build from and for industry to create a revised work process, using information technology, to assist in multidiscipline coordination efforts.     

Justifying Materials Selection for Reinforced Concrete Structures. I: Sensitivity Analysis

A substantial amount of research has been performed on the use of high performance construction materials and their effects on the anticipated frequency of maintenance and on the time to repair or replacement. Practical implementation of this work has been limited due to the lack of useable methods and information on the life-cycle costs and benefits of alternative approaches in the preliminary design stages of projects, when decisions regarding materials selection are typically made. The lack of simple methods for making quick life-cycle economic comparisons typically results in the use of conventional materials because their impact on performance is well known, even though high-performance materials may actually be more cost effective. This paper identifies the most significant parameters for evaluating the time to corrosion of reinforced concrete structures.