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This study investigates the geotechnical properties of seven paper mill sludges. Paper mill sludges have a high water content and a high degree of compressibility and behave like a highly organic soil. Consolidation tests reveal a large reduction in void ratio and high strain values that are expected due to the high compressibility. Triaxial shear-strength tests conducted on remolded and undisturbed samples showed variations in the strength parameters resulting from the differences in sludge composition (i.e., water content and organic content). Laboratory permeability tests conducted on in-situ specimens either met the regulatory requirement for the permeability of a landfill cover or were very close. With time, consolidation and dewatering of the paper sludge improved the permeability of cover. Freezing and thawing cycles increased the sludge permeability about one to two orders of magnitude. Maximum permeability changes occurred within 10 freeze and thaw cycles.

The pyrolysis kinetics of cellulosic uncoated printing and writing paper, which is one of the principal materials contributing to the municipal solid waste (MSW) of Taiwan, was investigated with a thermal gravimetric analysis (TGA) reaction system. The experiments were carried out in a nitrogen environment in the 450-850 K temperature range at various constant heating rates of 1, 2, and 5 K/min. The results indicated that there were two principal reactions in TGA curves as distinguished by the two significant and distinct mass changes over the experimental conditions. The pyrolysis of uncoated printing and writing paper can be adequately described by a two-reaction model. The corresponding activation energies, preexponential factors, and reaction orders were determined. The experimental results were satisfactorily fitted by the proposed chemical reaction model.

The paper-manufacturing industry generates more than 90,000,000 t of sludge annually in the United States, the disposal of which is a complex environmental issue. Test burns of pelletized and dried paper-mill sludge were performed in a small institutional boiler for the purpose of determining environmental feasibility of the operation. The sludge was from a facility processing 100% secondary fiber (40% postconsumer), and was co-fired with wood chips. Emission rates of various criteria and hazardous air pollutants were measured during the burns and compared to regulatory limits. Results indicated that criteria pollutant emissions from this 2.9 MW (10,000,000 Btu/h) operation were well within regulatory limits with the exception of particulate material. Emission control such as a baghouse or electrostatic precipitator would be needed for a facility performing energy recovery from sludge. Organic hazardous air-pollutant emissions were also well below mass rates that would qualify the boiler as a major source under the Clean Air Act Amendments of 1990, with the largest emissions being formaldehyde, followed by acetaldehyde, acrolein, and naphthalene.

Three of the four winning essays in the 1997 Daniel W. Mead Student Paper Contest are presented. The theme of the competition was the role of civil engineers in the drive towards sustainable development. The issue refers to the process of allocating resources for the sustenance of the present generation without depriving future generations of such resources. Thus, the recycling of raw materials is favored in this process over the use of fresh resources.

Hydraulic conductivities of three compacted paper mill sludges were measured in various ways to assess their viability for use in barrier layers in landfill final covers. Compaction tests showed that the sludges have compaction curves similar to those for clays, albeit with lower maximum dry unit weights and higher optimum water contents. Hydraulic conductivities less than 1 x [10.sup.-9] m/s can be attained for these sludges at low effective stresses (<10 kPa) when compacted using standard Proctor energy if the molding water content is 50-100 percentage points greater than optimum water content. The lowest hydraulic conductivities were obtained in this range. At higher effective stresses (>20 kPa), hydraulic conductivities less than 1 x [10.sup.-9] m/s can be achieved at higher molding water contents. Field tests conducted on barrier layers constructed with two of the sludges showed that field hydraulic conductivities can be obtained that are similar to those measured on laboratory compacted specimens prepared at the same molding water content. Laboratory tests on large and small undisturbed specimens removed from the field showed that no scale dependence existed in the hydraulic conductivity of the field compacted sludge. Additional tests showed that freezing increased the hydraulic conductivity of two of the sludges, regardless of whether the sludges were permeated between freeze-thaw cycles or only after the last thaw. In contrast, for the third sludge, increases in hydraulic conductivity only occurred if the sludge was not permeated between freeze-thaw cycles. Significant shrinkage and cracking of the sludges occurred when they were dried, suggesting that barrier layers constructed with sludge should not be permitted to desiccate. Long-term tests showed that the hydraulic conductivity remains stable or decreases slowly if permeation is continued over an extended period of time.

The need for reassessment of the fatigue life of existing structures is increasing as the world's infrastructure ages. A fatigue life reassessment typically begins with an assessment of the current condition of the structure. The condition assessment techniques range from visual inspection to X-ray inspection or detection of acoustic emissions. The fatigue reliability of the structure can be estimated from probabilistic fatigue life or fracture mechanics models. The data obtained from the condition assessment can be combined with these models to estimate the remaining service life of a structure using Bayes' theorem. Simulation techniques are often used to facilitate these calculations. If the remaining service life is inadequate, it may be desirable to repair the structure; however, repairs must be performed carefully to provide the desired benefit. On the other hand, economic factors may dictate a course of action other than repair, such as replacing the structure or changing the operation of the structure.

Educating the environmental engineer means proactive administration of university programs which should include a firm foundation on mathematics, chemistry, and biology. It is imperative that principles of environmental engineering, especially those that revolve around mass balance, mass transport, and reaction kinetics, be emphasized at the start of the program. It would also help if instructors promoted case discussions, group exercises and internships.

Alteration andaddition projects often pose the greatest problems in constructability. After aproject has been designed to function properly when completed, owners usually set time and manner constraints on the project. It is necessary to evaluate these constraints so that a feasible budget and schedule can be planned. Any misunderstanding over these constraints can lead to conflicting attitudes over the project.

Orlando Andersland's claim that the shear strength may gradually decline with time, thereby causing problems when employing paper mill sludges as landfill cover, is incorrect. However, actual experience has shown that shear strength improves with time. Robert Day doubts the accuracy of the test results on specific gravity, Proctor compaction tests, settlement data and shear strength parameters. However, the test data are reproducible even though the values are not appropriate for design use because the sludge properties can vary considerably.

A study on the geotechnical properties of seven paper mill sludges to be used in landfill covers is evaluated. It is argued that the authors failed to provide data on the size and quantity of fibers in the sludge samples. Questions were also raised on the decomposition and long-term behavior of the sludges in landfill covers. The impact of organic content on undrained vane shear strength at various consolidation pressures is discussed.

In 1991, approximately 37%, by weight, of the materials going to landfills was paper. Landfill space in the United States is becoming a critical problem in certain areas. This mixed paper fraction does not have a good use in traditional recycling applications. Wastepaper dealers have an excess of mixed wastepaper. This project explored the possibility of producing a value added product that would consume large amounts of mixed waste. The product selected was to produce 5 x 10 x 20 cm paper blocks. These blocks could find applications in building structures. The blocks were molded using a heated platen press and an aluminum mold, fitted with porous brass plates on the top and bottom in order to ease water removal. The material produced was similar to synthetic wood. Unlike wood, it could be molded into different shapes if desired. The density and physical properties of tensile strength and modulus were determined and compared to wood. The water absorption properties were evaluated and found to be a potential problem. Various coatings were investigated in order to improve the water holdout properties. A manufacturing process was laid out and the cost of block production was estimated to be from $0.15 to $0.24 per block, which would make it competitive with other blocks.

This paper provides a new analysis procedure for assessing the lateral response of an isolated pile in saturated sands as liquefaction develops in response to dynamic loading such as that generated during earthquake shaking. This new procedure predicts the degradation in pile response and soil resistance due to the free-field excess porewater pressure generated by the earthquake, along with the near-field excess porewater pressure generated by lateral loading from the superstructure. The new procedure involves the integration of the developing (free- and near-field) porewater pressure in the strain wedge (SW) model analysis. The current SW model, developed to evaluate drained response (a nonlinear three-dimensional model) of a flexible pile in soil, has been extended in this paper to incorporate the undrained response of a laterally loaded pile in liquefied sand. This new procedure has the capability of predicting the response of a laterally loaded isolated pile and the associated modulus of subgrade reaction (i.e., the p-y curve) in a mobilized fashion as a result of developing liquefaction in the sand. Current design procedures assume slight or no resistance for the lateral movement of the pile in the liquefied soil which is a conservative practice. Alternatively, if liquefaction is assessed not to occur, some practitioners take no account of the increased free-field porewater pressure, and none consider the additional near-field porewater pressure due to inertial interaction loading from the superstructure; a practice that is unsafe in loose sands. CE Database subject headings: Lateral loads; Piles; Saturated soils; Liquefaction; Earthquakes.

This paper discusses the rationality of the design force and damping reduction factors adopted by a few seismic design provisions for buildings with and without added passive energy dissipation systems. The issue will first be pointed out that the damping reduction factors adopted by those provisions are derived from the effects of viscous damping on displacement responses, but are used to reduce the design force of buildings. Statistical results from 1053 ground motions recorded in the U.S. show that it may lead to unconservative results, especially for systems with damping ratios greater than 10% and periods longer than 0.15 s. Furthermore, although there is no doubt that the additions of extra damping to a structure will always reduce the displacement responses, many documents argue the effect of added damping to reduce the force responses of the buildings. Therefore, this paper also addresses the effects of viscous damping on the inertial force and elastic restoring force in order to use the damping reduction factors correctly. Results of this study suggest that if the damping of structures comes from the hysteretic response of the building, the design force of the structures should be the inertial force and the damping reduction factors should be derived from the acceleration responses. Otherwise, if the additional damping of structures comes from the added energy dissipation devices, the design force should be the restoring force and the damping reduction factors should be derived from the displacement responses. CE Database keywords: Energy dissipation; Damping; Earthquake excitation; Buildings.

Earthwork volumes represent the basis on which contractors are paid for highway construction. The earthwork volumes between successive roadway stations are also used in determining the economic distribution of earthwork. It is essential that the volumes should be accurately computed because disagreements related to earthwork volumes often cause the owner and the contractor to look to the courts for settlement. The traditional model for estimating earthwork volumes of curved roadways (fiat horizontal curves) is suitable only for level terrains. For moderately fluctuating terrains, a mathematical model has been developed. This model, however, assumes that the longitudinal ground profile between successive stations is linear and the ground cross slope is constant. The mathematical model is not accurate for greatly fluctuating profiles, such as those in hilly and mountainous terrains. This paper develops a model for estimating earthwork volumes for such profiles using Monte Carlo simulation. The paper illustrates how a completely deterministic problem can be solved using a probabilistic simulation. The results show that the simulation model improves the estimates of earthwork volumes compared to traditional and mathematical models. DOI: 10.1061/(ASCE)0733-9453(2003)129:1(19) CE Database keywords: Earthwork; Simulation models; Highway construction; Volume measure; Estimation.

The main objective of this paper is to provide engineers with data on thickness loss of structural steel members resulting from corrosion. To this end, the writers have collected atmospheric exposure data from many research reports and journal papers. The data are presented in graphs of thickness loss versus exposure that demonstrate the effects of types of environment and steel. The environments include rural, industrial, and marine, becoming increasingly severe in that order. The steels under consideration are A242, A588, copper, and carbon steels, with their corrosion resistance decreasing in that order. Comparisons of the data with the medium corrosivity bands for weathering and carbon steels help to determine the severity of environments and the corrosion resistance of steel compositions. For bare exposed structures, a corrosion allowance should be added to all member thicknesses arrived at by stress calculations can be estimated by extrapolating an applicable thickness loss curve to the end of the service life of the structure. The corrosion allowance thickness loss data obtained from simple test specimens, mostly of the 150x100 mm size of an index card, must be applied carefully to complex structures such as a bridge, which has a variety of details with different exposure conditions. When portions of a bare, exposed structure remain damp or wet for long periods of time, thickness losses can be much higher than those reported for test specimens exposed at 30[degrees] facing south. Good structural detailing that prevents moisture accumulation is of utmost importance. DOI: 10.1061/(ASCE)0899-1561(2003)15:1(2) CE Database keywords: Corrosion; Weathering; Steel; Structures; Bridges.

This paper shows that the initial value of any instantaneous unit hydrograph (IUH) should be a positive value, however small. This unique characteristic is clearly demonstrated by the IUH of overland flow derived for a plane of uniform width based on the kinematic wave solution. Not only is a nonzero initial value a distinct and required characteristic of the IUH, it also provides an additional condition for determining the parameters of the IUH. The gamma probability density function has gained wide acceptance as an IUH for a watershed that is represented by a series of identical linear reservoirs. It has an initial zero value. This study shows that the model used in deriving the popular gamma probability density function IUH, with its characteristic zero initial value, is conceptually unsound. This paper presents a true form of IUH which results from a watershed represented by a series of identical linear reservoirs. Unlike the conceptual model used in deriving this gamma probability density function IUH, in this model the unit effective rainfall is distributed uniformly across all of the reservoirs. The resulting IUH contains both a gamma function and an incomplete gamma function, and it possesses the required positive initial value. This IUH may be viewed as a counterpart of the IUH derived from the kinematic wave solution and is named the pseudokinematic-wave IUH (PKW-IUH). By extending the PKW-IUH and using different weights for the series of linear reservoirs to reflect the shape of the watershed, a general form of IUH can be derived. For practical applications a three-parameter IUH, with a storage coefficient and two weights for the linear reservoirs, is proposed. Finally, an example to demonstrate the application of the proposed three-parameter IUH in predicting direct runoff is presented and the results are compared with the runoff predicted by the universally accepted gamma probability density function IUH. CE Database keywords: Hydrographs; Probability density functions; Reservoirs; Kinematic wave theory.

Macroeconomics data suggest that labor productivity declined significantly in the construction industry during the 1979-1998 period. However, microeconomic studies indicate the contrary. This paper critically examines the construction labor productivity macroeconomic data in the United States from 1979 to 1998 to determine their validity and reliability. Data collection, distribution, manipulation, analysis, and interpretation are reviewed and problems are identified. The paper also presents a comparison of construction and manufacturing labor productivity during this period. The main conclusion of the study is that the raw data used to calculate construction productivity values at the macroeconomic level and their further manipulation and interpretation present so many problems that the results should be deemed unreliable. The uncertainty generated in the process of computing these values is such that it cannot be determined if labor productivity has actually increased, decreased, or remained constant in the construction industry for the 1979-1998 period. DOI: 10.1061/(ASCE)0733-9364(2003)129:1(41) CE Database keywords: Construction management; Productivity.

This paper discusses the need for interface management within construction, with particular reference to building facade interfaces. It categorizes the three different types of interface management--physical, contractual, and organizational. The implication of interface management in construction contracting is discussed; it is explained how the U.K. procurement trends have changed, affecting the interface management within projects. U.K. cladding procurement is very fragmented, and the paper maps the development of a typical cladding system showing the complexities of interface management. Finally, the paper discusses CladdISS, a U.K. government funded research project to develop a standardized strategy for the design and management of window and cladding interfaces. It explains the principles of CladdISS with reference to process maps, action plans, management strategy, bibliography, advice on standards, materials, maintenance, joints, movement, and tolerances. This will enable strategies to be developed to avoid the endemic interface problems occurring on-site. It will also guide the management of the interfaces throughout the project. DOI: 10.1061/(ASCE)0733-9364(2003)129:1(8) CE Database keywords: Construction management; Management methods.

This paper describes the development of a general operating policy for a water supply system using the methodology of data mining. To define an operating policy using this approach, both a single-reservoir and a multireservoir water system were modeled and optimized for a set of historical inflows. These optimization results defined the best possible performance for the systems with historical hindsight, and were used as input for the data mining process. The data mining algorithm then generated the set of control rules that gave the best historical operating policy. The data mining tool used in this work is based on the induction tree technique, C5.0, reported by Quinlan in 1993. However, the process of reservoir control rule extraction is not straightforward and requires several data preparation steps to enhance the performance of the data mining algorithm. To demonstrate the effectiveness of the rules developed through data mining, simulation runs of the system were performed. The results of these simulations were compared with simulation results using operating policies derived from linear regression. Another comparison between operating rules derived using different methodologies was performed for the multireservoir system where, in addition to data mining and regression-based rules, there were rules available from the U.K. Environment Agency (South West). The paper shows that 'data-mined' rules come closest to the optimization results. CE Database keywords: Reservoir operation; Data collection; Inflow; Simulation.

The formation of shockwaves demarking boundaries between different flow states in time-space domains has been well studied and documented in the literature. Previous research concentrated on theoretical and mathematical analyses of shockwaves, providing valuable insights into shockwave phenomena. In the past few years, the traffic signal systems community has witnessed an increasing interest in adaptive control algorithms. These algorithms strive to achieve real-time platoon accommodation by assuming platoon speed and dispersion characteristics in order to predict its time of arrival at the downstream signal. Instead of assuming platoon speed and dispersion characteristics, we propose an on-line analysis of shockwaves at the downstream intersection to achieve the same purpose. This paper introduces a new metric that can detect and quantify shockwaves formed as a result of a suboptimal offset at an intersection. The new metric, the F' model, captures the effects of shockwaves using cycle-based tabulation of advance detector occupancy and count. A discriminant analysis is conducted to develop thresholds to which F' values can be compared to estimate the offset performance. The metric introduced in this paper can be used for implementing adaptive offset tuning algorithms in a traditional closed loop coordinated traffic signal system. CE Database keywords: Shock waves; Intersections; Algorithms; Traffic signals; Traffic control.