Showing papers in "Journal of Computing in Civil Engineering in 1989"

Computer Integration: Reducing Fragmentation in AEC Industry

Abstract: Emerging and existing computer technologies can be synthesized in ways that provide new kinds of decision support for integrating the data, design decisions, and knowledge normally dispersed among the many participants in the architecture/engineering/construction (AEC) process. This paper briefly examines the origins and impacts of fragmentation in the industry in the U.S. and describes six thrust areas where computer‐integrated design and construction can substantially improve the competitiveness of the U.S. AEC industry and the quality of its products. In each of these thrust areas, AEC problems pose important challenges to developing technologies for artificial intelligence, graphic and nongraphic databases, process automation and robotics, and management and dissemination of technology. The application of these advanced computer technologies and the AEC industry offers the promise of significant gains in productivity and will infuse new excitement into civil engineering education and practice.

Intelligent Decision Support and Reservoir Management and Operations

Abstract: Reservoir management and operations are very complex activities in the field of water resources engineering. During the last two decades, a number of systems analysis techniques, particularly optimization and simulation, have been adopted for reservoir planning, design, and operations. Recently, the area of knowledge-based engineering (expert systems) has emerged as a potential technique for incorporationg human expertise and some degree of intelligent judgment into decision-supporting software. This paper presents the potential benefits of this technology in the area of reservoir management and operations. The presentation is illustrated with an example of an engineering expert system for reservoir analysis that is currently in development.

Knowledge‐Based System for Soil Improvement

Abstract: The practice of soil improvement has received renewed attention in the last two decades. As a result, existing methods were improved and new ones developed. This paper presents a knowledge‐based decision support system for the selection of soil improvement methods, Improve. The system uses a knowledge representation structure based on “windows” together with a best‐first search algorithm. In this context, windows are mathematical representations of the restrictions to the values variables can take, combining the knowledge and its uncertainty in a unique entity. This form of knowledge representation has many advantages and allows for procedures not available in other systems, such as the development of composite solutions, the use of different evaluation functions, the search for lacunae, and the case‐based representation of knowledge.

Assessment of Computational Practices in Dynamic Soil‐Structure Interaction

Abstract: This paper presents a comparative study of the most widely used numerical methods in dynamic soil‐structure interaction (SSI). The developments follow in parallel treatments of representative SSI problems solved by frequency, the time‐domain boundary element method (BEM) and finite element method (FEM) formulations. Such treatments serve to enunciate the advantages and limitations of BEM and FEM formulations, and allow critical comparison of their differences and suitability to solve steady‐state and transient elastodynamic problems. Further, the in‐parallel presentation serves as a means of identifying possible sources of computational and modeling errors associated with several factors, such as improper modeling of the finite size structure and the supporting infinite soil medium, consideration of structural inertia, and appropriate coupling between boundary and finite element methods. Even though the examples are representative dynamic soil‐structure interaction problems, the remarks and observations a...

Interactive Design Optimization of Framed Structures

Abstract: A practical formulation for optimum design of framed structures under multiple loading and constraint conditions is described in this paper. The AISC (American Institute of Steel Construction) code limits on element stresses, member maximum deflection, stability and slenderness ratios, width thickness ratios, and nodal displacements are imposed in the design process. An optimization procedure that is capable of treating different cross‐sectional shapes is developed and described. In practical applications, it is important to interactively monitor the progress of the design process. Therefore, an interactive software system for the present research is designed and implemented. The system is based on modular approach and modern data base management concepts. It is used to solve two design optimization problems. A postprocessor is designed to select members from the AISC tables. The interactive program is another step in making practical use of optimization a reality.

Automatic Generation of Seepage Flow Nets by Finite Element Method

Abstract: An analytical method for automatically generating a seepage flow net using the finite element method (FEM) is described. This technique includes a new, more analytical (as compared with numerical) approach to determining the boundary conditions for computing the stream function and a refined approach to handling the transition between multiple layers. Equipotentials are obtained by contouring the results of the FEM solution where total head at each node is computed. The boundary conditions are then modified using the Cauchy‐Riemann equations governing conjugate harmonic functions, and a second FEM problem is solved to compute stream function at each node. Appropriately contouring these results produces the desired flow lines, and the flow net is complete. Procedures for confined flow, unconfined flow, and multilayer systems are presented with examples. A discussion for axisymmetric problems is also given.

Interactive graphing of simulation networks

Abstract: An approach to building a simulation model on-screen and automating the computer-input process is reported. This approach could be applicable to the class of simulation problems that can be represented by a network model. Such problems include those associated with manufacturing systems, transportation systems, equipment and manitenance scheduling, construction work-in-process, and parking facility design. Financial forecasting and risk analysis models can also be represented by networks. The simulation system for the application described here is called CYCLONE (Cyclic Operations NEtwork). Details are given of the graphic system, user menus, and the generation of CYCLONE input. Improvements that could be made to the graphics program and the translation program are noted. The error-checking program of the translation routine also could be expanded.

Numerical Approach for Generating Beta Random Variates

Abstract: There are a number of probability density functions available to model time durations and other activities of interest in computer simulation programs. Among the available functions, the beta probability density function has been popular with practitioners of simulation because of its versatility, in that it can take on a variety a of shapes and easily fit sample distributions. The beta function also has specific upper and lower limits. This latter property is attractive since many applications do not require values at plus and minus infinity as would be modeled by the Gaussian, or normal, distribution. This paper describes a numerical technique for the generation of beta random variates where the beta parameters are not limited to integer values. By not limiting parameters to integer values, one must evaluate the beta normalizing constant as a gamma function rather than as a factorial function. A numerical technique for evaluating this gamma function by using a Gauss‐Laguerre approximation is discussed. ...

Load Redistribution in Frame with Settling Footings

Abstract: A computer program is presented that can be used to estimate actual final settlements for any frame supported on isolated spread footings. These footings can be founded in any type of soil stratum consisting of any combination of sand layers, normally consolidated or overconsolidated clay layers. Settlements are computed based on one‐dimensional consolidation theory for normally consolidated and overconsolidated clays and on Schmertmann's technique for sand layers. Influence of load redistribution from surrounding footings due to frame action is incorporated directly into the settlement computations. Application of program methodology to three rigid frames indicates that forces induced by differential settlement can be significant, leading in some cases to stress reversal, when compared to the situation where the footings are assumed not to settle. On the other hand, rules of thumb traditionally used to limit differential settlement in a structure of the type investigated were found to be overly conservative.

HIBIC: Expert System for Highway Bridge Dynamics

Abstract: The current highway bridge design codes treat the dynamic effect of traffic loads by applying an empirical amplification factor, called the “impact factor,” which is a function of span length only and has little theoretical basis. This paper presents a new and more rational approach for determining the dynamic response of highway bridges to random traffic loads. This approach integrates design-independent knowledge about the dynamic effects of traffic loads into the algorithmic design process. The integration has been done by developing HIBIC (Highway Bridge Impact Consultant), an expert system for determining the most suitable impact stress amplification factor for use in the design of highway bridges. This approach uses heuristics concerning pavement and traffic conditions, as well as a detailed numerical methodology based on concepts of random vibrations and finite elements. The knowledge encoded in the expert system was extracted from the literature, bridge experts, and practicing engineers and was organized into rules. The prototype expert system was tested in several consultation sessions by the researchers and produced very satisfactory solutions in each case. Results of a consultation session for a 70-ft, single-span, composite steel girder/concrete deck structure are presented and discussed. The approach of integrating expert systems with numerical methods used in this paper will have applications in many other design areas.

Emulation for Control System Analysis in Automated Construction

Abstract: Advances in Computer‐Integrated Construction (CIC) and automation are heavily dependent on the development on communication links to integrate design with engineering and construction. Efforts are presently under way to standardize the communication protocol. In order to take full advantage of CIC, the shared data and information should also be used at the construction site to plan and control actual operations. Computer‐based systems have been developed and tested for automated control in many industries. For the application of computerized control in construction, detailed analysis of different control structures is required. This paper presents one aspect of control systems, namely hierarchical decomposition through commands and feedback and decision‐making in a rule‐based environment. Automated truss manufacturing has been used to demonstrate the use of a microcomputer‐based system developed to analyze control systems.

Unified activity network model

Abstract: Activity network models are usually represented by activity‐on‐node precedence diagramming or activity‐on‐branch arrow diagramming. We present a unified model in which each activity is represented by a start node, a finish node and an intervening link. In this representation, a link can represent an activity or one of up to sixteen different precedence or window constraint types. While the problem size increases with the unified representation, the complexity of the model and solution algorithms are substantially reduced. In particular, numerous precedence and window constraint types appear as the same type of link in this model. Standard network representations and manipulations are supported directly by the model. Algorithms to perform scheduling calculations are summarized and numerical examples presented.

Microcomputer Model for Oil Spill Simulation (MICROSS)

Abstract: An integrated microcomputer‐based model is developed for oil spill simulation, data preparation, and graphical display of results. The mathematical model for oil spills can simulate advection, horizontal diffusion, mechanical spreading, evaporation, dissolution, and shoreline deposition of oil spills in rivers and lakes. The graphical analysis of results can be in color or monochrome. The monochrome version represents the oil slick as an assembly of large number of dots, superimposed on river or lake maps. In the color version, square boxes represent the oil slick. Each of these boxes is assigned a color, based on the volume of oil it represents. The model can also prepare the data for the simulation programs, access the disk resident data bank, and add new data to the data bank. All actions—from data preparation to display of results—can be directed interactively from menus and by answering computer prompted questions.

Computer graphics in truss-model design approach

Abstract: The main objective of this paper is to extend and simplify the use of truss models in the design of reinforced concrete members for flexure and shear by means of user-friendly, interactive computer graphics. An interactive computer-graphics program, which replaces the traditional drawing board and calculator in the development of truss models for reinforced concrete members, is presented. The interactive program allows the designer to input the selected truss model graphically, then analyze it, display the results and revise the truss model if necessary. The interaction between the graphics and analysis tools was found to be the most efficient method to transfer the truss parameters to the analysis routines. The features of the truss-model program are demonstrated with the design example of an inverted-T bent cap in a bridge and structure.

Simplified second-order elastic-plastic analysis of frames

Abstract: A simplified nonlinear computer algorithm that calculates the elastic-plastic response of plane frames including the P-Delta effects as well as the reduction in the plastic moment capacity due to axial forces is presented. The proposed algorithm consists of a simplified second-order elastic-plastic analysis in which the effects of bowing and the incremental part of the stiffness matrix in each member are neglected. The NONLIN algorithm, as it is called in this paper, is particularly useful in the plastic design of steel frames. FORTRAN and BASIC versions of NONLIN are available for use in microcomputers. The validity of the proposed algorithm is checked against available experimental and analytical results.

CSTRUCT: computer environment for design of steel structures

Abstract: CSTRUCT is a recently developed interactive computational environment for the design and analysis of structures. This paper summarizes a recently developed CAD design methodology; briefly outlines some of the software development issues that have been considered in the planning of CSTRUCT; and describes the features of a prototype version of CSTRUCT. A command language and graphical tools have been developed to describe the design problem, define attributes of the design problem, identify critical frame actions and frame displacements, and determine the overall adequacy of a design. The paper presents a summary of recent developments in earthquake-resistant design philosophy and emphasizes the strong need for a computational environment to support this design philosophy, as well as traditional approaches to design.

Computerized Life‐Cycle Cost Systems in the Army

Abstract: The U.S. Army Construction Engineering Research Laboratory, Champaign, Illinois, has developed several sets of calculation methods for determining life cycle costs of facilities. Two calculation methods have been implemented in a relational database language on a national computer system and on a basic DOS personal computer. Four calculation methods have been implemented in a DOS environment for an embellished personal computer. All calculation methods can be applied by any organization (cities, universities, corporations) for resource prediction. The calculation methods are currently being applied by selected installations in Germany and the United States. Benefits and operation of the system are described in this paper. The main features of the system are presented as applicable to all elements within the Army.

Simulating Construction Robot Agents and Their Knowledge Environment

Abstract: In future construction environments, intelligent machines must harness considerable knowledge to plan and control autonomous tasks even though they will be limited in their own knowledge. However, no unifying theory and few guidelines exist for defining and communicating knowledge about designs and field operations in a way that can effectively be used by such machines. This paper first describes research needed to discover and formulate a general core of theory and software for such machines and the knowledge in their environment. For researchers interested in the cognitive aspects of construction robotics, it next surveys current research to simulate characteristics of robot agents themselves, simulate their knowledge environment, and develop means of communication. Finally, it suggests avenues researchers might pursue to integrate research in construction automation more effectively. The main benefit of this research will be to provide a theoretical base for the knowledge environment to sustain automation research for autonomous robots working in real and very challenging field conditions.

Expert System for Evaluating and Notifying Hazardous Waste Generators

Abstract: Monitoring and regulating hazardous waste generators is becoming increasingly difficult. Expert systems are used to expedite the process of evaluating information on generators and reporting the results to them. This system not only makes the technical analysis more efficient, it also effects significant reductions in the time required to generate the associated paperwork. A Lotus 1‐2‐3 spreadsheet has been used to develop a prototype of this system. The advantage of the spreadsheet is that the entire analysis can be done with a single software system that is widely used. The method of setting up the knowledge base, the rule base for user interaction, and the extraction table are discussed. Macro‐statements are used to run the extraction process for creating an action letter to the hazardous waste generators. A similar system can be used in other applications where paperwork needs to be generated as part of the engineering analysis and/or design.

Linking Civil Engineering Design and Drafting Software via IGES

Abstract: A Methodology for integrating application design programs and Computer Aided Drafting (CAD) packages is presented. Application of the methodology enables the automatic translation of the final design information into production drawings of the design, reducing the possibility of translation errors and increasing the engineering and drafting productivity. A model system to demonstrate the methodology has been designed and implemented, utilizing a reinforced concrete box culvert design program. The drawing files were generated using the Initial Graphics Exchange Specification (IGES), a neutral drawing file data format that can be utilized by a variety of CAD systems. The success of the model was demonstrated on three different CAD systems residing in the mainframe and microcomputer environments. One example problem is provided to illustrate the success of the methodology. Guidelines for implementing the methodology are summarized.

Modeling of Dynamic Systems: An Innovative Approach

Abstract: Engineers have always been interested in describing the timedependent response of physical systems, whether they be the motion of a spring or the biogeochemical state of a wastewater stabilization ...

Sensitivity analysis of construction contract prices using spreadsheets

Abstract: “Bad profits” are identified as the cause of more than one-half of all business failures in construction. To improve the profitability of the construction contractors, the Fair and Reasonable Markup (FaRM) is defined as the smallest markup that satisfies the Required Rate of Return (RRR) of the contractor for the particular (or at least the general) risk class of the project at hand. The microcomputer-based FaRM Pricing Model provides a systematic and efficient framework for analyzing the forecast cash-flow stream of the project and for estimating the Minimum Acceptable Price (MAP). The model utilizes LOTUS 1-2-3 spreadsheet and can be implemented on most IBM or compatible microcomputers. The computerized model delivers speedy responses to a variety of what-if questions investigating the sensitivity of FaRM and MAP to the billing policy and the Required Rate of Return (RRR) of the contractor and to the payments time lag and the retainage policy of the owner. Once the FaRM Pricing Model has been implemented, contractors should bid lower on projects which are more attractive; thereby, they should become more competitive. This should result in lower costs to owners while satisfying the RRR of the contractors. Conversely, contractors can maintain their RRR on the less attractive projects by submitting higher bid prices.

Seismic analysis of multistory building systems using microcomputers

Abstract: A simple mathematical model representing the full three‐dimensional linear elastic response of multistory building systems with horizontal rigid‐body floors subjected to multicomponent earthquake excitations is presented. The resulting time‐domain analysis technique relies on closed‐form algebraic expressions for the structural dynamic characteristics and subsequent modal decomposition developed by the writer in previous work. The corresponding algorithm was implemented in a program for automatic earthquake analysis on a microcomputer, and typical applications are illustrated by the solution of an example problem. The results of a series of parametric studies on the variation of effective earthquake story lateral forces and story torques with the gradient of elastic eccentricity along the building height are also presented.

PC-Based Data Acquisition System for Structural Monitoring

Abstract: While personal‐computer‐based data‐acquisition systems have become commonplace in the laboratory environment over the past several years, their use as remote, automatically triggered data‐collection systems has been somewhat limited in comparison to that of off‐the‐shelf, dedicated systems. This is somewhat surprising given the versatility and reliability of the devices now available. This paper describes the design, development and implementation of a personal‐computer‐based system for use in such a remote data‐collection application. The system developed is reliable, versatile, cost‐effective, and meets all the demands placed on such a system. The system is currently being installed in a 305‐m television transmission tower in Shenyang, the People's Republic of China, for the monitoring of wind and wind‐induced structural motions over a two‐year period.

Microcomputer-aided analysis and design of steel frames

Abstract: A microcomputer software package, FRAME‐AD Version 3.00, has been developed for the analysis and design of moment‐resisting steel frames. The main feature of the software is the use of interactive computer graphics. This feature facilitates the construction of the structural model, application of loading conditions, and displaying the results in a clear and concise manner. In addition, the software is menu driven, user friendly, and does not require previous experience with computer operating systems. The analysis is carried out using the stiffness method, and the design can be performed using either the “Load and Resistance Factor Design” or the “Allowable Stress Design” Specifications of the American Institute of Steel Construction. The software is developed for IBM or compatible personal computers, and is written in BASIC language using Microsoft Quick‐BASIC 4 compiler.