Efficient use of computers for design and construction of structures
This article is extracted from the paper presented by Dr T.V.S.R. Appa Rao at the recently held
two-day seminar of the Association of Consulting Civil Engineers in Hyderabad on the new
challenges being faced by the construction industry
Civil/structural engineers are among the pioneers in making use of computers initially to solve some of the large/complex computationally intensive problems of structural analysis starting in early 1960's. Rapid developments in computer technology (both in hardware and software, including operating systems) have enabled the users to have high speeds of computation, interactive use, time sharing, 2-D and 3-D graphic visualisation, animation, colour scanning and plotting facilities and user-friendly application development tools/facilities. Rapid developments in information technology and telecommunications have brought about phenomenal increase in speed and methods of communication of large volumes of information and data among the parties even located geographically wide apart. These developments in computer and information technologies provide enormous opportunity to the engineering professionals to save time and cost besides improving the quality of design and construction of structures and other infrastructural facilities.
Design and construction engineers as also developers of computer application software for design and construction of structures are interested in making efficient/best use of computers and IT to solve their problems. The main problems involved in this respect may be categorised under:
- Realistic (and simple) modelling of structures and loads for obtaining accurate and reliable structural analysis
- Availability/use of pre-and post-processing user-friendly facilities to minimise errors and to check input data and for graphic visualisation of results of analysis
- Optimal design of structural systems and members taking into account buildability considerations
- Automation or integration (with facility for designer interaction) of structural analysis, design, detailing and drafting of structural drawings
- Development of methodologies for using expert knowledge and information/data for design
- Construction planning, detailed cost estimation, and management, including time and cost control. This involves resource rescheduling and updating cost estimates based on real time information/data.
Integrated computer-aided design
- Creation of computer integrated design and construction environment to improve the overall productivity by avoiding repetitive input of information and by facilitating easy and fast transfer/communication of information among planners, designers, construction engineers and the owners.
Finite Element Modelling
Efficient and reliable techniques of structural analysis have to be used to arrive at safe and economical designs of large and complex structures such as multi-storeyed buildings, long-spanned bridges, shell structures etc. It is well recognised that finite element modelling (FEM) can be used to solve almost all types of structural analysis problems. The accuracy and reliability of the solution depends on how well the real structure and the problems modelled for Finite Element (FE) analysis, which in turn depends on the understanding of the basis and limitations of the FEM and the chosen software.
The first major step is to model/ idealise the geometry of the structure for particular requirements/goals of the structural analysis on hand. For example, in the preliminary design stage, a one-dimensional model of the structure (say a tall building) may be adequate for determination of natural frequencies and mode shapes while in the final design stage, one may have a 3-D model of the structure for evaluation of natural frequencies and mode shapes to determine its seismic response accurately. That is, the model will be different for different purposes or stages of analysis and design. Related consideration to this modelling is whether this process can be automated. The geometry of the real structure/component given by a solid model in the case of machine component or the architectural drawings in the case of a civil engineering structure is the starting point for development of a geometrical model for finite element analysis. Transforming the geometry of the real structure in the geometrical model for finite element analysis is a complex process in which engineering knowledge and expertise related to various aspects of structural behaviour/analysis, computer software and hardware facilities and their limitations have to be considered. It maybe noted that large amount of data and its manipulation will be involved in this process. Advances have been made to develop methodologies and expert systems in this area to facilitate automatic/integrated modelling for FE analysis.
Computers can be effectively used in conceptual planning in preliminary as well as detailed stages of design. AUTOCAD is the widely used general purpose drafting software package which provides many facilities for preparing general arrangement and also detailed drawings (both 2-D and 3-D). Design is basically an interactive process involving generation and examination/evaluation of different alternatives for arriving at an optimal solution satisfying both functional and structural safety requirements according to the relevant codes of practice. The process of arriving at optimal designs can be made efficient by making use of appropriate computational models and computer program for carrying out necessary structural analysis and by making use of engineering expertise to make decisions at various stages of the process by interaction in the interactive process or by making use of knowledge based expert systems for this purpose.
For more details please refer to Projectmonitor Prinit Version.