Athanasios P. Chassiakos

A web-based system for managing construction information

The efficient deployment of construction projects depends partly on the effective communication among project participants. This communication, however, is hindered by the large amount and wide variation of the information involved and the spatial dispersion of construction sites. This paper presents a web-based system that facilitates construction information management and communication. Unlike common document-based systems, the present work focuses on demonstrating the potential of data-centric web databases in enhancing the communication process during project execution. Further, this work has aimed to put emphasis on information modelling, i.e., representation of the construction process in data to facilitate exchange and interoperability of information. The proposed system consists of a relational database and a dynamic data-driven web application. The database contains 32 appropriately designed tables. End users access the database through the internet and can perform certain transactions according to their authorisation. The system implementation and testing have shown that it can provide structured and reliable information, quick and remote access, and prompt updating capabilities.

Dynamic pressures on rigid cantilever walls retaining poroelastic soil media. Part II. Second method of solution

The problem of the determination of the dynamic pressures and the associated forces on a rigid, vertical cantilever wall retaining a semi-infinite, uniform, fully-saturated poroelastic (with or without hysteretic damping) layer of soil under conditions of plane strain is considered. The rigid wall and the base of the soil layer are both excited by an acceleration harmonically varying with time and spatially invariant. The method of solution is based on the theory of Mei and Foda and considers the total field to be approximated by the superposition of an elastodynamic problem with modified elastic constants and mass density for the whole domain and a diffusion problem for the pore fluid pressure confined to a boundary layer at the free boundary (top) of the soil layer. Both problems are solved analytically in the frequency domain. Extensive parametric and comparison studies are conducted in order to assess the range of values of the various parameters (frequency, shear modulus, Poissons ratio, porosity and permeability) for which the accuracy of the present method against the direct one, reported in a companion paper, is satisfactory.

A knowledge-based system for maintenance planning of highway concrete bridges

This paper presents a knowledge-based system that is used for maintenance planning of highway concrete bridges. The system includes functions for maintenance priority setting among bridges, feasible treatment assessment in each case, and maintenance planning for a bridge stock. Maintenance priorities are set using a scoring model with decision parameters appropriately weighted. Feasible treatments are determined based on bridge condition and other factors that accelerate deterioration. Decisions for maintenance planning result from a linear programming model and are based on priority ranking, cost and effectiveness characteristics of feasible treatments, and existing budget constraints. The system has been successfully evaluated with actual and simulated data.

BIM and Lean-Business Process Reengineering for Energy Management Optimization of Existing Building Stock

Global warming and energy shortage has drastically increased the necessity to reduce energy use in buildings. Improving the energy efficiency of buildings is a key step-in achieving the energy and CO2 emission targets globally. In this effort, in the presented paper, advanced modeling methods like BIM and energy simulations are conjoined with lean waste elimination concepts into a building process-centric model. Integrating building systems, processes and energy data supports decision making for retrofitting and process reengineering actions within budget constraints. The proposed approach combines existing BIM-based energy performance tools with the development of a Business Process Reengineering architecture to develop an energy efficiency optimization model. In the first direction, BIM-based energy analysis is performed to automatically assess energy performance under varying building conditions. The Lean Business Process Reengineering (LBPR) architecture describes the fundamental layers needed to achieve more energy efficient organizational environments. These layers refer to “Definition”, “Data Information”, “Analysis” and “Therapy”. As Process Performance Indicators are also augmented to the process model, the impacts of modifications through generating different process views can be compared. An optimization model employing genetic algorithms is developed in which, considering the potential budget shortage for building asset interventions, preselected lean business process scenarios feed the optimization model to investigate the optimum solutions. A pilot case that shows the practicability of the proposed methodology is presented.

Safety Risk Assessment in Construction Projects Using Information Models

The identification of safety risks in construction sites has been a major concern of project managers who need to develop proactive safety plans to reduce accident and health related risks. This paper proposes a method which combines BIM technology, virtual reality tools, and Monte Carlo simulation to reveal possible accident conditions and to assess the probability of accident occurrence with the aim to promote safety management and accident reduction. Within the context of construction projects, the construction site is dynamically modelled employing BIM software. A programming language (Visual C #) is used to represent the human/machinery movements in the virtual environment. Finally, Monte Carlo simulation is performed to analyse specific work scenarios which may lead to hazardous conditions and assess the safety level. The aim is to link the risk output with the BIM model and to develop a heat map of accident risk throughout the project allowing, thus, prompt and effective implementation of preventive measures for accident reduction or avoidance.

Longest path time-cost analysis of construction projects with generalised activity constraints

Time-cost analysis is an important element of project scheduling, especially for lengthy and costly construction projects, as it evaluates alternative schedules and establishes an optimum one considering any project completion deadline. Existing methods for time-cost analysis have not adequately considered typical activity and project characteristics, such as generalised precedence relationships between activities and external time constraints, that would provide a more realistic representation of actual construction projects. The present work aims to incorporate such characteristics in the analysis and proposes a method for developing optimal project time-cost curves based on critical path analysis. In this method, the project is described through a matrix where all paths are tabulated with respect to activities. The project matrix includes values of 1, 0, or −1 depending on the type of precedence relation between an activity and its adjacent ones within a path. Integer programming is employed to choose among all activity crashing alternatives those which reduce path durations to a desired project length value with the lowest possible crashing cost. The method has been successfully tested on a number of cases and results are presented to illustrate its application and demonstrate its merits.