Actual Construction Time Research Articles

An automated nD model creation on BIM models

Abstract The construction technology (CONTEC) method was originally developed for automated CONTEC planning and project management based on the data in the form of a budget or bill of quantities. This article outlines a new approach in an automated creation of the discrete nD building information modeling (BIM) models by using data from the BIM model and their processing by existing CONTEC method through the CONTEC software. This article outlines the discrete modeling approach on BIM models as one of the applicable approaches for nD modeling. It also defines the methodology of interlinking BIM model data and CONTEC software through the classification of items. The interlink enables automation in the production of discrete nD BIM model data, such as schedule (4D) including work distribution end resource planning, budget (5D)—based on integrated pricing system, but also nD data such as health and safety risks (6D) plans (H&S Risk register), quality plans, and quality assurance checklists (7D) including their monitoring and environmental plans (8D). The methodology of the direct application of the selected classification system, as well as means of data transfer and conditions of data transferability, is described. The method was tested on the case study of an office building project, and acquired data were compared to actual construction time and costs. The case study proves the application of the CONTEC method as a usable method in the BIM model environment, enabling the creation of not only 4D, 5D models but also nD discrete models up to 8D models in the perception of the construction management process. In comparison with the existing BIM classification systems, further development of the method will enable full automated discrete nD model creation in the BIM model environment.

Adapting Gel Wax into an Ultrasound-Guided Pericardiocentesis Model at Low Cost.

Cardiac tamponade is a life-threatening emergency for which pericardiocentesis may be required. Real-time bedside ultrasound has obviated the need for routine blind procedures in cardiac arrest, and the number of pericardiocenteses being performed has declined. Despite this fact, pericardiocentesis remains an essential skill in emergency medicine. While commercially available training models exist, cost, durability, and lack of anatomical landmarks limit their usefulness. We sought to create a pericardiocentesis model that is realistic, simple to build, reusable, and cost efficient. We constructed the model using a red dye-filled ping pong ball (simulating the right ventricle) and a 250cc normal saline bag (simulating the effusion) encased in an artificial rib cage and held in place by gel wax. The inner saline bag was connected to a 1L saline bag outside of the main assembly to act as a fluid reservoir for repeat uses. The entire construction process takes approximately 16–20 hours, most of which is attributed to cooling of the gel wax. Actual construction time is approximately four hours at a cost of less than $200. The model was introduced to emergency medicine residents and medical students during a procedure simulation lab and compared to a model previously described by dell’Orto.1 The learners performed ultrasound-guided pericardiocentesis using both models. Learners who completed a survey comparing realism of the two models felt our model was more realistic than the previously described model. On a scale of 1–9, with 9 being very realistic, the previous model was rated a 4.5. Our model was rated a 7.8. There was also a marked improvement in the perceived recognition of the pericardium, the heart, and the pericardial sac. Additionally, 100% of the students were successful at performing the procedure using our model. In simulation, our model provided both palpable and ultrasound landmarks and held up to several months of repeated use. It was less expensive than commercial models ($200 vs up to $16,500) while being more realistic in simulation than other described “do-it-yourself models.” This model can be easily replicated to teach the necessary skill of pericardiocentesis.

Effects of uncertainty on scheduling of highway construction projects

Time and cost overruns in highway construction are usual in Colombia. Contractors regularly fail in cost estimation and construction scheduling. An analysis of important factors on time and cost overruns in highway construction in southwest Colombia is presented in this paper. Forty highway construction projects were reviewed. Data from construction documents were collected to prepare a data base for probabilistic analysis. Data collected include scheduled construction time and cost, actual construction time and cost, and unexpected events which could have affected the construction process. Data were used in a probabilistic cost and schedule risk analysis to identify critical factors in construction time and cost overruns in the region. It was found that the activities that most affect the time and cost overruns are the construction of the granular base and the asphalt layer. The most common causes of construction overruns were found to be poor cost and duration estimates, rain, and materials supply problems.

The effect of political unrest on construction time for food grain warehouses in Bangladesh

A range of poorly understood factors affect actual construction time in the context of food sector projects in Bangladesh. One factor of particular interest is political unrest. The data for this study were obtained from a leading design and construction management company in Bangladesh. The sample size consisted of data for 104 food grain warehouse projects scattered all over the country. The effect of political unrest on construction time was analysed in conjunction with other known variables for actual construction time, such as increase in project cost and delay in procurement of construction materials. The effect of local political unrest on construction time was statistically significant even in the presence of project cost and procurement of materials variables. Political unrest could be included in prediction models used for finding out actual construction time of food grain warehouse projects in Bangladesh. Based on these findings, a prediction model for construction time for such projects is developed.

3D coupled mechanical and hydraulic modeling of a geosynthetic-reinforced deep mixed column-supported embankment

Numerical studies were conducted to improve the understanding of the behavior of geosynthetic-reinforced column-supported embankments. Due to the complexity of the problem, so far, consolidation process and three-dimensional patterns of columns have not been well simulated in most published numerical studies. As a result, the time-dependant behavior and the serviceability of this system have not been well evaluated. In this study, a three-dimensional coupled mechanical and hydraulic modeling was conducted using FLAC3D to consider consolidation and three-dimensional arrangement of columns. This study was based on a well-documented bridge approach embankment reinforced by a layer of geotextile and supported by deep mixed (DM) columns. The foundation soils including soft clay and silt, the embankment fill, and the deep mixed columns were modeled as linearly elastic-perfectly plastic materials with Mohr–Coulomb failure criteria. The geotextile reinforcement was simulated by geogrid elements incorporated in the FLAC3D software, which can sustain in-plane tensile force only. The staged construction was simulated by building the embankment in lifts. The duration of each lift was the same as the actual construction time plus the lapse time between two consecutive stages. The development of settlement and tension in the geotextile with time is compared with the long-term monitoring data and yields good agreement. The generation and dissipation of excess pore water pressure during and after construction are presented and discussed.

Model for Estimation of Time and Cost for Tunnel Projects Based on Risk Evaluation

In the planning and procurement phases of tunnelling projects, numerous decisions have to be made regarding tender price and budget. Many case studies have shown that, in practice, the predicted costs and time schedules are often exceeded. This paper describes a study of the various risk factors in machine tunnelling and their differing impacts on cost and time. It has been concluded from the study that it is important to make a clear distinction between normal cost and time, and the undesirable events that cause exceptional cost and time. Existing decision-aid estimation models consider variation of the risk factors, but do not consider normal cost or time separately from undesirable events. Usually, estimations of project cost and time are made in a deterministic manner, but this does not allow one to consider uncertainty in cost and time variables. However, if the variables are treated probabilistically, the total cost of tunnelling can be expressed as a distribution curve, and a decision can be made on the tunnelling method by comparing the respective cost and time distributions. Based on such decisions, the budget and tender price can be determined separately, both by the client and contractor respectively. To meet the demands placed on decision-making for tender and procurement for currently favoured construction-contracting methods, a new model for estimating tender price and budget has been developed, and is described in this paper. This estimating technique has been applied to a case study of the Grauholz Tunnel. The predictions obtained from the estimation model are shown to be realistic, as the total construction cost and time obtained from the model correspond fairly well to the actual construction cost and time. The separate estimation of normal cost and time and exceptional cost and time contribute to the clarity of the results. The use of the proposed model also shows that the tunnelling method most suitable for the actual geological and hydrogeological conditions can be selected by this method.

Forecast models for actual construction time and cost

The actual construction time and cost of construction projects may be affected by the client, project and contractual characteristics and in many cases can be very different from the contract time and cost. In this paper, details of 93 Australian construction projects are used to develop several models for actual construction time and cost prediction. A forward crossvalidation regression analysis is used for the development of the model for actual construction time forecast when client sector, contractor selection method, contractual arrangement, project type, contract period and contract sum are known. The standard deviation of the deleted residual indicates the best model for actual construction time prediction to comprise the independent variables log contract time, lump sum procurement and non-standard contractor selection. Regression models are also developed for forecasting the actual construction time and cost when client sector, contractor selection method, contractual arrangement and project type are known while contract period and contract sum are estimated. Different forms of regression analyses, including the standard regression and the crossvalidation regression, are used and the crossvalidation regression model with the smallest deleted residual sum of squares is selected. Since these models for time and cost are dependent on the contract period and contract sum being known, it is necessary to investigate the effects in situations where these have to be estimated. The results of the sensitivity analyses show that the errors in predicted actual construction time become smaller as the contract period increases. In contrast, the errors in predicted actual construction cost are virtually the same for large and small projects. The effects of different project type, contractor selection method and contractual arrangement are also examined. The results indicate that the actual construction time for industrial project is the longest when compared with residential, educational and recreational projects and that significant savings in actual construction time can be achieved when negotiated tender and design and build contract are used instead of the traditional open tendering and lump sum contract approaches. Finally, some practical applications of the models are illustrated for predicting the actual construction time and cost based on the risks and uncertainties of different client sector, contractor selection method, contractual arrangement and project type.

Time–cost relationship of public sector projects in Malaysia

Earlier research by Bromilow in Australia found that the duration of construction period can be modelled by a time–cost formula expressed in the form of T= KC B , where T is the actual construction time in working days, C is the final cost of contract in millions, K is a constant characteristic of building time performance, and B is a constant indicative of the sensitivity of time performance to cost level. The aim of this paper is to identify whether such time–cost relationship can be extended to the building projects in Malaysia. Time and cost data from 51 public sector projects were collected to verify whether such a relationship holds in the Malaysian building industry. Regression analysis was used to compute the values of K, B and check how well the model actually fits. Analysis of these 51 projects identified that the best predictor of average construction time of public sector projects in Malaysia is T=269 C 0.32. The predicted time for a RM 1 million public project was 269 days. The time–cost relationship identified in this paper serves as a convenient tool for both project managers and clients to predict the average time required for delivery of a construction project.

Modelling building durations in Hong Kong

The duration of Australian construction has been modelled by a time-cost formula expressed in the form of T=KCB , where T is the actual construction time in working days, C is the final cost of contract in millions, K is a constant characteristic of building time performance, and B is a constant indicative of the sensitivity of time performance to cost level. This paper applies the relationship to building projects in Hong Kong using time and cost data from 110 projects. Regression analysis was used to compute the values of K and B and check how well the model actually fits, and the best predictor of average construction time of building projects in Hong Kong is found to be T=152C0.29. It is also found that the Hong Kong private sector takes a shorter time (120 days) to complete a hypothesized project with a contract sum of HK$1 million (at December 1994 price) than its government counterpart (166 days). The time-cost relationship serves as a convenient tool for both project managers and clients for predicting the actual optimum time required for delivery of a building project.

Net power and energy output of the German LWR nuclear power system

Net energy analysis is used to calculate the (annual) net energy output and the power and energy efficiencies of the German nuclear power system from the beginning of the construction program until 1982. For each individual power plant, actual construction time, start of operation and annual energy yield data are taken into account. The power expenditure data for construction, first core and reloading are taken from the literature on energy analysis, and the sensitivity of the results to the pertinent data uncertainties is shown. The problem of evaluation of thermal and electric forms of energy is also addressed. The results clearly show that an appreciable fraction of the power produced in the German nuclear power system is consumed within the nuclear industry, especially in the first period of expansion when small power plants are in operation and large ones under construction. This finding is contrary to what may be expected from the small payback time associated with individual power plants. However, nuclear power is not an energy sink. If the issue were to compare a nuclear power system with an alternative option such as an oil or coal-based technology, the same efficiency assessment would have to be carried out for the alternative system before a proper comparison can be made.