• Title/Summary/Keyword: Cost of Control

Search Result 5,861, Processing Time 0.039 seconds

Challenges to Prevent in Practice for Effective Cost and Time Control of Construction Projects

  • Olawale, Yakubu A.
    • Journal of Construction Engineering and Project Management
    • /
    • v.10 no.1
    • /
    • pp.16-32
    • /
    • 2020
  • Cost and time control of projects is important in preventing project failure. However, achieving effective cost and time control in practice is often challenging. The challenges of project cost and time control in practice are investigated by carrying out a questionnaire survey on the top 150 construction contractors in the UK followed by in-depth semi-structured interviews of practitioners from 15 construction companies in the country. Quantitative analysis reveals that design change is the most important factor inhibiting the ability of UK contractors from effectively controlling both the cost and time of construction projects. Four of the top five factors inhibiting effective cost control are also the top factors inhibiting effective time control albeit in a different order. These top factors-design changes, inaccurate evaluation of project time/duration, risk and uncertainty, non-performance of subcontractors and nominated suppliers were also found to be endogenous factors to the project. Additionally, qualitative analysis of the interviews reveals 16 key challenges to prevent for effective project cost and time control in practice. These are classified into four categorised based on where they stem from as follows; from the organisation (1. Lack of integration of cost and time during project control, 2. lack of management buy-in, 3. complicated project control systems and processes, 4. lack of a project control training regime); from the construction management/project management approach (5. Lapses in integration of interfaces, 6. project control not being implemented from the early stages of a project, 7. inefficient utilisation and control of labour, 8. limited time devoted to planning how a project will be controlled at the outset); from the client; (9. Excessive authorisation gates, 10. use of adversarial and non-collaborative forms of contracts, 11. communication problems within client set-up, 12. obstructive client representatives) and; from the project team (13. Lack of detailed/complete design, 14. lack of trust among the project partners, 15. limited time devoted to project control on site, 16. non-factual reporting). The study posits that knowledge of these project control inhibiting factors and challenges is the first step at ensuring they are avoided and enable the implementation of a more effective project cost and time control process in practice.

Analyses of the Cost function for the Reductions of the Dynamic Response and the Vibrational Intensity of a Discrete System and Its Elastic Supporting Beam (이산계와 탄성 지지보의 동응답 및 진동 인텐시티 저감을 위한 목적함수 해석)

  • Kim, Gi-Man;Choi, Seong-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.20 no.1
    • /
    • pp.83-91
    • /
    • 2010
  • In this paper, the feasibility of the cost function having two control factors were discussed in compared to two others which has one different control factor respectively. As of the control factors, the dynamic response of a discrete system and the vibrational intensity at the reference point which is the connecting point of a discrete system to a flexible beam were controlled actively by the control force obtained from the minimization of the cost function. The method of feedforward control was employed for the control strategy. The reduction levels of the dynamic response of a discrete system and the vibrational intensity at a reference point, and also the input power induced by the control force were evaluated numerically in cases of the three different cost functions. In comparison with the results obtained from the cost functions of one control factor, which is the dynamic response or the vibrational intensity, in most cases of the cost function of two control factors the better or similar results were obtained. As a conclusion, it is surely noted that both the dynamic response and the vibrational intensity of the vibrating system be controlled up to the expected level by using the single cost function having two control factors.

Cost-Effectiveness Evaluation of Semi-Active Control System for Cable-Stayed Bridge (사장교에 장착된 준능동형 제어시스템의 비용효율성 평가)

  • Hahm, Dae-Gi;Park, Won-Suk;Koh, Hyum-Moo;Ok, Seung-Yong;Park, Kwan-Soon
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • 2005.03a
    • /
    • pp.388-395
    • /
    • 2005
  • This paper presents cost-effectiveness evaluation of semi-active control system for cable-stayed bridge under earthquake excitation. Bi-state control method with Linear Quadratic Gaussian(LQG) optimal controller is used for generic semi-active dampers. Cost-effectiveness of the structural control system is investigated by using the life-cycle cost(LCC) concept. The evaluation results show that the efficiency of semi-active control system is increased when the damage cost due to the failure of bridge system or the bridge importance is enlarged. It was also found that the damper cost had little influence on the cost-effectiveness of semi-active control system if it was relatively small to the initial construction cost.

  • PDF

A Combined Process Control Procedure by Monitoring and Repeated Adjustment

  • Park, Changsoon
    • Communications for Statistical Applications and Methods
    • /
    • v.7 no.3
    • /
    • pp.773-788
    • /
    • 2000
  • Statistical process control (SPC) and engineering process control (EPC) are based on different strategies for processes quality improvement. SPC reduces process variability by detecting and eliminating special causes of process variation. while EPC reduces process variability by adjusting compensatory variables to keep the quality variable close to target. Recently there has been needs for a process control proceduce which combines the tow strategies. This paper considers a combined scheme which simultaneously applies SPC and EPC techniques to reduce the variation of a process. The process model under consideration is an integrated moving average(IMA) process with a step shift. The EPC part of the scheme adjusts the process back to target at every fixed monitoring intervals, which is referred to a repeated adjustment scheme. The SPC part of the scheme uses an exponentially weighted moving average(EWMA) of observed deviation from target to detect special causes. A Markov chain model is developed to relate the scheme's expected cost per unit time to the design parameters of he combined control scheme. The expected cost per unit time is composed of off-target cost, adjustment cost, monitoring cost, and false alarm cost.

  • PDF

Vibration Control and Cost-Effectiveness Evaluation of Cable-Stayed Bridges with Semi-Active Control System (준능동 제어시스템을 이용한 사장교의 진동제어 및 비용효율성 평가)

  • Hahm, Dae-Gi;Ok, Seung-Yong;Park, Wonsuk;Koh, Hyun-Moo;Park, Kwan-Soon
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.9 no.4 s.44
    • /
    • pp.43-54
    • /
    • 2005
  • This paper presents cost-effectiveness evaluation of semi-active control system for cable-stayed bridge under earthquake excitations with various magnitudes and frequency contents. Semi-active control system, which is operated by using Bi-stale control method on the basis of linear quadratic Gaussian (LQG) optimal controller, is designed for the benchmark control problem proposed by Dyke et at. The cost-effectiveness of the proposed control system is defined by the ratio of life-cycle costs between a bridge structure with shock transmission units and a bridge structure with the semi-active control devices. The simulated results show that the damper cost has little influence on the cost-effectiveness of the semi-active control system while the cost-effectiveness is quite sensitive to the damage cost induced by the bridge failure. It is also found that the semi-active control system guarantees relatively high cost-effectiveness for the cable-stayed bridge subject to the ground motions in the regions of moderate seismicity with soft soil condition and strong seismicity with stiff soil condition.

A Study on the Urban Transit Vehicle Reliability Improvement Method using Quality Control Technique (품질관리기법을 이용한 도시철도차량 신뢰도 향상방안 연구)

  • Park, Kee-Jun
    • Proceedings of the KSR Conference
    • /
    • 2011.05a
    • /
    • pp.860-869
    • /
    • 2011
  • It is very important that reduce the maintenance cost and extend life time of the urban transit EMU through effective maintenance method research. The maintenance cost of the urban transit EMU shares 60%~70% of it's life cycle cost. It means that the maintenance cost is bigger than the introduction cost of the urban transit EMU. In this study, I introduces a quality control technique to improve the urban transit vehicle reliability. I suggest the control chart using quality control technique. And the control charts apply to the Static Inverter of EMU.

  • PDF

Delay-dependent Guaranteed Cost Control for Uncertain Time-delay Systems (불확실 시간지연 시스템에 대한 지연량을 고려한 성능보장 제어)

  • 이영삼;문영수;권욱현
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 2000.10a
    • /
    • pp.13-13
    • /
    • 2000
  • This paper considers delay-dependent guaranteed cost control for uncertain time-delay systems with norm-bounded parametric uncertainties. A new delay-dependent condition for the existence of the guaranteed cost control law is presented in terms of linear matrix inequalities (LMI). An algorithm involving convex optimization is proposed to design a controller which guarantees the suboptimal minimum of the guaranteed cost of the closed-loop system for all admissible uncertainties.

  • PDF

The Cost Saving Method on Each Building Phase by Analyzing the Cost Structure (비용구조분석에 의한 건축단계별 공사비용 절감방법)

  • Park, Keun-Joon
    • Journal of the Korea Institute of Building Construction
    • /
    • v.5 no.1 s.15
    • /
    • pp.97-103
    • /
    • 2005
  • Building costs means capital costs which include cost of land, costs of acquiring and preparing the site, construction costs, professional fees, furnishings, cost of financing the project. and cost of management required to run and maintenance the building for use. There are several phases that determine the building costs : design phase, construction phase, and operation & maintenance phase. So, the cost of work could be set against the examining the full range of complexities that a building program might contain. To solve this problem, it needs to compute building cost systematically. This is still in the development stage, awaiting the organization of rational cost data base. The method of cost saving by cost control could be constituted by detailed knowledge of building costs for all possible combinations of components and subsystems that can be assembled into integration model of cost factor on each phase of project development. The model of cost saving in each building phase is available for procedures of cost control of building systems.

Guaranteed Cost Control of Parameter Uncertain Systems with Time Delay

  • Kim, Jong-Hae
    • Transactions on Control, Automation and Systems Engineering
    • /
    • v.2 no.1
    • /
    • pp.19-23
    • /
    • 2000
  • In this paper, we deal with the problem of designing guaranteed cost state feedback controller for the generalized time-varying delay systems with delayed state and control input. The generalized time delay system problems solved on the basis of LMI(linear matrix inequality) technique considering time-varying delays. The sufficient condition for the existence of controller and guaranteed cost state feedback controller design methods are presented. Also, using some changes of variables and Schur complements, the obtained sufficient condition can be reformulated as LMI forms in terms of transformed variables. Therefore, all solutions of LMIs, guaranteed cost controller gain, and guaranteed cost are obtained at the same time. The proposed controller design method can be extended into the problem of robust guaranteed cost controller design method for parameter uncertain systems with time-varying delays easily.

  • PDF

The cost-effectiveness of alternative control measures against the 2010-2011 epidemic of foot-and-mouth disease (FMD) in Andong, Republic of Korea

  • Kim, Eutteum;Pak, Son-Il
    • Journal of Preventive Veterinary Medicine
    • /
    • v.42 no.4
    • /
    • pp.163-170
    • /
    • 2018
  • The cost-effectiveness of foot-and-mouth disease (FMD) control strategies was evaluated using a simulation model fitted to the 2010/11 FMD epidemic in the city of Andong, Republic of Korea. Seven FMD-control strategies were evaluated with respect to the direct cost of a FMD-control strategy, such as slaughtering, movement restriction, and vaccination. All the strategies included pre-emptive slaughtering, movement restriction, and vaccination, but the levels of each control option were different. The simulated median cost of the baseline FMD-control strategy (three kilometers of pre-emptive slaughtering area, 100 days of movement restriction and vaccination of all FMD-susceptible animals in the study area) was estimated to be USD 99.7 million. When a five kilometer vaccination area was applied (with the other control measures being the same as the baseline strategy), the simulated median cost was reduced to USD 81.1 million from USD 99.7. The simulated median costs were USD 107.6 million for a five kilometer radius slaughtering area and USD 168.8 million for 60 days of movement restriction. The FMD-control strategy cost decreased with increasing number of farms depopulated per day. The probability of passive surveillance being effective or the probability of the successful implementation of movement restrictions were increased. Cost-effectiveness analysis is a suitable tool for evaluating the financial consequences of FMD-control strategies by comparing the cost of control strategies for a specific area.