자료책자

An Analysis of Safety Control Effectiveness

SON, Ki Sang

Department of Safety Engineering, Seoul National University of Technology, 172 Gongleung-Dong, Nowon-Gu, Seoul, 139-703 Korea

Abstract

The cost of injuries and "accidents" to an organization is very important in establishing how much it should spend on safety control. Despite the usefulness of information about the cost of a company's accidents, it is not customary accounting practice to make these data available. Of the two kinds of costs incurred by a company through occupational injuries and accidents, direct costs and indirect costs ; the direct costs are much easier to estimate. However, the uninsured costs are usually more critical and should be estimated by each company. The authors investigate a general model to estimate the above costs and hence to establish efficient safety control. One construction company has been pilot for this study. By analyzing actual company data for three years, it is found that the efficient safety control cost should be 1.2-1.3% of total contract costs.

Keywords: Safety control effectiveness; Accident; Safety control costs

1. Introduction

Safety management expenditure has been invested very differently in different fields of business despite the fact that in Korea there of Government guidance to suggest how to determine "Standard Safety Management Cost" for different classes of construction work [1]. While these classes are useful for planning more safety control measures, it is considered by the government that for giving greater flexibility, and having contractors self safety management conditions, differentdegrees of safety management expenditure might be available. For example it is considered by the Government that concentrated safety investment should be given in the following critical work areas; (ⅰ)foundations; (ⅱ) grading and backfilling; (ⅲ) reinforced concrete construction; (ⅳ) steel construction; and (ⅴ) water proofing. The expenditure on safety management for each of these areas might depend on the work process rateand other factors depending on the likelihood of accident occurrence.

In order to determine the most appropriate level of safety management investment a new practically oriented method of estimating direct costs, general insurance costs and compensation, and various indirect costs such as due to work stoppages, time taken to reach compromises, legal costs, cleaning of debris after an accident, and the costs associated with demoralization of the work force should be considered. An area of particular difficulty is the estimation of the indirect costs associate with the particular structural accident. Unfortunately it is difficult to determine these costs as usually no records are kept.

The level of safety management investment for each type of work must be subject to review and clarification to ascertain its cost effectiveness. Accordingly, it is appropriate that a detailed model be established for the optimum level of safety management investment. Such a model is possibly best set within the overall financial objectives of a particular enterprise. It need not relate, necessarily, to underlying engineering notions of structural safety. The present study focuses on the experiences of the SI Construction Company over a period of three years [2].

From the analysis of the data available, it is possible to deduce a criterion for the optimal expenditure on safety management. The whole treatment takes account of events and accidents only during construction. The results are compared with other empirical and numerical values.

2. Model for estimating safety control costs

2.1 Theory of safety control costs

Fig. 1 depicts a well-known relation between safety performance and total costs [3]. The higher the design, implementation and construction safety levels to be achieved, the lower will be the overall expected costs, because of the smaller probability of accident. However, to achieve thesehigher levels of safety will require extra costs, costs which normally have to be borne by the contractor. Hence, it pays the contractor to ascertain the minimal overall expected total costs [4].

Some limits can be set to the curves in Fig. 1. Thus, it is clear that under a perfect state of safety, there will be no accidents and hence no costs associated with them. Conversely, to achieve a perfect state of safety　implies that the costs are infinite. An achievable state of safety will lie somewhere between these two extremes (5). By adding the expected accident or damage costs and countermeasure control costs, the total expected costs curve for the structure could be obtained.

Fig. 1 Cost of safety

Evidently this curve has a minimum point T(n) for the total cost where the derivative of the total expected cost is zero. The total expected cost can be divided into two categories: (ⅰ) direct; and (ⅱ) indirect. The direct costs will include property damage, costs of injury and the costs involved in taking care of the dead.

The indirect costs are more difficult to determine. They relate primarily to loss of individual productivity, the loss of system productivity, and the unpredictable costs of insurance and litigation. It is often the case in practice that the indirect costs exceed the direct costs.

Direct countermeasure costs will include design changes principally for safety, provision of safety personnel, installation and management of safety systems, safety education, and training programs. The indirect countermeasure costs also may be restrictions on system operation.

2.2 Modeling for reasonable safety control cost

The minimum total expected costs of damage and accident prevention will be considered the criterion for setting optimal safety levels.

Fig. 2 depicts the annual total expected cost T(n). This is the total costs in year n as a function of year n:

T(n) = H(n) + G(n)                 (1)

Where H(n), is the annual cost of accidents, and G(n) is the annual countermeasure (or control) cost. R* depicts the minimum cost point.

Fig. 2 Total expected cost curve

G(n) in Fig. 2 can be represented as a function of the total contract amount and the investment cost as follows:

G(n) = P(n)[1 + R(n)]                        (2)

Where 

G(n) is the countermeasure costs invested for industrial accident prevention in year n,

R(n) the (countermeasure costs/total contract amount) of S construction company in year n,

P(n) the totalcontract amount of S construction of R(n).

Also let P(n) be taken as a constant amount in each year n.

The function H(n) can be obtained from statistical data for the accident rate, the directcosts of damage and loss per worker, and the number of workers per accident, as follows:

H(n) = DC + IC                               (3)

Where DC is the expected direct cost, IC the expected indirect cost. The direct cost can be given as:

DC = N(α) × dc                               (4)

Where N(α) is the total number of workers involved in accidents in year n, dc the direct cost of damage and loss pre worker and  the accident rate.

The total number of workers involved in accidents can be represented as a function of the accident rate as follows;

N(α) =  α×regular time workers              (5)

Whereα= (the number of  "accident" workers/number of workers)  100 and where the number of regular time workers can be obtained from the total costs of the project, being the proportion of labor for the project divided by the unit labor wage rates and the number of working days.

Since the accident rate decreases as the investment rate increases it is possible to develop a correlation between them. This can be done by regressing the accident rate  on the investment rate R as follows:

α= f(R)                                           (6)

For simplicity the indirect costs can be assumed to be  the direct costs of damage and loss. This allows the maximum loss cost H(n) to be represented as:

H(n) = (1 +β ) {N(α) × dc}                       (7)

It has been suggested that the indirect losses might be up to four times the direct costs(6) but in practice it seems extremely difficult to estimate this ratio.

Once the above expressions have been obtained it is possible to select R* as the reasonable investment and safety control rate.

Table 1. Collection of direct of loss(1 US$ = ￦800 won, unit ￦ 1000won)

Item	10.01.1992- 12.31.1992	01.01.1992- 12.31.1992	01.01.1992- 12.31.1992	01.01.1992- 12.31.1992	Total
Total amount paid of industrial accident insurance	85,903,710 US$85mil	270,444,000 US$2.7bil	211,029,520 US$2.1bil	150,183,500 US$1.5bil	717,560,730 US$7.1bil

3. Case study for analyzing effect of safety management

3.1 Direct and indirect costs of damage and loss

 In order to illustrate the above concept a pilot study was conducted for the SI Construction Company. Three years of statistical data were used. For these years the direct costs of loss and damage for the company amounted to total 97,560,720(US$896,950). The indirect costs amounted to
,097,314,000 won (US$ 11,371,642). Thus, the ratio of direct to indirect costs is 1:1.5.

The statistical data for the Company indicated that the direct costs constitute mainly the industrial accident insurance costs. In addition, it is clear that the indirect costs are considerably less than has been suggested in the literature.

It is likely that the difference may depend on the Company operating practices, including their safety management processes, but also on costs related to death and injury applicable to a particular country (Tables 1 and 2).

3.2 Reasonability review of current safety control cost

The data for the SI Construction Company shows that for the eleven years between 1985 and 1995 the accident rate has decreased steadily and was inversely proportional to the amount invested in safety control (see Fig. 3 and Table 3) (7). It should be noted that the 1988 Government decreed "Safety Control Cost Recommendations" (1) were easily met in most subsequent years. It is also clear that there is an apparent limit to the reduction in accident rates that can be achieved.

Table 2. Collection of indirect cost of loss(1 US$ = ￦800 won, unit ￦ 1000won)

Item	10.01.1992- 12.31.1992	01.01.1992- 12.31.1992	01.01.1992- 12.31.1992	01.01.1992- 12.31.1992	Total
Compensation including judged amount	108,000	218,524	57,000	44,190	427,714
Liquidated damage	-	-	94,500	-	94,500
Cost of litigation	7,000	25,000	11,000	8,000	51,000
The third party compensation	-	11,000	15,000	4,000	30,000
Labor cost due to accident investigation	15,000	26,500	18,400	16,250	76,150
Loss of work productivity due to work stoppage	19,000	31,800	84,200	5,500	140,500
Loss of equipment stoppage	-	-	60,000	-	60,000
Property damage	-	7,000	35,000	4,500	46,500
Loss of machine equipment and tools	12,000	1,950	148,000	9,000	170,950
Total	161,000	321,774	523,100	91,440	1,097,314

3.3 Comparison with national figures

The above results may be used with to estimate the effect of safety management for the particular case of the SI construction company, used here as a bench mark.

The following were used in the analysis:

● Total Contract Amount - this is the domestic Government contract amount for all construction, increased by 5% per annum to allow for inflation during the year.

● Number of Accident Workers - obtained from data collected by the Korean Department of Labor[1].

These include deaths.

● Direct Cost of Loss - as for the SI Construction Company, the direct costs were taken as the industrial accident insurance costs for each year increased by 5% per annum to allow for inflation during the year.

Fig. 3 Interrelation curve concerning Table

● Indirect costs - based on data obtained for the SI Construction Company, this was taken as 50% greater than the direct costs (see above).

● Amount of Loss Per Accident Worker - this was taken as the total amount of loss divided by the number of accident workers. The definition of "Accident workers" is given above.

● Number of Accident Workers - this was estimated as the target contract amount divided by the contract amount per accident worker.

● Estimated Loss - this was estimated from a number of accident workers multiplied by the loss amount per accident worker.

● Loss Prevention Efficiency Rate(%) - this was taken as the total loss amount divided by the total contract amount multiplied by 100.

Table 3. Interrelationship between safety control costs and accidents, 1985-1995

Kind	85	86	87	88	89	90	91	92	93	94	95
The number of injured workers Accident rate(%)	113	54	94	50	50	47	64	73	37	9	15
Safety control cost/ Total project amount(%)	4.99	2.80	5.42	2.94	3.31	1.62	1.41	1.48	1.22	0.35	0.40
Cost of safety control (hundred millions won)	0.62	0.53	0.47	2.38	2.52	6.16	10.8	19.65	16.64	17.15	27.44
Total selling amount (hundred millions won)	600	510	460	450	400	770	1200	2047	1293	1244	2033

Fig. 4 Target accident rate

Fig. 4 shows the analysis and calculation procedure. Table 4 gives the historical calculations for 1993 1995 and the predicted results for 1996.

 It is seen that the predicted loss prevention efficiency rate is 1.72% on the total contract amount (or project cost) for 1996. This gives an indication of the savings predicted to be made due to losses associated with accidents.

 외국첨단산업기술 단기연수 결과보고서

(    연수국 :   포루투갈    )

※ 규격을 준수하여 주시기 바랍니다.

연구과제명 : 구조물 손상의 안전관리와 신뢰성 확보 Safety Management and Reliability and Maintenance of degrading structures

서울산업대학교 외국첨단산업기술사업에 선정되어 연수를 수행한 본인의 연구보고서를 서울산업대학교에서 정한 양식에 따라 다음과 같이 제출합니다.

                              ․제출서류 : 1. 연구보고서

                                           2. 참고서류

                                           3. 출국 및 귀국 확인서(여권 사본등)

                                제출일자 : 2005. 2

                                        ․소    속 : 생산정보대학 안전공학과

                                        ․성    명 :  손  기  상   (인)

2003학년도 외국첨단산업기술 연수방문 연구보고서 ( 방문국 : 포루투갈  )
연 수 자	성      명			손 기 상
	소속기관 및 부  서  명			생산정보대학 안전공학과				직 급		부교수
	연  락  처			TEL	02-970-6388		FAX		02-978-4806
연구과제명	국      문			구조물 손상의 안전관리와 신뢰성 확보
	영      문			Safety management and reliability and maintenance of degrading structures
연수기간	2005 년 1 월 3 일 ～  2005 년 1 월 24 일  (연수국 도착일자 ～ 연수국 출발일자)
주요방문기관 및 접촉연구자 (영문)
방문기관명(소재지)		주요 면담 연구자				연 구 내 용
		성    명	소속부서 및 직위
Technical University of Lisbon Instituto Superio Technico , Lisbon Portugal		Carlos   Guedes   Soares	Professor unit of Marine Technology and Engineering Technical University of Lisbon Tel+351-1-841-7607 Fax+351-1-847-4015			1. safety of ship structure 2. risk analysis of ship structure 3. un certainty modeling in plate duckling 4. maximum still-water load effect 5. probabilistic model 6. establishment of target safety level (신청의 첨부 4참조)
Instituto deciencias de la constrcction Eduardo Torroja Madrid SPAIN		Carmen Andrade Dr Industrial Chemistry	Chemistry and Physics of Construction Materials Tel +34-91-302-0440 Fax+34-91-302-07-00			시멘트콘크리트의 원재료에 대한 기초연구, 철근부식, 중성화등 콘크리트 내구성 및 문화재 유지관리, 보수보강 (첨부부록 pp15~19참조)

방문연수내용 및 성과

[1] 강연

 박사, 교수들에게 발표토록 상대 과학자 Prof Carlos Guedes Soares 요청으로 An Analysis of Safety Control effectiveness (Vol 68, No   , June 2000, Joural of Reliability Engineering & Safety system) SCI논문집에 본인이 게재되었던 내용으로 발표하였다.

 건설현장에서 사고 예방을 위해 안전 관리비를 투자해야 하는데 적정 투자비용과 최적안전확보 사이의 수학관계식이 없이 정부에서 규정한 기준에 의해서만 지출하는 수동적인 투자를 국내건설 현장에서 수행해 왔다. 국내 처음이고 국제적으로도 처음인 본 연구에서 개발된 관계식을 이용하여 총 공사금액(=매출액)대비 최적 안전예방비용을 산출할 수 있어 공사 시작전에 계획성 있는 안전비용예산 절정이 가능하게 된다.

 상대국인 포루투갈 건설현장에도 외국인들이 많이 참여 하는 공사들이 이루어지고 있어 안전문제가 심각한 것으로 인식되고 있어 상대 과학자의 연구방향에 유익한 자료와 방법론을 제시한 것으로 사료된다.(사진 pp 12 필자의 장면)

[2] 연구협력

 국내의 외국인 건설근로자들의 언어 소통 장애로 인하여 더욱큰 사고 발생을 기록하고 있어 2004년에 발표된 외국인 건설 근로자들의 안전 대책에 대한 spss통계 팩키지와 AHP(우선적인 중요도 결정 팩키지) 두가지를 이용하여, 1차 인터뷰 조사 2차 설문조사로 진행된 결과를 분석하여 사고예방 방법을 제시하는 methodology로 제시한 것으로 상대 과학자의 검토를 거쳐 앞서 언급된 “Accident of foreign worker at construction" SCI논문인 RE&SS 저널에 게재토록 합의하였다.

 또한, 상대과학자가 정부로부터 받은 연구용역인 “산업사고 조사 및 대책”중에서 건설업 부분에 큰 도움이 될 수 있을 것으로 기대하면서 본인 체류중에 토의를 갖는 것으로 하였다.

 제조업에 대한 정보 또한 요청시 제공키로 하였다. 안전에 관한 집중적인 한국의 수준이 앞선 것으로 판단된다.

 특히 포루투갈의 특성상 조선공학이 집중되고 있는 것으로 볼때 국내와의 협력이 필요한 것으로 설명했고 서울산업대학교 토목공학과 기성태교수의 전공과 연계되어 연구실적을 전달했고 상호 교류방법을 찾아서 2005년도에 한국에 초빙되어 강연과 기술교류 정보교환을 요청하였다. 한국에서 연구기관에 공동연구원이 되는 방향을 계속 추진해 나갈 예정이다.

[3] 연구지도

 필자가 국내에서 진행하고 있는 부산항 바닷물 염도에 대한 철근 콘크리트 구조의 콘크리트 저항은 기존연구가 있으나 폐타이어가 혼입된 콘크리트저항을 전기적으로 측정하는 실험결과는 유익할 수 있는 것으로 아이디어를 제공하였다.

[4] 연구정보조사

 Technical University of Lisbon 밑에 공학대학인 Instituto Superior Technico에서 상대과학자는 Department of naval architecture and marine engineering unit of marine engineering을 담담하고 있으며 여기서 연구한 실적위주로 연구부분을 조사하였다. 학교 및 기술수준과 현황“에서 자세히 소개하고 있다.

 학교전체에 대한 조직과 unit of marine technology and engineering 에서의 연구실적을 조사하였다.

 5개 연구그룹 즉 marine environment, marine dynamics and hydrodynamics, marine structures, ship design and maritime transportation, safety relaiabjlity and maintenance

1) marine dynamics and hydro dynamics 그룹에서는

․Safe Passage and Navigation(SPAN)

․Advanced Method to Predict Wave Induced Loads for High Speed Ships

(WAVELOADS)

․VTS Management(COMFORTABLE)

․Identification and Simulation of Ship Manoeuvring

․Optimum Concept to Produce and Load with Underwater Storage(OCTOPLUS) 

2) Marine seructures 그룹에서는

․Reliability Methods for Ship Structural Design(SHIPREL)

․Optimum Structural Design of Ships Made from Advanced Fibre Reinforecd Plastic Materials(COMPOSITES)

3) marine environment 그룹에서는

․Probabilistic Methodology of Coastal Site Investigation for Stochastic Modelling of Waves and Currents(WAVEMOD)

․Computer System for Evaluation of the Environmental Impact of Polluting Maritime Accidents

․Rogue-Waves-Forecast and Impact on Marine Structures(MAXWAVE)

․Hindcast of Dynamic Processes of the Ocean and Coastal Areas of Europe(HIPOCAS)

․Safe Floating Offshore Structrues Structures under Impact Loading of Shippped Green Water and Waves(SAFE-FLOW)

4) Shipdesign and maritime transportation 그룹에서는

․Software Architectures for Ship Product Data Integration and Exchange(SEASPRITE)

․Maritime Virtual Enterprise Network(MARVIN)

․The European Maritme Virtual Institute(EVIMAR)

․Life-Cycle Virtual Reality Ship System(VRSHIPS-ROPAX)

․Prodabilistic Rules-based Optimal Design of Ro-RO Passenger Ships(ROROPROB)

․Tools and Routines to Assist Port and Improve Shipping(TRAPIST)

5) Safety Reliability and maintenance 그룹에서는

․Optimised Fire Safety of Offshore Structures(OFSOS)

․Safety of Shipping in Coastal Waters(SAFECO)

․Casualty Analysis Methodology for Maritime Operations (CASMET)

․Safety and Economic Assessment of Integrated Management of Multimodal Traffic in Ports(INTRASEAS)

․Tools to Optimise High Speed Craft to Port Interface Concepts(TOHPIC)

방문성과의 향후 활용방안

[1] 상대과학자의 한국 연구기관 참여

① 포루투갈의 국가특성상 해양 조선공학이 특히 중점연구되고 있으며 이 분야의 다양한 연구 결과 즉 해양 오일 누출사고, 조선 구조물 설계 및 구조물 손상 예측기술, 화재 예측기술들이 국내 관련 기관과 직접 연계될 수 있도록 해양연구소와 우리학교 토목공학과 기성태 교수와 연계토록 한다.

② 2005년도에 한국에 초빙 특강등 기술정보교환을 추진한다.

③ 국내 교수 지정 연구실을 과기부로부터 승인 받기 위한 공동연구원으로 구성되도록 한다.

[2] 서울산업대학교 건설 대학과 응용화학대학 교류추진

① 건설대학과는 좋은 학교간 교류상대가 될것으로 판단되어 이를 학교에 정보제공한다.

[3] 건설안전 분야 공동연구 참여

건설안전 분야에 대해서는 상대과학자 보다 앞서 있는 것으로 인정 받아 향후 연구에 지도가 가능하고 또한 2005년 9월 유럽지역 Safety & Reliability 가 상대과학자 주관으로 리스본에서 발표될 예정으로 국내 과학자 참여 및 상호의견 교환 및 심층 토의가 가능함.

연수국의 관련분야 연구 및 기술수준과 현황

[1] 상대국과학자의 연구소

 Unit of marine technology and engineering 에서는 30명의 연구원들이 연구에 종사하고 있으며(첨부부록 pp 1~16), Angelo Teixeira-accident analysis/human factor, pedro Ant'ao-structural reliability, yarden garbatov(romanian)-reliability-based maintenance and corrosion material 관련 연구를 하고 있다.

 연구논문은 SIC 급저널에 50 편이 현재 게재되어 있고, 그 외 포루투갈 국내 학회지 게재와 국제 학술 발표논문은  편이 되고 있다.(첨부부록 pp 1~16)

․Seakeeping                               ․Spectral Models of Sea States

․Non-linear Motions and Loads             ․Probabilistic Models of Wave Parameters

․Ship Manoeuvring and Loads              ․Time Series Models of Wave Parameters

․Dynamics of Propulsion Plants             ․Remote Sensed Data

․Probabilistic Models of Motions and Loads ․Wave Generation Models

․Computaional Fluid Dynamics             ․Modelling the Marine Pollntion

․Instrumentation and Measurement          ․Tide and Current Modelling

                                            ․Oceanographic Instrumentation and                                                     Measurement

․Collapse of Metal Structures               ․Computer Aided Ship Design

․Fatigue and Fracture of Marine Structures  ․Ship Product Modelling

․Impact Strength of Structrues              ․Plate Developing and Nesting

․Composite Materials                       ․Yacht Design

․Probabilistic Based Design                 ․Maritime Transportation

․Experimental Analysis of Marine Structures

․Reliability of Marine Structures

․Reliability Based Structural Maintenance

․Reliability and Availability of Equipment

․Safety of Shipping and Damaged Stability

․Industrual Risk Analysis

[2] 상대연구기관 조직

IST(Instituto Superior Technico)는 포루투갈에서는 최고의 교육기관의 대학으로서 명성있고 산학연이 잘되어 있는 대학교로서 서울산업대학교에서 벤치 마킹할수 있는 수준으로 평가되고 있다.

[3] 제2방문기관 스페인국립 건설 연구소

Institute de Ciencias de la Construction Eduardo Torroja(스페인 마드리드 소재)

1) 교량용의 polymer composite(element은 접착제로) 삼각형 유공고조위에 아스팔트 topping 한 후 구조하중 실험하는 것이 특별한 연구 인 것으로 사료된다(첨부부록 pp 15~19참조)

2) 콘크리트 철도 침목 고속철도용의 Fatigue test는 허용균열폭이 될 때까지 계속하중을 가하고 있다.(명함 pp 13 참조)

3) 알루미늄 골조 경량 격자법의 압축강도 테스트/동상적으로 휨강도 테스트를 하는데 앞으로 연구에 고려할 것으로 판단된다.(첨부부록 pp 15~19 참조)

4) 철근콘크리트 다공슬라브의 휨강도/전단 테스트/가 국내적용사상으로 평가된다.(첨부부록 pp   15~19 참조)

5) 한국 KOSEF-스페인 CSIC 간의 교류협정 체결로 2004년 2월 스페인 마드리드 현지에서 개최하였고 2005년 5월 한국에서 개최될 예정이어서 상대과학자중 3명을 국내 대학에 특강하도록 배치하고 있다.(명함 pp 13)

6) Safety reliability 분야에서 본인과 유사천공으로 보았기 때문에 Drpeter Tanner는 실무 bridge design 설계자로서 연구소에 근무하면서 실무 적용 가능한 구조안전 기준을 연구하고 저녁때에는 설계사무소에서 실제 설계에 참여하여 산․연 협력의 모범을 보이고 있다.

IABSE REPORT-Saving buildings in central and Eastern Europe", "Safety, Risk and Reliability-Trends in Engineering" conterentereport, "Risk Assessment and Risk Communication in Civil Engineering", CIB report, Evaluacion de extremos meteorologicos aplicados al codigo Technico dela Edificacion", Nota Technica 등 주요연구를 하고 있으며 이 분야 실력있는 과학자로 연구소에서 평가하고 있었음(첨부부록 pp 41~58)

7) Safety reliability 분야에서 또다른 연구자 Dr Angel arteaga는 Euro code 1에 대한 규정을 제정하는데 계속 참여하고 있었으며(첨부부록 pp 33), "Bond Between FRP and Concrete Elements Exposed to Dynamic Loads while the adhesive is curing", NCAPC, "Reliability Based calibration of Load Combinations For Fire Design Situation", "Fine Safety Conterence in Madrid, 19-21, Octob 2004, "Mechanical Tests on new FRP pultruded profile for bridge decking"등 주요연구를 하고 있다.