Assessing the ergonomic exposure for construction workers during construction of residential buildings

Abstract

BACKGROUND:

Construction workers are at greater risk of musculoskeletal disorders due to their exposure to physical ergonomic risk factors.

OBJECTIVES:

The purpose of this study is to quantify the ergonomic hazards for workers in the construction of residential buildings.

METHODS:

In this cross-sectional study, PATH method, a work-sampling observation method, was applied to study the working postures, handled loads, and manual material handling activities in construction workers. A total of 5832 observations were made on 10 workers involved in tasks of three jobs including reinforcing bar, formwork, and pouring concrete. The ergonomic exposure was characterized in terms of percentage of observations made for each task.

RESULTS:

Non-neutral trunk postures, especially mild and severe flexions, were frequently observed in all job tasks. High-strain leg postures of squatting, kneeling, and leg(s) bent were mostly observed in floor formwork (39%), concrete finishing (5%), and floor rebar construction (52.3%), respectively. The highest proportion of work time with one (5.8%) and two hands (9%) at/above shoulder was observed in column rebar construction. In concrete pouring and rebar cutting, workers were observed in 39.45% and 23.1% of work time doing carry and push/pull activities, respectively. Heavy loads (>15 kg) were mostly observed in concrete pouring and floor formwork tasks.

CONCLUSION:

In the construction of residential buildings with the concrete structure, workers perform their task with non-neutral postures of trunk and leg and handling heavy loads. The recommended controls could reduce the musculoskeletal stress in rebar tying, concrete pouring, and concrete finishing tasks.

Keywords

Construction industry posture analysis observation material handling

1. Introduction

Construction is one of the world’s biggest industrial sectors and contributes to significant numbers of occupational accidents and ill health globally. The main ergonomic risk factors in construction tasks are forceful exertions; awkward body postures; contact pressure; vibration; and extreme temperatures and humidity [1, 2]. Degree of exposure to these risk factors would be different in various types of frames such as timber, steel and concrete.

Concrete frame is a common type of structure for multistory residential building internationally. This type of building consists of a frame or skeleton of concrete. In order to improve the strength characteristics of concrete, it is reinforced with steel bars, called reinforcement bars, or rebars. The workers, or ironworkers, who make concrete reinforced structures are named reinforcing ironworkers (RIWs) [3]. RIWs prepare and assemble the steel rods. The preparation work involves a) pulling long steel rods out of a stack, b) cutting rods to the desired length manually or by a machine, and c) bending them according to sketches. In assembly, the rods are tied together to form a steel skeleton. Afterward, the fresh concrete is being poured into the framework containing steel skeleton by other workers [4]. When the concrete has reached the required strength, the formwork can be removed.

RIWs use different tools to complete their work. The typical tools are pliers, tie wire reel, and a rebar hook. The main tool is the pliers which cut soft annealed rebar tie wire and twist the wire into place [5]. Non-neutral postures of trunk and legs are frequent during concrete reinforcement works. Tying rebar at ground level requires working below the knee height and prolonged trunk flexion [6]. Therefore, tying tasks could put a substantial dynamic and static load on the musculoskeletal organs [4]. Continuous trunk flexion and tool use may subject RIWs to physical risk factors to develop back and upper limb MSDs [7].

In the construction of concrete frame structures, fresh concrete being poured into a framework containing steel rebar. The formwork provides support and containment for fresh concrete and must remain in place until the concrete is strong enough to carry its own weight. Of all construction tasks, formwork activities are associated with a high frequency of accidents and injuries [8]. During erection and assembly of formworks, awkward postures such as twisting, squatting, kneeling, forceful exertions, repetitive actions, and working with the hands overhead are required [9, 10]. Concrete pouring is one of the main tasks in the construction of concrete reinforced structures. This task is physically demanding and workers are most likely to be exposed to heavy loads and awkward postures [11]. Pouring and finishing concrete, especially moving the concrete-filled hoses, requires significant lower back, leg, and upper body strength [12, 13]. Figure 1 shows some representative works of construction workers.

Fig.1

(A) Rebar tying. (B) Formwork. (C) Concrete pouring. (D) Concrete finishing.

The cohort studies of concrete reinforcement workers in Finland showed that 80% of the concrete reinforcement workers had back trouble sometime during their lives, 51% had daily symptoms of backache, and 38% had some restriction of forward lumbar bending [14]. Different musculoskeletal morbidity such as the premature development of lumbar degeneration, disc space narrowing, and high incidence of sciatic pain have been correlated to the high physical demands of concrete reinforcement work. Large static loads, prolonged awkward postures, dynamic loading while heavy lifting, and pulling and carrying of steel rods were reported to cause back problems in the concrete reinforcement workers [15].

Several methods have been used to identify and quantify ergonomic risk factors within construction sector [16]. Among the assessment methods, PATH (posture, activities, tools, and handling), was developed to characterize ergonomic hazards in the construction industry [17]. This method has also been used in other industries with non-repetitive job activities including retail, agriculture, and healthcare [18 –20]. In construction, PATH method has been used to characterize the ergonomic hazards during concrete reinforcing [14], concrete pouring [21], manual materials handling (MMH) in highway construction [22], construction ironwork [3], and pile driving [23].

This study used PATH to analyze working postures and MMH of workers during constructing of the concrete structure of residential buildings. Therefore, the objectives of this study were to (1) estimate times spent in the non-neutral postures of trunk, legs, and arms, 2) identify the high risk tasks based on the non-neutral body postures, 3) compare the MMH among studied tasks, 4) recommend ergonomics solutions based on the previous researches.

2. Methods

2.1. Construction site and participants

This study was conducted in four residential buildings constructing in Urmia city, Northwest Iran. The buildings were selected by convenience but it was attempted that different areas of the city be covered. Ten male reinforcement workers with a mean age of 34.6 years (SD 8.4, range: 18–65) participated in this study. The average work experience of workers was 11.2 years (SD 6.8 range: 1–36).

2.2. Data collection

PATH, a fixed-interval observational method which developed by Buchholz et al. [17], was used to provide quantitative exposure estimates for working postures and MMH of workers. During data collection, three body postures (trunk, legs and arms), MMH activity, and the weight of tools and objects were recorded. The validity of fixed-interval observation for PATH method has been evaluated and it was suggested that the postural snapshot at regular intervals could provide accurate estimates of exposure frequency for broad categories of certain body postures [24]. The PATH posture codes are the modification of those originally suggested by Karhu et al. [25] in the ovako working posture analysis system (OWAS) method. PATH posture codes mainly include five trunk postures, three arm postures, and nine leg postures (Table 1).

Table 1
Definition of Postural Codes in PATH

Trunk Arm Leg

1 = Neutral 1 = Neutral 1 = Neutral 6 = Kneeling

2 = Moderate Forward Flexion* 2 = One Arm Raised 2 = One Leg in Air 7 = Sitting on Chair

3 = Severe Forward Flexion** 3 = Two Arms Raised 3 = Leg(s) Bent 8 = Sitting on Ground

4 = Lateral Bending or Twisting 4 = Squatting 9 = Crawling

5 = Flexion and Twisting 5 = Walking 10 = Legs Not Supporting Body

Trunk	Arm	Leg
1 = Neutral	1 = Neutral	1 = Neutral	6 = Kneeling
2 = Moderate Forward Flexion*	2 = One Arm Raised	2 = One Leg in Air	7 = Sitting on Chair
3 = Severe Forward Flexion**	3 = Two Arms Raised	3 = Leg(s) Bent	8 = Sitting on Ground
4 = Lateral Bending or Twisting		4 = Squatting	9 = Crawling
5 = Flexion and Twisting		5 = Walking	10 = Legs Not Supporting Body

*Trunk flexed≥20° to <45° **Trunk flexed≥45°.

Prior to PATH sampling, the weight of used tools or objects was measured by a force gauge. After obtaining informed consent, one observer collected PATH data on 25 days from June to August 2016. The number of workers involved in the constructing of residential buildings was limited; therefore all observable workers were observed on the site. In each observation, a worker was selected at regular intervals of 1 minute to collect necessary data.

The intra-observer agreement was checked before the main data collection. For this purpose, one hundred photographs were prepared from different working activities of construction workers. The photographs were displayed on the screen of a computer in the intervals of 1 minute to be coded by the observer. Then, the observer recorded the code of leg (among nine postures), trunk (among five postures), and arm (among nine postures) and MMH activities (among five categories). The whole procedure was repeated one week after the first assessment. The obtained data was processed using the statistical package to calculate the Kappa statistics.

2.3. Data analysis

PATH field data were manually entered into the Statistical Package for Social Sciences (SPSS) version 16.0 (SPSS Inc., Chicago, IL, USA). Descriptive data for body postures, MMH, and loads handled were calculated to determine the proportion of time workers were exposed to these factors. The kappa coefficient (K) was used to determine the intra-observer reliability.

3. Results

3.1. Intra-observer reliability

The intra-observer reliability was relatively high for study variables. The kappa coefficient was ranged from 0.85–0.98; leg posture (K = 0.85), trunk posture (K = 0.91), arm posture (K = 0.98), and MMH activities (K = 0.95).

3.2. Intra-observer reliability

3.3. Observations and job tasks

A total of 5832 observations were made on 10 workers involved in construction of concrete structure of residential buildings (Table 2). As can be seen, the major part of the observations was made on reinforcing bar job. In this job, all tasks were performed about equally other than floor rebar construction. Workers performed formwork near 25% of their working time. About 12% of the work time of workers was spent on pouring and finishing concrete.

Table 2
Number of workers observed, number (percentage) of observation for each job and task

Job Job Tasks Number of Workers* N(%) of Observations per job N(%) of Observations per task

Reinforcing bar Rebar cutting 4 3612 (61.93) 1164 (19.96)

Floor rebar tying 7 264 (4.53)

Column rebar tying 6 1104 (18.93)

Ceiling rebar tying 7 1080 (18.52)

Formwork Floor formwork 6 1500 (25.72) 264 (4.53)

Column formwork 5 372 (6.38)

Ceiling formwork 5 864 (14.81)

Pouring concrete Concrete pouring 4 720 (12.35) 216 (3.70)

Concrete finishing 6 504 (8.65)

Total 10 5832(100.00) 5832 (100.00)

Job	Job Tasks	Number of Workers*	N(%) of Observations per job	N(%) of Observations per task
Reinforcing bar	Rebar cutting	4	3612 (61.93)	1164 (19.96)
	Floor rebar tying	7		264 (4.53)
	Column rebar tying	6		1104 (18.93)
	Ceiling rebar tying	7		1080 (18.52)
Formwork	Floor formwork	6	1500 (25.72)	264 (4.53)
	Column formwork	5		372 (6.38)
	Ceiling formwork	5		864 (14.81)
Pouring concrete	Concrete pouring	4	720 (12.35)	216 (3.70)
	Concrete finishing	6		504 (8.65)
Total		10	5832(100.00)	5832 (100.00)

*All workers were observed performing more than one task.

3.4. Body postures

3.4.1. Trunk postures

Non-neutral trunk postures were frequently observed in all job tasks. Working non-neutral postures were ranged 7–13.7% for moderate flexion, 8.2–17.5% for severe flexion, 2–14% for twisting/lateral flexion, and 1.7–14.7% for simultaneous flexion and twisting (Fig. 2). The highest percent of moderate flexion, severe flexion, twisting/lateral flexion and simultaneous flexion and twisting postures were related to “pouring concrete”, “floor rebar tying”, “floor formwork” and “ceiling formwork” tasks, respectively.

Fig.2

Distribution of non-neutral trunk postures observed for three concrete reinforcement jobs.

3.4.2. Leg postures

Non-neutral leg postures, especially squatting, kneeling, and leg(s) bent were frequently observed. The distribution of these awkward postures is illustrated in Fig. 3. As can be seen, the awkward postures of squatting, kneeling, and leg(s) bent were mostly observed in floor formwork (39%),concrete finishing (5%), and floor rebar construction (52.3%), respectively.

Fig.3

Distribution of three non-neutral leg postures observed for three concrete reinforcement jobs.

3.4.3. Arm postures

Non-neutral arm postures were observed infrequently (Fig. 4). As can be seen, awkward postures of one and two hand(s) at/above shoulder were observed for workers during “column rebar construction” task. This could be related to the nature of work in this job which workers have to work at elevated height. In “column formwork” and “concrete pouring” tasks, workers had one arm raised at 6.7% and 4.4% of their work time, respectively.

Fig.4

Distribution of non-neutral arm postures observed for three concrete reinforcement jobs.

3.5. MMH activities

The activity of a worker was coded as MMH when he was observed during push/pull or carry, lower, and lift of loads greater than 5 kg [22]. MMH activities were observed infrequently during most of the observed tasks, except “concrete pouring” (Carry = 39.45% of work time) and “rebar cutting” (Push/Pull = 23.1% of work time) (Fig. 5). Lifting was observed in floor and column rebar tying in 13.6 and 10.5 percent of work time, respectively.

Fig.5

Distribution of MMH activities observed for three concrete reinforcement jobs.

3.6. Loads handled

The frequency of loads handled by tasks is shown in Fig. 6. As it is clear, construction workers handle loads, materials or tools, with different weights in most of the work shift. Loads of <5 kg were observed as the frequent weight category. During floor formwork and concrete pouring tasks, handling of 10–15 kg and >15 kg loads were mostly observed, respectively.

Fig.6

Distribution of loads handled for three concrete reinforcement jobs.

4. Discussion

The data presented in this study show the exposure of construction workers to some physical ergonomic risk factors during construction of residential buildings with the concrete structure. The studied construction sites were small in scale, and therefore, all tasks are completed by a group of workers. In other words, a worker observed in this study could work in reinforcing bar, formwork, and pouring concrete jobs in different working days. In some of the previous studies on construction workers, the characterized ergonomic risks could be attributed to a distinct job in a specific construction project. For instance, Forde and Buchholz [3] reported the physical ergonomic risk factors for seven specific ironwork tasks.

In this study, non-neutral trunk postures were frequently observed. Severe flexion was mostly observed in bar reinforcing and ceiling form workers. This awkward posture happens when workers tie rebar on the floor and accomplish formwork on the ceiling of a structure. Choi found that rebar-tying using pliers had high potential risks for musculoskeletal disorders and injuries and could causes discomforts in the lower back and right wrist/hand of the rodworkers due to repetitive and inaccurate posture [1]. Therefore, the awkward postures of trunk should be corrected in the studied construction workers. A powered rebar tying tool could be suggested to reduce the back bending during rebar tying, hand/wrist movements, and tying time. The benefits of this instrument have been reported by different studies [12 , 27].

Handling heavy load with non-neutral trunk postures should be avoided in any working environment. This situation could happen in the concrete pouring task because workers hold the concrete delivery hose with flexed trunk and applying excessive force. In a study by Hess et al., a skid plate was used to minimize the risk of this working condition. The skid plate facilitated the horizontal movement of the concrete-filled hoses by preventing the hose couplings from catching on rebar matting and by decreasing the overall friction of pulling the hose [11]. This intervention is suggested to reduce the back stress in the concrete workers of the current study.

Squatting, kneeling, and leg(s) bent has been reported as the non-neutral leg postures which could lead to WMSDs. A dose-response relationship was observed between severe low back pain and stooping or kneeling in construction workers [28]. Also, the potential role of these postures in developing LBP and lower limb symptoms were shown due to tissue strain [29]. In the current study, workers performed their work at squatting position in floor rebar reinforcement and floor formwork tasks than other tasks. As discussed above, a powered rebar tying tool which reduces the back strain could also minimize the non-neutral leg postures [26]. Therefore, this tool is suggested to be used by the rebar workers of the current study to perform their work with a less stress on their legs. Kneeling and leg(s) bent postures were observed as 5% and 70% of working time during concrete finishing. It is observed that the fresh cement was screeded and troweled manually by workers. For these workers, the recommended controls included the use of a power screed rather than a manual screed and re-design of the long trowel for concrete smoothing [12, 21].

Non-neutral arm postures were observed infrequently in the workers of the present study. The sum of one or two elbow at/above shoulder level postures were 14.8%, 8.3%, and 5.6% of work time in column rebar construction, column formwork, and concrete pouring tasks respectively. In these tasks, workers have to work with elevated hands, and therefore, these postures could lead to shoulder disorders. Correcting the height of work in these tasks can partly reduce the non-neutral postures of hand. In column rebar construction task, workers use tools with low weight while in two other tasks, column formwork and concrete pouring, workers might hold heavy steel forms and cement delivery hose with elevated hands which could pose significant ergonomic risks. Ford and Buchholz reported that 6–21% of the observations were made on non-neutral hand postures for different construction ironworkers which are similar to finding of this study [3]. Spielholz et al. quantified the ergonomic risks in formwork construction workers and concluded that there are opportunities for ergonomic intervention [30].

MMH activities were performed differently among studied tasks. Push-pull was observed as a frequent MMH in rebar cutting task because workers sometimes pull a bunch of steel bars to bring them to the desired location. For rebar cutting workers, it is recommended to use a mechanical aid to carry the bars to reduce the MMH activities, especially push/pull. Lifting of loads greater than 5 kg was observed mostly in reinforcing bar tasks that should be put in priorities of intervention. In this study, light loads (<5 kg) were handled mostly by workers that were related to the small tools and materials carried. The heaviest loads (>15 kg) were observed mostly in pouring concrete tasks which were mainly related to concrete filled hose and vibrator. The concrete pouring could be done by a skid plate proposed by Hess et al. to minimize the stress on the musculoskeletal system. It is observed that the workers carry the vibrator solely that should be avoided. Handling heavy objects, awkward postures of trunk, and extreme environmental conditions have been reported for concrete workers in a past study [15].

According to the results of this study, it can be concluded that in the construction of residential building with the concrete structure, awkward postures of trunk and leg(s) were frequent and workers may experience musculoskeletal stress on their back and leg(s). The recommended controls by the disscussed previous studies were not used by the workers of rebar tying, concrete pouring, and concrete finishing tasks. It is proposed that the possible barriers in the application of the proposed controls should be investigated in a well-designed follow-up study [31].

This study had some limitations. The main limitation of this study was that the workers selected for the study were from one city. A comprehensive study is suggested with larger sample size from more cities of Iran. In this study, one observer collected the data. Observation with more observers could provide a more precise estimate of ergonomic exposures. Videotaping of the work activities which could help the observer to record the inaccessible working postures was not used in the current study.

Conflict of interest

None of the authors has any conflict of interest.

Footnotes

Acknowledgments

The authors deeply appreciate the financial backing provided by Urmia University of Medical Sciences. We would also like to thank all the construction workers who participated in this study.

References

Choi

. Ergonomic assessment of musculoskeletal discomfort of iron workers in highway construction. Work. 2010;36(1):47–53.

Rahman

MNA

, Rani

MRA

, Rohani

. Investigation of work-related musculoskeletal disorders in wall plastering jobs within the construction industry. Work. 2012;43(4):507–14.

Forde

, Buchholz

. Task content and physical ergonomic risk factors in construction ironwork. International Journal of Industrial Ergonomics. 2004;34(4):319–33.

Saari

, Wickström

. Load on back in concrete reinforcement work. Scandinavian Journal of Work, Environment & Health. 1978:13–9.

Dababneh

, Waters

. Ergonomics of rebar tying. Applied Occupational and Environmental Hygiene. 2000;15(10):721–7.

Wickstrom

. Symptoms and signs of degenerative back disease in concrete reinforcement workers. Scandinavian Journal of Work, Environment & Health. 1978:54–8.

Salas

, Vi

, Reider

, Moore

. Factors affecting the risk of developing lower back musculoskeletal disorders (MSDs) in experienced and inexperienced rodworkers. Applied Ergonomics. 2016;52:62–8.

López-Arquillos

, Rubio-Romero

, Gibb

, Gam-batese

. Safety risk assessment for vertical concrete formwork activities in civil engineering construction. Work. 2014;49(2):183–92.

Ahankoob

, Charehzehi

. Mitigating Ergonomic Injuries In Construction Industry. IOSR Journal Of Mechanical And Civil Engineering. 2013;6(2):36–42.

10.

Moir

, Paquet

, Punnett

, Buchholz

, Wegman

. Making sense of highway construction: A taxonomic framework for ergonomic exposure assessment and intervention research. Applied Occupational and Environmental Hygiene. 2003;18(4):256–67.

11.

Hess

, Hecker

, Weinstein

, Lunger

. A participatory ergonomics intervention to reduce risk factors for low-back disorders in concrete laborers. Applied Ergonomics. 2004;35(5):427–41.

12.

Albers

, Estill

Simple solutions: Ergonomics for construction workers: U.S. Department of Health and Human Services, DHHS (NIOSH) Publication No. 2007-122; 2007.

13.

Schneider

, Susi

. Ergonomics and construction: A review of potential hazards in new construction. American Industrial Hygiene Association. 1994;55(7):635–49.

14.

Buchholz

, Paquet

, Wellman

, Forde

. Quantification of ergonomic hazards for ironworkers performing concrete reinforcement tasks during heavy highway construction. AIHA Journal. 2003;64(2):243–50.

15.

Goldsheyder

, Weiner

, Nordin

, Hiebert

. Musculoskeletal symptom survey among cement and concrete workers. Work. 2004;23(2):111–21.

16.

Valero

, Sivanathan

, Bosché

, Abdel-Wahab

. Musculoskeletal disorders in construction: A review and a novel system for activity tracking with body area network. Applied Ergonomics. 2016;54:120–30.

17.

Buchholz

, Paquet

, Punnett

, Lee

, Moir

. PATH: A work sampling-based approach to ergonomic job analysis for construction and other non-repetitive work. Applied Ergonomics. 1996;27(3):177–87.

18.

Kurowski

, Boyer

, Fulmer

, Gore

, Punnett

. Changes in ergonomic exposures of nursing assistants after the introduction of a safe resident handling program in nursing homes. International Journal of Industrial Ergonomics. 2012;42(6):525–32.

19.

Fulmer

, Jenkins

, Mason

, Bresee

, May

. Ergonomic analysis of New York apple harvest work using a Posture-Activities-Tools-Handling (PATH) work sampling approach. Journal of Agricultural Safety and Health. 2004;10(3):163.

20.

Pan

, Gardner

, Landsittel

, Hendricks

, Chiou

, Punnett

. Ergonomic exposure assessment: An application of the PATH systematic observation method to retail workers. International Journal of Occupational and Environmental Health. 1999;5(2):79–87.

21.

Ahn

, Paquet

, Buchholz

Ergonomic assessment of the concrete pouring operation during highway construction. State University of New York, Buffalo. 2000.

22.

Paquet

, Punnett

, Buchholz

. An evaluation of manual materials handling in highway construction work. International Journal of Industrial Ergonomics. 1999;24(4):431–44.

23.

Dasgupta

, Fulmer

, Jing

, Buchholz

. Assessing the ergonomic hazards for Pile Drivers. Work. 2012;43(4): 417–25.

24.

Paquet

, Punnett

, Buchholz

. Validity of fixed-interval observations for postural assessment in construction work. Applied Ergonomics. 2001;32(3):215–24.

25.

Karhu

, Kansi

, Kuorinka

. Correcting working postures in industry: A practical method for analysis. Applied Ergonomics. 1977;8(4):199–201.

26.

Albers

, Hudock

. Biomechanical assessment of three rebar tying techniques. International Journal of Occupational Safety and Ergonomics. 2007;13(3):279–89.

27.

. A field study investigating the effects of a rebar-tying machine on trunk flexion, tool usability and productivity. Ergonomics. 2006;49(14):1437–55.

28.

Holmström

, Lindell

, Moritz

. Low Back and Neck/Shoulder Pain in Construction Workers: Occupational Workload and Psychosocial Risk Factors. Spine. 1992;17(6):663–71.

29.

Coenen

, Douwes

, van den Heuvel

, Bosch

. Towards exposure limits for working postures and musculoskele-tal symptoms-a prospective cohort study. Ergonomics. 2016;59(9):1182–92.

30.

Spielholz

, Wiker

, Silverstein

. An ergonomic characterization of work in concrete form construction. American Industrial Hygiene Association. 1998;59(9):629–35.

31.

Boschman

, Frings-Dresen

, van der Molen

. Use of ergonomic measures related to musculoskeletal complaints among construction workers: A 2-year follow-up study. Safety and health at work. 2015;6(2):90–6.