Effect of the Full-body Harness Structure and the Suspension Angle on the Pressure Distribution

Effect of the Full-body Harness Structure and the Suspension Angle on the Pressure Distribution

He Zebo’ Chen Changjie’ Liu Ruiqiang Zhu Lin Wang Xinhou*

（1 College of Textiles,Donghua University,Shanghai,201620;2 Shandong rope technology Co.,Ltd,

Shandong Taian,271000)

【Abstract】

Full body harness,a construction safety life belt, is an essential part of the fall protection system.However,the limited pressure distribution during the suspension can cause trauma to the body and threaten life safety.Therefore,thestudy and analysis of the full-body harness’ pressure distribution are significant. This paper studied the influence of thefull body harness structure and the suspension angle on the pressure distribution. The three types of the full-body harnessinclude H-type,Y-lype and X-lype,selected as the test samples,and pressure-sensitive paper is used as a sensor to testthe pressure distribution.To study the pressure at a specific part of the frontal attachment and the dorsal attachment whenstatically suspended. A test method to characterize the pressure distribution of the full-body harness during staticsuspension been formed.The results show that the pressure distribution of the Y-structure harness and the largersuspension angle are uniform, and the maximum force value is small.

【Palabras clave】pressure distribution; full body harness;suspension angle;structure;uniform

Introducción

As time progresses, fall protection equipment demand increase, not only in traditional construction industry in electric power communication cleaning in the areas of high demand also more and more big, prompting the work high above the aerial work became a regular homework, because of work place safety facilities imperfect management supervision does not reach the designated position and homework personnel own safety consciousness is not high and the homework is difficult According to statistics, in the first half of 2019, there were 286 industrial safety accidents and 353 deaths in housing and municipal projects, among which 146 were falling from high ground and 155 people died, accounting for 51% and 44% respectively. The development of anti-fall systems has been greatly reduced. The occurrence of this kind of accident, and the anti-fall safety belt as a direct support for human work at high altitude, because the safety facilities in the workplace is not perfect management personnel’s parts, is an important part of the system（5）.

At present, the research of anti-fall safety belt mainly focuses on the upgrading of protective performance, namely, the improvement of safety, and the optimization of the comfort of anti-fall safety belt from the aspects of structure, material, size and so on. Since the comfort of safety belts directly affects the willingness of operators to wear them, the overall size of safety belts and the coordination between various parts should be fully considered when selecting and designing safety belts (11-12). Therefore, the future development trend of fall protection safety belts will be personalized, multi-functional and integrated

When falling, the body is in a state of suspension, suspension caused by venous pooling as easily happened the phenomenon of intolerance, although the body seat belts can impact from the internal organs to the pelvic area near the main (14) on the bones and muscles, but not well to all parts of the pressure evenly dispersed, can cause secondary damage to human body. At present, there is no systematic research result to optimize the structure of anti-fall safety belt based on the pressure distribution of each part of safety belt.

Aiming at the above problems, this paper selects three types of anti-fall safety belts with different structures common in the market and adopts static suspension, with the front and back hanging points as test hanging points, to explore the pressure distribution of different safety belts on specific parts Theoretically, the influence of the suspension Angle and the size of the force arm on the overall pressure distribution of the safety belt is studied to lay a foundation for the development of uniform pressure distribution of the comfort safety belt。

1 Experiment

1.1 Experiment Material

This study chose three different structure and on the market at the same time have a back up point and hanging point of fall prevention belts as the test and analysis sample, can be named according to its structure in H Y and X, as shown in figure 1 H structural belt, wear and ma3 jia3, similar to control type, include chest strap, but before hanging back points are not independent adjustment; Y structure safety belt, wearing mode is up and down, without chest belt, only the back hanging point can be adjusted independently; X structure seatbelt adjusts the shoulder strap and leg strap to make the position of the front hanging point change with the position of the back hanging point. In this study, the height of the back hanging point is uniformly adjusted to the position of the shoulder blade during the test. The test plane is used as the baseline for the height of each hanging point, and the specific height is shown in Figure 1

Pressure sensitive paper structure is mainly the two layers of polyester as the substrate membrane, as shown in figure 2 A membrane with color particles, C membrane with hair color particles, test, mainly through the two layers of thin film composite in test site, let the pressure lead to the micro capsule ruptures, adorn substance and chromogenic reaction, which will appear on the film the red areas Different degrees of red represent different sizes of pressure, and the distribution range of red also represents the pressure distribution at the test site。

1.2 Experimental Equipment

In this study, the safety belt will be put on a 100kg dummy in the test, the safety belt will be adjusted to make the suspension point at a specific position, and the suspension Angle and action arm will be measured at the same time.

1.3 BPMS Research

First of all, when selecting the main stress points that the safety belt applies to the human body, the external abdominus trapezius thigh biceps muscle and pectineus muscle were selected as test sites [16]. In the front hanging point test, the test sites were the trapezius of the back and the biceps of the thigh. When testing the dorsal hanging point, the external trapezius of the neck and the pectineus were selected as test sites。

Secondly, the pressure sensing paper is cut to 45mmx45mm size, pasted on the designated test site, and the test results and the contrast color card are photographed under the same exposure conditions. Then, THE PS software is used to take the color analysis of the test picture and the contrast color card. By analyzing the RGB(color standard,RGB stands for red-red green-green Finally, professional image analysis software was used to design the size of the picture and calculate the maximum pressure corresponding to the area of the color block. Formula (1) of the test pressure is as follows :F=PMaxxSPMax (1),F refers to the pressure of the test part; Puax means maximum pressure; SpMar is the area corresponding to the maximum pressure。

Meanwhile, the Angle test is shown in Figure 3. In the figure, the hanging Angle refers to the included Angle between the vertical line where the hook is located and the dummy’s vertical center line. Angle A refers to the Angle formed between the vertical line of the hanging point and the shoulder strap; The beta Angle refers to the Angle between the vertical line of the hanging point and the connecting belt of the leg belt。

2 Experiment Results and Discussion

2.1Influence of seat belt structure on pressure distribution

In order to explore the impact of seatbelt structure on pressure distribution, static suspension tests were carried out on the front and back hangpoints of three seatbelts.

2.1.1 Before hanging point

In the fall-proof safety belt, there are only the front and back hanging points that can prevent falling. The premise of using the front hanging points is that the falling distance is short and the impact force is low [17]. The actual scene and pressure distribution during the test

Based on liu Jinyue [18] ‘s research on the relationship between the turning time and the force on each part of the human body, the critical value of discomfort in each part was obtained in this study, and the pressure critical value curve of the studied part was drawn based on the test results, as shown in FIG. 5。

Research results show that H belt and Y type belt pressure distribution in the body below the critical value, a secondary injury but H belt outside the main stress parts of abdominal oblique muscle, the peak pressure is 69 n, the maximum differential pressure between the different parts of 47 n, accounting for 68% of the peak, low stress uniformity, appear this kind of pressure distribution is the main reason for the hanging point from outside abdominal oblique muscle, Action lever smaller And Y type belt main mechanical parts for trapezius muscle, peak and the critical value is close to, each place pressure differences between the small H belt, that’s because hip belt connected to the pressure has certain effect X seat belt outside the main stress parts of abdominal oblique muscle, acting on the external oblique abdominal muscle stress peak value is 121 N, more than 2 times of the critical value, and the maximum pressure difference between various parts accounts for 72% of the peak value, so the comfort and pressure dispersion effect of X-type safety belt are poor。

2.1.2Back hanging point

The back hanger point is the most common and essential hanger point of the anti-fall safety belt. Many simple safety belts only set the back hanger point, because it is the main load-bearing hanger point to prevent falling accidents [17]. The back hardpoint test scenario and pressure distribution are shown in FIG. 6 and 7。

According to the systematic research and analysis conducted by Chen Xingyi [19] Denton M J.[20] and Zhang Jianfeng [21] on the pressure threshold of comfortable feeling around the neck of human body, clothing comfort pressure threshold and Chinese pectineal pressure comfort threshold, this study obtained the pressure threshold of each part and drew the critical value curve as shown in FIG. 7。

As can be seen from Figure 7, only the pressure distribution of y-type safety belt is below the critical value of secondary injury at each position. H-type safety belt is mainly stressed at the pectineus muscle, and the peak pressure is 53N. Because the belt is soft at the pectineus muscle, the belt is easy to concentrate together when stressed, resulting in force aggregation effect The maximum pressure difference of each part is 35N, accounting for 66% of the peak value, and the pressure distribution of each part is uneven. Compared with the H-type safety belt, the maximum pressure difference of y-type safety belt decreases by nearly 15%, indicating that the pressure distribution is more uniform than that of h-type safety belt The main force position of X-type safety belt is the external oblique muscle, and the peak pressure is 70N, exceeding the critical value 20N, and the maximum pressure difference between various parts accounts for 72% of the peak value. It can be seen that the x-type safety belt structure has a greater impact on pressure distribution than the first two kinds of safety belt, which is not conducive to the uniform distribution of pressure。

2.2Influence of suspension Angle on pressure distribution

During the front and back lULL point tests, the dummy presented a state of leaning forward and leaning back, and the dummy’s center of gravity moved forward and backward. The three kinds of belt front hanger points can not be adjusted by themselves, so that the position of the front hanger point is different. Due to the difference in the structure of the belt itself, the size of the arm of the back hanger point acting on each part is different, resulting in the difference of the suspension Angle and the arm of action, and the pressure distribution of the belt also changes. The main stress position of human body changes with Angle and acting force arm [22-23]. Therefore, this study measured the suspension Angle of safety belt of three structures, and explored the influence of Angle change on pressure distribution. The Angle test results are shown in Table 2 and 3。

In this study, the hanging point was taken as the force analysis point, and the force analysis was carried out on each test part through the tension of each part of the shoulder strap, leg strap and belt (as shown in FIG. 8). Meanwhile, the Angle from the belt to the leg strap changed little, so it was ignored in this study According to Table 3, this study calculated the theoretical pressure value of each part and obtained the ratio of pressure in each part through the ratio of the force arm from the operating point to different parts。

Specifically, the pulling force of the hook is equal to the gravity F(F=980 N) of the dummy. In this study, the orthogonal decomposition of the three forces is carried out and the results are obtained according to the following formula (2)。

Faxsina+FBxsinβ=980           α>90°

FBxsinβ=Faxsina+980-           a<90°

Faxcosa=FBxcosβ              （2）

F总＝Fa+FB

It can be seen from Table 4-5 that in the test of the front hanging point of h-type safety belt, the force is external oblique muscle &gt. Trapezius muscle & gt; Biceps of the thigh, dorsal hang point test, the force is external oblique muscle &gt; Pubic bone muscle & gt; Trapezius muscle. Y type safety belt front hang point test, the force is trapezius muscle & GT; Biceps of thigh & GT; External oblique, dorsal hang point test, force is trapezius &gt; Biceps of thigh = external obliques; The pressure distribution of the X seat belt is similar to that of the H seat belt, except that the proportion of the pressure is different. The different pressure distribution is formed because of the difference in the ratio of the pressure in each part due to the difference in the suspension Angle and the difference in the moment arm at each part of the test point from the suspension point。

Force results from theory, and before hanging point test, the suspension Angle, the greater the ratio of the pressure of each part of more close, the pressure distribution more uniform Back hanging point test, H and Y type belt also satisfy the above laws, although the suspension of X type belt Angle is relatively larger H and Y type, but because of the test parts from dead lever difference is bigger, make each part pressure distribution is uneven。

3 Epilogue

Through the study of seat belts, three different structure found in H Y and X type three structure, Y type pressure evenly distributed structure is more advantageous to the belt Is determined by the hanging point of overall suspension of seat belts have a certain influence on the stress uniformity also, the study found that, the larger suspension Angle for pressure distribution more uniform Therefore, it is of great significance to develop an anti-fall safety belt structure that can freely adjust the position of the hanging point to change the hanging Angle and make the overall force of the safety belt more uniform。

Foundation Items: National Natural Science Foundation of China（51776034)

Referencia

［1]CAI Zhong, Yang Hui. Equipment and management of fall protection equipment at home and abroad［J］．labor protection，2021(03):10-12.

［2]Wang Ning, Wang Yizhen, Zhao Yuanfang. Research on falling protection equipment and technical measures for aerial work［J］.China Plant Engineering，2019(09):52-53.

［2]JianJianTao. Accident analysis and preventive measures of falling from high altitude in construction［J］。Building Materials and Decoration，2016,(25):117-117,118.

［4]Ministry of Housing and Urban-Rural Development of the People’s Republic of China ( MOHURD )．2019 Housing and municipal Engineering production safety accident Report，Jianan Office Letter [2018] No.5．

［5] Baszczynski K. Equipment protecting against falls from a height[J]. In :D.Koradecka(Ed.), Handbook of Occupational Safety and Health. NewYork,USA:CRC Taylor & Francis Group;2009(543-548).

［6]Tang Yiming, Tong Suifang, Jiang Ruiliang. The function and characteristic of safety belt in high altitude fall protection［C].／／The 20th Cross-strait and Hong Kong and Macao Occupational Safety and health Academic Conference and China Occupational Safety and Health Association 2012 Academic conference．2012:291-298.

［7]Shanghai ACE Ribbon Co., LTD. The utility model relates to a full-body high strength aerial work safety belt：CN201720997660.0[P].2018-05-10.

［8]Jin Hua Jie Ke Tools Co., LTD. Full body safety belt：CN201620104258.0[P].2016-06-21.

［9]Li Peng The utility model relates to a horse clip type whole body safety belt：CN201921788454.4[P].2020-07-14.

［10]WeiHongQuan. Whole body seat belt “lose weight” improvement research door. Guangxi electric power，2016(12):84-86.

［11]Rick. Wen Nick. How to choose a full body seat belt]. Labor protection，2005(06):60.

［12]The soldiers. Proper selection and use of fall protection equipmen［J］．China Personal Protective Equipment，2008(02):48-50.

［13]Cheng Wei, Li Yigao. Did you choose and wear the right fall protection［J］.labor protection，2021(03):13-15.

［14]Zhu Yan. Research on falling protection equipment and technical measures for aerial work［J］．China Personal Protective Equipment，2015(06):44-48.

［15]Li Rui．Fall-prevention technology for Electric Work at Height (2nd Edition)［M].Beijing：China Electric Power Press，2018:3-5.

［16]Ma Heng, Qian Ke, Gao Yibo, et al. Analysis and research of human falling process based on EMG signalJ].Computer Science and Application，2019,(06):1192-1207.

［17] American Standard ANSI/ASSE Z359.11-2014,Safety Requirementsfor Full Body Harnesses[S].

［18]Study on human body comfort and Turning Height and Pressure distribution of various parts. Machinery design and manufacture，2019(09):30-34.

［19]Chen Xingyi. Research on neck clothing pressure comfort based on human cardiovascular physiology［D].Jiangsu: Jiangnan University，2010:03-04.

［20] Denton M J.. Fit Stretch Comfort 3rd Shirley InternationalSeminar[M].England Manchester: Textile for Comfort,1970:15-17.

［21]Zhang Ji-feng, ZHOU Xue-lu, ZHOU Shang-jun, Yuan Xiao-qiang, ZHANG Jian-feng, MO Yan. Measurement of pectineal foramen size in Chinese and its clinical significance J. Chinese Journal of Hernia and Abdominal Wall Surgery (electronic version)，2012,6(03):835-839.

［22] Hsiao Hongwei, Turner Nina,Whisler Richard. Impact of Harness Fit on Suspension Tolerance[J].Human Factors: The Journal of Human Factors and Ergonomics Society,2012,54(3).

［23] Paul Seddon,Cavendish Court,Warehouse Hill,etc.Harness suspension:review and evaluation of existing information[].Health and Safety Executive,2002:61-62.