Factors Affecting Material-Cart Handling in the Roofing Industry: Evidence for Administrative Controls

Material-cart handling can be strenuous and lead to overexertion injuries. The aim of this study is to produce a thorough understanding of how the cart condition, tire type, physical environment-related factors, and load interact to influence the ergonomics and productivity of cart handling. Eighteen roofing carts with different conditions, tires, and loads were tested by one subject on three laboratory tracks: one L-shaped, one with ramps within constrained spaces, and one with obstacles within constrained spaces. A multiple linear regression analysis was performed to quantify the main and interaction effects of the factors of interest on the cart operations. The research findings confirm that using aged carts increases the injury risk by as much as 30.5% and decreases productivity by 35.4%. Our study also highlights the necessity of keeping an open space for cart operation; the travel distance from a cart to a ramp/obstacle should be greater than 61 cm. Finally, the results suggest the at-risk thresholds for different ramp slopes and obstacle heights, and the safe load capacities for the various working circumstances that are common on construction sites. The evidence created in this study can be translated into administrative controls for cart handling to reduce overexertion injuries and enhance performance.

Unequivocally Nonconservative Results From One Method of Imperfection Quantification in RCC-MR

Design against buckling of thin shells at high temperatures often follows the code RCC-MR. RCC-MR allows three methods to quantify shell imperfections for use in safe load calculations, where lower imperfection values raise the safe load estimates. In recent work, we showed that the third of these methods can sometimes yield remarkably low imperfection values, leading to potentially nonconservative designs, but nonconservatism of the method was not proved. Here, we prove nonconservatism in two designs based on the third method. Proving such nonconservatism is difficult using experiments or with large material nonlinearity in simulations. We first discuss these difficulties to motivate our approach. We then present two examples: a spherical shell and a torispherical shell, both under external pressure. The shell walls are thin enough so that plasticity is not encountered before structural collapse. For specific shape imperfections, we show with geometrically nonlinear, purely elastic, highly refined, post-buckling analysis using abaqus that the physical loads at which the imperfect shells collapse are overpredicted via RCC-MR's third method by factors of about 8/7 and 11/10, respectively. We emphasize that code-based design using nonlinear simulation prescribes a further safety factor of 2.5, which we have denied ourselves here in order to give the third method the benefit of doubt. We conclude that the third imperfection quantification method in RCC-MR should be reexamined.

Desain dan Analisis Artificial Exoskeleton pada Prajurit TNI

Soldier’s activities resulted in too much workload received by the body, especially in the back and waist. These conditions produce a high risk of musculoskeletal disorders especially if conducted continuously. The soldiers must carry a backpack containing supplies during training weighing up to 40 kg on average. All activities are conducted manually until the training is finish. Thus, the purposes of this study are to reduce spinal injury by identifying factors resulting from lifting loads that exceed the limits of the body, calculate the maximum load limit that can be carried by a soldier, and produce artificial exoskeleton as a tool for the Indonesian Armed Forces. The study used anthropometry, biomechanics, and physiological approach in solving the problem. The results show that the safe load can be carried by the soldiers is 30.46 kg. The body parts that feel the complaint are the upper neck, back, shoulder, buttocks. In addition, this study can produce a design of an artificial exoskeleton with the following dimensions: chest thickness 23 cm, chest width 32 cm, back length 52 cm. The soldiers can increase the force load by 9% of the initial weight of the load using this design.

Analysis of simply supported wood beams at ambient and high temperatures

The main objective of this work is to present a methodology for safety analysis of simply supported wood beams at ambient and high temperatures with a concentrated load at mid-span. Sixteen different beam configurations will be studied. All calculations were conducted according the Eurocode 5, part 1-1 and part 1-2. During this study will be analyzed the safe load bearing capacity according standards and compared with the elastic and plastic load from beam theory. The beam theory can provide sufficient accuracy up to the point of instability. The standard methods are generally conservative and they are suitable to be used for design purposes with safety. The studied beam cross sections will be in glued laminated wood, as yellow birch, with characteristics equals to a Glulam GL28H.