Background: Along with rapid economic growth, many natural regions, meadows, farms, etc. have been converted into unbridled urban areas. Urban development converts natural areas into districts full of buildings leading to disrupted ecological balance of the ecosystem. The Carrying Capacity (CC) of urban ecosystems needs to be estimated because they require large amounts of materials and energy as well as the ability of pollutant absorption in a small location. The amount of material and energy used in cities may be more than of that provided by urban CC. High consumption rate is associated with high levels of contamination that transcends the UCC. Therefore, the CC of the urban environment and its population Capacity must be evaluated for urban development planning. Materials and Methods: In this study, UCC Load number within the pressure-state-impact-response (PSIR) framework and 20 indicators were used to evaluate the CC and pressure on the urban ecosystem of Semnan. Results: According to the results, the Load number in the district 1 was equal to 180. 05with a low to moderate pressure on the urban ecosystem. The Load numbers in districts 2 and 3 were respectively 230. 41 and 272. 86 imposing a moderate to high pressure on urban ecosystem. Conclusions: Because of the greater population density in the District 3, materials and energy consumption and waste production was higher leading to a higher pressure on the urban ecosystem.

In this paper, an algorithm is proposed to improve the Maximum Load Carrying Capacity (MLCC) of flexible robot manipulators. The maximum allowable Load which can be achieved by a flexible manipulator along a given trajectory is limited by the joints' actuator Capacity and the end effector accuracy constraint. In an open-loop approach, the end effectors deviation from the predeffned path is significant and the accuracy constraint restrains the maximum payLoad before actuators go into saturation mode. By using a controller, the accuracy of tracking will improve. The actuator constraint is not a major concern and, therefore, the full power of the actuators, which leads to an increase in the Maximum Load Carrying Capacity, can be used. In this case, the controller can play an important role in improving the maximum payLoad, so a robust controller is designed. However, the control strategy requires measurement of the elastic variables' velocity, which is not conveniently measurable. So, a nonlinear observer is designed to estimate these variables. A stability analysis of the proposed controller and state observer is performed on the basis of the Lyapunov Direct Method. In order to verify the effectiveness of the presented method, simulation is done for a two link flexible manipulator. The obtained maximum payLoad for open and closed-loop cases is compared, and the superiority of the method is illustrated.

The calculation of the Load Carrying Capacity of variable thickness circular plates subjected to arbitrary rotational symmetric Loading is presented. The analysis considers plate materials that obey either the square or the Tresca yield criterion. By using upper and lower bound theorems of limit analysis, corresponding estimations for the Load Carrying Capacity of the plate are obtained. It is shown that these two bounds are identical. Therefore, the obtained solution would represent the exact amount of the Load Carrying Capacity of the variable thickness circular plate. Finally, in order to obtain solutions for some special cases, plates having step changes in thickness and those with linear thickness variation are considered and corresponding results are illustrated.

In this paper a performance analysis is presented for a cable-suspended parallel manipulator. Experimental results from some first tests are presented and discussed to validate the theoretical calculation of Load Carrying Capacity. The Load Carrying Capacity during a given trajectory is obtained. This computational technique is tested on a typical planar cable suspended manipulator. The experiment is performed to compare the calculated maximum Load with the actual Carrying payLoad on the path chosen for the comparison.

In this paper, a computational method for obtaining the maximum Dynamic Load Carrying Capacity (DLCC) for the 6-UPS Stewart platform manipulator is developed. In this paper, the manipulator is assumed to be non-rigid and the joint actuator torque Capacity and accuracy of motion are considered major limiting factors in determining the maximum payLoad. The maximum dynamic payLoad Carrying Capacity of the manipulator is established, while the dynamic model of a typical hydraulic actuator system is used in the joint actuator force Capacity for a given trajectory. The flexibility of the manipulator is assumed to be eventuated from the manipulator's joints flexibility. According to the high complexity of the dynamic equations system of the flexible joints parallel manipulators, the effects of the flexibility of the prismatic joints are considered in a static situation to show the considerable effects of the joint's flexibility on the motion accuracy of the 6UPS-Stewart platform. This method can be used for determining the maximum dynamic payLoad, which acts as an end-effector for the mechanical design of the manipulator and the optimized selection of the actuator, such as machine tools, based on the hexapod mechanism.

This paper proposes a control strategy for a cable-suspended robot based on sliding mode approach (SMC) which is faced to external disturbances and parametric uncertainties. This control algorithm is based on Lyapunov technique which is able to provide the stability of the end-effecter during tracking a desired path with an acceptable precision. The main contribution of the paper is to calculate the Dynamic Load Carrying Capacity (DLCC) of a spatial cable robot while tracking a desired trajectory based on SMC algorithm. In finale, the efficiency of the proposed method is illustrated by performing some simulation studies on the ICaSbot (IUST Cable Suspended Robot) which supports 6 DOFs using six cables. Simulation and experimental results confirm the validity of the authors’ claim corresponding to the accurate tracking capability of the proposed control, its robustness and its capability toward DLCC calculation.

The Presence of defects in the compressive structural members may reduce their Load-Carrying Capacity to a large extent. These defects may be in the form of cracks, corrosion, perforation, or dents existing on the smooth surface of the member. In most cases, the impact of an external object is the main cause of these damages. For example, tubular sections of offshore platforms which are mostly under axial Loads, may be damaged with the collision of supply vessels. Similarly, the columns of bridges and buildings, may be hit by heavy moving vehicles. The Existence of the mentioned defects in compressive members with circular cross-sections may cause premature failure of these structural elements due to local buckling followed by the member's overall instability. Hence, the effect of these damages on the buckling strength of tubular columns, and the effect of different influencing parameters should be studied in depth. This study presents a parametric investigation on the axial Load-Carrying Capacity of cylindrical columns damaged by a spherical indenter. For this purpose, the numerical models were generated in general purpose finite element software "Abaqus" and verified against results of two axial compression tests on intact and damaged thin-walled cylinders. The studied parameters included depth of the damage, shell slenderness ratio, location of the damage, length of the axial member, and radius of the indenter object. The analysis results showed that, the depth of the damage, shell slenderness ratio, and the damage location were the parameters affecting the buckling Capacity of the damaged cylinders under axial Load. The increase in damage depth or shell slenderness ratio decreased the buckling Load of the member. On the contrary, the buckled shape of the members with different damage depth values or shell slenderness ratios was almost identical. The post-buckling behavior of the studied specimens was affected by the shell slenderness ratio, the damage location, and the length of the compressive member. As the shell slenderness ratio or length of the member increased, the member strength in the post-buckling range experienced more rapid reduction. Also, as the damage became closer to the one of supporting ends, the buckling ring at the farther support vanished while the buckling ring at the closer support became more critical, resulting in an increased strength reduction. The radius of the indenter object had a negligible effect on the buckling Capacity and post-buckling behavior of the specimens. For samples with the same damage depth and different radius of the indenter object, the damage profile difference was very small. This small difference vanished during the buckling process, and the final deformation profile for the samples became almost identical. Finally, a regression analysis was conducted on the results of analyses considering the effect of different parameters, and two predictive equations were proposed to determine the buckling and residual Capacity of the studied members as functions of influencing parameters. The evaluations performed to estimate the accuracy of the proposed equations showed that they have good accuracy and provide reliable predictions for design rechecking of damaged cylindrical members subjected to axial compression.