Sharif Digital Repository

This paper focuses on the biomechanical aspects of human load carrying in order to provide a physiological framework for designing the more anthropometric assistive systems. An 8degrees-of-freedom musculoskeletal model with twenty functional muscle groups in the lower extremity was developed to simulate the movement in sagittal plane. Inverse dynamics based optimization approach was employed to estimate the excitation level of the muscles. Activation patterns of the muscles illustrate the importance role of the soleus in supporting of the body during load carrying. Also power distribution analysis of the muscles reveals that the plantar flexors of the ankle, extensors of the knee and hip... 

The endurance time (ET) method is a time history-based dynamic pushover analysis procedure that utilizes special intensifying acceleration functions for estimating the seismic performance of structures at different excitation levels. One of the potential applications of the ET method is in the three-dimensional analysis of buildings considering multidirectional excitation. In this paper, a procedure for multi-component analysis by the ET method has been developed. Several steel moment frames with heights from 9.6 to 48 m were designed according to the Iranian National Building Code. By applying the proposed algorithm for three-dimensional analysis of structures by the ET method, these frames... 

The endurance time (ET) method is a time history based dynamic analysis in which structures are subjected to gradually intensifying excitations and their performances are judged based on their responses at various excitation levels. Using this method, the computational effort required for estimating probable seismic demand parameters can be reduced by an order of magnitude. Calculation of the maximum displacement or target displacement is a basic requirement for estimating performance based on structural design. The purpose of this paper is to compare the results of the nonlinear ET method with the nonlinear static pushover (NSP) method of FEMA 356 by evaluating performances and target... 

In the endurance time (ET) method, structures are subjected to a specially designed intensifying ground acceleration function and their performance is judged based on their response at various excitation levels. A range of equivalent intensities can be covered in a single numerical or experimental simulation, thus significantly reducing the computational demand as compared to full nonlinear response-history analyses. The applied excitation intensity at various times has been correlated with those of the scaled ground motions. Response spectra of seven ground motions on stiff soil were used to produce intensifying acceleration functions that at each time window produce a response spectrum... 

This paper focuses on the biomechanical aspects of the human lower extremity loading condition during backpack load carrying. A biomechanical framework was generated with the aim of employing a block-oriented structure of Simulink integrated with the Virtual Reality Toolbox of MATLAB software to provide a simulation study of the musculoskeletal system in a virtual environment. In this case, a ten-degrees-of-freedom musculoskeletal model actuated with sixteen muscles in each leg was utilized to simulate movement in the sagittal plane. An inverse dynamics based optimization approach was employed to estimate the excitation level of the muscles. In addition, distributions of the mechanical power... 

This paper presents the results of a series of shake table tests carried out on a half-scale single-story unreinforced masonry building with asymmetric openings. First, the unretrofitted building is subjected to seven increasing steps of bidirectional seismic excitation. The damaged building is then rehabilitated using steel mesh and shotcrete layer with two walls retrofitted from the exterior face and the other two from the interior face. Afterward, the shake table test is again conducted on the retrofitted specimen in nine increasing excitation levels. Three cases of interior-to-interior, interior-to-exterior, and exterior-to-exterior shotcrete connections are considered at the... 

In this paper, application of the Endurance Time (ET) method in the performance-based design of steel moment frames is explained from a conceptual viewpoint. ET is a new dynamic pushover procedure that predicts the seismic performance of structures by subjecting them to a gradually intensifying dynamic action and monitoring their performance at various excitation levels. Structural responses at different excitation levels are obtained in a single time-history analysis, thus significantly reducing the computational demand. Results from three analyses are averaged to reduce the random scattering of the results at each time step. A target performance curve is presented based on the required...