mostafa khatami

Pounding of adjacent buildings during earthquake causes local and total damages in buildings. One of the ways to reduce the damage in pounding, is creating a separation gap between two adjacent buildings. Park-Ang's damage index computes the amount of damage to the structure, according to the amount of deformation and the amount of energy absorbed by the earthquake reciprocating forces. In this study, estimates the effect of far-field and near-field earthquakes, on the Park-Ange damage index in pounding of two adjacent frames and separation gap is equal to the value proposed by Standard 2800.The frames are arranged in three, regular and irregular soft story and very soft story frames on the first floor. These frames are analysed under 5 far-field records and 5 near-field earthquake records. Accordingly, three steel moment frames are placed in pair proximity states and Park-Ang's damage index is calculated using dynamic analysis of the nonlinear time history with the OPENSEES software. Non-linear viscoelastic element is considered as a link element. The results indicate that in the regular frames, the average damage magnitude in the near-field earthquakes is about 12% more than the far-field earthquakes. In the soft story and very soft story frames on the first floor, the mean values of the damage index in the near- field are about 5% and 3% more than the far-field earthquakes.

In crowded cities, building structures are usually constructed in close proximity to one another because of restricted availability of space. In many cases, every building in a block is in full or partial contact with its neighboring buildings. Because of insufficient separations, their different heights and seismic-resisting systems collision can occur between adjacent buildings during strong ground motions. This collision can make partial or general damages to the structural elements and accelerate their failure by affecting their stiffness. This phenomenon is commonly referred to as structural pounding. Pounding between inadequately separated buildings has been observed in most previous major earthquakes. Each time pounding occurs, building structures will sustain short duration large impact force not specifically considered in conventional designs. The severity of the impact depends on the dynamic characteristics of the adjacent buildings in combination with the earthquake characteristics. options to minimize the effect of pounding have to do with the decreasing of lateral motion by joining adjacent buildings at critical positions so that their motion could be in-phase or by increasing the damping capacity of building pounding by means of energy dissipation, for example, by passive structural control systems. Modern seismic design codes have many pioneering provisions on the non-linear behavior of structures, but amongst others, they do not consider structural pounding, a phenomenon with strong non-linearities, for which codes usually suggest a sufficient separation between adjacent buildings. On the one hand, irregularity in lateral stiffness (a soft or very soft story) due to the different use of the first floor of the building is one of the most common types of irregularity. Aiming to prevent such collisions, these study estimates demand of separation gap angle at the highest level of collision between two adjacent structures in regular steel moment frames with irregularity in the lateral stiffness (with changes in the height of the first floor) under seismic records of a near-field earthquake. Models were considered as two-dimensional, ductile, steel moment frames of 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20-story 3-span buildings. In order to create an irregularity in the lateral stiffness on the first floor, the height of this story was increased from 3.5 m to 4.5 and 5.5 m while the cross-section of the column at the first two stories was kept unchanged. These frames can be placed alongside in seven binary groups considering priority in the arrangement. Each group represents 100 different binary arrangements of the frames. In total, 700 cases of various adjacency were studied. The OPENSEES software was used to analyze the dynamics of the nonlinear history considering 20 perpendicular components to the fault with a progressive orientation of near-field earthquake records of pulse-like faults. The results suggest the increase in the irregularity in the lateral stiffness in the first floor of the building can increase the separation gap angle. On average, the combination of regular and irregular frames with the first-floor height of 4.5 and 5.5 m, is increased 1.19 and 1.38 times, respectively, compared to the combinations of regular frames. Moreover, among various adjacent combinations of regular and irregular frames, in case the taller structure is associated with lateral stiffness (soft floor), the average increase in the separation gap angle is larger than other cases.

This study investigates the coordination of production scheduling and maintenance planning in the flow shop scheduling environment. The problem is considered in a bi-objective form, minimizing the makespan as the production scheduling criterion and minimizing the system unavailability as the maintenance planning criterion. The time interval between consecutive maintenance activities as well as the number of maintenance activities on each machine are assumed to be non-fixed. A mixed integer programming formulation of the problem is presented. A special case of the problem, named as single server maintenance is also studied. Then, a bi-objective ant colony system algorithm is presented to solve the problem in focus. To obtain the appropriate components of the proposed algorithm, two sets of experiments are provided. Firstly, experiments are carried out to select the suitable heuristic method to build the heuristic information part of the algorithm between CDS and NEH. Secondly, experiments are reported to select the local search algorithm between iterated local search and adjacent pair-wise interchange. At last, experiments are generated to evaluate the performance of the proposed algorithm, comparing it to the results of an exhaustive search algorithm.