علي عدنان عبد شحاثة الزاهد

One way to provide safe buildings and to protect tenants from the terrorist attacks that have been increasing in the world is to study the behavior of buildings members after being exposed to dynamic loads. The attacks and buildings behaviour represent the thing that is inspired researchers all around the world to investigate the effect of impact loads on buildings members like slabs and to deeply study the properties of High Performance Concrete. HPC is well-known in its high performance and resistance to dynamic loads when it is compared with normal weight concrete. Therefore, the aim of this paper is finding out the impact of dynamic loads on RPC slabsꞌ flexural capacity, serviceability loads, and failure type. For that purpose and to get answers for these questions, three concrete slabs with 0.5, 1, and 2% steel fiber contents were experimentally tested. The tests results showed that the content of steel fiber plays the key role in specifying the static capacity of the concrete slabs after being dynamically loaded, and increasing the content of steel fiber led to improving the static loading capacity, decreased the cracks numbers and widths at the same time, and provided a safer environment for the buildings residents.

ABSTRACT A number of studies have been conducted to specify the most effecting factors on the success of projects. Those studies titled the most influencing factor, which is the bid selection criterion. By this criterion, the most qualified bidder/contractor could be chosen where the contractor has a considerable impact upon projects successes. Moreover, the published studies helped a lot in correcting the improper adopted criterion in selecting the best bid, which is the lowest price bid. Awarding the bid depending on the lowest price bid ended many projects in failure. Therefore, this study aimed to revise the popular mistaken selection criterion, recommend an evaluation criterion, and develop a computer program that works on finding the best bid according to the recommended criterion. The suggested criterion was followed in selecting one of the contractors to construct some projects in Iraq. That projects were felicitously finished; the projects were completed on time and budget

Recently, buildings have been exposed to terrorist attacks that generate impact loads on their elements and affect their serviceability loads, which is the thing that inspired researchers to investigate the properties of reactive powder concrete, such as strength, serviceability loads, impact load, and the influences of impact loads on standard weight concrete separately. Therefore, the main goal of this paper is studying the flexural behavior of reactive powder concrete after applying impact load caused by the attacks. For this study, three reactive powder concrete slabs: the first one is with 80-mm thickness, the second one is with 60-mm, and the third one is with 40-mm thickness, were statically loaded after being subjected to impact load. Moreover, then a number of the three slabsꞌ properties were investigated, such as flexural load capacity, deflection, and number and widths of cracks. The laboratory tests have approved that the slab with the higher thickness and steel fiber has improved and provided the best serviceability loads after being dynamically loaded.

Optimization of imperfect reactive powder concrete slabs under impact load is the aim of the current study, the study adopts to investigate the optimal imperfection to decrease the maximum dynamic deflection which affects negatively on structures. Optimization by using Modified Hooke-Jeevs method of imperfect slabs has been adopted in three cases according to the required variables, optimal thickness, optimal thickness-length and optimal thickness-length-imperfection. The results show that the optimal ratio of imperfect reactive powder concrete slab thickness to the one of its dimension is equal to (0.049) whereas the optimal ratio of imperfection to the thickness of slab is equal to (0.785) . The current study adopted preparing designable table which is considered informative for any future designs.

The complete derivation of the more exact solution that controlled the behaviour of reinforced concrete short rectangular column strengthened by steel lattice frame jacket is presented including the effect of bond slip between the concrete and reinforcement and that between concrete and steel jacket. Bond between these materials is considered well through assuming an existing of distributed frictional springs. An exact displacement field is derived utilizing the principle of minimum strain energy following Euler –Cauchy formula. Stress -strain diagram for confined concrete by internal reinforcement and external steel jacket is suggested. An empirical equation that controls the effect of interface spring stiffness between concrete and steel jacket is found through experimental investigation. A computer program is prepared using visual basic language and designated as (ARCC–SSJ)1 including all the above work. The validity and efficiency of the presented finite element is tested through comparison with others experimental results. Present study shows good agreement.