The high incidence of global terrorism and accidental explosions have highlighted the vulnerability of built infrastructure to blast loading. Thus, owners of iconic structures are looking for ways to protect their critical assets from the effects of explosions. Many of the research efforts, in this light, have been devoted to the effects of far-field explosions on structural elements. The effects of near-field explosions on structural elements, especially columns, have not been as widely investigated. This paper presents the results of a comprehensive research program designed to investigate the effects of near-field explosions on the behaviour of reinforced concrete columns designed and detailed for regions of different levels of seismicity. The numerical study shows that reinforced concrete columns subjected to blast loading from higher explosive charge masses have higher deflections than those subjected to blast loading from lower charge masses, but at the same scaled distance. Also, the effect of closely spaced transverse reinforcement is significant at smaller scaled distances. Thus, reinforced concrete columns designed and detailed for areas of high seismicity have an inherently high blast resistance.

Recent terrorist attacks and accidental explosions involving hazardous materials around the world have increased the need to study the behaviour of structures subjected to blast loadings. Most research work investigating the behaviour of reinforced concrete columns to blast loading have concentrated on their response to planar loading from far-field explosions. Limited amount of work is available on the effects of near-field explosion on the behaviour of reinforced concrete columns.This thesis presents the results of a numerical study designed to investigate the effects of near-field explosions on the behaviour of reinforced concrete columns. The numerical investigation is a follow up on a project to a live explosion testing of reinforced concrete columns subjected to explosion from scaled distances ranging from 0.25 to 1.0 m/kg 1/3 .The experimental results are used to validate the numerical models which are then used to conduct parametric studies to evaluate the effects of scaled distance, and concrete properties on the response of reinforced concrete columns.The numerical analysis showed that for increasing charge masses, the natural period of vibration of reinforced concrete columns increased. Also the effects of tie spacing were markedly noticeable at lower scaled distances. Peak column deflections at higher scaled distances occurred mid-height while peak column deflections at lower scaled distances occurred closer to the column supports.iii

With the increase of construction activities in Ghana, there is an increasing demand in building materials leading to the shortage of the conventional materials. The informal sector is gradually seeing the introduction of quarry dust as a substitute of sand in block production. This paper focuses on a comparative analysis of the quality of sandcrete blocks and quarry dust cement blocks. Block samples were gathered from various suppliers around the Prampram and Dawhenya areas and through various laboratory tests were tested for their dimension tolerance, water absorption and compressive strengths. Aggregate samples were also taken from suppliers for sieve analyses. The study revealed that the quarry dust cement blocks contained relatively higher percentages of coarse grade particles compared to the sandcrete blocks. The total average water absorption of sandcrete blocks was found to be 3.90% while quarry dust showed an improved value of 3.28%. Sandcrete blocks were averagely found to be of a higher compressive strength of 4.31N/mm2, with quarry dust at 3.0N/mm2. The study suggested the likelihood of a lesser use of cement in the production of quarry dust cement blocks due to the similarities in colour between the quarry dust and cement, hence, negatively affecting its compressive strength.