Cost optimisation for high-rise buildings considering number of levels of shores and reshores

Formwork consideration in terms of time, safety and cost forms a major aspect in construction phase. Number of levels of shores/reshores is decided based on experience and judgment of project engineer. It becomes necessary to optimize cost of formwork to reduce overall cost of construction of high rise RC buildings. A MATLAB® program has been developed in this study to calculate load transmission between inter-connected slabs and levels of shores/reshores using the simplified method. An optimization equation is developed for cost of construction considering cost of concrete, shores, and reshores. Cost is optimized using genetic algorithm while ensuring safety of construction, expressed in terms of factor of safety which is a ratio of strength gained by slab to imposed load at a particular time of construction. The study is carried out for a 10 storey building for different grades of concrete from M20 to M50, with an increment of 5 N/mm2. All combinations of levels of shores and reshores are economically undesirable for M20 grade of concrete for 1.5 factor of safety. It is also observed that five levels of shores and five levels of reshores are economically undesirable for all concrete grades from M25 to M35. The lowest cost cases are  observed with one level of shores and nine levels of reshores for M25 and M30 grades of concrete, one level of shores and four levels of reshores for M35 grade of concrete and one level of shore and two levels of reshores for M40, M45 and M50 grades of concrete. The study is further extended for 20, 40 and 60 storey buildings with different factors of safety and grades of concrete. This method is suitable for designers and practitioners to decide the levels of shores and reshores for construction based on economy and safety parameters.