SUMMARY
Every year thousands of square meters of building structures and slabs are built, being the highest number of crashes during the construction process. Seeking to improve construction time and costs without reducing the structural safety, in Spain a technique known as clearing or partial striking is used. The technique consists of removing the formwork and 50% of the slab-supporting shores several days after casting. This considerably reduces the material necessary for formwork and shoring, cuts costs and rationalizes the building process.
Several authors have carried out research studies to determine the load distribution during the construction process through theoretical models and experimental studies, but very few have studied the clearing technique. This is the reason that one of the main objectives of this PhD thesis is to carry out an experimental and theoretical research to study the load transmission between slabs and shores, using a construction process of shoring-clearing-striking, for the most common types of slab.
To be able to evaluate the load transmission between slabs and shores, during the construction of multistorey buildings, an experimental study in three real buildings has been carried out. All three buildings include the different types of slabs more common in construction and all of them have adopted a construction process of shoring, clearing and striking. The results showed that the load transmission varied according to the type of span studied, due to the different ways in which their deformability and/or stiffness are affected by their different geometries and boundary conditions.
In another phase of the research, the finite element model developed previously by the research group has been calibrated. The model has been adjusted to the different structural typologies, whose experimental behavior is known through the loads measured on shores. The FEM results showed a satisfactory fit with the readings obtained experimentally.
Finally, a simplified method to evaluate the load transmission between slabs and shores, during the process of shoring, clearing and striking of multistorey buildings, has been validated based on the experimental and numerical results. The method that has better fit with the experimental and numerical results is the New Simplified Procedure proposed by Calderón et al. (2011).
On the other hand, a factor that has received little attention to date is the effect of ambient temperature changes on load distribution between shores and floor slabs, even though certain authors have emphasized its importance. This is why the other main objective of this PhD Thesis is to evaluate the temperature changes of the different elements of the structure during construction and to determine their influence on the load distribution on shores.
To evaluate this effect, different building sites were monitored during construction in order to observe the temperature gradients inside reinforced concrete slabs during variations in the ambient temperature. It has been observed the magnitude and importance of temperature gradients in the slabs.
The experimental results have been used to determine the influence of temperature changes on load variations on shores by developing a theoretical finite element model. The numerical results show the importance of temperature variations in the loads on shores and slabs during construction of multistory buildings. These changes in loads are the product of the combination of two main effects: temperature changes on columns and shores and the temperature difference between the upper and the lower surface of the slabs
Palabras Clave: Clareado; Cimbrado; Descimbrado; Puntal; Edificios de hormigón armado; Forjados; Estudio experimental; Modelo de los elementos finitos; Temperatura del hormigón.
Keywords: Clearing; Shoring; Striking; Shore; Reinforced concrete buildings; Slabs; Experimental study; Finite element method; Simplified model; Temperature of concrete.