Experimental investigation of the mechanical behaviors of structural elements produced by cementitious composites

Structural systems should maintain the capacity of strength, stiffness and ductility capacities under the effect of earthquakes, change their displacement and strain capacity without creating collapse damage, preventing serious damage. The strength of concrete is low in the structures and the lack of sufficient amount of the confiment reinforcement causes serious damage to the structures under the earthquake effects and causes the building collapses. Most of the damages that occur in the buildings are located in column-beam joints, which are plastic joint points. The lack of adequate confinement in the column- beam joints causes non-ductility of the structure and in addition to the non-damping of the energy that is responsible for the earthquake effects. In addition, the bonding between the concrete and the reinforcement can not be achieved in an effective operation of the concrete and the joint together because the reinforcement density in these joints is high. Textile reinforced cementitious composites are very ductile materials with good tensile and flexural performances. Textile reinforced cement based composite structural elements, which is a new system in our country, can be applied as a permanent formwork system in reinforced concrete columns. Thus, reinforced concrete structural elements are confined and the ductility capacity is increased. As a result, the columns with insufficient transverse reinforcement will increase the strength, stiffness and ductility capacities in the most difficult disadvantaged elements during the earthquake. At the same time, the use of the permanent formwork system composites will lead to saving mold workmanship and transverse reinforcement (stirrup), which will result in reduced construction costs. In this dissertation, new generation composite structural elements were produced and used as permanent formwork systems in reinforced concrete columns. Initially, a new production technique and machine was developed to produce composite systems. PPR method (Pull-Pour-Roll) has been decided to be superior in terms of strength and durability. New generation polymer modified matrix mortars were designed and mechanical properties were tested in order to create composite products. In the scope of the study, three different types of textiles and two different types of matrix mortars were used, while producing TRCC elements. The PPR machine produced the circular and rectangular cross-section hollow, thin and three-dimensional composite elements. 5 circular and 4 rectangular full-scale reinforced concrete columns were produced by forming permanent formwork systems. A total of thirteen columns were produced with four reference samples that were suitable and not suitable according to DBYBHY (2007). The performance of reinforced concrete columns were investigated by testing the produced reinforced concrete columns with constant axial load and reversible repetitive horizontal loads in the laboratory environment. The performance of the permanent formwork composite column specimens with respect to the reference specimens was determined by evaluating the strength, stiffness, ductility, energy absorbtion capacity, structural damping and collapse damage obtained from the experimental results. Formwork systems used in the construction industry are auxiliary structural elements that enable concrete or reinforced concrete structural elements take necessary form and carry it to the concrete strength. Today, formworks are generally made of building materials such as wood, plywood, steel, hair, aluminum. These formwork systems are used in combination with other components made up of application mold carriers, stitchers and fasteners. Formwork systems; they should be a structure that can be easily installed with few parts, clean, suitable for measurement, leakproof, light as possible, safely bearing the vibration effects for concrete settlement and less workmanship. Formwork system operations with traditional materials have a lot of deficiencies. Temporary formwork system only helps forming structural form in the structural element in which it is applied, whereas the permanent formwork system provides structural strength, stiffness and durability in the structural system. For this reason, significant contributions are made to the building safety under the effect of the earthquake. The presence of ductility capacity in structural systems prevent the earthquake effects causing serious damage to the construction. The ductility capacity is possible by constructing the transverse reinforcement (stirrup) in the concrete core effect. When the transverse reinforcement is positioned very regularly in the structural elements such as columns, beams or shear walls, the loss of life and property that will occur in the structure will be reduced considerably. Due to labor mistakes in the temporary formwork systems made with wood or metal mold materials, insufficient transverse reinforcement is among most common weaknesses of columns against earthquakes. This weakness causes brittle behavior of structural members during earthquakes. However, the use of low-strength concretes in the structural element is a major drawback in construction. The most damaged areas during construction of the earthquake are column, beam or column-beam joints. The main reason for the damage in these areas is the inadequate of transverse reinforcement in these regions. Due to these deficiencies, the structures suddenly collapse without acting ductile during the earthquake. In a column, beam or column-to-beam joint, it is very difficult to position the transverse rebars regularly. Transverse reinforcements are virtually impossible due to the reinforcements in the column-beam joints. At the same time, while the concrete process is being carried out, the transverse rebars, which are not properly fixed, are dismounted. The elimination of the deficiencies of the above-mentioned manufacturing and workmanship deficiencies of the carrier elements produced by conventional formwork systems will also be ensured by the textile reinforced cement based permanent formwork composite. With the developing technology in the world, the use of composite materials, which is a modern building material, is increasing. Composite materials are used in civil engineering in many different areas. The composite materials in the construction industry are easy to produce and their cost is cheap allowing them to use more of these materials. For this reason, textile reinforced cement based composites will contribute to economics and scientific studies as a new material. By producing textile reinforced cement based composite permanent formwork systems; Gaining new generation and innovative composite materials to the construction industry; the production of composite materials by a cost effective, practical and economical method; increase the strength, stiffness and ductility of the structural elements by creating confiment effect on structural elements such as columns, beams or shear walls in reinforced concrete buildings; rapid and practical construction of structures by creating alternatives to traditional formwork systems.