Screw shear connectors are being more commonly used in compound concrete sections in Colombia; however, they have been designed in line with Colombian Seismic-Resistant Standards (NSR-98) rather than those established for stud shear connectors. This work represents a starting point for analysing screw shear connector behavior. 54 specimens were made for the experiment, consisting of a metallic profile and two concretes slabs where the connectors were embedded. 1/2” (12.7mm), 5/8” (15.9mm) and 3/4” (19.1mm) diameter screws were used and placed at different distances. The push-out test was used with these specimens and results were provided by using some equations for determining this type of connector’s strength in steel-concrete sections.
Over the past few decades, the use of steel-concrete composite sections has increased globally, in order to take advantage of compression strength in concrete and tensile strength in steel, ensuring its fastening through stress transfer elements denominated shear connectors. The main connection systems endorsed by the current design codes are used by applying welding as fastening mechanism to fix connectors. However, this thermal procedure produces concentration of residual stresses during cooling process, and risk of perforation in Cold-Formed Steel sections (CFS), affecting the behavior efficiency of the composite sections. In this research, self-drilling screws are proposed as an alternative mechanical system for connectors fastening. An experimental program was carried out to validate capacity and performance of the system, through Full-Scale Beam Tests. According to results, self-drilling screws are a viable alternative to be used as fastening mechanism in shear connectors for CFS and concrete composite sections. Composite system achieved to develop full capacity, even in inelastic range, without disconnection between materials. Self-drilling screws remained fixed on steel shapes without mechanical damage, allowing greater deformations, than structural service conditions.
This paper reports using theoretical-experimental analysis for obtaining and characterising the design parameters governing steel and concrete slab composite beams’ behaviour using shear connector screws. Currently no research has been found about such behaviour and Colombian seismic-resistant regulations (NSR-98) have not yet defined such design; these types of connectors are most used in constructing composite sections in Colombia. The results of 36 experimental scale tests for 21MPa and 28MPa concrete strengths were taken for the analysis; each concrete strength had three screw diameters (Ø1/2 ", Ø5/8 " and Ø3/4 ") with 0.10m and 0.30m separations. This research also studied other effects such as slip caused by steel and connector profile deformation or deformation due to concrete degradation. Formulations were thus used which included connector slip and separation. The article sets out a methodology for designing composite beams using shear connector screws. It also proposes a formulation for calculating connector shear strength, thereby obtaining almost 62% stud connector resistance when separation was 0.10m and an extra 13% for 0.30m separations in elastic parameters where 62% of theoretical effective inertia was obtained and 23% more composite beam average bending strength was found than that required by current regulations.
This work was aimed at establishing a wobble friction coefficient (K) from records regarding some post-stressed bridges built in Colombia. Such records were arranged and analysed together with stress diagrams resulting from the corresponding plans, calculations and reports. Suitable records were produced from this review to make the analysis. Once the records had been selected, the probable wobble friction coefficient (K) was then calculated for each case and this coefficient was related to the length of the cable and the total area of the strands composing the cable. These records and their results were subsequently grouped according to the type of bridge to produce a wobble friction coefficient (K) for each specific structure. The study indicated that the wobble friction coefficient was lower than that indicated by the Colombian Seismic Bridge Design Code, Instituto Nacional De Vías, 1995]. The influence of tensioning equipment, materials and labour suggested a format for recording tensioning to reduce inaccuracy when readings are being taken. A reduction in the costs of tensioning would arise from taking the forgoing into account.
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