Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

In this study the optimum replacement percentage of sintered fly ash aggregates in M30 grade of concrete was identified based on 28 days cubical compressive strength value. The optimum replacement of Sintered Fly ash Aggregates (SFA) is 40 %. Before identifying the optimum replacement percentage, the SFAs were tested for suitability test such as crushing strength test, impact test and water absorption test. Further, the optimum 40 % SFAs in concrete is tested for punching shear on the Reinforced Concrete (RC) slabs for a dimension of 1000 mm x 1000 mm x 100 mm. In addition to know the effect of steel fibers in RC slabs subjected to punching. A hook ended steel fibers having an aspect ratio of 55, 80 and 100 is selected and varied by volume of concrete for the punching shear values on RC slabs. The RC slabs concrete contains aspect ratio of steel fibers 55 is varied for 0.25 %, 0.5 %, 0.75 % and 1 % for volume of concrete. In addition to that a constant volume of steel fiber 0.5 % is selected for the aspect ratios of 80 and 100 for the punching shear tests. The punching shear values for the RC slabs shows that partial replacement of SFAs and steel fibers in concrete enhances the punching shear strength. These experimental tested results are compared with finite element programming (ABAQUS) and international codes such as IS 456 and ACI 2011. The experimental punching shear results were higher when compared to international codes.

This study investigated the effect of supplementary cementitious materials (SCMs) with pozzolanic nature fly-ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) on the properties of cement mortar with pyrogenic silica addition. First, standard reference (SR) samples were prepared using CEM I 42.5 R-type cement. Pyrogenic silica was added to cement (0.5% by weight) to prepare another group of reference (PR) mortar samples. Cement in PR mortars was replaced with FA, SF, and GGBFS up to 10, 20, and 30%. The mortar samples were placed in 40x40x160 mm metal molds using a vibrating table. The following day the samples were removed from the molds and water cured for 7, 28, and 90 days. The results showed that increases in curing times helped improve the mechanical properties of the mortars. Moreover, the physical properties of PR mortars were affected more positively than the SR mortars. SF-substituted mortars had highest compressive strength, followed by GGBFS- and FA- substituted mortars. In conclusion, pyrogenic silica contributed to some extent to early strength, followed by a decrease.

impact resistance represents a key property of fiber reinforced concrete (FRC). To study this property, a test method was recently proposed; which consists in repeated drops of a projectile on simply supported prisms, and allows to evaluate FRC behavior both at cracking and after cracking. With the aim of verifying the sensitiveness of this method, this paper analyzes the influence of the compressive strength of the FRC matrix on each parameter of the impact test. Three FRC incorporating 30 kg/m3 of hooked-end steel fibers were prepared, varying the water/cement ratio (0.59, 0.50 and 0.43). It was found that although only small effects on the cracking energy were observed as the concrete compressive strength increases, the post-cracking energy increased in a greater proportion. However, the cracking growth rate, an impact parameter strongly sensitive to the type and content of fibers, remained practically constant for different compressive strength levels.

In this study, a comparative experimental analysis is performed between steel-reinforced concrete beams, which are dimensioned based on NBR 6118 (2014), and beams reinforced with glass fiber-reinforced polymer (GFRP) rebar, which are dimensioned based on ACI 440.1R (2015) after being subjected to a four-point bending test. The beams are dimensioned to resist the same force and to satisfy the service limit state (SLS). Results show that the two groups of beams exhibit similar vertical displacement behaviors until the SLS-DEF, whereas the GFRP beams exhibit larger deflections. At the ultimate load, the beams with fiberglass bars indicate a higher resistance by approximately 64% compared with those with metal bars.

Magnesium phosphate cements are implemented for several purposes demonstrating significant mechanical properties in limited durations. However, brittle behavior of this material needs utmost concern and tensile performance may be enhanced with the proper application of fibers increasing both ductility and energy absorption capacity. This research studies the effect of basalt fibers (BF) and silica fume (SF) on the fracture parameters of magnesium phosphate cement (MPC). MPC mortar mixtures were prepared with different SF (0, 5, 10%) and BF amounts (0, 0.5, 0.75, 1 % by wt.). Also fly ash was adopted with a constant ratio for all mixes. Compressive strength and splitting tensile strength results indicated that addition of SF into mixtures extensively developed the matrix structure and improvements were noted with the increasing SF content. The inclusion of BF enhanced the flexural behavior although there were significant improvements in the fracture energy as well as the double-K parameters. Improvements in the tensile capacity of specimens with high BF were prone to the amount of SF percentage such that inclusion of 1 % BF performed best with 10 % SF added mixtures. Load-CMOD (crack mouth opening displacement) curves obtained from notched three-point tests were given for all specimen series and parameters were calculated according to the double-K criterion. Addition of BF resulted in higher toughness values however presence of SF was very significant in establishing appreciable development in toughness values. Brittleness index was implemented to establish clear conclusions on the findings and best performance was seen for specimens with 10% SF and 1% BF.

This study presents the physical and the mechanical properties of C class fly ash (FA) based lightweight geopolymer mortars produced with expanded vermiculite (EV) aggregate. The FA was activated with NaOH containing 12%, 14% and 16% sodium by weight. The volumetric ratios of EV/FA in the samples were chosen as 2,4 and 6 in the study. The liquid/solid ratio 0.23, 0.26 and 0.29. Lightweight geopolymer mortar (LGM) samples were produced by mixing FA, EV, NaOH and water in a mixer. The samples placed in molds were exposed to activation temperature of 100°C for 24 hours in the oven. The samples taken out of the oven were demoulded and kept in air curing for 28 days at 20°C±2°C room temperature. After curing, unit weight, apparent porosity, water absorption ratio, ultrasonic pulse velocity (UPV), flexural strength and compressive strength tests were performed on the samples. In addition, the thermal conductivity coefficients of the samples were determined. As a result of the experiment, a compressive strength varying between 0.59 MPa and 3.81 MPa was obtained in lightweight geopolymers samples with a unit weight between 906 kg/m3 and 1477 kg/m3. Expanded vermiculite showed a good performance on thermal conductivity of LGMs and a decrease in thermal conductivity up to the 0.094 W/mK was observed.

During last few decades, the researchers have developed new structural systems which have no or minor damage after being hit by severe events like earthquake. Development of self-centering wall having alternative energy dissipation mechanisms was one of these achievements. A wide variety of rocking wall systems, such as jointed walls, hybrid walls, precast walls with end columns (PreWEC), and PreWEC core wall systems, are proposed and studied. This paper describes an analytical investigation of the lateral load behavior of two new types of hybrid rocking wall systems. Core rocking wall is achieved by merging four single hybrid rocking walls and coupled rocking wall is accomplished by coupling two rocking walls using embedded reinforced concrete beams. The concept of coupling hybrid rocking walls using embedded reinforced coupling beam is emerged from previous coupled conventional shear walls studies. As single rocking wall system, in coupled and core rocking wall, post-tensioning tendons are used as a mean to provide self-centering force, and mild steel bars are used to dissipate energy. The nonlinear behavior of the wall is due to the gap opening at the base joint. Three-dimensional finite element model of each system was developed. The stress distribution, crack propagation, and critical sections of these systems are investigated. The effect of spalling concrete cover in the toe region due to rocking action is explained. In addition, the reduction in stiffness and lateral load resisting capacity of the systems due to cracks is monitored. Finally, the lateral load behavior of single rocking walls is compared to that of core and coupled rocking wall systems.

Construction work is one of the most dangerous business lines. As a result of occupational accidents in construction works, there are consequences that will affect human life such as injury and death, as well as serious financial losses. Especially in developing countries, despite the increase in precautions regarding occupational safety, occupational accidents continue to occur. Human behavior is an important factor in construction work accidents. In the sector where generally low-educated level workers work, analyzing the precautions and occupational safety training results are important to reduce construction work accidents. Eye-tracking technique, a technology that is spreading around the world, finds its place in different sectors. Especially with the use of mobile eye trackers instead of fixed eye trackers, this eye-tracking technology has also become usable in site implementations in the construction industry. In the construction sector, some studies are done especially on occupational safety issues using eye-tracking techniques in recent years. In this study, a site study was done with construction workers using a mobile eye-tracking approach by creating a track with different hazard sources in construction where a fatal occupational accident occurred. In this context, the attention levels of construction workers against different sources of danger and the risk of accidents created by these sources were measured with the mobile eye-tracking technique. The results obtained from the study were shared with the occupational safety experts on the site and the results are interpreted. All workers participating in the experimental study were workers that previously got occupational safety training. Therefore, according to the outcomes of this experiment, the effectiveness of the occupational safety training they received is measured and some suggestions are made.

Measures taken against preventing damages in structures against explosive load are a popular matter of investigation among researchers. Generally, numerous studies were conducted on reinforcement materials for outer surfaces, reinforcement design, and utilizing fibers produced from various materials. In this study, a hollow-core slab was manufactured with concrete, which had a regular strength, and a design that discharged the explosive energy upon contact explosion via the hollow cores of the slabs and prevented the redirection of the explosive energy to the area below the slabs was investigated. Because the hollow-core slab in the study did not have any lateral reinforcement, the utilization of the tensile strength of the concrete proved advantageous. For this purpose, in the experimental tests of the study, contact explosions were conducted on hollow-core slabs with hollow diameters of 14 cm for each core. Before the explosion tests, the TNT equivalent of 910gr explosive was determined by performing the TNT equivalent tests. In the explosion tests of prepared hollow core concrete slabs, 125 gr, 250 gr, 375 gr, and 500 gr dynamites were used as the explosive materials. In conclusion, the explosive loads that the slabs could withstand were calculated and various slabs with distinctive hollow-core diameters were determined depending on the amount of the explosives.

In view of the past earthquakes, it is stated that several structures are located in active seismic zones around the world. So, improvement of the earthquake performance levels of the existing buildings by using various strengthening methods has been the major interest in structural engineering. Non-linear analysis procedures that are defined in several seismic codes exhibit reliable results in the evaluation of seismic performances of existing buildings. In this study, seismic performances of three, five and eight storey existing and strengthened reinforced concrete buildings having the common floor plan, material and section properties of the structural members are investigated according to Turkish Building Earthquake Code-2018 and American Standard, ASCE. To obtain the earthquake performance results of reinforced concrete buildings, displacement demands of the buildings have been obtained and utilized in nonlinear analyses. SAP2000 structural analysis software is used in the solutions. The determined strengthening techniques are provided by adding concentric steel bracing members to existing reinforced concrete buildings and jacketing of the determined columns. As a result of non-linear analyses applied to the existing and strengthened buildings, damage situations of the structural members are determined, seismic performances of the buildings are evaluated according to both codes and the results are interpreted in the end.