Papers by Keyword: Crack Pattern

Abstract: The reinforced bubble deck slab or BubbleDeck is a unique system that improves the building design and performance of structures. This slab structure is a reinforced concrete structure that contains high-density polyethene (HDPE) hollow spherical plastic bubble balls with less concrete volume compared to a normal reinforced concrete slab. The system can facilitate up to a 50% longer span compared to a conventional reinforced concrete solid slab. But, eliminating the deadweight concrete may affect the actual performance of the slab structure such as its flexural and shear capacity. Thus, this paper investigates the effect of area loading and punching shear loading on the reinforced bubble deck slab in terms of flexural performance. The square slabs with 1200mm by 1200mm for width and length with a thickness of 230mm were designed as a one-way supported slab. A total of 36 HDPE hollow spherical plastic bubble balls with a 180mm diameter were placed in each bubble deck slab specimen. The high yield steel DA6 BRC reinforcement steel bar meshes and Grade-30 concrete were used for the slabs. The experimental results of the flexural performance of the reinforced bubble deck slab that were subjected to the static area and punching shear loadings are presented. The effect of the load applied in the experiments on the slabs such as flexural strength, bending stiffness and load-deflection behaviour were discussed including the crack propagation and crack pattern.

Abstract: Reinforced bubble deck slab is a structural slab that contains high-density polyethene (HDPE) hollow spherical plastic bubble balls forming a slab with less concrete volume compared to the normal reinforced concrete slab. Reducing certain volumes of concrete from 30 to 50% will affect the performance of the slab structure in particular the flexural and shear capacity. Thus, in this research the effect of area loading on the flexural performance of bubble deck slabs is investigated by considering the slabs to be one-way supported slabs. The square deck slabs used were 1200mm by 1200mm for the width and length with a thickness of 230mm. A total of 36 HDPE hollow spherical plastic bubble balls with a 180mm diameter were placed in the bubble deck slab specimens which reduce significantly the structural self-weight. In this paper, the experimental results of the flexural performance of the reinforced bubble deck slab, (BD slab) compared with a conventional reinforced concrete slab, simply supported, subjected to static area loadings, are presented. The effect of the load applied in the experiments on the flexural strength, bending stiffness and load-deflection behaviour of both types of slabs have been discussed including the crack propagation and crack pattern. In general, the conventionally reinforced solid slab, simply supported (SS) has a 60.6% higher resistance against bending deformation than the reinforced bubble deck slab.

Abstract: Structural elements such as beams most times experience shear failure suddenly without prior warning and this is different from bending failure which occurs by gradual yielding of tensile reinforcement. A previous experimental research showed that the use of lightweight foam concrete with a fiber mixture has a higher ductility in comparison to the normal concrete. It is also one of the solutions to increase the shear strength capacity of concrete and also has the ability to cause relatively small crack patterns and spread. This research, therefore, aimed to determine the shear behavior of fiber-reinforced foam concrete using a finite element with 3-dimensional modeling in an ATENA V5 software. Moreover, the results obtained were were compared with the findings of the experimental research. The test object used was a beam designed with 15 cm x 30 cm x 220 cm dimensions and the stirrup spacing for the fiber-reinforced foam concrete (BBSN-20) was 20 cm while the normal beam (BN-25) had 25 cm. The numerical analysis was observed to have shown closer values to the experimental results with the difference in the ultimate load on the BBSN-20 and BN-25 recorded to be only 7.73% and 12.6% while the ultimate deflection was 6.92% and 32.45% respectively. Meanwhile, the beam destruction patterns in both the numerical and experimental models were similar but the numerical analysis showed the two beams modeled did not experience shear failure as planned.

Abstract: This study simulates a procedure of rehabilitation of reinforced concrete beams with the aid of ANSYS 17 software. In this work, the BIRTH and DEATH procedure (in ANSYS) was adopted to model the post-repairing stage. This aspect has rarely been considered by previous studies that utilized a carbon fiber reinforced polymer (CFRP) sheet when retrofitting. To verify the suggested technique, six specimens were analyzed with two values of shear span-to-depth ratios (3 and 4) and three spaces of CFRP sheets (100mm, 150mm and 200mm). The effect of the repairing process on the structural performance of the retrofitted beam is also investigated.It is found that the suggested technique yielded a good agreement with the experimental results and the maximum differences in the failure loads between the numerical and experimental results were 10% and 4% for shear span-to-depth ratios of 3 and 4, respectively. It was also ascertained that upgrading reinforced concrete members within the early stages of loading showed a better enhancement in the loading capacity compared to upgrading reinforced concrete members close to the juncture of failure.

Abstract: Nut embedded disc grinding wheels, also known as disc grinding or F-Type wheels, are required for many production jobs. Nut pull-out is a common problem encountered in disc grinding wheels. The present work proposes a simple fixture, using which the integrity of the nut in the grinding wheel can be assessed. This method can be adopted by any grinding wheel manufacturer for a realistic estimate of nut pull out strength in double disc grinding wheels.

Abstract: The 12th C. Modena Cathedral is a masterpiece testimony of early Romanesque architecture, artand civic values of the time. Following the inclusion in the UNESCO list in 1997, studies, surveysand maintenance works have started. The Emilia’s seismic events of May 2012 have happenedwhen the maintenance operations were already in an advanced phase. The quakes caused damageand re-opening of some historical cracks, in particular in the thin vaults of the naves, near thefaçade and at the junction between naves and choir and crypt. Fragments of brick, mortar from thejoints between bricks and even limited portions of a diagonal rib have fallen to the ground. In viewof seismic assessment and strengthening for improvement of the structural behaviour, detailedstudies of the vaults’ mortar became necessary. The investigation approach was minimal andpreservative, combining on-site close-up visual inspections and micro-destructive testing of themortar joints by mortar penetrometer. For this purpose, openings of 0.25x0.25 m2 in the renderlayer of the 23 vaults were created. The outcome has allowed differentiating between repair mortarsof different strength, used in different historic periods. The mortar resistance was very low butdifferent for lime mortar and gypsum. Values, divided in 3 classes of strength, were found tocorrelate well with the location and severity of the crack pattern and damage map in the vaults. Theresults were useful for a correct design (minimal and reversible) of the cathedral strengtheningintervention.

Abstract: Fourting concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their crack patterns. Crack distributions in constant moment region of beams are compared. The propagation of side cracks along the beam depth is obtained. The results of this study indicate that the concrete cover of longitudinal tensile steel bars and the spacing of skin reinforcement has significant effect on crack distributions; substantial crack control in beams can be achieved if the spacing of skin reinforcement is limited to certain critical values. The curve of d-w(d is the distance between observation points of side cracks and tension face of beams, w refers to crack width at observation points) is approximately characterized by a zig-zag shape and concave-left near longitudinal tensile steel bars.

Abstract: In order to investigate the crack pattern and ductility of connection composed of cross shaped steel encased ultra high strength concrete (CSSEUHSC) columns and steel encased concrete (SEC) beams under cycle loads, six interior connection specimens were tested in the laboratory. It was found that cracks appeared in the connection core regions and at the beam end for all specimens, and all the connections behaved in a ductile manner and failed in bending with a beam plastic hinge and shearing in the connection core region. The experimental results indicated that test parameters of connection composed of CSSEUHSC columns and SEC beams with good crack resistance performance may be referred for engineering application.

Abstract: This paper presents the results of experimental tests carried out on steel fibre reinforced self-compacting concrete (SFR-SCC) beams without stirrups. Sixteen beams are cast using four mixtures of SCC with different steel fibre content, while the longitudinal reinforcement is kept constant in all test members. The beams are subjected to four point bending tests at a shear span-to-depth ratio of 2. The ultimate shear stress is recorded, as well as the crack pattern and the mid-span beam deflection. Test results show that as fibre content increases, higher ultimate shear stresses are achieved. When fibres are included, test members exhibit an increase in ductility and a more extensive crack pattern is observed. The experimental values of the ultimate shear stresses are also compared with theoretical values as given by empirical expressions in literature.

Abstract: Evidence regarding a fracture event is absolutely and definitively recorded by Nature during the fracture process. That record is in the form of the general macrocrack pattern and the surface topological features of the newly formed fracture surface. In reality, it is the only perfect record of what actually occurred during a fracture. Whenever a conflict or controversy arises regarding a fracture, it is the moral and scientific responsibility of the fractographer to analyze and interpret the record of the fracture as it was created by Nature. It is further necessary for the fractographer to then inform and educate the members of the legal community (lawyer, judge and jury) as to exactly what happened during the failure. This educational process is necessary so that the legal community can collectively understand the history of the fracture and arrive at a just and fair decision regarding responsibility and potential liability for the failure. This paper describes the overall process from the beginning of the fracture examination of the failed artifact to the final appearance in court leading to a decision by the judge or a jury. Both the technical and the human factors are addressed with varying degrees of detail.