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- Title
BEHAVIOR OF HIGH PERFORMANCE CONTINUOUS R. C. DEEP BEAMS WITH OPENINGS AND ITS STRENGTHENING.
- Authors
Rashwan, Mohamed M.; Elsayed, Aly Abdel Zaher; Abdallah, Ali Mohamed; Hassanean, Mahmoud Abdou Mahmoud
- Abstract
Reinforced concrete deep beams may exist in many structural applications such as offshore structures, transfer girders, pile caps, tall buildings and water tan ks. The depth of deep beams is much greater than normal in relation to their span. Since the beam is short in this case, shear deformations are more important and special design methods should be applied in this case rather than normal beam theory. Continuous deep beams are defined in the Egyptian Code of Practice (2012) [2]as those beams whose height to effective span ratio greater than 0.4. Deep beams are members with special features. In such beams, plane sections do not remain plane after bending, with significant warping of the cross- sections because of high shear stresses. The resulting strain distribution is no longer linear and flexural stresses are not linearly distributed even in the elastic range. Recently, high strength concrete, defined by the American Concrete Institute ACI318- 08 [3], as concrete with cylinder compressive strength greater than 60Mpa, is being widely used in the construction industry. However, limited research efforts were directed towards the study of the behavior and shear strength of reinforced high strength concrete continuous deep beams. Furthermore, sometimes web openings have to be provided in deep beams for the purpose of access or for providing services. The presence of such openings may affect the shear strength of deep beams. However, limited investigations were directed towards the study of continuous deep beams with openings. Also, strengthening simply supported deep beams using carbon fiber reinforced polymers (CFR P) was investigated by many researchers. However, limited research papers were directed towards CFRP strengthening of continuous deep beams. Experimental tests have been carried out on rectangular reinforced concrete continuous deep beams with a/d=1.17, under static loading up to failure. The study takes into consideration the following parameters: Percentage of web reinforcement (ρh), Positions of openings and number of openings. Also, strengthening of openings in continuous deep beams using glass fiber reinforced polymer (GFRP) was studied in this research. Test results indicated that th e presence of web openings within exterior or interior shear spans had great effect on the beam capacity and its behavior. Existence of web openings within exterior or interior shear spans caused a high reduction in the shear capacity of the beams by about 35%. Therefore and whenever should be kept clear of the natural load path joining the loading and reaction points (solid) free from openings. Also, the strengthening of openings contains the cracks and increase the crack and ultimate load. Finally we will compare the test results with the t heoretical values for beam A1 which were evaluated using strut and tie analysis according to Egyptian code (2012). The strut - and tie method can be used for the design of Disturbed regions (D- regions) of str uctures where the basic assumption of flexure theor y namely plane sections remaining discontinuities ari sing from concentrated forces or reactions and near geometric discontinuities such as abrupt changes in cross section etc. The strut - and- tie method of design is based on the assumption that the D-region s in concrete structures can be analyzed and design using hypothetical pin-jointed trusses consisting o f struts and ties interconnected at nodes. The usu al design practice for continuous deep beams has been to employ empirical equations which are invariably based on simple span deep beams testes. Given the u nique behavior pattern of continuous deep beams, this practice is unreliable. Since continuous deep beams contain significant extents of D-regions and they exhibit a marked truss or tied arch actions, the st rut- and - tie method offers a rational basis for the analysis and design of such beams. The mechanics an d behavior of continuous deep beams are briefly discussed from which a strut - a nd - tie model for such a beam is developed.
- Publication
Journal of Engineering Sciences, 2014, Vol 42, Issue 5, p1138
- ISSN
1687-0530
- Publication type
Academic Journal