Web Openings In Beams Research Articles

STRENGTHENING OF R.C BEAMS WITH OPENINGS CREATED AFTER CASTING USING F.R.P

Web openings in beams have found many applications in practice such as they provide convenient passages of electrical and mechanical conduits. Over the past several decades, many researchers exerted great efforts to predict and interpret the behavior of beams with web openings. They recommended convenient methods for the design of such beams. These methods are successfully used if openings were decided before casting of beams. But, what will be the case if it is required to provide new openings in existing beams? The current work aims to give a satisfactory answer for this question, in which CFRP were used to strengthen and improve the behavior of beams with created openings. Eighteen reinforced concrete beams with rectangular cross section (13 x 25 cm) were tested under two concentrated static load. Three of the beams were taken solid without openings as control beams. Each one of the other beams was provided with a rectangular web opening of 20cm length. CFRP was used to strengthen some beams. The variable parameters are the opening height, the percentage of cut web reinforcement, the distance between the opening edge and the nearest unaffected web reinforcement, the shear span to depth ratio and type of strengthening, as well as concrete strength. The pattern of cracks, final mode of failure, cracking load, failure load and deformational characteristics (deflection, and strains) were recorded, analyzed and discussed. Finally, some important conclusions were reported.

Design against cracking at openings in reinforced concrete beams strengthened with composite sheets

Web openings in beams and girders occur quite often in practice to provide a convenient passage for utility ducts. Accommodating the environmental services in such a manner eliminates a significant amount of dead space and results in a more compact and, often, more economical design. However, introducing an opening into the web of a reinforced concrete beam causes local cracking around the opening leading to reduction in stiffness and capacity of the beam. In this paper the use of fibre reinforced polymer (FRP) sheets to strengthen the opening region is presented. Several design parameters are varied including opening width and depth, and amount and configuration of the FRP sheets in the vicinity of the opening. The experimental program included testing of 10 reinforced concrete beams, five of which were strengthened with FRP sheets around the opening, four were tested without strengthening, and the remaining beam was solid without opening considered as a control beam. The effect of this strengthening technique on deflection, strain, cracking, and ultimate load is investigated.

Design Against Cracking at Openings in Prestressed Concrete Beams

Web openings in beams occur quite often in practice to provide convenient passage of electrical and mechanical conduits. In this paper, the analysis and design against cracking of simply supported prestressed concrete beams with rectangular openings are presented. Several design parameters are varied, including opening width and depth, horizontal and vertical locations of the opening, type of cross section, and amount and arrangement of reinforcement around the opening. The results from a finite element analysis are substantiated by test results. A simple design method for estimating the cracking load for the different crack patterns is proposed and two illustrative design examples are presented.

Design of Prestressed Concrete Beams with Openings

Web openings in beams occur quite often in practice to provide convenient passage of environmental services. As a result, story heights in buildings can be reduced resulting in major cost savings. In this paper the nonlinear analysis and design of simply supported posttensioned prestressed concrete beams with rectangular openings are presented. Several design parameters are varied such as: opening width and depth, horizontal and vertical locations of the opening, and type of cross section. The results from a nonlinear finite-element analysis are substantiated by test results from 13 unbonded posttensioned prestressed concrete beams, six of which are rectangular in section, five are T-section, and the remaining two are I-section. Good agreement is shown between the theoretical and the experimental results. The effect of the openings on the behavior of such beams at different stages of loading is presented. A simple design method for estimating the ultimate failure load for each type of failure mode is proposed. An illustrative design example is presented.

Analysis of prestressed girders with openings

Web openings in beams and girders occur quite often in practice to provide a convenient passage for environmental services. As a result storey heights in buildings can be reduced resulting in major cost savings. A theoretical and experimental study is carried out to determine the influence of openings on the static and dynamic responses of prestressed concrete girders. The ABAQUS computer code, based on the finite element technique, is used to examine the effects of opening size, eccentricity and horizontal location on the shear distribution as well as on the potentially-splitting tensile stress at the opening when the girder is subjected to static load applied at mid-span and at the opening. The computer code is also applied to study the dynamic response. Simply supported and two-span continuous girders of rectangular, T- and I-sections are considered. The theoretical results are verified and substantiated by experimental results.

Lateral Buckling of Doubly Symmetric Beams Containing Openings

When a slender beam is transversely loaded in the plane of its greatest flexural rigidity, it may buckle laterally at a critical load. It is common practice to provide web openings in beams for the passage of service ducts and pipings, for inspection purposes in beam structures, and for other reasons. The presence of web openings not only reduces the ultimate strength of beams, but also the lateral‐buckling capacity. This paper presents a numerical method, based on the energy approach, to predict the critical lateral‐buckling loads of slender, doubly symmetric beams containing unreinforced web openings. The beams are either cantilevered or simply supported and contain openings along their centerlines. The critical loads evaluated numerically are compared with the values obtained experimentally. The study shows good agreement between the numerial and experimental values.