Top PDF Aggregate interlock in lightweight concrete continuous deep beams

Aggregate interlock in lightweight concrete continuous deep beams

Aggregate interlock in lightweight concrete continuous deep beams

This paper presents the testing of 12 continuous beams made of all-lightweight, sand-lightweight and normal weight concrete having maximum aggregate sizes of 4, 8, 13 and 19 mm. All beams had the same geometrical dimensions and steel reinforcement. Load capacity of beams tested are compared with the predictions from strut-and-tie models recommended in ACI 318-08 and EC 2 provisions including the modification factor for lightweight concrete. Test results showed that the amount of load transferred to the intermediate support after the occurrence of the diagonal crack within the interior shear spans and load capacity increased with the increase of the maximum aggregate size, though the aggregate interlock contribution to load capacity in lightweight concrete deep beams was less than that in normal weight concrete deep beams. The lightweight concrete modification factor in EC2 is generally unconservative, while that in ACI318-08 is conservative for all-lightweight concrete but turns to be unconservative for sand-lightweight concrete with a maximum aggregate size above 13mm. It was also shown that the conservatism of the strut-and-tie models specified in ACI 318-08 and EC 2 decreased with the decrease of the maximum aggregate size, and was less in lightweight concrete deep beams than in normal weight concrete deep beams.
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STUDYING THE BEHAVIOUR OF LIGHTWEIGHT DEEP BEAMS WITH OPENINGS

STUDYING THE BEHAVIOUR OF LIGHTWEIGHT DEEP BEAMS WITH OPENINGS

In this study experimental tests were conducted to investigate the behavior of reinforced concrete deep beam with openings using lightweight concrete. The experimental program involved of testing thirteen simply supported deep beam specimens which tested under static two-point loads. Light expanding clay aggregate (LECA) was used to produce lightweight concrete. Test variables were the shape and size of openings, reinforcement around the openings, position of the openings and shear span to depth ratio. It was found that the behavior of deep beams which made of lightweight concrete is similar to that made of normal concrete. It was concluded that the ultimate load and the measured maximum deflection in beams that have circular openings are larger compared to that have rectangular openings. At the same time, the ultimate load decreased and the measured values of maximum deflection increased with increasing the size of the openings in deep beams. Also, it was found that providing steel reinforcement around the openings caused an increasing in the load capacity of the tested beams. Decreasing the shear span ratio from 0.5 to 0.4 caused an increasing in the ultimate load and the measured maximum deflection.
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Modification Factor for Shear Capacity of Lightweight Concrete Beams

Modification Factor for Shear Capacity of Lightweight Concrete Beams

database show that ACI 318-11 provisions for shear transfer capacity of concrete are more un- conservative for lightweight concrete (LWC) beams than in NWC beams. A rational approach based on the upper-bound theorem of concrete plasticity has been developed to assess the reduced aggregate interlock along the crack interfaces and predict the shear transfer capacity of concrete. A simplified model for the modification factor is then proposed as a function of the compressive strength and dry density of concrete and maximum aggregate size on the basis of analytical parametric studies on the ratios of shear transfer capacity of LWC to that of the companion NWC. The proposed modification factor decreases with the decrease in the dry density of concrete, gives closer predictions to experimental results than that in the ACI 318-11 shear provision and, overall, improves the safety of shear capacity of LWC beams.
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Load capacity predictions of continuous concrete deep beams reinforced with GFRP bars

Load capacity predictions of continuous concrete deep beams reinforced with GFRP bars

The presented upper bound analysis is used in the current study to predict the total failure load of the specimens reinforced with GFRP bars using two effectiveness factors developed by Ashour and his associates for upper bound technique as shown in Table 8 . The earlier one was developed by Ashour and Morley [ 35 ] based on the previous experimental investigations conducted on continuous concrete deep beams reinforced with steel rebars [ 36 , 37 ]. The suggested factor considered the effects of longitudinal and web reinforcements in addition to concrete compressive strength, while size effect was not taken into consideration. The second effectiveness factor was recommended by Yang et al. [ 38 ] based on that suggested by Vecchio and Collins [ 39 ] to consider the influences of concrete compressive strength and principal tensile and compressive strains. To reflect the size effect, ζ, Yang et al. adopted the same formula proposed by Bazant and Kim [ 40 ] which is a function of section depth and maximum aggregate size as shown in Table 8 .
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An Experimental Study on Shear Strengthening of RC Lightweight Deep Beams Using CFRP

An Experimental Study on Shear Strengthening of RC Lightweight Deep Beams Using CFRP

section, 120(mm) wide and 500(mm) in overall depth (500mm). As shown in Fig.1, the flexural reinforcement consisted of 4T16 deformed bars of yield strength 400MPa. These bars were placed in two layers and were welded to 10mm thick steel plates at both ends to provide the necessary anchorage. The shear reinforcement consisted of one layer of deformed bars having 150(mm) square openings. The bars diameter was 6(mm). the minimum web reinforcement requirements by ACI code [12] are not available by this value. A 20(mm) thick and 100(mm) long steel plate was used at each loading and reaction points covering the full width of the beams (Fig.1). Concrete having average 28 days cube strength of 30 MPa was made from ordinary Portland cement, river sand, crushed gravel of 10mm maximum size and leca (Light Expanded Clay Aggregate) of 3-10mm size. The aggregate cement ratio 5.1 by weight and the water-cement ratio were 0.49 by weight.
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Flexural Behaviour of Self-curing Concrete
with Lightweight Aggregate and Polyethylene
Glycol

Flexural Behaviour of Self-curing Concrete with Lightweight Aggregate and Polyethylene Glycol

In this project, the mix design for control concrete grade of M30 had been designed. Self-curing concrete is useful in water scarce areas and in places where good quality water is not available. The self- curing concrete required had been arrived from the control concrete by optimizing the percentage of lightweight aggregate and polyethylene glycol. From the test results observed, the following conclusion had been drawn:

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Non-Linear Analysis Of Reinforced Concrete Continuous Deep Beams With Openings Strengthened Using CFRP Sheets

Non-Linear Analysis Of Reinforced Concrete Continuous Deep Beams With Openings Strengthened Using CFRP Sheets

There are four material properties used in this analysis for the elements. The first one was material number one (No.1) refer to the element SOLID65 (concrete element). The requirements of this element are linear isotropic, multi-linear isotropic and concrete parameters as shown in table.2. The second one was the material number two (No.2) refer to the element LINK180. The requirements to define this element are linear isotropic and bilinear isotropic as shown in table.3. The third one was material number three (No.3) refer to the element SOLID185 (steel plates), which defined only by linear isotropic as shown in table.4. The last one was the material number four (No.4) refer to the element SHELL41 (CFRP sheets). It was assumed orthotropic material, which has the same properties in all directions perpendicular to the CFRP fibers. Table.5 shows the material properties of the element SHELL41.
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Strut-and-Tie Modelling of R.C. Continuous Deep Beams

Strut-and-Tie Modelling of R.C. Continuous Deep Beams

Abstract: A strut-and-tie model (STM) is proposed for the shear carrying capacity of continuous RC deep beams. First, the mathematical formulation is given to fully describe the geometry, derivation of internal forces, evaluation of compressive and tensile stresses, and consideration of concrete tension softening. Second, validation studies for the modified STM are made for number of tested beams from the literature. Finally, a comparative study is presented between the results of proposed STM with the models of ECP code and the ACI code.
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Effects of square openings in reinforced concrete deep beams

Effects of square openings in reinforced concrete deep beams

It offers a good indication of the ultimate load-carrying capacity of the beam which is affected by the size and location at which the natural load path is interrupted by an opening (G[r]

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Strut-and-Tie Modeling of Reinforced Concrete Deep Beams

Strut-and-Tie Modeling of Reinforced Concrete Deep Beams

524 Figure 3-Effect of concrete effectiveness factor on shear strength prediction of RC deep beams with 525 shear reinforcement by STM 526 Figure 4-Effect of concrete effectiveness facto[r]

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Shear Behaviour of Reinforced Concrete Continues Deep Beams

Shear Behaviour of Reinforced Concrete Continues Deep Beams

The nonlinear finite element program; ANSYS 10 was used to predict the behavior of tested deep beams. A correlative study based on the load- deflection response as well as the cracking patterns was conducted to verify the analytical model with the obtained experimental results. In the finite element discretization of the tested beams, a 50x50 mm mesh of eight- node brick elements (Element 65) was used for concrete. The top & bottom flexural steel bars and the horizontal & vertical web reinforcement were represented by bar elements. The area and spacing of such bar elements were similar to the experimental specimens. The concentrated loads were also applied to the top surface at mid-span of the tested beams. The supports were represented by restrained nodes at the corresponding locations. To model concrete behavior, nonlinear stress-strain curves were used in compression and tension. Such models account for compression & tension softening, tension stiffening and shear transfer mechanisms in cracked concrete. An elasto-plastic model was used for steel in compression and tension. The initial Young’s modulus in concrete was taken as 22 GPa and the steel modulus was 200 GPa. An incremental-iterative technique was employed to solve the nonlinear equilibrium equations. The load increment was set at 5% of the experimental ultimate load. The load increment was subject to adjustment to obtain results at certain specific load levels. The maximum number of iterations was set to 20 in each load step and the equilibrium tolerance of 0.5% was chosen.
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Shear Behaviour of Reinforced Concrete Deep Beams

Shear Behaviour of Reinforced Concrete Deep Beams

Most codes of practice rely on empirical or semi-empirical equations for design; however, these equations are limited by the extent of the experimental results used for their calibration. Although designing RC deep beams based on these empirical approaches is generally very conservative, they can also lead to very unsafe results [18]. Collins et al. [2] examined the accuracy of the shear approaches available in codes of practice such as EC2 and ACI, against and extensive database of RC beams, it was found that shear strength prediction of vast number of the beams are unconservative. There are also unsafe results even after application of the safety factors [2]. Approaches based on finite element analysis can account for the nonlinearities that describe the behaviour of this type of members, and can lead to good results if an accurate concrete material model is used; however, their implementation is not always practical for design purposes. Thus, design approaches based on the implementation of strut-and-tie mechanistic models have been adopted by modern design codes such as EC2 [3], ACI 318-14 [4] and Model Code [12] since they appear more rational and relatively simple to apply.
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Securing the implementation of openings in deep concrete beams

Securing the implementation of openings in deep concrete beams

Through this history of research, we will find that the following most of the researches that have been presented have studied the effect of openings and their locations and dimensions on the behavior of deep concrete beams with web openings. As well as the effect of continuity spans and strengthen the openings internally and externally using fibers and many other ideas. Through the paper of. Ashraf Ragab Mohamed et al. [16] and Based on other research we have done [17] a currency and it shows the effect of increasing the local stiffness of tie on the behavior of deep concrete beams we tried to clarify steps to implement an openings in deep concrete beams already exists with no effect on the safety of the beam and structure.
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Reinforced concrete deep beams with web openings

Reinforced concrete deep beams with web openings

the Author to complete the thesis in Cambridge. The, research reported in this thesis was supported by the Science Research Council.. This thesis is concerned with[r]

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Bond Behaviour of Reinforcement in Self Compacting Concrete Containing Lightweight Aggregate as Coarse Aggregate

Bond Behaviour of Reinforcement in Self Compacting Concrete Containing Lightweight Aggregate as Coarse Aggregate

ABSTRACT: Lightweight concrete is a special type of concrete which weights lighter than the conventional concrete. Density of this concrete is low (300kg/m 3 to 1850 kg/m 3 ) compared to the normal concrete (2200kg/m3 to 2600kg/m3). Three types of lightweight concrete are lightweight aggregate concrete, aerated concrete, no- fines concrete. The lightweight aggregate self compacting concrete have so many advantages such as reduced dead loads, high insulation capacity, improved durability and resistance against fire and chemical attack. This paper presents the comparison of the bond properties of lightweight self compacting concrete (LWSCC) and normal weight self compacting concrete (NWSCC) with strength of 50 MPa.
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A study of shear behavior of reinforced concrete deep beams

A study of shear behavior of reinforced concrete deep beams

beams with concentrated loads within twice the member depth from the support that are loaded on one face and supported on the opposite face so that compression struts can develop between the loads and supports. The shear behavior of deep beam is considerable different from that of slender beams that exceed the limits noted above. The assumptions of plane sections in analysis of normal beams can no longer be used for deep beams. The behavior of deep beams is dominated by shear deformation, thus in design of deep beam one needs a design procedure based on mechanisms of failure of deep beams. In practice, one typically encounters deep beams when designing transfer girders in tall buildings, pile supported foundation, or bent caps in bridges. Prior to 1999, ACI Code 318 included a design equation for designing reinforced concrete deep beams, but since 2002, the strut and tie model and nonlinear analysis have been specified. The strut and tie model is a powerful tool for designing reinforced concrete structures, but it is a multiple-step, complex procedure. Using Strut-and-Tie models requires some structural design and analysis experience. For nonlinear analysis, one needs a computer and a nonlinear program. In addition, designers need some finite element method knowledge, basic theory for algorithm, and an understanding of the primary variables. It is the reason that many practical designers are not confident using either procedure.
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Numerical analysis of reinforced lightweight aggregate concrete hollow 
		core slabs

Numerical analysis of reinforced lightweight aggregate concrete hollow core slabs

In 2016, AL-Azzawi and Abed [9], carried out an experimental and a numerical investigations on the performance of reinforced concrete slabs having longitudinal hollow core with various volumes and with different loading conditions by varying the shear span to effective depth values. The experimental study included eight moderately thick reinforced concrete slabs. The dimensional of the slab models (2.05m) length, (0.6m) width and (0.25m) thickness. The results showed that the ultimate capacity decreased by about (21% and 33%) for solid slabs with increasing shear span to effective depth values from (2 to 3) respectively. The ultimate capacity of circular hollow cores reduced by about (5.49%, 15.7% and 20.6%) with using circular diameter (75, 100 and 150). When shear span to effective depth values increased from (2) to (2.5 and 3) respectively, the ultimate strength of hollow core slab decreased by (31% and 45%) respectively. Numerically the finite element method by using ANSYS computer program was used to study the behavior of these reinforced concrete slabs.
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Strength of lightweight aggregate foamed concrete 
		(LWAFC) exposed to elevated 
		temperatures

Strength of lightweight aggregate foamed concrete (LWAFC) exposed to elevated temperatures

Since concrete is a composition of different materials, the behaviour of concrete under elevated temperatures depends on its constituents. The aggregate type and structure of cement paste has a great effect on thermal conductivity of concrete. The highly porous microstructure of lightweight aggregate (LWA) gives it low density and better insulation and that makes the concrete made with LWA exhibit lower thermal conductivity than that of normal weight concrete (NWC). Therefore, Lightweight Aggregate Foamed Concrete (LWAFC) provides more effective fire protection than other types of concrete as it is less liable to spalling and has a higher thermal insulation [2].
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STRUCTURAL BEHAVIOR OF NO FINE CONCRETE AND LIGHTWEIGHT AGGREGATE CONCRETEREINFORCED WITH STEEL FIBERS.

STRUCTURAL BEHAVIOR OF NO FINE CONCRETE AND LIGHTWEIGHT AGGREGATE CONCRETEREINFORCED WITH STEEL FIBERS.

Due to low values of mechanical properties of lightweight concrete , lightweight concrete is rarely used in structural members in buildings or structures , the lowest value of compressive strength can be used for concrete is 17 MPa, thus this investigation deals with improving the mechanical properties of two types of lightweight concrete , the first type is lightweight aggregate concrete (LWAC), and the second is no-fines concrete (NFC).The results show that adding steel fibers lead to high increment in flexural and tensile strength in NFC, the flexural strength increased from low value of 1.78 to 6.5MPa(more than 3 times) , the compressive strength also increased but less than the increment in flexural strength . compressive strength increased from 13.6 to 26.1 MPa (doubled) for optimum percentage of steel fiber which was 2.5% and also the study show increment in all mechanical properties in LWAC concrete when adding steel fibers.
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A Study on Concrete Deep Beams Using Nonlinear Analysis

A Study on Concrete Deep Beams Using Nonlinear Analysis

In this project work, an attempt is made to predict the shear strength for concrete deep beams at ultimate state, using ANSYS12.1 software. Two test beams will be accounted to predict their shear strength at ultimate state using ANSYS 12.1 software. The accuracy of the predicted values of shear strength based on ANSYS 12.1 software for the two test beams will be compared with their corresponding experimental results. In addition, the predicted values of shear strength for the two test beams using ANSYS 12.1 software will be compared with the results obtained by shear strength prediction models proposed by various researchers. The prediction of shear strength using ANSYS 12.1is found to be reasonably in good agreement with the corresponding experimental results.
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