4.2. Preliminary test results and discussion
The average strength for the control cylinders tested in displacement control mode, was 25.2 MPa. Under flexural load, the central area of the beam located inside the plates is subjected to a confining pressure obtained by linear displacement due to the tensile efforts in the metallic reinforcement. The force compressive transmitted by the steel reinforcement to the metallic plates is thus distributed over all the width of the beam thus creating a compressive force which comes to be opposed to the opening cracks. For some tested beams, we obtain the value of strength of rupture13.50 KN for RCB beams and 15.97KN for CRCB beams. For others confined concretebeam we observe cracks and rupture by shear force without densification of bending cracks in the central zone of the beam element. As we realized a few number of beams, since at this stage of study and to better understand the behavior of these beams confined by induced compression, tests are planned and will be implemented to support the effect of shear and optimization of the length between the two half cylindrical plates.
Y. Bouamra 1 , K. Ait tahar 1
1 University Akli Mohand Oulhadj of Bouira, Laboratory LM2D, Algeria
This study focused on the four-point bending behavior of the concretebeam subjected to an innovative internal axial confinement process. An experimental study was carried out to validate the effectiveness of this technique. The four-point bending tests was carried out on confined concrete beams by this technique which makes it possible to produce an induced a compression stress induced by the normal component of the tensile effort developed in the resistance reinforcement at the level of the anchoring of steel bars. The results show the increasing of the ultimate bending strength compared to the control beam. Two opposing half- cylindrical plates are welded to the level of the curvatures of the steel bars. Each bar has a hook at one end only. The two hooks are arranged in the taut area of the beam and diametrically opposite. This technique allows us to mobilize the confining stresses from the beginning of loading of the beam, contrary to the existing methods, without using other materials as a composite FRP. Furthermore, a theoretical study was proposed to predict the equivalent load to be applied to the reference concretebeam when it is subjected to an ultimate bending moment determinate in the confined concretebeam. The experimental and theoretical results confrontation shows a good agreement.
Figure 1: Post-tensioned concretebeam of 8 meter length by means of 3 steel cables (in red) - Optic fiber (in blue) on a longitudinal armature
3.2. Strain measurement using optic fiber
In civil engineering structures, there is a growing interest in fiber optic sen- sors because they offer interesting benefits when compared with traditional sensors. Their main advantages are small size, electrically passive operation,
A second gradient model has been used to model the three point bending test of a rein- forced concretebeam. The results show that the model is able to reproduce the force- displacement curve obtained experimentally. The damage localizes into bands and their width is controlled by the model parameters. The uniqueness of the solution is however not restored as shown by the results obtained with two different meshes. In these two cases the bands are of the same size but their numbers can vary (figure 6). Being a local theory, the second gradi- ent method avoids the limitations caused by the use of a non-local definition of the equivalent strain used in the non-local damage theory.
The advances in experimental investigation enable better understanding of the damage and failure mechanisms of RC structures under extreme external loads (Mohammed 2014 ). The objective of this paper was to present the development of a simpliied non-linear inite element analysis approach (NLFEA) to simulate the structural behavior of corrosion- damaged RC elements. The input data for the NLFEA come from an inspection enhanced with some measurements and material testing, whereas the nonlinear inite element approach is based on the nonlinear sectional analysis devel- oped by the authors (Mohammed 2014 ). The inspection pro- vides input data about the location and size of the damaged zone and the level of damage, while material testing enables the evaluation of the instantaneous material properties at the time of the assessment. NLFEA can serve as the basis of the SQAF, where the aged/damaged bridge load capacity can be estimated. The focus of the study is on the structural behavior of aged bridge beam-column elements such as: (1) the columns are the most critical elements for the stability and robustness of bridge structures; and (2) beam-column elements are the most general frame elements that simu- late the behavior of beams, columns, or beam-columns, and hence they can be adopted in modeling buildings as well (e.g., parking garages).
Load Capacity and Fire Endurance
Fire endurance of a building component or assembly is the length of time it can fulfill its load-bearing function or its fire separating function or both when exposed to the standard fire, as previously discussed . ASTM E119 and ULC S101 define failure for loaded unrestrained reinforced concretebeam-slabs and slabs in terms of load carrying-capacity, steel reinforcement temperature, and unexposed surface temperature. The steel reinforcement temperature must be less than 593°C (1099°F). The average temperature of the unexposed face of the specimen must not increase more than 139°C (282°F) and at any individual point the increase in temperature shall be below 180°C (356°F). For loaded restrained reinforced concretebeam-slabs and slabs, the temperature criteria are not required to achieve a fire endurance rating according to ASTM E119. However, maintaining the steel and unexposed concrete temperature below the temperature stated in ASTM E119 would allow the specimen to retain most of its unstrengthened capacity.
On the basis of the reviewer’s comments the following actions were performed.
1. The solution with 19 mm Nelson stud connectors welded around the column was finalized to increase the level of friction between the concrete slab and the composite column. As a result, the load transfer based on the strut mechanism shown in Fig. b) below was enhanced. This statement was clearly reported in Subsection 2.2. Relevant FE-based stress distributions based on different friction coefficients are depicted below, where a friction coefficient of 1 corresponds to the presence of horizontal shear studs around the column. For brevity, this figure was not reported in the paper.
3.2. Fixed-beam linearly-polarized transmitarray with 3 bits of phase resolution
A 400-element transmitarray has been designed using the 3-bit unit-cells proposed in section 3.1.3. These unit-cells present a good impedance matching, low insertion loss, and quasi-linear phase response in the band of interest (27 GHz -31 GHz) for SatCom Uplink applications. The TA has been optimized at 29 GHz using the ad-hoc simulation tool validated in the CEA previous works -. This code uses a hybrid technique of simulation which includes full-wave simulations and analytical formulations. The array is illuminated by a standard horn with a 10-dBi gain. The optimal focal distance (F = 75 mm, which corresponds to a focal ratio of F/D = 0.75) and phase distribution have been calculated in order to maximize the aperture efficiency. The frequency response of the transmitarray (gain at broadside as a function of frequency) performed with the ad-hoc simulation tool (named theoretical simulation), and compared to that obtained using Ansys HFSS (named full-wave simulation) are shown in Figure III-17. The theoretical and full-wave radiation patterns (co-, and cross polarizations) in E-, and H-planes at 29 GHz are shown in Figure III-18 and Figure III-19, respectively. The broadside gain at the frequency of optimization (29 GHz) is 27.4 dBi with an aperture efficiency of 47%. The 1-dB gain bandwidth is between 28.5 GHz and 31.8 GHz, which corresponds to a relative bandwidth of 11.4% at 29 GHz. The performance of the proposed TA is summarized in Table III-2. A good agreement is obtained between the theoretical and simulated results.
The range of z over which the inverse error function of sion is finite in Eq. (3) tells the maximum distance the drive beam can propagate. This theoretical limit is plotted in Fig. 4 by taking the reduction of the mean energy and the emittance growth predicted by Highland into account. The beam parameters in the Sec. II A are used except that the initial normalized emittance ϵ N0 is varied for both drive and trailing beams, and thus the beam radii σr are changed according to the matched beam radius for the plasma density n 0 ¼ 4.5 × 10 16 cm −3 . In the same figure, the ionization distances simulated for different target thickness Δz ¼ 0.5, 1 and 2 mm are shown. The results are shown
Polyester PC has good mechanical strength, relatively good adhesion to other materials, and good chemical and freeze-thaw resistance. It has, however large setting and post-setting shrinkage (up to ten times greater than Portland cement concrete), a serious disadvantage in certain applications. Polyester PC is used in various precast and cast-in place applications in construction works, public and commercial buildings, floor tiles, sewer pipes and stairs.
In this paper we present a novel multi- fiber beam finite element formulation based on the Timoshenko model to simulate failure of reinforced concrete structural elements sub- jected to static monotonic loadings. The new displacement-based Finite Element formulation proposed by [ 8 ] is used. This formulation uses shape functions of order three (3) for the trans- verse displacements, and two (2) for the rota- tions and an additional internal node. This re- sults to a finite element free of shear locking. We refer to [ 9 ] where we show the performance of this formulation with respect to other formu- lations in the literature [ 10 ], [ 11 ].
Even if the upper surface is protected with a waterproofing layer, it is often necessary to repair the under face for aesthetic or structural reasons. Dry-mixture shotcrete and patch repairs are two classical methods that can be used for repairing these concrete elements. The first method can give high values of adhesion and limit shrinkage by using an adapted W/C ratio and admixtures: the main disadvantage of shotcrete in this case is dust and rebound, which are unacceptable for areas like housing and buildings. Patch repairing is very time- and labour- consuming. A comparison of costs  shows that Self-Compacting Concrete (SCC) can be an interesting option if it is possible to fix and reuse a mould under the structure .