In this study an attempt is made to develop a method of analysis dealing with a multi-layer composite continuous beam , for linear material and shear connector behavior in which the slip (horizontal displacement) and uplift force (vertical displacement) are taken into consideration. The cross-sectional area for the beam consists of three layers varying in thickness and shear stiffness. The analysis is based on a approach presented by Roberts[1], basically for two layer simply supported beam, under uniform and point loads , which takes into consideration horizontal and vertical displacement in interfaces. The analysis led to a set of eight differential equations containing derivatives of the fourth and third order. A program based on the present analysis is built using finite difference method using boundary conditions. A comparison between the present analytical solution and previous studies shows close agreement. Continuous composite beams are very important element in construction of high rise buildings , multi-story frames and bridges, due to great advantages that can be obtained by using this sort of structural elements, such as reducing the beam moments, suitable reduction in deflections. The model deals with continuous beam consisting from three layers as a cross-sectional area with inter-layer slip. The cross-sectional area consist of composite material including intermediate layer from concrete and an upper and lower material with high strength in tension and compression ( i.e. steel plates or steel beams )
The presented work investigates the effect of addition admixtures (superplasticizer and polymer) to Chopped Worn-Out Tire concrete as a partial replacement of cement weight. Superpasticizer was addition by 4% and polymer (SBR) by 15%. The Chopped Worn-Out Tire (Ch.W.T.) addition to reference concrete with the three proportions as a Partial Replacement Ratio (PRR) of (25,25),(20,30),and (30,20) by volume of (sand and gravel) respectively. Three mixes were selected with above PRR for each type of admixture in additional to three mixes for Ch.W.T. concrete without admixtures and three reference mixes with admixtures without Ch.W.T. Thus, twelve mixes could be used in this investigation. Compressive strength and modulus of elasticity (static and dynamic) were tested. The test results indicated that the use of admixture led to significant improvement in concrete properties in general. Superplasticizer gave best results comparative with polymer, for example at 28 day the compressive strength of superplasticizer Ch.W.T. concrete Csp25,25 was 32.5 MPa, while compressive strength of polymer modified Ch.W.T. concrete CB25,25 was 28 MPa and compressive strength of Ch.W.T. concrete C25,25 was 21.2 MPa.
The main purpose of this search is to study the punching shear behavior of fourteen specimens of Reactive Powder Concrete (RPC) two-way flat plate slabs, half of these slabs have been exposed to a high temperature up to 400 C° by using an electric oven. All slabs have dimensions of (400x400x60) mm, with steel reinforcement mesh of (Ø6mm) diameter. Laboratory tests show that there is an increase in the value of First Crack Loading (FCL) and Ultimate Load (UL) by (208, and 216.67) % and a decrease in deflection by (56.85) % due using slab with complete reactive powder relative to a slap made of normal concrete. The use of the (RPC)mixture in layers in slabs gave results close to the slab which consists of full (RPC) this gives the benefit of more than the use of a slab that contains full reactive powder concrete in terms of cost, the increase was in FCL and UL by (130.8, 169.23, 102.7 and 135.135) % and a decrease in the value of deflection by (37.17, 47.64) %. The use of a partial reactive powder mixture also showed good results, and by increasing the dimensions of the RPC area, the results were better. the increase in FCL and UL by (54, 116, and 185) % and (53, 116.67, and 166.67) % and a decrease in value of deflection by (36.12, 42.4, and 50.26) % from reference slab. When slabs are subjected to high temperatures, there may be a decrease in the value of the FCL and UL and an increase in the value of deflection when compared to models not exposed to high temperature. But when compared to the reference slab with the same circumstance showed an increase in the value of the FCL and the rate ranged between (50- 200) % and the UL was the ratio ranged between (51.35-208.1) % and a decrease in the value of the deflection where the ratio ranged (21-46) %
New composite reinforced concrete beams, in which reinforced concrete component is connected to steel T-section, are proposed. The shear connection between the two components, the reinforced concrete and the T-section, is provided by the stirrups that are required for the reinforced concrete component to resist the applied shear. Experimental tests in addition to numerical analysis were conducted to determine the behaviour and strength of such beams under pure torsion. Full scale one conventional reinforced concrete beam, T1, and two composite reinforced concrete ones, T2 and T3, were tested. The degree of shear connection between the two components of beams T2 and T3 was changed by varying the number of stirrups which are used as shear connectors. The experimental results revealed approximately same torsional stiffness for the three beams at the uncracked concrete stage. The torsional strength of the composite reinforced concrete beams was greater than that of ordinary reinforced concrete one by 11% and 27% for beams T2 and T3, respectively. Three-dimensional finite element analysis was conducted using program ABAQUS. To model the shear connection in composite reinforced concrete beam, the stirrups were connected to the web of the steel T-section by springs at the location of the stirrups. Good agreement is obtained between the results of the experimental tests and the finite element analysis. The ratios of experimental results to those of finite element analysis for torsional strength are approximately one. Under the pure torsion loading the degree of shear connection is found to have no effect on torsional capacity of beams.
The Cooper-Harper rating of aircraft handling qualities has been adopted as a standard for measuring the performance of aircraft. In the present work, the tail plane design for satisfying longitudinal handling qualities has been investigated with different tail design for two flight conditions based on the Shomber and Gertsen method. Tail plane design is considered as the tail/wing area ratio. Parameters most affecting on the aircraft stability derivative is the tail/wing area ratio. The longitudinal handling qualities criteria were introduced in the mathematical contributions of stability derivative. This design technique has been applied to the Paris Jet; MS 760 Morane-Sualnier aircraft. The results show that when the tail/wing area ratio increases the aircraft stability derivative increases, the damping ratio and the natural frequency increases and the aircraft stability is improved. Three regions of flight conditions had been presented which are satisfactory, acceptable and unacceptable. The optimum tail/wing area ratio satisfying the longitudinal handling qualities and stability is (0.025KeywordsLongitudinal Handling---Stability---Tail Design
Progressive collapse is a partial or total failure of a building that mostly occurs when the build-ing loses primary structural elements (typically columns) due to accidental or natural hazards. The failure of structures due to an earthquake is one of the most important and frequent types of progressive collapse. In this study, the finite element method is used to assess the response of multistory reinforced concrete buildings subjected to column loss during an earthquake. Three-dimensional nonlinear dynamic analyses are carried out using SAP2000 V.20 program. The ef-fects of different parameters on the progressive collapse behavior are investigated, namely: the location of the removed column within the ground floor; the method of column removal (sudden, in two-steps, and in four-steps) and the removal timing during the earthquake. It is demonstrated that the collapse occurs when all or most of the hinges at the bases of the ground floor columns reach their collapse level. The chosen column removal timing and policy affect the structural behavior considerably. It is realized that, the risk of building collapse increases when the removal timing harmonizes with the peak ground acceleration timing. Based on the adopted earthquake characteristics and building configurations, it is found that, the two steps removal scenario is the most dangerous one.Keywords:Progressive collapse, Concrete buildings, Seismic load, Nonlinear dynamic analysis, Plastic hinge.© 2014
This work presents a compact reconfigurable antenna based on fractal geometry. The investigation discusses the challenges of lower antenna gain and bandwidth, critical for efficient data propagation in 5G systems, particularly for low-profile devices. Its goal is to develop a small, multiband antenna capable of operating in all current and future 5G bands and improve bandwidth and gain for mm-wave and sub-6 GHz applications. The proposed design covers the sub-6 band (2.8, 3.9, 4, 6.2) GHz and the mm-wave band (24.4, 27.1, 28.5, 29.3, 30.6, 33.9, 34.6, 35.2, 38.8, 44.4, 45.1, 59.7, 61.5, 62.3, 65.2, 67.4 and 69.5) GHz with S11 less than -10 dB. A maximum gain of 12.8 dB and a radiation efficiency of 94% are achieved. A partial ground plane with a 50 Ω feed line is used in this design. The antenna is printed on a Roger RT 5880 substrate with a relative dielectric constant 2.2 with a total dimension of 35×32.5×0.8 mm³. The proposed design is simulated using CST software, ensuring accurate calculations and performance evaluation.
Linearised dynamic analysis of beams subjected to lateral forces and composed of materials which have different moduli in tension and compression is presented. The position of the neutral surface was rendered independent of the spatial and temporal coordinates by introducing a special assumption which reduced the coupled nonlinear problem of the flexure of such a beam into a linear one. The actual position then became a function of section geometry and the two elastic moduli and was determined by the equivalent section method. The elemental dynamic stiffness matrix was derived using the exact displacement shape functions governed by the governing partial differential equation and the structural stiffness matrix was assembled according to the usual assembling methodology of structural analysis. Symbolic and numerical examples were solved to show the applicability and efficacy of the proposed method.
During the last years, several researches have been studying the final disposal of tyres wastes, due to the great volume generated worldwide, as well as the difficulty for discarding the disposal sites which become a serious environmental problem. In spite of this, recycling appears as the best solution for disposing tyres residues, due to its economical and ecological advantages. This research carried out to assess the feasibility of using crumb rubber (the product of shredding used rubber tyres) as a partial sand replacement in foamed concrete, and investigates the effect of it on some properties of foamed concrete such as, density, water absorption, compressive strength, tensile strength, flexural strength and impact resistance. Crumb rubber of tyres ranging from (0.7 to 5mm) in size was used in this research. Three proportioned mixes were designed in this research, have the same cement content, water-cement ratio, and foam content. The first mix represents a typical reference formulation of foamed concrete without crumb rubber (FC). In the others mixes (FCR-1 and FCR-2), respectively, 20 and 30% of volume of sand were replaced by crumb tyres rubber waste. Tests carried out to assess the behaviour of final product. The results obtained were demonstrated decreasing in foamed concrete strength (compressive, tensile, flexural, and impact) with the increasing of crumb tyres rubber content in the mixture and rubberized foamed concrete specimens (FCR-1 and FCR-2) show a cohesive behaviour than the specimens of reference mix (FC), especially in tensile strength. Comparing with the reference mix (FC), at an age of (28 days), the decreasing of compressive strength was (20.85%) for (FCR-1) and it for (FCR-2) was (37.76%).
The presented work investigates the effect of addition admixture (cement kiln dust) to concrete as a partial replacement of cement weight. Cement kiln dust was added by (10,30,50)% of cement weight.Four mixes were selected, three of them contain cement kiln dust (CKD) and one reference mix without any admixture for ages (7,28,90) days. Compressive strength ,flexural strength, ultra-sound velocity (UPV), slump, splitting tensile strength and static modulus of elasticity were tested.The test results indicated that the use of (CKD) led to significant decreasing in concrete strength in general and this decreasing increases with the increasing of (CKD), for example at 28 day the compressive strength of reference concrete (A) was 35 MPa, while the compressive strength of (B,C,D) contain (10,30,50)%CKD were (28,25,22) MPa respectively.