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This paper investigates the effect of using near-surface mounted carbon fiber-reinforced polymer (NSM-CFRP) on the shear strengthening of rectangle beams with low strength concrete (f′c = 17 MPa), medium strength concrete (f′c = 32 MPa), and high strength concrete (f′c = 47 MPa). The experimental program was performed by installing NSM-CFRP strips vertically in three different configurations: aligned with the internal stirrups, one vertical NSM-CFRP strip between every two internal stirrups, and two vertical NSM-CFRP strips between every two internal stirrups. All tested beams were simply supported beams and tested under a three-point loading test. The experimental results were compared with the theoretical capacities that were calculated according to the ACI 440.2R-17 and finite element analysis (FEA) that was conducted using ABAQUS software to simulate the behavior of all beams. The experimental results indicated that using NSM-CFRP limited the failure mode of all beams to pure shear failure with no debonding or rapture of the carbon strips. Moreover, the use of NSM-CFRP proved its efficiency by increasing the shear capacity of all beams by a range of 4% to 66%, in which the best enhancement was recorded for the case of using two unaligned NSM-CFRP strips. In general, the experimental shear capacities increased with the increase in the compressive strength of all beams. On the other hand, the ACI 440.2R-17 was conservative in predicting the theoretical shear capacities, and the FEA results agreed well with the experimental results.

The axial compressive behavior of fifteen reinforced concrete columns that were constructed from four types of aggregates: Natural Aggregate (NA), Recycled Asphalt Pavement (RAP), Recycled Coarse Aggregate (RCA), and RAP-RCA were studied experimentally and theoretically. The NA was replaced by RAP and RCA at five replacement levels: 20%, 40%, 60%, 80% and 100% by the total weight of NA. In addition of combining RAP and RCA in the same mixes with replacement levels of: 20% RAP-80% RCA; 40% RAP-60% RCA; 60% RAP-40% RCA; and 80% RAP-20% RCA. The axial compressive behavior of the columns was studied through reporting the ultimate load values and the crack propagation during static tests. The experimental axial capacity of the columns was compared with the theoretical values determined by ACI and Japanese codes. The experimental results showed that there was a reduction in the axial capacity of columns when the RAP, RCA, and RAP-RCA contents increased. However the calculated theoretical values were more conservative comparing to the experimental values. This provides a very positive indication that the RAP, RCA, and RAP-RCA columns can be used in the structures safely and the RAP-RCA combination is a promising technique.

Replacing traditional closed stirrups by rectangular spiral reinforcements in concrete beams constructed using self compacting concrete (SCC) is experimentally investigated in this paper by testing twenty beams under static loading. The shear performance of SCC beams is evaluated by measuring the maximum shear load values, load-deflection curves, and crack propagation for all tested beams. Two different spirals spacing of 200 and 150 mm and five different angles of inclination for the spiral reinforcement (85°, 80°, 77.2°, 75°, and 72.5°) are adopted. The experimental shear capacity results are compared with theoretical shear strength determined by the (ACI 318) code. The results indicated that using of continuous spiral reinforcement improves the shear capacity of SCC beams up to 16.67% increase in comparison to traditional closed stirrups. Moreover, the results showed that optimum performance depends on the angles of inclination, where 85° was the optimum angle of inclination regardless of pitch spacing. It is recommended to use the continuous spiral reinforcements in SCC beams because it enhances the shear capacity, and reduces time and labor cost needed in construction.

This paper presents the results of a study that investigated the improvement of the mechanical properties of recycled concrete aggregate (RCA) produced by adding chopped basalt fibers (BF) with contents of 0.1%, 0.3%, 0.5%, 1%, and 1.5% by total volume of the mix to treated and untreated recycled aggregates. The recycled aggregates were surface treated by pre-soaking them in a 0.1 M hydrochloric acid (HCl) solution for 24 h to remove the adhered mortars to improve the bond between the recycled aggregate and the cement. In addition, chopped BF was added to normal concrete (NA) mixes as a control for comparison. The results showed that using chopped BF minimally enhanced the compressive strength of the concrete mix but significantly improved its flexural and splitting tensile strength. Furthermore, the optimum BF content that produced the same splitting tensile and compressive strength as NA was 0.5% for untreated RCA and 0.3% for treated RCA, while the flexural strength was 0.3% for untreated RCA and 0.1% for treated RCA.

This paper presents the results of a study that investigated the improvement of the mechanical properties of coarse and fine recycled asphalt pavement (RAP) produced by adding silica fume (SF) with contents of 5%, 10%, and 15% by total weight of the cement. The coarse and fine natural aggregate (NA) were replaced by RAP with replacement ratio of 20%, 40% and 60% by the total weight of NA. In addition, SF was added to NA concrete mixes as a control for comparison. Twenty eight mixes were produced and tested for compressive, splitting tensile and flexural strength at the age of 28 days. The results show that the mechanical properties decrease with as the content of RAP increases. And the decrease in the compressive strength was more in the fine RAP mixes compared to the coarse RAP mixes, while the decrease in the splitting tensile and flexural strength was almost the same in both mixes. Furthermore, using SF enhances the mechanical properties of RAP mixes where the optimum content of SF was found to be 10%, and the mechanical properties enhancement of coarse RAP were better than fine RAP mixes. Accordingly, the RAP has the potential to be used in the concrete pavements or in other low strength construction applications in order to reduce the negative impact of RAP on the environment and human health.

This paper investigates experimentally and theoretically the shear behavior of thirteen reinforced concrete (RC) beams made of Recycled Asphalt Pavement (RAP) and Recycled Coarse Aggregate (RCA). The span length of the beams was 2240 mm, and the width and depth of the beams were 200 and 400 mm, respectively. Three groups of beams were used in this study: The first group was five beams made of RAP and natural aggregate (NA), where the NA was substituted by RAP with replacement levels of 20%, 40%, 60%, 80%, and 100% by the total weight of NA. The second group was four beams made entirely of RAP and RCA. The third group was four RC beams made of RCA and NA, where NA was replaced by RCA with replacement levels of 20%, 40%, 60%, and 80%. The beams were tested under four-point loading setup. The maximum shear forces, deflections, and cracking patterns were studied. The experimental results were compared with theoretical results determined from the equations of selected international codes and fracture mechanics approaches available in the literature. The results showed that the experimental shear capacity increased as the RAP and RCA replacement levels decreased for the beams in group one and three, and decreased for group two beams when the RCA replacement levels increased. The theoretical shear strength capacities were more conservative when compared to the experimental results. Therefore, the theoretical shear equations can be applicable to the beams constructed with recycled aggregates. In general, using RAP and RCA in RC beams can be considered as an effective approach.

The effect of fire on reinforced concrete (RC) structures is very important because it is threatening the human life and property safety. Using Recycled Asphalt Pavement (RAP) and Recycled Coarse Aggregate (RCA) in concrete mixtures can be considered economically and environmentally friendly because it saves our natural resources. This paper investigates experimentally the influence of incorporating RAP and RCA on the mechanical properties of concrete mixes after exposure to different temperatures: 20 °C, 200 °C, 400 °C, and 500 °C. The Natural Coarse Aggregate (NCA) was replaced by RAP aggregates at three replacement ratios (10%, 20% and 30%), and the NCA was replaced by RCA at four replacement ratios (20%, 40%, 60%, and 100%). As well as using three mixes of 90%RCA-10%RAP, 80%RCA-20%RAP, and 70%RCA-30%RAP. Compressive, splitting tensile and flexural strengths, compressive stress-strain curves, and modulus of elasticity were studied on two hundred sixty four cylinders and one hundred thirty two prisms. The results showed that the mechanical properties decreased as the replacement ratios of RAP and RCA increased for the same temperature. And the mechanical properties decreased for the same replacement ratio of recycled aggregates when the temperature increased. The decrease in mechanical properties at elevated temperatures for RAP-RCA mixes can be comparable with NCA, RAP and RCA only mixes. Therefore, the RAP and RCA have the potential to be incorporated in the concrete mixes on high temperatures since the decrease in the mechanical properties is not that significant relative to the efforts in reduction the negative impacts of recycled aggregates on the environment and human health.

The shear behavior of ten full scale reinforced concrete beams that were constructed from natural aggregate, recycled aggregate and treated recycled aggregate was experimentally and analytically studied. All beams were constructed without stirrups and with 50% and 100% recycled aggregate. The beams were tested for a shear span-to-depth ratio (a/d) equal to 2.0 and 3.0. The performance of recycled aggregate was improved through enhancement treatment methods. The recycled aggregate was pre-soaked in hydrochloric acid (HCl) for 24 h to remove adhered mortars attached to original recycled aggregates, and then they were impregnated with sodium metasilicate pentahydrate solution for one hour to coat their surfaces. The behavior of the shear-critical beams was studied through reporting the load-deflection curves, ultimate load values, and crack propagation during static tests. The experimental shear capacities of the beams were compared with theoretical values from different international codes and fracture mechanics approaches. The experimental results showed that in general using treated recycled aggregate improved slightly the shear capacity of the beams in comparison with natural and untreated recycled aggregate. Furthermore, the shear strength comparisons showed that the treated recycled aggregate beams were considered more conservative compared to the natural and untreated recycled aggregate beams regardless of the shear span-to-depth ratio.

The use of continuous rectangular spiral shear reinforcement as transverse reinforcement is experimentally investigated by testing 28 reinforced concrete beams in a static four-point bending setup. In this paper two shear span-to-depth ratios (2.5 and 3.0), three spacing (125, 150 and 200 mm) and five inclination angle of stirrups (62, 70, 75, 80 and 85°) are adopted. The behavior of the shear-critical beams is studied through monitoring the load–deflection curves, ultimate load values, vertical deflections measurements and crack propagation during static tests. The experimental shear capacity of the beams are compared with analytical values from the design shear formulas of ACI 318M-14 code. Test results clearly indicate that using rectangular spiral shear reinforcement improved the shear capacity and ductility of beams compared with traditional individual closed stirrup beams. Furthermore the results showed that the optimum inclination angle for spiral stirrups is 80°. Accordingly, using rectangular spiral shear reinforcement is recommended because it improves the shear capacity and ductility in beams and can reduce the total cost due to labor costs.

The standard design procedure for tube and fitting connections assumes that the connections are only subjected to non-cyclical loads. This paper presents the results of experimental tests and theoretical calculations of the moment-rotation capacities of three common connections – sleeve couplers, swivel couplers and right-angled couplers. The results show that under a cyclic side load, such as that occurring by wind loading, looseness affects the capacity of the connections. For all three types of coupler looseness is shown to be relatively high which will reduce the stiffness of the connection under side loads. For sleeve couplers the effects of axial load in the tubes also affects the coupler stiffness and the maximum bending capacity of the joint. This implies that the common European code BS EN 74–1 for the connection should be changed to consider the loss in stiffness and maximum side load capacity under axial loads and looseness which are ignored in the standard. The standard assumption for right-angled and swivel couplers is that the connection can be assumed to be rigid about an axis normal to the plane containing the two tubes being joined. This is shown to be incorrect as the connections are shown to have stiffnesses about this axis which is of a similar order to the stiffnesses about the other axes.

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A novcl system identification and structural hcalth assessment proccdurc of steel finn~ed structures with semi-rigid connectiol~s is prescntecl in tliis paper. It is capable of ilctecting damages at the local elc~ncr~t level under nonnal operating conditions; i.e., serviceability limit state. The procedure is a linear time-domain system identification tecllnique in which the structure responses arc required, whereas the dynamic excitation force is not recluircd to identifjl thc strtlctural parameters. The procedure hacks changcs in the stiffiiess properties of all the elements in a stnlcture. It can identify damage-frec ancl (lamaged stnictural elemenls vely accurately whcn excited by different types of' dy~ramie loadings. 'l'he method is elaborated witli the llclp of' several numerical examples. Tlle results indicate that the proposed i~lgoritll~n identified tlle structures correctly and detected the prc-imposed danlages in the frames when excited hy earthquake, impact, and harmonic loadings. '1:Ile algorithm can potentially be used for structural llealtli asse,ss~rie~~t and monitoring of existing shxctures witli lninimum clisnlption of operations. Since the procedure requires only a few time points of response infotmation, it is cxpccted to be economic and efficient.

A new technique was proposed for the large deflection problem of a prismatic composite cantilever beam made of two different nonlinear elastic materials and subjected to an inclined tip concentrated force. Two types of composite cantilever beams were considered in this study: A solid rectangular and a hollow circular cross-section beam. The proposed technique assumes that the behavior of a composite cantilever beam is equivalent to the behavior of two homogeneous cantilever beams. A semi-analytical solution describing the complete behavior of each homogeneous beam was derived and the complete deflection curve of the composite cantilever beam was obtained by considering the weighted average deflection curves of the two homogeneous cantilevers with respect to the tip forces. Several numerical examples were presented at the end of the study. Results obtained using the proposed technique were compared with results obtained using the software ADINA and found to be in good agreement.