قاسم محمد شاكر العباسي

In the present work, a new model of hybrid deep beams has been presented. The proposed model is based on the curved distribution of concrete types along the beam rather than the conventional hybrid model. Then, the highly cost (steel fiber concrete) is used within the regions of high concentration of stresses only, resulting in minimizing the total cost of the beam. Six specimens of deep beams have been tested under static loads applied in two arrangement, one and two point loads. The behavior has been tracked in terms of the cracking and failure loads, the rate of crack propagation; horizontally and vertically, the loading history, crack width, toughness, stiffness and ductility. Results revealed that for the conventional hybrid model, capacity improved by 23% and 27% for the two loading systems respectively. The respective values for the proposed arched hybrid model are 23% and 32%. Moreover, Toughness enhanced by 44.7% and 143.7% for the conventional hybrid model. Whereas the improvements for the arched hybrid model, the respective values are 65.5% and 144.3% relative to the control beams, referring to relatively highly ductile behavior with using two-point load system and the arched hybrid model. Furthermore, ductility enhanced by 11.5% and 32.5% for the horizontal hybridization, against 12% and 37.4% for the arched model of hybridization.

In the present study, a new model of hybrid deep beams has been proposed and discussed. Six specimens are tested experimentally with two types of loading which are one-point and two-point loading and two hybridization models for concrete section. It is aimed from this study to search for the optimum distribution of the concrete types of the hybrid deep beams such that the lowest cost and weight to be reached with keeping the capacity without significant reduction. All specimens had the same dimensions, overall span of 1700 mm, 180 mm wide and 450 mm overall depth and the same steel reinforcement details. Results showed an increase in the capacity in the horizontal and the arched hybrid model by 27.6% and 39%, respectively, with one-point system. Moreover, toughness, enhanced by 44% and 131% for the two models respectively whereas, stiffness enhanced by 6.5% and 34.2% respectively and ductility enhanced by 0% and 31.2% respectively. For tests under two point loads, capacity enhanced by 34% and 36.9%, respectively, Toughness increased by 188% and 301% respectively. Stiffness enhanced by 7.5% and 29.4% respectively. Ductility enhanced by 40.3% and 95.1% respectively.

In recent years, deep beam performance improvement has garnered significant interest, leading to several proposed solutions. This study introduces and compares two new models of hybrid concrete deep beams, aiming to outperform conventional designs. Nine experimental specimens were subjected to one-point and two-point static loadings. The specimens shared identical dimensions, with an overall span of 1700 mm, width of 180 mm, and overall depth of 450 mm. Response parameters such as cracking and failure loads, failure modes, crack propagation rates, toughness, stiffness, and ductility were evaluated. Results indicated substantial enhancements compared to the conventional hybrid model. The curved model achieved a 5 % and 12 % increase in failure load under one-point and two-point loading, respectively. The corresponding enhancements for the arched model were 13 % and 20 %. Notably, toughness improvements ranged from 32 to 39 % and 97 % under two-point loading for the curved and arched models, respectively. Ductility gains were 39 % and 45 % under two-point loading and (45–57)% and 74 % under one-point loading for the respective models. The findings highlight the potential of the curved model with reactive powder concrete-normal strength concrete (RN) composition, offering increased load-carrying capacity and the possibility of using low-strength concrete for cost and weight reduction. The arched model also demonstrated significant enhancements. Changing the loading configuration from two-point to one-point resulted in reduced capacity, but the proposed models mitigated this reduction. This study contributes valuable insights into the behaviour of precast hybrid concrete deep beams, showcasing the superior performance of the proposed curved and arched models.

In the present study, a new model of hybrid deep beams has been proposed and discussed. Six specimens are tested experimentally with two types of loading which are one-point and two-point loading and two hybridization models for concrete section. It is aimed from this study to search for the optimum distribution of the concrete types of the hybrid deep beams such that the lowest cost and weight to be reached with keeping the capacity without significant reduction. All specimens had the same dimensions, overall span of 1700 mm, 180 mm wide and 450 mm overall depth and the same steel reinforcement details. Results showed an increase in the capacity in the horizontal and the arched hybrid model by 27.6% and 39%, respectively, with one-point system. Moreover, toughness, enhanced by 44% and 131% for the two models respectively whereas, stiffness enhanced by 6.5% and 34.2% respectively and ductility enhanced by 0% and 31.2% respectively. For tests under two point loads, capacity enhanced by 34% and 36.9%, respectively, Toughness increased by 188% and 301% respectively. Stiffness enhanced by 7.5% and 29.4% respectively. Ductility enhanced by 40.3% and 95.1% respectively.

The present work presents the results of the experimental investigation of using crushed concrete as recycled coarse aggregates (RCA) and new models of hybrid deep beams. Six specimens of deep beams have been tested under static loads: two specimens as controls and three hybrid specimens with different types of hybridization models for concrete sections (horizontal, curved, and arched). This study aims to search for the optimum distribution of the concrete types for the hybrid deep beams such that the lowest cost is obtained and the RCA obtained from building demolition waste is introduced into the concrete mixes at 100%. The behavior has been tracked by the cracking and failure loads, loading history, crack width, and toughness. It was found that the capacities increased by 7.7, 18.7, 17.2, and 28.2%, respectively, in the horizontal, curved, arched, and arched with inclined stirrups hybrid models compared to the control specimen with RCA. Moreover, toughness was enhanced for the same specimens by 50.9, 71.1, 100.5, and 144.6%, respectively, compared to the control specimen with RCA.

In this study, a comparison has been done between the efficiency of repairing of partially damaged high strength self-compacting RC corbels using two techniques, namely are NSM steel bars and CFRP sheets. The experimental program consists of testing eleven specimens, one of which acted as a control corbel (without repairing) and the other ten are upgraded using several configurations of alignment with two damage levels (45% and 65%). The response has been discussed in terms of the first cracking load, ultimate load, maximum deflection, failure mode, loading history, crack pattern, toughness value, and ductility index. Results revealed that the NSM steel bars technique could be adopted as an adequate method within the early levels of damage whereas the EB CFRP sheet is more suitable for largely damaged corbels. Moreover, results revealed that NSM technique with the inclined, horizontal, and combined alignment yielded enhancements in ultimate load capacity of 98.6%, 55.1% and 74.2%, respectively for a damage level of 45% and 24%, 50% and 19% for damage level of 65%, respectively. Whereas, the corresponding improvement using the CFRP sheet with damage level of 45% are 52% and 50% for specimens repaired using horizontal and diagonal CFRP sheet, respectively. The respective values are 71%, 38% for damage level of 65%.

The present study aims to compare between efficiency of two strengthening techniques, namely CFRP sheets and near surface-mounted (NSM) steel bars in upgrading the high strength self-compacting reinforced concrete corbels. The experimental program consists of six specimens, one of which acts as a reference corbel (without strengthening) and the other five are upgraded using the two methods with three configurations of alignment. To identify the optimum strengthening proposal, the results have been expressed in terms of the cracking load, failure load, deflection at failure, mode of failure, history of loading, crack pattern, toughness, and ductility value. Results revealed that the NSM steel bars technique could be adopted as an adequate and promising method if compared with the external bounded (EB) CFRP technique. The enhancement in ultimate load capacity, relative to the non-strengthened specimen, are given by 95.1% and 91.6% for NSM technique with the inclined and horizontal alignment, respectively. Whereas the corresponding improvement using the CFRP sheet are 46.3% and 44.6%, respectively.

In the present study, a comparison has been conducted to investigate the efficiency of using the nearsurface mounted steel bars technique for strengthening and repairing the damaged reinforced concrete corbels. Three configurations for installing the steel bars have been considered; horizontal, diagonal, and combined. Results revealed that is better to use this technique within the early stages of loading. Moreover, results proved that the strengthening by the diagonal scheme yielded a better response in terms of cracking and failure loads with values of 166 and 95% relative to the control specimen. Also, it is found that for damage of 45%, the horizontal arrangement yielded the highest failure load of 99% whereas for damage of 65%, the diagonal system yielded the optimum value of 50% relative to the control specimen.

An experimental study has been conducted to explore the response of reinforced self-compacting concrete dapped ends retrofitted with NSM steel bars. Eleven specimens are tested with two shear slenderness ratio values (a/d), namely (1.0 and 1.5). Deficiencies in reinforcement in the nib and hanger zone are considered. The response is studied in terms of loading history, cracking and failure load, failure mode, cracking pattern, toughness, stiffness, and ductility. It is observed that retrofitting the nib region with horizontal bars improved the capacity by 29% and 20% for the two shears span/depth (a/d) values, respectively. The maximum enhancement in the capacity for upgraded hanger regions with a/d= 1 is about 21%. Regarding toughness, this research indicated that for reduced nib steel specimens with a/d=1.0 and 1.5, a reduction by 17% and 27%, respectively, were obtained. Whereas reducing the hanger steel by 30% led to a drop by 29%. Strengthening of deficient nib reinforced specimens with a/d =1.0 and 1.5 led to an improvement in toughness by 43% and 62%, respectively. For specimens with deficient hanger steel (a/d=1.0), the strengthening led to toughness enhancement by 87%. Strengthening of deficiently reinforced nib end with the two a/d values resulted in improving stiffness by 18% and 24%, whereas when strengthening the hanger zone, an enhancement of 9% is obtained. For ductility, it is concluded that the prediction of ductility ratio using the displacement ratio method is more efficient than the toughness ratio method because it is considered the premature failure cases. Also, it is obtained that increasing the a/d value resulted in reducing the ductility ratio.

In the present work, a new modified arrangement for shear reinforcement in corbels is proposed. Inclined, rather than horizontal, alignment of stirrups was studied. In addition, the performance of composite corbels incorporated with the usual and proposed alignments of the shear reinforcement were investigated. The experimental work consisted of testing 12 specimens. Four corbels are non-composite and eight are composite with two shapes of rolled steel, namely, WF and tapered WT sections. Two values of shear span to depth ratio (av/d) have been considered, which are 0.70 and 1.0, to study both when shear is dominant and when bending moment is dominant. The behavior of the tested specimens was discussed in terms of the history of loading, first cracking load, failure load, ductility, toughness, and history of the first crack development. It was found that the proposed configuration of shear reinforcement improved the ductility and toughness with respect to the conventional arrangement by 16% and 38%, respectively, for av/d value of 0.70, and 55% and 64%, respectively, for an av/d value of 1.0. Furthermore, the results revealed that using the composite corbel with the proposed alignment rather than RC corbel improved the ductility and toughness by 35%–80% and 45%–173%, respectively, for av/d = 0.70. The values for corbels with av/d = 1.0 are 38%–101% and 67%–88%, respectively. Moreover, tests revealed that the composite WF-steel corbel with diagonally aligned stirrups showed relative performance indicators (with respect to the conventional corbel) for av/d = 0.7 of 82%, 98%, 105%, and 273% for the first cracking load, failure load, ductility, and toughness, respectively. The respective values for av/d = 1.0 were 111%, 115%, 138%, and 188%, respectively.

In this work, a new proposal of composite corbels has been suggested based on incorporating a stiffened rolled steel in the RC corbel. The enhancement in response have been investigated in terms of tracking the map of crack propagation at failure, history of loading, cracking and failure load, failure mode, ductility index, toughness value, and rate of crack widening. Ten specimens have been tested experimentally with two values of shear span/ depth (a/d) ratio; 0.70 and 1.0. Two RC corbels are considered as control specimens and eight encased corbels with tapered WT- or WF- rolled steel sections, without or with stiffeners. Moreover, a theoretical proposal has been suggested to estimate shear capacity of the composite encased corbels. It is found that for a/d = 0.7, composite corbels with the stiffened elements yielded same cracking load as for RC corbel. For a/d = 1.0, stiffened composite corbels yielded relative increments of (11%–33%). Moreover, it is obtained that for a/d = 0.7, specimens with stiffened rolled steel yielded a relative capacity of (95–105)% to the RC corbel while for a/d = 1.0 the failure load ranged in (93–104)%. Significant enhancements in ductility have been noticed. For a/d = 0.7, the relative values ranged in (85%- 150%) with highest value with stiffened tapered WT-steel. For a/d = 1.0, specimen with non-stiffened rolled steel yielded relative ductility index of 152%. Regarding toughness, Relative values are (203%- 278%) have been obtained for a/d = 0.70, with highest value for that with stiffened tapered WT-steel. For a/d = 1.0, Relative values of (123%-154%) are obtained with highest value for that with non– stiffened WF-steel.

The present study aims to compare betweenIn precast grid systems, it is necessary to support the cross beams by the main girders using suitable methods. One of these proposals is by making voids or notches within the webs of the girder to include the supports of the cross beams. In this paper, an experimental study has been done on 10 reinforced concrete self-consolidating beams with loaded openings. The tested specimens have been categorized into two groups based on one inclusion of dapped ends. Each group consists of five specimens; one served as a control in which the opening is reinforced conventionally with two vertical stirrups at both sides. For the other specimens, the openings are reinforced with different schemes, namely using steel-fiber concrete, diagonal bars, jacketing by steel plates, and a composite section for the bottom chord. The behavior has been discussed in terms of history of crack propagation, loading history, ductility, and toughness. It was concluded that inclusion of the dapped ends reduced the capacity in range of 9%–12%. Moreover, results revealed that the composite section proposal yielded the highest enhancements of 21% and 23% for the two groups, respectively. Regarding ductility, maximum enhancements of 44% and 9% were noticed. For the toughness, the proposal of a composite section yielded the highest improvements by 91% and 19%, respectively

This study aims to investigate experimentally the behavior of self-compacting reinforced concrete beams with in-plane loaded openings strengthened with different techniques in the opening zone. The experimental program consists of testing five specimens with a rectangular opening at the midspan, one of the beams serves as a control beam (without strengthening), and four beams are strengthened at the opening zone with several methods including steel fibers, semi- rhombus crossed bars, jacketing with steel plates, and utilizing the composite section technique. The response has been discussed in terms of the first cracking load, ultimate load, maximum deflection, failure modes, loading history, crack patterns, toughness value, ductility index, and crack width to recognize the best strengthening proposal opening. Test results indicate that the technique of strengthening the WT-rolled steel recorded an increase in the ultimate load capacity, toughness, and ductility of about 21%, 91%, 44 %, respectively, relative to the control beam. However, the beam strengthened by steel fiber reinforced concrete around the opening yielded an increase in the cracking and the loadcarrying capacity of about 33.3%, 10.95%, respectively. Concerning the specimen strengthened by the crossed steel bar making a semi- rhombus shape around the opening yields a slight enhancement in the loading capacity of about 8.5%. Furthermore, strengthening the opening with steel plates increases the beam's load-carrying capacity by about 11.23% compared to the control beam.

An experimental study has been conducted to explore the response of self-compacting RC drop in- beams retrofitted with NSM steel bars under short-term static loading. Eleven specimens have been tested in this program, each of (200x400x1600 mm) dimensions with two values of (a/d), namely (1.0 and 1.5). Two of these beams have been considered as reference beams (efficiently reinforced). Three beams with reduced reinforcement, two with deficient main nib steel, while the third with reduced steel in hanger. The rest have been upgraded with different arrangements to retire the expected drop in strength. It was found that reduction of nib reinforcements to the half, results in decreasing load failure of about (11% & 5%) for (a/d) values of (1 and 1.5) respectively. Also, it is observed that retrofitting the nib region with horizontal NSM steel bars led to increase the failure load capacity by about (28.7%) for (a/d) =1. While, the enhancement in strength for specimen with (a/d) =1.5 was about (24%). The increase in the strength capacity for upgraded hanger regions vertical and inclined bars for a/d (1) was about (21.4% and 14.2%) respectively.

This paper represents a historical review of the theoretical and experimental studies carried out previously to study the behavior of reinforced concrete dapped end beams. Prestressing is one of the techniques that have been adopted to enhance the performance of such members. Furthermore, a dapped end needs to be strengthened due to various reasons to improve its performance. Consequently, the review has been extended to include studied such aspects. It was concluded that the ultimate capacity enhanced by reducing the shear-slenderness ratio and horizontal tension reaction and increasing the strength of concrete and fiber content. In addition, nib main reinforcement affects significantly the mode of failure, cracking and ultimate load. However, it was observed that the inclined hanger stirrups or bent performed better than that of vertical alignment and that the prestressing level and strand profile affect the shear capacity and performance significantly. On the other hand, it was found that the external bonding CFRP is the most adopted strengthening material and that the STM (Strut-and-Tie Model) approach results in better predictions of the ultimate load than the shear-friction method. Moreover, directions for future work are proposed, several conclusions have been drawn and a comprehensive list of references is provided.

In this work, an experimental study has been An experimental study has been conducted to scrutinize the response of reinforced self-compacting concrete half joints upgraded with CFRP strips. Fourteen RC half joints have been tested. Two values of shear slenderness ratio were considered, namely 1.5 and 1.0. Two beams have been treated as reference specimens (with the design steel), and the twelve other beams were casted with deficiency in steel of the hanger and the extended end regions relative to the control beams. Eight of these beams have been strengthened with different arrangements to discuss the influence of shear slenderness ratio and strengthening arrangement on the overall performance of such joint elements. It is found that the reduction in nib-main steel by about 50% results in decreasing load capacity by about 36% and 15% for shear slenderness ratio of 1.5 and 1.0 respectively. Also, it is found that the orthogonal arrangement combined with inclined strips yielded the best results in terms of preventing the diagonal shear failure at the re-entrant corner with maximum enhancement in load capacity by 18%. In addition, the maximum improvement in failure load when strengthening hanger region by such alignment was about 23%. Results also revealed that the effective stiffness and ductility ratio enhanced with reducing shear span of a half joint and may be adopted as a good indicator to evaluate the suitable strengthening scheme. Moreover, it is concluded that the relative displacement method for predicting the ductility ratio is more applicable than that based on the dissipated energy.

This work is devoted to discuss experimentally the behavior of high strength reinforced concrete (R.C.) encased corbels using the available commercial W-shape rolled steel. Eight specimens are tested and two shear slenderness ratio are considered, namely 0.70 and 1.00. The tested specimens are categorized in two groups according to (a/d) ratio. Each group included one conventional RC corbel and three composite corbels. Three configurations of composition are discussed, W-shape, WT shape and Tapered WT shape. Besides, two steel corbels have been tested, one W-shape while the other was WT-shape to get more understanding about the failure of composite corbels. The comparison between specimens is based on load-deflection curves, ductility, toughness, failure load, pattern of cracking propagation, failure mode and history of crack width development. Results revealed that the low properties commercial rolled steel can be used in composite corbels and such corbels could be adopted as a convenient alternative to the conventional RRC. In addition, it was found that the tested composite corbels yielded better behavior than the conventional ones, the composite corbels yielded toughness ranged from 120% to 170% from that of the RC conventional corbels with similar capacity for those composed using full W-shape with opening in webs. More ductile behavior is observed for corbels especially when shear force is dominant and low a/d ratio is adopted. Furthermore, Its found that that increasing a/d ratio from 0.7 to 1.0 for the control specimens, composite W-shaped and Tee-shaped encased beam result in reduction of capacity by 29%, 27% and 21%. Respectively. Moreover, a simple equation is suggested to estimate the composite corbels based on toughness and failure loads.

In this work, an experimental study has been conducted to investigate the behavior of self-consolidating high strength reinforced concrete dapped end beams upgraded with CFRP composites. A series of 14-specimens have been tested, each of with length of 1500 mm, total depth of 400mm and width of 200mm. Two values of shear slenderness ratio (a/d) namely (1.5 and 1.0) are adopted. Two specimens have been considered as a reference beams (with full Design reinforcement), four were deficiently reinforced in either hanger or the extended disturbed zone, and the other eight beams have been upgraded with a variety of arrangements by CFRP fabric. This work aims to observe the effects of deficiently reinforced disturbed zones on the resistance and overall behavior of such elements. Also, the extent of strength recovery using CFRP sheeting. It is observed that reducing the hanger reinforcements by a half, results in a drop of capacity by (13%) regardless of values of (a/d). Furthermore, it is noticed that adopting the inclined arrangement of CFRP sheets with (450) yielded the best results if compared with other arrangements. An enhancement in failure load was about (23%) for (a/d=1.0).

In this work, an experimental study has been conducted to investigate the behavior of self-consolidating high strength reinforced concrete dapped end beams upgraded with CFRP composites. A series of 14-specimens have been tested, each of with length of 1500 mm, total depth of 400mm and width of 200mm. Two values of shear slenderness ratio (a/d) namely (1.5 and 1.0) are adopted. Two specimens have been considered as a reference beams (with full Design reinforcement), four were deficiently reinforced in either hanger or the extended disturbed zone, and the other eight beams have been upgraded with a variety of arrangements by CFRP fabric. This work aims to observe the effects of deficiently reinforced disturbed zones on the resistance and overall behavior of such elements. Also, the extent of strength recovery using CFRP sheeting. It is observed that reducing the hanger reinforcements by a half, results in a drop of capacity by (13%) regardless of values of (a/d). Furthermore, it is noticed that adopting the inclined arrangement of CFRP sheets with (450) yielded the best results if compared with other arrangements. An enhancement in failure load was about (23%) for (a/d=1.0).

An experimental investigation conducted with studying the behavior high strength self-compacting reinforced concrete corbels strengthened with NSM steel bars. The experimental work involved testing ten corbel specimens. They are categorized into two groups with two values of shear span/depth ratio (a/d). Each group consists of five specimens, one considered as a control; others were strengthened with four different configurations of NSM steel bars. The load-deflection curves were traced, cracking and ultimate loads were recorded, crack width was measured and crack propagation up to failure was trucked. This research found that strengthening RC corbel with NSM steel bar system improved the failure load significantly by 57% and 41% for a/d of 0.85 and 1.25 respectively. The strengthening system named as "Upside down V-shaped" is more efficient for small values of a/d (a/d <1). The horizontal bars configuration is more convenient for large a/d values (a/d >1); with a/d greater than one, the general mode of failure is of Bond type. Also, it is found that the strengthening of specimens results in some elimination in ductility with a value depending on the strengthening configuration.

In this work study, a non-linear analysis has been conducted to investigate the performance of the one –way concrete slabs reinforced with basalt fiber reinforced polymer (BFRP) and carbon fiber reinforced polymer (CFRP) bars under static loading. ANSYS 15 has been utilized to study the behaviour of both simply supported and continuous slabs. Twelve specimens have been considered that are categorized into two groups: in the first one all slabs are reinforced with CFRP bars while the slabs of the second group are reinforced with BFRP bars. Each group consists of two simply supported and four continuous slabs. Some parameter have been studied such as continuity condition, reinforcement ratio, position of reinforcement. It is found that adopting high value of reinforcement ratio within bottom face (0.6%) and small value for reinforcement within top face (0.2%) rather than the reverse arrangement resulted in enhancement in capacity by 8% and 11% and for continuous slabs reinforced by basalts and carbon bars respectively. While adopting high ratios for both faces (0.6%) improved load capacity by 50% and 30% for the same bars reinforcements respectively. In addition, it is obtained that increasing reinforcement ratio in the bottom face of continuous slabs led to a reduction in deflection by about 50% and 35 % for those reinforced by basalts and carbon bars respectively. Comparing the finite element results with the experimental tests emphasized that the present model yield better results and has good agreement rather than ACI440 committee method.

In the present work, an experimental study is conducted to investigate the performance of lightly reinforced concrete flanged beams with stirrups having triangular shape under two-point static loading. Such beams are considered as the basic units of the reinforced concrete ribbed slabs with lightweight filling blocks. Six beams are tested in addition to the control one. Three parameters have been considered. These parameters are strength of concrete; (24, 36, 46) MPa, the span of beam;(1.50, 1.75, 2.00) m and the configuration of shear reinforcement;(closed, zigzag, spiral). Results stated that these parameters have considerable effects on the cracking load, ultimate load, type of cracking and the mode of failure. Some of the conclusions are that using zigzag shear reinforcement results in stiffer response along most of loading stages whereas the spiral type yielded more ductile behavior. In addition, it was found that ultimate capacity and maximum deflection have been improved by 9% and 37% respectively using the zigzag type of stirrups. While, adopting the spiral type of shear reinforcement results in improvements by 21% and 89% respectively.

A nonlinear finite element study has been conducted to evaluate the efficiency of the technique of strengthening reinforced concrete beams under static loads. No time-dependent effects (creep and shrinkage... etc.) are considered in this work. This concept is based on prestressing of CFRP sheets. In this research program, four reinforced concrete beams were tested to investigate the feasibility of such concept for flexural strengthening. One of the beams was retrofitted with non-prestressed CFRP sheet which was used as the control beam. The rest were retrofitted with prestressed CFRP sheet with three levels of prestressing. The static load was applied at the instant of full prestress load application. Prestress losses were ignored here. CFRP sheets have been simulated using two types of element (SHELL41 and LINK8). Prestressing effects have been represented using two models; the application as axial load and initial axial strain. The results showed that there is a good enhancement in performance of the beams strengthened using the prestressing technique in terms of the cracking loads and deflection occurs at such level of loading. The application of prestressing forces of 9 kN, 16 kN and 22 kN, was found to increase the cracking load by 57%, 106% and 170%, respectively.

Abstract: This paper considers the practical application of nonlinear models in the analysis of Vierendeel truss. Results of some analyses performed using the reinforced concrete model of the general purpose finite element code ANSYS which had been obtained from previous works are presented and discussed. An incremental loading procedure is adopted following step by step nonlinear response. ANSYS program has the ability to use conventional Newton-Raphson (N-R), full (N-R) and modified (N-R) Procedure to perform the analysis process. The defaulted choice (program chosen) is used in this work which allows for automatically chosen of the most suitable method. Number of sub-steps for each case was changed until converged solution and full load deflection curve were obtained. Good agreement with the experimental tests of some previous studies was obtained using ANSYS solution. The maximum difference with the experimental test is found to be less than 10%. The effect of shear transfer coefficients of an open and a closed cracks are also studied. It was found that changing shear transfer coefficient of an open crack has more effect than changing of closed crack on the behavior of Vierendeel truss.

beam-column joints. The 20-noded isoparametric brick element is adopted to represent concrete. The steel bars are idealized as axial members embedded within the concrete .full contact between steel and concrete is assumed. The material nonlinearities include the cracking of concrete

The analysis is based on the ultimate strength method and the must commonly used types of wire meshes have been considered . The effects of number of layers

theoretical analysis is presented for estimating the in-space large displacement elastic stability behavior of structures subjected to either proportional or non-proportional dynamic loads. The analysis adopts the beam-column approach, which models the structure's

ABSTRACT In the present work, a non-linear finite element (FEM) analysis has been conducted in order to investigate the performance of high strength R.C. beams including large openings. Seven beams have been considered with different opening sizes (max. size of 120*480). Further, a beam of (120*600) mm opening has been studied to investigate the behavior of beams with larger openings. To improve the performance of beams with large openings, two of the most commonly used methods in strengthening have been adopted. These are: increasing top and bottom steel ratios and jacketing of openings with steel plates. The analysis results showed that when the opening size was increased, the ultimate load capacity decreased gradually following a path very close to parabolic and that adopting high top and bottom steel ratios (about 8%) improved the ultimate load capacity by 59%. Also, it was found that strengthening the opening by a steel jacket of 3mm thickness improved the response of beams by 10% and 29% for cases of partial and full jacketing, respectively, while for a jacket of 5mm thickness, the capacity was improved by 22% and 44% for the two methods of jacketing.

Abstract A nonlinear finite element study has been conducted to investigate the effectiveness of strengthening RC beams with pre-stressed NSM CFRP rods in enhancing the flexural strength of the beams. Four beams have been considered. One acted as control to simulate an existing structural member. The other beams were strengthened with non-pre-stressed CFRP rod (0% pre-stressed), and pre-stressed CFRP rod (40%, or 60% pre-stressed of the CFRP rod tensile strength). The results of analysis showed that strengthening of the RC beams with non pre-stressed NSM CFRP rods improved both of the flexural capacity and deflection response. Increases in the cracking, yield and ultimate load of 17%, 20% and 48% were achieved. With a pre-stress level of 40%, an enhancement of 117%, 53% and 80% respectively over that of the control beam. For the beam strengthened with pre-stress level of 60%, more enhancements in response were achieved in term of the cracking and yield loads, but a slight reduction in ultimate loads (compared with lower level of pre-stress). Increments up to 160% and 67% in the cracking and yield load respectively. While 77% in ultimate load over that of the control beam were obtained.

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