shear capacity

In today's, the preservation and maintenance of masonry structures in historical areas have become very important. A significant part of this issue is rooted in the use of non-reinforced construction materials in the building of such structures. In Iran, most of the historical buildings were built using masonry materials. The buildings were designed according to the special architecture of this region. The existing structures mostly consist of masonry walls as well as some openings with arched configurations. In these types of walls, the wall consists of two piers and an arch on top of them. Since Iran is located in a highly seismic zone, investigating the performance of these types of structures is essential under the action of earthquakes and lateral loadings. Therefore, in this paper, a numerical investigation is accomplished on the in-plane behavior of traditional brick arches under the action of lateral loads. To this end, the numerical model of a sample of an existing arch (in Kerman’s Mesgari bazaar) was considered. The model was developed on STKO software. In this regard, the nonlinear response of bricks and mortar joints was simulated by using the DamageTC3D material. As well, the geometry of the wall was constructed with four-node plane-stress elements. The lateral capacity of the wall was assessed under the action of gravity loads. To this end, the wall was analyzed under gravity loads with intensities of 0.0 to 0.2 MPa. Next, it was pushed laterally through the pushover analysis and the shear force-displacement capacity curve of the wall was obtained. Through a specific procedure, the obtained capacity curves were estimated with a bilinear graph. By using this graph, the performance points corresponding to the wall’s capacity were extracted and a complete discussion was made regarding the shear capacity and the corresponding displacement to each performance point. Based on the obtained results from the analysis, it was observed that with an increase in the intensity of the applied gravity load, the maximum shear capacity of the walls increases. However, a higher increase in gravity load intensity (over a specific limit) would cause more damage to the arch which leads to a smaller shear capacity. Also, it is observed that the distribution of cracks and their pattern along the walls follow a similar outline. However, crack widths are affected strongly by the intensity of the applied gravity load on the wall.

The utilization of recycled materials in the concrete industry has become one of the most essential environmental needs today, and more technical and economic studies are being performed every day in this subject. The effect of recycled materials on the shear behavior of geopolymer concretes was investigated in this work, along with a comparison to conventional recycled concretes and the effect of recycled aggregates on both concrete groups. For this purpose, ten mixing designs with recycled aggregate replacement percentages of 0, 25, 50, 75, and 100 were made in two groups of ordinary concrete and geopolymer concrete, as well as mechanical tests such as compressive strength, modulus of elasticity, and pull-off test. A reinforced beam without a shear element was also created for each mixing design to study the effect of this type of aggregate on the shear behavior of the beam. The findings revealed that increasing the percentage of recycled aggregates causes a loss in mechanical characteristics in the designs and a reduction in beam bearing capacity, indicating that geopolymer concrete has a higher replacement capacity than regular concrete.

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

Composite special moment frames represent a novel type of special moment frames (SMFs) where a combination of concrete columns and steel beams is used. This paper evaluates the modeling of composite special moment frames and the behavior of the steel beam-concrete column connection. Due to the focus on hinge formation, the behavior of the connection with a hole drilled on the beam flange was analyzed. Numerical simulations were carried out in ABAQUS. The beam-column connection was subjected to one-five rows of holes. It was observed that the beam-column connection with three rows of holes had the optimal hinge formation behavior, stress distribution, and load. The connection with five rows of holes showed plastic strains in the first four rows, while the fifth row had no plastic strain. This suggests an increased drilling space since the fifth hole row did not contribute to the improvement of stress distribution uniformity. It was numerically found that the bending moment change varied from 8% to 46%; the model with three rows of holes had the lowest bending moment change, whereas the model with a single hole row showed the highest change in the bending moment. Moreover, energy absorption changed by 4-20%.

Considering the complexity of shear mechanisms of reinforced concrete beams and the effects of various parameters, creating a general model for the accurate estimation of the shear capacity is difficult. In addition, most guidelines for the determination of the shear capacity of reinforced concrete beams in empirical design codes have been obtained experimentally. Artificial intelligence algorithms have been widely used in this area in recent years. In this study, SVR, PANFIS, and GANFIS algorithms were used to predict the shear capacity of reinforced concrete beams. In this regard, the data of 175 experimental RC beam samples were collected. In these algorithms, values ​​of nine parameters affecting shear capacity were used as the input parameter and the shear capacity of the reinforced concrete beams as the output parameter. Using the Kfold validation method, training and test data were defined, and the predictions were performed accordingly. The results of predictions showed that the neuro-fuzzy inference system model with the genetic optimization algorithm had a higher accuracy than other algorithms with a second root mean square error of 0.06634 and a correlation coefficient of 0.996. Also, the grey system theory was used to determine the parametric sensitivity of the study variables on the shear capacity of reinforced concrete beams. The results showed that the mean coefficient of sensitivity analysis of the longitudinal rebar percentage parameter is greater than other parameters, indicating that the longitudinal rebar percentage parameter had more effects on shear capacity.

In recent years, the use of composite rebars in reinforced concrete structures has received much attention due to its high corrosion resistance, significant tensile strength, and appropriate non-magnetization characteristics.  Due to the lower modulus of elasticity of composite rebars than steel rebars, concrete beams reinforced with composite rebars have relatively lower shear strength compared to beams reinforced with steel rebars. On the other hand, shear failure in concrete beams reinforced with composite rebars is generally brittle and requires accurate prediction of the behavior of these members. Therefore, in this study, the shear strength of concrete beams reinforced with composite rebars is predicted using a combination of GMDH type neural networks and genetic algorithms based on a wide range of experimental results. The key effective parameters that consider in this study are the width of the web, effective depth of the beam, shear span to depth ratio, concrete compressive strength, modulus of elasticity of FRP longitudinal bars, and longitudinal reinforcement ratio. The accuracy of the proposed method has been verified by comparing the model predictions with the collected experimental results and existing shear design equations. The results show that the proposed model has more accurate results in calculating the shear strength of concrete beams than other existing relationships. A sensitivity analysis is also performed to assess the effect of the input parameters on the shear strength of FRP-reinforced concrete beams.

In the present study, a new model is derived to estimate the shear capacity of high-strength concrete slender beams without transverse reinforcement using hybrid adaptive neuro-fuzzy inference system (ANFIS) and particle swarm optimization (PSO) based on the wide range of experimental results. The proposed model relates the shear capacity of beam to effective depth, compressive strength of concrete, percent of longitudinal reinforcement, ratio of shear span to effective depth, and nominal maximum size of coarse aggregate. The experimental data are randomly categorized into two subsets of the training set and test set. After establishing the proposed model, a sensitivity analysis was carried out to assess the validity of proposed ANFIS-PSO model. For this purpose, the results of the proposed model are calculated by considering the variation of the two selected input parameters, whereas the values of other parameters are fixed at the corresponding median values. To check reliability of the proposed model more accurately, the predicted values are compared with the codes and standards such as: ACI 318-14, Eurocode-2, CEB-FIP Model Code, AS 3600-2009, and JSCE Guidelines against the whole experimental specimens based on the three well-known statistical measures; correlation coefficient (R^2), root mean squared error (RMSE), and mean absolute percentage error (MAPE). It can be found that the proposed ANFIS-PSO model passed desired conditions and could estimate the shear capacity of the high-strength concrete slender beams without transverse reinforcement with a good degree of accuracy.

Classic one-way shear design provisions began with 45 degrees truss analogy introduced by Ritter and then rectified by addition of a concrete contribution term (Vc</sub></em>) which was basically based upon the results of some academic tests of simply supported RC beams with concentrated loadings. There are some strong evidence and examples that this empirical approach and the difference between its experimental base and the effective mechanisms in many of existing applications can be disastrous. Shear failure of reinforced concrete falls in the category of brittle and undesirable failure modes and has caused unrectifiable incidents in structures and infrastructures throughout the world. Some of such examples are the shear failures observed in the event of Kobe earthquake, shear failure of US air force warehouse, fatal highway bridge failure in Laval, Canada, and damage of Sleipner offshore platform. After such observations, there have been some good efforts in development of methods based on the physical description of main mechanisms influencing the shear behavior of RC members and especially RC panels under in-plane stresses that led to development of theoretical approaches such as modified compression field theory (MCFT), softened truss model (STM), and critical shear crack theory (CSCT). These theories made some breakthrough in nonlinear analysis of RC structures and become the basis for shear design in some of advanced codes like AASHTO LRFD, fib model code and CSA. Due to the complex nature of shear behavior in reinforced concrete, consensus in this field has not been reached among researchers, yet. In this study, through a parametric study on shear capacity of reinforced concrete panels based on Local Stress Field Approach (LSFA), and assumption of a thorough and compatible physical description, an efficient method for shear capacity analysis of reinforced concrete members is introduced. The principal effecting input parameters in parametric study were selected randomly within a reasonable range in the n-dimensional space of variables. These variables included: ratio of longitudinal stress to shear stress, ratio of longitudinal reinforcement, yield stress of longitudinal reinforcement, characteristic strength of concrete, maximum aggregate size, transverse reinforcement amount, and yield strength of transverse reinforcement. The remaining input parameters, like concrete tensile strength, fracture energy, rebar size, etc. were picked reasonably, in accordance with main parameters.  Using an immense and strong experimental database of reinforced concrete slender beams failed in shear alongside with a database of reinforced concrete panels failed under in-plane loads, it is shown that the proposed method is a reliable, simple and easy to use approach that possesses high accuracy in calculation of shear capacity of slender reinforced concrete beams with or without transverse reinforcement, in comparison with existing reputed methods, and leads to safe and economic designs. Continuous transverse reinforcement (CTR) with a rectangular or polygonal shape is a relatively new technique that has been introduced in order to accelerate and facilitate the construction of RC structures. Studies show that rectangular continuous transverse reinforcement can improve the shear behavior and shear capacity of reinforced concrete beams, although existing shear design provisions, even the most advanced ones, are unable to predict this enhancement in capacity. It is shown that the proposed method is able to predict the aforementioned improved shear capacity of reinforced concrete beams with rectangular continuous transverse reinforcement.

One of major parameters in determining shear capacity of beams is the height of beam. Researches show that with increase in beam’s height, normalized shear strength decreases which this phenomena is called size effect. In recent years due to advances in construction methods, the idea of using lightweight concrete deep beams has been proposed, this should be done with a full understanding of the behavior of lightweight concrete. Moreover, truss models are recently used for analysis and design of deep beams in codes which their validity for lightweight concrete should be investigated.In this research to investigating size effect in lightweight concrete deep beams and comparison with normal concrete, two series of beams including 8 deep beam with shear span to height ratio of 0.5 were built in lab. First series included 4 beams with height of 30, 45, 60 and 90 cm using lightweight concrete in their construction, specimens of second series were similar to first but normal concrete was used in there construction. Results show that normalized shear strength in both groups of beams decreases with increase in height but the intensity of this decrease in lightweight concrete deep beams is more than normal concrete which shows that size effect in lightweight concrete is more than normal concrete. Results of Experiment were compared to truss methods in codes and some of proposed models in codes. Results indicate that all methods are conservative in low height beams and with increase in height, safety margin decreases.

Nowadays, Steel plate shear walls have been considered as the lateral load resisting system in buildings in increasing the strength and stiffness of structures in two sections of seismic reconstruction and improvement. In this paper, the shear strength and stiffness of a stiffened steel plate shear walls under various stiffeners configuration horizontal, vertical and combined structures with finite element method has been studied and finally the proposed equations for determining the unstiffened equivalent thickness of the steel plate The proposed model is used to design a stiffened steel plate shear wall using the proposed equations of the plate frame interaction method. The results indicate a acceptable prediction of the capacity and stiffness of the stiffened steel shear walls using proposed equations and the error rate has been less than 15%.Nowadays, Steel plate shear walls have been considered as the lateral load resisting system in buildings in increasing the strength and stiffness of structures in two sections of seismic reconstruction and improvement. In this paper, the shear strength and stiffness of a stiffened steel plate shear walls under various stiffeners configuration horizontal, vertical and combined structures with finite element method has been studied and finally the proposed equations for determining the unstiffened equivalent thickness of the steel plate The proposed model is used to design a stiffened steel plate shear wall using the proposed equations of the plate frame interaction method. The results indicate a acceptable prediction of the capacity and stiffness of the stiffened steel shear walls using proposed equations and the error rate has been less than 15%.

In this paper, the effect of parameters such as the distance, number of layers and cross-sectional area of FRP strips, the amount of longitudinal rebars, dimensions of beam and compressive strength of concrete on shear capacity of reinforced concrete beams with rectangular cross-section stiffened by FRP strips under symmetrical concentrated loads using the finite element method has been studied.The non-linear analysis of 101 reinforced beams has been performed for evaluation of the effect of the parameters on load capacity and mid-span deflection of the beams with and without strengthening. The samples are deivided into six groups, which ultimately have been compared and investigated for load capacity and displacement of the mid-span. Obtained results indicate that for a constant concrete compressive strength, increasing the width and the number of layers of FRP strips increases the load capacity by 26% and 23%, respectively, compared to the control beam. At same time, by increasing of these two parameters the increase of the load capacity decreases. By changing the layout of reinforcing strips with irregular intervals along the beam, the load capacity increase is about 6% to 35%. Also, the increase of the amount of longitudinal rebars from ∅10 to ∅14, increasing the compressive strength of the concrete from 30 MPa to 50 MPa, and increasing the cross-sectional area of the beam from 150 × 300 mm to 150 × 400 mm in unsitffened beams, increase the load capacity by 31%, 23% and 55%, respectively, and decrease the deflection of the mid-span.

The majority of building population in Iran and other developing countries consists of unreinforced masonry buildings and sometimes confined masonry (CM) buildings. In such buildings، masonry shear walls are the main earthquake resistant components. The Iranian seismic standard IS2800 provides some specifications for seismic design and construction of confined and reinforced masonry buildings which all are based on the observed behavior of them during the past destructive earthquakes. In other words، the specifications are merely qualitative. This shows the necessity of assessment of masonry buildings behavior both experimentally and numerically. Despite the extensive numerical studies available in the literature، it seems that the lateral load behavior of masonry buildings cannot be properly investigated by continuum mechanics based methods such as traditional finite element method. As an alternative to the available finite element methods، a distinct/discrete element method (DEM) can be used to investigate the nonlinear lateral load behavior of masonry buildings. Distinct element method has the capability to con-sider large displacements، shear sliding and complete joints openings between bricks as well as automatic detection of new contacts during the analysis process. In this paper a two-dimensional numerical model is developed using distinct element method using the specialized distinct element software UDEC (Itasca، 2004) for the nonlinear static analysis of unreinforced masonry buildings subjected to in-plane monotonic loading. The Univer-sal Distinct Element Code (UDEC) is a 2D program based on the DEM to simulate the behavior of jointed materials subjected to either static or dynamic loading. The developed DEM model is validated using the results of a two-story unreinforced masonry building designed and tested based on the Iranian seismic standard IS2800 regulations at the Building and Housing Research Center (BHRC). Due to low intensity of gravitational normall stresses in conventional masonry buildings، the bricks were built using an elastic material model. In order to develope a DEM micro-model based on interface elements with zero thickness، the size of the bricks was expanded by the mortar thickness in both directions and the elastic properties of the expanded brick were assumed to be the same as that of the real brick. Howevr، For the joints، simulating the characteristics of the mortar، a Mohr–Coulomb slip model was employed. It was found that the model can be used confidently to simulate nonlinear behavior of unreinforced masonry buildings for parametric studies. The Iranian seismic standard IS2800 specifications pertain mainly to the masonry shear walls percentage need in each direction. In other words، the perpendicular shear walls are not taken into account in masonry buildings’ lateral load capacity calculations. However، unreinforced masonry buildings resist lateral loads through box action behavior of all constituent components (i. e. walls، foundation and diaphragms). Therefore، a parametric study was conducted to investigate the contribution of perpendicular masonry shear walls on buildings’ lateral load capacity. Parametric study showed that perpendicular masonry shear walls contribute considerably to the shear capacity of the masonry building.

Today، corrosion in reinforcements is an important issue in many structures، especially those made in off-shore، resulting of reduction of the structural capacity under gravitational and lateral loads. Using FRP polymer can reduce this effect to some extents. A numerical and experimental investigation has been conducted on three different concrete beams to find out the effect of replacing steel stirrups with FRP ones under static loading. So، three beams were tested under concentrated loading on the middle of the span. One of the three beams، as the reference had steel stirrups، while the other two contained in-place FRP made stirrups. Longitudinal steel reinforcements were used in all three specimens. Also، two different beams with steel and FRP stirrups were analyzed by finite element method in ANSYS. After calibration، two other groups of concrete beams were modeled and analyzed. The results demonstrated that FRP stirrups had the better shear capacity performance compared to steel stirrups and the final strain in FRP stirrups reached %0. 8 which is two times of the value suggested by design code provisions.