Experimental and numerical investigations on reinforcement arrangements in RC deep beams

Husem, Metin,Yilmaz, Mehmet,Cosgun, Suleyman I. Techno-Press 2022 Advances in concrete construction Vol.13 No.3

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

Behavior of reinforced concrete plates under impact loading: different support conditions and sizes

Metin Husem,Suleyman I. Cosgun 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.3

In this study, effects of impact loads on reinforced concrete (RC) plates are examined analytically. During examination of RC plates, they were exposed to impact loading with two different support conditions in three different sizes. RC plates in different support conditions were analyzed with Concrete Damage Plasticity Model (CDP) and reinforcing steel was modeled with Classical Metal Plasticity Model (CMP) by ABAQUS finite element software. After the analysis it is found that impact loads, displacements, energy absorption capacities and damage patterns are changed due to support conditions and plate sizes. Results that are obtained from RC plate experiments in literature under impact loads are found to be similar with the results of numerical analysis with CDP material models.

Design of interlocking masonry units and mechanical properties of masonry assemblages

Metin Husem,Fatma Birinci Kayaalp 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.2

This paper describes the design of a new interlocking masonry system, the production of designed interlocking units and mechanical properties of interlocked masonry assemblages with mortar. In this proposed system, units have horizontal and vertical locks to integrate the units to the wall and have a channel to enable the use of horizontal reinforcements in the wall. Using these units, unfilled, filled or reinforced walls can be constructed with or without mortar. In the production of the interlocking units, it was decided to use foamed concrete. 12 trial productions have been carried out at different mix proportions to obtain the optimum concrete mix. At the end of the mentioned productions, the units were produced with foam concrete which is selected as the most suitable in terms of compressive strength and specific gravity. Then, axial compression, diagonal tension and bed joint shear tests were carried out to determine the mechanical properties of the interlocked masonry assemblages with mortar. Results from the tests showed that interlocks designed to strengthen the system against shear stresses by creating discontinuity throughout the joints have been successful to achieve their aim. Obtained data will enable structural analysis of walls to be constructed with these new units.

Diagonal bracing of steel frames with multi-cable arrangements

Metin Husem,Serhat Demir,Hong G. Park,Suleyman I. Cosgun 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.6

A large number of structure in the world were build with poor seismic details, with or without any lateral load resisting system like concentrically braced frames and steel plate shear walls. These structures can reveal deteriorating hysteretic behaviors with stiffness and strength degradation. Therefore, seismic retrofitting of such structures for drift control has vital importance. In this study a retrofit methodology has been developed, which involves diagonal bracing of steel frames with different cable arrangements. In the experimental and numerical program 5 different lateral load resisting system were tested and results compared with each other. The results indicated that multi-cable arrangements suggested in this study showed stable ductile behavior without any sudden decrease in strength. Due to the usage of more than one diagonal cable, fracture of any cable did not significantly affect the overall strength and deformation capacity of the system. In cable braced systems damages concentrated in the boundary zones of the cables and beams. That is why boundary zone must have enough stiffness and strength to resist tension field action of cables.

Finite element analysis of RC walls with different geometries under impact loading

Metin Husem,Suleyman I. Cosgun,Hasan Sesli 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.5

Today, buildings are exposed to the effects such as explosion and impact loads. Usually, explosion and impact loads that act on the buildings such as nuclear power plants, airports, defense industry and military facilities, can occur occasionally on the normal buildings because of some reasons like drop weight impacts, natural gas system explosions, and terrorist attacks. Therefore, it has become important to examine the behavior of reinforced concrete (RC) structures under impact loading. Development of computational mechanics has facilitated the modeling of such load conditions. In this study, three kinds of RC walls that have different geometric forms (square, ellipse, and circle) and used in guardhouses with same usage area were modeled with Abaqus finite element software. The three configurations were subjected to the same impact energy to determine the geometric form that gives the best behavior under the impact loading. As a result of the analyses, the transverse impact forces and failure modes of RC walls under impact loading were obtained. Circular formed (CF) reinforced concrete wall which has same impact resistance in each direction had more advantages. Nonetheless, in the case of the impact loading occurring in the major axis direction of the ellipse (EF-1), the elliptical formed reinforced concrete wall has higher impact resistance.

Failure analysis of steel column-RC base connections under lateral cyclic loading

Demir, Serhat,Husem, Metin,Pul, Selim Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

One of the most important structural components of steel structures is the column-base connections which are obliged to transfer horizontal and vertical loads safely to the reinforced concrete (RC) or concrete base. The column-base connections of steel or composite steel structures can be organized both moment resistant and non-moment resistant leading to different connection styles. Some of these connection styles are ordinary bolded systems, socket systems and embedded systems. The structures are frequently exposed to cycling lateral loading effects causing fatal damages on connections like columns-to-beams or columns-to-base. In this paper, connection of steel column with RC base was investigated analytically and experimentally. In the experiments, bolded connections, socket and embedded connection systems are taken into consideration by applying cyclic lateral loads. Performance curves for each connection were obtained according to experimental and analytical studies conducted and inelastic behavior of connections was evaluated accordingly. The cyclic lateral performance of the connection style of embedding the steel column into the reinforced concrete base and strengthening of steel column in upper level of base connection was found to be higher and effective than other connection systems. Also, all relevant test results were discussed.

Investigation of bond-slip modeling methods used in FE analysis of RC members

Serhat Demir,Metin Husem 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.2

Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members’ behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.

Failure analysis of steel column-RC base connections under lateral cyclic loading

Serhat Demir,Metin Husem,Selim Pul 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

One of the most important structural components of steel structures is the column-base connections which are obliged to transfer horizontal and vertical loads safely to the reinforced concrete (RC) or concrete base. The column-base connections of steel or composite steel structures can be organized both moment resistant and non-moment resistant leading to different connection styles. Some of these connection styles are ordinary bolded systems, socket systems and embedded systems. The structures are frequently exposed to cycling lateral loading effects causing fatal damages on connections like columns-to-beams or columns-to-base. In this paper, connection of steel column with RC base was investigated analytically andexperimentally. In the experiments, bolded connections, socket and embedded connection systems are taken into consideration by applying cyclic lateral loads. Performance curves for each connection were obtained according to experimental and analytical studies conducted and inelastic behavior of connections was evaluated accordingly. The cyclic lateral performance of the connection style of embedding the steel column into the reinforced concrete base and strengthening of steel column in upper level of base connection wasfound to be higher and effective than other connection systems. Also, all relevant test results were discussed.