Mechanical Properties of Cement-Clay Interlocking (CCI) Hollow Bricks

In this paper, an investigative study on mechanical properties of CCI hollow bricks, for example, compressive strength, modulus of rupture, splitting tensile strength, water absorption capacity and heat transfer is conducted. The experimental program is divided into two parts. In the 1st part, bricks from three different regions (A, B and C having different soil stratum) of Thailand were collected and their mechanical properties were investigated. The mechanical properties of CCI hollow bricks of region A were observed relatively very low as compared to other regions. The compressive strength values of region A bricks were found even below the standard values required by Thai Community Product Standards (TCPS). Then, in the 2nd part, change in three mix design ratios followed by sand, cement and fly ash for region A have been exercised to observe their effects on mechanical properties of bricks from said region. Results showed significant improvements as compared with previous results obtained in first part of the experimental program. Also, a cost-benefit analysis was performed to observe the effect of the manufacturing cost on the mechanical properties of CCI hollow bricks in Thailand. It has been investigated that the brick samples with more cement content (from region C, Mix – 2 & Mix – 3) are relatively expensive as compared with other brick samples with less cement content (from region A, region B & Mix – 1)

Experimental and Analytical Study on Reinforcing Steels with Threaded Mechanical Couplers under Monotonic and Cyclic Loadings

This study performs the experimental and analytical investigation on the effect of mechanical couplers on the axial behavior of spliced reinforcing bars. The effect of unsupported-length-to-bar-diameter (L/D) ratios on the monotonic and cyclic behavior was observed. The test configurations in monotonic tension, compression, and cyclic tests included reinforcing bars with and without threaded mechanical couplers. Specimens with mechanical couplers have higher strength in compression than the bars without couplers, especially when L/D is less than 10. The procedure for determining the effective unsupported length for bars with a mechanical splice was proposed. And the observation on the energy dissipation confirmed the proposed method.  The calculated hysteretic loops using the modified unsupported length model of the bar with mechanical splice agreed well with the test result

Strengthening of Shear-Critical RC Columns by High-Strength Steel-Rod Collars

This research investigates the strengthening of shear-dominated reinforced concrete (RC) square columns using the high-strength steel-rod collars, which enhance confinement by steel rods around the column perimeter. This method is less intrusive to the existing building with infilled walls because steel rods can penetrate through the walls with minimal openings (holes) at the location of collars. In this study, one control specimen and two specimens strengthened by steel-rod collars were tested. All specimens were subjected to lateral cyclic loading along with a constant axial load. The difference between the two strengthened specimens were the spacing of steel-rod collars mounted on the columns. The spacing of steel-rod collars was 200 mm in the column specimen SC-200, while the other strengthened specimen, SC-100 has a spacing of 100 mm. The unstrengthened column failed in shear while the strengthened columns failed in flexure. In addition, the strengthened specimens failed at the higher load and ductility. Comparing to the unstrengthened column, the lateral load capacity and ductility ratio of the column SC-200 increase by 18 % and 59%, respectively. While, the lateral load and ductility ratio of SC-100 increase by 16% and 69%, respectively. Furthermore, the finite element models of all column specimens are developed using the OpenSees program. The analysis results are found in a close agreement with the experimental results

Development of strength models for brick walls: Experimental and theoretical study

The low cost of cement-clay interlocking (CCI) bricks is an attractive feature, resulting in a wide utilization of CCI bricks in the construction of masonry walls. Despite this, an experimental database on the performance of CCI brick walls is scarce. This study tested ten large masonry walls constructed with CCI bricks in a running bond pattern. Two types of CCI bricks were used to assess the effect of chemical position on the diagonal compressive capacity of walls. Further, different grouts and steel bars were used within the openings in CCI bricks. A combination of grout and steel bars resulted in the optimal improvement of the diagonal compressive strength, whereas up to 110% higher improvement in the diagonal compressive strength was achieved by doubling the compressive strength of grout. Interestingly, the type of bricks did not influence the improvement in the diagonal compressive capacity of CCI brick masonry walls. A regression-based equation was proposed to predict the diagonal compressive capacity of CCI brick walls by including the yield strength of steel bars, the compressive strength of grout, and the diagonal compressive strength of ungrouted walls as explanatory variables. The predicted capacities of CCI brick walls were found to be in close agreement with experimental results

Shear Strengthening of RC Deep Beams with Sprayed Fiber-reinforced Polymer Composites (SFRP): Part 2 Finite Element Analysis

AbstractThis paper presents the finite element analysis conducted on SFRP strengthened reinforced concrete (RC) deep beams. The analysis variables included SFRP material (glass and carbon), SFRP thickness (3 mm and 5 mm), SFRP configuration and strength of concrete. The externally applied SFRP technique is significantly effective to enhance the ultimate load carrying capacity of RC deep beams. In the finite element analysis, realistic material constitutive laws were utilized which were capable of accounting for the non-linear behavior of materials. The finite element analysis was performed using computer software WCOMD. In the analysis, two dimensional eight-node reinforced concrete planar elements for concrete and planar elements with elastic-brittle behavior for SFRP were used to simulate the physical models. The concept of smeared cracking in concrete and steel was adopted over the element. The calculated finite element results are found to be in good agreement with the experimental results and to capture the structural response of both un-strengthened and SFRP strengthened RC deep beams. A comparison between the finite element results and experimental data proved the validity of the finite element models. Further, the finite element models were utilized to investigate the behavior of RC deep beams strengthened with different directions of SFRP Strips (vertical and horizontal). The vertical SFRP strips are found to be more effective than horizontal ones

Performance of Concrete Confined with a Jute–Polyester Hybrid Fiber Reinforced Polymer Composite: A Novel Strengthening Technique

The strengthening and rehabilitation of concrete members is an important issue which arises worldwide. Carbon, aramid and glass fiber reinforced polymer (FRP) composites are mainly used for strengthening and rehabilitation. However, its use is limited on a small scale because of its high price, lack of availability and environmental impacts. The solution of this issue gives rise to the use of locally available natural fibers and low-cost synthetic fibers. This paper presents the experimental and analytical results of circular and square concrete columns confined with jute–polyester hybrid FRP composites. The main objective of this study is to evaluate the viability and performance of concrete confined with the hybridization of jute and polyester (FRP) composite sheets to utilize its superior properties. A novel hybrid technique has been applied for the wrapping of fiber sheets. The fiber sheets were applied in such a way that a uniform bond between the inner and outer layer was achieved. A total of 32 plain, standard size circular and square concrete specimens, externally wrapped with a jute–polyester FRP (JPFRP) composite, were tested under monotonic axial compressive loads. The result shows that JPFRP confinement increased the strength, strain and ductility index ranged between 1.24 and 2.61, 1.38 and 8.97, and 4.94 and 26.5 times the un-jacketed specimen, respectively. Furthermore, the wrapping has a significant effect on the low-strength specimens, having a circular cross-section. For high strength specimens, the post-peak stress-strain behavior was dominated by the outer polyester jacket because of its large rupture strain. Additionally, the test results were used to evaluate the existing strength-strain models derived for conventional FRPs. The models predicted values either underestimating or overestimating the compressive strength and strain of JPFRP-confined specimens. However, the strength models performed better than the strain models. The JPFRP wrapping significantly enhanced the strength, fracture energy, ductility index, and post-peak response. Therefore, JPFRP confinement can be used for a small-scale application, where little strength and high ductility is demanded. Moreover, it can be used to prevent the peeling of the concrete cover and moisture penetration into the concrete

Shear Enhancement of RC Beams Using Low-Cost Natural Fiber Rope Reinforced Polymer Composites

The aim of this research work is to investigate the efficiency of newly developed Natural Fiber Rope Reinforced Polymer (NFRRP) composites to enhance the shear strength of reinforced concrete (RC) beams. Two types of NFRRP composites were made using low-cost hemp and cotton fiber ropes. The effectiveness of this NFRRP confinement in increasing the shear, energy dissipation, and deformation capacities of concrete beams was studied. The effect of these natural fiber ropes with different configurations on beams was investigated. The responses of seven RC beams with different spacing arrangements of natural fiber ropes were evaluated in terms of shear enhancement, deflection, energy dissipation capacity, effect of strengthening configuration, rope types, and ultimate failure modes. The NFRRP composites exceptionally enhanced the load carrying abilities, energy dissipation, and deformation capabilities of RC beams as compared to the control beam. The ultimate load carrying capacities of natural hemp and cotton Fiber Rope Reinforced Polymer (FRRP) composite confined beams were found to be 63% and 56% higher than that of the control beam, respectively. Thus, the shear strengthening of RC beams using natural fiber ropes is found to be an effective technique. Finite Element Analysis was also carried out by using the Advanced Tool for Engineering Nonlinear Analysis (ATENA) software. The analysis results compare favorably with the tests’ results

Stress and strain relations of RC circular, square and rectangular columns externally wrapped with fiber ropes

Abstract This study explores the potential use of low-cost natural fiber reinforced rope polymers (FRRP) to improve the compressive behavior of circular, square, and rectangular reinforced concrete (RC) specimens. A total of 42 specimens were tested under monotonic axial compression in three groups. Groups were formed to differentiate specimens with different cross-sectional shapes such as circular, square, and rectangular. The findings demonstrate that FRRP can effectively boost the compressive behavior of RC columns. Circular specimens with three-layer hemp FRRP exhibited a 200% increase in compressive strength and a 270% improvement in corresponding strain. Cotton FRRP provided a 117% boost in compressive strength and a 233% enhancement in strain. In square specimens, three-layer hemp FRRP resulted in a 110% rise in compressive strength and a 186% increase in strain, while cotton confinement yielded improvements of 95% and 144%, respectively. For the square and rectangular specimens, the improvement in the compressive behavior was reduced compared to the circular specimens because of stress concentrations near corners. Moreover, the study showed that the hemp FRRP confinement outperformed the cotton confinement. The investigation also revealed that the existing analytical models were inadequate in predicting the mechanical properties of RC confined with natural FRRP. Therefore, the study introduces novel equations to predict the compressive strength and corresponding strain for both hemp and cotton confined concrete in various cross-sectional types. These proposed equations exhibit a good level of accuracy in predicting the compressive strength and corresponding strain

Shear Enhancement of RC Beams Using Low-Cost Natural Fiber Rope Reinforced Polymer Composites

The aim of this research work is to investigate the efficiency of newly developed Natural Fiber Rope Reinforced Polymer (NFRRP) composites to enhance the shear strength of reinforced concrete (RC) beams. Two types of NFRRP composites were made using low-cost hemp and cotton fiber ropes. The effectiveness of this NFRRP confinement in increasing the shear, energy dissipation, and deformation capacities of concrete beams was studied. The effect of these natural fiber ropes with different configurations on beams was investigated. The responses of seven RC beams with different spacing arrangements of natural fiber ropes were evaluated in terms of shear enhancement, deflection, energy dissipation capacity, effect of strengthening configuration, rope types, and ultimate failure modes. The NFRRP composites exceptionally enhanced the load carrying abilities, energy dissipation, and deformation capabilities of RC beams as compared to the control beam. The ultimate load carrying capacities of natural hemp and cotton Fiber Rope Reinforced Polymer (FRRP) composite confined beams were found to be 63% and 56% higher than that of the control beam, respectively. Thus, the shear strengthening of RC beams using natural fiber ropes is found to be an effective technique. Finite Element Analysis was also carried out by using the Advanced Tool for Engineering Nonlinear Analysis (ATENA) software. The analysis results compare favorably with the tests’ results

Low-Cost Fiber Rope Reinforced Polymer (FRRP) Confinement of Square Columns with Different Corner Radii

This research investigates the behavior of square concrete columns externally wrapped by low-cost and easily available fiber rope reinforced polymer (FRRP) composites. This study mainly aims to explore the axial stress-strain relationships of FRRP-confined square columns. Another objective is to assess suitable predictive models for the ultimate strength and strain of FRRP-confined square columns. A total of 60 square concrete columns were cast, strengthened, and tested under compression. The parameters were the corner radii of square columns (0, 13, and 26 mm) and different materials of FRRP composites (polyester, hemp, and cotton FRRP composites). The strength and deformability of FRRP-confined specimens were observed to be higher than the unconfined specimens. It was observed that strength gains of FRRP-confined concrete columns and corner radii were directly proportional. The accuracy of ultimate strength and strain models developed for synthetic FRRP-confined square columns was assessed using the test results of this study, showing the need for the development of improved predictive models for FRRP-confined square columns. Newly developed unified models were found to be accurate in predicting the ultimate strength and strain of FRRP-confined columns