An investigation on effect of rebar on structural behaviour for wall-slab system
The government is taking the leading role to persuade the construction industry to engage a more systematic approach and methodology in construction by adapting the Industrialized Building Systems [IBS]. Wall-slab structural system is an IBS system which is suitable for use in residential building. Moment transfer of joint is an important aspect for proper structurally functioning of wall-slab system. Hence, the main aim of this study is to investigate the effect of reinforcement details in the wall on bending capacity for support stiffness in wall-slab system for residential project in Malaysia. A total of six wall specimens were tested. Three of this specimens consisted single layer of rebar while another three specimen consisted of double layer of rebar. The size of the wall-slab's specimens is 1000 mm in length [L], 1080 mm in width [W], 1000 mm in height [H] and 80 mm in thickness [T]. The average concrete strength Grade 30 N/mm2 and the average yield strength of R5 bar was 817 MPa. The bending capacity at failure for single layered of rebar in wall for specimen 1, 2 and 3 were found to be 3.59 kNm, 3.81 kNm and 3.15 kNm, respectively. The bending capacity at failure for double layered of rebar in wall for specimen 1, 2 and 3 were 5.50 kNm, 6.31 kNm and 7.00 kNm, respectively. The difference in stiffness of double layered reinforced concrete wall based on load-deflection curve 116.2 % to 289.9 % higher than single layered reinforced concrete wall. While based on the experimental results, specimens with double layered rebar in wall is found with higher bending capacity by 56.3 % to 98.9 % compared to single layered of rebar in wall. Experimental data on bending capacity provides important input in the process of structure analysis. Others than that, the outcome obtained from the study can serve as an useful guideline in the design of an efficient joint in wall-slab structural system.
IMPROVED TRUSS MODEL FOR DESIGN OF WELDED STEEL MOMENT-RESISTING FRAME CONNECTIONS
Results are given from finite element analysis of 18 strong-axis steel welded beam-column subassemblages with connection reinforcement. For the type of connection configuration considered, Federal Emergency Management Agency (FEMA) recommends connection forces be obtained by locating the plastic hinge at 1/3 depth of beam away from the end of connection reinforcement region. Also, a recent study pointed the location of plastic hinge to be at a distance of depth of beam from the column face. However, the present study shows that the plastic hinge is located at 1/2 depth of beam away from the end of connection reinforcement region. It is observed that connection design forces obtained from the present study are higher as compared to those obtained using the FEMA recommendations. A noniterative procedure for the design of beam-to-column connections using a truss for obtaining connection forces is also presented, which uses this location of the plastic hinge.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.