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.
Moment–Rotation Parameters for Composite Shear Tab Connections
Shear tab connections, acting compositely with the floor slab, are capable of providing some lateral resistance in steel frame buildings. This resistance was suspected from the events of the 1994 Northridge Earthquake and verified in a series of tests. For performance evaluation of steel structures, it is necessary to quantify the non-negligible rotational strength and stiffness of these composite connections, a task that cannot be accomplished through the use of simple rules of thumb. Therefore, trends in the moment–rotation behavior of the connections are identified from comparison of the cyclic behavior against parameters such as number of bolts, type of concrete, use of slab reinforcement, and the presence of a column web cavity. Analysis of these trends leads to guidelines for determining parameters for a basic backbone moment–rotation curve. These guidelines depend heavily on applicable limit states for elements of the connections and connection geometry. Predicted values of moment and rotation capa...
LESSONS LEARNED FROM THE NORTHRIDGE EARTHQUAKE
Abstract The performance of welded connections in special moment resisting frames (SMRF) during the Northridge, California earthquake in January 1994 was influenced by many variables. The actual ground motions experienced by the buildings, the design details employed in the connections, material properties, fabrication workmanship and inspection practices. The evidences of workmanship-related problems were primarily the result of lack of conformance to the requirements specified in the AWS Structural Welding Code D1.1. Lack of emphasis on in-process visual inspection may have permitted questionable fabrication practices to go undetected. A fundamental expectation regarding the performance of the SMRF is that of ‘ductility’. In concept, the seismic energies are to be absorbed by the formation of plastic hinges within the structure. The pre-Northridge connection detail is examined in light of quality, fracture and multi-directional stresses, and its relative performance regarding expectations of ductile behavior. Post-Northridge research specimens are examined with respect to the same factors, along with their relative level of ductile behavior. Details that enhance ductile behavior and the reasons that this behavior can be expected are presented.