SUMMARYA series of pseudo-dynamic tests (PDTs) of a full-scale 3-story 3-bay buckling-restrained braced frame (BRBF) using concrete-filled tube columns was tested in the Taiwan National Center for Research on Earthquake Engineering using networked PDT techniques in October 2003. During the tests, real-time experimental responses and video were webcasted to Internet viewers. The input ground motions adopted for the PDTs were chosen from the 1999 Chi-Chi and the 1989 Loma Prieta earthquakes and scaled to represent three seismic hazard levels. This paper is in two parts, focusing on the investigations of the overall structure and the local members. This paper constitutes Part I and discusses the design, analytical investigations, and key experimental results of the specimen frame, such as the buckling of the brace-to-gusset joints. Part II of the paper, the companion paper, describes the gusset stiffening schemes and detailed experimental behavior of the BRBs and their connections. Experimental peak inter-story drifts of 0.019 and 0.023 radians, prescribed for the design basis and the maximum credible earthquakes, respectively, are within the target design limits of 0.020 and 0.025 radians. These tests confirmed that the PISA3D and OpenSees nonlinear structural analysis computer programs can simulate the experimental peak shears and floor displacements well.

This paper reports an experimental program aiming to shed some light on the response of non-seismic RC beam-column joints to excitations of different frequencies. The RC connections tested were designed only for gravity loads, thus rendering the joint cores weaker than the adjoining members when subjected to a lateral load. Altogether, six tests were conducted on full-scale specimens, which were subjected to reversed cyclic displacements applied at different speeds varying from slow quasi-static loading to high-speed dynamic loading as fast as 20 Hz. Although all specimens expectedly suffered joint shear failure, the maximum joint shear stresses observed in the tested specimens, despite lacking transverse hoops inside the joint cores, were more than the horizontal shear stresses allowed in ductile RC joints with the same grade of concrete according to the existing seismic design codes. The damage patterns and failures of the specimens showed a better correlation with the residual storey shear stiffness rather than with the loss of storey shear strength during the repeated cycles. By analysing the test results, this paper also discusses how an inadvertent inertial force develops during high-speed displacement reversals.Key words: Gravity-designed; beam-column joint; high-speed; inertial force; joint shear; residual stiffness Introduction Structures in low and moderate seismicity regions are designed to resist gravity loads comprising self-weight and superimposed weight. As seismic forces do not control the design, the beams and columns in an RC building in such regions intersect at joints that have no or very little transverse reinforcement. Even in seismic zones, RC buildings that were designed and built before seismic codes were fully matured may have a small amount of confining hoops in their joints, thereby failing to satisfy the stricter requirements of current design codes [1]. RC frames with such lightly reinforced joints, though being sound against gravity loads, are vulnerable when subjected to lateral loads. Although strong earthquakes are not likely to occur, buildings in non-seismic zones may in some cases be exposed to ground excitations of different frequencies that are induced by underground explosions, construction vibrations, long-distance earthquakes, etc. In order to assess the safety of buildings in non-seismic regions, the response and damage of such gravity-designed connections due to lateral cyclic loadings of static and dynamic natures should be well understood. The results of such studies also provide vital information and database that might finally lead to the development of new building design guidelines and recommendations on the nature and extent of strengthening needed to ensure the safety of existing buildings in such regions.Although mechanisms related to seismic response of ductile RC connections with adequate shear reinforcement have been widely investigated and well documented [2][3][4][5][6], test data on gravity-designed joints are still scarce [1,7]. Indeed, most o...

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In recent years, the T-Headed bar has been gradually applied to bridge and building structures. However, until Year 2008, a debut of the headed bar in the ACI 318 Design Code was found. There were six limitations on materials’ strength properties, bearing area of head and concrete-cover thickness and spacing of the reinforcement with the head to be made in the Section 12.6 of the ACI 318-08 Code. This paper concerns some issues that were difficult application for the practical engineering or had potential to be improved. They include the clear spacing of the headed bars not less than 4 times the diameter of the bars, the bearing area of head of the headed bar not less than 4 times cross-sectional area of the bars and concrete limit on normal-weight and its effective compression strength not more than 42 MPa. In this study, a total of 43 specimens with a CCT node (Compression-Compression-Tension Node) experimental model were conducted to evaluate anchored performance of the headed bars. Study parameters in this work included strength of concrete, size of reinforcement, bearing area of T head, spacing of bars and confinement condition provided by horizontal reinforcement. Additionally, some benchmark specimens those placed straight bars, and standard 90º and 180º hook bars were carried out for comparison. Test results showed that for anchorage performance, the T-headed bars could provide better than the standard 90º and 180º hook bars. Test results also indicated that the headed bars with head bearing area of three times sectional area of the bar were able to perform as well anchored behavior as their head bearing area with four times sectional area of the bar. In addition, comparing the test results of specimens their spacing having 1.5 and 4 times diameter of the bar, it was found that their anchored strength capacities were similar.