scholarly journals Comparison of recent New Zealand and United States seismic design provisions for reinforced concrete beam-column joints and test results from four units designed according to the New Zealand code

Author(s):  
R. Park ◽  
J. R. Milburn

A comparison is made of the seismic design provisions for reinforced concrete beam-column joints required by the new New Zealand concrete design code NZS 3101 and recently proposed United States procedures. Large differences are shown to exist between these new provisions of the two countries. Results are reported
of cyclic load tests which were conducted according to the requirements of the new NZS 3101. The test results showed that location
of plastic hinges in beams away from the column faces may be of considerable advantage in the design of joints, when member sizes are small and joint shears are high, due to less congestion of reinforcement and better anchorage conditions.

Author(s):  
R. W. G. Blakeley ◽  
F. D. Edmonds ◽  
L. M. Megget ◽  
J. H. Wood

The paper describes the testing of two reinforced concrete beam-column joint units tested under incremented-static cyclic
 loading. The full size test units were based upon an interior beam-column joint of a four-storey 
framed building designed to the current NZ loading code and represent 
refinements on two previously tested conventional joints of similar dimensions. One unit differed from common practice by having a post-tensioned beam stressed to balance the floor dead load of the prototype structure whilst the second unit was detailed with haunched beams. Hinge formation occurred in the beams and stable hysteretic behaviour was obtained up to displacement ductilities of 10 for the prestressed unit and 6 for the haunched unit. The test results are analysed in terms of the draft NZ design code, DZ 3101, and the ACI Recommendations for beam-column joint design.


Author(s):  
R. Park ◽  
Ruitong Dai

Four beam-interior column Units were designed, constructed and tested subjected to simulated earthquake and gravity loading. One Unit followed the requirements of the New Zealand concrete design code NZS 3101:1982 for structures designed for ductility. The other three Units only partly followed the requirements of NZS 3101, in order to obtain information on the behaviour of beam-column joints of limited ductility. Plastic hinging was designed to occur in the beams. The major test variables were the quantity of horizontal and vertical shear reinforcement in the beam-interior column joint cores and the diameter of the beam longitudinal reinforcing bars passing through the joint cores. The test results indicted that the current NZS 3101 detailing requirements for shear and bond in the beam-interior column joint core regions of ductile reinforced concrete frames could be relaxed.


2003 ◽  
Vol 19 (4) ◽  
pp. 863-895 ◽  
Author(s):  
Leslie M. Megget

The seismic performance of eleven half-scale and three full-sized reinforced concrete beam-column knee joints was tested under inelastic cyclic loading. Twelve joints were designed to the current New Zealand Concrete Standard, NZS 3101 while the remaining two were designed to the 1964 New Zealand Code, which contained few seismic provisions. All the 1995 designs approached or exceeded their nominal beam strengths in both directions and only degraded in strength at displacement ductility factors greater than 2, while the 1960 designs failed prematurely in joint shear at about 70% of the beam nominal strengths. Many of the half-scale joints failed when cover concrete split off in the joint zone, allowing loss of anchorage and slip of the top beam bars. Two full-scale joints were designed to carry the maximum specified code joint shear stress (0.2 fc′), and one subsequently failed due to joint shear when the concrete compressive strength did not reach the specified design value. A third full-size joint was tested with distributed beam reinforcement. This joint performed in a ductile manner to displacement ductility 4 but failed in the second cycle at that displacement, due to buckling of several rows of beam bars.


1989 ◽  
Vol 16 (5) ◽  
pp. 627-649 ◽  
Author(s):  
Patrick Paultre ◽  
Daniel Castele ◽  
Suzanne Rattray ◽  
Denis Mitchell

The 1984 CSA standard for the design of concrete structures for buildings provided new seismic design and detailing requirements for concrete structures. Full-scale, reversed cyclic loading tests of reinforced concrete beam–slab–column subassemblages were carried out to investigate the seismic performance of frame structures designed with the latest Canadian code. The test results indicate the importance of including the influence of slab reinforcement in computing the beam capacity as well as the need to carefully design the joint regions for shear. The test results indicate the excellent performance of frame components designed with K = 0.7 (R = 4.0) and the poor performance of those designed and detailed with K = 2.0 (R = 1.5). The performance of subassemblages designed with K = 1.3 (R = 2.0) depends on the column to beam strength ratio and on the shear strength of the joints. Models to predict the flexural response as well as the shear response of key elements are described and the role of the spandrel beam in limiting the effective slab width is explained. Key words: seismic design, reinforced concrete, detailing, structures, codes.


2013 ◽  
Vol 438-439 ◽  
pp. 477-481
Author(s):  
Feng Lan Li ◽  
Xiong Huai Yu ◽  
Cheng Chen ◽  
Song Chen

A large impaired reinforced concrete beam with cracks was strengthened under self-weight action by the externally bonded steel frame composed with bottom steel plate and side hoop steel belts. The normal service loading behaviors of this beam were tested to verify the effectiveness of this strengthening method specified in current Chinese design code. Based on the analyses of test results, it can be concluded that: the deformation of flexural cross section of this beam fitted the assumption of plain cross section, the steel plate could effectively enhance the flexural stiffness and decrease the deflection of this beam, no new cracks appeared under the normal service loads, the cracks at bottom of this beam were more confined by the steel frame than those at web zone. Therefore, other measure should be taken to avoid the opening of web cracks.


Author(s):  
Leslie M. Megget

Four external reinforced concrete beam-column sub-assemblages were tested under pseudo seismic cyclic loading. The approximately 2/3 scale units incorporated the new Grade 500E reinforcing steel as the beam bars. Two different forms of beam bar anchorage were tested, the normal 90-degree "standard hook" and the continuous U-bar detail. In all units the farthest point of the beam bar anchorage was positioned at the minimum limit prescribed in the NZ Concrete Standard (NZS3101), namely ¾ of the column depth from the inner column face. All 4 units formed plastic hinges in the beam and joint degradation was minor. Failure occurred at drift ratios between 4 and 6% (approximate ductility factors of between 4 and 6) predominantly due to buckling of the beam bars in the plastic hinge zone. The stiffness of these units was significantly less than similar units reinforced with 300E Grade reinforcing or the recently replaced 430 MPa reinforcement. The decreased stiffness will cause higher lateral drifts during large earthquakes, than those anticipated in current Standards.


The flexural behavior of concrete beams reinforced with bamboo was studied experimentally. Bamboo was used as the main reinforcement with different bonding materials in place of steel. A nominal mix of M20 grade concrete was adopted for the beam design. The Bamboo surface was treated with common binding materials like Araldite and Bitumen. Araldite and Bitumen are good binding materials used to connect materials like steel, carbon and many different materials. Two specimens were casted with bitumen coating, two specimens were coated with araldite, two specimens were casted without any binder coating and a specimen was casted using normal steel reinforcement. Beams were casted with bamboo reinforcement and cured for 28 days. Deflection and flexural behavior of the beams were monitored. The test results imply that araldite coating in concrete beams with bamboo reinforcement increased the flexural strength to that of bamboo reinforced concrete using bitumen which is lesser strength to that of steel reinforced concrete beam.


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