Seismic Load Tests Research Articles

A SUMMARY OF RESULTS OF SIMULATED SEISMIC LOAD TESTS ON REINFORCED CONCRETE BEAM-COLUMN JOINTS, BEAMS AND COLUMNS WITH SUBSTANDARD REINFORCING DETAILS

The results of some simulated seismic load tests on reinforced concrete one-way interior and exterior beam-column joints with substandard reinforcing details typical of buildings constructed in New Zealand before the 1970s are described. The tests were conducted using both deformed and plain round longitudinal reinforcement. The interior beam-column joint cores lacked transverse reinforcement and the longitudinal bars passing through the joint core were poorly anchored. The exterior beam-column joint units contained very little transverse reinforcement in the members and in the joint core. In one exterior beam-column joint unit the beam bar hooks were not bent into the joint core. That is, the hooks at the ends of the top bars were bent up and the hooks at the ends of the bottom bars were bent down. This anchorage detail was common in many older buildings constructed before the 1970s. In the other exterior beam-column joint unit the hooks at the ends of the bars were bent into the joint core as in current practice. The improvement in performance of the joint with beam bars anchored according to current practice is demonstrated. In addition, tests were conducted on interior joints with lap splices in the beam longitudinal reinforcement bars near the column face. The tests were conducted using both deformed and plain round longitudinal reinforcement. Tests were also conducted on columns with plain round bar longitudinal reinforcement and inadequate transverse reinforcement. The reinforcing details were close to identical to those in an existing seven storey reinforced concrete building that was designed and built in New Zealand in the late 1950s. The test results give an indication of the performance of beam-column joints and members with the above now out-of-date reinforcing details. The test results reported are a summary of results reported in a number of publications written since 1994.

Seismic Load Tests on Interior and Exterior Beam-Column Joints with Substandard Reinforcing Details

Seismic Load Tests on Interior and Exterior Beam-Column Joints with Substandard Reinforcing Details

Seismic load tests on two concrete interior beam-column joints reinforced by plain round bars designed to pre-1970s codes

Two identical reinforced concrete interior beam-column joint assemblies were tested under simulated seismic loading as part of an investigation of the behaviour of existing reinforced concrete structures designed to pre-1970s codes when subjected to severe earthquake forces. The test units were full-scale in size, and were replicas of part of the moment resisting frame of an existing building in Christchurch that was constructed in the 1950s. The longitudinal and transverse reinforcement were from plain round bars, the beams and columns had low quantities of transverse reinforcement and the joints had no shear reinforcement at all, as was typical of pre-1970s construction in New Zealand. One unit was tested with zero axial column load, and the other unit with a constant axial column load of 0.12 f’c Ag, where f’c = concrete cylinder compressive strength and Ag = the gross column section area. The units displayed very low structural stiffness, flexural strength less than conventionally calculated, and significant degradation of stiffness and strength during testing. The low structural stiffness and flexural strength could be attributed to the slip of the plain round longitudinal bars through the joint. However, the utilisation of plain round bars although leading to bond slip was found to improve the joint shear strength and to result in reduced shear distortion of the joint. Buckling of longitudinal column bars was found to initiate failure, due to inadequate ties.

Simulated Seismic Load Tests on Two-Story Waffle- Flat-Plate Structure Rehabilitated

Simulated Seismic Load Tests on Two-Story Waffle- Flat-Plate Structure Rehabilitated

Seismic load tests on two-story waffle-flat-plate structure: M. E. Rodriguez, S. Santiago & R. Meli, Journal of Structural Engineering - ASCE, 121(9), 1995, pp 1287–1293

Seismic load tests on two-story waffle-flat-plate structure: M. E. Rodriguez, S. Santiago & R. Meli, Journal of Structural Engineering - ASCE, 121(9), 1995, pp 1287–1293

Discussion: Simulated Seismic Load Tests on Reinforced Concrete Columns

Discussion: Simulated Seismic Load Tests on Reinforced Concrete Columns

Closure to “Simulated Seismic Load Tests on Reinforced Concrete Columns” by S. Watson and R. Park

Closure to “Simulated Seismic Load Tests on Reinforced Concrete Columns” by S. Watson and R. Park

Seismic Load Tests on Two-Story Waffle–Flat-Plate Structure

A two-story waffle–flat-plate reinforced-concrete model structure was subjected to cyclic loading simulating a severe earthquake. The test structure was a one-third-scale model that represented a structural system that is common in Mexico City and that had a high rate of damage during the 1985 Mexico earthquake. The structure was designed with widely spaced column transverse reinforcement and with closed stirrups in the slab solid heads around the columns. At failure, the specimen showed severe flexural and shear damage in columns, and large flexural distress in waffle slabs. The structure had a low lateral stiffness, which is overestimated by current building code provisions. Results also demonstrated that the specimen had relatively low energy-dissipation and displacement-ductility capacities, which are commonly associated with poor seismic behavior during strong earthquakes. It is considered that a satisfactory seismic behavior in terms of lateral stiffness and strength can only be attained by the addition of bracing or structural walls.

Mechanical characteristics and seismic response of divertor support structure with locking system

A full-scale divertor support structure with hydraulic jacks was fabricated, and mechanical and seismic loading tests were carried out. This mock-up structure has four hydraulic jacks for locking the divertor plate and three jacks for lifting. The weight of the divertor plate model is 1.2 tons, similar to practical plate. The mechanical test results show that the divertor locking system provides high positioning tolerance within 0.3 mm and 0.2 mm in the toroidal and vertical directions respectively. To confirm the seismic response of the hydraulic cotter, a dynamic loading test was carried out. The fundamental frequency of 27 Hz is the mode of toroidal direction vibration, and is relatively high compared with the predominant earthquake frequencies. No damage of the hydraulic jacks appears under seismic loads. According to the results of mechanical and dynamic loading tests, the feasibility of the divertor support structure is verified.

Simulated seismic load tests on reinforced concrete columns : S. Watson & R. Park, Journal of Structural Engineering — ASCE, 120(6), 1994, pp 1825–1849

Simulated seismic load tests on reinforced concrete columns : S. Watson & R. Park, Journal of Structural Engineering — ASCE, 120(6), 1994, pp 1825–1849

Simulated Seismic Load Tests on Reinforced Concrete Columns

Simulated seismic load tests conducted on 11 reinforced concrete columns are described. The columns had a 400‐mm (15.7‐in.) square or octagonal cross section and contained various quantities of transverse reinforcement. The columns were subjected to either low, moderate, or high axial compressive loads and to reversible quasi‐state lateral loads that simulated severe earthquake loading. The tests were conducted to check an analytical approach for the determination of the available flexural ductility and the enhancement of flexural strength of columns with various levels of transverse confining reinforcement. The analytical approach for determining the quantities of transverse reinforcement required for confinement is shown to be conservative and to lead to equations more suitable for the design of transverse reinforcement for confinement than current code equations. Conclusions are also reached concerning the required length of the confined region in the potential plastic‐hinge zones of reinforced concrete columns.

Seismic Load Tests on Reinforced Concrete Columns Strengthened by Jacketing

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Assessment and Retrofit of a Reinforced Concrete Bridge Pier for Seismic Resistance

Typical structural deficiencies in some reinforced concrete bridges designed for seismic resistance before current seismic codes were introduced are briefly outlined. Results of simulated seismic load tests conducted on the critical region of a reinforced concrete bridge pier designed in New Zealand in 1936 are presented. The tests involved the application of compressive axial loading and quasi-static cyclic lateral loading to a full-scale subassemblage representing the column-cap beam region of the as-built pier. Subsequent loading tests were conducted on the pier retrofitted mainly by the addition of steel plates welded to the ends of the plain round longitudinal bars to improve anchorage. The improved bar anchorage enabled the pier to develop its full theoretical flexural strength, but the considerable loss of stiffness due to bond degradation which occurred in the initial test on the as-built pier was not restored.

Single frequency seismic loading tests on pressurized branch pipe intersections machined from solid

Four CNC machined, equal-thickness branch pipe intersections ( dm/ Dm = 1 and 0.746) have been tested under conditions of internal pressure, simulated seismic loading that induced resonant in-plane run pipe bending and, in one case, a superimposed gravity stress. The manufacturing method and testing conditions are described and the behaviour of the branches is reported. The strain responses of the components show that ratchetting is clearly significant while the response moment data suggest that collapse may not be the failure mechanism under these loading conditions. Failure for all components occurred by cracks on the flanks in the branch hoop stress direction just above the junction.

Simulated Seismic Load Tests on Prestressed Concrete Piles and Pile-Pile Cap Connections

The results of tests conducted in New Zealand on prestressed concrete piles and pile-pile cap connections subjected to simulated seismic loading are summarized. The piles were of prestressed pretensioned concrete with a 400 mm (15.7 in.) octagonal cross section and contained spiral reinforcement. The pile caps were of reinforced concrete. The range of pile-pile cap connection details tested included piles with ends embedded in the cap either with or without the ends of the longitudinal steel exposed, and the use of longitudinal steel dowel bars. The test results showed that well detailed prestressed concrete piles and pile-pile cap connections are capable of undergoing large post-elastic deformations without significant loss in strength when subjected to severe seismic loading.