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International Concrete Abstracts Portal

Showing 1-10 of 17 Abstracts search results

Document: 

SP211-16

Date: 

February 1, 2003

Author(s):

J. Warner

Publication:

Special Publication

Volume:

211

Abstract:

ACI 437 provides requirements for the performance of large scale structural load tests. These include mapping and monitoring cracks, shoring, and actual application of the load in a minimum of four separate increments. Any walls or other improvements that might provide support to the element being evaluated must be cut free. Deflection is to be monitored and load deflection curves prepared for each increment, and the full load is to remain in place for a minimum of 24 hours. Straightforward as these requirements appear, they can present a daunting task for those actually conducting the test. Where reaction is available for simple tests such as for beams and girders, either hydraulic jacks or pneumatic bags can be used to supply the load. Where large horizontal areas such as floors are involved, such simplicity is often not possible and some form of physical mass must be used. In areas that are open, the load can be applied with a crane, but on the interior of structures it must often be applied by hand or with the aid of small handling equipment, which severely limits the choice of load media. Whereas load tests are usually designed by structural engineers, the actual application is performed by construction workers. In order to assure optimal performance, it is imperative that both work together during the design as well as the application. The schedule and logistics of the loading operation must be well thought out prior to the actual work. Obviously, safety of the overall operation must be assured. Consideration must be given to not only the potential failure of the element being evaluated, but damage to other portions of the structure as well. This can include overloading of other elements during movement and handling of the load media, or damage by flooding where water is used. The logistics of load tests are discussed in detail, including preloading surveys and documentation, provision of shoring and other required preparation of the test area, selection of the load media and its application, and the required monitoring and control.

10.14359/12597


Document: 

SP211-15

Date: 

February 1, 2003

Author(s):

G. Mullins, R. Sen, R. Sosa, and M. A. Issa

Publication:

Special Publication

Volume:

211

Abstract:

The construction of submerged or partially submerged pile caps often requires the use of a cast-in-place unreinforced slab referred to as a seal slab. This slab is cast underwater around piling and inside sheet pile walls to form the bottom of a cofferdam and withstand upward hydrostatic pressure. As the seal slab is only used for a relatively short period of time during placement of the reinforcing steel and concreting, its design has received little attention in refinement tending toward conservatism. Therein, the magnitude of available bond strength between the seal slab and piling to resist the uplift pressure has been poorly quantified and largely underutilized. This paper presents experimental results from 32 full-scale tests conducted to define the interface bond between cast-in-place concrete seal slabs and piling (sixteen 356 mm square prestressed concrete piles and sixteen 356 mm deep steel H-piles). Three different concrete placement environments--dry, fresh water, and bentonite slurry--were evaluated using the dry environment (where no fluid had to be displaced by the concrete) as the control. The effective seal slab thickness was varied between 0.5d and 2d, where d was either the width or depth of the pile section. Both "soil-caked" and normal, clean pile surfaces were investigated. Additionally, four of the sixteen concrete piles were cast with embedded gages located at the top, middle and bottom of the interface region to define the shear distribution. The study showed that: (1) significant bond stresses developed even for the worst placement environment, and (2) the entire embedded surface area should not be used in calculating the pile-to-seal slab bond capacity. Current design values in the Florida Department of Transportation specifications reflect the findings of this study.

10.14359/12596


Document: 

SP211-14

Date: 

February 1, 2003

Author(s):

A. G. Sherif and W. H. Dilger

Publication:

Special Publication

Volume:

211

Abstract:

A unique test set-up is described which facilitates the testing of full scale continuous reinforced concrete flat slabs with spans up to 6 m under vertical loading. In the past, tests were done either on full scale isolated slab-column connections or on reduced scale slab systems. Both test methods are not ideal to establish the shear behaviour of flat slabs. The test set-up which was designed and built at the University of Calgary avoids the major sources of error by providing realistic boundary conditions along lines of zero shear of part of a slab centered about an exterior column and the adjacent interior column. The boundary conditions are created by boundary frames which allow vertical displacement but no rotation along the lines of zero shear. By using this set-up the effect of moment redistribution as well as membrane action can be determined. In this paper the boundary frames and their effects on the behaviour of the tested slab were evalutated experimentally and theoretically by finite element analysis. Based on the results, modifications to the original boundary frames were made.

10.14359/12595


Document: 

SP211-13

Date: 

February 1, 2003

Author(s):

Y. J. Chiou, Y. W. Liou, Y. L. Mo, F. P. Hsiao, M. S. Sheu, and C. T. Shih

Publication:

Special Publication

Volume:

211

Abstract:

The seismic performance of repaired reinforced concrete framed shear walls with openings is quantitatively investigated in this study. Ten large-scale repaired framed wall specimens subjected to reversed cyclic lateral loading had been tested, and a simple prediction model was proposed to analyze the test specimens. According to the failure mechanism of the prototypes, three specimens were repaired with epoxy and the other specimens were repaired by various methods, such as enlargement of the column size, additon of wing walls adjacent to the boundary columns, jacket addition to the joints of beam-column, and use of steel bracings on the wall. The experimental results show that the maximum strength of framed shear walls repaired with epoxy is close to the prototype specimen. However, their lateral displacement obviously increases and rigidity tends to be smaller. The maximum strength and energy dissipation of most other repaired specimens are greater than those of the prototype specimens, and their cyclic resistance capacities are better than those of the prototypes.

10.14359/12594


Document: 

SP211-12

Date: 

February 1, 2003

Author(s):

G. Al-Chaar, G. E. Lamb, and M. A. Issa

Publication:

Special Publication

Volume:

211

Abstract:

Door or window openngs in masonry infill panels can reduce the lateral strength and stiffness on infill-frame systems. In an effort to study these effects, a series of tests were conducted on half-scale test structures consisting each of three stories and three bays. Infill panels of the control structure were solid with no openings while panels of the second structue were perforated with window and door openings of varying size and location. The test structures were designed to replicate typical building practice of the early 1950's with little or no seismic detailing of frame reinforcement. The test structures were subjected to cyclic in-plane lateral forces to study their strength and deformation capacity under seismic excitation. The cyclic loading was chosen to apply displacemet demands on the structures, representative of those that are expected to occur during strong earthquake motions. Test results discussed in this paper are presented in terms of observed changes in strength, stiffness and deformation capacity of both test structures. Damage patterns and propagation of cracks in the concrete frame and masonry infill during loading are illustrated and discussed in terms of measured histories of force and deflection. Experimental results supported by analytical studies are used to estimate overall reductions in strent, deformation capacity and stiffness due to the presence of openings in the panels.

10.14359/12593


Document: 

SP211-11

Date: 

February 1, 2003

Author(s):

B. M. Shahrooz, G. Tunc, and J. T. Deason

Publication:

Special Publication

Volume:

211

Abstract:

A common connection between steel outrigger beams and reinforced concrete walls involves a shear tab welded onto a plate that is conncected to the wall through headed studs. Previous studies focused on behavior of headed studs have ignored a number of major issues, e.g., (a) cyclic behavior of studs under multiple loads was not studied, (b) the concrete around studs was not reinforced or the reinforcement did not represent what would commonly be present in wall boundary elements, and ( c) effects of cracking and yielding of reinforcement around headed studs were not included. To remedy these deficiencies and to develop seismic design guidelines for outrigger beam-wall connections, a coordinated experimental and analytical research program was conducted. Through a number of tests, involving a wall subassembly and an outrigger beam, the behavior of studs subjected to cyclic tension and constant gravity shear was examined, and a design methodology was developed to control the mode of failure. To further investigate the cyclic performance of outrigger beam-wall connections and to validate the design guidelines, two 1/4-scale walls with two outrigger beams were tested. The wall reinforcement details around the connection were selected according to the anticipated level of cracking and plastic hinge formation. The two outrigger connections were subjected to constant gravity loads and cyclic tensile forces, which were controlled as a function of the wall shear. This paper provides an overview of the experimental program, testing procedures, relevant test results, and design implications. The design methodology followed in this research resulted in connections that could develop and exceed the design forces despite extensive cracking and yielding of wall reinforcement around the headed studs. Presence of heavily confined wall boundary elements around headed studs increases the capacity. A simple method to account for strengthening effects of boundary elements was develped. This model could accurately assess the expected mode of failure and capacity of outrigger beam-wall connections. Test results indicate that the outrigger beam transfers the majority of diaphragm forces directly to the core wall, and participation of floor slab toward transferring the loads to the core wall is negligible. Therefore, floor diaphragm-wall connections can be based on simplle details, and designed to resist only gravity loads.

10.14359/12592


Document: 

SP211-10

Date: 

February 1, 2003

Author(s):

Y. J. Chiou, Y. L. Mo, F. P. Hsiao, Y. W. Liou, and M. S. Sheu

Publication:

Special Publication

Volume:

211

Abstract:

The structural behavior of reinforced concrete framed shear walls subjected to reversed cyclic lateral loading were studied by testing ten large-scale specimens, including high-, middle-, and low-rise shear walls. An analytical model was also proposed to predict the behavior of the tested specimens. The parameters of concrete strength and vertical stell ratio of walls were investigated. The predicted maximum load and corresponding displacement, and load-displacement curves satisfactorily agreed with the experimental results. In addition, the experimental results showed that the failure mode of high-rise shear walls was flexural; their ductility factors were greater than those of low-rise shear walls; their displacements were also greater. The mid-rise shear walls failed by a combination of both flexure and shear. The experimental results also showed that the maximum loads were greater for specimens with higher concrete strength or higher verical stell ratio. The vertical stell ratio of walls has more significant effect on flexure-predominant walls. However, it is insensitive to shear-critical walls. It was found that the simple model develped from previous small-scale tests could not closely reflect the experimental results of all specimens. This suggests that the size effect needs to be taken into account in the analytical model.

10.14359/12591


Document: 

SP211-09

Date: 

February 1, 2003

Author(s):

K.-C. Tsai and M.-L. Lin

Publication:

Special Publication

Volume:

211

Abstract:

Axial compression test results for square RC columns incorporation Taiwanese construction practice in the placement of stirrups and various kinds of jacketing schemes are presented. The jacketing schemes include circular, octagonal and square shapes. The jacketing materials vary from stell plate to carbon fiber reinforced polymer (CFRP) COMPOSITES. It is found from the monotonic axial load test results that the failure mode of the benchmark non-retrofitted specimen is identical to that observed in real damage cases subsequent to the 1999 Chi-Chi Taiwan earthquake. The benchmark specimen developed its design strength but a non-ductile failure mode occurred soon after the peak load was reached. Among the retrofitted specimens, the steel jacketed specimens exhibit not only greatly enhanced load carrying capacity but also excellent ductility performance. Test results show that CFRP sheets are effective in increasing the column axial strength, but the sheets could fracture suddenly in high strain conditions due to their brittle material characteristics. Test results indicate that CFRP sheet wrapping in general is not as effective as steel jacketing in improving the axial ductility capacity of RC columsn. However, the proposed octagon-shaped CFRP wrapping scheme exhibits an improved performance compared to rectangular-wrapped columns using the same layers of CFRP sheets. Tests confirm that all octagonal stell or CFRP jacketed specimens have axial load capacities more that 2 time the nominal capacity.

10.14359/12590


Document: 

SP211-08

Date: 

February 1, 2003

Author(s):

F. J. Perez, S. Pessiki, R. Sause, and L.-W. Lu

Publication:

Special Publication

Volume:

211

Abstract:

This paper reports on the experimentally and analytically observed behavior of unbounded post-tensioned precast concrete walls under static monotonic and cyclic lateral loads. Results show that the limit states that characterize that lateral load behavior of the walls occur as anticipated in the design of the walls and at force and drift levels predicted by the analytical model, except that the experimentally observed drift capacity exceeds the drift capacity predicted by the analytical model. Cyclic lateral load results how that unbonded post-tensioned precast walls can undergo significant nonlinear lateral drift without significant damage, and can maintain their ability to self-center, thus eliminating residual lateral drift.

10.14359/12589


Document: 

SP211-07

Date: 

February 1, 2003

Author(s):

P. Paultre, J. Proulx, S. Mousseau, T. Prevoust, and C. Savard

Publication:

Special Publication

Volume:

211

Abstract:

Full-scale dynamic tests provide valuable information on the characteristics of building structures that can be used to calibrate finite element models, to rate modeling techniques, to determine damage levels, and to evaluate design and detailing requirements for seismic loading. These tests usually provide the most complete information about the dynamic properties of a structure, I.e., mass, stiffness, and modal damping. In the paper, the dynamic behavior of a two-story reinforced high-performance concrete building is evaluated by repeated pseudo-dynamic tests, during which increasing seismic loads are applied and with resulting greater levels of permanent damage to the structure. In order to monitor the level of damage, a series of successive forced-vibration tests are also carried out at each step of the process and are used to track changes in the key dynamic properties of the building. The paper presents the design of the test structure, the series of forced vibration and pseudo-dynamic tests, the evaluation of the dynamic characteristics of te undamaged structure prior to and after pseudo-dynamic tests, and the evaluation of the damages to the building.

10.14359/12588


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