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International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

Document: 

SP-339_02

Date: 

March 1, 2020

Author(s):

Saeed Fathali, Bret Lizundia, and Francisco Parisi

Publication:

Symposium Papers

Volume:

339

Abstract:

This paper summarizes the benefits and challenges of implementing performance-based seismic design (PBSD) for two concrete buildings of the Lower Sproul Plaza Redevelopment Project in one of the busiest areas of the UC Berkeley campus. The project included new construction of Eshleman Hall and the additions to Martin Luther King (MLK) Hall, and the seismic retrofit of the existing MLK Student Union as a result of the expansion. The peer-reviewed PBSD implemented three-dimensional nonlinear response history analyses at two levels of seismic hazard. The analytical simulations using pairs of near-fault ground motions, scaled to match the site-specific spectrum, were intended to establish the expected seismic behavior of the buildings under rare and frequent earthquakes. The choice of PBSD over code-prescriptive procedures was prompted by multiple layers of complexity of the project. Several challenges including those related to the horizontal and vertical irregularities, or connecting new and existing concrete buildings with different lateral force-resisting systems would have made a code-prescriptive design a cumbersome analytical endeavor without providing reliable insight about the expected seismic behavior of the buildings. The PBSD, however, proved a powerful framework to design for a reliably predictable seismic behavior with sufficient ductility, and a designated ductile hinge zones with sufficient confinement and shear capacity. The PBSD methodology also enabled the designers to avoid unnecessary conservatism to deal with the complexities, when designing drift- and acceleration-sensitive elements including the cladding system. Finally, the PBSD methodology allowed the design to consider all potential modes of failure of concrete elements retrofitted by FRP material including the debonding failure between FRP material and substrate.

DOI:

10.14359/51724690


Document: 

SP-339_04

Date: 

March 1, 2020

Author(s):

Mark Sarkisian, Eric Long, and David Shook

Publication:

Symposium Papers

Volume:

339

Abstract:

Performance based seismic design (PBSD) has created new opportunities for enhanced performance, improved cost efficiencies, and increased reliability of tall buildings. More specifically, flexibility with initial design methods and the utilization of response history results for design, not just verification, have emerged. This paper explores four refined design methods made available by the employment PBSD to influence seismic performance and identify areas of importance. First is the initial proportioning of reinforcement to encourage plastic hinge behavior at specific locations. Second is the initial proportioning of wall thicknesses and reinforcements to encourage a capacity-based design approach for force-controlled actions. Third is the mapping of observed strain demands in shear walls to specific detailing types such as ordinary and special boundary zones. Fourth is an efficient envelope method for the design of foundations. Through these design methods, initial proportioning can be conducted in a more refined way and targeted detailing can result in cost savings. A case study of a recently designed high-rise residential building demonstrates that cost savings can be achieved with these methods.

DOI:

10.14359/51724692


Document: 

SP-339_13

Date: 

March 1, 2020

Author(s):

Giulio Leon Flores, Reza V. Farahani, Hussien Abdel Baky, and Paul C. Rizzo

Publication:

Symposium Papers

Volume:

339

Abstract:

This paper presents the structural testing of four full-scale reinforced concrete beam-column connections, extracted from reinforced concrete buildings that suffered minor damage from the Canterbury Earthquakes in New Zealand. Two connections are extracted from a moment frame comprising the secondary seismic-resisting system of a concrete building; two are extracted from moment frames of the primary seismic-resisting systems of a precast concrete building. The seismic performance of the connections is evaluated from the test results and compared to recommendations in ASCE 41 (2013) for the evaluation of existing buildings. Due to the size of the specimens, the tests were stopped when the actuator reached its maximum stroke, at interstory drifts between 2.5% and 3. The cast-in-place connections showed moderate damage after the tests, at ductility levels above 2.9, and their initial lateral stiffness was approximately 80% of the lateral stiffness of numerical models representing the undamaged state. The precast connections exhibited extensive damage along the construction joint between the precast beams and the cast-in-place beam-column joint, at ductility levels above 3.4. The plastic mechanism was governed by sliding shear of the precast beams, which caused severe stiffness deterioration at the end of the tests. The measured stiffness in this case was approximately half of the stiffness predicted by numerical models in which nonlinearity is considered in the form of flexural plastic hinges only. This unexpected behavior is attributed to the low quantity of reinforcing steel crossing the construction joint, and presumably earthquake damage.

DOI:

10.14359/51724704


Document: 

SP-339_12

Date: 

March 1, 2020

Author(s):

Burkhart Trost, Harald Schuler, and Bozidar Stojadinovic

Publication:

Symposium Papers

Volume:

339

Abstract:

Sliding failure of reinforced concrete shear walls was observed after the Chilean earthquakes in 1985 and 2010, during shaking table tests, and in many quasi-static cyclic shear walls tests. Sliding may occur along cold joints or flexural cracks that remain open due to permanent deformations induced during cyclic loading. If it occurs, sliding can significantly reduce the horizontal force resistance and change the deformation mechanism of reinforced concrete shear walls, and thereby markedly affect the seismic performance of shear wall buildings. This study provides the interaction diagrams intended to help reinforced concrete shear wall designers exclude the sliding failure mode. Regions where sliding, shear, and flexural failure modes are expected are delineated according to the shear wall shear span to length ratio, the axial force, the horizontal and vertical reinforcement ratios, and the concrete strength. These interaction diagrams are derived using a cyclic reinforced concrete wall response model that considers flexure, shear and sliding load-deformation relationships and the interaction between them. The inter-action diagram is used to develop design recommendations on how to avoid the sliding failure of reinforced concrete shear walls under earthquake loading.

DOI:

10.14359/51724703


Document: 

SP-339_07

Date: 

March 1, 2020

Author(s):

Tom C. Xia and Doug Lindquist

Publication:

Symposium Papers

Volume:

339

Abstract:

Performance based seismic design (PBSD) has been widely used for tall buildings as a code alternative design method for concrete shear wall structures. However, most PBSD studies are done for buildings taller than 240’ (73 m). Very few studies have been done for buildings shorter than 240’ (73 m) because PBSD is not required for buildings under 240’ (73 m). It is unclear if and how the shear demand increases observed in typical PBSD analysis should be applied to buildings shorter than 240’ (73 m). This study includes two buildings in the Seattle area that are designed per current codes. The study compares the shear demands predicted by the elastic analysis method with the demands predicated by the nonlinear time history analysis used in PBSD method. The intent of this study is to examine the merits of the new Seattle requirement using a factor to amplify the shear demand for buildings designed at code level and for the building height in the range of 160’ (48.8 m) to 240’ (73 m). It also explores the proper factor to be used in ACI 318 to determine the shear wall capacity.

DOI:

10.14359/51724698


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