Precast Concrete Parking Structures Research Articles

Seismic fragility assessment of multistory precast concrete parking structures

In this study, fragility and collapse mechanisms of multistory precast concrete parking structures were assessed. The variation of a set of structural parameters was considered, including shear stiffness and tensile stiffness of connectors, number of stories, and two orthogonal directions of the seismic action. A probabilistic analysis based on fragility curves was regarded a robust technique for assessing the influence of these parameters on the expected seismic performance. Additionally, fragility curves were obtained using the SPO2FRAG procedure. The results indicate that variation of the considered parameters significantly affects the seismic response and seismic fragilities of precast concrete parking structures.

Verification of diaphragm seismic design factors for precast concrete parking structures

A new seismic design methodology was proposed for precast concrete diaphragms. This methodology adopts seismic design factors applied on top of current diaphragm design forces. These factors are aimed to produce diaphragm design strengths aligned with different seismic performance targets. These factors were established through extensive parametric studies. These studies used a simple evaluation structure with a single-bay rectangular diaphragm. The simple evaluation structure is suitable for establishment of the design factors over comprehensive structural geometry and design parameters. However, the application of the design factors to prototype structures with realistic layouts requires further verification and investigation. This paper presents diaphragm design of several precast concrete parking structures using the new design methodology and verification of the design factor through nonlinear dynamic time history analyses. The seismic behavior and performance of the diaphragm were investigated for the precast concrete parking structures. It was found that the design factor established for the new design methodology is applicable to the realistic precast concrete parking structures.

Project Spotlight: Hollow-core structural flooring saves time on Massachusetts mixed-use project

The Assembly Row mixed-use complex in Somerville, Mass., features 600,000 sq.ft. (56,000 sq.m.) of retail space, 2.8 million sq.ft. (260,000 sq.m.) of office space, and 1800 residential units. Block 5A of the project, called the Alloy Residences and Autograph Collection Hotel, features 122 high-end condo¬miniums in a 13-story building with an underground parking structure. Block 6 features a 20-story, 273-unit apartment building, along with a six-story, 174-unit wooden structure and a seven-story, 650-car precast concrete parking structure. For several reasons, designers specified precast concrete hol¬low-core for the structural flooring systems in both block proj¬ects. They selected J. P. Carrara & Sons Inc. of Middlebury, Vt., for the work.

Long-term lateral deflection of precast, prestressed concrete spandrel beams

Slender precast concrete spandrels are used to increase cost effectiveness of precast concrete parking structures. They reduce the number of column lines in building floor plans and the number of elements to transport and erect. However, these spandrels can be prone to larger deflections, as the increased slenderness can reduce sectional stiffness. Design of these structures should also consider vertical and lateral deflections because of the eccentric loading transferred from the deck double-tee beams. In this paper, the authors provide realistic estimates of long-term deflections for the next generation of spandrels. They also examine the sensitivity of long-term deflection to parameters such as spandrel type, span length, creep and load eccentricity. The results of their numerical study included the finding that long-term lateral deflections are less than corresponding lateral deflections.

Design on a Total Precast Concrete Parking Structures

The construction noise and wasted material of total precast concrete structure are reduced by factory production of components and assembled construction, green construction can be achieved.Combined with the first total precast parking structure in China, the connection modes of precast components are introduced,such as between precast columns and precast columns, between precast columns and precast inverted beams, between precast double tee slabs and precast columns or precast shear wall, which can provide a reference for the design of similar engineering.

Analytical investigation of vehicle fires in precast concrete parking structures

In this paper, the authors examine the effect of vehicle fire loads (temperature and heat flux histories) in precast concrete parking structures. Using a computational fluid dynamics program, analyses were conducted, using such variables as structure geometry and fire characteristics. Heat flux histories were used as input to finite element analyses to determine temperature rise in the prestressing strand of double-tee floor members. Estimates of reduction of steel strength were derived using the increased prestressing steel temperatures. Nine fire scenarios were considered; within them, vehicle fires were found to cause only minor reductions (maximum of 15%) in the strength of the prestressing steel of double-tee floor members. The authors concluded that the geometry of a precast concrete parking structure can have a significant effect on the movement of combustion gasses in the structure. They also concluded that multivehicle fires cause greater increases in prestressing steel temperatures (and thus greater reductions in steel strength) than do single-vehicle fires, and that large multivehicle fires lead only to minor reductions in prestressing steel strength.

Volume-change response of precast concrete buildings

This paper summarizes the findings of the authors' recent study on the volume-change response of precast concrete buildings. The objective of this research was twofold: to develop a better understanding of volume-change movement and forces based on measured performance of precast concrete parking structures and calibration to analytical models and to recommend revised design procedures that reflect this understanding and account for the influence of flexible connections. The primary research tasks included field monitoring and finite-element analyses of actual structures as well as evaluation of the predictability of volume-change forces. The research revealed that deformations of flexible deck and spandrel connections change the deformation pattern and thereby substantially reduce volume-change movement and force at the lowest supported level, where volume-change forces are most significant. The study also developed new findings with respect to other volume-change parameters, including the thermal-expansion coefficient, the design temperature range, the degree of member softening due to creep and microcracking, and the load factor for volume-change effects. Design recommendations are provided for qualitative consideration of volume-change effects as well as quantitative analysis. Although the new research indicates that the procedures recommended in the PCI Design Handbook: Precast and Prestressed Concrete result in a conservative estimate of volume-change force, certain aspects of the PCI Design Handbook procedures were found to be unconservative. Therefore, the research findings should be considered in their entirety. The full research report is available from PCI.

Precast concrete parking structure lighting study

Among some members of the design community, there is a perception that lighting of precast concrete parking structures is not as efficient as lighting of posttensioned (PT) concrete parking structures. This perception occurs because it is assumed there is more light blockage from the closely spaced, precast concrete double-tee stems compared with wider spacing of beams in a PT concrete parking structure. This paper details a study performed to compare the lighting systems for precast concrete parking structures vs. PT concrete parking structures. The study indicates there is no difference in horizontal illuminance on the floor, or vertical illuminance on the perimeter walls, for identical lighting configurations in precast concrete and PT concrete parking structures. This conclusion requires that the bottom of each luminaire in the precast concrete parking structure is pendant-mounted and that the luminaires are no more than 6 in. above the bottom of the double-tee stem and centered between the 5 ft. double-tee stem spacing. The configuration of the 2 parking structures, the lighting configurations, the design methodology, and the results of the analysis are described.

Joints in Precast Parking Structures

This paper provides essential information to all stakeholders involved in the design, construction, and maintenance of a parking structure so that the investment involved in the facility will be optimized. Specifically, guidelines and recommendations concerning design, installation, and maintenance of sealant joints in precast concrete parking structures are presented and discussed.

Seismic Design Recommendations for Precast Concrete Diaphragms in Long Floor Span Construction

The paper Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms, published in the September-October 2003 PCI JOURNAL, presented the effect of structural dimension and construction detail on the capacity of precast concrete floor diaphragms, using parking structures as the prototype structure. Parallel research by the authors has established seismic demands for flexible diaphragm structures. In this paper, the findings of these two research steps are interpreted to propose design recommendations for precast concrete diaphragms in long floor span construction. These recommendations include provisions for diaphragm design strength, allowable flexibility, and ductility capacity based on seismic performance requirements. The provisions are incorporated into a design procedure employing performance-based design concepts. Application of the procedure is shown in a design example (Appendix B) for precast parking structure diaphragms. Research on this subject will continue over the next several years, with funding provided by both governmental and industry organizations.

Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms

The paper presents a study that focuses on diaphragms in precast parking structures. The analytical study presented represents an examination of precast concrete diaphragm capacity. In this stage, the global stiffness, strength, and ductility capacity of the diaphragm are examined with respect to structural dimensions and diaphragm reinforcing details. Many of the findings can equally be appplied to long-span precast concrete diaphgrams in general. The paper presents conclusions that pertain to internal load paths, service level behavior, and ultimate capacity of precast parking structure diaphgrams. The conclusions are qualitative in nature; the quantitative realizations of these conclusions are presented in a companion paper recommendations.

Parking Structures for Sprint World Headquarters - A Precast Bonanza

Twenty buildings and 14 precast concrete parking structures make up the new Sprint World Headquarters in Overland Park, Kansas. Creating such a massive complex required close communication among trades and coordination of all design elements. The parking structures were designed using two basic plans, for a three- and four-bay layout, with the only variation coming in ramp access and first-floor designs due to the sloping grade across the campus. The design used pocketed spandrels to eliminate ledges around the structures' perimeters and clean, simple finishes with ribbed details to add interest. The 14 parking structures were completed in slightly more than three years. This article presents the design considerations and construction highlights of the project.

New Seismic Design Provisions for Diaphragms in Precast Concrete Parking Structures

Diaphragm damage was observed in several precast concrete parking structures following the 1994 Northridge earthquake. In order to reduce the likelihood of damage in future earthquakes, the design provisions for chord reinforcement in diaphragms were modified in the 1997 Uniform Building Code, and new provisions for selecting web reinforcement were introduced in the 1999 ACI Building Code. This paper focuses on recent changes to the ACI Building Code and summarizes the results of a series of analyses of idealized buildings to demonstrate that diaphragms proportioned in accordance with earlier codes may be vulnerable to seismic damage. A diverse set of factors, including the orientation of precast members and the stress-strain characteristics of welded wire fabric, contributed to the observed damage in precast concrete parking structures.

Damage to concrete structures due to the 1994 Northridge earthquake

Observations on damage to concrete structures, due to the 1994 Northridge earthquake, are reported from a Canadian code perspective. Most of the damaged structures were older, nonductile, structures that do not conform to current design and detailing requirements. Concern is expressed about the seismic hazard of older Canadian structures having similar deficiencies. A significant number of parking structures suffered extensive damage and a number of precast concrete parking structures collapsed. Deficiencies in these structures include lack of proper diaphragm connections, a mix of gravity load columns with ductile framing, inappropriate number and distribution of shear walls, torsional effects caused by ramps, and the creation of short columns due to geometric features. This earthquake also demonstrated the deficiencies in connections of pre-1973 tilt-up structures. Key words: seismic design, earthquake, Northridge, structures, codes, concrete, precast concrete.