Precast Cladding Research Articles

Composite behaviour of fibre-reinforced concrete sandwich panels with FRP shear connectors

The flexural behaviour of a precast concrete sandwich panel constructed of high performance fibre reinforced concrete wythes and foam insulation, connected together with carbon fibre reinforced polymer grid connectors, is investigated in this paper. This study tests and analyses the thin concrete cladding system which omits conventional steel reinforcement, the use of which requires concrete cover to the reinforcement layer that typically dictates the minimum thickness of the concrete wythes. A total of four full height panels are constructed in a precast concrete facility and are tested by way of three point bending. To complement the experimental study, finite element analysis is used to better understand the bending behaviour beyond what was discerned from the results obtained through experimentation. The experimental results showed that the thin concrete sandwich panel is a plausible solution for precast cladding systems with ultimate moment capacities in excess of those required to meet design wind loads. Ductile behaviour was observed in all of the four tested panels as a result of the high dosage of small 24 mm coated glass fibres used in the mix design for the concrete wythes. The experimental results showed no evidence of the FRP grid connector providing any significant degree of composite action. Finite element analysis suggests that this is due to, one or a combination of, the insulation′s stiffness being too low or because the tensile members in the grid connector being under an initial compressive strain and not fully engaged during initial loading.

Damage and collapses in industrial precast buildings after the 2012 Emilia earthquake

The present paper presents a complete and commented collection of cases of damage and collapse in reinforced concrete (RC) precast industrial buildings, observed by the authors during a series of field surveys after the 2012 Emilia earthquake in Northern Italy. They were selected among a total of about 2000 industrial RC precast buildings, whose structural characteristics and damage have been collected in a large database by the authors.The main causes of the collapses were vulnerabilities related to the structural characteristics of Italian precast buildings not designed with seismic criteria. In particular, these structures were typically built as an assembly of monolithic elements (roof elements, main and secondary beams, columns) in statically determinate configurations. The most common failure causes identified were: the absence of mechanical connectors between precast monolithic elements, the interaction of structural elements with non-structural walls, the insufficient column bending capacity, the rotation of pocket foundations, the inadequacy of connections of external precast cladding walls to bearing elements (columns and beams), the overturning of racks in buildings used as warehouses or in automated storage facilities.

Effects of Precast Cladding Systems on Dynamic Characteristics of Steel Frame Buildings by Ambient and Free Vibration Tests

Full-scale tests on a one-story steel frame structure with a typical precast cladding system using ambient and free vibration methods are described in detail. The cladding system is primarily composed of ALC (Autoclaved Lightweight Concrete) external wall cladding panels, gypsum plasterboard interior linings, and window glazing systems. Ten test cases including the bare steel frame and the steel frame with addition of different parts of the precast cladding system are prepared for detailed investigations. The amplitude-dependent dynamic characteristics of the test cases including natural frequencies and damping ratios determined from the tests are presented. The effects of the ALC external wall cladding panels, the gypsum plasterboard interior linings, and the window glazing systems on the stiffness and structural damping of the steel frame are discussed in detail. The effect of the precast cladding systems on the amplitude dependency of the dynamic characteristics and the tendencies of the dynamic parameters with respect to the structural response amplitude are investigated over a wide range. Furthermore, results estimated from the ambient vibration method are compared with those from the free vibration tests to evaluate the feasibility of the ambient vibration method.

Condensation Problems in Precast Concrete Cladding Systems in Cold Climates

Abstract The use of precast concrete panels as a cladding material can provide an economical and attractive method to enclose contemporary buildings. In cold climates, improper detailing or inappropriate construction of precast clad walls can result in widespread water problems due to condensation forming within the wall construction. Condensation may form at the interior of the wall assembly due to inadequate protection against air flow through the wall, such as exfiltration of warm, moist indoor air, or by infiltration of cold outdoor air reaching the interior wall components. The condensation within the wall assembly can also be caused by water vapor diffusion into the wall from the building interior. In addition, inadequate separation and/or insulation between precast panels and adjacent cladding components, such as windows, curtain wall, or metal framing components, can result in surface condensation on these wall elements. The moisture from condensation can cause extensive damage to finish materials, including insulation and gypsum wallboard; can result in corrosion and deterioration of metal components, such as structural connections and metal wall framing; and may result in mold and mildew. This paper will (1) present examples of precast clad building wall construction where significant condensation problems have occurred; (2) discuss typical causes of condensation in precast clad buildings in cold climates; (3) review design considerations to reduce the potential for condensation in new buildings; and (4) present repair methods to address condensation in existing buildings.

Perceptions of Precast Concrete Cladding in the UK Market

Precast concrete cladding accounts for about 5% of the UK cladding market, despite its performance and aesthetic advantages over competitor materials. A study of perceptions of precast concrete cladding (PCC) was undertaken with the aim of assessing awareness and use of PCC in the UK in its most popular applications (i.e. commercial and residential buildings), in addition to identifying possible directions for future research and development. Interviews were undertaken with participants who were familiar with PCC (predominantly on commercial buildings) and who had had experience of stone-faced, reconstituted stone, cast stone and brickfaced precast cladding. The interviewees identified major opportunities/impelling factors thought to encourage the use of PCC and major barriers/impeding factors thought to discourage its use. A simple scoring system was used to combine the number of responses for each factor with the relative importance assigned to each response. ‘Buildability’, ‘quality’ and ‘speed of erection’ were the most highly rated impelling factors whereas ‘lead time’, ‘initial cost’ and ‘logistics and cranage’ were the most highly rated impeding factors. Developments in production techniques, finishes and sustainability performance together with the need for improved marketing of the product were identified by interviewees as key activities to improve PCC's share of the UK cladding market.

Renovation of Poindexter Office Building Kansas City, Missouri

Precast and prestressed concrete played a prominent role in renovating two old deteriorated buildings in Kansas City, Missouri, into a single state-of-the-art office facility. The solution required the demolition of part of one building (Gatlin Building) with a stabilizing vertical core using a precast, prestressed structural frame. When this structural work was completed, the exterior facade of the Gatlin Building was clad with architectural precast panels using a thin brick in-fill to match the building's original appearance. Note that the larger Poindexter Building required significant masonry tuckpointing on the exterior surface but no precast cladding. The precast solution saved $750,000 on this project. The article describes the major features of the repair program.

Effect of Precast Cladding on the Wind Load Response of Tall Building Structures

The results of a theoretical investigation of the effects of architectural precast concrete cladding panels on the static wind load response of representative tall building structures are presented. On the basis of deductions from a previously reported detailed study of a cladding panel interacting with a moment-resisting frame, analyses of complete clad structures are made with the panels represented in the models of the structures by equivalent bracing members. The displacements, deflected shapes and member forces resulting from static wind load three-dimensional analyses of the structures, with and without the effects of the panels, are compared and discussed. In providing additional stiffness to the structures, the cladding panels attract loads, some of which exceed the design loads of the panels. The capabilities of the panels and their connections to withstand the induced loads are also discussed. Finally, a procedure for the analysis of the buildings braced by precast concrete cladding panels is proposed.

Analytical Studies of Building Cladding

Four different analytical models are presented for architectural precast cladding on highrise buildings. An interstory shear stiffness model, an incremental failure model, a hysteresis model and a slotted connection model were used to study cladding performance from the linear elastic range up to failure. The models were added to a finite element model of the structural frame of a 25-story steel frame office building to account for the lateral stiffening effect of the building facade. Cladding stiffness values were based upon a comparison of measured and computed vibration frequencies for the building. Results of the study include peak interstory drift plots and a representation of the cladding failure state for the case of moderate earthquake ground motion input. Cladding stiffness was found to have a substantial effect on building dynamic properties and linear seismic response.