Precast Concrete Cladding Research Articles

Blast-resistant architectural precast concrete cladding for government buildings

Blast-resistant architectural precast concrete cladding for government buildings

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.

Development of analytical modeling for an energy-dissipating cladding panel

Modern earthquake-resistant design aims to isolate architectural precast concrete panels from the structural system so as to reduce the interaction with the supporting structure and hence minimize damage. The present study seeks to maximize the cladding-structure interaction by developing an energy-dissipating cladding system (EDCS) that is capable of functioning both as a structural brace, as well as a source of energy dissipation. The EDCS is designed to provide added stiffness and damping to buildings with steel moment resisting frames with the goal of favorably modifying the building response to earthquake-induced forces without demanding any inelastic action and ductility from the basic lateral force resisting system. Because many modern building facades typically have continuous and large openings on top of the precast cladding panels at each floor level for window system, the present study focuses on spandrel type precast concrete cladding panel. The preliminary design of the EDCS was based on existing guidelines and research data on architectural precast concrete cladding and supplemental energy dissipation devices. For the component-level study, the preliminary design was validated and further refined based on the results of nonlinear finite element analyses. The stiffness and strength characteristics of the EDCS were established from a series of nonlinear finite element analyses and are discussed in detail in this paper.

Finite Element Modeling of Reinforced Concrete Cladding Panels H.

Architectural precast concrete cladding systems are considered non-load bearing wall systems and are designed primarily to transfer their self-weight and out-of-plane lateral loads to the supporting building structure. They are typically not designed for significant structural in-plane forces resulting from cladding-structure interaction. In fact, modern earthquake-resistant design requires that these cladding panels be isolated from the lateral force-resisting system. Finite element technique was employed to study precast concrete panels and special modeling strategies were developed for panel connections to the structural frame. The precast concrete panel was designed to participate in the building lateral force-resisting. Finite element modeling techniques were adopted to better understand the strength and stiffness characteristics of these concrete cladding panels subjected to significant in-plane loading. Good correlation was obtained between finite element modeling results and existing experimental results. The analytical results were used to develop a simplified mathematical model that can be incorporated into suitable building models to evaluate its performance as a lateral force-resisting system to withstand earthquake-induced lateral loads.

Delayed Ettringite Formation (DEF) Within Pre-Cast Concrete Cladding Panels on a Mid-Rise Commercial Office Building: A Case Study

Abstract This paper will present the findings of multiple forensic investigations on a fourteen-story office building located in Houston, Texas. During our initial survey, widespread cracking was observed within the concrete cladding panels that warranted a more extensive investigation. Construction of the building was completed in 1985; 17 years prior to our initial investigation. Exterior cladding components are comprised of pre-cast concrete panels over each of the floor lines, with a continuous, structurally glazed, horizontal window system at each floor level. The cladding panels are nonload bearing, pre-cast concrete panels, installed at the time of the building’s construction. The concrete panels are attached to the structure via steel plates that are welded and bolted to the building’s frame. It is intended that this paper will present the results of observations made at the site over a period of several years, as well as the results of testing conducted to assist in the evaluation. A system was developed to locate and catalog the visible anomalies on the panels; including cracks, exposed steel, spalls, pop-outs, and efflorescence on the panels. Full-depth cores were removed from select panels to perform a petrographic analysis and scanning electron microscopy/energy dispersive x-ray microanalysis (SEM/EDXA). The results revealed the presence of delayed ettringite formation (DEF) and alkali-silica reactivity (ASR), with varying degrees of severity. Specific conclusions will be derived related to the conditions at this project and how these anomalies have affected the cladding system performance. Current repair and maintenance provisions will be discussed, in addition to the necessary recladding that will be required in the future. Recommendations will be developed regarding construction practices so that the cladding panel failure observed may be avoided in the future.

Modelling Trade Contractor Information Production

Design management research usually deals with the processes within the professional design team and yet, in the UK, the volume of the total project information produced by the specialist trade contractors equals or exceeds that produced by the design team. There is a need to understand the scale of this production task and to plan and manage it accordingly. The model of the process on which the plan is to be based, while generic, must be sufficiently robust to cover the majority of instances. An approach using design elements, in sufficient depth to possibly develop tools for a predictive model of the process, is described. The starting point is that each construction element and its components have a generic sequence of design activities. Specific requirements tailor the element's application to the building. Then there are the constraints produced due to the interaction with other elements. Therefore, the selection of a component within the element may impose a set of constraints that will affect the choice of other design elements. Thus, a design decision can be seen as an interrelated element—constraint—element (ECE) sub-net. To illustrate this approach, an example of the process within precast concrete cladding has been used.

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.

Study of the Effect of Near-Source Vertical Ground Motion on Seismic Design of Precast Concrete Cladding Panels

This paper is an attempt to determine the effect of vertical ground motion on design of precast concrete cladding panels in seismic regions, particularly in near-source areas. A spandrel-type precast concrete cladding panel is chosen for detailed study and assumed attached to a building in San Francisco. The seismic provisions of International Building Code 2000 and Uniform Building Code 1997 are used to determine the design forces on the cladding panel, which was originally designed as an example in a PCI publication. The provisions of the two codes are compared in light of their requirements related to vertical ground motion consideration and near-source effects. Results of recent research on the relation between vertical and horizontal ground acceleration components as a function of source-to-site distance are also used to illustrate an example of incorporating vertical spectral acceleration effects directly in load combinations. Finally, finite-element modeling and frequency analysis results of the sp...

Structural design for vibration isolation at Benaroya Hall

Vibration and noise isolation criteria, together with an urban site for the Seattle Symphony Hall, created unusual constraints for its structural design. A massive concrete mat foundation bridges and isolates the railroad tunnel running diagonally under the site. Two garage levels and an isolation level further separate the Auditorium from the tunnel, while 30 ft of unexcavated soil remain between the Auditorium and an adjacent underground transit station. Heavy concrete construction is used extensively to add mass for isolation. Concrete topping was added to the Auditorium roof for isolation, and double concrete walls surround the Auditorium. Exterior precast concrete cladding adds further mass and isolation. To speed construction time, the Auditorium balconies, including the inner walls which were cast to odd geometric shapes, are precast concrete. The Auditorium structure is isolated from the surrounding structure by an uninterrupted, 7-in.-wide joint, creating a ‘‘box within a box’’ The only structural connections to the Auditorium inner box are two types of special, natural rubber isolation bearings at its base. One bearing type takes gravity loads. The other type, initially prestressed, takes lateral loads. The need for bearing access under the base of the Auditorium created unusually shaped transfer girders.

TESTING OF ENERGY DISSIPATING CLADDING CONNECTIONS

Properly designed precast concrete cladding could potentially provide lateral stiffness, ductility, and energy dissipation for an overall building structure, especially during earthquakes. This paper describes a set of advanced connections that take advantage of the interaction between facade panels and structure (mainly due to horizontal interstorey drift) to dissipate energy, thereby reducing the response of the main structure. The results of an experimental program to characterize the hysteretic behaviour of advanced connections are presented. Design equations for the advanced connections are then calibrated against the test results, and the corresponding design charts are presented. It is anticipated that this research will lead to innovative ways of viewing the entire cladding system of a building.

Construction methods and planning

The book is intended to create authoritative introduction to the planning process and the factors that affect it. It is designed to be an initial step for persons beginning a career in construction management. Consideration of careful planning in the construction process requires an early introduction into the minds of students. The book is based on lectures given over several years to students attending a final degree course in building construction management at the University of Reading in England. The 409 page paperback book contains 19 chapters and is divided into two parts. Part one covers factors affecting construction method assessment. Following the introduction, chapters 1 to 7 cover site inspections; the influence of the construction site and its boundaries on equipment and method selection; temporary works, their role, and association with equipment; scaffolding, support of excavations, formwork and falsework; the influence of design on construction cost; cost elements in tender and contract planning; and the selection of equipment and methods. Part two covers the establishment of methods and their planning and control. Following an introduction to the second part, chapters 8 to 19 cover nonpiled foundations, piled foundations, deep basements, in situ concrete structures, precast concrete structures, steel structures, cladding and internal works, external works, waste in the construction process, method statements, project planning control, and the role of planning in the claims process. The book generally covers the basic aspects of construction methods and planning. One of the many good features of the book is that there is a list of references and a suggested list of further reading at the end of most chapters, although there are no assignment problems presented for students to attempt. The figures, tables, and diagrams are excellent. They help in making the two-column pages of text easily readable. A photograph of a C-hook for relocating table (flying) formwork, and a figure showing details and nomenclature for independent tied scaffolds demonstrate the extremely good educational and descriptive value of figures and photographs in a book of this type. The text is divided up into chapters, sections, subsections, and lists in a point by point typical lecture format, and hence makes the text easy to read and comprehensible. There are good checklists in the text. One example is a checklist relating to design and buildability .

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.

Stiffening of Moment-Resisting Frame by Precast Concrete Cladding

The paper describes a study of the interaction that occurs between moment-resisting reinforced concrete or steel frames and precast concrete cladding panels when such buildings, designed according to current practice, are subjected to horizontal loading. The significant structural parameters are identified and their relative importance in influencing the racking stiffness of the structure is investigated. A simple model for representing the panels in the total structure model is proposed. The structure model may then be analyzed by computer using a general purpose structural analysis program to provide the horizontal deflections, and the forces in the frame, panels and their connections.