Demountable Column - Girder Joint

Traditional precast reinforced concrete structures are characterised by joints of individual components executed with the use of cement grouts or mortars, or by welding reinforcement. The joints produced in this way cannot be demounted in the case of need without damaging the precast components. Demountable precast structures with a long life cycle enable repeated assembly and demounting thus contributing to the saving of the basic input resources and the environment. The main feature of demountable precast structures are patent-protected joints which allow the assembly of the precast components without the necessity of using “wet” processes. The article addresses the characteristics of a demountable girder - column joint. It presents the results of static load tests carried out within extensive experimental research. To conclude, the article specifies the benefits and the applications of demountable structures.

Seismic Behavior of Precast Buildings With Dissipative Connections

Recent earthquakes in southern Europe highlighted that the connections of cladding panels to R.C. frames in precast buildings had a major role in the structural collapse. For this reason, there is an urgent need for a review of the design methods for these connections as well as for an improvement in the manufacturing technology. This article aimed to assess the efficiency of dissipative panel-to-structure and roof connections in R.C. precast buildings. A parametric study consisting of linear and non-linear analyses on one case-study building is performed. Different sensitivity analyses are performed varying their mechanical properties (i.e., stiffness, strength, and ductility) to analyze the behavior of the CP/frame connections. The study focuses on dissipative connections with an elastic–plastic behavior, placed between cladding panels (CPs) and frames in precast buildings with stacked horizontal cladding panels. The introduction of dissipative CP/frame connections implies the inclusion of panels in the global seismic resisting system. The “panels + frame” system highlights a high stiffness until the yield strength of the CP/frame connections is reached. The results, obtained from non-linear dynamic analyses (NLDAs), clearly show how the proposed connection improves the structural seismic performance. By contrast, this is no longer true for R.C. precast structures with flexible diaphragms, especially for intermediate columns, far from panels aligned to seismic action. In this case, significant and unexpected axial forces arise on out-of-plane connections between panels and columns. The integration of an efficient diaphragm is essential to prevent these critical issues both on intermediate columns and CP/column connections; it enables the dissipative capacity of the “panels + frame” system, and it significantly limits the forces and displacements of intermediate alignments. Unfortunately, the achievement of a rigid diaphragm is not always feasible in precast buildings. A possible alternative to activate dissipative capacities of the roof diaphragm with limited in-plane stiffness is the use of dissipative connections linking roof beams and main beams. The solutions described in this article can be applied both in the design of new buildings and for the seismic upgrading of existing ones with easy-to-install and low-impact applications.

Influence of Precast Member Corbels on Seismic Performance of Precast Beam-Slab-Column Joints

To improve the construction efficiency of precast structures, reinforced concrete corbels acted as support members are the most common connection method. This work presents the performance of a specific beam-to-column connection using corbels with different anchorage arrangements in precast beam-slab-column interior joint taken out from precast underground subway station. This paper investigates the performance of a specific full-scale precast concrete beam-slab-column interior joint with corbels and various connected methods subjected to low-cycle repeated loading. Meanwhile, the influences of concrete corbels (including column- and beam-end corbels) on the shear strength and deformation are investigated. The analyses results indicated that (1) corbels of the laminated beam (composite beam) can obviously improve the shear stress of the core region, which was beneficial for specimen design followed the strong-joint-weak-member concept; (2) a simplified approach to deal with the uneven thickness of corbels in the core region was proposed, which was utilized to study the effect of thickness on the shear performance of the core region; (3) the shear stress increased with respect to the compression stress, and the shear strain had a trend of decreasing according to calculating results using modified compression field theory; and (4) the deterministic expressions were proposed to predict the designed load of column corbels based on three different connection methods between laminated beams and core region of joint.

NUMERICAL STUDY OF REINFORCED CONCRETE CORBELS WITH DIFFERENT LAYUP SCHEMES OF CFRP LAMINATES

Reinforced concrete short corbels are widely used in engineering structures, such as bridges and precast structures. Therefore, the present comparative study was conducted on the structural behavior of the reinforced concrete corbels strengthened with carbon fiber-reinforced polymer (CFRP) laminates. For this purpose, numerical analysis was done using the finite element method. Therefore, nine models consisting of eight corbels strengthened with different CFRP arrangements in addition to an unstrengthened model were studied. The maximum load capacity, stiffness, ductility, and amount of absorbed energy were compared. In one of the above structure models, an innovative hunch was added at the top side of the corbel to column connection to investigate the differences with ordinary types of connections. Results revealed that the model used three bonded CFRP laminates all around the column and outside edges showed an 81% increase in loading capacity. Moreover, the corbel equipped with hunches had an 8% increase in stiffness compared to an ordinary corbel.

PRESSAFE-Disp: A Method For The Fast Seismic Assessment of Existing Precast RC Buildings After The Emilia Earthquake Of May 2012

The existing precast reinforced concrete structures, especially those not specifically designed against the earthquakes, have proved to be inadequate to withstand the remarkable seismic demands related to the presence of heavy roof elements. In fact, the cantilever columns entailing large top displacements and the poor devices adopted to connect different precast elements have shown high sensitivity to seismic actions. After the lesson learned from the recent Emilia earthquake of May 2012, causing many collapses and severe damage, reliable seismic design criteria have been established for the design of new precast structures and for the strengthening of the existing ones. Despite this, a large percentage of the existing precast buildings in the Italian territories actually has not been object of interventions and remains in an unsafe condition with regards to the seismic actions. In this context, the methods for a rapid seismic assessment can be very helpful both to estimate the current safety level of large building stocks and to plan the necessary strengthening interventions, possibly at the wide scale of an industrial area. To this aim, the paper proposes a new method, named PRESSAFE-disp (PRecast Existing Structure Seismic Assessment by Fast Evaluation-displacements), for the fast evaluation of the fragility curves of precast structures. The method follows the approach of the PRESSAFE method, but different damage criteria have been introduced in order to take into account the relative displacements and the sliding between different precast elements. The damage criteria considered, applicable to both structural elements and perimeter cladding elements conceived as non-structural elements, have been properly selected in order to capture the damage mechanisms observed during the several building inspections conducted by the authors in the aftermath of the 2012 Emilia earthquakes. In the present configuration, the method allows a comprehensive explanation of the seismic behaviour of the existing precast buildings and could be effectively adopted, for example, in earthquake loss estimations and seismic risk assessments of large Italian industrial areas, as well as of wide seismic-prone territories of the Mediterranean area.

Stressstrain state of cast-in-place and precast structure with loaded cast-in-place element

The paper presents the strength analysis of cast-in-place and precast structures in accordance with regulatory documents, which require clarifications, since the properties of such structures distinguish them from conventional reinforced concrete structures. These properties include the beginning of the deformation process, ultimate strain, physical properties, and others. The strength analysis of cast-in-place and precast structure is conducted with regard to these properties.The proposed analysis is based on the load-bearing capacity exhaustion of deformed concrete or reinforcement and allows considering the different time of involvement in the deformation process of cast-in-place and precast structures as well different stress and strain properties of concrete. The experimental data are in good agreement with theoretical calculations.

Experimental Investigation of Rubberized Functionally Graded Concrete

Concrete is a basic engineering material used for developing modern structures. The engineering properties of structures can be enhanced by using different concrete grades in the same structural element based on its specific requirement in functionally graded concrete (FGC). For meticulous critical inspection, an experimental investigation was prosecuted on three different types of concrete (conventional concrete (CC), rubber fiber concrete (RFC) and rubberized functionally graded concrete (RFGC)), and their properties were compared. The fine aggregate was substituted (by volume) with waste rubber fiber by 5, 10, 15, 20 and 30% to prepare RFC and RFGC. Tests were performed on concrete samples to analyze compressive strength, flexural strength, water permeability, and drying shrinkage. Moreover, scanning electron microscopy (SEM) was utilized to observe the microstructures. Results indicated that RFGC performed better than CC and RFC and can be used to prepare precast structures and for the applications where high flexural load acts.

A Review and Scientometric Analysis of Global Research on Prefabricated Buildings

Prefabricated building has become one of the most significant research directions in the architecture, engineering, and construction (AEC) industry and has attracted a large number of scholars and practitioners in recent years. However, few studies have conducted a systematic review on the development of prefabricated building research around the world. In this study, the scientometric method is used to analyze the literature on prefabricated buildings in the past ten years through analysis of co-authors, co-words, and co-citation. From the Web of Science (WOS) core collection database, a total of 1224 articles were collected for statistics and analysis. The analysis results indicated that Bruno Dal Lago obtained the maximum number of co-citations, and the most significant country/region and research institution in prefabricated building research were China and Tongji University, respectively. It was also found that engineering, civil engineering, and construction and building technology were the top three subject categories that prefabricated building research belonged to. Among all the keywords of the collected articles, citation bursts were received by “cladding panel,” “precast concrete,” and “project.” Moreover, there were 11 co-citation clusters identified from the articles, and their themes included precast structures, waste management, progressive collapse, delay, precast facades, carbon reduction, laser scanning, and prefabricated residential building. This paper is expected to provide researchers and practitioners in this field a detailed and in-depth understanding of the trend and status of global research on prefabricated buildings.