The Influence of Various Types of Reinforcement of the Concrete Pillars of Precast Walls with an Opening

The subject of the article is a comparison of the precast reinforced concrete pillars with different types of reinforcement. These are the pillars simulating parts of walls that can, for example, form in the precast wall of residential buildings after an opening has been carved. The pillars are variously reinforced: from the simple reinforcement with wire mesh to the reinforcement with standard reinforcement bars. Behavior of the pillars, that have been subjected to two types of experiments in the past, is verified by software for non-linear analysis for concrete structures. Depending on the types of loading, the ultimate limit state, deformation and stress state of the individual pillars are studied.

RESEARCH PROGRAMME ON SEISMIC PERFORMANCE OF REINFORCED CONCRETE WALLS: KEY RECOMMENDATIONS

A wide range of reinforced concrete (RC) wall performance was observed following the 2010/2011 Canterbury earthquakes, with most walls performing as expected, but some exhibiting undesirable and unexpected damage and failure characteristics. A comprehensive research programme, funded by the Building Performance Branch of the New Zealand Ministry of Business, Innovation and Employment, and involving both numerical and experimental studies, was developed to investigate the unexpected damage observed in the earthquakes and provide recommendations for the design and assessment procedures for RC walls. In particular, the studies focused on the performance of lightly reinforced walls; precast walls and connections; ductile walls; walls subjected to bi-directional loading; and walls prone to out-of-plane instability. This paper summarises each research programme and provides practical recommendations for the design and assessment of RC walls based on key findings, including recommended changes to NZS 3101 and the NZ Seismic Assessment Guidelines.

Seismic Performance Assessments of RC Frame Structures Strengthened by External Precast Wall Panel

In recent years, a variety of strengthening methods have been developed to improve the seismic performance of reinforced concrete (RC) frame structures with non-seismic details. In this regard, this study proposes a new type of seismic strengthening method that compresses prefabricated precast concrete (PC) walls from the outside of a building. In order to verify the proposed method, a RC frame structure strengthened with precast walls was fabricated, and cyclic loading tests were performed. The results showed that specimens strengthened using the proposed method exhibited further improvements in strength, stiffness and energy dissipation capacity, compared to RC frame structures with non-seismic details. In addition, a nonlinear analysis method, capable of considering the flexural compression and shear behaviors of the walls, was suggested to analytically evaluate the structural behavior of the frame structures strengthened by the proposed method. Using this, an analysis model for frame structures strengthened with precast walls was proposed. Through the proposed model, the analysis and test results were compared in relation to stiffness, strength, and energy dissipation capacity. Then, the failure mode of the column was evaluated based on the pushover analysis. In addition, this study proposed a simplified analysis model that considered the placement of longitudinal reinforcements in shear walls.

Shake-Table Testing of a Full-Scale Two-Story Precast Wall-Slab-Wall Structure

Precast wall-slab-wall buildings can be found in many different earthquake-prone areas of the world. This type of building structure features no beams or columns but rather precast walls and slabs alone that are joined together by means of steel connectors and mortar, both of which will not necessarily prevent the formation of relative sliding between structural members when the structure is subjected to certain levels of horizontal excitation, rendering them particularly vulnerable to seismic loading. Given the scarce amount of information/data on the seismic behavior of these structures, a dynamic shake-table test was undertaken to investigate the response/performance of a full-scale two-story reinforced precast concrete wall-slab-wall structure, up to incipient/near collapse. The building mock-up was subjected to five test runs of progressively increased intensity and collapsed because of failure of the steel connectors used to join the longitudinal and transverse walls. Test data are openly available and archived at the Natural Hazards Engineering Research Infrastructure DesignSafe Data Depot.

Behaviour of Horizontal Connections in Precast Walls under Lateral Loading

The design of connections is one of the most important considerations in the structural design of precast concrete structures. The purpose of the connection is to transfer loads, restrain movement and provide stability. Within one joint there may be several load transfers, each one must be designed for adequate strength and ductility and appropriately detailed. The proposed investigation aims to achieve efficient horizontal connections in precast walls with improved structural performance under various loads. HYSD reinforcement dowels are used as connectors. The arrangement of dowels is varied to achieve the efficient load transfer in the walls. The experimental investigation on three precast wall and one monolithic wall depicts that the precast wall exhibits high strength than the monolithic wall specimen and structural performance were found to be better than the monolithic wall specimen and also the efficient load transfer is achieved in the precast wall