The following article is sourced from the First Company of China Construction Eighth Engineering Division and Prefabricated Building Network  

         
Recently, a new prefabricated structural system proposed jointly by Academician Xiao Xuwen and the Engineering Research Institute of China Construction Eighth Engineering Division — the prefabricated concrete shear wall system with unconnected vertical distributed reinforcement — was implemented in the B-11 plot of the Wenzhuang Area Rental Housing Pilot Project in Jinan. This system eliminates the complex construction process of sleeve grouting connections in traditional prefabricated shear wall structures, improving engineering quality.

         

         

B-11 Plot of the Wenzhuang Area Rental Housing Pilot Project

         

In this system, the vertical distributed reinforcement of the precast wall panels is arranged according to structural requirements and is disconnected at the floor levels; meanwhile, the load-bearing capacity is ensured by appropriately increasing the length and reinforcement of the cast-in-situ edge members at both ends. The upper and lower precast wall panels are connected at the floor levels by extruded mortar-bed joints, ensuring the overall performance of the shear wall structural system. For walls with a low shear-span ratio and high shear-resistance requirements, diagonal reinforcement can be added to improve the wall's ductility, shear resistance, and energy dissipation capacity.

         

Prefabricated Concrete Shear Wall System with Unconnected Vertical Distributed Reinforcement

         

Reliable Performance and Quality

         

After systematic theoretical research, a review of current codes, and finite element analysis, Academician Xiao Xuwen's research team proposed a design method for this system and verified the structural reliability through tests: under the same axial compression ratio, the seismic performance of the precast specimens was equivalent to that of the cast-in-situ comparison specimens, and certain indicators such as ductility and energy dissipation were slightly better than those of the cast-in-situ comparison specimens.

         

         

Simple Construction Process

         

The southern zone of the project's second bid section comprises 6 construction units, all of which are prefabricated shear wall structures. Among them, the precast shear walls on floors 1-18 of Building 3# and floors 1-16 of Buildings 4# and 6# all adopt this technology. Currently, Building 3# has been constructed up to the 7th floor and Building 4# up to the 4th floor. In practice, the components of this technological system have no sleeves; the preparation work only requires checking the elevation and applying the mortar bed, without the need for traditional positioning dowels. The process is simple and no on-site grouting is required, resulting in higher construction efficiency while ensuring quality.

         

         

Improved Construction Efficiency

         

After applying this technological system, hoisting and positioning only require controlling the elevation and horizontal positioning. Compared with the traditional grouted sleeve connection system, the hoisting time is reduced by more than half, formwork usage is reduced by 50-60%, and the number of grouted sleeves per floor is reduced by more than 200. Since the shear walls require no grouting, one day of construction time can be saved per floor; moreover, with no large number of grout inlet and outlet holes at the bottom of the precast walls, component acceptance time can be reduced by 50%.

         

         

The successful application of this shear wall with unconnected vertical distributed reinforcement has laid a solid foundation for its subsequent promotion and application.

         

Monolithic Prefabricated 

Shear Wall Structural System with Unconnected Vertical Distributed Reinforcement

         

Main Technical Content

         

Currently, the vertical reinforcement connection methods for prefabricated concrete shear wall structures mainly include sleeve grouting connections, grout-anchored connections, and bolted connections. Although these have been incorporated into relevant codes, some problems still exist during construction implementation:

         

(1) There are many connections, and the material cost of the connection accessories is high;

         

(2) The fabrication and construction precision requirements are high, installation and positioning are difficult, and construction efficiency is low;

         

(3) The quality of grouted connections is difficult to guarantee.

         

To solve the above problems, the research team proposed a monolithic prefabricated shear wall structural system in which the edge members are cast in situ and the vertical distributed reinforcement of the intermediate precast wall panels is left unconnected. The development of this new system took three years and achieved major breakthroughs in design theory and experimental research.

         

(1) A design and calculation method for this system was developed;

         

(2) Full-scale tests of 8 wall specimens for this system, parameterized by axial compression ratio and shear-span ratio, were completed;

         

(3) Shaking-table tests of the shear wall structural system at a 1/2 scale were completed;

         

(4) A “four-in-one” high-performance precast exterior wall integration technology was developed.

         

This new system has achieved abundant research results, and under the appraisal organized by the Science and Technology Committee of the Shanghai Municipal Commission of Housing and Urban-Rural Development, its overall technology reached the “internationally advanced level.”The relevant research results have been incorporated into a China Association for Engineering Construction Standardization specification — Technical Specification for Monolithic Precast Concrete Shear Wall Structures with Unconnected Vertical Distributed Reinforcement.

         

Main Technical Indicators

         

(1) The seismic performance of this new system is equivalent to that of cast-in-situ shear wall systems, but its ductility and energy dissipation are superior to the latter.

         

(2) Tests verified that the design and calculation method is reasonable and that the structure is safe and reliable.

         

(3) Under a rare earthquake of intensity 9, the bottom-story edge members of the shaking-table test model underwent flexural failure, and the maximum inter-story drift was less than 1/120, meeting the requirements of the seismic design code.

         

(4) A “four-in-one” high-performance precast exterior wall product was developed; under the same energy-saving requirements, its thickness can be reduced by 2/3, increasing the building's usable area by 2%.

         

Comprehensive Benefit Analysis

         

Economic Benefits

         

(1) Compared with prefabricated shear walls using traditional sleeve grouting connections, the structural investment cost is reduced by about 10%.

         

(2) Traditional prefabricated shear wall structures require 5-7 days per floor for construction, whereas prefabricated shear walls with unconnected vertical distributed reinforcement can achieve 4-6 days per floor, improving construction efficiency by 15%.

         

(3) The comprehensive benefit is improved by about 18% compared with traditional precast shear wall structures.

         

Social Benefits

         

Compared with the existing shear wall exterior-wall connection methods in China, the monolithic prefabricated shear wall structural system with unconnected vertical distributed reinforcement has the following advantages: by ensuring equal flexural strength and appropriately increasing the load-bearing reinforcement area of the edge members, it eliminates the sleeve grouting, grout-anchored, or bolted connections for the vertical distributed reinforcement without reducing seismic performance, thereby lowering material costs and the precision and difficulty of production and construction, improving construction efficiency, and avoiding the safety hazards associated with these connections. It thus has strong market competitiveness and application prospects. The introduction of this system completely avoids the drawbacks of traditional shear wall connection methods and is of milestone significance for the development of the building industry and prefabricated buildings.

         

Scope of Application

         

(1) Applicable to monolithic prefabricated shear wall structures with unconnected vertical distributed reinforcement in seismic fortification intensity zones of 6 to 8.

         

(2) The maximum applicable height shall meet the requirements in the table below.

         

         

(3) The seismic grade is determined as shown in the table below:

         

         

         

(4) Shear walls with an axial compression ratio not greater than 0.5.

         

(5) When precast shear walls are used in the strengthened bottom zone, their edge members shall adopt appropriate reinforcement measures.

         

END

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