| High energy consumption is a common problem in China’s construction industry.With the development of China’s social economy,the state has issued a series of policies to support the industrialization of construction.At present,composite slabs are widely used in prefabricated floors in China.The current code stipulates that two-way composite floors use integral joints,and prefabricated floors need to reserve beard ribs,which brings a series of inconvenient problems.Although the composite floor can improve the construction speed and integrity to a certain extent,the site construction is inconvenient,and a large amount of post-pouring concrete is needed,which wastes labor,and the assembly efficiency is not high,so the construction efficiency can not be improved essentially.Therefore,this paper puts forward a kind of fully prefabricated floor slab with high-strength steel plate combined with unilateral bolt connection.The fully prefabricated floor slab pulls through the stressed steel bars of its prefabricated splicing plate through the high-strength steel plate combined with unilateral bolt reinforcement connector,forming equal strength,and it is convenient to operate,fast and does not have a lot of post-pouring concrete on site.In order to systematically study the flexural behavior of fully prefabricated floor slabs connected by high-strength steel plate combined with unilateral bolts,the following research work has been carried out:Firstly,the flexural performance test of a new fully precast floor slab with single reinforcement was carried out,and two new fully precast slabs with single reinforcement and one cast-in-place slab connected by connectors with different reinforcement anchorage lengths were designed.The main purpose of this experiment is to find out which kind of connectors with anchorage length are more suitable for single-reinforced new-type full precast slab.It is found that the ultimate bearing capacity of single-reinforced new-type full precast slab connected with connectors with anchorage length of 3 times steel bar diameter is only 78.3%of that of single-reinforced cast-in-place slab,while that of single-reinforced new-type full precast slab connected with connectors with anchorage length of 4 times steel bar diameter can reach 86.4% of that of single-reinforced cast-in-place slab,which shows that connectors with anchorage length of 4 times steel bar diameter are more suitable for single-reinforced new-type full precast slab.The flexural performance test of a new type of fully precast slab was carried out by using the connector with anchorage length of 4 times the diameter of steel bar.In this experiment,two new full precast slabs and one cast-in-place slab are designed.The difference between the two new full precast slabs lies in whether epoxy resin glue is coated in the middle of the prefabricated splicing slab.It is found that the early stiffness of the new full precast slab without epoxy resin glue is lower than that of the other two slabs,and the stiffness of the castin-place slab is similar to that of the new full precast slab coated with epoxy resin glue,and the cracking load also conforms to this law.The cracks in the three slabs are evenly distributed and the distribution patterns are basically the same.The ultimate bearing capacity of the new full precast slab can reach the level of cast-in-place slab,even slightly higher than that of cast-inplace slab.On the basis of experimental research,the numerical simulation analysis of fully prefabricated floor slab connected by high-strength steel plate combined with single-side bolts is carried out by ABAQUS finite element software,and the load-midspan deflection curve obtained is in good agreement with the experimental curve,which verifies the rationality of finite element simulation.On this basis,the influence of the size of steel bar connectors and the form of post-pouring trough on the flexural performance of the new full precast slab is further analyzed.It is found that the change of the length of steel bar connectors from 80 mm to 90 mm and 100 mm has no obvious influence on the flexural performance of the new full precast slab,and the ultimate bearing capacity of the new full precast slab with the width of steel bar connectors of 70 mm is increased by 4.2% compared with the widths of 50 mm and 60 mm,that is,the greater the width,the greater the stiffness and ultimate bearing capacity after cracking;The cracking load of post-pouring with small groove and long groove is different,and the cracking load of the new full precast slab with long groove is increased by 7.1% compared with that with small groove.Based on the finite element simulation of one-way slab,the finite element model of new fully prefabricated two-way slab is established,and the bending performance of two-way slab and three-way slab with different length-width ratios is further studied.At the same time,the ultimate bearing capacity of two-way slab with different spacing of steel connectors is discussed when the length-width ratio is 1: 1.It is found that,when the length-width ratio is 1: 0.75,the shape of two-piece new fully prefabricated two-way slabs and three-piece new fully prefabricated two-way slabs is similar to that of cast-in-place two-way slabs when a large number of cracks appear,and both of them present butterfly cracks unique to two-way slabs;The greater the aspect ratio,the closer the cracking load of the new fully prefabricated two-way slab is to the cast-in-place two-way slab,but the ultimate load does not conform to this law.Only when the aspect ratio is 1: 0.75,the ultimate load of the new fully prefabricated two-way slab is the closest to the cast-in-place two-way slab.When the length-width ratio is 1: 1,the two-piece new fully prefabricated two-way slab is closer to the cast-in-place two-way slab,and it is suggested to use the two-piece new fully prefabricated two-way slab under this lengthwidth ratio;When the length-width ratio is 1: 0.75,if there are high requirements for cracking load and early stiffness,it is suggested to use a new fully prefabricated two-way slab with three joints,otherwise,you can choose both at will;When the ratio of length to width is 1: 0.5,the ultimate bearing capacity of the two-piece new fully prefabricated two-way slab is not much different from that of the three-piece new fully prefabricated two-way slab,so they can be used at will.The ultimate bearing capacity of rebar connectors with spacing of 400 mm and 600 mm is 85.59% and 79.98% of that with spacing of 200 mm.The larger the spacing,the smaller the bearing capacity.On the basis of the bending performance test of the new full precast slab,combining theory with test,the calculation formula of bending bearing capacity of the normal section of the new full precast slab and the method of calculating cracking load of T-shaped equivalent section are put forward,which can provide reference for engineering. |
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