Research Of In-situ Pull-out Method Of Masonry Mortar Strength Test

As a traditional form of structure, masonry structure has been widely used in buildingstructures in our country,the existing hundreds of millions of square meters of the structures are masonrystructures.such as residential, office buildings and other civil buildings, industrial buildings and other structures, and in some towns, lots of masonry structuresare under construction. Because of shortage of masonry structure and inappropriate use, a large number of masonry structureshave potential safety problems, and they need material strength test and safety evaluation, but the existing detection methods have some defects, such as low reliability test results, and large damage to local parts of walls.To this problem, on the basis of In-situ pull out method which is proposed by Zhenchao Wei, this articleconducted exhaustive research and put forward new In-situ pull out method. This new method has many advantages such as strongly intuitionistic, being simple to operateand large range of intensity that can be detected, and it can also reflectthe comprehensive strength of materials and construction quality. This article designed a set of put-out device as needed and optimized it by ANSYS.By discovering problems in field tests, summarized the defects of the device and brought two improvement programs.Due to the weight of the upper structure and other load effect, in-situ test station will be affected by the vertical stress, the traditional practice ofhollowing out the horizontal mortar joint to release stress cannot effectively avoid the influence of the vertical stress, and the operation is complex, this paper puts forward the method of selecting the measure point fromthe third or fourth floor brick under the staircase window wall, vertical stress at this location is small, and this method can avoid the nuisance problems brought by hollowing out the horizontal mortar joint and detection work. Then constructed numbers of models with different sizes and number of layers by ANSYS, and analyzed the vertical stresses of the measuring points, selected the bricks with small vertical stresses as detection targets and gave reduction coefficients of different mortars in relevant positions.Shear strength of the bonding mortar is refer to the shearing strength of the masonry when the vertical stress is equal to zero, our specification takes the experimental values of standard test specimens as themortar shear strength values, and calculate the relationship of shear strength and compressive strength.In in-situ test, the stress conditions of the sample and standard specimen are different, so the shear strength of the in-situ test is not equal to the mortar shear strength in the specification., it need to be multiplied by a coefficient less than 1 which is effected by constraint condition and size, based on the experimental data, this article calculated thatthe coefficient is 0.2.