International Concrete Abstracts Portal

Bottom-frame structures are a prevalent construction form in the mountainous regions of China. The bottom frame and the upper masonry have irregular stiffness. This may lead to concentrated damage in the weak story of buildings under earthquake loading. Additionally, the coupling effect of mountainous region earthquakes and secondary earthquake-induced disasters, such as rockfalls, significantly exacerbates structural damage risks. In this study, a three-dimensional solid model of a bottom-frame structure in mountainous areas was developed using ABAQUS, while the ROCFALL software was employed to simulate the trajectory of rockfalls triggered by earthquake acceleration. A systematic investigation into the dynamic response and damage mechanisms of structures under the coupled effects of earthquakes and rockfalls was conducted. Furthermore, the sensitivity of structural damage to rockfall size, impact velocity, and incident angle under the earthquake-rockfall coupling effect was explored. The results indicate that the coupled earthquake-rockfall effects cause greater structural damage compared to individual hazard actions. The velocity, size, and impact angle of the falling rocks have a significant influence on the extent of structural damage.

This study investigates the structural performance improvement when bond beams are included in stack bond walls. Nine 4.0 x 2.4 x 0.20 m masonry walls were tested under out-of-plane and axial loads. The walls were constructed in three configurations: running bond, stack bond without bond beams, and stack bond with bond beams following TMS 402/602 standard. Results show similar failure patterns and crack formation between running bond and stack bond walls, but stack bond walls with bond beams exhibited distinct behavior. Stack bond walls with bond beams showed slightly higher out-of-plane flexural capacity compared to running bond walls, with a difference ranging from 4 to 5%. These findings provide valuable insights for evaluating the structural performance of concrete masonry walls with different bonding patterns. This study suggests a potential revision to the Canadian (CSA S304) masonry design standard, potentially lifting restrictions on stack bond masonry wall construction.

In this study, a shear strengthening method for lightly reinforced concrete columns with partial-height masonry infills was proposed. Perforated steel jackets were attached to one face or both faces of the column without removing the cover concrete and finishing mortar. The steel jackets were designed to provide additional shear resistance to the column through interlocking of the ribs at both ends. To investigate the seismic strengthening effects, six column specimens with partial masonry infills were tested under cyclic loading. The tests showed that the specimens with double-face jacketing exhibited an improved seismic performance, whereas there was little or no strengthening effect for the specimens with single-face jacketing. For further investigation on the short column effects due to partial-height infills, modeling parameters to define the stiffness and force-deformation relation of the column and masonry walls were proposed, and the modeling results were compared with the test results. Based on the investigation results, the detailing requirements of steel jacketing and the nonlinear modeling methods of the columns with partial masonry infills were discussed.

This paper presents the details of experimental testing of block masonry triplets using the direct shear test to investigate the shear behaviors of block unit-mortar interfaces. Hollow blocks of 100 and 150 mm (4 and 6 in.) thickness and solid blocks of 100 mm (4 in.) thickness were included in the testing program. These were combined with mortars of three grades to cast a total of 84 triplets. In addition to testing the triplets in an unconfined state, three increasing levels of precompression stresses were used separately to test the confined specimens. The shear behaviors of the tested triplets were not influenced by block strength, while shear strength increased (almost) linearly with mortar strength. The mean peak shear stress for the unconfined triplets was 0.4 MPa (58 psi), whereas the average shear modulus of the joint for these triplets was 6.20 times the mortar compressive strength. The Mode II fracture energy of the masonry joints increased at higher precompression levels. The methods of determining shear strength, shear modulus, and shear strength parameters for the mortar joint in block masonry are proposed using the observed data.

An experimental study on the shear behavior of autoclaved aerated concrete (AAC) confined masonry walls is presented. A total of eight full-scale confined walls were tested in the laboratory under in-plane reverse cyclic loads. The variables studied were the aspect ratio and the axial compressive stress of walls. The shear behavior was characterized by diagonal cracks or flexure-shear and diagonal cracks. The final cracking pattern of the walls was defined by the traditional “X” pattern. Equations for shear strength and flexure-shear strength based on experimental data obtained in this and previous studies are proposed for AAC confined walls. A limit is established for the shear strength of walls as a function of axial compressive stress. The proposed equations predicted well the experimental strength of the AAC confined walls considered in this study.