Material Parameters Identification for Modelling of Carbon Rod Structures Delamination

The aim of the present work is to compare the interlaminar shear strength and fracture toughness of glued carbon fiber rods obtained using different experimental approaches and provide the effective way to characterise the interlaminar properties for reliable simulation of the delamination. Five different test methods (tension, single shear test, and double shear test, mode I and mode II delamination tests) were performed. Using the explicit LS-DYNA code the finite element model capable of simulating the damage process of bonded connection was developed. The interlaminar connection and delamination criteria were calibrated using the parameter identification methodology implemented in LS-OPT optimization tool.

Study on Double-Shear Test of Anchor Cable and C-Shaped Tube

The free section of prestressed anchor cable is a weak part of support. A new supporting structure named Anchor Cable and C-Shaped Tube, which can bear transverse shear force, solves the problem that rock bolt and anchor cable are prone to shear failure in the free section and also solves the contradiction between high preload and low shear bearing capacity of support materials. Double-shear tests of Anchor Cable and C-Shaped Tube with smooth joint planes were carried out. Double-shear tests were carried out on the anchor cables with the diameter of 21.6 mm and the same type of Anchor Cable and C-Shaped Tube under different preload conditions. The influence of the preload on the shear performance of supporting materials and the enhancement effect of Anchor Cable and C-Shaped Tube supporting structure on the shear performance of anchor cables were analyzed. The test results confirm that Anchor Cable and C-Shaped Tube can improve the transverse shear resistance of the supporting material and increase the axial ultimate bearing capacity of the anchor cable during the shearing process. It is found that, during the double-shear test, the fracture form of the supporting materials is tensile fracture, and when it is sheared, Anchor Cable and C-Shaped Tube can reduce the stress concentration of the interaction between the joint surface and the surrounding rock and reduce the damage to the surrounding rock.

Performance Evaluation of GFRP Rock Bolt Sensor for Rock Slope Monitoring by Double Shear Test

This study aims to evaluate the sensing performance of glass fiber-reinforced polymer (GFRP) rock bolt sensors instrumented with strain gauges for monitoring rockslides. Experimental studies are conducted with four different types of GFRP rock bolt sensors and concrete blocks having central holes and two shear joints. Two GFRP rock bolt sensors are inserted into holes and then fixed in concrete blocks with cement grout and soil, respectively. The other two are coated with heat-shrink tubes to protect strain gauges and wires, which are then fixed in concrete blocks with cement grout and soil, respectively. Double shear tests are performed to produce shear deformations of GFRP rock bolt sensors, and then strain change with shear displacement is monitored. The results manifest that the variation in strain with shear displacement is more sensitive in the GFRP rock bolt sensor fixed with soil than with cement grout. Also, strain gauge wires in the GFRP rock bolt sensor fixed with cement grout are broken earlier than with soil. Furthermore, it is confirmed that the heat-shrink tube effectively protects strain gauges and wires, so that GFRP rock bolt sensors coated with heat-shrink tubes work for a longer time than the uncoated sensors. The present study shows that the GFRP rock bolt sensor can be useful for monitoring rock slope failure.

Analisa Kekuatan Tahanan Lateral Pada Sistem Komposit LVL Kayu Sengon dan Beton Pracetak

LVL Sengon and concrete can be used to form a composite structure of the floor system. Connections between LVL Sengon and concrete on this composite floor system are the weakest part so that a majority of structural damages are concentrated at these joints. This study discusses the lateral resistance of lag screw joints in a composite system of LVL Sengon and precast concrete. The lateral joint resistance was evaluated through quasi-static loading upon double shear test specimens having two screws at every single shear. Variation of the specimens includes precast concrete compressive strength of 20.71 MPa and 25.29 MPa, screw diameter of 6 mm length 101.6 mm and 8 mm length 101.6 mm and 127 mm, and angle of lag screw axis against the wood fiber of 60° and 90°. The result shows that lateral resistance of the test is greater than that of EYM, SNI, and EC5 predictions. Joint failure in this experiment is due to failure in wood fiber along with the occurrence of one up to two plastic hinges in the screw.

BOND AND SHEAR-STRENGTHENING PERFORMANCE OF FRCM COMPOSITES

This paper is aimed at studying the bond and shear-strengthening performance of fabric reinforced cementitious matrix (FRCM) systems. Three FRCM systems were compared, namely, polyparaphenylene benzobisoxazole (PBO)-FRCM, Carbon-FRCM, and Glass-FRCM. At first, six double-shear specimens were tested to investigate the FRCM/concrete bond, with the test variables including the fabric type and the bond length. After that, seven shear-critical reinforced concrete (RC) beams were tested under three-point loading, considering the fabric type and strengthening configuration (full/intermittent) as the test variables. As for the double-shear test results, the failure observed was fabric/matrix debonding in carbon-FRCM, matrix/concrete debonding in PBO-FRCM, and fabric rapture in glass-FRCM. The FRCM/concrete bond increased with the bonded length, and the PBO-FRCM showed the highest bond to concrete. Regarding the RC beam tests, the FRCM-strengthened beams showed the same failure mode that is debonding at the FRCM/concrete interface. Nonetheless, FRCM had successfully strengthened the beams in shear: an average gain of 57% in the load carrying capacity was achieved as compared to the non-strengthened reference. Indeed, the full-length strengthening resulted in a better structural improvement compared to the intermittent-strengthening configuration. Amongst the three systems, carbon-FRCM systems were the most efficient in shear-strengthening RC beams.

Experimental study on the mechanical behavior of BFRP-bamboo composite beam

This article proposes a basalt fiber-reinforced plastic–bamboo (BFRP-bamboo) composite beam consisting of BFRP sheet and laminated bamboo, aiming at fully utilizing advantages of bamboo and BFRP to improve the mechanical behavior of the laminated bamboo beam. A two-step test program is involved: (1) double shear test for bonding behavior between the BFRP and laminated bamboo and (2) loading test for mechanical behaviors of both laminated bamboo and BFRP-bamboo composite beams. Parameters affecting the bonding behavior are firstly concluded as the coated surface resin, types of bonding materials, and interfacial treatment. Then, the failure patterns of both laminated bamboo and BFRP-bamboo composite beam are discussed based on experimental observations. Key mechanical indexes, including the yield force, yield displacement, ultimate load, ultimate displacement, ductility, and stiffness, are analyzed based on load–displacement curves of tested specimens. Besides, theoretical analyses of bearing capacity of the BFRP-bamboo composite beam, featured as fracture failure, are conducted.