In-plane Quasi-static Loading Research Articles

Analysis and design of 3D printed reinforced concrete walls under in-plane quasi-static loading

Construction three-dimensional (3D) printing is an emerging technology within the area of Additive Construction and has the potential of revolutionizing the construction industry and the structural engineering discipline through construction automation. One of the major challenges in construction 3D printing is the lack of understanding of the response of 3D printed elements as well as the lack of design methodologies for such elements. This study proposes a 3D printed concrete (3DPC) wall design, termed RC-framed 3DPC wall, for applications in the seismic force resisting system of low-rise 3DPC buildings. The proposed 3DPC wall is reinforced by an internal reinforced concrete frame that strengthens the 3DPC wall similarly to boundary elements in masonry walls. The proposed 3DPC wall further includes bed-joint reinforcement that provides strength against shear demands and provides stability during printing. This study further discusses connection strategies of the proposed 3DPC wall to roof slabs and the foundation, and, following a limit states approach, formulates strength capacity equations for different in-plane failure mechanisms. In lack of experimental data, the strength equations are validated through finite element analyses as well as through experimental data on concrete block masonry (CBM) walls, with which 3DPC walls bear similarities in terms of the construction approach and are expected to share similar response mechanisms. Comparisons with experimental data were conducted for 16 partially grouted (PG) CBM walls and for 10 confined CBM walls. Comparisons with finite element analysis predictions were conducted for 96 3DPC walls, which varied in terms of bed-joint reinforcement, concrete compressive strength, height-to-length ratio, layer width, and cross-section infill pattern. These comparisons focused on predictions of strength and failure mechanisms. It was observed that the proposed strength design equations could predict the mechanical strength and failure mechanism of 3DPC walls with reasonable accuracy, thus, paving the way to 3DPC building design.

Mechanical characterisation and crashworthiness performance of additively manufactured polymer-based honeycomb structures under in-plane quasi-static loading

ABSTRACT Additive manufacturing technology is suitable for producing energy-absorbing devices with tunable mechanical properties and improved crashworthiness performance. In this study, the mechanical properties and macrostructural crushing behaviour of five additively manufactured polymer-based honeycomb structures (HS) are investigated. Subjected to in-plane loading, the experimental results of the HS are compared with numerical findings and theoretical predictions. Results indicate that deformation modes and overall crushing performance are influenced by utilising different parent materials. The polymer HS made from polyethylene terephthalate glycol gives the best overall crushing performance over the other polymers and polymer-fibre reinforcement HS. However, the crush force efficiency of HS made from polylactic acid is the least promising. The polymer-fibre reinforced HS outperforms some of the pure polymer-based ones in terms of specific energy absorption and shows a characteristic lightweight advantage. Hence, spotting it as a promising energy absorber utilised for crashworthiness application especially where ultra-lightweight property is highly desired.

Effects of aspect ratios and strengthening methods on seismic behavior of masonry piers strengthened by using hybrid-fibers modified reactive powder concrete

Piers are the main load-bearing elements of masonry structures. Damage to piers in earthquakes will lead to the collapse of the whole structure, so piers need to be strengthened. In order to study the effectiveness of hybrid-fibers modified reactive powder concrete (HFMRPC) coating strengthening on masonry piers and the influence of different strengthening methods and aspect ratios on the seismic behavior of masonry structures, six masonry walls with different aspect ratios (0.8, 1.0, and 1.4) and strengthened by different methods (unreinforced, single-sided coverage in piers, double-sided coverage in piers, and double-sided cross-bracing) were tested under in-plane quasi-static loading. The test and analysis results showed that the seismic behavior of masonry walls in terms of bearing capacity, displacement ductility, stiffness, and energy dissipation was effectively enhanced by HFMRPC coating. The improvement range of ductility coefficient, initial stiffness, and cumulative energy dissipation were 86.3% ∼ 229.3%, 18.2% ∼ 104.0%, and 57.0% ∼ 139.7%, respectively. The most suitable strengthening method for strengthening piers was double-sided cross-bracing compared with other methods. The strengthening effect of the double-sided coverage in piers was improved with the increased aspect ratio. Additionally, masonry wall shear strength and flexural capacity calculation methods were proposed based on GB 50003-2011, N-M interaction diagrams, and equivalent rectangular stress block.

Failure Analysis of High-Strength Bolts in Spherical Joint Assembly under In-Plane Quasi-Static Loading

Failure Analysis of High-Strength Bolts in Spherical Joint Assembly under In-Plane Quasi-Static Loading

Seismic performance of Chinese traditional timber frames

Chinese traditional timber frames are known for their mortise-tenon joints and wooden planks shear walls. To investigate the seismic behavior of the structural system, three full-scale timber frames were subjected to in-plane quasi-static loading. The hysteresis characteristics, lateral load-carrying capacities, lateral stiffnesses, and energy dissipation capacities of the timber frames were investigated. The results showed that the hysteretic loops of all specimens exhibited pinching, and the column and beam components were nearly intact after the test. The traditional wooden frames had large deformability. The installation of the infilled timber shear wall brought great improvements in lateral resistance and energy dissipation to the bare frames. The initial stiffness of the timber frame infilled with timber shear wall was 0.113 kN/mm, which was 56.9% and 11.9% greater than those of the bare frame specimen F1 and specimen F2, respectively. The results from the experimental analyses can serve as a technical basis for the development of seismic design methods and strengthening designs of such structures in practical engineering.

Design and modeling of bamboo biomorphic structure for in-plane energy absorption improvement

Bamboo cell wall exhibits a microscopically graded architecture, and micro-layer distributed cells around individual cell walls, which leads to the preferred mechanical properties of bamboo for impact loading. This work proposes a cellular structure, as called Bamboo Biomorphic Structure (BBS), which is a functionally graded honeycomb cellular structure inspired by the microstructure of bamboo and manufactured using fused filament fabrication (FFF). It is hypothesized that, by introducing bamboo biomorphic micro-unit cells, including a range of thickness step differences within an individual honeycomb unit cell, the successive stages of deformation of the honeycomb structure can be controlled, making the system absorb impact energy more efficiently. Characterization of the designed structures was conducted under in-plane quasi-static loading conditions, and then evaluated using a nonlinear finite element commercial code LS-DYNA. The proposed gradient BBS showed higher absorbed impact energies by four times compared with the conventional Honeycomb structure.The proposed parametric design would aid engineering design principles for the development of a novel biomorphic cellular structure, which has the potential for large-scale manufacturing of efficient energy-absorbing engineering structures. Such an energy-absorbing structure can help improve the lightweight structure design for various applications, including automobiles and aircrafts, while ensuring safety under impact load.

Incorporation of localizing gradient-enhanced damage model into layered membrane elements for reinforced concrete structures subject to in-plane loading

Implementation of the localizing gradient-enhanced concrete model and the Menegotto-Pinto steel model into eight-node quadrilateral layered membrane elements for reinforcement concrete (RC) members subject to in-plane quasi-static loading is presented and evaluated. This RC element circumvents the pathological mesh-sensitivity of continuum damage models and the spurious damage growth of standard gradient damage models. Drilling DOFs are adopted, which improve the smoothness of strain distributions and aid in numerical convergence. The layered cross-section consists of fully bonded/smeared steel reinforcement layers and concrete layers. Different properties over the thickness can be easily assigned to each layer to account for heterogeneity. Several benchmark tests are simulated to demonstrate the versatility and effectiveness of the RC element. It is highlighted that all analyses are performed with the fully implicit incremental-iterative Newton-Raphson algorithm. Consequently, the RC element is suitable for modeling quasi-static behaviors of RC members, especially those coupled with other physical processes (creep, shrinkage, corrosion, etc.).

Behavior of masonry infilled Chuandou timber frames subjected to in-plane cyclic loading

The Chuandou timber frame is a traditional timber structural system widely used for nonengineered residential houses in southwestern China; this system is featured by beam-to-column joints with direct penetration tenons and free-standing column bases. As concluded by a previous study, the Chuandou timber frames with proper infills have exhibited better seismic performance than un-reinforced masonry structures in terms of collapse prevention, although the mortise-tenon connections, masonry infills, timber beams and columns may have sustained various extents of damage. To investigate the seismic behavior of the structural system, six full-scale Chuandou timber frame subassemblies were subjected to in-plane quasi-static loading, four of which were infilled with masonry walls. The test results show that the masonry infills provided the most lateral resistance of the system, whereas the timber frames could sustain a large lateral drift without losing their vertical stability. The observed failure modes were identified from different specimens. The lateral strengths of the specimens in the current test were evaluated using the existing code equations. The results suggest the necessity of considering the aspect ratio in calculating the shear strength of masonry walls.

Experimental Study on Cast-In-Situ Masonry Cavity Walls Subjected to In-Plane Cyclic Loading

This study investigates the behavior of cast-in-situ masonry cavity walls subjected to in-plane quasi-static loading. Thirteen cast-in-situ masonry cavity walls and one solid wall were tested under combined axial and quasi-static lateral loads. Test parameters included the tie shape, tie layout, thickness of the insulating layer, and the level of axial compression. The problems related to shear capacity and failure mechanisms of cast-in-situ masonry cavity walls were analyzed. Experimental results indicate that failure of most wall specimens occurred via crushing at corners, accompanied by flexural and diagonal cracks in the inner leaves. The shape and layout of the ties had a limited effect on the shear strength of cast-in-situ masonry cavity walls, while axial compression had a positive influence on shear strength. The relative displacement between the inner and outer leaves was nearly zero before walls cracked and reached less than 2 mm at the ultimate load. The shape and layout of the ties had a slight influence on the coordination of inner and outer leaves, while the insulating layer thickness and axial compression had a negative effect. Hysteretic loops under quasi-static loading were spindle-like, and wall specimens exhibited large nonlinear deformation capacity, indicating adequate aseismic capability. A new formula for calculating the shear capacity of the cast-in-situ cavity masonry walls was proposed and was demonstrated to be accurate.

Experimental Investigation of In-Plane Mechanical Performance of Carbon/Glass Hybrid Woven Composite

Woven composites have been increasingly employed in engineering applications. For effective use of woven composites in engineering applications, it is essential to fully understand the mechanical behavior. In the present study, both tensile and compressive behavior of a carbon/glass hybrid woven composite manufactured by vacuum infusion process was experimentally investigated under in-plane quasi-static loading. The experiments were performed at both the axial and off-axial directions. The results indicated that the in-plane mechanical performance of the studied composite was highly directional dependent and tension/compression asymmetric.

Mechanical behavior and failure mode of woven carbon/epoxy laminate composites under dynamic compressive loading

The compressive behavior of woven carbon/epoxy laminate composites is investigated under in-plane and out-of-plane loading. The Material Testing System (MTS) and the Split Hopkinson Pressure Bar (SHPB) are employed to test the quasi-static and high strain rate dynamic mechanical properties of the material, respectively. Dynamic compression properties are compared with those of static loading. It is observed that the failure strength varies with different fiber woven directions. The results indicate that the stress–strain curves, maximum compressive stress and strain all evolve as strain rate varies. The specimens are mainly damaged in shear failure mode under out-of plane loading and the shear failure mode is independent of loading states and strain rates (500–1000/s). Comparatively, the different failure mechanisms of the material between quasi-static and dynamic in-plane loading at strain rates ranging from 50 to 400/s are obtained and studied. Delamination is only found at high strain rates under in-plane dynamical loading while shear deformation and delamination are both found under in-plane quasi-static loading. Shear bands and deformation zones are also observed under in-plane quasi-static loading.

Hybrid composites made of carbon and glass woven fabrics under quasi-static loading

Experimental studies are presented on in-plane mechanical properties for two types of hybrid composites made using 8H satin weave T300 carbon fabrics and plain weave E-glass fabrics with epoxy resin. Results are also presented for 8H satin weave T300 carbon/epoxy and plain weave E-glass/epoxy. Studies are carried out under both tensile and compressive in-plane quasi-static loading. It is observed that for hybrid composites, placing glass fabric layers in the exterior and carbon fabric layers in the interior gives higher tensile strength and ultimate tensile strain than placing carbon fabric layers in the exterior and glass fabric layers in the interior. Quantitative data is given for different mechanical properties.