Azrul A. Mutalib

Numerical analysis of FRP-composite-strengthened RC panels with anchorages against blast loads

Extensive research has been conducted to investigate the blast effects on building structures and the protective design methods using the fiber-reinforced polymer (FRP) strengthening concepts in resisting structural damage and preventing injuries against dynamic explosive impacts. Both numerical and experimental studies have proved the effectiveness of FRP in strengthening structures to resist blast loads. However, problems related to end anchorage, bond length, and premature peeling have been concerns when strengthening structures in flexure or shear using FRP. In this paper, numerical analyses of FRP-composite-strengthened RC walls with or without additional anchors are carried out to examine the structural response under blast loads. The results illustrated that an anchor system is often necessary when using external FRP laminates for strengthening RC walls to prevent premature peeling. This study presents three simulations of RC walls, namely, an unstrengthened RC wall, an FRP-composite-strengthened R...

Quasi-Static Behavior of Palm-Based Elastomeric Polyurethane: For Strengthening Application of Structures under Impulsive Loadings

In recent years, attention has been focused on elastomeric polymers as a potential retrofitting material considering their capability in contributing towards the impact resistance of various structural elements. A comprehensive understanding of the behavior and the morphology of this material are essential to propose an effective and feasible alternative to existing structural strengthening and retrofitting materials. This article presents the findings obtained from a series of experimental investigations to characterize the physical, mechanical, chemical and thermal behavior of eight types of palm-based polyurethane (PU) elastomers, which were synthesized from the reaction between palm kernel oil-based monoester polyol (PKO-p) and 4,4-diphenylmethane diisocyanate (MDI) with polyethylene glycol (PEG) as the plasticizer via pre-polymerization. Fourier transform infrared (FT-IR) spectroscopy analysis was conducted to examine the functional groups in PU systems. Mechanical and physical behavior was studied with focus on elongation, stresses, modulus, energy absorption and dissipation, and load dispersion capacities by conducting hardness, tensile, flexural, Izod impact, and differential scanning calorimetry tests. Experimental results suggest that the palm-based PU has positive effects as a strengthening and retrofitting material against dynamic impulsive loadings both in terms of energy absorption and dissipation, and load dispersion. In addition, among all PUs with different plasticizer contents, PU2 to PU8 (which contain 2% to 8% (w/w) PEG with respect to PKO-p content) show the best correlation with mechanical response under quasi-static conditions focusing on energy absorption and dissipation and load dispersion characteristics.

Dynamic Properties of High Volume Fly Ash Nanosilica (HVFANS) Concrete Subjected to Combined Effect of High Strain Rate and Temperature

The study aims to determine the dynamic properties of high volume fly ash nanosilica HVFANS concrete exposed to strain rates between 30.12 to 101.42 s‐1 and temperatures of 25, 400, and 700 oC by using split Hopkinson pressure bar SHPB machine. The static and dynamic compressive strengths of HVFANS concrete were slightly lower than plain concrete PC at room temperature, while its values were higher at 400 and 700 oC. The results proved that the CEB model of dynamic increase factor is more reliable to estimate the behaviour of HVFANS concrete at studied temperatures. The toughness, critical strain, and damage of HVFANS concrete recorded a superior performance than PC under studied strain rates and temperatures that would reflect the possibility of use HVFANS concrete in structures to improve its resistant of fire and impact loads, as well as to decrease the demand on Portland cement which could lead to restrict the risks of liberated gases during cement production. Furthermore, equations were proposed to estimate the dynamic increase factor, toughness, and critical strain of both concretes under investigated conditions.

Blast damage assessment of symmetrical box-shaped underground tunnel according to peak particle velocity (PPV) and single degree of freedom (SDOF) criteria

This study aimed to determine the reliability of the damage criteria that was adopted by the peak particle velocity (PPV) method and the single degree of freedom (SDOF) approach to assess the damage level of a box-shaped underground tunnel. An advanced arbitrary Lagrangian Eulerian (ALE) technique available in LS-DYNA software was used to simulate a symmetrical underground tunnel that was subjected to a surface detonation. The validation results of peak pressure into the soil revealed a good consistency with the TM5-855-1 manual within differences that were much less than previous numerical studies. The pressure contours revealed that the blast waves travelled into the soil in a hemispherical shape and the peak reflected the pressure of the tunnel that occurred immediately before the incident pressure reached its highest value. The assessment results proved that the criteria of the above methods could efficiently predict the damage level of a box-shaped tunnel under different circumstances of explosive charge weight and lining thickness at a depth of 4 m within slight differences that were observed during van and small delivery truck (SDT) explosions. However, the efficiency of both the methods was varied with the increase of burial depth. Whereas, using the PPV method significantly underestimated or overestimated the damage level of the tunnel, especially during SDT and container explosions with a lining thickness of 250 mm at burial depths of 6 and 8 m, respectively, the damage level that was obtained by the SDOF method greatly matched with the observed failure modes of the tunnel. Furthermore, new boundary conditions and equations were proposed for the damage criteria of the PVV method.

Physical Damages Effect on Residential Houses Caused by the Earthquake at Ranau, Sabah Malaysia

Earthquake, the destructive natural disaster had recently stormed East Malaysia. This study aims to identify the physical effects of the earthquake to the building that occurred in Sabah, Malaysia. A survey method had been conducted among 221 citizens in the affected area to meet the requirements of this research objective. The result shows that 68% responded that building cracks had formed on the wall, 48% cracked floor, 23% cracked columns, 10% damages on roof and 8% responded no damages at all while only 2% stated the total collapse of the houses’ structures. Researchers have also identified that the impact of the earthquake towards their house yards shows that 55% and 12% responded experienced cracks on ground and landslide respectively, 25% with flood occurrence and 1% are caught with fire. Finally, almost 90% of the respondents are ready to upgrade their house structures. Thus, this research will be continued by developing the retrofitting and strengthening methods for the low rise buildings.

Bio-Based Polyurethane Elastomer for Strengthening Application of Concrete Structures Under Dynamic Loadings

Feasibility of application of a bio-based elastomeric polyurethane (PU) coating to improve the dynamic resistance of concrete specimens by enhancing their energy absorption capability was investigated. A series of experimental investigation were conducted using scaled concrete specimens with dimensions of 160 × 40 × 40 mm, which were coated with eight different coating configurations by varying the coating thickness and location. Three-point bending test was conducted under quasi-static and dynamic conditions, by varying the strain rates (0.00033 s−1 and 0.067 s−1). The maximum flexural stress, failure strain, and strain energy density characteristics were used to assess the effectiveness of the proposed retrofitting technique. Polymer layers of 1–4 mm thick provided 2.9–8.9 times enhancement in failure strain, 3.0–11.3 times enhancement in strain energy density, and a marginal enhancement in the maximum flexural stress under dynamic conditions compared to the dynamic response of uncoated concrete specimens. In addition, the dynamic response of concrete specimens was improved when the thickness of the PU coating was increased and when the coating was applied on both faces.

Numerical Analysis of Underground Tunnels Induced by Ground Truck Explosion

The present study attempts to analyze the dynamic response of underground box tunnel at depth 4m using nonlinear finite element software Ansys/LS-Dyna. Arbitrary Lagrangian-Eularian (ALE) numerical solver had been used to evaluate tunnel responses when it subjected to two kinds of trucks explosion (small delivery and container/water truck) filled with maximum TNT charge weight 1814 and 4536 kg, respectively. The results indicate that the container truck explosion caused great increment in displacement, velocity, and effective stress values as compared with small delivery truck. The top wall corner and roof center of the tunnel had faced maximum deformation and velocity in both cases of trucks explosion. In addition the value of effective stresses was high in roof edge and top wall corner.