To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested specimens were significantly enhanced with the technique. An analytical model which is based on Distinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls before and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.

A problem for a central crack in a plate subjected to plane strain conditions is investigated. Mode I crack loading is created by a dynamic pressure pulse applied at a large distance from the crack. It was found that for a certain combination of amplitude and duration of the pulse applied, the energy transmitted to the sample has a strongly marked minimum, meaning that with the pulse amplitude or duration moving away from the optimal values, minimum energy required for initiation of crack growth increases rapidly. The results obtained indicate a possibility to optimise energy consumption of different industrial processes connected with fracture. Much could be gained in, for example, drilling or rock pounding where energy input accounts for the largest part of the process cost. Presumably further investigation of the effect observed can make it possible to predict optimal energy saving parameters, i.e. frequency and amplitude of impacts, for industrial devices, e.g. bores, grinding machines, and hence significantly reduce the process cost. The prediction can be given based on the parameters of the media fractured (material parameters, prevalent crack length and orientation, etc.).

The constitutive laws of the collapse of underground openings in a rock massif were investigated based on the results of laboratory and field experiments, and computations using analytical and numerical models. It is shown that the principal mechanism of failure of underground openings over important for practice peak particle velocity amplitude range of 1 to 10 m/s is the roof and wall breakage due to the fall of key blocks. Over this load range the material crushing is of considerably less importance. The geometry of discontinuities influences mainly the stability of key blocks. Further caving depends weakly on block structure of near-tunnel zone. The mean volume of fall material is a rather stable quantity for rock massifs of different structures. Lower tunnel stability in the zones of high fracturing is caused by a higher probability of the presence of the unstable key blocks and the decrease of strength characteristics of fractured bounding blocks. The decrease of average block size is a less important accompanying factor.

An explosive blast mitigation alternative has increased the safety of structures by using “catcher” systems. These systems “catch” or repel the failure of the window or in-fill wall protecting life and property from ballistic shards or fragments. They can be designed to be standalone in new construction and structural retrofits or used to augment structural hardening techniques. Cables, fabrics, and thin gauge sheet steel are examples of catcher systems used in the past. A new and evolving category of catcher systems are based on polymeric materials that can be used for both wall and window upgrades. These products are a proven blast mitigation concept and K&C Protective Technologies Pte Ltd (KCPT) together with Sherwin-Williams(SW) use KCPT’s blast engineering capacity and SW’s material engineering principles to create engineered systems for even greater in-use performance.

Since the jets and detonation gaseous products are separated by sharp interfaces, the traditional smoothed particle hydrodynamics (SPH) method is difficult to avoid the computational instability at interfaces. The multi-phase SPH (MSPH) method was applied to improving the stability, which smoothes the particle density and makes pressure continuous at interfaces. Numerical examples of jet forming process were used to test capability of the MSPH method. The results show that the method remains algorithm stability for large density gradient between the jets and gaseous products and has potential application to both the explosion and the jet problems. The effect of initiation ways of the shaped charge was discussed as well.

This paper discusses the collapse mode of thin reinforced concrete (RC) plates subjected to blast load. To extend the well known plastic-mode method to analyze, not only perfect-plastic plates, but also RC plates, it is needed to investigate the effect of material cracking on the collapse mode because the plate might have been cracked on both upper and lower surface before the plastic-mode fully develops, creating an unexpected type of collapse mode shape. A new failure mode is proposed and verified by numerical analysis in this paper. The new mode is a result of the material cracking and has an un-negligible effect on the reaction mechanism of the RC plate to the blast load.

In the investigation of accidental explosion scene, the damage on the glass is one of the typical traces which can be used to decide the characteristic of the explosion source. To analyze the response of glass under the blast load, a numerical model was developed. In the model, the brittleness glass model was adopted. A ‘node release’ method, which had some special merits compared with the erosion method was used to simulate the rupture of the glass In the calculation, several problems which play major role in the response of the glass were discussed. The velocity and the displacement of the glass fragment were two major factors. The numerical results are very helpful for the design and hazard assessment.

To study the dynamic properties of the concrete subjected to impulsive loading, stress-time curves of concrete in different velocities were measured using split Hopkinson pressure bar (SHPB). Effects of temperature and strain rate on the dynamic yield strength and constitutive relation of the concrete were analyzed. The dynamic mechanical properties of the reinforced concrete are subjected to high strain rates when it is at a relatively low temperature. But with temperature increasing, the temperature softening effect makes the strength of the concrete weaken and the impact toughness of the concrete is saliently relative to strain rate effect. So, strain rate effect, strain hardening and temperature softening work together on the dynamic mechanical capability of concrete and the relation between them is relatively complex.

The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM. The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites, as well as in the comparison between the test and numerical calculation. The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m, the distribution of overpressure behind wall was gained according to variety law based on small-large-small. It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5–2.5 multiples, and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall.

Numerical simulation of TNT underwater explosion was carried out with AUTODYN software. Influences of artificial viscosity and mesh density on simulation results were discussed. Detonation waves in explosive and shock wave in water during early time of explosion are high frequency waves. Fine meshes (less than 1,mm) in explosive and water nearby, and small linear viscosity coefficients and quadratic viscosity coefficients (0.02 and 0.1 respectively, 1/10 of default values) are needed in numerical simulation model. According to these rules, numerical computing pressure profiles can match well with those calculated by Zamyshlyayev empirical formula. Otherwise peak pressure would be smeared off and upstream relative errors would be cumulated downstream to make downstream peak pressure lower.

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, structural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves, and columns lost carrying capacity, subsequently leading to the collapse of the whole structure. The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.

By means of the improved split Hopkionson pressure bar(SHPB) with axial pre-pressure and confined pressure, two series of experiments on sandstone are carried out to research the failure mode of rock during the course of exploitation of resources in deep. One is under the conditions that the confining pressure is fixed and the axial pressure is changeable. The other is under the conditions that the confining pressure becomes and the axial pressure is fixed. It is found that samples break up evenly after impacting when axial static pressures are low, there is great disparity in size of fragments when axial static pressures are high, and the main bodies of samples after the tests under the combination of dynamic and static loads frequently show the type of V or X. The samples are more close-grained at the elastic stage and impacts make many cracks be generated and developed, as makes samples more crackable. At the initial phase of damage stage, the static pressures make some cracks in the samples which are undeveloped and the impacts’ role is similar to that at the elastic stage. At the metaphase or anaphase of damage stage, these cracks in the samples develop adequately and the impacts mainly accelerate samples’ failure. The main bodies of samples show the type of V or X after impacting due to the confining pressures’ restraining samples’ lateral formation at the elastic stage or the initial phase of damage stage, the main bodies of samples have almost formed at the stage loading static pressures and the results after impacting usually are similar to those under the axial pressures tests.

As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the temperature of bars increases when specimen starts to contact with bars, which induces the nonuniform temperature distribution in specimen, and may result in inaccuracy of experimental results. In this paper, the temperature distributions of specimen and bars in high temperature SHPB experiments were investigated while the specimen was heated alone. Firstly, the temperature history of specimen was measured at different initial temperatures by experiments, then simulation was carried out. Simulation results were consistent with experimental results by adjusting the thermal contact coefficient between specimen and bars. By this way, the thermal contact coefficient and simulation results were validated, and the proper cold contact times of specimen and bars in high temperature SHPB experiments were discussed. Finally, the results were compared with those in references.

A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads. In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied experimentally in order to investigate its isolation performance under the impact loads. A new mechanical model of MRD was proposed according to the data obtained by impact test. A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads. It is also demonstrated that MRD can improve the acceleration and displacement response of the structure obviously under impact loads.

The paper presents the theory of Hamilton variation principle which is the current method for impact problem, central difference method which is efficient solution of finite element (FE) method for impact problem and adapts to solve non-linear dynamic problem. And it introduces the ANSYS/LS-DYNA which is the popular FE software for impact problem both at home and abroad. Then it gives solutions for one simple model by analytical method and ANSYS/LS-DYNA respectively to validate function of software, and they are consistent. Afterward, it gives model of single-layer Kiewitt reticulated dome with a span of 60 m, and the cylinder impactor, and introduces the contact interface arithmetic, especially the material model of steel (piecewise linear plasticity model) which takes stain rate into account and makes steel failure stress higher under impact loads. The vertical displacement, stress in main members, and the plastic deformation for dome under impact loads were obtained. Then four failure modes (no failure, moderate failure, global failure and slight failure) were summarized according to the rules of dynamic response. And the characteristics of dynamic response for each failure mode were shown.

No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. T _E (the time that the end of impact force) and T _F (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consumption. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain E _LF (the energy left in the main reticulated dome) from the initial kinetic energy of impactor. Moreover, the distribution of failure modes is decided by E _LF which leads to the maximum dynamic response of the reticulated dome, but not by the initial impact kinetic energy of impactor.

Terrorist attacks using improvised explosive devices (IED) can result in unreinforced masonry (URM) wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the performance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the performance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elastoplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.

In order to design and retrofit a subway station to resist an internal blast, the distribution of blast loading and its effects on structures should be investigated firstly. In this paper, the behavior of a typical subway station subjected to different internal blast loadings was analyzed. It briefly introduced the geometric characteristics and material constitutive model of an existing two-layer and three-span frame subway station. Then three cases of different explosive charges were considered to analyze the dynamic responses of the structure. Finally, the maximum principal stress, displacement and velocity of the columns in the three cases were obtained and discussed. It concluded that the responses of the columns are sensitive to the charge of explosive and the distance from the detonation. It’s also found that the stairs between the two layers have significant effects on the distribution of the maximum principal stress of the columns in the upper layer. The explicit dynamic nonlinear finite element software—ANSYS/LS-DYNA was used in this study.

According to the blasting construction of the diaphragm wall of Puxi approaching section of East Fuxing Road river-crossing tunnel, the monitoring project of the vibration of the existing tunnel induced by the blasting construction is put forward, which includes the sensors’ location, monitor method and the vibration monitoring system. Based on the monitoring data of the explosion vibration, the vibration wave forms, velocities, acceleration responses, main frequencies and fields of measure points are analyzed under the conditions of three locations and different charge quantities. According to the safety-judging standard of explosion vibration, the conclusion that the existing tunnel is safe under the explosion vibration is then drawn. Furthermore, the spectrum characteristics of three explosion vibrations and the spectrum changing properties of explosion vibration wave transmitting in different directions are concluded, which can provide reference to similar projects.