Advanced Materials Research Vols. 250-253

Abstract: Based on the field investigation for secondary geological hazards induced by 5.12 Wenchuan Earthquake, the types of geological disasters during or after earthquake are analyzed in this paper. The main secondary geological hazards are rock fall and collapse, landslide, debris flow, dammed lake，sand liquefaction and so on. The development and distribution rules of secondary geo-hazards, with a long-term sustainability and a formation of hazard chains, are of relation with earthquake fault zone, and consistent with seismic intensity. The buildings located in secondary geo-hazards areas with a high risk are damaged severely, thus the site selection for post-earthquake reconstruction and related geotechnical engineering issue are discussed, which are useful in reconstruction of Wenchuan earthquake area.

Abstract: According to the characteristic of multi-arch highway tunnel,based on a practice engineering, the monitoring work was consisted of four sections:the displacement of surrounding rock; such as crown settlement, displacement of the ground, displacement of inner surrounding rock; that of stress and stain of support structure; that of force in middle-wall. In course of construction,monitoring data was analyzed in time.Structural timbering parameters were modified in response to abnormal monitoring data in order to guarantee safety.the testing results of the safety monitoring system are satisfactory, which serves as a symbol of our research work. Thus, our engineering practice has proved the applicability and feasibility of the safety monitoring and information construction methods.

Abstract: With a large-scale physical model test of active ground fissure, the rules of the soil stress and displacement changes induced by active ground fissure are studied. The results show that, the active ground fissure causes soil stress and displacement field changes within a certain area, namely, soil stress reduce in the hanging wall, but increase in the foot wall. The farther from ground fissure the area is, the smaller the reduction and increase of soil stress caused by ground fissure movement. There are generally 4 soil stress distribution zones induced by active ground fissure, which are, original stress zone of the foot wall, stress increase zone, stress reduction zone and original stress zone of the hanging wall and among which, stress reduction zone is 1.0 to 1.5 times that of stress increase zone. The active ground fissure leads to abrupt displacement phenomena, taking the step shape at its both sides, and as the strata goes from deep to shallow, soil deformation area in section increases obviously. The influence area in the hanging wall is bigger than that in the foot wall.

Abstract: The objective of this paper is to present the behaviour of composite beam using Trapezoid Web Profiled (TWP) steel section by determining the moment resistance and the deflection of the beam with composite and non-composite connections. The TWP steel section is a built up section where the flange is of S355 steel section and the corrugated web of S275 steel section. Three full scales testing setting-up as sub-assemblage frame have been carried out. It was concluded that the use of composite connection and extended end-plate has reduced significantly the deflection and has significantly increased the loading capacity of composite beam.

Abstract: This paper presents the experimental investigation result from a composite beam strengthened by shaped-steel underpinning (CBSSU) test. There were 3 specimens with one was common R.C beam to compare and others were strengthened by shaped-steel underpinning and jointed with short welding rebars. The main emphasis in undertaking this test was to show the effect of short welding rebars in the strengthening beams and collect more detailed data on the performance of CBSSU such as load capacities, load-deformation behaviors, slipping between shaped-steel and R.C beams, stresses distribution and failure mode. The test shows that the short welding rebars was effective to improve the bearing capacity and stiffness. With limited increase in height of the beam can substantially increase the ultimate flexural capacity and flexural rigidity. The cracks of the beam can also be controlled effectively.

Abstract: A smart base-isolation system, composed of low damping bearings and piezoelectric friction damper is studied in this paper. The semi-active piezoelectric friction damper (PFD^[1]) is proposed for control of peak dynamic response of seismic-excited structures. In the proposed PFD device, the friction force between two sliding plates is regulated by controlling the normal force using piezoelectricity across the damper, and its advantage is that its operation requires only minimal external power. A high efficient control algorithm is proposed for the semi-active control of the friction damper using a simple static output. The effectiveness of the PFD device and the control strategy in reducing the peak dynamic response of structures is investigated through an application to a 5-story base-isolated building. Numerical results demonstrate that the proposed PFD device and the control strategy are effective in reducing the peak drift of rubber-bearings of the base-isolated building subject to earthquakes.

Abstract: Based on the low reversed cyclic loading experiment of a specimen of three-story prestressed fabricated concrete frame, this paper investigates the carrying capacity, the failure mode, the load-displacement hysteresis curve of frame. The research includes the seismic performances such as failure mechanism, rigidity degradation, hysteretic behavior and etc. The results indicate that the plastic hinge first appears at the ends of beam at lower story. The connections of frame are in a state of bi-direction compression and have more joint stiffness, which therefore enhances the frame lateral stiffness and improves the deformation recovery capability. The carrying capacity of the frame hasn’t serious degradation at story drifts between 1/39 and 1/64. The post-tensioned prestressed fabricated concrete frame is a “strong column weak beam” structure.

Abstract: This paper offers the model that can estimate the cementing efficiency of fly ash (k value) based on a mix proportion of concrete containing fly ash (FA). The prediction model was derived using various statistical analyses, based on a wide range of mix proportions and a number of strength test results of ready mixed concretes used in eight construction sites. The k value increases with increasing water-binder ratio. As the FA replacement ratios increase, the k value increases at FA replacement ratios of less than 15%, but decreases at ratios of 15% or more. The k values obtained from the cementing efficiency estimate model range from 0.1 to 2.1.

Abstract: The aim of this paper is to study elasto-plastic behavior of the doubler plate reinforced tubular T-joints (DP-T-joints) subjected to axial tension or compression loading at the top of brace. Finite-element method is adopted in the numerical parametric studies to evaluate the ultimate strength of DP-T-joints. To verify numerical analysis, a typical full-scale doubler plate reinforced tubular T joints experimental study has been modeled using ABAQUS package. The load-displacement curves of the numerical results agree with the experiment curve very well. Then, affect of parameter (doubler plate width parameter α, doubler plate length parameter Δ, doubler plate to chord wall thickness ratio λ) on the elasto-plastic behavior has been investigated.

Abstract: Valencia is a city located in the East of Spain by the Mediterranean Sea. It has a huge historic centre with ancient winding streets that contains buildings with a singular architectural heritage. The buildings’ façades are protected by a traditional external rendering, sometimes in bad state of conservation or modified or substituted in restoration works. The study carried out on historic renderings in Valencia points out the great employment of gypsum mortar or gypsum-lime mortar, among other peculiarities. Gypsum external rendering is one of the many uses for gypsum mortars in Valencia traditional architecture. This fact contradicts the general belief of the exclusive use of lime mortars for rendering a façade. The knowledge of the characteristics of historic mortars will allow us to implement a proper restoration work of architectural heritage with suitable mortars, as it is essential to guarantee the adherence and compatibility of any repair.