Asian journal of civil engineering
Volume:18 Issue: 8, Dec 2017

The analysis of thin shell structures has generally been purely carried out based on a theoretical basis, usually by superposing the membrane and bending behavior. It is of great importance to carry out experimental tests to validate the numerical models. In this paper, a series of tests have been conducted on cylindrical shell models with different types of boundary conditions and wall thicknesses under the effect of concentrated progressive loads. The experimental results obtained are compared to those derived numerically. A new flat shell element called ACM-Q4SBE1composed of strain-based quadrilateral membrane element Q4SBE1and the standard plate bending element ACM is used for the numerical analysis, in addition to the S4R ABAQUS element. The results obtained confirm the effectiveness and superiority of the flat shell approach for the linear analysis of shell structures.

In this paper, an analytical approach is presented for the determination of the natural frequencies of tall structures with a combined system of the framed tube, shear core and outrigger-belt truss. It has been assumed that the structure has variable stiffness and mass along the height. The framed tube is modeled as a cantilevered beam with variable box cross section and effects of outrigger-belt truss and shear core on the framed tube system are modeled as a concentrated moment applied at outrigger-belt truss locations. Through repetitive integrations, the governing partial differential equations are converted into weak form integral equations. By applying the boundary conditions, the integration constants are determined. The mode shape function is approximated by a power series. Substitution of the power series into weak form integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of the non-trivial solution for the resulting system of equations. Accuracy of the proposed method is verified through several numerical examples, in which the results of the analysis are compared with those obtained from other references.

Masonry structures are popularly used in the construction for the several thousand years. The masonry walls have showed inferior performance during any uncertain loads. Lightweight wall panels are the better alternative for the masonry structures. Lightweight concrete is developed by mixing the 3 mm diameter EPS (Expanded Polystyrene) beads and a flowable concrete. The sandwich wall panel is developed using the lightweight concrete with a density of about 920 kg/m3. Cubes and cylinders are tested and developed a material model for the lightweight concrete. A wall panel of size 1.25 m * 1.25 m * 150 mm is cast with a lightweight concrete inner core and tested for in-plane compression loading. A nonlinear finite element analysis is carried out with material nonlinearities and compared with experimental results. The results are found comparable and it confirms the material model developed. The present study showed that the lightweight concrete sandwiched with ferrocement skin is well suitable for the wall construction.

The principal aim of this case study includes the determining of wind pressure co-efficient and wind velocity analysis of N-plan shape tall building using k-ε method. The wind angles varying from 0° to 180° at 30° interval scale of 1:300 and terrain category 2. A square plan with same area compared with the N-shape model also validated with different codes AS/NZS: 1170.2 (2002), ASCE/SEI 7-10 (2010), BS: 6399-2 (1997), EN: 1991-1-4 (2005) and IS 875 (part 3) (1987). The wind velocity and force coefficients around this model at different faces are also discussed here.

This paper investigates the reduction of stiffness, variation of flexural rigidity and nonlinear response of RC member to detect flexural cracks. The positive cyclic pseudo static load was applied stepwise to the specimen to induce damage. Flexural rigidity characteristics were studied by conducting free vibration test on RC beam at various stages. Vibration characteristics of each damage state were successfully identified to detect the relationship between damage levels and fundamental frequencies under various failure loads. Due to flexural cracks longitudinal bars may yield resulting in reduction in effective flexural rigidity and hence frequency. This yielding of reinforcement in longitudinal bars can be detected from change in natural frequency. The non-linearity was detected by checking the changes in the fundamental frequency during various stages of loading.

The work introduced in this article is a theoretical study of the behaviour of composite beams with respect to the shrinkage of concrete. In fact, our contribution resides essentially in consideration of the degree of connection (N/Nf) between the slab and steel beam. While using the theory of the linear viscoelasticity of the concrete, and on the basis of the Rate of Creep Method of concrete, in proposing an analytical model, made up by a system of two linear differential equations, emphasizing the effects caused by shrinkage on the resistance of a steel-concrete composite beams regardless degree of connection employed.

There are limited studies available regarding the repair of steel beams and steel-concrete composite girders using fibre-reinforced polymer (FRP) reinforcements. However, among these studies there are a few resources dealing with numerical modelling of such beams using the finite element (FE) method. In this research a finite element simulation was developed to evaluate efficiency of various types of FRP plates, externally bonded on tension flange, on the enhancement of flexural strength of damaged composite girders. The primary defect in girders was simulated by inserting a notch through the tension flange and partial in web at mid-span. The occurrences of initiation and propagation of debonding as well as the effect of partial shear connection between the steel beam and concrete slab were taken into account. To ensure the validity of the proposed numerical model, the obtained results from the current analysis were compared with those existing experimental studies. This study focused on varying types of FRP and the amount of damage. Four common FRP types varying in modulus elasticity were employed to evaluate their influences on flexural strength and stress concentration at the critical region, i.e. the root of the notch. It was observed that higher modulus FRPs have more capability to limit the high principle strain in the critical region and, consequently, to reduce the rate of crack propagation across the steel section. Finally, the interaction between the FRP thicknesses and the notch depths in the web of steel beam was examined.

Structural engineers often come across buildings, which exhibit certain degrees of plan asymmetry. It may in fact even exist in a nominally symmetric structure, because of the uncertainty in the distribution of floor loads, uncertainty in the evaluation of the centre of mass and centre of stiffness, inaccuracy in the measurement of dimensions of the structural elements, or lack of precise data on the material properties. The performance of asymmetric buildings under seismic excitation is very poor and its behaviour is highly complex when compared to that of regular buildings. This paper focuses on the seismic induced torsion in asymmetric RC buildings. Equivalent Lateral Force Method (ELF) is adopted as per IS:1893(Part-1)-2002 codal provisions to study the induced torsion. ETABS software package is used to carry all the static and dynamic analysis by keeping these models in different seismic zones from Zone II to Zone V. The discontinuities in a lateral force resistance path, such as vertical offsets, are also considered here. The main framework involved studying the effect of irregular distribution of mass, asymmetric distribution of stiffness and irregular plan configurations and comparing it with the seismic response of a regular structure. The results showed that Base shear and lateral displacement were increasing with increase in the seismic intensity from Zone II to Zone V. Also the Base shear for mass irregularity is found more compared to all other irregularities.

The paper investigates the long-run effect of alkali-silica reaction (ASR) on the integrity of a multi-story reinforced concrete building. Alkali-silica reaction is one of the major causes of damage to the concrete. It is produced by the formation of expansive calcium silicate hydrate (C-S-H) compounds as a result of the reaction between alkaline cement paste and non-crystalline silica in the aggregates. The expansive resultant causes outward pressure on the microstructure of the concrete. Because concrete is brittle, especially in tension, the outward pressure leads to its eventual fracture and failure. In general moisture has been found a critical element in initiating ASR. The cement alkaline content and the percentage of siliceous compounds in the aggregates are two other deciding factors which determine the potential for ASR. Although, the reaction phenomenon itself has been vastly explored in the literature, its eventual effect on the structure is not as equally well studied. This paper investigates the evidence and progress status of alkali-silica reaction (ASR) in a thirty-year-old half-built reinforced concrete building. The methodology to inspect the development of ASR in the structure is presented. Then, the effect of ASR on the structural integrity of the building is assessed using direct loading test.

This paper investigates the effective parameters on seismic efficiency of tuned mass dampers, TMD, in dual systems of moment resisting frame and cross bracing with 15, 20 and 25 stories. TMDs with different mass ratio were located at different heights. Non-linear time history analyses were conducted under three earthquake records. The results showed that the reduction of base shear is significant at all the cases, and by increasing the number of stories, reduction of the base shear is increased. However, in terms of displacement and acceleration of the roof, TMD could be very sensitive to its parameters.

In recent years, it has been observed that historical unreinforced masonry buildings are the most damaged structures after an earthquake event, mainly due to the degradation of materials and the non symmetric distribution of bearing walls. Its conservation is then important when it represent an architectural artistic asset especially when it is still functional. In this paper, the seismic performance-based assessment developed within the European PERPETUATE project was applied adopting two different modeling strategies, structural element model SEM for macroelements with regular geometric forms and continuum constitutive law model CCLM for arcades. The case of this study is an historical masonry building, considered as a valuable architectural heritage of Mostaganem city in Algeria. The assessment is performed by static non linear analysis of the building assuming that the response of the structure is well described by a set of macroelements that are analyzed separately. Pushover analysis of each bearing wall was implemented using Tremuri software for SEM model and the finite element Ansys software for CCLM model by supposing a micro-modeling of materials. The results obtained by combination of the aforementioned models allowed us to establish fragility curves that represent the response of the whole asset corresponding to four performances levels.