Experimental Study on Improving Seismic Behavior of Load-Bearing Masonry Wall Made of Autoclaved Aerated Concrete

To investigate the seismic behavior of autoclaved aerated concrete load-bearing masonry wall(AACLMW), a piece of control block wall without constructional measures and five pieces of block walls with different constructional measures were tested under low reversed cyclic loading which imitated low to moderate earthquake force. The seismic behavior of AACLMW with different constructional measures in terms of failure mode, hysteretic curve, deformation capacity and displacement ductility was studied and compared with that without constructional measures. The experimental results indicate that the constructional measures comprising constructional columns and horizontal concrete strips are effective for improving the seismic behavior of AACLMW. The study in this paper can provide a reliable experimental basis for further analysis and engineering application of AACLMW in the future.

Investigation on Cracking of Concrete Shear Wall under Exceeded Temperature Differences Rate

In situ, the changes of temperature, deformation, and stressing of steel bar of C40 reinforced concrete shear wall were measured, respectively. The results are obvious that the temperature change of climate is one of the most effective factors which could lead the concrete shear wall to cracking at earlier age. The temperature differences between inside and outside concrete shear wall are so large that the concrete will gain larger shrinkage. This larger shrinkage which is caused by the temperature reducing ratio will gain the strained action of head, end and reinforced steel bar of concrete shear wall. This action can lead to tensile stress on the surface and inside concrete shear wall. If the tensile stress would exceed the pull strength of concrete, the concrete shear wall would crack and cause deterioration. Thus, the enhancing curing of concrete shear wall in suit at earlier age, and controlling temperature reducing ratio and deform caused by shrinkage, will be available treatments which control occurring and developing of cracking on concrete shear wall.

Assessment of seismic design response factors of concrete wall buildings

To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region （UAE）. A large number of Inelastic Pushover Analyses （IPAs） and Incremental Dynamic Collapse Analyses （IDCAs） were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics.

Long-lived neutron-induced radioisotopes in OKTAVIAN facility concrete wall after 38 year-operation

An intense 14 MeV neutron source facility named OKTAVIAN was installed in the A15 building,Osaka University in 1981.Along the operation period,new radioisotopes with various half-life have been produced as neutron activation products in its concrete wall shield.In this work,we investigated the concrete wall in the heavy irradiation room of OKTAVIAN using gamma spectrometry method to discover the presence of radioisotope having large half-life value(long-lived radioisotope)as neutron activation products.Computational simulations were performed prior to measurement to predict the presence of long-lived radioisotopes by employing MCNP5 and FISPACT codes.A pre-calibrated Germanium detector with high energy resolution was employed to measure the concrete.Several long-lived activation products have been observed such as 152 Eu,54 Mn,65 Zn,22 Na and 60 Co.The activity of each radioisotope was derived after estimating the detector efficiency using MCNP5.As a result of the measurement and analysis,the followings are concluded:(1)Though presence of activation products represents radiological risk to everyone who performs an experimental activity in the irradiation room of the OKTAVIAN facility,the present result shows that past experiments were carried out safely without any significant additional exposure dose coming from the wall for the last 38 years.(2)The approximated total fluence of D-T neutrons to the wall was successfully estimated from the produced radioisotope,152 Eu,because it has the longest half-life of 13.5 years among the observed radioisotopes.(3)From the results of(1)and(2),it could be possible to estimate the total activity of the concrete wall in the OKTAVIAN facility,which is very essential and important information,because this would be very valuable for decommissioning or disposal of the facility in the future.

Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

The Continuum Analytical Method of Steel Frame- Reinforced Concrete Shear Wall Mixed Structure

The inter-story drift stiffness considered the semirigidity of beam and column joints connection, and P-Delta second order effect of steel frame parts in the mixed structure is presented in the paper. After considering on the influence of semirigidity between steel beams and steel columns, second order effect of beam-column members for steel frame and structural second order effect, the traditional continuum analytial method used in RC shear-frames wall structure is developed to steel frames-reinforced concrete shear wall mixed structure subject to horizontal load in this paper. A continuum approach, which is suitable for analyzing steel frames-reinforced concrete shear wall mixed structure subject to horizontal load, is presented. The method is relatively simple and more practical. It will be referred to structural design for steel frames-reinforced concrete shear wall mixed structure.

Experimental testing of RC shear wall seismic retrofit using selective weakening,self-centering and Ultra High performance concrete

Traditional retrofit methods often focus on increasing the structure’s strength,stiffness,or both.This may in-crease seismic demand on the structure and could lead to irreparable damage during a seismic event.This paper presents a retrofit method,integrating concepts of selective weakening and self-centering(rocking)to achieve low seismic damage for non-code compliant reinforced concrete shear walls.The proposed method involves con-verting traditional cast-in-place concrete shear walls into rocking walls,which helps to lower the shear demand,while allowing re-centering.Two large-scale lateral load tests were performed to validate the retrofit concept on a concrete shear wall designed according to pre-1970s standards.The design parameters investigated were amount of energy dissipating reinforcements and confinement enhancement.Two different methods using Ultra High Performance Concrete(UHPC)were investigated to provide additional confinement to boundary elements of older shear walls.Observations from the tests showed minimized damage and enhanced recentering in the retrofitted wall specimens.Use of UHPC in the boundary elements of the retrofitted walls provided additional confinement and reduced damage in the rocking corners.

The analysis for stress-strain characteristics of concrete cutoff wall built in deep cladding foundation

Combined with a proposed homogeneous earth dam in deep cladding foundation, Duncan E-B model is applied to simulate dam-filled material, apply to three-dimensional nonlinear finite element method, attain the stress-strain distribution and alteration in concrete cutoff wall in completion and water storage periods, analysis the stress state in the contact element between concrete cutoff wall and cladding foundation, provide the corresponding measures. The calculation results show that the design of concrete cutoff wall and homogeneous earth dam is reasonable.

Structural Analysis of a RC Shear Wall by Use of a Truss Model

Purpose of present work is to develop a reliable and simple method for structural analysis of RC Shear Walls. The shear wall is simulated by a truss model as the bar of a truss is the simplest finite element. An iterative method is used. Initially, there are only concrete bars. Repeated structural analyses are performed. After each structural analysis, every concrete bar exceeding tensile strength is replaced by a steel bar. For every concrete bar exceeding compressive strength, first its section area is increased. If this is not enough, a steel bar is placed at the side of it. For every steel bar exceeding tensile or compressive strength, its section area is increased. After the end of every structural analysis, if all concrete and steel bars fall within tensile and compressive strengths, the output data are written and the analysis is terminated. Otherwise, the structural analysis is repeated. As all the necessary conditions (static, elastic, linearized geometric) are satisfied and the stresses of ALL concrete and steel bars fall within the tensile and compressive strengths, the results are acceptable. Usually, the proposed method exhibits a fast convergence in 4 - 5 repeats of structural analysis of the RC Shear Wall.

Numerical simulation of squat reinforced concrete wall strengthened by FRP composite material

The advanced design rules and the latest known earthquakes, have imposed a strengthening of reinforced concrete structures. Many research works and practical achievements of the application of the external reinforcement by using FRP composite materials have been particularly developed in the recent years. This type of strengthening seems promising for the seismic reinforcement of buildings. Among of the components of structures that could affect the stability of the structure in case of an earthquake is the reinforced concrete walls, which require in many cases a strengthening, especially in case where the diagonal cracks can be developed. The intent of this paper is to present a numerical simulation of squat reinforced concrete wall strengthened by FRP composite material （carbon fiber epoxy）. The intent of this study is to perform finite element model to investigate the effects of such reinforcement in the squat reinforced concrete walls. Taking advantage of a commercial finite element package ABAQUS code, three-dimensional numerical simulations were performed, addressing the parameters associated with the squat reinforced concrete walls. An elasto-plastic damage model material is used for concrete, for steel, an elastic-plastic behavior is adopted, and the FRP composite is considered unidirectional and orthotropic. The obtained results in terms of displacements, stresses, damage illustrate clearly the importance of this strengthening strategy.

Structural Retrofitting of Old Illyria Hote

Illyria hotel （formerly Bozhur） was built during the sixties in the heart of the actual Kosovo＇s capital Prishtina, according to former old Yugoslav standards in a Modernist architectural style. It represents a massive structural system with brick walls up to 54 cm thick and ＂avramenko＂ type reinforced concrete floors. The investor＇s aim was to add another two floors on the top of the existing ones and to build two level underground parking floors, a health spa centre, whilst at the vicinity of the existing building （the northern side） to erect a new 17 story-high brand new hotel and administration building. The retrofitting of the structure as well as construction of the new structure has been done in full accordance with the new structural Eurocodes＇ recommendations. 3D FEM （finite element method） modeling was used for the analysis and design, using ETABS v 9.5 nonlinear and ARSAP 2010 （Autodesk Robot Structural Analysis Professional 2010）. Response spectrum design according to EC 8,3.2.2.4 has been used for seismic analysis and design with a reference peak ground acceleration on type A ground Of AgR = 0.25 g.

Experimental study on out-of-plane seismic performance of precast composite sidewalls of utility tunnel with grouting-sleeve joints

The precast composite reinforced concrete wall with the advantages of fewer joints,superior impermeability and rapid construction provides an efficient and environmental friendly alternative in the construction of underground utility tunnels in the last few years.To investigate the seismic performance of precast concrete composite walls of utility tunnels with grouting-sleeve connection under out-ofplane loads,a series of quasi-static cyclic tests were performed on the full-scale sidewall specimens with different axial compression ratios in this study.The experimental results including the failure modes,crack distributions,and the influence of different connections on the out-of-plane seismic performance of precast concrete composite wall were carefully examined and compared with those from the cyclic tests of the cast-in-place sidewalls of the utility tunnel.The test results show that the seismic performance of the precast concrete composite sidewall specimen,such as the hysteresis curves,the ultimate bearing capacity,stiffness degradation pattern and the ductility ratio,is basically the same as that of the cast-in-place specimen,indicating that the seismic performance of the prefabricated structure is equivalent to that of the cast-in-place structure.Moreover,the grouting-sleeves of the joints can effectively transfer the reinforcement stress until the failure of the precast concrete composite sidewall specimens,which exhibits excellent out-of-plane ductility and serviceability.

Seismic design and analysis of a high-rise self-centering wallbuilding:Case study

Post-tensioning self-centering walls are a well-developed and resilient technology.However,despite extensive research,the application of this technology has previously been limited to low-rise buildings.A ten-story selfcentering wall building has now been designed and constructed using the state-of-art design methodologies and construction detailing,as described in this paper.The building is designed in accordance with direct displacement-based design methodology,with modification of seismic demand due to relevant issues including higher-mode effects,second order effects,torsional effects,and flexural deformation of wall panels.Wall sections are designed with external energydissipating devices of steel dampers,and seismic performance of such designed self-centering walls is evaluated through numerical simulation.It is the first engineering project that uses self-centering walls in a high-rise building.The seismic design procedure of such a high-rise building,using self-centering wall structures,is comprehensively reviewed in this work,and additional proposals are put forward.Description of construction detailing,including slotted beams,flexible wall-to-floor connections,embedded beams,and damper installation,is provided.The demonstration project promotes the concept of seismic resilient structures and contributes to the most appealing city planning strategy of resilient cities at present.The paper could be a reference for industry engineers to promote the self-centering wall systems worldwide.

Seismic assessment of RC frames infilled with innovative CFS walls considering seismic orientation effect

The metal tailings porous concrete cold-formed steel(MCFS)wall is an innovative cold-formed steel(CFS)wall with good thermal and mechanical properties,which has the potential to be widely utilized as the infilled wall(IW).In this paper,the MCFS walls are adopted in the reinforced concrete(RC)frame,and the seismic performance of the building subjected to ground motions with various incidence angles are investigated.Three-dimensional finite element model of the studied building is developed with full consideration of the in-plain(IP)and out-of-plane(OP)behavior of MCFS walls.Incremental dynamic analysis is conducted to obtain the deformation responses of frames and damage ratios of MCFS walls under the combined effect of seismic intensity and orientation.Fragility curves are generated to assess the seismic performance of the building and investigate the effect of ground motion orientation.The results validate the superior performance of infilled MCFS walls,and reveal that the seismic orientation has a considerable impact on the response along each reference axis of the structure.Furthermore,different incidence angles induce up to 10.2%and 14.4%variations in the median Sa(T1)of fragilities for the frames in X and Y axes,and the corresponding change rates in the median Sa(T1)for the walls are 13.5%and 15.1%,respectively.However,for the overall performance of the building,the seismic orientation effect is less significant.The rates of changes in median Sa(T1)are less than 4%for both frames and MCFS walls.

HYGROTHERMAL PERFORMANCE ASSESSMENT OF ICF WALLS WITH DIFFERENT MOISTURE CONTROL STRATEGIES AND WALL DESIGNS

The initial high moisture content of concrete and the low vapor permeability of insu-lation layers on both sides of the concrete complicate the drying process of Insulated Concrete Forms(ICF).In order to facilitate the moisture transport and enhance the drying process,different moisture control stratcgics and wall designs can be implc-mented.The application of an air and vapor barrier is one of the most common moisture control stratcgics.In this paper,the impact of vapor permcance of an air and vapor barriers on the hygrothermal performance of an ICF wall in three differ cnt cold and wet climates is examined using a validated Hcat-Air-Moisture transfer model.The hygrothermal performance of an ICF wall assembly with different types of barriers and locations in the wall system for scveral wall designs is invcstigated.Results indicate that a smaller thickness of insulation on the outside facilitates remov-ing the moisture towards the outside and installing low permcance air/vapor barrier systems on the outside prohibits drying and drives the moisture to the inside.Our findings also show that with the proper sclection of insulation thickncss and vapor control stratcgy moisture-related problems can be avoided.