Amir Mirmiran

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Verified

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• PhD
• Sam Lindsey Professor and Provost at The University of Texas at Tyler

This study presents experimental and numerical investigations on the mechanical properties of ultra-high-performance concrete (UHPC) reinforced with single and hybrid micro-and macro-steel and polypropylene fibers. For this purpose, a series of cubic, cylindrical, dog-bone, and prismatic beam specimens (total fiber by volume = 1%, and 2%) were test...

Compressive, tensile, and flexural properties of ultra-high-performance concrete (UHPFRC) specimens were studied in this research. Binary and ternary combinations of micro steel (MS), round crimped (RC), crimped (C), hooked-end (H), and polypropylene (PP) fibers were used in overall ratios of 2 % by volume of concrete. For this purpose, 100×200 mm...

A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (...

This paper presents experimental and numerical investigations on mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) with four types of steel fibers; micro steel (MS), crimped (C), round crimped (RC) and hooked-end (H), in two fiber contents of 1% and 2% (by volume) and two lengths of 13 and 30 mm. Compression, direct...

This study investigates the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams with and without initial notch both experimentally and numerically. Parameters of the study were the modulus of elasticity, flexural strength, crack mouth-opening displacement (CMOD), crack tip-opening displacement (CTOD), notch-to-depth...

This study investigates the behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) with hybrid macro-micro steel and macro steel-polypropylene (PP) fibers. Compression, direct and indirect tension tests were carried out on cubic and cylindrical, dogbone and prismatic specimens, respectively. Three types of macro steel fibers, i.e., r...

This article compares the flexural responses of ultrahigh-performance fiber-reinforced concrete (UHPFRC) specimens and their normal-strength concrete (NSC) counterparts through an experimental study. Four UHPFRC specimens reinforced with 2 % steel fiber (by total volume of concrete) with a length of 13 mm and a diameter of 0.2 mm were used with lon...

In this research, the flexural and shear behavior of five locally developed ultra-high-performance fiber-reinforced concrete beams was experimentally investigated. Four-point loading tests were carried out on concrete specimens which were further compared with five normal-strength concrete beams constructed at the laboratory. The objective of this...

A roof system includes a roof panel formed of concrete and an architectural surface such as a corrugated surface. A first layer of reinforcing material is disposed along and spaced inwardly from a first surface of the roof panel, and an optional second layer of reinforcing material is disposed along and spaced inwardly from a second surface of the...

Abstract: The application of ultra-high performance concrete (UHPC) as an alternative to conventional/normal concrete (NC) has grown rapidly in recent years. However, there is limited knowledge on its shear behavior, which is essential for developing design guidelines for structural applications. A detailed parametric study was conducted on 38 beam...

Sectional flexural analysis, as performed in normal strength concrete design, requires uniaxial constitutive models. For ultra-high performance fiber reinforced concrete (UHPFRC), the constitutive model tensile backbone varies with section heights for different flexural members, due to the size-dependent stress-crack opening relation used to derive...

An innovative composite flat roof was developed to resist hurricane wind forces for industrial, commercial, and low- to midrise residential building applications. Combining two advanced materials, ultra-high-performance concrete (UHPC) and high-strength steel (HSS), the proposed engineered system is superlight, with only 83 kg/m² (17 lb/ft²) self-w...

A new lightweight, low-profile composite deck system is presented that was fabricated using vacuum-assisted resin transfer molding. The deck in this system is composed of ultrahigh-performance concrete (UHPC) for high compressive strength and durability, carbon-fiber-reinforced polymer (CFRP) for high tensile strength, and glass-fiber-reinforced po...

The Texas Department of Transportation frequently constructs prestressed concrete piles for use in bridge foundations. Such prestressed concrete piles are typically built with steel strands that are highly susceptible to environmental degradation and corrosion in harsh marine environments. The department currently employs many techniques to combat...

A new lightweight, low-profile composite deck system is presented that was fabricated using vacuum-assisted resin transfer molding. The deck in this system is composed of ultrahigh-performance concrete (UHPC) for high compressive strength and durability, carbon-fiber-reinforced polymer (CFRP) for high tensile strength, and glass-fiber-reinforced po...

Carbon fiber–reinforced polymer (CFRP) tendons can serve as a viable alternative to steel strands in prestressing applications in which the noncorrosive nature of the strands helps reduce maintenance costs and extend the service life of the structure. An important consideration for CFRP tendons is the prestress level, which is currently limited by...

A new lightweight flat roof system is proposed for wind mitigation, using a novel material combination: Ultrahigh Performance Concrete (UHPC) and High Strength Steel (HSS). The proposed system is shallow in profile (4 in.), light in weight (17 lb/sqf), and ultra thin-walled of only 0.75 in., all possible with no shear reinforcement needed. A compre...

An experimental and analytical study was conducted on the seismic performance of a 0.3-scale two-column bent incorporating two precast columns with advanced materials, a precast footing, and a precast cap beam. The objective was to determine if the connection details and construction methods used in this study are appropriate for accelerated bridge...

Roofs are the most vulnerable building components when subjected to extreme wind events such as hurricanes. An innovative wind-resistant composite roof structure is engineered for commercial, industrial, and multistory residential buildings to withstand hurricanes and other windstorms up to 200 miles per hour (322 kilometers per hour). The design i...

A roof system includes a roof panel formed of concrete and an architectural surface such as a corrugated surface. A first layer of reinforcing material is disposed along and spaced inwardly from a first surface of the roof panel, and an optional second layer of reinforcing material is disposed along and spaced inwardly from a second surface of the...

Ultrahigh-performance concrete (UHPC) offers a superior alternative to normal-strength concrete (NSC) due to its significantly higher compressive and tensile strengths, improved ductility, and enhanced durability. This paper presents an experimental study of the stress-strain behavior of UHPC confined by conventional transverse steel reinforcement....

Movable bridges often include open grid steel deck for its light weight and ease of installation. These decks, however, suffer from poor rideability and high maintenance costs. The primary objective of this research project was to search for a new generation of lightweight solid decks that address these issues. Alternative deck systems, including u...

Movable bridges often include open grid steel deck for its light weight and ease of installation. These decks, however, suffer from poor rideability and high maintenance costs. In search for a new generation of lightweight solid decks that address these issues, a novel system was recently developed using ultra-high performance concrete (UHPC) in th...

Segmental bridges are widely used for accelerated construction and lower costs and environmental impact. The major concern with such bridges is in the corrosion protection of posttensioning steel strands. Noncorrosive carbon fiber strands can serve as viable alternatives to help reduce maintenance costs. A novel carbon fiber strand was tested for p...

High wind-induced suctions cause significant damage in traditional roofing systems, leading to subsequent rain intrusion and loss of interior contents. Damages include, among others, failure of tiles or shingles and in many roofing systems are related to workmanship-related issues, such as inadequate spacing of nails or poor application of foam adh...

Of the over 605,000 bridges in the U.S., about 12% are structurally deficient and another 16% are functionally obsolete (FHWA 2012). Three out of four structurally deficient bridges have major problems with their decks. For example, the most recent case of the collapsed bridge on I-5 in Washington is reported to have been on the state’s structurall...

Roofing is one of the most vulnerable parts of the building envelope in a residential structure, often damaged during extreme wind events such as hurricanes or tornadoes. Conventional roofing systems in residential buildings mostly consist of separate the main wind force resisting system (MWFRS) and components and cladding (C&C). High wind uplift f...

A novel deck system is developed as an ultralightweight low profile waffle slab of ultrahigh-performance concrete (UHPC) reinforced with carbon-fiber-reinforced polymer (CFRP) bars. The proposed system lends itself to accelerated bridge construction, and has great potential for deck replacement in bridges with load restrictions, and as well for bri...

Carbon fiber strands offer a viable alternative to corrosion-prone steel strands in posttensioning applications. This study focused on a side-by-side comparison of two types of carbon fiber strands with different elastic moduli against steel strands in a 51 scaled model of a typical interior hammerhead pier of the San Antonio Downtown Y project wit...

Carbon-fiber-composite cables (CFCC) offer a corrosion-free alternative to steel strands. This paper describes the construction and testing of a 31/2:1 scale model of the Long Key segmental box girder bridge model posttensioned with CFCC or steel strands at different prestress and for different loading configurations. The study shows the feasibilit...

Contrary to military or essential government buildings, most bridges are designed without any consideration for blast resistance. Fiber reinforced polymers (FRPs) can provide an effective means for strengthening of critical bridges against such loading. This study has focused on the effectiveness of FRP retrofitting in the dynamic response of reinf...

Previous studies have clearly shown that flat slabs made of ultrahigh-performance concrete (UHPC) have considerably higher punching shear strength than their counterparts made of conventional concrete. However, it may not be economically feasible to construct an entire slab out of UHPC. As such, the objective of the research reported in this paper...

The influence of dowel action is usually ignored during normal reinforced concrete beam designs since vertical shear reinforcing bars always offer significant shear resistance. However, for ultra-high performance concrete (UHPC) beams without shear reinforcement, the dowel action contribution to the shear strength becomes considerable and is import...

A lightweight, low-profile ultrahigh-performance concrete (UHPC) deck system reinforced with high-strength steel (HSS) has been proposed by the authors as an alternative to open grid steel deck. The system consists of a thin slab with primary ribs spanning between girders and shallower secondary ribs, parallel to the girders, connecting the primary...

The application of ultrahigh performance concrete (UHPC) as an alternative to conventional concrete has grown rapidly in recent years. However, to date, little is known about the confinement behavior of UHPC, knowledge that is necessary to develop design guidelines for UHPC columns. In a previous study, the authors investigated the stress-strain be...

A novel hybrid column made of fiber-reinforced polymer (FRP) and ultra-high-performance concrete (UHPC) was developed in a previous study by the authors. The steel-free UHPC-filled FRP tube (UHPCFFT) system proved promising as an alternative to conventional reinforced concrete (RC) columns. This study investigates the effect of column cross section...

Ultrahigh performance concrete (UHPC) is increasingly making its way into the construction field. Characterization of UHPC has therefore received much-needed attention in the research arena. One effective application of UHPC is in combination with high-strength steel (HSS) reinforcing rebar in shallow beams or slabs. However, bond and development c...

Concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) were initially developed without any internal steel reinforcement as viable alternatives to conventional RC columns in nonseismic regions. Studies have shown that extending CFFT application to seismic regions requires a moderate amount of internal steel reinforcement. To date, cyclic perf...

Concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) were initially developed without any internal steel reinforcement as viable alternatives to conventional RC columns in nonseismic regions. Studies have shown that extending CFFT application to seismic regions requires a moderate amount of internal steel reinforcement. To date, cyclic perf...

The application of externally bonded carbon fiber-reinforced polymer (CFRP) stirrups is by now proven as an effective technique to strengthen slab-column connections for punching shear. However, there has not been adequate study into its effectiveness for repair and rehabilitation of existing slab-column connections with different levels of prior d...

Concrete confinement has an important role in reinforced concrete columns, especially for strengthening applications and in hybrid construction. It is well known that confinement increases axial strength and ultimate strain of concrete. However, existing confinement models are extremely dependent on the type of confinement, i.e., passive or active;...

Extensive damage to residential wood-frame buildings caused by failures of roof-to-wall connections during extreme wind events underscores the need to improve their performance. Most of these connections use mechanical connectors, e.g., metal clips and straps (sometimes referred to as hurricane clips and hurricane straps). The allowable capacity of...

This study investigated the shear performance of an RC beam strengthened in shear with externally bonded carbon fiber-reinforced polymer (CFRP) strips, subjected to a cyclic loading for 2 million cycles at 1 Hz. The stress level in the stirrups caused by the cyclic loading used in this study was higher than those typically used in fatigue studies,...

Fiber-reinforced polymer (FRP) composites have become an integral part of the construction industry because of their versatility, enhanced durability and resistance to fatigue and corrosion, high strength-to-weight ratio, accelerated construction, and lower maintenance and life-cycle costs. Advanced FRP composite materials are also emerging for a w...

The seismic performance of a concrete filled fiber reinforced polymer (FRP) tube (CFFT) bridge column was studied through shake table testing and nonlinear dynamic analyses of a one-fifth scale two-column bridge pier that also incorporated a conventional RC column. The FRP tube in the CFFT column was a prefabricated composite pipe with glass fibers...

Among the states, Florida has the largest stock of moveable bridges, most of which with open grid steel decks. These decks are often associated with poor rideability, high noise levels, susceptibility to fatigue damage, and high maintenance costs. To address these issues, two alternative lightweight shallow deck systems are proposed. One with a thi...

The unique features of ultra-high-performance concrete (UHPC) in damage tolerance, energy absorption, and deformability were combined with the superior performance of concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) to develop a novel hybrid system of FRP tube and UHPC, and the cyclic behavior of this system evaluated. Four specimens we...

The seismic response of a novel hybrid column made of a fiber-reinforced polymer (FRP) tube filled with ultra-high performance concrete (UHPC) was studied. A methodology was proposed to estimate the maximum ground acceleration capacity of five UHPC-filled FRP tubes (UHPCFFT) and one reference concrete (RC) column based on the results of their pseud...

Most of the movable bridges in the United States have open grid steel decks, primarily because they are factory assembled, lightweight, and easy to install. Open grid steel decks, however, are not as skid resistant as solid decks. Costly maintenance, high noise levels, poor riding comfort, and susceptibility to vibrations are among the other disadv...

It is all but certain that the 21st century will see more and larger mega cities as magnets for population and economic activities in developed and developing countries around the world. It is similarly certain that the problems associated with the growth of mega cities would only deepen, persist and prolong, unless a new approach is taken to the d...

A new deck system for moveable bridges was developed that makes use of ultra-high performance concrete (UHPC) reinforced with high strength steel (HSS) rebar to achieve the light weight and high strength requirements in moveable bridge applications. However, the typical deck strips of this deck system failed predominantly due to shear cracks in sim...

Over a decade of studies have demonstrated the benefits of ultra high performance concrete (UHPC) in terms of damage tolerance, energy absorption, crack distribution, and deformation capacity. However, little information is available on the confinement behavior of UHPC, especially when confined with fiber-reinforced polymers (FRP). Sixteen UHPC-fil...

Concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) were initially proposed for bridge substructures in corrosive environments in the early 1990s. Systematic studies have since demonstrated the feasibility and merits of CFFTs with or without internal mild steel reinforcement. However, the experimental database in this field is still quite...

There is currently a need to develop lightweight bridge deck systems with solid riding surfaces to replace the open-grid steel decks from moveable bridges. Open-grid steel decks present several problems, including poor rideability, high noise levels, susceptibility to fatigue damage, and high maintenance costs. There is a great opportunity to use a...

The allowable capacity of conventional roof-to-wall metal connectors is based on results of unidirectional component tests that do not simulate triaxial aerodynamic loading effects induced by high-wind events. The results of wind and wind-driven rain tests conducted at a full-scale facility were used to create a database on aerodynamic and aerohydr...

Roof coverings, particularly barrel tiles, have experienced significant damage over the last few years from storms, even weaker storms such as Category 1 Hurricane Wilma in 2005. Efforts have been made to ban mortar-set attachments in southern Florida in favor of adhesive sets. Moreover, some homeowners have generalized the poor performance of clay...

A significant proportion of damage to buildings in hurricanes occurs owing to weak roof-to-wall connections. The objective of this study was to develop an innovative, efficient, and nonintrusive roof-to-wall connection for wood-frame structures by using high-performance fiber reinforced polymer (FRP) composites. Several connection configurations we...

Aging infrastructure worldwide has made rapid means of repair and retrofitting a growing necessity. Fiber reinforced polymers (FRP) can provide a cost-effective and accelerated repair technique with near surface mounting (NSM) of pre-cured bars or strips in a bed of epoxy placed in pre-cut grooves. The performance of NSM FRP reinforcement depends o...

This paper summarizes the findings of an extensive research program that examined the shrinkage and creep behavior of high-strength concrete (HSC) up to a strength of 18 ksi (124 MPa). Creep and shrinkage strains of 60 specimens were monitored for up to two years. The variables considered in this investigation were the concrete compressive strength...

Florida has the largest stock of moveable bridges in the United States. More than half of these bridges are located along the inter-coastal waterways in Miami and Ft Lauderdale. Most of the moveable bridges use open grid steel decks. These open grid decks have several disadvantages, including poor skid resistance, high maintenance costs, high noise...

This study is based on merging two promising materials to develop a new hybrid system. Engineered cementitious composites (ECC) allow optimization of the micro structure of the material to achieve ultra-high strength, ductility and fracture toughness. Studies during past two decades have also shown that fiber reinforced polymer (FRP) tubes can help...

While the effectiveness of corrosion-inhibiting admixtures in new concrete has been well documented, there is little research on their surface-applied counterparts for existing structures. This study was undertaken to assess whether surface-applied products can delay, slow, or stop the corrosion process in contaminated concrete. A total of 348 spec...

One of the most critical connections in wood frame construction is that of the roof rafter and the top plate of the wall. This type of connection typically uses mechanical fasteners, such as metal straps or clips fastened with nails. Manufacturers base the allowable capacity of connections with one fastener on results of tests performed on such con...

An extensive experimental and analytical research program was undertaken to recommend revisions to extend the applicability of flexural and compression design provisions for reinforced and prestressed concrete members of the AASHTO LRFD Bridge Design Specifications to concrete compressive strengths up to 18 ksi (124 MPa). The recommended provisions...

Field applications and laboratory research have shown the feasibility of concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) in bridges. Yet, their widespread applications require developing appropriate design and analysis tools for different types of loading, particularly fatigue loads. An analytical tool is developed to trace the response...

Retrofitting concrete structures with externally bonded fiber-reinforced polymer (FRP) laminates has become an increasingly common practice. Disbonds at the concrete-FRP interface, if left untreated, may adversely affect the performance of the retrofitted system. Disbonds in the form of surface voids and cracks are the subject of this paper. Voids...

A comprehensive experimental program was undertaken to determine the short-term mechanical properties of high-strength concrete (HSC). Modulus of rupture beams and two different sizes of concrete cylinders with three different target compressive strengths ranging from 10 to 18 ksi (69 to 124 MPa) were subjected to three different curing methods and...

Fiber reinforced polymer (FRP) has become increasingly popular for the repair and retrofit of reinforced concrete structures. Surface condition of the substrate, in particular its flatness, plays a significant role on the performance of retrofitted structure. This paper reports on the effects of out-of-flatness as a surface defect oil the flexural...

Widespread damage to tile roofs over the last few years, even for weaker hurricanes, has raised concerns regarding construction practices and codes. An experimental study was carried out for clay and concrete roof tiles with adhesive- and mortar-set attachments using a "Wall of Wind" apparatus. The estimated peak 3-s gust wind speeds achieved in th...

An experimental and analytical study was undertaken to assess the flexural behavior of a new fiber reinforced polymer (FRP) deck system. The deck consists of a series of pultruted FRP tubes, post-tensioned in between each two stringers. Seven pure compression tests and eleven flexural tests were carried out to investigate the effect of tube size, b...

While most low-rise buildings suffered little structural damage under typhoons, many experienced roof covering failures, and especially lost a large number of roof tiles. A detailed wind tunnel tests were carried out at Tongji University to acquire the wind loads on clay and concrete roof tiles. Test data were fed into a finite element model (FEM)...

While most studies have focused on short term behavior of fiber reinforced polymer(FRP). reinforced concrete (RC) members, it is important and necessary to study their time-dependent behavior, if FRP is to be used as a viable alternative reinforcement for the infrastructure. The present study provides an analytical tool to assess serviceability iss...

Performance of fiber-reinforced polymer (FRP) composites in repair and retrofit of concrete structures depends to a great extent on the substrate condition to which it is bonded. The present research investigated the effect of concrete surface roughness on the bond behavior and general performance of FRP strengthening systems. The study included fl...

This paper proposes provisions to extend the current American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications to include prediction of the ultimate flexural strength of prestressed concrete girders with concrete compressive strengths up to 18 ksi (124 MPa). The proposed design provisions include c...

This paper describes fundamental characteristics of the compressive stress distribution in the compression zone of flexural members with concrete compressive strengths up to 18 ksi (124 Wet). The proposed model is based on testing of 21 plain concrete specimens subjected to combined flexure and axial compression up to failure. The main variable con...

In this study, the problem of vehicular impact on a portable concrete barrier (PCB) is investigated. An available crash test is modeled and the impact response was simulated through a finite element (FE) model. On the basis of insight gained through this detailed FE analysis, a simpler rigid body model is then used to perform a comprehensive study...

Although use of high-strength reinforced concrete (RC) jackets has become common practice worldwide, there are still two unresolved issues regarding the contribution of the original concrete and the effects of existing loads. Twelve RC-jacketed columns were tested with and without preloading under uniaxial compression. Tests showed the entire core...

To date, research on concrete-filled fiber-reinforced polymer (FRP) tubes (CFFT) has focused on the effect of static loads, simulated seismic loads, and long-term sustained loads. Dynamic fatigue behavior of CFFTs, on the other hand, has received little or no attention. This paper reports on an experimental study to evaluate damage accumulation, st...

Behavior of short and deep beams made of concrete-filled fiber-reinforced polymer (FRP) tubes (CFFT) was compared experimentally to that of their slender counterparts. Ten specimens made from four types of glass FRP tubes with different fiber architecture and lamina lay-up were tested with shear span to depth ratio between 0.9 and 6.25, diameter to...

TRB's National Cooperative Highway Research Program (NCHRP) Report 609: Recommended Construction Specifications and Process Control Manual for Repair and Retrofit of Concrete Structures Using Bonded FRP Composites explores recommended construction specifications to facilitate highway agencies’ use of bonded fiber-reinforced polymer (FRP) composites...

Five different configurations of carbon fiber-reinforced polymer (FRP) grids were tested for the control of plastic shrinkage cracking of concrete using carbon FRP rods with two different spacings, two configurations of conventional steel wire meshes, and fiber reinforced concrete with two different fiber volume fractions. The experimental program...

Fiber reinforced polymer (FRP) composites have become popular in recent years both in the construction of new facilities and in the renewal of existing structures owing to their technical advantages and economic benefits over traditional materials. However, there is a concern in the civil engineering industry over the lack of information on the lon...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 595, Application of the LRFD Bridge Design Specifications to High-Strength Structural Concrete: Flexure and Compression Provisions explores recommended revisions to the American Association of State Highway and Transportation Officials’ Load and Resistance Factor Design (LRFD) Bridg...

Concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) are an alternative to reinforced concrete, providing for rapid construction with comparable strengths and higher ductility. Despite encouraging test data, it is not clear as to whether traditional analytical tools may be used for prediction of structural performance of CFFT, especially in...

Confinement by fiber reinforced polymer (FRP) wraps can significantly enhance strength and ductility of concrete columns. Behavior of FRP-confined concrete in uniaxial compression can be characterized by its bilinear stress–strain and unique dilation properties. A number of models have in recent years been developed to capture these characteristics...

This paper reports on a feasibility study of splicing techniques for precast concrete-filled fiber-reinforced polymer (FRP) tubes (CFFT). A total of four spliced beams were tested. Three were internally spliced using grouted steel bars, grouted FRP bars, or unbonded posttensioning bars, and the fourth was spliced with FRP socket, commonly used in t...

A set of column-footing subassemblies were prepared to investigate construction feasibility and seismic performance of structural joints for concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) as bridge substructure. Based on the common practices of the precast industry and previous research on CFFT, the test matrix included a control reinf...

This paper summarizes the research findings of the fundamental characteristics of high-strength concrete for the flexural design of bridge girders. The main objective of the research is to provide recommended provisions to the AASHTO-LRFD Bridge Design Specifications to extend the use of concrete strength up to 18 ksi. A total of 15 plain concrete...